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Unpublished release-notes preview. The version below is a placeholder, not an installable release.

Roslyn Workbench MCP — VERSION

This minor release adds a downloadable agent skill served through MCP resources, improves tool descriptions and reduces repeated input-schema content. Resource-read failures now receive correlated diagnostics, and unexpected fatal Host failures report details on standard error and exit with a non-zero status. Existing tool semantics, plugin APIs and recovery formats retain their 1.x compatibility guarantees.

Changes in this release

  • Added a Roslyn Workbench agent skill with focused references for workspace selection, inspection, diagnostics, dependency analysis and transactional changes. The server exposes the skill and its Markdown references as MCP resources; the README and documentation also provide a separate download containing the skill, references, agent metadata and application logo.
  • Expanded descriptions across inspection, lifecycle, discovery, Code Action, flow and dependency analysis, diagnostics, symbol relationships, context, mutation, transaction and status tools. The guidance explains when to use each tool, relevant prerequisites, defaults, result bounds and recovery steps. Tool names, execution behaviour and parameter meanings are unchanged.
  • Reduced duplication within tool input schemas by sharing repeated definitions through local $defs and $ref entries with property-derived names. Descriptions are preserved. Clients that expand references can continue to use the equivalent expanded schema.
  • Extended local correlated error capture to unexpected MCP resource-read failures. Clients receive a generic protocol error with a diagnostic identifier and reporting guidance; retained details remain available through the existing explicit, consent-controlled error-reporting workflow. Expected cancellation and deliberate protocol errors retain their handling.
  • Added a final exception boundary around the Host entry point. Unexpected startup, runtime or disposal failures write a diagnostic identifier and full exception details to standard error and exit with status 1, keeping the MCP standard-output channel clear. These fatal diagnostics are available in standard error rather than the process-local error store.

The release includes the Host .NET tool and a separate plugin-authoring package, with a 1.x compatibility policy for the published surfaces.

What is included

  • Multiple long-lived Workspace sessions and semantic inspection of symbols, references, diagnostics, code structure and change impact.
  • Bounded, snapshot-aware results, a versioned tool reference and structured continuation guidance.
  • Transaction staging, preview or receipt-based review, history, undo/redo, rollback, conflict detection and durable recovery.
  • Roslyn Code Action discovery, Fix All preparation and staging through the same transaction boundary.
  • Optional Workspace admission roots, effective-root capping and external-document policy for limiting accidental agent scope.
  • Optional compiler-impact validation that rejects commits introducing new compiler errors. It does not replace analyser validation or tests.
  • Opt-in mutation-provider provenance, local correlated diagnostics and an explicit, consent-controlled error-reporting workflow.
  • The Lantean.Roslyn.Workbench.Mcp.Plugins authoring package, containing Plugins and Abstractions contracts and the authoring analyser. Users install trusted plugins manually; no curated plugin repository is included.

Requirements and operating defaults

A supported .NET 10 SDK and an MCP client able to launch a local stdio process are required. Install the SDKs and build tooling needed by the projects being analysed. Windows x64, Linux x64 and WSL2 x64 are supported. macOS x64 and ARM64 are best effort; Windows ARM64 and Linux ARM64 are unsupported release targets. Supported workspaces contain SDK-style C# projects; unsupported languages and project systems are skipped with diagnostics.

The default mode is inspection-only, which exposes no transaction or source-mutation tools. External plugin loading is independently disabled by default. Choose an operational mode deliberately:

Mode Commit workflow
inspection-only Inspection and Workspace lifecycle only.
transactional Preview, then client-mediated confirmation for one commit or the Host session.
approval-required Review an exact transaction receipt, then confirm the receipt-bound commit.
autonomous-trusted Preview and commit without Host confirmation.

The two confirmation modes require the client to advertise and permit MCP elicitation. A decline, cancellation or unavailable prompt does not commit; inspect the structured result before retrying. Compiler-impact validation is separately opt-in. See Configuration for switches, environment variables, defaults and precedence.

Install and connect

Both products are distributed through NuGet.org. Run the exact Host package without a permanent installation:

dnx Lantean.Roslyn.Workbench.Mcp@VERSION --yes -- --version

Alternatively, install the same package as a global tool:

dotnet tool install --global Lantean.Roslyn.Workbench.Mcp --version VERSION
roslyn-workbench-mcp --version

The reported version must match the release. Configure the client to launch roslyn-workbench-mcp, or dnx with the exact package version and Host arguments after --. See Getting started. The running server's tools/list is authoritative for the enabled tools and their mode-specific contracts. Native installers are not provided.

Plugin projects reference Lantean.Roslyn.Workbench.Mcp.Plugins at the matching release version. See Plugin authoring for the package boundary, deployment and compatibility requirements.

Compatibility and upgrade

MCP tools

The stable built-in catalogue follows an additive 1.x policy. Existing tool names and input/output meanings are preserved; clients should ignore unknown output fields and rediscover tools/list after a restart or upgrade. Canonical baselines cover both output-schema publication modes and each supported operational configuration.

Errors and continuations

Stable error codes retain their meanings. RequiredAction values and continuation kinds and targets are stable contracts; human-readable messages may improve. Surface unknown codes safely and do not guess a recovery action from message prose.

Recovery formats

Recovery format V1 remains readable throughout 1.x. Unsupported formats are reported and retained without reinterpretation or cleanup; use the same or a newer compatible Host to recover them. Finish or roll back active transactions and stop the Host before upgrading. Retain unresolved state and follow Recovery guidance.

Plugin APIs

Plugin API V1 and the shipped Plugins and Abstractions public APIs are stable for 1.x. Plugin authors own their tool contracts and should use the supported package rather than Host or Workspace implementation assemblies.

For an existing global installation, run dotnet tool update --global Lantean.Roslyn.Workbench.Mcp --version VERSION. For dnx, update the pinned package version in client configuration. The published 0.1.0 beta did not carry the stable guarantee; review the operating defaults and plugin opt-in before reconnecting. If an older installation uses the former package ID Roslyn.Workbench.Mcp, uninstall it before installing Lantean.Roslyn.Workbench.Mcp; the command name remains unchanged.

Trust boundary and known limitations

Open only fully trusted repositories. MSBuild evaluation, project analysers and explicitly enabled plugins execute with the Host's permissions; Roslyn Workbench is not an operating-system sandbox. Workspace roots and transactional controls protect against accidental agent scope and source-change errors, not untrusted executable build inputs. Avoid concurrent writes to commit-owned paths or structural repository changes during commit application and startup recovery.

Error reporting requires explicit consent. Review prepared payloads because exception messages can contain source text, paths, identifiers or secrets. Choose the option without exception messages when necessary. A declined or unavailable prompt sends no report.

Platform limitations, client-dependent elicitation, trusted executable inputs and the limits of compiler-impact validation are explicit parts of the supported security model.

Feedback and contributions

Use Issues for reproducible defects, Q&A for help and Ideas for proposals. Follow the security policy for private vulnerability reports. Include redacted reproduction details rather than private source or credentials.

External pull requests are accepted. Agree the scope first and sign every contributed commit with a cryptographic signature that GitHub can verify. No separate DCO sign-off or contributor licence agreement is required; see Contributing.

Uninstall and release evidence

Remove the client's server entry, stop the Host and run dotnet tool uninstall --global Lantean.Roslyn.Workbench.Mcp. A dnx configuration has no global tool installation to uninstall. Keep unresolved recovery evidence until recovery is understood.

Both packages are MIT-licensed. Release assets include both .nupkg and .snupkg pairs, SHA-256 checksums, source and release identity, coverage evidence, SPDX SBOMs and validated dependency-vulnerability evidence. Published package hashes receive GitHub build-provenance and SBOM attestations. See Supply-chain evidence for verification and its trust boundaries.