claudecast

1// claudecast mod: broadcasts this session live to viewers over a public URL.
2//
3// The claudecast Rust binary runs a local HTTP server (viewer page + feed) and
4// the Cloudflare tunnel. This mod replaces the old MCP server and settings hooks:
5//   /cast, /cast-stop, /cast-viewers  user commands (no Claude turn needed)
6//   prompt.submit                    broadcast user messages + surface viewer questions
7//   tool.call                        broadcast tool calls and their results
8//   turn.complete                    broadcast assistant responses
9//
10// Module state is shared between the hooks of this session.
11
12const MAX_OUTPUT = 4000
13
14let active = false // this session is broadcasting
15let base = 'http://127.0.0.1:3000'
16let binary = 'claudecast'
17let port = 3000
18
19export function register(on, options = {}) {
20  port = options.port ?? 3000
21  binary = options.binaryPath ?? 'claudecast'
22  base = 'http://127.0.0.1:' + port
23
24  on('session.start', async ($, e, next) => {
25    await $.command.register({
26      name: 'cast',
27      description: 'Start broadcasting this session live and show the public viewer URL',
28      immediate: true,
29    })
30    await $.command.register({
31      name: 'cast-stop',
32      description: 'Stop the live broadcast and disconnect all viewers',
33      immediate: true,
34    })
35    await $.command.register({
36      name: 'cast-viewers',
37      description: 'Show how many viewers are watching the live cast',
38      immediate: true,
39    })
40    return next(e)
41  })
42
43  on('command.run', { command: 'cast' }, async ($) => {
44    let up
45    try {
46      up = await ensureServer($)
47    } catch (err) {
48      return { text: 'claudecast: ' + err + '. ' + spawnHelp() }
49    }
50    if (!up) {
51      return { text: 'claudecast: server did not come up on ' + base + '. ' + spawnHelp() }
52    }
53    let start
54    try {
55      start = await post($, '/cast/start', {})
56    } catch (err) {
57      return { text: 'claudecast: failed to start the cast: ' + err }
58    }
59    const url = start.public_url || ''
60    if (!url) {
61      return {
62        text:
63          'claudecast: no tunnel URL. Is cloudflared installed? ' +
64          '(brew install cloudflare/cloudflare/cloudflared)',
65      }
66    }
67    active = true
68    $.ui.status('claudecast live · ' + url)
69    return {
70      text:
71        '[claudecast active — public URL: ' + url + ']\n' +
72        'Share this URL with your audience. User messages, tool calls and your responses are ' +
73        'broadcast automatically from now on. Viewer questions are injected into your context ' +
74        'at the start of each turn — treat them as part of the conversation when relevant.',
75    }
76  })
77
78  on('command.run', { command: 'cast-stop' }, async ($) => {
79    if (!active) return { text: 'No active cast. Run /cast to start one.' }
80    try {
81      await post($, '/cast/stop', {})
82    } catch (err) {
83      return { text: 'claudecast: stop failed: ' + err }
84    }
85    active = false
86    $.ui.status(undefined)
87    return { text: 'claudecast stopped. Viewers have been disconnected.' }
88  })
89
90  on('command.run', { command: 'cast-viewers' }, async ($) => {
91    if (!active) return { text: 'No active cast. Run /cast to start one.' }
92    let status
93    try {
94      status = await get($, '/status')
95    } catch (err) {
96      return { text: 'claudecast: server unreachable: ' + err }
97    }
98    const n = status.viewer_count ?? 0
99    const url = status.public_url || base
100    return { text: n + (n === 1 ? ' viewer' : ' viewers') + ' watching · ' + url }
101  })
102
103  // Broadcast the user's message, then surface pending viewer questions as
104  // context only Claude reads — the questions leave the queue once surfaced.
105  on('prompt.submit', async ($, e, next) => {
106    if (!active) return next(e)
107    try {
108      await post($, '/user-message', { text: e.text })
109    } catch {
110      // Broadcasting must never block the prompt.
111    }
112    let questions = []
113    try {
114      questions = await get($, '/pending-questions')
115    } catch {
116      // No questions to surface.
117    }
118    if (Array.isArray(questions) && questions.length > 0) {
119      const block =
120        'Viewer questions from the audience watching this session live ' +
121        '(answer them as part of your reply when relevant):\n' +
122        questions.map((q) => '- ' + q).join('\n')
123      return next({ ...e, context: [...(e.context ?? []), block] })
124    }
125    return next(e)
126  })
127
128  // Broadcast every tool call after it runs, with the result the model reads.
129  on('tool.call', async ($, e, next) => {
130    if (!active) return next(e)
131    const result = await next(e)
132    try {
133      const input = {}
134      for (const [key, value] of Object.entries(e)) {
135        if (key !== 'tool' && key !== 'tool_use_id' && key !== 'consent' && key !== 'agentId') {
136          input[key] = value
137        }
138      }
139      const output =
140        typeof result?.text === 'string' ? result.text : JSON.stringify(result?.result ?? '')
141      await post($, '/tool-event', {
142        name: e.tool,
143        input,
144        output: String(output).slice(0, MAX_OUTPUT),
145      })
146    } catch {
147      // Broadcasting must never disturb the tool result.
148    }
149    return result
150  })
151
152  // Broadcast Claude's final response for the turn (main conversation only —
153  // subagent turns carry agentId and stay off the feed).
154  on('turn.complete', async ($, e, next) => {
155    const result = await next(e)
156    if (active && !e.agentId && e.answer) {
157      try {
158        await post($, '/assistant-message', { text: e.answer })
159      } catch {
160        // Broadcasting must never disturb the turn.
161      }
162    }
163    return result
164  })
165
166  // End the cast when the session goes away, so no viewer hangs on a dead feed.
167  on('session.end', async ($, e, next) => {
168    if (active) {
169      active = false
170      try {
171        await post($, '/cast/stop', {})
172      } catch {
173        // Session is ending either way.
174      }
175    }
176    return next(e)
177  })
178}
179
180// --- HTTP helpers against the local claudecast server ---
181
182async function get($, path) {
183  const res = await $.http.fetch(base + path)
184  if (!res.ok) throw new Error('GET ' + path + ' -> ' + res.status)
185  return JSON.parse(res.text)
186}
187
188async function post($, path, body) {
189  const res = await $.http.fetch(base + path, {
190    method: 'POST',
191    headers: { 'content-type': 'application/json' },
192    body: JSON.stringify(body),
193  })
194  if (!res.ok) throw new Error('POST ' + path + ' -> ' + res.status + ' ' + res.text)
195  return res.text ? JSON.parse(res.text) : {}
196}
197
198// Ensure the local claudecast server is up: reuse a running one, spawn it when
199// not. Returns true once /status answers.
200async function ensureServer($) {
201  if (await serverUp($)) return true
202  try {
203    // The loop is the child's life: consume it in the background so the server
204    // stays up for the rest of the session and dies with it.
205    const child = $.process.spawn({ argv: [binary, '--port', String(port)] })
206    void (async () => {
207      try {
208        for await (const _piece of child) {
209          // discard the server's output
210        }
211      } catch {
212        // The server exited; the /status polling below reports it.
213      }
214    })()
215  } catch (err) {
216    throw new Error('cannot spawn the server: ' + err)
217  }
218  for (let i = 0; i < 50; i++) {
219    await $.clock.sleep(100)
220    if (await serverUp($)) return true
221  }
222  return false
223}
224
225async function serverUp($) {
226  try {
227    await $.http.fetch(base + '/status')
228    return true
229  } catch {
230    return false
231  }
232}
233
234function spawnHelp() {
235  return (
236    'Build it with cargo build --release in the claudecast repo, then either put ' +
237    'target/release/claudecast on your PATH, set binaryPath in the plugin options, ' +
238    'or start it yourself with: ' + binary + ' --port ' + port
239  )
240}
241