diff --git a/packages/catalog/CHANGELOG.md b/packages/catalog/CHANGELOG.md
index 556fd7fed..eab557183 100644
--- a/packages/catalog/CHANGELOG.md
+++ b/packages/catalog/CHANGELOG.md
@@ -18,6 +18,7 @@
 - Stopped emitting stale `thinking.efforts` dials on paid xAI Responses catalog rows that reject `reasoning.effort` (`grok-code-fast-1`, `grok-build-0.1`, `grok-4.20-0309-reasoning`, and other off-allowlist reasoners).
 - Marked first-party xAI Responses hosts (`xai` and `xai-oauth`) as not supporting `reasoning.summary`, so paid `xai/grok-4.5` effort requests omit the unsupported field instead of sending `summary: "auto"`.
 - Removed unsupported `xhigh` (and `max`) thinking tiers from first-party Grok Responses catalog rows; leftover `xhigh`/`max` requests clamp to `high`.
+- Stopped baking `reasoningEffortMap` on first-party xAI catalog rows that omit `reasoning.effort` (`omitReasoningEffort: true`).
 
 ## [17.3.4] - 2026-08-14
 
diff --git a/packages/catalog/scripts/generated-policies.ts b/packages/catalog/scripts/generated-policies.ts
index 0002dab3e..1d1737155 100644
--- a/packages/catalog/scripts/generated-policies.ts
+++ b/packages/catalog/scripts/generated-policies.ts
@@ -354,7 +354,7 @@ export function applyOllamaCloudOutputCap(models: ModelSpec<Api>[]): void {
 }
 
 function applyGeneratedModelPolicy(model: ModelSpec<Api>): void {
-	if (model.provider === "xai" && model.api === "openai-responses") {
+	if ((model.provider === "xai" || model.provider === "xai-oauth") && model.api === "openai-responses") {
 		const updated = applyXaiResponsesThinkingPolicy(model as ModelSpec<"openai-responses">);
 		model.compat = updated.compat;
 	}
diff --git a/packages/catalog/src/models.json b/packages/catalog/src/models.json
index ec12711b7..dcb91951b 100644
--- a/packages/catalog/src/models.json
+++ b/packages/catalog/src/models.json
@@ -103732,11 +103732,6 @@
 			"contextWindow": 131072,
 			"maxTokens": 8192,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -103760,11 +103755,6 @@
 			"contextWindow": 131072,
 			"maxTokens": 8192,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -103788,11 +103778,6 @@
 			"contextWindow": 131072,
 			"maxTokens": 8192,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -103817,11 +103802,6 @@
 			"contextWindow": 8192,
 			"maxTokens": 4096,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -103846,11 +103826,6 @@
 			"contextWindow": 8192,
 			"maxTokens": 4096,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -103875,11 +103850,6 @@
 			"contextWindow": 8192,
 			"maxTokens": 4096,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -103903,11 +103873,6 @@
 			"contextWindow": 131072,
 			"maxTokens": 8192,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -103931,11 +103896,6 @@
 			"contextWindow": 131072,
 			"maxTokens": 8192,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -103959,11 +103919,6 @@
 			"contextWindow": 131072,
 			"maxTokens": 8192,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -103987,11 +103942,6 @@
 			"contextWindow": 131072,
 			"maxTokens": 8192,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -104175,11 +104125,6 @@
 			"contextWindow": 256000,
 			"maxTokens": 64000,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -104204,11 +104149,6 @@
 			"contextWindow": 2000000,
 			"maxTokens": 30000,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -104233,11 +104173,6 @@
 			"contextWindow": 2000000,
 			"maxTokens": 30000,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -104262,11 +104197,6 @@
 			"contextWindow": 2000000,
 			"maxTokens": 30000,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -104291,11 +104221,6 @@
 			"contextWindow": 2000000,
 			"maxTokens": 30000,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -104320,11 +104245,6 @@
 			"contextWindow": 1000000,
 			"maxTokens": 30000,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -104349,11 +104269,6 @@
 			"contextWindow": 1000000,
 			"maxTokens": 30000,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -104378,11 +104293,6 @@
 			"contextWindow": 2000000,
 			"maxTokens": 30000,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -104407,11 +104317,6 @@
 			"contextWindow": 2000000,
 			"maxTokens": 30000,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -104587,11 +104492,6 @@
 			"contextWindow": 131072,
 			"maxTokens": 4096,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -104616,11 +104516,6 @@
 			"contextWindow": 256000,
 			"maxTokens": 256000,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -104644,11 +104539,6 @@
 			"contextWindow": 256000,
 			"maxTokens": 10000,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -104673,11 +104563,6 @@
 			"contextWindow": 8192,
 			"maxTokens": 4096,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low",
-					"xhigh": "high",
-					"max": "high"
-				},
 				"supportsReasoningEffort": false,
 				"omitReasoningEffort": true
 			}
@@ -104706,9 +104591,6 @@
 			"supportsComputerUse": false,
 			"supportsComputerUseConfig": false,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low"
-				},
 				"includeEncryptedReasoning": true,
 				"filterReasoningHistory": false,
 				"supportsImageDetailOriginal": false,
@@ -104738,9 +104620,6 @@
 			"supportsComputerUse": false,
 			"supportsComputerUseConfig": false,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low"
-				},
 				"includeEncryptedReasoning": true,
 				"filterReasoningHistory": false,
 				"supportsImageDetailOriginal": false,
@@ -104782,7 +104661,9 @@
 			"supportsComputerUseConfig": false,
 			"compat": {
 				"reasoningEffortMap": {
-					"minimal": "low"
+					"minimal": "low",
+					"xhigh": "high",
+					"max": "high"
 				},
 				"includeEncryptedReasoning": true,
 				"filterReasoningHistory": false,
@@ -104826,7 +104707,9 @@
 			"supportsComputerUseConfig": false,
 			"compat": {
 				"reasoningEffortMap": {
-					"minimal": "low"
+					"minimal": "low",
+					"xhigh": "high",
+					"max": "high"
 				},
 				"includeEncryptedReasoning": true,
 				"filterReasoningHistory": false,
@@ -104870,7 +104753,9 @@
 			"supportsComputerUseConfig": false,
 			"compat": {
 				"reasoningEffortMap": {
-					"minimal": "low"
+					"minimal": "low",
+					"xhigh": "high",
+					"max": "high"
 				},
 				"includeEncryptedReasoning": true,
 				"filterReasoningHistory": false,
@@ -104929,9 +104814,6 @@
 			"supportsComputerUse": false,
 			"supportsComputerUseConfig": false,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low"
-				},
 				"includeEncryptedReasoning": true,
 				"filterReasoningHistory": false,
 				"supportsImageDetailOriginal": false,
@@ -104961,9 +104843,6 @@
 			"supportsComputerUse": false,
 			"supportsComputerUseConfig": false,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low"
-				},
 				"includeEncryptedReasoning": true,
 				"filterReasoningHistory": false,
 				"supportsImageDetailOriginal": false,
@@ -104992,9 +104871,6 @@
 			"supportsComputerUse": false,
 			"supportsComputerUseConfig": false,
 			"compat": {
-				"reasoningEffortMap": {
-					"minimal": "low"
-				},
 				"includeEncryptedReasoning": true,
 				"filterReasoningHistory": false,
 				"supportsImageDetailOriginal": false,
diff --git a/packages/catalog/src/provider-models/openai-compat.ts b/packages/catalog/src/provider-models/openai-compat.ts
index ae5c60ec0..0a2e12022 100644
--- a/packages/catalog/src/provider-models/openai-compat.ts
+++ b/packages/catalog/src/provider-models/openai-compat.ts
@@ -1396,18 +1396,20 @@ const XAI_REASONING_EFFORT_MAP = { minimal: "low", xhigh: "high", max: "high" }
  */
 export function applyXaiResponsesThinkingPolicy(model: ModelSpec<"openai-responses">): ModelSpec<"openai-responses"> {
 	const effortCapable = model.compat?.supportsReasoningEffort ?? isGrokReasoningEffortCapable(model.id);
-	return {
-		...model,
-		compat: {
-			...(model.compat ?? {}),
-			reasoningEffortMap: {
-				...XAI_REASONING_EFFORT_MAP,
-				...(model.compat?.reasoningEffortMap ?? {}),
-			},
-			supportsReasoningEffort: effortCapable,
-			omitReasoningEffort: model.compat?.omitReasoningEffort ?? !effortCapable,
-		},
+	const compat = {
+		...(model.compat ?? {}),
+		supportsReasoningEffort: effortCapable,
+		omitReasoningEffort: model.compat?.omitReasoningEffort ?? !effortCapable,
 	};
+	if (effortCapable) {
+		compat.reasoningEffortMap = {
+			...XAI_REASONING_EFFORT_MAP,
+			...(model.compat?.reasoningEffortMap ?? {}),
+		};
+	} else {
+		delete compat.reasoningEffortMap;
+	}
+	return { ...model, compat };
 }
 
 // xai-oauth's /v1/models exposes no per-request output limit on the OAuth
@@ -1423,9 +1425,9 @@ export function applyXaiResponsesThinkingPolicy(model: ModelSpec<"openai-respons
 // reasoning metadata and fetchOpenAICompatibleModels defaults reasoning to
 // false). Caller supplies a `base` Model (either a freshly synthesised seed
 // or a dynamic-fetched entry); the helper layers curated fields on top.
-// The `minimal -> low` effort clamp (XAI_REASONING_EFFORT_MAP) is always
-// merged in so dynamic-fetched models — which arrive without curated
-// compat keys — still get the clamp applyResponsesReasoningParams expects.
+// The `minimal -> low` effort clamp (XAI_REASONING_EFFORT_MAP) is merged
+// only onto effort-capable rows. Off-allowlist reasoners omit the wire
+// param, so a map on those specs is dead weight.
 // The effort-dial pair (`supportsReasoningEffort`/`omitReasoningEffort`) is
 // authoritative: a stale flag on `base` (previous snapshot or dynamic fetch)
 // must not outlive an allowlist change in identity/family.ts.
@@ -1436,13 +1438,17 @@ function mergeCuratedIntoModel(
 	const effortCapable = curated.supportsReasoningEffort ?? isGrokReasoningEffortCapable(curated.id);
 	const compat = {
 		...(base.compat ?? {}),
-		reasoningEffortMap: { ...XAI_REASONING_EFFORT_MAP, ...(base.compat?.reasoningEffortMap ?? {}) },
 		includeEncryptedReasoning: base.compat?.includeEncryptedReasoning ?? true,
 		filterReasoningHistory: false,
 		supportsImageDetailOriginal: base.compat?.supportsImageDetailOriginal ?? false,
 		omitReasoningEffort: !effortCapable,
 		supportsReasoningEffort: effortCapable,
 	};
+	if (effortCapable) {
+		compat.reasoningEffortMap = { ...XAI_REASONING_EFFORT_MAP, ...(base.compat?.reasoningEffortMap ?? {}) };
+	} else {
+		delete compat.reasoningEffortMap;
+	}
 	return {
 		...base,
 		contextWindow: curated.contextWindow,
diff --git a/packages/catalog/test/generated-policies.test.ts b/packages/catalog/test/generated-policies.test.ts
index e26115a41..fcb33cdcf 100644
--- a/packages/catalog/test/generated-policies.test.ts
+++ b/packages/catalog/test/generated-policies.test.ts
@@ -496,8 +496,8 @@ describe("generated model policies", () => {
 		expect(models[0]?.compat).toMatchObject({
 			supportsReasoningEffort: false,
 			omitReasoningEffort: true,
-			reasoningEffortMap: { minimal: "low" },
 		});
+		expect(models[0]?.compat).not.toHaveProperty("reasoningEffortMap");
 		expect(models[1]?.thinking?.efforts).toEqual([Effort.Minimal, Effort.Low, Effort.Medium, Effort.High]);
 		expect(models[1]?.compat?.supportsReasoningEffort).toBe(true);
 		// Non-xAI hosts are outside this policy — no baked no-dial compat.
diff --git a/packages/catalog/test/xai-responses-thinking-policy.test.ts b/packages/catalog/test/xai-responses-thinking-policy.test.ts
index 26b8824f4..0217a5271 100644
--- a/packages/catalog/test/xai-responses-thinking-policy.test.ts
+++ b/packages/catalog/test/xai-responses-thinking-policy.test.ts
@@ -73,13 +73,14 @@ describe("paid xAI Responses thinking policy", () => {
 			expect(byId[id]?.compat, id).toMatchObject({
 				supportsReasoningEffort: false,
 				omitReasoningEffort: true,
-				reasoningEffortMap: { minimal: "low" },
 			});
+			expect(byId[id]?.compat, id).not.toHaveProperty("reasoningEffortMap");
 		}
 		expect(byId["grok-2"]?.compat).toMatchObject({
 			supportsReasoningEffort: false,
 			omitReasoningEffort: true,
 		});
+		expect(byId["grok-2"]?.compat).not.toHaveProperty("reasoningEffortMap");
 	});
 
 	it("strips stale thinking dials from off-allowlist paid xAI reasoners during generation", () => {