[lidge-jun]

Acknowledged optimistic messages remained in local state until a timer ran, while delayed send updates could reach a different thread. A send failure after acknowledgement could also revoke the blob preview still displayed by the server's message.

Upstream commit	Upstream PR	Decision	What GOAT got
71ba6b374c0b0181130c0cc3b3d5aaa3387ada67	#25710	Adapt	Immediate acknowledgement retirement, scoped late-update rejection, and explicit blob/handoff ownership.

GOAT adjustments

• Scope optimistic state, preview ownership, and dispatch reset with GOAT's environment/thread key, preserving draft promotion and isolating identical thread IDs on different servers.
• Retain GOAT's queued-message acknowledgement sources, existing image preload path, and composer behavior. Apply the scoped setter to all existing optimistic send entry points; remove the two obsolete preview-revocation helpers after checking consumers.
• Add eight regression cases beside the new state module for permanent retirement, navigation, late updates across environments, and preview ownership before/after acknowledgement. They were not executed locally under the task's explicit verification override.
• Web and desktop share this chat lifecycle. No mobile, provider, contract, layout, styling, or documentation behavior changes are required.

Rename residue

git show 71ba6b374c | rg '^\+.*\b[Tt]3' lists three added imports of @t3tools/contracts:

Upstream file	Disposition
chat/optimisticUserMessages.test.ts	Adapted as @goat/contracts; package-scope rule in scripts/lib/goat-rename/rules.ts.
chat/optimisticUserMessages.ts	Adapted as @goat/contracts; same rule.
chat/useAttachmentPreviewHandoff.ts	Adapted as @goat/contracts; same rule.

No T3 identifiers were kept and no upstream commit was left out.

Verification

• vp fmt apps/web/src/components/ChatView.logic.ts apps/web/src/components/ChatView.tsx apps/web/src/components/chat/optimisticUserMessages.ts apps/web/src/components/chat/optimisticUserMessages.test.ts apps/web/src/components/chat/useAttachmentPreviewHandoff.ts apps/web/src/components/chat/useComposerSend.ts — exit 0, six files.
• node scripts/goat-rename.ts --check — exit 0: 0 lines with T3 residue in 0 files, 0 dropped paths.
• git diff --check and git diff --cached --check — exit 0.

NOT RUN: vp test run apps/web/src/components/ChatView.logic.test.ts apps/web/src/components/chat/optimisticUserMessages.test.ts (including red/green regression proof), vp run check:changed, vp run typecheck, vitest, builds, server suites, and lockf-wrapped runs, per the task's explicit no-local-suites override. Browser captures, real-client verification, and native mobile verification are unavailable on this machine. goat-ci is the verification gate; this lane does not wait for CI, request reviews, watch, or merge.

Model: gpt-6.1-sol via GOAT delegated task (Codex harness)

[lidge-jun]

Landed as part of the combined chase PR #1982 (squash 5a9569e), at the user's request to merge the rest of cycle 261028 as one PR. Closing.