orca/notes/terminal-performance-initiative.md

Terminal Performance Initiative

Working plan for the orca-performance branch. Goal: make Orca's terminal as performant as the architecture allows, with every claim backed by a number. Started 2026-07-02.

Why (user-reported, from the team meeting)

1. Typing in the terminal is sometimes laggy — occasionally seconds of delay.
2. Users say the terminal is slower than iTerm (unclear if typing or scrolling).
3. Scrolling in Claude Code / OpenCode is slow.
4. Idle memory is high (1–2 GB).
5. Battery usage is high.

Goals: legit performance complaints ≤ 1/week; sampled P90 typing/scrolling latency down significantly; lower memory with 0–1 agents.

Ground truth (verified against source, 2026-07-02)

Research corpus: xterm.js 6 / VS Code / Ghostty internals study (verified file:line claims) — see the archived digest and the "xterm.js vs Ghostty" deep-dive. The Orca-specific findings below were re-verified against this repo's code:

• Electron main sits on every terminal byte's path (daemon → main → renderer). VS Code ships the same xterm.js but bypasses main entirely: its ptyHost is a UtilityProcess with a direct MessagePort to each renderer.
• The PTY producer is never paused. acknowledgeDataEvent is a no-op in both LocalPtyProvider and DaemonPtyAdapter. Only main→renderer delivery is watermarked (512 KB, src/main/ipc/pty.ts:1374); main's own buffer can grow toward a 512 MB cap under flood. VS Code pauses the actual pty at 100k unacked chars (kernel backpressure blocks the shell).
• Renderer terminals share one thread with the entire React app; xterm.js parses in 12 ms slices at a documented 5–35 MB/s ceiling.
• Renderer scrollback default is 5,000 rows (src/shared/terminal-scrollback-policy.ts), 5× VS Code's default; 12 B/cell plus per-line JS objects; O(all lines) reflow on column resize.
• Latency physics: Ghostty ~4 ms median keypress latency, VS Code ~31 ms (same-library reference), native class 5–10 ms. Realistic target: beat VS Code, close on iTerm2, eliminate the stall/jank class entirely (P99 dominates perception).

Current state

Branch orca-performance (long-lived testing line, from main @ 8e8a08ac7):

1. tools/benchmarks/terminal-pipeline-bench.mjs — cross-terminal rig (see Benchmark protocol below).
2. Merge of PR #7153 = #7150 (freeze/memory: backlog caps, wedge guards, probe-certified replay release) + #7139 (cooperative drain: paced backlog draining keeps typing responsive under floods). Post-merge on this base: pnpm typecheck clean, 626 targeted tests green (scheduler, guards, pty/pty-connection/pty-transport suites). #7153 itself is a disposable testing PR; #7139 and #7150 land separately on main.

Workstreams

1. Baseline benchmarks (now; human-in-terminal required)

Run the rig in each terminal on the same machine — Orca pane, iTerm2, Ghostty, Terminal.app, VS Code (T3Code if available):

node tools/benchmarks/terminal-pipeline-bench.mjs --label <machine>-<date>
node tools/benchmarks/terminal-pipeline-bench.mjs report

These numbers answer "are we actually slower than iTerm, and where," and are the before/after for everything below.

2. Validate #7153 on orca-performance (this week, extended testing)

Watch for: typing responsiveness under agent floods, bounded memory, skip-notice + snapshot repaint on overflow, no permanent input loss. When validated, land #7139 and #7150 as separate PRs on main.

3. Revive term-speed-2 (the headline structural work)

History: nwparker's ~38-branch chain (+20k lines) implementing the terminal model/view contract — hidden view parking, hidden delivery gate, side-effect authority in main, model query authority, skip-grammar deletion — all kill-switched, documented in origin/nwparker/term-speed-2-architecture-docs:docs/reference/terminal-model-view-contract.md. It shipped only in v1.4.78-rc.1, a deliberate personal-testing build; it was never rejected and never reached main. Directly targets complaints 3–5 (hidden panes stop receiving bytes and unmount their xterm + WebGL atlases).

Merge scout (2026-07-02, chain tip into orca-performance): 144 files, 34 conflicted, 115 hunks. Hotspots: pty-connection.ts (31), pty.ts (16), daemon-pty-adapter.ts (6), orca-runtime.ts (5). pane-terminal-output-scheduler.ts does NOT conflict — #7139/#7150 and the chain touch different layers; runtime interaction (drain pacing × hidden gate) still needs deliberate testing.

Execution: dedicated focused session; resolve on revive/term-speed-2 off orca-performance; keep both sides' kill switches; validate with typecheck + the contract tests listed in the model-view-contract doc + #7153's suites; merge back to orca-performance for extended testing. Estimated ~1 day of careful resolution + validation.

4. Remaining stall-bug fixes (parallel, independently shippable)

The "seconds of delay" class = discrete thread-blocking events, not steady-state latency:

• PR #7105 (open): skip synchronous cold-restore replay for live daemon sessions in doSpawn.
• SerializeAddon.serialize() audit: ~1.2 s renderer block at 50k scrollback rows (#5096 follow-up, never done). Call sites include the mobile snapshot path (pty-connection.ts:2861) and sleep/hibernate serialization.
• #2836 frozen-terminal leads: replay-guard latch, codex-stale gate, uncapped buffers (repro harness exists).
• Checkpoint-RPC main-thread scrub (measured ~2–10 ms bursts per hot 5 s tick; small, part of the same program).

5. Producer-side PTY flow control

Ack-driven pause/resume of the actual PTY through the daemon protocol (node-pty supports it), watermarks per the xterm.js flow-control guide (≤500 KB). Converts flood-induced buffered lag into shell blocking — the correct physics. Sequence after #7139 lands (interacts with its drain pacing).

Design (2026-07-03, implement after the term-speed-2 revival merges — same files):

• Signal source: main already tracks per-pty pending + in-flight (pendingData, rendererInFlightCharsByPty in ipc/pty.ts). When a pty's pending exceeds HIGH (256 KB), main asks the producer to pause; below LOW (32 KB), resume.
• Producer side: two new protocol notifications (pausePty/resumePty, protocol vNext, version-gated like supportsIncrementalCheckpoints); daemon Session calls node-pty pause()/resume() — stops reading the pty fd, kernel buffer fills, the shell blocks on write: true kernel backpressure, identical physics to VS Code's 100k/5k design. LocalPtyProvider calls pause/resume directly.
• Safety invariants: (1) failsafe auto-resume after 5 s regardless of watermark, so a lost resume can never wedge a shell; (2) resume on detach/exit/kill/daemon-reconnect; (3) pause must not suppress the interactive-echo bypass — with the pipeline fixed (11.5 MB/s dev), the HIGH watermark is only reachable during genuine floods where echo is already queued; (4) PTY reads never stop for model/tail ingestion (term-speed-2 invariant #1) — pause gates the fd read, so daemon-side emulator state pauses with it, which is correct (state = what was read).
• Tests: watermark transition unit tests, lost-resume failsafe, kill/exit cleanup, plus an e2e pressure scenario asserting bounded main memory and a blocked producer (yes exits promptly on SIGINT while paused).

6. Extend the measurement rig

• True keypress→pixel latency: Typometer manual protocol (the DSR probe stops at the parser reply, before paint).
• Idle memory + battery: per-process RSS breakdown + powermetrics sampling at 0/1/5 agents (goal-3 metric).
• FPS under flood; event-loop-delay probes (monitorEventLoopDelay) in main/daemon/renderer behind a debug flag for pipeline attribution.

7. utilityProcess terminal router (structural endgame; gated on data)

An Electron UtilityProcess owns the daemon socket and hands each renderer a MessagePort — VS Code's topology while keeping Orca's detached daemon (warm reattach). Takes main off the terminal data path entirely; daemon-side history persistence falls out naturally. Prototype only after baselines show how much tail latency lives in the main hop.

8. Production P90 telemetry

Sampled keypress→echo latency + long-task/stall counts from real users; defines the success criterion and becomes the permanent regression gate. Design after the local rig stabilizes so the metrics match.

Benchmark protocol

tools/benchmarks/terminal-pipeline-bench.mjs measures, from inside any terminal:

• DSR idle latency — ESC[6n round trips (p50/p90/p99); replies come only after the parser reaches the query, so it proxies the input pipeline without keystroke injection.
• Fenced throughput — 4 deterministic fixtures (ascii-log, cjk-emoji, agent-tui — Claude-Code-shaped transcript + DEC-2026 status repaints — and labeled-pathological styles-stress), each run ended by a DSR fence so xterm.js-class ingest queues can't flatter the result.
• DSR under load — latency sampled during a paced 1 MB/s agent-TUI stream: "typing while the agent works," quantified.

Rules: same machine, AC power, comparable window size, no tmux/screen, hands off the keyboard during runs. Never compare numbers across machines.

Sequencing

now:        [1] baselines        [2] #7153 testing      (parallel)
next:       [3] term-speed-2 revival (dedicated session)
parallel:   [4] stall fixes, [6] rig extensions
after 2/3:  [5] flow control
gated:      [7] utility router   [8] telemetry

BMW-group crash work remains the team's priority gate above all of this (#7150's wedge guards overlap it); this plan runs measurement and revival prep in parallel without displacing it.

Findings log

2026-07-02 — baseline + decomposition (results committed in tools/benchmarks/results/)

Same machine, unattended serial runs (Orca 1.4.91 prod, Terminal.app, Ghostty 1.3.1; iTerm2 not installed, VS Code pending):

metric	Orca prod	Terminal.app	Ghostty
DSR idle p50/p99 (ms)	0.69 / 22.7	0.35 / 0.68	0.19 / 0.72
DSR under 1 MB/s agent load p50/p99 (ms)	134 / 292	0.45 / 7.9	0.21 / 6.1
agent-tui fenced throughput	2.0 MB/s	37	78
ascii-log fenced throughput	13 MB/s	39	93

Decomposition of the 51× agent-tui gap — both pipeline ends are fast:

• Bare @xterm/headless (114×85, scrollback 5000): agent-tui 103 MB/s (terminal-headless-parse-bench.mjs). The xterm parser is not the problem.
• Daemon Session ingest (emulator + pending-output recording + fanout): agent-tui 103 MB/s (session-ingest-throughput.bench.test.ts, ORCA_TERMINAL_PERF_BENCH=1). The daemon is not the problem.

Conclusions: (1) idle latency is fine — the extra process hop costs ~0.5 ms, so the utilityProcess router is deprioritized by data; (2) the crisis is queueing between daemon egress and renderer parse completion — main per-chunk processing, the 512 KB delivery/ACK pacing (ACKs fire after renderer write callbacks, so renderer slowness throttles delivery multiplicatively), and renderer per-chunk layers above xterm; (3) the agent-TUI shape (DEC-2026 frames + erase/repaint) is 6.5× worse than plain text inside Orca while being equal-cost everywhere else — profile it in the renderer first (task #9).

2026-07-02 — dev-build check of #7139/#7150 (confounded; directional only)

Dev build of orca-performance (282-col window, 3MB fixtures, dev-mode overhead): DSR idle p50 0.64 ms (unchanged), DSR under load p50 161 ms — the cooperative-drain branch does not move the under-load class. In hindsight this is structural: DSR replies are ordered within the output stream, so the metric measures output-queue depth; #7139 paces draining to protect input-send responsiveness but cannot reorder the queue. Implications: (1) the 134 ms-class number is fixed only by shrinking the queue (producer flow control) or raising drain rate (the 51× throughput hunt); (2) #7153's own wins (freeze class, bounded memory, input-loss guards) must be validated with freeze scenarios and real typing, not DSR. Also learned: dev-mode runs are ~2× slower across the board and fences need --dsr-timeout-ms headroom.

2026-07-02 — 51× loss attributed: scheduler fixed-nap drip (task #9)

The renderer output scheduler (pane-terminal-output-scheduler.ts) drained at most 2×16KB per tick, then slept 4ms (high-priority) / 16ms (background) regardless of parse speed. Isolation bench (fake timers, instant-parse terminal — pane-terminal-output-scheduler-throughput.bench.test.ts, ORCA_TERMINAL_PERF_BENCH=1): background cadence = 1.9 MB/s — matching prod's measured 2.0 MB/s agent-tui ceiling; foreground = 27 MB/s (only when arrivals re-poke 0ms drains; Chromium's ~4ms timer clamp makes the sustained real-world HP ceiling ~8 MB/s). Classification: pty-connection's isLatencySensitiveForegroundOutput routes sizable no-recent-input chunks to the queue, so floods always ride the drip.

Fix (committed 9e8bb2243): high-priority drains are now parse-clocked — a pacer re-arms a 0ms drain when xterm's write callback confirms the batch parsed — and carry 8 writes/tick (128KB ≈ 1.3ms parse). Isolation ceiling: 27 → 117.6 MB/s (parse-limited). Background cadence deliberately unchanged (protects the focused pane; hidden panes are term-speed-2's job). DRAIN_TIME_BUDGET_MS still bounds tick work (cooperative-drain intent of #7139 preserved; its budget-yield test still passes). 621 tests green.

Open follow-ups from this attribution: (a) end-to-end dev verification (in progress); (b) whether main's background:true delivery marking demotes visible-pane floods to the background drip — check window.__terminalOutputSchedulerDebug counters in a dev run; (c) ascii-log gap (13 vs 83 MB/s headless) — likely per-chunk beforeWrite side-effect scanning; profile after (a).

2026-07-03 — THE WHALE: main's retained-tail redraw path is O(tail) per chunk

Parse-clock fix didn't move end-to-end (agent-tui still 0.7 MB/s dev). Layered probes (renderer scheduler counters → main whole-method timer → per-section timers → targeted micro-benches) attributed it fully:

• Renderer receives only ~350–770 KB/s — it is starved, not slow.
• OrcaRuntime.onPtyData consumes ~93% of main's event loop during the flood (~950 ms/s at ~450 chunks/s ≈ 2.1 ms/chunk).
• All wrapped sub-calls (OSC scanners, agent detect, watchers, headless track, leaves loop, mobile touch) together: ~3.5%. The remainder is the pty-record tail block.
• Micro-bench (appendNormalizedToTailBuffer with a real agent-TUI frame containing ESC[10A ESC[0J): 0.888 ms/chunk at a 2,000-line tail — 32× the plain-append path. Cause: appendNormalizedToMultilineTailBuffer materializes ~2,001 row objects per chunk (orca-runtime.ts:22324) and finalizeRetainedTerminalRows allocates them all again plus runs a trailing-whitespace regex per row (:22458) — ~4k allocations + 2k regexes per tiny chunk, twice the tail length in O(n) passes. Every Claude-Code frame (cursor-up + erase-below) takes this path; plain logs don't — which is exactly the measured agent-tui vs ascii asymmetry.

Chain: TUI flood → O(tail) work per chunk in main → main event loop saturates → daemon socket backpressures → renderer starved at ~0.4 MB/s → deep queue → 134 ms DSR-under-load.

Fix (in progress): run the existing algorithm on a lazy suffix window (the cursor's maximum upward reach, computed from the chunk) with the untouched prefix shared by reference; differential fuzz test proves output equality against the original implementation. Worst case (pathological full-height cursor-up) falls back to today's cost.

2026-07-03 — windowed-tail fix: partial end-to-end win; next suspect queued

Dev-build bench after the windowed redraw-tail fix (label dev-tailfix, same protocol as dev-parseclock): agent-tui 0.7 → 1.0 MB/s (+43%), DSR-under- load p50 161 → 108 ms, p99 624 → 154 ms (4×). Real movement for the first time, but the pipeline is still far from the renderer's 27–117 MB/s capacity — another main-side consumer remains hot.

Next cycle (exact recipe): re-apply the whole-method main probe (onPtyDataMs sampler in pty.ts bindProviderListeners) on the fixed build. If onPtyData still dominates, the remaining O(tail)/per-chunk suspects in priority order: (1) buildTerminalWaitText ×2 per chunk (full tail join, 0.116 ms/chunk in prod-node isolation — likely 2-4× that in dev); (2) normalizeTerminalChunk (regex over every chunk, never measured); (3) the per-leaf duplicate tail path when tailStateMatches fails. If onPtyData no longer dominates, probe the main→renderer delivery batching next. The probe/bench cycle is mechanical: relaunch dev (ELECTRON_ENABLE_LOGGING=1 pnpm dev), orca-dev terminal create --command "<bench> --label X --size-mb 3 --dsr-timeout-ms 120000", grep the log.

2026-07-03 — post-fix attribution: blockedCheck is the remaining whale

Post-windowed-tail probe run (dev build, agent-tui): onPtyData still ~90% of main's event loop (~930 ms/s). Bucket split per second: blockedCheck ≈ 700–790 ms (~85%), waitText ≈ 70, append ≈ 25 (windowed fix confirmed), normalize ≈ 7, preview ≈ 0.

Mechanism (orca-runtime.ts:23128 nextTailHasNewerBlockedReason + its callers): per chunk, TWO full wait texts are built (buildTerminalWaitText joins the whole ≤256KB tail), then the check calls .toLowerCase() on both (another ~512KB of string allocation per chunk) and runs multi-pattern blocked/ready scans (findTerminalWaitBlockedSignal, findKnownReadyPromptIndex — lastIndexOf/regex passes over the full text) — all to timestamp waitBlockedAt for terminal wait.

Fix design (next session): blocked/ready prompts are end-anchored — an actionable prompt is at the END of output. (1) Run the check on a bounded suffix of the wait text (last ~64 lines / 16KB) instead of the full tail; (2) cheap pre-filter: skip entirely unless the appended chunk (plus a small carry for split keywords) can contain a blocked keyword; (3) build the two wait texts only when the check runs. Verification mirrors the windowed-tail pattern: keep the full-text check as reference + differential fuzz over randomized tails/prompts (split-across-chunks cases included — the appendCandidateSignal ordering semantics at :23146 must be preserved), plus the terminal-wait contract tests. Expected effect: removes ~85% of remaining onPtyData cost; combined with the two landed fixes should finally unlock the pipeline toward the renderer's measured 27–117 MB/s.

2026-07-03 — pipeline unlocked: three stacked fixes, 16× throughput, 9× latency

Dev-build bench with all three fixes (parse-clocked drains 9e8bb2243, windowed tail 4e08a28cd, throttled blocked-check 66f20258e), label dev-blockedfix, same protocol/config as prior dev rows:

metric	pre-fix dev	+tail fix	+blocked fix
agent-tui MB/s	0.7	1.0	11.5
DSR load p50/p99 (ms)	161 / 624	108 / 154	18.8 / 24.9
DSR idle p50/p99 (ms)	0.95 / 21	1.09 / 18	0.52 / 8.6
ascii-log MB/s	6.4	4.7	9.6

The agent-TUI-specific penalty is gone (agent-tui ≈ cjk ≈ ascii now). The throttled blocked-check delivered the predicted ~85% cut. Dev mode carries ~2× overhead vs prod, so the prod build should land near ~10ms DSR-under- load — from the 134ms baseline (~13×) — pending a packaged-build rerun. Remaining floor is structural cadence (8ms daemon batch + 4ms HP drain ticks + xterm 12ms slices), which flow control (#6) does not target; re-evaluate the "within 10× of Terminal.app" goal line after a prod measurement. Next: term-speed-2 revival (#4), then flow control (#6).

2026-07-03 — term-speed-2 revival: merged, green, NOT yet mergeable (perf gate)

revive/term-speed-2 pushed (merge a5052c35f, tip 64b6f7abe): 144 files, typecheck clean, ~2,776 targeted tests green, all three of our fixes verified present, chain features present and kill-switched (subagent's six review risks recorded in its report). Bench verdict on the revived build (dev): DSR-load p50 ~19ms holds, but throughput regressed ~35% unconditionally (agent-tui 11.5 → 7.2–7.4 MB/s; all-switches-OFF round proved the kill switches are NOT the cost) and idle p50 doubled.

Attribution so far: main exonerated (whole-method probe: onPtyData ~60ms/s ≈ 6%); renderer reconcile + HP-first selection O(1)-checked; daemon CONVICTED by unit bench — Session ingest 103 → 39.5/47.7 MB/s (2.2–2.6×) on the revive branch (session-ingest-throughput.bench.test.ts, ORCA_TERMINAL_PERF_BENCH=1). Cause: the chain's headless-emulator restructure (scanner classes / query-reply forwarding / view-attribute responder) added per-byte cost to the daemon hot path. Chunks reaching main are now ~5.8KB vs ~650B (daemon emits slower, batches bigger).

NEXT (fast inner loop — pure unit bench, no app restarts): on revive/term-speed-2, diff headless-emulator.ts/session.ts vs 7839fb9db, find the per-chunk scanner cost, restore our bounded-parser fast paths (the daemon emulator must never pay per-byte JS scanning for bytes that contain no ESC — same pre-filter pattern as the blocked-check keyword bypass), verify with the ingest bench back at ~100 MB/s, then full dev bench expecting blockedfix parity (~11.5 MB/s), THEN merge to orca-performance. A residual renderer-side share is possible once the daemon is fixed — re-attribute after.

Merge gate: revive branch merges only at ≥ blockedfix numbers.

RETRACTION (2026-07-03, later): the daemon conviction above was a confounded measurement — the 39–48 MB/s ingest runs executed while a dev app was still running. On a quiet machine the revive branch ingests at 82–109 MB/s (≈ pre-merge) and its HeadlessEmulator alone does 99.5 MB/s vs raw xterm 77.7. The daemon is innocent. Consequently the end-to-end revival delta (11.5 → 7.2/7.4 dev) is also UNTRUSTED — none of those runs were load-controlled, and unit benches show up to 2.6× machine-load variance. Scanner pre-filters landed anyway on revive (71c89da9b; strictly positive, 641 daemon tests green).

New measurement protocol (mandatory from here): quiet machine (no dev apps or benches concurrent), paired A/B runs back-to-back alternating branches, n≥2 per side, report spread not just p50. The merge-gate comparison (blockedfix vs revive) must be redone under this protocol before any verdict. Next: run the controlled A/B; if the delta disappears, merge revive into orca-performance and proceed to flow control (#6); if it persists, resume attribution renderer-side (probe pty-connection dataCallback additions per chunk).

2026-07-03 — A/B gate passed; term-speed-2 MERGED to orca-performance

Load-controlled alternating A/B (fresh app per run, n=2/side, agent-tui + DSR-load): perf 6.7/5.2 MB/s, dsr p50 19.9/21.3, p99 107.8/218.1; revive 6.1/3.6 MB/s, dsr p50 21.4/20.3, p99 63.4/26.1. Verdict: latency p50 tied, p99 better on revive, throughput within overlapping noise (revive2's 3.6 followed two runtime-busy create failures). The earlier "35% regression" is confirmed noise. Note: both branches ~5-7 MB/s today vs 11.5 yesterday — dev benches carry ~2x day-to-day machine variance; absolute dev numbers are only comparable within one A/B session.

Merged revive/term-speed-2 → orca-performance; typecheck clean, 288 post-merge spot tests green. orca-performance now = main-ish base + #7153

• three perf fixes + full term-speed-2 chain (kill-switched, default ON)
• scanner pre-filters. Extended user testing now covers everything. Remaining from the revival agent's risk list: gate×drain e2e specs (terminal-hidden-*, parked-memory, sleep-wake) still not run — queue them. Next: producer flow control (#6) per design §5; prod packaged-build bench for the real headline numbers.

2026-07-03 — flow control merged; goal-state accounting

Producer flow control merged to orca-performance (348aeb325): protocol v19 pausePty/resumePty, 256KB/32KB watermarks on main's pendingData, node-pty kernel backpressure, 5s daemon-side lost-resume failsafe + main-side pause re-assert, resume on every teardown path, version-gated (v≤18/SSH no-op), kill switch PRODUCER_FLOW_CONTROL_ENABLED (ipc/pty.ts:143), 29 new tests. Typecheck + 292 post-merge spot tests green.

Definition-of-done accounting:

• 51× loss: ATTRIBUTED AND FIXED (three fixes; agent-tui 0.7→11.5 MB/s and DSR-load p50 161→18.8 dev, results committed).
• term-speed-2: REVIVED AND MERGED (A/B gate passed).
• Flow control: IMPLEMENTED AND MERGED.
• "Within 10× of Terminal.app (4.5ms)": RE-SCOPED to pending a packaged RC measurement. Evidence: dev = 18.8ms with ~2× dev overhead → prod projection ~9-10ms ≈ 20× Terminal.app (vs 300× at baseline). The remaining gap is structural cadence (daemon 8ms batch, renderer drain ticks, xterm 12ms parse slices) — tunable follow-ups, distinct from the waste class this initiative eliminated. Prod verification path: electron-vite preview CANNOT host the bench (CLI-created panes are not adopted by the preview window's renderer → no ACKs → pending-cap drop; two attempts, documented) — measure on the next packaged RC cut from orca-performance using the committed rig + protocol instead.

Deferred, ordered: (1) sync orca-performance with main — conflicts incl. stream-opcode collision (chain Ack=12 vs main's #7205-era Metadata=12; renumber chain side, audit mobile/web stream consumers); (2) chain's e2e specs (hidden parking / parked memory / sleep-wake) — gate×drain risk; (3) cadence tuning toward the 10× line; (4) rig extensions + P90 telemetry (tasks #3/#8).

2026-07-03 — PROD VERDICT: v1.4.121-rc.0 benchmarked (the headline numbers)

Same rig, same protocol, same machine as the 1.4.91 baseline:

metric	1.4.91 baseline	v1.4.121-rc.0	change
DSR idle p50	0.69 ms	0.44 ms	= Terminal.app (0.45)
DSR under load p50	134 ms	18.6 ms	7.2x
DSR under load p99	292 ms	29.7 ms	9.8x
agent-tui	2.0 MB/s	11.2 MB/s	5.6x
styles-stress	7.8 MB/s	10.4 MB/s	1.3x
ascii-log	13 MB/s	11.0 MB/s	~0.85x
cjk-emoji	15 MB/s	12.2 MB/s	~0.81x

Reading: the anomalous TUI penalty is GONE — all four fixtures now sit at a uniform ~11-12 MB/s, which is the scheduler pacing ceiling, not parse CPU (prod ≈ dev for both latency and throughput; the pipeline is cadence-bound, so faster prod code changes nothing). That uniform cap also explains plain-text dipping slightly below baseline: ascii/cjk used to run unpaced ahead of the old scheduler; now everything flows through the same parse-clocked path. Goal line check: 18.6 ms = 41x Terminal.app under load (goal was 10x = 4.5 ms) — NOT met; down from 300x. Idle IS at parity. The remaining 4x is the named cadence stack (daemon 8 ms batch, scheduler drain ticks + 8x16KB per-tick budget, xterm 12 ms slices) — next lever, tunable, tracked as follow-up. p99 tail (the freeze class) is 29.7 ms — users cannot perceive it.

Caveat: measured on the user's live app (this session active in it); idle p99 118 ms reflects that activity, not the terminal path.

2026-07-03 — Same-engine reference: VS Code head-to-head (same machine, same rig)

metric	Orca v1.4.121-rc.0	VS Code	verdict
DSR idle p50	0.44 ms	7.00 ms	Orca 16x faster
DSR load p50	18.6 ms	7.18 ms	VS Code 2.6x faster
DSR load p99	29.7 ms	43.4 ms	Orca 1.5x better tail
ascii-log	11.0 MB/s	9.0	Orca +22%
cjk-emoji	12.2	11.3	tie
agent-tui	11.2	11.7	tie
styles-stress	10.4 MB/s	2.0	Orca 5.2x

Orca now beats or ties the best-known xterm.js terminal on 5 of 6 metrics — including 16x at idle (what users feel all day) and 5x on SGR-heavy output — and holds a better p99 tail under load. Throughput sits at the shared engine ceiling (~9-12 MB/s), confirming the class limit.

The one loss (load p50) has a clean mechanism: VS Code's producer flow control caps unacked output at ~100KB, so its standing queue is ~100KB / 11.7 MB/s ≈ 8.5 ms — matching its 7.18. Our standing queue (18.6 ms ≈ ~200KB at 11 MB/s) is set by the main→renderer ACK window (512KB/pty high water) + drain re-arm cadence (Chromium clamps nested setTimeout to ~4ms). Two levers, both cheap to test: (1) MessageChannel drain scheduling (sub-ms re-arm; also raises the throughput ceiling); (2) tighter effective in-flight window on the renderer delivery path. Target: VS Code's ~7ms class or below without giving back throughput.

2026-07-03 — Batch windows were the gap: dev DSR-load p50 19 -> 8.0ms

Lever results (dev, 3MB protocol, same session):

• MessageChannel drains (2434dfaae): 19.01ms — NO change. Proved the ~19ms was NOT queue depth: at 1MB/s vs ~11MB/s capacity (9% util) there is no standing queue. Kept (correct, removes a real clamp).
• Batch windows 8->2ms on BOTH hops (e67a91d7a: daemon STREAM_DATA_BATCH_INTERVAL_MS + main PTY_BATCH_INTERVAL_MS): p50 8.00 / p90 10.13 / p99 12.26ms (from 19.01/22.7/28.1). Throughput unchanged (agent-tui 9.8 vs 9.1, ambient noise). 239 batcher+pty tests green after timing updates.

Dev-mode 8.0ms already matches VS Code prod (7.18); prod build should land BELOW VS Code. p99: ours 12.3 vs VS Code 43.4. The remaining fixed-latency terms are renderer/xterm-internal (12ms parse slices). Note: main's interactive bypass (input-gated) means real keystroke echo skips batching entirely — the DSR metric understates real typing responsiveness; VS Code measured on the same freight path, comparison fair.

Next: cut RC, confirm in prod, re-baseline vs Terminal.app (expect ~8-15x from 300x at baseline; goal line 10x = 4.5ms now plausibly in reach).

2026-07-03 — Chain e2e debt PAID: all 6 hidden-pane specs green

terminal-hidden-view-parking (parks + restores rich TUI on reveal; bell/ title side effects live while parked), terminal-sleep-wake-restore (output restored + input accepted after wake), terminal-parked-memory (renderer memory released on park; views retained when kill-switched off): 6/6 passed, electron-headless, 1.1m. The gate x drain interplay — the revival's top flagged risk — now has e2e coverage on the exact branch the RC ships from. Remaining garble-hardening: differential hide/reveal fuzz harness (next build), reveal-time seq diagnostics.

Success criteria (baseline-relative; finalize after task 1)

• DSR-under-load p90 in Orca within striking distance of iTerm2 on the same box; zero DSR timeouts (today's freeze class).
• Fenced agent-tui throughput ≥ VS Code on the same box.
• Idle RSS with 0–1 agents materially down (target set after the memory harness lands; hidden-pane parking is the main lever).
• Zero >100 ms event-loop stalls in main/renderer during a 10 MB flood.
• Production P90 typing latency down and monitored continuously.