> Premium standalone component (part of no design system, works in any React + Tailwind app) from AI Canvas. Index of every component and install setup: https://aicanvas.me/llms.txt

# Streaming Answer

An assistant answer that streams in word by word, already formatted, with new words fading in, a stop and continue control, and message actions.

- Category: AI Agent UI
- Built with: Motion, Tailwind CSS
- License: Premium (proprietary, not in the public repo)
- Page: https://aicanvas.me/components/token-stream

## Install

```bash
npx shadcn@latest add @aicanvas/token-stream
```

Requires Premium. Set your AI Canvas token as AICANVAS_TOKEN and register the @aicanvas registry with it, as described in the Install section of https://aicanvas.me/llms.txt. Without a Premium token the command writes a placeholder file instead of the component.

AI agents can also get its install command from the read-only AI Canvas MCP server (`npx -y @aicanvas/mcp`) and run it. Setup: https://aicanvas.me/mcp

Peer dependencies:

```bash
npm install framer-motion
```

## Props

| Prop | Type | Default | Description |
| --- | --- | --- | --- |
| `markdown?` | `string` |  | Supplies the answer parsed and revealed as Markdown; left out, the demo uses sample text and host mode uses an empty answer, while passing it turns the demo off. |
| `status?` | `TokenStreamStatus` |  | Controls waiting, writing, done or stopped presentation; left out, host mode infers done from nonempty Markdown and waiting otherwise, while passing it turns the demo off. |
| `waitingPhrases?` | `string[]` |  | Supplies rotating work messages before the answer; left out, the demo uses sample messages and host mode shows none, while passing it turns the demo off. |
| `wordsPerSecond?` | `number` |  | Sets a positive reveal speed; left out or nonpositive, the tuned word timing is used. |
| `label?` | `string` |  | Adds metadata text to the answer header; left out, no label is shown, while passing it turns the demo off. |
| `onStop?` | `() => void` |  | Handles stopping and makes the stop control available during host writing; left out, host streams have no stop control. |
| `onContinue?` | `() => void` |  | Handles continuing and makes the Continue control available after a host stop; left out, host stopped answers have no Continue control. |
| `onRetry?` | `() => void` |  | Handles retrying and makes retry controls available in host mode; left out, host answers have no retry controls. |
| `onFeedback?` | `(value: 'up'\|'down'\|null) => void` |  | Reports the current rating while rating state remains local; left out, rating controls still update locally. |
| `elapsedMs?` | `number` |  | Shows how long a host answer took in milliseconds; left out, no host duration is shown, while passing it turns the demo off. |
| `className?` | `string` |  | Adds classes to the outermost root; left out, only the built-in classes are used. |
| `tuning?` | `Partial<Tuning>` |  | Overrides stream measurements, timing and motion values; left out, every value in TUNING is used. |

## About

Token Stream renders an answer as it arrives: inline markdown, lists, headings and fenced code, with a steady word by word reveal that smooths bursty delivery. An open code fence renders as code from its first character, so nothing reflows when it closes. The cursor blinks only while waiting, Stop freezes what you have and Continue resumes, and if the reader scrolls up a small Jump to latest pill appears instead of dragging them down. Feed it chunks or a controlled content string; without props it streams a scripted answer on a loop.

Use cases: Chat assistants, AI writing tools, Documentation bots.

## Source

The source is Premium and is not published. Preview it at https://aicanvas.me/components/token-stream.

## Remix prompt

The public part of the remix prompt: 1. Setup and 2. Constants. The rest of the build spec (state, markup, how it works) is part of Premium.

````markdown
# TokenStream
An agent answer card that reveals Markdown word by word, then settles with copy, retry and rating controls.

## 1. Setup
// npm install framer-motion
File: components-workspace/token-stream/index.tsx  ·  'use client'  ·  export default function TokenStream(props: TokenStreamProps)
Tailwind CSS v4, with the dark: variant following your theme. Colors come from the component variables in THEME_VARS.
The @/app/_icons imports are the AI Canvas icon set. Without it, use any icon components that accept size, weight and SVG props, with a matching IconProps type.

import { memo, useCallback, useEffect, useLayoutEffect, useMemo, useRef, useState, useSyncExternalStore } from 'react'
import type * as React from 'react'
import { animate, AnimatePresence, motion, useMotionTemplate, useMotionValue } from 'framer-motion'
import { RotateCw } from '@/app/_icons/icons/rotate-cw'
import { RotateCcw } from '@/app/_icons/icons/rotate-ccw'
import { Check } from '@/app/_icons/icons/check'
import { Copy } from '@/app/_icons/icons/copy'
import { Play } from '@/app/_icons/icons/play'
import { Stop } from '@/app/_icons/icons/stop'
import { ThumbsDown } from '@/app/_icons/icons/thumbs-down'
import { ThumbsUp } from '@/app/_icons/icons/thumbs-up'
import { SparkleDuotone } from '@/app/_icons/icons/sparkle-duotone'
import { CircleCheckDuotone } from '@/app/_icons/icons/circle-check-duotone'
import { CircleStopDuotone } from '@/app/_icons/icons/circle-stop-duotone'
import { CircleMinusDuotone } from '@/app/_icons/icons/circle-minus-duotone'

## 2. Constants
export type Tuning = {
  cardMaxW: number
  firstPhraseMs: number
  phraseMs: number
  wordMs: number
  commaPauseMs: number
  sentencePauseMs: number
  blockPauseMs: number
  fenceOpenMs: number
  lineEndMs: number
  inkMs: number
  risePx: number
  paceJitter: number
  flowCapMs: number
  reducedChunk: number
  reducedStepMs: number
  codeHeaderH: number
  codeLineH: number
  codePadY: number
  codeMaxLines: number
  dotFieldH: number
  dotPitch: number
  waitMinH: number
  hoverMs: number
  stateMs: number
  panelMs: number
  lightMs: number
  copiedMs: number
  shimmerS: number
  pressScale: number
  growS: number
  followS: number
  tailRoomPx: number
  blockHoldMs: number
  holdMs: number
}

export const TUNING: Tuning = {
  cardMaxW: 560,
  firstPhraseMs: 1200,
  phraseMs: 800,
  wordMs: 35,
  commaPauseMs: 70,
  sentencePauseMs: 150,
  blockPauseMs: 220,
  fenceOpenMs: 260,
  lineEndMs: 70,
  inkMs: 260,
  risePx: 4,
  paceJitter: 0.45,
  flowCapMs: 600,
  reducedChunk: 8,
  reducedStepMs: 180,
  codeHeaderH: 36,
  codeLineH: 20,
  codePadY: 12,
  codeMaxLines: 8,
  dotFieldH: 64,
  dotPitch: 6,
  waitMinH: 28,
  hoverMs: 150,
  stateMs: 200,
  panelMs: 280,
  lightMs: 600,
  copiedMs: 1500,
  shimmerS: 2.6,
  pressScale: 0.97,
  growS: 0.35,
  followS: 0.45,
  tailRoomPx: 20,
  blockHoldMs: 140,
  holdMs: 8000,
}

const EASE = [0.23, 1, 0.32, 1] as const

const INK_EASE = `cubic-bezier(${EASE.join(', ')})`

export type TokenStreamStatus = 'waiting' | 'writing' | 'done' | 'stopped'

export type TokenStreamProps = {
  markdown?: string
  status?: TokenStreamStatus
  waitingPhrases?: string[]
  wordsPerSecond?: number
  label?: string
  onStop?: () => void
  onContinue?: () => void
  onRetry?: () => void
  onFeedback?: (value: 'up' | 'down' | null) => void
  elapsedMs?: number
  className?: string
  tuning?: Partial<Tuning>
}

// A number stays on the same line as its unit.
const NBSP = String.fromCharCode(160)

const FENCE = '```'

const DEMO_MARKDOWN = [
  '### Rate limits',
  '',
  'Every request counts against a **per-key budget**. The budget refills on a rolling one-minute window, so a burst that fails at 12:00 can succeed at 12:01. Read `x-ratelimit-remaining` on every response.',
  '',
  '### What to do on a 429',
  '',
  '- Wait for the time in `retry-after`, not a fixed delay',
  '- Back off with jitter so parallel workers do not retry together',
  '- Stop after five attempts and surface the error',
  '',
  `${FENCE}ts`,
  'for (let attempt = 1; attempt <= 5; attempt++) {',
  '  const res = await fetch(url, init)',
  '  if (res.status !== 429) return res',
  "  const secs = Number(res.headers.get('retry-after') ?? 1)",
  '  await sleep(secs * 1000 + Math.random() * 250)',
  '}',
  FENCE,
  '',
  'With this in place the burst at 12:00 drains instead of failing.',
].join('\n')

const DEMO_PHRASES = [`Searching 4${NBSP}sources`, 'Reading the rate limit docs']

const NO_PHRASES: string[] = []

type TokenKind = 'keyword' | 'string' | 'number' | 'comment' | 'ident' | 'fn' | 'punct'

type Token = { text: string; kind: TokenKind }

type ScanState = { block: boolean; template: boolean }

const KEYWORDS = new Set([
  'abstract', 'any', 'as', 'async', 'await', 'bigint', 'boolean', 'break', 'case', 'catch',
  'class', 'const', 'continue', 'declare', 'default', 'delete', 'do', 'else', 'enum', 'export',
  'extends', 'finally', 'for', 'from', 'function', 'if', 'implements', 'import', 'in', 'infer',
  'instanceof', 'interface', 'is', 'keyof', 'let', 'never', 'new', 'number', 'object', 'of',
  'private', 'protected', 'public', 'readonly', 'return', 'satisfies', 'static', 'string',
  'super', 'switch', 'symbol', 'this', 'throw', 'try', 'type', 'typeof', 'unknown', 'var',
  'void', 'while', 'yield',
])

const LITERALS = new Set(['false', 'Infinity', 'NaN', 'null', 'true', 'undefined'])

function closingQuote(line: string, from: number, quote: string) {
  for (let i = from; i < line.length; i += 1) {
    if (line[i] === '\\') {
      i += 1
      continue
    }
    if (line[i] === quote) return i
  }
  return -1
}

function scanLine(line: string, state: ScanState, out: Token[]) {
  let i = 0
  while (i < line.length) {
    if (state.block || state.template) {
      const end = state.block ? line.indexOf('*/', i) : closingQuote(line, i, '`')
      const kind: TokenKind = state.block ? 'comment' : 'string'
      if (end === -1) {
        out.push({ text: line.slice(i), kind })
        return
      }
      const stop = state.block ? end + 2 : end + 1
      out.push({ text: line.slice(i, stop), kind })
      state.block = false
      state.template = false
      i = stop
      continue
    }
    const ch = line[i]
    if (ch === '/' && line[i + 1] === '/') {
      out.push({ text: line.slice(i), kind: 'comment' })
      return
    }
    if (ch === '/' && line[i + 1] === '*') {
      state.block = true
      out.push({ text: '/*', kind: 'comment' })
      i += 2
      continue
    }
    if (ch === '"' || ch === "'" || ch === '`') {
      const end = closingQuote(line, i + 1, ch)
      if (end === -1) {
        out.push({ text: line.slice(i), kind: 'string' })
        if (ch === '`') state.template = true
        return
      }
      out.push({ text: line.slice(i, end + 1), kind: 'string' })
      i = end + 1
      continue
    }
    if (/[0-9]/.test(ch)) {
      let j = i + 1
      while (j < line.length && /[0-9a-fA-FxXoObBn._]/.test(line[j])) j += 1
      out.push({ text: line.slice(i, j), kind: 'number' })
      i = j
      continue
    }
    if (/[A-Za-z_$]/.test(ch)) {
      let j = i + 1
      while (j < line.length && /[A-Za-z0-9_$]/.test(line[j])) j += 1
      const word = line.slice(i, j)
      let kind: TokenKind = 'ident'
      if (KEYWORDS.has(word)) kind = 'keyword'
      else if (LITERALS.has(word)) kind = 'number'
      else if (line[j] === '(' && /^[a-z_$]/.test(word)) kind = 'fn'
      out.push({ text: word, kind })
      i = j
      continue
    }
    let j = i + 1
    while (j < line.length && !/[A-Za-z0-9_$"'`/]/.test(line[j])) j += 1
    out.push({ text: line.slice(i, j), kind: 'punct' })
    i = j
  }
}

function tokenize(lines: string[]): Token[][] {
  const state: ScanState = { block: false, template: false }
  return lines.map((line) => {
    const out: Token[] = []
    scanLine(line, state, out)
    return out
  })
}

const TOKEN_CLASS: Record<TokenKind, string> = {
  keyword: 'text-(color:--ts-ai)',
  string: 'text-(color:--ts-success)',
  number: 'text-(color:--ts-attention)',
  comment: 'italic text-(color:--ts-muted)',
  ident: 'text-(color:--ts-text)',
  fn: 'font-semibold text-(color:--ts-text)',
  punct: 'text-(color:--ts-body)',
}

// A unit never splits, so a line break is set once and settled text never reflows.
type PartKind = 'text' | 'bold' | 'italic' | 'bolditalic' | 'code' | 'link'

type Part = { text: string; kind: PartKind; href?: string }

type Unit = Part[]

// sig: the block's content as one string, so a re-parse of the same text compares equal.
type TextBlock = {
  type: 'h' | 'p' | 'li' | 'oli'
  first: number
  count: number
  units: Unit[]
  level: number
  num: number
  sig: string
}

type RuleBlock = { type: 'hr'; first: number; count: 1; sig: string }

type Chunk = { line: number; from: number; to: number }

type CodeBlock = {
  type: 'code'
  first: number
  count: number
  lang: string
  lines: string[]
  tokens: Token[][]
  chunks: Chunk[]
  closed: boolean
  sig: string
}

type Block = TextBlock | RuleBlock | CodeBlock

type Doc = { blocks: Block[]; total: number; wordsUpTo: number[] }

const TICK = '`'

const WORD_CHAR = /[A-Za-z0-9]/

function addPart(unit: Unit, part: Part) {
  const last = unit[unit.length - 1]
  if (last && last.kind === part.kind && last.href === part.href && part.kind !== 'link')
    unit[unit.length - 1] = { ...last, text: last.text + part.text }
  else unit.push(part)
}

function styleOf(bold: boolean, italic: boolean): PartKind {
  if (bold) return italic ? 'bolditalic' : 'bold'
  return italic ? 'italic' : 'text'
}

// Only http(s) and relative addresses become links; any other scheme stays plain text.
function safeHref(raw: string): string | undefined {
  const first = raw.trim().split(/\s/)[0] ?? ''
  const href = Array.from(first)
    .filter((c) => c.charCodeAt(0) > 32)
    .join('')
  if (!href) return undefined
  if (/^https?:\/\//i.test(href)) return href
  if (/^[a-z][a-z0-9+.-]*:/i.test(href)) return undefined
  return href
}

// A link whose address has not closed shows its text alone, so brackets never flash.
function linkAt(s: string, i: number, tail: boolean): { part: Part; end: number } | null {
  const close = s.indexOf(']', i + 1)
  const pending = (text: string) => (tail ? { part: { text, kind: 'link' as const }, end: s.length } : null)
  if (close === -1) return pending(s.slice(i + 1))
  const text = s.slice(i + 1, close)
  if (close + 1 === s.length) return pending(text)
  if (s[close + 1] !== '(') return null
  const end = s.indexOf(')', close + 2)
  if (end === -1) return pending(text)
  return { part: { text, kind: 'link', href: safeHref(s.slice(close + 2, end)) }, end: end + 1 }
}

// tail: an open mark closes where the text ends, so half a mark never shows raw.
function inlineUnits(src: string, tail: boolean): Unit[] {
  const s = tail && src.endsWith('*') && !src.endsWith('**') ? src.slice(0, -1) : src
  const runs: Part[] = []
  let bold = false
  let italic = ''
  let buf = ''
  const flush = () => {
    if (buf) runs.push({ text: buf, kind: styleOf(bold, !!italic) })
    buf = ''
  }
  let i = 0
  while (i < s.length) {
    const ch = s[i]
    if (s.startsWith('**', i)) {
      flush()
      bold = !bold
      i += 2
      continue
    }
    if (ch === '*' || ch === '_') {
      const prev = s[i - 1] ?? ''
      const next = s[i + 1] ?? ''
      // An underscore inside a word (snake_case) is a letter, not a mark.
      const closes = italic === ch && prev !== '' && !/\s/.test(prev) && (ch === '*' || !WORD_CHAR.test(next))
      const opens = !italic && next !== '' && !/\s/.test(next) && (ch === '*' || !WORD_CHAR.test(prev))
      if (closes || opens) {
        flush()
        italic = closes ? '' : ch
        i += 1
        continue
      }
    }
    if (ch === TICK) {
      flush()
      const end = s.indexOf(TICK, i + 1)
      const code = end === -1 ? s.slice(i + 1) : s.slice(i + 1, end)
      if (code) runs.push({ text: code, kind: 'code' })
      i = end === -1 ? s.length : end + 1
      continue
    }
    if (ch === '[') {
      const link = linkAt(s, i, tail)
      if (link) {
        flush()
        if (link.part.text) runs.push(link.part)
        i = link.end
        continue
      }
    }
    buf += ch
    i += 1
  }
  flush()

  const units: Unit[] = []
  let cur: Unit | null = null
  let spaced = false
  for (const run of runs) {
    const whole = run.kind === 'code' || run.kind === 'link'
    const pieces = whole ? [run.text] : run.text.split(/(\s+)/).filter(Boolean)
    for (const piece of pieces) {
      if (!whole && /^\s+$/.test(piece)) {
        if (cur) {
          addPart(cur, { text: ' ', kind: run.kind })
          spaced = true
        }
        continue
      }
      if (!cur || spaced) {
        cur = []
        units.push(cur)
        spaced = false
      }
      addPart(cur, { ...run, text: piece })
    }
  }
  return units
}

function chunksOf(lines: string[]): Chunk[] {
  const out: Chunk[] = []
  lines.forEach((line, n) => {
    let first = true
    for (const m of line.matchAll(/\S+\s*/g)) {
      const at = m.index ?? 0
      out.push({ line: n, from: first ? 0 : at, to: at + m[0].length })
      first = false
    }
    if (first) out.push({ line: n, from: 0, to: line.length })
  })
  return out
}

const FENCE_OPEN = /^\s{0,3}```\s*([\w+-]*)\s*$/

const FENCE_CLOSE = /^\s{0,3}```\s*$/

const FENCE_PARTIAL = /^\s{0,3}`{1,2}$/

const MARK_PARTIAL = /^\s{0,3}(`{1,2}|#{1,6}|[-*+]|-{2}|\*{2}|_{1,2}|\d{1,9}[.)]?)\s*$/

const RULE = /^\s{0,3}([-*_])(?:\s*\1){2,}\s*$/

const HEAD = /^\s{0,3}(#{1,6})\s+(.*)$/

const ITEM = /^\s{0,3}[-*+]\s+(.*)$/

const ORDERED = /^\s{0,3}(\d{1,9})[.)]\s+(.*)$/

function parseDoc(src: string, open: boolean): Doc {
  const lines = src.replace(/\r\n?/g, '\n').split('\n')
  const lastLine = lines.length - 1
  const blocks: Block[] = []
  const isWord: boolean[] = []
  let next = 0
  let para: string[] = []
  let paraEnd = -1
  const pushText = (type: TextBlock['type'], text: string, tail: boolean, level = 0, num = 0) => {
    const units = inlineUnits(text, open && tail)
    if (!units.length) return
    const sig = JSON.stringify([type, next, level, num, units])
    blocks.push({ type, first: next, count: units.length, units, level, num, sig })
    units.forEach(() => isWord.push(true))
    next += units.length
  }
  const flush = () => {
    if (para.length) pushText('p', para.join(' '), paraEnd === lastLine)
    para = []
  }
  for (let i = 0; i < lines.length; i += 1) {
    const line = lines[i]
    const fence = FENCE_OPEN.exec(line)
    if (fence) {
      flush()
      const body: string[] = []
      let closed = false
      for (i += 1; i < lines.length; i += 1) {
        if (FENCE_CLOSE.test(lines[i])) {
          closed = true
          break
        }
        body.push(lines[i])
      }
      if (!closed && body.length && FENCE_PARTIAL.test(body[body.length - 1])) body.pop()
      const chunks = chunksOf(body)
      const count = 1 + chunks.length + (closed ? 1 : 0)
      const lang = fence[1] || 'text'
      blocks.push({
        type: 'code',
        first: next,
        count,
        lang,
        lines: body,
        tokens: tokenize(body),
        chunks,
        closed,
        sig: JSON.stringify(['code', next, lang, closed, body]),
      })
      isWord.push(false)
      chunks.forEach((c) => isWord.push(c.to > c.from))
      if (closed) isWord.push(false)
      next += count
      continue
    }
    if (i === lastLine && MARK_PARTIAL.test(line)) continue
    if (RULE.test(line)) {
      flush()
      blocks.push({ type: 'hr', first: next, count: 1, sig: `hr|${next}` })
      isWord.push(false)
      next += 1
      continue
    }
    const head = HEAD.exec(line)
    if (head) {
      flush()
      pushText('h', head[2], i === lastLine, head[1].length)
      continue
    }
    const item = ITEM.exec(line)
    if (item) {
      flush()
      pushText('li', item[1], i === lastLine)
      continue
    }
    const ordered = ORDERED.exec(line)
    if (ordered) {
      flush()
      pushText('oli', ordered[2], i === lastLine, 0, Number(ordered[1]))
      continue
    }
    if (!line.trim()) {
      flush()
      continue
    }
    para.push(line.trim())
    paraEnd = i
  }
  flush()
  const wordsUpTo = [0]
  isWord.forEach((w, i) => wordsUpTo.push(wordsUpTo[i] + (w ? 1 : 0)))
  return { blocks, total: next, wordsUpTo }
}

const MARK: Partial<Record<PartKind, string>> = { bold: '**', italic: '*', bolditalic: '***' }

function inlineText(units: Unit[]) {
  const runs: Part[] = []
  for (const unit of units)
    for (const p of unit) {
      const last = runs[runs.length - 1]
      if (last && last.kind === p.kind && p.kind !== 'code' && p.kind !== 'link')
        runs[runs.length - 1] = { ...last, text: last.text + p.text }
      else runs.push(p)
    }
  return runs
    .map((p) => {
      if (p.kind === 'code') return TICK + p.text + TICK
      if (p.kind === 'link') return p.href ? `[${p.text}](${p.href})` : p.text
      const mark = MARK[p.kind]
      if (!mark) return p.text
      const inner = p.text.trimEnd()
      return mark + inner + mark + p.text.slice(inner.length)
    })
    .join('')
    .trimEnd()
}

function docText(doc: Doc, shown: number) {
  let out = ''
  let prev: Block['type'] | null = null
  for (const b of doc.blocks) {
    if (b.first >= shown) break
    const local = Math.min(b.count, shown - b.first)
    let text: string
    if (b.type === 'code') {
      const lines: string[] = []
      b.chunks.slice(0, Math.max(0, local - 1)).forEach((c) => {
        lines[c.line] = (lines[c.line] ?? '') + b.lines[c.line].slice(c.from, c.to)
      })
      // A cut-short block still closes its fence, so the copy pastes as valid markdown.
      text = [FENCE + (b.lang === 'text' ? '' : b.lang), ...Array.from(lines, (l) => (l ?? '').trimEnd()), FENCE].join('\n')
    } else if (b.type === 'hr') {
      text = '---'
    } else {
      const inline = inlineText(b.units.slice(0, local))
      if (b.type === 'h') text = `${'#'.repeat(b.level)} ${inline}`
      else if (b.type === 'li') text = `- ${inline}`
      else if (b.type === 'oli') text = `${b.num}. ${inline}`
      else text = inline
    }
    const tight = prev === b.type && (b.type === 'li' || b.type === 'oli')
    out += (out ? (tight ? '\n' : '\n\n') : '') + text
    prev = b.type
  }
  return out
}

type Pace = { word: number; comma: number; sentence: number; block: number; fence: number; line: number; jitter: number }

function wobble(i: number) {
  const r = Math.sin((i + 1) * 12.9898) * 43758.5453
  return (r - Math.floor(r)) * 2 - 1
}

function scheduleOf(doc: Doc, p: Pace): number[] {
  const at: number[] = []
  let time = 0
  let k = 0
  const beat = (len: number) => p.word * (1 + p.jitter * wobble(k++)) * (0.82 + 0.035 * Math.min(10, len))
  for (const b of doc.blocks) {
    if (b.type === 'code') {
      at.push(time)
      time += p.fence
      b.chunks.forEach((c, j) => {
        at.push(time)
        time += beat(c.to - c.from)
        const nextChunk = b.chunks[j + 1]
        if (!nextChunk || nextChunk.line !== c.line) time += p.line
      })
      if (b.closed) at.push(time)
      time += p.block
      continue
    }
    if (b.type === 'hr') {
      at.push(time)
      time += p.block
      continue
    }
    b.units.forEach((u) => {
      at.push(time)
      const word = u.map((part) => part.text).join('').trimEnd()
      time += beat(word.length)
      if (/[.!?]$/.test(word)) time += p.sentence
      else if (/[,;:]$/.test(word)) time += p.comma
    })
    time += p.block
  }
  return at
}

function chunkedSchedule(total: number, chunk: number, stepMs: number): number[] {
  return Array.from({ length: total }, (_, i) => Math.floor(i / Math.max(1, chunk)) * stepMs)
}

function phraseStart(k: number, firstMs: number, stepMs: number) {
  return k === 0 ? 0 : firstMs + (k - 1) * stepMs
}

function phraseIndex(ms: number, n: number, firstMs: number, stepMs: number) {
  let k = 0
  while (k + 1 < n && phraseStart(k + 1, firstMs, stepMs) <= ms) k += 1
  return k
}

const THEME_VARS = [
  '[--ts-page:#EEEEF3] dark:[--ts-page:#0E0E0F]',
  '[--ts-panel:#F4F4FA] dark:[--ts-panel:#1B1B1C]',
  '[--ts-well:#EEEEF3] dark:[--ts-well:#0E0E0F]',
  '[--ts-raised:#DFDFE3] dark:[--ts-raised:#2D2D2E]',
  '[--ts-raised-hover:#CACACD] dark:[--ts-raised-hover:#373738]',
  '[--ts-border:#DFDFE3] dark:[--ts-border:#2D2D2E]',
  '[--ts-border-strong:#CACACD] dark:[--ts-border-strong:#373738]',
  '[--ts-hairline:#DFDFE3] dark:[--ts-hairline:#2D2D2E]',
  '[--ts-rim:#CACACD] dark:[--ts-rim:#F4F4FA2E]',
  '[--ts-text:#1B1B1C] dark:[--ts-text:#F4F4FA]',
  '[--ts-body:#373738] dark:[--ts-body:#CACACD]',
  '[--ts-muted:#575759] dark:[--ts-muted:#9B9B9E]',
  '[--ts-faint:#7B7B7D]',
  '[--ts-selection:#A0A0A233] dark:[--ts-selection:#5E5E6333]',
  '[--ts-success:#047857] dark:[--ts-success:#34D399]',
  '[--ts-ai:#0369A1] dark:[--ts-ai:#7DD3FC]',
  '[--ts-attention:#B45309] dark:[--ts-attention:#FFB574]',
  '[--ts-red:#C8262C] dark:[--ts-red:#E5484D]',
  '[--ts-primary:#1B1B1C] dark:[--ts-primary:#F4F4FA]',
  '[--ts-primary-hover:#373738] dark:[--ts-primary-hover:#FFFFFF]',
  '[--ts-on-primary:#F4F4FA] dark:[--ts-on-primary:#0E0E0F]',
  '[--ts-focus:#1B1B1C99] dark:[--ts-focus:#F4F4FA99]',
  '[--ts-focus-gap:#F4F4FA] dark:[--ts-focus-gap:#1B1B1C]',
  '[--ts-dot:#1B1B1C] dark:[--ts-dot:#F4F4FA]',
  '[--ts-elev-card:0_2px_6px_rgba(0,0,0,0.06),0_28px_56px_-16px_rgba(0,0,0,0.25)] dark:[--ts-elev-card:0_2px_6px_rgba(0,0,0,0.5),0_36px_72px_-18px_rgba(0,0,0,0.9)]',
  '[--ts-elev-1:0_1px_2px_rgba(0,0,0,0.08)] dark:[--ts-elev-1:0_1px_2px_rgba(0,0,0,0.5)]',
].join(' ')

// Padding lives on the measured inner box, so the card's height can follow it.
const CARD =
  'relative w-full overflow-hidden rounded-[24px] border border-(color:--ts-border) bg-(--ts-panel) shadow-(--ts-elev-card)'

const CARD_PAD = 'p-4 min-[400px]:p-5'

const FOOTER_PAD = 'mx-4 mb-4 min-[400px]:mx-5 min-[400px]:mb-5'

const NO_FLOW = { lead: 0, step: 0 }

const WELL = 'rounded-2xl border border-(color:--ts-border) bg-(--ts-well)'

const TITLE = 'min-w-0 truncate text-[15px] leading-6 font-semibold text-(color:--ts-text)'

const META = 'shrink-0 text-[12px] leading-4 tabular-nums text-(color:--ts-muted)'

const FOCUS =
  'outline-none focus-visible:ring-2 focus-visible:ring-(color:--ts-focus) focus-visible:ring-offset-2 focus-visible:ring-offset-(color:--ts-focus-gap)'

// A scroll box clips an offset ring, so its ring draws inward.
const FOCUS_INSET = 'outline-none focus-visible:ring-2 focus-visible:ring-inset focus-visible:ring-(color:--ts-focus)'

const HIT_BASE = "relative pointer-coarse:after:absolute pointer-coarse:after:content-['']"

const HIT_ICON = `${HIT_BASE} pointer-coarse:after:-inset-1.5`

const HIT_ROW = `${HIT_BASE} pointer-coarse:after:-inset-y-1.5 min-[360px]:pointer-coarse:after:-inset-x-1.5 max-[359px]:pointer-coarse:after:-inset-x-1`

const ROW_GAP = 'gap-1 min-[360px]:pointer-coarse:gap-3 max-[359px]:pointer-coarse:gap-2'

const BTN = `${FOCUS} inline-flex h-8 shrink-0 items-center justify-center gap-1.5 rounded-full px-4 text-[12px] leading-4 font-semibold transition-[background-color,color,border-color,box-shadow] duration-150 disabled:opacity-50`

const BTN_PRIMARY = `${BTN} bg-(--ts-primary) text-(color:--ts-on-primary) shadow-(--ts-elev-1) hover:bg-(--ts-primary-hover)`

// Opaque, so the dots behind the footer never show through the label.
const BTN_SECONDARY = `${BTN} border border-(color:--ts-border-strong) bg-(--ts-panel) text-(color:--ts-text) hover:bg-(--ts-raised)`

const BTN_GHOST = `${BTN} text-(color:--ts-muted) hover:bg-(--ts-raised) hover:text-(color:--ts-text)`

const BTN_ICON = `${FOCUS} inline-grid size-8 shrink-0 place-items-center rounded-full text-(color:--ts-muted) transition-[background-color,color] duration-150 hover:bg-(--ts-raised) hover:text-(color:--ts-text)`

type Tone = 'neutral' | 'ai' | 'attention' | 'success' | 'red'

const TONE_VAR: Record<Tone, string> = {
  neutral: 'var(--ts-dot)',
  ai: 'var(--ts-ai)',
  attention: 'var(--ts-attention)',
  success: 'var(--ts-success)',
  red: 'var(--ts-red)',
}

const TONE_STRENGTH: Record<Tone, number> = { neutral: 6, ai: 14, attention: 14, success: 10, red: 12 }

const REDUCED_QUERY = '(prefers-reduced-motion: reduce)'

function subscribeReduced(onChange: () => void) {
  if (typeof window === 'undefined' || !window.matchMedia) return () => {}
  const mq = window.matchMedia(REDUCED_QUERY)
  mq.addEventListener('change', onChange)
  return () => mq.removeEventListener('change', onChange)
}

function getReduced() {
  return typeof window !== 'undefined' && !!window.matchMedia && window.matchMedia(REDUCED_QUERY).matches
}

function getReducedServer() {
  return false
}

function plural(n: number, word: string) {
  return `${n}${NBSP}${word}${n === 1 ? '' : 's'}`
}

function fmtDuration(ms: number) {
  const s = ms / 1000
  if (s < 60) return `${s.toFixed(1)}s`
  const whole = Math.round(s)
  return `${Math.floor(whole / 60)}m${NBSP}${String(whole % 60).padStart(2, '0')}s`
}

function legacyCopy(text: string) {
  // Selecting the scratch field moves focus; hand it back to whatever held it.
  const prev = document.activeElement instanceof HTMLElement ? document.activeElement : null
  const area = document.createElement('textarea')
  area.value = text
  area.setAttribute('readonly', '')
  area.style.position = 'fixed'
  area.style.opacity = '0'
  document.body.appendChild(area)
  area.select()
  let ok = false
  try {
    ok = document.execCommand('copy')
  } catch {
    ok = false
  }
  area.remove()
  prev?.focus({ preventScroll: true })
  return ok
}

// An embedded frame may refuse the clipboard API; the selection copy still works there.
function copyText(text: string): Promise<boolean> {
  if (typeof navigator === 'undefined' || !navigator.clipboard) return Promise.resolve(legacyCopy(text))
  return navigator.clipboard.writeText(text).then(
    () => true,
    () => legacyCopy(text),
  )
}

function useCopied(ms: number) {
  const [copied, setCopied] = useState(0)
  useEffect(() => {
    if (!copied) return
    const id = window.setTimeout(() => setCopied(0), ms)
    return () => window.clearTimeout(id)
  }, [copied, ms])
  return [copied > 0, () => setCopied((n) => n + 1)] as const
}

type Mode = TokenStreamStatus

type Feedback = 'up' | 'down' | null

const LIVE_LINE: Record<Mode, string> = {
  waiting: 'Working on an answer',
  writing: 'Writing an answer',
  done: 'Answer ready',
  stopped: 'Stopped',
}

/**
 * @typedef {object} TokenStreamProps
 * @property {string} [markdown] Supplies the answer parsed and revealed as Markdown; left out, the demo uses sample text and host mode uses an empty answer, while passing it turns the demo off.
 * @property {TokenStreamStatus} [status] Controls waiting, writing, done or stopped presentation; left out, host mode infers done from nonempty Markdown and waiting otherwise, while passing it turns the demo off.
 * @property {string[]} [waitingPhrases] Supplies rotating work messages before the answer; left out, the demo uses sample messages and host mode shows none, while passing it turns the demo off.
 * @property {number} [wordsPerSecond] Sets a positive reveal speed; left out or nonpositive, the tuned word timing is used.
 * @property {string} [label] Adds metadata text to the answer header; left out, no label is shown, while passing it turns the demo off.
 * @property {() => void} [onStop] Handles stopping and makes the stop control available during host writing; left out, host streams have no stop control.
 * @property {() => void} [onContinue] Handles continuing and makes the Continue control available after a host stop; left out, host stopped answers have no Continue control.
 * @property {() => void} [onRetry] Handles retrying and makes retry controls available in host mode; left out, host answers have no retry controls.
 * @property {(value: 'up'|'down'|null) => void} [onFeedback] Reports the current rating while rating state remains local; left out, rating controls still update locally.
 * @property {number} [elapsedMs] Shows how long a host answer took in milliseconds; left out, no host duration is shown, while passing it turns the demo off.
 * @property {string} [className] Adds classes to the outermost root; left out, only the built-in classes are used.
 * @property {Partial<Tuning>} [tuning] Overrides stream measurements, timing and motion values; left out, every value in TUNING is used.
 */

type AnswerCardProps = {
  doc: Doc
  phrases: string[]
  label?: string
  reduce: boolean
  t: Tuning
  ghost: boolean
  mode: Mode
  tone: Tone
  shown: number
  wordMs: number
  words: number
  tookMs: number | null
  feedback: Feedback
  phraseStartAt: number
  runKey: number
  segKey?: number
  stopRef?: React.RefObject<HTMLButtonElement | null>
  continueRef?: React.RefObject<HTMLButtonElement | null>
  copyRef?: React.RefObject<HTMLButtonElement | null>
  onStop?: () => void
  onContinue?: () => void
  onRetry?: () => void
  onRate?: (up: boolean) => void
  onCopyAnswer?: (done: () => void) => void
  onCopyCode?: (code: string, done: () => void) => void
}

function gapBefore(prev: Block['type'] | null, cur: Block['type']) {
  if (prev === null) return ''
  if (cur === 'h') return 'mt-5'
  if (cur === 'hr' || prev === 'hr') return 'mt-4'
  if (prev === 'h') return 'mt-2'
  if (cur === 'li' || cur === 'oli') return prev === cur ? '' : 'mt-2'
  return 'mt-3'
}

type InkProps = { inkMs: number; risePx: number }

function useInk<T extends HTMLElement>(delay: number, inkMs: number, risePx: number) {
  const ref = useRef<T>(null)
  const atMount = useRef({ delay, inkMs, risePx })
  useLayoutEffect(() => {
    const el = ref.current
    const { delay: wait, inkMs: ms, risePx: rise } = atMount.current
    if (!el || wait < 0 || typeof el.animate !== 'function') return
    const a = el.animate(
      [
        { opacity: 0, transform: `translateY(${rise}px)` },
        { opacity: 1, transform: 'none' },
      ],
      { duration: ms, delay: wait, easing: INK_EASE, fill: 'backwards' },
    )
    return () => a.cancel()
  }, [])
  return ref
}

// These compare content, so settled blocks skip renders when a controlled answer grows.
function sameUnit(a: Unit, b: Unit) {
  return (
    a === b ||
    (a.length === b.length &&
      a.every((p, i) => p.text === b[i].text && p.kind === b[i].kind && p.href === b[i].href))
  )
}

function sameTokens(a: Token[], b: Token[]) {
  return a === b || (a.length === b.length && a.every((tok, i) => tok.text === b[i].text && tok.kind === b[i].kind))
}

function sameBlockProps<P extends { block: { sig: string } }>(a: Readonly<P>, b: Readonly<P>) {
  const keys = Object.keys(a) as (keyof P)[]
  if (keys.length !== Object.keys(b).length) return false
  return keys.every((k) => (k === 'block' ? a.block.sig === b.block.sig : Object.is(a[k], b[k])))
}

type BlockEl = HTMLHeadingElement & HTMLLIElement & HTMLParagraphElement
````

## Related

- [Agent Status](https://aicanvas.me/components/agent-status.md): A status pill that says what the agent is doing, whose move it is, time and cost, and opens to the step history and token bill.
- [Cited Answer](https://aicanvas.me/components/source-rail.md): An answer with numbered citations: pick a number or a source to see the quoted passage and whether it really backs the sentence.
- [Agent Composer](https://aicanvas.me/components/agent-composer.md): The message input an agent sits behind: a textarea that grows to six rows, inline slash commands, @file mentions as removable chips, a drag-and-drop attachment row, a model picker with each provider's logo, and a round send button whose glyph becomes a pulsing stop square while the agent works.
- [Thinking Trace](https://aicanvas.me/components/reasoning-trace.md): A single steady line shows what an agent is thinking right now, then settles into how long it thought, with every step one click away.
- [Checkpoint](https://aicanvas.me/components/agent-checkpoint.md): An agent checkpoint card that pauses for a decision on a question, command or plan, then collapses into a one-line receipt with undo, edit-before-allow and a risk grade.