diff --git a/src/__tests__/providers/cliProvider.test.ts b/src/__tests__/providers/cliProvider.test.ts
index 7e69b2b..6bd58a5 100644
--- a/src/__tests__/providers/cliProvider.test.ts
+++ b/src/__tests__/providers/cliProvider.test.ts
@@ -68,7 +68,9 @@ describe('CliProvider', () => {
     });
 
     describe('arguments', () => {
-        it('passes correct args to spawn', async () => {
+        it('passes correct args to spawn (non-Windows)', async () => {
+            Object.defineProperty(process, 'platform', { value: 'linux', configurable: true });
+
             const provider = new CliProvider('/my/cwd');
             const token = createMockCancellationToken();
 
@@ -88,6 +90,35 @@ describe('CliProvider', () => {
                     stdio: ['pipe', 'pipe', 'pipe'],
                 }
             );
+
+            Object.defineProperty(process, 'platform', { value: process.platform, configurable: true });
+        });
+
+        it('routes through cmd /c on Windows so the npm .cmd shim is resolved', async () => {
+            Object.defineProperty(process, 'platform', { value: 'win32', configurable: true });
+
+            const provider = new CliProvider('/my/cwd');
+            const token = createMockCancellationToken();
+
+            const promise = provider.generateMessage('my instruction', 'ctx', token);
+            mockProcess.emitClose(0);
+            await promise;
+
+            expect(mockSpawn).toHaveBeenCalledWith(
+                'cmd',
+                [
+                    '/c', 'claude',
+                    '-p', 'my instruction',
+                    '--model', 'sonnet',
+                    '--system-prompt', expect.any(String),
+                ],
+                {
+                    cwd: '/my/cwd',
+                    stdio: ['pipe', 'pipe', 'pipe'],
+                }
+            );
+
+            Object.defineProperty(process, 'platform', { value: process.platform, configurable: true });
         });
 
         it('default model is sonnet when no options', async () => {
@@ -99,7 +130,7 @@ describe('CliProvider', () => {
             await promise;
 
             expect(mockSpawn).toHaveBeenCalledWith(
-                'claude',
+                expect.any(String),
                 expect.arrayContaining(['--model', 'sonnet']),
                 expect.any(Object)
             );
@@ -114,12 +145,8 @@ describe('CliProvider', () => {
             await promise;
 
             expect(mockSpawn).toHaveBeenCalledWith(
-                'claude',
-                [
-                    '-p', 'inst',
-                    '--model', 'opus',
-                    '--system-prompt', expect.any(String),
-                ],
+                expect.any(String),
+                expect.arrayContaining(['-p', 'inst', '--model', 'opus', '--system-prompt', expect.any(String)]),
                 expect.any(Object)
             );
         });
@@ -137,7 +164,7 @@ describe('CliProvider', () => {
             await promise;
 
             expect(mockSpawn).toHaveBeenCalledWith(
-                'claude',
+                expect.any(String),
                 expect.arrayContaining(['--model', 'sonnet']),
                 expect.any(Object)
             );
diff --git a/src/providers/cliProvider.ts b/src/providers/cliProvider.ts
index 62c25de..5d2f026 100644
--- a/src/providers/cliProvider.ts
+++ b/src/providers/cliProvider.ts
@@ -25,13 +25,20 @@ export class CliProvider implements CommitMessageProvider {
                 return;
             }
 
+            // On Windows, npm wraps the claude binary as claude.cmd which
+            // Node's spawn cannot execute without a shell. Route through
+            // cmd /c so Windows resolves the .cmd shim correctly while
+            // still passing each argument as a discrete array element
+            // (avoiding the quoting/newline pitfalls of shell:true).
+            const isWindows = process.platform === 'win32';
+            const command = isWindows ? 'cmd' : 'claude';
+            const args = isWindows
+                ? ['/c', 'claude', '-p', instruction, '--model', model, '--system-prompt', buildSystemPrompt()]
+                : ['-p', instruction, '--model', model, '--system-prompt', buildSystemPrompt()];
+
             const child: ChildProcess = spawn(
-                'claude',
-                [
-                    '-p', instruction,
-                    '--model', model,
-                    '--system-prompt', buildSystemPrompt(),
-                ],
+                command,
+                args,
                 {
                     cwd: this.cwd,
                     stdio: ['pipe', 'pipe', 'pipe'],