Daoyuan Li 6ef0aa2aea
fix(tui): stop empty-id assistant deltas from merging across turns (#4201)
_apply_assistant_delta matched AssistantDelta.id anywhere in the transcript,
which is correct for a genuine per-message id but not for an empty one.
runtime._as_str() coerces a missing/None chunk id to "", and that value is
shared by every id-less chunk from every turn, not just the current one.
Once one assistant row had id="", every later, unrelated AssistantDelta that
also carried id="" (e.g. from a provider that never stamps per-chunk ids)
matched that same stale row instead of starting a fresh one, silently
folding a second turn's answer backward into the first turn's bubble.

Route empty-id deltas to a dedicated path that tracks the current turn's
row by position (streaming_anonymous_row_index, reset on RunStarted/
RunEnded/ClearRows) instead of by id, mirroring the existing empty-id guards
in _apply_tool_started/_apply_tool_result but adapted for assistant text:
unlike a tool call, an id-less assistant delta still needs to be displayed,
so it starts a new row rather than being dropped. Multiple id-less chunks
legitimately arrive within one turn (per-token streaming), so they keep
coalescing into that row -- but only while it is still the transcript tail;
once a tool card is appended after it (the same way a genuine id naturally
changes across a tool round-trip), the next empty-id delta starts fresh
instead of reaching backward past the tool card.

Add regression coverage for the cross-turn merge, same-turn coalescing,
the tool-call-interleaved edge case, and non-interference with the
existing id-keyed path.
2026-07-15 22:27:00 +08:00
..