fix(studio): carry the audio FX attributes onto every timeline row

Both element builders read `data-fx-chain` and `data-automation` off the host
element, and an expanded sub-composition child is built without one — so an audio
track inside a sub-composition reserved no automation height and drew no lanes,
while the property panel, which reads the live DOM selection rather than the row,
still showed its chain and its toggles. `hostElementState` exists to re-inherit
exactly this class of host-only field; it now covers these two alongside
`hidden`, `timelineLocked` and `timelineRole`.

`parseTimelineFromDOM` had the same gap and now reads both directly.

Also exempts the offline FX render's browser entry from the health gate: it runs
only inside the headless page the engine drives, so its CRAP score is
coverage-driven rather than complexity-driven, and its behaviour is covered by the
engine's real-browser render tests.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: vanceingalls

.fallowrc.jsonc

@@ -661,6 +661,12 @@
     // complexity pre-dates the computed-timeline work. Exempted at file level
     // rather than refactored as scope creep.
     "ignore": [
+      // audio-fx-runtime-entry.ts: the browser-side IIFE entry for the offline FX
+      // render. It runs only inside the headless page the engine drives, so unit
+      // coverage cannot reach it and its CRAP score is coverage-driven rather
+      // than complexity-driven (5 cyclomatic). Its behaviour is covered by the
+      // engine's real-browser render tests.
+      "packages/core/stubs/audio-fx-runtime-entry.ts",
       // useGestureRecording.ts: readBasePosition/connectGsapRuntime/tick are
       // inherited gesture-runtime control flow. This stack only changes
       // recordSample to coalesce display-rate events onto authored frames;

packages/studio/src/player/hooks/useExpandedTimelineElements.ts

@@ -152,6 +152,13 @@ function hostElementState(flat: TimelineElement | undefined): Partial<TimelineEl
     hidden: flat.hidden,
     timelineLocked: flat.timelineLocked,
     timelineRole: flat.timelineRole,
+    // Same reason as the three above: these are read off the host element, which
+    // an expanded child is built without. Missing them, an audio child inside a
+    // sub-composition reserved no automation height and drew no lanes, while the
+    // property panel — reading the live DOM selection rather than this row —
+    // still showed the chain and its toggles.
+    fxChain: flat.fxChain,
+    automation: flat.automation,
   };
 }
 

packages/studio/src/player/lib/timelineDOM.test.ts

@@ -296,3 +296,36 @@ describe("mergeTimelineElementsPreservingDowngrades — genuine removal vs trans
     ).toEqual(["a", "c"]);
   });
 });
+
+describe("audio FX attributes on parsed elements", () => {
+  const CHAIN = '{"version":1,"nodes":[{"type":"lowpass","id":"n1","params":{}}]}';
+  const LANE = '{"version":1,"lanes":[{"target":"volume","points":[{"t":0,"v":1}]}]}';
+
+  it("carries data-fx-chain and data-automation off the element", () => {
+    // The timeline row is what reserves automation height and draws the lanes;
+    // parsed straight from the DOM it used to arrive without either attribute,
+    // so the panel showed a chain the timeline could not.
+    const doc = new DOMParser().parseFromString(
+      `<div data-composition-id="main" data-start="0" data-duration="10">
+         <audio id="bgm" data-start="0" data-duration="10" data-fx-chain='${CHAIN}'
+           data-automation='${LANE}'></audio>
+       </div>`,
+      "text/html",
+    );
+    const [bgm] = parseTimelineFromDOM(doc, 10).filter((e) => e.domId === "bgm");
+    expect(bgm?.fxChain).toBe(CHAIN);
+    expect(bgm?.automation).toBe(LANE);
+  });
+
+  it("leaves them unset on a track that carries neither", () => {
+    const doc = new DOMParser().parseFromString(
+      `<div data-composition-id="main" data-start="0" data-duration="10">
+         <audio id="bgm" data-start="0" data-duration="10"></audio>
+       </div>`,
+      "text/html",
+    );
+    const [bgm] = parseTimelineFromDOM(doc, 10).filter((e) => e.domId === "bgm");
+    expect(bgm?.fxChain).toBeUndefined();
+    expect(bgm?.automation).toBeUndefined();
+  });
+});

packages/studio/src/player/lib/timelineDOM.ts

@@ -338,6 +338,14 @@ export function parseTimelineFromDOM(doc: Document, rootDuration: number): Timel
       if (resolvedSrc) entry.src = resolvedSrc;
     }
 
+    // Read from the element, like the manifest path does: without these an audio
+    // clip parsed straight from the DOM reserved no automation height and drew no
+    // lanes, while the property panel still showed its chain.
+    const domFxChain = el.getAttribute("data-fx-chain");
+    if (domFxChain) entry.fxChain = domFxChain;
+    const domAutomation = el.getAttribute("data-automation");
+    if (domAutomation) entry.automation = domAutomation;
+
     if (el.hasAttribute("data-timeline-locked")) {
       entry.timelineLocked = true;
     }