diff --git a/src/shared/model-settings-compatibility.test.ts b/src/shared/model-settings-compatibility.test.ts
index d9b8a455d..6e7a7b590 100644
--- a/src/shared/model-settings-compatibility.test.ts
+++ b/src/shared/model-settings-compatibility.test.ts
@@ -486,6 +486,30 @@ describe("resolveCompatibleModelSettings", () => {
     ])
   })
 
+  test("#given capabilities.maxOutputTokens is 0 #then maxTokens preserved unchanged", () => {
+    const result = resolveCompatibleModelSettings({
+      providerID: "openai",
+      modelID: "gpt-5.4",
+      desired: { maxTokens: 200_000 },
+      capabilities: { maxOutputTokens: 0 },
+    })
+
+    expect(result.maxTokens).toBe(200_000)
+    expect(result.changes).toEqual([])
+  })
+
+  test("#given capabilities.maxOutputTokens is -1 #then maxTokens preserved unchanged", () => {
+    const result = resolveCompatibleModelSettings({
+      providerID: "openai",
+      modelID: "gpt-5.4",
+      desired: { maxTokens: 200_000 },
+      capabilities: { maxOutputTokens: -1 },
+    })
+
+    expect(result.maxTokens).toBe(200_000)
+    expect(result.changes).toEqual([])
+  })
+
   // Passthrough: undefined desired values produce no changes
   test("no-op when desired settings are empty", () => {
     const result = resolveCompatibleModelSettings({
diff --git a/src/shared/model-settings-compatibility.ts b/src/shared/model-settings-compatibility.ts
index f39875f43..974d75619 100644
--- a/src/shared/model-settings-compatibility.ts
+++ b/src/shared/model-settings-compatibility.ts
@@ -165,6 +165,7 @@ export function resolveCompatibleModelSettings(
   if (
     maxTokens !== undefined &&
     input.capabilities?.maxOutputTokens !== undefined &&
+    input.capabilities.maxOutputTokens > 0 &&
     maxTokens > input.capabilities.maxOutputTokens
   ) {
     changes.push({