diff --git a/scripts/commands/remove-credentials.ps1 b/scripts/commands/remove-credentials.ps1
new file mode 100644
index 0000000..92473a0
--- /dev/null
+++ b/scripts/commands/remove-credentials.ps1
@@ -0,0 +1,27 @@
+[CmdletBinding()]
+param(
+    [ValidateSet('Codex','Claude','Both')][string]$Client,
+    [string]$Key
+)
+$ErrorActionPreference = 'Stop'
+$root = Split-Path (Split-Path $PSScriptRoot -Parent) -Parent
+. (Join-Path $root 'scripts/lib/install-targets.ps1')
+$selectedClient = $Client
+$selectedKey = $Key
+. (Join-Path $root 'scripts/lib/credentials.ps1')
+$Client = $selectedClient
+$Key = $selectedKey
+
+if (-not $Client) { $Client = Read-InstallClient -Client $Client }
+if (-not $Key) { $Key = Read-Host 'Credential key to remove' }
+Assert-CredentialKey $Key
+
+foreach ($target in $(if ($Client -eq 'Both') { @('Codex', 'Claude') } else { @($Client) })) {
+    try {
+        Remove-ManagedCredential $target $Key
+        Write-Output "Credential removed for $($target.ToLowerInvariant())."
+    } catch [ComponentModel.Win32Exception] {
+        if ($_.Exception.NativeErrorCode -ne 1168) { throw }
+        Write-Output "Credential not found for $($target.ToLowerInvariant())."
+    }
+}
diff --git a/scripts/commands/remove-credentials.sh b/scripts/commands/remove-credentials.sh
new file mode 100644
index 0000000..75ebdd9
--- /dev/null
+++ b/scripts/commands/remove-credentials.sh
@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+client=
+key=
+while [ $# -gt 0 ]; do
+  case "$1" in
+    --client) client=${2:?--client requires a value}; shift 2 ;;
+    --key) key=${2:?--key requires a value}; shift 2 ;;
+    *) printf 'Unknown argument: %s\n' "$1" >&2; exit 1 ;;
+  esac
+done
+
+[ -n "$client" ] || read -r -p 'Select client (codex, claude, or both) ' client
+[ -n "$key" ] || read -r -p 'Credential key to remove ' key
+case "$client" in codex|Codex|claude|Claude|both|Both) ;; *) printf 'Unknown --client value: %s\n' "$client" >&2; exit 1 ;; esac
+[[ "$key" =~ ^[A-Za-z_][A-Za-z0-9_]{0,127}$ ]] || { printf 'Credential key must be an environment-variable-compatible name.\n' >&2; exit 1; }
+
+powershell_command=$(command -v powershell.exe || command -v powershell || command -v pwsh || true)
+[ -n "$powershell_command" ] || { printf 'PowerShell is required to remove credentials from the Windows credential store.\n' >&2; exit 1; }
+script_dir=$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)
+"$powershell_command" -NoProfile -ExecutionPolicy Bypass -File "$script_dir/remove-credentials.ps1" -Client "$client" -Key "$key"
diff --git a/scripts/commands/remove-instruction.ps1 b/scripts/commands/remove-instruction.ps1
new file mode 100644
index 0000000..48ce9e5
--- /dev/null
+++ b/scripts/commands/remove-instruction.ps1
@@ -0,0 +1,15 @@
+[CmdletBinding()]
+param(
+    [ValidateSet('Codex','Claude','Both')][string]$Client,
+    [AllowEmptyString()][string]$Instruction,
+    [string]$HomePath = [Environment]::GetFolderPath('UserProfile')
+)
+$ErrorActionPreference = 'Stop'
+$root = Split-Path (Split-Path $PSScriptRoot -Parent) -Parent
+. (Join-Path $root 'scripts/lib/install-targets.ps1')
+
+if (-not $Client) { $Client = Read-InstallClient -Client $Client }
+if (-not $PSBoundParameters.ContainsKey('Instruction')) { $Instruction = Read-Host 'Instruction to remove' }
+if ([string]::IsNullOrWhiteSpace($Instruction) -or $Instruction.Length -gt 65536) { throw 'Instruction must contain between 1 and 65536 characters.' }
+& python (Join-Path $root 'scripts/lib/remove-instruction.py') --client $Client.ToLowerInvariant() --instruction $Instruction.TrimEnd() --home $HomePath
+if ($LASTEXITCODE -ne 0) { throw 'Instruction removal failed.' }
diff --git a/scripts/commands/remove-instruction.sh b/scripts/commands/remove-instruction.sh
new file mode 100644
index 0000000..ebf2f9d
--- /dev/null
+++ b/scripts/commands/remove-instruction.sh
@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+client=
+instruction=
+home_path=${HOME:?HOME is required}
+while [ $# -gt 0 ]; do
+  case "$1" in
+    --client) client=${2:?--client requires a value}; shift 2 ;;
+    --instruction) instruction=${2:?--instruction requires a value}; shift 2 ;;
+    --home) home_path=${2:?--home requires a value}; shift 2 ;;
+    *) printf 'Unknown argument: %s\n' "$1" >&2; exit 1 ;;
+  esac
+done
+
+[ -n "$client" ] || read -r -p 'Select client (codex, claude, or both) ' client
+[ -n "$instruction" ] || read -r -p 'Instruction to remove ' instruction
+case "$client" in codex|Codex|claude|Claude|both|Both) ;; *) printf 'Unknown --client value: %s\n' "$client" >&2; exit 1 ;; esac
+case "$home_path" in /*|[A-Za-z]:[\\/]*) ;; *) printf 'Home path must be absolute.\n' >&2; exit 1 ;; esac
+
+script_dir=$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd)
+python_command=$(command -v python || command -v python3 || true)
+[ -n "$python_command" ] || { printf 'Python is required to remove instructions.\n' >&2; exit 1; }
+"$python_command" "$script_dir/../lib/remove-instruction.py" --client "${client,,}" --instruction "$instruction" --home "$home_path"
diff --git a/scripts/lib/remove-instruction.py b/scripts/lib/remove-instruction.py
new file mode 100644
index 0000000..2e67c52
--- /dev/null
+++ b/scripts/lib/remove-instruction.py
@@ -0,0 +1,82 @@
+#!/usr/bin/env python3
+"""Remove the last exact instruction block added to a client overlay."""
+
+import argparse
+import os
+import stat
+import tempfile
+from pathlib import Path
+
+
+def remove_instruction(path: Path, instruction: str) -> bool:
+    if not path.exists():
+        return False
+    if path.is_symlink() or not path.is_file():
+        raise ValueError(f'Instruction path is not a regular file: {path}')
+
+    raw = path.read_bytes()
+    encoding = 'utf-8-sig' if raw.startswith(b'\xef\xbb\xbf') else 'utf-8'
+    lines = raw.decode(encoding).splitlines(keepends=True)
+    wanted = instruction.rstrip('\r\n').splitlines()
+    values = [line.rstrip('\r\n') for line in lines]
+    offset = next((i for i in range(len(values) - len(wanted), -1, -1)
+                   if values[i:i + len(wanted)] == wanted), None)
+    if offset is None:
+        return False
+
+    updated = ''.join(lines[:offset] + lines[offset + len(wanted):])
+    if not updated:
+        path.unlink()
+        return True
+
+    temporary = None
+    try:
+        with tempfile.NamedTemporaryFile(dir=path.parent, prefix='.instruction-', delete=False) as file:
+            temporary = Path(file.name)
+            file.write(updated.encode(encoding))
+        os.chmod(temporary, stat.S_IMODE(path.stat().st_mode))
+        os.replace(temporary, path)
+    finally:
+        if temporary is not None:
+            temporary.unlink(missing_ok=True)
+    return True
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument('--client', choices=('codex', 'claude', 'both'), required=True)
+    parser.add_argument('--instruction', required=True)
+    parser.add_argument('--home', required=True)
+    args = parser.parse_args()
+    if not args.instruction.strip() or len(args.instruction) > 65536:
+        parser.error('Instruction must contain between 1 and 65536 characters.')
+    home = Path(args.home)
+    if not home.is_absolute():
+        parser.error('Home path must be absolute.')
+    directory = home / '.my-ai-configuration' / 'instructions'
+    if (home / '.my-ai-configuration').is_symlink() or directory.is_symlink():
+        parser.error('Instruction directory must not be a link.')
+    try:
+        inside_home = os.path.commonpath((home.resolve(), directory.resolve())) == str(home.resolve())
+    except ValueError:
+        inside_home = False
+    if not inside_home:
+        parser.error('Instruction directory must remain inside the home directory.')
+
+    targets = ('codex', 'claude') if args.client == 'both' else (args.client,)
+    paths = [(target, directory / f'{target}.md') for target in targets]
+    for _, path in paths:
+        if path.is_symlink():
+            parser.error('Instruction path must not be a link.')
+        if path.exists() and not path.is_file():
+            parser.error('Instruction path must be a regular file.')
+    for target, path in paths:
+        if remove_instruction(path, args.instruction):
+            print(f'Instruction removed for {target}.')
+        else:
+            print(f'Instruction not found for {target}.')
+    return 0
+
+
+if __name__ == '__main__':
+    raise SystemExit(main())
diff --git a/scripts/tests/test-remove-customizations.py b/scripts/tests/test-remove-customizations.py
new file mode 100644
index 0000000..7c00c37
--- /dev/null
+++ b/scripts/tests/test-remove-customizations.py
@@ -0,0 +1,163 @@
+import os
+import shutil
+import subprocess
+import sys
+import tempfile
+import unittest
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[2]
+TEST_ROOT = ROOT / '.ai-session' / 'test-remove-customizations'
+
+
+class RemoveCustomizationTests(unittest.TestCase):
+    def setUp(self):
+        TEST_ROOT.mkdir(parents=True, exist_ok=True)
+        self.assertTrue(TEST_ROOT.resolve().is_relative_to(ROOT.resolve()))
+        self.temporary = tempfile.TemporaryDirectory(dir=TEST_ROOT)
+        self.addCleanup(self.temporary.cleanup)
+        self.home = Path(self.temporary.name)
+        self.environment = os.environ.copy()
+        for name in ('TEMP', 'TMP', 'TMPDIR'):
+            self.environment[name] = str(self.home)
+
+    def run_command(self, *arguments, input=None):
+        return subprocess.run(arguments, input=input, capture_output=True, text=True,
+                              cwd=ROOT, env=self.environment, timeout=20)
+
+    def test_remove_last_exact_instruction_and_keep_other_lines(self):
+        directory = self.home / '.my-ai-configuration' / 'instructions'
+        directory.mkdir(parents=True)
+        path = directory / 'codex.md'
+        path.write_bytes(b'Before\r\nRemove this\r\nKeep this\r\nRemove this\r\n')
+        command = (sys.executable, str(ROOT / 'scripts/lib/remove-instruction.py'),
+                   '--client', 'codex', '--instruction', 'Remove this', '--home', str(self.home))
+
+        first = self.run_command(*command)
+        self.assertEqual(0, first.returncode, first.stderr)
+        self.assertEqual(b'Before\r\nRemove this\r\nKeep this\r\n', path.read_bytes())
+        second = self.run_command(*command)
+        self.assertEqual(0, second.returncode, second.stderr)
+        self.assertEqual(b'Before\r\nKeep this\r\n', path.read_bytes())
+        third = self.run_command(*command)
+        self.assertEqual(0, third.returncode, third.stderr)
+        self.assertIn('Instruction not found for codex.', third.stdout)
+
+    def test_remove_both(self):
+        directory = self.home / '.my-ai-configuration' / 'instructions'
+        directory.mkdir(parents=True)
+        for client in ('codex', 'claude'):
+            (directory / f'{client}.md').write_text('Remove me\n', encoding='utf-8')
+        result = self.run_command(sys.executable, str(ROOT / 'scripts/lib/remove-instruction.py'),
+                                  '--client', 'both', '--instruction', 'Remove me', '--home', str(self.home))
+        self.assertEqual(0, result.returncode, result.stderr)
+        self.assertFalse((directory / 'codex.md').exists())
+        self.assertFalse((directory / 'claude.md').exists())
+
+    def test_linked_instruction_directory_is_rejected(self):
+        parent = self.home / '.my-ai-configuration'
+        parent.mkdir()
+        elsewhere = self.home / 'elsewhere'
+        elsewhere.mkdir()
+        path = elsewhere / 'codex.md'
+        path.write_text('Keep this\n', encoding='utf-8')
+        try:
+            (parent / 'instructions').symlink_to(elsewhere, target_is_directory=True)
+        except OSError:
+            self.skipTest('Directory symlinks are unavailable.')
+        result = self.run_command(sys.executable, str(ROOT / 'scripts/lib/remove-instruction.py'),
+                                  '--client', 'codex', '--instruction', 'Keep this', '--home', str(self.home))
+        self.assertNotEqual(0, result.returncode)
+        self.assertEqual('Keep this\n', path.read_text(encoding='utf-8'))
+
+    def test_powershell_remove_instruction_entry_point(self):
+        powershell = shutil.which('powershell') or shutil.which('pwsh')
+        if powershell is None:
+            self.skipTest('PowerShell is unavailable.')
+        path = self.home / '.my-ai-configuration' / 'instructions' / 'codex.md'
+        path.parent.mkdir(parents=True)
+        path.write_text('Keep this\nRemove this\n', encoding='utf-8')
+        result = self.run_command(powershell, '-NoProfile', '-ExecutionPolicy', 'Bypass', '-File',
+                                  str(ROOT / 'scripts/commands/remove-instruction.ps1'),
+                                  '-Client', 'Codex', '-Instruction', 'Remove this   ', '-HomePath', str(self.home))
+        self.assertEqual(0, result.returncode, result.stderr)
+        self.assertEqual('Keep this\n', path.read_text(encoding='utf-8'))
+
+        bash = Path('C:/Program Files/Git/bin/bash.exe') if os.name == 'nt' else shutil.which('bash')
+        if bash and Path(bash).is_file():
+            path.write_text('Keep this\nRemove from Bash\n', encoding='utf-8')
+            self.environment['TEST_HOME'] = str(self.home)
+            if os.name == 'nt':
+                script = ('python3() { python.exe "$@"; }; '
+                          'source scripts/commands/remove-instruction.sh --client codex '
+                          '--instruction "Remove from Bash" --home "$TEST_HOME"')
+                removed = self.run_command(str(bash), '-c', script)
+            else:
+                removed = self.run_command(str(bash), str(ROOT / 'scripts/commands/remove-instruction.sh'),
+                                           '--client', 'codex', '--instruction', 'Remove from Bash', '--home', str(self.home))
+            self.assertEqual(0, removed.returncode, removed.stderr)
+            self.assertEqual('Keep this\n', path.read_text(encoding='utf-8'))
+
+        added = self.run_command(powershell, '-NoProfile', '-ExecutionPolicy', 'Bypass', '-File',
+                                 str(ROOT / 'scripts/commands/add-instruction.ps1'),
+                                 '-Client', 'Both', '-Instruction', 'New shared instruction', '-HomePath', str(self.home))
+        self.assertEqual(0, added.returncode, added.stderr)
+        removed = self.run_command(powershell, '-NoProfile', '-ExecutionPolicy', 'Bypass', '-File',
+                                   str(ROOT / 'scripts/commands/remove-instruction.ps1'),
+                                   '-Client', 'Both', '-Instruction', 'New shared instruction', '-HomePath', str(self.home))
+        self.assertEqual(0, removed.returncode, removed.stderr)
+        self.assertEqual('Keep this\n', path.read_text(encoding='utf-8'))
+        self.assertFalse((path.parent / 'claude.md').exists())
+
+    def test_powershell_remove_credential_scopes_and_missing_key(self):
+        powershell = shutil.which('powershell') or shutil.which('pwsh')
+        if powershell is None:
+            self.skipTest('PowerShell is unavailable.')
+        commands = self.home / 'fixture' / 'scripts' / 'commands'
+        library = self.home / 'fixture' / 'scripts' / 'lib'
+        commands.mkdir(parents=True)
+        library.mkdir(parents=True)
+        for name in ('remove-credentials.ps1', 'remove-credentials.sh'):
+            shutil.copy2(ROOT / 'scripts' / 'commands' / name, commands / name)
+        shutil.copy2(ROOT / 'scripts/lib/install-targets.ps1', library / 'install-targets.ps1')
+        (library / 'credentials.ps1').write_text('''
+function Assert-CredentialKey { param([string]$Value)
+    if ($Value -notmatch '^[A-Za-z_][A-Za-z0-9_]{0,127}$') { throw 'Invalid credential key.' }
+}
+function Remove-ManagedCredential { param([string]$Client, [string]$Key)
+    if ($Key -eq 'MISSING') { throw [ComponentModel.Win32Exception]::new(1168) }
+    [IO.File]::AppendAllText($env:TEST_CREDENTIAL_LOG, "$Client/$Key`n")
+}
+''', encoding='utf-8')
+        log = self.home / 'credential-calls.txt'
+        self.environment['TEST_CREDENTIAL_LOG'] = str(log)
+        base = (powershell, '-NoProfile', '-ExecutionPolicy', 'Bypass', '-File',
+                str(commands / 'remove-credentials.ps1'), '-Client', 'Both', '-Key')
+
+        removed = self.run_command(*base, 'TEST_KEY')
+        self.assertEqual(0, removed.returncode, removed.stderr)
+        self.assertEqual(['Codex/TEST_KEY', 'Claude/TEST_KEY'], log.read_text().splitlines())
+        missing = self.run_command(*base, 'MISSING')
+        self.assertEqual(0, missing.returncode, missing.stderr)
+        self.assertEqual(2, missing.stdout.count('Credential not found'))
+        rejected = self.run_command(*base, 'BAD-KEY')
+        self.assertNotEqual(0, rejected.returncode)
+        self.assertEqual(['Codex/TEST_KEY', 'Claude/TEST_KEY'], log.read_text().splitlines())
+
+        bash = Path('C:/Program Files/Git/bin/bash.exe') if os.name == 'nt' else shutil.which('bash')
+        if bash and Path(bash).is_file():
+            if os.name == 'nt':
+                self.environment['TEST_SCRIPT'] = str(commands / 'remove-credentials.sh')
+                removed = self.run_command(str(bash), '-c',
+                                           'source "$(cygpath -u "$TEST_SCRIPT")" --client codex --key TEST_KEY')
+            else:
+                removed = self.run_command(str(bash), str(commands / 'remove-credentials.sh'),
+                                           '--client', 'codex', '--key', 'TEST_KEY')
+            self.assertEqual(0, removed.returncode, removed.stderr)
+            self.assertEqual(['Codex/TEST_KEY', 'Claude/TEST_KEY', 'codex/TEST_KEY'],
+                             log.read_text().splitlines())
+
+
+if __name__ == '__main__':
+    unittest.main()