simplify-ignore hook

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

Setup

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 */

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"
          }
        ]
      }
    ]
  }
}

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 --}}) 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.
File renaming leaves placeholders. If the model renames or moves a file via a shell command, the new file will retain BLOCK_<hash> placeholders. The original code is saved as <old-filename>.recovered when the session stops. You must manually restore the recovered code into the new file.

Requirements

jq, shasum or sha1sum (auto-detected), Bash 3.2+

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