[teamleaderleo]

An open written-file artifact follows later successful rewrites of the same canonical file, including a tool completion that React coalesces out of its rendered snapshots. Choosing a historical version keeps it selected; failed or stale writes do not replace it.

Leo: "the /side thing i heard somebody really liked in codex... and i think html/html artifacts and that kinda good viewing and good support for it would be cool" / "like the claude.ai artifacts but imagien you didnt need to only have it on claude.ai...".

B2 extends B1's single RowUpdates producer with a per-open subscription and a changed-tool pending map. Publication flushes that map even without listeners, carries event order across producer replacement, and never retains a prior-snapshot chain. Closing the panel, switching chats or unmounting disposes the subscription. No timer, file read, project artifact storage, new scroll correction or scan of loaded rows per token is added.

This is the written-file part recovered from this PR's original combined implementation. The stack is A (sandboxed HTML), D (complete-write detection), B1 (streamed fences), then this B2. It preserves A's explicit Run/no-network/file boundary and D's canonical path identity. The #25208 activity/command/transcript metadata stamps remain independent of the artifact producer.

Observed / Not run

• The recovered combined source45aa passed23/23 focused tests in hosted40497592765, including the intentionally-red semantic write-order discriminator. These are prior-source evidence, not a new-head SHIP.
• Hosted40493008642 captured the real shared renderer in light/dark: before remains at Preparing release; after reaches Release ready. Existing media remains below.
• Integrated head 51ef5efb8cf0fecc23d7f10d2f5961876c5b0e45 (tree 99ca2e51f449d09a4925d7300860e3417be3f5de) is stacked on B1 feat(agent-chat): live reload streamed artifact fences #26230 head bd110c44d31b9a3a20c0b86b95611b1a555ae72d; own delta +420/-71 across nine files. Final-head focused behavioral red→green, current web checks and independent Astra xhigh review are pending.

Agent session: agent session

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[blacksmith-sh]

Found 84 test failures on Blacksmith runners:

Failures

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...and 74 more test failures. View all on Blacksmith

^{Need help on this PR? Tag @codesmith-bot with what you need.}

[cmux-bot]

cmux status _{(one comment, edited in place; each line is updated by the job that owns it)}

Unclear: web / react-apps-check failed: no known signature; failed step: Check webview test shards.

CI failed on b7f3400717 (run 40537300967 attempt 1): 1 code, 1 unknown.

Job	Verdict	Why
web / react-apps-check (1)	code	a web test failed
web / react-apps-check	unknown	no known signature; failed step: Check webview test shards

Failures:

• seen on other PRs agent-pane-background-tasks.test.ts the summary card lists the chat's background tasks: running ones first, the finished folded: failed (job)
• seen on other PRs agent-pane-hairline-focus.test.ts composer at 1x: focus is the resting hairline a step brighter, no ring: failed (job)
• seen on other PRs agent-pane-hairline-focus.test.ts newtab at 1x: focus is the resting hairline a step brighter, no ring: failed (job)
• seen on other PRs agent-pane-hairline-focus.test.ts composer at 2x: focus is the resting hairline a step brighter, no ring: failed (job)
• seen on other PRs agent-pane-hairline-focus.test.ts newtab at 2x: focus is the resting hairline a step brighter, no ring: failed (job)
• seen on other PRs agent-pane-hairline-focus.test.ts under Increase Contrast a focused edge keeps the resting edge, never a dimmer one: failed (job)
• seen on other PRs agent-pane-hairline-focus.test.ts keyboard focus changes what a solid Send, Stop, the prompt editor's Send and a plain button paint; s...: failed (job)
• seen on other PRs agent-pane-jump-latest-motion.test.ts chromium: a reply streaming in during Jump to latest's glide is followed to its latest row: failed (job)

Matched log lines

web / react-apps-check (1): (fail) the summary card lists the chat's background tasks: running ones first, the finished folded [2476.95ms]

Not re-run automatically: web / react-apps-check (1), web / react-apps-check are not machine failures.

Written by scripts/ci/classify_failures.py (ci-failure-attribution.yml); signatures are its SIGNATURES table. A machine verdict is the runner's fault, not this PR's; yours means the failing file is one this PR changes, also red on main that main's latest full suite fails the same way, seen on other PRs that it failed on another pull request's run lately.

CI fast guards failed on b7f3400717 (https://github.com/manaflow-ai/cmux/actions/runs/40537300967). It does not block the merge; a red guard merged into main breaks it for every open PR.
The log named no failed step; see the run.

Agents: python3 scripts/ci/guard_attribution.py fix applies the mechanical fixes locally.

[teamleaderleo]

For awareness: two P2s from #26159's review (now closed as superseded by this stack) still apply at b7f3400.

1. artifactWrittenLive.ts:72 resets this.order = -Infinity when the producer is replaced, so a replay after a reconnect can roll the preview backward. That contradicts the body's "carries event order across producer replacement".
2. OutputsSection.tsx builds its write map in transcript order, so the last row wins rather than the last completed write.

[teamleaderleo]

Review (codex gpt-6.1-sol high, sweep, via the review router; full diff from merge base aa82735 to this head): SHIP at b7f3400

No P1/P2 findings.

[teamleaderleo]

Review (subagent claude-opus-5-5 medium): BLOCK at b7f3400
Visual verdict: unchanged by this diff (no new images at this head; the artifact panel behaviour is covered by its gallery entries).

The B2 code is sound as written. I read the delta from the B1 head (bd110c4) to this head: ArtifactWrittenLive, the per-open RowUpdates subscription and pending map, the OrderedRows.set changed-item and removed-tool hints, the fresh OrderedRows on session reset, and the keyed frame remount. The problem is the branch, not that code. Its merge base is 5.8k commits behind feat-cmux-next, B1 (#26230) has since squash-landed, and git merge-tree against the current base conflicts in 24 files, including App.tsx, direct.ts, ArtifactPanel.tsx, artifactLive.ts, the Swift render frame and bun.lock. This head cannot land. Resolving those files by hand produces a substantially new tree, and none of this head's CI or reviews can vouch for it.

Follow-ups:

• [blocking] Rebase or merge onto current feat-cmux-next, dropping the already-landed A/D/B1 commits, then review the resolved head.
• [follow-up] artifactWrittenLive.ts read(): on producer replacement it still resets this.order = -Infinity before replay, the earlier P2. The replay picks the highest order in the new rows, so a reconnect whose rows end before the last write can still move the preview back.
• [follow-up] OutputsSection.tsx: the write map is built in transcript order, so the last row wins rather than the last completed write (earlier P2).

[teamleaderleo]

Owned by an agent session · session

[teamleaderleo]

Superseded by #33165: re-ported onto the current feat-cmux-next (#26230 landed; this branch conflicted in 24 files). It carries the written-file live reload and fixes both review P2s (no move back on producer replacement; Outputs picks the last completed write).