pi-fence

A pi coding agent extension that detects decorative fence/divider comments in code written by the model and warns, blocks, or removes them automatically.

What it catches

Comments whose inner text (after stripping //, #, /* */ markers) contains a sequence of 3 or more separator characters:

// ---- helpers ----        ← caught
// ===== Auth Module =====  ← caught
# ################          ← caught
/* ~~~ utilities ~~~ */     ← caught
// ────────────────         ← caught (Unicode box-drawing)

// TODO: fix this           ← NOT caught
// Copyright (c) 2024       ← NOT caught

Supported languages

| Extension(s) | Language | |---|---| | .ts, .tsx, .cts, .mts | TypeScript | | .js, .jsx, .mjs, .cjs | JavaScript | | .py | Python | | .go | Go | | .rs | Rust | | .rb | Ruby | | .java | Java | | .sh, .bash | Shell / Bash | | .c, .h | C | | .css | CSS |

Files with other extensions are passed through without inspection.

Install

pi install npm:@piotr-oles/pi-fence

Modes

Control via the --pi-fence-mode CLI flag (takes precedence) or the PI_FENCE_MODE environment variable:

pi --pi-fence-mode warn    # default: write proceeds, warning shown to model
pi --pi-fence-mode block   # write is blocked; model must remove fences and retry
pi --pi-fence-mode remove  # fence comments are stripped silently before writing

PI_FENCE_MODE=block pi    # same, via env variable

How it works

1. Injects a short system-prompt instruction telling the model not to add fence comments.
2. On every write and edit tool call, parses the new content with tree-sitter to extract comment nodes.
3. Compares against the existing file — only newly introduced fences trigger (a fence at the same line as in the old file is not re-reported).
4. Acts according to the configured mode.

System-Prompt

Do not insert decorative fence comments like // ---- section ----. Code-smell, if needed, extract to function or file instead.

Development

pnpm install
pnpm test
pnpm typecheck
pnpm check

To test changes manually, pass the source entry point directly to pi with the -e flag:

pi -ne -e src/index.ts
pi -ne -e src/index.ts --pi-fence-mode block
pi -ne -e src/index.ts --pi-fence-mode remove