## Why
#3094 fixed one way the mount and render paths disagreed, and added the gate that catches disagreement. It deliberately left the rest.
Four divergences are still live. Each one means a composition assembles differently depending on whether it is being previewed or rendered — the same class of defect that shipped three catalog components unstyled, just with smaller blast radii.
## How
Both paths now derive root discovery, scope identity, asset sources and order, hoisted links, variable carriers and nested-host enumeration from the shared module #3094 introduced. Each keeps its own I/O, which is where they genuinely differ. The compiler's local depth cap and root lookup and the runtime's three pre-filtered head parameters are gone; the runtime hands over the head node and lets the module decide what comes out of it.
Four behaviour changes, each stated by what actually differs rather than by the edit:
**Inline `<head>` scripts.** The compiler looped head scripts with a `src` branch and no `else`, so an inline one was silently discarded on render while the runtime ran it. That is losing code, not holding a convention — the runtime's answer wins. Head and content scripts now share one loop, head first, order preserved. A non-templated sub-composition with an inline head script went from **0 collected scripts to 1**, wrapped, body intact.
**`<link>` hoisting.** Conditional on render, unconditional on mount, so a templated sub-composition's webfont link was dropped in video and kept in preview. Hoisting is the superset and matches what the author declared. A templated composition with a stylesheet link went from **no external links to that link**. The parity fixture that previously recorded this shape as a known exclusion now gates it.
**Anonymous hosts.** With a host naming no id, the compiler fell back to the first declared composition and scoped to it; the mount left the content unflattened and injected its stylesheet into the host `<head>` **unscoped**, so a composition's CSS leaked into whatever mounted it. The compiler's answer wins. The injected rule went from a bare `.label { … }` to `[data-composition-id="scoped-text"] .label { … }`.
**Scope ids.** The compiler splits the CSS scope id from the script composition id; they differ only when a host names an id the content does not declare, and there the scripts follow the declared id so their self-referencing queries resolve. The runtime used one for both. The split wins: a host naming `captions-comp` over content declaring `captions` now emits scripts bound to `captions` while its CSS still scopes to `captions-comp`.
## Test plan
- [x] Unit tests added/updated
- [x] Manual testing performed
- [ ] Documentation updated (if applicable)
Core 1694 passing, producer 574 passing, the parity contract now gates the two divergences it can observe (the other two carry no contract field, so they are gated by unit tests naming the exact before/after). Lint 0, `typecheck:runtime` and the runtime preview guards clean, package cycles unchanged.
Characterization-first: both suites were run and recorded green before any decision moved, so a behavioural drift would surface as a red test rather than a silent difference.
**One assertion changed, deliberately.** A runtime test asserted that an anonymous host's composition is *not* flattened, and documented that as intentional. That premise is now false. What the test actually cared about — the root and its content present under the host — still holds and is still asserted; the "not flattened" claim flipped, and the test now also asserts the scoping that was missing.
## Not covered
The variable-carrier divergence and its `TODO(template-var-carriers)` are untouched by design, as is recursion on the mount path — a sub-composition containing its own `data-composition-src` is still silently dropped in live preview. Both are behaviour changes with their own units, and both are now one-line-ish changes because the shared module already reports what they need.
`runtimeScopeCompositionId` no longer falls back to the authored scope id. This is a functional change beyond the four above, surfaced in review: for an anonymous host with authored variable defaults, the runtime previously stashed them under the declared id, and now does not. It removes a runtime-vs-compiler divergence in the correct direction — the runtime was doing work the compiler never did, and the compiler is authoritative for a shipped composition — but a caller relying on runtime-only variable exposure loses it.
The three copies each of the flattened-root helper and the id assignment are left alone: they look mergeable and are not cheaply, and they touch the instancing contract the pixel harness guards.
## Worth knowing
The parity test's compiler arms import core's **built dist** while the mount arm imports source, so core must be rebuilt before that lane means anything after a compiler change. Skipping it produces a phantom divergence that looks exactly like a real one.
Extends the studio-preview fix to the render path and the asset-discovery
utilities, which share the same resolver and had the same defect.
`rewriteAssetPath` takes an optional `assetExists` probe. A plain relative ref
authored in a sub-composition (`_shared.css`, `clip.mp4`) is re-pointed at the
composition's own directory when that sibling exists on disk; project-root refs
with no sibling (the registry's `assets/logo.png` convention) stay as authored.
Callers that can see the filesystem supply the probe, so the module stays free
of node:fs.
Also fixes a second defect in the inliner: `<head>` <link> hrefs and external
script srcs are hoisted into the root document but never went through the
rewrite at all, so even the documented `../` form escaped the project and 404'd
at render time.
Wired into the preview bundler, the producer compiler, the studio preview
builder, the HEVC preview lint, the project lint's asset scans, publish proxy
baking, and media-treatment source resolution.
* fix(core): discover sub-composition hosts to a fixed point during inlining
inlineSubCompositions collected [data-composition-src] hosts from the
document once, before inlining began, then processed that fixed list in
a single flat loop. A host's inlined content could introduce new hosts
of its own (a sub-composition nesting another sub-composition), and
those were never discovered: two-level nesting worked because the
second level's host already existed in the root document, but any
third level's host only appeared inside content the single pass had
already finished walking, so its content silently never rendered.
Host discovery now runs as a work queue: after a host is inlined, the
newly inserted subtree is re-scanned for further hosts, which are
enqueued with their ancestry chain. A host whose source already appears
in its own ancestry is a circular reference and is reported through the
existing onMissingComposition channel instead of being inlined; a depth
ceiling backstops any gap in that check. Existing single- and two-level
fixtures are unaffected.
* fix(producer): assign runtime composition ids to hosts discovered mid-inline
The producer's per-instance runtime id assignment (assignBundledRuntimeCompositionIds)
ran once over the root document's initial hosts, before inlining. With
host discovery now iterating to a fixed point (previous commit), hosts
revealed inside an already-inlined sub-composition were never in that
pre-pass, so the identity map returned undefined for them: two sibling
instances of the same sub-composition, discovered mid-traversal, both
fell back to their shared authored id and clobbered each other's
variablesByComp entry.
hostIdentityMap is now a lazy map: a pre-pass cache hit returns
unchanged, a miss reads the host's authored data-composition-id,
allocates a collision-checked runtime id by scanning the live document,
writes it back, and caches it. No change to the shared inliner's call
signature. Existing single-instance and root-level reusable-template
cases (#2064) are unaffected.
* test(producer): add depth-3 nested sub-composition regression fixture
Adds a minimal three-level chain (root -> level-2 -> level-3) where the
deepest level renders a distinguishing full-frame marker, following the
existing sub-comp-* fixture pattern. Confirmed against the pre-fix
commit (735128a61) in a separate scratch checkout that the fixture fails
without the previous two commits (level-3's marker absent, ~0.4B fewer
matching pixels than the golden expects) and passes with them.
The golden reference video was captured on the team's render host
(devbox) rather than locally, to avoid PSNR drift from font/GPU
differences against whatever renders the regression suite in CI. Local
render against that golden also passes (PSNR ~24.5dB throughout, 0
failed frames of 100 checkpoints), confirming cross-machine consistency
as well.
Fixes#1847
The producer's render path stripped a sub-composition's authored root element and inlined only its children, so any CSS anchored on that root (its id or classes) matched nothing in the compiled HTML even though it resolved fine in Studio preview.
Changes:
- Wire flattenInnerRoot into the producer's sub-composition inliner (packages/producer/src/services/htmlCompiler.ts) so its render-time DOM shape matches the preview bundler's.
- Rewrite a bare root [data-composition-id="X"] box selector to a :has()/:not() pair that lands on exactly one of the host or the flattened wrapper (packages/core/src/compiler/compositionScoping.ts), avoiding double-applying additive properties like padding.
- Restore the composition's own id onto the flattened wrapper when the host has no id of its own, an "anonymous" host (packages/core/src/compiler/inlineSubCompositions.ts).
- Fix the runtime's startResolver to find a composition's start time through the post-inlining data-composition-file marker, not just data-composition-src or data-composition-id (packages/core/src/runtime/startResolver.ts).
Also adds regression coverage for the literal issue #1847 repro (a class, not just an id, on the authored root, styled via a descendant selector), a test proving the runtime compositionLoader's anonymous-host path doesn't share this bug, and fixes stale test documentation and a misattributed code comment surfaced during review.
Verified: 29-fixture Docker regression sweep on linux/amd64 (matching CI) run 3x clean, 967/967 core unit tests, full CI green.
* fix(core,producer,cli): pre-flight validation for empty/malformed sub-compositions
The #1 render failure bucket in production telemetry (PostHog project 356858,
dashboard 1783183 "HyperFrames — Bottom-Line & Activation"; ~65-69K
occurrences / ~27-28K affected users over 30 days, ~80% via AI-agent
authoring flows) is a `data-composition-src` reference pointing at a scene
file that is empty, malformed, or missing.
Root cause, traced end-to-end:
- The literal error "Composition HTML is empty or could not be parsed: <path>"
is real (not a PostHog paraphrase) — thrown by a since-reverted guard in
packages/core/src/compiler/inlineSubCompositions.ts (#1364), then changed to
a silent skip in #1678 to avoid aborting renders on partial content during
authoring. #1629 added per-assembler guards for 3 skill workflows
(product-launch-video, faceless-explainer, pr-to-video), but general-video
and hand-authored flows — where the dominant filename `scene-title.html`
(40K+/68K of the bucket) originates — have no assembler and thus no guard.
#1678 assumed the assembler guards from #1629 covered this pre-render; they
only covered 3 of the many authoring flows.
- On current `main`, an empty/malformed data-composition-src file no longer
crashes or throws during render — it's silently dropped by the tolerant
inliner. Reproduced locally: `hyperframes render` on a project with an
empty scene-title.html "succeeds" after ~93s (two 45s
pollSubCompositionTimelines timeouts) with the scene silently missing from
the output video. `hyperframes validate` also reports "No console errors"
for the same broken project.
- The raw `Cannot destructure property 'firstElementChild' of
'documentElement' as it is null` crash reproduces directly against
linkedom (the DOMParser polyfill packages/cli/src/utils/dom.ts installs in
the real CLI runtime) for empty and non-HTML input — confirmed with a
standalone repro script, not just inferred. jsdom/happy-dom (used in this
repo's own test environment) are spec-compliant and never produce a null
documentElement, which is why this needed a linkedom-specific test file.
Fix:
- New shared helper `checkSubCompositionUsability`
(packages/core/src/compiler/subCompositionValidity.ts) is the single
source of truth for "is this data-composition-src file usable" — mirrors
the inliner's own parse/template/body logic so all callers agree.
- `inlineSubCompositions.ts` (preview/studio bundling) now uses the shared
helper internally but keeps its #1678 tolerant skip-and-continue behavior
unchanged — mid-authoring iteration on a partial project must keep
working. `onMissingComposition` now also receives a human-readable reason.
- New render-only pre-flight (`assertSubCompositionsUsable` in
packages/producer/src/services/htmlCompiler.ts) walks every
data-composition-src reference (including nested ones, root-relative,
matching parseSubCompositions' own resolution) before any compilation
work starts, and throws naming every offending file at once. This is
unconditional — not gated behind --strict — because a render that
silently drops a scene is strictly worse than one that refuses to start.
Confirmed locally: render now fails in ~0.4s with an actionable message
instead of "succeeding" after 93s with a missing scene.
- New `hyperframes lint` rule `missing_or_empty_sub_composition`
(packages/cli/src/utils/lintProject.ts) surfaces the same check as a
file-scoped, actionable lint error (already unconditional — lint exits 1
on any error).
- `hyperframes validate` now also runs this check before launching a
browser, so it no longer reports "No console errors" for a project with a
broken sub-composition.
- `packages/core/src/parsers/htmlParser.ts`: guarded every
`documentElement`-may-be-null access (parseHtml, updateElementInHtml,
addElementToHtml, removeElementFromHtml, extractCompositionMetadata,
validateCompositionHtml) with a new typed `CompositionHtmlParseError` (or,
for validateCompositionHtml's collect-and-report contract, a typed
validation failure) instead of a raw crash.
Tests: empty file, whitespace-only, malformed/non-HTML, missing file, nested
sub-compositions (both happy path and broken-grandchild), and the happy path
— at the shared-helper, lint, and render pre-flight layers.
Not changed: the AI-agent authoring skills (skills/*). general-video and
hand-authored flows have no assemble-index.mjs equivalent to guard, so the
fix is at the CLI/render layer instead — flow-agnostic, covers every
authoring path, and the skills' existing "run lint/validate and stop on
failure" guidance now actually catches this class of mistake once run.
Not run in this environment: the producer package's full regression-harness
test suite (`bun test` in packages/producer) — it performs heavy real
rendering (S3 asset downloads, Google Fonts fetches, full video encodes) and
did not complete in a reasonable time in this sandbox. Verified instead via
the targeted test file for all touched code (76/76 passing), whole-repo
typecheck/build/oxlint, `fallow audit` (complexity/duplication/dead-code
gate, clean), and manual end-to-end CLI runs (render/lint/validate) against
reproduction projects, including a nested sub-composition scenario. CI
should run the full producer suite before merge.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
* refactor(parsers,lint): port empty-composition pre-flight to extracted packages
Rebased onto main, which extracted @hyperframes/lint from core (lint depends
only on parsers, not core). Relocate checkSubCompositionUsability from core to
@hyperframes/parsers so both core (inliner) and lint can consume it without a
core<->lint cycle; core keeps a @deprecated re-export shim.
Correctness fixes from code review:
- checkSubCompositionUsability now returns "no-composition-root" when the
<template>/<body> content has no [data-composition-id] element (previously
a marker-free placeholder body passed both guards).
- lint's missing/empty sub-composition rule now only checks files reachable
via data-composition-src from the root (matching render pre-flight), instead
of a raw filesystem walk that false-positived on orphaned files.
- drop `as string` cast in inlineSubCompositions in favor of an explicit
null guard (per CLAUDE.md).
Review-comment items:
- move EmptyCompositionError JSDoc above the class (was above the adapter fn).
- correct stale circular-ref comment to match actual silent-skip behavior.
- rewrite self-contradicting lint message ("silently drop") to describe the
new loud render-pre-flight abort.
- add the __PLACEHOLDER__ (/^__[A-Z_]+__$/) skip to the render pre-flight so
it agrees with lint.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---------
Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>
## Problem
The most common render failure in recent reports is:
```
Cannot destructure property 'firstElementChild' of 'documentElement' as it is null.
```
It appears when a `data-composition-src` file resolves to empty or unparsable HTML, and started showing up after the render pipeline change in 0.6.73.
## Root cause
When a sub-composition file is empty or unparsable, linkedom's `parseHTML` returns a document with a null `documentElement`, and the shared inliner (`packages/core/src/compiler/inlineSubCompositions.ts`) dereferences `.body`/`.head` on it, crashing inside linkedom internals with the cryptic destructure error instead of telling the user what's wrong.
## Fix
Guard the resolved sub-composition HTML and the extracted content HTML in the shared inliner: empty or unparsable input now fails with an actionable error naming the offending file.
## Testing
- New tests in core and producer reproducing the empty sub-composition case (previously crashed with the destructure error, now throws the actionable message).
- `bun run build` green, all tests pass in the changed test files.
Root-cause fix for edits being wiped after refresh: the studio's
inspector edits were patched client-side via regex matching in
sourcePatcher.ts, which silently failed for many compositions ("Unable
to patch" toast). Replaced with a server-side patch-element API endpoint
using linkedom for proper DOM parsing via querySelector.
Also fixes the WYSIWYG render bug where sub-composition CSS was not
applied. The CSS scoping generated descendant selectors when both
attributes coexist on the same host element. Fixed to use compound
selectors for the authored root.
Edit persistence:
- New POST /file-mutations/patch-element endpoint using linkedom
- persistDomEditOperations calls server instead of client regex
- 15 tests covering all patch operation types
Render CSS scoping:
- Compound selector for authored root on host element
- Regression test: wysiwyg-subcomp-css (baseline pending Docker)
- 3 unit tests + 1 integration test
GSAP CDN fallback:
- Preview: error-handler catches gsap 404 and loads from CDN
- Producer: rewrites missing local gsap paths to CDN before compile
Studio resilience:
- Error boundary with recoverable UI
- Lazy mediabunny import prevents crash cascade
- Hash routing listens for hashchange events
- Sub-composition duration reads data-hf-authored-duration fallback
- Save debounce 600ms to requestAnimationFrame
Observability:
- PostHog telemetry for crashes, save failures, tab switches, playback,
toolbar actions, navigation, and render starts
The runtime path (compositionLoader.ts) already propagated
data-timeline-locked from inner root to host, but both compiler
inliners (bundler + producer) did not. Bundled output re-opened in
Studio would lose the lock. Now propagated in inlineSubCompositions
alongside the existing data-hf-authored-id propagation.
Escape href values in querySelector calls for link dedup in both
htmlBundler.ts and htmlCompiler.ts to match the runtime path (which
uses CSS.escape). Prevents SyntaxError on hrefs containing quotes.
Add two tests for inlineSubCompositions font-link extraction:
- Verifies <link> elements are extracted with original rel + crossorigin
- Verifies dedup across multiple sub-compositions sharing the same font
When the producer inlines a sub-composition with compId match, it takes
innerRoot.innerHTML which strips the wrapper div and its id attribute.
CSS/GSAP selectors rewritten from #ID to [data-hf-authored-id=ID] then
match nothing.
Fix: after innerHTML injection, copy the inner root's id as
data-hf-authored-id on the host element. This makes #ID selectors work
identically in both preview (bundler) and render (producer) paths.
Closes#969
- Rename activateNestedChildTimelines → activateSiblingTimelines (matches player.ts)
- Use tl.play() instead of tl.paused(false) for consistency
- Convert positional activateChildren boolean to { activateChildren } opts
- Add FIXME(#969) to divergence test with tracking issue link
- Add [id="intro"] no-rewrite boundary test
- Add comment about deliberate no-restore behavior in render-seek path
- Create sub-comp-t0 and sub-comp-id-selector as proper regression tests
under packages/producer/tests/ with golden MP4 baselines
- Add both to shard-7 in regression.yml
- Add clarifying comment on activateNestedChildTimelines scope
- Confirm test fixture network safety in comment
The producer inlining path strips the inner root element (taking innerHTML
when compId matches), losing the id attribute. The bundler path preserves it
via flattenInnerRoot + data-hf-authored-root-id. This causes #ID selectors
in sub-comp CSS and GSAP to fail silently during render while working in
preview.
Adds a minimal fixture with a sub-comp using #intro scope to catch this
divergence in future compiler changes.
Miguel Ángel