diff --git a/src/lib/claude-client.ts b/src/lib/claude-client.ts
index bcf63ed..a081f42 100644
--- a/src/lib/claude-client.ts
+++ b/src/lib/claude-client.ts
@@ -18,7 +18,7 @@ import type {
 import type { ClaudeStreamOptions, SSEEvent, TokenUsage, MCPServerConfig, PermissionRequestEvent } from '@/types';
 import { registerPendingPermission } from './permission-registry';
 import { getSetting, getActiveProvider } from './db';
-import { findClaudeBinary, getExpandedPath } from './platform';
+import { findClaudeBinary, findGitBash, getExpandedPath } from './platform';
 import os from 'os';
 
 let cachedClaudePath: string | null | undefined;
@@ -157,6 +157,14 @@ export function streamClaude(options: ClaudeStreamOptions): ReadableStream<strin
         // Ensure SDK subprocess has expanded PATH (consistent with Electron mode)
         sdkEnv.PATH = getExpandedPath();
 
+        // On Windows, auto-detect Git Bash if not already configured
+        if (process.platform === 'win32' && !process.env.CLAUDE_CODE_GIT_BASH_PATH) {
+          const gitBashPath = findGitBash();
+          if (gitBashPath) {
+            sdkEnv.CLAUDE_CODE_GIT_BASH_PATH = gitBashPath;
+          }
+        }
+
         // Try to get config from active provider first
         const activeProvider = getActiveProvider();
 
@@ -192,11 +200,22 @@ export function streamClaude(options: ClaudeStreamOptions): ReadableStream<strin
             // ignore malformed extra_env
           }
         } else {
-          // Fall back to legacy settings
+          // No active provider — check legacy DB settings first, then fall back to
+          // environment variables already present in process.env (copied into sdkEnv above).
+          // This allows users who set ANTHROPIC_API_KEY / ANTHROPIC_AUTH_TOKEN / ANTHROPIC_BASE_URL
+          // in their shell environment to use them without configuring a provider in the UI.
           const appToken = getSetting('anthropic_auth_token');
           const appBaseUrl = getSetting('anthropic_base_url');
-          if (appToken) sdkEnv.ANTHROPIC_AUTH_TOKEN = appToken;
-          if (appBaseUrl) sdkEnv.ANTHROPIC_BASE_URL = appBaseUrl;
+          if (appToken) {
+            sdkEnv.ANTHROPIC_AUTH_TOKEN = appToken;
+          }
+          if (appBaseUrl) {
+            sdkEnv.ANTHROPIC_BASE_URL = appBaseUrl;
+          }
+          // If neither legacy settings nor env vars provide a key, log a warning
+          if (!appToken && !sdkEnv.ANTHROPIC_API_KEY && !sdkEnv.ANTHROPIC_AUTH_TOKEN) {
+            console.warn('[claude-client] No API key found: no active provider, no legacy settings, and no ANTHROPIC_API_KEY/ANTHROPIC_AUTH_TOKEN in environment');
+          }
         }
 
         const queryOptions: Options = {
diff --git a/src/lib/platform.ts b/src/lib/platform.ts
index 414e7bf..fa4d0ea 100644
--- a/src/lib/platform.ts
+++ b/src/lib/platform.ts
@@ -1,4 +1,5 @@
 import { execFileSync, execFile } from 'child_process';
+import fs from 'fs';
 import { promisify } from 'util';
 import os from 'os';
 import path from 'path';
@@ -162,3 +163,50 @@ export async function getClaudeVersion(claudePath: string): Promise<string | nul
     return null;
   }
 }
+
+/**
+ * Find Git Bash (bash.exe) on Windows.
+ * Returns the path to bash.exe or null if not found.
+ */
+export function findGitBash(): string | null {
+  // 1. Check user-specified environment variable
+  const envPath = process.env.CLAUDE_CODE_GIT_BASH_PATH;
+  if (envPath && fs.existsSync(envPath)) {
+    return envPath;
+  }
+
+  // 2. Check common installation paths
+  const commonPaths = [
+    'C:\\Program Files\\Git\\bin\\bash.exe',
+    'C:\\Program Files (x86)\\Git\\bin\\bash.exe',
+  ];
+  for (const p of commonPaths) {
+    if (fs.existsSync(p)) {
+      return p;
+    }
+  }
+
+  // 3. Try to locate git.exe via `where git` and derive bash.exe path
+  try {
+    const result = execFileSync('where', ['git'], {
+      timeout: 3000,
+      stdio: 'pipe',
+      shell: true,
+    });
+    const lines = result.toString().trim().split(/\r?\n/);
+    for (const line of lines) {
+      const gitExe = line.trim();
+      if (!gitExe) continue;
+      // git.exe is typically at <GitDir>\cmd\git.exe or <GitDir>\bin\git.exe
+      const gitDir = path.dirname(path.dirname(gitExe));
+      const bashPath = path.join(gitDir, 'bin', 'bash.exe');
+      if (fs.existsSync(bashPath)) {
+        return bashPath;
+      }
+    }
+  } catch {
+    // where git failed or timed out
+  }
+
+  return null;
+}