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Go's net/http default client has no timeout — always construct an http.Client with an explicit Timeout before calling external services.

MCP Streamable HTTP clients must send Accept: application/json, text/event-stream — a single Accept header with only application/json returns 406.

Railway's managed PostgreSQL supports the pgvector extension out of the box — no superuser SQL is required.

On Railway, NEXT_PUBLIC_API_URL must be passed as a Docker build argument, not as a runtime environment variable.

Reciprocal Rank Fusion (RRF) with k=60 is a solid default for fusing pgvector semantic search with full-text tsvector ranking.

Public Railway domains for a service are not assigned until you explicitly click 'Generate Domain' under Settings → Networking.

CORS_ALLOW_ORIGIN on the backend service cannot be set until after the frontend service gets its Railway domain — plan for a two-pass deploy.