# Perf Audit (reviewed 2026-05-15) Findings that survived the 2026-05-15 review pass. Low and marginal items from the original sweep were removed; remaining items have enough measured or workflow evidence to justify action. Baseline benchmark numbers (`go test -bench=. ./internal/app/`, AMD Ryzen 7 7800X3D, libghostty-vt **ReleaseFast** after the Makefile fix landed): ``` # Renderer alone ViewportRenderer_PlainASCII 229 MB/s 1.3 KB/op 6 allocs/op ViewportRenderer_StyledLines 89 MB/s 91 KB/op 4325 allocs/op ViewportRenderer_RatatuiBurst 40 MB/s 365 KB/op 17306 allocs/op RendererThroughput_ReuseInstance 90 MB/s 316 KB/op 17380 allocs/op ContainsOSC_NoOSC 3050 MB/s 0 B/op 0 allocs/op # ASCII-video stream (renderer only — 3 sec at the target fps) ASCIIVideo_Stream_8Color_120fps 260 µs/frame 3845 fps_ceiling 3.1% budget ASCIIVideo_Stream_TrueColor_120fps 576 µs/frame 1735 fps_ceiling 6.9% budget # Full pipeline (em.Write + renderer + io.Discard write) Pipeline_ASCIIVideo_8Color_120fps 493 µs/frame 2030 fps_ceiling 5.9% budget Pipeline_ASCIIVideo_TrueColor_120fps 1075 µs/frame 931 fps_ceiling 12.9% budget # Emulator alone (libghostty-vt CSI/SGR parser) Emulator_Write_Stream_8Color_120fps 257 µs/frame 3890 fps_ceiling Emulator_Write_Stream_TrueColor_120fps 488 µs/frame 2051 fps_ceiling ``` The current pipeline still has large 120 fps headroom. The remaining renderer concern is multi-MiB styled replay latency and allocation churn, not normal steady-state frame budget. - [ ] **viewport renderer allocates heavily on SGR/CSI-heavy chunks.** [MEDIUM] - Review evidence: five benchmark reps confirmed `ViewportRenderer_StyledLines` at about 4,325 allocs per 16 KiB chunk (~91.5 KB/op, roughly 1 alloc per 3.8 input bytes), and `ViewportRenderer_RatatuiBurst` at about 17,306 allocs per chunk (~365 KB/op). A 5 MiB styled resume benchmark allocated about 31 MB across 1.38M objects. - Likely hot paths: generic CSI/SGR output in `internal/app/viewport_renderer.go` sends many sequences through `vr.shifter.Shift(vr.buf)`, while `internal/app/cursorshift.go` returns a fresh `[]byte` via `pending.String()` on every `Shift` call and parses CSI params through `string(raw)` / `strings.Split`. The mode-helper `string(params)` conversions are real, but probably not the main SGR-heavy cost. - Fix direction: make `cursorShifter` write into caller-owned scratch output or directly into the viewport renderer's pending builder; parse CSI params from byte slices; pre-grow/reuse renderer and shifter buffers. Re-run styled-lines, ratatui, and 5 MiB resume benchmarks; use pprof when available to confirm the top allocation sites. - [ ] **large styled resume/replay dumps spend visible time in viewport rendering.** [MEDIUM] - Review evidence: `BenchmarkSessionResume_5MiBStyled` measured about 58 ms median and 63 ms p95 over five reps. The plain 5 MiB benchmark was about 23-24 ms with only 21 allocs. The live path renders focused PTY chunks through `renderer.Render`, then still pays emulator writes, ring writes, event dispatch, stdout writes, and real terminal paint. - Scope: this is not a Codex steady-state throughput limit. A 100 KB/s stream is far below the styled renderer's ~80-90 MB/s ceiling. It matters for multi-MiB burst replay, resume/startup dumps, and dense full-screen churn. - Fix direction: do the allocation fix first, since it should also improve throughput. After that, invest further only if styled resume traces remain user-visible or the styled-lines benchmark is still under roughly 300 MB/s. - [ ] **wait_for_pattern re-scans the entire stream/grid while waiting.** [MEDIUM] - `internal/app/host.go:476-493` (the `check` closure). On `scope="scrollback"` it calls `c.StreamRead(0)` followed by `stripANSIBytes(nil, b)`, so each check can copy, strip, and search the full 1 MiB ring. On `scope="grid"` it calls `PlainText()` and runs the regex against the full grid string. - Caveat from review: the current chunk notifier coalesces bursts with a buffered channel and has a 500 ms fallback, so this is not necessarily one full scan per PTY chunk. It is still meaningful for active waits on chatty panes. - Fix direction: for `scrollback`, track the last checked stream offset and search only new output plus a bounded overlap/scratch buffer so matches spanning chunks are not missed. For `grid`, dedupe on `ScreenVersion()` and skip work when the version has not changed. - [ ] **search_output rebuilds and searches whole scrollback on every call.** [MEDIUM] - `internal/app/host.go:428-437` compiles a fresh regex, reads the stream from offset 0, strips ANSI for `kind="rendered"`, converts the full buffer to a string, and splits it into lines before applying `limit`. This is meaningful when agents poll the same pattern; it is low impact for ad hoc searches. - Fix direction: cache compiled regexes by pattern; cache stripped rendered output by child id and stream end offset; avoid `strings.Split` over the whole ring when only the first `limit` matches are needed. Prefer an incremental search shape if this becomes the standard "watch for marker" path. # On Hold - [ ] There's a unicode being displayed in opencode [ON HOLD] - Investigated 2026-05-14: patterm passes ghostty grapheme codepoints through unchanged (vt/ghostty.go:452-462), so the `` glyph is most likely the *host* terminal's font fallback for opencode's Nerd Font private-use codepoints, not a patterm substitution. Need a concrete reproduction (which codepoint, which host terminal/font) before changing rendering. - [ ] After codex rips for like 15 minutes, the terminal becomes quite slow. [ON HOLD / VERIFYING] - 2026-05-14: Perf plan P1-P11 landed (see CHANGELOG). Needs a real long-running codex session to confirm whether the steady-state slowdown is gone or some hotspot remains. Capture a pprof if it still feels slow after ≥15 minutes — the structural drivers the audit named are all addressed, so a remaining symptom is a new one and probably wants fresh profiling.