---
id: openclaw-defaults-a-url-server-to-sse
title: An OpenClaw server configured by URL alone gets SSE, not Streamable HTTP
kind: idiosyncrasy
summary: OpenClaw only builds a Streamable HTTP transport when the config names it explicitly. With no `type` or `transport` field the resolver falls through to SSE, the transport deprecated in 2025-03-26. Cline does the same thing for a different stated reason.
capabilities:
  - transports.sse
  - transports.streamableHttp
clients:
  - openclaw
  - cline
specVersions:
  - 2025-03-26
  - 2025-11-25
sources:
  - url: https://github.com/openclaw/openclaw
    title: src/agents/mcp-transport-config.ts, resolveMcpTransportConfig fallthrough
    commit: a2d54319
    path: src/agents/mcp-transport-config.ts:258-286
    date: 2026-08-26
  - url: https://github.com/openclaw/openclaw
    title: src/agents/mcp-transport.ts, transport factory
    commit: a2d54319
    path: src/agents/mcp-transport.ts:1-40
    date: 2026-08-26
status: current
lastVerified: 2026-08-26
related:
  - cline-defaults-a-url-server-to-sse
canonical: https://canimcp.io/research/openclaw-defaults-a-url-server-to-sse
last-updated: 2026-11-11
---

# An OpenClaw server configured by URL alone gets SSE, not Streamable HTTP

Kind: idiosyncrasy · Status: current · Last verified: 2026-08-26 · Clients: [openclaw](/clients/openclaw.md), [cline](/clients/cline.md) · Revisions: `2025-03-26`, `2025-11-25`

The resolver checks stdio first. If the server is not stdio, it reads an effective transport name from the config's `type` or `transport` field, normalized through a shared alias resolver. Streamable HTTP is built only inside `if (effectiveTransport === "streamable-http")`. When no transport was named, that branch is skipped and the next statement builds an SSE transport unconditionally. SSE is therefore the default for a URL-only server, and also the fallback when a config asks for Streamable HTTP and that resolution returns nothing.

This is the second client entry with an SSE default for a bare URL, and the two arrived by different routes. Cline's extension schema orders a union with SSE first and carries a comment saying why: reordering it would break configs written before Streamable HTTP existed. OpenClaw's is structural — the modern transport is behind a name check and the deprecated one is the fallthrough — with no comment defending it.

The practical consequence is the same either way. An operator who pastes a URL into config and assumes the current transport gets the one deprecated in `2025-03-26`, and nothing in either client says so at connect time.

Recorded as an idiosyncrasy on both clients rather than a gap. The spec does not tell a client how to guess a transport from a bare URL, which is arguably the thing worth fixing.

## Sources

- [src/agents/mcp-transport-config.ts, resolveMcpTransportConfig fallthrough](https://github.com/openclaw/openclaw), commit `a2d54319`, `src/agents/mcp-transport-config.ts:258-286`, 2026-08-26
- [src/agents/mcp-transport.ts, transport factory](https://github.com/openclaw/openclaw), commit `a2d54319`, `src/agents/mcp-transport.ts:1-40`, 2026-08-26

## Related notes

- [cline-defaults-a-url-server-to-sse](/research/cline-defaults-a-url-server-to-sse.md)