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BifrostFree to useApache-2.0

OpenCode

OpenCode can use Bifrost in three complementary ways. Its native LSP client provides definitions, references, hover, symbols, implementations, hierarchy, and diagnostics. MCP exposes Bifrost-specific analyzer tools such as get_summaries and query_code.

For OpenCode’s underlying host conventions, see the official LSP server, tools, MCP server documentation.

Configure LSP

Section titled “Configure LSP”

Install Bifrost first:

Terminal window
cargo install brokk-bifrost --locked --force

Add a project-local opencode.json at the root of the repository you want Bifrost to analyze. Use absolute paths for the executable and project root:

{
  "$schema": "https://opencode.ai/config.json",
  "lsp": {
    "bifrost": {
      "command": [
        "/absolute/path/to/bifrost",
        "--root",
        "/absolute/path/to/project",
        "--lsp"
      ],
      "extensions": [
        ".java",
        ".go",
        ".c",
        ".cc",
        ".cpp",
        ".cxx",
        ".h",
        ".hpp",
        ".hh",
        ".hxx",
        ".js",
        ".mjs",
        ".cjs",
        ".jsx",
        ".ts",
        ".tsx",
        ".py",
        ".rs",
        ".php",
        ".scala",
        ".cs",
        ".rb",
        ".kt",
        ".kts"
      ]
    }
  },
  "permission": {
    "lsp": "allow"
  },
  "mcp": {
    "bifrost": {
      "type": "local",
      "command": [
        "/absolute/path/to/bifrost",
        "--root",
        "/absolute/path/to/project",
        "--mcp",
        "symbol|extended"
      ],
      "enabled": true,
      "timeout": 300000
    }
  }
}

On Windows, use forward slashes in these JSON paths or escape each backslash.

The extensions above are Bifrost’s primary analyzable document types. Bifrost can index .vue, .svelte, .razor, and .cshtml files as supporting reference context, but those files are not primary LSP document types and should not activate the server.

The --root value is a deterministic fallback. A valid workspaceFolders, rootUri, or rootPath sent by OpenCode during LSP initialization takes precedence. Absolute paths avoid accidentally binding Bifrost to another launch directory.

For local Bifrost development, build the checkout and use the absolute debug binary path in the command:

Terminal window
cargo build --bin bifrost

Expose LSP to the agent

Section titled “Expose LSP to the agent”

OpenCode’s agent-facing lsp tool is experimental in the tested OpenCode 1.18.3 release. Set the feature flag in the environment that starts OpenCode:

macOS and Linux:

Terminal window
OPENCODE_EXPERIMENTAL_LSP_TOOL=true opencode /absolute/path/to/project

PowerShell:

Terminal window
$env:OPENCODE_EXPERIMENTAL_LSP_TOOL = "true"
opencode C:/absolute/path/to/project

The permission.lsp setting above lets the agent call the tool. The tool supports definitions, references, hover, document and workspace symbols, implementations, and incoming and outgoing call hierarchy. Its line and character inputs are one-based even though returned LSP ranges are zero-based.

The evidence on this page was collected with OpenCode 1.18.3 and a Bifrost 0.8.19 checkout at commit 5c479d140d8a1452167a88863e070735faa8d400. Record both versions when validating another installation:

Terminal window
opencode --version
/absolute/path/to/bifrost --version

OpenCode V2 currently accepts the lsp configuration shape but does not have an active LSP runtime; do not treat a successfully parsed V2 configuration as a working integration.

Validate native LSP

Section titled “Validate native LSP”

OpenCode starts a configured language server lazily when it opens a file whose extension matches. Run a file-specific debug command or ask the agent to make an LSP call on a real source file before interpreting an empty workspace-symbol result or checking for a server process.

The debug commands provide a model-independent smoke test:

Terminal window
opencode debug config
opencode debug lsp document-symbols file:///absolute/path/to/project/src/main.rs
opencode debug lsp diagnostics /absolute/path/to/project/src/main.rs

Then start OpenCode with the experimental flag and ask the agent to use only the lsp tool on a declaration unique to that checkout:

Use only the lsp tool. Call documentSymbol on src/main.rs, then call
goToDefinition and findReferences on unique_probe_symbol. Report the returned
file paths and ranges. Do not use file reading, text search, shell, or MCP.

A valid pass shows real documentSymbol, goToDefinition, and findReferences tool events and returns paths under the configured project. OpenCode 1.18.3 was also validated against Bifrost for hover, workspace symbols, implementation lookup, and incoming and outgoing call hierarchy. For diagnostics and edit synchronization, have OpenCode edit a temporary source file to introduce a syntax error. A working integration reports an LSP error immediately after the edit; opencode debug lsp diagnostics identifies its source as bifrost-tree-sitter. A clean file returning no diagnostics does not by itself prove which server answered. Remove the probe after retaining the evidence.

Coexist with built-in servers

Section titled “Coexist with built-in servers”

The object form of OpenCode’s lsp configuration keeps matching built-in servers enabled. This can be useful: a compiler-backed server can provide build-aware diagnostics while Bifrost provides build-independent repository navigation. Keep both unless overlap causes duplicate or ambiguous results or unacceptable startup latency.

To prove that Bifrost handled a smoke test, or to avoid a concrete conflict, disable only the matching built-in server. For example:

{
  "lsp": {
    "rust": {
      "disabled": true
    },
    "bifrost": {
      "command": [
        "/absolute/path/to/bifrost",
        "--root",
        "/absolute/path/to/project",
        "--lsp"
      ],
      "extensions": [".rs"]
    }
  }
}

Do not disable all built-in servers globally just to add Bifrost.

Troubleshoot LSP

Section titled “Troubleshoot LSP”
  • If no server starts, run a file-specific LSP debug command or ask the agent to make an LSP call on a configured source file first.
  • If the agent has no lsp tool, restart OpenCode from an environment with OPENCODE_EXPERIMENTAL_LSP_TOOL=true.
  • If the tool is denied, allow the lsp permission in the applicable config.
  • If results come from the wrong checkout, replace relative command and root values with absolute paths and repeat the unique-declaration smoke.
  • If an old Bifrost release is running, set the command to the intended absolute binary instead of relying on PATH.
  • If two servers produce overlap or slow startup, disable only the exact built-in server key for the affected language.
  • Restart OpenCode after changing its configuration or launch environment.

Native LSP does not expose get_summaries, query_code, policies, or other Bifrost-specific tools. Keep the MCP setup below when you want that surface.

Configure MCP

Section titled “Configure MCP”

The canonical opencode.json above includes the project-local mcp.bifrost entry alongside lsp.bifrost; keep both top-level members when you want both surfaces. If you already have an OpenCode configuration, merge those members into the existing object instead of replacing the file or its other servers.

Use absolute paths for both the Bifrost binary and project root. OpenCode’s default MCP discovery timeout is five seconds; the longer timeout above allows Bifrost to initialize and index a larger workspace on its first connection.

For local Bifrost development, use the same absolute debug binary built in the LSP setup above.

Quit and restart OpenCode after adding or changing MCP configuration. Then verify the server connection from the project root:

Terminal window
opencode mcp list

The output should list bifrost as connected.

Validate the Setup

Section titled “Validate the Setup”

Start OpenCode from the configured project root and use a prompt that requires an actual Bifrost MCP result:

Call the Bifrost get_summaries MCP tool on src/main.rs and report only the declared symbol names returned by that tool.

Replace src/main.rs with a source file that exists in the target repository. A successful smoke shows a bifrost_get_summaries tool call before the answer. Avoid prompts that only ask about README.md or documentation files; those can pass through ordinary file reading without proving that the analyzer-backed MCP server ran.

Apply the shared host-integration evidence contract: retain the Bifrost tool event and structured result for a known workspace declaration, verify its project-relative source path, and reject file-reading fallbacks.

Can My Agent Run RQL?

Section titled “Can My Agent Run RQL?”

The configuration above uses symbol|extended, so a fresh OpenCode session should advertise Bifrost’s query_code tool. Ask OpenCode to call it with the inline canonical JSON fields:

{"match":{"kind":"declaration"},"limit":1}

To validate saved RQL, add a workspace file named bifrost-smoke.rql:

(limit 1 (declaration))

Then ask OpenCode to call Bifrost query_code with exactly:

{"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.