roslyn-mcp-overview

RoslynMcpServer overview

MCP server (stdio) for C# analysis: Roslyn workspaces + ILSpy decompile. TFM net10.0, version in RoslynMcpServer.csproj (currently 1.1.0). Package id SampleMcpServer. Self-contained publish for win/osx/linux RIDs.

Layout

• Program.cs — MSBuild bootstrap, optional ROSLYN_MCP_WORKSPACE → cwd, Serilog to logs/mcp-*.log under AppContext.BaseDirectory
• Hosting/ — DI (AddRoslynMcpServerTools), McpToolRegistry
• Tools/ — MCP tool classes (Workspace, CodeAnalysis, Skeleton, Build, Run, Test, NuGet, Utility, …)
• Services/ — SolutionManager, decompile/resolve, DotNet CLI, health
• Diagnostics/ — parsers (build, VSTest, NuGet audit), SDK mismatch, MSBuild locator
• RoslynMcpServer.Tests/ — xUnit; InternalsVisibleTo
• Docs: README.md (EN+RU), AGENTS.md.sample (copy to app repos as AGENTS.md)

DI / tools

Tools are singletons registered in RoslynMcpServiceCollectionExtensions. Inject SolutionManager — do not new workspaces/HTTP. Heavy services via constructor.

Related consumer

Real-world validation often uses BrqMover (c:\Devel\BrqMover) — app repo with its own AGENTS.md; do not hardcode that path into this repo’s docs/rules.

Version history (agent-relevant)

• 1.1.0 — disk watcher: saved .cs (IDE/git) sync into MSBuildWorkspace before symbol search; no keystroke/unsaved buffers; .csproj changes skip load cache, not OpenSolutionAsync from the watcher
• 1.0.35 — Roslyn 5.9.0; dedicated VS 2026 / MSBuild 18 BuildHost (XMakeElements) load/symbol failure (not SDK mismatch)
• 1.0.34 — load_workspace: wrapped design-time MSBuild warnings (ASPDEPR007 / IncludeOpenAPIAnalyzers, MSB3270, analyzer metadata refs) are warnings, not hard Failure
• 1.0.33 — load_workspace optional targetFramework (inner TFM for CrossTargeting / TargetFrameworks); dedicated missing-Compile load report
• 1.0.32 — run_specific_test: VSTest Passed/Failed lines accept [1 s] / [1 m 28 s] durations (not only ms)
• 1.0.31 — run_dotnet_test / run_specific_test: separate incremental dotnet build then dotnet test --no-build (parser sees test output only)
• 1.0.30 — apply_patch replaceAll: advance past inserted text (hang when newString contains oldString)
• 1.0.29 — load_workspace optional Configuration/Platform (cached for build/test); empty-TFM ResolvePackageAssets dedicated fail
• 1.0.28 — run_dotnet_test: infer Passed when .slnx VSTest omits the Passed: line
• 1.0.27 — load_workspace: NU1701 / TFM-compat restore warnings soft (not fatal); Msbuild failed wrapper word failed is not blocking by itself
• 1.0.26 — agent diagnostics: client-abort load_workspace, empty get_test_list, run_specific_test path/filter mismatch hints
• 1.0.25 — run_dotnet_build: default --no-incremental; effective exit = last build step (restore cannot mask)
• 1.0.22 — run_specific_test: VSTest-safe method filters (~, no (), no bogus leading . on dotted FQNs)
• 1.0.21 — load_workspace: NuGet prune / unused PackageReference advisories soft (warnings), not hard Failure
• 1.0.20 — optional configuration (-c) on run_dotnet_build / run_dotnet_test / run_specific_test
• 1.0.19 — .slnx accepted by load_workspace / build / test / discovery (prefer solution files for multi-config)
• 1.0.18 — tool [Description] accuracy pass (build probe, decompile resolve, NuGet timeouts, AST params)
• 1.0.17 — run_dotnet_test / run_specific_test optional noBuild / noRestore
• 1.0.15 — search_code caseSensitive; no-workspace candidate paths; rename_project; branding recipe in AGENTS
• 1.0.14 — run_dotnet_run, run_nuget_audit, get_changed_files, workspace health on load_workspace
• 1.0.13 — exact assembly resolve (deps.json + NuGet), no fuzzy Contains
• 1.0.10+ — SDK pin from global.json, build probe, VSTest parser, MCP_MSBUILD_SDK_MISMATCH