[raiseCatError]

Output bursts repaint and rewrap the transcript for every PTY chunk, making a 10,000-line command take ~29 seconds in the baseline workload. Coalesce only output-triggered paints within one display tick; keep parsing, terminal queries, passthrough and input/prompt/resize frames synchronous.

Pending mouse events resolve against the last displayed viewport; active selection drags retain synchronous output painting so release cannot copy an unseen redraw. The snapshot retains only visible rows. No shell bytes are discarded and no queue/input approval semantics change.

Measured on Apple M2 / 8 GiB / macOS 27 / Node 26.12, built CLI with disposable config/services:

• 1,000 Unicode lines: Native median 349.30 → 124.70 ms; None 348.06 → 126.38 ms (11 warm samples/provider).
• 10,000 lines: warm median 29,065.60 → 297.24 ms; sampled post-output frontend RSS 475.30 → 361.02 MiB (5 warm samples/variant). Every journaled line verified in order.
• Alternating startup control shows no material startup gain/regression; no supported idle CPU/RSS gain. Peak profiled RSS was essentially unchanged; one profiled event-loop p95 sample worsened. Full data and limitations: docs/performance/2026-10-25-runtime.md.

Independent static review approved after pointer/selection findings were fixed. Focused production-path regressions pass. Full canonical npm run verify passed with two workers, private short T7 fixtures and explicit xterm-256color/truecolor capabilities (NO_COLOR unset). No tests excluded or assertions changed. Four-worker completion-helper failure and an invalid-color cancelled attempt are documented in the evidence. Existing Arcade disposal TODO and intermittent macOS read issue are not claimed fixed.

Physical Ghostty/Zed QA: NOT RUN. Check large Unicode output while typing, selection/copy during live redraw, detached scrolling/resizing, Ctrl+C/Ctrl+Z, fullscreen entry/return, NO_COLOR and Reduced Motion. Keep the issue open pending real terminal validation.

Refs #505

Do not merge automatically.

Exact-head CI: 792fb1ad7e687cc0e2e4e93af58029e59409b146 passed macOS/Ubuntu shards, Quality and Node 22 compatibility; aggregate CI green. Fedora/timing jobs were skipped by workflow conditions. CI run. PR remains unmerged.

Environment clarification: t7run supplies NODE_COMPILE_CACHE=/Volumes/T7Tmp/ai-dev/caches/node-compile; the original before/after runs inherited it. No OS-cache purge or true cold-start claim. The one four-worker completion capture failure returned zero after ~2.45 s, consistent with a helper deadline under load; its root cause is not proven. Focused and full two-worker reruns passed unchanged.