Source Intelligence

DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

All of v2.1.251 Home All releases olderv2.1.250
Claude Code v2.1.251

Relay checks whether its runtime reports WebSocket backpressure

Under the hood
Useful1 Signal3
Agent Proxy

The relay tests at startup that its runtime reports backpressure, warning if it doesn't.

What

When the agent-proxy relay starts with a reachability probe configured, it opens a loopback WebSocket, pushes enough data that backpressure should register, and verifies the runtime actually reports queued bytes. If it does not, the relay logs a warning and sends telemetry, because the tunnel's upload throttling relies on that number.

Details
  • Runs whenever the relay's startup probe is set, not behind a separate feature flag.
  • Warning states the upload gate cannot engage on that runtime; the relay still starts.
Evidence

WebSocket.bufferedAmount stays 0 with bytes queued: the upload gate cannot engage on this runtime

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

Related

Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.

See this entry in the whole of v2.1.251 →