diff --git a/src/commands/hook.ts b/src/commands/hook.ts
index 9f28ed2c..a3ec3e93 100644
--- a/src/commands/hook.ts
+++ b/src/commands/hook.ts
@@ -111,6 +111,22 @@ function findGitRoot(cwd: string): string {
   return resolveGitRoot(cwd);
 }
 
+/**
+ * Normalize hook cwd values across shell environments.
+ * On Windows Git Bash/MSYS may pass "/c/path" which Node cannot use as cwd.
+ */
+export function normalizeHookCwd(cwd: string, platform: NodeJS.Platform = process.platform): string {
+  if (platform !== 'win32') return cwd;
+
+  const msysDrivePath = /^\/([a-zA-Z])(?:\/(.*))?$/;
+  const match = cwd.match(msysDrivePath);
+  if (!match) return cwd;
+
+  const drive = match[1].toUpperCase();
+  const rest = match[2] ?? '';
+  return rest.length > 0 ? `${drive}:/${rest}` : `${drive}:/`;
+}
+
 /** Stderr labels per event for user-facing messages. */
 const STDERR_LABELS: Record<HookEventType, { success: string; prefix: string }> = {
   'session:start': { success: 'Memory loaded.', prefix: 'Memory loaded' },
@@ -131,7 +147,8 @@ export async function hookCommand(eventName: string, _logger?: ILogger): Promise
 
   try {
     const input = await readStdin<IHookInput>();
-    const cwd = input.cwd ?? process.cwd();
+    const cwd = normalizeHookCwd(input.cwd ?? process.cwd());
+    const normalizedInput: IHookInput = { ...input, cwd };
     const repoRoot = findGitRoot(cwd);
 
     // Load .env from repository root for API keys (e.g., ANTHROPIC_API_KEY)
@@ -147,7 +164,7 @@ export async function hookCommand(eventName: string, _logger?: ILogger): Promise
     const container = createContainer({ scope: `hook:${eventName}` });
     const { eventBus } = container.cradle;
 
-    const event = buildEvent(eventType, input);
+    const event = buildEvent(eventType, normalizedInput);
     const results = await eventBus.emit(event);
 
     // Successful handler output → stdout (Claude context)
diff --git a/src/hooks/commit-msg.ts b/src/hooks/commit-msg.ts
index 6ca86942..1fc38d56 100644
--- a/src/hooks/commit-msg.ts
+++ b/src/hooks/commit-msg.ts
@@ -17,7 +17,7 @@ import { execFileSync } from 'child_process';
 const HOOK_FINGERPRINT_PREFIX = '# git-mem:commit-msg';
 
 /** Full fingerprint with version — used for upgrade detection. */
-const HOOK_FINGERPRINT = `${HOOK_FINGERPRINT_PREFIX} v4`;
+const HOOK_FINGERPRINT = `${HOOK_FINGERPRINT_PREFIX} v6`;
 
 /**
  * The shell hook script.
@@ -44,13 +44,16 @@ head -1 "$COMMIT_MSG_FILE" | grep -qiE "^(fixup|squash|amend)! " && exit 0
 # Skip revert commits (auto-generated)
 head -1 "$COMMIT_MSG_FILE" | grep -qiE '^Revert "' && exit 0
 
+# Resolve repository root for hook context.
+REPO_ROOT=$(git rev-parse --show-toplevel 2>/dev/null || pwd)
+
 # Escape values for safe JSON inclusion (handles quotes, backslashes)
 COMMIT_MSG_FILE_ESC=$(printf '%s' "$COMMIT_MSG_FILE" | sed 's/\\\\/\\\\\\\\/g; s/"/\\\\"/g')
-CWD_ESC=$(pwd | sed 's/\\\\/\\\\\\\\/g; s/"/\\\\"/g')
+REPO_ROOT_ESC=$(printf '%s' "$REPO_ROOT" | sed 's/\\\\/\\\\\\\\/g; s/"/\\\\"/g')
 
 # Run git-mem commit-msg analyzer
 # Pass commit message file path via JSON stdin
-echo "{\\"commit_msg_path\\": \\"$COMMIT_MSG_FILE_ESC\\", \\"cwd\\": \\"$CWD_ESC\\"}" | \\
+echo "{\\"commit_msg_path\\": \\"$COMMIT_MSG_FILE_ESC\\", \\"cwd\\": \\"$REPO_ROOT_ESC\\"}" | \\
   git-mem hook commit-msg 2>/dev/null || true
 
 exit 0
diff --git a/tests/unit/commands/hook.test.ts b/tests/unit/commands/hook.test.ts
index 0e63b344..b5459ebd 100644
--- a/tests/unit/commands/hook.test.ts
+++ b/tests/unit/commands/hook.test.ts
@@ -8,7 +8,7 @@
 
 import { describe, it } from 'node:test';
 import assert from 'node:assert/strict';
-import { EVENT_MAP, isEventEnabled, buildEvent } from '../../../src/commands/hook';
+import { EVENT_MAP, isEventEnabled, buildEvent, normalizeHookCwd } from '../../../src/commands/hook';
 import type { IHooksConfig } from '../../../src/domain/interfaces/IHookConfig';
 
 // ── Fixture helpers ──────────────────────────────────────────────────
@@ -146,3 +146,27 @@ describe('buildEvent', () => {
     assert.equal('prompt' in event && event.prompt, '');
   });
 });
+
+// ── normalizeHookCwd ────────────────────────────────────────────────
+
+describe('normalizeHookCwd', () => {
+  it('should normalize MSYS drive path on win32', () => {
+    const normalized = normalizeHookCwd('/c/dev/git-mem', 'win32');
+    assert.equal(normalized, 'C:/dev/git-mem');
+  });
+
+  it('should normalize MSYS drive root on win32', () => {
+    const normalized = normalizeHookCwd('/d', 'win32');
+    assert.equal(normalized, 'D:/');
+  });
+
+  it('should leave non-MSYS path unchanged on win32', () => {
+    const normalized = normalizeHookCwd('C:/dev/git-mem', 'win32');
+    assert.equal(normalized, 'C:/dev/git-mem');
+  });
+
+  it('should leave path unchanged on non-win32', () => {
+    const normalized = normalizeHookCwd('/c/dev/git-mem', 'linux');
+    assert.equal(normalized, '/c/dev/git-mem');
+  });
+});
diff --git a/tests/unit/hooks/commit-msg.test.ts b/tests/unit/hooks/commit-msg.test.ts
index b9bda7c1..1732e03e 100644
--- a/tests/unit/hooks/commit-msg.test.ts
+++ b/tests/unit/hooks/commit-msg.test.ts
@@ -39,8 +39,10 @@ describe('installCommitMsgHook', () => {
 
     const content = readFileSync(result.hookPath, 'utf8');
     assert.ok(content.includes('#!/bin/sh'));
-    assert.ok(content.includes('git-mem:commit-msg v4'));
+    assert.ok(content.includes('git-mem:commit-msg v6'));
     assert.ok(content.includes('git-mem hook commit-msg'));
+    assert.ok(content.includes('\\"cwd\\"'));
+    assert.ok(content.includes('git rev-parse --show-toplevel'));
   });
 
   it('should be idempotent — second install is a no-op', () => {
@@ -74,7 +76,7 @@ describe('installCommitMsgHook', () => {
 
       // Installed hook should contain both fingerprint and wrapper reference
       const content = readFileSync(hookPath, 'utf8');
-      assert.ok(content.includes('git-mem:commit-msg v4'));
+      assert.ok(content.includes('git-mem:commit-msg v6'));
       assert.ok(content.includes('user-backup'));
     } finally {
       rmSync(freshRepo, { recursive: true, force: true });
@@ -102,7 +104,7 @@ describe('installCommitMsgHook', () => {
       assert.equal(result.wrapped, false);
 
       const content = readFileSync(hookPath, 'utf8');
-      assert.ok(content.includes('git-mem:commit-msg v4'), 'Should be upgraded to v4');
+      assert.ok(content.includes('git-mem:commit-msg v6'), 'Should be upgraded to v6');
       assert.ok(content.includes('git-mem hook commit-msg'), 'Should include git-mem command');
 
       // Second install should be idempotent