Add fakechat channel plugin (#738)

Localhost web chat UI for testing the channel notification flow.
No tokens, no access control, no third-party service. Serves an
iMessage-style UI on localhost; messages posted there arrive as
channel notifications, replies render in the UI.

Useful for developing against the channel protocol without a live
messaging account.

Ships full source — server.ts runs locally via bun, started by the
.mcp.json command.

external_plugins/fakechat/.claude-plugin/plugin.json

@@ -0,0 +1,13 @@
+{
+  "name": "fakechat",
+  "description": "Localhost iMessage-style web chat for Claude Code \u2014 test surface with file upload and edits. No tokens, no access control.",
+  "version": "0.0.1",
+  "keywords": [
+    "fakechat",
+    "web",
+    "localhost",
+    "testing",
+    "channel",
+    "mcp"
+  ]
+}

external_plugins/fakechat/.mcp.json

@@ -0,0 +1,8 @@
+{
+  "mcpServers": {
+    "fakechat": {
+      "command": "bun",
+      "args": ["run", "--cwd", "${CLAUDE_PLUGIN_ROOT}", "--shell=bun", "--silent", "start"]
+    }
+  }
+}

external_plugins/fakechat/.npmrc

@@ -0,0 +1 @@
+registry=https://registry.npmjs.org/

external_plugins/fakechat/LICENSE

@@ -0,0 +1,202 @@
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external_plugins/fakechat/README.md

@@ -0,0 +1,47 @@
+# fakechat
+
+Simple UI for testing the channel contract without an
+external service. Open a browser, type, messages go to your Claude Code
+session, replies come back.
+
+
+## Setup
+
+These are Claude Code commands — run `claude` to start a session first.
+
+Install the plugin:
+```
+/plugin install fakechat@claude-plugins-official
+```
+
+**Relaunch with the channel flag** — the server won't connect without this. Exit your session and start a new one:
+
+```sh
+claude --channels plugin:fakechat@claude-plugins-official
+```
+
+The server prints the URL to stderr on startup:
+
+```
+fakechat: http://localhost:8787
+```
+
+Open it. Type. The assistant replies in-thread.
+
+Set `FAKECHAT_PORT` to change the port.
+
+## Tools
+
+| Tool | Purpose |
+| --- | --- |
+| `reply` | Send to the UI. Takes `text`, optionally `reply_to` (message ID) and `files` (absolute path, 50MB). Attachment shows as `[filename]` under the text. |
+| `edit_message` | Edit a previously-sent message in place. |
+
+Inbound images/files save to `~/.claude/channels/fakechat/inbox/` and the path
+is included in the notification. Outbound files are copied to `outbox/` and
+served over HTTP.
+
+## Not a real channel
+
+There's no history, no search, no access.json, no skill. Single browser tab,
+fresh on every reload. This is a dev tool, not a messaging bridge.

external_plugins/fakechat/bun.lock

@@ -0,0 +1,206 @@
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+    "ip-address": ["ip-address@10.1.0", "", {}, "sha512-XXADHxXmvT9+CRxhXg56LJovE+bmWnEWB78LB83VZTprKTmaC5QfruXocxzTZ2Kl0DNwKuBdlIhjL8LeY8Sf8Q=="],
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+    "ipaddr.js": ["ipaddr.js@1.9.1", "", {}, "sha512-0KI/607xoxSToH7GjN1FfSbLoU0+btTicjsQSWQlh/hZykN8KpmMf7uYwPW3R+akZ6R/w18ZlXSHBYXiYUPO3g=="],
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+    "is-promise": ["is-promise@4.0.0", "", {}, "sha512-hvpoI6korhJMnej285dSg6nu1+e6uxs7zG3BYAm5byqDsgJNWwxzM6z6iZiAgQR4TJ30JmBTOwqZUw3WlyH3AQ=="],
+
+    "isexe": ["isexe@2.0.0", "", {}, "sha512-RHxMLp9lnKHGHRng9QFhRCMbYAcVpn69smSGcq3f36xjgVVWThj4qqLbTLlq7Ssj8B+fIQ1EuCEGI2lKsyQeIw=="],
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+    "jose": ["jose@6.2.1", "", {}, "sha512-jUaKr1yrbfaImV7R2TN/b3IcZzsw38/chqMpo2XJ7i2F8AfM/lA4G1goC3JVEwg0H7UldTmSt3P68nt31W7/mw=="],
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+    "json-schema-traverse": ["json-schema-traverse@1.0.0", "", {}, "sha512-NM8/P9n3XjXhIZn1lLhkFaACTOURQXjWhV4BA/RnOv8xvgqtqpAX9IO4mRQxSx1Rlo4tqzeqb0sOlruaOy3dug=="],
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+
+    "media-typer": ["media-typer@1.1.0", "", {}, "sha512-aisnrDP4GNe06UcKFnV5bfMNPBUw4jsLGaWwWfnH3v02GnBuXX2MCVn5RbrWo0j3pczUilYblq7fQ7Nw2t5XKw=="],
+
+    "merge-descriptors": ["merge-descriptors@2.0.0", "", {}, "sha512-Snk314V5ayFLhp3fkUREub6WtjBfPdCPY1Ln8/8munuLuiYhsABgBVWsozAG+MWMbVEvcdcpbi9R7ww22l9Q3g=="],
+
+    "mime-db": ["mime-db@1.54.0", "", {}, "sha512-aU5EJuIN2WDemCcAp2vFBfp/m4EAhWJnUNSSw0ixs7/kXbd6Pg64EmwJkNdFhB8aWt1sH2CTXrLxo/iAGV3oPQ=="],
+
+    "mime-types": ["mime-types@3.0.2", "", { "dependencies": { "mime-db": "^1.54.0" } }, "sha512-Lbgzdk0h4juoQ9fCKXW4by0UJqj+nOOrI9MJ1sSj4nI8aI2eo1qmvQEie4VD1glsS250n15LsWsYtCugiStS5A=="],
+
+    "ms": ["ms@2.1.3", "", {}, "sha512-6FlzubTLZG3J2a/NVCAleEhjzq5oxgHyaCU9yYXvcLsvoVaHJq/s5xXI6/XXP6tz7R9xAOtHnSO/tXtF3WRTlA=="],
+
+    "negotiator": ["negotiator@1.0.0", "", {}, "sha512-8Ofs/AUQh8MaEcrlq5xOX0CQ9ypTF5dl78mjlMNfOK08fzpgTHQRQPBxcPlEtIw0yRpws+Zo/3r+5WRby7u3Gg=="],
+
+    "object-assign": ["object-assign@4.1.1", "", {}, "sha512-rJgTQnkUnH1sFw8yT6VSU3zD3sWmu6sZhIseY8VX+GRu3P6F7Fu+JNDoXfklElbLJSnc3FUQHVe4cU5hj+BcUg=="],
+
+    "object-inspect": ["object-inspect@1.13.4", "", {}, "sha512-W67iLl4J2EXEGTbfeHCffrjDfitvLANg0UlX3wFUUSTx92KXRFegMHUVgSqE+wvhAbi4WqjGg9czysTV2Epbew=="],
+
+    "on-finished": ["on-finished@2.4.1", "", { "dependencies": { "ee-first": "1.1.1" } }, "sha512-oVlzkg3ENAhCk2zdv7IJwd/QUD4z2RxRwpkcGY8psCVcCYZNq4wYnVWALHM+brtuJjePWiYF/ClmuDr8Ch5+kg=="],
+
+    "once": ["once@1.4.0", "", { "dependencies": { "wrappy": "1" } }, "sha512-lNaJgI+2Q5URQBkccEKHTQOPaXdUxnZZElQTZY0MFUAuaEqe1E+Nyvgdz/aIyNi6Z9MzO5dv1H8n58/GELp3+w=="],
+
+    "parseurl": ["parseurl@1.3.3", "", {}, "sha512-CiyeOxFT/JZyN5m0z9PfXw4SCBJ6Sygz1Dpl0wqjlhDEGGBP1GnsUVEL0p63hoG1fcj3fHynXi9NYO4nWOL+qQ=="],
+
+    "path-key": ["path-key@3.1.1", "", {}, "sha512-ojmeN0qd+y0jszEtoY48r0Peq5dwMEkIlCOu6Q5f41lfkswXuKtYrhgoTpLnyIcHm24Uhqx+5Tqm2InSwLhE6Q=="],
+
+    "path-to-regexp": ["path-to-regexp@8.3.0", "", {}, "sha512-7jdwVIRtsP8MYpdXSwOS0YdD0Du+qOoF/AEPIt88PcCFrZCzx41oxku1jD88hZBwbNUIEfpqvuhjFaMAqMTWnA=="],
+
+    "pkce-challenge": ["pkce-challenge@5.0.1", "", {}, "sha512-wQ0b/W4Fr01qtpHlqSqspcj3EhBvimsdh0KlHhH8HRZnMsEa0ea2fTULOXOS9ccQr3om+GcGRk4e+isrZWV8qQ=="],
+
+    "proxy-addr": ["proxy-addr@2.0.7", "", { "dependencies": { "forwarded": "0.2.0", "ipaddr.js": "1.9.1" } }, "sha512-llQsMLSUDUPT44jdrU/O37qlnifitDP+ZwrmmZcoSKyLKvtZxpyV0n2/bD/N4tBAAZ/gJEdZU7KMraoK1+XYAg=="],
+
+    "qs": ["qs@6.15.0", "", { "dependencies": { "side-channel": "^1.1.0" } }, "sha512-mAZTtNCeetKMH+pSjrb76NAM8V9a05I9aBZOHztWy/UqcJdQYNsf59vrRKWnojAT9Y+GbIvoTBC++CPHqpDBhQ=="],
+
+    "range-parser": ["range-parser@1.2.1", "", {}, "sha512-Hrgsx+orqoygnmhFbKaHE6c296J+HTAQXoxEF6gNupROmmGJRoyzfG3ccAveqCBrwr/2yxQ5BVd/GTl5agOwSg=="],
+
+    "raw-body": ["raw-body@3.0.2", "", { "dependencies": { "bytes": "~3.1.2", "http-errors": "~2.0.1", "iconv-lite": "~0.7.0", "unpipe": "~1.0.0" } }, "sha512-K5zQjDllxWkf7Z5xJdV0/B0WTNqx6vxG70zJE4N0kBs4LovmEYWJzQGxC9bS9RAKu3bgM40lrd5zoLJ12MQ5BA=="],
+
+    "require-from-string": ["require-from-string@2.0.2", "", {}, "sha512-Xf0nWe6RseziFMu+Ap9biiUbmplq6S9/p+7w7YXP/JBHhrUDDUhwa+vANyubuqfZWTveU//DYVGsDG7RKL/vEw=="],
+
+    "router": ["router@2.2.0", "", { "dependencies": { "debug": "^4.4.0", "depd": "^2.0.0", "is-promise": "^4.0.0", "parseurl": "^1.3.3", "path-to-regexp": "^8.0.0" } }, "sha512-nLTrUKm2UyiL7rlhapu/Zl45FwNgkZGaCpZbIHajDYgwlJCOzLSk+cIPAnsEqV955GjILJnKbdQC1nVPz+gAYQ=="],
+
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+
+    "send": ["send@1.2.1", "", { "dependencies": { "debug": "^4.4.3", "encodeurl": "^2.0.0", "escape-html": "^1.0.3", "etag": "^1.8.1", "fresh": "^2.0.0", "http-errors": "^2.0.1", "mime-types": "^3.0.2", "ms": "^2.1.3", "on-finished": "^2.4.1", "range-parser": "^1.2.1", "statuses": "^2.0.2" } }, "sha512-1gnZf7DFcoIcajTjTwjwuDjzuz4PPcY2StKPlsGAQ1+YH20IRVrBaXSWmdjowTJ6u8Rc01PoYOGHXfP1mYcZNQ=="],
+
+    "serve-static": ["serve-static@2.2.1", "", { "dependencies": { "encodeurl": "^2.0.0", "escape-html": "^1.0.3", "parseurl": "^1.3.3", "send": "^1.2.0" } }, "sha512-xRXBn0pPqQTVQiC8wyQrKs2MOlX24zQ0POGaj0kultvoOCstBQM5yvOhAVSUwOMjQtTvsPWoNCHfPGwaaQJhTw=="],
+
+    "setprototypeof": ["setprototypeof@1.2.0", "", {}, "sha512-E5LDX7Wrp85Kil5bhZv46j8jOeboKq5JMmYM3gVGdGH8xFpPWXUMsNrlODCrkoxMEeNi/XZIwuRvY4XNwYMJpw=="],
+
+    "shebang-command": ["shebang-command@2.0.0", "", { "dependencies": { "shebang-regex": "^3.0.0" } }, "sha512-kHxr2zZpYtdmrN1qDjrrX/Z1rR1kG8Dx+gkpK1G4eXmvXswmcE1hTWBWYUzlraYw1/yZp6YuDY77YtvbN0dmDA=="],
+
+    "shebang-regex": ["shebang-regex@3.0.0", "", {}, "sha512-7++dFhtcx3353uBaq8DDR4NuxBetBzC7ZQOhmTQInHEd6bSrXdiEyzCvG07Z44UYdLShWUyXt5M/yhz8ekcb1A=="],
+
+    "side-channel": ["side-channel@1.1.0", "", { "dependencies": { "es-errors": "^1.3.0", "object-inspect": "^1.13.3", "side-channel-list": "^1.0.0", "side-channel-map": "^1.0.1", "side-channel-weakmap": "^1.0.2" } }, "sha512-ZX99e6tRweoUXqR+VBrslhda51Nh5MTQwou5tnUDgbtyM0dBgmhEDtWGP/xbKn6hqfPRHujUNwz5fy/wbbhnpw=="],
+
+    "side-channel-list": ["side-channel-list@1.0.0", "", { "dependencies": { "es-errors": "^1.3.0", "object-inspect": "^1.13.3" } }, "sha512-FCLHtRD/gnpCiCHEiJLOwdmFP+wzCmDEkc9y7NsYxeF4u7Btsn1ZuwgwJGxImImHicJArLP4R0yX4c2KCrMrTA=="],
+
+    "side-channel-map": ["side-channel-map@1.0.1", "", { "dependencies": { "call-bound": "^1.0.2", "es-errors": "^1.3.0", "get-intrinsic": "^1.2.5", "object-inspect": "^1.13.3" } }, "sha512-VCjCNfgMsby3tTdo02nbjtM/ewra6jPHmpThenkTYh8pG9ucZ/1P8So4u4FGBek/BjpOVsDCMoLA/iuBKIFXRA=="],
+
+    "side-channel-weakmap": ["side-channel-weakmap@1.0.2", "", { "dependencies": { "call-bound": "^1.0.2", "es-errors": "^1.3.0", "get-intrinsic": "^1.2.5", "object-inspect": "^1.13.3", "side-channel-map": "^1.0.1" } }, "sha512-WPS/HvHQTYnHisLo9McqBHOJk2FkHO/tlpvldyrnem4aeQp4hai3gythswg6p01oSoTl58rcpiFAjF2br2Ak2A=="],
+
+    "statuses": ["statuses@2.0.2", "", {}, "sha512-DvEy55V3DB7uknRo+4iOGT5fP1slR8wQohVdknigZPMpMstaKJQWhwiYBACJE3Ul2pTnATihhBYnRhZQHGBiRw=="],
+
+    "toidentifier": ["toidentifier@1.0.1", "", {}, "sha512-o5sSPKEkg/DIQNmH43V0/uerLrpzVedkUh8tGNvaeXpfpuwjKenlSox/2O/BTlZUtEe+JG7s5YhEz608PlAHRA=="],
+
+    "type-is": ["type-is@2.0.1", "", { "dependencies": { "content-type": "^1.0.5", "media-typer": "^1.1.0", "mime-types": "^3.0.0" } }, "sha512-OZs6gsjF4vMp32qrCbiVSkrFmXtG/AZhY3t0iAMrMBiAZyV9oALtXO8hsrHbMXF9x6L3grlFuwW2oAz7cav+Gw=="],
+
+    "undici-types": ["undici-types@7.18.2", "", {}, "sha512-AsuCzffGHJybSaRrmr5eHr81mwJU3kjw6M+uprWvCXiNeN9SOGwQ3Jn8jb8m3Z6izVgknn1R0FTCEAP2QrLY/w=="],
+
+    "unpipe": ["unpipe@1.0.0", "", {}, "sha512-pjy2bYhSsufwWlKwPc+l3cN7+wuJlK6uz0YdJEOlQDbl6jo/YlPi4mb8agUkVC8BF7V8NuzeyPNqRksA3hztKQ=="],
+
+    "vary": ["vary@1.1.2", "", {}, "sha512-BNGbWLfd0eUPabhkXUVm0j8uuvREyTh5ovRa/dyow/BqAbZJyC+5fU+IzQOzmAKzYqYRAISoRhdQr3eIZ/PXqg=="],
+
+    "which": ["which@2.0.2", "", { "dependencies": { "isexe": "^2.0.0" }, "bin": { "node-which": "./bin/node-which" } }, "sha512-BLI3Tl1TW3Pvl70l3yq3Y64i+awpwXqsGBYWkkqMtnbXgrMD+yj7rhW0kuEDxzJaYXGjEW5ogapKNMEKNMjibA=="],
+
+    "wrappy": ["wrappy@1.0.2", "", {}, "sha512-l4Sp/DRseor9wL6EvV2+TuQn63dMkPjZ/sp9XkghTEbV9KlPS1xUsZ3u7/IQO4wxtcFB4bgpQPRcR3QCvezPcQ=="],
+
+    "zod": ["zod@4.3.6", "", {}, "sha512-rftlrkhHZOcjDwkGlnUtZZkvaPHCsDATp4pGpuOOMDaTdDDXF91wuVDJoWoPsKX/3YPQ5fHuF3STjcYyKr+Qhg=="],
+
+    "zod-to-json-schema": ["zod-to-json-schema@3.25.1", "", { "peerDependencies": { "zod": "^3.25 || ^4" } }, "sha512-pM/SU9d3YAggzi6MtR4h7ruuQlqKtad8e9S0fmxcMi+ueAK5Korys/aWcV9LIIHTVbj01NdzxcnXSN+O74ZIVA=="],
+  }
+}

external_plugins/fakechat/package.json

@@ -0,0 +1,16 @@
+{
+  "name": "claude-channel-fakechat",
+  "version": "0.0.1",
+  "license": "Apache-2.0",
+  "type": "module",
+  "bin": "./server.ts",
+  "scripts": {
+    "start": "bun install --no-summary && bun server.ts"
+  },
+  "dependencies": {
+    "@modelcontextprotocol/sdk": "^1.0.0"
+  },
+  "devDependencies": {
+    "@types/bun": "^1.3.10"
+  }
+}

external_plugins/fakechat/server.ts

@@ -0,0 +1,295 @@
+#!/usr/bin/env bun
+/**
+ * Fake chat for Claude Code.
+ *
+ * Localhost web UI for testing the channel contract. No external service,
+ * no tokens, no access control.
+ */
+
+import { Server } from '@modelcontextprotocol/sdk/server/index.js'
+import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js'
+import {
+  ListToolsRequestSchema,
+  CallToolRequestSchema,
+} from '@modelcontextprotocol/sdk/types.js'
+import { readFileSync, writeFileSync, mkdirSync, statSync, copyFileSync } from 'fs'
+import { homedir } from 'os'
+import { join, extname, basename } from 'path'
+import type { ServerWebSocket } from 'bun'
+
+const PORT = Number(process.env.FAKECHAT_PORT ?? 8787)
+const STATE_DIR = join(homedir(), '.claude', 'channels', 'fakechat')
+const INBOX_DIR = join(STATE_DIR, 'inbox')
+const OUTBOX_DIR = join(STATE_DIR, 'outbox')
+
+type Msg = {
+  id: string
+  from: 'user' | 'assistant'
+  text: string
+  ts: number
+  replyTo?: string
+  file?: { url: string; name: string }
+}
+
+type Wire =
+  | ({ type: 'msg' } & Msg)
+  | { type: 'edit'; id: string; text: string }
+
+const clients = new Set<ServerWebSocket<unknown>>()
+let seq = 0
+
+function nextId() {
+  return `m${Date.now()}-${++seq}`
+}
+
+function broadcast(m: Wire) {
+  const data = JSON.stringify(m)
+  for (const ws of clients) if (ws.readyState === 1) ws.send(data)
+}
+
+function mime(ext: string) {
+  const m: Record<string, string> = {
+    '.jpg': 'image/jpeg', '.jpeg': 'image/jpeg', '.png': 'image/png',
+    '.gif': 'image/gif', '.webp': 'image/webp', '.svg': 'image/svg+xml',
+    '.pdf': 'application/pdf', '.txt': 'text/plain',
+  }
+  return m[ext] ?? 'application/octet-stream'
+}
+
+const mcp = new Server(
+  { name: 'fakechat', version: '0.1.0' },
+  {
+    capabilities: { tools: {}, experimental: { 'claude/channel': {} } },
+    instructions: `The sender reads the fakechat UI, not this session. Anything you want them to see must go through the reply tool — your transcript output never reaches the UI.\n\nMessages from the fakechat web UI arrive as <channel source="fakechat" chat_id="web" message_id="...">. If the tag has a file_path attribute, Read that file — it is an upload from the UI. Reply with the reply tool. UI is at http://localhost:${PORT}.`,
+  },
+)
+
+mcp.setRequestHandler(ListToolsRequestSchema, async () => ({
+  tools: [
+    {
+      name: 'reply',
+      description: 'Send a message to the fakechat UI. Pass reply_to for quote-reply, files for attachments.',
+      inputSchema: {
+        type: 'object',
+        properties: {
+          text: { type: 'string' },
+          reply_to: { type: 'string' },
+          files: { type: 'array', items: { type: 'string' } },
+        },
+        required: ['text'],
+      },
+    },
+    {
+      name: 'edit_message',
+      description: 'Edit a previously sent message.',
+      inputSchema: {
+        type: 'object',
+        properties: { message_id: { type: 'string' }, text: { type: 'string' } },
+        required: ['message_id', 'text'],
+      },
+    },
+  ],
+}))
+
+mcp.setRequestHandler(CallToolRequestSchema, async req => {
+  const args = (req.params.arguments ?? {}) as Record<string, unknown>
+  try {
+    switch (req.params.name) {
+      case 'reply': {
+        const text = args.text as string
+        const replyTo = args.reply_to as string | undefined
+        const files = (args.files as string[] | undefined) ?? []
+        const ids: string[] = []
+
+        // Text + files collapse into a single message, matching the client's [filename]-under-text rendering.
+        mkdirSync(OUTBOX_DIR, { recursive: true })
+        let file: { url: string; name: string } | undefined
+        if (files[0]) {
+          const f = files[0]
+          const st = statSync(f)
+          if (st.size > 50 * 1024 * 1024) throw new Error(`file too large: ${f}`)
+          const ext = extname(f).toLowerCase()
+          const out = `${Date.now()}-${Math.random().toString(36).slice(2, 8)}${ext}`
+          copyFileSync(f, join(OUTBOX_DIR, out))
+          file = { url: `/files/${out}`, name: basename(f) }
+        }
+        const id = nextId()
+        broadcast({ type: 'msg', id, from: 'assistant', text, ts: Date.now(), replyTo, file })
+        ids.push(id)
+        return { content: [{ type: 'text', text: `sent (${ids.join(', ')})` }] }
+      }
+      case 'edit_message': {
+        broadcast({ type: 'edit', id: args.message_id as string, text: args.text as string })
+        return { content: [{ type: 'text', text: 'ok' }] }
+      }
+      default:
+        return { content: [{ type: 'text', text: `unknown: ${req.params.name}` }], isError: true }
+    }
+  } catch (err) {
+    return { content: [{ type: 'text', text: `${req.params.name}: ${err instanceof Error ? err.message : err}` }], isError: true }
+  }
+})
+
+await mcp.connect(new StdioServerTransport())
+
+function deliver(id: string, text: string, file?: { path: string; name: string }): void {
+  // file_path goes in meta only — an in-content "[attached — Read: PATH]"
+  // annotation is forgeable by typing that string into the UI.
+  void mcp.notification({
+    method: 'notifications/claude/channel',
+    params: {
+      content: text || `(${file?.name ?? 'attachment'})`,
+      meta: {
+        chat_id: 'web', message_id: id, user: 'web', ts: new Date().toISOString(),
+        ...(file ? { file_path: file.path } : {}),
+      },
+    },
+  })
+}
+
+Bun.serve({
+  port: PORT,
+  hostname: '127.0.0.1',
+  fetch(req, server) {
+    const url = new URL(req.url)
+
+    if (url.pathname === '/ws') {
+      if (server.upgrade(req)) return
+      return new Response('upgrade failed', { status: 400 })
+    }
+
+    if (url.pathname.startsWith('/files/')) {
+      const f = url.pathname.slice(7)
+      if (f.includes('..') || f.includes('/')) return new Response('bad', { status: 400 })
+      try {
+        return new Response(readFileSync(join(OUTBOX_DIR, f)), {
+          headers: { 'content-type': mime(extname(f).toLowerCase()) },
+        })
+      } catch {
+        return new Response('404', { status: 404 })
+      }
+    }
+
+    if (url.pathname === '/upload' && req.method === 'POST') {
+      return (async () => {
+        const form = await req.formData()
+        const id = String(form.get('id') ?? '')
+        const text = String(form.get('text') ?? '')
+        const f = form.get('file')
+        if (!id) return new Response('missing id', { status: 400 })
+        let file: { path: string; name: string } | undefined
+        if (f instanceof File && f.size > 0) {
+          mkdirSync(INBOX_DIR, { recursive: true })
+          const ext = extname(f.name).toLowerCase() || '.bin'
+          const path = join(INBOX_DIR, `${Date.now()}${ext}`)
+          writeFileSync(path, Buffer.from(await f.arrayBuffer()))
+          file = { path, name: f.name }
+        }
+        deliver(id, text, file)
+        return new Response(null, { status: 204 })
+      })()
+    }
+
+    if (url.pathname === '/') {
+      return new Response(HTML, { headers: { 'content-type': 'text/html; charset=utf-8' } })
+    }
+    return new Response('404', { status: 404 })
+  },
+  websocket: {
+    open: ws => { clients.add(ws) },
+    close: ws => { clients.delete(ws) },
+    message: (_, raw) => {
+      try {
+        const { id, text } = JSON.parse(String(raw)) as { id: string; text: string }
+        if (id && text?.trim()) deliver(id, text.trim())
+      } catch {}
+    },
+  },
+})
+
+process.stderr.write(`fakechat: http://localhost:${PORT}\n`)
+
+const HTML = `<!doctype html>
+<meta charset="utf-8">
+<title>fakechat</title>
+<style>
+body { font-family: monospace; margin: 0; padding: 1em 1em 7em; }
+#log { white-space: pre-wrap; word-break: break-word; }
+form { position: fixed; bottom: 0; left: 0; right: 0; padding: 1em; background: #fff; }
+#text { width: 100%; box-sizing: border-box; font: inherit; margin-bottom: 0.5em; }
+#file { display: none; }
+#row { display: flex; gap: 1ch; }
+#row button[type=submit] { margin-left: auto; }
+</style>
+<h3>fakechat</h3>
+<pre id=log></pre>
+<form id=form>
+  <textarea id=text rows=2 autocomplete=off autofocus></textarea>
+  <div id=row>
+    <button type=button onclick="file.click()">attach</button><input type=file id=file>
+    <span id=chip></span>
+    <button type=submit>send</button>
+  </div>
+</form>
+
+<script>
+const log = document.getElementById('log')
+document.getElementById('file').onchange = e => { const f = e.target.files[0]; chip.textContent = f ? '[' + f.name + ']' : '' }
+const form = document.getElementById('form')
+const input = document.getElementById('text')
+const fileIn = document.getElementById('file')
+const chip = document.getElementById('chip')
+const msgs = {}
+
+const ws = new WebSocket('ws://' + location.host + '/ws')
+ws.onmessage = e => {
+  const m = JSON.parse(e.data)
+  if (m.type === 'msg') add(m)
+  if (m.type === 'edit') { const x = msgs[m.id]; if (x) { x.body.textContent = m.text + ' (edited)' } }
+}
+
+let uid = 0
+form.onsubmit = e => {
+  e.preventDefault()
+  const text = input.value.trim()
+  const file = fileIn.files[0]
+  if (!text && !file) return
+  input.value = ''; fileIn.value = ''; chip.textContent = ''
+  const id = 'u' + Date.now() + '-' + (++uid)
+  add({ id, from: 'user', text, file: file ? { url: URL.createObjectURL(file), name: file.name } : undefined })
+  if (file) {
+    const fd = new FormData(); fd.set('id', id); fd.set('text', text); fd.set('file', file)
+    fetch('/upload', { method: 'POST', body: fd })
+  } else {
+    ws.send(JSON.stringify({ id, text }))
+  }
+}
+
+function add(m) {
+  const who = m.from === 'user' ? 'you' : 'bot'
+  const el = line(who, m.text, m.replyTo, m.file)
+  log.appendChild(el); scroll()
+  msgs[m.id] = { body: el.querySelector('.body') }
+}
+
+function line(who, text, replyTo, file) {
+  const div = document.createElement('div')
+  const t = new Date().toTimeString().slice(0, 8)
+  const reply = replyTo && msgs[replyTo] ? ' ↳ ' + (msgs[replyTo].body.textContent || '(file)').slice(0, 40) : ''
+  div.innerHTML = '[' + t + '] <b>' + who + '</b>' + reply + ': <span class=body></span>'
+  const body = div.querySelector('.body')
+  body.textContent = text || ''
+  if (file) {
+    const indent = 11 + who.length + 2  // '[HH:MM:SS] ' + who + ': '
+    if (text) body.appendChild(document.createTextNode('\\n' + ' '.repeat(indent)))
+    const a = document.createElement('a')
+    a.href = file.url; a.download = file.name; a.textContent = '[' + file.name + ']'
+    body.appendChild(a)
+  }
+  return div
+}
+
+function scroll() { window.scrollTo(0, document.body.scrollHeight) }
+input.addEventListener('keydown', e => { if (e.key === 'Enter' && !e.shiftKey) { e.preventDefault(); form.requestSubmit() } })
+</script>
+`