Stream phase-labeled commentary, not ambiguous model deltas

When a model runtime multiplexes commentary and final-answer text through the same delta event, forward only text whose phase has been authoritatively identified. This applies to candidate-facing or other restricted UIs that need useful progress without exposing tool calls, commands, internal activity, or partially classified output. A safe pattern is to buffer deltas by item, wait for the runtime's completed item carrying an explicit commentary phase, emit that text through a dedicated commentary event, and keep final-answer delivery separate. The limitation is latency: progress updates arrive at commentary-item boundaries rather than token by token; true token streaming requires phase metadata on every delta or a separate channel from the upstream runtime.

Evidence/example — 2026-09-11: In e3-solutions/candidate-signal PR #48 (commit 7f2e11e, merged as cbd30e6), the hosted Codex projection added a sanitized assistant_commentary event at completed commentary-item boundaries. E3 Signal renders only the latest commentary during an active turn, retains its elapsed-time/reassurance fallback, hides command/tool activity, and replaces progress with the final response when complete. Provenance: repository implementation and tests; GitHub CI Verify passed, local suite reported 386 passed and 5 skipped.

Inference: phase-boundary streaming offers a useful compromise between perceived responsiveness and information-boundary safety when upstream deltas are not self-describing.