British English Spelling Hook

Hook Type

PostToolUse -- Runs after Claude writes or edits a file.

Description

This hook detects American English spellings in written files and converts them to British English. It is context-aware: it only transforms human-readable text (comments, strings, documentation) and leaves code identifiers unchanged when they follow API naming conventions.

Patterns/Rules

Common Conversions

American	British
color	colour
favor	favour
organize	organise
analyze	analyse
center	centre
license (noun)	licence
catalog	catalogue
defense	defence
gray	grey
canceled	cancelled

Context Rules

• Convert: Comments, docstrings, string literals, markdown content, error messages
• Do NOT convert: CSS property names (color, background-color), API identifiers, imported library names, variable names matching external APIs
• Filetype scope: .ts, .js, .jsx, .tsx, .md, .mdx, .txt, .html, .css (comments only for CSS)

Configuration

Add to .claude/settings.json:

Copy
{
  "hooks": {
    "PostToolUse": [
      {
        "matcher": "(Write|Edit)",
        "hooks": [
          {
            "type": "command",
            "command": "python3 .claude/hooks/britfix.py \"$CLAUDE_FILE_PATH\""
          }
        ]
      }
    ]
  }
}

Action

The hook script (.claude/hooks/britfix.py):

Copy
#!/usr/bin/env python3
"""Convert American spellings to British English in text content."""
import sys
import re
from pathlib import Path

REPLACEMENTS = {
    "color": "colour", "Color": "Colour",
    "favor": "favour", "Favor": "Favour",
    "favorite": "favourite", "Favorite": "Favourite",
    "organize": "organise", "Organize": "Organise",
    "recognize": "recognise", "Recognize": "Recognise",
    "analyze": "analyse", "Analyze": "Analyse",
    "center": "centre", "Center": "Centre",
    "theater": "theatre", "Theater": "Theatre",
    "defense": "defence", "Defense": "Defence",
    "offense": "offence", "Offense": "Offence",
    "gray": "grey", "Gray": "Grey",
    "canceled": "cancelled", "Canceled": "Cancelled",
    "catalog": "catalogue", "Catalog": "Catalogue",
    "dialog": "dialogue", "Dialog": "Dialogue",
}

# Skip these in code contexts
CODE_EXCEPTIONS = {"color", "background-color", "border-color", "text-decoration-color"}

def is_text_context(line: str, match_start: int) -> bool:
    """Check if match is in a comment or string, not code."""
    prefix = line[:match_start]
    return bool(re.search(r'(//|/\*|#|\*|"|\'|`)', prefix))

def process_file(filepath: str) -> None:
    path = Path(filepath)
    if path.suffix not in {".ts", ".js", ".jsx", ".tsx", ".md", ".mdx", ".txt", ".html"}:
        return
    text = path.read_text()
    for american, british in REPLACEMENTS.items():
        text = re.sub(
            rf'\b{re.escape(american)}\b',
            lambda m: british if is_text_context(m.string[m.start()-80:m.start()+80], 80) or path.suffix in {".md", ".mdx", ".txt"} else m.group(),
            text
        )
    path.write_text(text)

if __name__ == "__main__":
    if len(sys.argv) > 1:
        process_file(sys.argv[1])