RunVODPipeline could reach PLAYING and then block forever on the bus when a demuxer never produced output (no usable pad, unsupported codec, or a wedged source). Nothing logged between "starting" and "done", so a hang was indistinguishable from a stall mid-stream. Wrap the appsink output in a progressWriter and run a watchdog that emits an info-level heartbeat every 5s and cancels the context after 30s of no output, surfacing ErrPipelineStalled instead of hanging indefinitely. Add a matching segment-level heartbeat in the muxl consumer so the production path is visible too. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>