fix: resolve Claude CLI not found on Windows - PATH, prompt size, cwd (#1661)

apps/backend/core/client.py

@@ -29,6 +29,18 @@
 
 logger = logging.getLogger(__name__)
 
+# =============================================================================
+# Windows System Prompt Limits
+# =============================================================================
+# Windows CreateProcessW has a 32,768 character limit for the entire command line.
+# When CLAUDE.md is very large and passed as --system-prompt, the command can exceed
+# this limit, causing ERROR_FILE_NOT_FOUND. We cap CLAUDE.md content to stay safe.
+# 20,000 chars leaves ~12KB headroom for CLI overhead (model, tools, MCP config, etc.)
+WINDOWS_MAX_SYSTEM_PROMPT_CHARS = 20000
+WINDOWS_TRUNCATION_MESSAGE = (
+    "\n\n[... CLAUDE.md truncated due to Windows command-line length limit ...]"
+)
+
 # =============================================================================
 # Project Index Cache
 # =============================================================================
@@ -821,8 +833,31 @@ def create_client(
     if should_use_claude_md():
         claude_md_content = load_claude_md(project_dir)
         if claude_md_content:
+            # On Windows, the SDK passes system_prompt as a --system-prompt CLI argument.
+            # Windows CreateProcessW has a 32,768 character limit for the entire command line.
+            # When CLAUDE.md is very large, the command can exceed this limit, causing Windows
+            # to return ERROR_FILE_NOT_FOUND which the SDK misreports as "Claude Code not found".
+            # Cap CLAUDE.md content to keep total command line under the limit. (#1661)
+            was_truncated = False
+            if is_windows():
+                max_claude_md_chars = (
+                    WINDOWS_MAX_SYSTEM_PROMPT_CHARS
+                    - len(base_prompt)
+                    - len(WINDOWS_TRUNCATION_MESSAGE)
+                    - len("\n\n# Project Instructions (from CLAUDE.md)\n\n")
+                )
+                if len(claude_md_content) > max_claude_md_chars > 0:
+                    claude_md_content = (
+                        claude_md_content[:max_claude_md_chars]
+                        + WINDOWS_TRUNCATION_MESSAGE
+                    )
+                    print(
+                        "   - CLAUDE.md: truncated (exceeded Windows command-line limit)"
+                    )
+                    was_truncated = True
             base_prompt = f"{base_prompt}\n\n# Project Instructions (from CLAUDE.md)\n\n{claude_md_content}"
-            print("   - CLAUDE.md: included in system prompt")
+            if not was_truncated:
+                print("   - CLAUDE.md: included in system prompt")
         else:
             print("   - CLAUDE.md: not found in project root")
     else:

apps/frontend/src/__tests__/integration/subprocess-spawn.test.ts

@@ -186,7 +186,7 @@ describe('Subprocess Spawn Integration', () => {
           'Test task description'
         ]),
         expect.objectContaining({
-          cwd: AUTO_CLAUDE_SOURCE,  // Process runs from auto-claude source directory
+          cwd: TEST_PROJECT_PATH,  // Process runs from project directory to avoid cross-drive issues on Windows (#1661)
           env: expect.objectContaining({
             PYTHONUNBUFFERED: '1'
           })
@@ -218,7 +218,7 @@ describe('Subprocess Spawn Integration', () => {
           'spec-001'
         ]),
         expect.objectContaining({
-          cwd: AUTO_CLAUDE_SOURCE  // Process runs from auto-claude source directory
+          cwd: TEST_PROJECT_PATH  // Process runs from project directory to avoid cross-drive issues on Windows (#1661)
         })
       );
     }, 30000);  // Increase timeout for Windows CI (dynamic imports are slow)
@@ -248,7 +248,7 @@ describe('Subprocess Spawn Integration', () => {
           '--qa'
         ]),
         expect.objectContaining({
-          cwd: AUTO_CLAUDE_SOURCE  // Process runs from auto-claude source directory
+          cwd: TEST_PROJECT_PATH  // Process runs from project directory to avoid cross-drive issues on Windows (#1661)
         })
       );
     }, 30000);  // Increase timeout for Windows CI (dynamic imports are slow)

apps/frontend/src/main/agent/agent-manager.ts

@@ -329,7 +329,9 @@ export class AgentManager extends EventEmitter {
     this.registerTaskWithOperationRegistry(taskId, 'spec-creation', { projectPath, taskDescription, specDir });
 
     // Note: This is spec-creation but it chains to task-execution via run.py
-    await this.processManager.spawnProcess(taskId, autoBuildSource, args, combinedEnv, 'task-execution', projectId);
+    // Use projectPath as cwd instead of autoBuildSource to avoid cross-drive file access
+    // issues on Windows. The script path is absolute so Python finds its modules via sys.path[0]. (#1661)
+    await this.processManager.spawnProcess(taskId, projectPath, args, combinedEnv, 'task-execution', projectId);
   }
 
   /**
@@ -410,7 +412,10 @@ export class AgentManager extends EventEmitter {
     // Register with unified OperationRegistry for proactive swap support
     this.registerTaskWithOperationRegistry(taskId, 'task-execution', { projectPath, specId, options });
 
-    await this.processManager.spawnProcess(taskId, autoBuildSource, args, combinedEnv, 'task-execution', projectId);
+    // Use projectPath as cwd instead of autoBuildSource to avoid cross-drive file access
+    // issues on Windows. The script path (runPath) is absolute so Python finds its modules
+    // via sys.path[0] which is set to the script's directory. (#1661)
+    await this.processManager.spawnProcess(taskId, projectPath, args, combinedEnv, 'task-execution', projectId);
   }
 
   /**
@@ -448,7 +453,8 @@ export class AgentManager extends EventEmitter {
 
     const args = [runPath, '--spec', specId, '--project-dir', projectPath, '--qa'];
 
-    await this.processManager.spawnProcess(taskId, autoBuildSource, args, combinedEnv, 'qa-process', projectId);
+    // Use projectPath as cwd instead of autoBuildSource to avoid cross-drive issues on Windows (#1661)
+    await this.processManager.spawnProcess(taskId, projectPath, args, combinedEnv, 'qa-process', projectId);
   }
 
   /**

apps/frontend/src/main/agent/agent-process.ts

@@ -22,10 +22,10 @@
 import { buildMemoryEnvVars } from '../memory-env-builder';
 import { readSettingsFile } from '../settings-utils';
 import type { AppSettings } from '../../shared/types/settings';
-import { getOAuthModeClearVars } from './env-utils';
+import { getOAuthModeClearVars, normalizeEnvPathKey, mergePythonEnvPath } from './env-utils';
 import { getAugmentedEnv } from '../env-utils';
 import { getToolInfo, getClaudeCliPathForSdk } from '../cli-tool-manager';
-import { killProcessGracefully, isWindows } from '../platform';
+import { killProcessGracefully, isWindows, getPathDelimiter } from '../platform';
 import { debugLog } from '../../shared/utils/debug-logger';
 
 /**
@@ -679,15 +679,25 @@
       },
     });
 
-    // Parse Python commandto handle space-separated commands like "py -3"
+    // Merge PATH from pythonEnv with augmented PATH from env.
+    // pythonEnv may contain its own PATH (e.g., on Windows with pywin32_system32 prepended).
+    // Simply spreading pythonEnv after env would overwrite the augmented PATH (which includes
+    // npm globals, homebrew, etc.), causing "Claude code not found" on Windows (#1661).
+    // mergePythonEnvPath() normalizes PATH key casing and prepends pythonEnv-specific paths.
+    const mergedPythonEnv = { ...pythonEnv };
+    const pathSep = getPathDelimiter();
+
+    mergePythonEnvPath(env as Record<string, string | undefined>, mergedPythonEnv as Record<string, string | undefined>, pathSep);
+
+    // Parse Python command to handle space-separated commands like "py -3"
     const [pythonCommand, pythonBaseArgs] = parsePythonCommand(this.getPythonPath());
     let childProcess;
     try {
       childProcess = spawn(pythonCommand, [...pythonBaseArgs, ...args], {
         cwd,
         env: {
           ...env, // Already includes process.env, extraEnv, profileEnv, PYTHONUNBUFFERED, PYTHONUTF8
-          ...pythonEnv, // Include Python environment (PYTHONPATH for bundled packages)
+          ...mergedPythonEnv, // Python env with merged PATH (preserves augmented PATH entries)
           ...oauthModeClearVars, // Clear stale ANTHROPIC_* vars when in OAuth mode
           ...apiProfileEnv // Include active API profile config (highest priority for ANTHROPIC_* vars)
         }

apps/frontend/src/main/agent/agent-queue.ts

@@ -10,7 +10,7 @@ import type { IdeationConfig, Idea } from '../../shared/types';
 import { AUTO_BUILD_PATHS } from '../../shared/constants';
 import { detectRateLimit, createSDKRateLimitInfo, getBestAvailableProfileEnv } from '../rate-limit-detector';
 import { getAPIProfileEnv } from '../services/profile';
-import { getOAuthModeClearVars } from './env-utils';
+import { getOAuthModeClearVars, normalizeEnvPathKey } from './env-utils';
 import { debugLog, debugError } from '../../shared/utils/debug-logger';
 import { stripAnsiCodes } from '../../shared/utils/ansi-sanitizer';
 import { parsePythonCommand } from '../python-detector';
@@ -397,6 +397,12 @@ export class AgentQueueManager {
       PYTHONUTF8: '1'
     };
 
+    // Normalize PATH key to a single uppercase 'PATH' entry.
+    // On Windows, process.env spread produces 'Path' while pythonEnv may write 'PATH',
+    // resulting in duplicate keys in the final object. Without normalization the child
+    // process inherits both keys, which can cause tool-not-found errors (#1661).
+    normalizeEnvPathKey(finalEnv as Record<string, string | undefined>);
+
     // Debug: Show OAuth token source (token values intentionally omitted for security - AC4)
     const tokenSource = profileEnv['CLAUDE_CODE_OAUTH_TOKEN']
       ? 'Electron app profile'
@@ -730,6 +736,12 @@ export class AgentQueueManager {
       PYTHONUTF8: '1'
     };
 
+    // Normalize PATH key to a single uppercase 'PATH' entry.
+    // On Windows, process.env spread produces 'Path' while pythonEnv may write 'PATH',
+    // resulting in duplicate keys in the final object. Without normalization the child
+    // process inherits both keys, which can cause tool-not-found errors (#1661).
+    normalizeEnvPathKey(finalEnv as Record<string, string | undefined>);
+
     // Debug: Show OAuth token source (token values intentionally omitted for security - AC4)
     const tokenSource = profileEnv['CLAUDE_CODE_OAUTH_TOKEN']
       ? 'Electron app profile'

apps/frontend/src/main/agent/env-utils.test.ts

@@ -4,7 +4,7 @@
  */
 
 import { describe, it, expect } from 'vitest';
-import { getOAuthModeClearVars } from './env-utils';
+import { getOAuthModeClearVars, normalizeEnvPathKey, mergePythonEnvPath } from './env-utils';
 
 describe('getOAuthModeClearVars', () => {
   describe('OAuth mode (no active API profile)', () => {
@@ -132,3 +132,166 @@ describe('getOAuthModeClearVars', () => {
     });
   });
 });
+
+describe('normalizeEnvPathKey', () => {
+  it('should leave an already-uppercase PATH key untouched', () => {
+    const env: Record<string, string | undefined> = { PATH: '/usr/bin:/bin', HOME: '/home/user' };
+    normalizeEnvPathKey(env);
+    expect(env).toEqual({ PATH: '/usr/bin:/bin', HOME: '/home/user' });
+  });
+
+  it('should rename a lowercase-variant "Path" key to "PATH"', () => {
+    const env: Record<string, string | undefined> = { Path: 'C:\\Windows\\system32', HOME: '/home/user' };
+    normalizeEnvPathKey(env);
+    expect(env['PATH']).toBe('C:\\Windows\\system32');
+    expect('Path' in env).toBe(false);
+  });
+
+  it('should prefer existing "PATH" and remove "Path" when both keys coexist', () => {
+    // Simulates process.env spread ('Path') after getAugmentedEnv writes ('PATH')
+    const env: Record<string, string | undefined> = {
+      Path: 'C:\\old',
+      PATH: 'C:\\Windows\\system32;C:\\augmented',
+      HOME: '/home/user'
+    };
+    normalizeEnvPathKey(env);
+    expect(env.PATH).toBe('C:\\Windows\\system32;C:\\augmented');
+    expect('Path' in env).toBe(false);
+  });
+
+  it('should remove all case-variant PATH duplicates when PATH is already present', () => {
+    const env: Record<string, string | undefined> = {
+      PATH: '/correct',
+      Path: '/old1',
+      path: '/old2'
+    };
+    normalizeEnvPathKey(env);
+    expect(env.PATH).toBe('/correct');
+    expect('Path' in env).toBe(false);
+    expect('path' in env).toBe(false);
+  });
+
+  it('should handle env with no PATH-like key gracefully', () => {
+    const env: Record<string, string | undefined> = { HOME: '/home/user', SHELL: '/bin/zsh' };
+    normalizeEnvPathKey(env);
+    expect(env).toEqual({ HOME: '/home/user', SHELL: '/bin/zsh' });
+  });
+
+  it('should return the same env object reference (mutates in place)', () => {
+    const env: Record<string, string | undefined> = { PATH: '/usr/bin' };
+    const result = normalizeEnvPathKey(env);
+    expect(result).toBe(env);
+  });
+});
+
+describe('mergePythonEnvPath - Windows PATH merge logic (#1661)', () => {
+  const SEP = ';'; // Use Windows separator for these tests
+
+  it('should prepend pythonEnv-only entries to the augmented PATH', () => {
+    const env: Record<string, string | undefined> = {
+      PATH: 'C:\\npm;C:\\homebrew'
+    };
+    const mergedPythonEnv: Record<string, string | undefined> = {
+      PATH: 'C:\\pywin32_system32;C:\\npm;C:\\homebrew'
+    };
+
+    mergePythonEnvPath(env, mergedPythonEnv, SEP);
+
+    // pywin32_system32 is unique to pythonEnv, so it should be prepended
+    expect(mergedPythonEnv.PATH).toBe('C:\\pywin32_system32;C:\\npm;C:\\homebrew');
+  });
+
+  it('should deduplicate entries that already exist in augmented PATH', () => {
+    const env: Record<string, string | undefined> = {
+      PATH: 'C:\\npm;C:\\homebrew;C:\\pywin32_system32'
+    };
+    const mergedPythonEnv: Record<string, string | undefined> = {
+      PATH: 'C:\\pywin32_system32;C:\\npm'
+    };
+
+    mergePythonEnvPath(env, mergedPythonEnv, SEP);
+
+    // All pythonEnv entries are already in env.PATH, so mergedPythonEnv.PATH should equal env.PATH
+    expect(mergedPythonEnv.PATH).toBe('C:\\npm;C:\\homebrew;C:\\pywin32_system32');
+  });
+
+  it('should normalize Windows-style "Path" key in pythonEnv to "PATH"', () => {
+    const env: Record<string, string | undefined> = {
+      PATH: 'C:\\npm;C:\\homebrew'
+    };
+    // pythonEnv uses 'Path' (Windows native casing)
+    const mergedPythonEnv: Record<string, string | undefined> = {
+      Path: 'C:\\pywin32_system32;C:\\npm'
+    };
+
+    mergePythonEnvPath(env, mergedPythonEnv, SEP);
+
+    // 'Path' should be normalized to 'PATH' and pythonEnv-specific entry prepended
+    expect('Path' in mergedPythonEnv).toBe(false);
+    expect(mergedPythonEnv.PATH).toBe('C:\\pywin32_system32;C:\\npm;C:\\homebrew');
+  });
+
+  it('should normalize Windows-style "Path" in env and deduplicate duplicates', () => {
+    // Simulates process.env spread ('Path') + getAugmentedEnv write ('PATH') leaving both
+    const env: Record<string, string | undefined> = {
+      Path: 'C:\\old',
+      PATH: 'C:\\npm;C:\\homebrew'
+    };
+    const mergedPythonEnv: Record<string, string | undefined> = {
+      PATH: 'C:\\pywin32_system32;C:\\npm'
+    };
+
+    mergePythonEnvPath(env, mergedPythonEnv, SEP);
+
+    // env 'Path' should be removed; augmented 'PATH' value preserved
+    expect('Path' in env).toBe(false);
+    expect(env.PATH).toBe('C:\\npm;C:\\homebrew');
+    // Only the unique pywin32_system32 entry prepended
+    expect(mergedPythonEnv.PATH).toBe('C:\\pywin32_system32;C:\\npm;C:\\homebrew');
+  });
+
+  it('should use env.PATH unchanged when pythonEnv has no unique entries', () => {
+    const env: Record<string, string | undefined> = {
+      PATH: 'C:\\npm;C:\\homebrew'
+    };
+    const mergedPythonEnv: Record<string, string | undefined> = {
+      PATH: 'C:\\npm;C:\\homebrew'
+    };
+
+    mergePythonEnvPath(env, mergedPythonEnv, SEP);
+
+    expect(mergedPythonEnv.PATH).toBe('C:\\npm;C:\\homebrew');
+  });
+
+  it('should work correctly with Unix colon separator', () => {
+    const unixSep = ':';
+    const env: Record<string, string | undefined> = {
+      PATH: '/usr/bin:/bin'
+    };
+    const mergedPythonEnv: Record<string, string | undefined> = {
+      PATH: '/opt/pyenv/shims:/usr/bin:/bin'
+    };
+
+    mergePythonEnvPath(env, mergedPythonEnv, unixSep);
+
+    // /opt/pyenv/shims is unique and should be prepended
+    expect(mergedPythonEnv.PATH).toBe('/opt/pyenv/shims:/usr/bin:/bin');
+  });
+
+  it('should handle missing PATH in pythonEnv gracefully (no-op)', () => {
+    const env: Record<string, string | undefined> = {
+      PATH: 'C:\\npm;C:\\homebrew'
+    };
+    // pythonEnv has no PATH at all
+    const mergedPythonEnv: Record<string, string | undefined> = {
+      PYTHONPATH: '/site-packages'
+    };
+
+    mergePythonEnvPath(env, mergedPythonEnv, SEP);
+
+    // Nothing should change
+    expect(mergedPythonEnv.PATH).toBeUndefined();
+    expect(mergedPythonEnv.PYTHONPATH).toBe('/site-packages');
+    expect(env.PATH).toBe('C:\\npm;C:\\homebrew');
+  });
+});