[johnnyelwailer]

Problem

With the 2026-09-17 upstream sync (#11784 'show provider thinking traces'), the web timeline can show two 'Thinking' surfaces at once on a live turn: the provider's native reasoning-trace row and the t3team working-row state word ('Thinking', GHE #208/#236). Owner: if native thinking already shows, the redundant 'thinking' should not show; 'working'/'writing'/etc state words are fine.

Fix

When an active activity group ends in a reasoning entry (i.e. the native trace owns the live 'Thinking' surface for the current unsettled turn), the working-row lead word resolves 'Thinking' -> 'Working'. Everything else (state-word mechanism, working/writing/waiting words, the live-activity row, the trace row) is untouched. Implemented by extending the existing row-activity context (new 'liveReasoningTrace' flag beside 'suppressLiveActivityRow') — no new parallel mechanism.

Tests

• New deterministic suite cases: exactly one 'Thinking' surface when the native trace streams (with activity state 'thinking' and with the no-state base-word fallback); 'Writing' state word unchanged while the trace is live.
• Full 'MessagesTimeline' suite: 72 passed; 4 pre-existing 'restores the composer' failures are identical with and without this change (the suite cannot even load on clean main — see below).
• 'tsc --noEmit' (apps/web): identical error set to clean main (single pre-existing error in 'openPullRequestLink.ts', out of scope).
• Additive guard: zero delta for t3team-prefixed files; both touched files are already whitelisted in '.t3team-additive-guard.json'.

Also mocks 't3team-threadComposingSignal' in the timeline test file (test-only): the 'composerDraftStore -> composing-signal -> primaryEnvironment -> catalog -> connection/runtime' import cycle makes the whole suite unloadable under vitest entry order on post-sync main — pre-existing, independent of this fix.

Model: Nexi (Nexplore AI), harness: t3team.