From caf91bdc0e16c0e2c643b1c5c8f681e2bc2789b8 Mon Sep 17 00:00:00 2001
From: Keyvanhardani <hardani@hotmail.de>
Date: Sat, 10 Jan 2026 16:04:20 +0100
Subject: [PATCH] feat: Add German umlaut validation for Write/Edit operations
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Adds a new plugin and hook example for validating German text content
to ensure correct umlaut usage (ä, ö, ü, ß).

Problem:
When working with German language projects, incorrect umlaut
representations are frequently written (e.g., 'fuer' instead of 'für',
'ueber' instead of 'über'). This causes issues in production code,
documentation, and user-facing content.

Solution:
- New plugin: german-language-validator
- New hook example: german_umlaut_validator_example.py
- Validates 35+ common German words that must have umlauts
- Blocks Write/Edit operations with clear warnings when errors found
- Supports common file types (.md, .tsx, .py, .json, etc.)

Closes #17324
---
 .../hooks/german_umlaut_validator_example.py  | 194 ++++++++++++++++++
 .../.claude-plugin/plugin.json                |  10 +
 plugins/german-language-validator/README.md   |  81 ++++++++
 .../hooks/hooks.json                          |  24 +++
 .../hooks/umlaut_validator.py                 | 118 +++++++++++
 5 files changed, 427 insertions(+)
 create mode 100644 examples/hooks/german_umlaut_validator_example.py
 create mode 100644 plugins/german-language-validator/.claude-plugin/plugin.json
 create mode 100644 plugins/german-language-validator/README.md
 create mode 100644 plugins/german-language-validator/hooks/hooks.json
 create mode 100644 plugins/german-language-validator/hooks/umlaut_validator.py

diff --git a/examples/hooks/german_umlaut_validator_example.py b/examples/hooks/german_umlaut_validator_example.py
new file mode 100644
index 0000000000..1e85acfdf0
--- /dev/null
+++ b/examples/hooks/german_umlaut_validator_example.py
@@ -0,0 +1,194 @@
+#!/usr/bin/env python3
+"""
+Claude Code Hook: German Umlaut Validator
+==========================================
+This hook runs as a PreToolUse hook for Write and Edit tools.
+It validates German text content for common umlaut mistakes like
+'fuer' instead of 'für', 'ueber' instead of 'über', etc.
+
+Read more about hooks here: https://docs.anthropic.com/en/docs/claude-code/hooks
+
+Configuration example for settings.json:
+
+{
+  "hooks": {
+    "PreToolUse": [
+      {
+        "matcher": "Write",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "python3 /path/to/claude-code/examples/hooks/german_umlaut_validator_example.py"
+          }
+        ]
+      },
+      {
+        "matcher": "Edit",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "python3 /path/to/claude-code/examples/hooks/german_umlaut_validator_example.py"
+          }
+        ]
+      }
+    ]
+  }
+}
+
+This helps prevent common mistakes when working with German language content,
+which is especially important for:
+- User-facing text in applications
+- Documentation and README files
+- Error messages and validation text
+- Database content and exports
+"""
+
+import json
+import re
+import sys
+from typing import List, Tuple
+
+# Common German words that MUST have umlauts
+# Format: (wrong_pattern, correct_form, description)
+UMLAUT_RULES: List[Tuple[re.Pattern, str, str]] = [
+    # für/über family
+    (re.compile(r'\bfuer\b', re.IGNORECASE), 'für', 'fuer → für'),
+    (re.compile(r'\bueber\b', re.IGNORECASE), 'über', 'ueber → über'),
+
+    # können/müssen/würden family (modal verbs)
+    (re.compile(r'\bkoennen\b', re.IGNORECASE), 'können', 'koennen → können'),
+    (re.compile(r'\bkoennte\b', re.IGNORECASE), 'könnte', 'koennte → könnte'),
+    (re.compile(r'\bmuessen\b', re.IGNORECASE), 'müssen', 'muessen → müssen'),
+    (re.compile(r'\bmuesste\b', re.IGNORECASE), 'müsste', 'muesste → müsste'),
+    (re.compile(r'\bwuerden\b', re.IGNORECASE), 'würden', 'wuerden → würden'),
+    (re.compile(r'\bwuerde\b', re.IGNORECASE), 'würde', 'wuerde → würde'),
+
+    # hätte/wäre family (subjunctive)
+    (re.compile(r'\bhaette\b', re.IGNORECASE), 'hätte', 'haette → hätte'),
+    (re.compile(r'\bwaere\b', re.IGNORECASE), 'wäre', 'waere → wäre'),
+
+    # möchte/mögen family
+    (re.compile(r'\bmoechte\b', re.IGNORECASE), 'möchte', 'moechte → möchte'),
+    (re.compile(r'\bmoegen\b', re.IGNORECASE), 'mögen', 'moegen → mögen'),
+
+    # Größe/große family
+    (re.compile(r'\bgroesse\b', re.IGNORECASE), 'Größe', 'groesse → Größe'),
+    (re.compile(r'\bgrosse\b', re.IGNORECASE), 'große', 'grosse → große'),
+    (re.compile(r'\bgroesste\b', re.IGNORECASE), 'größte', 'groesste → größte'),
+
+    # ß words
+    (re.compile(r'\bstrasse\b', re.IGNORECASE), 'Straße', 'strasse → Straße'),
+    (re.compile(r'\bschliessen\b', re.IGNORECASE), 'schließen', 'schliessen → schließen'),
+    (re.compile(r'\bheissen\b', re.IGNORECASE), 'heißen', 'heissen → heißen'),
+    (re.compile(r'\bweiss\b', re.IGNORECASE), 'weiß', 'weiss → weiß'),
+
+    # ä words
+    (re.compile(r'\baehnlich\b', re.IGNORECASE), 'ähnlich', 'aehnlich → ähnlich'),
+    (re.compile(r'\baendern\b', re.IGNORECASE), 'ändern', 'aendern → ändern'),
+    (re.compile(r'\baenderung\b', re.IGNORECASE), 'Änderung', 'aenderung → Änderung'),
+    (re.compile(r'\bspaeter\b', re.IGNORECASE), 'später', 'spaeter → später'),
+    (re.compile(r'\bnaechste\b', re.IGNORECASE), 'nächste', 'naechste → nächste'),
+    (re.compile(r'\bwaehrend\b', re.IGNORECASE), 'während', 'waehrend → während'),
+    (re.compile(r'\berklaeren\b', re.IGNORECASE), 'erklären', 'erklaeren → erklären'),
+    (re.compile(r'\bbestaetigen\b', re.IGNORECASE), 'bestätigen', 'bestaetigen → bestätigen'),
+
+    # ö words
+    (re.compile(r'\boeffnen\b', re.IGNORECASE), 'öffnen', 'oeffnen → öffnen'),
+    (re.compile(r'\boeffentlich\b', re.IGNORECASE), 'öffentlich', 'oeffentlich → öffentlich'),
+    (re.compile(r'\bloesung\b', re.IGNORECASE), 'Lösung', 'loesung → Lösung'),
+    (re.compile(r'\bloeschen\b', re.IGNORECASE), 'löschen', 'loeschen → löschen'),
+    (re.compile(r'\bhoechste\b', re.IGNORECASE), 'höchste', 'hoechste → höchste'),
+    (re.compile(r'\bmoeglichkeit\b', re.IGNORECASE), 'Möglichkeit', 'moeglichkeit → Möglichkeit'),
+    (re.compile(r'\bveroeffentlichen\b', re.IGNORECASE), 'veröffentlichen', 'veroeffentlichen → veröffentlichen'),
+
+    # ü words
+    (re.compile(r'\bpruefung\b', re.IGNORECASE), 'Prüfung', 'pruefung → Prüfung'),
+    (re.compile(r'\bpruefen\b', re.IGNORECASE), 'prüfen', 'pruefen → prüfen'),
+    (re.compile(r'\bzurueck\b', re.IGNORECASE), 'zurück', 'zurueck → zurück'),
+    (re.compile(r'\bnatuerlich\b', re.IGNORECASE), 'natürlich', 'natuerlich → natürlich'),
+    (re.compile(r'\bverfuegbar\b', re.IGNORECASE), 'verfügbar', 'verfuegbar → verfügbar'),
+    (re.compile(r'\bdurchfuehren\b', re.IGNORECASE), 'durchführen', 'durchfuehren → durchführen'),
+    (re.compile(r'\bhinzufuegen\b', re.IGNORECASE), 'hinzufügen', 'hinzufuegen → hinzufügen'),
+    (re.compile(r'\bgueltig\b', re.IGNORECASE), 'gültig', 'gueltig → gültig'),
+    (re.compile(r'\bungueltig\b', re.IGNORECASE), 'ungültig', 'ungueltig → ungültig'),
+    (re.compile(r'\bausfuehren\b', re.IGNORECASE), 'ausführen', 'ausfuehren → ausführen'),
+    (re.compile(r'\bfuehren\b', re.IGNORECASE), 'führen', 'fuehren → führen'),
+]
+
+# File extensions that should be checked (files likely to contain German text)
+GERMAN_FILE_EXTENSIONS = {
+    '.md', '.txt', '.html', '.htm', '.tsx', '.ts', '.jsx', '.js',
+    '.json', '.py', '.yml', '.yaml', '.xml', '.vue', '.svelte'
+}
+
+
+def should_check_file(file_path: str) -> bool:
+    """Check if file should be validated for German umlauts."""
+    if not file_path:
+        return False
+
+    # Get file extension
+    dot_index = file_path.rfind('.')
+    if dot_index == -1:
+        return False
+
+    ext = file_path[dot_index:].lower()
+    return ext in GERMAN_FILE_EXTENSIONS
+
+
+def find_umlaut_errors(content: str) -> List[str]:
+    """Find all umlaut errors in content."""
+    errors = []
+
+    for pattern, correct, description in UMLAUT_RULES:
+        matches = pattern.findall(content)
+        if matches:
+            count = len(matches)
+            errors.append(f"{description} ({count}x found)")
+
+    return errors
+
+
+def main():
+    try:
+        input_data = json.load(sys.stdin)
+    except json.JSONDecodeError as e:
+        print(f"Error: Invalid JSON input: {e}", file=sys.stderr)
+        sys.exit(1)
+
+    tool_name = input_data.get("tool_name", "")
+
+    # Only check Write and Edit tools
+    if tool_name not in ("Write", "Edit"):
+        sys.exit(0)
+
+    tool_input = input_data.get("tool_input", {})
+    file_path = tool_input.get("file_path", "")
+
+    # Get content based on tool type
+    content = tool_input.get("content", "") or tool_input.get("new_string", "")
+
+    if not content:
+        sys.exit(0)
+
+    # Only check files that might contain German text
+    if not should_check_file(file_path):
+        sys.exit(0)
+
+    # Find umlaut errors
+    errors = find_umlaut_errors(content)
+
+    if errors:
+        print(f"\n⚠️  GERMAN UMLAUT WARNING in {file_path}:", file=sys.stderr)
+        for error in errors:
+            print(f"  • {error}", file=sys.stderr)
+        print("\nPlease use correct German umlauts (ä, ö, ü, ß)!", file=sys.stderr)
+        print("", file=sys.stderr)
+
+        # Exit code 2 blocks the tool call and shows stderr to Claude
+        # Change to sys.exit(0) if you only want warnings without blocking
+        sys.exit(2)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/plugins/german-language-validator/.claude-plugin/plugin.json b/plugins/german-language-validator/.claude-plugin/plugin.json
new file mode 100644
index 0000000000..9769d2b857
--- /dev/null
+++ b/plugins/german-language-validator/.claude-plugin/plugin.json
@@ -0,0 +1,10 @@
+{
+  "name": "german-language-validator",
+  "version": "1.0.0",
+  "description": "Validates German text for correct umlaut usage (ä, ö, ü, ß) in Write/Edit operations",
+  "author": "Community",
+  "license": "MIT",
+  "keywords": ["german", "umlaut", "validation", "i18n", "localization"],
+  "repository": "https://github.com/anthropics/claude-code",
+  "hooks": "hooks/hooks.json"
+}
diff --git a/plugins/german-language-validator/README.md b/plugins/german-language-validator/README.md
new file mode 100644
index 0000000000..f3be91b354
--- /dev/null
+++ b/plugins/german-language-validator/README.md
@@ -0,0 +1,81 @@
+# German Language Validator Plugin
+
+A Claude Code plugin that validates German text for correct umlaut usage (ä, ö, ü, ß) during Write and Edit operations.
+
+## Problem
+
+When working with German language content, AI assistants frequently write incorrect umlaut representations:
+- `fuer` instead of `für`
+- `ueber` instead of `über`
+- `koennen` instead of `können`
+- `groesse` instead of `Größe`
+- `strasse` instead of `Straße`
+
+These errors can cause issues in production code, documentation, and user-facing content.
+
+## Solution
+
+This plugin automatically validates text content before it's written or edited, checking for common German umlaut mistakes and blocking the operation with a warning if errors are found.
+
+## Installation
+
+```bash
+# Enable the plugin in your settings.json
+{
+  "enabledPlugins": {
+    "german-language-validator@anthropic": true
+  }
+}
+```
+
+Or install manually by copying the plugin to your `.claude/plugins` directory.
+
+## Supported File Types
+
+The validator checks these file extensions:
+- `.md`, `.txt` - Documentation
+- `.html`, `.htm` - Web content
+- `.tsx`, `.ts`, `.jsx`, `.js` - JavaScript/TypeScript
+- `.json` - Configuration files
+- `.py` - Python files
+- `.yml`, `.yaml` - YAML files
+- `.xml`, `.vue` - Other markup
+
+## Validated Words
+
+The plugin checks for 35+ common German words including:
+
+### Modal Verbs
+- können, könnte, müssen, würden, würde
+
+### Subjunctive Forms
+- hätte, wäre, möchte, mögen
+
+### Common Nouns & Adjectives
+- Größe, große, Straße, Änderung, Lösung
+- ähnlich, später, nächste, öffentlich
+- natürlich, verfügbar, gültig, ungültig
+
+### Common Verbs
+- ändern, öffnen, prüfen, löschen
+- schließen, heißen, führen, zurück
+
+## Customization
+
+To add more words to validate, edit `hooks/umlaut_validator.py` and add entries to the `UMLAUT_RULES` list:
+
+```python
+(re.compile(r'\byourword\b', re.IGNORECASE), 'correct', 'yourword → correct'),
+```
+
+## Behavior
+
+- **Blocks** Write/Edit operations that contain umlaut errors
+- Shows a warning message listing all found errors
+- Does not modify content automatically (user must fix)
+
+To change to warning-only mode (don't block), change `sys.exit(2)` to `sys.exit(0)` in the validator.
+
+## License
+
+MIT
diff --git a/plugins/german-language-validator/hooks/hooks.json b/plugins/german-language-validator/hooks/hooks.json
new file mode 100644
index 0000000000..71c682bafd
--- /dev/null
+++ b/plugins/german-language-validator/hooks/hooks.json
@@ -0,0 +1,24 @@
+{
+  "PreToolUse": [
+    {
+      "matcher": "Write",
+      "hooks": [
+        {
+          "type": "command",
+          "command": "python3 $PLUGIN_DIR/hooks/umlaut_validator.py",
+          "statusMessage": "Validating German umlauts..."
+        }
+      ]
+    },
+    {
+      "matcher": "Edit",
+      "hooks": [
+        {
+          "type": "command",
+          "command": "python3 $PLUGIN_DIR/hooks/umlaut_validator.py",
+          "statusMessage": "Validating German umlauts..."
+        }
+      ]
+    }
+  ]
+}
diff --git a/plugins/german-language-validator/hooks/umlaut_validator.py b/plugins/german-language-validator/hooks/umlaut_validator.py
new file mode 100644
index 0000000000..cccf7ccac4
--- /dev/null
+++ b/plugins/german-language-validator/hooks/umlaut_validator.py
@@ -0,0 +1,118 @@
+#!/usr/bin/env python3
+"""
+German Umlaut Validator Hook
+Validates German text for correct umlaut usage (ä, ö, ü, ß)
+"""
+
+import json
+import re
+import sys
+from typing import List, Tuple
+
+# Common German words that MUST have umlauts
+UMLAUT_RULES: List[Tuple[re.Pattern, str, str]] = [
+    # für/über family
+    (re.compile(r'\bfuer\b', re.IGNORECASE), 'für', 'fuer → für'),
+    (re.compile(r'\bueber\b', re.IGNORECASE), 'über', 'ueber → über'),
+
+    # Modal verbs
+    (re.compile(r'\bkoennen\b', re.IGNORECASE), 'können', 'koennen → können'),
+    (re.compile(r'\bkoennte\b', re.IGNORECASE), 'könnte', 'koennte → könnte'),
+    (re.compile(r'\bmuessen\b', re.IGNORECASE), 'müssen', 'muessen → müssen'),
+    (re.compile(r'\bwuerden\b', re.IGNORECASE), 'würden', 'wuerden → würden'),
+    (re.compile(r'\bwuerde\b', re.IGNORECASE), 'würde', 'wuerde → würde'),
+
+    # Subjunctive
+    (re.compile(r'\bhaette\b', re.IGNORECASE), 'hätte', 'haette → hätte'),
+    (re.compile(r'\bwaere\b', re.IGNORECASE), 'wäre', 'waere → wäre'),
+
+    # möchte family
+    (re.compile(r'\bmoechte\b', re.IGNORECASE), 'möchte', 'moechte → möchte'),
+    (re.compile(r'\bmoegen\b', re.IGNORECASE), 'mögen', 'moegen → mögen'),
+
+    # Größe family
+    (re.compile(r'\bgroesse\b', re.IGNORECASE), 'Größe', 'groesse → Größe'),
+    (re.compile(r'\bgrosse\b', re.IGNORECASE), 'große', 'grosse → große'),
+
+    # ß words
+    (re.compile(r'\bstrasse\b', re.IGNORECASE), 'Straße', 'strasse → Straße'),
+    (re.compile(r'\bschliessen\b', re.IGNORECASE), 'schließen', 'schliessen → schließen'),
+    (re.compile(r'\bheissen\b', re.IGNORECASE), 'heißen', 'heissen → heißen'),
+
+    # ä words
+    (re.compile(r'\baehnlich\b', re.IGNORECASE), 'ähnlich', 'aehnlich → ähnlich'),
+    (re.compile(r'\baendern\b', re.IGNORECASE), 'ändern', 'aendern → ändern'),
+    (re.compile(r'\baenderung\b', re.IGNORECASE), 'Änderung', 'aenderung → Änderung'),
+    (re.compile(r'\bspaeter\b', re.IGNORECASE), 'später', 'spaeter → später'),
+    (re.compile(r'\bnaechste\b', re.IGNORECASE), 'nächste', 'naechste → nächste'),
+
+    # ö words
+    (re.compile(r'\boeffnen\b', re.IGNORECASE), 'öffnen', 'oeffnen → öffnen'),
+    (re.compile(r'\boeffentlich\b', re.IGNORECASE), 'öffentlich', 'oeffentlich → öffentlich'),
+    (re.compile(r'\bloesung\b', re.IGNORECASE), 'Lösung', 'loesung → Lösung'),
+    (re.compile(r'\bloeschen\b', re.IGNORECASE), 'löschen', 'loeschen → löschen'),
+
+    # ü words
+    (re.compile(r'\bpruefung\b', re.IGNORECASE), 'Prüfung', 'pruefung → Prüfung'),
+    (re.compile(r'\bpruefen\b', re.IGNORECASE), 'prüfen', 'pruefen → prüfen'),
+    (re.compile(r'\bzurueck\b', re.IGNORECASE), 'zurück', 'zurueck → zurück'),
+    (re.compile(r'\bnatuerlich\b', re.IGNORECASE), 'natürlich', 'natuerlich → natürlich'),
+    (re.compile(r'\bverfuegbar\b', re.IGNORECASE), 'verfügbar', 'verfuegbar → verfügbar'),
+    (re.compile(r'\bgueltig\b', re.IGNORECASE), 'gültig', 'gueltig → gültig'),
+    (re.compile(r'\bungueltig\b', re.IGNORECASE), 'ungültig', 'ungueltig → ungültig'),
+]
+
+GERMAN_FILE_EXTENSIONS = {
+    '.md', '.txt', '.html', '.tsx', '.ts', '.jsx', '.js',
+    '.json', '.py', '.yml', '.yaml', '.xml', '.vue'
+}
+
+
+def should_check_file(file_path: str) -> bool:
+    if not file_path:
+        return False
+    dot_index = file_path.rfind('.')
+    if dot_index == -1:
+        return False
+    ext = file_path[dot_index:].lower()
+    return ext in GERMAN_FILE_EXTENSIONS
+
+
+def find_umlaut_errors(content: str) -> List[str]:
+    errors = []
+    for pattern, correct, description in UMLAUT_RULES:
+        matches = pattern.findall(content)
+        if matches:
+            errors.append(f"{description} ({len(matches)}x)")
+    return errors
+
+
+def main():
+    try:
+        input_data = json.load(sys.stdin)
+    except json.JSONDecodeError:
+        sys.exit(0)
+
+    tool_name = input_data.get("tool_name", "")
+    if tool_name not in ("Write", "Edit"):
+        sys.exit(0)
+
+    tool_input = input_data.get("tool_input", {})
+    file_path = tool_input.get("file_path", "")
+    content = tool_input.get("content", "") or tool_input.get("new_string", "")
+
+    if not content or not should_check_file(file_path):
+        sys.exit(0)
+
+    errors = find_umlaut_errors(content)
+
+    if errors:
+        print(f"\n⚠️  UMLAUT WARNING in {file_path}:", file=sys.stderr)
+        for error in errors:
+            print(f"  • {error}", file=sys.stderr)
+        print("\nUse correct German umlauts: ä, ö, ü, ß", file=sys.stderr)
+        sys.exit(2)
+
+
+if __name__ == "__main__":
+    main()