Merge pull request #28829 from NousResearch/bb/tui-no-history-truncation

fix(tui): render full assistant text in scrollback (no history truncation)

ui-tui/src/lib/text.ts

@@ -1,6 +1,4 @@
 import {
-  HISTORY_RENDER_MAX_CHARS,
-  HISTORY_RENDER_MAX_LINES,
   LIVE_RENDER_MAX_CHARS,
   LIVE_RENDER_MAX_LINES,
   THINKING_COT_MAX
@@ -129,11 +127,6 @@ export const boundedLiveRenderText = (
   { maxChars = LIVE_RENDER_MAX_CHARS, maxLines = LIVE_RENDER_MAX_LINES } = {}
 ) => boundedRenderText(text, 'showing live tail', { maxChars, maxLines })
 
-export const boundedHistoryRenderText = (
-  text: string,
-  { maxChars = HISTORY_RENDER_MAX_CHARS, maxLines = HISTORY_RENDER_MAX_LINES } = {}
-) => boundedRenderText(text, 'showing tail', { maxChars, maxLines })
-
 const boundedRenderText = (
   text: string,
   labelPrefix: string,

ui-tui/src/lib/virtualHeights.ts

@@ -1,7 +1,6 @@
 import type { Msg } from '../types.js'
 
 import { transcriptBodyWidth } from './inputMetrics.js'
-import { boundedHistoryRenderText } from './text.js'
 
 const hashText = (text: string) => {
   let h = 5381
@@ -30,10 +29,40 @@ export const messageHeightKey = (msg: Msg) => {
   ].join(':')
 }
 
-export const wrappedLines = (text: string, width: number) => {
-  const w = Math.max(1, width)
+// Hard cap on rows the estimator will count. Each row above this is
+// invisible to the estimator (gets clipped to MAX_ESTIMATE_LINES), but
+// post-mount Yoga measurement converges to the real height on first
+// render. Without this, a long assistant turn (10k+ chars) costs O(text)
+// per offset rebuild × every uncached item — cold-mounting a 1000-row
+// transcript becomes a multi-million-char wrap walk that blocks the UI.
+//
+// 800 covers any realistic assistant message (the prior history-clip
+// ceiling was 16 lines, then full text — this is the sane middle).
+const MAX_ESTIMATE_LINES = 800
 
-  return text.split('\n').reduce((n, line) => n + Math.max(1, Math.ceil(line.length / w)), 0)
+export const wrappedLines = (text: string, width: number, maxLines: number = MAX_ESTIMATE_LINES) => {
+  const w = Math.max(1, width)
+  // Worst case: every cell is its own row at width=1, plus a small
+  // slack for the trailing partial line. Walking past this byte budget
+  // cannot increase n any further once n is already past maxLines, so
+  // bail. Saves O(text) walks on multi-megabyte single-line messages.
+  const budget = Math.min(text.length, maxLines * w + maxLines)
+  let n = 0
+  let start = 0
+
+  for (let i = 0; i <= budget; i++) {
+    if (i === text.length || i === budget || text.charCodeAt(i) === 10) {
+      const rows = Math.max(1, Math.ceil((i - start) / w))
+      n += rows >= maxLines - n ? maxLines - n : rows
+      start = i + 1
+
+      if (n >= maxLines) {
+        return maxLines
+      }
+    }
+  }
+
+  return n
 }
 
 export const estimatedMsgHeight = (
@@ -42,13 +71,11 @@ export const estimatedMsgHeight = (
   {
     compact,
     details,
-    limitHistory = false,
     userPrompt = '',
     withSeparator = false
   }: {
     compact: boolean
     details: boolean
-    limitHistory?: boolean
     userPrompt?: string
     withSeparator?: boolean
   }
@@ -70,11 +97,16 @@ export const estimatedMsgHeight = (
   }
 
   const bodyWidth = transcriptBodyWidth(cols, msg.role, userPrompt)
-  const text = msg.role === 'assistant' && limitHistory ? boundedHistoryRenderText(msg.text) : msg.text
+  const text = msg.text
   let h = wrappedLines(text || ' ', bodyWidth)
 
   if (!compact && msg.role === 'assistant') {
-    h += Math.min(6, (text.match(/\n\s*\n/g) ?? []).length)
+    // Paragraph gaps add up to 6 extra rows of breathing room. Slice
+    // first so the regex never walks more than the first ~16k chars of
+    // a giant assistant message — post-mount Yoga measurement converges
+    // to the real height regardless of how the estimate undercounts.
+    const scan = text.length > 16_000 ? text.slice(0, 16_000) : text
+    h += Math.min(6, (scan.match(/\n\s*\n/g) ?? []).length)
   }
 
   if (details) {