fix(web): closing Settings or Usage no longer jumps back to a quote's source#29013

Problem

After Go to source on a quote, the thread URL keeps #assistant-citation=…. Closing Settings or Usage, or pressing the sidebar Back button on Pull requests, then scrolls the thread back to the quote's source, even after the user has scrolled away. To reproduce: Go to source on a sent quote, scroll to the end of the thread, open Usage, and press Esc. The thread jumps back up to the source.

Change

The return location for Settings, Usage, and the sidebar utility pages is recorded in mainAppLocation.ts, and that record kept the full href, citation hash included. Returning navigated to it as a new history entry, and the thread treated the restored hash as a new Go to source. The tracker now records the href without a leading #assistant-citation= fragment, using withoutAssistantCitationHash from assistantCitationNavigation.ts, where the hash prefix already lives. The path, the search, and any other hash are kept. Go to source itself, shared citation links, and reloads are unchanged.

Scope and approval

Fixes pingdotgg/t3code#29002

Verification

• mainAppLocation.browser.test.tsx (new) goes to the thread through assistantCitationNavigation, then leaves through Usage (close) and Pull requests (sidebar Back). It fails on main because both return hrefs keep #assistant-citation=…. It also fails when only the Settings/Usage return is fixed and not the sidebar Back. It passes with this change. assistantCitationNavigation.test.ts still passes, and vp run check:changed passes.
• Runtime check in the web dev server (fresh database, Replay (dev) provider, Chromium 1280×800, a thread of about 20 turns with one quoted message). The values are the timeline scroller's scrollTop against its maximum:

• Not checked: before/after recordings are not attached. Desktop (Electron hash history) was not run; it uses the same tracker, and reading TanStack's hash history shows that location.href has the same path#hash shape there. Pressing Esc on Pull requests and the navigation.back shortcut use browser history rather than this saved location, and this change does not touch them.

Triaged, fixed and reviewed by Claude Opus 5.5 (Claude Code) with GPT-6.1 Sol (Codex) reviews, running the T3 Code issue flow.

🤖 Generated with Claude Code

Takeover

No code changes; evidence and verification added below. The "Not checked: before/after recordings are not attached" and "Desktop was not run" lines above are now covered: before/after recordings for every return path are below, and a real Electron run is included (P1).

Evidence

Before dd6c05ec31 (merge-base) · After 77041abe04 (head). Environment: real web app from each checkout, fresh database per side (T3CODE_DEV_SEED=0), the same synthetic Replay (dev) thread of about 20 turns with one sent quote, driven through the app's own controls. Playwright 1.60.0 / Chromium 148, Linux, 1280×800 (R4 390×844), dark, DPR 1, 100% scale, reduced motion, fixed clock. Diff0 = absolute RGB delta ×16; DiffT32 = channel delta > 32/255. Each step is narrated with its timestamp in the narrated index; the fixture matrix lists the rows.

Scroll values are the timeline scroller's scrollTop / max after returning, with the user scrolled back to the end after Go to source:

Recordings, before · after: R1 + R7 before · after; R2 before · after; R3 before · after.

Controls, head only (after 77041abe04):

What else changed between Before and After: the transcript position (source versus end) and with it the quote chips, timeline markers and the composer's translucent blur over different content; the diagnostic overlay text; synthetic message timestamps from separate seeds. Header, sidebar and utility panels outside the overlay have zero changed pixels at zero threshold. No other product change.

Scripts (uploaded, not committed): seed · driver · additional driver · rebuild wrapper · all scripts · pixel stats.