diff --git a/src/utils/hooks.ts b/src/utils/hooks.ts
index de33f3b90a..8408c742df 100644
--- a/src/utils/hooks.ts
+++ b/src/utils/hooks.ts
@@ -120,6 +120,7 @@ import type {
   SkillHookMatcher,
 } from './settings/types.js'
 import { getHookDisplayText } from './hooks/hooksSettings.js'
+import { getWindowsBashHookCommand } from './hooks/windowsBashCommand.js'
 import { logForDebugging } from './debug.js'
 import { logForDiagnosticsNoPII } from './diagLogs.js'
 import { firstLineOf } from './stringUtils.js'
@@ -1048,10 +1049,8 @@ async function execCommandHook(
   // On Windows (bash only), auto-prepend `bash` for .sh scripts so they
   // execute instead of opening in the default file handler. PowerShell
   // runs .ps1 files natively — no prepend needed.
-  if (isWindows && !isPowerShell && command.trim().match(/\.sh(\s|$|")/)) {
-    if (!command.trim().startsWith('bash ')) {
-      command = `bash ${command}`
-    }
+  if (isWindows && !isPowerShell) {
+    command = getWindowsBashHookCommand(command)
   }
 
   // CLAUDE_CODE_SHELL_PREFIX wraps the command via POSIX quoting
diff --git a/src/utils/hooks/windowsBashCommand.test.ts b/src/utils/hooks/windowsBashCommand.test.ts
new file mode 100644
index 0000000000..e3c26a36e9
--- /dev/null
+++ b/src/utils/hooks/windowsBashCommand.test.ts
@@ -0,0 +1,176 @@
+import { describe, expect, test } from 'bun:test'
+import { mkdtemp, rm, writeFile } from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { getWindowsBashHookCommand } from './windowsBashCommand.js'
+
+describe('Windows bash hook commands', () => {
+  test.each([
+    'if [ -f ./hook.sh ]; then bash ./hook.sh; fi',
+    'for script in ./hook.sh; do bash "$script"; done',
+    'while false; do ./hook.sh; done',
+    'case "$file" in *.sh) echo shell;; esac',
+    '(bash ./hook.sh)',
+    '{ bash ./hook.sh; }',
+    'echo ./hook.sh',
+    'echo "./hook.sh"',
+    'bash ./hook.sh',
+    'bash\t./hook.sh',
+    'sh ./hook.sh',
+    '/usr/bin/bash ./hook.sh',
+    'env bash ./hook.sh',
+    'SCRIPT=./hook.sh bash "$SCRIPT"',
+    'FOO="a b" BAR=./hook.sh bash ./hook.sh',
+    'FOO=./hook.sh',
+    'FOO=bar; ./hook.sh',
+    'FOO=bar\n./hook.sh',
+    'FOO=bar # ./hook.sh',
+    'FOO=${FOO:-bash ./hook.sh --flag} /bin/sh -c \'printf "%s\\n" "$FOO"\'',
+    'node ./hook.sh.js',
+    './hook.sh.backup',
+    'printf "ready\\n"\n./hook.sh',
+    '"${HOOK_COMMAND:-./hook.sh}" OK',
+    '${HOOK_SCRIPT%.sh}',
+    '#hook.sh',
+    'hook.sh() { printf done; }',
+    'hook.sh () { printf done; }',
+  ])('preserves shell command: %s', command => {
+    expect(getWindowsBashHookCommand(command)).toBe(command)
+  })
+
+  test.each([
+    './hook.sh',
+    './hook.sh argument',
+    '  /c/work/hooks/hook.sh --check',
+    '"/c/Program Files/hooks/hook.sh" argument',
+    "'/c/Program Files/hooks/hook.sh' argument",
+    '"$CLAUDE_PROJECT_DIR/hooks/hook.sh"',
+    '${CLAUDE_PROJECT_DIR}/hooks/hook.sh',
+    './hooks/my\\ hook.sh argument',
+    '"./hooks/my hook".sh argument',
+    './hook.sh && printf done',
+    './hook.sh; printf done',
+    './C#/hooks/hook.sh',
+  ])('runs a directly invoked script with bash: %s', command => {
+    expect(getWindowsBashHookCommand(command)).toBe(`bash ${command}`)
+  })
+
+  test.each([
+    ['FOO=bar ./hook.sh', 'FOO=bar bash ./hook.sh'],
+    [
+      'FOO="a b" BAR=\'c d\' "./hook script.sh" argument',
+      'FOO="a b" BAR=\'c d\' bash "./hook script.sh" argument',
+    ],
+    ['FOO=bar \\\n ./hook.sh', 'FOO=bar \\\n bash ./hook.sh'],
+  ])('preserves assignments before a direct script: %s', (command, expected) => {
+    expect(getWindowsBashHookCommand(command)).toBe(expected)
+  })
+
+  test.skipIf(process.platform === 'win32')(
+    'passes quoted environment assignments to a non-executable script',
+    async () => {
+      const directory = await mkdtemp(join(tmpdir(), 'openclaude-hook-env-'))
+      try {
+        await writeFile(join(directory, 'hook script.sh'), 'printf "%s|%s\\n" "$FOO" "$BAR"\n', {
+          mode: 0o600,
+        })
+        for (const command of [
+          'FOO="a b" BAR=\'c d\' "./hook script.sh"',
+          'FOO="a b" \\\n BAR=\'c d\' "./hook script.sh"',
+        ]) {
+          const child = Bun.spawn(['bash', '-c', getWindowsBashHookCommand(command)], {
+            cwd: directory,
+            stdout: 'pipe',
+            stderr: 'pipe',
+          })
+          const [status, stdout, stderr] = await Promise.all([
+            child.exited,
+            new Response(child.stdout).text(),
+            new Response(child.stderr).text(),
+          ])
+          expect({ command, status, stdout, stderr }).toEqual({
+            command,
+            status: 0,
+            stdout: 'a b|c d\n',
+            stderr: '',
+          })
+        }
+      } finally {
+        await rm(directory, { recursive: true, force: true })
+      }
+    },
+  )
+
+  test.skipIf(process.platform === 'win32')(
+    'does not insert an interpreter inside expanded assignment values',
+    async () => {
+      for (const value of [
+        '${FOO:-bash ./hook.sh --flag}',
+        '"${FOO:-"bash ./hook.sh --flag"}"',
+        '"$(printf "%s" "bash ./hook.sh --flag")"',
+      ]) {
+        const command = `FOO=${value} /bin/sh -c 'printf "%s\\n" "$FOO"'`
+        const child = Bun.spawn(['bash', '-c', getWindowsBashHookCommand(command)], {
+          env: { ...process.env, FOO: '' },
+          stdout: 'pipe',
+          stderr: 'pipe',
+        })
+        const [status, stdout, stderr] = await Promise.all([
+          child.exited,
+          new Response(child.stdout).text(),
+          new Response(child.stderr).text(),
+        ])
+        expect({ value, status, stdout, stderr }).toEqual({
+          value,
+          status: 0,
+          stdout: 'bash ./hook.sh --flag\n',
+          stderr: '',
+        })
+      }
+    },
+  )
+
+  test.skipIf(process.platform === 'win32')(
+    'executes compound hooks and non-executable script paths with real bash',
+    async () => {
+      const directory = await mkdtemp(join(tmpdir(), 'openclaude-hook-command-'))
+      try {
+        await writeFile(join(directory, 'hook script.sh'), 'printf "{}\\n"\n', {
+          mode: 0o600,
+        })
+        await writeFile(join(directory, 'C# hook.sh'), 'printf "{}\\n"\n', {
+          mode: 0o600,
+        })
+        for (const command of [
+          'if [ -f "./hook script.sh" ]; then bash "./hook script.sh"; else printf "missing\\n"; fi',
+          '"./hook script.sh"',
+          "'./hook script.sh'",
+          './hook\\ script.sh',
+          'bash "./hook script.sh"',
+          './C#\\ hook.sh',
+          '"${HOOK_COMMAND:-./hook.sh}" "{}"',
+        ]) {
+          const child = Bun.spawn(['bash', '-c', getWindowsBashHookCommand(command)], {
+            cwd: directory,
+            env: { ...process.env, HOOK_COMMAND: '/bin/echo' },
+            stdout: 'pipe',
+            stderr: 'pipe',
+          })
+          const [status, stdout, stderr] = await Promise.all([
+            child.exited,
+            new Response(child.stdout).text(),
+            new Response(child.stderr).text(),
+          ])
+          expect({ command, status, stdout, stderr }).toEqual({
+            command,
+            status: 0,
+            stdout: '{}\n',
+            stderr: '',
+          })
+        }
+      } finally {
+        await rm(directory, { recursive: true, force: true })
+      }
+    },
+  )
+})
diff --git a/src/utils/hooks/windowsBashCommand.ts b/src/utils/hooks/windowsBashCommand.ts
new file mode 100644
index 0000000000..9162cb318c
--- /dev/null
+++ b/src/utils/hooks/windowsBashCommand.ts
@@ -0,0 +1,32 @@
+export function getWindowsBashHookCommand(command: string): string {
+  let offset = 0
+  while (true) {
+    // Read the command word after any assignments, not a .sh argument or a
+    // script inside a compound command. Keep the original quoting intact.
+    const rest = command.slice(offset)
+    const match = rest.match(
+      /^\s*((?:[^\s"'\\;&|<>()`]|\\[\s\S]|"(?:[^"\\]|\\[\s\S])*"|'[^']*')+)(?=\s|[;&|<>]|$)/,
+    )
+    const word = match?.[1]
+    if (!match || !word || word.startsWith('#')) return command
+
+    if (/^[A-Za-z_][A-Za-z_0-9]*=/.test(word)) {
+      // Expansions can contain their own words and quotes. Leave those commands
+      // untouched rather than mistake part of an assignment for the executable.
+      if (/\$[({]|`/.test(word)) return command
+      const separator = rest.slice(match[0].length).match(/^(?:[ \t]|\\\n)+/)?.[0]
+      if (!separator) return command
+      offset += match[0].length + separator.length
+      // A newline ends an assignment-only command, unlike spaces and tabs.
+      if (/^[\r\n]/.test(command.slice(offset))) return command
+      continue
+    }
+    if (/^\s*\(\s*\)/.test(rest.trimStart().slice(word.length))) return command
+
+    // Require a literal suffix, not .sh inside a parameter expansion such as
+    // "${HOOK_COMMAND:-./hook.sh}" whose actual executable is unknown here.
+    return /\.sh["']?$/.test(word)
+      ? `${command.slice(0, offset)}bash ${rest}`
+      : command
+  }
+}