diff --git a/apps/server/src/textGeneration/AntigravityTextGeneration.test.ts b/apps/server/src/textGeneration/AntigravityTextGeneration.test.ts
index 7e1f1446d1a55..62205d2835985 100644
--- a/apps/server/src/textGeneration/AntigravityTextGeneration.test.ts
+++ b/apps/server/src/textGeneration/AntigravityTextGeneration.test.ts
@@ -16,7 +16,7 @@ import * as Queue from "effect/Queue";
 import * as Schema from "effect/Schema";
 import * as Scope from "effect/Scope";
 import * as Stream from "effect/Stream";
-import { type AcpError } from "effect-acp/errors";
+import { type AcpError, AcpRequestError } from "effect-acp/errors";
 import type * as AcpSchema from "effect-acp/compat";
 import { expect } from "vite-plus/test";
 
@@ -452,6 +452,27 @@ it.layer(NodeServices.layer)("AntigravityTextGeneration", (it) => {
     }).pipe(Effect.scoped),
   );
 
+  it.effect.each([
+    {
+      code: -32000,
+      detail: "Sign in to Antigravity in Settings before you continue.",
+    },
+    { code: -32603, detail: "Antigravity text generation failed." },
+  ])("maps ACP error $code from the prompt request to a fixed detail", ({ code, detail }) =>
+    Effect.gen(function* () {
+      const fixture = yield* makeFixture({
+        prompt: () =>
+          Effect.fail(new AcpRequestError({ code, errorMessage: "Raw provider failure text." })),
+      });
+      const error = yield* fixture.textGeneration
+        .generateThreadTitle(fixture.titleInput)
+        .pipe(Effect.flip);
+      expect(error.detail).toBe(detail);
+      expect(error.detail).not.toContain("Raw provider failure text.");
+      yield* fixture.assertCleaned;
+    }).pipe(Effect.scoped),
+  );
+
   it.effect.each([
     { relativePath: "unexpected.txt", kind: "file" },
     { relativePath: ".agents/skills/unexpected.txt", kind: "file" },
@@ -551,6 +572,7 @@ it.layer(NodeServices.layer)("AntigravityTextGeneration", (it) => {
         .generateThreadTitle(fixture.titleInput)
         .pipe(Effect.flip);
       expect(error._tag).toBe("TextGenerationError");
+      expect(error.detail).toBe("Sign in before starting Antigravity.");
       expect(fixture.state.workspaces).toEqual([]);
       yield* fixture.assertCleaned;
     }).pipe(Effect.scoped),
diff --git a/apps/server/src/textGeneration/AntigravityTextGeneration.ts b/apps/server/src/textGeneration/AntigravityTextGeneration.ts
index 22fce172b1836..b7e7cfaeb40e8 100644
--- a/apps/server/src/textGeneration/AntigravityTextGeneration.ts
+++ b/apps/server/src/textGeneration/AntigravityTextGeneration.ts
@@ -1,4 +1,4 @@
-import { type ProviderSetupError, TextGenerationError } from "@t3tools/contracts";
+import { ProviderSetupError, TextGenerationError } from "@t3tools/contracts";
 import * as Deferred from "effect/Deferred";
 import * as Effect from "effect/Effect";
 import * as Exit from "effect/Exit";
@@ -13,12 +13,17 @@ import { type AcpError, AcpRequestError } from "effect-acp/errors";
 
 import { applyAntigravityAcpModelSelection } from "../provider/acp/AntigravityAcpSupport.ts";
 import { removeAntigravitySessionFiles } from "../provider/acp/AntigravitySessionFiles.ts";
+import {
+  ANTIGRAVITY_SIGN_IN_REQUIRED_MESSAGE,
+  isAntigravitySignInRequiredError,
+} from "../provider/antigravityAuthSupport.ts";
 import type * as AcpSessionRuntime from "@t3tools/provider-acp/server/AcpSessionRuntime";
 import * as TextGenerationOperations from "@t3tools/provider-core/server/textGenerationOperations";
 
 const ANTIGRAVITY_TIMEOUT_MS = 180_000;
 const MAX_OUTPUT_CHARS = 128_000;
 const isTextGenerationError = Schema.is(TextGenerationError);
+const isProviderSetupError = Schema.is(ProviderSetupError);
 const isNativeSessionId = Schema.is(Schema.String.check(Schema.isUUID(4)));
 const Configuration = Schema.Record(Schema.String, Schema.Unknown);
 const decodeConfiguration = Schema.decodeEffect(Schema.fromJsonString(Configuration));
@@ -322,7 +327,11 @@ export const makeAntigravityTextGeneration = Effect.fn("makeAntigravityTextGener
             ? cause
             : new TextGenerationError({
                 operation: input.operation,
-                detail: "Antigravity text generation failed.",
+                detail: isProviderSetupError(cause)
+                  ? cause.detail
+                  : isAntigravitySignInRequiredError(cause)
+                    ? ANTIGRAVITY_SIGN_IN_REQUIRED_MESSAGE
+                    : "Antigravity text generation failed.",
                 cause,
               }),
         ),