WebAssembly (WASM)

WASM shows up in two subsystems: Tree-sitter for code parsing across 7 languages, and sql.js for local SQLite. Both ship as portable .wasm — no native compilation, one bundle works on macOS, Linux, and Windows.

Why WASM here:

Approach	Platform builds	Install friction	Perf
Native addon	6+ (os × arch)	node-gyp + Python + C++ toolchain	Fastest
Pure JS	1	None	10–100× slower
WASM	1	None	Near-native (1.2–2×)

Tree-sitter grammars

web-tree-sitter wraps the Tree-sitter C library as WASM. Grammars are loaded lazily — only when a file of that language is first opened.

Grammar	Extensions	Extracts
tree-sitter-javascript.wasm	.js, .jsx, .mjs, .cjs	Functions, classes, methods, Express/Fastify routes
tree-sitter-tsx.wasm	.ts, .tsx, .mts, .cts	Functions, classes, methods, NestJS + React
tree-sitter-python.wasm	.py	Functions, classes, FastAPI / Flask / Django
tree-sitter-java.wasm	.java	Methods, classes, Spring / JAX-RS annotations
tree-sitter-go.wasm	.go	Functions, structs, Gin / Chi / Echo handlers
tree-sitter-rust.wasm	.rs	Functions, structs, Actix / Axum / Rocket macros
tree-sitter-php.wasm	.php, .phtml	Functions, classes, interfaces, Laravel / Symfony

Runtime path resolution. Parser.init searches for tree-sitter.wasm in dist/grammars/, grammars/, out/grammars/, then node_modules/web-tree-sitter/. Handles different bundling strategies.

Parser pool. Per-language Map<language, { available: Parser[], inUse: Set<Parser> }>. Checks out a parser per file → returns after use. Avoids new Parser() + setLanguage() per file when analyzing many.

Fallback. If WASM fails to load, AstAnalyzerWorker + TreeSitterAnalyzer fall back to regex extraction covering the same languages with less accuracy (no nested structures, no multi-line signatures). Analysis always produces a result.

sql.js — SQLite in WASM

Every persistent store the extension owns:

DB file	Service	Purpose
.codebuddy/codebase_analysis.db	SqliteDatabaseService	Codebase snapshots, git state, and chat history (table chat_history)
.codebuddy/vector_store.db	SqliteVectorStore	Vector embeddings + FTS index + file metadata
~/.codebuddy/telemetry/traces.db	TelemetryPersistenceService	OTel spans + metrics (global, not per-workspace)
.codebuddy/checkpoints.db	SqljsCheckpointSaver	LangGraph state checkpoints
.codebuddy/team_graph.db	TeamGraphStore	Team collaboration graph

Vector store schema:

Column	Type	Purpose
id	TEXT	Chunk ID (filePath::offset)
text	TEXT	Source chunk
vector	BLOB	Float32 embedding (3072 bytes for 768-dim)
filePath	TEXT	Source file
startLine	INTEGER	Chunk start
endLine	INTEGER	Chunk end
chunkType	TEXT	function, class, method, text_chunk
language	TEXT	Programming language

FTS4 virtual table auto-synced via SQLite triggers. Cosine similarity computed in JavaScript with event-loop yielding for large result sets.

Persistence strategy — dirty-flag debounce:

1. Any write sets isDirty = true.
2. 5-second debounce timer (resets on subsequent writes).
3. On fire: db.export() → fs.writeFileSync (atomic write-temp-rename).
4. Extension deactivation triggers a final flush.

Batches rapid writes (e.g. indexing 200 files) into one disk write.

Memory model. sql.js runs entirely in memory. Fast reads, no disk I/O for queries. Memory proportional to data — a 50 MB vector store uses ~50 MB of heap. No WAL — concurrency handled at the JS layer via singletons + the chat-history worker’s concurrency guard.

Workers

Tree-sitter WASM runs in main thread AND worker threads:

Context	Service	WASM loaded
Main	TreeSitterParser	tree-sitter.wasm + language grammars
Codebase Analysis Worker	TreeSitterAnalyzer	tree-sitter.wasm + language grammars
AST Analyzer Worker	web-tree-sitter	tree-sitter.wasm (grammar loading optional)

Each worker initializes its own WASM instance — memory isn’t shared across threads. grammarsPath passed via workerData so workers locate .wasm relative to the install dir.

Disposal

WASM memory isn’t GC’d by V8. Explicit disposal is required:

• TreeSitterAnalyzer.dispose() in a finally after analysis completes
• Parser pool entries cleaned on service deactivation
• worker.terminate() releases all WASM allocations for that worker

Bundle layout

dist/
  grammars/
    tree-sitter.wasm            (~400 KB core runtime)
    tree-sitter-javascript.wasm
    tree-sitter-tsx.wasm
    tree-sitter-python.wasm
    tree-sitter-java.wasm
    tree-sitter-go.wasm
    tree-sitter-rust.wasm
    tree-sitter-php.wasm
    sql-wasm.wasm               (~1.2 MB SQLite runtime)

Excluded from the esbuild bundle (loaded at runtime via fs.readFileSync), copied as static assets during build.

Related

• Workers — worker-thread architecture that uses these WASMs
• Semantic search — the primary consumer of sql-wasm.wasm