[loganj]

🤖

Summary

• Fixes the channel timeline "jumping back" while you sit in a channel. The reader is pushed up into older history, and the Jump to latest button shows "35 new messages", then "67", then "78". When you scroll down there is nothing new.
• Cause: agents, search and previews read channel messages through your session (for example, a goose agent reading a thread root, or agent catch-up after a reconnect). Each read result was merged into the open channel's timeline, even a message from well before the loaded history. That old message showed at the top of the list with a gap below it. Each older history page then filled the gap in the middle of the list. The timeline only anchors the reader and ignores the count for rows added at the top, so a middle insert moved the view and was counted as new messages.
• Now a channel timeline shows only messages from its loaded history and newer. An older message from a read waits until history paging reaches it, and then it shows in its correct place.

Details

• The rule is in one place: the channel store builds the timeline rows from loaded pages, live traffic and read results. Message rows older than the oldest loaded page are left out while more history exists. Reactions, edits and deletions still apply to loaded rows, and messages newer than that limit (live or read) still show at once. With all history loaded, nothing is left out.
• This started with the agent features of the last few days, which read through the owner's session: agent read tools (refactor(agents): separate the agent runner and its reads from the desktop app #961), goose context reads (feat(goose): add the goose agent type #1125) and catch-up after a reconnect (feat(agents): catch chat watches up on messages missed while offline #957).
• Inbox previews: an out-of-range anchor is no longer put into the preview's timeline as a stray row. It opens in the thread reader as designed. fix(inbox): show each row's newest message #1212 (open) pages the preview back to the anchor instead, and this change does not conflict with it.
• New store test: a read before the channel opens and a read while it is open do not add an old row; a newer read still lands; the page that reaches the old row shows it in order. The test fails on main at the first assertion.
• Not changed: the timeline still detects "older rows added" from the first and last rows only. When the store keeps the list contiguous, that check is correct.

Also in this PR

One line in src/features/agents/launch-boundary.test.ts adds the missing effort field to the Goose fixture. Main fails typecheck without it since #1250 and #1185 landed together. #1257 and #1260 carry the same line, so the hunks merge cleanly in any order.