[ZacxDev]

What

Long agent replies are now clamped from the tail. The bubble shows its last ~15 lines, the fade is at the top, and Show more sits at the top of the bubble. Opening it reveals the earlier text above, and the end stays where it was on screen: the log's scroll follows the bubble's growth on every animation frame. Show less is also at the top. The user's own messages and kickoffs still clamp head-first, as before. Relayed plugin mail is still a relay row, not a bubble. Both directions now show about 15 lines (was 12).

The rules that already held still hold:

• a tap on the bubble only ever opens it;
• controls inside the bubble keep their own taps;
• an opened message stays open across a redraw, keyed by data-msg-id;
• the log sticks to the bottom when it is at its end;
• a streaming reply is never clamped.

How

• The server sets the direction from the role, never from the text. chatBubbleOf adds data-clamp-from="tail" for assistant (clampFrom). Every surface draws through it: the agent chat page, the chief panel, and the mirrored Claude Code and opencode views (opencode becomes the same events). The agent chat's live bubble() follows the same rule in JS.
• bubbleClampScript changes:
  • It pins a closed tail bubble's own box to its end, in the same task that clamps it, so the first paint already shows the end.
  • It puts the control before the bubble, marked data-clamp-toggle="tail".
  • It keeps the end in place while the bubble opens.
  • It re-pins the bubble when a code block (<details>) inside it is toggled.
• The CSS fade is mirrored (to top) for [data-clamp-from="tail"][data-clamp="closed"].
• The chief panel body now includes the clamp script, ahead of agentChatScript. Its frame, which every page loads, still does not.
• Chat logs are bottom-aligned (round 1, operator decision): a transcript shorter than its log sits at its bottom, next to the composer, on the mirrored view, the agent chat page and the chief panel. A zero-height ::before flex item takes the free space, so a full log is laid out exactly as before. Because of this, a reply in a short transcript also opens with its end in place.
• Trade-off of bottom alignment, worth a look: in a short transcript, a new message now pushes the earlier bubbles up, as a messaging app does. CLS counts this: 0.018 at 390px in bfcache-restore "the Rendered view restored at 390px does not shift". That case guards the restore, so its fixture now fills the log first (with a check that the log scrolls). The bar is unchanged.
• A code block in the middle of a closed reply opens below its summary, and the summary stays where it was. Only the last block re-pins the bubble to its end, and never past its own summary.
• Docs: docs/mirroring.md now describes the clamp.

Tests

• Go: TestAnAgentReplyIsClampedFromItsTailOnEverySurface checks the rendered HTML of the agent chat page, the chief panel body, and the mirrored Claude Code and opencode views. Replies are tail-first; user messages and kickoffs are not; relay rows are not bubbles. It also checks the live bubble(). TestTheChiefPanelBodyCarriesTheBubbleClamp replaces the old "no clamp" test. TestTheChatLogsGapMatchesTheBottomAlignRule pins the bottom-align rule's coupling to the logs' gap-3.

• e2e tail-clamp.spec.ts (new, leg 2) runs at 390×844 with touch and at 1280×800, both set in the spec. On the mirrored view, the agent chat page and the chief panel:

  • the reply shows its last line and not its first;
  • Show more is above the bubble;
  • after opening, the last line is at the same screen y (within 2px), and the first line is reachable by scrolling up;
  • Show less, at the top, closes it again;
  • a long user message still shows its first line.

  Other cases in the same spec:

  • a reply in the middle of the log, where stick-to-bottom cannot help;
  • a transcript shorter than the log: it sits at the bottom, and the reply's end stays within 2px when it opens (agent chat page), plus bottom alignment on the mirrored view;
  • a code block in the middle of a closed reply: its summary stays on screen and in place after opening;
  • stay-open across a #chat-log refresh;
  • a 40-reply tail-clamped transcript that opens at its end with CLS < 0.01.

• mirror-chat.spec.ts is updated for 15 lines, for the tail control that now sits next to a short user bubble, and for the code-block fixture (the block moved to the end of the reply).

Red/green

Round 1 (at f10623ee): the new short-transcript, bottom-alignment and mid-reply code-block e2e cases (6, both widths) are red at 431b4f8c and green at the head; so is TestTheChatLogsGapMatchesTheBottomAlignRule. TestTheClampScriptReadsTheServersDirection was removed: it only checked for strings.

Round 0:

At origin/main (2b469c0), with the new tests copied in:

• all 3 new or changed Go tests fail;
• all 14 new e2e cases fail;
• mirror-chat "a long bubble is clamped…" fails (15-line bound).

At the head, all of them pass. The related specs were also run locally and are green: mirror-chat, agent-chat-markdown, chief-fold-in, chief-thread-search and attention-delivery.

Mutations

Each mutant was applied at the head, the tests were run, and the file was restored (checked by sha256).

Mutant	Killed by
Direction attribute ignored (everything head-first)	e2e "the reply shows its LAST line" (all surfaces, both widths)
Scroll compensation removed	e2e "the last line stayed put" (8), "the last line is still on screen" (2)
Compensation replaced by stick-to-bottom only	e2e "the last line stayed put"; mid-log case: 405 → 1069 px
Button placed at the bottom (created and found there)	e2e "Show more" control-before-the-bubble assertion (data-clamp-toggle="tail" on the preceding sibling), on all surfaces
Re-measure re-pins a bubble the reader moved off its end (round 1)	e2e "the tapped summary is still on screen" (both widths)
Chief panel without the script	e2e chief panel case (both widths); Go TestTheChiefPanelBodyCarriesTheBubbleClamp

🤖 Generated with Claude Code

[ZacxDev]

Round 0 (requirements & deletion) — round 0 · requirements: 11 (unattributed: 1) · deletion candidates: 0 · verdict: proceed to the checklist.

none — examined: bubble_clamp.go (tail/pin/toggleOf/bubbleOf/animate anchorEnd/toggle re-pin), agents_detail.go (chatBubbleOf + clampFrom, live bubble(), relay-row branch), chief_panel.go (clamp script added, old no-clamp invariant removed per the operator's decision), input.css mask, all 3 chatBubbleOf callers, tail-clamp.spec.ts (7 cases x 2 viewports) vs mirror-chat.spec.ts stay-open (user bubble, distinct path), the 2 new Go tests. Every behaviour answers an operator decision or is a direct consequence of one; nothing to delete.

[ZacxDev]

Round 1 (nine axes) at 431b4f8: 0 🔴, 2 🟡, 2 🟢 — the ladder ends here. Three mutations re-run independently (clampFrom never tail; chief panel without the script; script after agentChatScript): all killed; a fourth (tail() returns false, string kept) survived the Go tests (finding 4). Operator decision on finding 1: bottom-align short chats. All four fixed in a final commit (not re-audited).

1. a short transcript moves the reply's end down on Show more (264px measured); a bottom-aligned log keeps it fixed (0px), so the documented limit is a choice — bubble_clamp.go:20-22
2. opening a code block in the middle of a closed reply re-scrolls the bubble to its end and hides the summary just tapped (548->120, above the bubble's top at 364) — bubble_clamp.go:263-269
3. the comment that Show less keeps a reply's top in place is false near the log's end (+124px at bottom, +300px when the scroll range shrinks) — bubble_clamp.go:33-34
4. TestTheClampScriptReadsTheServersDirection only checks a string; a tail() that returns false but keeps that string passes every Go test — bubble_clamp_tail_test.go:144