Mistral chat completions uses random_seed not seed; map the field via a new seed_field on the provider registry so the new seed control actually works on Mistral. Default for other providers stays seed.
DeepSeek and Mistral both accept up to 16 stop sequences but the default OAI-compat branch was hard-capping at 4 (the OpenAI Chat limit). Studio routes the openai provider through /v1/responses not /v1/chat/completions so the 4-cap only applies if we explicitly added an openai entry. Raise the default to 16 and let per-provider stop_max overrides tighten if needed.
The local GGUF direct chat path (gguf_generate / gguf_generate_with_tools) bypassed _build_openai_passthrough_body and therefore dropped frequency_penalty, seed, stop, and parallel_tool_calls on the floor for users on the default no-tools and with-tools paths. Thread the new fields through LlamaCppBackend.generate_chat_completion and generate_chat_completion_with_tools and the two callsites that invoke them.
Also tighten comments to drop review-process narration that crept in and to remove the em dashes I had introduced in this PR's earlier commits.
Tests pin the Mistral random_seed rename, the DeepSeek 16-cap, and confirm the openai-compat default cap is 16.
b48d68f8bf