---
format: typebulb/v1
name: Chat
---

**code.tsx**

```tsx
import React, { useState, useEffect, useRef } from "react";
import { createRoot } from "react-dom/client";

interface Message {
  role: "user" | "assistant";
  content: string;
  reasoning?: string;
  model?: string;
  error?: boolean;
}

interface Model {
  provider: string;
  name: string;
  friendlyName: string;
  default?: boolean;
}

const fmtK = (n: number) => (n >= 1000 ? `${(n / 1000).toFixed(1)}k` : String(n));

// Streaming: a live clip pinned to the newest lines. Finished: collapsed, expandable to re-read.
function Thinking({ text, streaming }: { text?: string; streaming?: boolean }) {
  if (!text?.trim()) return null;
  if (streaming) {
    return (
      <div className="think-live">
        <span className="think-pulse">Thinking…</span>
        <div className="think-clip"><div>{text}</div></div>
      </div>
    );
  }
  return (
    <details className="think">
      <summary>Thought · {fmtK(text.length)} chars</summary>
      <div className="think-body">{text}</div>
    </details>
  );
}

function ModelOptions({ models }: { models: Model[] }) {
  const groups = models.reduce((g: Record<string, Model[]>, m) => { (g[m.provider] ??= []).push(m); return g; }, {});
  return <>{Object.entries(groups).map(([provider, ms]) => (
    <optgroup key={provider} label={provider}>{ms.map(m => <option key={m.name} value={m.name}>{m.friendlyName}</option>)}</optgroup>
  ))}</>;
}

function App() {
  const [models, setModels] = useState<Model[]>([]);
  const [model, setModel] = useState<Model | null>(null);
  const [system, setSystem] = useState("You are a helpful assistant.");
  const [editingSystem, setEditingSystem] = useState(false);
  // "default" = omit the effort param entirely (vendor default — on some models, e.g. Opus 4.8,
  // that means no thinking at all; the resolved level is provider-dependent).
  const [effort, setEffort] = useState<number | "default">(1);
  const [messages, setMessages] = useState<Message[]>([]);
  const [input, setInput] = useState("");
  const [isLoading, setIsLoading] = useState(false);
  const [access, setAccess] = useState<AiAccess>("own");
  const scrollRef = useRef<HTMLDivElement>(null);
  const inputRef = useRef<HTMLTextAreaElement>(null);
  const stopRef = useRef(false);

  useEffect(() => {
    async function load() {
      const available = await tb.models();
      setModels(available);
      if (available.length > 0) setModel(available.find(m => m.default) ?? available[0]);
      setAccess(await tb.aiAccess());
    }
    load();
  }, []);

  useEffect(() => {
    if (scrollRef.current) {
      scrollRef.current.scrollTop = scrollRef.current.scrollHeight;
    }
  }, [messages]);

  const run = async (history: Message[]) => {
    if (!model || isLoading) return;
    const reply: Message = { role: "assistant", content: "", model: model.friendlyName };
    setMessages([...history, reply]);
    setIsLoading(true);
    stopRef.current = false;

    try {
      let answer = "";
      let reasoning = "";
      for await (const c of tb.ai.stream({
        provider: model.provider,
        model: model.name,
        webSearch: false,   // provider default ADDS a web_search tool; opt out so calls match the identity-probe batches
        system,
        ...(effort === "default" ? {} : { effort: effort as 0 | 1 | 2 | 3 }),
        messages: history.map(({ role, content }) => ({ role, content }))
      })) {
        if (stopRef.current) break;   // breaking the loop aborts the stream
        if (c.kind === "reasoning") reasoning += c.text;
        else answer += c.text;
        setMessages([...history, { ...reply, content: answer, reasoning }]);
      }
    } catch (error: any) {
      setMessages([...history, { ...reply, content: `⚠ ${error?.message ?? error}`, error: true }]);
    } finally {
      setIsLoading(false);
      inputRef.current?.focus();
    }
  };

  const send = () => {
    const text = input.trim();
    if (!text || !model || isLoading) return;
    setInput("");
    run([...messages, { role: "user", content: text }]);
  };

  // Wind the conversation back to message i: a user message returns to the composer for editing,
  // an assistant one is dropped and re-run from the history before it.
  const rewind = (i: number) => {
    if (isLoading) return;
    const target = messages[i];
    if (target.role === "user") {
      setMessages(messages.slice(0, i));
      setInput(target.content);
      inputRef.current?.focus();
    } else {
      run(messages.slice(0, i));
    }
  };

  const onKeyDown = (e: React.KeyboardEvent) => {
    if (e.key === "Enter" && !e.shiftKey) {
      e.preventDefault();
      send();
    }
  };

  const resetChat = () => setMessages([]);

  return (
    <div className="app">
      <header>
        <span className="brand">Chat</span>
        <select className="model-pick" title="Model" value={model?.name || ""} onChange={e => {
          const selected = models.find(m => m.name === e.target.value);
          if (selected) setModel(selected);
        }}>
          <ModelOptions models={models} />
        </select>
        <select title="Reasoning effort — Default sends no effort param (provider decides)" value={effort}
          onChange={e => setEffort(e.target.value === "default" ? "default" : +e.target.value)}>
          <option value="default">Default</option>
          <option value={0}>Minimal</option>
          <option value={1}>Low</option>
          <option value={2}>Med</option>
          <option value={3}>High</option>
        </select>
        <button className="ghost" onClick={resetChat} disabled={messages.length === 0}>Reset</button>
      </header>

      {access === "none" && (
        <div className="keys-note">
          No API keys found — set a provider key in <code>.env</code> to chat.
        </div>
      )}

      <div className="messages" ref={scrollRef}>
        <div className="col">
          <div className="msg system">
            <div className="model-tag sys-tag">
              <span>System</span>
              <button className="link" onClick={() => setEditingSystem(e => !e)}>{editingSystem ? "done" : "edit"}</button>
              <button className="link" onClick={() => setSystem("")} disabled={!system}>clear</button>
            </div>
            {editingSystem ? (
              <textarea
                autoFocus
                value={system}
                onChange={e => setSystem(e.target.value)}
                onKeyDown={e => { if (e.key === "Escape") setEditingSystem(false); }}
                placeholder="System instructions…"
              />
            ) : (
              <div className="system-text" onClick={() => setEditingSystem(true)}>{system || "No system prompt."}</div>
            )}
          </div>
          {messages.length === 0 && (
            <div className="empty-state">Say something to start the conversation.</div>
          )}
          {messages.map((m, i) => {
            const streaming = isLoading && i === messages.length - 1;
            return m.role === "user" ? (
              <div key={i} className="msg user">
                <button className="rewind" title="Rewind to here — puts this message back in the composer"
                  onClick={() => rewind(i)} disabled={isLoading}>↩</button>
                <div className="bubble">{m.content}</div>
              </div>
            ) : (
              <div key={i} className="msg assistant">
                <div className="model-tag">
                  <span>{m.model ?? "Assistant"}</span>
                  <button className="rewind" title="Rewind to here — re-runs this reply"
                    onClick={() => rewind(i)} disabled={isLoading}>↻</button>
                </div>
                <Thinking text={m.reasoning} streaming={streaming} />
                <div className="content">{m.content || (streaming ? <span className="cursor" /> : "…")}</div>
                {m.error && !isLoading && i === messages.length - 1 && (
                  <button className="retry" onClick={() => rewind(i)}>↻ Retry</button>
                )}
              </div>
            );
          })}
        </div>
      </div>

      <div className="composer">
        <div className="composer-box">
          <textarea
            ref={inputRef}
            rows={1}
            placeholder={model ? "Message… (Enter to send, Shift+Enter for newline)" : "Loading models…"}
            value={input}
            onChange={e => setInput(e.target.value)}
            onKeyDown={onKeyDown}
            disabled={!model}
          />
          {isLoading ? (
            <button className="send" title="Stop" onClick={() => { stopRef.current = true; }}>■</button>
          ) : (
            <button className="send" title="Send" onClick={send} disabled={!model || !input.trim()}>↑</button>
          )}
        </div>
      </div>
    </div>
  );
}

const container = document.getElementById("root");

const root = createRoot(container!);

root.render(<App />);
```
**styles.css**

```css
:root {
  --bg: #ffffff;
  --text: #1c1c1e;
  --muted: #6e6e78;
  --border: #e4e4e7;
  --accent: #2563eb;
  --user-bg: #f1f3f6;
  --raise: #fafafa;
}

html[data-theme="dark"] {
  --bg: #151517;
  --text: #ececf1;
  --muted: #9d9da7;
  --border: #2c2c31;
  --accent: #4f8ef7;
  --user-bg: #26262b;
  --raise: #1b1b1e;
}

body {
  margin: 0;
  font: 15px/1.55 system-ui, -apple-system, "Segoe UI", sans-serif;
  background: var(--bg);
  color: var(--text);
  height: 100dvh;
  overflow: hidden;
}

#root { height: 100%; }

.app {
  display: flex;
  flex-direction: column;
  height: 100%;
}

header {
  width: 100%;
  max-width: 760px;
  margin: 0 auto;
  box-sizing: border-box;
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
  padding: 8px 14px;
}

.brand { font-weight: 650; margin-right: 4px; }

header select {
  font: inherit;
  font-size: 13.5px;
  padding: 4px 6px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--bg);
  color: var(--text);
  min-width: 0;
  max-width: 42ch;
}

.ghost {
  font: inherit;
  font-size: 13.5px;
  padding: 4px 12px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: transparent;
  color: var(--muted);
  cursor: pointer;
}

.ghost:disabled { opacity: 0.4; cursor: default; }

.keys-note {
  padding: 6px 14px;
  font-size: 13.5px;
  text-align: center;
  color: var(--muted);
}

.messages {
  flex: 1;
  overflow-y: auto;
  padding: 20px 14px;
}

.messages .col {
  max-width: 760px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.msg { animation: rise 0.18s ease-out; }

@keyframes rise {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: none; }
}

.msg.user {
  align-self: flex-end;
  max-width: 80%;
  display: flex;
  align-items: center;
  gap: 6px;
}

.msg.user .bubble {
  min-width: 0;
  background: var(--user-bg);
  padding: 8px 14px;
  border-radius: 16px 16px 4px 16px;
  white-space: pre-wrap;
}

/* Wind-back handle on every message — revealed on hover, out of the way otherwise */
.rewind {
  flex-shrink: 0;
  padding: 0 2px;
  border: none;
  background: none;
  font: inherit;
  font-size: 13px;
  line-height: 1;
  color: var(--muted);
  cursor: pointer;
  opacity: 0;
  transition: opacity 0.12s;
}

.msg:hover .rewind:not(:disabled), .rewind:focus-visible { opacity: 1; }

@media (hover: none) { .rewind:not(:disabled) { opacity: 0.6; } }

/* The system prompt, shown as the conversation's implicit first message */
.msg.system { color: var(--muted); }

.system-text { white-space: pre-wrap; cursor: text; }

.msg.system textarea {
  width: 100%;
  box-sizing: border-box;
  min-height: 64px;
  resize: vertical;
  font: inherit;
  padding: 6px 10px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--raise);
  color: var(--text);
}

.link {
  font: inherit;
  font-size: 12.5px;
  padding: 0;
  border: none;
  background: none;
  color: var(--accent);
  cursor: pointer;
}

.link:disabled { color: var(--muted); cursor: default; }

.model-tag {
  display: flex;
  align-items: baseline;
  gap: 8px;
  font-size: 12.5px;
  color: var(--muted);
  margin-bottom: 2px;
}

.sys-tag { gap: 10px; }

.content { white-space: pre-wrap; }

.retry {
  margin-top: 6px;
  font: inherit;
  font-size: 13.5px;
  padding: 4px 12px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: transparent;
  color: var(--muted);
  cursor: pointer;
}

.cursor {
  display: inline-block;
  width: 8px;
  height: 1em;
  background: var(--muted);
  vertical-align: text-bottom;
  animation: blink 1s steps(2) infinite;
}

@keyframes blink { 50% { opacity: 0; } }

/* Reasoning streaming in: a clip pinned to the newest lines, fading out at the top */
.think-live { margin: 2px 0 8px; }

.think-pulse {
  font-size: 12.5px;
  color: var(--muted);
  animation: pulse 1.4s ease-in-out infinite;
}

@keyframes pulse { 50% { opacity: 0.35; } }

.think-clip {
  max-height: 108px;
  overflow: hidden;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;   /* content taller than the clip overflows at the top */
  margin-top: 4px;
  mask-image: linear-gradient(to bottom, transparent, black 32px);
}

.think-clip > div {
  font-size: 13px;
  line-height: 1.5;
  color: var(--muted);
  white-space: pre-wrap;
}

/* Collapsed thinking transcript on a finished reply */
.think { margin: 2px 0 8px; }

.think > summary {
  cursor: pointer;
  width: fit-content;
  font-size: 12.5px;
  color: var(--muted);
  list-style: none;
}

.think > summary::-webkit-details-marker { display: none; }

.think > summary::before { content: "▸ "; }

.think[open] > summary::before { content: "▾ "; }

.think-body {
  margin-top: 6px;
  max-height: 240px;
  overflow-y: auto;
  font-size: 13px;
  line-height: 1.55;
  color: var(--muted);
  white-space: pre-wrap;
  border-left: 2px solid var(--border);
  padding-left: 10px;
}

.empty-state {
  text-align: center;
  margin-top: 10vh;
  color: var(--muted);
}

.composer { padding: 8px 14px 14px; }

.composer-box {
  max-width: 760px;
  margin: 0 auto;
  display: flex;
  align-items: flex-end;
  gap: 8px;
  padding: 6px 6px 6px 12px;
  border: 1px solid var(--border);
  border-radius: 14px;
  background: var(--raise);
}

.composer-box:focus-within { border-color: var(--accent); }

.composer-box textarea {
  flex: 1;
  min-width: 0;
  border: none;
  outline: none;
  background: transparent;
  color: inherit;
  font: inherit;
  resize: none;
  padding: 6px 0;
  max-height: 180px;
  field-sizing: content;   /* grows with input where supported */
}

.send {
  width: 34px;
  height: 34px;
  flex-shrink: 0;
  display: grid;
  place-items: center;
  border: none;
  border-radius: 50%;
  background: var(--accent);
  color: #fff;
  font-size: 16px;
  cursor: pointer;
}

.send:disabled { opacity: 0.35; cursor: default; }

@media (max-width: 640px) {
  .msg.user { max-width: 92%; }
  header select.model-pick { max-width: 24ch; }
}
```
**index.html**

```html
<div id="root"></div>
```
**config.json**

```json
{
  "description": "Basic chat with an AI model of your choice — streaming replies, editable system prompt.",
  "dependencies": {
    "react": "^19.2.4",
    "react-dom": "^19.2.4"
  }
}
```