## What
Part 2 of the GSAP seek-safety rules (stacks on #2611): the two rules that touch existing catalog content and required reconciliation with an existing rule.
- `gsap_relative_value_second_writer` (error) — a relative var value (`y: "-=15"`) on a property whose target has another writer **active at the relative tween's start**. The relative base is captured at tween init, which reads a different partial state per seek path: sequential seek inits it mid-entrance, a cold render worker inits it at the entrance's end state, and the element teleports at chunk boundaries (production case: all scene nodes jumping ~20px mid-scene). Writers that complete strictly before the start are safe (children render in start-time order within a seek pass — verified against gsap 3.15.0) and are not flagged; neither are single-writer relatives, `from()`/`fromTo()`, build-time `gsap.set`, or relative position parameters (`"+=0.5"`). Selector resolution bails on combinators and cross-composition scoping rather than guessing. Findings aggregate per tween pair and report the overlap window.
- `gsap_timeline_set_initial_hide` (warning) — initial-state hiding via `tl.set(target, vars, 0)` on a paused timeline is not rendered while the playhead sits at exactly 0, so frame 0 shows the unhidden state (verified against gsap 3.15.0: opacity stays 1 after `tl.time(0)`, applies only past 0). Exempt when the target is already hidden by authored CSS/inline styles or a standalone `gsap.set()`, and only sets preceding every tween in source order qualify (mutated position variables resolve to their initial binding in the parser — outro hard-kills don't masquerade as position-0 sets).
- Reconciliation: `gsap_fullscreen_overlay_starts_visible`'s fixHint previously recommended exactly the flagged `tl.set(sel, {opacity:0}, 0)` pattern; it now recommends authored CSS hiding or immediate `gsap.set()`.
- Docs for the full rule family in `docs/packages/lint.mdx`.
## Corpus impact (the reason this is its own PR)
These two rules are the ones that fire on repo-shipped content:
- `gsap_relative_value_second_writer`: 4 errors in `gooey-metaball`, all genuine overlaps. Measured with gsap 3.15.0: ballD diverges **3.31 xPercent / 1.99 yPercent (~8px/5px at 240px ball size)** between sequential and cold seek — a permanent base offset that appears as a teleport at a chunk boundary. Real but modest; happy to fix the block in a follow-up (start the drift at the entrance's end, or use absolute `fromTo`).
- `gsap_timeline_set_initial_hide`: 10 warnings across the catalog after the CSS-hidden exemption (down from 54 pre-narrowing); spot-checked as genuine frame-0 pops with no authored hide (e.g. `vfx-text-cursor` `#phrase-b`).
Adversarially reviewed the same way as #2611 (393-composition corpus + gsap semantics experiments); FP classes fixed and locked as negative tests: precede-only second writers, descendant/cross-composition selector mis-joins, CSS-hidden re-assertions, mutated position variables.
## Tests
Full `packages/lint` suite green at 440 tests including multi-composition roots; `tsc`, oxlint, fallow audit clean.
Exhaustive audit of every MDX file in docs/ against skill references
and package source code. Every API signature, default value, flag,
and technical claim verified against ground truth.
* refactor: make @hyperframes/lint depend only on parsers, not core
Relocates the leaf utilities lint pulled from core — URL/asset-path helpers,
font aliases, and the slideshow manifest parser — into the standalone
@hyperframes/parsers base, and drops @hyperframes/core from lint's
dependencies. Core keeps back-compat re-export stubs at the old paths, so
producer/studio/cli are unchanged.
Why: lint was the lightweight validator from #1749, but depending on core
transitively pulled studio-server (hono) and bpm-detective — irrelevant to
linting. Now installing @hyperframes/lint pulls only parsers + postcss, and
the core<->lint dependency cycle is gone.
- parsers main entry stays browser-safe (pure utils only); the node:path
asset helpers live behind the new @hyperframes/parsers/asset-paths subpath
- slideshow parser exposed via @hyperframes/parsers/slideshow
* feat(lint): add browser entry; harden CSS url() regex (ReDoS)
@hyperframes/lint/browser — a fully client-side rule engine (lintHyperframeHtml,
lintMediaUrls, shouldBlockRender) with zero node: builtins, so browser-only
editors can validate compositions with no Node.js and no server round-trip.
Closes the browser-validation ask on #1749.
- shouldBlockRender extracted from the fs-bound project.ts into its own pure
module so the browser entry stays node-free
- pure composition primitives (data types, font aliases, URL helper) exposed via
a new recast-free @hyperframes/parsers/composition subpath, so the browser
bundle tree-shakes out the GSAP/recast machinery (verified: esbuild
platform=browser bundles with 0 node builtins)
- lint built with a platform:browser tsup pass — compile-time guarantee the
browser entry never pulls a node builtin
- harden CSS_URL_RE against polynomial ReDoS (CodeQL js/polynomial-redos);
behavior-preserving, verified against existing tests + an old/new parity check
- parsers/lint marked sideEffects:false
New docs pages for the three packages extracted from core (#1755, #1756,
#1757), wired into the Packages nav after @hyperframes/core. Each covers
when-to-use, exports, and API with cross-links. Core's parser/lint sections
now point at the dedicated packages and its Related Packages lists all three.
ukimsanov