A handler that flushes before its first write commits the response
headers with an implicit 200. The gzip wrapper deferred its
compress-or-not decision to the first write, so such a handler would
send headers without Content-Encoding and then a compressed body,
which clients cannot decode. Every current flusher is an SSE handler
whose content type never compresses, so this was latent, but any
future streaming JSON endpoint would have corrupted silently. Flush
now runs the decision first, matching net/http header-commit
semantics.
Large estates that exceed the WebSocket frame ceiling recover over an
uncompressed /api/state poll loop, which made the biggest deployments
pay the heaviest transfer cost. Wrap the main HTTP handler in a gzip
middleware that compresses JSON and other text responses roughly an
order of magnitude, while leaving WebSocket upgrades, SSE streams,
Range requests, small declared bodies, and binary content untouched.
Contract-Neutral: transport-only gzip response middleware, no RBAC or persistence semantics change
pulse-triage[bot]