Semamerge

npm version License: MIT semamerge MCP server

An MCP (Model Context Protocol) server that detects semantic merge conflicts between Git branches using AST-level analysis.

When two branches change code in ways that Git merges cleanly but are functionally incompatible, SemaMerge catches it before the merge breaks your app.

What It Detects

Conflict Type	Example
Type signature change	Branch A changes getUser() return type, Branch B calls getUser().address
Removed/renamed export	Branch A removes export function validate(), Branch B adds import { validate }
Parameter change	Branch A adds required param to function, Branch B calls with old signature
Interface/contract break	Branch A adds required field to interface, Branch B implements without it
Enum/constant change	Branch A removes Status.PENDING, Branch B uses Status.PENDING
Import path change	Branch A moves file, Branch B imports from old path

Installation

npx semamerge

Or install globally:

npm install -g semamerge

Or clone and build from source:

git clone https://github.com/vineethwilson15/semamerge.git
cd semamerge
npm install
npm run build

MCP Tools

check_merge_safety

Quick pre-merge check. Returns a risk score (safe/warning/danger).

{
  "repoPath": "/path/to/repo",
  "sourceBranch": "feature-x",
  "targetBranch": "main"
}

analyze_branches

Deep analysis with per-file breakdown of all semantic conflicts.

{
  "repoPath": "/path/to/repo",
  "branchA": "feature-x",
  "branchB": "feature-y",
  "baseBranch": "main"
}

list_semantic_changes

Lists all semantic changes on a branch (functions, exports, types, etc.).

{
  "repoPath": "/path/to/repo",
  "branch": "feature-x",
  "baseBranch": "main"
}

analyze_file_pair

Deep-dive into a specific file's semantic diff between two branches.

{
  "repoPath": "/path/to/repo",
  "filePath": "src/utils.ts",
  "branchA": "feature-x",
  "branchB": "main"
}

Configuration

VS Code (Copilot)

Add to your VS Code settings.json:

{
  "mcp": {
    "servers": {
      "semamerge": {
        "command": "node",
        "args": ["/path/to/semamerge/dist/index.js"]
      }
    }
  }
}

Claude Desktop

Add to claude_desktop_config.json:

{
  "mcpServers": {
    "semamerge": {
      "command": "node",
      "args": ["/path/to/semamerge/dist/index.js"]
    }
  }
}

Supported Languages

• TypeScript / JavaScript (.ts, .tsx, .js, .jsx, .mjs, .cjs)
• Python support planned

How It Works

1. Git layer — Reads file content from branches without checkout using git show
2. AST parsing — Parses source code with tree-sitter (WASM) into syntax trees
3. Semantic extraction — Walks ASTs to extract function signatures, types, exports, imports, enums
4. Three-way comparison — Computes semantic diffs from common ancestor to each branch
5. Conflict detection — Cross-references changes to find incompatibilities

Development

npm run build    # Compile TypeScript
npm run dev      # Watch mode
npm test         # Run tests

License

MIT