# System map — sveltejs/svelte

> Canonical page: https://codevetter.com/unpack/svelte/system-map

# System map — sveltejs/svelte

Scanned commit 636eaaaa6f064b55072e7d192bb76dc9d8c4516e (2026-09-18). Generated by codevetter codevetter 1.12.0 on 2026-09-22.

The repo is a pnpm workspace (`pnpm-workspace.yaml` globs `packages/*` and `playgrounds/*`) with exactly one real package, `packages/svelte`, plus a Vite sandbox playground and a Node benchmarking harness at the root. The package has two runtime boundaries encoded in its `exports` map — `browser`/`worker` conditions split every entry into client and server implementations — and a third, the compiler, which is deliberately firewalled from runtime code by a custom ESLint rule. Storage is entirely file-based: there is no database; the only persistent artefacts are compiled test fixtures under `tests/*/samples/*/_output/`, generated docs under `documentation/docs/98-reference/.generated/`, and the checked-in `types/index.d.ts`. External integrations are all build-time libraries (acorn, zimmerframe, esrap, magic-string, devalue) rather than services. Deployment is npm publish via Changesets on push to `main`.
- The published artifact is unbundled ESM source: `packages/svelte/package.json` sets `"main"`/`"module"` to `./src/index-client.js` and its `files` array ships `src` directly, so consumers import the raw runtime sources rather than a bundle. — [packages/svelte/package.json](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/package.json)
- Client/server split is done entirely through export conditions — `.`, `./legacy`, `./reactivity`, and `./store` each map `worker` and `default` to `*-server.js` and `browser` to `*-client.js` (e.g. `./src/index-server.js` vs `./src/index-client.js`). — [packages/svelte/package.json](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/package.json) [packages/svelte/src/index-client.js](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/src/index-client.js) [packages/svelte/src/server/index.js](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/src/server/index.js)
- The compiler's public surface is five functions exported from `src/compiler/index.js`: `compile` (L23), `compileModule` (L69), `parse` (L117), `parseCss` (L131), plus re-exported `preprocess`, `print`, and `migrate` (L202). — [packages/svelte/src/compiler/index.js#L1-60](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/src/compiler/index.js#L1-L60) [packages/svelte/src/compiler/index.js#L195-202](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/src/compiler/index.js#L195-L202)
- Compilation is a fixed three-phase pipeline — `_parse` from `phases/1-parse/index.js`, then `analyze_component` (2-analyze/index.js:333), then `transform_component` (3-transform/index.js) — with `state.reset()` called first to clear module-global compiler state. — [packages/svelte/src/compiler/index.js#L23-60](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/src/compiler/index.js#L23-L60) [packages/svelte/src/compiler/phases/2-analyze/index.js#L333](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/src/compiler/phases/2-analyze/index.js#L333) [packages/svelte/src/compiler/phases/3-transform/index.js#L19-60](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/src/compiler/phases/3-transform/index.js#L19-L60)
- Codegen forks per target inside `transform_component`: `options.generate === 'server'` dispatches to `server_component` in `3-transform/server/transform-server.js`, otherwise `client_component` in `3-transform/client/transform-client.js`; both emit an ESTree program that `esrap`'s `print` serialises with a source map. — [packages/svelte/src/compiler/phases/3-transform/index.js#L19-62](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/src/compiler/phases/3-transform/index.js#L19-L62) [packages/svelte/src/compiler/phases/3-transform/client/transform-client.js#L135-200](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/src/compiler/phases/3-transform/client/transform-client.js#L135-L200)
- The runtime reactivity core lives in four files — `internal/client/runtime.js` (866 lines: `get`, `update_reaction`, `update_effect`, `is_dirty`), `reactivity/sources.js`, `reactivity/deriveds.js`, and `reactivity/batch.js` (1475 lines, the `Batch` class and `flushSync`). — [packages/svelte/src/internal/client/runtime.js#L548-600](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/src/internal/client/runtime.js#L548-L600) [packages/svelte/src/internal/client/reactivity/batch.js#L97-210](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/src/internal/client/reactivity/batch.js#L97-L210) [packages/svelte/src/internal/client/reactivity/deriveds.js#L71-113](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/src/internal/client/reactivity/deriveds.js#L71-L113)
- Signal identity and lifecycle are encoded as bitflags in `internal/client/constants.js` — `DERIVED`, `EFFECT`, `RENDER_EFFECT`, `BLOCK_EFFECT`, `BRANCH_EFFECT`, `BOUNDARY_EFFECT`, `CLEAN`/`DIRTY`/`MAYBE_DIRTY`, `ASYNC`, `ERROR_VALUE` — rather than as distinct classes. — [packages/svelte/src/internal/client/constants.js#L1-60](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/src/internal/client/constants.js#L1-L60)
- Server rendering is a string-accumulating `Renderer` class (`internal/server/renderer.js`) with a private `#out` array and a separate `head` sub-renderer; `render()` in `internal/server/index.js:71` is a thin wrapper over `Renderer.render`. — [packages/svelte/src/internal/server/index.js#L60-80](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/src/internal/server/index.js#L60-L80) [packages/svelte/src/internal/server/renderer.js#L116-210](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/src/internal/server/renderer.js#L116-L210)
- Build commands: `pnpm build` at root fans out to `packages/*`; inside `packages/svelte`, `build` = `rollup -c && pnpm generate && node scripts/check-treeshakeability.js`, where rollup produces only the UMD `compiler/index.js` for CommonJS/browser consumers. — [package.json](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/package.json) [packages/svelte/package.json](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/package.json) [packages/svelte/rollup.config.js](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/rollup.config.js)
- `pnpm generate` is a three-step codegen chain: `scripts/process-messages` (markdown → `errors.js`/`warnings.js` + docs), `scripts/generate-types.js` (dts-buddy), and `scripts/generate-browser-support.ts` (web-features → docs page). — [packages/svelte/package.json](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/package.json) [packages/svelte/scripts/process-messages/index.js#L1-50](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/scripts/process-messages/index.js#L1-L50) [packages/svelte/scripts/generate-browser-support.ts](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/scripts/generate-browser-support.ts)
- Tests run from the repo root via a single Vitest config that aliases every `svelte/*` import back to `packages/svelte` source using the package's own `exports` map, and picks the `server` export when the importer path contains `_output/server`. — [vitest.config.js#L1-35](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/vitest.config.js#L1-L35)
- Deployment shape is npm publish driven by Changesets: `.github/workflows/release.yml` runs on push to `main`, calls `changesets/action` with `pnpm changeset:version` / `pnpm changeset:publish`, and sets `NPM_CONFIG_PROVENANCE: true` with `id-token: write`. — [.github/workflows/release.yml](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/.github/workflows/release.yml) [package.json](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/package.json)
- The only non-library workspace member is `playgrounds/sandbox`, a Vite + `@sveltejs/vite-plugin-svelte` app that consumes `svelte` as `workspace:*` and excludes it from `optimizeDeps` so source edits are picked up without a dev-server restart. — [playgrounds/sandbox/vite.config.js](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/playgrounds/sandbox/vite.config.js) [playgrounds/sandbox/package.json](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/playgrounds/sandbox/package.json)
- Benchmarking is a separate root-level Node harness (`benchmarking/run.js`) that forks each benchmark into its own child process 'so that heap/GC/JIT state from one benchmark cannot contaminate the others', across compiler, reactivity, and SSR suites. — [benchmarking/run.js#L1-50](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/benchmarking/run.js#L1-L50) [package.json](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/package.json)
- There is no persistent datastore anywhere in the repo; the closest thing to a storage layer is `compile_directory` in `tests/helpers.js`, which wipes and rewrites `<sample>/_output/{client,server}` on every test run. — [packages/svelte/tests/helpers.js#L63-90](https://github.com/sveltejs/svelte/blob/636eaaaa6f064b55072e7d192bb76dc9d8c4516e/packages/svelte/tests/helpers.js#L63-L90)

Every claim links to its cited files at the pinned commit. Citations identify source evidence; they do not establish runtime correctness. Independent CodeVetter scan — not reviewed by upstream maintainers.

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