Slaunt MCP transport: sessions, headers and limits

Slaunt is a standard Streamable HTTP MCP server, so MCP SDKs handle this page for you. Read it if you’re writing a client by hand or debugging one. The parts that differ from a generic server are strict session binding and thread boundaries.

Method	Path	Purpose
`POST`	`/mcp`	JSON-RPC requests
`GET`	`/mcp` with `Accept: text/event-stream`	Server notifications, mainly `tools/list_changed`
`DELETE`	`/mcp`	End the session (`204`)

Sessions

Send initialize without an Mcp-Session-Id header. The response header carries the new session ID, which you send on every request after that.

curl -i https://central-mcp-ccr-production.up.railway.app/mcp \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-11-25","capabilities":{},"clientInfo":{"name":"my-agent","version":"1.0.0"}}}'

Sessions are bound to the user and the client that created them, so a session ID can’t be shared between tools or tokens. Reuse one session per connection: each new session can show up as a separate agent in Quaero.

Case	Response	Fix
No header on a non-initialize request	`400`, `-32600`	Send the header
Session unknown, expired, or used with another token/client	`404`, `-32001`, `data.required_action: "initialize"`	Re-initialize without the header
Session was deleted	`404`, `MCP session terminated (deleted)...`	Re-initialize

Notification stream

Open it if you cache tools/list: Slaunt sends notifications/tools/list_changed when the workspace’s provider tools change.

Status	Cause
`400`	No session header
`403` `mcp_origin_not_allowed`	Browser request from a disallowed origin
`409`	Too many streams open for this session
`429`	Server stream capacity exhausted; retry later

Thread boundaries

By default one session equals one runtime. If your client runs several chats over one connection, tag each request with a boundary so Slaunt keeps them as separate threads instead of merging them. Put it in params._meta or a header. Values are strings up to 1,024 characters and are stored only as hashes. Conflicting values on one request are rejected.

Boundary	`_meta` key	Header
Slaunt thread (preferred)	`ai.slaunt/thread-instance`	`Ai-Slaunt-Thread-Instance`
OpenAI session	`openai/session`	`OpenAI-Session`
Generic	`mcp/thread-id`	`Mcp-Thread-Id`, `X-Conversation-Id`
Session instance	`ai.slaunt/session-instance`	`Ai-Slaunt-Session-Instance`

Without a boundary, each new chat must call thread_begin. Codex has its own routing.

Limits

Limit	Value	When exceeded
Requests	240/min	`429` `http_rate_limited` with `Retry-After`
Request body	1 MiB	Rejected
`ccr_search` query	1,000 chars	Tool error

Every response carries X-RateLimit-Limit, X-RateLimit-Remaining and X-RateLimit-Reset (Unix seconds).

Results

Each tools/call result has content[0].text, a readable summary meant for the model, and structuredContent, the full data meant for code. Failures come back as a JSON-RPC error, not as an isError result, so check for error first.

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