[BunsDev]

Summary

Extract the typed presentation seam for TUI v2 (#408): runtime events scoped to session generations, a reducer step that returns its external effects, an interactive-only renderer selector and an opt-in Next renderer over a shared projection. Classic stays the default and renders unchanged.

Context

• Related: [TUI v2][P0] T1: extract a typed presentation seam and support Classic/Next without runtime divergence #408 under epic [TUI v2] Epic: a unified Coven terminal for coding, tasks, research, and memory #406. The design baseline is docs: establish the TUI v2 source and compatibility baseline #421 (accepted, merge pending). That PR's file-ownership decision is that [TUI v2][P0] T1: extract a typed presentation seam and support Classic/Next without runtime divergence #408 lands App/CLI plumbing first; [TUI v2][P0] T2: build Brand-aligned terminal primitives, accessible themes, and safe customization #409 rebases onto this.
• Base: 4bbef53 (main).
• Scope: tui/src/application/, tui/src/next/, the App query-event reducer, and the interactive loop in cli/src/main.rs.
• Non-goals:
  • Next surfaces for overlays, permissions and tools ([TUI v2][P0] T3: deliver the responsive transcript/composer shell and unified command navigation #410/[TUI v2][P0] T4: ship first-class tools, diffs, and authoritative approval workflows #411).
  • Daemon capability negotiation ([TUI v2][P0] T5: unify session/familiar navigation, identity visibility, and reconnect recovery #412).
  • Brand primitives ([TUI v2][P0] T2: build Brand-aligned terminal primitives, accessible themes, and safe customization #409).
  • Changes to query-crate APIs, headless/stream-json/ACP behavior, session formats or settings.

Changes

• Session generations. Each interactive query worker now tags its events with the SessionGeneration it was spawned under. Clear, rewind (command and in-App) and resume advance the generation. Presentation discards stale events, so late output from a replaced conversation no longer mutates the new one. Bridge and relay consumers still see every event.
  • Before: one untagged channel served every turn, and events left behind at turn end were applied after /clear or /resume.
• Reducer split. App::apply_query_event is the reducer step. The completion bell is returned as PresentationEffect::RingBell, and the loop performs it in the same drain step. handle_query_event keeps its existing behavior for other callers.
• Bounded delivery. A queue of 1024 now sits between the per-turn forwarders and the loop. Forwarders wait for space and never drop events.
  • The query loop's own per-turn buffer stays unbounded, because run_query_loop takes an UnboundedSender. Bounding the producer needs a query-crate change and is documented as such.
• Selector. COVEN_CODE_UI=classic|next is read only on the interactive route. Unset or empty selects Classic.
  • Deviation from [TUI v2][P0] T1: extract a typed presentation seam and support Classic/Next without runtime divergence #408 wording: an unsupported value does not abort. It prints a warning on stderr and as a TUI notification, then starts Classic, following the accepted docs: establish the TUI v2 source and compatibility baseline #421 compatibility decision.
• Next renderer (preview): one transcript, a status row and a composer, drawn from TranscriptView.
  • Any frame where a surface owns input is drawn entirely by Classic, so no choice is ever invisible. That covers permission requests, every overlay/picker/dialog in any_modal_open, the familiar switcher, the effort picker and slash suggestions. An error modal is handled the same way.
  • Next clears Classic's mouse hit-test geometry. It does not implement scrollback (PageUp) yet.

Validation

Failing-first runs:

• Before implementation, 4 new tests failed for the intended reasons: 2 selector tests, the stale-delta test ("stale delta leaked into new conversation") and the bell-effect test.
• After independent review, restoring the old Next predicate makes next_hands_every_input_owning_surface_to_classic fail on the familiar switcher and next_draws_permission_requests_through_classic fail. Both pass with the fix.

Commands, run from src-rust/ on the final tree:

• git diff --check
• cargo fmt --all -- --check
• cargo check --workspace --locked
• cargo clippy --workspace --all-targets --locked -- -D warnings
• cargo test --workspace --locked: 2789 passed, 0 failed, 52 ignored (--no-fail-fast)
• Targeted suites:
  • cargo test -p claurst-tui --test presentation_parity: 7 passed. Covers deterministic replay, identical outgoing operations (submitted input, permission decision, draft) for both renderers under the same keys, delegation of every input-owning surface, permission through Classic, cleared mouse geometry, and newest-output visibility at 40x12, 80x24 and 1x4.
  • cargo test -p claurst-tui --lib -- application:: turn_completion_bell: 6 passed.
  • cargo test -p claurst --bin coven-code -- scoped_forwarder goal_dispatch: 14 passed. Covers ordered delivery of 200 events through a capacity-1 queue with a slow consumer, the forwarder stopping when the loop is gone, and, in every goal-dispatch test, the queue closing within 1 s of the turn finishing.
  • cargo test -p claurst --test engine_contract: 18 passed. New: --version, --print and stream-json produce identical stdout and exit codes, and no selector warning, with COVEN_CODE_UI set to next, classic or an unsupported value.
  • cargo test -p claurst --test acp_smoke: 6 passed, with an unsupported COVEN_CODE_UI set for every ACP run.
• scripts/tui-tests/run.sh with REQUIRE_TMUX=1 and a disposable HOME, Classic default, 120x40: 48 passed, 0 failed, 0 skipped. python3 -m unittest discover -s scripts/tui-tests -p 'test_*.py': OK.
• Manual tmux check, debug binary, COVEN_CODE_UI=next, 100x24:
  • The preview shell renders and the draft echoes.
  • F2 draws Classic's familiar switcher, and Esc returns to Next.
  • COVEN_CODE_UI=fancy shows the warning notification and starts Classic.
• Note: in one full-workspace run under load, goal_dispatch_payload_decision_injection_and_spawn_fences hit its fixture's 45 s timeout. In isolation it passes in 24.2 s on this branch versus 31.8 s on the base commit, so it is a pre-existing load-sensitive limit, not a regression.
• Note: one earlier full run hit the intermittent ACP child-exit timeout tracked in Diagnose ACP smoke startup timeouts and preserve failure diagnostics #379 (large_response_stream_does_not_block_child_exit); acp_smoke then passed 5/5 in isolation and in the final full run.
• Not run:
  • Windows: the engine contract is Unix-gated.
  • Release-build performance comparison of Classic vs Next ([TUI v2][P0] T10: establish terminal safety, accessibility, performance, and cross-platform acceptance gates #417).
  • Real-daemon journeys ([TUI v2][P0] T5: unify session/familiar navigation, identity visibility, and reconnect recovery #412).

PR Readiness

• Diff is limited to the intended files. No generated files changed.
• Independent review: no deadlock, lost events or Classic regression found. Its Important findings are fixed in this head:
  • Next hid input-capturing surfaces.
  • The queue-bound claim overstated what it delivers.
  • The parity test proved determinism only.
  • The invalid-selector behavior is now documented as a deviation.
  • Its Minor findings are fixed: rewind generation, stale mouse geometry, ACP coverage, completion-implies-delivery coverage, and module docs.
• Remaining risks:
  • Producer-side buffer bounding needs a query-crate change.
  • Next has no scrollback or mouse selection yet ([TUI v2][P0] T3: deliver the responsive transcript/composer shell and unified command navigation #410).
  • Default switch and rollout remain [TUI v2][P0] T10: establish terminal safety, accessibility, performance, and cross-platform acceptance gates #417/[TUI v2][P0] T11: qualify packaged compatibility, staged rollout, and tested rollback #418.

Refs #408

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Project	Deployment	Actions	Updated
docs	Ready	Preview	Oct 31, 2026 3:08am UTC