feat: add strip-license-headers plugin to reduce token usage

[ng-galien]

Summary

Add a new plugin that automatically strips license headers from source files when Claude reads them, reducing context token consumption by 50-150+ tokens per file.

Problem

When working with codebases that have standard license headers (Apache, MIT, GPL, proprietary, etc.), these blocks consume significant tokens without providing value for coding tasks:

/*
 * Copyright 2024 Acme Corporation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * ...
 */

Impact: ~100 tokens per file × 50 files = 5,000+ wasted tokens per session.

Solution

A PreToolUse hook that intercepts Read tool calls and adjusts the offset parameter to skip license header lines.

How it works

Read tool called
       ↓
Hook intercepts (PreToolUse)
       ↓
Check: supported extension? config enabled? offset not set?
       ↓
Scan first 50 lines for license patterns
       ↓
Return updatedInput.offset to skip header
       ↓
Read tool executes with adjusted offset

Files added

File	Purpose
.claude-plugin/plugin.json	Plugin metadata
hooks/hooks.json	PreToolUse hook configuration
hooks/strip_headers.py	Main implementation (~200 lines)
examples/strip-license-headers.local.md	User configuration template
README.md	Documentation

Features

License patterns detected

• SPDX: SPDX-License-Identifier:
• Apache 2.0: Licensed under the Apache License, apache.org/licenses
• MIT: MIT License, Permission is hereby granted, free of charge
• GPL/LGPL: GNU General Public License, Free Software Foundation
• BSD: BSD License, Redistribution and use in source and binary forms
• Generic: Copyright (c), All rights reserved, This file is part of

Supported file extensions (20+)

• JavaScript/TypeScript: .js, .ts, .tsx, .jsx, .mjs, .cjs
• Python: .py, .pyi
• Java/JVM: .java, .kt, .scala
• Systems: .go, .rs, .c, .cpp, .h, .swift
• Other: .rb, .php, .lua, .sql, .sh, .html, .xml, .vue

Comment syntax support

Language family	Block	Line
C-style (JS, Java, Go, Rust...)	/* */	//
Python	""" """	#
Shell/Ruby	-	#
HTML/XML	<!-- -->	-
Lua	--[[ ]]	--
SQL	/* */	--

Configuration

Opt-in via .claude/strip-license-headers.local.md:

---
enabled: true
max_header_lines: 50
---

Edge cases handled

Scenario	Behavior
File doesn't exist	Exit 0, let Read handle error
Binary file	Skip (detected by null bytes)
File < 3 lines	Skip, don't strip from tiny files
No license detected	Exit 0, no modification
User set explicit offset	Respect it, don't interfere
Non-license comment at top	Preserve (only strips if license keywords found)
Shebang line (#!/...)	Preserved, detection starts after

Performance

• Overhead: ~5-10ms per Read operation
• Non-blocking: All errors result in exit 0 (allows Read to proceed normally)

Test plan

• Python syntax validation (python3 -m py_compile)
• Apache 2.0 license (16 lines) - correctly detected and skipped
• MIT license - correctly detected
• File without license - no modification, passes through unchanged
• Non-source file extensions - skipped, no processing
• Manual testing: Install plugin, enable config, read files in real session

Token savings estimate

Scenario	Without plugin	With plugin
1 file with header	~100 tokens	0 tokens
50 files session	~5,000 tokens	0 tokens
Heavy session (100 files)	~10,000 tokens	0 tokens

Installation

# Copy plugin
cp -r plugins/strip-license-headers ~/.claude/plugins/

# Enable in project
mkdir -p .claude
echo -e "---\nenabled: true\n---" > .claude/strip-license-headers.local.md

# Restart Claude Code

Related issues

• Closes Reduce token waste from redundant file change notifications #9388

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🤖 Generated with Claude Code