chatgpt-proxy

An MCP server that lets any AI agent (Hermes Agent, Claude Desktop, Codebuff-style assistants, …) use ChatGPT Web — for free, through your own logged-in session, no API key.

The agent calls ask_chatgpt(prompt), the proxy drives chatgpt.com in a dedicated Chrome profile via CDP (Chrome DevTools Protocol), and returns the answer as plain text.

┌────────────────────┐   MCP (stdio / HTTP)    ┌───────────────┐   CDP    ┌───────────────┐
│  AI agent          │ ───────────────────────▶│ chatgpt-proxy │ ───────▶ │ Chrome        │
│  (Hermes, you, …)  │   ask_chatgpt(prompt)   │  (local MCP   │          │ (chatgpt.com) │
│                    │ ◀───────────────────────│   server)     │ ◀─────── │ your session  │
└────────────────────┘   answer as text        └───────────────┘          └───────────────┘

• Free & unlimited — rides your ChatGPT Web account (login once, session persists in a dedicated Chrome profile).
• Browser automation, not API — uses the real web UI via CDP, so it survives UI changes better than reverse-engineered endpoints.
• Standard MCP — works with any MCP client over stdio or Streamable HTTP.

Quick start

# 1. Build
go build -o bin/chatgpt-proxy ./cmd/proxy

# 2. First run — open Chrome and log in once
./bin/chatgpt-proxy -wait-login
#    → a Chrome window opens on chatgpt.com; log in there.
#    → the session is saved to ~/.chatgpt-proxy and reused forever.

# 3. Run the MCP server (stdio — what most agents spawn)
./bin/chatgpt-proxy

After step 3 the proxy reads MCP messages from stdin and writes responses to stdout. Wire it into any MCP client.

Connect Hermes Agent (stdio)

Add to your Hermes ~/.hermes/ MCP config:

mcp_servers:
  - name: chatgpt
    command: /Users/you/.../chatgpt-proxy/bin/chatgpt-proxy

Then Hermes can call ask_chatgpt like any other tool.

Streamable HTTP mode (for remote / other clients)

./bin/chatgpt-proxy -transport http -addr 127.0.0.1:8787
# POST http://127.0.0.1:8787/mcp   (SSE or JSON)
# GET  http://127.0.0.1:8787/healthz

Tools

Tool	Description
ask_chatgpt	Send a prompt to ChatGPT Web and return the answer as text.
chatgpt_status	Check that the bridge is ready (logged in, composer present, profile path).

ask_chatgpt arguments

Arg	Type	Default	Meaning
prompt	string	—	Required. The prompt to send.
new_session	boolean	true	Start a fresh conversation each call. Set false to continue the previous one.
timeout_seconds	number	600	Max seconds to wait for the answer.

Flags

Flag	Default	Meaning
-transport	stdio	stdio or http
-addr	127.0.0.1:8787	Listen address (http transport)
-chrome-port	9222 (auto-picks if busy)	Chrome remote-debugging port
-profile	~/.chatgpt-proxy	Chrome profile dir (holds the ChatGPT login)
-chrome	auto-detected	Chrome binary path override
-open	—	Open Chrome with the profile and exit
-wait-login	—	Open Chrome and poll until logged in, then exit
-background	false	Run Chrome in background (off-screen/minimized)

API (HTTP mode, for debugging)

# initialize
curl -X POST http://127.0.0.1:8787/mcp \
  -H 'Content-Type: application/json' -H 'Accept: application/json, text/event-stream' \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","clientInfo":{"name":"curl","version":"1"}}}'

# ask
curl -X POST http://127.0.0.1:8787/mcp \
  -H 'Content-Type: application/json' -H 'Accept: application/json, text/event-stream' \
  -d '{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"ask_chatgpt","arguments":{"prompt":"hello"}}}'

Project layout

cmd/proxy/              MCP server entrypoint (stdio + HTTP)
internal/mcp/           MCP / JSON-RPC protocol types
internal/chatgpt/       Chrome CDP automation of chatgpt.com
internal/server/        MCP dispatch + tool implementations + transports
legacy/                 the earlier relay/agent (outbound tunnel) — kept for reference

Troubleshooting

Symptom	Cause / fix
not logged in	The Chrome window opened but you didn't log in. Run -wait-login and log in once.
chatgpt composer not found	Page layout changed, or a modal is up. Open the proxy Chrome window and check, then retry.
timed out waiting for an answer	Long response or slow network. Raise timeout_seconds.
chrome binary not found	Pass -chrome /path/to/chrome, or install Chrome.
Response looks truncated	The proxy auto-clicks "Continue generating" up to 3 times; very long answers still stop there.
Port 9222 was busy	The proxy auto-picks the next free port — no action needed.

⚠️ This uses your personal ChatGPT session. Only expose the HTTP transport to agents you trust; stdio mode binds to nothing on the network.

Tests

go test ./...

Covers MCP dispatch (initialize, tools/list, tools/call, error paths, SSE + JSON HTTP responses). The browser layer is verified by the live flow — run -wait-login once, then call ask_chatgpt.