# Agent Note: Web composer stats detail and input-zone polish

Status: implemented

English | [中文](2026-07-30-web-composer-stats-and-input-polish.zh.md)

## Problem

The web composer footer showed a single joined stats string (cache/tokens/turns/steps) in its own stack row, visually detached from the input card and missing the design's duration and token-split details. The input zone itself had accumulated per-entry spacing hacks: dock strips carried their own margins, the sticky seat sat on a solid fill that clipped the transcript hard, the back-to-bottom control cleared the composer by a hardcoded offset that broke as the draft grew, and the goal and todo strips disagreed on surface color and column width.

## Decision

**The stats line renders inside the InputBar's width column through a new `footer` owner prop and expands to the design's grouped detail row; the composer stack owns one 6px rhythm; the seat fades the transcript through a fixed 36px token-bound gradient; the back-to-bottom control follows a live `--dsh-composer-height`; goal, todo, and queue share one 752px tip-fill column.**

- `'conversation.composer.dock'` entries reach the page as the `ComposerBarOwnerProps.footer` slot, rendered under the card inside the bar's `.root`, so the stats line and the card share one width constraint. `StatsLine` derives everything client-side from the snapshot: turns/steps, LLM wall time from assistant `timing` (`completedTime - stepStartTime`), tool wall time from tool-result `time - callTime` pairs, prompt/output token split with cache-read folded into input, and cache-hit percentage. Groups render pipe-separated and drop out whole when empty; `formatTokens` (517 / 12.2K / 1.2M) and `formatDuration` (45.2s / 2m42s) are exported for tests. Durations cover only in-window nodes — the README owns that limitation.
- `.composerStack` carries the Figma composition matrix's 6px gap. Goal and Todo remain standalone cards; the terminal Queue entry subtracts that gap plus the named 5px layout overlap so the later composer card paints over only the queue edge. The [composer context stack decision](../bug-fix/2026-07-30-composer-context-stack-order.md) owns the order and overlap contract.
- The sticky seat's background is a `linear-gradient` from `color-mix(bg-base 0%, transparent)` at 0px to solid `bg-base` at 36px — pixel stops, not the figma export's percentage, so a growing draft widens only the solid region; `color-mix` keeps both themes fading from their own base.
- A `useCallback` ref on the seat attaches a ResizeObserver that publishes `--dsh-composer-height` on the scroll body; ChatView's back-to-bottom slot computes `bottom` from it (152px first-paint fallback) instead of the prior hardcoded 168px.
- The textarea's 52px two-line floor applies to the hero variant only; the docked composer collapses to content height. Goal, Todo, and Queue panels use the 44px-gutter / 752px-cap column with `tip` fill and l1 border; the standalone Goal and collapsed Todo cards are 36px and 44px tall.

## Alternatives considered

**Percentage gradient stops (the figma export's 24%).** Rejected: the stop scales with seat height, so a tall draft stretches the fade band over most of the transcript; the fixed 36px band equals the design's 24% at the resting ~150px composer and stays constant as the composer grows.

**A generic "bottommost entry tucks" contract.** Rejected because Goal and Todo are independent cards even when either is the last visible dock entry. Queue owns the one intentional composer overlap, while the stack owns its shared gap and overlap values.

**Backend-supplied duration fields for the stats line.** Unnecessary: assistant `timing` and tool call/result pairs already reach the snapshot, so wall times fold client-side with no new session event or host projection.

**Keeping the stats line as a composer-stack sibling.** Rejected: as a stack row it carried its own width constraint that drifted from the card's; as the bar's `footer` both share one column and the stats participate in the seat's sticky/gradient region by construction.

## Consequences

The stats row reads turns/steps, LLM and tool durations, cache hit, and input/output tokens at a glance, at the cost that durations cover only the loaded event window (README Known Limitation). The stack's fixed order keeps standalone context cards independent and makes Queue the only panel joined to the composer; a future dock entry must choose its order relative to those roles. The fade band is a constant 36px, so any future design retune is one stop value. `chat-stats-bash-sample.spec.tsx` pins the derivation (timing/tool folds, token split), both formatters, the grouped render, and the zero-renders-during-streaming acceptance.
