Live mode scaffolds each Svelte variant with a props script that annotated the
declaration:
/** @type {{ title: string; }} */
let { title } = $props();
A JSDoc `@type` written directly before a value is also JSDoc's cast syntax,
and esrap 2.3.3, the printer Svelte emits JS through, moves that annotation
onto the template's own declaration:
var /** @type {{ title: string; }} */ (h1) = root();
`var (h1) = ...` does not parse. The .svelte source is valid, the compile
succeeds, and the failure lands in the browser's dynamic import as "Unexpected
token '('": the variant never mounts and the session shows nothing. `@typedef`
carries the same shape without being a cast, so both builders emit that.
This is not test-only. Every Svelte variant we generate carried the construct,
so live mode was broken for any user whose install resolved esrap 2.3.3.
Svelte declares `esrap: ^2.2.12`, so a fresh install takes it; this repo's
lockfile pins 2.3.0, which is why unit tests stayed green while the fixture,
which installs into a temp dir, did not.
Two reasons the existing pre-publish guard could not have caught it, now
recorded next to it:
- `compileCheckVariants` compiles with `generate: false`, so there is no
emitted JS to inspect.
- `loadSvelteCompiler` resolves the compiler through createRequire, which
Svelte's export map routes to a prebuilt CJS build. A dev server imports
`src/compiler`, and only that path runs the app's installed printer. The
guard was checking a different compiler than the browser runs.
The new suite therefore imports the compiler as ESM and asserts the emitted
JavaScript parses, rather than pinning the comment style: a future printer that
mangles some other construct fails it too. The first draft used createRequire
and reported green against the exact input that breaks in a browser, which is
the mistake worth not repeating.
Verified against svelte 5.56.9 with esrap 2.3.3. Full live-e2e sweep green,
26 fixtures.
Written with AI assistance (Claude Code).
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Addresses two cursor findings on extractMatchingSourceCss plus an adjacent
hazard in the same removal machinery:
- Class matching is token-bounded, never substring: .btn no longer seeds
.btn-primary and .stage no longer seeds .stages. A falsely seeded
selector was an accept-time deletion of a hand-written rule, since any
seeded selector the variant does not re-declare is removed as
superseded.
- Tag rules that style the pick (h1, a, p) now seed the preview stub, so
unclassed selections start from the real cascade. They are excluded
from the supersedable set: tag rules style shared elements across the
route and must never be removal candidates.
- Supersession removal is now bounded by ownership: a seeded class
selector whose class is still used by markup OUTSIDE the replaced
region survives the accept, because removing it would strip styling
from markup the accept never touched.
Tests cover substring non-matches, tag seeding with a tag-free
supersedable set, and a shared-class accept where .card is used both
inside the pick and elsewhere.
AI-assisted (Claude Code).
Co-Authored-By: Claude Code <noreply@anthropic.com>
Field failure (Codex session, 2026-07-28): the agent kept the seeded
stub style block and appended its own second top-level style element in
all three variants. Svelte forbids that, so the user saw a red Vite
compile overlay; the mount-ack loop then self-healed (failure event,
repair, republish, clean accept), but the overlay window is exactly the
kind of thing the user should never see.
The publish gate closes the class: a done reply for a component session
now compile-checks every variant with the app's own compiler BEFORE the
revision bump and the browser broadcast. Failures bounce as a 422 with
file, line, and message plus _instructions; live-poll surfaces the
details in the thrown reply error. The browser never imports a variant
that cannot compile.
Also: the stub guard comments warn that all CSS belongs in the single
existing style block, worded to never contain the literal "<style"
sequence (a mention inside a CSS comment truncates the string surgery
agents use to find the block; the fake test agent caught exactly that).
The JIT svelte instructions carry the same warning.
This work was produced with AI assistance (Claude Code).
Co-Authored-By: Claude Code <noreply@anthropic.com>
Field failure from a real Codex session: accepting a variant into
Pitch.svelte appended 23 selectors and removed none, so the source's old
.decisions grid rules re-attached through the kept root class and forced
the accepted board into a stale three-column layout; some appended base
rules also landed after the source's media block, weakening the mobile
cascade.
Two mechanical fixes:
- Preview truth: the scaffolder records the seeded selectors (the source
rules that styled the replaced selection, which the isolated preview
never applied). On accept, any seeded selector the variant does not
re-declare is removed; the selector-loss postcondition treats those
removals like compiler prunes. A regression test reproduces the exact
Pitch shape end to end.
- Cascade order: reconciliation inserts new base rules BEFORE existing
top-level media blocks instead of appending after them.
Init-latency reductions from the same transcript:
- live.mjs inlines the resolved surface brief (removes three
surface-brief.mjs round-trips including a --help miss before first poll).
- The wrap/scaffold payload carries componentStubMarkup, and live.md
instructs editing stubs in place (the session read the manifest + stub
back and then deleted/recreated the files).
- live.md notes that a busy default port usually means the dev server is
already running (the session spawned a duplicate).
This work was produced with AI assistance (Claude Code).
Co-Authored-By: Claude Code <noreply@anthropic.com>
A ground-up hardening of live mode, driven by a production session in a
nested-app monorepo that hit six distinct failure classes. Full design
rationale in docs/LIVE-REWRITE-PLAN.md; every Codex-reported failure now
has a mechanical fix and a regression test.
Roots: live/roots.mjs resolves appRoot/repoRoot/contextRoot once at boot
(keyed on dev-server configs, not monorepo brand markers), persists a
manifest, and every live CLI re-anchors onto it at startup, so a helper
run from the wrong directory can no longer fork session state. Context
files are discovered upward to the git root.
Render truth: variant_mounted / variant_mount_failed events give the
journal per-variant mount state; failures reach the agent's poll queue,
raise a persistent error card with Retry (no more localStorage wipe), and
an attach probe names root/dev-server mismatches explicitly. The browser
rehydrates from the server when localStorage is gone.
Svelte: the scaffolder now parses with the app's own svelte 5 compiler.
Control flow survives (an each collection crosses the contract as one
structured prop), keyed each blocks hydrate synthetic keys, and anything
a detached preview cannot support falls back to source-preview instead of
shipping a wrong scaffold. Preview modules live in per-publish revision
directories, defeating stale transform caches.
Accept: CSS is reconciled, not appended. Matching selectors are replaced,
params bake from params.json kinds, the compiler's unused-selector pass
prunes superseded rules (pre-existing dead rules protected), a selector-
loss postcondition refuses any write that would drop hand-written rules,
and live-complete refuses to finish while live plumbing remains in source.
Also: framework registry (live/frameworks/) with a crash-safe injection
journal, session-store snapshot caching with read-only reads, protocol
enum consolidation, steer Send button, honest DESIGN-panel empty states.
Testing: new unit suites (roots, AST scaffolder, accept CSS, accept
pipeline, framework conformance); e2e now fails on preview-tree 404s,
proves computed-style mount for every variant, drives the Tune panel
through baked params, and injects failures (broken mounts, republish,
storage loss). New runtime fixtures: monorepo-nested-vite (repo root !=
app root) and vite8-sveltekit-stateful (each blocks + state). Nightly
full-matrix cron. An independent adversarial review pass preceded this
commit; its blocker and major findings are fixed and regression-tested.
This work was produced with AI assistance (Claude Code).
Co-Authored-By: Claude Code <noreply@anthropic.com>
Paul BakausandClaude Opus 5