Fan ONE prompt across N branch/agent lanes: N worktrees, N Claude sessions on the
same prompt, watched side-by-side in the split-grid board, approve/kill per lane,
🏆 keep the winner (losers' worktrees removed). ~90% composition of shipped parts.
- src/http/session-groups.ts (new, pure, no git exec): deriveRepoRoot /
groupSessionsByRepo (cluster sessions by their <repo>-worktrees parent).
- GET /live-sessions/grouped (read-only; registered BEFORE /live-sessions/:id so
"grouped" isn't captured as an id). MAX_FANOUT_LANES env (default 6, = grid-6 cap).
- public/fanout.ts (new, pure): buildFanoutCmd shell-quotes the prompt (single-quote
wrap with '\''-escaping so $(...)/backticks/;/&& can't execute) + collapses newlines
+ caps 4000 chars; laneBranch/slugify. Effective N = min(lanes, maxFanoutLanes, 6),
≥2; the maxSessions cap is enforced server-side ("Started K of N" banner).
- public/tabs.ts launchFanout (N× createWorktree → openProject w/ prompt pre-injected
via the existing initialInput) + keepFanoutWinner; public/projects.ts renderFanoutForm
+ extracted shared createWorktreeReq (DRY). Byte-shuttle preserved (lane = own PTY).
One-click merge deferred (winner session stays open for a manual merge).
Reused unchanged: createWorktree/removeWorktree, addEntry/initialInput, split-grid +
per-quadrant approve/maximize/monitor + gauges. Verified: typecheck + build:web clean,
2063 pass at --test-timeout=30000 (only the known tmux/PTY flake red). Fixed 3
/config/ui exact-shape tests to include the new maxFanoutLanes field.
9683a16f4f