llmignore

Parse and match .llmignore files — the .gitignore for AI.

Prevent AI coding tools from ingesting secrets, credentials, large binaries, and sensitive data into LLM context windows. Works with all 13 known AI ignore formats.

Spec: rival.tips/llmignore

Installation

pip install llmignore

Usage

Parse and match

from llmignore import parse, match

content = """
# Secrets
.env
.env.*
**/*.pem
**/*.key

# Large binaries
**/*.wasm
**/node_modules/**

# But keep the example env
!.env.example
"""

patterns = parse(content)

match(patterns, ".env")              # True  (ignored)
match(patterns, ".env.local")        # True  (ignored)
match(patterns, ".env.example")      # False (negation re-includes it)
match(patterns, "certs/server.pem")  # True  (ignored)
match(patterns, "src/index.ts")      # False (not matched)

Debug which patterns match

from llmignore import parse, match_all

patterns = parse(open(".llmignore").read())
matching = match_all(patterns, "secrets/api-key.pem")

for p in matching:
    prefix = "!" if p.is_negation else " "
    print(f"  line {p.line_number}: {prefix}{p.pattern}")

Read from file

from pathlib import Path
from llmignore import parse, match

llmignore_path = Path(".llmignore")
if llmignore_path.exists():
    patterns = parse(llmignore_path.read_text())
    # Use patterns to filter files...

Explore supported formats

from llmignore import FORMATS

for fmt in FORMATS:
    negation = "yes" if fmt.supports_negation else "no"
    official = "official" if fmt.official else "community"
    print(f"  {fmt.filename:<20} {fmt.tool:<16} negation={negation}  ({official})")

Supported Formats

Glob Syntax

The syntax is identical to .gitignore:

API Reference

parse(content: str) -> list[Pattern]

Parse ignore file content into a list of Pattern objects. Handles comments, blank lines, negation, and escaped characters.

match(patterns: list[Pattern], path: str) -> bool

Check whether a path should be ignored. Evaluates patterns in order with last-match-wins semantics. Negation patterns (!) re-include previously excluded files.

match_all(patterns: list[Pattern], path: str) -> list[Pattern]

Return all patterns that match a path (both inclusions and negations). Useful for debugging ignore rules.

FORMATS: list[Format]

All 13 known AI ignore file format definitions with metadata about tool support, negation, and cascading behavior.

Pattern

Dataclass with fields: pattern (str), is_negation (bool), line_number (int).

Format

Dataclass with fields: id, filename, tool, tool_url, description, official, supports_negation, supports_cascading, docs_url, notes.

Zero Dependencies

This library uses only the Python standard library. No external packages required.

Links

• .llmignore spec
• Template builder
• RIVAL — AI model comparison

License

MIT