opencode-ast

AST plugin for OpenCode that parses source files with tree-sitter (via WASM) and exposes structural queries: outline, extract, deps, and scope.

Handles broken syntax fine since tree-sitter is error-tolerant. No language server involved.

Supported languages

TypeScript, JavaScript, Python, Go, Rust, Java, C, C++, Ruby, C#, JSON, JSONC, YAML, Markdown.

Operations

outline

Structural overview of a file — functions, classes, types with line ranges and export status.

ast { operation: "outline", filePath: "src/parser.ts" }

Output looks like:

Functions:
  parse (lines 57-76, exported)
  query (lines 78-84, exported)

Variables:
  ready (lines 24-32)
  load (lines 18-22)

You can pass filter: "struct,function" to limit output to specific kinds.

extract

Pull one symbol's source by name. Optionally pass kind to disambiguate, or signature: true to get just the declaration line.

ast { operation: "extract", filePath: "src/parser.ts", name: "parse" }
ast { operation: "extract", filePath: "src/parser.ts", name: "Parser", kind: "class" }

deps

List imports, classified as local or external.

ast { operation: "deps", filePath: "src/parser.ts" }

scope

Given a line number, returns the enclosing scope chain.

ast { operation: "scope", filePath: "src/parser.ts", line: 15 }

Line 15 is inside:
  process (function, lines 13-18)
    if block (lines 14-16)

Both outline and deps skip test-scoped symbols by default — set includeTests: true to include them.

Install

Build and copy to the plugins directory:

bun run bundle.ts
cp dist/ast.js ~/.config/opencode/plugins/ast.js

OpenCode auto-loads .js files from ~/.config/opencode/plugins/.

For per-project use, put the bundle in .opencode/plugins/ast.js and add "plugin": ["file://.opencode/plugins/ast.js"] to opencode.json.

Grammars

WASM grammar files are fetched from tree-sitter GitHub releases on first use and cached in ~/.cache/opencode-ast/.

Behavior details:

• Downloads use a 15s timeout and up to 3 attempts for transient failures.
• In-flight downloads are deduplicated per process to avoid duplicate fetches.
• Runtime and grammar WASM files are pinned with SHA-256 checksums.
• Downloaded and cached WASM files are checksum-verified before load; mismatches fail closed.
• Query objects are cached with an LRU cap of 100 entries per language.
• Source parsing is limited to 8 MiB per file by default. Override with OPENCODE_AST_MAX_SOURCE_BYTES=<bytes>.
• .h files are auto-routed to C or C++ grammar based on lightweight syntax heuristics.

When upgrading grammar/runtime URLs, refresh checksums:

bun run update:wasm-manifest

Optional flags:

• Bump all selected WASM URLs to latest before hashing:

bun run update:wasm-manifest -- --bump-latest

• Bump/hash only one target (runtime or one grammar id such as typescript):

bun run update:wasm-manifest -- --only typescript
bun run update:wasm-manifest -- --bump-latest --only runtime

Safety

• filePath can resolve outside the active workspace/worktree. OpenCode may prompt for permission before reading external paths.

Development

Requires Bun.

bun install
bun test
bunx tsc --noEmit
bun run bundle.ts