Upstream batch E: inbox navigation, live thread caches, deferred chunks

[theRealBithive]

Batch E of the upstream back-merge, and the last of the five. Two upstream commits were in scope; one is picked, one is skipped.

What is different after deploying

Switching conversations no longer takes the page down to a spinner. The inbox route had loaderDeps naming the selection and every filter, so picking a row re-ran the loader and the whole outlet went to the pending state while it did. The loader now runs once, for the server render, and the list and the thread arrive on their own.

A thread warmed by hovering its row is no longer a snapshot. Before this, a live frame for any conversation other than the selected one was dropped. A row you hovered and opened a minute later showed what the server said at hover time — new messages, read receipts, reactions and deletions in between were simply not there, and nothing refetched because the cache was fresh. Every cached thread now follows the stream, whether or not it is the one on screen. Rows nobody has looked at still get no cache.

Three ticket frames now reach the browser at all. ticket_message, ticket_updated and ticket_read were being published and dropped — EventSource discards a named frame with no registered listener, silently. A ticket's inbox row and its cached thread went stale with no symptom.

A connection that comes up after a failed attempt now catches up. The reconnect refetch only fired for a second successful open. An initial connection that failed once and succeeded on the retry counted as a first connect, so the gap it left was never caught up.

The admin ships less on first load. The post modal, the workflow builder and the TipTap editor are code-split behind their own chunks, each with a skeleton holding its place. Four @fontsource/inter static weights are gone (the variable font already covers them), and avatars and content images are lazy.

Nothing changes for a visitor. No migration.

The two decisions

344bcaf62 (QuackbackIO#554, "update all dependencies to latest") is skipped. It is one commit holding 1,447 lockfile lines and two major bumps — the shape Renovate produces one pull request per package for, and Renovate is now actually configured to do that (v0.13.3-exkulpa.32). Taking it would move the whole tree at once with no per-package review and no way to revert one bump. Recorded in UPSTREAM.md with that reason.

f8062929a (QuackbackIO#553) is picked, with three conflicts resolved.

• content-html.ts — upstream dropped our aspect-ratio: auto keyword while adding the lazy-loading attributes. The two are independent, so this keeps both. Without auto, a pasted screenshot is pinned to the editor extension's 500×500 default for good.
• admin.tsx — upstream parallelises the workspace-role import with a billing lock-out helper and redirects an over-quota workspace to /admin/billing. Billing is excluded from this fork, and shouldLockAdminToBillingFn does not exist here. The hunk is dropped; a test now holds that no string in that route can name a billing destination.
• inbox.tsx — the loader rewrite against our own divergence.

The contract

E1–E11 were confirmed before any test was written. E12 and E13 were added during the work and confirmed the same way: the hover-prefetch debounce and the code-split boundaries are both new non-trivial logic that none of E1–E11 reached, and deriving a property for them from the code they were about would have proved nothing.

E1	Switching conversations never takes the surrounding page down to a spinner.
E2	A prefetched or previously-opened thread stays in step with the live stream.
E3	A prefetch nobody is waiting on is abandoned; a fetch the open pane waits on never is.
E4	A response already in flight never wins over the event that raced it.
E5	No cache is created for a conversation nobody has looked at.
E6	Every frame kind the inbox relies on is listened for.
E7	A clean first connection does not catch up; one that follows a failure does.
E8	A priority or SLA change reorders the queues that sort by them. Held one step weaker than it reads: agentEventChangesInboxList answers on the event's kind and never looks at which field moved, so the test pins "a conversation change reorders". The predicate is untouched by this pick.
E9	One normalizer, read by the page and the loader alike.
E10	A pasted screenshot keeps its proportions; an image below the fold is not fetched.
E11	The admin area never redirects to a billing page.
E12	A thread is warmed only when the pointer rests on its row.
E13	The heavy admin chunks are not in the first load, and a skeleton holds their place.

Nine suites, 97 tests. Two of them are properties rather than examples: the reconcile state machine as one law over the six situations a row can be in, and the stream's catch-up as two conservation laws plus one boundary.

Gates

• Diff coverage: 85 of 85 added lines executed. Nothing named, nothing excused.
• Mutation: 1 file, 28 mutants, 100.00%, 0 survived, 0 recorded as equivalent. The first run scored 82.14% with five survivors; all five were real holes and all five are now caught — the detail is in c76d2d58f.
• typecheck (both projects), lint, i18n: clean.

reconcileCachedThread is the one file added to the mutation manifest. The other thirteen the change touches are named by the gate and left ungraded on purpose: use-conversation-stream.ts and content-html.ts are large files whose behaviour these suites reach only in part, inbox.tsx is a route, and the components are mostly Tailwind strings — the same call batch C made. An entry asserts the listed suites pin the whole file, and none of these would.

What is left open

• The hover-prefetch delay (120 ms) and the launch-checklist poll (30 s) are tuning constants. The suites exercise them and say in their own words that the number is not the promise.
• packages/widget is untouched.

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