simplify-ignore hook

Block-level protection for /code-simplify. Mark code that should never be simplified — the model won't see it.

Setup

1. Annotate blocks you want to protect:

/* simplify-ignore-start: perf-critical */
// manually unrolled XOR — 3x faster than a loop
result[0] = buf[0] ^ key[0];
result[1] = buf[1] ^ key[1];
result[2] = buf[2] ^ key[2];
result[3] = buf[3] ^ key[3];
/* simplify-ignore-end */

2. Add hooks to .claude/settings.json:

{
  "hooks": {
    "PreToolUse": [
      {
        "matcher": "Read",
        "hooks": [{ "type": "command", "command": "bash \"${CLAUDE_PROJECT_DIR}/hooks/simplify-ignore.sh\"" }]
      }
    ],
    "PostToolUse": [
      {
        "matcher": "Edit|Write",
        "hooks": [{ "type": "command", "command": "bash \"${CLAUDE_PROJECT_DIR}/hooks/simplify-ignore.sh\"" }]
      }
    ],
    "Stop": [
      {
        "hooks": [{ "type": "command", "command": "bash \"${CLAUDE_PROJECT_DIR}/hooks/simplify-ignore.sh\"" }]
      }
    ]
  }
}

3. Run /code-simplify — protected blocks become /* BLOCK_de115a1d: perf-critical */ placeholders. The model reasons about surrounding code without seeing the protected implementation.

Note: The hook stores temporary backups in .claude/.simplify-ignore-cache/. Make sure this path is in your .gitignore.

How it works

One script, three hook events:

Event	Action
PreToolUse Read	Backs up file, replaces blocks with BLOCK_<hash> placeholders in-place
PostToolUse Edit|Write	Expands placeholders back to real code, saves model's changes, re-filters
Stop	Restores all files from backup when session ends

Each block is content-hashed (8 hex chars via shasum/sha1sum) so the round-trip is unambiguous even if the model duplicates or reorders placeholders. Cache is project-scoped to prevent cross-session interference.

Annotation syntax

/* simplify-ignore-start */           // basic — hides the block
/* simplify-ignore-start: reason */   // with reason — appears in placeholder
/* simplify-ignore-end */

Any comment style works (//, /*, #, `` for HTML).

Crash recovery

If Claude Code crashes without triggering the Stop hook, files on disk may still have BLOCK_<hash> placeholders. To restore manually:

echo '{}' | bash hooks/simplify-ignore.sh

Backups are stored in .claude/.simplify-ignore-cache/ within your project directory.

Known limitations

• Single-line blocks hide the entire line. If simplify-ignore-start and simplify-ignore-end appear on the same line as other code, the whole line is hidden from the model, not just the annotated portion. Use dedicated lines for annotations.
• Comment suffix detection covers */ and --> only. Template engines with non-standard comment closers (ERB %>, Blade <code v-pre>--}}</code>) may produce unbalanced placeholders. Use # or // style comments instead.
• Fallback expansion is progressive, not exact. If the model alters a placeholder's formatting (e.g. changes the reason text), the hook tries progressively simpler matches: full placeholder → prefix+hash+suffix → hash-only. The hash-only fallback may leave cosmetic debris (e.g. stray : or reason text). A warning is printed to stderr when this happens.