DeepSeek's Responses stream sends ``response.reasoning_text.delta`` fragments and then ``response.reasoning_text.done`` carrying the whole chain of thought those fragments spelled out. The loop folded a full delta into the round — it replaces the fragments, and that is what the assistant message hands back to the API — but streamed every delta verbatim, so the chain of thought was printed twice: once as it arrived and again as the ``.done`` text.
A full delta now streams only a tail the fragments did not cover, and nothing at all when it merely repeats them; a round whose fragments never arrived still streams the full text once. The message keeps the complete text either way.
DeepSeek dropped the `v4` prefix from its flash model, and the old id stays
valid only as a compatibility alias. Seed the default catalog with the current
name so a provider that omits `models` no longer offers a deprecated id, and
follow the rename in the wire fixtures and the minimal config template. An
explicit `deepseek-v4-flash` in TOML still passes through unchanged.
NCBM