Unity Debugger Pure MCP

Unity Debugger Pure MCP is the independent local MCP companion for Unity Debugger Pure 0.2.0 and its public debugger API v1. It supports Windows x64, VS Code 1.101 or newer, companion version 0.1.0, and trusted workspaces. Install both VS Code extensions and keep the matching VS Code window open: the companion controls only debug sessions owned by that running extension host.

The companion declares kpk.unity-debugger-pure as an extension dependency. It never imports the debugger repository's internal source and does not bundle the Unity debugger Adapter or any Mono debugging assembly.

The two client paths deliberately use the same Extension Host:

• VS Code Agent uses the native provider and bridge direct mode.

• Codex uses the pinned uvx launcher and bridge registry mode.

Starting a bridge for VS Code Agent does not block Codex. Both clients connect to the same companion Host and share its session state, reference generations, breakpoint ownership, and serialized command queue. Prefer only one Agent to issue control mutations at a time so human intent remains clear.

The companion provides 19 tools in these groups:

• target and session lifecycle: list, attach, status, and disconnect;

• source breakpoints and exception policy;

• snapshots, threads, stack frames, scopes, and variables;

• safe evaluation and separately authorized explicit evaluation; and

• pause, continue, step in/over/out, and normalized event waiting.

Safe evaluation uses the debugger's non-executing inspection context. Explicit evaluation can execute target code and is accepted only when allowSideEffects is the literal value true.

The companion sends no telemetry and opens no TCP listener. Its bundled MCP executable connects to the matching VS Code extension host through a capability-protected, current-user named pipe.

VS Code Agent

Install Unity Debugger Pure 0.2.0 and this companion VSIX, then reload the VS Code window once. The native MCP provider starts the packaged bridge in direct mode; no MCP configuration or Python installation is required.

Related MCP server: Watchtower DAP Windows Debugging

Codex and other external clients

External clients require uv and the published Windows launcher package. After version 0.1.0 is available from PyPI, add the following project-scoped Codex configuration:

[mcp_servers.unity_debugger_pure]
command = "uvx"
args = [
  "--from",
  "unity-debugger-pure-mcp==0.1.0",
  "unity-debugger-pure-mcp"
]
startup_timeout_sec = 60
tool_timeout_sec = 70
enabled = true
required = false

No username, installation directory, environment shim, pipe name, or capability token belongs in client configuration. The launcher uses the client's current project directory to select one live, trusted VS Code window. Start or reload that window before starting the external MCP client. If no matching Host exists, tools fail closed with BRIDGE_UNAVAILABLE; after a VS Code reload, the next call reconnects through the refreshed registration.

The earlier global-storage installer design is superseded by this versioned launcher package. The extension does not copy launchers or edit client configuration.

Local validation

Use exact Node.js 26.5.0 for the SEA and release artifact:

npm ci
npm run typecheck
npm test
npm run package
npm run test:package

The package command creates and audits the companion VSIX, a py3-none-win_amd64 launcher wheel, and its source distribution. The VSIX retains an 11-file allowlist and contains no Python launcher; the launcher artifacts contain no Adapter, Mono runtime, Node bundle, live capability, or machine-specific path.

Release channels

• VS Code Marketplace: manual upload under kpk; the initial 0.1.0 listing exists.

• Open VSX and companion GitHub Release: companion-v<version>.

• PyPI and launcher GitHub Release: launcher-v<version>.

The two automated release streams rebuild and audit only their own product. GitHub Actions never uploads to the VS Code Marketplace.