patterm/TODO.md

Perf Audit (auto-generated 2026-05-15)

Findings from a codebase sweep — not user-reported, needs review before action. Each item names the anchor and a sketched fix.

• Session.Children() allocates a fresh slice on every call. [MEDIUM]

  • internal/app/session.go:530-541 walks s.order under s.mu and builds a new []*Child slice every time. Callers on hot paths: drawSidebar calls it twice per frame (internal/app/sidebar.go:139 and :171); drawTabBar calls it once per frame (internal/app/tabbar.go:37); the classifier iterates it every 250 ms (internal/app/classifier.go:38); and palette/navigation hit it on every Ctrl-A/D/W/S keystroke.
  • Fix direction: store the snapshot in an atomic.Pointer[[]*Child] on Session, refresh it under s.mu only when Spawn / delete mutates the map. Readers get O(1) Load() with zero allocation — same pattern already used for listeners (session.go:118-123).

• wait_for_pattern re-scans the entire stream/grid every iteration. [MEDIUM]

  • internal/app/host.go:476-493 (the check closure). On scope = "scrollback" it calls c.StreamRead(0) followed by stripANSIBytes(nil, b) over the entire ring on every wake — a full O(ring size) walk per chunk arrival. On grid it goes through PlainText (one CGO call) plus a regex match against the full grid string. For an agent waiting on a marker in a chatty pane, every PTY chunk fires check().
  • Fix direction: for scrollback, track the offset of the last check and run the regex only over the new tail, reusing a per-call scratch buffer for ANSI stripping. For grid, dedupe on ScreenVersion() — skip when version hasn't changed.

• search_output compiles regex + strips ANSI on every call. [MEDIUM]

  • internal/app/host.go:428 compiles a fresh regexp.Regexp per invocation; :434 strips ANSI over the entire ring buffer when kind="rendered". Agents that poll search_output with the same pattern (the typical "watch for marker" loop) repay both costs on every call.
  • Fix direction: small LRU of compiled regexes keyed by pattern string (cap maybe 32) on toolHost. Cache the stripped-ANSI buffer keyed by c.ScreenVersion() so consecutive searches over an unchanged ring reuse the strip.

• GetProcessOutput grid mode acquires the emulator twice. [MEDIUM]

  • internal/app/host.go:375-391 does em := c.Emulator() for ActiveScreen / Cursor / Size, then at line 387 re-fetches em := c.Emulator() for PlainText. Each Emulator() call goes through ptyMu and inspects the live PTY pointer. Under a chatty agent polling get_process_output every 100 ms this is a redundant lock and pointer chase per call.
  • Fix direction: hold the emulator reference from the first lookup; reuse it for PlainText. The check if em == nil still runs cleanly because the variable is captured.

• FindChildByIdentity is O(N) under the session lock. [LOW]

  • internal/app/session.go:553-565 scans the children map looking for a matching Identity token on every new mcp-stdio connection. Not a steady-state hot path — only fires once per child spawn — but with many short-lived sub-agents it adds up and contends with everyone else taking s.mu.
  • Fix direction: maintain an identityIndex map[string]string (identity → child id) updated alongside spawn / exit, give the lookup an O(1) read.

• Per-promoter regex matches in the idle classifier. [LOW]

  • internal/app/idle.go:175-182 (matchAny) walks each compiled pattern and runs the DFA over the same 4 KiB tail. A preset with five permission patterns + five error patterns is ten DFA invocations per child per 250 ms tick.
  • Fix direction: at preset load time, compile each _patterns list into a single alternation regex ((?:p1)|(?:p2)|…). The classifier then makes one Match call per category per tick.

• Port-detection dedup is O(N²) over c.ports. [LOW]

  • internal/app/child.go:461-467: for each fresh URL match the code linearly scans the existing port list. The list rarely grows past a handful, but a dev server that lists "all open ports" in one log line interacts badly: M new matches × N existing entries.
  • Fix direction: keep a seenPorts map[int]struct{} next to c.ports, rebuilt on prune (none today). O(1) per match.

• Port-sighting string allocations happen before the dedup check. [LOW]

  • internal/app/child.go:455-456 allocates urlForm and portStr before line 461's seen walk. Both strings are wasted when the port is already in c.ports. Inside c.portsMu for the whole loop body too, blocking the Ports() reader path.
  • Fix direction: bind the port int first (cheap parse from m[1]), do the seen check, only then allocate the URL string for the surviving sighting.

• classifier time.Now() syscall per child per tick. [LOW]

  • internal/app/classifier.go:54 (and the IdleMS / TitleIdleMS helpers it transitively calls in internal/app/child.go:343-374) each call time.Now(). Reading time on Linux is fast (vDSO) but with N children × 4 time.Now() per tick × 4 ticks/sec it's wasted work that can be batched.
  • Fix direction: capture now := time.Now().UnixNano() once at the top of classifyAll and thread it into classifyOne and the helpers as a parameter.

• wait_for_pattern subscribes a listener for every call. [LOW]

  • internal/app/host.go:472-474: each invocation calls Session.Subscribe(wake) which clones the listener slice and swaps the atomic pointer; the defer Unsubscribe does the same on exit. Two allocations per wait_for_pattern. The agent pattern of looping on wait_for_pattern after every tool call pays this churn on the steady-state path.
  • Fix direction: a per-child chunkBroadcaster registered once at child spawn that hands out lightweight subscriber tokens, rather than going through the full session listener machinery.

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.