diff --git a/apps/server/src/provider/testFixtures/grok-text-mock-agent.mjs b/apps/server/src/provider/testFixtures/grok-text-mock-agent.mjs
index 357bdb7fe564d..b3c6e49ec6b4c 100644
--- a/apps/server/src/provider/testFixtures/grok-text-mock-agent.mjs
+++ b/apps/server/src/provider/testFixtures/grok-text-mock-agent.mjs
@@ -12,6 +12,17 @@ for await (const line of NodeReadline.createInterface({ input: process.stdin }))
     NodeFS.appendFileSync(process.env.T3_ACP_REQUEST_LOG_PATH, `${line}\n`);
   }
   if (request.id === undefined) continue;
+  if (request.method === "session/prompt" && process.env.T3_ACP_PROMPT_ERROR_MESSAGE) {
+    write({
+      jsonrpc: "2.0",
+      id: request.id,
+      error: {
+        code: Number(process.env.T3_ACP_PROMPT_ERROR_CODE ?? -32003),
+        message: process.env.T3_ACP_PROMPT_ERROR_MESSAGE,
+      },
+    });
+    continue;
+  }
   let result;
   switch (request.method) {
     case "initialize":
diff --git a/apps/server/src/textGeneration/GrokTextGeneration.test.ts b/apps/server/src/textGeneration/GrokTextGeneration.test.ts
index 26ab9e79c7103..f91a06c627827 100644
--- a/apps/server/src/textGeneration/GrokTextGeneration.test.ts
+++ b/apps/server/src/textGeneration/GrokTextGeneration.test.ts
@@ -133,4 +133,58 @@ it.layer(layerGrokTextGenerationTest)("GrokTextGeneration", (it) => {
         }),
     ),
   );
+
+  it.effect("maps ACP failures to safe details and preserves their cause", () =>
+    Effect.gen(function* () {
+      for (const [code, detail] of [
+        [-32003, "Grok usage limit reached. Try again later."],
+        [-32000, "Grok authentication is required."],
+        [-32602, "Grok ACP request failed."],
+      ] as const) {
+        yield* withFakeAcpGrok(
+          {
+            T3_ACP_PROMPT_ERROR_MESSAGE: "private provider payload",
+            T3_ACP_PROMPT_ERROR_CODE: String(code),
+          },
+          (textGeneration) =>
+            Effect.gen(function* () {
+              const error = yield* textGeneration
+                .generateThreadTitle({
+                  cwd: process.cwd(),
+                  message: "the lint job is red",
+                  modelSelection: createModelSelection(
+                    ProviderInstanceId.make("grok"),
+                    "grok-mock-alt",
+                  ),
+                })
+                .pipe(Effect.flip);
+              expect(error.detail).toBe(detail);
+              expect(error.cause).toMatchObject({
+                code,
+                errorMessage: "private provider payload",
+              });
+            }),
+        );
+      }
+    }),
+  );
+
+  it.effect("explains rejected model settings without copying provider text", () =>
+    withFakeAcpGrok({}, (textGeneration) =>
+      Effect.gen(function* () {
+        const error = yield* textGeneration
+          .generateThreadTitle({
+            cwd: process.cwd(),
+            message: "the lint job is red",
+            modelSelection: createModelSelection(
+              ProviderInstanceId.make("grok"),
+              "grok-mock-missing",
+            ),
+          })
+          .pipe(Effect.flip);
+        expect(error.cause).toMatchObject({ code: -32602, errorMessage: "Unknown Grok model" });
+        expect(error.detail).toBe("Grok rejected the text generation model settings.");
+      }),
+    ),
+  );
 });
diff --git a/packages/provider-grok/src/server/textGeneration.ts b/packages/provider-grok/src/server/textGeneration.ts
index 61a6b2d482f53..1b9ede6652e85 100644
--- a/packages/provider-grok/src/server/textGeneration.ts
+++ b/packages/provider-grok/src/server/textGeneration.ts
@@ -4,7 +4,7 @@ import * as Option from "effect/Option";
 import * as Ref from "effect/Ref";
 import * as Schema from "effect/Schema";
 import * as ChildProcessSpawner from "effect/process/ChildProcessSpawner";
-import type * as EffectAcpErrors from "effect-acp/errors";
+import * as EffectAcpErrors from "effect-acp/errors";
 
 import { TextGenerationError } from "@t3tools/contracts";
 import type { GrokSettings } from "../settings.ts";
@@ -18,10 +18,25 @@ import {
   makeGrokAcpRuntime,
   resolveGrokAcpBaseModelId,
 } from "./acpSupport.ts";
+import { xAiRateLimitedErrorCode } from "./xaiAcpExtension.ts";
 
 const GROK_TIMEOUT_MS = 180_000;
 
 const isTextGenerationError = Schema.is(TextGenerationError);
+const isAcpRequestError = Schema.is(EffectAcpErrors.AcpRequestError);
+
+function grokAcpFailureDetail(cause: EffectAcpErrors.AcpError, fallback: string) {
+  if (!isAcpRequestError(cause)) return fallback;
+  switch (cause.code) {
+    case xAiRateLimitedErrorCode:
+      return "Grok usage limit reached. Try again later.";
+    // ACP auth_required
+    case -32000:
+      return "Grok authentication is required.";
+    default:
+      return fallback;
+  }
+}
 
 export const makeGrokTextGeneration = Effect.fn("makeGrokTextGeneration")(function* (
   grokSettings: GrokSettings,
@@ -75,7 +90,12 @@ export const makeGrokTextGeneration = Effect.fn("makeGrokTextGeneration")(functi
           mapError: (cause) =>
             new TextGenerationError({
               operation,
-              detail: "Failed to set Grok ACP base model for text generation.",
+              detail: grokAcpFailureDetail(
+                cause,
+                isAcpRequestError(cause) && cause.code === -32602
+                  ? "Grok rejected the text generation model settings."
+                  : "Failed to set Grok ACP base model for text generation.",
+              ),
               cause,
             }),
         });
@@ -98,7 +118,7 @@ export const makeGrokTextGeneration = Effect.fn("makeGrokTextGeneration")(functi
             ? cause
             : new TextGenerationError({
                 operation,
-                detail: "Grok ACP request failed.",
+                detail: grokAcpFailureDetail(cause, "Grok ACP request failed."),
                 cause,
               }),
         ),