diff --git a/docs/provider-endpoint-constraints.md b/docs/provider-endpoint-constraints.md
index 0193702a2..99264c9b4 100644
--- a/docs/provider-endpoint-constraints.md
+++ b/docs/provider-endpoint-constraints.md
@@ -235,12 +235,13 @@ Reasoning fields are not interchangeable.
 - Compat needs both policies: disable reasoning for any tool choice, and disable
   reasoning only for forced tool choice.
 
-### xAI Grok through Responses/SuperGrok
+### xAI Grok through Responses (`xai` and `xai-oauth`)
 
-Keep these independent:
+Both the paid API-key provider (`xai` / `XAI_API_KEY`) and SuperGrok OAuth
+(`xai-oauth`) chat over `https://api.x.ai/v1/responses`. Keep these independent:
 
 - omit `reasoning.effort`
-- include or drop encrypted reasoning replay
+- include `reasoning.encrypted_content` (request `include`) vs replay history
 - filter reasoning-history wrappers
 
 Some models reject only one of those fields; do not collapse them into one
diff --git a/packages/ai/test/openai-completions-cache-affinity.test.ts b/packages/ai/test/openai-completions-cache-affinity.test.ts
index 2506e031c..c081b4380 100644
--- a/packages/ai/test/openai-completions-cache-affinity.test.ts
+++ b/packages/ai/test/openai-completions-cache-affinity.test.ts
@@ -5,9 +5,6 @@ import type { AssistantMessage, Context, FetchImpl, Model, SimpleStreamOptions,
 import { buildOpenAICompat } from "@oh-my-pi/pi-catalog/compat/openai";
 import { getBundledModel } from "@oh-my-pi/pi-catalog/models";
 
-const model = getBundledModel<"openai-completions">("xai", "grok-code-fast-1");
-if (!model) throw new Error("Expected bundled xAI Grok model");
-if (model.api !== "openai-completions") throw new Error(`Expected Chat Completions model, received ${model.api}`);
 const context: Context = { messages: [{ role: "user", content: "hello", timestamp: 0 }] };
 
 const openAI56ResponsesModel = getBundledModel<"openai-responses">("openai", "gpt-5.6");
@@ -44,7 +41,7 @@ function chatCompletionsSse(): Response {
 			id: "chatcmpl-affinity",
 			object: "chat.completion.chunk",
 			created: 0,
-			model: model.id,
+			model: openAI56CompletionsModel.id,
 			choices: [{ index: 0, delta, finish_reason: finishReason }],
 		});
 
@@ -56,7 +53,7 @@ function chatCompletionsSse(): Response {
 
 async function captureRequest(
 	options: OpenAICompletionsOptions,
-	requestModel: Model<"openai-completions"> = model,
+	requestModel: Model<"openai-completions"> = openAI56CompletionsModel,
 	requestContext: Context = context,
 ): Promise<{ headers: Headers; body: Record<string, unknown> }> {
 	let requestHeaders: Headers | undefined;
@@ -83,7 +80,7 @@ async function captureRequest(
 
 async function captureSimpleRequest(
 	options: SimpleStreamOptions,
-	requestModel: Model<"openai-completions"> = model,
+	requestModel: Model<"openai-completions"> = openAI56CompletionsModel,
 	requestContext: Context = context,
 ): Promise<{ headers: Headers; body: Record<string, unknown> }> {
 	let requestHeaders: Headers | undefined;
@@ -104,51 +101,6 @@ async function captureSimpleRequest(
 	return { headers: requestHeaders, body };
 }
 
-describe("openai-completions xAI cache affinity", () => {
-	const cases: Array<{
-		name: string;
-		options: OpenAICompletionsOptions;
-		expectedHeader: string | null;
-	}> = [
-		{
-			name: "uses sessionId when no prompt cache key is provided",
-			options: { sessionId: "session-fallback" },
-			expectedHeader: "session-fallback",
-		},
-		{
-			name: "keeps the prompt cache key stable across a distinct side-channel session",
-			options: { promptCacheKey: "stable-cache-key", sessionId: "side-channel-session" },
-			expectedHeader: "stable-cache-key",
-		},
-		{
-			name: "omits automatic affinity when caching is disabled",
-			options: {
-				promptCacheKey: "disabled-cache-key",
-				sessionId: "disabled-session",
-				cacheRetention: "none",
-			},
-			expectedHeader: null,
-		},
-		{
-			name: "preserves a caller-provided mixed-case affinity header",
-			options: {
-				promptCacheKey: "automatic-cache-key",
-				sessionId: "automatic-session",
-				headers: { "X-Grok-Conv-Id": "caller-affinity" },
-			},
-			expectedHeader: "caller-affinity",
-		},
-	];
-
-	for (const { name, options, expectedHeader } of cases) {
-		it(name, async () => {
-			const { headers } = await captureRequest(options);
-
-			expect(headers.get("x-grok-conv-id")).toBe(expectedHeader);
-		});
-	}
-});
-
 describe("OpenAI Chat Completions explicit prompt cache policy", () => {
 	const historicalContext: Context = {
 		messages: [
diff --git a/packages/ai/test/openai-responses-cache-affinity.test.ts b/packages/ai/test/openai-responses-cache-affinity.test.ts
index fd10d44cf..4eb32abca 100644
--- a/packages/ai/test/openai-responses-cache-affinity.test.ts
+++ b/packages/ai/test/openai-responses-cache-affinity.test.ts
@@ -57,6 +57,20 @@ const xaiOAuthResponsesModel: Model<"openai-responses"> = {
 		reasoning: true,
 	}),
 };
+const xaiApiKeyResponsesModel: Model<"openai-responses"> = {
+	...model,
+	id: "grok-code-fast-1",
+	name: "Grok Code Fast 1",
+	provider: "xai",
+	baseUrl: "https://api.x.ai/v1",
+	compat: buildOpenAIResponsesCompat({
+		id: "grok-code-fast-1",
+		name: "Grok Code Fast 1",
+		provider: "xai",
+		baseUrl: "https://api.x.ai/v1",
+		reasoning: true,
+	}),
+};
 
 const openAI56ResponsesModel: Model<"openai-responses"> = {
 	...model,
@@ -675,6 +689,16 @@ describe("openai-responses cache affinity", () => {
 		}
 	});
 
+	it("sets x-grok-conv-id cache affinity for paid xai Responses requests", async () => {
+		const captured = await captureDispatchedOpenAIResponseHeaders(
+			{ sessionId: "session-fallback" },
+			xaiApiKeyResponsesModel,
+		);
+
+		expect(getHeader(captured.headers, "x-grok-conv-id")).toBe("session-fallback");
+		expect(captured.body?.prompt_cache_key).toBe("session-fallback");
+	});
+
 	it("sets OpenRouter Responses session_id from sessionId in the body", async () => {
 		const captured = await captureOpenAIResponseHeaders(
 			{ sessionId: "workflow-123", promptCacheKey: "cache-key-123" },
diff --git a/packages/ai/test/stream.test.ts b/packages/ai/test/stream.test.ts
index 0add12576..8017e13bd 100644
--- a/packages/ai/test/stream.test.ts
+++ b/packages/ai/test/stream.test.ts
@@ -1000,7 +1000,7 @@ describe("Generate E2E Tests", () => {
 		);
 	});
 
-	describe.skipIf(!e2eApiKey("XAI_API_KEY"))("xAI Provider (grok-code-fast-1 via OpenAI Completions)", () => {
+	describe.skipIf(!e2eApiKey("XAI_API_KEY"))("xAI Provider (grok-code-fast-1 via OpenAI Responses)", () => {
 		const llm = getBundledModel("xai", "grok-code-fast-1");
 
 		it(
diff --git a/packages/ai/test/xai-oauth-effort-strip.test.ts b/packages/ai/test/xai-oauth-effort-strip.test.ts
index c84012057..428ac8d03 100644
--- a/packages/ai/test/xai-oauth-effort-strip.test.ts
+++ b/packages/ai/test/xai-oauth-effort-strip.test.ts
@@ -38,6 +38,23 @@ describe("effort-dial-less reasoner encoding (regression)", () => {
 		expect(grokR.thinking).toBeUndefined();
 	});
 
+	test("paid xai/grok-code-fast-1 reasons but carries no thinking config", () => {
+		const grokCodeFast = getBundledModel("xai", "grok-code-fast-1");
+		if (!grokCodeFast) throw new Error("xai/grok-code-fast-1 must be in bundled models.json");
+		expect(grokCodeFast.api).toBe("openai-responses");
+		expect(grokCodeFast.reasoning).toBe(true);
+		expect(grokCodeFast.thinking).toBeUndefined();
+		expect(getSupportedEfforts(grokCodeFast)).toEqual([]);
+	});
+
+	test("paid xai/grok-4.3 keeps its effort dial", () => {
+		const grok43 = getBundledModel("xai", "grok-4.3");
+		if (!grok43) throw new Error("xai/grok-4.3 must be in bundled models.json");
+		expect(grok43.api).toBe("openai-responses");
+		expect(grok43.thinking).toBeDefined();
+		expect(getSupportedEfforts(grok43).length).toBeGreaterThan(0);
+	});
+
 	test("the no-dial encoding stays scoped to openai-responses*", () => {
 		const claude = getBundledModel("anthropic", "claude-sonnet-4-6");
 		if (!claude) throw new Error("anthropic/claude-sonnet-4-6 must be in bundled models.json");
@@ -57,6 +74,7 @@ describe("xAI OAuth Responses reasoning payload (regression)", () => {
 		const { params } = buildParams(grok45, singleUserContext, undefined, undefined);
 
 		expect(params.reasoning).toBeUndefined();
+		expect(params.include).toContain("reasoning.encrypted_content");
 	});
 
 	test("xai-oauth/grok-4.5 omits unsupported reasoning summary", () => {
@@ -66,5 +84,15 @@ describe("xAI OAuth Responses reasoning payload (regression)", () => {
 		const { params } = buildParams(grok45, singleUserContext, { reasoning: Effort.High }, undefined);
 
 		expect(params.reasoning).toEqual({ effort: "high" });
+		expect(params.include).toContain("reasoning.encrypted_content");
+	});
+
+	test("paid xai/grok-4.5 requests encrypted reasoning content", () => {
+		const grok45 = getBundledModel<"openai-responses">("xai", "grok-4.5");
+		if (!grok45) throw new Error("xai/grok-4.5 must be in bundled models.json");
+
+		const { params } = buildParams(grok45, singleUserContext, { reasoning: Effort.High }, undefined);
+
+		expect(params.include).toContain("reasoning.encrypted_content");
 	});
 });
diff --git a/packages/catalog/CHANGELOG.md b/packages/catalog/CHANGELOG.md
index 9f7534918..8c03fcdf9 100644
--- a/packages/catalog/CHANGELOG.md
+++ b/packages/catalog/CHANGELOG.md
@@ -2,6 +2,13 @@
 
 ## [Unreleased]
 
+### Changed
+
+- Switched the paid xAI provider (`xai` / `XAI_API_KEY`) from Chat Completions to the OpenAI Responses API (`POST https://api.x.ai/v1/responses`), matching SuperGrok `xai-oauth`. Prompt-cache affinity (`x-grok-conv-id`), reasoning-effort allowlisting, and encrypted-reasoning replay rules are now shared across both first-party xAI hosts.
+- Changed the paid xAI (`XAI_API_KEY`) default model from `grok-4-fast-non-reasoning` to `grok-4.5`.
+- Changed the SuperGrok (`xai-oauth`) default model from `grok-4.3` to `grok-4.5`.
+- Requested `reasoning.encrypted_content` on first-party xAI Responses calls (`xai` and `xai-oauth`) via the `include` parameter.
+
 ## [17.3.4] - 2026-08-14
 
 ### Added
diff --git a/packages/catalog/src/compat/openai.ts b/packages/catalog/src/compat/openai.ts
index ad7ba06b0..940568814 100644
--- a/packages/catalog/src/compat/openai.ts
+++ b/packages/catalog/src/compat/openai.ts
@@ -684,24 +684,28 @@ export function buildOpenAIResponsesCompat(spec: OpenAIResponsesSpecLike): Resol
 	const isLocalServingBackend =
 		(!PROXY_OPENAI_COMPAT_PROVIDERS.has(spec.provider) && LOCAL_OPENAI_COMPAT_PROVIDERS.has(spec.provider)) ||
 		hasLocalLoopbackBaseUrl(baseUrl);
+	const isXaiHost = modelMatchesHost({ provider: spec.provider, baseUrl }, "xai");
 
 	const compat: ResolvedOpenAIResponsesCompat = {
 		supportsDeveloperRole: isAzure || isOpenAIUrl || hostMatchesUrl(baseUrl, "githubCopilot"),
 		supportsStrictMode: isAzure || detectStrictModeSupport(spec.provider, baseUrl),
-		supportsReasoningEffort: spec.provider !== "xai-oauth" || isGrokReasoningEffortCapable(id),
+		// Paid `xai` and SuperGrok `xai-oauth` share api.x.ai `/v1/responses`.
+		// Only the Grok effort-capable allowlist accepts `reasoning.effort`;
+		// other reasoners (grok-build, grok-code-fast-1, …) 400 if it is sent.
+		supportsReasoningEffort: !isXaiHost || isGrokReasoningEffortCapable(id),
 		supportsLongPromptCacheRetention: isOpenAIUrl,
 		supportsPromptCacheBreakpoints,
 		promptCacheBreakpointTtl: supportsPromptCacheBreakpoints ? "30m" : undefined,
 		// Azure OpenAI and GitHub Copilot Responses paths require tool results
 		// to strictly match prior tool calls when building Responses inputs.
 		strictResponsesPairing: isAzure || spec.provider === "github-copilot",
-		// GitHub Copilot and xAI OAuth reject `detail: "original"` (400 / 422).
-		// Every other host preserves native-resolution frames (snapcompact relies
-		// on `original`). Detect Copilot by provider id or base-URL host so a
-		// model pointed at the Copilot host under a different provider id still
-		// clamps; xai-oauth is provider-id only (same host family as paid `xai`).
+		// GitHub Copilot and first-party xAI `/v1/responses` reject
+		// `detail: "original"` (400 / 422). Every other host preserves
+		// native-resolution frames (snapcompact relies on `original`). Detect
+		// Copilot by provider id or base-URL host so a model pointed at the
+		// Copilot host under a different provider id still clamps.
 		supportsImageDetailOriginal:
-			spec.provider !== "xai-oauth" && !modelMatchesHost({ provider: spec.provider, baseUrl }, "githubCopilot"),
+			!isXaiHost && !modelMatchesHost({ provider: spec.provider, baseUrl }, "githubCopilot"),
 		reasoningEffortMap: {},
 		supportsReasoningParams: true,
 		// OpenAI proprietary reasoning models (o-series, gpt-5+) reject explicit
@@ -710,8 +714,12 @@ export function buildOpenAIResponsesCompat(spec: OpenAIResponsesSpecLike): Resol
 		thinkingFormat,
 		reasoningDisableMode: resolveReasoningDisableMode(thinkingFormat),
 		omitReasoningEffort: false,
-		includeEncryptedReasoning: spec.provider !== "xai-oauth",
-		filterReasoningHistory: spec.provider === "xai-oauth" || (isOpenRouter && isAnthropicModel),
+		// Ask xAI `/v1/responses` for `reasoning.encrypted_content` the same way
+		// first-party OpenAI Responses does. History still drops `type:
+		// "reasoning"` wrappers (`filterReasoningHistory`) independently —
+		// those two flags must not be collapsed.
+		includeEncryptedReasoning: true,
+		filterReasoningHistory: isXaiHost || (isOpenRouter && isAnthropicModel),
 		disableReasoningOnForcedToolChoice: isKimiModel,
 		disableReasoningOnToolChoice: isDeepseekFamily && reasoningCapable && !isOpenRouter,
 		supportsToolChoice: true,
@@ -752,7 +760,7 @@ export function buildOpenAIResponsesCompat(spec: OpenAIResponsesSpecLike): Resol
 			MINIMAX_PROVIDER_OR_ID_PATTERN.test(spec.provider) || (id ? MINIMAX_PROVIDER_OR_ID_PATTERN.test(id) : false),
 		emptyLengthFinishIsContextError: spec.provider === "ollama",
 		usesOpenAIToolCallIdLimit: spec.provider === "openai",
-		promptCacheSessionHeader: spec.provider === "xai-oauth" ? "x-grok-conv-id" : undefined,
+		promptCacheSessionHeader: isXaiHost ? "x-grok-conv-id" : undefined,
 		streamFirstEventTimeoutMs: isLocalServingBackend ? 0 : spec.compat?.streamFirstEventTimeoutMs,
 		streamIdleTimeoutMs: isLocalServingBackend
 			? LOCAL_OPENAI_COMPAT_STREAM_IDLE_TIMEOUT_MS
diff --git a/packages/catalog/src/hosts.ts b/packages/catalog/src/hosts.ts
index 176f77125..5c7f3e2fb 100644
--- a/packages/catalog/src/hosts.ts
+++ b/packages/catalog/src/hosts.ts
@@ -47,7 +47,7 @@ export const KNOWN_HOSTS = {
 	},
 	umans: { providers: ["umans"], urlMarkers: ["api.code.umans.ai"] },
 	xiaomi: { providers: ["xiaomi"], providerPrefixes: ["xiaomi-token-plan-"], urlMarkers: ["xiaomimimo.com"] },
-	xai: { providers: ["xai"], urlMarkers: ["api.x.ai"] },
+	xai: { providers: ["xai", "xai-oauth"], urlMarkers: ["api.x.ai"] },
 	mistral: { providers: ["mistral"], urlMarkers: ["mistral.ai"] },
 	together: { providers: ["together"], urlMarkers: ["api.together.xyz"] },
 	baseten: { providers: ["baseten"], urlMarkers: ["baseten.co"] },
diff --git a/packages/catalog/src/models.json b/packages/catalog/src/models.json
index 5dc7d1f9b..67e785669 100644
--- a/packages/catalog/src/models.json
+++ b/packages/catalog/src/models.json
@@ -103716,7 +103716,7 @@
 		"grok-2": {
 			"id": "grok-2",
 			"name": "Grok 2",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": false,
@@ -103735,7 +103735,7 @@
 		"grok-2-1212": {
 			"id": "grok-2-1212",
 			"name": "Grok 2 (1212)",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": false,
@@ -103754,7 +103754,7 @@
 		"grok-2-latest": {
 			"id": "grok-2-latest",
 			"name": "Grok 2 Latest",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": false,
@@ -103773,7 +103773,7 @@
 		"grok-2-vision": {
 			"id": "grok-2-vision",
 			"name": "Grok 2 Vision",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": false,
@@ -103793,7 +103793,7 @@
 		"grok-2-vision-1212": {
 			"id": "grok-2-vision-1212",
 			"name": "Grok 2 Vision (1212)",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": false,
@@ -103813,7 +103813,7 @@
 		"grok-2-vision-latest": {
 			"id": "grok-2-vision-latest",
 			"name": "Grok 2 Vision Latest",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": false,
@@ -103833,7 +103833,7 @@
 		"grok-3": {
 			"id": "grok-3",
 			"name": "Grok 3",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": false,
@@ -103852,7 +103852,7 @@
 		"grok-3-fast": {
 			"id": "grok-3-fast",
 			"name": "Grok 3 Fast",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": false,
@@ -103871,7 +103871,7 @@
 		"grok-3-fast-latest": {
 			"id": "grok-3-fast-latest",
 			"name": "Grok 3 Fast Latest",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": false,
@@ -103890,7 +103890,7 @@
 		"grok-3-latest": {
 			"id": "grok-3-latest",
 			"name": "Grok 3 Latest",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": false,
@@ -103909,7 +103909,7 @@
 		"grok-3-mini": {
 			"id": "grok-3-mini",
 			"name": "Grok 3 Mini",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": true,
@@ -103937,7 +103937,7 @@
 		"grok-3-mini-fast": {
 			"id": "grok-3-mini-fast",
 			"name": "Grok 3 Mini Fast",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": true,
@@ -103965,7 +103965,7 @@
 		"grok-3-mini-fast-latest": {
 			"id": "grok-3-mini-fast-latest",
 			"name": "Grok 3 Mini Fast Latest",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": true,
@@ -103993,7 +103993,7 @@
 		"grok-3-mini-latest": {
 			"id": "grok-3-mini-latest",
 			"name": "Grok 3 Mini Latest",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": true,
@@ -104021,7 +104021,7 @@
 		"grok-4": {
 			"id": "grok-4",
 			"name": "Grok 4",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": true,
@@ -104049,7 +104049,7 @@
 		"grok-4-1-fast": {
 			"id": "grok-4-1-fast",
 			"name": "Grok 4.1 Fast",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": true,
@@ -104078,7 +104078,7 @@
 		"grok-4-1-fast-non-reasoning": {
 			"id": "grok-4-1-fast-non-reasoning",
 			"name": "Grok 4.1 Fast (Non-Reasoning)",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": false,
@@ -104098,7 +104098,7 @@
 		"grok-4-fast": {
 			"id": "grok-4-fast",
 			"name": "Grok 4 Fast",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": true,
@@ -104127,7 +104127,7 @@
 		"grok-4-fast-non-reasoning": {
 			"id": "grok-4-fast-non-reasoning",
 			"name": "Grok 4 Fast (Non-Reasoning)",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": false,
@@ -104147,7 +104147,7 @@
 		"grok-4.20-0309-non-reasoning": {
 			"id": "grok-4.20-0309-non-reasoning",
 			"name": "Grok 4.20 (Non-Reasoning)",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": false,
@@ -104167,7 +104167,7 @@
 		"grok-4.20-0309-reasoning": {
 			"id": "grok-4.20-0309-reasoning",
 			"name": "Grok 4.20 (Reasoning)",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": true,
@@ -104197,7 +104197,7 @@
 		"grok-4.20-beta-latest-non-reasoning": {
 			"id": "grok-4.20-beta-latest-non-reasoning",
 			"name": "Grok 4.20 Beta (Non-Reasoning)",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": false,
@@ -104217,7 +104217,7 @@
 		"grok-4.20-beta-latest-reasoning": {
 			"id": "grok-4.20-beta-latest-reasoning",
 			"name": "Grok 4.20 Beta (Reasoning)",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": true,
@@ -104247,7 +104247,7 @@
 		"grok-4.20-multi-agent-beta-latest": {
 			"id": "grok-4.20-multi-agent-beta-latest",
 			"name": "Grok 4.20 Multi-Agent Beta",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": true,
@@ -104276,7 +104276,7 @@
 		"grok-4.3": {
 			"id": "grok-4.3",
 			"name": "Grok 4.3",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": true,
@@ -104305,7 +104305,7 @@
 		"grok-4.5": {
 			"id": "grok-4.5",
 			"name": "Grok 4.5",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": true,
@@ -104363,7 +104363,7 @@
 		"grok-beta": {
 			"id": "grok-beta",
 			"name": "Grok Beta",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": false,
@@ -104382,7 +104382,7 @@
 		"grok-build-0.1": {
 			"id": "grok-build-0.1",
 			"name": "Grok Build 0.1",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": true,
@@ -104411,7 +104411,7 @@
 		"grok-code-fast-1": {
 			"id": "grok-code-fast-1",
 			"name": "Grok Code Fast 1",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": true,
@@ -104439,7 +104439,7 @@
 		"grok-vision-beta": {
 			"id": "grok-vision-beta",
 			"name": "Grok Vision Beta",
-			"api": "openai-completions",
+			"api": "openai-responses",
 			"provider": "xai",
 			"baseUrl": "https://api.x.ai/v1",
 			"reasoning": false,
@@ -104483,7 +104483,7 @@
 				"reasoningEffortMap": {
 					"minimal": "low"
 				},
-				"includeEncryptedReasoning": false,
+				"includeEncryptedReasoning": true,
 				"filterReasoningHistory": true,
 				"supportsImageDetailOriginal": false,
 				"omitReasoningEffort": true,
@@ -104515,7 +104515,7 @@
 				"reasoningEffortMap": {
 					"minimal": "low"
 				},
-				"includeEncryptedReasoning": false,
+				"includeEncryptedReasoning": true,
 				"filterReasoningHistory": true,
 				"supportsImageDetailOriginal": false,
 				"omitReasoningEffort": true,
@@ -104559,7 +104559,7 @@
 				"reasoningEffortMap": {
 					"minimal": "low"
 				},
-				"includeEncryptedReasoning": false,
+				"includeEncryptedReasoning": true,
 				"filterReasoningHistory": true,
 				"supportsImageDetailOriginal": false,
 				"omitReasoningEffort": false,
@@ -104604,7 +104604,7 @@
 				"reasoningEffortMap": {
 					"minimal": "low"
 				},
-				"includeEncryptedReasoning": false,
+				"includeEncryptedReasoning": true,
 				"filterReasoningHistory": true,
 				"supportsImageDetailOriginal": false,
 				"omitReasoningEffort": false,
@@ -104649,7 +104649,7 @@
 				"reasoningEffortMap": {
 					"minimal": "low"
 				},
-				"includeEncryptedReasoning": false,
+				"includeEncryptedReasoning": true,
 				"filterReasoningHistory": true,
 				"supportsImageDetailOriginal": false,
 				"omitReasoningEffort": false,
@@ -104709,7 +104709,7 @@
 				"reasoningEffortMap": {
 					"minimal": "low"
 				},
-				"includeEncryptedReasoning": false,
+				"includeEncryptedReasoning": true,
 				"filterReasoningHistory": true,
 				"supportsImageDetailOriginal": false,
 				"omitReasoningEffort": true,
@@ -104741,7 +104741,7 @@
 				"reasoningEffortMap": {
 					"minimal": "low"
 				},
-				"includeEncryptedReasoning": false,
+				"includeEncryptedReasoning": true,
 				"filterReasoningHistory": true,
 				"supportsImageDetailOriginal": false,
 				"omitReasoningEffort": true,
@@ -104772,7 +104772,7 @@
 				"reasoningEffortMap": {
 					"minimal": "low"
 				},
-				"includeEncryptedReasoning": false,
+				"includeEncryptedReasoning": true,
 				"filterReasoningHistory": true,
 				"supportsImageDetailOriginal": false,
 				"omitReasoningEffort": true,
@@ -111996,4 +111996,4 @@
 			}
 		}
 	}
-}
\ No newline at end of file
+}
diff --git a/packages/catalog/src/provider-models/descriptors.ts b/packages/catalog/src/provider-models/descriptors.ts
index 20af095aa..1cbb2c016 100644
--- a/packages/catalog/src/provider-models/descriptors.ts
+++ b/packages/catalog/src/provider-models/descriptors.ts
@@ -478,13 +478,13 @@ export const CATALOG_PROVIDERS = [
 	},
 	{
 		id: "xai",
-		defaultModel: "grok-4-fast-non-reasoning",
+		defaultModel: "grok-4.5",
 		envVars: ["XAI_API_KEY"],
 		createModelManagerOptions: (config: ModelManagerConfig) => xaiModelManagerOptions(config),
 	},
 	{
 		id: "xai-oauth",
-		defaultModel: "grok-4.3",
+		defaultModel: "grok-4.5",
 		envVars: ["XAI_OAUTH_TOKEN", "XAI_API_KEY"],
 		createModelManagerOptions: (config: ModelManagerConfig) => xaiOAuthModelManagerOptions(config),
 		catalogDiscovery: {
diff --git a/packages/catalog/src/provider-models/openai-compat.ts b/packages/catalog/src/provider-models/openai-compat.ts
index bf985c9a5..a5f90aeb8 100644
--- a/packages/catalog/src/provider-models/openai-compat.ts
+++ b/packages/catalog/src/provider-models/openai-compat.ts
@@ -1257,8 +1257,8 @@ export interface XaiModelManagerConfig {
 	fetch?: FetchImpl;
 }
 
-export function xaiModelManagerOptions(config?: XaiModelManagerConfig): ModelManagerOptions<"openai-completions"> {
-	return createSimpleOpenAICompletionsOptions("xai", "https://api.x.ai/v1", config);
+export function xaiModelManagerOptions(config?: XaiModelManagerConfig): ModelManagerOptions<"openai-responses"> {
+	return createSimpleOpenAIResponsesOptions("xai", "https://api.x.ai/v1", config);
 }
 
 export interface XaiOAuthModelManagerConfig {
@@ -1352,7 +1352,7 @@ const XAI_NON_CHAT_PREFIXES = ["grok-imagine-", "grok-stt-", "grok-voice-"] as c
 function withXaiOAuthCompatDefaults(model: ModelSpec<"openai-responses">): ModelSpec<"openai-responses"> {
 	const compat = {
 		...(model.compat ?? {}),
-		includeEncryptedReasoning: model.compat?.includeEncryptedReasoning ?? false,
+		includeEncryptedReasoning: model.compat?.includeEncryptedReasoning ?? true,
 		filterReasoningHistory: model.compat?.filterReasoningHistory ?? true,
 		supportsImageDetailOriginal: model.compat?.supportsImageDetailOriginal ?? false,
 		omitReasoningEffort: model.compat?.omitReasoningEffort ?? !isGrokReasoningEffortCapable(model.id),
@@ -1395,7 +1395,7 @@ function mergeCuratedIntoModel(
 	const compat = {
 		...(base.compat ?? {}),
 		reasoningEffortMap: { ...XAI_REASONING_EFFORT_MAP, ...(base.compat?.reasoningEffortMap ?? {}) },
-		includeEncryptedReasoning: base.compat?.includeEncryptedReasoning ?? false,
+		includeEncryptedReasoning: base.compat?.includeEncryptedReasoning ?? true,
 		filterReasoningHistory: base.compat?.filterReasoningHistory ?? true,
 		supportsImageDetailOriginal: base.compat?.supportsImageDetailOriginal ?? false,
 		omitReasoningEffort: !effortCapable,
@@ -5713,6 +5713,15 @@ function openAiCompletionsDescriptor(
 	return simpleModelsDevDescriptor(modelsDevKey, providerId, "openai-completions", baseUrl, options);
 }
 
+function openAiResponsesDescriptor(
+	modelsDevKey: string,
+	providerId: string,
+	baseUrl: string,
+	options: Omit<ModelsDevProviderDescriptor, "modelsDevKey" | "providerId" | "api" | "baseUrl"> = {},
+): ModelsDevProviderDescriptor {
+	return simpleModelsDevDescriptor(modelsDevKey, providerId, "openai-responses", baseUrl, options);
+}
+
 function anthropicMessagesDescriptor(
 	modelsDevKey: string,
 	providerId: string,
@@ -5837,7 +5846,7 @@ const MODELS_DEV_PROVIDER_DESCRIPTORS_CORE: readonly ModelsDevProviderDescriptor
 		defaultContextWindow: 131072,
 	}),
 	// --- xAI ---
-	openAiCompletionsDescriptor("xai", "xai", "https://api.x.ai/v1"),
+	openAiResponsesDescriptor("xai", "xai", "https://api.x.ai/v1"),
 	// --- DeepSeek ---
 	openAiCompletionsDescriptor("deepseek", "deepseek", "https://api.deepseek.com", {
 		// Only ship the v4 family as built-ins; older deepseek-chat / deepseek-reasoner
diff --git a/packages/catalog/test/build.test.ts b/packages/catalog/test/build.test.ts
index cf9a672d2..9c5cbeb16 100644
--- a/packages/catalog/test/build.test.ts
+++ b/packages/catalog/test/build.test.ts
@@ -223,12 +223,15 @@ describe("buildModel", () => {
 	});
 });
 
-describe("xAI-OAuth Responses reasoning-effort suppression", () => {
-	const grokResponsesSpec = (id: string): ModelSpec<"openai-responses"> => ({
+describe("xAI Responses reasoning-effort suppression", () => {
+	const grokResponsesSpec = (
+		id: string,
+		provider: "xai" | "xai-oauth" = "xai-oauth",
+	): ModelSpec<"openai-responses"> => ({
 		id,
 		name: id,
 		api: "openai-responses",
-		provider: "xai-oauth",
+		provider,
 		baseUrl: "https://api.x.ai/v1",
 		reasoning: true,
 		input: ["text"],
@@ -248,6 +251,28 @@ describe("xAI-OAuth Responses reasoning-effort suppression", () => {
 		expect(buildOpenAIResponsesCompat(grokResponsesSpec("grok-4.3")).supportsReasoningEffort).toBe(true);
 	});
 
+	it("applies the same Responses dialect to paid xai and xai-oauth", () => {
+		const paid = buildOpenAIResponsesCompat(grokResponsesSpec("grok-4.3", "xai"));
+		const oauth = buildOpenAIResponsesCompat(grokResponsesSpec("grok-4.3", "xai-oauth"));
+		expect(paid.promptCacheSessionHeader).toBe("x-grok-conv-id");
+		expect(oauth.promptCacheSessionHeader).toBe("x-grok-conv-id");
+		expect(paid.includeEncryptedReasoning).toBe(true);
+		expect(oauth.includeEncryptedReasoning).toBe(true);
+		expect(paid.filterReasoningHistory).toBe(true);
+		expect(oauth.filterReasoningHistory).toBe(true);
+		expect(paid.supportsImageDetailOriginal).toBe(false);
+		expect(oauth.supportsImageDetailOriginal).toBe(false);
+		expect(paid.supportsReasoningEffort).toBe(true);
+		expect(oauth.supportsReasoningEffort).toBe(true);
+	});
+
+	it("omits effort for paid xai models off the Grok allowlist", () => {
+		const compat = buildOpenAIResponsesCompat(grokResponsesSpec("grok-code-fast-1", "xai"));
+		expect(compat.supportsReasoningEffort).toBe(false);
+		expect(compat.omitReasoningEffort).toBe(true);
+		expect(buildModel(grokResponsesSpec("grok-code-fast-1", "xai")).thinking).toBeUndefined();
+	});
+
 	it("lets an explicit compat.supportsReasoningEffort override the allowlist default", () => {
 		const compat = buildOpenAIResponsesCompat({
 			...grokResponsesSpec("grok-build"),
@@ -256,7 +281,7 @@ describe("xAI-OAuth Responses reasoning-effort suppression", () => {
 		expect(compat.supportsReasoningEffort).toBe(true);
 	});
 
-	it("does not suppress effort for a non-xai-oauth provider with a grok-like id", () => {
+	it("does not suppress effort for a non-xAI provider with a grok-like id", () => {
 		const compat = buildOpenAIResponsesCompat({
 			...grokResponsesSpec("grok-build"),
 			provider: "openai",
diff --git a/packages/catalog/test/xai-api-key-responses.test.ts b/packages/catalog/test/xai-api-key-responses.test.ts
new file mode 100644
index 000000000..5f605eb5c
--- /dev/null
+++ b/packages/catalog/test/xai-api-key-responses.test.ts
@@ -0,0 +1,25 @@
+import { describe, expect, it } from "bun:test";
+import { getBundledModels } from "@oh-my-pi/pi-catalog/models";
+import { CATALOG_PROVIDERS } from "@oh-my-pi/pi-catalog/provider-models/descriptors";
+import { xaiModelManagerOptions } from "@oh-my-pi/pi-catalog/provider-models/openai-compat";
+
+describe("paid xai (XAI_API_KEY) Responses contract", () => {
+	it("registers xai on the catalog Responses discovery path", () => {
+		const entry = CATALOG_PROVIDERS.find(provider => provider.id === "xai");
+		expect(entry, "xai catalog descriptor").toBeDefined();
+		expect(entry!.defaultModel).toBe("grok-4.5");
+		expect(entry!.envVars).toContain("XAI_API_KEY");
+		const options = xaiModelManagerOptions({ apiKey: "test-key" });
+		expect(options.providerId).toBe("xai");
+		expect(options.fetchDynamicModels, "live /v1/models overlay").toBeTypeOf("function");
+	});
+
+	it("bundles every paid xai chat model on openai-responses", () => {
+		const models = getBundledModels("xai");
+		expect(models.length).toBeGreaterThan(0);
+		for (const model of models) {
+			expect(model.api, `${model.provider}/${model.id}`).toBe("openai-responses");
+			expect(model.baseUrl).toBe("https://api.x.ai/v1");
+		}
+	});
+});
diff --git a/packages/catalog/test/xai-oauth-bundle.test.ts b/packages/catalog/test/xai-oauth-bundle.test.ts
new file mode 100644
index 000000000..534cc488c
--- /dev/null
+++ b/packages/catalog/test/xai-oauth-bundle.test.ts
@@ -0,0 +1,86 @@
+import { describe, expect, it } from "bun:test";
+import MODELS_JSON from "@oh-my-pi/pi-catalog/models.json" with { type: "json" };
+import { CATALOG_PROVIDERS, DEFAULT_MODEL_PER_PROVIDER } from "@oh-my-pi/pi-catalog/provider-models/descriptors";
+import { buildXaiOAuthStaticSeed } from "@oh-my-pi/pi-catalog/provider-models/openai-compat";
+import type { ModelSpec } from "@oh-my-pi/pi-catalog/types";
+
+// Pins the invariant: bundled `models.json` carries every entry the runtime
+// curated catalog (XAI_OAUTH_CURATED_MODELS, surfaced via
+// buildXaiOAuthStaticSeed) emits. Without this, editing the curated list
+// without regenerating `models.json` silently regresses the boot-time
+// default-model resolver — the registry sees the runtime seed only after
+// `refresh()`, but interactive boot resolves the persisted default
+// synchronously from `#loadModels()`, which reads only `models.json`.
+//
+// Failure here means: run `bun run gen:models` and commit the diff.
+describe("xai-oauth bundled catalog (regression)", () => {
+	const bundled =
+		(MODELS_JSON as unknown as Record<string, Record<string, ModelSpec<"openai-responses">>>)["xai-oauth"] ?? {};
+	const seed = buildXaiOAuthStaticSeed();
+
+	it("defaults SuperGrok selection to grok-4.5", () => {
+		const entry = CATALOG_PROVIDERS.find(provider => provider.id === "xai-oauth");
+		expect(entry?.defaultModel).toBe("grok-4.5");
+		expect(DEFAULT_MODEL_PER_PROVIDER["xai-oauth"]).toBe("grok-4.5");
+		expect(bundled["grok-4.5"], "xai-oauth/grok-4.5 must be bundled for the default").toBeDefined();
+	});
+
+	it("bundles every curated id", () => {
+		const seededIds = seed.map(model => model.id).sort();
+		const bundledIds = Object.keys(bundled).sort();
+		expect(bundledIds).toEqual(seededIds);
+	});
+
+	for (const seededModel of seed) {
+		it(`matches contract for ${seededModel.id}`, () => {
+			const bundledEntry = bundled[seededModel.id];
+			expect(bundledEntry, `xai-oauth/${seededModel.id} missing from models.json`).toBeDefined();
+			expect(bundledEntry.id).toBe(seededModel.id);
+			expect(bundledEntry.name).toBe(seededModel.name);
+			expect(bundledEntry.provider).toBe("xai-oauth");
+			expect(bundledEntry.api).toBe("openai-responses");
+			expect(bundledEntry.contextWindow).toBe(seededModel.contextWindow);
+			expect(bundledEntry.reasoning).toBe(seededModel.reasoning);
+			// Input modality must survive both the curated seed and the bundle.
+			// Without this the static fallback used on offline boot strips
+			// vision capability silently (Codex PR #1127 review).
+			expect(bundledEntry.input).toEqual(seededModel.input);
+			expect(bundledEntry.compat?.supportsReasoningEffort).toBe(seededModel.compat?.supportsReasoningEffort);
+		});
+	}
+
+	// Absolute contract for the user-specified SuperGrok addition. The parity
+	// loop above can't catch a value typo (e.g. 2_000_000) or a flipped
+	// reasoning flag — both sides regenerate from the same seed together — so
+	// pin the literal attributes here.
+	it("exposes grok-composer-2.5-fast as a non-reasoning 200K text model", () => {
+		const composer = seed.find(model => model.id === "grok-composer-2.5-fast");
+		expect(composer, "grok-composer-2.5-fast must be in the SuperGrok curated seed").toBeDefined();
+		expect(composer!.reasoning).toBe(false);
+		expect(composer!.contextWindow).toBe(200_000);
+		expect(composer!.input).toEqual(["text"]);
+		// The bundled models.json entry is byte-identical to the generator's
+		// deterministic xai-oauth output: gen:models pushes
+		// buildXaiOAuthStaticSeed() (offline — xai-oauth has no upstream catalog
+		// source) and applyGeneratedModelPolicies(), so a regen reproduces these
+		// exact bytes; only unrelated other-provider network churn was excluded
+		// to keep the diff scoped. Pin its zero-cost invariant (overlay-stable
+		// for the SuperGrok subscription), which the parity loop above never
+		// compares. (maxTokens is pinned by the maxTokens-equals-contextWindow
+		// test below.)
+		expect(bundled["grok-composer-2.5-fast"]?.cost).toEqual({ input: 0, output: 0, cacheRead: 0, cacheWrite: 0 });
+	});
+
+	// The OAuth surface's /v1/models reports no per-request output limit, so the
+	// curated catalog owns maxTokens — set to mirror each model's contextWindow
+	// (the openai-responses wire still clamps the actual request to
+	// OPENAI_MAX_OUTPUT_TOKENS). Pin maxTokens === contextWindow on both the
+	// static-seed and bundled paths so a null placeholder can
+	// never silently leak back into the bundle.
+	it("sets maxTokens equal to contextWindow for every xai-oauth model", () => {
+		for (const model of seed) {
+			expect(model.maxTokens, `seed ${model.id} maxTokens`).toBe(model.contextWindow);
+			expect(bundled[model.id]?.maxTokens, `bundled ${model.id} maxTokens`).toBe(model.contextWindow);
+		}
+	});
+});
diff --git a/packages/coding-agent/CHANGELOG.md b/packages/coding-agent/CHANGELOG.md
index 5597d222b..6abd5a44f 100644
--- a/packages/coding-agent/CHANGELOG.md
+++ b/packages/coding-agent/CHANGELOG.md
@@ -2,6 +2,13 @@
 
 ## [Unreleased]
 
+### Changed
+
+- Routed paid xAI models (`XAI_API_KEY` / `xai/…`) through the Responses API used by SuperGrok OAuth instead of Chat Completions.
+- Changed the default model for `XAI_API_KEY` (`xai`) from `grok-4-fast-non-reasoning` to `grok-4.5`.
+- Changed the default model for SuperGrok OAuth (`xai-oauth`) from `grok-4.3` to `grok-4.5`.
+- Included `reasoning.encrypted_content` in Responses `include` for paid xAI and SuperGrok OAuth models.
+
 ## [17.3.4] - 2026-08-14
 
 ### Changed