Synapse MCP

What myelixlabs/synapse-mcp MCP server does

The myelixlabs/synapse-mcp MCP server converts a codebase into a persistent, in-memory AST knowledge graph that MCP-compatible agents can query locally. It exposes structural information such as symbols, callers, callees, contracts, summaries, tests, dependencies, and public API surfaces instead of requiring an agent to repeatedly inspect unrelated files.

The graph is intended for code navigation and maintenance tasks. Agents can search for code, trace relationships, inspect likely change effects, map stack traces to AST locations, assess test coverage, and identify refactoring opportunities. The server also supports guarded file modification: a proposed change is simulated, checked against the compiler and linter, and written atomically only if the validation gates pass.

How it works

Synapse runs as a persistent BEAM daemon rather than as a one-shot command. It keeps the graph in memory between agent sessions and monitors workspace changes through platform file-notification mechanisms. When files change, it re-indexes the affected files instead of rebuilding the entire workspace. It also detects a new Git HEAD and processes the relevant diff.

The myelixlabs/synapse-mcp MCP server operates locally, with the README stating that code does not leave the machine. Its indexing uses AST-aware chunks and call-graph edge extraction, and its search supports semantic search using BM25F and embeddings, symbol search, and regular expressions. The exact supported language list is described as more than 50 languages.

For modifications, the workflow is simulate, validate, write atomically, and roll back if validation fails. Change review can rank blast radius and detect broken contracts before a change is pushed.

Setup and configuration

Install the server with the published shell installer on Linux or macOS:

curl -fsSL https://downloads.synapse-mcp.dev/install.sh | sh

On Windows PowerShell, use:

irm https://downloads.synapse-mcp.dev/install.ps1 | iex

After installation, register the repository with Synapse so the agent can use its graph. The supplied material does not specify a configuration file format, command-line registration syntax, port, or environment variables. It also does not document client-specific setup steps.

Tools and capabilities

The server groups its MCP tools by task:

• ask_synapse provides a natural-language entry point that routes requests to an appropriate tool.
• synapse_get_context returns structural context, including callers, callees, contracts, and summaries.
• synapse_search_codebase supports semantic, symbol, and regular-expression search with structured chunk IDs.
• synapse_explore_graph traverses caller and callee relationships, including transitive paths and cycles.
• synapse_modify_files validates proposed edits before committing them atomically, with rollback on lint failure.
• synapse_change_review analyzes diffs, ranks blast radius, and checks for broken contracts.
• synapse_debug_trace maps stack traces to AST root causes and suggests reproducing tests.
• synapse_test_quality reports coverage bands, maps tests, and ranks coverage gaps.
• synapse_codebase_insights examines dead-code deletion safety, public APIs, dependencies, and refactoring opportunities.
• synapse_knowledge_cache stores summaries for retrieval across sessions.
• synapse_manage_repos manages a multi-repository registry, including archive, restore, and Git worktree support.

Limitations and notes

The myelixlabs/synapse-mcp MCP server is currently in preview and may change as development continues. The README describes it as free, local, and without data egress, but does not provide independent performance guarantees beyond the included benchmark. The provided material names Claude, Cursor, and Copilot as agent examples; the directory client list does not include a Copilot slug. Language support is stated as 50-plus languages, while no complete list is included in the supplied excerpt.