chore(tui): /clean recent perf work — KISS/DRY pass

24 files, -319 LoC. Behaviour preserved, 369/369 tests green.

- hermes-ink caches: shared lruEvict helper for the four parallel LRU
  caches (stringWidth, wrapText, sliceAnsi, lineWidth); touch-on-read
  stays inlined per cache; tightened output.ts skip-slice fast path.
- wheelAccel: trimmed provenance header, collapsed env parsing, ternary
  dispatch in computeWheelStep.
- perfPane: folded ensureLogDir into once-flag, spread-with-overrides
  for fastPath/phases instead of full rebuilds.
- env: extracted truthy() (used 4×).
- virtualHeights: collapsed user/diff/slash height bumps; trail+todos
  estimate.
- useInputHandlers: scrollIdleTimer cleanup on unmount, ?? undefined
  shorthand.
- useMainApp: dropped dead liveTailVisible IIFE and liveProgress
  indirection.
- appLayout, markdown, messageLine, entry: vertical rhythm, dropped
  narration comments, inlined one-shot vars.
- fix: empty catch blocks → /* best-effort */ for no-empty lint.

ui-tui/packages/hermes-ink/src/entry-exports.ts

@@ -1,12 +1,7 @@
 export { default as useStderr } from './hooks/use-stderr.js'
 export { default as useStdout } from './hooks/use-stdout.js'
 export { Ansi } from './ink/Ansi.js'
-export {
+export { evictInkCaches, type EvictLevel, type InkCacheSizes, inkCacheSizes } from './ink/cache-eviction.js'
-  evictInkCaches,
-  type EvictLevel,
-  type InkCacheSizes,
-  inkCacheSizes
-} from './ink/cache-eviction.js'
 export { AlternateScreen } from './ink/components/AlternateScreen.js'
 export { default as Box } from './ink/components/Box.js'
 export { default as Link } from './ink/components/Link.js'
@@ -26,13 +21,9 @@ export { useTabStatus } from './ink/hooks/use-tab-status.js'
 export { useTerminalFocus } from './ink/hooks/use-terminal-focus.js'
 export { useTerminalTitle } from './ink/hooks/use-terminal-title.js'
 export { useTerminalViewport } from './ink/hooks/use-terminal-viewport.js'
-export { isXtermJs } from './ink/terminal.js'
 export { default as measureElement } from './ink/measure-element.js'
-export {
+export { resetScrollFastPathStats, scrollFastPathStats, type ScrollFastPathStats } from './ink/render-node-to-output.js'
-  resetScrollFastPathStats,
-  scrollFastPathStats,
-  type ScrollFastPathStats
-} from './ink/render-node-to-output.js'
 export { createRoot, default as render, renderSync } from './ink/root.js'
 export { stringWidth } from './ink/stringWidth.js'
+export { isXtermJs } from './ink/terminal.js'
 export { default as TextInput, UncontrolledTextInput } from 'ink-text-input'

ui-tui/packages/hermes-ink/src/ink/cache-eviction.ts

@@ -9,12 +9,12 @@
 // (not session-keyed), so cross-session sharing is normally beneficial —
 // only evict when memory tightens or when the user explicitly resets.
 
+import { evictSliceCache, sliceCacheSize } from '../utils/sliceAnsi.js'
+
 import { evictLineWidthCache, lineWidthCacheSize } from './line-width-cache.js'
 import { evictWidthCache, widthCacheSize } from './stringWidth.js'
 import { evictWrapCache, wrapCacheSize } from './wrap-text.js'
 
-import { evictSliceCache, sliceCacheSize } from '../utils/sliceAnsi.js'
-
 export interface InkCacheSizes {
   lineWidth: number
   slice: number

ui-tui/packages/hermes-ink/src/ink/ink.tsx

@@ -979,15 +979,13 @@ export default class Ink {
     }
 
     const tWrite = performance.now()
+
     // Capture any stale pending write BEFORE starting this frame's write —
     // if the callback already fired, pendingWriteStart is null and lastDrainMs
     // already reflects the previous frame's drain.  If it hasn't fired, we
     // report "still pending" via a non-zero duration based on now-then so
     // backpressure shows up even if Node never flushes this session.
-    const staleDrain =
+    const staleDrain = this.pendingWriteStart !== null ? performance.now() - this.pendingWriteStart : this.lastDrainMs
-      this.pendingWriteStart !== null
-        ? performance.now() - this.pendingWriteStart
-        : this.lastDrainMs
 
     const prevFrameDrainMs = Math.round(staleDrain * 100) / 100
     this.lastDrainMs = 0
@@ -1016,6 +1014,7 @@ export default class Ink {
           }
         : undefined
     )
+
     const writeMs = performance.now() - tWrite
 
     // Update blit safety for the NEXT frame. The frame just rendered

ui-tui/packages/hermes-ink/src/ink/line-width-cache.ts

@@ -1,3 +1,4 @@
+import { lruEvict } from './lru.js'
 import { stringWidth } from './stringWidth.js'
 
 // During streaming, text grows but completed lines are immutable.
@@ -13,6 +14,7 @@ export function lineWidth(line: string): number {
   if (cached !== undefined) {
     cache.delete(line)
     cache.set(line, cached)
+
     return cached
   }
 
@@ -32,14 +34,5 @@ export function lineWidthCacheSize(): number {
 }
 
 export function evictLineWidthCache(keepRatio = 0): void {
-  if (keepRatio <= 0) {
+  lruEvict(cache, keepRatio)
-    cache.clear()
-    return
-  }
-
-  const target = Math.floor(cache.size * keepRatio)
-
-  while (cache.size > target) {
-    cache.delete(cache.keys().next().value!)
-  }
 }

ui-tui/packages/hermes-ink/src/ink/lru.ts

@@ -0,0 +1,14 @@
+// Shared eviction for the hot Ink LRU caches (widthCache, wrapCache,
+// sliceCache, lineWidthCache). Hot-path touch-on-read stays inlined per
+// cache — only the bulk eviction is factored here.
+export function lruEvict<K, V>(cache: Map<K, V>, keepRatio: number): void {
+  if (keepRatio <= 0) {
+    return cache.clear()
+  }
+
+  const target = Math.floor(cache.size * keepRatio)
+
+  while (cache.size > target) {
+    cache.delete(cache.keys().next().value!)
+  }
+}

ui-tui/packages/hermes-ink/src/ink/output.ts

@@ -467,15 +467,15 @@ export default class Output {
 
             if (clipHorizontally) {
               lines = lines.map(line => {
-                const startsBefore = x < clip.x1!
                 const width = stringWidth(line)
+                const startsBefore = x < clip.x1!
                 const endsAfter = x + width > clip.x2!
 
                 // Fast path: line fits entirely within the clip box — skip
-                // the tokenize/slice. This is the common case for transcript
+                // tokenize/slice. Common case for transcript text where
-                // text where containers are wider than the rendered content.
+                // containers are wider than rendered content. CPU profile
-                // CPU profile (Apr 2026) showed sliceAnsi at 18% total time;
+                // (Apr 2026): sliceAnsi at 18% total during scroll, mostly
-                // most calls were no-op slices like (line, 0, width).
+                // no-op (line, 0, width) slices.
                 if (!startsBefore && !endsAfter) {
                   return line
                 }

ui-tui/packages/hermes-ink/src/ink/render-node-to-output.ts

@@ -111,7 +111,6 @@ export function resetScrollFastPathStats(): void {
   scrollFastPathStats.lastPrevHeight = undefined
 }
 
-
 export function getScrollHint(): ScrollHint | null {
   return scrollHint
 }

ui-tui/packages/hermes-ink/src/ink/stringWidth.ts

@@ -4,6 +4,8 @@ import stripAnsi from 'strip-ansi'
 
 import { getGraphemeSegmenter } from '../utils/intl.js'
 
+import { lruEvict } from './lru.js'
+
 const EMOJI_REGEX = emojiRegex()
 
 /**
@@ -299,6 +301,7 @@ export const stringWidth: (str: string) => number = str => {
 
       if (code >= 127 || code === 0x1b) {
         asciiOnly = false
+
         break
       }
     }
@@ -334,14 +337,5 @@ export function widthCacheSize(): number {
 }
 
 export function evictWidthCache(keepRatio = 0): void {
-  if (keepRatio <= 0) {
+  lruEvict(widthCache, keepRatio)
-    widthCache.clear()
-    return
-  }
-
-  const target = Math.floor(widthCache.size * keepRatio)
-
-  while (widthCache.size > target) {
-    widthCache.delete(widthCache.keys().next().value!)
-  }
 }

ui-tui/packages/hermes-ink/src/ink/terminal.ts

@@ -289,9 +289,7 @@ export function writeDiffToTerminal(
   // The 2-arg form attaches a drain callback that fires once the chunk
   // is actually flushed to the OS socket/pipe — giving us end-to-end
   // drain timing, not just "queued in Node".
-  const wrote = onDrain
+  const wrote = onDrain ? terminal.stdout.write(buffer, () => onDrain()) : terminal.stdout.write(buffer)
-    ? terminal.stdout.write(buffer, () => onDrain())
-    : terminal.stdout.write(buffer)
 
   return { bytes: Buffer.byteLength(buffer, 'utf8'), backpressure: !wrote }
 }

ui-tui/packages/hermes-ink/src/ink/wrap-text.ts

@@ -1,5 +1,6 @@
 import sliceAnsi from '../utils/sliceAnsi.js'
 
+import { lruEvict } from './lru.js'
 import { stringWidth } from './stringWidth.js'
 import type { Styles } from './styles.js'
 import { wrapAnsi } from './wrapAnsi.js'
@@ -113,14 +114,5 @@ export function wrapCacheSize(): number {
 }
 
 export function evictWrapCache(keepRatio = 0): void {
-  if (keepRatio <= 0) {
+  lruEvict(wrapCache, keepRatio)
-    wrapCache.clear()
-    return
-  }
-
-  const target = Math.floor(wrapCache.size * keepRatio)
-
-  while (wrapCache.size > target) {
-    wrapCache.delete(wrapCache.keys().next().value!)
-  }
 }

ui-tui/packages/hermes-ink/src/utils/sliceAnsi.ts

@@ -1,5 +1,6 @@
 import { type AnsiCode, ansiCodesToString, reduceAnsiCodes, tokenize, undoAnsiCodes } from '@alcalzone/ansi-tokenize'
 
+import { lruEvict } from '../ink/lru.js'
 import { stringWidth } from '../ink/stringWidth.js'
 
 function isEndCode(code: AnsiCode): boolean {
@@ -19,7 +20,9 @@ const sliceCache = new Map<string, string>()
 const SLICE_CACHE_LIMIT = 4096
 
 export default function sliceAnsi(str: string, start: number, end?: number): string {
-  if (!str) return ''
+  if (!str) {
+    return ''
+  }
 
   // Hot-path: only cache when end is defined (the Output.get() use-case).
   if (end !== undefined) {
@@ -29,6 +32,7 @@ export default function sliceAnsi(str: string, start: number, end?: number): str
     if (cached !== undefined) {
       sliceCache.delete(key)
       sliceCache.set(key, cached)
+
       return cached
     }
 
@@ -39,6 +43,7 @@ export default function sliceAnsi(str: string, start: number, end?: number): str
     }
 
     sliceCache.set(key, result)
+
     return result
   }
 
@@ -50,16 +55,7 @@ export function sliceCacheSize(): number {
 }
 
 export function evictSliceCache(keepRatio = 0): void {
-  if (keepRatio <= 0) {
+  lruEvict(sliceCache, keepRatio)
-    sliceCache.clear()
-    return
-  }
-
-  const target = Math.floor(sliceCache.size * keepRatio)
-
-  while (sliceCache.size > target) {
-    sliceCache.delete(sliceCache.keys().next().value!)
-  }
 }
 
 function computeSlice(str: string, start: number, end?: number): string {

ui-tui/src/__tests__/virtualHeights.test.ts

@@ -5,10 +5,9 @@ import type { Msg } from '../types.js'
 
 describe('virtual height estimates', () => {
   it('uses stable content keys across resumed message objects', () => {
-    const a: Msg = { role: 'assistant', text: 'same text', tools: ['Search Files [long message]'] }
+    const msg: Msg = { role: 'assistant', text: 'same text', tools: ['Search Files [long message]'] }
-    const b: Msg = { role: 'assistant', text: 'same text', tools: ['Search Files [long message]'] }
 
-    expect(messageHeightKey(a)).toBe(messageHeightKey(b))
+    expect(messageHeightKey(msg)).toBe(messageHeightKey({ ...msg }))
   })
 
   it('accounts for wrapping and preserved blank-block rhythm', () => {

ui-tui/src/__tests__/wheelAccel.test.ts

@@ -12,38 +12,29 @@ describe('wheelAccel — native path', () => {
   it('same-direction fast events ramp mult (window-mode)', () => {
     const s = initWheelAccel(false, 1)
 
-    // First click establishes dir. Subsequent clicks inside the 40ms
-    // window ramp by +0.3 each (capped at 6).
     computeWheelStep(s, 1, 1000)
     computeWheelStep(s, 1, 1020)
     computeWheelStep(s, 1, 1040)
-    const fourth = computeWheelStep(s, 1, 1060)
 
-    // After 3 window events: mult starts at 1 → stays 1 on first ramp
+    // Key property: doesn't shrink below base.
-    // (first event just sets baseline), then +0.3 × 3 = 1.9 → floor=1.
+    expect(computeWheelStep(s, 1, 1060)).toBeGreaterThanOrEqual(1)
-    // The key property: doesn't shrink below base.
-    expect(fourth).toBeGreaterThanOrEqual(1)
   })
 
   it('gap beyond window resets mult to base', () => {
     const s = initWheelAccel(false, 1)
 
-    // Ramp up
     for (let t = 1000; t < 1100; t += 20) {
       computeWheelStep(s, 1, t)
     }
 
-    // Long pause, then click
+    expect(computeWheelStep(s, 1, 2000)).toBe(1)
-    const afterPause = computeWheelStep(s, 1, 2000)
-
-    expect(afterPause).toBe(1)
   })
 
   it('direction flip defers one event for bounce detection', () => {
     const s = initWheelAccel(false, 1)
 
     computeWheelStep(s, 1, 1000)
-    // Flip — should defer
+
     expect(computeWheelStep(s, -1, 1050)).toBe(0)
   })
 
@@ -51,9 +42,7 @@ describe('wheelAccel — native path', () => {
     const s = initWheelAccel(false, 1)
 
     computeWheelStep(s, 1, 1000)
-    // Flip (deferred)
     computeWheelStep(s, -1, 1050)
-    // Flip BACK within 200ms → bounce confirmed → wheelMode engaged
     computeWheelStep(s, 1, 1100)
 
     expect(s.wheelMode).toBe(true)
@@ -63,8 +52,7 @@ describe('wheelAccel — native path', () => {
     const s = initWheelAccel(false, 1)
 
     computeWheelStep(s, 1, 1000)
-    computeWheelStep(s, -1, 1050) // defer
+    computeWheelStep(s, -1, 1050)
-    // Flip-back arrives 300ms later → too late → real reversal
     computeWheelStep(s, 1, 1400)
 
     expect(s.wheelMode).toBe(false)
@@ -76,12 +64,9 @@ describe('wheelAccel — native path', () => {
     s.dir = 1
     s.time = 1000
 
-    // 5 bursts <5ms apart (trackpad flick)
+    for (let t = 1002; t <= 1010; t += 2) {
-    computeWheelStep(s, 1, 1002)
+      computeWheelStep(s, 1, t)
-    computeWheelStep(s, 1, 1004)
+    }
-    computeWheelStep(s, 1, 1006)
-    computeWheelStep(s, 1, 1008)
-    computeWheelStep(s, 1, 1010)
 
     expect(s.wheelMode).toBe(false)
   })
@@ -92,7 +77,7 @@ describe('wheelAccel — native path', () => {
     s.dir = 1
     s.time = 1000
 
-    computeWheelStep(s, 1, 3000) // 2 second gap
+    computeWheelStep(s, 1, 3000)
 
     expect(s.wheelMode).toBe(false)
   })
@@ -102,34 +87,23 @@ describe('wheelAccel — xterm.js path', () => {
   it('first click returns 2 after long idle', () => {
     const s = initWheelAccel(true, 1)
 
-    // First event — "sameDir && gap > WHEEL_DECAY_IDLE_MS" triggers
+    expect(computeWheelStep(s, 1, 1000)).toBeGreaterThanOrEqual(1)
-    // reset-to-2 branch since dir starts at 0 and 0 !== 1.
-    const n = computeWheelStep(s, 1, 1000)
-
-    expect(n).toBeGreaterThanOrEqual(1)
   })
 
   it('sub-5ms burst returns 1 (same-direction, same-batch)', () => {
     const s = initWheelAccel(true, 1)
 
     computeWheelStep(s, 1, 1000)
-    const burst = computeWheelStep(s, 1, 1002)
 
-    expect(burst).toBe(1)
+    expect(computeWheelStep(s, 1, 1002)).toBe(1)
   })
 
   it('slow steady scroll stays in precision range', () => {
     const s = initWheelAccel(true, 1)
 
-    // Simulated 30Hz sustained scroll: 33ms gap
-    const results: number[] = []
-
     for (let t = 1000; t < 2000; t += 33) {
-      results.push(computeWheelStep(s, 1, t))
+      const r = computeWheelStep(s, 1, t)
-    }
 
-    // Every event should produce 1-6 rows.  No runaway.
-    for (const r of results) {
       expect(r).toBeGreaterThanOrEqual(1)
       expect(r).toBeLessThanOrEqual(6)
     }
@@ -138,27 +112,22 @@ describe('wheelAccel — xterm.js path', () => {
   it('direction reversal resets mult', () => {
     const s = initWheelAccel(true, 1)
 
-    // Ramp up
     for (let t = 1000; t < 1100; t += 20) {
       computeWheelStep(s, 1, t)
     }
+
     const beforeFlip = s.mult
 
-    // Flip
     computeWheelStep(s, -1, 1200)
 
     expect(s.mult).toBeLessThanOrEqual(beforeFlip)
-    // Reset branch sets mult=2
     expect(s.mult).toBe(2)
   })
 
   it('frac stays in [0,1) across events', () => {
     const s = initWheelAccel(true, 1)
 
-    // frac must never go negative or reach 1.0 — that's the correctness
+    // Correctness invariant of fractional carry: never negative, never reaches 1.
-    // invariant of the fractional carry.  Whether a specific series of
-    // inputs produces a nonzero frac depends on tuning constants; just
-    // check the bound is maintained across a realistic scroll pattern.
     for (let t = 1000; t < 1200; t += 30) {
       computeWheelStep(s, 1, t)
 

ui-tui/src/app/turnStore.ts

@@ -50,6 +50,7 @@ export const archiveTodosAtTurnEnd = () => {
   }
 
   const done = isTodoDone(state.todos)
+
   const msg: Msg = {
     kind: 'trail',
     role: 'system',

ui-tui/src/app/useInputHandlers.ts

@@ -29,35 +29,19 @@ export function useInputHandlers(ctx: InputHandlerContext): InputHandlerResult {
   const overlay = useStore($overlayState)
   const isBlocked = useStore($isBlocked)
   const pagerPageSize = Math.max(5, (terminal.stdout?.rows ?? 24) - 6)
-  const scrollIdleTimer = useRef<ReturnType<typeof setTimeout> | null>(null)
+  const scrollIdleTimer = useRef<null | ReturnType<typeof setTimeout>>(null)
 
-  // Wheel acceleration state machine (ported from claude-code).  Adapts
+  // Wheel accel ported from claude-code: inter-event timing drives step size,
-  // step size per wheel event based on inter-event timing: fast flicks
+  // direction flips reset. wheelStep (WHEEL_SCROLL_STEP) is the base; final
-  // ramp up, slow clicks stay at 1 row, direction flips reset.  See
+  // rows = wheelStep × accelMult. State mutates in place across renders.
-  // lib/wheelAccel.ts for the full tuning rationale.  The accel state
-  // mutates in place and is kept across renders via a ref.  wheelStep
-  // (passed from useMainApp / the WHEEL_SCROLL_STEP constant) is used
-  // as the BASE — final rows = wheelStep × accelMult.
   const wheelAccelRef = useRef(initWheelAccelForHost())
 
-  useEffect(
+  useEffect(() => () => clearTimeout(scrollIdleTimer.current ?? undefined), [])
-    () => () => {
-      if (scrollIdleTimer.current) {
-        clearTimeout(scrollIdleTimer.current)
-        scrollIdleTimer.current = null
-      }
-    },
-    []
-  )
 
   const scrollTranscript = (delta: number) => {
     if (getUiState().busy) {
       turnController.boostStreamingForScroll()
-
+      clearTimeout(scrollIdleTimer.current ?? undefined)
-      if (scrollIdleTimer.current) {
-        clearTimeout(scrollIdleTimer.current)
-      }
-
       scrollIdleTimer.current = setTimeout(() => {
         scrollIdleTimer.current = null
         turnController.relaxStreaming()
@@ -300,16 +284,10 @@ export function useInputHandlers(ctx: InputHandlerContext): InputHandlerResult {
 
     if (key.wheelUp || key.wheelDown) {
       const dir: -1 | 1 = key.wheelUp ? -1 : 1
-      const accelRows = computeWheelStep(wheelAccelRef.current, dir, Date.now())
+      // 0 = direction-flip bounce deferred; skip the no-op scroll.
+      const rows = computeWheelStep(wheelAccelRef.current, dir, Date.now())
 
-      // computeWheelStep returns 0 when a direction flip is deferred for
+      return rows ? scrollTranscript(dir * rows * wheelStep) : undefined
-      // bounce detection — scrollBy(0) is a no-op; skip the call to avoid
-      // needless render scheduling.
-      if (accelRows === 0) {
-        return
-      }
-
-      return scrollTranscript(dir * accelRows * wheelStep)
     }
 
     if (key.shift && key.upArrow) {
@@ -321,14 +299,9 @@ export function useInputHandlers(ctx: InputHandlerContext): InputHandlerResult {
     }
 
     if (key.pageUp || key.pageDown) {
+      // Half-viewport keeps 50% continuity and stays under Ink's
+      // `delta < innerHeight` DECSTBM fast-path threshold.
       const viewport = terminal.scrollRef.current?.getViewportHeight() ?? Math.max(6, (terminal.stdout?.rows ?? 24) - 8)
-      // Half-viewport per keystroke.  A whole-viewport jump (our old
-      // `viewport - 2`) fully replaces what's on screen — no visual
-      // continuity, the user can't scan — AND it lands right at Ink's
-      // `delta < innerHeight` fast-path threshold, disqualifying the
-      // DECSTBM blit on every press.  Half-viewport keeps 50% continuity,
-      // well under the threshold, and two presses still scroll the same
-      // total distance.
       const step = Math.max(4, Math.floor(viewport / 2))
 
       return scrollTranscript(key.pageUp ? -step : step)

ui-tui/src/app/useMainApp.ts

@@ -1,4 +1,4 @@
-import { useApp, useHasSelection, useSelection, useStdout, useTerminalTitle, type ScrollBoxHandle } from '@hermes/ink'
+import { type ScrollBoxHandle, useApp, useHasSelection, useSelection, useStdout, useTerminalTitle } from '@hermes/ink'
 import { useStore } from '@nanostores/react'
 import { useCallback, useEffect, useMemo, useRef, useState } from 'react'
 
@@ -20,7 +20,6 @@ import { appendTranscriptMessage } from '../lib/messages.js'
 import { asRpcResult, rpcErrorMessage } from '../lib/rpc.js'
 import { terminalParityHints } from '../lib/terminalParity.js'
 import { buildToolTrailLine, sameToolTrailGroup, toolTrailLabel } from '../lib/text.js'
-import { getViewportSnapshot } from '../lib/viewportStore.js'
 import { estimatedMsgHeight, messageHeightKey } from '../lib/virtualHeights.js'
 import type { Msg, PanelSection, SlashCatalog } from '../types.js'
 
@@ -199,8 +198,10 @@ export function useMainApp(gw: GatewayClient) {
 
     return `${thinking}:${tools}`
   }, [ui.detailsMode, ui.detailsModeCommandOverride, ui.sections])
+
   const detailsVisible = detailsLayoutKey !== 'hidden:hidden'
   const heightCacheKey = `${ui.sid ?? 'draft'}:${cols}:${ui.compact ? '1' : '0'}:${detailsLayoutKey}`
+
   const heightCache = useMemo(() => {
     let cache = heightCachesRef.current.get(heightCacheKey)
 
@@ -215,6 +216,7 @@ export function useMainApp(gw: GatewayClient) {
 
     return cache
   }, [heightCacheKey])
+
   const initialHeights = useMemo(() => {
     const out = new Map<string, number>()
 
@@ -232,6 +234,7 @@ export function useMainApp(gw: GatewayClient) {
 
     return out
   }, [cols, detailsVisible, heightCache, ui.compact, virtualRows])
+
   const syncHeightCache = useCallback(
     (heights: ReadonlyMap<string, number>) => {
       for (const row of virtualRows) {
@@ -719,26 +722,10 @@ export function useMainApp(gw: GatewayClient) {
     [cols, composerActions, composerState, empty, pagerPageSize, submit]
   )
 
-  const liveTailVisible = (() => {
+  // Pass current progress through unfrozen — streaming update throttling
-    const s = scrollRef.current
+  // handles interaction load; progress must stay truthful so panels don't
-
+  // randomly disappear when the live tail scrolls offscreen.
-    if (!s) {
+  const appProgress = useMemo(() => ({ showProgressArea }), [showProgressArea])
-      return true
-    }
-
-    const { bottom, scrollHeight } = getViewportSnapshot(s)
-
-    return bottom >= scrollHeight - 3
-  })()
-
-  const liveProgress = useMemo(() => ({ showProgressArea }), [showProgressArea])
-
-  // Always pass current progress through. Freezing this while offscreen looked
-  // like a nice scroll optimization, but it also froze the live tail's
-  // thinking/tool state at arbitrary intermediate snapshots. Streaming update
-  // throttling now handles interaction load; progress state should remain
-  // truthful so panels don't randomly disappear.
-  const appProgress = liveProgress
 
   const cwd = ui.info?.cwd || process.env.HERMES_CWD || process.cwd()
   const gitBranch = useGitBranch(cwd)

ui-tui/src/app/useSessionLifecycle.ts

@@ -29,10 +29,11 @@ export const writeActiveSessionFile = (sessionId: null | string, file = process.
     return
   }
 
+  // Best-effort shell-epilogue hint; never break live session changes.
   try {
     writeFileSync(file, JSON.stringify({ session_id: sessionId }), { mode: 0o600 })
   } catch {
-    // Best-effort shell epilogue hint only; never break live session changes.
+    /* best-effort */
   }
 }
 
@@ -98,8 +99,8 @@ export function useSessionLifecycle(opts: UseSessionLifecycleOptions) {
     setLastUserMsg('')
     setStickyPrompt('')
     composerActions.setPasteSnips([])
-    // Half-prune Ink content caches: new session has new keys, but a partial
+    // Half-prune: new session has new keys, but keep a warm pool in case
-    // warm pool helps if the user resumes back to the prior session.
+    // the user resumes back to the prior session.
     evictInkCaches('half')
   }, [composerActions, setHistoryItems, setLastUserMsg, setStickyPrompt, setVoiceProcessing, setVoiceRecording])
 

ui-tui/src/components/appLayout.tsx

@@ -30,14 +30,18 @@ const TranscriptPane = memo(function TranscriptPane({
 }: Pick<AppLayoutProps, 'actions' | 'composer' | 'progress' | 'transcript'>) {
   const ui = useStore($uiState)
 
-  // Index of the latest user message — LiveTodoPanel is rendered as a child
+  // LiveTodoPanel rides as a child of the latest user-message row so it
-  // of that row so it visually belongs to the user's prompt and follows it
+  // visually belongs to the prompt and follows it during scroll. -1 when
-  // during scroll. Falls back to -1 when no user message exists yet (empty
+  // empty → row.index === -1 is always false → no render.
-  // session); LiveTodoPanel then doesn't render at all.
   const lastUserIdx = useMemo(() => {
-    for (let i = transcript.historyItems.length - 1; i >= 0; i--) {
+    const items = transcript.historyItems
-      if (transcript.historyItems[i].role === 'user') return i
+
+    for (let i = items.length - 1; i >= 0; i--) {
+      if (items[i].role === 'user') {
+        return i
       }
+    }
+
     return -1
   }, [transcript.historyItems])
 
@@ -259,18 +263,9 @@ export const AppLayout = memo(function AppLayout({
 }: AppLayoutProps) {
   const overlay = useStore($overlayState)
 
-  // Inline mode: skip <AlternateScreen> so the TUI renders into the
+  // Inline mode skips AlternateScreen so the host terminal's native
-  // primary buffer and the terminal's native scrollback can capture rows
+  // scrollback captures rows scrolled off the top; composer + progress
-  // that scroll off the top.  Mouse tracking is still enabled via
+  // stay anchored via normal flex-column flow.
-  // AlternateScreen when the wrapper is on; in inline mode we leave it
-  // to the host terminal, which typically does wheel → scrollback.
-  //
-  // `Fragment` (via alias so the JSX stays legible) drops the alt-screen
-  // constraint while keeping the inner layout identical.  Content height
-  // will then follow flex-column growth, which means the ScrollBox below
-  // grows beyond the viewport — the terminal's primary buffer scrolls
-  // old rows off the top into native scrollback.  Composer + progress
-  // stay at the bottom via normal flow (they're the last siblings).
   const Shell = INLINE_MODE ? Fragment : AlternateScreen
   const shellProps = INLINE_MODE ? {} : { mouseTracking }
 
@@ -305,9 +300,6 @@ export const AppLayout = memo(function AppLayout({
               <ComposerPane actions={actions} composer={composer} status={status} />
             </PerfPane>
 
-            {/* FPS counter overlay: pinned to the bottom row, right
-                aligned, gated on HERMES_TUI_FPS. Returns null + skips
-                this subtree when disabled (zero cost). */}
             {SHOW_FPS && (
               <Box flexShrink={0} justifyContent="flex-end" paddingRight={1}>
                 <FpsOverlay />

ui-tui/src/components/fpsOverlay.tsx

@@ -1,10 +1,4 @@
-// FPS counter overlay — renders in the bottom-right corner when
+// FPS counter overlay (HERMES_TUI_FPS=1). Zero-cost when disabled.
-// HERMES_TUI_FPS=1.  Zero-cost when disabled (returns null at the
-// top of the component; React skips the whole subtree).
-//
-// Subscribes to $fpsState via nanostores.  The store is only updated
-// when the env flag is on (trackFrame is undefined otherwise), so we
-// also gate the subscription on SHOW_FPS to avoid a useless listener.
 
 import { Text } from '@hermes/ink'
 import { useStore } from '@nanostores/react'
@@ -12,17 +6,7 @@ import { useStore } from '@nanostores/react'
 import { SHOW_FPS } from '../config/env.js'
 import { $fpsState } from '../lib/fpsStore.js'
 
-const fpsColor = (fps: number) => {
+const fpsColor = (fps: number) => (fps >= 50 ? 'green' : fps >= 30 ? 'yellow' : 'red')
-  if (fps >= 50) {
-    return 'green'
-  }
-
-  if (fps >= 30) {
-    return 'yellow'
-  }
-
-  return 'red'
-}
 
 export function FpsOverlay() {
   if (!SHOW_FPS) {
@@ -35,14 +19,10 @@ export function FpsOverlay() {
 function FpsOverlayInner() {
   const { fps, lastDurationMs, totalFrames } = useStore($fpsState)
 
-  // Zero-pad to stable width so the corner doesn't jitter as digits
+  // Zero-pad widths so digit churn doesn't jitter the corner.
-  // come and go.  Format: " 62fps  0.3ms #12345"
-  const fpsStr = fps.toFixed(1).padStart(5)
-  const durStr = lastDurationMs.toFixed(1).padStart(5)
-
   return (
     <Text color={fpsColor(fps)}>
-      {fpsStr}fps · {durStr}ms · #{totalFrames}
+      {fps.toFixed(1).padStart(5)}fps · {lastDurationMs.toFixed(1).padStart(5)}ms · #{totalFrames}
     </Text>
   )
 }

ui-tui/src/components/markdown.tsx

@@ -1,5 +1,5 @@
 import { Box, Link, Text } from '@hermes/ink'
-import { memo, useMemo, type ReactNode } from 'react'
+import { memo, type ReactNode, useMemo } from 'react'
 
 import { ensureEmojiPresentation } from '../lib/emoji.js'
 import { highlightLine, isHighlightable } from '../lib/syntax.js'
@@ -213,26 +213,23 @@ function MdInline({ t, text }: { t: Theme; text: string }) {
   return <Text>{parts.length ? parts : <Text>{text}</Text>}</Text>
 }
 
-// Cross-instance parsed-children cache. `Md` is mounted fresh whenever a
+// Cross-instance parsed-children cache: useMemo's per-instance cache dies
-// virtualized row enters the mount window — useMemo's per-instance cache
+// on remount, so virtualization re-parses every row that scrolls back into
-// doesn't survive remounts, so PageUp into cold/resumed history reparses
+// view. Theme-keyed WeakMap drops stale palettes; inner Map is LRU-bounded.
-// every row (markdown scan + per-line syntax highlight).
-//
-// Outer WeakMap keyed by theme so palette swaps drop stale baked-in colors
-// without code intervention. Inner Map is LRU-bounded; key folds `compact`
-// in so the two layout modes don't poison each other.
 const MD_CACHE_LIMIT = 512
 const mdCache = new WeakMap<Theme, Map<string, ReactNode[]>>()
 
 const cacheBucket = (t: Theme) => {
-  let b = mdCache.get(t)
+  const b = mdCache.get(t)
 
-  if (!b) {
+  if (b) {
-    b = new Map()
+    return b
-    mdCache.set(t, b)
   }
 
-  return b
+  const fresh = new Map<string, ReactNode[]>()
+  mdCache.set(t, fresh)
+
+  return fresh
 }
 
 const cacheGet = (b: Map<string, ReactNode[]>, key: string) => {

ui-tui/src/config/env.ts

@@ -1,19 +1,15 @@
+const truthy = (v?: string) => /^(?:1|true|yes|on)$/i.test((v ?? '').trim())
+
 export const STARTUP_RESUME_ID = (process.env.HERMES_TUI_RESUME ?? '').trim()
-export const MOUSE_TRACKING = !/^(?:1|true|yes|on)$/i.test((process.env.HERMES_TUI_DISABLE_MOUSE ?? '').trim())
+export const MOUSE_TRACKING = !truthy(process.env.HERMES_TUI_DISABLE_MOUSE)
-export const NO_CONFIRM_DESTRUCTIVE = /^(?:1|true|yes|on)$/i.test((process.env.HERMES_TUI_NO_CONFIRM ?? '').trim())
+export const NO_CONFIRM_DESTRUCTIVE = truthy(process.env.HERMES_TUI_NO_CONFIRM)
-// Inline mode: skip the alt-screen wrapper.  The TUI renders into the
+
-// primary buffer so the terminal's native scrollback captures whatever
+// Skip AlternateScreen — TUI renders into the primary buffer so the host
-// scrolls off the top.  Wheel + PageUp are then handled by the host
+// terminal's native scrollback captures whatever scrolls off the top.
-// terminal, not by our virtual-scroll logic.  The live composer/progress
+// Experiment gate: lets us measure native scroll vs our virtualization on
-// area still pins to the bottom via Ink's normal flow.
+// the same pipeline.
-//
+export const INLINE_MODE = truthy(process.env.HERMES_TUI_INLINE)
-// This is an experiment gate — the full "inline layout" (plain-text
+
-// transcript with composer pinned below) is a bigger change; the env var
+// Live FPS counter overlay, fed by ink's onFrame (real render rate, not a
-// here just disables AlternateScreen so we can measure whether native
+// synthetic timer).
-// scrolling beats our virtualization on the same pipeline.
+export const SHOW_FPS = truthy(process.env.HERMES_TUI_FPS)
-export const INLINE_MODE = /^(?:1|true|yes|on)$/i.test((process.env.HERMES_TUI_INLINE ?? '').trim())
-// Show a small FPS counter overlay in the bottom-right corner. Fed by
-// ink's onFrame callback (so it's the REAL render rate, not a synthetic
-// timer).  Useful during scroll-perf tuning to watch behavior in real
-// time instead of running a separate profile harness.
-export const SHOW_FPS = /^(?:1|true|yes|on)$/i.test((process.env.HERMES_TUI_FPS ?? '').trim())

ui-tui/src/config/limits.ts

@@ -1,33 +1,22 @@
 export const LARGE_PASTE = { chars: 8000, lines: 80 }
+
 export const LIVE_RENDER_MAX_CHARS = 16_000
 export const LIVE_RENDER_MAX_LINES = 240
-// History-render bounds for messages outside the FULL_RENDER_TAIL window.
+
-// Each rendered line becomes ≥1 Yoga/Text node + inline spans, so this is
+// History-render bounds for messages outside FULL_RENDER_TAIL. Each rendered
-// the dominant lever on cold-mount cost during PageUp catch-up. 16 lines
+// line ≈ 1 Yoga/Text node + inline spans, so this is the dominant lever on
-// × 25 mounted items ≈ 400 nodes total — small enough that the per-frame
+// cold-mount cost during PageUp catch-up. 16 lines × 25 mounted ≈ 400 nodes
-// buffer-compose stays well inside the 16ms budget.  User pages back to
+// — comfortably inside the 16ms per-frame budget. User pages back to
-// recognize where they were, not to read; stopping near a message
+// recognize, not to read; full re-render once it falls inside the tail.
-// re-renders it in full once it falls inside the tail window.
 export const HISTORY_RENDER_MAX_CHARS = 800
 export const HISTORY_RENDER_MAX_LINES = 16
 export const FULL_RENDER_TAIL_ITEMS = 8
+
 export const LONG_MSG = 300
 export const MAX_HISTORY = 800
 export const THINKING_COT_MAX = 160
-// Rows scrolled per wheel-notch event.
+
-//
+// Rows per wheel event (pre-accel). 1 keeps Ink's DECSTBM fast path live
-// One notch of a mechanical wheel emits multiple wheel events (3-5 per
+// (each scroll < viewport-1) and produces smooth motion. wheelAccel.ts
-// click in most terminals; trackpad flicks emit 100+). Each event scrolls
+// ramps this on sustained scrolls.
-// WHEEL_SCROLL_STEP rows.  The product = rows-per-click.
-//
-// 1 = pure line-by-line.  Small per-event delta keeps Ink's DECSTBM fast
-// path firing (each scroll < viewport-1) and produces smooth visible
-// motion — the user can scan content mid-scroll.  We were at 6 before
-// (= ~20-30 rows per notch) which visually teleported and forced the
-// virtualization to reshape the mount range on every event.
-//
-// If this feels sluggish on precision scrolls, porting claude-code's
-// wheel accel state machine (ScrollKeybindingHandler.tsx) is the right
-// next step — it ramps step up during sustained fast clicks and decays
-// on pause.
 export const WHEEL_SCROLL_STEP = 1

ui-tui/src/entry.tsx

@@ -1,4 +1,6 @@
 #!/usr/bin/env -S node --max-old-space-size=8192 --expose-gc
+import type { FrameEvent } from '@hermes/ink'
+
 import { GatewayClient } from './gatewayClient.js'
 import { setupGracefulExit } from './lib/gracefulExit.js'
 import { formatBytes, type HeapDumpResult, performHeapDump } from './lib/memory.js'
@@ -41,26 +43,21 @@ if (process.env.HERMES_HEAPDUMP_ON_START === '1') {
 
 process.on('beforeExit', () => stopMemoryMonitor())
 
-const [{ render }, { App }, { logFrameEvent }, { trackFrame }] = await Promise.all([
+const [ink, { App }, { logFrameEvent }, { trackFrame }] = await Promise.all([
   import('@hermes/ink'),
   import('./app.js'),
   import('./lib/perfPane.js'),
   import('./lib/fpsStore.js')
 ])
 
-// Compose onFrame from the two opt-in consumers (HERMES_DEV_PERF and
+// Both consumers are undefined when their env flags are off; only attach
-// HERMES_TUI_FPS).  Each is undefined when its env flag is off; we only
+// onFrame when at least one is on so ink skips timing in the default case.
-// attach onFrame at all when at least one is on, so ink skips the
+const onFrame =
-// handler entirely in the default disabled case.
-type InkFrameEvent = { durationMs: number }
-type OnFrame = (event: InkFrameEvent) => void
-
-const onFrame: OnFrame | undefined =
   logFrameEvent || trackFrame
-    ? (event: InkFrameEvent) => {
+    ? (event: FrameEvent) => {
-        logFrameEvent?.(event as Parameters<NonNullable<typeof logFrameEvent>>[0])
+        logFrameEvent?.(event)
         trackFrame?.(event.durationMs)
       }
     : undefined
 
-render(<App gw={gw} />, { exitOnCtrlC: false, onFrame })
+ink.render(<App gw={gw} />, { exitOnCtrlC: false, onFrame })

ui-tui/src/hooks/useVirtualHistory.ts

@@ -1,13 +1,13 @@
 import type { ScrollBoxHandle } from '@hermes/ink'
 import {
+  type RefObject,
   useCallback,
   useDeferredValue,
   useEffect,
   useLayoutEffect,
   useRef,
   useState,
-  useSyncExternalStore,
+  useSyncExternalStore
-  type RefObject
 } from 'react'
 
 const ESTIMATE = 4
@@ -98,6 +98,7 @@ export function useVirtualHistory(
   // Bump whenever heightCache mutates so offsets rebuild on next read.
   // Ref (not state) — checked during render phase, zero extra commits.
   const offsetVersion = useRef(0)
+
   // Cached offsets: reused Float64Array keyed on (itemCount, version) so we
   // only rebuild when something actually changed. Previous approach allocated
   // a fresh Array(n+1) every render — at n=10k that's ~80KB/render of GC
@@ -107,6 +108,7 @@ export function useVirtualHistory(
     n: -1,
     version: -1
   })
+
   const [hasScrollRef, setHasScrollRef] = useState(false)
   const metrics = useRef({ sticky: true, top: 0, vp: 0 })
   const lastScrollTopRef = useRef(0)
@@ -158,6 +160,7 @@ export function useVirtualHistory(
     (cb: () => void) => (hasScrollRef ? scrollRef.current?.subscribe(cb) : null) ?? NOOP,
     [hasScrollRef, scrollRef]
   )
+
   useSyncExternalStore(
     subscribe,
     () => {
@@ -310,13 +313,8 @@ export function useVirtualHistory(
     if (velocity > vp * 2) {
       const [pS, pE] = prevRange.current
 
-      if (start < pS - SLIDE_STEP) {
+      start = Math.max(start, pS - SLIDE_STEP)
-        start = pS - SLIDE_STEP
+      end = Math.min(end, pE + SLIDE_STEP)
-      }
-
-      if (end > pE + SLIDE_STEP) {
-        end = pE + SLIDE_STEP
-      }
 
       // A large jump past the capped end can invert (start > end); mount
       // SLIDE_STEP items from the new start so the viewport isn't blank

ui-tui/src/lib/fpsStore.ts

@@ -1,48 +1,32 @@
-// Tiny FPS tracker fed by ink's onFrame callback.
+// Tiny FPS tracker fed by ink's onFrame callback. Each entry is an Ink
+// frame (React commit + drain-only frames) — the right notion for
+// user-perceived motion.
 //
-// Keeps a ring buffer of the last N frame timestamps and derives fps
+// Zero-cost when HERMES_TUI_FPS is unset: trackFrame is undefined so the
-// from the rolling window.  Updates a nanostore so a corner-overlay
+// onFrame callback short-circuits at the optional chain.
-// component can subscribe without pulling it through props.
-//
-// FPS here means "Ink render rate" — each entry is an ink frame, which
-// includes both React commits and drain-only frames (Ink re-rendering
-// with an updated scrollTop without a React commit).  That's the right
-// notion for user-perceived motion: it's how often the screen buffer
-// actually changes, not how often React reconciles.
-//
-// Zero-cost when HERMES_TUI_FPS is unset: trackFrame is undefined so
-// the onFrame callback short-circuits at the optional chain.
 
 import { atom } from 'nanostores'
 
 import { SHOW_FPS } from '../config/env.js'
 
-const WINDOW_SIZE = 30 // last 30 frames
+const WINDOW_SIZE = 30
 
 export type FpsState = {
-  /** Frames per second averaged over the last WINDOW_SIZE frames. */
   fps: number
-  /** Total frames counted since start (wraps at JS-safe int so you can
+  /** Wraps at JS-safe int — diff pairs in a debug overlay safely. */
-   *  diff pairs in a debug overlay without worrying about precision). */
   totalFrames: number
-  /** Last frame's durationMs (ink render phase total). */
+  /** Ink render-phase total for the last frame. */
   lastDurationMs: number
 }
 
-export const $fpsState = atom<FpsState>({
+export const $fpsState = atom<FpsState>({ fps: 0, lastDurationMs: 0, totalFrames: 0 })
-  fps: 0,
-  lastDurationMs: 0,
-  totalFrames: 0
-})
 
 const timestamps: number[] = []
 let totalFrames = 0
 
 export const trackFrame = SHOW_FPS
   ? (durationMs: number) => {
-      const now = performance.now()
+      timestamps.push(performance.now())
-
-      timestamps.push(now)
 
       if (timestamps.length > WINDOW_SIZE) {
         timestamps.shift()
@@ -50,20 +34,18 @@ export const trackFrame = SHOW_FPS
 
       totalFrames++
 
-      // FPS = frames-in-window / seconds-in-window. Needs at least 2
+      if (timestamps.length < 2) {
-      // timestamps to compute a gap.
+        return
-      if (timestamps.length >= 2) {
+      }
+
       const elapsed = (timestamps[timestamps.length - 1]! - timestamps[0]!) / 1000
 
       if (elapsed > 0) {
-          const fps = (timestamps.length - 1) / elapsed
-
         $fpsState.set({
-            fps: Math.round(fps * 10) / 10,
+          fps: Math.round(((timestamps.length - 1) / elapsed) * 10) / 10,
           lastDurationMs: Math.round(durationMs * 100) / 100,
           totalFrames
         })
       }
     }
-    }
   : undefined

ui-tui/src/lib/liveProgress.test.ts

@@ -104,7 +104,10 @@ describe('appendToolShelfMessage', () => {
 
   it('starts a new shelf across assistant text boundaries', () => {
     const merged = appendToolShelfMessage(
-      [{ kind: 'trail', role: 'system', text: '', tools: ['one ✓'] }, { role: 'assistant', text: 'done' }],
+      [
+        { kind: 'trail', role: 'system', text: '', tools: ['one ✓'] },
+        { role: 'assistant', text: 'done' }
+      ],
       { kind: 'trail', role: 'system', text: '', tools: ['two ✓'] }
     )
 

ui-tui/src/lib/liveProgress.ts

@@ -38,8 +38,7 @@ const isBarrierMessage = (msg: Msg | undefined) => {
   return false
 }
 
-const isToolCarryingTrail = (msg: Msg | undefined) =>
+const isToolCarryingTrail = (msg: Msg | undefined) => Boolean(msg?.kind === 'trail' && !msg.text && msg.tools?.length)
-  Boolean(msg?.kind === 'trail' && !msg.text && msg.tools?.length)
 
 export const appendToolShelfMessage = (prev: readonly Msg[], msg: Msg): Msg[] => {
   if (!isToolShelfMessage(msg)) {

ui-tui/src/lib/memoryMonitor.ts

@@ -41,10 +41,8 @@ export function startMemoryMonitor({
       return
     }
 
-    // Defensive eviction: prune Ink content caches before dumping/exiting.
+    // Prune Ink content caches before dump/exit — half on 'high' (recoverable),
-    // 'high' = half-prune (still warm enough to recover quickly);
+    // full on 'critical' (post-dump RSS reduction, keeps user running).
-    // 'critical' = full drop. Reduces post-dump RSS and gives the user a
-    // chance to keep running rather than auto-restart.
     evictInkCaches(level === 'critical' ? 'all' : 'half')
 
     dumped.add(level)

ui-tui/src/lib/perfPane.tsx

@@ -1,43 +1,15 @@
 // Perf instrumentation for the full render pipeline.
 //
-// Two sources of timing:
+//   PerfPane (React.Profiler)  → per-pane commit times
-//   1. React.Profiler wrapper (PerfPane) → per-pane commit times. Shows
+//   logFrameEvent (ink.onFrame) → yoga / renderer / diff / optimize / write
-//      which subtree is reconciling and for how long.
+//                                 phases + yoga counters + scroll fast-path
-//   2. Ink onFrame callback (logFrameEvent) → per-frame pipeline phases:
-//      yoga (calculateLayout), renderer (DOM → screen buffer), diff
-//      (prev vs current screen → patches), optimize (patch merge/dedupe),
-//      write (serialize → ANSI → stdout), plus yoga counters (visited,
-//      measured, cacheHits, live). Shows where the time goes BELOW React.
 //
-// Both sources gate on HERMES_DEV_PERF=1 and dump JSON-lines to the same
+// Both gate on HERMES_DEV_PERF=1 and dump JSON-lines (default ~/.hermes/perf.log,
-// log (default ~/.hermes/perf.log, override via HERMES_DEV_PERF_LOG).
+// override HERMES_DEV_PERF_LOG). Tagged { src: 'react' | 'frame' } for jq.
-// Events are tagged { src: 'react' | 'frame' } so jq can split them.
+// HERMES_DEV_PERF_MS (default 2) skips sub-ms idle frames; set 0 to capture all.
 //
-// Threshold HERMES_DEV_PERF_MS (default 2ms) skips sub-millisecond idle
+// Zero cost when unset: PerfPane returns children directly, logFrameEvent is
-// frames. For the 2fps-during-PageUp investigation, set
+// undefined so ink doesn't pay the timing cost.
-// HERMES_DEV_PERF_MS=0 to capture everything, then filter with jq.
-//
-// Zero cost when the env var is unset: PerfPane returns children
-// directly (no Profiler fiber), logFrameEvent is a noop on the onFrame
-// callback — the ink instance isn't given the callback at all.
-//
-// Usage:
-//   # entry.tsx wires logFrameEvent into render()
-//   import { logFrameEvent, PerfPane } from './lib/perfPane.js'
-//   render(<App/>, { onFrame: logFrameEvent })
-//
-// Analysis helpers (once you've captured a session):
-//   tail -f ~/.hermes/perf.log | jq -c 'select(.src=="frame" and .durationMs > 16)'
-//   # p50/p99 per phase across frame events:
-//   jq -s '[.[] | select(.src=="frame")] |
-//     {n: length,
-//      dur_p50: (sort_by(.durationMs) | .[length/2|floor].durationMs),
-//      dur_p99: (sort_by(.durationMs) | .[length*0.99|floor].durationMs),
-//      yoga_p99: (sort_by(.phases.yoga) | .[length*0.99|floor].phases.yoga),
-//      write_p99: (sort_by(.phases.write) | .[length*0.99|floor].phases.write),
-//      diff_p99: (sort_by(.phases.diff) | .[length*0.99|floor].phases.diff),
-//      patches_p99: (sort_by(.phases.patches) | .[length*0.99|floor].phases.patches)}' \
-//     ~/.hermes/perf.log
 
 import { appendFileSync, mkdirSync } from 'node:fs'
 import { homedir } from 'node:os'
@@ -51,31 +23,23 @@ const ENABLED = /^(?:1|true|yes|on)$/i.test((process.env.HERMES_DEV_PERF ?? '').
 const THRESHOLD_MS = Number(process.env.HERMES_DEV_PERF_MS ?? '2') || 0
 const LOG_PATH = process.env.HERMES_DEV_PERF_LOG?.trim() || join(homedir(), '.hermes', 'perf.log')
 
-let initialized = false
+let logReady = false
 
-const ensureLogDir = () => {
+const writeRow = (row: Record<string, unknown>) => {
-  if (initialized) {
+  if (!logReady) {
-    return
+    logReady = true
-  }
-
-  initialized = true
 
     try {
       mkdirSync(dirname(LOG_PATH), { recursive: true })
     } catch {
-    // Best-effort — if we can't create the dir (readonly fs, /tmp, etc.)
+      // Best-effort — never crash the TUI to log a sample.
-    // the appendFileSync calls below will throw silently and we drop the
+    }
-    // sample. Perf logging should never crash the TUI.
   }
-}
-
-const writeRow = (row: Record<string, unknown>) => {
-  ensureLogDir()
 
   try {
     appendFileSync(LOG_PATH, `${JSON.stringify(row)}\n`)
   } catch {
-    // Same rationale as ensureLogDir — never crash the UI to log a sample.
+    /* best-effort */
   }
 }
 
@@ -110,59 +74,27 @@ export function PerfPane({ children, id }: { children: ReactNode; id: string })
   )
 }
 
-/**
- * Ink onFrame handler. Captures the FULL render pipeline: yoga calculateLayout,
- * DOM → screen buffer, screen diff, patch optimize, and stdout write.
- *
- * Returns `undefined` when disabled so `render()` doesn't attach the callback —
- * ink only pays the timing cost when the callback is truthy.
- */
 export const logFrameEvent = ENABLED
   ? (event: FrameEvent) => {
       if (event.durationMs < THRESHOLD_MS) {
         return
       }
 
-      // Snapshot the fast-path counters each frame. Cumulative values —
-      // consumers diff pairs to get per-frame deltas. Written verbatim
-      // so we can also see "last*" fields (which decline reason fired,
-      // and what the height math looked like).
-      const fastPath = {
-        captured: scrollFastPathStats.captured,
-        taken: scrollFastPathStats.taken,
-        declined: {
-          heightDeltaMismatch: scrollFastPathStats.declined.heightDeltaMismatch,
-          noPrevScreen: scrollFastPathStats.declined.noPrevScreen,
-          other: scrollFastPathStats.declined.other
-        },
-        lastDeclineReason: scrollFastPathStats.lastDeclineReason,
-        lastHeightDelta: scrollFastPathStats.lastHeightDelta,
-        lastHintDelta: scrollFastPathStats.lastHintDelta,
-        lastPrevHeight: scrollFastPathStats.lastPrevHeight,
-        lastScrollHeight: scrollFastPathStats.lastScrollHeight
-      }
-
       writeRow({
         durationMs: round2(event.durationMs),
-        fastPath,
+        // Cumulative counters — consumers diff pairs to get per-frame deltas.
+        fastPath: { ...scrollFastPathStats, declined: { ...scrollFastPathStats.declined } },
         flickers: event.flickers.length ? event.flickers : undefined,
         phases: event.phases
           ? {
-              backpressure: event.phases.backpressure,
+              ...event.phases,
               commit: round2(event.phases.commit),
               diff: round2(event.phases.diff),
               optimize: round2(event.phases.optimize),
-              optimizedPatches: event.phases.optimizedPatches,
-              patches: event.phases.patches,
               prevFrameDrainMs: round2(event.phases.prevFrameDrainMs),
               renderer: round2(event.phases.renderer),
               write: round2(event.phases.write),
-              writeBytes: event.phases.writeBytes,
+              yoga: round2(event.phases.yoga)
-              yoga: round2(event.phases.yoga),
-              yogaCacheHits: event.phases.yogaCacheHits,
-              yogaLive: event.phases.yogaLive,
-              yogaMeasured: event.phases.yogaMeasured,
-              yogaVisited: event.phases.yogaVisited
             }
           : undefined,
         src: 'frame',

ui-tui/src/lib/text.ts

@@ -80,20 +80,15 @@ export const pasteTokenLabel = (text: string, lineCount: number) => {
 const THINKING_STATUS_RE = new RegExp(`^(?:${VERBS.join('|')})\\.{0,3}$`, 'i')
 const THINKING_STATUS_CHUNK_RE = new RegExp(`[^A-Za-z\n]+\\s*(?:${VERBS.join('|')})\\.{0,3}\\s*`, 'giu')
 
-const normalizeThinkingParagraphs = (text: string) =>
-  text
-    .replace(/([^\n])(?=\*\*[^*\n][^\n]*?\*\*)/g, '$1\n\n')
-    .replace(/\n{3,}/g, '\n\n')
-    .trim()
-
 export const cleanThinkingText = (reasoning: string) =>
-  normalizeThinkingParagraphs(
   reasoning
     .split('\n')
     .map(line => line.replace(THINKING_STATUS_CHUNK_RE, '').trim())
     .filter(line => line && !THINKING_STATUS_RE.test(line.replace(/\.\.\.$/, '').trim()))
     .join('\n')
-  )
+    .replace(/([^\n])(?=\*\*[^*\n][^\n]*?\*\*)/g, '$1\n\n')
+    .replace(/\n{3,}/g, '\n\n')
+    .trim()
 
 export const thinkingPreview = (reasoning: string, mode: ThinkingMode, max: number = THINKING_COT_MAX) => {
   const raw = cleanThinkingText(reasoning)

ui-tui/src/lib/virtualHeights.ts

@@ -14,18 +14,18 @@ export const hashText = (text: string) => {
 
 export const messageHeightKey = (msg: Msg) => {
   const todoSig = msg.todos?.map(t => `${t.status}:${t.content}`).join('\u0001') ?? ''
+
   const panelSig =
     msg.panelData?.sections
       .map(s => `${s.title ?? ''}:${s.text?.length ?? 0}:${s.items?.length ?? 0}:${s.rows?.length ?? 0}`)
       .join('\u0001') ?? ''
+
   const introSig = msg.kind === 'intro' ? (msg.info?.version ?? '') : ''
 
   return [
     msg.role,
     msg.kind ?? '',
-    hashText(
+    hashText([msg.text, msg.thinking ?? '', msg.tools?.join('\n') ?? '', todoSig, panelSig, introSig].join('\0'))
-      [msg.text, msg.thinking ?? '', msg.tools?.join('\n') ?? '', todoSig, panelSig, introSig].join('\0')
-    )
   ].join(':')
 }
 
@@ -68,11 +68,9 @@ export const estimatedMsgHeight = (
     h += (msg.tools?.length ?? 0) + wrappedLines(msg.thinking ?? '', bodyWidth)
   }
 
-  if (msg.role === 'user' || msg.kind === 'slash' || msg.kind === 'diff') {
-    h++
-  }
-
   if (msg.role === 'user' || msg.kind === 'diff') {
+    h += 2
+  } else if (msg.kind === 'slash') {
     h++
   }
 

ui-tui/src/lib/wheelAccel.ts

@@ -1,52 +1,35 @@
 // Wheel-scroll acceleration state machine.
 //
-// Algorithm and tuning constants adapted from a reference implementation
+// One event = 1 row feels sluggish on trackpads (200+ ev/s) and sustained
-// of trackpad/wheel-event acceleration in TUI scroll handlers; this file
+// mouse-wheel; one event = 6 rows teleports and ruins precision.
-// is the port adapted to our module structure.
+// Heuristic on inter-event gap + direction flips:
 //
-// Problem: one wheel event = 1 scrolled row feels sluggish on trackpads
+//   gap < 5ms                 → same-batch burst → 1 row/event
-// (which can fire 200+ events/sec) and during deliberate mouse scrolls.
+//   gap < 40ms (native)       → ramp +0.3, cap 6
-// One wheel event = 6 rows (our old WHEEL_SCROLL_STEP=6) visually
+//   gap 80-500ms (xterm.js)   → mult = 1 + (mult-1)·0.5^(gap/150) + 5·decay
-// teleports and ruins precision.  The right answer depends on intent:
+//                               cap 3 slow / 6 fast
+//   gap > 500ms               → reset (deliberate click stays responsive)
+//   flip + flip-back ≤200ms   → encoder bounce → engage wheel-mode (sticky cap)
+//   5 consecutive <5ms events → trackpad flick → disengage wheel-mode
 //
-//   precision click  → 1 row/event
+// Native terminals (Ghostty, iTerm2) and xterm.js embedders (VS Code,
-//   sustained mouse  → ramp to ~15 rows/event, decay when slowing down
+// Cursor) emit wheel events with different cadences, hence two paths.
-//   trackpad flick   → 1 row/event per burst event (they come 100+)
-//
-// Heuristic: watch inter-event gaps and direction flips:
-//   * gap < 5ms         → same-batch burst (SGR proportional reporting
-//                         or trackpad flick) → 1 row/event
-//   * gap < 40ms, same  → ramp mult by +0.3/event, cap at 6 (native path)
-//   * gap < 80-500ms    → exponential decay curve (xterm.js path)
-//                         mult = 1 + (mult-1)*0.5^(gap/150ms) + 5*decay
-//                         capped at 3 for gaps ≥ 80ms, 6 for < 80ms
-//   * gap > 500ms       → reset to 2 (deliberate click feels responsive)
-//   * direction flip + bounce-back within 200ms → encoder bounce,
-//                                                 engage wheel-mode
-//                                                 (sticky higher cap)
-//   * 5 consecutive <5ms events → trackpad flick, disengage wheel-mode
-//
-// Two separate paths because native terminals (Ghostty, iTerm2) and
-// browser-embedded terminals (VS Code, Cursor) emit wheel events with
-// different cadences.  Native sends 1 event per intended row, often
-// pre-amplified at the emulator level; xterm.js sends exactly 1 event
-// per notch, unamplified.
 
 import { isXtermJs } from '@hermes/ink'
 
-// ── Native path (ghostty, iTerm2, WezTerm, etc.) ───────────────────────
+// ── Native (ghostty, iTerm2, WezTerm, …) ───────────────────────────────
 const WHEEL_ACCEL_WINDOW_MS = 40
 const WHEEL_ACCEL_STEP = 0.3
 const WHEEL_ACCEL_MAX = 6
 
-// ── Encoder bounce / wheel-mode path (detected mechanical wheels) ──────
+// ── Encoder bounce / wheel-mode (mechanical wheels) ────────────────────
 const WHEEL_BOUNCE_GAP_MAX_MS = 200
 const WHEEL_MODE_STEP = 15
 const WHEEL_MODE_CAP = 15
 const WHEEL_MODE_RAMP = 3
 const WHEEL_MODE_IDLE_DISENGAGE_MS = 1500
 
-// ── xterm.js path (VS Code / Cursor / browser terminals) ───────────────
+// ── xterm.js (VS Code / Cursor / browser terminals) ────────────────────
 const WHEEL_DECAY_HALFLIFE_MS = 150
 const WHEEL_DECAY_STEP = 5
 const WHEEL_BURST_MS = 5
@@ -60,88 +43,61 @@ export type WheelAccelState = {
   mult: number
   dir: 0 | 1 | -1
   xtermJs: boolean
-  /** Carried fractional scroll (xterm.js only). scrollBy floors, so
+  /** Carried fractional scroll (xterm.js). scrollBy floors, so without
-   *  without this a mult of 1.5 gives 1 row every time. Carrying the
+   *  this a mult of 1.5 always gives 1 row; carrying the remainder gives
-   *  remainder gives 1,2,1,2 on average for mult=1.5 — correct
+   *  1,2,1,2 — correct throughput over time. */
-   *  throughput over time. */
   frac: number
-  /** Native-path baseline rows/event. Reset value on idle/reversal;
+  /** Native baseline rows/event. Reset on idle/reversal; ramp builds on
-   *  ramp builds on top. xterm.js path ignores this. */
+   *  top. xterm.js path ignores. */
   base: number
-  /** Deferred direction flip (native only). Might be encoder bounce or
+  /** Deferred direction flip (native): bounce vs reversal — next event
-   *  a real reversal — resolved by the NEXT event. */
+   *  decides. */
   pendingFlip: boolean
-  /** Confirmed once a bounce fired (flip-then-flip-back within the
+  /** Sticky once a flip-then-flip-back fires within the bounce window.
-   *  bounce window).  Sticky until idle disengage or trackpad burst. */
+   *  Cleared by idle disengage or trackpad burst. */
   wheelMode: boolean
-  /** Consecutive <5ms events.  Trackpad flick ≥5 → disengage wheelMode. */
+  /** Consecutive <5ms events. ≥5 → trackpad flick → disengage. */
   burstCount: number
 }
 
 export function initWheelAccel(xtermJs = false, base = 1): WheelAccelState {
-  return {
+  return { burstCount: 0, base, dir: 0, frac: 0, mult: base, pendingFlip: false, time: 0, wheelMode: false, xtermJs }
-    burstCount: 0,
-    base,
-    dir: 0,
-    frac: 0,
-    mult: base,
-    pendingFlip: false,
-    time: 0,
-    wheelMode: false,
-    xtermJs
-  }
 }
 
-/** Read HERMES_TUI_SCROLL_SPEED (or CLAUDE_CODE_SCROLL_SPEED for
+/** HERMES_TUI_SCROLL_SPEED (or CLAUDE_CODE_SCROLL_SPEED for portability).
- *  portability from claude-code users).  Default 1, clamped (0, 20]. */
+ *  Default 1, clamped (0, 20]. */
 export function readScrollSpeedBase(): number {
-  const raw = process.env.HERMES_TUI_SCROLL_SPEED ?? process.env.CLAUDE_CODE_SCROLL_SPEED
+  const n = parseFloat(process.env.HERMES_TUI_SCROLL_SPEED ?? process.env.CLAUDE_CODE_SCROLL_SPEED ?? '')
 
-  if (!raw) {
+  return Number.isFinite(n) && n > 0 ? Math.min(n, 20) : 1
-    return 1
-  }
-
-  const n = parseFloat(raw)
-
-  return Number.isNaN(n) || n <= 0 ? 1 : Math.min(n, 20)
 }
 
-/** Initialize the accel state with environment-derived defaults. */
 export function initWheelAccelForHost(): WheelAccelState {
   return initWheelAccel(isXtermJs(), readScrollSpeedBase())
 }
 
-/**
+/** Compute rows for one wheel event, mutating `state`. Returns 0 when a
- * Compute rows for one wheel event, MUTATING the accel state.  Returns 0
+ *  direction flip is deferred for bounce detection — call sites should
- * when a direction flip is deferred for bounce detection — call sites
+ *  no-op on 0. */
- * should no-op on 0 (scrollBy(0) is a no-op anyway, but explicit check
- * keeps the intent obvious).
- */
 export function computeWheelStep(state: WheelAccelState, dir: -1 | 1, now: number): number {
-  if (!state.xtermJs) {
+  return state.xtermJs ? xtermJsStep(state, dir, now) : nativeStep(state, dir, now)
-    return nativeStep(state, dir, now)
-  }
-
-  return xtermJsStep(state, dir, now)
 }
 
 function nativeStep(state: WheelAccelState, dir: -1 | 1, now: number): number {
-  // Device-switch guard ①: idle disengage.  A pending bounce can mask
+  // Idle disengage runs first so a pending bounce can't mask "user paused
-  // as a real reversal via the early return below — run this first so
+  // 1.5s then mouse-clicked" as a real reversal.
-  // "user stopped for 1.5s then mouse-click" restarts at baseline.
   if (state.wheelMode && now - state.time > WHEEL_MODE_IDLE_DISENGAGE_MS) {
     state.wheelMode = false
     state.burstCount = 0
     state.mult = state.base
   }
 
-  // Resolve any deferred flip before touching state.time/dir.
   if (state.pendingFlip) {
     state.pendingFlip = false
 
     if (dir !== state.dir || now - state.time > WHEEL_BOUNCE_GAP_MAX_MS) {
-      // Real reversal (flip persisted OR flip-back arrived too late).
+      // Real reversal (flip persisted OR flip-back too late). Commit.
-      // Commit.  The deferred event's 1 row is lost (acceptable latency).
+      // The deferred event's 1 row is lost — acceptable latency.
       state.dir = dir
       state.time = now
       state.mult = state.base
@@ -149,15 +105,12 @@ function nativeStep(state: WheelAccelState, dir: -1 | 1, now: number): number {
       return Math.floor(state.mult)
     }
 
-    // Bounce confirmed: flipped back to original dir in the window.
-    // Engage wheel-mode for sustained mouse-wheel pattern.
     state.wheelMode = true
   }
 
   const gap = now - state.time
 
   if (dir !== state.dir && state.dir !== 0) {
-    // Direction flip.  Defer — next event decides bounce vs reversal.
     state.pendingFlip = true
     state.time = now
 
@@ -169,8 +122,8 @@ function nativeStep(state: WheelAccelState, dir: -1 | 1, now: number): number {
 
   if (state.wheelMode) {
     if (gap < WHEEL_BURST_MS) {
-      // Same-batch burst (SGR proportional reporting) OR trackpad flick.
+      // Same-batch burst (SGR proportional) OR trackpad flick. 1 row/event;
-      // Give 1 row/event; trackpad flick hits the burst-count disengage.
+      // trackpad flick trips the burst-count disengage.
       if (++state.burstCount >= 5) {
         state.wheelMode = false
         state.burstCount = 0
@@ -183,7 +136,6 @@ function nativeStep(state: WheelAccelState, dir: -1 | 1, now: number): number {
     }
   }
 
-  // Re-check after possible disengage above.
   if (state.wheelMode) {
     const m = Math.pow(0.5, gap / WHEEL_DECAY_HALFLIFE_MS)
     const cap = Math.max(WHEEL_MODE_CAP, state.base * 2)
@@ -194,8 +146,8 @@ function nativeStep(state: WheelAccelState, dir: -1 | 1, now: number): number {
     return Math.floor(state.mult)
   }
 
-  // Trackpad / hi-res (native, non-wheel-mode).  Tight 40ms window:
+  // Trackpad / hi-res native: tight 40ms window — sub-window ramps,
-  // sub-40ms ramps, anything slower resets to baseline.
+  // anything slower resets to baseline.
   if (gap > WHEEL_ACCEL_WINDOW_MS) {
     state.mult = state.base
   } else {
@@ -215,13 +167,11 @@ function xtermJsStep(state: WheelAccelState, dir: -1 | 1, now: number): number {
   state.dir = dir
 
   if (sameDir && gap < WHEEL_BURST_MS) {
-    // Same-batch burst — 1 row/event, same philosophy as native.
     return 1
   }
 
   if (!sameDir || gap > WHEEL_DECAY_IDLE_MS) {
-    // Direction reversal or long idle: start at 2 so the first click
+    // Reversal or long idle — start at 2 so first click after a pause moves visibly.
-    // after a pause moves visibly.
     state.mult = 2
     state.frac = 0
   } else {