Upstream integration cycle: web chat rendering, navigation and diff safety

[rynfar]

Bound

• Upstream bound (frozen): b44c1ce5d25ee0d5a5be82e380618a886c19ea96
• Pylon head at open: 2725b650086814b55ca3a935175a71e59ac69fd7
• Review cursor unchanged: bbedad0278bbf753503184c00e0c09a0eab6679c

Cycle #650 closed with ~214 unclassified sources. Re-fetching added 24 more past the previous bound 93e04160a0. This cycle classifies 8; the rest stay unclassified for later bounded cycles. The cursor does not move.

Selected sources

Group A — chat feed and composer rendering (4)

SHA	Upstream
4749035bda13b4b6260499caedbc0d69a2f60e6f	#12166 keep composer banners compact and readable
592021f008010ee947c326df0452d093ead8aeb1	#12302 collapse thoughts within tool groups
fbc8b960026e408c163ea55db8075bbf1a42d628	#12270 keep thoughts and failed tool calls in one activity row
fcfd9f911a27ee3b813d64582c53d82dfa2e892b	#12317 keep chat from jumping when the scroll-to-end pill mounts

Touches ChatView.tsx, MessagesTimeline.tsx/.logic.ts, the composer banner components, and apps/mobile/src/lib/threadActivity.ts — fbc8b96002 is cross-client.

Group B — navigation, search and diff safety (4)

SHA	Upstream
886c83450797c46ee84ae28fc16c2208cafa965e	#10909 folder links from chat open the file tree instead of a broken preview
3fd5d6439d8fd49d173503ecda96500463a39bd2	#12315 keep numbered jumps from stealing browser tabs
9ea9c3d5d2c444133e3ddff40eecf38737951589	#11075 keep a file-to-symlink type change from crashing the diff view
c557bb10aa7cbb78a50df230d1e8e24af79cb662	#11761 sidebar search matches message content

Touches the files panel and projectFilesQueryState, rightPanelStore, keybindings on web and in packages/shared, the diff file tree and diffRendering, and Sidebar/CommandPaletteResults.

The two groups share no files and land as two independent PRs.

Review method

Every group gets adversarial review at the maintainer's request: an independent reviewer that did not write the code tries to break each port — wrong Pylon adaptation, lost Pylon-specific behavior, missing reverse transition, unhandled empty/error state, regression in a diverged file — before the parent's own review and CI. Implementation claims are not accepted as verification; the parent re-runs checks on the final head.

Boundaries to preserve

Pylon's diverged ChatView.tsx and timeline behavior, delivery holds and provider-bound drafts, Pylon routing and panel-choice semantics, environment-scoped caches, Pylon keybinding identity and its packages/shared contract, and Pylon branding. 3fd5d6439d also touches pnpm-lock.yaml upstream — the lockfile must be regenerated from Pylon's own inputs with the pinned tool, never copied.

Verification plan

Focused web tests for each changed area, @t3tools/web and @t3tools/shared typechecks, t3 where the mobile/shared logic is touched, scoped lint, and green CI on each final PR head. These are user-visible UI changes, so integrated client evidence is wanted for the final behavior; browser use is pending the maintainer's authorization for this cycle and is recorded as outstanding until then.

Not in scope

The ~230 remaining unclassified sources, including the Effect rc.115 / Alchemy beta.78 upgrade and its .repos/effect-smol reference sync (deserves its own cycle), the npm_and_yarn dependency bumps, the mobile header/platform-split refactor series, OTLP telemetry export, and all new feature work. Release and installation are not authorized.

[rynfar]

Group A disposition — two adopted, two parked

PR #668 carries 4749035bda… (#12166) and fcfd9f911a… (#12317), both adopted. 284 focused tests, @t3tools/web typecheck exit 0, scoped lint 0 errors.

592021f008… (#12302) and fbc8b960026… (#12270) are deferred as DEF-18, recorded in the ledger on that PR.

Neither refines anything Pylon has. Verified, not assumed: Pylon's MessagesTimeline.tsx has no ActivityGroupTimelineRow and no ReasoningTraceBlock; MessagesTimeline.logic.ts has no isActivityEntry or reasoningMessages; expandedReasoningMessageIds and onToggleReasoning appear nowhere in apps/web/src; and packages/contracts/src/orchestration.ts contains no reasoning fields. Pylon's ThinkingTimelineRow is a transient indicator, not persisted provider reasoning text.

Porting them first requires the architecture they refine — 052c7ae53e… (#11784, 32 files / 1,923 insertions across contracts, client-runtime, settings and web) plus 22539f2a42… (#12147, web + mobile). That is a new full-stack capability for Pylon, not a catch-up adaptation.

Maintainer decision 2026-09-19: parked behind the orchestration upgrade. Orchestration v2 is unmerged upstream on t3code-upstream/t3code/codex-turn-mapping — 442 commits off main, last touched 2026-09-12 — and Pylon is already built to swap to it (subagentRuntime.ts calls itself legacy-bridge code copying the v2 stack's field names from upstream #4779; deriveAgentPanelModel takes a v2Projection that is null "until orchestration-v2 lands"). Since v2 will rewrite orchestration contracts, adopting main-line reasoning fields now risks rework. Confirmed there is no orchestration v3 upstream: no such reference in the repo, no matching commit subject across 1,122 upstream branches, and every orchestration/v-generation branch is v1 or v2.

DEF-18's trigger is dependency-driven, not dated: Pylon resolves the v2 adoption question, that line merges to upstream main, or Pylon adopts the activity-group timeline independently.

Group B (navigation, search and diff safety — 4 sources) is unaffected and still to do.

[rynfar]

Completed in:

• PR fix(web): keep composer banners readable and stop scroll jumps when the pill mounts #668: Group A (composer banner density and scroll-to-end clearance; #12302 and #12270 deferred as DEF-18 parked behind orchestration upgrade)
• PR fix(web): fix folder links, sidebar search and diff symlink crashes #671: Group B (folder links, diff symlink safety, message content sidebar search, and numbered tab jump guard)

All changes merged into origin/pylon.