Bun on macOS: sqlite-vec fails because Apple SQLite omits extension loading

[mogsl]

Problem

When running qmd under Bun on macOS, vector embedding fails at startup with:

sqlite-vec is not available. Vector operations require a SQLite build with extension loading support.
    at ensureVecTableInternal (store.js:608)

Root cause: Bun on macOS uses Apple's system SQLite for performance, but Apple's build sets SQLITE_OMIT_LOAD_EXTENSION, which disables sqlite3_load_extension(). The sqlite-vec npm packages are installed and the native vec0.dylib is present, but db.loadExtension() is rejected by the runtime.

Environment

• qmd 1.0.7
• Bun 1.3.9
• macOS arm64 (Darwin 23.1.0)
• sqlite-vec 0.1.7 + sqlite-vec-darwin-arm64 (vec0.dylib present)
• Homebrew SQLite installed at /opt/homebrew/opt/sqlite/lib/libsqlite3.dylib

Fix

Bun exposes Database.setCustomSQLite(path) to swap out Apple's restricted SQLite for a vanilla build that supports extension loading. The Bun branch in db.ts needs to call this before creating any Database instances.

Workaround patch applied to dist/db.js:

if (isBun) {
    const bunSqlite = "bun:" + "sqlite";
    _Database = (await import(bunSqlite)).Database;
    // macOS: Apple's SQLite has SQLITE_OMIT_LOAD_EXTENSION; swap in Homebrew's vanilla build
    if (process.platform === "darwin") {
        const brewPrefix = process.env.BREW_PREFIX || (process.arch === "arm64" ? "/opt/homebrew" : "/usr/local");
        const customPath = `${brewPrefix}/opt/sqlite/lib/libsqlite3.dylib`;
        try {
            _Database.setCustomSQLite(customPath);
        } catch (e) {
            console.warn(`[qmd] failed to load Homebrew SQLite from ${customPath}: ${e.message}`);
        }
    }
    const { getLoadablePath } = await import("sqlite-vec");
    _sqliteVecLoad = (db) => db.loadExtension(getLoadablePath());
}

After applying this patch, qmd embed completes successfully and vector search works.

References

• Bun SQLite docs: Database.setCustomSQLite()
• sqlite-vec Bun usage guide
• The error message in store.ts line ~474 already hints at Homebrew SQLite but the code path in db.ts never uses it