MCP transport: moving from SSE to Streamable HTTP

Context

The March journal and platform specifications record the primary MCP bridge’s migration from SSE to Streamable HTTP on 29 March 2026 (VW-177). The earlier website date and ADR number were part of an example record, not a canonical decision allocation.

Design rationale

The bridge uses a stateless HTTP application for tool requests. Current source explicitly selects stateless_http=True for its HTTP path. Streamable HTTP can also be stateful; the transport name alone does not establish session affinity, cold-start time or safe scale-to-zero behaviour.

Current context

On 14 October, the primary bridge deployment declared MCP_TRANSPORT=http and had one desired and one ready replica. The source still includes a legacy SSE branch. This check does not remeasure the historical 40-second-to-1.6-second latency claim, prove SSE retirement, or demonstrate scale-to-zero.

Record correction

The previous claim that this superseded ADR-029 has been removed: canonical ADR-029 concerns GPU scheduling. Canonical ADR-046 concerns memory embedding. Neither is the predecessor decision for this transport note.

Source and record history

Read the published episode. Website Git history shows this page began as an explicitly labelled example reconstructed from the journal. Its original URL is retained, but the number in that URL is not a canonical ADR identity. Reconciled on 14 October 2026.