Live fault 2026-11-08: node-engines on two machines logged only "nats: slow consumer, messages dropped" and applied nothing. The
client's watch sends into its channel from inside the subscription's callback; KVWatch forwarded that channel to its reader
blocking, and the reader (composing for minutes) stopped draining, so the subscription's pending limit overflowed.
Quick fix: a larger buffer on the watch's channel; it only moves the limit. Thorough fix (chosen): the forwarder always drains the
client's channel and, while its reader is busy, coalesces the pending updates by key (newest value and revision, first-seen
order, Caught kept in its place), so no reader's pace can back the client up, whatever the burst. A slow consumer error now
names its subscription and what it holds pending.
Claude-Session: https://claude.ai/code/session_01NcbgfFfQ4Z9UE5jK32PmE5
jschoubben
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