Slnmap

Slnmap (sln-map) — a semantic map of your .sln for AI coding agents.

Open source under the MIT license.

Your AI agent can't refactor .NET code it can't see. Ask an agent "what breaks if I change this interface?" and it guesses from the files in its context — missing callers in other projects and files it never opened. Slnmap gives the agent a precise, compiler-accurate map of your whole solution, so it answers correctly: every caller, every implementation, across every project. Fewer broken changes, no hallucinated dependencies. It runs locally and serves the map to your agent or editor over MCP.

Quickstart (3 steps)

1. Install the global tool (requires the .NET SDK 9.0+):

dotnet tool install --global Slnmap

2. Analyze your solution (or a single .csproj) — this builds slnmap.db in the current folder:

slnmap analyze path/to/YourSolution.sln

3. Connect your MCP client. For Claude Code, add this to .mcp.json in your project. Use an absolute path to the slnmap.db you just built — an MCP client's working directory is usually not your project folder, so a relative path can silently resolve to the wrong (or a missing) file:

{
  "mcpServers": {
    "slnmap": {
      "command": "slnmap",
      "args": ["serve", "--db", "C:/path/to/your/project/slnmap.db"]
    }
  }
}

On macOS/Linux, use a POSIX absolute path instead, e.g. /home/you/project/slnmap.db.

That's it. Ask your agent an architecture question and it will call Slnmap. (Run slnmap doctor first if anything looks off — see Troubleshooting.)

What you can ask

The server exposes eleven read-only tools. Give them fully qualified names; results are capped and counts-first. (A note the tools also carry: an FQN does not reveal whether a member is an explicit interface implementation.)

Tool	Example question
find_symbol	"Find the IBasketService interface."
get_dependencies	"What does CartController.Index depend on?"
impact_analysis	"What breaks if I change IBasketService?"
get_architecture_overview	"Show me the projects and how they depend on each other."
find_usages	"Where is BasketService.GetBasket used?"
find_implementations	"Who implements IBasketService / overrides this virtual member?"
get_type_hierarchy	"Show the base and derived type tree for BaseEntity."
find_tests_for_symbol	"Which tests exercise BasketService.AddItemToBasket?"
get_project_dependencies	"How do the projects reference each other, and where is the coupling worst?"
find_circular_dependencies	"Are there dependency cycles between projects or namespaces?"
get_symbol_source	"Show me the actual source of IBasketService."

For an interface (or interface member), impact_analysis follows both the interface's callers and its concrete implementations/overrides — so the answer includes code that only touches the interface, across projects, in files nobody has open.

CLI

slnmap analyze <solution>   # build or update the code graph (incremental on re-run)
slnmap serve                # serve the graph to MCP clients over stdio
slnmap status               # show node/edge counts and when it was last analyzed
slnmap viz                  # export the graph as a self-contained interactive HTML file
slnmap doctor               # check the environment can run Slnmap

--db <path> selects the database file (default slnmap.db).

Visualizing the graph

slnmap viz --output graph.html      # export the whole graph
slnmap viz --project YourProject    # export one project's subtree; others render as collapsed stubs

Opens as a single HTML file — double-click it, no server or internet connection required. It starts collapsed to one node per project; click a project, namespace, or class to drill into it. Like the rest of Slnmap, the export is self-contained: the graph library is embedded in the file, so nothing is fetched from a CDN and it works fully offline.

Updating

.NET tools do not update themselves, and Slnmap makes no network calls — so it will never nag you about (or check for) new versions. To update:

dotnet tool update -g Slnmap

To hear about releases, watch the GitHub repo (Watch → Custom → Releases); each release ships with notes in the changelog. After a major-version update, re-run slnmap analyze if the tool asks for it — release notes call out when a graph rebuild is needed.

Build from source

Slnmap is a standard .NET solution — clone, build, and test it with the SDK:

git clone https://github.com/EMahmoudNabil/slnmap.git
cd slnmap
dotnet build -c Release
dotnet test  -c Release

To run the CLI without installing the global tool:

dotnet run --project src/Slnmap.Cli -- analyze path/to/YourSolution.sln

Compatibility

Analyzes C# solutions targeting .NET 8 and .NET 9 (earlier targets are untested — feedback welcome); runs on Windows, macOS, and Linux; works with any MCP client (tested with Claude Code).

Privacy

100% local — and now you can verify it. Slnmap runs on your machine, reads your source with Roslyn, and writes a single local SQLite file. The MCP server reads only that local file. There is no telemetry, no network calls, and no cloud service — analysis works fully offline. Now that the CLI and MCP server are open source, that claim is auditable: read the code, or watch the process — nothing leaves your machine.

Performance

Measured on eShopOnWeb (10 projects, net8.0), .NET 9 SDK, on a 2-core laptop. Each timing is the median of 3 runs; full methodology, machine spec, and pinned commit are in BENCHMARKS.md.

Metric	Result
Graph size	1,111 nodes / 2,175 edges
Cold analyze (10 projects)	~25.6 s (median of 3)
Re-analyze after a one-file change	~27.1 s (median of 3 — see note)
impact_analysis on IBasketService (18 dependents)	~270 ms (end-to-end MCP round-trip)

Graph counts are for v0.3.0: the entry-point fix (see the changelog) makes each project's top-level Program distinct, so counts grew slightly versus v0.2.x (1,107 / 2,168). Timings were measured on v0.2.1; the analyzer work per document is unchanged in v0.3.0.

Incremental re-analysis. Re-analysis re-walks only the changed file and its dependents, but each run still pays a full workspace load of the solution — because the CLI is run-and-exit and does not keep a warm workspace. In practice that means re-analysis is currently about as fast as a cold run, not faster. A resident watch mode that keeps the workspace warm (targeting sub-second re-analysis) is the top item on the roadmap.

Troubleshooting

Run slnmap doctor first — it checks the three things that actually block analysis and prints a fix for each:

$ slnmap doctor
[ok] .NET SDK: 1 SDK(s) installed; newest: 9.0.314 …
[ok] MSBuild workspace: Roslyn MSBuild workspace initialized …
[ok] Graph directory: Writable: /path/to/cwd

• "No .NET SDKs are installed" / MSBuild fails to load projects. Slnmap analyzes via MSBuildWorkspace, which runs design-time builds using your installed .NET SDK. Install the SDK (not just the runtime) from https://dotnet.microsoft.com/download. On Windows, if projects still fail to load, install the Visual Studio Build Tools (or Visual Studio) so MSBuild and the targeting packs resolve.
• Analysis reports warnings but finishes. That is expected and safe: a project that can't be loaded (e.g. a missing SDK or targeting pack) is reported as a warning and skipped — Slnmap indexes everything that did load rather than failing the whole run (a partial load). By default these are condensed into a single Warnings: N (M unique) summary line; run slnmap analyze --verbose for the full, grouped detail.
• The first analysis of a large solution takes a while. Cold analysis compiles every project once. Re-runs are faster on graph work but still reload the workspace — see the performance note above. This is normal; the graph is cached in slnmap.db between runs.
• slnmap: command not found after install. Ensure the .NET global tools directory (~/.dotnet/tools) is on your PATH, then open a new shell.

How it works

Slnmap uses the Roslyn compiler platform to build a precise semantic graph of your solution — every type and member, and the relationships between them (calls, implementations, inheritance, references). The graph is stored locally and served to your AI agent or editor over MCP. Updates are incremental and crash-safe: an interrupted run never corrupts your existing graph.

License & support

Slnmap is open source under the MIT license.

The CLI and MCP server are MIT-licensed and will stay that way. Future hosted or team-oriented features may be commercial.

For questions or to report an issue, open a GitHub issue or contact hello@slnmap.dev. Contributions are welcome — see CONTRIBUTING.md.