diff --git a/packages/cli/src/__tests__/dev-with-memory-lib.test.ts b/packages/cli/src/__tests__/dev-with-memory-lib.test.ts
index ddc93fee31..306b6b2031 100644
--- a/packages/cli/src/__tests__/dev-with-memory-lib.test.ts
+++ b/packages/cli/src/__tests__/dev-with-memory-lib.test.ts
@@ -69,22 +69,17 @@ describe("dev-with-memory prebuild options", () => {
     ]);
   });
 
-  it("rebuilds core + engine + dashboard (UI) for dashboard startup, not the full workspace", () => {
+  it("rebuilds core + engine + dashboard (UI) + changed plugins for dashboard startup, not the full workspace", () => {
     // FN-6638/stale-dist: dev dashboard must refresh engine + core dist (not
     // just the client bundle) so landed fixes are not silently stale.
+    // FN-7779/stale-plugin-dist: it must ALSO incrementally rebuild changed
+    // plugins (plugin dist loads at runtime), so the client prebuild is now a
+    // single orchestrator command covering both.
     expect(resolvePrebuildMode("auto", ["dashboard", "--port", "4050"])).toBe("client");
     expect(getPrebuildCommand("client")).toEqual({
-      command: "pnpm",
-      args: [
-        "--filter",
-        "@fusion/core",
-        "--filter",
-        "@fusion/engine",
-        "--filter",
-        "@fusion/dashboard",
-        "build",
-      ],
-      label: "core + engine + dashboard build",
+      command: "node",
+      args: ["scripts/dev-prebuild-client.mjs"],
+      label: "core + engine + dashboard + changed plugins build",
     });
   });
 
diff --git a/scripts/__tests__/dist-freshness.test.mjs b/scripts/__tests__/dist-freshness.test.mjs
index 2c8dc79e50..c13e906290 100644
--- a/scripts/__tests__/dist-freshness.test.mjs
+++ b/scripts/__tests__/dist-freshness.test.mjs
@@ -88,3 +88,42 @@ test("skips packages with no src (packaged install)", () => {
   assert.equal(result.stale, false);
   assert.equal(result.packages.length, 0);
 });
+
+// FN-7779: plugin dist loads at runtime, so a src-ahead-of-dist plugin must be
+// flagged too — and the warning names the plugin dir, not @fusion/<name>.
+test("flags a stale plugin under a plugin root and labels it by dir name", () => {
+  const pluginsRoot = `${ROOT}/plugins`;
+  const srcDir = `${pluginsRoot}/fusion-plugin-grok-runtime/src`;
+  const distDir = `${pluginsRoot}/fusion-plugin-grok-runtime/dist`;
+  const fs = makeFs({
+    dirs: [pluginsRoot, srcDir, distDir],
+    files: {
+      [pluginsRoot]: [{ name: "fusion-plugin-grok-runtime", isDir: true }],
+      [srcDir]: [{ name: "runtime-adapter.ts", mtimeMs: 10_000 }],
+      [distDir]: [{ name: "runtime-adapter.js", mtimeMs: 1_000 }],
+    },
+  });
+  const result = computeDistStaleness({ rootDir: ROOT, packages: [], pluginRoots: ["plugins"], fs });
+  assert.equal(result.stale, true);
+  const warning = formatDistStalenessWarning(result);
+  assert.match(warning, /STALE BUILD/);
+  assert.match(warning, /fusion-plugin-grok-runtime/);
+  assert.doesNotMatch(warning, /@fusion\/fusion-plugin-grok-runtime/);
+});
+
+test("does not flag a fresh plugin (dist newer than src)", () => {
+  const pluginsRoot = `${ROOT}/plugins`;
+  const srcDir = `${pluginsRoot}/fusion-plugin-grok-runtime/src`;
+  const distDir = `${pluginsRoot}/fusion-plugin-grok-runtime/dist`;
+  const fs = makeFs({
+    dirs: [pluginsRoot, srcDir, distDir],
+    files: {
+      [pluginsRoot]: [{ name: "fusion-plugin-grok-runtime", isDir: true }],
+      [srcDir]: [{ name: "runtime-adapter.ts", mtimeMs: 1_000 }],
+      [distDir]: [{ name: "runtime-adapter.js", mtimeMs: 10_000 }],
+    },
+  });
+  const result = computeDistStaleness({ rootDir: ROOT, packages: [], pluginRoots: ["plugins"], fs });
+  assert.equal(result.stale, false);
+  assert.equal(formatDistStalenessWarning(result), null);
+});
diff --git a/scripts/build-workspace.mjs b/scripts/build-workspace.mjs
index 90dca00533..3143afc765 100644
--- a/scripts/build-workspace.mjs
+++ b/scripts/build-workspace.mjs
@@ -407,25 +407,36 @@ function formatPlanLine(pkg) {
   return `${pkg.name} (${pkg.buildReason})`;
 }
 
-export function main({ rootDir = repoRoot, spawnFn = spawnSync, gitFn = defaultGitRunner } = {}) {
+/*
+ * FNXC:WorkspaceBuild 2026-07-10-15:40:
+ * FN-7779 stale-plugin-dist: `--plugins-only` narrows the plan to plugin
+ * packages so the fast `pnpm dev dashboard` prebuild can incrementally rebuild
+ * ONLY changed plugins (reusing the content-hash skip cache) without also
+ * rebuilding every non-plugin workspace package. Plugins load their built
+ * dist/ at runtime, so a never-rebuilt plugin dist silently runs phantom-old
+ * code — exactly the Grok "messages aren't sending" wrong-CLI-flags failure.
+ */
+export function main({ rootDir = repoRoot, spawnFn = spawnSync, gitFn = defaultGitRunner, pluginsOnly = false } = {}) {
   const cache = readPluginBuildCache(rootDir);
   const snapshot = createRepoContentSnapshot({ rootDir, gitFn });
   const plan = planWorkspaceBuild({ rootDir, cache, gitFn, snapshot });
-  const plannedNames = plan.plannedPackages.map(formatPlanLine);
+  const plannedPackages = pluginsOnly ? plan.plannedPackages.filter((pkg) => pkg.isPlugin) : plan.plannedPackages;
+  const plannedNames = plannedPackages.map(formatPlanLine);
   const skippedNames = plan.skippedPlugins.map((pkg) => pkg.name);
 
-  console.log(`[build-workspace] planned builds: ${plannedNames.join(", ") || "(none)"}`);
+  const scope = pluginsOnly ? "changed plugins" : "planned builds";
+  console.log(`[build-workspace] ${scope}: ${plannedNames.join(", ") || "(none)"}`);
   if (skippedNames.length > 0) {
     console.log(`[build-workspace] skipped unchanged plugins: ${skippedNames.join(", ")}`);
   }
 
-  const result = runPlannedBuilds(plan.plannedPackages, rootDir, spawnFn);
+  const result = runPlannedBuilds(plannedPackages, rootDir, spawnFn);
   if (result.status !== 0) {
     process.stderr.write(`[build-workspace] FAILED packages: ${result.packageNames.join(", ") || "(none)"}\n`);
     return result.status;
   }
 
-  recordSuccessfulPluginBuilds(plan.plannedPackages, { rootDir, cache, gitFn });
+  recordSuccessfulPluginBuilds(plannedPackages, { rootDir, cache, gitFn });
   return 0;
 }
 
@@ -439,5 +450,6 @@ export function main({ rootDir = repoRoot, spawnFn = spawnSync, gitFn = defaultG
  * file URL of argv[1] so the guard is correct on Windows, macOS, and Linux.
  */
 if (process.argv[1] && import.meta.url === pathToFileURL(process.argv[1]).href) {
-  process.exit(main());
+  const pluginsOnly = process.argv.slice(2).includes("--plugins-only");
+  process.exit(main({ pluginsOnly }));
 }
diff --git a/scripts/dev-prebuild-client.mjs b/scripts/dev-prebuild-client.mjs
new file mode 100644
index 0000000000..3bf7ee7355
--- /dev/null
+++ b/scripts/dev-prebuild-client.mjs
@@ -0,0 +1,43 @@
+#!/usr/bin/env node
+/*
+FNXC:DevWorkflow 2026-07-10-15:40:
+FN-7779 stale-plugin-dist: the `client` prebuild for `pnpm dev dashboard`.
+
+Runs in two ordered steps so a dev restart never runs phantom-old code:
+  1. The FN-6638 fast path — rebuild @fusion/core + @fusion/engine +
+     @fusion/dashboard dist (NOT the full workspace) so landed engine/core/UI
+     fixes take effect.
+  2. Incrementally rebuild ONLY changed plugins via build-workspace's
+     content-hash skip cache (`--plugins-only`). Plugins load their built
+     dist/ at runtime, so a source-only plugin fix (e.g. the Grok CLI-flag fix
+     that caused "messages aren't sending") was silently stale until this step
+     existed — the old client prebuild rebuilt the three app packages but never
+     the plugins.
+
+Unchanged plugins are a cheap content-hash no-op, so step 2 stays fast. Node
+(not a shell `&&`) sequences the steps for cross-platform correctness.
+*/
+import { spawnSync } from "node:child_process";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+
+const repoRoot = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "..");
+// Windows resolves `pnpm` to a `.cmd` shim Node can't spawn without a shell
+// (ENOENT since CVE-2024-27980); these args carry no shell metacharacters.
+const useShell = process.platform === "win32";
+
+function run(command, args, options = {}) {
+  const result = spawnSync(command, args, { cwd: repoRoot, stdio: "inherit", ...options });
+  return result.status ?? 1;
+}
+
+// Step 1: fast app-package build (core -> engine -> dashboard, dependency order).
+const appStatus = run(
+  "pnpm",
+  ["--filter", "@fusion/core", "--filter", "@fusion/engine", "--filter", "@fusion/dashboard", "build"],
+  { shell: useShell },
+);
+if (appStatus !== 0) process.exit(appStatus);
+
+// Step 2: incremental changed-plugin rebuild.
+process.exit(run("node", ["scripts/build-workspace.mjs", "--plugins-only"]));
diff --git a/scripts/dev-with-memory-lib.mjs b/scripts/dev-with-memory-lib.mjs
index bbf0f378b0..b58a34913e 100644
--- a/scripts/dev-with-memory-lib.mjs
+++ b/scripts/dev-with-memory-lib.mjs
@@ -101,22 +101,22 @@ export function getPrebuildCommand(mode) {
       src), the running process and any dist-resolving consumer (plugins,
       sub-imports, a later non-dev `fn`/`pnpm local`) load built dist. Leaving
       engine/core dist stale is exactly how landed fixes (FN-6644/6647/6648,
-      etc.) silently failed to run for ~2 days. pnpm builds these in dependency
-      order (core → engine → dashboard); dashboard `build` runs the vite client
-      bundle + server tsc, so the UI is rebuilt too.
+      etc.) silently failed to run for ~2 days.
+
+      FNXC:DevWorkflow 2026-07-10-15:40:
+      FN-7779/stale-plugin-dist: the app-package build alone left plugin dist/
+      stale — a source-only plugin fix (the Grok CLI-flag fix behind "messages
+      aren't sending") never took effect until a manual rebuild. The client
+      prebuild is now an orchestrator (scripts/dev-prebuild-client.mjs) that
+      first runs the fast core → engine → dashboard build (dependency order;
+      dashboard `build` also runs the vite client bundle + server tsc) and then
+      incrementally rebuilds ONLY changed plugins via the content-hash skip
+      cache. A single node command keeps the spawn contract cross-platform.
       */
       return {
-        command: "pnpm",
-        args: [
-          "--filter",
-          "@fusion/core",
-          "--filter",
-          "@fusion/engine",
-          "--filter",
-          "@fusion/dashboard",
-          "build",
-        ],
-        label: "core + engine + dashboard build",
+        command: "node",
+        args: ["scripts/dev-prebuild-client.mjs"],
+        label: "core + engine + dashboard + changed plugins build",
       };
     case "none":
     case "auto":
diff --git a/scripts/lib/dist-freshness.mjs b/scripts/lib/dist-freshness.mjs
index 7da4d37221..80fc648b05 100644
--- a/scripts/lib/dist-freshness.mjs
+++ b/scripts/lib/dist-freshness.mjs
@@ -24,6 +24,15 @@ import { existsSync, readdirSync, statSync } from "node:fs";
 import { join } from "node:path";
 
 const DEFAULT_PACKAGES = ["core", "engine", "dashboard"];
+/*
+FNXC:DevWorkflow 2026-07-10-15:40:
+FN-7779 stale-plugin-dist: plugins load their built dist/ at runtime, so a
+never-rebuilt plugin dist runs phantom-old code the same way a stale package
+dist does (the Grok wrong-CLI-flags "messages aren't sending" failure). The
+freshness guard now also scans plugin package dirs one level under these roots
+so the operator is warned even if the prebuild is skipped (`--prebuild none`).
+*/
+const DEFAULT_PLUGIN_ROOTS = ["plugins", "plugins/examples"];
 // Slack absorbs build/checkout mtime jitter so we only flag a real source-ahead.
 const DEFAULT_SLACK_MS = 2_000;
 const SRC_EXTENSIONS = [".ts", ".tsx"];
@@ -70,23 +79,64 @@ function newestMtimeMs(dir, extensions, fs) {
  * @param {object} [options.fs] fs seam ({ existsSync, readdirSync, statSync })
  * @returns {{ stale: boolean, packages: Array<{ name: string, srcNewestMs: number, distNewestMs: number, stale: boolean }> }}
  */
+/**
+ * Discover plugin package dirs one level under each plugin root. A plugin is a
+ * candidate only when it has both a `src/` and a `dist/` (same src+dist gate as
+ * packages). Never throws — an unreadable root yields no candidates.
+ *
+ * @returns {Array<{ label: string, srcDir: string, distDir: string }>}
+ */
+function discoverPluginCandidates(rootDir, pluginRoots, fs) {
+  const candidates = [];
+  for (const root of pluginRoots) {
+    const rootDirPath = join(rootDir, root);
+    if (!fs.existsSync(rootDirPath)) continue;
+    let entries;
+    try {
+      entries = fs.readdirSync(rootDirPath, { withFileTypes: true });
+    } catch {
+      continue;
+    }
+    for (const entry of entries) {
+      if (!entry.isDirectory()) continue;
+      const srcDir = join(rootDirPath, entry.name, "src");
+      const distDir = join(rootDirPath, entry.name, "dist");
+      if (!fs.existsSync(srcDir) || !fs.existsSync(distDir)) continue;
+      candidates.push({ label: entry.name, srcDir, distDir });
+    }
+  }
+  return candidates;
+}
+
 export function computeDistStaleness(options = {}) {
   const rootDir = options.rootDir ?? process.cwd();
   const packages = options.packages ?? DEFAULT_PACKAGES;
+  const pluginRoots = options.pluginRoots ?? DEFAULT_PLUGIN_ROOTS;
   const slackMs = options.slackMs ?? DEFAULT_SLACK_MS;
   const fs = options.fs ?? { existsSync, readdirSync, statSync };
 
+  // Packages under packages/<name>, plus plugin packages under the plugin
+  // roots. `label` drives the warning text; packages keep the `@fusion/<name>`
+  // form via a null label, plugins surface their dir name.
+  const candidates = [
+    ...packages.map((name) => ({
+      label: null,
+      name,
+      srcDir: join(rootDir, "packages", name, "src"),
+      distDir: join(rootDir, "packages", name, "dist"),
+    })),
+    ...discoverPluginCandidates(rootDir, pluginRoots, fs).map((c) => ({ label: c.label, name: c.label, srcDir: c.srcDir, distDir: c.distDir })),
+  ];
+
   const results = [];
-  for (const name of packages) {
-    const srcDir = join(rootDir, "packages", name, "src");
-    const distDir = join(rootDir, "packages", name, "dist");
+  for (const { label, name, srcDir, distDir } of candidates) {
     // Both must exist: no src = packaged install; no dist = pure source run.
     if (!fs.existsSync(srcDir) || !fs.existsSync(distDir)) continue;
     const srcNewestMs = newestMtimeMs(srcDir, SRC_EXTENSIONS, fs);
     const distNewestMs = newestMtimeMs(distDir, DIST_EXTENSIONS, fs);
     if (srcNewestMs === 0 || distNewestMs === 0) continue;
     const stale = srcNewestMs - distNewestMs > slackMs;
-    results.push({ name, srcNewestMs, distNewestMs, stale });
+    results.push({ name, label, srcNewestMs, distNewestMs, stale });
   }
   return { stale: results.some((r) => r.stale), packages: results };
 }
@@ -97,10 +147,11 @@ export function computeDistStaleness(options = {}) {
  */
 export function formatDistStalenessWarning(result) {
   if (!result || !result.stale) return null;
-  const staleNames = result.packages.filter((p) => p.stale).map((p) => p.name);
+  // Plugins carry a `label` (their dir name); packages use the `@fusion/<name>` form.
+  const staleNames = result.packages.filter((p) => p.stale).map((p) => p.label ?? `@fusion/${p.name}`);
   return [
     "",
-    `[fusion] ⚠ STALE BUILD: ${staleNames.map((n) => `@fusion/${n}`).join(", ")} dist/ is OLDER than src/.`,
+    `[fusion] ⚠ STALE BUILD: ${staleNames.join(", ")} dist/ is OLDER than src/.`,
     "[fusion]   The running process may execute outdated compiled code, so recently landed",
     "[fusion]   fixes will NOT take effect until you rebuild AND restart:",
     "[fusion]     pnpm build   # then restart the dashboard/engine process",