v3.12.0 (2026-04-25)
Features
- Streaming heartbeat — opt-in SSE comment frame (
: keepalive\n\n) emitted during silent windows on the streaming response. Controlled byCLAUDE_HEARTBEAT_INTERVALenv var (ms;0= disabled, default). Covers both pre-first-byte and mid-stream tool-use pauses. Addresses #47. See design doc. X-Accel-Buffering: noresponse header added to SSE responses so heartbeats survive nginx/Cloudflare default buffering.
Behavior changes
- SSE headers are now sent immediately after the claude CLI spawns successfully, not on first stdout byte. The rare "spawn succeeded but subprocess died before any byte" path now closes the SSE stream cleanly rather than returning a JSON error.
Config additions
| Variable | Default | Description |
|---|---|---|
CLAUDE_HEARTBEAT_INTERVAL
| 0 (disabled)
| Interval in ms for SSE keepalive comment frames on streaming path. Resets on every real frame. |