Port from openclaw/openclaw#123194: a hostile or misbehaving remote MCP
server could stream an unbounded HTTP catalog/tool-result body that the
MCP SDK buffers and JSON-parses before any of Hermes' post-parse limits
(resource cap, tool-result truncation) run.
New _make_mcp_body_cap_transport wraps the owned httpx AsyncClient's
transport on the Streamable HTTP (mcp >= 1.24) and SSE paths:
- finite HTTP bodies capped at 10 MiB (Content-Length rejected up front,
streamed bodies capped chunk-by-chunk);
- each SSE event capped at 10 MiB, with accounting reset at completed
event boundaries so long-lived streams/keepalives are unlimited;
- violations raise httpx.ReadError naming the byte cap, handled by the
existing transport teardown/reconnect path (#66092).
verify/cert now live on the inner AsyncHTTPTransport (client-level TLS
kwargs are inert once a custom transport is passed); the SSE
httpx_client_factory is always injected so the cap applies with default
TLS too. Legacy mcp < 1.24 path (SDK-internal client, no hook) stays
uncapped — same degradation as strict_redirect_headers.
Teknium
a6fdadfcee