diff --git a/src/shared/model-settings-compatibility.test.ts b/src/shared/model-settings-compatibility.test.ts
index 134bb9e71..9d92b2c7d 100644
--- a/src/shared/model-settings-compatibility.test.ts
+++ b/src/shared/model-settings-compatibility.test.ts
@@ -359,6 +359,29 @@ describe("resolveCompatibleModelSettings", () => {
     }
   })
 
+  test("DeepSeek maps generic reasoningEffort levels when capabilities come from heuristics", () => {
+    const capabilities = getModelCapabilities({
+      providerID: "openai-compatible",
+      modelID: "deepseek-v4-pro",
+    })
+    const result = resolveCompatibleModelSettings({
+      providerID: "openai-compatible",
+      modelID: "deepseek-v4-pro",
+      desired: { reasoningEffort: "xhigh" },
+      capabilities,
+    })
+
+    expect(result.reasoningEffort).toBe("max")
+    expect(result.changes).toEqual([
+      {
+        field: "reasoningEffort",
+        from: "xhigh",
+        to: "max",
+        reason: "unsupported-by-model-family",
+      },
+    ])
+  })
+
   test("GPT-5 downgrades unsupported max variant to xhigh", () => {
     const result = resolveCompatibleModelSettings({
       providerID: "openai",
diff --git a/src/shared/model-settings-compatibility.ts b/src/shared/model-settings-compatibility.ts
index 76f20bf09..414638fef 100644
--- a/src/shared/model-settings-compatibility.ts
+++ b/src/shared/model-settings-compatibility.ts
@@ -88,6 +88,11 @@ function resolveField(
   metadataOverride?: string[],
   familyAliases?: Record<string, string>,
 ): FieldResolution {
+  const aliased = familyAliases?.[normalized]
+  if (aliased && (metadataOverride?.includes(aliased) || familyCaps?.includes(aliased))) {
+    return { value: aliased, reason: "unsupported-by-model-family" }
+  }
+
   if (metadataOverride) {
     if (metadataOverride.includes(normalized)) return { value: normalized }
     return {
@@ -98,10 +103,6 @@ function resolveField(
 
   if (familyCaps) {
     if (familyCaps.includes(normalized)) return { value: normalized }
-    const aliased = familyAliases?.[normalized]
-    if (aliased && familyCaps.includes(aliased)) {
-      return { value: aliased, reason: "unsupported-by-model-family" }
-    }
     return {
       value: downgradeWithinLadder(normalized, familyCaps, ladder),
       reason: "unsupported-by-model-family",