Kaption WhatsApp (Cloud)

io.github.Kaption-AIv1.0.0Updated Oct 5, 2026

Use WhatsApp from AI apps through the Kaption extension. OAuth 2.1 relay that cannot read messages.

VerifiedStreamable HTTPWeb executableProductivity & WorkflowCommunication & Collaboration

Overview

AI-generated overview

Lets an AI assistant read and manage WhatsApp conversations, contacts, labels, reminders and scheduled messages through a browser extension.

What it does
A cloud relay that forwards MCP tool calls to the Kaption browser extension, which runs in a WhatsApp Web tab and does the actual work. Sixteen public tools cover querying conversations, contacts, messages and transcriptions; summarizing conversations; managing WhatsApp Business labels and contact notes; downloading media; archiving, pinning, muting and marking chats read; and managing reminders, scheduled messages, chat lists, contacts, groups, contact exports and activity analytics. The relay itself does not execute the tools and states it cannot read messages.
When to use it
Worth adding when an assistant should work with an existing WhatsApp account — searching and summarizing chats, organizing labels and lists, exporting contacts, or scheduling messages — without a local bridge process. The extension must be installed and connected, so it suits users already using Kaption rather than a general-purpose WhatsApp integration.
Requirements
A remote endpoint at mcp.kaptionai.com over Streamable HTTP or SSE; no local runtime or package. OAuth 2.1 authorization with a WhatsApp one-time passcode at the authorize step, plus the Kaption browser extension installed and connected in a WhatsApp Web tab. No environment variables or headers are declared for the client.
Before you install
Authorization is by WhatsApp OTP, so anyone completing that step gains access to the connected account's conversations. Several tools write or send: manage_labels, manage_notes, manage_chat, manage_reminders, manage_scheduled_messages and manage_lists change account state, and scheduled messages can be sent from the user's own number in local mode, including to groups. Tool calls and results pass through a third-party cloud relay before reaching the extension.

Installation

In SourceWeft

  1. Open Kaption WhatsApp (Cloud) in the dashboard and add it to a workspace.
  2. Enable the server for the chats that should use its tools.

Web executable via Streamable HTTP. Remote servers run from the web runtime once configured in a workspace.

Other MCP clients

Add this to your client's mcpServers config.

{
  "mcpServers": {
    "mcp-extension-remote": {
      "type": "http",
      "url": "https://mcp.kaptionai.com/mcp"
    }
  }
}

README

kaption-mcp-remote

Cloud MCP relay for WhatsApp — lets AI assistants (Claude, ChatGPT, Cursor, etc.) interact with your WhatsApp conversations through the Model Context Protocol.

Setup guide: kaptionai.com/mcp — connect WhatsApp to Claude, ChatGPT or Cursor.

Live at: mcp.kaptionai.com (canonical) and mcp-ext.kaptionai.com (backward-compatible alias for existing connections)

The relay cannot read your messages. It forwards MCP tool calls between the AI client and the Kaption browser extension, which processes everything locally in your browser. Its source code is public (BUSL-1.1), so you can verify it yourself.

Architecture

AI Client (Claude/ChatGPT/Cursor)    │    │ OAuth 2.1 + SSE/Streamable HTTP    ▼┌─────────────────────────────────────┐│  Cloudflare Worker                  ││  mcp.kaptionai.com                 ││                                     ││  ┌────────────┐  ┌──────────────┐  ││  │ OAuthProv  │  │ Next.js      │  ││  │ /sse /mcp  │  │ /authorize   │  ││  │ /token     │  │ /ext-auth    │  ││  │ /register  │  │ / (landing)  │  ││  └─────┬──────┘  └──────────────┘  ││        │                            ││  ┌─────▼──────┐  ┌──────────────┐  ││  │ RelayMCP   │  │ Deployment   │  ││  │ (DO)       │  │ ChainDO      │  ││  └─────┬──────┘  └──────────────┘  ││        │                            ││  ┌─────▼──────┐                    ││  │ RelayRoom  │ ◄── WebSocket ──┐  ││  │ (DO/accountRef) │            │  ││  └────────────┘                 │  │└─────────────────────────────────┼──┘                                  │                          Browser Extension                          (WhatsApp Web tab)

Durable Objects

DOKeyed ByPurpose
RelayMCPOAuth sessionMcpAgent — registers tools, relays JSON-RPC to RelayRoom
RelayRoomOpaque accountRefWebSocket bridge to extension, auth handshake, request/response matching
DeploymentChainDO"main"Append-only hash chain for deployment transparency

Request Flow

  1. AI client discovers the MCP server via /.well-known/oauth-authorization-server
  2. Client registers dynamically via POST /register (RFC 7591)
  3. User authenticates with WhatsApp OTP at /authorize
  4. Client exchanges code for token at /token
  5. Client sends tool calls via SSE (/sse) or Streamable HTTP (/mcp)
  6. RelayMCP DO receives the call, routes to RelayRoom for the accountRef
  7. RelayRoom forwards JSON-RPC to the extension over WebSocket
  8. Extension executes in WhatsApp Web context, returns result
  9. Result flows back: RelayRoom → RelayMCP → AI client

Routing Table

PathMethodAuthHandler
/GET—Next.js landing page
/authorizeGET—Next.js OTP form (HMAC-signed oauthReqInfo)
/authorize/send-otpPOST—Next.js API route → rest-api
/authorize/verifyGET/POST—Next.js OTP verify → OAuthProvider completeAuthorization
/authorize/reviewer-loginPOSTStatic review credentialsPassword completion for the configured synthetic review phone
/registerPOST—OAuthProvider (RFC 7591 dynamic client registration)
/tokenPOST—OAuthProvider (token exchange)
/sseGETOAuth tokenRelayMCP DO (SSE transport)
/mcpPOSTOAuth tokenRelayMCP DO (Streamable HTTP)
/ws/extGETJWT/token in auth msgRelayRoom DO (WebSocket upgrade)
/ext-auth/*Various—Next.js extension auth pages + API
/transparencyGET—DeploymentChainDO (chain history)
/transparency/latestGET—DeploymentChainDO (latest entry)
/transparency/verifyGET—DeploymentChainDO (chain integrity)
/transparency/gapsGETCF tokenCross-reference CF deploys with chain
/transparency/appendPOSTDEPLOY_API_KEYAppend entry (CI only)

MCP Tools

16 public tools are forwarded to the extension (the relay does not execute them):

ToolDescription
queryQuery conversations, contacts, messages, transcriptions, labels, communities, sessions
summarize_conversationGet or generate a conversation summary
manage_labelsAdd/remove/create/delete WhatsApp Business labels
manage_notesGet/set contact notes (Business accounts)
download_mediaDownload image/video/audio/document from a message
manage_chatArchive, pin, mute, mark read/unread, set/clear draft
manage_remindersCreate/list/complete/delete personal reminders
manage_scheduled_messagesSchedule messages for future delivery — from Kaption's number (bot, default) or from your own number on this computer (mode: "local", also to groups)
manage_listsManage personal chat lists (custom categories)
list_contacts, get_contact, get_contact_groupsRead contacts and their group memberships
list_groups, get_groupRead cached or live group metadata
export_contactsExport contacts as CSV or JSON
get_analyticsAnalyze WhatsApp activity, rankings, response times, and exports

get_api_info is local-only and is deliberately excluded from the cloud surface because it returns private REST connection credentials.

Deployment Security

Every deployment is cryptographically signed and recorded in a tamper-evident transparency chain. See SECURITY.md for full details.

Pipeline

GitHub Actions (push to main)    │    ├─ 1. Run tests    ├─ 2. Build worker (OpenNext + wrap)    ├─ 3. SHA-256 manifest every generated code and asset file    ├─ 4. Pre-deploy: Sigstore sign the manifest → Rekor log    ├─ 5. Deploy to Cloudflare    ├─ 6. Post-deploy: verify hash unchanged, sign attestation → Rekor    └─ 7. Append to transparency chain (hash-linked)

Daily heartbeat redeploys (6am UTC) ensure the chain stays active even without code changes.

Deploys are gated — do NOT run wrangler deploy locally

All production deploys go through GitHub Actions. Multiple layers enforce this:

  1. wrangler.jsonc is gitignored; scripts/build-config.mjs renders it from wrangler.template.jsonc and refuses to run unless GITHUB_ACTIONS=true + GITHUB_RUN_ID are set (or KAPTIONAI_LOCAL_DEV=1 for dev).
  2. npm run predeploy aborts unless those same CI env vars are present.
  3. main is branch-protected: requires a reviewed PR + green test, deploy, and verify checks.
  4. CODEOWNERS routes every PR through @kshmir.

To ship a change: open a PR → review + CI green → merge to main → Actions builds, signs (Sigstore), deploys, and appends to the transparency chain. npx wrangler deploy from a laptop will fail at step 1 because there is no wrangler.jsonc to deploy.

Verify a Deployment

bash
# 1. Check the transparency chaincurl -s https://mcp.kaptionai.com/transparency/latest | jq .
# 2. Verify chain integritycurl -s https://mcp.kaptionai.com/transparency/verify | jq .
# 3. Verify Sigstore signature (requires cosign)COMMIT=$(curl -s https://mcp.kaptionai.com/transparency/latest | jq -r '.event.commitSha')cosign verify-blob \  --bundle build-manifest.sigstore.json \  --certificate-identity-regexp "https://github.com/Kaption-AI/mcp-extension-remote/.*" \  --certificate-oidc-issuer "https://token.actions.githubusercontent.com" \  build-manifest.json

API Endpoints

Transparency API (public, no auth)

bash
# Full chain history (paginated)GET /transparency?limit=50&offset=0
# Latest deploymentGET /transparency/latest
# Verify chain integrityGET /transparency/verify

MCP (OAuth-protected)

bash
# SSE transport (for Claude Code, Cursor)GET /sse
# Streamable HTTP transportPOST /mcp

Development

bash
# Install dependenciesnpm install
# Run testsnpm test
# Dev server (Next.js only — no Worker routing)npm run dev
# Build the full worker (OpenNext + custom wrapper)npm run build:worker

Project Structure

src/  index.ts            # Worker entry — Hono routing, OAuthProvider composition  relay-mcp.ts        # RelayMCP Durable Object (McpAgent)  relay-room.ts       # RelayRoom Durable Object (WebSocket bridge)  deployment-chain.ts # DeploymentChainDO (transparency log)  otp.ts              # OTP generation, verification, JWT, HMAC, rate limiting  schemas.ts          # Zod schemas for API request validation  tools.ts            # MCP tool definitions (forwarded, not executed)  types.ts            # TypeScript interfaces (Env, DeploymentEvent, etc.)app/  page.tsx            # Landing page (multilingual, client-side i18n)  layout.tsx          # Root layout  i18n.ts             # i18next init (8 languages)  locales/            # Translation JSON files  authorize/          # OAuth OTP flow pages + API routes  ext-auth/           # Extension auth pages + API routesscripts/  wrap-worker.mjs     # Post-build: wraps OpenNext output with custom routing

Environment Variables

Vars (wrangler.jsonc)

VariableDescription
INTERNAL_API_BASE_URLBackend API base URL
BUILD_HASHSHA-256 of worker bundle (set by CI)
COMMIT_SHAGit commit SHA (set by CI)

Secrets (wrangler secret put)

SecretDescription
INTERNAL_API_KEYAPI key for rest-api OTP endpoint
DEPLOY_API_KEYAPI key for transparency chain append
JWT_SECRETShared JWT signing secret (same as rest-api, schedule, metadata workers)
PHONE_REF_SECRETHMAC secret used to derive opaque durable account references from phone numbers
EPHEMERAL_STATE_SECRETEncryption secret for short-lived login hints, verify tickets, and encrypted session phone payloads
OPENAI_APPS_CHALLENGE_TOKENExact domain-verification token issued by the OpenAI plugin portal
OPENAI_REVIEW_PASSWORD_SHA256Lowercase SHA-256 hex digest of the high-entropy reviewer password
OPENAI_REVIEW_PHONEPhone number used as the dedicated review username and to derive the synthetic account's opaque reference

The three OPENAI_* values are also configured as GitHub Actions repository secrets. Add all three together, then run the manual Test, Build & Deploy workflow. CI writes them to an ephemeral mode-0600 file and passes that file to wrangler deploy --secrets-file, so the review configuration ships in the same signed, attested Worker version as the code. The workflow fails closed if only part of the three-value set is present and deletes the temporary file immediately after deployment. Existing Worker secrets not listed in that file are preserved.

Related Projects

License

BUSL-1.1

Source: README.md at commit ba9ed57

Tools

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Version history

1
  1. v1.0.0LatestOct 5, 2026