Fix Claude stderr diagnostics and hide max effort

packages/server/src/server/agent/agent-manager.ts

@@ -2022,6 +2022,9 @@ export class AgentManager {
             lifecycle: agent.lifecycle,
             activeForegroundTurnId: agent.activeForegroundTurnId,
             eventTurnId,
+            error: event.error,
+            code: event.code,
+            diagnostic: event.diagnostic,
           },
           "handleStreamEvent: turn_failed",
         );

packages/server/src/server/agent/providers/claude-agent.max-effort.real.e2e.test.ts

@@ -0,0 +1,63 @@
+import { describe, expect, test } from "vitest";
+import pino from "pino";
+
+import type { AgentStreamEvent, AgentSession } from "../agent-sdk-types.js";
+import { isCommandAvailable } from "../provider-launch-config.js";
+import { ClaudeAgentClient } from "./claude-agent.js";
+import { streamSession } from "./test-utils/session-stream-adapter.js";
+
+const hasClaudeCredentials =
+  !!process.env.CLAUDE_CODE_OAUTH_TOKEN || !!process.env.ANTHROPIC_API_KEY;
+
+function isTerminalEvent(event: AgentStreamEvent): boolean {
+  return (
+    event.type === "turn_completed" ||
+    event.type === "turn_failed" ||
+    event.type === "turn_canceled"
+  );
+}
+
+async function collectUntilTerminal(session: AgentSession): Promise<AgentStreamEvent[]> {
+  const events: AgentStreamEvent[] = [];
+  for await (const event of streamSession(session, "Respond with exactly: HELLO_MAX")) {
+    events.push(event);
+    if (isTerminalEvent(event)) {
+      return events;
+    }
+  }
+  return events;
+}
+
+describe("Claude max effort availability (real)", () => {
+  test.runIf(isCommandAvailable("claude") && hasClaudeCredentials)(
+    "surfaces the Claude stderr diagnostic when bypassPermissions + max effort is unavailable",
+    async () => {
+      const client = new ClaudeAgentClient({
+        logger: pino({ level: "silent" }),
+      });
+      const session = await client.createSession({
+        provider: "claude",
+        cwd: process.cwd(),
+        modeId: "bypassPermissions",
+        model: "claude-opus-4-6",
+        thinkingOptionId: "max",
+      });
+
+      try {
+        const events = await collectUntilTerminal(session);
+        const failure = events.find(
+          (event): event is Extract<AgentStreamEvent, { type: "turn_failed" }> =>
+            event.type === "turn_failed",
+        );
+
+        expect(failure).toBeDefined();
+        expect(failure?.error).toContain("Claude Code process exited with code 1");
+        expect(failure?.code).toBe("1");
+        expect(failure?.diagnostic).toContain('Effort level "max" is not available');
+      } finally {
+        await session.close().catch(() => undefined);
+      }
+    },
+    30_000,
+  );
+});

packages/server/src/server/agent/providers/claude-agent.redesign.test.ts

@@ -718,6 +718,72 @@ describe("ClaudeAgentSession redesign invariants", () => {
     }
   });
 
+  test("captures Claude stderr in the turn failure diagnostic when stderr arrives after process exit", async () => {
+    const stderrMessage =
+      'Error: Effort level "max" is not available for Claude.ai subscribers. Please use "low", "medium", or "high".';
+    let capturedOptions:
+      | {
+          stderr?: (data: string) => void;
+          effort?: string;
+          permissionMode?: string;
+        }
+      | undefined;
+
+    sdkQueryFactory.mockImplementation(
+      ({ options }: { options: { stderr?: (data: string) => void; effort?: string } }) => {
+        capturedOptions = options;
+        let failed = false;
+        return createBaseQueryMock(
+          vi.fn(async () => {
+            if (!failed) {
+              failed = true;
+              setTimeout(() => {
+                options.stderr?.(`${stderrMessage}\n`);
+              }, 0);
+              throw new Error("Claude Code process exited with code 1");
+            }
+            return { done: true, value: undefined };
+          }),
+        );
+      },
+    );
+
+    const loggerSpy = createSpyLogger();
+    const client = new ClaudeAgentClient({
+      logger: loggerSpy.logger,
+      queryFactory: sdkQueryFactory,
+    });
+    const session = await client.createSession({
+      provider: "claude",
+      cwd: process.cwd(),
+      modeId: "bypassPermissions",
+      thinkingOptionId: "max",
+    });
+
+    try {
+      const events = await collectUntilTerminal(streamSession(session, "trigger max failure"));
+      const failure = events.find(
+        (event): event is Extract<AgentStreamEvent, { type: "turn_failed" }> =>
+          event.type === "turn_failed",
+      );
+
+      expect(capturedOptions?.permissionMode).toBe("bypassPermissions");
+      expect(capturedOptions?.effort).toBe("max");
+      expect(failure).toMatchObject({
+        type: "turn_failed",
+        error: "Claude Code process exited with code 1",
+        code: "1",
+        diagnostic: stderrMessage,
+      });
+      expect(loggerSpy.error).toHaveBeenCalledWith(
+        expect.objectContaining({ stderr: stderrMessage }),
+        "Claude Agent SDK stderr",
+      );
+    } finally {
+      await session.close();
+    }
+  });
+
   test("reuses one autonomous run for unbound stream_event bursts with no foreground run", async () => {
     const session = await createSession();
     const internal = session as unknown as {

packages/server/src/server/agent/providers/claude-agent.test.ts

@@ -320,7 +320,6 @@ describe("ClaudeAgentClient.listModels", () => {
           { id: "low", label: "Low" },
           { id: "medium", label: "Medium" },
           { id: "high", label: "High" },
-          { id: "max", label: "Max" },
         ],
       }),
       expect.objectContaining({

packages/server/src/server/agent/providers/claude-agent.ts

@@ -206,7 +206,7 @@ function applyRuntimeSettingsToClaudeOptions(
       // Always use process.execPath — the actual node binary running the daemon.
       const command =
         resolved.command === spawnOptions.command ? process.execPath : resolved.command;
-      return spawn(command, resolved.args, {
+      const child = spawn(command, resolved.args, {
         cwd: spawnOptions.cwd,
         env: {
           ...applyProviderEnv(spawnOptions.env, runtimeSettings),
@@ -215,6 +215,12 @@ function applyRuntimeSettingsToClaudeOptions(
         signal: spawnOptions.signal,
         stdio: ["pipe", "pipe", "pipe"],
       });
+      if (typeof options.stderr === "function") {
+        child.stderr?.on("data", (chunk: Buffer | string) => {
+          options.stderr?.(chunk.toString());
+        });
+      }
+      return child;
     },
   };
 }
@@ -248,6 +254,8 @@ type ClaudeOptionsLogSummary = {
 };
 
 const MAX_RECENT_STDERR_CHARS = 4000;
+const STDERR_FLUSH_WAIT_MS = 150;
+const STDERR_FLUSH_POLL_INTERVAL_MS = 10;
 
 function summarizeClaudeOptionsForLog(options: ClaudeOptions): ClaudeOptionsLogSummary {
   const systemPromptRaw = options.systemPrompt;
@@ -1996,6 +2004,25 @@ class ClaudeAgentSession implements AgentSession {
     return this.recentStderr.trim() || undefined;
   }
 
+  private async awaitRecentStderrAfterProcessExit(error: unknown): Promise<void> {
+    if (this.getRecentStderrDiagnostic()) {
+      return;
+    }
+    const message =
+      typeof error === "string" ? error : error instanceof Error ? error.message : "";
+    if (!/\bprocess exited with code\b/i.test(message) && !/\bterminated by signal\b/i.test(message)) {
+      return;
+    }
+
+    const startedAt = Date.now();
+    while (!this.closed && !this.getRecentStderrDiagnostic()) {
+      if (Date.now() - startedAt >= STDERR_FLUSH_WAIT_MS) {
+        return;
+      }
+      await new Promise((resolve) => setTimeout(resolve, STDERR_FLUSH_POLL_INTERVAL_MS));
+    }
+  }
+
   private createTurnId(owner: "foreground" | "autonomous"): string {
     return `${owner}-turn-${this.nextTurnOrdinal++}`;
   }
@@ -2213,6 +2240,7 @@ class ClaudeAgentSession implements AgentSession {
             continue;
           }
           if (!this.closed && this.query === activeQuery) {
+            await this.awaitRecentStderrAfterProcessExit(error);
             this.failActiveTurns(error instanceof Error ? error.message : "Claude stream failed");
           }
           return;

packages/server/src/server/agent/providers/claude/sdk-model-resolver.test.ts

@@ -72,7 +72,6 @@ describe("resolveClaudeModelsFromSdkModels", () => {
           { id: "low", label: "Low" },
           { id: "medium", label: "Medium" },
           { id: "high", label: "High" },
-          { id: "max", label: "Max" },
         ],
       }),
       expect.objectContaining({

packages/server/src/server/agent/providers/claude/sdk-model-resolver.ts

@@ -7,6 +7,9 @@ type ParsedClaudeSdkModelDescriptor = {
   version: string;
 };
 
+// Claude may advertise effort levels that are not usable for all account types.
+const DISABLED_CLAUDE_THINKING_EFFORT_LEVELS: readonly string[] = ["max"];
+
 function normalizeWhitespace(value: string): string {
   return value.replace(/\s+/g, " ").trim();
 }
@@ -67,15 +70,17 @@ function buildThinkingOptions(model: ModelInfo): {
   thinkingOptions?: AgentSelectOption[];
   defaultThinkingOptionId?: string;
 } {
-  const effortLevels = model.supportedEffortLevels ?? [];
+  const effortLevels = (model.supportedEffortLevels ?? []).filter(
+    (level) => !DISABLED_CLAUDE_THINKING_EFFORT_LEVELS.includes(level),
+  );
   if (!model.supportsEffort || effortLevels.length === 0) {
     return {};
   }
 
   const thinkingOptions: AgentSelectOption[] = effortLevels.map((level) => ({
-      id: level,
-      label: titleCase(level),
-    }));
+    id: level,
+    label: titleCase(level),
+  }));
 
   return {
     thinkingOptions,