fix(web): Cite button opens below the selection, not under the pointer#29218

Problem

After a mouse selection in an assistant response, the Cite button opened with its top-left corner exactly where the pointer was released. A click a few pixels right and down, such as one meant to clear the selection, landed on the button and added a citation the user did not ask for. On main @ 47f2c8d29e, double-clicking "keepers" opened the button at the release point. A click 5px right and 5px down inserted a keepers citation into the composer. Drags, triple-clicks and a 390px-wide viewport behaved the same way.

Change

AssistantSelectionToolbar no longer passes the release point to resolveSelectionActionPosition. Mouse selections now use the anchor keyboard selections and off-text releases already used: the right edge of the selection's last line, 4px below it. The existing window clamp still applies. After a double-click, the button now sits at the end of the word, not in the middle. The terminal's selection actions are unchanged.

Scope and approval

Fixes pingdotgg/t3code#29209

Triaged via the automated issue flow; GitCafe issue #29209.

Verification

• AssistantSelectionToolbar.browser.test.tsx › "does not cite when the user clicks just past where a double-click selection ended". The test double-clicks a word through Playwright, waits for Cite, then clicks 5px right and 5px down of the release point. It fails on main with expected [ 'keepers' ] to deeply equal [] and passes with the fix.
• vp run check:changed passes: format, lint, knip, typecheck, tests, React compiler.

Evidence

Real web app, each revision run from its own checkout with T3CODE_DEV_SEED=0. One real Codex reply was produced on each side from the same exact-text prompt, so both sides render identical text. Rendering: Playwright 1.60.0, headless Chromium 148, no device emulation, DPR 1, 100% font scaling, prefers-reduced-motion: reduce, fixed clock. Before = 47f2c8d29e, after = cee7ea2f4b. Diff0 marks every changed pixel in red. DiffT marks changes above 16/255. Red rings in the recordings are an injected click indicator; red dots in the stills mark the release point.

R1: double-click, then click +5,+5 (1280×800, light). Steps: 0.0 s ready; ≈1.4 s double-click released on "keepers"; ≈3.5 s Cite visible; ≈4.5 s single click at +5,+5; ≈6.3 s outcome. Before: Cite opens at (251,418), on the release point, and the click cites "keepers". After: Cite opens at (278,431), below the end of the word, and the click only clears the selection.

	Before (47f2c8d29e)	After (cee7ea2f4b)	Diff0	DiffT
Recording	R1 before (GIF)	R1 after (GIF)
Cite visible
After the click

R2: forward drag ending mid-line, then click +5,+5 (1280×800, light). Steps: 0.0 s ready; drag released ≈2.1 s (before) / ≈1.9 s (after); ≈3.3 s Cite visible; ≈4.2 s click at +5,+5; ≈6.0 s outcome. Before: Cite at (389,418), on the release point, and the click cites. After: Cite at (390,431), and no citation is added.

	Before (47f2c8d29e)	After (cee7ea2f4b)	Diff0	DiffT
Recording	R2 before (GIF)	R2 after (GIF)
Cite visible
After the click

R3: 390×844, dark. (a) Backward drag across two wrapped lines, released at (115,471): before opens at the release point; after opens at (300,506), below the last selected line. (b) Triple-click on paragraph 2, released at (320,471): before opens at the release point; after opens at (169,574), below the paragraph's last line.

	Before (47f2c8d29e)	After (cee7ea2f4b)	Diff0	DiffT
R3a backward drag
R3b triple-click

R4: right-edge clamp (390×844, dark). Double-click "oil", the last word of a line near the column's right edge. The preferred x=368 would overflow, so the existing clamp places the 57px button at x=325, fully visible with an 8px window margin. Only the vertical position changes from before.

Before (47f2c8d29e)	After (cee7ea2f4b)	Diff0	DiffT

R5: over-limit selection, "Shorten selection" label (1280×800, light). A mouse selection of about 9,100 characters, past the citation limit. The selection was extended with native Range offsets while the mouse button was still down, then released with a real mouse-up. The disabled, wider 129×24 button is fully visible in both. After, it moves 4px right and about 13px down, to below the end of the selection.

	Before (47f2c8d29e)	After (cee7ea2f4b)	Diff0	DiffT
R5 Shorten selection

R6: horizontally clipped code block (390×844, dark). A token selected inside an overflowing code line whose selection ends at x=2208, far past the clip edge. The existing clamp keeps the button fully visible at x=325. After, it moves to below the selected code line.

	Before (47f2c8d29e)	After (cee7ea2f4b)	Diff0	DiffT
R6 clipped code

R7: drag ending on the last line above the composer (1280×800, light). Release at (973,647). Before, the button opens there. After, it opens at (974,660), below the last selected line. In both it straddles the composer's top border, fully visible and clickable. The timeline runs behind the composer, so this release does not reach the vertical clamp. A scroll-restored control pair, where the selection end is pushed past the bottom edge, is pixel-identical on both revisions: before, Diff0.

	Before (47f2c8d29e)	After (cee7ea2f4b)	Diff0	DiffT
R7 above composer

What else changed. In the selected-state pairs (R1–R7), only the Cite button's position changes (with its shadow and the glass background over the text). In the R1/R2 outcomes, the before side also shows the inserted chip, source highlight, comment popover, hidden placeholder and enabled Send button, all downstream of the accidental citation. No unrelated difference appears at zero threshold.

Not captured. These paths get the new anchor point and run it through the same clamp and render code as the rows above: side chats, a selection inside a streaming reply, a rejected citation, coarse-pointer hit areas, and a direct mouse release that hits the vertical clamp. Also not checked: Safari/WebKit and macOS selection geometry, Firefox, Electron, and right-to-left text.

The recordings were converted from Playwright WebM to GIF, because the attachment store accepts only images. Chromium's screencast sometimes yields a single half-composited frame during a repaint. Those frames (R1 before 2.93 s and 8.07 s, R1 after 3.20 s, R2 before 8.53–8.60 s, R2 after 3.27 s and 8.40 s) were replaced by the next stable frame. Seed text, capture drivers, diff and GIF-repair scripts: capture drivers (secret gist).

Claude Opus 5.5 (lead, red test, implementation, review B) and GPT-6.1 Sol (review A, proof audit, captures), in T3 Code.

🤖 Generated with Claude Code