agent-transport-http Specification

Purpose

HTTP transport (Hono) for the Robota SDK, split out of the consolidated agent-transport package so the hono dependency is an isolated unit.

Depends on agent-interface-transport for transport contracts and on agent-transport/node only for the transport admission seam (resolveAdmission, bearerCredential, credentialMatches); that admission decision is deliberately not re-made here.
Contract-pure otherwise: the one side concern of where a stream-failure detail goes is injected via IAgentRoutesOptions.onStreamFailure, never imported.
No other transport package may depend on this one.

createHttpTransport is a frozen service lifecycle: readiness is construction of the Hono app (getApp()), not binding a network listener. A repeated active start rejects TransportLifecycleError; repeated stop is safe and supports a new attach/start generation.
/submit refuses a second concurrent turn on a session, keyed by getSession().getSessionId() rather than object identity — a factory that returns a fresh wrapper per call (proxy, adapter, spread copy) is therefore safe, since only the reported session id determines the claim. Two sessions that report the same id are treated as one and will 409 each other; that is a contract violation upstream, since getSessionId() is supposed to name a session.
A session that cannot name itself cannot be claimed: /submit refuses it (HTTP 500) rather than falling back to isExecuting(), because that fallback would start a turn this route cannot guarantee belongs to the caller. /executing is the one place an unnameable session still answers, from isExecuting() alone — reporting what a session is doing is not the same act as admitting a new turn to it.

HTTP errors surface as Hono responses; no new error classes are introduced.

The session's error event is relayed verbatim on the SSE error channel (its own client-facing wording); the WS transport relays it identically.
An exception escaping the stream callback after headers were sent is not a message composed for the client: the client gets a generic line, and the detail goes only to the host's injected onStreamFailure (absent means the host chose to drop it) — the same withholding the /submit 500 branch practices.
The callback swallows its own failures rather than passing an onError to streamSSE, because Hono's runner writes an escaped exception's raw message verbatim to the stream on any onError, which would leak the withheld detail regardless of what the handler intended.