Slnmap

Slnmap (sln-map) is an open-source CLI tool and MCP server built by Mahmoud Nabil that gives AI coding agents a precise, compiler-accurate map of .NET solutions. It uses the Roslyn compiler platform to build a semantic graph of every type, member, and relationship in a solution, stores it locally as a SQLite database, and serves it to agents or editors over the Model Context Protocol (MCP). The project is MIT-licensed and available on GitHub.

What It Is

Slnmap solves a concrete problem: AI agents refactoring .NET code can only see files already in their context window, so they miss callers in other projects, misidentify dependencies, and hallucinate breaking changes. Slnmap builds a whole-solution graph — every caller, every implementation, every inheritance edge — and exposes it through fifteen read-only MCP tools so an agent can answer architecture questions correctly across every project in the solution. It runs entirely locally with no telemetry and no cloud service.

How the Graph Is Built

Slnmap uses MSBuildWorkspace (Roslyn) to perform design-time builds of each project, extracting:

• Symbols: types, members, interfaces, events, endpoints
• Relationships: Calls, Implements, Inherits, References edges
• HTTP endpoints: ASP.NET Core Minimal APIs and attribute-routed controllers, resolved statically including MapGroup prefixes, const patterns, class-level [Route], and controller base classes from packages like Ardalis.ApiEndpoints
• Frontend call sites (via analyze-ts): TypeScript/React HTTP calls resolved through const-through-barrel re-exports and template literals, linked to C# endpoints via slnmap link

The graph is stored in a local slnmap.db SQLite file. Updates are incremental and crash-safe — an interrupted run never corrupts the existing graph. The slnmap watch command (added in v0.10.0) keeps a warm Roslyn workspace in memory and re-analyzes on file save, bringing a one-file semantic change down to roughly one second end-to-end on a representative solution.

MCP Tool Surface

The MCP server exposes fifteen read-only tools covering the most common agent architecture queries:

• find_symbol, get_symbol_source — locate and read any symbol by FQN
• impact_analysis — every symbol that transitively depends on a given one, depth 5, counts-first
• find_usages, find_implementations, get_type_hierarchy — reference and inheritance traversal
• get_architecture_overview, get_project_dependencies, find_circular_dependencies — solution-level structure
• list_endpoints, find_endpoint — HTTP endpoint discovery across Minimal APIs and controllers
• find_orphan_calls, list_frontend_callsites — cross-stack frontend→backend linking (after slnmap link)
• find_tests_for_symbol — test members that transitively exercise a symbol

Malformed calls return a structured JSON payload (status/code/message/hint) rather than opaque errors, so agents can self-correct without human intervention.

Update: v0.12.0 — Cross-Stack Impact Analysis

The latest release (v0.12.0, published August 2026) is titled "Change a handler, see the React call sites that break." It completes the cross-stack linking feature: after running slnmap analyze, slnmap analyze-ts, and slnmap link, impact_analysis and find_usages on a C# handler continue straight through to its frontend callers — surfacing the exact React call sites that break when a backend handler changes, with no separate query. Earlier notable releases include v0.10.0 (slnmap watch for warm-workspace incremental analysis) and v0.8.0 (attribute-routed controller endpoint support).

Privacy and Deployment Model

Slnmap is fully local by design. The README states that analyze, watch, serve, viz, status, and doctor make no network calls at all — analysis works fully offline. The one documented exception is analyze-ts, which fetches the slnmap-ts npm extractor via npx on first use; no source code is ever sent anywhere. Because the CLI and MCP server are open source, the no-telemetry claim is auditable from the source code. The tool runs on Windows, macOS, and Linux and requires the .NET 9 SDK; analyze-ts additionally requires Node.js 18+.