CodeMap — Turn Your AI Agent Into a Semantic Dragon

Stop feeding your AI agent raw source files. Give it a semantic index instead.

CodeMap is a Roslyn-powered MCP server that lets AI agents navigate C#, VB.NET, and F# codebases by symbol, call graph, and architectural fact — instead of brute-reading thousands of lines of source code. One tool call. Precise answer. No context flood.

Average token savings: 90%+ versus reading files directly.

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Install via Claude Code or manually

The fastest way to install is to paste the prompt below into a Claude Code shell. Claude will check your environment, install the tool, and register it as an MCP server — no manual steps needed.

Check whether .NET 10 SDK is installed by running dotnet --version. If the reported version is below 10.0, install it: on Windows run winget install Microsoft.DotNet.SDK.10, on macOS/Linux download from https://dotnet.microsoft.com/download/dotnet/10.0. Verify with dotnet --version once done. Once .NET 10 is confirmed, install CodeMap: if codemap-mcp is not yet installed run dotnet tool install --global codemap-mcp, otherwise run dotnet tool update --global codemap-mcp to get the latest version. Verify the binary is reachable with codemap-mcp --version. Finally, register it as a global MCP server in Claude Code by running claude mcp add codemap-mcp codemap-mcp --scope user and confirm it appears in the output of claude mcp list.

Or install manually:

# Install .NET 10 SDK if needed (Windows)
winget install Microsoft.DotNet.SDK.10

dotnet tool install --global codemap-mcp
codemap-mcp --version
claude mcp add codemap-mcp codemap-mcp --scope user

Requires .NET 10 (LTS). If you're working on a C# or VB.NET codebase you almost certainly have it already — check with dotnet --version.

Upgrading from v1.x

v2.0.0 uses a new binary storage engine (memory-mapped segments instead of SQLite). Your old .db baselines are not auto-migrated — run index.ensure_baseline once per repo to rebuild. Old baselines are harmless and can be cleaned with index.cleanup. If you need the old engine temporarily, set CODEMAP_ENGINE=sqlite.

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The Problem

An AI agent working on a C# codebase without CodeMap does this:

Agent: I need to find who calls OrderService.SubmitAsync.
→ Read OrderService.cs       (3,600 tokens)
→ Read Controllers/...       (3,600 tokens)
→ Grep across src/           (another 3,600 tokens)
→ Maybe find it. Maybe not.

With CodeMap:

refs.find { symbol_id: "M:MyApp.Services.OrderService.SubmitAsync", kind: "Call" }
→ 220 tokens. Exact file, line, and excerpt for every call site. Done.

That's 93.9% fewer tokens for a task agents do dozens of times per session. On a real production codebase (100k+ lines), savings are 95–99%+.

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What It Does

CodeMap builds a persistent semantic index from your solution file using Roslyn — the same compiler that powers Visual Studio. Supports both .sln (all Visual Studio versions) and .slnx (VS 2022 17.12+ / .NET SDK 9+) solution formats — auto-discovered when solution_path is omitted (prefers .slnx). Short commit SHAs are auto-expanded. The index captures:

• Every symbol (classes, methods, properties, interfaces, records)
• Every call relationship and reference (who calls what, where)
• Type hierarchy (inheritance chains, interface implementations)
• Architectural facts extracted from code: HTTP endpoints, config keys, DB tables, DI registrations, middleware pipeline, retry policies, exception throw points, structured log templates

All of this is exposed via 28 MCP tools that any MCP-compatible AI agent can call. Starting from v1.3, CodeMap also navigates DLL boundaries — lazily resolving NuGet and SDK symbols on first access, with optional ICSharpCode.Decompiler source reconstruction and cross-DLL call graphs.

Supported languages: C#, VB.NET, and F#. Mixed-language solutions (.sln / .slnx containing C#, VB.NET, and F# projects) are indexed in a single pass. All 28 MCP tools work identically for symbols from any language. C# and VB.NET use Roslyn's MSBuildWorkspace; F# uses FSharp.Compiler.Service (MSBuildWorkspace doesn't support .fsproj). F# architectural fact extractors (endpoints, DI, config) are not yet implemented — symbol search, call graphs, references, and type hierarchy all work.

Blazor / Razor (v2.5.0+): .razor components are indexed via the Razor source generator. ComponentBase-derived classes appear in symbols.search. @page routes surface in surfaces.list_endpoints with a PAGE HTTP method. [Inject] and [Parameter] properties emit dedicated RazorInject / RazorParameter facts.

Multi-target projects (v2.5.1+): <TargetFrameworks>net8.0;net9.0;net10.0</TargetFrameworks> previously produced one extraction per TFM (3× duplication). CodeMap now collapses to a single extraction on the highest-ranked TFM, with ProjectDiagnostic.TargetFrameworks listing every TFM in the group. Symbol counts on heavily multi-targeted Blazor libraries drop 60–80%.

Interface-aware graph.callers (v2.6.0+): in DI-dispatched codebases (most production .NET) graph.callers on a concrete method silently under-reported because real call sites resolve through the registered interface. CodeMap now detects interface implementation at query time and surfaces an interface_implementation_hint listing the interface members and an estimated count of additional callers routed through them. Pass follow_interface: true to union those into the result (deduped by from_symbol). No baseline-format change, no re-index required. Handles both implicit and explicit interface implementations.

Indexing perf + correctness (v2.5.2): large reduction in indexing wall-clock by skipping auto-generated trees (*.g.cs, *.Designer.cs, files with <auto-generated>, paths under obj/), short-circuiting type-position identifier classification (typeof / generic args / base lists / attributes), and parallelizing Pass-2 reference & fact extraction across projects. Validated on a 9-repo Blazor corpus: Blazorise drops from 408 s → 95 s (−77 %), ant-design-blazor from 47 s → 25 s (−47 %), OrchardCore (single-target sentinel) from 131 s → 96 s (−27 %), and a 78-csproj distributed-database project (ByTech.Bedrock) indexes in 27 s with an 11.2× Pass-2 parallel speedup. Five query-correctness bugs also fixed: symbols.search browse-by-kinds now honours namespace / file_path / project_name filters; workspace-mode namespace filter is case-insensitive (matches committed mode); refs.find cache key includes resolution_state; workspace browse-by-kinds now includes overlay-new symbols; codemap.guide's decision table no longer advertises surfaces.list_di_registrations (which was never a registered tool).

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The Transformation

Here's what changes when you give an agent CodeMap:

The agent stops reading your codebase and starts understanding it.

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Showpiece: graph.trace_feature

The most powerful tool. Replaces 5–10 manual calls with one:

graph.trace_feature {
  "repo_path": "/path/to/repo",
  "entry_point": "M:MyApp.Controllers.OrdersController.Create",
  "depth": 3
}

Returns an annotated call tree with architectural facts at every node:

OrdersController.Create  [POST /api/orders]
  → OrderService.SubmitAsync
      → [Config: App:MaxRetries]
      → [DI: IOrderService → OrderService | Scoped]
      → Repository<Order>.SaveAsync
            → [DB: orders | DbSet<Order>]
            → [Retry: WaitAndRetryAsync(3) | Polly]

One query. Full feature flow. Every config key touched, every table written, every retry policy applied — surfaced automatically from the index.

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Token Savings Benchmark

Measured across 24 canonical agent tasks on a real .NET solution:

Raw tokens = reading all source files. On production codebases (100k+ lines), savings reach 95–99%+.

Run it yourself:

dotnet test --filter "Category=Benchmark" -v normal

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28 Tools Across Six Categories

Discover

Navigate

Architecture

Workspace

Index Management

Repo

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Workspace Mode — See Your Own Edits

CodeMap tracks uncommitted changes via an overlay index. Every agent session gets its own isolated workspace:

1. index.ensure_baseline   → index HEAD once
2. workspace.create        → agent gets isolated overlay
3. Edit files on disk
4. index.refresh_overlay   → re-indexes only changed files (~63ms)
5. Query with workspace_id → results include your in-progress code

Three consistency modes:

• Committed — baseline index only (default, no workspace needed)
• Workspace — baseline + your uncommitted edits merged
• Ephemeral — workspace + virtual file contents (unsaved buffer content)

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Multi-Agent Supervisor Support

Running multiple agents in parallel? CodeMap has you covered:

• Each agent gets its own isolated workspace — no cross-contamination
• workspace.list shows every workspace: IsStale, SemanticLevel, fact count
• Stale detection fires when a workspace's base commit diverges from HEAD
• Supervisor can inspect, clean up, or re-provision any agent's workspace

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Self-Healing Under Broken Builds

When a file doesn't compile, CodeMap doesn't drop references. It stores unresolved edges with syntactic hints. When compilation succeeds again (after a fix), a resolution worker automatically upgrades them to fully-resolved semantic edges.

refs.find returns both. Filter with resolution_state: "resolved" if you need certainty.

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DLL Boundary Navigation

CodeMap resolves DLL symbols lazily on first agent access — NOT_FOUND at a DLL boundary triggers automatic extraction rather than a dead end.

Two levels, both permanent (cached in baseline DB):

After Level 2, cross-DLL call graph edges are extracted so graph.callees and graph.trace_feature traverse INTO and THROUGH DLL code seamlessly.

source discriminator in symbols.get_card response:

• "source_code" — symbol is from your own source
• "metadata_stub" — Level 1 only (decompilation unavailable)
• "decompiled" — Level 2 source reconstructed and ready

graph.trace_feature applies a max_lazy_resolutions_per_query budget (default 20) when encountering previously-unseen DLL types to bound decompilation latency.

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Shared Baseline Cache

Index once, reuse everywhere — across machines, CI, Docker containers:

export CODEMAP_CACHE_DIR=/shared/codemap-cache

• index.ensure_baseline pulls from cache first (~2ms vs ~30s Roslyn build)
• Auto-push after every new baseline build
• Self-healing: corrupt cache entries are detected and overwritten
• Zero config when CODEMAP_CACHE_DIR is unset — all cache ops are no-ops

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v2 Storage Engine — 10x Faster Queries

v2.0.0 replaces SQLite with a custom binary storage engine using memory-mapped segment files. The Roslyn extraction pipeline is unchanged — only the on-disk format is new.

Query speedup (measured across 15 query types on real repos):

Indexing speedup (Roslyn compilation dominates, but I/O is faster):

What changed:

• Baselines stored as contiguous packed binary segments (symbols, edges, files, facts) with mmap reads — no SQL parsing overhead
• Custom search index with tokenized FTS (CamelCase splitting, signature/documentation indexing)
• WAL-backed overlay for workspace mutations (same isolation model)
• Zero native DLL dependencies (no e_sqlite3.dll)

Validated on 9+ repos including dotnet/roslyn (174K symbols, 768K references), dotnet/fsharp (157K symbols via FCS), and Bitwarden. Zero functional bugs. See docs/ENGINE-COMPARISON-RESULTS.MD for full data.

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Self-Hosting Validated

CodeMap indexes its own 18-project solution (5,576 symbols, 20,960 references). All 28 tools verified against real-world architectural complexity. Self-hosting exposed and fixed cross-project reference bugs, CamelCase FTS edge cases, overlay StringId resolution issues, and multi-line SQL extraction gaps. Every tool in this README was tested against the codebase that implements it.

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Installation

.NET Global Tool — NuGet (recommended)

See the Install via Claude Code or manually section at the top for the one-paste Claude Code prompt and manual steps.

NuGet package: nuget.org/packages/codemap-mcp

Docker

docker build -t codemap-mcp .
docker run -i \
  -v /path/to/your/repo:/repo:ro \
  -v /path/to/cache:/cache \
  codemap-mcp

-i is required — MCP uses stdio transport. Without it the container gets immediate EOF.

Uses the .NET SDK base image (~800MB) because MSBuildWorkspace needs MSBuild at runtime for index.ensure_baseline. Mount a cache volume (-v /path/to/cache:/cache) to avoid rebuilding the index on every container start.

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Connect to Your AI Agent

Claude Code (Claude Desktop / claude.ai)

Add to claude_desktop_config.json:

{
  "mcpServers": {
    "codemap": {
      "command": "codemap-mcp"
    }
  }
}

Any MCP-Compatible Client

CodeMap speaks standard MCP over stdin/stdout (JSON-RPC 2.0). Any MCP client works.

CLAUDE.md Integration

Drop the instruction block from docs/CLAUDE-INSERT.MD into your project's CLAUDE.md to wire up automatic CodeMap usage for any Claude agent working on that project. The block includes the session startup sequence, a tool substitution decision table, and the "refresh before grep" rule that keeps agents in semantic mode.

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Tip: Write XML Docs — CodeMap Uses Them

CodeMap indexes /// <summary> XML doc comments on all classes, methods, and interfaces. They appear in symbols.get_card, symbols.get_context, and symbols.search results — giving agents intent and context without reading implementations.

When writing C# code with CodeMap enabled, always add XML doc comments. This isn't just style — it directly improves every downstream query. Agents using graph.trace_feature see annotated call trees that read like specs. codemap.export includes docs in the portable context for other LLMs.

See docs/CODEMAP-AGENT-GUIDE.MD for the full agent workflow guide.

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Architecture

Your Git repo              CodeMap Server
     │                          │
     │  repo_path               │
     ├─────────────────────────►│ GitService         (repo identity, HEAD SHA)
     │                          │      │
     │  solution.sln/.slnx      │      ▼
     ├─────────────────────────►│ RoslynCompiler     (MSBuildWorkspace for C#/VB, FCS for F#)
     │                          │      │
     │                          │      ▼
     │                          │ Extractors         (Symbols + Refs + TypeRelations + Facts)
     │                          │      │
     │                          │      ▼
     │                          │ CustomSymbolStore   (v2 binary segments, mmap'd)
     │                          │      │        ↕
     │                          │      │   SharedCache  (file-based, optional)
     │                          │      ▼
     │  your uncommitted edits  │      ▼
     ├─────────────────────────►│ OverlayStore        (WAL-backed incremental overlay)
     │                          │      │
     │                          │      ▼
     │                          │ MergedQueryEngine  (baseline + overlay, transparent merge)
     │                          │      │
     │  MCP tool call           │      ▼
     ├─────────────────────────►│ McpServer          (stdio JSON-RPC 2.0, 28 tools)
     │                          │      │
     │  JSON response           │      ▼
     │◄─────────────────────────│ ResponseEnvelope   (answer + evidence + timing + token savings)

Layer dependencies (enforced at build time — violations are build errors):

CodeMap.Core      ← zero dependencies (domain types + interfaces)
CodeMap.Git       ← Core (LibGit2Sharp)
CodeMap.Roslyn    ← Core (Roslyn 5.x + MSBuildWorkspace)
CodeMap.Storage.Engine ← Core (v2 binary segments, sole engine since v2.1.0)
CodeMap.Query     ← Core + Storage.Engine (query engine + cache + overlay merge)
CodeMap.Mcp       ← Core + Query (MCP tool handlers)
CodeMap.Daemon    ← ALL (DI composition root, the executable)

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Observability

Every response includes:

• Per-phase timing — cache_lookup_ms, db_query_ms, ranking_ms (sub-millisecond on v2)
• Token savings — tokens saved and cost avoided vs raw file reading
• Semantic level — Full / Partial / SyntaxOnly (index quality signal)
• Overlay revision — which workspace revision answered the query
• Workspace ID — which workspace context answered (null for committed mode)

Structured logs to ~/.codemap/logs/codemap-{date}.log (daily rotation, JSON lines). Cumulative savings to ~/.codemap/_savings.json (persists across restarts). Config at ~/.codemap/config.json (log level, cache dir, budget overrides).

v2 Data Directory

Baselines are stored in ~/.codemap/store/<repoId>/baselines/<commitSha>/ as binary segment files. Overlays in ~/.codemap/store/overlays/<workspaceId>/. Use index.list_baselines to inspect and index.cleanup to reclaim space.

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Known Limitations & Coverage Gaps

CodeMap won't surface a hit in every situation a grep would. The most common reasons are documented in docs/KNOWN-LIMITATIONS.md. Top items to be aware of:

• Multi-target conditional symbols. #if NET8_0-only types are invisible — extraction runs on the highest TFM only (L-01).
• Legacy MVC MapControllerRoute — convention-routed actions don't surface in surfaces.list_endpoints. Only attribute routing, minimal API, and Blazor @page are extracted (L-02).
• F# fact extractors not yet wired — F# gets symbols/refs/hierarchy only; endpoints / DI / config / DB tables don't extract from .fsproj yet (L-05).
• Fresh clone with no build — Razor source-generator output may be invisible until you dotnet build once (L-08).

When symbols.search returns nothing for code you can see in the editor, scan KNOWN-LIMITATIONS first before falling back to grep.

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Documentation

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Build & Test

# Build (zero warnings enforced)
dotnet build -warnaserror

# Fast unit tests
dotnet test --filter "Category!=Integration&Category!=Benchmark"

# Integration tests (requires MSBuild)
dotnet test --filter "Category=Integration"

# Token savings benchmark
dotnet test --filter "Category=Benchmark" -v normal

# Performance microbenchmarks (BenchmarkDotNet)
cd tests/CodeMap.Benchmarks && dotnet run -c Release

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Performance Reference

What to expect when running CodeMap on your codebase. All v2 engine numbers (default since v2.0.0).

Indexing time by repo size

Subsequent runs on the same commit return immediately (already_existed: true). Incremental overlay refresh (after editing files) takes ~63ms.

Query response time (v2 engine)

Cold times scale with repo size (more symbols = more BFS/join work). Warm times are nearly flat across all repo sizes — L1 cache caps at 10,000 entries with LRU eviction.

Memory footprint (v2 engine)

mmap pages are demand-loaded by the OS — resident memory stays proportional to queries made, not total index size.

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28 MCP tools. 90%+ token savings. Roslyn-grade semantics. C#, VB.NET, F#, Blazor/Razor. DLL boundary navigation. .sln + .slnx auto-discovery. v2.5.1 — multi-target compilation collapse (one extraction per .csproj, not per TFM), KNOWN-LIMITATIONS register surfaced via codemap.guide. Validated on dotnet/roslyn (174K symbols), dotnet/fsharp (157K symbols), and a 9-repo Blazor corpus including Blazorise, MudBlazor, ant-design-blazor, OrchardCore. Your agent deserves better than grep.