The composer seat is one node laid out against two different edges: in Chat it
is a sticky child of the column's scroller and rides its content box, which a
space-consuming scrollbar shortens, while a view declaring a composer overlay
gets an absolutely positioned seat against the padding box, which no bar
reduces. With the transcript scrolling the two tabs disagreed by the bar's
width, so the centred input card moved 4px sideways on every switch — and the
same 4px inside Chat when a growing transcript began to scroll.
The column now reserves its scrollbar gutter unconditionally and states the
overlay branch a scroll container on the same axes, so both states measure
against the same width.
Making `.sources` a scroll container turned its `padding-left` from spacing
into a correctness constraint. A scroll container clips inline-start overflow
with no way to scroll it back, and `::marker` is right-aligned to the content
edge, so past nine sources the markers rendered as `0.` and `1.` where `10.`
and `11.` belonged.
`searchMaxResults` is an unbounded positive integer, so size the padding in
`em` against the list's own font to hold a three-digit marker. The browser e2e
measures a `999. ` marker in that inherited font and requires the computed
padding to be at least that wide, pinning the room against the widest marker
rather than one fixture's source count.
The READMEs of ui-primitives and ui-conversation still documented the
removed maxSources prop, DEFAULT_WEB_MAX_SOURCES, CHAT_WEB_MAX_SOURCES,
and the head/tail collapse; the 2026-07-30 frontend note described the
same as current behavior. Restate all of them as the fixed-height scroll
container and cross-link the two notes both ways.
Bound the model-visible/card-visible correspondence: spill-policy's
tools/post-execute replaces an oversized result's content while leaving
presentationMeta whole, so the card's contract is the view it receives,
not the model's context.
Narrow the unit test's name and header comment to what jsdom establishes
(one <ol>, no expand control); jsdom does not resolve CSS Modules layout,
so the scroll geometry belongs to an assembled browser case.
Replace the WebBlock search card's head/tail collapse and expand button
with a fixed-height scroll container that lists every source the tool
returned. The model-facing side is unchanged: the seam still caps sources
at searchMaxResults and the truncated indicator stays, so model-visible
and frontend-visible sources remain identical.
Remove CHAT_WEB_MAX_SOURCES and DEFAULT_WEB_MAX_SOURCES: with scroll, the
chat row and details panel show the same full list.
