diffchunk

MCP server that enables LLMs to navigate large diff files efficiently. Instead of reading entire diffs sequentially, LLMs can jump directly to relevant changes using pattern-based navigation.

Problem

Large diffs exceed LLM context limits and waste tokens on irrelevant changes. A 50k+ line diff can't be processed directly and manual splitting loses file relationships.

Solution

MCP server with 4 navigation tools:

• load_diff - Parse diff file with custom settings (optional)
• list_chunks - Show chunk overview with file mappings (auto-loads)
• get_chunk - Retrieve specific chunk content (auto-loads)
• find_chunks_for_files - Locate chunks by file patterns (auto-loads)

Setup

Prerequisite: Install uv (an extremely fast Python package manager) which provides the uvx command.

Add to your MCP client configuration:

{
  "mcpServers": {
    "diffchunk": {
      "command": "uvx",
      "args": ["--from", "diffchunk", "diffchunk-mcp"]
    }
  }
}

Usage

Basic Workflow

# Generate diff file
git diff main..feature-branch > /tmp/changes.diff

# LLM analyzes using diffchunk tools
Use diffchunk to analyze the diff at /tmp/changes.diff and find any bugs.

Tracking Analysis Progress

For large diffs requiring systematic analysis, LLMs can maintain tracking documents to resume work:

# Initial analysis with tracking
Use diffchunk to analyze /tmp/large-feature.diff. Create a tracking document 
to monitor progress through all chunks, then provide final summary.

# LLM maintains internal tracking:
# - Chunk 1/15: API endpoints - ANALYZED
# - Chunk 2/15: Database models - ANALYZED  
# - Chunk 3/15: Tests - IN PROGRESS
# - Chunks 4-15: PENDING

# Clean up tracking before final results

The tracking document concept allows LLMs to:

• Resume analysis where they left off
• Ensure comprehensive coverage of large diffs
• Maintain context across multiple chunks
• Provide complete analysis results

Tool Usage Patterns

Overview first:

list_chunks("/tmp/changes.diff")
# → 5 chunks across 12 files, 3,847 total lines

Target specific files:

find_chunks_for_files("/tmp/changes.diff", "*.py")
# → [1, 3, 5] - Python file chunks

get_chunk("/tmp/changes.diff", 1)
# → Content of first Python chunk

Systematic analysis:

# Process each chunk in sequence
get_chunk("/tmp/changes.diff", 1)
get_chunk("/tmp/changes.diff", 2)
# ... continue through all chunks

Configuration

Path Requirements

• Absolute paths only: /home/user/project/changes.diff
• Cross-platform: Windows (C:\path) and Unix (/path)
• Home expansion: ~/project/changes.diff

Auto-Loading Defaults

Tools auto-load with optimized settings:

• max_chunk_lines: 1000
• skip_trivial: true (whitespace-only)
• skip_generated: true (lock files, build artifacts)

Custom Settings

Use load_diff for non-default behavior:

load_diff(
    "/tmp/large.diff",
    max_chunk_lines=2000,
    include_patterns="*.py,*.js",
    exclude_patterns="*test*"
)

Supported Formats

• Git diff output (git diff, git show)
• Unified diff format (diff -u)
• Multiple files in single diff
• Binary file change indicators

Performance

• Efficiently handles 100k+ line diffs
• Memory efficient streaming
• Auto-reload on file changes

Documentation

• Design - Architecture and implementation details
• Contributing - Development setup and workflows

License

MIT