Copilot review on #14968 caught that the early returns gated on the
global `detailsMode === 'hidden'` short-circuited every render path
before sectionMode() got a chance to apply per-section overrides — so
`details_mode: hidden` + `sections.tools: expanded` was silently a no-op.
Three call sites had the same bug shape; all now key off the resolved
section modes:
- ToolTrail: replace the `detailsMode === 'hidden'` early return with
an `allHidden = every section resolved to hidden` check. When that's
true, fall back to the floating-alert backstop (errors/warnings) so
quiet-mode users aren't blind to ambient failures, and update the
comment block to match the actual condition.
- messageLine.tsx: drop the same `detailsMode === 'hidden'` pre-check
on `msg.kind === 'trail'`; only skip rendering the wrapper when every
section resolves to hidden (`SECTION_NAMES.some(...) !== 'hidden'`).
- useMainApp.ts: rebuild `showProgressArea` around `anyPanelVisible`
instead of branching on the global mode. This also fixes the
suppressed Copilot concern about an empty wrapper Box rendering above
the streaming area when ToolTrail returns null.
Regression test in details.test.ts pins the override-escapes-hidden
behaviour for tools/thinking/activity. 271/271 vitest, lints clean.
70925363b6