diff --git a/packages/pi-fff/README.md b/packages/pi-fff/README.md
index 9375c5ab..3157d953 100644
--- a/packages/pi-fff/README.md
+++ b/packages/pi-fff/README.md
@@ -162,6 +162,8 @@ All fields are optional:
 | `warnOnHomeDirScan` | boolean | `true` |
 | `followSymlinks` | boolean | `true` |
 
+Starting a session in a directory the config opts out of indexing (`$HOME` with `enableHomeDirScanning: false`, `/` with `enableFsRootScanning: false`) disables FFF workspace search for that session: the extension reports it once as a warning and keeps the `ffgrep`/`fffind` names even in `override` mode, so pi's built-in `grep`/`find` stay reachable.
+
 CLI flags take precedence over environment variables, which take precedence over this file. A missing file is ignored. Malformed JSON, unknown fields, and invalid values stop the extension from loading and report the file path and error. `/fff-mode` changes the current session; it does not edit this file.
 
 The file is global only. Project-level config cannot safely control tool names because pi decides which tools an extension registers before project configuration can be trusted.
diff --git a/packages/pi-fff/src/index.ts b/packages/pi-fff/src/index.ts
index 75d93cfe..66fb5bcd 100644
--- a/packages/pi-fff/src/index.ts
+++ b/packages/pi-fff/src/index.ts
@@ -28,7 +28,7 @@ import { Type, type TSchema } from "@sinclair/typebox";
 import { AuxFinderPool, routePathConstraint } from "./aux-finders";
 import { type FffMode, loadConfig, VALID_MODES } from "./config";
 import { FilePickerFactory } from "./file-picker";
-import { isHomeDir, resolveDbPaths } from "./paths";
+import { isFsRoot, isHomeDir, resolveDbPaths } from "./paths";
 import { buildQuery } from "./query";
 
 export { SCAN_TIMEOUT_MS } from "./sdk";
@@ -460,8 +460,22 @@ export default function fffExtension(pi: ExtensionAPI) {
     });
   }
 
+  // The native layer refuses a picker rooted at $HOME / the fs root unless the
+  // matching opt-in is set (crates/fff-core/src/file_picker.rs). Detect that here
+  // so the opt-out reads as "search off" instead of an init failure (issue #857).
+  function scanOptOutReason(cwd: string): string | null {
+    if (!enableHomeDirScanning && isHomeDir(cwd))
+      return `(fff): cwd is $HOME and "enableHomeDirScanning" is false, so FFF search is disabled for this session. Start pi from a project directory, or set "enableHomeDirScanning": true / --fff-enable-home-scan=true to index $HOME.`;
+    if (!enableFsRootScanning && isFsRoot(cwd))
+      return `(fff): cwd is the filesystem root and "enableFsRootScanning" is false, so FFF search is disabled for this session. Start pi from a project directory, or set "enableFsRootScanning": true / --fff-enable-root-scan=true to index it.`;
+    return null;
+  }
+
   // in case cwd changes we need to figure this out
   function ensureFinder(cwd: string): Promise<FileFinderApi> {
+    const optOut = scanOptOutReason(cwd);
+    if (optOut) return Promise.reject(new Error(optOut));
+
     if (mainFinder && !mainFinder.isDestroyed && finderCwd === cwd)
       return Promise.resolve(mainFinder);
 
@@ -741,6 +755,13 @@ export default function fffExtension(pi: ExtensionAPI) {
     }
 
     initializeFinderFactories();
+
+    // `override` replaces pi's built-in grep/find. With the cwd opted out of
+    // indexing that would leave the session without any working workspace
+    // search, so keep the FFF names and let the built-ins stand (issue #857).
+    if (currentMode === "override" && scanOptOutReason(activeCwd))
+      toolNames = FFF_TOOL_NAMES;
+
     registerPendingTools();
   }
 
@@ -748,6 +769,15 @@ export default function fffExtension(pi: ExtensionAPI) {
     try {
       prepareSession(ctx);
       registerAutocompleteProvider(ctx);
+
+      // The user opted out of indexing this cwd, so skip the picker entirely
+      // instead of letting the native refusal surface as an error (issue #857).
+      const optOut = scanOptOutReason(activeCwd);
+      if (optOut) {
+        ctx.ui.notify(optOut, "warning");
+        return;
+      }
+
       await ensureFinder(activeCwd);
 
       // Warn when launched from $HOME with home scanning on: indexing a large
diff --git a/packages/pi-fff/src/paths.ts b/packages/pi-fff/src/paths.ts
index aa1b68e0..63f77254 100644
--- a/packages/pi-fff/src/paths.ts
+++ b/packages/pi-fff/src/paths.ts
@@ -18,6 +18,12 @@ export function isHomeDir(dir: string): boolean {
   return path.resolve(dir) === HOME_DIR;
 }
 
+// Mirrors the native `path.parent().is_none()` check: a path that is its own parent.
+export function isFsRoot(dir: string): boolean {
+  const resolved = path.resolve(dir);
+  return path.dirname(resolved) === resolved;
+}
+
 // Resolution order: explicit override > existing fff.nvim db > pi-local data dir.
 // Reusing the nvim db lets pi rank files by the frecency the user built in their editor.
 export function resolveDbPaths(overrides: {
diff --git a/packages/pi-fff/test/extension.test.ts b/packages/pi-fff/test/extension.test.ts
index e9d7fd58..adb3c180 100644
--- a/packages/pi-fff/test/extension.test.ts
+++ b/packages/pi-fff/test/extension.test.ts
@@ -67,10 +67,27 @@ function createMockFinder(): MockFinder {
   };
 }
 
+const NATIVE_ROOT_REFUSAL =
+  "Failed to init file picker: Can not run certain FFF features in a file system root or home directories. Consider smaller per-project directories.";
+
+// Mirrors the native guard in crates/fff-core/src/file_picker.rs: a picker rooted
+// at $HOME or `/` is refused unless the matching opt-in is set.
+function nativeRefusal(options: {
+  basePath: string;
+  enableHomeDirScanning?: boolean;
+  enableFsRootScanning?: boolean;
+}): boolean {
+  const base = path.resolve(options.basePath);
+  if (options.enableHomeDirScanning === false && base === path.resolve(os.homedir()))
+    return true;
+  return options.enableFsRootScanning === false && path.dirname(base) === base;
+}
+
 const finderModule = {
   FileFinder: {
-    create: mock((options: unknown) => {
+    create: mock((options: any) => {
       createCalls.push(options);
+      if (nativeRefusal(options)) return { ok: false, error: NATIVE_ROOT_REFUSAL };
       const finder = createMockFinder();
       finders.push(finder);
       return { ok: true, value: finder };
@@ -452,12 +469,41 @@ describe("pi-fff $HOME scan warning", () => {
     expect(setup.ctx.ui.setStatus).toHaveBeenLastCalledWith("fff", undefined);
   });
 
-  test("no warning when home scanning is disabled", async () => {
+  // #857: the opt-out must skip the picker, not surface the native refusal as an
+  // init error, and must not shadow pi's built-in search tools in override mode.
+  test("skips the picker and stays out of the way when home scanning is off", async () => {
     process.env.FFF_ENABLE_HOME_SCAN = "0";
-    const setup = await start(undefined, os.homedir());
+    const setup = await start("override", os.homedir());
 
-    expect(setup.ctx.ui.notify).not.toHaveBeenCalled();
+    expect(createCalls).toHaveLength(0);
     expect(setup.ctx.ui.setStatus).not.toHaveBeenCalled();
+
+    const [message, level] = setup.ctx.ui.notify.mock.calls[0];
+    expect(setup.ctx.ui.notify).toHaveBeenCalledTimes(1);
+    expect(level).toBe("warning");
+    expect(message).not.toContain("FFF init failed");
+    expect(message).toContain("enableHomeDirScanning");
+
+    const toolNames = setup.pi.registerTool.mock.calls.map(([tool]) => tool.name);
+    expect(toolNames).toEqual(["ffgrep", "fffind"]);
+    await shutdown(setup);
+  });
+
+  test("skips the picker at the filesystem root without root scanning", async () => {
+    const setup = await start(undefined, path.parse(process.cwd()).root);
+
+    expect(createCalls).toHaveLength(0);
+    const [message, level] = setup.ctx.ui.notify.mock.calls[0];
+    expect(level).toBe("warning");
+    expect(message).toContain("enableFsRootScanning");
+    await shutdown(setup);
+  });
+
+  test("still indexes $HOME when the opt-out is not set", async () => {
+    const setup = await start(undefined, os.homedir());
+
+    expect(createCalls).toHaveLength(1);
+    expect((createCalls[0] as { basePath: string }).basePath).toBe(os.homedir());
     await shutdown(setup);
   });