diff --git a/packages/catalog/CHANGELOG.md b/packages/catalog/CHANGELOG.md
index 390d0adee..55e2e64aa 100644
--- a/packages/catalog/CHANGELOG.md
+++ b/packages/catalog/CHANGELOG.md
@@ -14,6 +14,7 @@
 - Fixed SuperGrok (`xai-oauth`) Grok 4.6 hiding the thinking-level picker: the Responses effort-capable allowlist now includes `grok-4.6`, so `/model` can select the documented `low`/`medium`/`high`/`xhigh` ladder (`max` is rejected by api.x.ai).
 - Marked CoreWeave runtime discovery as authoritative so stale bundled model ids that the endpoint no longer serves stop appearing as selectable models.
 - ChatGPT Codex discovery that advertises only worker `-wm` SKUs now also registers the plain model route, so a configured `openai-codex/<model>` keeps resolving instead of fuzzy-falling-back to the `-wm` SKU some accounts reject.
+- Fixed GitHub Copilot `grok-4.6` / `grok-4.6-1m` failing with HTTP 400 `unsupported_api_for_model` by routing them through the OpenAI Responses API (`/responses`) instead of `/chat/completions`, matching `grok-4.5`. Stale cached completion routes are invalidated on refresh ([#8807](https://github.com/can1357/oh-my-pi/issues/8807)).
 
 ## [17.3.6] - 2026-08-17
 
diff --git a/packages/catalog/src/models.json b/packages/catalog/src/models.json
index e7215b13a..1315b34e8 100644
--- a/packages/catalog/src/models.json
+++ b/packages/catalog/src/models.json
@@ -24448,7 +24448,7 @@
 		"grok-4.6": {
 			"id": "grok-4.6",
 			"name": "Grok 4.6",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "github-copilot",
 			"baseUrl": "https://api.githubcopilot.com",
 			"reasoning": true,
@@ -24468,18 +24468,14 @@
 				"User-Agent": "opencode/1.3.15",
 				"X-GitHub-Api-Version": "2026-06-01"
 			},
-			"compat": {
-				"supportsStore": false,
-				"supportsDeveloperRole": false,
-				"supportsReasoningEffort": false
-			},
 			"thinking": {
 				"mode": "effort",
 				"efforts": [
 					"minimal",
 					"low",
 					"medium",
-					"high"
+					"high",
+					"xhigh"
 				]
 			}
 		},
diff --git a/packages/catalog/src/provider-models/openai-compat.ts b/packages/catalog/src/provider-models/openai-compat.ts
index 7fc21a0ab..24bf52b5e 100644
--- a/packages/catalog/src/provider-models/openai-compat.ts
+++ b/packages/catalog/src/provider-models/openai-compat.ts
@@ -5081,8 +5081,18 @@ export interface GithubCopilotModelManagerConfig {
 
 const COPILOT_ANTHROPIC_MODEL_PATTERN = /^claude-(haiku|sonnet|opus|fable|mythos)-\d/;
 const isCopilotResponsesModelId = (modelId: string): boolean =>
-	modelId === "grok-4.5" || modelId.startsWith("gpt-5") || modelId.startsWith("oswe") || modelId.startsWith("mai-");
-const COPILOT_CACHE_INVALIDATED_MODEL_IDS = ["grok-4.5", "grok-4.5-1m", "mai-code-1-flash-picker"];
+	modelId === "grok-4.5" ||
+	modelId === "grok-4.6" ||
+	modelId.startsWith("gpt-5") ||
+	modelId.startsWith("oswe") ||
+	modelId.startsWith("mai-");
+const COPILOT_CACHE_INVALIDATED_MODEL_IDS = [
+	"grok-4.5",
+	"grok-4.5-1m",
+	"grok-4.6",
+	"grok-4.6-1m",
+	"mai-code-1-flash-picker",
+];
 
 function inferCopilotApi(modelId: string): Api {
 	if (COPILOT_ANTHROPIC_MODEL_PATTERN.test(modelId)) {
diff --git a/packages/catalog/test/github-copilot-model-limits.test.ts b/packages/catalog/test/github-copilot-model-limits.test.ts
index b3aff18a2..ad777511f 100644
--- a/packages/catalog/test/github-copilot-model-limits.test.ts
+++ b/packages/catalog/test/github-copilot-model-limits.test.ts
@@ -390,9 +390,23 @@ describe("github copilot model limits mapping", () => {
 		const model = models.find(candidate => candidate.id === "grok-4.5");
 		expect(model?.api).toBe("openai-responses");
 	});
+	it("routes grok-4.6 to the openai-responses endpoint (#8807)", async () => {
+		const { models } = await discoverCopilotModels({
+			data: [
+				{
+					id: "grok-4.6",
+					name: "Grok 4.6",
+				},
+			],
+		});
+
+		const model = models.find(candidate => candidate.id === "grok-4.6");
+		expect(model?.api).toBe("openai-responses");
+	});
 	for (const migration of [
 		{ id: "mai-code-1-flash-picker", name: "MAI-Code-1-Flash" },
 		{ id: "grok-4.5", name: "Grok 4.5" },
+		{ id: "grok-4.6", name: "Grok 4.6" },
 	]) {
 		it(`refreshes a cached ${migration.name} completion route after the endpoint migration`, async () => {
 			const tempDir = await fs.mkdtemp(path.join(os.tmpdir(), `pi-ai-copilot-${migration.id}-cache-`));