fix: support Claude subcommands and background sessions

Squash merge PR #1240.\n\nValidated locally from the PR head because trusted-author GitHub CI was skipped for this fork PR:\n- bun run validate\n- bun run build:all\n- bun run test:all\n- CCS_E2E_SKIP_BUILD=1 bun run test:e2e

tests/unit/utils/claude-subcommand-detector.test.ts

@@ -1,5 +1,9 @@
 import { describe, expect, it } from 'bun:test';
-import { isClaudeSubcommandInvocation } from '../../../src/utils/claude-subcommand-detector';
+import {
+  isClaudeSubcommandInvocation,
+  stripClaudeCodeFeatureBlockingEnv,
+  stripClaudeSubcommandSessionArgs,
+} from '../../../src/utils/claude-subcommand-detector';
 import { appendThirdPartyWebSearchToolArgs } from '../../../src/utils/websearch/claude-tool-args';
 import { appendThirdPartyImageAnalysisToolArgs } from '../../../src/utils/image-analysis/claude-tool-args';
 import { appendBrowserToolArgs } from '../../../src/utils/browser/claude-tool-args';
@@ -36,6 +40,14 @@ describe('isClaudeSubcommandInvocation', () => {
   it('skips past value-taking flags before the positional', () => {
     expect(isClaudeSubcommandInvocation(['--model', 'sonnet', 'agents'])).toBe(true);
     expect(isClaudeSubcommandInvocation(['--settings', '/tmp/s.json', 'doctor'])).toBe(true);
+    expect(
+      isClaudeSubcommandInvocation([
+        '--dangerously-skip-permissions',
+        '--teammate-mode',
+        'in-process',
+        'agents',
+      ])
+    ).toBe(true);
   });
 
   it('does not treat a flag value matching a subcommand name as a subcommand', () => {
@@ -57,6 +69,59 @@ describe('isClaudeSubcommandInvocation', () => {
   });
 });
 
+describe('stripClaudeCodeFeatureBlockingEnv', () => {
+  it('removes telemetry disable env that blocks Claude Code background features', () => {
+    const env = stripClaudeCodeFeatureBlockingEnv({
+      DISABLE_TELEMETRY: '1',
+      DISABLE_BUG_COMMAND: '1',
+      DISABLE_ERROR_REPORTING: '1',
+      ANTHROPIC_MODEL: 'gpt-5.5',
+    });
+
+    expect(env.DISABLE_TELEMETRY).toBeUndefined();
+    expect(env.DISABLE_BUG_COMMAND).toBe('1');
+    expect(env.DISABLE_ERROR_REPORTING).toBe('1');
+    expect(env.ANTHROPIC_MODEL).toBe('gpt-5.5');
+  });
+});
+
+describe('stripClaudeSubcommandSessionArgs', () => {
+  it('removes session-only flags before a Claude subcommand', () => {
+    expect(
+      stripClaudeSubcommandSessionArgs([
+        '--dangerously-skip-permissions',
+        '--teammate-mode',
+        'in-process',
+        'agents',
+      ])
+    ).toEqual(['agents']);
+  });
+
+  it('removes session-only flags after a Claude subcommand while preserving subcommand flags', () => {
+    expect(
+      stripClaudeSubcommandSessionArgs([
+        'agents',
+        '--dangerously-skip-permissions',
+        '--teammate-mode',
+        'in-process',
+        '--setting-sources',
+        'user',
+      ])
+    ).toEqual(['agents', '--setting-sources', 'user']);
+  });
+
+  it('leaves non-subcommand interactive launches unchanged', () => {
+    expect(
+      stripClaudeSubcommandSessionArgs([
+        '--dangerously-skip-permissions',
+        '--teammate-mode',
+        'in-process',
+        'fix the bug',
+      ])
+    ).toEqual(['--dangerously-skip-permissions', '--teammate-mode', 'in-process', 'fix the bug']);
+  });
+});
+
 describe('subcommand passthrough — injectors short-circuit', () => {
   it('appendThirdPartyWebSearchToolArgs returns args unchanged for subcommand invocations', () => {
     expect(appendThirdPartyWebSearchToolArgs(['agents'])).toEqual(['agents']);