diff --git a/.changeset/fn-7711-grok-cli-model-registry.md b/.changeset/fn-7711-grok-cli-model-registry.md
new file mode 100644
index 0000000000..fb99a406f1
--- /dev/null
+++ b/.changeset/fn-7711-grok-cli-model-registry.md
@@ -0,0 +1,7 @@
+---
+"@runfusion/fusion": patch
+---
+
+summary: Grok CLI models now run instead of failing with "not found in the pi model registry".
+category: fix
+dev: Adds a built-in grok-cli provider (packages/core/src/grok-provider.ts) — xAI OpenAI-compatible endpoint https://api.x.ai/v1, api openai-completions, apiKey $GROK_API_KEY — registered into the execution registry (pi.ts registerExtensionProviders), seedDashboardProviders, and CLI serve/daemon/dashboard, mirroring the built-in Z.ai provider. Grok CLI binary remains discovery/probe only; GrokRuntimeAdapter streaming is still a stub (tracked follow-up).
diff --git a/docs/settings-reference.md b/docs/settings-reference.md
index 64e85dfb23..df498ca96f 100644
--- a/docs/settings-reference.md
+++ b/docs/settings-reference.md
@@ -966,6 +966,8 @@ Fusion resolves task models through workflow-backed lane values first, then glob
 
 Z.ai's built-in provider uses the existing `zai` auth entry / `ZAI_API_KEY` environment variable and includes `zai/glm-5.2` as a selectable model in the same dropdowns and workflow lane controls as the other built-in GLM models. If a pi extension also registers the `zai` provider, Fusion preserves the extension's models and re-adds any missing built-in Z.ai models so built-in GLM choices remain available.
 
+Grok (`grok-cli`) is likewise seeded as a built-in provider — xAI's OpenAI-compatible endpoint (`https://api.x.ai/v1`, api type `openai-completions`), API key `GROK_API_KEY` — into every model registry Fusion seeds (task execution, dashboard `/api/models`, and CLI `serve`/`daemon`/`dashboard`), mirroring the Z.ai pattern above. This makes `grok-cli/<model>` selections (e.g. `grok-cli/grok-4.5`) resolvable for execution even before the `grok` CLI binary is discovered or the picker surfaces additional Grok models (see the CLI-discovery paragraph below); a missing `GROK_API_KEY` surfaces only as a normal auth error at stream time, not a model-resolution failure.
+
 When the Hermes Runtime plugin (`fusion-plugin-hermes-runtime`) is installed and the local `hermes` CLI has configured profiles (`hermes profile list`), those profiles are surfaced additively in `/api/models` under the `hermes` provider — one row per profile, id/name derived from the profile name and its configured model. This surfacing is read-only (Fusion does not create or edit Hermes profiles) and is fetched through a short-TTL, single-flight cache so the model picker never spawns the `hermes` CLI on every request; a missing/failed `hermes` binary simply yields zero Hermes rows without affecting other providers.
 
 When the Cursor Runtime plugin (`fusion-plugin-cursor-runtime`) is installed and the `useCursorCli` toggle is enabled (Settings → Authentication), Cursor CLI-discovered models (`cursor-agent models --json`, with text/`model list` fallbacks) are surfaced additively in `/api/models` under the `cursor-cli` provider — id/name derived from the discovered model id/label. This surfacing is fetched through a short-TTL, single-flight cache so the model picker never spawns `cursor-agent` on every request; a missing/failed/unavailable Cursor CLI binary simply yields zero `cursor-cli` rows without affecting other providers. Disabling `useCursorCli` hides all `cursor-cli` rows.
diff --git a/packages/cli/src/commands/daemon.ts b/packages/cli/src/commands/daemon.ts
index f0c72701c4..c63c0cf18b 100644
--- a/packages/cli/src/commands/daemon.ts
+++ b/packages/cli/src/commands/daemon.ts
@@ -20,8 +20,10 @@ import {
   GlobalSettingsStore,
   resolveGlobalDir,
   getEnabledPiExtensionPaths,
+  mergeBuiltInGrokProviderModels,
   mergeBuiltInZaiProviderModels,
   reconcileClaudeCliPaths,
+  registerBuiltInGrokProvider,
   registerBuiltInZaiProvider,
 } from "@fusion/core";
 import type { AutomationRunResult, ScheduledTask } from "@fusion/core";
@@ -550,6 +552,7 @@ export async function runDaemon(opts: DaemonOptions = {}) {
   const authStorage = createFusionAuthStorage();
   const modelRegistry = ModelRegistry.create(authStorage, getModelRegistryModelsPath());
   registerBuiltInZaiProvider(modelRegistry, (message) => console.log(`[extensions] ${message}`));
+  registerBuiltInGrokProvider(modelRegistry, (message) => console.log(`[extensions] ${message}`));
   const dashboardAuthStorage = wrapAuthStorageWithApiKeyProviders(authStorage, modelRegistry);
 
   // PackageManager may be used for skills adapter even if extension loading fails
@@ -665,6 +668,7 @@ export async function runDaemon(opts: DaemonOptions = {}) {
 
     extensionsResult.runtime.pendingProviderRegistrations = [];
     mergeBuiltInZaiProviderModels(modelRegistry, (message) => console.log(`[extensions] ${message}`));
+    mergeBuiltInGrokProviderModels(modelRegistry, (message) => console.log(`[extensions] ${message}`));
     modelRegistry.refresh();
 
     try {
diff --git a/packages/cli/src/commands/dashboard.ts b/packages/cli/src/commands/dashboard.ts
index fa5d0a09d6..d86adc0e0a 100644
--- a/packages/cli/src/commands/dashboard.ts
+++ b/packages/cli/src/commands/dashboard.ts
@@ -20,8 +20,10 @@ import {
   isWorkspaceTask,
   resolveColumnFlags,
   BUILTIN_CODING_WORKFLOW_IR,
+  mergeBuiltInGrokProviderModels,
   mergeBuiltInZaiProviderModels,
   parseWorkflowIr,
+  registerBuiltInGrokProvider,
   registerBuiltInZaiProvider,
   type WorkflowIrColumn,
   type TraitFlags,
@@ -1485,6 +1487,7 @@ export async function runDashboard(port: number, opts: { paused?: boolean; dev?:
   const authStorage = createFusionAuthStorage();
   const modelRegistry = ModelRegistry.create(authStorage, getModelRegistryModelsPath());
   registerBuiltInZaiProvider(modelRegistry, (message) => logSink.log(message, "extensions"));
+  registerBuiltInGrokProvider(modelRegistry, (message) => logSink.log(message, "extensions"));
   const dashboardAuthStorage = wrapAuthStorageWithApiKeyProviders(authStorage, modelRegistry);
 
   // PackageManager may be used for skills adapter even if extension loading fails.
@@ -1605,6 +1608,7 @@ export async function runDashboard(port: number, opts: { paused?: boolean; dev?:
 
     extensionsResult.runtime.pendingProviderRegistrations = [];
     mergeBuiltInZaiProviderModels(modelRegistry, (message) => logSink.log(message, "extensions"));
+    mergeBuiltInGrokProviderModels(modelRegistry, (message) => logSink.log(message, "extensions"));
     modelRegistry.refresh();
 
     try {
diff --git a/packages/cli/src/commands/serve.ts b/packages/cli/src/commands/serve.ts
index 441f4d8a28..6e8db5f946 100644
--- a/packages/cli/src/commands/serve.ts
+++ b/packages/cli/src/commands/serve.ts
@@ -21,7 +21,9 @@ import {
   GlobalSettingsStore,
   resolveGlobalDir,
   getEnabledPiExtensionPaths,
+  mergeBuiltInGrokProviderModels,
   mergeBuiltInZaiProviderModels,
+  registerBuiltInGrokProvider,
   registerBuiltInZaiProvider,
 } from "@fusion/core";
 import type { AutomationRunResult, ScheduledTask } from "@fusion/core";
@@ -599,6 +601,7 @@ export async function runServe(
   const authStorage = createFusionAuthStorage();
   const modelRegistry = ModelRegistry.create(authStorage, getModelRegistryModelsPath());
   registerBuiltInZaiProvider(modelRegistry, (message) => console.log(`[extensions] ${message}`));
+  registerBuiltInGrokProvider(modelRegistry, (message) => console.log(`[extensions] ${message}`));
   const dashboardAuthStorage = wrapAuthStorageWithApiKeyProviders(authStorage, modelRegistry);
 
   // PackageManager may be used for skills adapter even if extension loading fails
@@ -715,6 +718,7 @@ export async function runServe(
 
     extensionsResult.runtime.pendingProviderRegistrations = [];
     mergeBuiltInZaiProviderModels(modelRegistry, (message) => console.log(`[extensions] ${message}`));
+    mergeBuiltInGrokProviderModels(modelRegistry, (message) => console.log(`[extensions] ${message}`));
     modelRegistry.refresh();
 
     try {
diff --git a/packages/core/src/__tests__/grok-provider.test.ts b/packages/core/src/__tests__/grok-provider.test.ts
new file mode 100644
index 0000000000..cdc41114f5
--- /dev/null
+++ b/packages/core/src/__tests__/grok-provider.test.ts
@@ -0,0 +1,130 @@
+import { describe, expect, it } from "vitest";
+import {
+  GROK_CLI_PROVIDER_ID,
+  GROK_PROVIDER_REGISTRATION,
+  mergeBuiltInGrokProviderModels,
+  registerBuiltInGrokProvider,
+} from "../grok-provider.js";
+import { ZAI_PROVIDER_ID, ZAI_PROVIDER_REGISTRATION, registerBuiltInZaiProvider } from "../zai-provider.js";
+
+const EXPECTED_GROK_MODELS = ["grok-4.5", "grok-4", "grok-code-fast-1", "grok-3", "grok-3-mini"];
+
+describe("GROK_PROVIDER_REGISTRATION", () => {
+  it("uses the xAI OpenAI-compatible endpoint and API-key auth", () => {
+    expect(GROK_CLI_PROVIDER_ID).toBe("grok-cli");
+    expect(GROK_PROVIDER_REGISTRATION).toMatchObject({
+      name: "Grok",
+      baseUrl: "https://api.x.ai/v1",
+      apiKey: "$GROK_API_KEY",
+      api: "openai-completions",
+    });
+  });
+
+  it("seeds the reported default model plus a conservative catalog", () => {
+    const modelIds = GROK_PROVIDER_REGISTRATION.models.map((model) => model.id);
+    expect(modelIds).toEqual(EXPECTED_GROK_MODELS);
+    expect(modelIds).toContain("grok-4.5");
+  });
+
+  it("does not copy Z.ai's thinkingFormat compat field", () => {
+    for (const model of GROK_PROVIDER_REGISTRATION.models) {
+      expect(model.compat).not.toHaveProperty("thinkingFormat");
+    }
+  });
+});
+
+describe("registerBuiltInGrokProvider", () => {
+  it("registers grok-cli with the expected baseUrl/api/models", () => {
+    const registeredProviders = new Map<string, unknown>();
+    const registry = {
+      registeredProviders,
+      registerProvider(providerName: string, config: unknown) {
+        registeredProviders.set(providerName, config);
+      },
+    };
+
+    registerBuiltInGrokProvider(registry);
+
+    const registered = registeredProviders.get(GROK_CLI_PROVIDER_ID) as typeof GROK_PROVIDER_REGISTRATION;
+    expect(registered).toMatchObject({
+      name: "Grok",
+      baseUrl: "https://api.x.ai/v1",
+      apiKey: "$GROK_API_KEY",
+      api: "openai-completions",
+    });
+    expect(registered.models.map((model) => model.id)).toEqual(EXPECTED_GROK_MODELS);
+  });
+
+  it("is additive — does not displace a pre-existing zai provider registration", () => {
+    const registeredProviders = new Map<string, unknown>();
+    const registry = {
+      registeredProviders,
+      registerProvider(providerName: string, config: unknown) {
+        registeredProviders.set(providerName, config);
+      },
+    };
+
+    registerBuiltInZaiProvider(registry);
+    registerBuiltInGrokProvider(registry);
+
+    expect(registeredProviders.has(ZAI_PROVIDER_ID)).toBe(true);
+    expect(registeredProviders.has(GROK_CLI_PROVIDER_ID)).toBe(true);
+    expect((registeredProviders.get(ZAI_PROVIDER_ID) as typeof ZAI_PROVIDER_REGISTRATION).models.map((m) => m.id))
+      .toEqual(ZAI_PROVIDER_REGISTRATION.models.map((m) => m.id));
+  });
+
+  it("does not throw when registerProvider throws", () => {
+    const registry = {
+      registerProvider() {
+        throw new Error("boom");
+      },
+    };
+    const warnings: string[] = [];
+    expect(() => registerBuiltInGrokProvider(registry, (message) => warnings.push(message))).not.toThrow();
+    expect(warnings[0]).toContain("Failed to register built-in grok-cli provider");
+  });
+});
+
+describe("mergeBuiltInGrokProviderModels", () => {
+  it("re-adds missing built-in models after a user grok extension replacement", () => {
+    const extensionModels = GROK_PROVIDER_REGISTRATION.models
+      .filter((model) => model.id !== "grok-4.5")
+      .map((model) => ({ ...model }));
+    const registeredProviders = new Map<string, Partial<typeof GROK_PROVIDER_REGISTRATION>>();
+    const registry = {
+      registeredProviders,
+      registerProvider(providerName: string, config: typeof GROK_PROVIDER_REGISTRATION) {
+        registeredProviders.set(providerName, { ...registeredProviders.get(providerName), ...config });
+      },
+    };
+
+    registerBuiltInGrokProvider(registry);
+    registry.registerProvider(GROK_CLI_PROVIDER_ID, {
+      ...GROK_PROVIDER_REGISTRATION,
+      name: "User Grok extension",
+      models: extensionModels,
+    });
+
+    mergeBuiltInGrokProviderModels(registry);
+
+    const mergedIds = registeredProviders.get(GROK_CLI_PROVIDER_ID)?.models?.map((model) => model.id);
+    expect(mergedIds).toEqual(expect.arrayContaining(EXPECTED_GROK_MODELS));
+    expect(mergedIds).toContain("grok-4.5");
+    expect(registeredProviders.get(GROK_CLI_PROVIDER_ID)?.name).toBe("User Grok extension");
+  });
+
+  it("is a no-op when all built-in models are already present", () => {
+    const registeredProviders = new Map<string, Partial<typeof GROK_PROVIDER_REGISTRATION>>();
+    const registry = {
+      registeredProviders,
+      registerProvider(providerName: string, config: typeof GROK_PROVIDER_REGISTRATION) {
+        registeredProviders.set(providerName, { ...registeredProviders.get(providerName), ...config });
+      },
+    };
+
+    registerBuiltInGrokProvider(registry);
+    expect(() => mergeBuiltInGrokProviderModels(registry)).not.toThrow();
+    const mergedIds = registeredProviders.get(GROK_CLI_PROVIDER_ID)?.models?.map((model) => model.id);
+    expect(mergedIds).toEqual(EXPECTED_GROK_MODELS);
+  });
+});
diff --git a/packages/core/src/grok-provider.ts b/packages/core/src/grok-provider.ts
new file mode 100644
index 0000000000..22902854b3
--- /dev/null
+++ b/packages/core/src/grok-provider.ts
@@ -0,0 +1,224 @@
+/**
+ * FNXC:ModelRegistry 2026-07-09-00:00:
+ * FN-7711 registers `grok-cli` as a built-in, OpenAI-compatible xAI provider so the
+ * execution model registry (packages/engine/src/pi.ts `createFnAgent`) can resolve
+ * `grok-cli/*` model selections. Before this, selecting a `grok-cli` model hard-failed
+ * at session creation with "not found in the pi model registry" because FN-7705/FN-7710
+ * only made Grok models appear in the `/api/models` picker — they were never registered
+ * into the execution registry that `resolveConfiguredModel()` reads from.
+ *
+ * The operator-installed `grok` CLI binary (landed by FN-7705) remains discovery/probe
+ * only — this module does not shell out to it. The Grok plugin's `GrokRuntimeAdapter` is
+ * a no-op streaming stub, so once this provider exists, execution streams against xAI's
+ * OpenAI-compatible endpoint (`https://api.x.ai/v1`, api type `openai-completions`) via
+ * the standard pi/openai-completions path, not the plugin runtime.
+ *
+ * This module mirrors `zai-provider.ts` (the canonical built-in-provider pattern):
+ * a static provider registration, `registerBuiltInGrokProvider` to seed it, and
+ * `mergeBuiltInGrokProviderModels` to re-add any built-in models an extension's
+ * provider registration may have dropped (pi's `registerProvider()` replaces the
+ * provider's model list wholesale rather than merging).
+ */
+
+export const GROK_CLI_PROVIDER_ID = "grok-cli";
+
+type GrokModelInput = "text" | "image";
+
+interface GrokModelRegistration {
+  id: string;
+  name: string;
+  reasoning: boolean;
+  input: GrokModelInput[];
+  cost: {
+    input: number;
+    output: number;
+    cacheRead: number;
+    cacheWrite: number;
+  };
+  contextWindow: number;
+  maxTokens: number;
+  compat: {
+    supportsDeveloperRole: boolean;
+  };
+}
+
+export interface GrokProviderRegistration {
+  name: string;
+  baseUrl: string;
+  apiKey: string;
+  api: "openai-completions";
+  models: GrokModelRegistration[];
+}
+
+// pi registerProvider() replaces the provider's model list, so keep every
+// currently built-in Grok model here and append new models as xAI ships them.
+export const GROK_PROVIDER_REGISTRATION: GrokProviderRegistration = {
+  name: "Grok",
+  baseUrl: "https://api.x.ai/v1",
+  apiKey: "$GROK_API_KEY",
+  api: "openai-completions",
+  models: [
+    {
+      id: "grok-4.5",
+      name: "Grok 4.5",
+      reasoning: true,
+      input: ["text"],
+      cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+      contextWindow: 256000,
+      maxTokens: 65536,
+      compat: {
+        supportsDeveloperRole: false,
+      },
+    },
+    {
+      id: "grok-4",
+      name: "Grok 4",
+      reasoning: true,
+      input: ["text"],
+      cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+      contextWindow: 256000,
+      maxTokens: 65536,
+      compat: {
+        supportsDeveloperRole: false,
+      },
+    },
+    {
+      id: "grok-code-fast-1",
+      name: "Grok Code Fast 1",
+      reasoning: false,
+      input: ["text"],
+      cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+      contextWindow: 131072,
+      maxTokens: 32768,
+      compat: {
+        supportsDeveloperRole: false,
+      },
+    },
+    {
+      id: "grok-3",
+      name: "Grok 3",
+      reasoning: false,
+      input: ["text"],
+      cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+      contextWindow: 131072,
+      maxTokens: 32768,
+      compat: {
+        supportsDeveloperRole: false,
+      },
+    },
+    {
+      id: "grok-3-mini",
+      name: "Grok 3 Mini",
+      reasoning: false,
+      input: ["text"],
+      cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+      contextWindow: 131072,
+      maxTokens: 32768,
+      compat: {
+        supportsDeveloperRole: false,
+      },
+    },
+  ],
+};
+
+type GrokModelLike = Partial<Omit<GrokModelRegistration, "name" | "api" | "baseUrl" | "compat">> & {
+  id: string;
+  name?: unknown;
+  provider?: string;
+  baseUrl?: unknown;
+  api?: unknown;
+  compat?: unknown;
+};
+
+interface GrokModelRegistryLike {
+  registerProvider(providerName: string, config: GrokProviderRegistration): void;
+  getAll?: () => GrokModelLike[];
+}
+
+type RegistryWithProviderState = GrokModelRegistryLike & {
+  registeredProviders?: Map<string, Partial<GrokProviderRegistration>>;
+};
+
+function toGrokModelRegistration(model: GrokModelLike): GrokModelRegistration & { baseUrl?: string; api?: string } {
+  return {
+    id: model.id,
+    name: String(model.name ?? model.id),
+    api: typeof model.api === "string" ? model.api : undefined,
+    baseUrl: typeof model.baseUrl === "string" ? model.baseUrl : undefined,
+    reasoning: model.reasoning === true,
+    input: Array.isArray(model.input) ? model.input as GrokModelInput[] : ["text"],
+    cost: model.cost ?? { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+    contextWindow: Number(model.contextWindow ?? 0),
+    maxTokens: Number(model.maxTokens ?? 0),
+    compat: typeof model.compat === "object" && model.compat !== null
+      ? { ...(model.compat as GrokModelRegistration["compat"]) }
+      : GROK_PROVIDER_REGISTRATION.models.find((builtInModel) => builtInModel.id === model.id)?.compat ?? {
+        supportsDeveloperRole: false,
+      },
+  };
+}
+
+function cloneGrokProviderRegistration(config: GrokProviderRegistration): GrokProviderRegistration {
+  return {
+    ...config,
+    models: config.models.map((model) => toGrokModelRegistration(model)),
+  };
+}
+
+/**
+ * FNXC:ModelRegistry 2026-07-09-00:00:
+ * Seeds the built-in `grok-cli` provider (mirrors `registerBuiltInZaiProvider`). Registration
+ * is unconditional and harmless without a `GROK_API_KEY` — a missing key only surfaces as a
+ * normal downstream auth error at stream time, never as the "not found in the pi model
+ * registry" hard-fail this task fixes. Always pass a cloned config because pi's
+ * registerProvider() stores and mutates the config object during later upserts.
+ */
+export function registerBuiltInGrokProvider(
+  modelRegistry: GrokModelRegistryLike,
+  logWarning: (message: string) => void = () => {},
+): void {
+  try {
+    modelRegistry.registerProvider(GROK_CLI_PROVIDER_ID, cloneGrokProviderRegistration(GROK_PROVIDER_REGISTRATION));
+  } catch (error) {
+    const message = error instanceof Error ? error.message : String(error);
+    logWarning(`Failed to register built-in ${GROK_CLI_PROVIDER_ID} provider: ${message}`);
+  }
+}
+
+/**
+ * FNXC:ModelRegistry 2026-07-09-00:00:
+ * pi's registerProvider() treats a provider config with models as a full provider replacement,
+ * and user extensions load after Fusion's built-in provider registration. Re-merge missing
+ * built-in Grok models after extension registration so grok-4.5 remains visible wherever the
+ * user's existing Grok extension models are visible, without deleting extension-supplied models
+ * (mirrors `mergeBuiltInZaiProviderModels`).
+ */
+export function mergeBuiltInGrokProviderModels(
+  modelRegistry: GrokModelRegistryLike,
+  logWarning: (message: string) => void = () => {},
+): void {
+  try {
+    const registryWithState = modelRegistry as RegistryWithProviderState;
+    const registeredProvider = registryWithState.registeredProviders?.get(GROK_CLI_PROVIDER_ID);
+    if (!registeredProvider && !modelRegistry.getAll) return;
+    const registeredModels = registeredProvider?.models?.map((model) => toGrokModelRegistration(model)) ?? [];
+    const currentModels = registeredModels.length > 0
+      ? registeredModels
+      : modelRegistry.getAll?.()
+        .filter((model) => model.provider === GROK_CLI_PROVIDER_ID)
+        .map((model) => toGrokModelRegistration(model)) ?? [];
+    const currentModelIds = new Set(currentModels.map((model) => model.id));
+    const missingBuiltInModels = GROK_PROVIDER_REGISTRATION.models.filter((model) => !currentModelIds.has(model.id));
+
+    if (missingBuiltInModels.length === 0) return;
+
+    modelRegistry.registerProvider(GROK_CLI_PROVIDER_ID, {
+      ...cloneGrokProviderRegistration(GROK_PROVIDER_REGISTRATION),
+      ...registeredProvider,
+      models: [...currentModels, ...missingBuiltInModels.map((model) => toGrokModelRegistration(model))],
+    });
+  } catch (error) {
+    const message = error instanceof Error ? error.message : String(error);
+    logWarning(`Failed to merge built-in ${GROK_CLI_PROVIDER_ID} models: ${message}`);
+  }
+}
diff --git a/packages/core/src/index.gate.ts b/packages/core/src/index.gate.ts
index 3cd12e6727..59772b722e 100644
--- a/packages/core/src/index.gate.ts
+++ b/packages/core/src/index.gate.ts
@@ -86,6 +86,13 @@ export {
   registerBuiltInZaiProvider,
 } from "./zai-provider.js";
 export type { ZaiProviderRegistration } from "./zai-provider.js";
+export {
+  GROK_CLI_PROVIDER_ID,
+  GROK_PROVIDER_REGISTRATION,
+  mergeBuiltInGrokProviderModels,
+  registerBuiltInGrokProvider,
+} from "./grok-provider.js";
+export type { GrokProviderRegistration } from "./grok-provider.js";
 export {
   resolveWorktrunkSettings,
   requiresWorktrunkInstallVerification,
diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
index b9f245e52c..ea605f3292 100644
--- a/packages/core/src/index.ts
+++ b/packages/core/src/index.ts
@@ -53,6 +53,13 @@ export {
   registerBuiltInZaiProvider,
 } from "./zai-provider.js";
 export type { ZaiProviderRegistration } from "./zai-provider.js";
+export {
+  GROK_CLI_PROVIDER_ID,
+  GROK_PROVIDER_REGISTRATION,
+  mergeBuiltInGrokProviderModels,
+  registerBuiltInGrokProvider,
+} from "./grok-provider.js";
+export type { GrokProviderRegistration } from "./grok-provider.js";
 export {
   resolveWorktrunkSettings,
   requiresWorktrunkInstallVerification,
diff --git a/packages/engine/src/__tests__/pi-create-fn-agent.test.ts b/packages/engine/src/__tests__/pi-create-fn-agent.test.ts
index 563cd67222..8cce7063aa 100644
--- a/packages/engine/src/__tests__/pi-create-fn-agent.test.ts
+++ b/packages/engine/src/__tests__/pi-create-fn-agent.test.ts
@@ -1537,7 +1537,12 @@ describe("createFnAgent", () => {
     expect(registerProviderMock).toHaveBeenNthCalledWith(1, "zai", expect.objectContaining({
       models: expect.arrayContaining([expect.objectContaining({ id: "glm-5.2" })]),
     }));
-    expect(registerProviderMock).toHaveBeenNthCalledWith(2, "zai", expect.objectContaining({
+    // FN-7711: registerBuiltInGrokProvider seeds grok-cli immediately after the built-in zai
+    // registration, before the extension's pending provider registrations replay.
+    expect(registerProviderMock).toHaveBeenNthCalledWith(2, "grok-cli", expect.objectContaining({
+      models: expect.arrayContaining([expect.objectContaining({ id: "grok-4.5" })]),
+    }));
+    expect(registerProviderMock).toHaveBeenNthCalledWith(3, "zai", expect.objectContaining({
       models: [{ id: "glm-5.1" }],
     }));
     expect(refreshMock).toHaveBeenCalled();
@@ -1786,6 +1791,77 @@ describe("createFnAgent", () => {
     expect(createAgentSessionMock).not.toHaveBeenCalled();
   });
 
+  // FNXC:ModelRegistry 2026-07-09-00:00:
+  // FN-7711 symptom verification: selecting grok-cli/grok-4.5 used to hard-fail at session
+  // creation with "not found in the pi model registry" because the grok-cli provider was never
+  // registered into the execution registry (see registerExtensionProviders in ../pi.js). This
+  // mirrors the zai/glm-5.1 throw test above to reproduce the exact original failure, then proves
+  // it is gone once the registry resolves a grok-cli model (mirroring how registerBuiltInGrokProvider
+  // makes the provider resolvable), and that an unlisted grok-cli id also resolves via the
+  // provider-base-model on-the-fly fallback.
+  it("reproduces then proves gone the grok-cli/grok-4.5 'not found in the pi model registry' hard-fail", async () => {
+    // Without any grok-cli provider registration, find() returns nothing and getAll() has no
+    // grok-cli models — resolveConfiguredModel must throw the exact original error message.
+    findMock.mockImplementation((provider: string, modelId: string) => (
+      provider === "grok-cli" && modelId === "grok-4.5" ? undefined : { provider, id: modelId }
+    ));
+    getAllMock.mockReturnValue([]);
+
+    const { createFnAgent } = await import("../pi.js");
+
+    await expect(createFnAgent({
+      cwd: "/tmp",
+      systemPrompt: "test",
+      tools: "readonly",
+      defaultProvider: "grok-cli",
+      defaultModelId: "grok-4.5",
+    })).rejects.toThrow("Configured model grok-cli/grok-4.5 (primary selection) was not found in the pi model registry");
+    expect(createAgentSessionMock).not.toHaveBeenCalled();
+
+    // Once the grok-cli provider is resolvable (as it is after registerBuiltInGrokProvider seeds
+    // it into the real execution registry via registerExtensionProviders), find() returns a model
+    // and the session is created successfully — the hard-fail is gone.
+    findMock.mockImplementation((provider: string, modelId: string) => ({ provider, id: modelId }));
+
+    await createFnAgent({
+      cwd: "/tmp",
+      systemPrompt: "test",
+      tools: "readonly",
+      defaultProvider: "grok-cli",
+      defaultModelId: "grok-4.5",
+    });
+
+    expect(createAgentSessionMock).toHaveBeenCalledTimes(1);
+    expect(createAgentSessionMock.mock.calls[0]?.[0]).toMatchObject({
+      model: { provider: "grok-cli", id: "grok-4.5" },
+    });
+  });
+
+  it("resolves an unlisted grok-cli model id via the provider-base-model on-the-fly fallback", async () => {
+    // find() has no entry for the unlisted id, but getAll() reports the provider has at least one
+    // registered grok-cli model (as it does once registerBuiltInGrokProvider seeds the provider) —
+    // resolveConfiguredModel should synthesize a model from the base model rather than throwing.
+    findMock.mockImplementation((provider: string, modelId: string) => (
+      provider === "grok-cli" && modelId === "grok-4-fast" ? undefined : { provider, id: modelId }
+    ));
+    getAllMock.mockReturnValue([{ provider: "grok-cli", id: "grok-4.5", name: "Grok 4.5" }]);
+
+    const { createFnAgent } = await import("../pi.js");
+
+    await createFnAgent({
+      cwd: "/tmp",
+      systemPrompt: "test",
+      tools: "readonly",
+      defaultProvider: "grok-cli",
+      defaultModelId: "grok-4-fast",
+    });
+
+    expect(createAgentSessionMock).toHaveBeenCalledTimes(1);
+    expect(createAgentSessionMock.mock.calls[0]?.[0]).toMatchObject({
+      model: { provider: "grok-cli", id: "grok-4-fast" },
+    });
+  });
+
   it("creates a session when configured models resolve successfully", async () => {
     const { createFnAgent } = await import("../pi.js");
 
diff --git a/packages/engine/src/__tests__/provider-registration.test.ts b/packages/engine/src/__tests__/provider-registration.test.ts
index 788f5af241..5ce68242c0 100644
--- a/packages/engine/src/__tests__/provider-registration.test.ts
+++ b/packages/engine/src/__tests__/provider-registration.test.ts
@@ -104,7 +104,7 @@ describe("seedDashboardProviders", () => {
     const { authStorage: wrapped } = await seedDashboardProviders({ store, authStorage, modelRegistry });
 
     const providerIds = wrapped.getApiKeyProviders().map((p) => p.id);
-    expect(providerIds).toEqual(expect.arrayContaining(["zai", "openrouter", "kimi-coding"]));
+    expect(providerIds).toEqual(expect.arrayContaining(["zai", "openrouter", "kimi-coding", "grok-cli"]));
   });
 
   it("registers built-in API-key providers with an empty customProviders array", async () => {
@@ -115,7 +115,7 @@ describe("seedDashboardProviders", () => {
     const { authStorage: wrapped } = await seedDashboardProviders({ store, authStorage, modelRegistry });
 
     const providerIds = wrapped.getApiKeyProviders().map((p) => p.id);
-    expect(providerIds).toEqual(expect.arrayContaining(["zai", "openrouter", "kimi-coding"]));
+    expect(providerIds).toEqual(expect.arrayContaining(["zai", "openrouter", "kimi-coding", "grok-cli"]));
   });
 
   it("registers one custom provider alongside built-ins", async () => {
diff --git a/packages/engine/src/pi.ts b/packages/engine/src/pi.ts
index bb39a7084b..f5e01ac520 100644
--- a/packages/engine/src/pi.ts
+++ b/packages/engine/src/pi.ts
@@ -42,8 +42,10 @@ import {
   getProjectRootFromWorktree,
   reconcileClaudeCliPaths,
   reconcileDroidCliPaths,
+  mergeBuiltInGrokProviderModels,
   mergeBuiltInZaiProviderModels,
   mergeSupplementalAnthropicModels,
+  registerBuiltInGrokProvider,
   registerBuiltInZaiProvider,
   resolvePiExtensionProjectRoot,
 } from "@fusion/core";
@@ -1463,6 +1465,7 @@ function resolveVendoredDroidCliEntry(): string | null {
 
 async function registerExtensionProviders(cwd: string, modelRegistry: ModelRegistry): Promise<void> {
   registerBuiltInZaiProvider(modelRegistry, (message) => extensionsLog.warn(message));
+  registerBuiltInGrokProvider(modelRegistry, (message) => extensionsLog.warn(message));
 
   try {
     const agentDir = getPackageManagerAgentDir();
@@ -1525,6 +1528,7 @@ async function registerExtensionProviders(cwd: string, modelRegistry: ModelRegis
 
     extensionsResult.runtime.pendingProviderRegistrations = [];
     mergeBuiltInZaiProviderModels(modelRegistry, (message) => extensionsLog.warn(message));
+    mergeBuiltInGrokProviderModels(modelRegistry, (message) => extensionsLog.warn(message));
     modelRegistry.refresh();
   } catch (error) {
     const message = error instanceof Error ? error.message : String(error);
diff --git a/packages/engine/src/provider-registration.ts b/packages/engine/src/provider-registration.ts
index b24890157e..cc7fe90a83 100644
--- a/packages/engine/src/provider-registration.ts
+++ b/packages/engine/src/provider-registration.ts
@@ -14,7 +14,9 @@ DashboardAuthStorage callers MUST pass to `createServer(...)` (not the raw authS
 disposer to unsubscribe the settings listener on shutdown.
 */
 import {
+  mergeBuiltInGrokProviderModels,
   mergeBuiltInZaiProviderModels,
+  registerBuiltInGrokProvider,
   registerBuiltInZaiProvider,
   type CustomProvider,
   type TaskStore,
@@ -62,9 +64,11 @@ export async function seedDashboardProviders(
   const log = options.log ?? (() => {});
 
   registerBuiltInZaiProvider(modelRegistry, (message) => log("extensions", message));
+  registerBuiltInGrokProvider(modelRegistry, (message) => log("extensions", message));
   const dashboardAuthStorage = wrapAuthStorageWithApiKeyProviders(authStorage, modelRegistry);
 
   mergeBuiltInZaiProviderModels(modelRegistry, (message) => log("extensions", message));
+  mergeBuiltInGrokProviderModels(modelRegistry, (message) => log("extensions", message));
   modelRegistry.refresh();
 
   try {