Cursor

Cursor has two independent Bifrost integrations:

Integration	Process	Surface
Bifrost editor extension	Version 0.11.5: bifrost --root <workspace> --lsp, using its own Bifrost 0.11.5 binary. Next version: bifrost-lsp --root <workspace>.	Editor features such as definitions, references, hover, rename, diagnostics, and workspace symbols, plus RQL and Rune editor features
Bifrost agent plugin	bifrost --mcp symbol|extended, started by the plugin’s launcher	Bifrost tools that Cursor agents can call

Install either integration for its own surface, or install both. They run separate processes. Never point the agent plugin at the extension’s language server.

The language server moved to bifrost-lsp

Bifrost built after release 0.12.0 does not serve LSP: bifrost --lsp exits with an error. The language server is now the separate bifrost-lsp program, and bifrost-lsp has no release yet. The extension version on Open VSX, 0.11.5, still works because it downloads its own Bifrost 0.11.5 binary. See LSP Server.

Install the Editor Extension

Install the Bifrost extension from Open VSX, or open Cursor’s Extensions view and search for brokk.bifrost-vscode. Confirm that the publisher is brokk, choose Install, and open a supported source workspace. With the default auto launch mode, accept the prompt to install the managed server binary.

Open Output > Bifrost and keep the lines that show the download and the installed version and path. The managed installer:

1. downloads the platform archive and its .sha256 file from the GitHub release. Version 0.11.5 downloads Bifrost from BrokkAi/bifrost. The next version downloads bifrost-lsp from BrokkAi/bifrost-lsp;
2. checks that the .sha256 file and the archive both match the hash built into the extension package; and
3. runs the binary with --version before it starts the language server.

A visible Bifrost status item does not by itself show that these checks passed or that the server serves the active workspace.

To upgrade, choose Update for Bifrost in Cursor’s Extensions view. Fully quit and reopen Cursor. Then check the installed extension version and the managed server version in Output > Bifrost. If the extension asks to install a new managed binary, choose Update.

See VS Code LSP for all extension settings, commands, and launch modes.

Validate the Editor Extension

Use a normal workspace rather than a Cursor agent worktree for this smoke. Add a temporary, uniquely named declaration and usage in a supported language. For example, in Rust:

pub fn cursor_bifrost_lsp_probe_4f6f2b7() {}

pub fn call_cursor_bifrost_lsp_probe_4f6f2b7() {
    cursor_bifrost_lsp_probe_4f6f2b7();
}

From the usage, verify Go to Definition, Find All References, and hover. Run Rename Symbol, confirm that both declaration and usage change, then undo the rename. To exercise diagnostics, temporarily enable bifrost.unrecognizedSymbolDiagnostics, replace the call with a unique missing symbol, and confirm that Bifrost reports it before restoring the valid call and disabling the experimental setting.

Pass only if every result belongs to the active checkout and Output > Bifrost shows the language-server launch for that workspace. Remove the temporary probe after you record the Cursor version, extension version, managed server version, platform, output, and operation results.

Troubleshoot the Editor Extension

• Run Bifrost: Show Output and check the full launch command, download, checksum, version, and handler errors.
• Run Bifrost: Restart Language Server after changing roots, exclusions, or launch settings.
• Set bifrost.launchMode to bundled to require the managed binary, or use path with bifrost.serverPath to diagnose a specific local binary.
• Set bifrost.debug to true for LSP request tracing and lower bifrost.slowRequestMs when investigating latency.
• If the output shows the LSP server has moved out of this repository, the extension started a Bifrost CLI newer than 0.12.0. Use auto or bundled mode, or point bifrost.serverPath at a server binary that serves LSP.
• Do not use healthy MCP status as evidence that the editor extension works; it is a different process and protocol.

Install the Agent Plugin From GitHub

The shared agent plugin package lives in plugins/bifrost-agent, and the repository root includes .cursor-plugin/marketplace.json so Cursor can discover the package.

Use the dedicated Cursor Agents window. In a new agent, type /add-plugin, select the Add Plugin slash-command suggestion, and press Return. Cursor opens its Plugins view; in Search or Paste Link, paste:

https://github.com/BrokkAi/bifrost

Open the Bifrost result, choose Add to Cursor, and confirm Add Plugin. Cursor reads .cursor-plugin/marketplace.json, finds the bifrost package at plugins/bifrost-agent, and installs it.

Cursor’s settings labels vary by build. If Customize -> Plugins exposes Search or Paste Link, pasting the same repository URL there is equivalent. Typing the slash-command text as an ordinary chat prompt is not: select the slash-command suggestion before submitting it.

To upgrade an existing installation, remove the GitHub-installed Bifrost package from the Plugins view and repeat the GitHub install flow. Fully quit and reopen Cursor afterward, then confirm that the installed plugin metadata reports the expected version.

What the Plugin Installs

The Cursor manifest of the plugin, version 0.12.0, installs one MCP server and eight subagents.

Item	Name	What it does
MCP server	bifrost	Runs the plugin’s launcher, which finds or installs a Bifrost binary and starts bifrost --mcp symbol|extended over stdio. Cursor allows 180 seconds for startup and 300 seconds per tool call.
Subagent	architect-reviewer	Reviews a pull request’s design: coupling, cohesion, SOLID principles, abstraction levels, and fit with existing patterns.
Subagent	devops-reviewer	Reviews infrastructure code, CI/CD configuration, resource management, logging, timeouts, and error handling.
Subagent	dry-reviewer	Looks for code added in a pull request that duplicates logic already in the codebase.
Subagent	issue-diagnostician	Finds the affected files and code paths for a GitHub issue and forms a root-cause hypothesis.
Subagent	issue-enhancer	Adds source references, affected components, and technical context to a draft GitHub issue.
Subagent	issue-planner	Turns a diagnosis into an ordered list of code changes with file paths and method names.
Subagent	security-reviewer	Looks for injection, authentication bypass, data leaks, cryptographic misuse, backdoors, and vulnerable dependencies in a pull request.
Subagent	senior-dev-reviewer	Checks that a pull request’s changes match its description, and looks for unrelated changes, scope creep, incomplete refactors, and missing tests.

All eight subagents are read-only: they cannot use the Write or Edit tools.

The package directory also contains four skills. The Cursor manifest does not list them.

Skill	What it covers
bifrost-code-navigation	Find definitions, references, call sites, and related files with search_symbols, get_symbol_locations, scan_usages_by_location, and most_relevant_files.
bifrost-code-reading	Read implementation details and structure with get_summaries and get_symbol_sources.
bifrost-codebase-search	Find symbols, code shapes, and files with search_symbols, query_code, scan_usages_by_location, and most_relevant_files.
bifrost-policy-checking	Find policy packs and categories, run built-in and repository RQL policies, and read clean, finding, and unreliable results.

The portable package uses root plugin.json and mcp.json files. It can also include optional skills/ files. Cursor still needs its native .cursor-plugin/plugin.json and cursor-mcp.json adapter. The adapter resolves its launcher from Cursor’s installed plugin directory. Bifrost also accepts the absolute native path that Cursor returns from roots/list. A connected MCP status or visible tool list is not sufficient evidence that both boundaries worked; complete the smoke test below.

If an agent reports that Bifrost is not bound to a workspace, Cursor did not supply a usable root. For one fixed project, you can bypass roots negotiation: fully quit Cursor, change to that project, and start Cursor with BIFROST_WORKSPACE_ROOT="$(pwd)" cursor .. The plugin launcher passes that directory to Bifrost as --root. Quit and repeat the command when you change projects. Do not use this for a multi-root setup.

Local Plugin Testing

Build Bifrost first:

cargo build --bin bifrost

Open Cursor with the local binary selected:

BIFROST_BINARY_PATH="$(pwd)/target/debug/bifrost" cursor .

In the Cursor Agents window, open Customize -> Plugins, choose Add -> From Local Repo, and select the repository root. Do not select plugins/bifrost-agent directly: From Local Repo expects the marketplace manifest at .cursor-plugin/marketplace.json.

This flow imports the marketplace definition, but the tested Cursor build resolved the plugin contents from the repository’s remote default branch. It ignored both uncommitted files and the selected feature-branch commit. Use it only to test a snapshot already reachable from the default branch. For a local Rust change, fully quit Cursor before starting it with BIFROST_BINARY_PATH as shown above; do not use From Local Repo as evidence for an unpublished plugin-manifest change.

Enable MCP Tools

After installing the plugin, stay in the Cursor Agents window, open Customize -> MCPs, and enable Bifrost for the workspace. Check that its status is healthy, then start a fresh agent so the newly enabled tools are attached to that agent. If a restored app session reports that Bifrost is not bound, select the workspace first, open Bifrost’s MCP details, choose Reload, and then start another fresh agent.

Enabling the plugin’s MCP entry is sufficient; do not create a duplicate manual Bifrost server. The packaged Cursor definition supplies the installed launcher location, starts Bifrost without an inferred root, and lets Cursor authorize the active workspace through the standard roots/list mechanism with compatibility for Cursor’s native-path response. Bifrost never treats Cursor’s process directory or the installed plugin directory as the analyzer workspace.

Cursor can also import an installed Claude Code plugin automatically. If the MCP list contains both the native plugin-bifrost-bifrost entry and an imported plugin-brokk-bifrost entry, leave the native Cursor entry enabled and disable the imported duplicate in Cursor. This does not disable the Claude Code installation itself.

For strong exact-checkout evidence, add a temporary declaration whose name is unique to the smoke:

src/cursor_bifrost_host_probe_4f6f2b7.rs

pub fn cursor_bifrost_host_probe_4f6f2b7() {}

Use this strict smoke prompt to prove Cursor called the plugin’s MCP server instead of silently falling back to file or shell tools:

Use only the installed Bifrost plugin MCP tools. First confirm query_code is in the callable Bifrost MCP surface. Call search_symbols with patterns ["cursor_bifrost_host_probe_4f6f2b7"]. Then call query_code with schema_version 1, languages ["rust"], match {"kind":"function","name":"cursor_bifrost_host_probe_4f6f2b7"}, limit 10, and result_detail "full". Do not use Shell, terminal, rg, codebase search, file reading, or the bifrost CLI. Show both exact structured MCP results. PASS only if both return src/cursor_bifrost_host_probe_4f6f2b7.rs.

Apply the shared host-integration evidence contract: retain Cursor’s Bifrost tool event and structured result, verify the result belongs to the active workspace, and reject ordinary file-reading fallbacks or paths under the installed plugin. Remove the temporary declaration after retaining the evidence.

Cursor Agents worktrees

In Cursor Agents 3.12.30, roots/list can name the base repository while the agent composer shows a separate worktree. Bifrost correctly accepts the native root supplied by Cursor, but it cannot infer that Cursor meant a different checkout. A relative result from a file shared by both checkouts cannot prove the binding is correct. When using a worktree, run the unique-declaration smoke above and reject results from the base checkout. Cursor remains unchecked in the cross-host verification matrix until this exact-checkout boundary passes.

The cursor agent --plugin-dir CLI path is useful for checking plugin loading, but it has not proven reliable for plugin-provided MCP servers. Treat the desktop Customize/MCP flow as the MCP validation path.

Can My Agent Run RQL?

The packaged plugin uses symbol|extended. In a fresh chat after enabling MCP, confirm that the Bifrost tool list includes query_code, then call it with the inline JSON fields {"match":{"kind":"declaration"},"limit":1}. To validate saved RQL, check a workspace file named bifrost-smoke.rql containing (limit 1 (declaration)), then call query_code with {"query_file":"bifrost-smoke.rql"}.

The inline call is canonical JSON. MCP accepts RQL only from a workspace .rql file through query_file. See MCP query and RQL availability for the full surface matrix and Agent Result Safety before making completeness claims.