feat(tui): CC-parity task checklist HUD, and make the checklist actually appear

[ericleepi314]

What

The task checklist now renders and behaves like real Claude Code's — and, more
importantly, actually shows up. Two user reports drove this: the HUD didn't
match CC's layout, and "I don't see the todo checklist often" (with a guess at
auto-planning as the cause — it isn't; plan mode is at parity on both sides).

The HUD (ui-tui)

While busy, the list hangs off the busy line through the └ connector,
exactly the original's Spinner→MessageResponse→TaskListV2 mount:

✳ Mapping harbor adapter pattern + pi APIs… (3m 12s · ↓ 11.3k tokens)
  └  ◼ Map harbor adapter pattern + pi headless/extension APIs
     ◻ Write pi harbor agent adapter
     ◻ Build pi vision + Tavily websearch extension
     ◻ Validate on sample TB2.1 tasks
     ◻ Document the full-run command

• Busy verb = the in-progress todo's activeForm (already true; now the list
  below matches). ✔ green strikethrough-dim / ◼ orange bold / ◻ plain —
  figures.tick / squareSmallFilled / squareSmall, already exact.
• ctrl+t toggles the checklist (app:toggleTodos, defaultBindings.ts:43).
  The composer's key allowlist had to learn it — shouldPassThroughToGlobalHandler
  swallowed it otherwise. Hidden, the busy line falls back to CC's one-line
  Next: … (the original's expandedView='none' render); the two never
  show together.
• Footer gains esc to interrupt · ctrl+t to hide tasks (wording flips to
  show when hidden), only while busy with tasks — the original's
  getSpinnerHintParts.
• Idle keeps the standalone header render (N tasks (X done, …)), still
  click-collapsible.

Why the checklist rarely appeared (three causes, all fixed)

1. The system-prompt bullet was damped — a deliberate TB2.1 harness-tuning
   change (measured 0.21 vs 0.00 steps/trial of task-tool bookkeeping) whose
   rationale, "a task list you are the only reader of is overhead," is false
   interactively: the checklist is the pinned HUD the user watches. The bullet
   is now per-surface: interactive gets the reference's imperative wording
   verbatim (getUsingYourToolsSection); non-interactive keeps the damped
   wording byte-for-byte. The tool NAME now follows is_todo_v2_enabled too —
   headless sessions were being told about TaskCreate, a tool their toolkit
   doesn't carry (they expose TodoWrite).
2. CC's periodic reminder was never ported. getTaskReminderAttachments —
   the "task tools haven't been used recently" <system-reminder> injected
   every 10 assistant turns, throttled to one per 10 — now exists as
   src/context_system/task_reminder.py: exact turn-counting port
   (before-increment ordering, thinking-only messages skipped, independent
   counters), CC's reminder text verbatim, current task list attached.
   Injected beside the plan-mode attachments in agent_loop_compat, persisted
   via on_attachment so the throttle can find the previous reminder across
   turns.
3. The HUD archived at every turn end (archiveTodosAtTurnEnd), so the
   pinned panel vanished the moment a turn completed and the checklist
   survived only as a transcript block that scrolls away. CC keeps the list
   until it's done (REPL.tsx:4934 renders TaskListV2 idle). Incomplete
   lists now stay live across turns — startMessage/reset already left
   todos alone, so no other lifecycle change was needed. Finished lists
   archive exactly as before.

Deliberate deltas from the reference

• Headless gets no reminder and keeps the damped prompt bullet (the
  reference nudges both surfaces; headless had no reminder before either, so
  this preserves the status quo there rather than inventing an asymmetry).
  One headless byte DID change: the damped bullet now names TodoWrite
  instead of TaskCreate — fixing a prompt that named a tool headless
  sessions don't carry. This invalidates headless prompt prefix caches once;
  the TB2.1 step-efficiency measurement was taken with the old (wrong) name,
  and naming a nonexistent tool could only have hurt.
• The checklist defaults to visible, and ctrl+t is session-scoped. The
  reference ships collapsed (showExpandedTodos defaults false) and
  persists the toggle to global config. Hiding by default would recreate the
  exact complaint this change fixes. Persisting the toggle is deferred: the
  TUI has no settings channel for display prefs in either direction — review
  traced config.get {key:'full'} → get_settings, whose reply is a flat
  dict with no display block, meaning applyDisplay's entire
  config.display surface (bell_on_complete, tui_statusbar,
  tui_compact, …) is a pre-existing dead read that no backend populates.
  Reviving that surface is its own change (see follow-ups).
• The reference's Brief-tool gate on the reminder is not ported. In CC,
  Brief-in-toolkit marks the coworker surface where SendUserMessage owns
  communication. clawcodex registers Brief unconditionally, so the
  transplanted gate simply disabled the reminder everywhere — caught by the
  wiring test, which drives the real run_query_as_agent_loop and asserts
  the reminder reaches the provider.
• Idle render keeps the collapsible chevron header rather than CC's
  bare-nothing when toggled off — the click affordance to reopen is worth the
  delta.

Also fixed along the way

• Persisted attachments lost isMeta — Conversation.add_message
  dropped the flag, so a persisted reminder (or plan-mode attachment)
  counted as a real user turn in the stats odometer and became a /rewind
  boundary (/rewind 1 landed on the reminder, not the user's message).
  Pre-existing for plan mode; the reminder made it common. add_message now
  threads isMeta, both on_attachment call sites pass it, and rewind's
  is_prompt skips meta messages.
• Removed the now-producerless todoIncomplete transcript path (types, the
  TodoPanel.incomplete prop, the unreachable virtualHeights arm).

Follow-up (out of scope)

• Resume doesn't rehydrate the checklist HUD. The reminder re-lists tasks
  to the model, but the user sees nothing until the next TaskCreate/TaskUpdate.
  Restoring it needs the backend task store persisted across resume plus a
  control verb to fetch it — its own change.
• applyDisplay's config.display surface is dead end-to-end (found in
  review): get_settings returns a flat dict, src/config.py has no
  display section, so every display.* key the TUI reads
  (bell_on_complete, tui_statusbar, tui_compact, details_mode, …) is
  currently unreachable by users. Wiring a real settings channel would also
  unlock persisting the ctrl+t toggle.

Testing

• tests/test_task_reminder.py (16) — turn-counting port fidelity (including
  the before-increment ordering and thinking-skip), every gate, throttling
  both ways, the kill-switch envs.
• tests/test_task_reminder_wiring.py (2) — end-to-end through the real
  agent loop with a recording provider: the reminder reaches the model wrapped
  in <system-reminder> and persists via on_attachment; short conversations
  get nothing. This test caught the Brief-gate transplant bug.
• tests/test_system_prompt_full.py — per-surface bullet: damped+TodoWrite
  headless, imperative+TaskCreate interactive, damped+TaskCreate under
  CLAUDE_CODE_ENABLE_TASKS.
• ui-tui/src/__tests__/todoHud.test.tsx (10) — rendered-output assertions:
  connector + 5-column alignment, no header while attached, Next:-suppression,
  ctrl+t fallback, footer hint wording in all states.
• Two tests updated that pinned the replaced behavior (busyLine Next:-always,
  turnStore archive-incomplete); passthrough allowlist test extended.

Full suites: Python 9991 passed / 1 failed — test_sigint_during_prefetch_clean_exit,
a SIGINT-timing subprocess race that passes on retry, references nothing in
this diff, and predates it. ui-tui 1725 passed / 8 failed = the pre-existing
baseline (same 5 files, verified against a stashed clean tree), plus one
parallel-run flake (execFileNoThrow) that passes in isolation. Changed files
lint clean; the tree-wide 46 pre-existing lint errors are unchanged.

🤖 Generated with Claude Code

[github-actions]

Test Results

     2 files       2 suites   27m 40s ⏱️
10 004 tests  9 983 ✅ 13 💤 8 ❌
20 688 runs  20 633 ✅ 47 💤 8 ❌

For more details on these failures, see this check.

Results for commit 0b1fabc.