[AGE-4279] fix(frontend): open a chat at its latest message - #6664
[AGE-4279] fix(frontend): open a chat at its latest message#6664ardaerzin wants to merge 1 commit into
Conversation
The transcript pin measures at layout time, but a transcript keeps growing after that — a code fence finishes highlighting, an image loads, a tool card lays itself out. On a cold open (no cached messages for the session) every turn arrives in a single commit, so the pin lands on a fraction of the final height and a long chat opens at its first message instead of its latest one. Follow that growth with a ResizeObserver while the reader is at the bottom, and ignore a zero-height measurement, which is a pane hidden behind the config split rather than the reader moving. Measured on a 10-turn chat, cold open with cleared localStorage: 390x844 before: top=0 of max 6480 after: top=6375 (bottom) 1440x900 before: top=0 of max 3997 after: top=3892 (bottom) A reader parked mid-transcript is not moved. The EE transcript already does this through the SC-3 observer in useTranscriptScroll, so it needs no change.
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📝 SummarySummary by CodeRabbit
WalkthroughThe transcript auto-scroll hook now ignores hidden-pane measurements and observes transcript resizing. It restores the bottom position while the reader remains near the latest message. ChangesTranscript auto-scroll
Priority: ➖ Normal — Schedule the mobile chat auto-scroll fix because it keeps existing conversations opening at the latest message after content finishes loading. Estimated code review effort: 2 (Simple) | ~10 minutes Severity of issue fixed: Medium Merge Risk: 🔵 Low · up to Mobile chat reopening is improved for post-layout transcript growth, but a status line added after setup may still leave readers above the newest content. Addressing late-added status nodes would complete the latest-message behavior. 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
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🧪 Generate unit tests (beta)
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Actionable comments posted: 2
ℹ️ Review info
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web/mobile/src/features/chat/useTranscriptAutoScroll.ts
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| // The pin above measures at layout time, but a transcript keeps growing after that — a fence | ||
| // finishes highlighting, an image loads, a tool card lays itself out. Without this the opening | ||
| // pin lands on a fraction of the final height and a long chat reads as starting at the top. | ||
| // Follow the growth while the reader is at the bottom; the moment they scroll up this no-ops. |
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📐 Maintainability & Code Quality | 🟡 Minor | ⚡ Quick win
Keep the new comment to one short line.
The added comment spans Line 52 through Line 55 and violates the repository rule.
As per coding guidelines, comments must be at most one short line.
Source: Coding guidelines
| el.scrollTop = el.scrollHeight | ||
| }) | ||
| observer.observe(el) | ||
| for (const child of Array.from(el.children)) observer.observe(child) |
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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win
🔎 Supported by static analysis
🏁 Script executed:
#!/bin/bash
set -euo pipefail
rg -n -C 10 'useTranscriptAutoScroll|TurnStatusLine|return null|working=|waitingForInput=' web/mobile/srcRepository: Agenta-AI/agenta
Length of output: 50372
🏁 Script executed:
#!/bin/bash
set -euo pipefail
printf '%s\n' '--- useTranscriptAutoScroll.ts ---'
cat -n web/mobile/src/features/chat/useTranscriptAutoScroll.ts | sed -n '1,120p'
printf '%s\n' '--- ChatScreen.tsx ---'
cat -n web/mobile/src/features/chat/ChatScreen.tsx | sed -n '185,225p'
printf '%s\n' '--- LiveConversation.tsx ---'
cat -n web/mobile/src/features/chat/LiveConversation.tsx | sed -n '485,500p;630,648p'
printf '%s\n' '--- TurnStatusLine.tsx ---'
cat -n web/mobile/src/features/chat/TurnStatusLine.tsx | sed -n '1,50p'Repository: Agenta-AI/agenta
Length of output: 9310
🏁 Script executed:
#!/bin/bash
set -euo pipefail
printf '%s\n' '--- scroll container and ContentRail definitions ---'
rg -n -C 8 'function ScreenScaffold|const ScreenScaffold|export.*ScreenScaffold|function ContentRail|const ContentRail|export.*ContentRail|overflow-(auto|y)' web/mobile/src/features web/mobile/src/components web/mobile/src 2>/dev/null | head -n 240Repository: Agenta-AI/agenta
Length of output: 24518
🏁 Script executed:
#!/bin/bash
set -euo pipefail
cat -n web/mobile/src/features/chat/useTranscriptAutoScroll.ts | sed -n '1,120p'
cat -n web/mobile/src/features/chat/TurnStatusLine.tsx | sed -n '11,42p'
cat -n web/mobile/src/features/chat/ChatScreen.tsx | sed -n '203,225p'
cat -n web/mobile/src/features/chat/LiveConversation.tsx | sed -n '630,648p'Repository: Agenta-AI/agenta
Length of output: 6840
Observe late-added status nodes. TurnStatusLine can mount after content changes, but the hook observes only the initial children, so its growth can leave a near-bottom reader above the latest content. Observe child-list changes or keep a stable status node.
Railway Preview Environment
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1 participant
Closes #6623.
Opening an existing chat on
/mshowed the first message of the conversation, not the latest, so any long chat had to be scrolled from the top every time it was opened.Why it happened
useTranscriptAutoScrollpins the transcript in auseLayoutEffectkeyed on turn-array identity. That measures the height at layout time, but a transcript keeps growing afterwards: a code fence finishes highlighting, an image loads, a tool card lays itself out.web/mobilehad noResizeObserveranywhere, so nothing followed that growth — the pin stayed at what had been the bottom of a much shorter document, which on a long chat is the very top.It only reproduces on a cold open, where the session has no cached messages and every turn arrives in one commit. With a warm
localStoragecache the turns land in a later commit and re-fire the pin after layout, which hides it entirely. That is why it reads as "on mobile or desktop" in the report: a second device is a cold open by definition.The EE transcript is unaffected — its SC-3
ResizeObserverinuseTranscriptScrollalready re-pins on post-layout growth. This change makes/mdo the same thing.Before / after
Cold open (cleared
localStorage) of a 10-turn chat, sampled every 4s:top=0of max 6480top=6375= bottomtop=0of max 3997top=3892= bottomAt 390x844 the pre-fix transcript happened to correct itself after ~20s, when a background poll changed the turns array and re-fired the pin. At 1440x900 nothing rescued it — it stayed on the first message for the whole sample. Since
/mnow serves large viewports, that is the more reliable case, not a secondary one.Not regressed
A reader parked mid-transcript is not pulled to the bottom: the observer no-ops while
nearBottomRefis false. Verified at both viewports (parked at 900 and at 1500, held across samples). The zero-height guard keeps a pane hidden behind the config split from being read as the reader moving.Verified in a real browser against the local EE stack, not only in tests.