dnspymcp

A Model-Context-Protocol server that exposes dnSpy’s static analysis and ICorDebug live-debug capabilities to LLM clients. Designed to make reverse-engineering a .NET binary or attached process feel as productive from a chat client as it does in the dnSpy GUI.

Two binaries:

dnspymcp talks to dnspymcpagent over one persistent TCP connection (no HTTP, no per-call headers, no reconnect storms). The debug session is opened once and stays warm until the MCP server exits.

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Why two binaries?

ICorDebug lives under .NET Framework. For cross-version debugging the only safe host is an out-of-process net48 debugger that loads the right mscordbi.dll through ICLRMetaHost. That’s the agent.

The MCP-facing half lives on net9 so it can use the official ModelContextProtocol + AspNetCore packages and run side-by-side with other modern-.NET tooling.

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No-handroll philosophy

dnspymcp does not duplicate dnSpy’s source — when dnSpy already does the heavy work, we drive its types directly. The agent uses dndbg’s DnDebugger for ICorDebug; the static surface uses dnSpy.Analyzer.x.dll’s ScopedWhereUsedAnalyzer and every concrete analyzer node (MethodUsedByNode, TypeUsedByNode, FieldAccessNode, SubtypesNode, MethodOverridesNode, …) end-to-end. Krafs.Publicizer opens the internal types at build time so we can new them up from C# without forking dnSpy or copying any .cs file.

The thin layer in this repo is glue:

• Services/AnalyzerDriver.cs — adapter that satisfies the WPF-coupled bits of IAnalyzerTreeNodeDataContext (Decompiler via DispatchProxy, the rest null-stubbed) so we can pull FetchChildrenInternal off any SearchNode subclass.
• Services/WorkspaceDocumentService.cs — minimal IDsDocumentService that wraps the workspace’s opened-DLL list.
• Services/CrossDllIndex.cs — the only legitimately hand-rolled engine, because dnSpy ships no library-accessible string-literal index (FilterSearcher lives in the WPF main project).

The result: every cross-DLL reverse_xref_* query reuses the production analyzer with full TypeRef pre-filtering, accessibility scoping, friend- assembly handling, type-equivalence and virtual-dispatch awareness.

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Tool naming convention

Every MCP tool is tagged either [REVERSE] or [DEBUG] and prefixed accordingly:

• [REVERSE] — operates on a .dll / .exe on disk via dnlib +