feat(FN-XXXX): add fnBinaryCheckEnabled global setting

Defaults to true so existing behaviour (dashboard probes PATH for `fn` /
`fusion` and surfaces install / version-mismatch states) is unchanged.
When the user toggles it off in Settings → General → CLI Binary:

- `GET /system/fn-binary/status` short-circuits before `detectFnBinary()`
  and returns `state: "skipped"`. No `<bin> --version` subprocess is
  spawned at all, so an outdated globally-installed CLI cannot run as a
  side effect of opening the dashboard.
- The install banner is hidden when `state` is `"skipped"`.
- `POST /system/fn-binary/install` rejects with HTTP 409 since install
  is the user action that the status check informs.
- The Settings UI gains a checkbox under the existing CLI binary panel.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.changeset/fn-binary-check-setting.md

@@ -0,0 +1,5 @@
+---
+"@runfusion/fusion": patch
+---
+
+Add a global `fnBinaryCheckEnabled` setting that lets users opt out of the dashboard's `fn`/`fusion` CLI binary probe. Default remains true (probe runs as before). When set to false, `GET /system/fn-binary/status` returns `state: "skipped"` without spawning a subprocess, the install banner stays hidden, and `POST /system/fn-binary/install` rejects with HTTP 409. Useful when the running dev process is the source of truth and shelling out to whichever globally-installed `runfusion.ai` happens to be on PATH is unwanted.

packages/core/src/settings-schema.ts

@@ -37,6 +37,7 @@ export const DEFAULT_GLOBAL_SETTINGS = {
   favoriteModels: undefined,
   openrouterModelSync: true,
   updateCheckEnabled: true,
+  fnBinaryCheckEnabled: true,
   updateCheckFrequency: "daily",
   showGitHubStarButton: true,
   modelOnboardingComplete: undefined,

packages/core/src/types.ts

@@ -1319,6 +1319,13 @@ export interface GlobalSettings {
    *  shows update notices in the CLI and dashboard. The actual cadence is
    *  governed by `updateCheckFrequency`. Disabled = no automatic checks at all. */
   updateCheckEnabled?: boolean;
+  /** When true (default), the dashboard probes PATH for a globally-installed
+   *  `fn`/`fusion` CLI binary so it can advertise install/upgrade actions in
+   *  the UI. The probe spawns `<bin> --version`, which executes whichever
+   *  `runfusion.ai` is on PATH. Set to false to skip the probe entirely —
+   *  useful when the local dev process is the source of truth and shelling
+   *  out to an outdated globally-installed binary is unwanted. */
+  fnBinaryCheckEnabled?: boolean;
   /** When false, hides the "Star on GitHub" button in the Settings modal
    *  header. Defaults to true (visible). The button is also hidden once the
    *  user has clicked it (tracked client-side in localStorage). */

packages/dashboard/app/api/legacy.ts

@@ -1309,7 +1309,7 @@ export interface FnBinaryStatus {
     invocation: string;
   };
   expectedVersion: string;
-  state: "installed" | "missing" | "version-mismatch";
+  state: "installed" | "missing" | "version-mismatch" | "skipped";
   install: { npm: string; curl: string; package: string };
 }
 

packages/dashboard/app/components/CliBinaryInstallBanner.tsx

@@ -99,6 +99,9 @@ export function CliBinaryInstallBanner({ onOpenSettings }: Props) {
   if (dismissed) return null;
   if (!status) return null;
   if (status.state === "installed") return null;
+  // Honour the global `fnBinaryCheckEnabled` opt-out — when checks are
+  // disabled the install banner would be misleading.
+  if (status.state === "skipped") return null;
 
   return (
     <div className="cli-binary-banner" role="status">

packages/dashboard/app/components/CliBinaryPanel.tsx

@@ -20,6 +20,7 @@ const STATE_LABELS: Record<FnBinaryStatus["state"], { text: string; tone: "ok" |
   installed: { text: "Installed", tone: "ok" },
   missing: { text: "Not installed", tone: "err" },
   "version-mismatch": { text: "Version mismatch", tone: "warn" },
+  skipped: { text: "Check disabled", tone: "warn" },
 };
 
 /**

packages/dashboard/app/components/SettingsModal.tsx

@@ -1846,6 +1846,26 @@ export function SettingsModal({
               </small>
             </div>
             <CliBinaryPanel />
+            <div className="form-group">
+              <label htmlFor="fnBinaryCheckEnabled" className="checkbox-label">
+                <input
+                  id="fnBinaryCheckEnabled"
+                  type="checkbox"
+                  checked={form.fnBinaryCheckEnabled !== false}
+                  onChange={(e) =>
+                    setForm((f) => ({ ...f, fnBinaryCheckEnabled: e.target.checked }))
+                  }
+                />
+                Check for the <code>fn</code> CLI binary on PATH
+              </label>
+              <small>
+                When enabled, the dashboard probes for a globally-installed{" "}
+                <code>fn</code> / <code>fusion</code> CLI by spawning{" "}
+                <code>&lt;bin&gt; --version</code>. Disable this if your local
+                dev process is the source of truth and you don&apos;t want any
+                outdated globally-installed binary executed during the probe.
+              </small>
+            </div>
             <h4 className="settings-section-heading settings-section-heading--spaced">Updates</h4>
             <div className="form-group">
               <label htmlFor="updateCheckEnabled" className="checkbox-label">

packages/dashboard/src/routes/register-fn-binary-routes.ts

@@ -129,8 +129,44 @@ function runNpmInstall(): Promise<InstallResult> {
   });
 }
 
+/**
+ * Build a status payload for the case where the user has disabled the
+ * fn-binary check via the global setting. We still return a well-formed
+ * response (the UI consumes the same shape regardless) but skip the
+ * subprocess probe entirely. `state: "skipped"` lets the dashboard hide
+ * install / version-mismatch surfaces without inferring "missing".
+ */
+function buildSkippedStatusPayload(expectedVersion: string) {
+  return {
+    binary: {
+      installed: false,
+      invocation: FN_INSTALL_NPM,
+    } satisfies FnBinaryStatus,
+    expectedVersion,
+    state: "skipped" as const,
+    install: {
+      npm: FN_INSTALL_NPM,
+      curl: FN_INSTALL_CURL,
+      package: FN_NPM_PACKAGE,
+    },
+  };
+}
+
 export const registerFnBinaryRoutes: ApiRouteRegistrar = (ctx) => {
-  const { router, rethrowAsApiError } = ctx;
+  const { router, rethrowAsApiError, store } = ctx;
+
+  async function isCheckEnabled(): Promise<boolean> {
+    try {
+      const settings = await store.getSettings();
+      // Default true — only treat an explicit false as opt-out.
+      return settings.fnBinaryCheckEnabled !== false;
+    } catch {
+      // If settings can't be read, fall back to the safe default and
+      // perform the probe so the dashboard's onboarding banner still
+      // renders.
+      return true;
+    }
+  }
 
   /**
    * GET /system/fn-binary/status
@@ -138,11 +174,18 @@ export const registerFnBinaryRoutes: ApiRouteRegistrar = (ctx) => {
    * Probes PATH for `fn` then `fusion`, returning install state and the
    * canonical install commands. No auth — this is read-only introspection
    * the dashboard banner needs before the user signs in.
+   *
+   * Honours `fnBinaryCheckEnabled` (global setting, default true). When
+   * disabled the route returns `state: "skipped"` without spawning a probe.
    */
   router.get("/system/fn-binary/status", async (_req, res) => {
     try {
-      const binary = await detectFnBinary();
       const expectedVersion = getCliPackageVersion();
+      if (!(await isCheckEnabled())) {
+        res.json(buildSkippedStatusPayload(expectedVersion));
+        return;
+      }
+      const binary = await detectFnBinary();
       res.json(buildStatusPayload(binary, expectedVersion));
     } catch (err) {
       if (err instanceof ApiError) throw err;
@@ -155,9 +198,18 @@ export const registerFnBinaryRoutes: ApiRouteRegistrar = (ctx) => {
    *
    * Runs `npm install -g runfusion.ai`. Returns the install result and the
    * post-install probe so the UI can refresh its state in one round trip.
+   * Disabled when `fnBinaryCheckEnabled` is false — install is the user
+   * action that the status check informs, so it follows the same gate.
    */
   router.post("/system/fn-binary/install", async (_req, res) => {
     try {
+      if (!(await isCheckEnabled())) {
+        throw new ApiError(
+          409,
+          "fn-binary checks are disabled in global settings (fnBinaryCheckEnabled=false). Re-enable them to install via the dashboard.",
+          { code: "FN_BINARY_CHECK_DISABLED" },
+        );
+      }
       const installResult = await runNpmInstall();
       // Re-probe even on failure — the binary may already exist from a
       // previous attempt and we want the UI to reflect reality.