diff --git a/.gitignore b/.gitignore
index fcbfeeb..0c4efd6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
 # TypeScript / Node
 extension/background.js
+extension/test-dist/
 node_modules/
 dist/
 
@@ -8,4 +9,4 @@ __pycache__/
 *.pyc
 
 # IDE
-.vscode/
\ No newline at end of file
+.vscode/
diff --git a/extension/src/classes/CommandGroup.ts b/extension/src/classes/CommandGroup.ts
new file mode 100644
index 0000000..e291f9d
--- /dev/null
+++ b/extension/src/classes/CommandGroup.ts
@@ -0,0 +1,21 @@
+import type { CommandArgs, Serializable } from '../types';
+import type { JobManager } from './JobManager';
+
+export type CommandRun = (args: CommandArgs) => Promise<Serializable> | Serializable;
+export interface CommandSpec { background?: boolean; run: CommandRun; }
+export type CommandEntry = CommandRun | CommandSpec;
+
+/** Shared state handed to every command group at construction. */
+export interface CommandContext { jobs: JobManager; }
+
+/**
+ * A command group bundles a set of related subcommands. `commands` is keyed by
+ * the FULL command id (e.g. "tabs.close") so groups spanning multiple
+ * namespaces (dom/extract/page, storage/cookies, session/clients) register
+ * uniformly. `namespace` is documentation/grouping only.
+ */
+export abstract class CommandGroup {
+  constructor(protected readonly ctx: CommandContext) {}
+  abstract readonly namespace: string;
+  abstract readonly commands: Record<string, CommandEntry>;
+}
diff --git a/extension/src/classes/CommandRegistry.ts b/extension/src/classes/CommandRegistry.ts
new file mode 100644
index 0000000..6466ad6
--- /dev/null
+++ b/extension/src/classes/CommandRegistry.ts
@@ -0,0 +1,94 @@
+import { CommandGroup } from './CommandGroup';
+import type { CommandContext, CommandEntry, CommandSpec } from './CommandGroup';
+import { NavigationCommands } from '../commands/navigation';
+import { TabsMutationCommands } from '../commands/tabs';
+import { TabsQueryCommands } from '../commands/tabs-query';
+import { GroupsCommands } from '../commands/groups';
+import { WindowsCommands } from '../commands/windows';
+import { DomCommands } from '../commands/dom';
+import { BrowserDataCommands } from '../commands/browser-data';
+import { SessionCommands } from '../commands/session';
+import { PerfCommands } from '../commands/perf';
+import { ExtensionCommands } from '../commands/extension';
+import type { CommandArgs, Serializable, DispatchArgs, PageRequest } from '../types';
+
+function isCommandSpec(entry: CommandEntry): entry is CommandSpec {
+  return typeof entry !== "function";
+}
+
+export function makePagedData(items: Serializable[], page: PageRequest) {
+  const total = items.length;
+  const offset = Math.max(0, Number(page.offset) || 0);
+  const requestedLimit = Math.max(1, Number(page.limit) || 100);
+  const limit = Math.min(requestedLimit, 1000);
+  const end = Math.min(offset + limit, total);
+  return {
+    __browserCliPage: true,
+    items: items.slice(offset, end),
+    offset,
+    limit,
+    total,
+    nextOffset: end < total ? end : null,
+  };
+}
+
+export class CommandRegistry {
+  private readonly entries = new Map<string, CommandEntry>();
+
+  constructor(private readonly ctx: CommandContext) {}
+
+  /** Flattens a group's full-id-keyed commands into the registry map. */
+  register(group: CommandGroup): void {
+    for (const [command, entry] of Object.entries(group.commands)) {
+      if (this.entries.has(command)) {
+        throw new Error(`Duplicate command registration: ${command}`);
+      }
+      this.entries.set(command, entry);
+    }
+  }
+
+  private resolve(command: string): CommandEntry {
+    const entry = this.entries.get(command);
+    if (!entry) throw new Error(`Unknown command: ${command}`);
+    return entry;
+  }
+
+  async dispatch(command: string, args: DispatchArgs, opts: { background?: boolean; page?: PageRequest }): Promise<Serializable> {
+    const entry = this.resolve(command);
+
+    if (isCommandSpec(entry) && entry.background && opts.background) {
+      // Narrow the dynamic IPC dict to the handler's declared arg type at the
+      // call boundary.
+      return this.ctx.jobs.start(command, args, jobArgs => Promise.resolve(entry.run(jobArgs as CommandArgs)));
+    }
+
+    const run = isCommandSpec(entry) ? entry.run : entry;
+    let result = await run(args as CommandArgs);
+    if (opts.page && Array.isArray(result)) {
+      result = makePagedData(result, opts.page);
+    }
+    return result;
+  }
+}
+
+/**
+ * Builds the registry and registers every command group. The SessionCommands
+ * instance is returned alongside because index.ts wires its lifecycle methods
+ * (chrome.tabs.onActivated → activateLazyTab) and NativeConnection references it
+ * for the clients.rename_profile reconnect side-effect.
+ */
+export function assembleRegistry(ctx: CommandContext): { registry: CommandRegistry; session: SessionCommands } {
+  const registry = new CommandRegistry(ctx);
+  const session = new SessionCommands(ctx);
+  registry.register(new NavigationCommands(ctx));
+  registry.register(new TabsMutationCommands(ctx));
+  registry.register(new TabsQueryCommands(ctx));
+  registry.register(new GroupsCommands(ctx));
+  registry.register(new WindowsCommands(ctx));
+  registry.register(new DomCommands(ctx));
+  registry.register(new BrowserDataCommands(ctx));
+  registry.register(session);
+  registry.register(new PerfCommands(ctx));
+  registry.register(new ExtensionCommands(ctx));
+  return { registry, session };
+}
diff --git a/extension/src/classes/JobManager.ts b/extension/src/classes/JobManager.ts
new file mode 100644
index 0000000..860cebf
--- /dev/null
+++ b/extension/src/classes/JobManager.ts
@@ -0,0 +1,160 @@
+/**
+ * Background-job retention helpers + the JobManager that owns the live job map.
+ *
+ * `pruneFinishedJobs` / `MAX_FINISHED_JOBS` are kept free of chrome.* /
+ * service-worker side effects so the retention logic (memory-leak guard) can be
+ * unit-tested in isolation.
+ */
+
+import { getErrorMessage } from '../core';
+import type { Job, Serializable, ErrorLike, DispatchArgs } from '../types';
+
+// Cap retained finished jobs so the in-memory Map cannot grow unbounded while
+// the service worker is pinned alive by the native port. Kept small: finished
+// jobs only need to survive long enough for the CLI to poll their result.
+export const MAX_FINISHED_JOBS = 20;
+
+// Watchdog: if a runner never resolves/rejects (e.g. executeScript against a
+// dead tab), finalize the job as an error so its persist interval stops instead
+// of writing to chrome.storage.local every second forever.
+export const JOB_TIMEOUT_MS = 5 * 60 * 1000;
+
+/**
+ * Evict the oldest *finished* jobs from `jobs` once their count exceeds `max`.
+ * Running jobs are always kept. Each evicted job's persistence timer (if any)
+ * is cleared via `clearTimer` so no interval is leaked.
+ *
+ * Returns the list of evicted job ids (useful for assertions/logging).
+ */
+export function pruneFinishedJobs(
+  jobs: Map<string, Job>,
+  max = MAX_FINISHED_JOBS,
+  clearTimer: (handle: NonNullable<Job["__timer"]>) => void = clearInterval,
+): string[] {
+  const finished = [...jobs.values()].filter(job => job.status !== "running");
+  const excess = finished.length - max;
+  if (excess <= 0) return [];
+  const evicted = finished
+    .sort((a, b) => (a.finishedAt || 0) - (b.finishedAt || 0))
+    .slice(0, excess);
+  for (const job of evicted) {
+    if (job.__timer) clearTimer(job.__timer);
+    jobs.delete(job.id);
+  }
+  return evicted.map(job => job.id);
+}
+
+/** Runs a background command, threading the live `__job` handle for progress. */
+export type JobRunner = (args: DispatchArgs) => Promise<Serializable>;
+
+/** Owns the live job map plus its persistence + retention lifecycle. */
+export class JobManager {
+  private readonly jobs = new Map<string, Job>();
+
+  /** Snapshot of live jobs (for perf.status etc.). */
+  list(): Job[] {
+    return [...this.jobs.values()];
+  }
+
+  private async persistJobs() {
+    // Persist all running jobs plus the most recent finished ones. Running jobs
+    // must never be dropped by the cap, otherwise a burst of finished jobs could
+    // evict a still-active job from storage. Live timer handles are stripped —
+    // they are not meaningful once stored.
+    const all = [...this.jobs.values()];
+    const running = all.filter(job => job.status === "running");
+    const finished = all.filter(job => job.status !== "running").slice(-MAX_FINISHED_JOBS);
+    const recentJobs = [...running, ...finished].map(({ __timer, __watchdog, ...rest }) => rest);
+    await chrome.storage.local.set({ recentJobs });
+  }
+
+  // Evict the oldest finished jobs once their count exceeds the retention cap.
+  // Recent finished jobs remain queryable via chrome.storage.local (persistJobs)
+  // even after eviction from the in-memory Map.
+  private pruneJobs() {
+    pruneFinishedJobs(this.jobs, MAX_FINISHED_JOBS);
+  }
+
+  async start(command: string, args: DispatchArgs, runner: JobRunner) {
+    const jobId = `${Date.now().toString(36)}-${Math.random().toString(36).slice(2, 10)}`;
+    const job: Job = {
+      id: jobId,
+      command,
+      status: "running",
+      phase: "queued",
+      current: 0,
+      total: null,
+      percent: 0,
+      cancelRequested: false,
+      startedAt: Date.now(),
+      updatedAt: Date.now(),
+      finishedAt: null,
+      result: null,
+      error: null,
+    };
+    this.jobs.set(jobId, job);
+    job.__timer = setInterval(() => this.persistJobs(), 1000);
+    job.__watchdog = setTimeout(() => {
+      job.cancelRequested = true;
+      void this.finalize(job, "error", { error: `Job timed out after ${JOB_TIMEOUT_MS}ms` });
+    }, JOB_TIMEOUT_MS);
+    await this.persistJobs();
+    runner({ ...args, __job: job })
+      .then(result => this.finalize(job, "done", { result }))
+      .catch((error: ErrorLike) =>
+        this.finalize(job, job.cancelRequested ? "cancelled" : "error", {
+          error: getErrorMessage(error),
+        }),
+      );
+    return { jobId, command, status: job.status };
+  }
+
+  /**
+   * Move a running job to a terminal state exactly once. Late settlements (a
+   * runner that resolves after the watchdog already fired) are ignored so a
+   * timed-out job cannot be resurrected. Clears both the persist interval and
+   * the watchdog so no timer outlives the job.
+   */
+  private async finalize(
+    job: Job,
+    status: "done" | "error" | "cancelled",
+    { result = null, error = null }: { result?: Serializable; error?: string | null },
+  ) {
+    if (job.status !== "running") return;
+    job.status = status;
+    job.phase = status;
+    if (status === "done") {
+      job.result = result;
+      job.current = job.total || job.current;
+      job.percent = 100;
+    } else {
+      job.error = error;
+    }
+    job.finishedAt = Date.now();
+    job.updatedAt = Date.now();
+    if (job.__timer) clearInterval(job.__timer);
+    if (job.__watchdog) clearTimeout(job.__watchdog);
+    job.__timer = null;
+    job.__watchdog = null;
+    this.pruneJobs();
+    await this.persistJobs();
+  }
+
+  async status({ jobId }: { jobId?: string }) {
+    const job = this.jobs.get(jobId);
+    if (job) return { ...job };
+    const { recentJobs } = await chrome.storage.local.get<{ recentJobs?: Job[] }>("recentJobs");
+    const stored = (recentJobs || []).find(entry => entry.id === jobId);
+    if (!stored) throw new Error(`Job '${jobId}' not found`);
+    return stored;
+  }
+
+  async cancel({ jobId }: { jobId?: string }) {
+    const job = this.jobs.get(jobId);
+    if (!job) throw new Error(`Job '${jobId}' not running`);
+    job.cancelRequested = true;
+    job.updatedAt = Date.now();
+    await this.persistJobs();
+    return { jobId, cancelled: true };
+  }
+}
diff --git a/extension/src/classes/NativeConnection.ts b/extension/src/classes/NativeConnection.ts
new file mode 100644
index 0000000..405078c
--- /dev/null
+++ b/extension/src/classes/NativeConnection.ts
@@ -0,0 +1,147 @@
+/**
+ * Native-messaging port lifecycle: connect/keepalive/reconnect plus the inbound
+ * message router that hands commands to the CommandRegistry.
+ */
+
+import { getErrorMessage, getProfileAlias } from '../core';
+import type { CommandRegistry } from './CommandRegistry';
+import type { SessionCommands } from '../commands/session';
+import type { ControlMessage, ResponseMessage, IncomingMessage, PageRequest, DispatchArgs, Serializable } from '../types';
+
+const NATIVE_HOST = "com.browsercli.host";
+
+export class NativeConnection {
+  private port: chrome.runtime.Port | null = null;
+  private keepaliveEnabled = true;
+
+  constructor(
+    private readonly registry: CommandRegistry,
+    private readonly session: SessionCommands,
+  ) {}
+
+  /** Registers all runtime listeners and opens the initial connection. */
+  start() {
+    chrome.runtime.onInstalled.addListener(() => this.connect());
+    chrome.runtime.onStartup.addListener(() => this.connect());
+    chrome.runtime.onSuspend.addListener(() => {
+      this.disconnectPort({ sendBye: true });
+    });
+    chrome.windows.onCreated.addListener(() => {
+      this.keepaliveEnabled = true;
+      if (!this.port) this.connect();
+    });
+    chrome.windows.onRemoved.addListener(async () => {
+      const windows = await chrome.windows.getAll({});
+      if (windows.length > 0) return;
+
+      this.keepaliveEnabled = false;
+      this.disconnectPort({ sendBye: true });
+    });
+
+    // Reconnect poll — wakes the worker to re-establish the native port if it
+    // dropped. 0.5 min is Chrome's minimum alarm period; lower values (e.g. 0.4)
+    // are silently clamped and log a warning, so we set it explicitly.
+    chrome.alarms.create("keepalive", { periodInMinutes: 0.5 });
+    chrome.alarms.onAlarm.addListener((alarm) => {
+      if (alarm.name === "keepalive") {
+        if (!this.port && this.keepaliveEnabled) this.connect();
+      }
+    });
+  }
+
+  private sendControlMessage(targetPort: chrome.runtime.Port | null, message: ControlMessage) {
+    if (!targetPort) return;
+    try {
+      targetPort.postMessage(message);
+    } catch (e) {
+      console.warn("[browser-cli] Failed to send control message:", e);
+    }
+  }
+
+  private sendResponse(targetPort: chrome.runtime.Port | null, message: ResponseMessage) {
+    if (!targetPort) return;
+    try {
+      targetPort.postMessage(message);
+    } catch (e) {
+      console.warn("[browser-cli] Failed to send response:", e);
+    }
+  }
+
+  private disconnectPort({ sendBye = false }: { sendBye?: boolean } = {}) {
+    const currentPort = this.port;
+    if (!currentPort) return;
+
+    if (sendBye) this.sendControlMessage(currentPort, { type: "bye" });
+
+    if (this.port === currentPort) this.port = null;
+
+    try {
+      currentPort.disconnect();
+    } catch (e) {
+      console.warn("[browser-cli] Failed to disconnect native port:", e);
+    }
+  }
+
+  private async connect() {
+    if (this.port || !this.keepaliveEnabled) return;
+    try {
+      const nativePort = chrome.runtime.connectNative(NATIVE_HOST);
+      this.port = nativePort;
+      nativePort.onMessage.addListener((msg: IncomingMessage) => this.onMessage(msg));
+      nativePort.onDisconnect.addListener(() => {
+        if (this.port === nativePort) this.port = null;
+        const err = chrome.runtime.lastError;
+        if (err) console.warn("[browser-cli] Native host disconnected:", err.message);
+      });
+      // Send hello so native host knows which profile/alias this is
+      const alias = await getProfileAlias();
+      nativePort.postMessage({ type: "hello", alias });
+      console.log("[browser-cli] Connected to native host as profile:", alias);
+    } catch (e) {
+      this.port = null;
+      console.error("[browser-cli] Failed to connect:", e);
+    }
+  }
+
+  private async onMessage(msg: IncomingMessage) {
+    const { id, command, args } = msg;
+    if (!id || !command) return;
+
+    // Capture the port that delivered this message. dispatch() is awaited, and
+    // during that await onDisconnect/rename can null out this.port — so we reply
+    // on the captured port and bail if it (or this.port) is already gone.
+    const replyPort = this.port;
+
+    console.log("[browser-cli] ←", command, args);
+
+    let data: Serializable, error: string | undefined;
+    try {
+      const { __page, __background, ...commandArgs } = args || {};
+      data = await this.registry.dispatch(command, commandArgs as DispatchArgs, {
+        background: Boolean(__background),
+        page: __page as PageRequest | undefined,
+      });
+    } catch (e) {
+      error = getErrorMessage(e);
+    }
+
+    if (this.port !== replyPort) {
+      console.warn("[browser-cli] Port changed before reply, dropping:", command);
+      return;
+    }
+
+    if (error !== undefined) {
+      console.log("[browser-cli] → ERROR", command, error);
+      this.sendResponse(replyPort, { id, success: false, error });
+    } else {
+      console.log("[browser-cli] →", command, data);
+      this.sendResponse(replyPort, { id, success: true, data });
+    }
+
+    if (command === "clients.rename_profile" && error === undefined) {
+      this.disconnectPort({ sendBye: true });
+      this.keepaliveEnabled = true;
+      await this.connect();
+    }
+  }
+}
diff --git a/extension/src/commands/autosave.ts b/extension/src/commands/autosave.ts
new file mode 100644
index 0000000..9bb61dd
--- /dev/null
+++ b/extension/src/commands/autosave.ts
@@ -0,0 +1,84 @@
+import { getSessions, runLargeOperation } from '../core';
+import { captureCurrentSession } from './session-snapshot';
+
+// Debounce window for autosave. A full-tab snapshot + storage write runs on
+// every tab open/close/move; a longer window coalesces rapid bursts (e.g.
+// opening or closing many tabs at once) into a single snapshot.
+const AUTOSAVE_DEBOUNCE_MS = 3000;
+
+export class AutoSaveManager {
+  private autoSaveTimer: ReturnType<typeof setTimeout> | null = null;
+  private autoSaveInFlight = false;
+  private autoSavePending = false;
+
+  // Bound handler references — stored so add/removeListener share identity
+  // (removeListener must use the SAME reference that was added).
+  readonly autoSaveHandler = async (): Promise<void> => {
+    await this.scheduleAutoSave();
+  };
+  readonly autoSaveUpdatedHandler = async (_tabId: number, changeInfo: chrome.tabs.OnUpdatedInfo = {}): Promise<void> => {
+    // Ignore noisy media/title/favicon/loading updates. Sessions only store URL and group/window structure.
+    if (!("url" in changeInfo)) return;
+    await this.scheduleAutoSave();
+  };
+
+  async setEnabled(enabled: boolean) {
+    await chrome.storage.local.set({ autoSave: enabled });
+    chrome.tabs.onCreated.removeListener(this.autoSaveHandler);
+    chrome.tabs.onRemoved.removeListener(this.autoSaveHandler);
+    chrome.tabs.onMoved.removeListener(this.autoSaveHandler);
+    chrome.tabs.onAttached.removeListener(this.autoSaveHandler);
+    chrome.tabs.onDetached.removeListener(this.autoSaveHandler);
+    chrome.tabs.onUpdated.removeListener(this.autoSaveUpdatedHandler);
+    if (chrome.tabGroups?.onUpdated) chrome.tabGroups.onUpdated.removeListener(this.autoSaveHandler);
+    if (this.autoSaveTimer) clearTimeout(this.autoSaveTimer);
+    this.autoSaveTimer = null;
+    this.autoSavePending = false;
+    if (enabled) {
+      chrome.tabs.onCreated.addListener(this.autoSaveHandler);
+      chrome.tabs.onRemoved.addListener(this.autoSaveHandler);
+      chrome.tabs.onMoved.addListener(this.autoSaveHandler);
+      chrome.tabs.onAttached.addListener(this.autoSaveHandler);
+      chrome.tabs.onDetached.addListener(this.autoSaveHandler);
+      chrome.tabs.onUpdated.addListener(this.autoSaveUpdatedHandler);
+      if (chrome.tabGroups?.onUpdated) chrome.tabGroups.onUpdated.addListener(this.autoSaveHandler);
+    }
+    return { enabled };
+  }
+
+  private async saveAutoSessionIfChanged() {
+    const { session, signature, tabCount } = await captureCurrentSession();
+    const { autoSaveSignature } = await chrome.storage.local.get("autoSaveSignature");
+    if (autoSaveSignature === signature) return { skipped: true, tabs: tabCount };
+
+    const sessions = await getSessions();
+    sessions.__auto__ = session;
+    await chrome.storage.local.set({ sessions, autoSaveSignature: signature });
+    return { skipped: false, tabs: tabCount };
+  }
+
+  private async runAutoSave() {
+    if (this.autoSaveInFlight) {
+      this.autoSavePending = true;
+      return;
+    }
+    this.autoSaveInFlight = true;
+    try {
+      const { autoSave } = await chrome.storage.local.get("autoSave");
+      if (autoSave) await runLargeOperation("session.auto_save", () => this.saveAutoSessionIfChanged());
+    } finally {
+      this.autoSaveInFlight = false;
+      if (this.autoSavePending) {
+        this.autoSavePending = false;
+        this.autoSaveTimer = setTimeout(() => this.runAutoSave(), AUTOSAVE_DEBOUNCE_MS);
+      }
+    }
+  }
+
+  private async scheduleAutoSave(delayMs = AUTOSAVE_DEBOUNCE_MS) {
+    const { autoSave } = await chrome.storage.local.get("autoSave");
+    if (!autoSave) return;
+    if (this.autoSaveTimer) clearTimeout(this.autoSaveTimer);
+    this.autoSaveTimer = setTimeout(() => this.runAutoSave(), delayMs);
+  }
+}
diff --git a/extension/src/commands/browser-data.ts b/extension/src/commands/browser-data.ts
index 6883271..75f9e76 100644
--- a/extension/src/commands/browser-data.ts
+++ b/extension/src/commands/browser-data.ts
@@ -1,62 +1,74 @@
-// @ts-nocheck
-import { executeScript, getActiveTab, isScriptableUrl } from '../core';
-export async function storageGet({ key, type = "local", tabId } = {}) {
-  const tab = tabId ? await chrome.tabs.get(tabId) : await getActiveTab();
-  if (!isScriptableUrl(tab.url)) {
-    throw new Error(`Cannot access storage on ${tab.url} — navigate to a regular web page first`);
+import { executeScript, isScriptableUrl, resolveTabUrl } from '../core';
+import { CommandGroup } from '../classes/CommandGroup';
+import type { CommandEntry } from '../classes/CommandGroup';
+import type { Json, StorageGetArgs, StorageSetArgs, CookiesListArgs, CookiesGetArgs, CookiesSetArgs } from '../types';
+
+export class BrowserDataCommands extends CommandGroup {
+  readonly namespace = "storage";
+  readonly commands: Record<string, CommandEntry> = {
+    "storage.get":  (a: StorageGetArgs) => this.storageGet(a),
+    "storage.set":  (a: StorageSetArgs) => this.storageSet(a),
+    "cookies.list": (a: CookiesListArgs) => this.cookiesList(a),
+    "cookies.get":  (a: CookiesGetArgs) => this.cookiesGet(a),
+    "cookies.set":  (a: CookiesSetArgs) => this.cookiesSet(a),
+  };
+
+  private async storageGet({ key, type = "local", tabId }: StorageGetArgs = {}) {
+    const { tab } = await resolveTabUrl(tabId);
+    if (!isScriptableUrl(tab.url)) {
+      throw new Error(`Cannot access storage on ${tab.url} — navigate to a regular web page first`);
+    }
+    const results = await executeScript({
+      target: { tabId: tab.id },
+      world: "MAIN",
+      func: (k: string | null, t: string) => {
+        const store = t === "session" ? sessionStorage : localStorage;
+        if (k) return store.getItem(k);
+        return Object.fromEntries(Object.keys(store).map(key => [key, store.getItem(key)]));
+      },
+      args: [key || null, type],
+    });
+    return results[0]?.result ?? null;
   }
-  const results = await executeScript({
-    target: { tabId: tab.id },
-    world: "MAIN",
-    func: (k, t) => {
-      const store = t === "session" ? sessionStorage : localStorage;
-      if (k) return store.getItem(k);
-      return Object.fromEntries(Object.keys(store).map(key => [key, store.getItem(key)]));
-    },
-    args: [key || null, type],
-  });
-  return results[0]?.result ?? null;
-}
 
-export async function storageSet({ key, value, type = "local", tabId } = {}) {
-  const tab = tabId ? await chrome.tabs.get(tabId) : await getActiveTab();
-  if (!isScriptableUrl(tab.url)) {
-    throw new Error(`Cannot access storage on ${tab.url} — navigate to a regular web page first`);
+  private async storageSet({ key, value, type = "local", tabId }: StorageSetArgs = {}) {
+    const { tab } = await resolveTabUrl(tabId);
+    if (!isScriptableUrl(tab.url)) {
+      throw new Error(`Cannot access storage on ${tab.url} — navigate to a regular web page first`);
+    }
+    const results = await executeScript({
+      target: { tabId: tab.id },
+      world: "MAIN",
+      func: (k: string, v: Json, t: string) => {
+        const store = t === "session" ? sessionStorage : localStorage;
+        store.setItem(k, typeof v === "string" ? v : JSON.stringify(v));
+        return true;
+      },
+      args: [key, value, type],
+    });
+    return results[0]?.result ?? false;
   }
-  const results = await executeScript({
-    target: { tabId: tab.id },
-    world: "MAIN",
-    func: (k, v, t) => {
-      const store = t === "session" ? sessionStorage : localStorage;
-      store.setItem(k, typeof v === "string" ? v : JSON.stringify(v));
-      return true;
-    },
-    args: [key, value, type],
-  });
-  return results[0]?.result ?? false;
-}
 
-export async function cookiesList({ url, domain, name } = {}) {
-  const details = {};
-  if (url)    details.url    = url;
-  if (domain) details.domain = domain;
-  if (name)   details.name   = name;
-  return await chrome.cookies.getAll(details);
-}
+  private async cookiesList({ url, domain, name }: CookiesListArgs = {}) {
+    const details: chrome.cookies.GetAllDetails = {};
+    if (url)    details.url    = url;
+    if (domain) details.domain = domain;
+    if (name)   details.name   = name;
+    return await chrome.cookies.getAll(details);
+  }
 
-export async function cookiesGet({ url, name }) {
-  return await chrome.cookies.get({ url, name });
-}
+  private async cookiesGet({ url, name }: CookiesGetArgs) {
+    return await chrome.cookies.get({ url, name });
+  }
 
-export async function cookiesSet({ url, name, value, domain, path, secure, httpOnly, expirationDate, sameSite } = {}) {
-  const details = { url, name, value };
-  if (domain          != null) details.domain          = domain;
-  if (path            != null) details.path            = path;
-  if (secure          != null) details.secure          = secure;
-  if (httpOnly        != null) details.httpOnly        = httpOnly;
-  if (expirationDate  != null) details.expirationDate  = expirationDate;
-  if (sameSite        != null) details.sameSite        = sameSite;
-  return await chrome.cookies.set(details);
+  private async cookiesSet({ url, name, value, domain, path, secure, httpOnly, expirationDate, sameSite }: CookiesSetArgs = {}) {
+    const details: chrome.cookies.SetDetails = { url, name, value };
+    if (domain          != null) details.domain          = domain;
+    if (path            != null) details.path            = path;
+    if (secure          != null) details.secure          = secure;
+    if (httpOnly        != null) details.httpOnly        = httpOnly;
+    if (expirationDate  != null) details.expirationDate  = expirationDate;
+    if (sameSite        != null) details.sameSite        = sameSite;
+    return await chrome.cookies.set(details);
+  }
 }
-
-// This function is serialized and injected into the page by chrome.scripting
diff --git a/extension/src/commands/dom.ts b/extension/src/commands/dom.ts
index c9bffae..8c6751a 100644
--- a/extension/src/commands/dom.ts
+++ b/extension/src/commands/dom.ts
@@ -1,8 +1,10 @@
-// @ts-nocheck
-import { executeScript, getActiveTab, isBrowserErrorUrl, isErrorPageScriptError, isScriptableUrl } from '../core';
+import { assertScriptableUrl, executeScript, fetchTabHtml, isBrowserErrorUrl, isErrorPageScriptError, resolveTabUrl } from '../core';
 import { contentDispatch } from './injected';
+import { CommandGroup } from '../classes/CommandGroup';
+import type { CommandEntry } from '../classes/CommandGroup';
+import type { DomArgs, DomEvalArgs, DomWaitForArgs, DomPollArgs, Serializable } from '../types';
 
-function fallbackForErrorPageDomOp(funcName, tab) {
+function fallbackForErrorPageDomOp(funcName: string, tab: chrome.tabs.Tab): Serializable {
   switch (funcName) {
     case "domExists":
       return false;
@@ -20,7 +22,7 @@ function fallbackForErrorPageDomOp(funcName, tab) {
         title: tab.title || "",
         url: tab.url || tab.pendingUrl || "",
         readyState: "error",
-        lang: null,
+        lang: null as string | null,
         meta: {},
       };
     default:
@@ -28,113 +30,143 @@ function fallbackForErrorPageDomOp(funcName, tab) {
   }
 }
 
-export async function domOp(funcName, args = {}) {
-  const tab = args?.tabId ? await chrome.tabs.get(args.tabId) : await getActiveTab();
-  const tabUrl = tab.url || tab.pendingUrl || "";
-  if (isBrowserErrorUrl(tabUrl)) {
-    const fallback = fallbackForErrorPageDomOp(funcName, tab);
-    if (fallback !== undefined) return fallback;
-  }
-  if (!isScriptableUrl(tabUrl)) {
-    throw new Error(`Cannot run DOM commands on ${tabUrl} — navigate to a regular web page first`);
-  }
-  try {
-    const results = await executeScript({
-      target: { tabId: tab.id },
-      func: contentDispatch,
-      args: [funcName, args],
-    });
-    return results[0]?.result;
-  } catch (e) {
-    if (isErrorPageScriptError(e)) {
+export class DomCommands extends CommandGroup {
+  readonly namespace = "dom";
+
+  readonly commands: Record<string, CommandEntry> = {
+    // ── DOM ──────────────────────────────────────────────────────────────
+    "dom.query":    (a: DomArgs) => this.domOp("domQuery", a),
+    "dom.click":    (a: DomArgs) => this.domOp("domClick", a),
+    "dom.type":     (a: DomArgs) => this.domOp("domType", a),
+    "dom.attr":     (a: DomArgs) => this.domOp("domAttr", a),
+    "dom.text":     (a: DomArgs) => this.domOp("domText", a),
+    "dom.exists":   (a: DomArgs) => this.domOp("domExists", a),
+    "dom.scroll":   (a: DomArgs) => this.domOp("domScroll", a),
+    "dom.select":   (a: DomArgs) => this.domOp("domSelect", a),
+    "dom.key":      (a: DomArgs) => this.domOp("domKey", a),
+    "dom.hover":    (a: DomArgs) => this.domOp("domHover", a),
+    "dom.check":    (a: DomArgs) => this.domOp("domCheck", { ...a, checked: true }),
+    "dom.uncheck":  (a: DomArgs) => this.domOp("domCheck", { ...a, checked: false }),
+    "dom.clear":    (a: DomArgs) => this.domOp("domClear", a),
+    "dom.focus":    (a: DomArgs) => this.domOp("domFocus", a),
+    "dom.submit":   (a: DomArgs) => this.domOp("domSubmit", a),
+    "dom.eval":     (a: DomEvalArgs) => this.domEval(a),
+    "dom.wait_for": (a: DomWaitForArgs) => this.domWaitFor(a),
+    "dom.poll":     (a: DomPollArgs) => this.domPoll(a),
+
+    // ── Page ─────────────────────────────────────────────────────────────
+    "page.info":    () => this.domOp("pageInfo", {}),
+
+    // ── Extract ──────────────────────────────────────────────────────────
+    "extract.links":    (a: DomArgs) => this.domOp("extractLinks", a),
+    "extract.images":   (a: DomArgs) => this.domOp("extractImages", a),
+    "extract.text":     (a: DomArgs) => this.domOp("extractText", a),
+    "extract.json":     (a: DomArgs) => this.domOp("extractJson", a),
+    "extract.markdown": (a: DomArgs) => this.domOp("extractMarkdown", a),
+    "extract.html":     () => fetchTabHtml(undefined),
+  };
+
+  private async domOp(funcName: string, args: DomArgs = {}) {
+    const { tab, url: tabUrl } = await resolveTabUrl(args?.tabId);
+    if (isBrowserErrorUrl(tabUrl)) {
       const fallback = fallbackForErrorPageDomOp(funcName, tab);
       if (fallback !== undefined) return fallback;
     }
-    throw e;
-  }
-}
-
-export async function domEval({ code, tabId } = {}) {
-  const tab = tabId ? await chrome.tabs.get(tabId) : await getActiveTab();
-  const tabUrl = tab.url || tab.pendingUrl || "";
-  if (!isScriptableUrl(tabUrl) || isBrowserErrorUrl(tabUrl)) {
-    throw new Error(`Cannot run DOM commands on ${tabUrl} — navigate to a regular web page first`);
-  }
-  const results = await executeScript({
-    target: { tabId: tab.id },
-    world: "MAIN",
-    func: (c) => (0, eval)(c),
-    args: [code],
-  });
-  return results[0]?.result ?? null;
-}
-
-export async function domWaitFor({ selector, timeout = 10000, visible = false, hidden = false, tabId } = {}) {
-  const tab = tabId ? await chrome.tabs.get(tabId) : await getActiveTab();
-  const tabUrl = tab.url || tab.pendingUrl || "";
-  if (isBrowserErrorUrl(tabUrl)) {
-    if (hidden) return { selector, found: false };
-    throw new Error(`Cannot wait for DOM on browser error page ${tabUrl}`);
-  }
-  if (!isScriptableUrl(tabUrl)) {
-    throw new Error(`Cannot run DOM commands on ${tabUrl} — navigate to a regular web page first`);
-  }
-  const deadline = Date.now() + timeout;
-  while (Date.now() < deadline) {
+    assertScriptableUrl(tabUrl, "run DOM commands on");
     try {
       const results = await executeScript({
         target: { tabId: tab.id },
-        func: (sel, vis, hid) => {
-          const el = document.querySelector(sel);
-          if (hid) return !el || el.offsetParent === null;
-          if (!el) return false;
-          if (vis) {
-            const r = el.getBoundingClientRect();
-            return r.width > 0 && r.height > 0;
-          }
-          return true;
-        },
-        args: [selector, visible, hidden],
+        func: contentDispatch,
+        args: [funcName, args],
       });
-      if (results[0]?.result) return { selector, found: !hidden };
+      return results[0]?.result;
     } catch (e) {
-      if (hidden && isErrorPageScriptError(e)) return { selector, found: false };
-      if (!isErrorPageScriptError(e)) throw e;
+      if (isErrorPageScriptError(e)) {
+        const fallback = fallbackForErrorPageDomOp(funcName, tab);
+        if (fallback !== undefined) return fallback;
+      }
+      throw e;
     }
-    await new Promise(r => setTimeout(r, 200));
   }
-  throw new Error(`Selector '${selector}' condition not met within ${timeout}ms`);
-}
 
-export async function domPoll({ selector, pattern, attr, timeout = 30000, interval = 500, tabId } = {}) {
-  const tab = tabId ? await chrome.tabs.get(tabId) : await getActiveTab();
-  const tabUrl = tab.url || tab.pendingUrl || "";
-  if (isBrowserErrorUrl(tabUrl)) {
-    throw new Error(`Cannot poll DOM on browser error page ${tabUrl}`);
-  }
-  if (!isScriptableUrl(tabUrl)) {
-    throw new Error(`Cannot run DOM commands on ${tabUrl} — navigate to a regular web page first`);
-  }
-  const deadline = Date.now() + timeout;
-  const regex = new RegExp(pattern);
-  while (Date.now() < deadline) {
-    try {
-      const results = await executeScript({
-        target: { tabId: tab.id },
-        func: (sel, a) => {
-          const el = document.querySelector(sel);
-          if (!el) return null;
-          if (a) return el.getAttribute(a) ?? el[a] ?? null;
-          return el.value !== undefined ? el.value : el.textContent.trim();
-        },
-        args: [selector, attr || null],
-      });
-      const value = results[0]?.result;
-      if (value != null && regex.test(String(value))) return { selector, value, pattern };
-    } catch (e) {
-      if (!isErrorPageScriptError(e)) throw e;
+  private async domEval({ code, tabId }: DomEvalArgs = {}) {
+    const { tab, url: tabUrl } = await resolveTabUrl(tabId);
+    if (isBrowserErrorUrl(tabUrl)) {
+      throw new Error(`Cannot run DOM commands on ${tabUrl} — navigate to a regular web page first`);
     }
-    await new Promise(r => setTimeout(r, interval));
+    assertScriptableUrl(tabUrl, "run DOM commands on");
+    const results = await executeScript({
+      target: { tabId: tab.id },
+      world: "MAIN",
+      func: (c: string) => (0, eval)(c),
+      args: [code],
+    });
+    return results[0]?.result ?? null;
+  }
+
+  private async domWaitFor({ selector, timeout = 10000, visible = false, hidden = false, tabId }: DomWaitForArgs = {}) {
+    const { tab, url: tabUrl } = await resolveTabUrl(tabId);
+    if (isBrowserErrorUrl(tabUrl)) {
+      if (hidden) return { selector, found: false };
+      throw new Error(`Cannot wait for DOM on browser error page ${tabUrl}`);
+    }
+    assertScriptableUrl(tabUrl, "run DOM commands on");
+    const deadline = Date.now() + timeout;
+    while (Date.now() < deadline) {
+      try {
+        const results = await executeScript({
+          target: { tabId: tab.id },
+          func: (sel: string, vis: boolean, hid: boolean) => {
+            const el = document.querySelector(sel) as HTMLElement | null;
+            if (hid) return !el || el.offsetParent === null;
+            if (!el) return false;
+            if (vis) {
+              const r = el.getBoundingClientRect();
+              return r.width > 0 && r.height > 0;
+            }
+            return true;
+          },
+          args: [selector, visible, hidden],
+        });
+        if (results[0]?.result) return { selector, found: !hidden };
+      } catch (e) {
+        if (hidden && isErrorPageScriptError(e)) return { selector, found: false };
+        if (!isErrorPageScriptError(e)) throw e;
+      }
+      await new Promise(r => setTimeout(r, 200));
+    }
+    throw new Error(`Selector '${selector}' condition not met within ${timeout}ms`);
+  }
+
+  private async domPoll({ selector, pattern, attr, timeout = 30000, interval = 500, tabId }: DomPollArgs = {}) {
+    const { tab, url: tabUrl } = await resolveTabUrl(tabId);
+    if (isBrowserErrorUrl(tabUrl)) {
+      throw new Error(`Cannot poll DOM on browser error page ${tabUrl}`);
+    }
+    assertScriptableUrl(tabUrl, "run DOM commands on");
+    const deadline = Date.now() + timeout;
+    const regex = new RegExp(pattern);
+    while (Date.now() < deadline) {
+      try {
+        const results = await executeScript({
+          target: { tabId: tab.id },
+          func: (sel: string, a: string | null) => {
+            const el = document.querySelector(sel);
+            if (!el) return null;
+            // Page elements are accessed dynamically (arbitrary attr / .value).
+            const dyn = el as Element & { value?: string } & Record<string, string | null | undefined>;
+            if (a) return el.getAttribute(a) ?? dyn[a] ?? null;
+            return dyn.value !== undefined ? dyn.value : el.textContent.trim();
+          },
+          args: [selector, attr || null],
+        });
+        const value = results[0]?.result;
+        if (value != null && regex.test(String(value))) return { selector, value, pattern };
+      } catch (e) {
+        if (!isErrorPageScriptError(e)) throw e;
+      }
+      await new Promise(r => setTimeout(r, interval));
+    }
+    throw new Error(`Selector '${selector}' did not match '${pattern}' within ${timeout}ms`);
   }
-  throw new Error(`Selector '${selector}' did not match '${pattern}' within ${timeout}ms`);
 }
diff --git a/extension/src/commands/extension.ts b/extension/src/commands/extension.ts
new file mode 100644
index 0000000..feea565
--- /dev/null
+++ b/extension/src/commands/extension.ts
@@ -0,0 +1,12 @@
+import { CommandGroup } from '../classes/CommandGroup';
+import type { CommandEntry } from '../classes/CommandGroup';
+
+export class ExtensionCommands extends CommandGroup {
+  readonly namespace = "extension";
+  readonly commands: Record<string, CommandEntry> = {
+    "extension.reload": () => {
+      setTimeout(() => chrome.runtime.reload(), 200);
+      return { reloading: true };
+    },
+  };
+}
diff --git a/extension/src/commands/groups.ts b/extension/src/commands/groups.ts
index 1eed4b8..a1d212a 100644
--- a/extension/src/commands/groups.ts
+++ b/extension/src/commands/groups.ts
@@ -1,105 +1,114 @@
-// @ts-nocheck
-import { buildTabBlocks, getLargeOperationThrottle, resolveGroupId, runLargeOperation, tabInfo, throwIfJobCancelled, updateJobProgress, yieldForLargeOperation } from '../core';
-export async function groupList() {
-  const groups = await chrome.tabGroups.query({});
-  const all = await chrome.tabs.query({});
-  return groups.map(g => ({
-    id: g.id,
-    title: g.title,
-    color: g.color,
-    collapsed: g.collapsed,
-    windowId: g.windowId,
-    tabCount: all.filter(t => t.groupId === g.id).length,
-  }));
-}
+import { asTabIds, buildTabBlocks, getLargeOperationThrottle, processInBatches, resolveGroupId, runLargeOperation, tabInfo } from '../core';
+import { CommandGroup } from '../classes/CommandGroup';
+import type { CommandEntry } from '../classes/CommandGroup';
+import type { GroupTabsArgs, GroupQueryArgs, GroupCloseArgs, GroupOpenArgs, GroupAddTabArgs, GroupMoveArgs } from '../types';
 
-export async function groupTabs({ groupId }) {
-  const all = await chrome.tabs.query({});
-  return all.filter(t => t.groupId === groupId).map(tabInfo);
-}
+export class GroupsCommands extends CommandGroup {
+  readonly namespace = "group";
+  readonly commands: Record<string, CommandEntry> = {
+    "group.list":    () => this.groupList(),
+    "group.tabs":    (a: GroupTabsArgs) => this.groupTabs(a),
+    "group.count":   () => this.groupCount(),
+    "group.query":   (a: GroupQueryArgs) => this.groupQuery(a),
+    "group.close":   { background: true, run: (a: GroupCloseArgs) => this.groupClose(a) },
+    "group.open":    (a: GroupOpenArgs) => this.groupOpen(a),
+    "group.add_tab": (a: GroupAddTabArgs) => this.groupAddTab(a),
+    "group.move":    (a: GroupMoveArgs) => this.groupMove(a),
+  };
 
-export async function groupCount() {
-  const groups = await chrome.tabGroups.query({});
-  return groups.length;
-}
+  private async groupList() {
+    const groups = await chrome.tabGroups.query({});
+    const all = await chrome.tabs.query({});
+    return groups.map(g => ({
+      id: g.id,
+      title: g.title,
+      color: g.color,
+      collapsed: g.collapsed,
+      windowId: g.windowId,
+      tabCount: all.filter(t => t.groupId === g.id).length,
+    }));
+  }
 
-export async function groupQuery({ search }) {
-  const q = search.toLowerCase();
-  const groups = await chrome.tabGroups.query({});
-  return groups.filter(g => g.title && g.title.toLowerCase().includes(q));
-}
+  private async groupTabs({ groupId }: GroupTabsArgs) {
+    const all = await chrome.tabs.query({});
+    return all.filter(t => t.groupId === groupId).map(tabInfo);
+  }
 
-export async function groupClose({ groupId, gentleMode, __job } = {}) {
-  return runLargeOperation("group.close", async () => {
-    const tabs = await chrome.tabs.query({});
-    const groupTabs = tabs.filter(t => t.groupId === groupId);
-    const tabIds = groupTabs.map(t => t.id);
-    const throttle = await getLargeOperationThrottle(tabIds.length, gentleMode);
-    updateJobProgress(__job, { phase: "ungrouping tabs", current: 0, total: tabIds.length });
-    for (let i = 0; i < tabIds.length; i += throttle.batchSize) {
-      throwIfJobCancelled(__job);
-      await chrome.tabs.ungroup(tabIds.slice(i, i + throttle.batchSize));
-      updateJobProgress(__job, { phase: "ungrouping tabs", current: Math.min(i + throttle.batchSize, tabIds.length), total: tabIds.length });
-      await yieldForLargeOperation(i + throttle.batchSize, throttle.batchSize, throttle.pauseMs);
+  private async groupCount() {
+    const groups = await chrome.tabGroups.query({});
+    return groups.length;
+  }
+
+  private async groupQuery({ search }: GroupQueryArgs) {
+    const q = search.toLowerCase();
+    const groups = await chrome.tabGroups.query({});
+    return groups.filter(g => g.title && g.title.toLowerCase().includes(q));
+  }
+
+  private async groupClose({ groupId, gentleMode, __job }: GroupCloseArgs = {}) {
+    return runLargeOperation("group.close", async () => {
+      const tabs = await chrome.tabs.query({});
+      const groupTabs = tabs.filter(t => t.groupId === groupId);
+      const tabIds = groupTabs.map(t => t.id);
+      const throttle = await getLargeOperationThrottle(tabIds.length, gentleMode);
+      await processInBatches(tabIds, throttle, batch => chrome.tabs.ungroup(asTabIds(batch)), { job: __job, phase: "ungrouping tabs" });
+      return { groupId, gentle: throttle.gentle, audible: throttle.audible };
+    });
+  }
+
+  private async groupOpen({ name }: GroupOpenArgs) {
+    const tab = await chrome.tabs.create({ active: true });
+    const groupId = await chrome.tabs.group({ tabIds: asTabIds([tab.id]) });
+    await chrome.tabGroups.update(groupId, { title: name });
+    return { id: groupId, name };
+  }
+
+  private async groupAddTab({ group, url }: GroupAddTabArgs) {
+    const groupId = await resolveGroupId(group);
+    const existingTabs = await chrome.tabs.query({ groupId });
+    const tab = await chrome.tabs.create({ url: url || "chrome://newtab/", active: true });
+    await chrome.tabs.group({ tabIds: asTabIds([tab.id]), groupId });
+    // If a URL was provided, close any blank placeholder tabs left from group creation
+    if (url) {
+      const placeholders = existingTabs.filter(t =>
+        t.url === "chrome://newtab/" || t.url === "about:blank" || t.pendingUrl === "chrome://newtab/"
+      );
+      if (placeholders.length) await chrome.tabs.remove(placeholders.map(t => t.id));
     }
-    return { groupId, gentle: throttle.gentle, audible: throttle.audible };
-  });
-}
-
-export async function groupOpen({ name }) {
-  const tab = await chrome.tabs.create({ active: true });
-  const groupId = await chrome.tabs.group({ tabIds: [tab.id] });
-  await chrome.tabGroups.update(groupId, { title: name });
-  return { id: groupId, name };
-}
-
-export async function groupAddTab({ group, url }) {
-  const groupId = await resolveGroupId(group);
-  const existingTabs = await chrome.tabs.query({ groupId });
-  const tab = await chrome.tabs.create({ url: url || "chrome://newtab/", active: true });
-  await chrome.tabs.group({ tabIds: [tab.id], groupId });
-  // If a URL was provided, close any blank placeholder tabs left from group creation
-  if (url) {
-    const placeholders = existingTabs.filter(t =>
-      t.url === "chrome://newtab/" || t.url === "about:blank" || t.pendingUrl === "chrome://newtab/"
-    );
-    if (placeholders.length) await chrome.tabs.remove(placeholders.map(t => t.id));
-  }
-  return { tabId: tab.id, groupId };
-}
-
-export async function groupMove({ group, forward, backward }) {
-  const groupId = await resolveGroupId(group);
-  const groupInfo = await chrome.tabGroups.get(groupId);
-  const allTabs = await chrome.tabs.query({ windowId: groupInfo.windowId });
-  allTabs.sort((a, b) => a.index - b.index);
-
-  const blocks = buildTabBlocks(allTabs);
-  const currentIdx = blocks.findIndex(block => block.groupId === groupId);
-  if (currentIdx === -1) throw new Error(`No tabs found in group '${group}'`);
-
-  const currentBlock = blocks[currentIdx];
-  const currentLength = currentBlock.tabIds.length;
-
-  if (forward) {
-    const nextBlock = blocks[currentIdx + 1];
-    if (!nextBlock) return { groupId, moved: false };
-    const targetIndex =
-      nextBlock.groupId === null
-        ? currentBlock.startIndex + 1
-        : nextBlock.endIndex - currentLength + 1;
-    await chrome.tabGroups.move(groupId, { index: targetIndex });
-  } else if (backward) {
-    const previousBlock = blocks[currentIdx - 1];
-    if (!previousBlock) return { groupId, moved: false };
-    const targetIndex =
-      previousBlock.groupId === null
-        ? currentBlock.startIndex - 1
-        : previousBlock.startIndex;
-    await chrome.tabGroups.move(groupId, { index: targetIndex });
+    return { tabId: tab.id, groupId };
   }
 
-  return { groupId, moved: true };
-}
+  private async groupMove({ group, forward, backward }: GroupMoveArgs) {
+    const groupId = await resolveGroupId(group);
+    const groupInfo = await chrome.tabGroups.get(groupId);
+    const allTabs = await chrome.tabs.query({ windowId: groupInfo.windowId });
+    allTabs.sort((a, b) => a.index - b.index);
 
-// ── Windows ───────────────────────────────────────────────────────────────────
+    const blocks = buildTabBlocks(allTabs);
+    const currentIdx = blocks.findIndex(block => block.groupId === groupId);
+    if (currentIdx === -1) throw new Error(`No tabs found in group '${group}'`);
+
+    const currentBlock = blocks[currentIdx];
+    const currentLength = currentBlock.tabIds.length;
+
+    if (forward) {
+      const nextBlock = blocks[currentIdx + 1];
+      if (!nextBlock) return { groupId, moved: false };
+      const targetIndex =
+        nextBlock.groupId === null
+          ? currentBlock.startIndex + 1
+          : nextBlock.endIndex - currentLength + 1;
+      await chrome.tabGroups.move(groupId, { index: targetIndex });
+    } else if (backward) {
+      const previousBlock = blocks[currentIdx - 1];
+      if (!previousBlock) return { groupId, moved: false };
+      const targetIndex =
+        previousBlock.groupId === null
+          ? currentBlock.startIndex - 1
+          : previousBlock.startIndex;
+      await chrome.tabGroups.move(groupId, { index: targetIndex });
+    }
+
+    return { groupId, moved: true };
+  }
+}
diff --git a/extension/src/commands/injected.ts b/extension/src/commands/injected.ts
index 2c86b7a..694d865 100644
--- a/extension/src/commands/injected.ts
+++ b/extension/src/commands/injected.ts
@@ -1,20 +1,21 @@
-// @ts-nocheck
-export function contentDispatch(funcName, args) {
-  function domQuery({ selector }) {
+import type { ContentArgs } from '../types';
+
+export function contentDispatch(funcName: string, args: ContentArgs) {
+  function domQuery({ selector }: ContentArgs) {
     return Array.from(document.querySelectorAll(selector)).map(el => ({
       tag: el.tagName.toLowerCase(),
       text: el.textContent.trim().slice(0, 200),
       attrs: Object.fromEntries(Array.from(el.attributes).map(a => [a.name, a.value])),
     }));
   }
-  function domClick({ selector }) {
-    const el = document.querySelector(selector);
+  function domClick({ selector }: ContentArgs) {
+    const el = document.querySelector(selector) as HTMLElement | null;
     if (!el) throw new Error(`No element: ${selector}`);
     el.click();
     return true;
   }
-  function domType({ selector, text }) {
-    const el = document.querySelector(selector);
+  function domType({ selector, text }: ContentArgs) {
+    const el = document.querySelector(selector) as HTMLInputElement | null;
     if (!el) throw new Error(`No element: ${selector}`);
     el.focus();
     el.value = text;
@@ -22,20 +23,20 @@ export function contentDispatch(funcName, args) {
     el.dispatchEvent(new Event("change", { bubbles: true }));
     return true;
   }
-  function domAttr({ selector, attr }) {
+  function domAttr({ selector, attr }: ContentArgs) {
     return Array.from(document.querySelectorAll(selector))
       .map(el => el.getAttribute(attr))
       .filter(v => v !== null);
   }
-  function domText({ selector }) {
+  function domText({ selector }: ContentArgs) {
     return Array.from(document.querySelectorAll(selector))
       .map(el => el.textContent.trim())
       .filter(Boolean);
   }
-  function domExists({ selector }) {
+  function domExists({ selector }: ContentArgs) {
     return document.querySelector(selector) !== null;
   }
-  function domKey({ selector, key }) {
+  function domKey({ selector, key }: ContentArgs) {
     const el = selector ? document.querySelector(selector) : document.activeElement;
     if (selector && !el) throw new Error(`No element: ${selector}`);
     const target = el || document.body;
@@ -44,44 +45,44 @@ export function contentDispatch(funcName, args) {
     });
     return true;
   }
-  function domHover({ selector }) {
+  function domHover({ selector }: ContentArgs) {
     const el = document.querySelector(selector);
     if (!el) throw new Error(`No element: ${selector}`);
     el.dispatchEvent(new MouseEvent("mouseover",  { bubbles: true }));
     el.dispatchEvent(new MouseEvent("mouseenter", { bubbles: true }));
     return true;
   }
-  function domCheck({ selector, checked }) {
-    const el = document.querySelector(selector);
+  function domCheck({ selector, checked }: ContentArgs) {
+    const el = document.querySelector(selector) as HTMLInputElement | null;
     if (!el) throw new Error(`No element: ${selector}`);
     el.checked = checked;
     el.dispatchEvent(new Event("change", { bubbles: true }));
     return true;
   }
-  function domClear({ selector }) {
-    const el = document.querySelector(selector);
+  function domClear({ selector }: ContentArgs) {
+    const el = document.querySelector(selector) as HTMLInputElement | null;
     if (!el) throw new Error(`No element: ${selector}`);
     el.value = "";
     el.dispatchEvent(new Event("input",  { bubbles: true }));
     el.dispatchEvent(new Event("change", { bubbles: true }));
     return true;
   }
-  function domFocus({ selector }) {
-    const el = document.querySelector(selector);
+  function domFocus({ selector }: ContentArgs) {
+    const el = document.querySelector(selector) as HTMLElement | null;
     if (!el) throw new Error(`No element: ${selector}`);
     el.focus();
     return true;
   }
-  function domSubmit({ selector }) {
+  function domSubmit({ selector }: ContentArgs) {
     const el = document.querySelector(selector);
     if (!el) throw new Error(`No element: ${selector}`);
-    const form = el.tagName === "FORM" ? el : el.closest("form");
+    const form = (el.tagName === "FORM" ? el : el.closest("form")) as HTMLFormElement | null;
     if (!form) throw new Error(`No form found for: ${selector}`);
     form.submit();
     return true;
   }
   function pageInfo() {
-    const metas = {};
+    const metas: Record<string, string> = {};
     document.querySelectorAll("meta[name], meta[property]").forEach(m => {
       const k = m.getAttribute("name") || m.getAttribute("property");
       if (k) metas[k] = m.getAttribute("content") || "";
@@ -94,7 +95,7 @@ export function contentDispatch(funcName, args) {
       meta: metas,
     };
   }
-  function domScroll({ selector, x, y }) {
+  function domScroll({ selector, x, y }: ContentArgs) {
     if (selector) {
       const el = document.querySelector(selector);
       if (!el) throw new Error(`No element: ${selector}`);
@@ -104,8 +105,8 @@ export function contentDispatch(funcName, args) {
     window.scrollTo({ top: y || 0, left: x || 0, behavior: "smooth" });
     return true;
   }
-  function domSelect({ selector, value }) {
-    const el = document.querySelector(selector);
+  function domSelect({ selector, value }: ContentArgs) {
+    const el = document.querySelector(selector) as HTMLSelectElement | null;
     if (!el) throw new Error(`No element: ${selector}`);
     el.value = value;
     el.dispatchEvent(new Event("change", { bubbles: true }));
@@ -113,9 +114,9 @@ export function contentDispatch(funcName, args) {
     return true;
   }
   function extractLinks() {
-    const seen = new Set();
-    return Array.from(document.querySelectorAll("a[href]")).reduce((links, a) => {
-      const href = a.href;
+    const seen = new Set<string>();
+    return Array.from(document.querySelectorAll("a[href]")).reduce<Array<{ text: string; href: string }>>((links, a) => {
+      const href = (a as HTMLAnchorElement).href;
       if (!href || seen.has(href)) return links;
       seen.add(href);
       links.push({
@@ -126,8 +127,8 @@ export function contentDispatch(funcName, args) {
     }, []);
   }
   function extractImages() {
-    const seen = new Set();
-    return Array.from(document.querySelectorAll("img")).reduce((images, img) => {
+    const seen = new Set<string>();
+    return Array.from(document.querySelectorAll("img")).reduce<Array<{ alt: string; src: string }>>((images, img) => {
       const src =
         img.src ||
         img.getAttribute("data-src") ||
@@ -146,12 +147,12 @@ export function contentDispatch(funcName, args) {
   function extractText() {
     return document.body.innerText;
   }
-  function extractJson({ selector }) {
+  function extractJson({ selector }: ContentArgs) {
     const el = document.querySelector(selector);
     if (!el) throw new Error(`No element: ${selector}`);
     return JSON.parse(el.textContent);
   }
-  function extractMarkdown({ selector }) {
+  function extractMarkdown({ selector }: ContentArgs) {
     const BLOCKS = new Set([
       "article", "aside", "blockquote", "body", "div", "dl", "fieldset", "figcaption",
       "figure", "footer", "form", "h1", "h2", "h3", "h4", "h5", "h6", "header", "hr",
@@ -185,11 +186,11 @@ export function contentDispatch(funcName, args) {
       "[data-testid*='action-button']",
     ].join(", ");
 
-    function normalizeText(value) {
+    function normalizeText(value: string) {
       return value.replace(/\s+/g, " ").trim();
     }
 
-    function normalizeInline(value) {
+    function normalizeInline(value: string) {
       return value
         .replace(/[ \t]+\n/g, "\n")
         .replace(/\n[ \t]+/g, "\n")
@@ -198,46 +199,47 @@ export function contentDispatch(funcName, args) {
         .trim();
     }
 
-    function collapseBlankLines(value) {
+    function collapseBlankLines(value: string) {
       return value
         .replace(/[ \t]+\n/g, "\n")
         .replace(/\n{3,}/g, "\n\n")
         .trim();
     }
 
-    function escapeMarkdown(text) {
+    function escapeMarkdown(text: string) {
       return text.replace(/([\\`[\]])/g, "\\$1");
     }
 
-    function escapeTableCell(text) {
+    function escapeTableCell(text: string) {
       return text.replace(/\|/g, "\\|").replace(/\n+/g, " ").trim();
     }
 
-    function absoluteUrl(attr, fallback) {
+    function absoluteUrl(attr: string | null | undefined, fallback?: string) {
       return attr || fallback || "";
     }
 
-    function isNoiseElement(node) {
+    function isNoiseElement(node: Node | null): boolean {
       if (!node || node.nodeType !== Node.ELEMENT_NODE) return false;
-      const tag = node.tagName.toLowerCase();
+      const el = node as Element;
+      const tag = el.tagName.toLowerCase();
       if (["script", "style", "noscript", "template", "svg", "canvas", "iframe", "dialog"].includes(tag)) return true;
       if (["button", "input", "textarea", "select", "option", "form"].includes(tag)) return true;
-      if (node.hasAttribute("hidden")) return true;
-      if ((node.getAttribute("aria-hidden") || "").toLowerCase() === "true") return true;
-      if (node.matches(".sr-only, [class*='sr-only']")) return true;
-      if (node.matches("[class*='file-tile'], form[data-type='unified-composer'], .composer-btn, [data-composer-surface='true'], #thread-bottom-container")) return true;
-      if (node.matches("[data-testid*='action-button']")) return true;
+      if (el.hasAttribute("hidden")) return true;
+      if ((el.getAttribute("aria-hidden") || "").toLowerCase() === "true") return true;
+      if (el.matches(".sr-only, [class*='sr-only']")) return true;
+      if (el.matches("[class*='file-tile'], form[data-type='unified-composer'], .composer-btn, [data-composer-surface='true'], #thread-bottom-container")) return true;
+      if (el.matches("[data-testid*='action-button']")) return true;
       return false;
     }
 
-    function stripNoise(root) {
-      const clone = root.cloneNode(true);
+    function stripNoise(root: Element): Element {
+      const clone = root.cloneNode(true) as Element;
       clone.querySelectorAll(NOISE_SELECTOR).forEach(node => node.remove());
       return clone;
     }
 
-    function candidateScore(node) {
-      const text = normalizeText(node.innerText || "");
+    function candidateScore(node: Element) {
+      const text = normalizeText((node as HTMLElement).innerText || "");
       if (!text) return -Infinity;
 
       const headings = node.querySelectorAll("h1, h2, h3, h4, h5, h6").length;
@@ -276,73 +278,76 @@ export function contentDispatch(funcName, args) {
       const candidates = Array.from(document.querySelectorAll(
         "main, article, [role='main'], section, .markdown, .prose, [data-message-author-role]"
       ))
-        .filter(node => normalizeText(node.innerText || "").length > 0);
+        .filter(node => normalizeText((node as HTMLElement).innerText || "").length > 0);
       if (!candidates.length) return document.body;
       candidates.sort((a, b) => candidateScore(b) - candidateScore(a));
       return candidates[0];
     }
 
-    function inlineText(node) {
+    function inlineText(node: Node): string {
       if (node.nodeType === Node.TEXT_NODE) {
         return escapeMarkdown(node.textContent || "");
       }
       if (node.nodeType !== Node.ELEMENT_NODE) return "";
       if (isNoiseElement(node)) return "";
 
-      const tag = node.tagName.toLowerCase();
+      const el = node as HTMLElement;
+      const tag = el.tagName.toLowerCase();
       if (tag === "br") return "\n";
       if (tag === "img") {
-        const src = absoluteUrl(node.getAttribute("src"), node.src);
+        const img = el as HTMLImageElement;
+        const src = absoluteUrl(img.getAttribute("src"), img.src);
         if (!src) return "";
-        const alt = normalizeText(node.getAttribute("alt") || "");
+        const alt = normalizeText(img.getAttribute("alt") || "");
         return alt ? `![${escapeMarkdown(alt)}](${src})` : `![](${src})`;
       }
       if (tag === "a") {
-        const text = normalizeInline(Array.from(node.childNodes).map(inlineText).join(""));
-        const href = absoluteUrl(node.getAttribute("href"), node.href);
+        const text = normalizeInline(Array.from(el.childNodes).map(inlineText).join(""));
+        const href = absoluteUrl(el.getAttribute("href"), (el as HTMLAnchorElement).href);
         if (!href) return text;
         return `[${text || href}](${href})`;
       }
       if (tag === "code") {
-        const text = normalizeInline(Array.from(node.childNodes).map(inlineText).join(""));
+        const text = normalizeInline(Array.from(el.childNodes).map(inlineText).join(""));
         return text ? `\`${text.replace(/`/g, "\\`")}\`` : "";
       }
       if (tag === "strong" || tag === "b") {
-        const text = normalizeInline(Array.from(node.childNodes).map(inlineText).join(""));
+        const text = normalizeInline(Array.from(el.childNodes).map(inlineText).join(""));
         return text ? `**${text}**` : "";
       }
       if (tag === "em" || tag === "i") {
-        const text = normalizeInline(Array.from(node.childNodes).map(inlineText).join(""));
+        const text = normalizeInline(Array.from(el.childNodes).map(inlineText).join(""));
         return text ? `*${text}*` : "";
       }
 
-      const chunks = [];
-      for (const child of node.childNodes) {
+      const chunks: string[] = [];
+      for (const child of el.childNodes) {
         const rendered = inlineText(child);
         if (!rendered) continue;
         chunks.push(rendered);
-        if (child.nodeType === Node.ELEMENT_NODE && BLOCKS.has(child.tagName.toLowerCase())) {
+        if (child.nodeType === Node.ELEMENT_NODE && BLOCKS.has((child as Element).tagName.toLowerCase())) {
           chunks.push("\n");
         }
       }
       return chunks.join("");
     }
 
-    function textBlock(node) {
+    function textBlock(node: Node): string {
       return collapseBlankLines(normalizeInline(Array.from(node.childNodes).map(inlineText).join("")));
     }
 
-    function preserveNodeText(node) {
+    function preserveNodeText(node: Node): string {
       if (node.nodeType === Node.TEXT_NODE) {
         return node.textContent || "";
       }
       if (node.nodeType !== Node.ELEMENT_NODE) return "";
 
-      const tag = node.tagName.toLowerCase();
+      const el = node as HTMLElement;
+      const tag = el.tagName.toLowerCase();
       if (tag === "br") return "\n";
 
-      const parts = [];
-      for (const child of node.childNodes) {
+      const parts: string[] = [];
+      for (const child of el.childNodes) {
         const rendered = preserveNodeText(child);
         if (!rendered) continue;
         parts.push(rendered);
@@ -354,7 +359,7 @@ export function contentDispatch(funcName, args) {
       return parts.join("");
     }
 
-    function repairFlattenedDiagram(text) {
+    function repairFlattenedDiagram(text: string): string {
       if (text.includes("\n")) return text;
       const markerCount = (text.match(/[│▼├└]/g) || []).length;
       if (markerCount < 2) return text;
@@ -372,8 +377,8 @@ export function contentDispatch(funcName, args) {
         .join("\n");
     }
 
-    function convertDashListsToBranches(lines) {
-      const converted = [];
+    function convertDashListsToBranches(lines: string[]): string[] {
+      const converted: string[] = [];
       let index = 0;
       while (index < lines.length) {
         const match = lines[index].match(/^(\s*)-\s+(.*)$/);
@@ -400,7 +405,7 @@ export function contentDispatch(funcName, args) {
       return converted;
     }
 
-    function normalizeCodeBlock(text) {
+    function normalizeCodeBlock(text: string): string {
       let lines = text.replace(/\r\n?/g, "\n").split("\n").map(line => line.replace(/\s+$/, ""));
       while (lines.length && !lines[0].trim()) lines.shift();
       while (lines.length && !lines[lines.length - 1].trim()) lines.pop();
@@ -418,7 +423,7 @@ export function contentDispatch(funcName, args) {
       return lines.join("\n");
     }
 
-    function tableToMarkdown(table) {
+    function tableToMarkdown(table: Element) {
       const rows = Array.from(table.querySelectorAll("tr"))
         .map(row => Array.from(row.children)
           .filter(cell => cell.tagName === "TD" || cell.tagName === "TH")
@@ -461,19 +466,20 @@ export function contentDispatch(funcName, args) {
       return lines.join("\n");
     }
 
-    function listToMarkdown(list, depth = 0) {
+    function listToMarkdown(list: Element, depth = 0): string {
       const ordered = list.tagName.toLowerCase() === "ol";
-      const items = [];
+      const items: string[] = [];
       const children = Array.from(list.children).filter(child => child.tagName === "LI");
       children.forEach((item, index) => {
         const marker = ordered ? `${index + 1}. ` : "- ";
         const indent = "  ".repeat(depth);
-        const nested = [];
-        const content = [];
+        const nested: string[] = [];
+        const content: string[] = [];
 
         for (const child of item.childNodes) {
-          if (child.nodeType === Node.ELEMENT_NODE && (child.tagName === "UL" || child.tagName === "OL")) {
-            nested.push(listToMarkdown(child, depth + 1));
+          const childEl = child as Element;
+          if (child.nodeType === Node.ELEMENT_NODE && (childEl.tagName === "UL" || childEl.tagName === "OL")) {
+            nested.push(listToMarkdown(childEl, depth + 1));
           } else {
             content.push(inlineText(child));
           }
@@ -491,18 +497,19 @@ export function contentDispatch(funcName, args) {
       return items.join("\n");
     }
 
-    function blockToMarkdown(node) {
+    function blockToMarkdown(node: Node): string {
       if (node.nodeType === Node.TEXT_NODE) {
         return normalizeText(node.textContent || "");
       }
       if (node.nodeType !== Node.ELEMENT_NODE) return "";
       if (isNoiseElement(node)) return "";
 
-      const tag = node.tagName.toLowerCase();
-      if (tag === "table") return tableToMarkdown(node);
-      if (tag === "ul" || tag === "ol") return listToMarkdown(node);
-      if (node.matches(".cm-editor[data-is-code-block-view='true']")) {
-        const lines = Array.from(node.querySelectorAll(".cm-line")).map(line => {
+      const el = node as HTMLElement;
+      const tag = el.tagName.toLowerCase();
+      if (tag === "table") return tableToMarkdown(el);
+      if (tag === "ul" || tag === "ol") return listToMarkdown(el);
+      if (el.matches(".cm-editor[data-is-code-block-view='true']")) {
+        const lines = Array.from(el.querySelectorAll(".cm-line")).map(line => {
           const text = preserveNodeText(line);
           return text === "\n" ? "" : text.replace(/\n$/, "");
         });
@@ -510,11 +517,11 @@ export function contentDispatch(funcName, args) {
         return code ? `\`\`\`\n${code}\n\`\`\`` : "";
       }
       if (tag === "pre") {
-        const code = normalizeCodeBlock(preserveNodeText(node));
+        const code = normalizeCodeBlock(preserveNodeText(el));
         return code ? `\`\`\`\n${code}\n\`\`\`` : "";
       }
       if (tag === "blockquote") {
-        const content = collapseBlankLines(Array.from(node.childNodes).map(blockToMarkdown).join("\n\n"));
+        const content = collapseBlankLines(Array.from(el.childNodes).map(blockToMarkdown).join("\n\n"));
         return content
           .split("\n")
           .map(line => line ? `> ${line}` : ">")
@@ -522,20 +529,20 @@ export function contentDispatch(funcName, args) {
       }
       if (/^h[1-6]$/.test(tag)) {
         const level = Number(tag.slice(1));
-        const text = textBlock(node);
+        const text = textBlock(el);
         return text ? `${"#".repeat(level)} ${text}` : "";
       }
       if (tag === "p" || tag === "figcaption") {
-        return textBlock(node);
+        return textBlock(el);
       }
       if (tag === "hr") {
         return "---";
       }
       if (tag === "img") {
-        return inlineText(node);
+        return inlineText(el);
       }
 
-      const childBlocks = Array.from(node.childNodes)
+      const childBlocks = Array.from(el.childNodes)
         .map(child => blockToMarkdown(child))
         .filter(Boolean);
       if (childBlocks.length) return collapseBlankLines(childBlocks.join("\n\n"));
@@ -552,7 +559,7 @@ export function contentDispatch(funcName, args) {
                  domScroll, domSelect, domKey, domHover, domCheck, domClear, domFocus, domSubmit,
                  pageInfo,
                  extractLinks, extractImages, extractText, extractJson, extractMarkdown };
-  const fn = fns[funcName];
+  const fn = fns[funcName as keyof typeof fns];
   if (!fn) throw new Error(`Unknown content function: ${funcName}`);
   return fn(args);
 }
diff --git a/extension/src/commands/navigation.ts b/extension/src/commands/navigation.ts
index 168c92c..dcb0e39 100644
--- a/extension/src/commands/navigation.ts
+++ b/extension/src/commands/navigation.ts
@@ -1,97 +1,113 @@
-// @ts-nocheck
 import { getActiveTab, getAliases, isBrowserErrorUrl, resolveGroupId, tabInfo } from '../core';
-export async function navOpen({ url, background, window: windowName, windowId: explicitWindowId, group: groupNameOrId }) {
-  let windowId;
-  if (explicitWindowId != null) {
-    windowId = explicitWindowId;
-  } else if (windowName) {
-    const aliases = await getAliases();
-    const entry = Object.entries(aliases).find(([, v]) => v === windowName);
-    if (entry) windowId = parseInt(entry[0]);
-  }
-  const tab = await chrome.tabs.create({ url, active: !background, windowId });
-  if (groupNameOrId != null) {
-    let groupId;
-    try {
-      groupId = await resolveGroupId(groupNameOrId);
-      // Close any blank placeholder tabs that were created when the group was made
-      const groupTabs = await chrome.tabs.query({ groupId });
-      const placeholders = groupTabs.filter(t =>
-        t.id !== tab.id &&
-        (t.url === "chrome://newtab/" || t.url === "about:blank" || t.pendingUrl === "chrome://newtab/")
-      );
-      await chrome.tabs.group({ tabIds: [tab.id], groupId });
-      if (placeholders.length) await chrome.tabs.remove(placeholders.map(t => t.id));
-    } catch (e) {
-      if (!e.message.startsWith("No tab group found")) throw e;
-      // Group doesn't exist — create it with the tab already in it
-      groupId = await chrome.tabs.group({ tabIds: [tab.id] });
-      await chrome.tabGroups.update(groupId, { title: String(groupNameOrId) });
+import { CommandGroup } from '../classes/CommandGroup';
+import type { CommandEntry } from '../classes/CommandGroup';
+import type { NavOpenArgs, NavToArgs, NavTabArgs, NavFocusArgs, NavWaitArgs, NavOpenWaitArgs } from '../types';
+
+export class NavigationCommands extends CommandGroup {
+  readonly namespace = "navigate";
+  readonly commands: Record<string, CommandEntry> = {
+    "navigate.open":        (a: NavOpenArgs) => this.navOpen(a),
+    "navigate.to":          (a: NavToArgs) => this.navTo(a),
+    "navigate.reload":      (a: NavTabArgs) => this.navReload(a, false),
+    "navigate.hard_reload": (a: NavTabArgs) => this.navReload(a, true),
+    "navigate.back":        (a: NavTabArgs) => this.navBack(a),
+    "navigate.forward":     (a: NavTabArgs) => this.navForward(a),
+    "navigate.focus":       (a: NavFocusArgs) => this.navFocus(a),
+    "navigate.wait":        (a: NavWaitArgs) => this.navWait(a),
+    "navigate.open_wait":   (a: NavOpenWaitArgs) => this.navOpenWait(a),
+  };
+
+  private async navOpen({ url, background, window: windowName, windowId: explicitWindowId, group: groupNameOrId }: NavOpenArgs) {
+    let windowId: number | undefined;
+    if (explicitWindowId != null) {
+      windowId = explicitWindowId;
+    } else if (windowName) {
+      const aliases = await getAliases();
+      const entry = Object.entries(aliases).find(([, v]) => v === windowName);
+      if (entry) windowId = parseInt(entry[0]);
     }
-  }
-  return { id: tab.id, url: tab.url };
-}
-
-export async function navTo({ tabId, url }) {
-  const tab = await chrome.tabs.update(tabId, { url });
-  return { id: tab.id, url: tab.url || url };
-}
-
-export async function navReload({ tabId }, bypassCache) {
-  const tab = tabId ? { id: tabId } : await getActiveTab();
-  await chrome.tabs.reload(tab.id, { bypassCache });
-  return { tabId: tab.id };
-}
-
-export async function navBack({ tabId }) {
-  const tab = tabId ? { id: tabId } : await getActiveTab();
-  await chrome.tabs.goBack(tab.id);
-  return { tabId: tab.id };
-}
-
-export async function navForward({ tabId }) {
-  const tab = tabId ? { id: tabId } : await getActiveTab();
-  await chrome.tabs.goForward(tab.id);
-  return { tabId: tab.id };
-}
-
-export async function navFocus({ pattern }) {
-  // If pattern is a plain integer, treat it as a tab ID
-  const asInt = parseInt(pattern);
-  let match;
-  if (!isNaN(asInt) && String(asInt) === String(pattern)) {
-    match = await chrome.tabs.get(asInt);
-  } else {
-    const all = await chrome.tabs.query({});
-    match = all.find(t => (t.url && t.url.includes(pattern)) || (t.pendingUrl && t.pendingUrl.includes(pattern)));
-  }
-  if (!match) return null;
-  await chrome.windows.update(match.windowId, { focused: true });
-  await chrome.tabs.update(match.id, { active: true });
-  return { id: match.id, url: match.url || match.pendingUrl, title: match.title };
-}
-
-export async function navWait({ tabId, timeout = 30000, readyState = "complete" } = {}) {
-  const tab = tabId ? { id: tabId } : await getActiveTab();
-  const deadline = Date.now() + timeout;
-  const interval = 200;
-  while (Date.now() < deadline) {
-    const t = await chrome.tabs.get(tab.id);
-    const currentUrl = t.url || t.pendingUrl || "";
-    if (isBrowserErrorUrl(currentUrl)) {
-      throw new Error(`Tab ${tab.id} is showing an error page while waiting for load (${currentUrl})`);
+    const tab = await chrome.tabs.create({ url, active: !background, windowId });
+    if (groupNameOrId != null) {
+      let groupId;
+      try {
+        groupId = await resolveGroupId(groupNameOrId);
+        // Close any blank placeholder tabs that were created when the group was made
+        const groupTabs = await chrome.tabs.query({ groupId });
+        const placeholders = groupTabs.filter(t =>
+          t.id !== tab.id &&
+          (t.url === "chrome://newtab/" || t.url === "about:blank" || t.pendingUrl === "chrome://newtab/")
+        );
+        await chrome.tabs.group({ tabIds: [tab.id], groupId });
+        if (placeholders.length) await chrome.tabs.remove(placeholders.map(t => t.id));
+      } catch (e) {
+        if (!(e instanceof Error) || !e.message.startsWith("No tab group found")) throw e;
+        // Group doesn't exist — create it with the tab already in it
+        groupId = await chrome.tabs.group({ tabIds: [tab.id] });
+        await chrome.tabGroups.update(groupId, { title: String(groupNameOrId) });
+      }
     }
-    if (readyState === "complete" ? t.status === "complete" : t.status !== "loading") {
-      return tabInfo(t);
-    }
-    await new Promise(r => setTimeout(r, interval));
+    return { id: tab.id, url: tab.url };
   }
-  throw new Error(`Tab ${tab.id} did not reach status '${readyState}' within ${timeout}ms`);
-}
 
-export async function navOpenWait({ url, timeout = 30000, background, window: windowName, group } = {}) {
-  const opened = await navOpen({ url, background, window: windowName, group });
-  return await navWait({ tabId: opened.id, timeout });
-}
+  private async navTo({ tabId, url }: NavToArgs) {
+    const tab = await chrome.tabs.update(tabId, { url });
+    return { id: tab.id, url: tab.url || url };
+  }
 
-// ── Tabs ──────────────────────────────────────────────────────────────────────
+  private async navReload({ tabId }: NavTabArgs, bypassCache: boolean) {
+    const tab = tabId ? { id: tabId } : await getActiveTab();
+    await chrome.tabs.reload(tab.id, { bypassCache });
+    return { tabId: tab.id };
+  }
+
+  private async navBack({ tabId }: NavTabArgs) {
+    const tab = tabId ? { id: tabId } : await getActiveTab();
+    await chrome.tabs.goBack(tab.id);
+    return { tabId: tab.id };
+  }
+
+  private async navForward({ tabId }: NavTabArgs) {
+    const tab = tabId ? { id: tabId } : await getActiveTab();
+    await chrome.tabs.goForward(tab.id);
+    return { tabId: tab.id };
+  }
+
+  private async navFocus({ pattern }: NavFocusArgs) {
+    // If pattern is a plain integer, treat it as a tab ID
+    const asInt = parseInt(pattern);
+    let match: chrome.tabs.Tab | undefined;
+    if (!isNaN(asInt) && String(asInt) === String(pattern)) {
+      match = await chrome.tabs.get(asInt);
+    } else {
+      const all = await chrome.tabs.query({});
+      match = all.find(t => (t.url && t.url.includes(pattern)) || (t.pendingUrl && t.pendingUrl.includes(pattern)));
+    }
+    if (!match) return null;
+    await chrome.windows.update(match.windowId, { focused: true });
+    await chrome.tabs.update(match.id, { active: true });
+    return { id: match.id, url: match.url || match.pendingUrl, title: match.title };
+  }
+
+  private async navWait({ tabId, timeout = 30000, readyState = "complete" }: NavWaitArgs = {}) {
+    const tab = tabId ? { id: tabId } : await getActiveTab();
+    const deadline = Date.now() + timeout;
+    const interval = 200;
+    while (Date.now() < deadline) {
+      const t = await chrome.tabs.get(tab.id);
+      const currentUrl = t.url || t.pendingUrl || "";
+      if (isBrowserErrorUrl(currentUrl)) {
+        throw new Error(`Tab ${tab.id} is showing an error page while waiting for load (${currentUrl})`);
+      }
+      if (readyState === "complete" ? t.status === "complete" : t.status !== "loading") {
+        return tabInfo(t);
+      }
+      await new Promise(r => setTimeout(r, interval));
+    }
+    throw new Error(`Tab ${tab.id} did not reach status '${readyState}' within ${timeout}ms`);
+  }
+
+  private async navOpenWait({ url, timeout = 30000, background, window: windowName, group }: NavOpenWaitArgs = {}) {
+    const opened = await this.navOpen({ url, background, window: windowName, group });
+    return await this.navWait({ tabId: opened.id, timeout });
+  }
+}
diff --git a/extension/src/commands/perf.ts b/extension/src/commands/perf.ts
new file mode 100644
index 0000000..ea86e84
--- /dev/null
+++ b/extension/src/commands/perf.ts
@@ -0,0 +1,38 @@
+import { getLargeOperationThrottle, getPerformanceProfile, hasAudibleTabs, setPerformanceProfile } from '../core';
+import { CommandGroup } from '../classes/CommandGroup';
+import type { CommandEntry } from '../classes/CommandGroup';
+import type { PerfSetProfileArgs, JobIdArgs } from '../types';
+
+// PerfCommands also owns the jobs.* status/cancel queries: they read the same
+// JobManager (ctx.jobs) that perf.status reports, and there is no dedicated
+// jobs command group.
+export class PerfCommands extends CommandGroup {
+  readonly namespace = "perf";
+  readonly commands: Record<string, CommandEntry> = {
+    "perf.status":      () => this.perfStatus(),
+    "perf.set_profile": (a: PerfSetProfileArgs) => setPerformanceProfile(typeof a.profile === "string" ? a.profile : undefined),
+    "jobs.status":      (a: JobIdArgs) => this.ctx.jobs.status(a),
+    "jobs.cancel":      (a: JobIdArgs) => this.ctx.jobs.cancel(a),
+  };
+
+  private async perfStatus() {
+    const profile = await getPerformanceProfile();
+    const audible = await hasAudibleTabs();
+    const throttle = await getLargeOperationThrottle(0, "auto");
+    return {
+      performanceProfile: profile,
+      audible,
+      throttle,
+      jobs: this.ctx.jobs.list().map(job => ({
+        id: job.id,
+        command: job.command,
+        status: job.status,
+        phase: job.phase,
+        current: job.current,
+        total: job.total,
+        percent: job.percent,
+        cancelRequested: job.cancelRequested,
+      })),
+    };
+  }
+}
diff --git a/extension/src/commands/session-snapshot.ts b/extension/src/commands/session-snapshot.ts
new file mode 100644
index 0000000..b21d1cc
--- /dev/null
+++ b/extension/src/commands/session-snapshot.ts
@@ -0,0 +1,54 @@
+import { normalizeGroupColor } from '../core';
+import type { SessionTab, StoredSession } from '../types';
+
+export function buildSessionSnapshot(tabs: chrome.tabs.Tab[], groups: chrome.tabGroups.TabGroup[]): SessionTab[] {
+  const groupById = new Map(groups.map(group => [group.id, group]));
+  return tabs
+    .filter(tab => Boolean(tab.url || tab.pendingUrl))
+    .sort((a, b) => (a.windowId - b.windowId) || (a.index - b.index))
+    .map(tab => {
+      const entry: SessionTab = { url: tab.url || tab.pendingUrl };
+      if (tab.pinned) entry.pinned = true;
+      if (tab.groupId >= 0) {
+        const group = groupById.get(tab.groupId);
+        entry.group = {
+          key: `${tab.windowId}:${tab.groupId}`,
+          title: group?.title || "",
+          color: normalizeGroupColor(group?.color),
+          collapsed: Boolean(group?.collapsed),
+        };
+      }
+      return entry;
+    });
+}
+
+/**
+ * Snapshot the current windows/tabs/groups into a ready-to-store session plus
+ * its change-detection signature. Shared by session.save and the autosave path.
+ */
+export async function captureCurrentSession(): Promise<{ session: StoredSession; signature: string; tabCount: number }> {
+  const tabs = await chrome.tabs.query({});
+  const groups = await chrome.tabGroups.query({});
+  const sessionTabs = buildSessionSnapshot(tabs, groups);
+  const signature = sessionSignature(sessionTabs);
+  const session: StoredSession = {
+    tabs: sessionTabs,
+    urls: sessionTabs.map(tab => tab.url),
+    savedAt: Date.now(),
+    signature,
+  };
+  return { session, signature, tabCount: sessionTabs.length };
+}
+
+export function sessionSignature(sessionTabs: SessionTab[]) {
+  return JSON.stringify(sessionTabs.map(tab => ({
+    url: tab.url,
+    pinned: Boolean(tab.pinned),
+    group: tab.group ? {
+      key: tab.group.key || "",
+      title: tab.group.title || "",
+      color: normalizeGroupColor(tab.group.color),
+      collapsed: Boolean(tab.group.collapsed),
+    } : null,
+  })));
+}
diff --git a/extension/src/commands/session.ts b/extension/src/commands/session.ts
index 6d9edff..78806f6 100644
--- a/extension/src/commands/session.ts
+++ b/extension/src/commands/session.ts
@@ -1,255 +1,150 @@
-// @ts-nocheck
 import { getLargeOperationThrottle, getProfileAlias, getSessionTabs, getSessions, normalizeGroupColor, runLargeOperation, throwIfJobCancelled, updateJobProgress, yieldForLargeOperation } from '../core';
+import { CommandGroup } from '../classes/CommandGroup';
+import { AutoSaveManager } from './autosave';
+import { captureCurrentSession } from './session-snapshot';
+import type { CommandEntry } from '../classes/CommandGroup';
+import type { LazySessionMap, SessionSaveArgs, SessionRemoveArgs, SessionDiffArgs, SessionLoadArgs, SessionAutoSaveArgs, ClientsRenameProfileArgs } from '../types';
 
-function buildSessionSnapshot(tabs, groups) {
-  const groupById = new Map(groups.map(group => [group.id, group]));
-  return tabs
-    .filter(tab => Boolean(tab.url || tab.pendingUrl))
-    .sort((a, b) => (a.windowId - b.windowId) || (a.index - b.index))
-    .map(tab => {
-      const entry = { url: tab.url || tab.pendingUrl };
-      if (tab.pinned) entry.pinned = true;
-      if (tab.groupId >= 0) {
-        const group = groupById.get(tab.groupId);
-        entry.group = {
-          key: `${tab.windowId}:${tab.groupId}`,
-          title: group?.title || "",
-          color: normalizeGroupColor(group?.color),
-          collapsed: Boolean(group?.collapsed),
-        };
-      }
-      return entry;
-    });
-}
-
-function sessionSignature(sessionTabs) {
-  return JSON.stringify(sessionTabs.map(tab => ({
-    url: tab.url,
-    pinned: Boolean(tab.pinned),
-    group: tab.group ? {
-      key: tab.group.key || "",
-      title: tab.group.title || "",
-      color: normalizeGroupColor(tab.group.color),
-      collapsed: Boolean(tab.group.collapsed),
-    } : null,
-  })));
-}
-
-export async function sessionSave({ name }) {
-  const tabs = await chrome.tabs.query({});
-  const groups = await chrome.tabGroups.query({});
-  const sessionTabs = buildSessionSnapshot(tabs, groups);
-  const signature = sessionSignature(sessionTabs);
-  const sessions = await getSessions();
-  sessions[name] = {
-    tabs: sessionTabs,
-    urls: sessionTabs.map(tab => tab.url),
-    savedAt: Date.now(),
-    signature,
-  };
-  await chrome.storage.local.set({ sessions });
-  return { name, tabs: sessionTabs.length };
-}
-
-function lazyPlaceholderUrl(url) {
+function lazyPlaceholderUrl(url: string) {
   const escaped = String(url).replace(/[&<>"']/g, ch => ({ "&": "&amp;", "<": "&lt;", ">": "&gt;", "\"": "&quot;", "'": "&#39;" }[ch]));
   const html = `<!doctype html><title>Lazy tab</title><body style="font-family:sans-serif;padding:2rem"><h1>Lazy tab</h1><p>This tab will load when selected.</p><p><a href="${escaped}">${escaped}</a></p></body>`;
   return `data:text/html;charset=utf-8,${encodeURIComponent(html)}`;
 }
 
-export async function activateLazyTab(tabId) {
-  const { lazySessionTabs } = await chrome.storage.local.get("lazySessionTabs");
-  const entry = lazySessionTabs?.[tabId];
-  if (!entry?.url) return false;
-  delete lazySessionTabs[tabId];
-  await chrome.storage.local.set({ lazySessionTabs });
-  await chrome.tabs.update(Number(tabId), { url: entry.url });
-  return true;
-}
+export class SessionCommands extends CommandGroup {
+  readonly namespace = "session";
+  readonly commands: Record<string, CommandEntry> = {
+    "session.save":      (a: SessionSaveArgs) => this.sessionSave(a),
+    "session.load":      { background: true, run: (a: SessionLoadArgs) => this.sessionLoad(a) },
+    "session.list":      () => this.sessionList(),
+    "session.remove":    (a: SessionRemoveArgs) => this.sessionRemove(a),
+    "session.diff":      (a: SessionDiffArgs) => this.sessionDiff(a),
+    "session.auto_save": (a: SessionAutoSaveArgs) => this.autoSaveManager.setEnabled(Boolean(a.enabled)),
+    "clients.list":           () => this.clientsList(),
+    "clients.rename_profile": (a: ClientsRenameProfileArgs) => this.clientsRenameProfile(a),
+  };
 
-export async function sessionLoad({ name, gentleMode, discardBackgroundTabs = false, lazy = false, eagerTabs = 10, __job } = {}) {
-  return runLargeOperation("session.load", async () => {
+  private readonly autoSaveManager = new AutoSaveManager();
+
+  private async sessionSave({ name }: SessionSaveArgs) {
+    const { session, tabCount } = await captureCurrentSession();
     const sessions = await getSessions();
-    const session = sessions[name];
-    if (!session) throw new Error(`Session '${name}' not found`);
+    sessions[name] = session;
+    await chrome.storage.local.set({ sessions });
+    return { name, tabs: tabCount };
+  }
 
-    const sessionTabs = getSessionTabs(session).sort((a, b) => Number(Boolean(b.pinned)) - Number(Boolean(a.pinned)));
-    const createdTabs = [];
-    const throttle = await getLargeOperationThrottle(sessionTabs.length, gentleMode);
-    const createBatchSize = Math.max(1, Math.min(10, throttle.batchSize));
-    const eagerLimit = lazy ? Math.max(0, Number(eagerTabs) || 0) : sessionTabs.length;
-    const { lazySessionTabs } = await chrome.storage.local.get("lazySessionTabs");
-    const lazyMap = lazySessionTabs || {};
-    updateJobProgress(__job, { phase: "opening", current: 0, total: sessionTabs.length });
+  // Public: invoked from index.ts on chrome.tabs.onActivated.
+  async activateLazyTab(tabId: number | string) {
+    const { lazySessionTabs } = await chrome.storage.local.get<{ lazySessionTabs?: LazySessionMap }>("lazySessionTabs");
+    const entry = lazySessionTabs?.[tabId];
+    if (!entry?.url) return false;
+    delete lazySessionTabs[tabId];
+    await chrome.storage.local.set({ lazySessionTabs });
+    await chrome.tabs.update(Number(tabId), { url: entry.url });
+    return true;
+  }
 
-    for (const [idx, entry] of sessionTabs.entries()) {
-      throwIfJobCancelled(__job);
-      const shouldLazy = lazy && idx >= eagerLimit;
-      const tab = await chrome.tabs.create({ url: shouldLazy ? lazyPlaceholderUrl(entry.url) : entry.url, active: false, pinned: Boolean(entry.pinned) });
-      createdTabs.push({ tabId: tab.id, entry });
-      if (shouldLazy) {
-        lazyMap[String(tab.id)] = { url: entry.url, createdAt: Date.now() };
-      } else if (discardBackgroundTabs && !entry.pinned && chrome.tabs.discard) {
-        try { await chrome.tabs.discard(tab.id); } catch (_) {}
+  private async sessionLoad({ name, gentleMode, discardBackgroundTabs = false, lazy = false, eagerTabs = 10, __job }: SessionLoadArgs = {}) {
+    return runLargeOperation("session.load", async () => {
+      const sessions = await getSessions();
+      const session = sessions[name];
+      if (!session) throw new Error(`Session '${name}' not found`);
+
+      const sessionTabs = getSessionTabs(session).sort((a, b) => Number(Boolean(b.pinned)) - Number(Boolean(a.pinned)));
+      const createdTabs = [];
+      const throttle = await getLargeOperationThrottle(sessionTabs.length, gentleMode);
+      const createBatchSize = Math.max(1, Math.min(10, throttle.batchSize));
+      const eagerLimit = lazy ? Math.max(0, Number(eagerTabs) || 0) : sessionTabs.length;
+      const { lazySessionTabs } = await chrome.storage.local.get<{ lazySessionTabs?: LazySessionMap }>("lazySessionTabs");
+      const lazyMap: LazySessionMap = lazySessionTabs || {};
+      updateJobProgress(__job, { phase: "opening", current: 0, total: sessionTabs.length });
+
+      for (const [idx, entry] of sessionTabs.entries()) {
+        throwIfJobCancelled(__job);
+        const shouldLazy = lazy && idx >= eagerLimit;
+        const tab = await chrome.tabs.create({ url: shouldLazy ? lazyPlaceholderUrl(entry.url) : entry.url, active: false, pinned: Boolean(entry.pinned) });
+        createdTabs.push({ tabId: tab.id, entry });
+        if (shouldLazy) {
+          lazyMap[String(tab.id)] = { url: entry.url, createdAt: Date.now() };
+        } else if (discardBackgroundTabs && !entry.pinned && chrome.tabs.discard) {
+          try { await chrome.tabs.discard(tab.id); } catch (_) {}
+        }
+        updateJobProgress(__job, { phase: shouldLazy ? "creating lazy placeholders" : "opening", current: createdTabs.length, total: sessionTabs.length });
+        await yieldForLargeOperation(createdTabs.length, createBatchSize, Math.max(50, throttle.pauseMs));
       }
-      updateJobProgress(__job, { phase: shouldLazy ? "creating lazy placeholders" : "opening", current: createdTabs.length, total: sessionTabs.length });
-      await yieldForLargeOperation(createdTabs.length, createBatchSize, Math.max(50, throttle.pauseMs));
-    }
-    if (lazy) await chrome.storage.local.set({ lazySessionTabs: lazyMap });
+      if (lazy) await chrome.storage.local.set({ lazySessionTabs: lazyMap });
 
-    const groups = new Map();
-    for (const { tabId, entry } of createdTabs) {
-      if (!entry.group) continue;
-      const key = entry.group.key || `${entry.group.title || "group"}:${groups.size}`;
-      if (!groups.has(key)) {
-        groups.set(key, { meta: entry.group, tabIds: [] });
+      const groups = new Map();
+      for (const { tabId, entry } of createdTabs) {
+        if (!entry.group) continue;
+        const key = entry.group.key || `${entry.group.title || "group"}:${groups.size}`;
+        if (!groups.has(key)) {
+          groups.set(key, { meta: entry.group, tabIds: [] });
+        }
+        groups.get(key).tabIds.push(tabId);
       }
-      groups.get(key).tabIds.push(tabId);
-    }
 
-    let restoredGroups = 0;
-    updateJobProgress(__job, { phase: "restoring groups", current: 0, total: groups.size });
-    for (const { meta, tabIds } of groups.values()) {
-      throwIfJobCancelled(__job);
-      const restoredGroupId = await chrome.tabs.group({ tabIds });
-      await chrome.tabGroups.update(restoredGroupId, {
-        title: meta.title || "",
-        color: normalizeGroupColor(meta.color),
-        collapsed: Boolean(meta.collapsed),
-      });
-      restoredGroups++;
-      updateJobProgress(__job, { phase: "restoring groups", current: restoredGroups, total: groups.size });
-      await yieldForLargeOperation(restoredGroups, 5, Math.max(50, throttle.pauseMs));
-    }
+      let restoredGroups = 0;
+      updateJobProgress(__job, { phase: "restoring groups", current: 0, total: groups.size });
+      for (const { meta, tabIds } of groups.values()) {
+        throwIfJobCancelled(__job);
+        const restoredGroupId = await chrome.tabs.group({ tabIds });
+        await chrome.tabGroups.update(restoredGroupId, {
+          title: meta.title || "",
+          color: normalizeGroupColor(meta.color),
+          collapsed: Boolean(meta.collapsed),
+        });
+        restoredGroups++;
+        updateJobProgress(__job, { phase: "restoring groups", current: restoredGroups, total: groups.size });
+        await yieldForLargeOperation(restoredGroups, 5, Math.max(50, throttle.pauseMs));
+      }
 
-    return { name, tabs: sessionTabs.length, gentle: throttle.gentle, audible: throttle.audible, discarded: Boolean(discardBackgroundTabs), lazy: Boolean(lazy), eagerTabs: eagerLimit };
-  });
-}
-
-export async function sessionList() {
-  const sessions = await getSessions();
-  return Object.entries(sessions).map(([name, s]) => ({
-    name,
-    tabs: getSessionTabs(s).length,
-    savedAt: s.savedAt || null,
-  }));
-}
-
-export async function sessionRemove({ name }) {
-  const sessions = await getSessions();
-  if (!(name in sessions)) throw new Error(`Session '${name}' not found`);
-  delete sessions[name];
-  await chrome.storage.local.set({ sessions });
-  return { name };
-}
-
-export async function sessionDiff({ nameA, nameB }) {
-  const sessions = await getSessions();
-  const a = new Set(getSessionTabs(sessions[nameA]).map(tab => tab.url));
-  const b = new Set(getSessionTabs(sessions[nameB]).map(tab => tab.url));
-  return {
-    added:   [...b].filter(u => !a.has(u)),
-    removed: [...a].filter(u => !b.has(u)),
-  };
-}
-
-let autoSaveTimer = null;
-let autoSaveInFlight = false;
-let autoSavePending = false;
-
-export async function sessionAutoSave({ enabled }) {
-  await chrome.storage.local.set({ autoSave: enabled });
-  chrome.tabs.onCreated.removeListener(autoSaveHandler);
-  chrome.tabs.onRemoved.removeListener(autoSaveHandler);
-  chrome.tabs.onMoved.removeListener(autoSaveHandler);
-  chrome.tabs.onAttached.removeListener(autoSaveHandler);
-  chrome.tabs.onDetached.removeListener(autoSaveHandler);
-  chrome.tabs.onUpdated.removeListener(autoSaveUpdatedHandler);
-  if (chrome.tabGroups?.onUpdated) chrome.tabGroups.onUpdated.removeListener(autoSaveHandler);
-  if (autoSaveTimer) clearTimeout(autoSaveTimer);
-  autoSaveTimer = null;
-  autoSavePending = false;
-  if (enabled) {
-    chrome.tabs.onCreated.addListener(autoSaveHandler);
-    chrome.tabs.onRemoved.addListener(autoSaveHandler);
-    chrome.tabs.onMoved.addListener(autoSaveHandler);
-    chrome.tabs.onAttached.addListener(autoSaveHandler);
-    chrome.tabs.onDetached.addListener(autoSaveHandler);
-    chrome.tabs.onUpdated.addListener(autoSaveUpdatedHandler);
-    if (chrome.tabGroups?.onUpdated) chrome.tabGroups.onUpdated.addListener(autoSaveHandler);
+      return { name, tabs: sessionTabs.length, gentle: throttle.gentle, audible: throttle.audible, discarded: Boolean(discardBackgroundTabs), lazy: Boolean(lazy), eagerTabs: eagerLimit };
+    });
   }
-  return { enabled };
-}
 
-async function saveAutoSessionIfChanged() {
-  const tabs = await chrome.tabs.query({});
-  const groups = await chrome.tabGroups.query({});
-  const sessionTabs = buildSessionSnapshot(tabs, groups);
-  const signature = sessionSignature(sessionTabs);
-  const { autoSaveSignature } = await chrome.storage.local.get("autoSaveSignature");
-  if (autoSaveSignature === signature) return { skipped: true, tabs: sessionTabs.length };
-
-  const sessions = await getSessions();
-  sessions.__auto__ = {
-    tabs: sessionTabs,
-    urls: sessionTabs.map(tab => tab.url),
-    savedAt: Date.now(),
-    signature,
-  };
-  await chrome.storage.local.set({ sessions, autoSaveSignature: signature });
-  return { skipped: false, tabs: sessionTabs.length };
-}
-
-async function runAutoSave() {
-  if (autoSaveInFlight) {
-    autoSavePending = true;
-    return;
+  private async sessionList() {
+    const sessions = await getSessions();
+    return Object.entries(sessions).map(([name, s]) => ({
+      name,
+      tabs: getSessionTabs(s).length,
+      savedAt: s.savedAt || null,
+    }));
   }
-  autoSaveInFlight = true;
-  try {
-    const { autoSave } = await chrome.storage.local.get("autoSave");
-    if (autoSave) await runLargeOperation("session.auto_save", saveAutoSessionIfChanged);
-  } finally {
-    autoSaveInFlight = false;
-    if (autoSavePending) {
-      autoSavePending = false;
-      autoSaveTimer = setTimeout(runAutoSave, 1000);
-    }
+
+  private async sessionRemove({ name }: SessionRemoveArgs) {
+    const sessions = await getSessions();
+    if (!(name in sessions)) throw new Error(`Session '${name}' not found`);
+    delete sessions[name];
+    await chrome.storage.local.set({ sessions });
+    return { name };
+  }
+
+  private async sessionDiff({ nameA, nameB }: SessionDiffArgs) {
+    const sessions = await getSessions();
+    const a = new Set(getSessionTabs(sessions[nameA]).map(tab => tab.url));
+    const b = new Set(getSessionTabs(sessions[nameB]).map(tab => tab.url));
+    return {
+      added:   [...b].filter(u => !a.has(u)),
+      removed: [...a].filter(u => !b.has(u)),
+    };
+  }
+
+  private async clientsList() {
+    const manifest = chrome.runtime.getManifest();
+    const alias = await getProfileAlias();
+    return [{
+      name: "Chrome",
+      version: navigator.userAgent.match(/Chrome\/([\d.]+)/)?.[1] || "unknown",
+      platform: navigator.platform,
+      extensionVersion: manifest.version,
+      profile: alias,
+    }];
+  }
+
+  private async clientsRenameProfile({ alias }: ClientsRenameProfileArgs) {
+    await chrome.storage.local.set({ profileAlias: alias });
+    return { alias };
   }
 }
-
-async function scheduleAutoSave(delayMs = 1000) {
-  const { autoSave } = await chrome.storage.local.get("autoSave");
-  if (!autoSave) return;
-  if (autoSaveTimer) clearTimeout(autoSaveTimer);
-  autoSaveTimer = setTimeout(runAutoSave, delayMs);
-}
-
-export async function autoSaveHandler() {
-  await scheduleAutoSave();
-}
-
-export async function autoSaveUpdatedHandler(_tabId, changeInfo = {}) {
-  // Ignore noisy media/title/favicon/loading updates. Sessions only store URL and group/window structure.
-  if (!("url" in changeInfo)) return;
-  await scheduleAutoSave();
-}
-
-// ── Misc ──────────────────────────────────────────────────────────────────────
-
-export async function clientsList() {
-  const manifest = chrome.runtime.getManifest();
-  const alias = await getProfileAlias();
-  return [{
-    name: "Chrome",
-    version: navigator.userAgent.match(/Chrome\/([\d.]+)/)?.[1] || "unknown",
-    platform: navigator.platform,
-    extensionVersion: manifest.version,
-    profile: alias,
-  }];
-}
-
-export async function clientsRenameProfile({ alias }) {
-  await chrome.storage.local.set({ profileAlias: alias });
-  return { alias };
-}
diff --git a/extension/src/commands/tabs-query.ts b/extension/src/commands/tabs-query.ts
new file mode 100644
index 0000000..1203c58
--- /dev/null
+++ b/extension/src/commands/tabs-query.ts
@@ -0,0 +1,95 @@
+import { fetchTabHtml, getActiveTab, getAliases, isBrowserErrorUrl, tabInfo } from '../core';
+import { CommandGroup } from '../classes/CommandGroup';
+import type { CommandEntry } from '../classes/CommandGroup';
+import type { TabIdArgs, TabsActiveInWindowArgs, TabsPatternArgs, TabsQueryArgs, TabsWatchUrlArgs } from '../types';
+
+export class TabsQueryCommands extends CommandGroup {
+  readonly namespace = "tabs";
+  readonly commands: Record<string, CommandEntry> = {
+    "tabs.list":             () => this.tabsList(),
+    "tabs.active_in_window": (a: TabsActiveInWindowArgs) => this.tabsActiveInWindow(a),
+    "tabs.status":           (a: TabIdArgs) => this.tabsStatus(a),
+    "tabs.filter":           (a: TabsPatternArgs) => this.tabsFilter(a),
+    "tabs.count":            (a: TabsPatternArgs) => this.tabsCount(a),
+    "tabs.query":            (a: TabsQueryArgs) => this.tabsQuery(a),
+    "tabs.html":             (a: TabIdArgs) => fetchTabHtml(a.tabId),
+    "tabs.watch_url":        (a: TabsWatchUrlArgs) => this.tabsWatchUrl(a),
+  };
+
+  private async tabsList() {
+    const windows = await chrome.windows.getAll({ populate: true });
+    const aliases = await getAliases();
+    const tabs = [];
+    for (const w of windows) {
+      for (const t of w.tabs) {
+        tabs.push({
+          ...tabInfo(t),
+          windowAlias: aliases[t.windowId] || null,
+          pinned: t.pinned,
+          favIconUrl: t.favIconUrl,
+        });
+      }
+    }
+    return tabs;
+  }
+
+  private async tabsActiveInWindow({ windowId }: TabsActiveInWindowArgs) {
+    const activeTabs = await chrome.tabs.query({ windowId, active: true });
+    const tab = activeTabs[0];
+    if (!tab) {
+      throw new Error(`No active tab found for window ${windowId}`);
+    }
+    return tabInfo(tab);
+  }
+
+  private async tabsStatus({ tabId }: TabIdArgs) {
+    const tab = tabId ? await chrome.tabs.get(tabId) : await getActiveTab();
+    return tabInfo(tab);
+  }
+
+  private async tabsFilter({ pattern }: TabsPatternArgs) {
+    const all = await chrome.tabs.query({});
+    return all.filter(t => t.url && t.url.includes(pattern)).map(tabInfo);
+  }
+
+  private async tabsCount({ pattern }: TabsPatternArgs) {
+    const all = await chrome.tabs.query({});
+    if (pattern) return all.filter(t => t.url && t.url.includes(pattern)).length;
+    return all.length;
+  }
+
+  private async tabsQuery({ search }: TabsQueryArgs) {
+    const q = search.toLowerCase();
+    const all = await chrome.tabs.query({});
+    return all.filter(t =>
+      (t.url && t.url.toLowerCase().includes(q)) ||
+      (t.title && t.title.toLowerCase().includes(q))
+    ).map(tabInfo);
+  }
+
+  private async tabsWatchUrl({ pattern, timeout = 30000, tabId }: TabsWatchUrlArgs = {}) {
+    const tab = tabId ? await chrome.tabs.get(tabId) : await getActiveTab();
+    const deadline = Date.now() + timeout;
+    const regex = new RegExp(pattern);
+    let lastUrl = tab.url || tab.pendingUrl || "";
+    let lastStatus = tab.status || "unknown";
+
+    const matches = (url: string) => {
+      regex.lastIndex = 0;
+      return Boolean(url && regex.test(url));
+    };
+    if (matches(lastUrl)) return tabInfo(tab);
+
+    while (Date.now() < deadline) {
+      const t = await chrome.tabs.get(tab.id);
+      lastUrl = t.url || t.pendingUrl || "";
+      lastStatus = t.status || "unknown";
+      if (matches(t.pendingUrl || "") || matches(t.url || "")) return tabInfo(t);
+      if (isBrowserErrorUrl(t.url || "")) {
+        throw new Error(`Tab ${tab.id} is showing an error page while waiting for URL to match '${pattern}'`);
+      }
+      await new Promise(r => setTimeout(r, 200));
+    }
+    throw new Error(`Tab ${tab.id} URL did not match '${pattern}' within ${timeout}ms (last URL: '${lastUrl}', status: '${lastStatus}')`);
+  }
+}
diff --git a/extension/src/commands/tabs.ts b/extension/src/commands/tabs.ts
index 3d8be7e..78789b5 100644
--- a/extension/src/commands/tabs.ts
+++ b/extension/src/commands/tabs.ts
@@ -1,262 +1,166 @@
-// @ts-nocheck
-import { executeScript, getActiveTab, getAliases, getLargeOperationThrottle, isBrowserErrorUrl, isErrorPageScriptError, isScriptableUrl, resolveTabForDirectAction, runLargeOperation, tabInfo, throwIfJobCancelled, updateJobProgress, yieldForLargeOperation } from '../core';
-export async function tabsList() {
-  const windows = await chrome.windows.getAll({ populate: true });
-  const aliases = await getAliases();
-  const tabs = [];
-  for (const w of windows) {
-    for (const t of w.tabs) {
-      tabs.push({
-        ...tabInfo(t),
-        windowAlias: aliases[t.windowId] || null,
-        pinned: t.pinned,
-        favIconUrl: t.favIconUrl,
-      });
-    }
-  }
-  return tabs;
-}
+import { asTabIds, getActiveTab, getLargeOperationThrottle, processInBatches, resolveTabForDirectAction, runLargeOperation, throwIfJobCancelled, updateJobProgress, yieldForLargeOperation } from '../core';
+import { CommandGroup } from '../classes/CommandGroup';
+import type { CommandEntry } from '../classes/CommandGroup';
+import type { TabsCloseArgs, TabsMoveArgs, TabIdArgs, TabsSortArgs, TabsMergeWindowsArgs, TabsScreenshotArgs } from '../types';
 
-export async function tabsClose({ tabId, inactive, duplicates, gentleMode, __job } = {}) {
-  return runLargeOperation("tabs.close", async () => {
-    let toClose = [];
-    if (duplicates) {
-      const all = await chrome.tabs.query({});
-      const seen = new Set();
-      for (const t of all) {
-        if (!t.url) continue;
-        if (seen.has(t.url)) toClose.push(t.id);
-        else seen.add(t.url);
-      }
-    } else if (inactive) {
-      const all = await chrome.tabs.query({});
-      toClose = all.filter(t => !t.active).map(t => t.id);
-    } else if (tabId) {
-      toClose = [tabId];
-    }
-    const throttle = await getLargeOperationThrottle(toClose.length, gentleMode);
-    updateJobProgress(__job, { phase: "closing tabs", current: 0, total: toClose.length });
-    for (let i = 0; i < toClose.length; i += throttle.batchSize) {
-      throwIfJobCancelled(__job);
-      await chrome.tabs.remove(toClose.slice(i, i + throttle.batchSize));
-      updateJobProgress(__job, { phase: "closing tabs", current: Math.min(i + throttle.batchSize, toClose.length), total: toClose.length });
-      await yieldForLargeOperation(i + throttle.batchSize, throttle.batchSize, throttle.pauseMs);
-    }
-    return { closed: toClose.length, gentle: throttle.gentle, audible: throttle.audible };
-  });
-}
-
-export async function tabsMove({ tabId, groupId, windowId, index, forward, backward }) {
-  const moveProps = {};
-  if (windowId != null) moveProps.windowId = windowId;
-
-  if (forward || backward) {
-    const tab = await chrome.tabs.get(tabId);
-    if (forward) moveProps.index = tab.index + 2; // +2 because Chrome shifts after removal
-    else moveProps.index = Math.max(0, tab.index - 1);
-  } else if (index != null) {
-    moveProps.index = index;
-  } else {
-    moveProps.index = -1;
-  }
-
-  await chrome.tabs.move(tabId, moveProps);
-  if (groupId != null) {
-    await chrome.tabs.group({ tabIds: [tabId], groupId });
-  }
-  return { tabId };
-}
-
-export async function tabsActive({ tabId }) {
-  const tab = await chrome.tabs.get(tabId);
-  await chrome.windows.update(tab.windowId, { focused: true });
-  await chrome.tabs.update(tabId, { active: true });
-  return { tabId };
-}
-
-export async function tabsActiveInWindow({ windowId }) {
-  const activeTabs = await chrome.tabs.query({ windowId, active: true });
-  const tab = activeTabs[0];
-  if (!tab) {
-    throw new Error(`No active tab found for window ${windowId}`);
-  }
-  return tabInfo(tab);
-}
-
-export async function tabsStatus({ tabId }) {
-  const tab = tabId ? await chrome.tabs.get(tabId) : await getActiveTab();
-  return tabInfo(tab);
-}
-
-export async function tabsFilter({ pattern }) {
-  const all = await chrome.tabs.query({});
-  return all.filter(t => t.url && t.url.includes(pattern)).map(tabInfo);
-}
-
-export async function tabsCount({ pattern }) {
-  const all = await chrome.tabs.query({});
-  if (pattern) return all.filter(t => t.url && t.url.includes(pattern)).length;
-  return all.length;
-}
-
-export async function tabsQuery({ search }) {
-  const q = search.toLowerCase();
-  const all = await chrome.tabs.query({});
-  return all.filter(t =>
-    (t.url && t.url.toLowerCase().includes(q)) ||
-    (t.title && t.title.toLowerCase().includes(q))
-  ).map(tabInfo);
-}
-
-export async function tabsHtml({ tabId }) {
-  for (let i = 0; i < 3; i++) {
-    const tab = tabId ? await chrome.tabs.get(tabId) : await getActiveTab();
-    const tabUrl = tab.url || tab.pendingUrl || "";
-    if (isBrowserErrorUrl(tabUrl)) {
-      return "";
-    }
-    if (!isScriptableUrl(tabUrl)) {
-      throw new Error(`Cannot get HTML of ${tabUrl} — navigate to a regular web page first`);
-    }
-    try {
-      const results = await executeScript({
-        target: { tabId: tab.id },
-        func: () => document.documentElement.outerHTML,
-      });
-      return results[0]?.result || "";
-    } catch (e) {
-      if (isErrorPageScriptError(e)) return "";
-      const transient = e.message && (e.message.includes("Frame with ID") || e.message.includes("No tab with id"));
-      if (i < 2 && transient) {
-        await new Promise(r => setTimeout(r, 300));
-        continue;
-      }
-      throw e;
-    }
-  }
-}
-
-export async function tabsDedupe(args = {}) {
-  return tabsClose({ ...args, duplicates: true });
-}
-
-export async function tabsSort({ by, gentleMode, __job } = {}) {
-  return runLargeOperation("tabs.sort", async () => {
-    const windows = await chrome.windows.getAll({ populate: true });
-    let moved = 0;
-    const totalTabs = windows.reduce((sum, w) => sum + (w.tabs?.length || 0), 0);
-    updateJobProgress(__job, { phase: "sorting tabs", current: 0, total: totalTabs });
-    for (const w of windows) {
-      const sorted = [...w.tabs].sort((a, b) => {
-        if (by === "title") return (a.title || "").localeCompare(b.title || "");
-        if (by === "time")  return a.id - b.id; // lower id = opened earlier
-        // domain (default)
-        const da = new URL(a.url || a.pendingUrl || "about:blank").hostname;
-        const db = new URL(b.url || b.pendingUrl || "about:blank").hostname;
-        return da.localeCompare(db);
-      });
-      if (w.tabs.every((tab, index) => tab.id === sorted[index]?.id)) continue;
-      const throttle = await getLargeOperationThrottle(sorted.length, gentleMode);
-      const moveBatchSize = Math.max(1, Math.min(10, throttle.batchSize));
-      for (let i = 0; i < sorted.length; i++) {
-        throwIfJobCancelled(__job);
-        await chrome.tabs.move(sorted[i].id, { index: i });
-        moved++;
-        updateJobProgress(__job, { phase: "sorting tabs", current: moved, total: totalTabs });
-        await yieldForLargeOperation(moved, moveBatchSize, throttle.pauseMs);
-      }
-    }
-    return { moved };
-  });
-}
-
-export async function tabsMergeWindows({ gentleMode, __job } = {}) {
-  return runLargeOperation("tabs.merge_windows", async () => {
-    const current = await chrome.windows.getCurrent();
-    const all = await chrome.windows.getAll({ populate: true });
-    let moved = 0;
-    const totalTabs = all.filter(w => w.id !== current.id).reduce((sum, w) => sum + (w.tabs?.length || 0), 0);
-    updateJobProgress(__job, { phase: "merging windows", current: 0, total: totalTabs });
-    for (const w of all) {
-      if (w.id === current.id) continue;
-      const ids = w.tabs.map(t => t.id);
-      const throttle = await getLargeOperationThrottle(ids.length, gentleMode);
-      for (let i = 0; i < ids.length; i += throttle.batchSize) {
-        throwIfJobCancelled(__job);
-        const chunk = ids.slice(i, i + throttle.batchSize);
-        await chrome.tabs.move(chunk, { windowId: current.id, index: -1 });
-        moved += chunk.length;
-        updateJobProgress(__job, { phase: "merging windows", current: moved, total: totalTabs });
-        await yieldForLargeOperation(moved, throttle.batchSize, throttle.pauseMs);
-      }
-    }
-    return { moved };
-  });
-}
-
-export async function tabsPin({ tabId }) {
-  const tab = tabId ? await chrome.tabs.get(tabId) : await getActiveTab();
-  await chrome.tabs.update(tab.id, { pinned: true });
-  return { tabId: tab.id, pinned: true };
-}
-
-export async function tabsUnpin({ tabId }) {
-  const tab = tabId ? await chrome.tabs.get(tabId) : await getActiveTab();
-  await chrome.tabs.update(tab.id, { pinned: false });
-  return { tabId: tab.id, pinned: false };
-}
-
-export async function tabsScreenshot({ tabId, format = "png", quality } = {}) {
-  let windowId;
-  if (tabId) {
-    const tab = await chrome.tabs.get(tabId);
-    await chrome.tabs.update(tabId, { active: true });
-    windowId = tab.windowId;
-  } else {
-    const tab = await getActiveTab();
-    windowId = tab.windowId;
-  }
-  const opts = { format };
-  if (format === "jpeg" && quality != null) opts.quality = quality;
-  const dataUrl = await chrome.tabs.captureVisibleTab(windowId, opts);
-  return { dataUrl, format };
-}
-
-export async function tabsWatchUrl({ pattern, timeout = 30000, tabId } = {}) {
-  const tab = tabId ? await chrome.tabs.get(tabId) : await getActiveTab();
-  const deadline = Date.now() + timeout;
-  const regex = new RegExp(pattern);
-  let lastUrl = tab.url || tab.pendingUrl || "";
-  let lastStatus = tab.status || "unknown";
-
-  const matches = (url) => {
-    regex.lastIndex = 0;
-    return Boolean(url && regex.test(url));
+export class TabsMutationCommands extends CommandGroup {
+  readonly namespace = "tabs";
+  readonly commands: Record<string, CommandEntry> = {
+    "tabs.close":            { background: true, run: (a: TabsCloseArgs) => this.tabsClose(a) },
+    "tabs.move":             (a: TabsMoveArgs) => this.tabsMove(a),
+    "tabs.active":           (a: TabIdArgs) => this.tabsActive(a),
+    "tabs.dedupe":           { background: true, run: (a: TabsCloseArgs) => this.tabsDedupe(a) },
+    "tabs.sort":             { background: true, run: (a: TabsSortArgs) => this.tabsSort(a) },
+    "tabs.merge_windows":    { background: true, run: (a: TabsMergeWindowsArgs) => this.tabsMergeWindows(a) },
+    "tabs.mute":             (a: TabIdArgs) => this.tabsMute(a),
+    "tabs.unmute":           (a: TabIdArgs) => this.tabsUnmute(a),
+    "tabs.pin":              (a: TabIdArgs) => this.tabsPin(a),
+    "tabs.unpin":            (a: TabIdArgs) => this.tabsUnpin(a),
+    "tabs.screenshot":       (a: TabsScreenshotArgs) => this.tabsScreenshot(a),
   };
-  if (matches(lastUrl)) return tabInfo(tab);
 
-  while (Date.now() < deadline) {
-    const t = await chrome.tabs.get(tab.id);
-    lastUrl = t.url || t.pendingUrl || "";
-    lastStatus = t.status || "unknown";
-    if (matches(t.pendingUrl || "") || matches(t.url || "")) return tabInfo(t);
-    if (isBrowserErrorUrl(t.url || "")) {
-      throw new Error(`Tab ${tab.id} is showing an error page while waiting for URL to match '${pattern}'`);
-    }
-    await new Promise(r => setTimeout(r, 200));
+  private async tabsClose({ tabId, inactive, duplicates, gentleMode, __job }: TabsCloseArgs = {}) {
+    return runLargeOperation("tabs.close", async () => {
+      let toClose: number[] = [];
+      if (duplicates) {
+        const all = await chrome.tabs.query({});
+        const seen = new Set();
+        for (const t of all) {
+          if (!t.url) continue;
+          if (seen.has(t.url)) toClose.push(t.id);
+          else seen.add(t.url);
+        }
+      } else if (inactive) {
+        const all = await chrome.tabs.query({});
+        toClose = all.filter(t => !t.active).map(t => t.id);
+      } else if (tabId) {
+        toClose = [tabId];
+      }
+      const throttle = await getLargeOperationThrottle(toClose.length, gentleMode);
+      await processInBatches(toClose, throttle, batch => chrome.tabs.remove(batch), { job: __job, phase: "closing tabs" });
+      return { closed: toClose.length, gentle: throttle.gentle, audible: throttle.audible };
+    });
   }
-  throw new Error(`Tab ${tab.id} URL did not match '${pattern}' within ${timeout}ms (last URL: '${lastUrl}', status: '${lastStatus}')`);
-}
 
-export async function tabsMute({ tabId }) {
-  const tab = await resolveTabForDirectAction(tabId, "mute");
-  await chrome.tabs.update(tab.id, { muted: true });
-  return { tabId: tab.id, muted: true };
-}
+  private async tabsMove({ tabId, groupId, windowId, index, forward, backward }: TabsMoveArgs) {
+    const moveProps: Partial<chrome.tabs.MoveProperties> = {};
+    if (windowId != null) moveProps.windowId = windowId;
 
-export async function tabsUnmute({ tabId }) {
-  const tab = await resolveTabForDirectAction(tabId, "unmute");
-  await chrome.tabs.update(tab.id, { muted: false });
-  return { tabId: tab.id, muted: false };
-}
+    if (forward || backward) {
+      const tab = await chrome.tabs.get(tabId);
+      if (forward) moveProps.index = tab.index + 2; // +2 because Chrome shifts after removal
+      else moveProps.index = Math.max(0, tab.index - 1);
+    } else if (index != null) {
+      moveProps.index = index;
+    } else {
+      moveProps.index = -1;
+    }
 
+    // `index` is always assigned by one of the branches above before this call.
+    await chrome.tabs.move(tabId, moveProps as chrome.tabs.MoveProperties);
+    if (groupId != null) {
+      await chrome.tabs.group({ tabIds: asTabIds([tabId]), groupId });
+    }
+    return { tabId };
+  }
+
+  private async tabsActive({ tabId }: TabIdArgs) {
+    const tab = await chrome.tabs.get(tabId);
+    await chrome.windows.update(tab.windowId, { focused: true });
+    await chrome.tabs.update(tabId, { active: true });
+    return { tabId };
+  }
+
+  private async tabsDedupe(args: TabsCloseArgs = {}) {
+    return this.tabsClose({ ...args, duplicates: true });
+  }
+
+  private async tabsSort({ by, gentleMode, __job }: TabsSortArgs = {}) {
+    return runLargeOperation("tabs.sort", async () => {
+      const windows = await chrome.windows.getAll({ populate: true });
+      let moved = 0;
+      const totalTabs = windows.reduce((sum, w) => sum + (w.tabs?.length || 0), 0);
+      updateJobProgress(__job, { phase: "sorting tabs", current: 0, total: totalTabs });
+      for (const w of windows) {
+        const sorted = [...w.tabs].sort((a, b) => {
+          if (by === "title") return (a.title || "").localeCompare(b.title || "");
+          if (by === "time")  return a.id - b.id; // lower id = opened earlier
+          // domain (default)
+          const da = new URL(a.url || a.pendingUrl || "about:blank").hostname;
+          const db = new URL(b.url || b.pendingUrl || "about:blank").hostname;
+          return da.localeCompare(db);
+        });
+        if (w.tabs.every((tab, index) => tab.id === sorted[index]?.id)) continue;
+        const throttle = await getLargeOperationThrottle(sorted.length, gentleMode);
+        const moveBatchSize = Math.max(1, Math.min(10, throttle.batchSize));
+        for (let i = 0; i < sorted.length; i++) {
+          throwIfJobCancelled(__job);
+          await chrome.tabs.move(sorted[i].id, { index: i });
+          moved++;
+          updateJobProgress(__job, { phase: "sorting tabs", current: moved, total: totalTabs });
+          await yieldForLargeOperation(moved, moveBatchSize, throttle.pauseMs);
+        }
+      }
+      return { moved };
+    });
+  }
+
+  private async tabsMergeWindows({ gentleMode, __job }: TabsMergeWindowsArgs = {}) {
+    return runLargeOperation("tabs.merge_windows", async () => {
+      const current = await chrome.windows.getCurrent();
+      const all = await chrome.windows.getAll({ populate: true });
+      let moved = 0;
+      const totalTabs = all.filter(w => w.id !== current.id).reduce((sum, w) => sum + (w.tabs?.length || 0), 0);
+      updateJobProgress(__job, { phase: "merging windows", current: 0, total: totalTabs });
+      for (const w of all) {
+        if (w.id === current.id) continue;
+        const ids = w.tabs.map(t => t.id);
+        const throttle = await getLargeOperationThrottle(ids.length, gentleMode);
+        moved = await processInBatches(ids, throttle,
+          batch => chrome.tabs.move(batch, { windowId: current.id, index: -1 }),
+          { job: __job, phase: "merging windows", total: totalTabs, baseCurrent: moved });
+      }
+      return { moved };
+    });
+  }
+
+  private async tabsPin({ tabId }: TabIdArgs) {
+    const tab = tabId ? await chrome.tabs.get(tabId) : await getActiveTab();
+    await chrome.tabs.update(tab.id, { pinned: true });
+    return { tabId: tab.id, pinned: true };
+  }
+
+  private async tabsUnpin({ tabId }: TabIdArgs) {
+    const tab = tabId ? await chrome.tabs.get(tabId) : await getActiveTab();
+    await chrome.tabs.update(tab.id, { pinned: false });
+    return { tabId: tab.id, pinned: false };
+  }
+
+  private async tabsScreenshot({ tabId, format = "png", quality }: TabsScreenshotArgs = {}) {
+    let windowId: number | undefined;
+    if (tabId) {
+      const tab = await chrome.tabs.get(tabId);
+      await chrome.tabs.update(tabId, { active: true });
+      windowId = tab.windowId;
+    } else {
+      const tab = await getActiveTab();
+      windowId = tab.windowId;
+    }
+    const opts: chrome.extensionTypes.ImageDetails = { format: format as chrome.extensionTypes.ImageFormat };
+    if (format === "jpeg" && quality != null) opts.quality = quality;
+    const dataUrl = await chrome.tabs.captureVisibleTab(windowId, opts);
+    return { dataUrl, format };
+  }
+
+  private async tabsMute({ tabId }: TabIdArgs) {
+    const tab = await resolveTabForDirectAction(tabId, "mute");
+    await chrome.tabs.update(tab.id, { muted: true });
+    return { tabId: tab.id, muted: true };
+  }
+
+  private async tabsUnmute({ tabId }: TabIdArgs) {
+    const tab = await resolveTabForDirectAction(tabId, "unmute");
+    await chrome.tabs.update(tab.id, { muted: false });
+    return { tabId: tab.id, muted: false };
+  }
+}
diff --git a/extension/src/commands/windows.ts b/extension/src/commands/windows.ts
index 6be245a..a2cbbcb 100644
--- a/extension/src/commands/windows.ts
+++ b/extension/src/commands/windows.ts
@@ -1,34 +1,45 @@
-// @ts-nocheck
 import { getAliases } from '../core';
-export async function windowsList() {
-  const windows = await chrome.windows.getAll({ populate: true });
-  const aliases = await getAliases();
-  return windows.map(w => ({
-    id: w.id,
-    alias: aliases[w.id] || null,
-    focused: w.focused,
-    state: w.state,
-    tabCount: (w.tabs || []).length,
-  }));
-}
+import { CommandGroup } from '../classes/CommandGroup';
+import type { CommandEntry } from '../classes/CommandGroup';
+import type { WindowsRenameArgs, WindowsCloseArgs, WindowsOpenArgs } from '../types';
 
-export async function windowsRename({ windowId, name }) {
-  const aliases = await getAliases();
-  aliases[windowId] = name;
-  await chrome.storage.local.set({ windowAliases: aliases });
-  return { windowId, name };
-}
+export class WindowsCommands extends CommandGroup {
+  readonly namespace = "windows";
+  readonly commands: Record<string, CommandEntry> = {
+    "windows.list":   () => this.windowsList(),
+    "windows.rename": (a: WindowsRenameArgs) => this.windowsRename(a),
+    "windows.close":  (a: WindowsCloseArgs) => this.windowsClose(a),
+    "windows.open":   (a: WindowsOpenArgs) => this.windowsOpen(a),
+  };
 
-export async function windowsClose({ windowId }) {
-  await chrome.windows.remove(windowId);
-  return { windowId };
-}
+  private async windowsList() {
+    const windows = await chrome.windows.getAll({ populate: true });
+    const aliases = await getAliases();
+    return windows.map(w => ({
+      id: w.id,
+      alias: aliases[w.id] || null,
+      focused: w.focused,
+      state: w.state,
+      tabCount: (w.tabs || []).length,
+    }));
+  }
 
-export async function windowsOpen({ url }) {
-  const createData = { focused: true };
-  if (url) createData.url = url;
-  const w = await chrome.windows.create(createData);
-  return { id: w.id };
-}
+  private async windowsRename({ windowId, name }: WindowsRenameArgs) {
+    const aliases = await getAliases();
+    aliases[windowId] = name;
+    await chrome.storage.local.set({ windowAliases: aliases });
+    return { windowId, name };
+  }
 
-// ── DOM / Extract ─────────────────────────────────────────────────────────────
+  private async windowsClose({ windowId }: WindowsCloseArgs) {
+    await chrome.windows.remove(windowId);
+    return { windowId };
+  }
+
+  private async windowsOpen({ url }: WindowsOpenArgs) {
+    const createData: chrome.windows.CreateData = { focused: true };
+    if (url) createData.url = url;
+    const w = await chrome.windows.create(createData);
+    return { id: w.id };
+  }
+}
diff --git a/extension/src/core.ts b/extension/src/core.ts
deleted file mode 100644
index 9ec813c..0000000
--- a/extension/src/core.ts
+++ /dev/null
@@ -1,240 +0,0 @@
-// @ts-nocheck
-// Shared helpers for browser-cli extension command handlers.
-export async function getProfileAlias() {
-  const { profileAlias } = await chrome.storage.local.get("profileAlias");
-  return profileAlias || "default";
-}
-
-export function isBrowserErrorUrl(url) {
-  const value = String(url || "").toLowerCase();
-  return value.startsWith("chrome-error://") ||
-         value.startsWith("edge-error://") ||
-         value.startsWith("brave-error://") ||
-         value.startsWith("about:neterror") ||
-         value.startsWith("about:certerror") ||
-         value.startsWith("about:blocked") ||
-         value.startsWith("about:tabcrashed");
-}
-
-export function isErrorPageScriptError(error) {
-  const message = String(error?.message || error || "").toLowerCase();
-  return message.includes("error page") ||
-         message.includes("chrome-error://") ||
-         message.includes("edge-error://") ||
-         message.includes("brave-error://") ||
-         message.includes("about:neterror") ||
-         message.includes("about:certerror") ||
-         message.includes("about:tabcrashed");
-}
-
-export function isTransientScriptError(error) {
-  const message = String(error?.message || error || "");
-  return message.includes("Frame with ID") || message.includes("No tab with id") || isErrorPageScriptError(error);
-}
-
-export function sleep(ms) {
-  return new Promise(resolve => setTimeout(resolve, ms));
-}
-
-export const LARGE_OPERATION_BATCH_SIZE = 25;
-export const LARGE_OPERATION_PAUSE_MS = 25;
-export const GENTLE_OPERATION_BATCH_SIZE = 8;
-export const GENTLE_OPERATION_PAUSE_MS = 100;
-
-export async function hasAudibleTabs() {
-  const audibleTabs = await chrome.tabs.query({ audible: true });
-  return audibleTabs.some(tab => !(tab.mutedInfo && tab.mutedInfo.muted));
-}
-
-let largeOperationQueue = Promise.resolve();
-
-export async function runLargeOperation(name, fn) {
-  const run = largeOperationQueue.then(async () => {
-    console.log(`[browser-cli] large operation start: ${name}`);
-    try {
-      return await fn();
-    } finally {
-      console.log(`[browser-cli] large operation done: ${name}`);
-    }
-  });
-  largeOperationQueue = run.catch(() => {});
-  return run;
-}
-
-export async function getPerformanceProfile() {
-  const { performanceProfile } = await chrome.storage.local.get("performanceProfile");
-  return performanceProfile || "auto";
-}
-
-export async function setPerformanceProfile(profile) {
-  const allowed = new Set(["auto", "normal", "gentle", "ultra"]);
-  const performanceProfile = allowed.has(profile) ? profile : "auto";
-  await chrome.storage.local.set({ performanceProfile });
-  return { performanceProfile };
-}
-
-export async function getLargeOperationThrottle(itemCount = 0, mode = "auto") {
-  const audible = await hasAudibleTabs();
-  const storedProfile = await getPerformanceProfile();
-  const configuredMode = mode && mode !== "auto" ? mode : storedProfile;
-  const gentle = configuredMode === "gentle" || configuredMode === "ultra" || (configuredMode === "auto" && audible);
-  let batchSize = gentle ? GENTLE_OPERATION_BATCH_SIZE : LARGE_OPERATION_BATCH_SIZE;
-  let pauseMs = gentle ? GENTLE_OPERATION_PAUSE_MS : LARGE_OPERATION_PAUSE_MS;
-
-  if (configuredMode === "ultra" || itemCount >= 300) {
-    batchSize = Math.max(3, Math.floor(batchSize / 2));
-    pauseMs *= 2;
-  } else if (itemCount >= 100) {
-    batchSize = Math.max(5, Math.floor(batchSize * 0.75));
-    pauseMs = Math.max(pauseMs, 75);
-  }
-
-  return { batchSize, pauseMs, gentle, audible, itemCount, mode: configuredMode };
-}
-
-export function updateJobProgress(job, { phase, current, total } = {}) {
-  if (!job) return;
-  if (phase) job.phase = phase;
-  if (total != null) job.total = total;
-  if (current != null) job.current = current;
-  if (job.total) job.percent = Math.min(100, Math.round((job.current || 0) * 100 / job.total));
-  job.updatedAt = Date.now();
-}
-
-export function throwIfJobCancelled(job) {
-  if (job?.cancelRequested) {
-    throw new Error(`Job '${job.id}' cancelled`);
-  }
-}
-
-export async function yieldForLargeOperation(processed, batchSize = LARGE_OPERATION_BATCH_SIZE, pauseMs = LARGE_OPERATION_PAUSE_MS) {
-  if (processed > 0 && processed % batchSize === 0) {
-    await sleep(pauseMs);
-  }
-}
-
-export async function executeScript(options, retries = 3) {
-  for (let i = 0; i < retries; i++) {
-    try {
-      return await chrome.scripting.executeScript(options);
-    } catch (e) {
-      if (i < retries - 1 && isTransientScriptError(e)) {
-        await sleep(300);
-        continue;
-      }
-      throw e;
-    }
-  }
-}
-
-export function tabInfo(t) {
-  return {
-    id: t.id,
-    windowId: t.windowId,
-    active: t.active,
-    muted: Boolean(t.mutedInfo && t.mutedInfo.muted),
-    groupId: t.groupId >= 0 ? t.groupId : null,
-    title: t.title,
-    url: t.url || t.pendingUrl || "",
-  };
-}
-
-// ── Groups ────────────────────────────────────────────────────────────────────
-
-export function isScriptableUrl(url) {
-  if (!url) return false;
-  return !url.startsWith("chrome://") &&
-         !url.startsWith("brave://") &&
-         !url.startsWith("about:") &&
-         !url.startsWith("edge://") &&
-         !url.startsWith("chrome-extension://");
-}
-
-export async function getActiveTab() {
-  const activeTabs = await chrome.tabs.query({ active: true });
-  if (!activeTabs.length) throw new Error("No active tab found");
-
-  const windows = await chrome.windows.getAll({ populate: false });
-  const focusedWindowIds = new Set(windows.filter(window => window.focused).map(window => window.id));
-
-  const chooseTab = (predicate) => activeTabs.find(predicate);
-  const byFocusAndScriptable = tab => focusedWindowIds.has(tab.windowId) && isScriptableUrl(tab.url || tab.pendingUrl || "");
-  const byScriptable = tab => isScriptableUrl(tab.url || tab.pendingUrl || "");
-  const byFocus = tab => focusedWindowIds.has(tab.windowId);
-
-  return chooseTab(byFocusAndScriptable)
-    || chooseTab(byScriptable)
-    || chooseTab(byFocus)
-    || activeTabs[0];
-}
-
-export async function resolveTabForDirectAction(tabId, actionName) {
-  if (tabId != null) {
-    return chrome.tabs.get(tabId);
-  }
-  const allTabs = await chrome.tabs.query({});
-  if (allTabs.length !== 1) {
-    throw new Error(
-      `Refusing to ${actionName} without explicit tab ID when ${allTabs.length} tabs are open`
-    );
-  }
-  return allTabs[0];
-}
-
-export async function resolveGroupId(nameOrId) {
-  const asInt = parseInt(nameOrId);
-  if (!isNaN(asInt)) return asInt;
-  const groups = await chrome.tabGroups.query({});
-  const match = groups.find(g => g.title && g.title.toLowerCase() === String(nameOrId).toLowerCase());
-  if (!match) throw new Error(`No tab group found with name '${nameOrId}'`);
-  return match.id;
-}
-
-export function buildTabBlocks(tabs) {
-  const blocks = [];
-  for (const tab of tabs) {
-    const normalizedGroupId = tab.groupId >= 0 ? tab.groupId : null;
-    const lastBlock = blocks[blocks.length - 1];
-    if (lastBlock?.groupId === normalizedGroupId) {
-      lastBlock.tabIds.push(tab.id);
-      lastBlock.endIndex = tab.index;
-      continue;
-    }
-
-    blocks.push({
-      groupId: normalizedGroupId,
-      startIndex: tab.index,
-      endIndex: tab.index,
-      tabIds: [tab.id],
-    });
-  }
-  return blocks;
-}
-
-export function getSessionTabs(session) {
-  if (!session) return [];
-  if (Array.isArray(session.tabs)) {
-    return session.tabs
-      .map(entry => typeof entry === "string" ? { url: entry } : entry)
-      .filter(entry => entry?.url);
-  }
-  if (Array.isArray(session.urls)) {
-    return session.urls.filter(Boolean).map(url => ({ url }));
-  }
-  return [];
-}
-
-export function normalizeGroupColor(color) {
-  const allowed = new Set(["grey", "blue", "red", "yellow", "green", "pink", "purple", "cyan", "orange"]);
-  return allowed.has(color) ? color : "grey";
-}
-
-export async function getAliases() {
-  const { windowAliases } = await chrome.storage.local.get("windowAliases");
-  return windowAliases || {};
-}
-
-export async function getSessions() {
-  const { sessions } = await chrome.storage.local.get("sessions");
-  return sessions || {};
-}
diff --git a/extension/src/core/errors.ts b/extension/src/core/errors.ts
new file mode 100644
index 0000000..38cafff
--- /dev/null
+++ b/extension/src/core/errors.ts
@@ -0,0 +1,35 @@
+// Shared error helpers for browser-cli extension command handlers.
+import type { ErrorLike } from '../types';
+
+/** Extract a human-readable message from a caught/rejected value. */
+export function getErrorMessage(error: ErrorLike): string {
+  if (typeof error === "string") return error;
+  return (error && error.message) || String(error);
+}
+
+export function isBrowserErrorUrl(url: string | null | undefined): boolean {
+  const value = String(url || "").toLowerCase();
+  return value.startsWith("chrome-error://") ||
+         value.startsWith("edge-error://") ||
+         value.startsWith("brave-error://") ||
+         value.startsWith("about:neterror") ||
+         value.startsWith("about:certerror") ||
+         value.startsWith("about:blocked") ||
+         value.startsWith("about:tabcrashed");
+}
+
+export function isErrorPageScriptError(error: ErrorLike): boolean {
+  const message = getErrorMessage(error).toLowerCase();
+  return message.includes("error page") ||
+         message.includes("chrome-error://") ||
+         message.includes("edge-error://") ||
+         message.includes("brave-error://") ||
+         message.includes("about:neterror") ||
+         message.includes("about:certerror") ||
+         message.includes("about:tabcrashed");
+}
+
+export function isTransientScriptError(error: ErrorLike): boolean {
+  const message = getErrorMessage(error);
+  return message.includes("Frame with ID") || message.includes("No tab with id") || isErrorPageScriptError(error);
+}
diff --git a/extension/src/core/group-helpers.ts b/extension/src/core/group-helpers.ts
new file mode 100644
index 0000000..22fdccb
--- /dev/null
+++ b/extension/src/core/group-helpers.ts
@@ -0,0 +1,15 @@
+// Tab-group resolution and normalization helpers.
+
+export async function resolveGroupId(nameOrId: string | number): Promise<number> {
+  const asInt = parseInt(String(nameOrId));
+  if (!isNaN(asInt)) return asInt;
+  const groups = await chrome.tabGroups.query({});
+  const match = groups.find(g => g.title && g.title.toLowerCase() === String(nameOrId).toLowerCase());
+  if (!match) throw new Error(`No tab group found with name '${nameOrId}'`);
+  return match.id;
+}
+
+export function normalizeGroupColor(color: string | undefined): chrome.tabGroups.Color {
+  const allowed = new Set(["grey", "blue", "red", "yellow", "green", "pink", "purple", "cyan", "orange"]);
+  return (allowed.has(color as string) ? color : "grey") as chrome.tabGroups.Color;
+}
diff --git a/extension/src/core/index.ts b/extension/src/core/index.ts
new file mode 100644
index 0000000..6889c97
--- /dev/null
+++ b/extension/src/core/index.ts
@@ -0,0 +1,6 @@
+export * from './errors';
+export * from './throttle';
+export * from './scripting';
+export * from './tab-helpers';
+export * from './group-helpers';
+export * from './storage';
diff --git a/extension/src/core/scripting.ts b/extension/src/core/scripting.ts
new file mode 100644
index 0000000..c5f73e2
--- /dev/null
+++ b/extension/src/core/scripting.ts
@@ -0,0 +1,23 @@
+// chrome.scripting.executeScript wrapper with transient-error retry.
+import { isTransientScriptError } from './errors';
+import { sleep } from './throttle';
+import type { Serializable } from '../types';
+
+export async function executeScript<Args extends Serializable[], Result>(
+  options: chrome.scripting.ScriptInjection<Args, Result>,
+  retries = 3,
+): Promise<chrome.scripting.InjectionResult<chrome.scripting.Awaited<Result>>[]> {
+  for (let i = 0; i < retries; i++) {
+    try {
+      return await chrome.scripting.executeScript(options);
+    } catch (e) {
+      if (i < retries - 1 && isTransientScriptError(e)) {
+        await sleep(300);
+        continue;
+      }
+      throw e;
+    }
+  }
+  // Unreachable: the loop either returns or throws on the final iteration.
+  throw new Error("executeScript: exhausted retries");
+}
diff --git a/extension/src/core/storage.ts b/extension/src/core/storage.ts
new file mode 100644
index 0000000..e1a9fc5
--- /dev/null
+++ b/extension/src/core/storage.ts
@@ -0,0 +1,30 @@
+// chrome.storage.local accessors for profile alias, window aliases, and sessions.
+import type { SessionTab, StoredSession } from '../types';
+
+export async function getProfileAlias(): Promise<string> {
+  const { profileAlias } = await chrome.storage.local.get<{ profileAlias?: string }>("profileAlias");
+  return profileAlias || "default";
+}
+
+export function getSessionTabs(session: StoredSession | undefined | null): SessionTab[] {
+  if (!session) return [];
+  if (Array.isArray(session.tabs)) {
+    return session.tabs
+      .map(entry => typeof entry === "string" ? { url: entry } : entry)
+      .filter(entry => entry?.url);
+  }
+  if (Array.isArray(session.urls)) {
+    return session.urls.filter(Boolean).map(url => ({ url }));
+  }
+  return [];
+}
+
+export async function getAliases(): Promise<Record<string, string>> {
+  const { windowAliases } = await chrome.storage.local.get<{ windowAliases?: Record<string, string> }>("windowAliases");
+  return windowAliases || {};
+}
+
+export async function getSessions(): Promise<Record<string, StoredSession>> {
+  const { sessions } = await chrome.storage.local.get<{ sessions?: Record<string, StoredSession> }>("sessions");
+  return sessions || {};
+}
diff --git a/extension/src/core/tab-helpers.ts b/extension/src/core/tab-helpers.ts
new file mode 100644
index 0000000..5cca827
--- /dev/null
+++ b/extension/src/core/tab-helpers.ts
@@ -0,0 +1,123 @@
+// Tab-related shared helpers: info shaping, scriptable-url checks, active-tab
+// resolution, and HTML fetching.
+import { isBrowserErrorUrl, isErrorPageScriptError } from './errors';
+import { executeScript } from './scripting';
+import type { TabBlock } from '../types';
+
+/**
+ * Narrow a plain id array to the non-empty-tuple shape that chrome.tabs.group /
+ * chrome.tabs.ungroup declare. The runtime happily accepts any array (including
+ * a single element); the published @types/chrome just over-constrain the param
+ * to `[number, ...number[]]`. Callers guarantee non-emptiness before calling.
+ */
+export function asTabIds(ids: number[]): [number, ...number[]] {
+  return ids as [number, ...number[]];
+}
+
+export function tabInfo(t: chrome.tabs.Tab) {
+  return {
+    id: t.id,
+    windowId: t.windowId,
+    active: t.active,
+    muted: Boolean(t.mutedInfo && t.mutedInfo.muted),
+    groupId: t.groupId >= 0 ? t.groupId : null,
+    title: t.title,
+    url: t.url || t.pendingUrl || "",
+  };
+}
+
+export function isScriptableUrl(url: string | undefined | null): boolean {
+  if (!url) return false;
+  return !url.startsWith("chrome://") &&
+         !url.startsWith("brave://") &&
+         !url.startsWith("about:") &&
+         !url.startsWith("edge://") &&
+         !url.startsWith("chrome-extension://");
+}
+
+export async function getActiveTab() {
+  const activeTabs = await chrome.tabs.query({ active: true });
+  if (!activeTabs.length) throw new Error("No active tab found");
+
+  const windows = await chrome.windows.getAll({ populate: false });
+  const focusedWindowIds = new Set(windows.filter(window => window.focused).map(window => window.id));
+
+  const chooseTab = (predicate: (tab: chrome.tabs.Tab) => boolean) => activeTabs.find(predicate);
+  const byFocusAndScriptable = (tab: chrome.tabs.Tab) => focusedWindowIds.has(tab.windowId) && isScriptableUrl(tab.url || tab.pendingUrl || "");
+  const byScriptable = (tab: chrome.tabs.Tab) => isScriptableUrl(tab.url || tab.pendingUrl || "");
+  const byFocus = (tab: chrome.tabs.Tab) => focusedWindowIds.has(tab.windowId);
+
+  return chooseTab(byFocusAndScriptable)
+    || chooseTab(byScriptable)
+    || chooseTab(byFocus)
+    || activeTabs[0];
+}
+
+/** Resolve the target tab (explicit id or the active tab) and its current URL. */
+export async function resolveTabUrl(tabId?: number | null): Promise<{ tab: chrome.tabs.Tab; url: string }> {
+  const tab = tabId ? await chrome.tabs.get(tabId) : await getActiveTab();
+  return { tab, url: tab.url || tab.pendingUrl || "" };
+}
+
+/**
+ * Throw the standard "navigate to a regular web page first" error if `url` is
+ * not scriptable. `action` is the verb phrase incl. preposition, e.g.
+ * "run DOM commands on" or "get HTML of".
+ */
+export function assertScriptableUrl(url: string, action: string): void {
+  if (!isScriptableUrl(url)) {
+    throw new Error(`Cannot ${action} ${url} — navigate to a regular web page first`);
+  }
+}
+
+export async function resolveTabForDirectAction(tabId: number | undefined | null, actionName: string): Promise<chrome.tabs.Tab> {
+  if (tabId != null) {
+    return chrome.tabs.get(tabId);
+  }
+  const allTabs = await chrome.tabs.query({});
+  if (allTabs.length !== 1) {
+    throw new Error(
+      `Refusing to ${actionName} without explicit tab ID when ${allTabs.length} tabs are open`
+    );
+  }
+  return allTabs[0];
+}
+
+export function buildTabBlocks(tabs: chrome.tabs.Tab[]): TabBlock[] {
+  const blocks: TabBlock[] = [];
+  for (const tab of tabs) {
+    const normalizedGroupId = tab.groupId >= 0 ? tab.groupId : null;
+    const lastBlock = blocks[blocks.length - 1];
+    if (lastBlock?.groupId === normalizedGroupId) {
+      lastBlock.tabIds.push(tab.id);
+      lastBlock.endIndex = tab.index;
+      continue;
+    }
+
+    blocks.push({
+      groupId: normalizedGroupId,
+      startIndex: tab.index,
+      endIndex: tab.index,
+      tabIds: [tab.id],
+    });
+  }
+  return blocks;
+}
+
+export async function fetchTabHtml(tabId?: number): Promise<string> {
+  // executeScript already retries transient frame/tab errors internally, so a
+  // single attempt here is enough — we only add error-page handling on top.
+  const { tab, url } = await resolveTabUrl(tabId);
+  if (isBrowserErrorUrl(url)) return "";
+  assertScriptableUrl(url, "get HTML of");
+  try {
+    const results = await executeScript({
+      target: { tabId: tab.id },
+      func: () => document.documentElement.outerHTML,
+    });
+    return results[0]?.result || "";
+  } catch (e) {
+    if (isErrorPageScriptError(e)) return "";
+    throw e;
+  }
+}
diff --git a/extension/src/core/throttle.ts b/extension/src/core/throttle.ts
new file mode 100644
index 0000000..4576b36
--- /dev/null
+++ b/extension/src/core/throttle.ts
@@ -0,0 +1,112 @@
+// Large-operation throttling, performance profile, and job-progress helpers.
+import type { Job, JobProgressUpdate } from '../types';
+
+export function sleep(ms: number): Promise<void> {
+  return new Promise(resolve => setTimeout(resolve, ms));
+}
+
+export const LARGE_OPERATION_BATCH_SIZE = 25;
+export const LARGE_OPERATION_PAUSE_MS = 25;
+export const GENTLE_OPERATION_BATCH_SIZE = 8;
+export const GENTLE_OPERATION_PAUSE_MS = 100;
+
+export async function hasAudibleTabs() {
+  const audibleTabs = await chrome.tabs.query({ audible: true });
+  return audibleTabs.some(tab => !(tab.mutedInfo && tab.mutedInfo.muted));
+}
+
+let largeOperationQueue: Promise<void> = Promise.resolve();
+
+export async function runLargeOperation<T>(name: string, fn: () => Promise<T>): Promise<T> {
+  const run = largeOperationQueue.then(async () => {
+    console.log(`[browser-cli] large operation start: ${name}`);
+    try {
+      return await fn();
+    } finally {
+      console.log(`[browser-cli] large operation done: ${name}`);
+    }
+  });
+  largeOperationQueue = run.then(() => {}, () => {});
+  return run;
+}
+
+export async function getPerformanceProfile() {
+  const { performanceProfile } = await chrome.storage.local.get<{ performanceProfile?: string }>("performanceProfile");
+  return performanceProfile || "auto";
+}
+
+export async function setPerformanceProfile(profile: string) {
+  const allowed = new Set(["auto", "normal", "gentle", "ultra"]);
+  const performanceProfile = allowed.has(profile) ? profile : "auto";
+  await chrome.storage.local.set({ performanceProfile });
+  return { performanceProfile };
+}
+
+export async function getLargeOperationThrottle(itemCount = 0, mode: string = "auto") {
+  const audible = await hasAudibleTabs();
+  const storedProfile = await getPerformanceProfile();
+  const configuredMode = mode && mode !== "auto" ? mode : storedProfile;
+  const gentle = configuredMode === "gentle" || configuredMode === "ultra" || (configuredMode === "auto" && audible);
+  let batchSize = gentle ? GENTLE_OPERATION_BATCH_SIZE : LARGE_OPERATION_BATCH_SIZE;
+  let pauseMs = gentle ? GENTLE_OPERATION_PAUSE_MS : LARGE_OPERATION_PAUSE_MS;
+
+  if (configuredMode === "ultra" || itemCount >= 300) {
+    batchSize = Math.max(3, Math.floor(batchSize / 2));
+    pauseMs *= 2;
+  } else if (itemCount >= 100) {
+    batchSize = Math.max(5, Math.floor(batchSize * 0.75));
+    pauseMs = Math.max(pauseMs, 75);
+  }
+
+  return { batchSize, pauseMs, gentle, audible, itemCount, mode: configuredMode };
+}
+
+export function updateJobProgress(job: Job | undefined | null, { phase, current, total }: JobProgressUpdate = {}) {
+  if (!job) return;
+  if (phase) job.phase = phase;
+  if (total != null) job.total = total;
+  if (current != null) job.current = current;
+  if (job.total) job.percent = Math.min(100, Math.round((job.current || 0) * 100 / job.total));
+  job.updatedAt = Date.now();
+}
+
+export function throwIfJobCancelled(job: Job | undefined | null) {
+  if (job?.cancelRequested) {
+    throw new Error(`Job '${job.id}' cancelled`);
+  }
+}
+
+export async function yieldForLargeOperation(processed: number, batchSize = LARGE_OPERATION_BATCH_SIZE, pauseMs = LARGE_OPERATION_PAUSE_MS) {
+  if (processed > 0 && processed % batchSize === 0) {
+    await sleep(pauseMs);
+  }
+}
+
+/**
+ * Run `handler` over `items` in throttle-sized slices, threading job progress
+ * and cancellation. Each slice is one `handler` call (so chrome batch APIs like
+ * tabs.remove get an array); between slices it reports progress and yields.
+ *
+ * `total`/`baseCurrent` let callers report against a fixed total accumulated
+ * across several calls (e.g. merging tabs from many windows). Returns the
+ * running processed count so the next call can continue from it.
+ */
+export async function processInBatches<T>(
+  items: T[],
+  throttle: { batchSize: number; pauseMs: number },
+  handler: (batch: T[]) => Promise<unknown>,
+  progress: { job?: Job | null; phase: string; total?: number; baseCurrent?: number },
+): Promise<number> {
+  const total = progress.total ?? items.length;
+  let done = progress.baseCurrent ?? 0;
+  updateJobProgress(progress.job, { phase: progress.phase, current: done, total });
+  for (let i = 0; i < items.length; i += throttle.batchSize) {
+    throwIfJobCancelled(progress.job);
+    const batch = items.slice(i, i + throttle.batchSize);
+    await handler(batch);
+    done += batch.length;
+    updateJobProgress(progress.job, { phase: progress.phase, current: done, total });
+    await yieldForLargeOperation(done, throttle.batchSize, throttle.pauseMs);
+  }
+  return done;
+}
diff --git a/extension/src/index.ts b/extension/src/index.ts
index 904ffc8..36f5c13 100644
--- a/extension/src/index.ts
+++ b/extension/src/index.ts
@@ -1,365 +1,23 @@
-// @ts-nocheck
 /**
  * browser-cli Extension — Background Service Worker
  *
  * Connects to the native host (com.browsercli.host) via Native Messaging.
+ * Thin wiring entry point: build the job manager + command registry, then start
+ * the native connection.
  */
 
-import { getLargeOperationThrottle, getPerformanceProfile, hasAudibleTabs, setPerformanceProfile, getProfileAlias } from './core';
-import * as nav from './commands/navigation';
-import * as tabs from './commands/tabs';
-import * as groups from './commands/groups';
-import * as windowsCmd from './commands/windows';
-import * as dom from './commands/dom';
-import * as browserData from './commands/browser-data';
-import * as session from './commands/session';
+import { JobManager } from './classes/JobManager';
+import { assembleRegistry } from './classes/CommandRegistry';
+import { NativeConnection } from './classes/NativeConnection';
+import type { CommandContext } from './classes/CommandGroup';
 
-const NATIVE_HOST = "com.browsercli.host";
-let port = null;
-let keepaliveEnabled = true;
-const jobs = new Map();
-const BACKGROUND_COMMANDS = new Set([
-  "session.load",
-  "tabs.close",
-  "tabs.dedupe",
-  "tabs.sort",
-  "tabs.merge_windows",
-  "group.close",
-]);
-
-// ── Connection management ─────────────────────────────────────────────────────
-function sendControlMessage(targetPort, message) {
-  if (!targetPort) return;
-  try {
-    targetPort.postMessage(message);
-  } catch (e) {
-    console.warn("[browser-cli] Failed to send control message:", e);
-  }
-}
-
-function disconnectPort({ sendBye = false } = {}) {
-  const currentPort = port;
-  if (!currentPort) return;
-
-  if (sendBye) sendControlMessage(currentPort, { type: "bye" });
-
-  if (port === currentPort) port = null;
-
-  try {
-    currentPort.disconnect();
-  } catch (e) {
-    console.warn("[browser-cli] Failed to disconnect native port:", e);
-  }
-}
-async function connect() {
-  if (port || !keepaliveEnabled) return;
-  try {
-    const nativePort = chrome.runtime.connectNative(NATIVE_HOST);
-    port = nativePort;
-    nativePort.onMessage.addListener(onMessage);
-    nativePort.onDisconnect.addListener(() => {
-      if (port === nativePort) port = null;
-      const err = chrome.runtime.lastError;
-      if (err) console.warn("[browser-cli] Native host disconnected:", err.message);
-    });
-    // Send hello so native host knows which profile/alias this is
-    const alias = await getProfileAlias();
-    nativePort.postMessage({ type: "hello", alias });
-    console.log("[browser-cli] Connected to native host as profile:", alias);
-  } catch (e) {
-    port = null;
-    console.error("[browser-cli] Failed to connect:", e);
-  }
-}
-
-chrome.runtime.onInstalled.addListener(connect);
-chrome.runtime.onStartup.addListener(connect);
-chrome.runtime.onSuspend.addListener(() => {
-  disconnectPort({ sendBye: true });
-});
-chrome.windows.onCreated.addListener(() => {
-  keepaliveEnabled = true;
-  if (!port) connect();
-});
-chrome.windows.onRemoved.addListener(async () => {
-  const windows = await chrome.windows.getAll({});
-  if (windows.length > 0) return;
-
-  keepaliveEnabled = false;
-  disconnectPort({ sendBye: true });
-});
-
-// Keepalive alarm — prevents service worker suspension and reconnects if needed
-chrome.alarms.create("keepalive", { periodInMinutes: 0.4 });
-chrome.alarms.onAlarm.addListener((alarm) => {
-  if (alarm.name === "keepalive") {
-    if (!port && keepaliveEnabled) connect();
-  }
-});
+const jobs = new JobManager();
+const ctx: CommandContext = { jobs };
+const { registry, session } = assembleRegistry(ctx);
 
 chrome.tabs.onActivated.addListener(async ({ tabId }) => {
   await session.activateLazyTab(tabId);
 });
 
-// ── Message dispatcher ────────────────────────────────────────────────────────
-
-async function onMessage(msg) {
-  const { id, command, args } = msg;
-  if (!id || !command) return;
-
-  console.log("[browser-cli] ←", command, args);
-
-  let data, error;
-  try {
-    const { __page, __background, ...commandArgs } = args || {};
-    if (__background && BACKGROUND_COMMANDS.has(command)) {
-      data = await startBackgroundJob(command, commandArgs);
-    } else {
-      data = await dispatch(command, commandArgs);
-      if (__page && Array.isArray(data)) {
-        data = makePagedData(data, __page);
-      }
-    }
-  } catch (e) {
-    error = e.message || String(e);
-  }
-
-  if (error !== undefined) {
-    console.log("[browser-cli] → ERROR", command, error);
-    port.postMessage({ id, success: false, error });
-  } else {
-    console.log("[browser-cli] →", command, data);
-    port.postMessage({ id, success: true, data });
-  }
-
-  if (command === "clients.rename_profile" && error === undefined) {
-    disconnectPort({ sendBye: true });
-    keepaliveEnabled = true;
-    await connect();
-  }
-}
-async function persistJobs() {
-  const recentJobs = [...jobs.values()].slice(-50).map(job => ({ ...job, __timer: undefined }));
-  await chrome.storage.local.set({ recentJobs });
-}
-
-async function startBackgroundJob(command, args) {
-  const jobId = `${Date.now().toString(36)}-${Math.random().toString(36).slice(2, 10)}`;
-  const job = {
-    id: jobId,
-    command,
-    status: "running",
-    phase: "queued",
-    current: 0,
-    total: null,
-    percent: 0,
-    cancelRequested: false,
-    startedAt: Date.now(),
-    updatedAt: Date.now(),
-    finishedAt: null,
-    result: null,
-    error: null,
-  };
-  jobs.set(jobId, job);
-  job.__timer = setInterval(persistJobs, 1000);
-  await persistJobs();
-  dispatch(command, { ...args, __job: job })
-    .then(async result => {
-      job.status = "done";
-      job.phase = "done";
-      job.result = result;
-      job.current = job.total || job.current;
-      job.percent = 100;
-      job.finishedAt = Date.now();
-      job.updatedAt = Date.now();
-      if (job.__timer) clearInterval(job.__timer);
-      await persistJobs();
-    })
-    .catch(async error => {
-      job.status = job.cancelRequested ? "cancelled" : "error";
-      job.phase = job.status;
-      job.error = error?.message || String(error);
-      job.finishedAt = Date.now();
-      job.updatedAt = Date.now();
-      if (job.__timer) clearInterval(job.__timer);
-      await persistJobs();
-    });
-  return { jobId, command, status: job.status };
-}
-
-async function jobStatus({ jobId }) {
-  const job = jobs.get(jobId);
-  if (job) return { ...job };
-  const { recentJobs } = await chrome.storage.local.get("recentJobs");
-  const stored = (recentJobs || []).find(entry => entry.id === jobId);
-  if (!stored) throw new Error(`Job '${jobId}' not found`);
-  return stored;
-}
-
-async function jobCancel({ jobId }) {
-  const job = jobs.get(jobId);
-  if (!job) throw new Error(`Job '${jobId}' not running`);
-  job.cancelRequested = true;
-  job.updatedAt = Date.now();
-  await persistJobs();
-  return { jobId, cancelled: true };
-}
-
-async function perfStatus() {
-  const profile = await getPerformanceProfile();
-  const audible = await hasAudibleTabs();
-  const throttle = await getLargeOperationThrottle(0, "auto");
-  return {
-    performanceProfile: profile,
-    audible,
-    throttle,
-    jobs: [...jobs.values()].map(job => ({
-      id: job.id,
-      command: job.command,
-      status: job.status,
-      phase: job.phase,
-      current: job.current,
-      total: job.total,
-      percent: job.percent,
-      cancelRequested: job.cancelRequested,
-    })),
-  };
-}
-
-function makePagedData(items, page) {
-  const total = items.length;
-  const offset = Math.max(0, Number(page.offset) || 0);
-  const requestedLimit = Math.max(1, Number(page.limit) || 100);
-  const limit = Math.min(requestedLimit, 1000);
-  const end = Math.min(offset + limit, total);
-  return {
-    __browserCliPage: true,
-    items: items.slice(offset, end),
-    offset,
-    limit,
-    total,
-    nextOffset: end < total ? end : null,
-  };
-}
-async function dispatch(command, args) {
-  switch (command) {
-    // ── Navigation ────────────────────────────────────────────────────────
-    case "navigate.open":    return nav.navOpen(args);
-    case "navigate.to":      return nav.navTo(args);
-    case "navigate.reload":  return nav.navReload(args, false);
-    case "navigate.hard_reload": return nav.navReload(args, true);
-    case "navigate.back":    return nav.navBack(args);
-    case "navigate.forward": return nav.navForward(args);
-    case "navigate.focus":   return nav.navFocus(args);
-    case "navigate.wait":      return nav.navWait(args);
-    case "navigate.open_wait": return nav.navOpenWait(args);
-
-    // ── Tabs ──────────────────────────────────────────────────────────────
-    case "tabs.list":         return tabs.tabsList();
-    case "tabs.close":        return tabs.tabsClose(args);
-    case "tabs.move":         return tabs.tabsMove(args);
-    case "tabs.active":       return tabs.tabsActive(args);
-    case "tabs.active_in_window": return tabs.tabsActiveInWindow(args);
-    case "tabs.status":       return tabs.tabsStatus(args);
-    case "tabs.filter":       return tabs.tabsFilter(args);
-    case "tabs.count":        return tabs.tabsCount(args);
-    case "tabs.query":        return tabs.tabsQuery(args);
-    case "tabs.html":         return tabs.tabsHtml(args);
-    case "tabs.dedupe":       return tabs.tabsDedupe(args);
-    case "tabs.sort":         return tabs.tabsSort(args);
-    case "tabs.merge_windows": return tabs.tabsMergeWindows(args);
-    case "tabs.mute":         return tabs.tabsMute(args);
-    case "tabs.unmute":       return tabs.tabsUnmute(args);
-    case "tabs.pin":          return tabs.tabsPin(args);
-    case "tabs.unpin":        return tabs.tabsUnpin(args);
-    case "tabs.screenshot":   return tabs.tabsScreenshot(args);
-    case "tabs.watch_url":    return tabs.tabsWatchUrl(args);
-
-    // ── Groups ────────────────────────────────────────────────────────────
-    case "group.list":   return groups.groupList();
-    case "group.tabs":   return groups.groupTabs(args);
-    case "group.count":  return groups.groupCount();
-    case "group.query":  return groups.groupQuery(args);
-    case "group.close":   return groups.groupClose(args);
-    case "group.open":    return groups.groupOpen(args);
-    case "group.add_tab": return groups.groupAddTab(args);
-    case "group.move":    return groups.groupMove(args);
-
-    // ── Windows ───────────────────────────────────────────────────────────
-    case "windows.list":   return windowsCmd.windowsList();
-    case "windows.rename": return windowsCmd.windowsRename(args);
-    case "windows.close":  return windowsCmd.windowsClose(args);
-    case "windows.open":   return windowsCmd.windowsOpen(args);
-
-    // ── DOM ───────────────────────────────────────────────────────────────
-    case "dom.query":    return dom.domOp("domQuery",    args);
-    case "dom.click":    return dom.domOp("domClick",    args);
-    case "dom.type":     return dom.domOp("domType",     args);
-    case "dom.attr":     return dom.domOp("domAttr",     args);
-    case "dom.text":     return dom.domOp("domText",     args);
-    case "dom.exists":   return dom.domOp("domExists",   args);
-    case "dom.scroll":   return dom.domOp("domScroll",   args);
-    case "dom.select":   return dom.domOp("domSelect",   args);
-    case "dom.key":      return dom.domOp("domKey",      args);
-    case "dom.hover":    return dom.domOp("domHover",    args);
-    case "dom.check":    return dom.domOp("domCheck",    { ...args, checked: true });
-    case "dom.uncheck":  return dom.domOp("domCheck",    { ...args, checked: false });
-    case "dom.clear":    return dom.domOp("domClear",    args);
-    case "dom.focus":    return dom.domOp("domFocus",    args);
-    case "dom.submit":   return dom.domOp("domSubmit",   args);
-    case "dom.eval":     return dom.domEval(args);
-    case "dom.wait_for": return dom.domWaitFor(args);
-    case "dom.poll":     return dom.domPoll(args);
-
-    // ── Page ──────────────────────────────────────────────────────────────
-    case "page.info":    return dom.domOp("pageInfo", {});
-
-    // ── Storage ───────────────────────────────────────────────────────────
-    case "storage.get":  return browserData.storageGet(args);
-    case "storage.set":  return browserData.storageSet(args);
-
-    // ── Cookies ───────────────────────────────────────────────────────────
-    case "cookies.list": return browserData.cookiesList(args);
-    case "cookies.get":  return browserData.cookiesGet(args);
-    case "cookies.set":  return browserData.cookiesSet(args);
-
-    // ── Extract ───────────────────────────────────────────────────────────
-    case "extract.links":  return dom.domOp("extractLinks",  args);
-    case "extract.images": return dom.domOp("extractImages", args);
-    case "extract.text":   return dom.domOp("extractText",   args);
-    case "extract.json":   return dom.domOp("extractJson",   args);
-    case "extract.markdown": return dom.domOp("extractMarkdown", args);
-    case "extract.html":   return tabs.tabsHtml({});
-
-    // ── Session ───────────────────────────────────────────────────────────
-    case "session.save":      return session.sessionSave(args);
-    case "session.load":      return session.sessionLoad(args);
-    case "session.list":      return session.sessionList();
-    case "session.remove":    return session.sessionRemove(args);
-    case "session.diff":      return session.sessionDiff(args);
-    case "session.auto_save": return session.sessionAutoSave(args);
-
-    // ── Jobs ──────────────────────────────────────────────────────────────
-    case "jobs.status": return jobStatus(args);
-    case "jobs.cancel": return jobCancel(args);
-
-    // ── Performance ───────────────────────────────────────────────────────
-    case "perf.status": return perfStatus();
-    case "perf.set_profile": return setPerformanceProfile(args.profile);
-
-    // ── Extension ─────────────────────────────────────────────────────────
-    case "extension.reload": {
-      setTimeout(() => chrome.runtime.reload(), 200);
-      return { reloading: true };
-    }
-
-    // ── Misc ──────────────────────────────────────────────────────────────
-    case "clients.list":           return session.clientsList();
-    case "clients.rename_profile": return session.clientsRenameProfile(args);
-
-    default:
-      throw new Error(`Unknown command: ${command}`);
-  }
-}
-
-// ── Navigation ────────────────────────────────────────────────────────────────
+const connection = new NativeConnection(registry, session);
+connection.start();
diff --git a/extension/src/types/command-args.ts b/extension/src/types/command-args.ts
new file mode 100644
index 0000000..1ed9e1e
--- /dev/null
+++ b/extension/src/types/command-args.ts
@@ -0,0 +1,106 @@
+import type { Json } from './json';
+import type { Job } from './jobs';
+
+// ── Navigation ────────────────────────────────────────────────────────────────
+export interface NavOpenArgs {
+  url?: string;
+  background?: boolean;
+  window?: string;
+  windowId?: number;
+  group?: string | number;
+}
+
+export interface NavToArgs { tabId?: number; url?: string; }
+export interface NavTabArgs { tabId?: number; }
+export interface NavFocusArgs { pattern?: string; }
+export interface NavWaitArgs { tabId?: number; timeout?: number; readyState?: string; }
+export interface NavOpenWaitArgs {
+  url?: string;
+  timeout?: number;
+  background?: boolean;
+  window?: string;
+  group?: string | number;
+}
+
+// ── Tabs ──────────────────────────────────────────────────────────────────────
+export interface TabsCloseArgs { tabId?: number; inactive?: boolean; duplicates?: boolean; gentleMode?: string; __job?: Job; }
+export interface TabsMoveArgs { tabId?: number; groupId?: number; windowId?: number; index?: number; forward?: boolean; backward?: boolean; }
+export interface TabIdArgs { tabId?: number; }
+export interface TabsActiveInWindowArgs { windowId?: number; }
+export interface TabsPatternArgs { pattern?: string; }
+export interface TabsQueryArgs { search?: string; }
+export interface TabsSortArgs { by?: string; gentleMode?: string; __job?: Job; }
+export interface TabsMergeWindowsArgs { gentleMode?: string; __job?: Job; }
+export interface TabsScreenshotArgs { tabId?: number; format?: string; quality?: number; }
+export interface TabsWatchUrlArgs { pattern?: string; timeout?: number; tabId?: number; }
+
+// ── Groups ──────────────────────────────────────────────────────────────────────
+export interface GroupTabsArgs { groupId?: number; }
+export interface GroupQueryArgs { search?: string; }
+export interface GroupCloseArgs { groupId?: number; gentleMode?: string; __job?: Job; }
+export interface GroupOpenArgs { name?: string; }
+export interface GroupAddTabArgs { group?: string | number; url?: string; }
+export interface GroupMoveArgs { group?: string | number; forward?: boolean; backward?: boolean; }
+
+// ── Windows ─────────────────────────────────────────────────────────────────────
+export interface WindowsRenameArgs { windowId?: number; name?: string; }
+export interface WindowsCloseArgs { windowId?: number; }
+export interface WindowsOpenArgs { url?: string; }
+
+// ── DOM ─────────────────────────────────────────────────────────────────────────
+export interface DomEvalArgs { code?: string; tabId?: number; }
+export interface DomWaitForArgs { selector?: string; timeout?: number; visible?: boolean; hidden?: boolean; tabId?: number; }
+export interface DomPollArgs { selector?: string; pattern?: string; attr?: string; timeout?: number; interval?: number; tabId?: number; }
+
+/** Arguments forwarded to the in-page content functions over chrome.scripting. */
+export interface ContentArgs {
+  selector?: string;
+  text?: string;
+  attr?: string;
+  key?: string;
+  checked?: boolean;
+  value?: string;
+  x?: number;
+  y?: number;
+}
+
+/** A content-function arg set targeting a specific tab (defaults to active). */
+export type DomArgs = ContentArgs & { tabId?: number };
+
+// ── Browser data ────────────────────────────────────────────────────────────────
+export interface StorageGetArgs { key?: string; type?: string; tabId?: number; }
+export interface StorageSetArgs { key?: string; value?: Json; type?: string; tabId?: number; }
+export interface CookiesListArgs { url?: string; domain?: string; name?: string; }
+export interface CookiesGetArgs { url?: string; name?: string; }
+export interface CookiesSetArgs {
+  url?: string;
+  name?: string;
+  value?: string;
+  domain?: string;
+  path?: string;
+  secure?: boolean;
+  httpOnly?: boolean;
+  expirationDate?: number;
+  sameSite?: `${chrome.cookies.SameSiteStatus}`;
+}
+
+// ── Session ─────────────────────────────────────────────────────────────────────
+export interface SessionSaveArgs { name?: string; }
+export interface SessionRemoveArgs { name?: string; }
+export interface SessionDiffArgs { nameA?: string; nameB?: string; }
+export interface SessionLoadArgs {
+  name?: string;
+  gentleMode?: string;
+  discardBackgroundTabs?: boolean;
+  lazy?: boolean;
+  eagerTabs?: number;
+  __job?: Job;
+}
+export interface SessionAutoSaveArgs { enabled?: boolean; }
+export interface ClientsRenameProfileArgs { alias?: string; }
+
+// ── Jobs ──────────────────────────────────────────────────────────────────────
+export interface JobIdArgs { jobId?: string; }
+
+// ── Performance ───────────────────────────────────────────────────────────────
+export interface PerfSetProfileArgs { profile?: Json; }
diff --git a/extension/src/types/index.ts b/extension/src/types/index.ts
new file mode 100644
index 0000000..6564de8
--- /dev/null
+++ b/extension/src/types/index.ts
@@ -0,0 +1,6 @@
+export * from './json';
+export * from './jobs';
+export * from './session';
+export * from './tabs';
+export * from './messages';
+export * from './command-args';
diff --git a/extension/src/types/jobs.ts b/extension/src/types/jobs.ts
new file mode 100644
index 0000000..d33cee6
--- /dev/null
+++ b/extension/src/types/jobs.ts
@@ -0,0 +1,28 @@
+import type { Serializable } from './json';
+
+/** A background job tracked by the service worker. */
+export interface Job {
+  id: string;
+  command: string;
+  status: string;
+  phase: string;
+  current: number;
+  total: number | null;
+  percent: number;
+  cancelRequested: boolean;
+  startedAt: number;
+  updatedAt: number;
+  finishedAt: number | null;
+  result: Serializable;
+  error: string | null;
+  /** Handle of the persistence interval; cleared when the job finishes/evicts. */
+  __timer?: ReturnType<typeof setInterval> | null;
+  /** Handle of the watchdog timeout; clears the persist timer if the runner hangs. */
+  __watchdog?: ReturnType<typeof setTimeout> | null;
+}
+
+export interface JobProgressUpdate {
+  phase?: string;
+  current?: number;
+  total?: number | null;
+}
diff --git a/extension/src/types/json.ts b/extension/src/types/json.ts
new file mode 100644
index 0000000..11f0bc0
--- /dev/null
+++ b/extension/src/types/json.ts
@@ -0,0 +1,23 @@
+// Core JSON / IPC value types shared across the extension.
+
+/** Any JSON value as sent/received over the native-messaging IPC. */
+export type Json = string | number | boolean | null | Json[] | { [key: string]: Json };
+
+/**
+ * The deserialized IPC argument dictionary. Concrete index-signature type
+ * (no `any`): individual handlers narrow it to their own arg interface at the
+ * dispatch boundary.
+ */
+export type CommandArgs = { [key: string]: Json | undefined };
+
+/**
+ * Anything a command handler returns or that is passed as a script argument:
+ * a JSON primitive or some object/array. `object` (not `any`) is deliberate —
+ * it accepts arrays and named interfaces (e.g. chrome's Cookie/TabGroup, Job)
+ * which a recursive index-signature type cannot, while still excluding
+ * primitives-as-properties and forbidding unchecked property access.
+ */
+export type Serializable = string | number | boolean | null | undefined | object;
+
+/** Realistic shapes a thrown value can take (JS can throw anything). */
+export type ErrorLike = Error | string | { message?: string } | null | undefined;
diff --git a/extension/src/types/messages.ts b/extension/src/types/messages.ts
new file mode 100644
index 0000000..1ccedfb
--- /dev/null
+++ b/extension/src/types/messages.ts
@@ -0,0 +1,27 @@
+import type { Json, CommandArgs, Serializable } from './json';
+import type { Job } from './jobs';
+
+/** Control message sent over the native port (hello/bye/etc.). */
+export interface ControlMessage { type: string; alias?: string }
+
+/** Reply to a command, correlated to the request via `id`. */
+export interface ResponseMessage {
+  id: string;
+  success: boolean;
+  data?: Serializable;
+  error?: string;
+}
+
+/** A message received from the native host over the port. */
+export interface IncomingMessage {
+  id?: string;
+  command?: string;
+  args?: CommandArgs;
+}
+
+/** Pagination request threaded through via the internal `__page` arg. */
+export interface PageRequest { offset?: number; limit?: number; }
+
+// Args as seen by dispatch: the deserialized IPC dictionary, plus the optional
+// internal `__job` handle that background commands thread through for progress.
+export type DispatchArgs = { [key: string]: Json | Job | undefined; __job?: Job };
diff --git a/extension/src/types/session.ts b/extension/src/types/session.ts
new file mode 100644
index 0000000..ed71e5f
--- /dev/null
+++ b/extension/src/types/session.ts
@@ -0,0 +1,21 @@
+/** A tab entry stored inside a saved session. */
+export interface SessionTabGroup {
+  key?: string;
+  title?: string;
+  color?: string;
+  collapsed?: boolean;
+}
+export interface SessionTab {
+  url: string;
+  pinned?: boolean;
+  group?: SessionTabGroup;
+}
+export interface StoredSession {
+  tabs?: Array<SessionTab | string>;
+  urls?: string[];
+  savedAt?: number;
+  signature?: string;
+}
+
+export interface LazyTabEntry { url: string; createdAt: number; }
+export type LazySessionMap = Record<string, LazyTabEntry>;
diff --git a/extension/src/types/tabs.ts b/extension/src/types/tabs.ts
new file mode 100644
index 0000000..c3d1f4c
--- /dev/null
+++ b/extension/src/types/tabs.ts
@@ -0,0 +1,6 @@
+export interface TabBlock {
+  groupId: number | null;
+  startIndex: number;
+  endIndex: number;
+  tabIds: number[];
+}
diff --git a/extension/test/autosave.test.ts b/extension/test/autosave.test.ts
new file mode 100644
index 0000000..9b01da7
--- /dev/null
+++ b/extension/test/autosave.test.ts
@@ -0,0 +1,127 @@
+// @ts-nocheck
+import { describe, it, beforeEach, afterEach, mock } from 'node:test';
+import assert from 'node:assert/strict';
+import { makeChromeMock } from './chrome-mock';
+import { AutoSaveManager } from '../src/commands/autosave';
+
+let chromeMock;
+let session;
+
+// Flush pending microtasks/promise chains after advancing fake timers.
+// setImmediate stays real (only setTimeout is mocked), so it yields a
+// macrotask boundary that drains the microtask queue between iterations.
+async function drain() {
+  for (let i = 0; i < 10; i++) await new Promise(r => setImmediate(r));
+}
+async function tick(ms) {
+  mock.timers.tick(ms);
+  await drain();
+}
+
+beforeEach(() => {
+  chromeMock = makeChromeMock();
+  globalThis.chrome = chromeMock;
+  mock.timers.enable({ apis: ['setTimeout'] });
+  session = new AutoSaveManager();
+});
+
+afterEach(async () => {
+  // Clear any pending debounce timer + instance state before tearing down timers.
+  await session.setEnabled(false);
+  await drain();
+  mock.timers.reset();
+  delete globalThis.chrome;
+});
+
+const TAB_EVENTS = ['onCreated', 'onRemoved', 'onMoved', 'onAttached', 'onDetached'];
+
+describe('sessionAutoSave listener wiring', () => {
+  it('registers a handler on every tab mutation event + tabGroups when enabled', async () => {
+    await session.setEnabled(true);
+    for (const ev of TAB_EVENTS) {
+      assert.equal(chromeMock.tabs[ev]._size(), 1, `tabs.${ev}`);
+    }
+    assert.equal(chromeMock.tabs.onUpdated._size(), 1);
+    assert.equal(chromeMock.tabGroups.onUpdated._size(), 1);
+  });
+
+  it('removes all listeners when disabled (no leaked subscriptions)', async () => {
+    await session.setEnabled(true);
+    await session.setEnabled(false);
+    for (const ev of TAB_EVENTS) {
+      assert.equal(chromeMock.tabs[ev]._size(), 0, `tabs.${ev}`);
+    }
+    assert.equal(chromeMock.tabs.onUpdated._size(), 0);
+    assert.equal(chromeMock.tabGroups.onUpdated._size(), 0);
+  });
+
+  it('does not double-register when enabled twice', async () => {
+    await session.setEnabled(true);
+    await session.setEnabled(true);
+    for (const ev of TAB_EVENTS) {
+      assert.equal(chromeMock.tabs[ev]._size(), 1, `tabs.${ev}`);
+    }
+  });
+});
+
+describe('autosave debounce / coalescing', () => {
+  it('collapses a burst of tab events into a single snapshot+save', async () => {
+    await session.setEnabled(true);
+    chromeMock.tabs.query.mock.resetCalls();
+
+    // Simulate rapidly opening/closing several tabs.
+    await session.autoSaveHandler();
+    await session.autoSaveHandler();
+    await session.autoSaveHandler();
+    await session.autoSaveHandler();
+
+    // Nothing should have run yet — still inside the debounce window.
+    assert.equal(chromeMock.tabs.query.mock.callCount(), 0);
+
+    await tick(3000);
+
+    // The whole burst produced exactly one snapshot read.
+    assert.equal(chromeMock.tabs.query.mock.callCount(), 1);
+  });
+
+  it('does not fire before the (raised) 3s debounce window elapses', async () => {
+    await session.setEnabled(true);
+    chromeMock.tabs.query.mock.resetCalls();
+
+    await session.autoSaveHandler();
+    await tick(2999);
+    assert.equal(chromeMock.tabs.query.mock.callCount(), 0);
+
+    await tick(1);
+    assert.equal(chromeMock.tabs.query.mock.callCount(), 1);
+  });
+
+  it('ignores tab updates that do not change the URL (no save scheduled)', async () => {
+    await session.setEnabled(true);
+    chromeMock.tabs.query.mock.resetCalls();
+
+    // status/favicon/title churn — not a URL change.
+    await session.autoSaveUpdatedHandler(1, { status: 'loading' });
+    await session.autoSaveUpdatedHandler(1, { favIconUrl: 'x' });
+    await session.autoSaveUpdatedHandler(1, { title: 'y' });
+
+    await tick(3000);
+    assert.equal(chromeMock.tabs.query.mock.callCount(), 0);
+  });
+
+  it('schedules a save when a URL change is observed', async () => {
+    await session.setEnabled(true);
+    chromeMock.tabs.query.mock.resetCalls();
+
+    await session.autoSaveUpdatedHandler(1, { url: 'https://example.com' });
+    await tick(3000);
+    assert.equal(chromeMock.tabs.query.mock.callCount(), 1);
+  });
+
+  it('does nothing when autosave is disabled even if a handler fires', async () => {
+    // Never enabled: storage has no autoSave flag.
+    await session.autoSaveHandler();
+    await tick(3000);
+    assert.equal(chromeMock.tabs.query.mock.callCount(), 0);
+  });
+});
diff --git a/extension/test/chrome-mock.ts b/extension/test/chrome-mock.ts
new file mode 100644
index 0000000..61bd2bc
--- /dev/null
+++ b/extension/test/chrome-mock.ts
@@ -0,0 +1,55 @@
+// @ts-nocheck
+import { mock } from 'node:test';
+
+/**
+ * Minimal in-memory chrome.* stub for service-worker unit tests.
+ * Only the surface the tested modules touch is implemented.
+ * Mock functions use node:test's `mock.fn` (callCount/resetCalls via `.mock`).
+ */
+export function makeChromeMock() {
+  const store: Record<string, any> = {};
+  const listeners = new Map<string, Set<Function>>();
+
+  function event(name: string) {
+    if (!listeners.has(name)) listeners.set(name, new Set());
+    const set = listeners.get(name)!;
+    return {
+      addListener: (fn: Function) => set.add(fn),
+      removeListener: (fn: Function) => set.delete(fn),
+      hasListener: (fn: Function) => set.has(fn),
+      // test helper: count registered listeners
+      _size: () => set.size,
+    };
+  }
+
+  return {
+    storage: {
+      local: {
+        get: mock.fn(async (key: string | string[]) => {
+          const keys = Array.isArray(key) ? key : [key];
+          const out: Record<string, any> = {};
+          for (const k of keys) if (k in store) out[k] = store[k];
+          return out;
+        }),
+        set: mock.fn(async (obj: Record<string, any>) => {
+          Object.assign(store, obj);
+        }),
+        _store: store,
+      },
+    },
+    tabs: {
+      query: mock.fn(async () => []),
+      onCreated: event('tabs.onCreated'),
+      onRemoved: event('tabs.onRemoved'),
+      onMoved: event('tabs.onMoved'),
+      onAttached: event('tabs.onAttached'),
+      onDetached: event('tabs.onDetached'),
+      onUpdated: event('tabs.onUpdated'),
+    },
+    tabGroups: {
+      query: mock.fn(async () => []),
+      onUpdated: event('tabGroups.onUpdated'),
+    },
+    _event: event,
+  };
+}
diff --git a/extension/test/jobs.test.ts b/extension/test/jobs.test.ts
new file mode 100644
index 0000000..f5b8dac
--- /dev/null
+++ b/extension/test/jobs.test.ts
@@ -0,0 +1,146 @@
+// @ts-nocheck
+import { test, mock } from 'node:test';
+import assert from 'node:assert/strict';
+import { JobManager, JOB_TIMEOUT_MS, MAX_FINISHED_JOBS, pruneFinishedJobs } from '../src/classes/JobManager';
+import { makeChromeMock } from './chrome-mock';
+
+// Drain pending microtasks (finalize() chains several awaits). setImmediate is
+// never mocked here, so it fires after the current microtask queue is empty.
+const flush = () => new Promise(r => setImmediate(r));
+
+function makeJobs(specs) {
+  const map = new Map();
+  for (const s of specs) map.set(s.id, { __timer: null, ...s });
+  return map;
+}
+
+test('pruneFinishedJobs: keeps everything when under the cap', () => {
+  const jobs = makeJobs([
+    { id: 'a', status: 'done', finishedAt: 1 },
+    { id: 'b', status: 'done', finishedAt: 2 },
+  ]);
+  const evicted = pruneFinishedJobs(jobs, 5);
+  assert.deepEqual(evicted, []);
+  assert.equal(jobs.size, 2);
+});
+
+test('pruneFinishedJobs: evicts the oldest finished jobs beyond the cap', () => {
+  const jobs = makeJobs([
+    { id: 'old', status: 'done', finishedAt: 10 },
+    { id: 'mid', status: 'error', finishedAt: 20 },
+    { id: 'new', status: 'done', finishedAt: 30 },
+  ]);
+  const evicted = pruneFinishedJobs(jobs, 2);
+  assert.deepEqual(evicted, ['old']);
+  assert.deepEqual([...jobs.keys()], ['mid', 'new']);
+});
+
+test('pruneFinishedJobs: never evicts running jobs, even past the cap', () => {
+  const jobs = makeJobs([
+    { id: 'run1', status: 'running' },
+    { id: 'run2', status: 'running' },
+    { id: 'f1', status: 'done', finishedAt: 1 },
+    { id: 'f2', status: 'done', finishedAt: 2 },
+    { id: 'f3', status: 'done', finishedAt: 3 },
+  ]);
+  pruneFinishedJobs(jobs, 1);
+  // both running kept; only newest finished (f3) kept
+  assert.deepEqual([...jobs.keys()].sort(), ['f3', 'run1', 'run2']);
+});
+
+test('pruneFinishedJobs: clears the timer of every evicted job (no interval leak)', () => {
+  const clear = mock.fn();
+  const jobs = makeJobs([
+    { id: 'a', status: 'done', finishedAt: 1, __timer: 101 },
+    { id: 'b', status: 'done', finishedAt: 2, __timer: 102 },
+    { id: 'c', status: 'done', finishedAt: 3, __timer: 103 },
+  ]);
+  pruneFinishedJobs(jobs, 1, clear);
+  const clearedArgs = clear.mock.calls.map(c => c.arguments[0]);
+  assert.ok(clearedArgs.includes(101));
+  assert.ok(clearedArgs.includes(102));
+  assert.ok(!clearedArgs.includes(103)); // surviving job's timer untouched
+});
+
+test('pruneFinishedJobs: treats missing finishedAt as oldest (evicted first)', () => {
+  const jobs = makeJobs([
+    { id: 'nofin', status: 'done' },
+    { id: 'has', status: 'done', finishedAt: 5 },
+  ]);
+  pruneFinishedJobs(jobs, 1);
+  assert.deepEqual([...jobs.keys()], ['has']);
+});
+
+test('pruneFinishedJobs: defaults to MAX_FINISHED_JOBS and bounds the retained set', () => {
+  const specs = Array.from({ length: MAX_FINISHED_JOBS + 25 }, (_, i) => ({
+    id: `j${i}`, status: 'done', finishedAt: i,
+  }));
+  const jobs = makeJobs(specs);
+  pruneFinishedJobs(jobs);
+  assert.equal(jobs.size, MAX_FINISHED_JOBS);
+  // the 25 oldest (j0..j24) are gone; newest survive
+  assert.equal(jobs.has('j0'), false);
+  assert.equal(jobs.has('j24'), false);
+  assert.equal(jobs.has('j25'), true);
+});
+
+test('JobManager: a resolving runner finishes the job and clears its timers', async () => {
+  globalThis.chrome = makeChromeMock();
+  const mgr = new JobManager();
+  const { jobId } = await mgr.start('demo', {}, async () => ({ ok: 1 }));
+  await flush();
+  const job = await mgr.status({ jobId });
+  assert.equal(job.status, 'done');
+  assert.deepEqual(job.result, { ok: 1 });
+  assert.equal(job.percent, 100);
+  assert.equal(job.__timer ?? null, null);
+  assert.equal(job.__watchdog ?? null, null);
+});
+
+test('JobManager: watchdog finalizes a hung runner and stops the persist timer', async () => {
+  mock.timers.enable({ apis: ['setInterval', 'setTimeout'] });
+  globalThis.chrome = makeChromeMock();
+  const mgr = new JobManager();
+  // Runner never settles — only the watchdog can finish this job.
+  const { jobId } = await mgr.start('hang', {}, () => new Promise(() => {}));
+  mock.timers.tick(JOB_TIMEOUT_MS);
+  await flush();
+  const job = await mgr.status({ jobId });
+  assert.equal(job.status, 'error');
+  assert.match(job.error, /timed out/);
+  assert.equal(job.cancelRequested, true);
+  assert.equal(job.__timer ?? null, null);
+  mock.timers.reset();
+});
+
+test('JobManager: a runner that settles after the watchdog cannot resurrect the job', async () => {
+  mock.timers.enable({ apis: ['setInterval', 'setTimeout'] });
+  globalThis.chrome = makeChromeMock();
+  const mgr = new JobManager();
+  let settle;
+  const { jobId } = await mgr.start('late', {}, () => new Promise(r => { settle = r; }));
+  mock.timers.tick(JOB_TIMEOUT_MS);
+  await flush();
+  settle({ tooLate: true }); // runner resolves only after the watchdog fired
+  await flush();
+  const job = await mgr.status({ jobId });
+  assert.equal(job.status, 'error'); // stayed error — finalize() ran exactly once
+  assert.equal(job.result, null);
+  mock.timers.reset();
+});
+
+test('JobManager: persisted set keeps running jobs even past the finished cap', async () => {
+  mock.timers.enable({ apis: ['setInterval', 'setTimeout'] });
+  globalThis.chrome = makeChromeMock();
+  const mgr = new JobManager();
+  await mgr.start('runner', {}, () => new Promise(() => {})); // stays running
+  for (let i = 0; i < MAX_FINISHED_JOBS + 5; i++) {
+    await mgr.start(`done${i}`, {}, async () => i);
+  }
+  await flush();
+  const stored = globalThis.chrome.storage.local._store.recentJobs;
+  const running = stored.filter(j => j.status === 'running');
+  assert.equal(running.length, 1, 'the running job must never be evicted from storage');
+  assert.ok(stored.length <= MAX_FINISHED_JOBS + 1, 'finished jobs stay capped');
+  mock.timers.reset();
+});
diff --git a/package-lock.json b/package-lock.json
index d21b4ad..815de9e 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -454,9 +454,9 @@
       }
     },
     "node_modules/@types/chrome": {
-      "version": "0.1.40",
-      "resolved": "https://registry.npmjs.org/@types/chrome/-/chrome-0.1.40.tgz",
-      "integrity": "sha512-UnfyRAe8ORu9HSuTH0EqyOEUin3JrWW9Nl/gDXezNfTUrfIoxw+WRZgKOxGz0t5BnjbfXBnS2eCYfW2PxH1wcA==",
+      "version": "0.1.43",
+      "resolved": "https://registry.npmjs.org/@types/chrome/-/chrome-0.1.43.tgz",
+      "integrity": "sha512-ukH/HhmR6ht+UTX3PLUWJxgJ/RQcK2Foj4lBzsF24SIWsXgqhGuXqjd8FFuwioPP7d/JUKLM4g8GZxw3F4HTcA==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
diff --git a/package.json b/package.json
index ed9ef4e..9d6da2f 100644
--- a/package.json
+++ b/package.json
@@ -4,7 +4,9 @@
   "type": "module",
   "scripts": {
     "build:extension": "esbuild extension/src/index.ts --bundle --format=iife --target=chrome120 --outfile=extension/background.js",
-    "check:extension": "tsc -p tsconfig.json --noEmit && npm run build:extension && node --check extension/background.js"
+    "build:tests": "esbuild extension/test/*.test.ts --bundle --format=esm --platform=node --outdir=extension/test-dist --out-extension:.js=.mjs",
+    "test:extension": "npm run build:tests && node --test extension/test-dist/*.test.mjs",
+    "check:extension": "tsc -p tsconfig.json --noEmit && npm run build:extension && node --check extension/background.js && npm run test:extension"
   },
   "devDependencies": {
     "@types/chrome": "^0.1.40",
diff --git a/tests/test_extension_error_page_handling.py b/tests/test_extension_error_page_handling.py
index f6f1ca2..195e4e4 100644
--- a/tests/test_extension_error_page_handling.py
+++ b/tests/test_extension_error_page_handling.py
@@ -3,16 +3,20 @@ from pathlib import Path
 ROOT = Path(__file__).resolve().parents[1]
 
 def test_extension_retries_error_page_script_injection_before_failing():
-    core = (ROOT / "extension" / "src" / "core.ts").read_text()
+    # core.ts was split into a core/ subfolder during the structure refactor:
+    # the URL/error classifiers live in core/errors.ts and the executeScript
+    # retry wrapper (which calls isTransientScriptError) lives in core/scripting.ts.
+    errors = (ROOT / "extension" / "src" / "core" / "errors.ts").read_text()
+    scripting = (ROOT / "extension" / "src" / "core" / "scripting.ts").read_text()
 
-    assert "isBrowserErrorUrl" in core
-    assert "isErrorPageScriptError" in core
-    assert "chrome-error://" in core
-    assert "edge-error://" in core
-    assert "brave-error://" in core
-    assert "about:neterror" in core
-    assert "about:certerror" in core
-    assert "isTransientScriptError(e)" in core
+    assert "isBrowserErrorUrl" in errors
+    assert "isErrorPageScriptError" in errors
+    assert "chrome-error://" in errors
+    assert "edge-error://" in errors
+    assert "brave-error://" in errors
+    assert "about:neterror" in errors
+    assert "about:certerror" in errors
+    assert "isTransientScriptError(e)" in scripting
 
 def test_read_only_dom_commands_have_error_page_fallbacks():
     dom = (ROOT / "extension" / "src" / "commands" / "dom.ts").read_text()
@@ -26,7 +30,9 @@ def test_read_only_dom_commands_have_error_page_fallbacks():
     assert "isErrorPageScriptError(e)" in dom
 
 def test_navigation_and_tabs_report_browser_error_pages():
-    tabs = (ROOT / "extension" / "src" / "commands" / "tabs.ts").read_text()
+    # tabs.watch_url (which reports tab error pages) moved into the read-only
+    # TabsQueryCommands class in tabs-query.ts during the structure refactor.
+    tabs = (ROOT / "extension" / "src" / "commands" / "tabs-query.ts").read_text()
     navigation = (ROOT / "extension" / "src" / "commands" / "navigation.ts").read_text()
 
     assert "lastUrl" in tabs
@@ -37,7 +43,12 @@ def test_navigation_and_tabs_report_browser_error_pages():
     assert "showing an error page while waiting for load" in navigation
 
 def test_large_extension_operations_yield_between_batches():
-    core = (ROOT / "extension" / "src" / "core.ts").read_text()
+    # The large-operation throttling/queue helpers moved from core.ts into
+    # core/throttle.ts when core was split into a subfolder. The slice-based
+    # batch loop (cancel-check -> batch call -> progress -> yield) was then
+    # centralized into the processInBatches() helper in core/throttle.ts, so the
+    # command modules call that instead of inlining the loop.
+    core = (ROOT / "extension" / "src" / "core" / "throttle.ts").read_text()
     tabs = (ROOT / "extension" / "src" / "commands" / "tabs.ts").read_text()
     groups = (ROOT / "extension" / "src" / "commands" / "groups.ts").read_text()
     session = (ROOT / "extension" / "src" / "commands" / "session.ts").read_text()
@@ -56,14 +67,19 @@ def test_large_extension_operations_yield_between_batches():
     assert "itemCount >= 300" in core
     assert "itemCount >= 100" in core
     assert "chrome.tabs.query({ audible: true })" in core
+    # The centralized batch loop drives cancellation + progress + throttled yield.
+    assert "processInBatches" in core
+    assert "throwIfJobCancelled(progress.job)" in core
+    assert "yieldForLargeOperation(done" in core
+    # tabs.close / tabs.merge_windows now batch via processInBatches; tabs.sort
+    # still runs its own per-item move loop with yieldForLargeOperation.
+    assert "processInBatches(toClose" in tabs
+    assert "processInBatches(ids" in tabs
     assert "yieldForLargeOperation" in tabs
-    assert "toClose.slice" in tabs
-    assert "ids.slice" in tabs
     assert "w.tabs.every" in tabs
     assert "getLargeOperationThrottle" in tabs
     assert "runLargeOperation(\"tabs.sort\"" in tabs
-    assert "yieldForLargeOperation" in groups
-    assert "tabIds.slice" in groups
+    assert "processInBatches(tabIds" in groups
     assert "getLargeOperationThrottle" in groups
     assert "runLargeOperation(\"group.close\"" in groups
     assert "yieldForLargeOperation(createdTabs.length" in session
@@ -76,35 +92,50 @@ def test_large_extension_operations_yield_between_batches():
     assert "throwIfJobCancelled" in session
     assert "updateJobProgress" in session
 
-    index = (ROOT / "extension" / "src" / "index.ts").read_text()
-    assert "BACKGROUND_COMMANDS" in index
-    assert "startBackgroundJob" in index
-    assert "persistJobs" in index
-    assert "recentJobs" in index
-    assert "jobs.status" in index
-    assert "jobs.cancel" in index
-    assert "perf.status" in index
-    assert "perf.set_profile" in index
-    assert "__background" in index
+    # The background-job machinery moved out of index.ts into the JobManager
+    # (classes/JobManager.ts), the message router (classes/NativeConnection.ts)
+    # and the command registry/groups during the class-based refactor. The
+    # behavior is identical; assert the defining patterns still exist in their
+    # new homes.
+    jobs_module = (ROOT / "extension" / "src" / "classes" / "JobManager.ts").read_text()
+    connection = (ROOT / "extension" / "src" / "classes" / "NativeConnection.ts").read_text()
+    perf = (ROOT / "extension" / "src" / "commands" / "perf.ts").read_text()
+    tabs_module = (ROOT / "extension" / "src" / "commands" / "tabs.ts").read_text()
+
+    assert "background: true" in tabs_module       # background command flag (was BACKGROUND_COMMANDS)
+    assert "persistJobs" in jobs_module
+    assert "recentJobs" in jobs_module
+    assert "jobs.status" in perf
+    assert "jobs.cancel" in perf
+    assert "perf.status" in perf
+    assert "perf.set_profile" in perf
+    assert "__background" in connection
 
 
 def test_session_autosave_is_debounced_and_non_overlapping():
-    session = (ROOT / "extension" / "src" / "commands" / "session.ts").read_text()
+    # The autosave lifecycle moved out of session.ts into a dedicated
+    # AutoSaveManager (autosave.ts) during the structure refactor; the shared
+    # snapshot/signature helpers live in session-snapshot.ts. Behavior is
+    # identical — the defining patterns just live in their new homes.
+    autosave = (ROOT / "extension" / "src" / "commands" / "autosave.ts").read_text()
+    snapshot = (ROOT / "extension" / "src" / "commands" / "session-snapshot.ts").read_text()
 
-    assert "autoSaveTimer" in session
-    assert "autoSaveInFlight" in session
-    assert "autoSavePending" in session
-    assert "scheduleAutoSave" in session
-    assert "autoSaveUpdatedHandler" in session
-    assert "saveAutoSessionIfChanged" in session
-    assert "sessionSignature" in session
-    assert "autoSaveSignature" in session
-    assert "chrome.tabs.onUpdated.addListener(autoSaveUpdatedHandler)" in session
-    assert "chrome.tabs.onCreated.addListener(autoSaveHandler)" in session
-    assert "chrome.tabs.onMoved.addListener(autoSaveHandler)" in session
-    assert "if (!(\"url\" in changeInfo)) return;" in session
-    assert "setTimeout(runAutoSave, delayMs)" in session
-    assert "clearTimeout(autoSaveTimer)" in session
+    assert "autoSaveTimer" in autosave
+    assert "autoSaveInFlight" in autosave
+    assert "autoSavePending" in autosave
+    assert "scheduleAutoSave" in autosave
+    assert "autoSaveUpdatedHandler" in autosave
+    assert "saveAutoSessionIfChanged" in autosave
+    assert "sessionSignature" in snapshot
+    assert "autoSaveSignature" in autosave
+    # AutoSaveManager binds the handlers as instance fields (this.*), so the
+    # add/removeListener references stay identity-stable across enable/disable.
+    assert "chrome.tabs.onUpdated.addListener(this.autoSaveUpdatedHandler)" in autosave
+    assert "chrome.tabs.onCreated.addListener(this.autoSaveHandler)" in autosave
+    assert "chrome.tabs.onMoved.addListener(this.autoSaveHandler)" in autosave
+    assert "if (!(\"url\" in changeInfo)) return;" in autosave
+    assert "setTimeout(() => this.runAutoSave(), delayMs)" in autosave
+    assert "clearTimeout(this.autoSaveTimer)" in autosave
 
 
 def test_cli_and_sdk_expose_gentle_restore_controls():
diff --git a/tsconfig.json b/tsconfig.json
index 42c45db..b5e6610 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -7,6 +7,7 @@
     "types": ["chrome"],
     "allowJs": false,
     "strict": false,
+    "noImplicitAny": true,
     "noEmit": true,
     "skipLibCheck": true
   },