[miguel-heygen]

What

Composition.dispose() now drops the parsed document and the element snapshot caches.

Why

A disposed session kept its whole parsed (linkedom) document. Anything that still referenced the session, such as a stale closure or a React fiber's old props, therefore kept the replaced film alive, so Studio's memory grew with every film swap.

Measured

Headless Chrome, a generated fixture project (150 clips, 2 videos, 25 off-canvas elements), swapping between two films 25 times with no other interaction, heap read after a forced GC:

	Heap at swap 0	Heap at swap 25	Growth
Before	76.8 MB	91.9 MB	+15.1 MB
After	76.1 MB	83.7 MB	+7.6 MB

Retained copies of the parsed film HTML in a heap snapshot at swap 25: 29 before, 4 after (the live session plus interned strings). Live documents, DOM nodes and listeners were flat in both runs.

Not fixed here

Growth is halved, not gone: about 0.26 MB per swap remains. Stale render scopes of several memoized callbacks still chain to one another and keep a lower-case copy of each film's source and other per-swap data alive. That needs changes in several components, so it is a separate PR.

Test

session.dispose-release.test.ts opens ten sessions, keeps every disposed session referenced, forces a GC and requires every parsed document to be collected. It fails on main (10 of 10 documents retained) and passes with this change, three runs in a row.

A disposed session now answers reads from an empty document instead of its old one, and outside production logs one warning with a stack the first time it is read, so a caller still holding a stale session can be found.

[github-actions]

Edit accuracy: accurate 271 (base branch 271), smooth 138 of those

The gate passes.
Smoothness is reported in the artifact, not gated. A case fails only if it fails 2 of 3 runs.

Quarantined, measured but not gated (0)

Unstable (1)

• seqplainkeys-none-pct-r0-nested-z100: tracking 0.05, pressJump 0, drop 0, reload 0, render 0.02, renderKey -, undo false, teleport true / tracking 0.05, pressJump 0, drop 0, reload 0, render 0.02, renderKey -, undo true, teleport true / tracking 0.05, pressJump 0, drop 0, reload 0, render 0.02, renderKey -, undo true, teleport true

[heygengenesis]

Verdict: APPROVE · 0 blocker · 0 important · 0 nits · b0bf28bd

Reviewed at b0bf28bd, which includes the follow-up commit that adds the disposed-read warning. 1e7cf53e alone failed the comment ratchet. That is green here.

Scope

• Both files read end-to-end. Every document read goes through the parsed getter, so all post-dispose reads and dispatches hit the empty document and warn once outside production. dispose() is idempotent.
• Studio paths that can touch a stale session (useGsapPropertyDebounce unmount flush, sdkEditTransaction candidates, useSdkSession swap): edits on an empty document decline or fail. The persist queue is already guarded by disposed, so nothing writes an emptied film to disk.
• CI is green on this head. session.dispose-release.test.ts ran in SDK: unit + contract + smoke (2 tests).