Configured sampling parameters never reach most providers

• Status: Todo
• Kind: Bug
• Authors: jp
• Date: 2026-09-22
• Label: domain=llm
• Label: package=jp_config
• Label: package=jp_llm
• Label: type=bug

assistant.model.parameters accepts settings that no request builder reads. A user writes them in config.toml, sees them in the generated file and in the JSON schema, and the request goes out with the server's defaults. Nothing reports the gap: the query succeeds and the answer looks plausible.

Three separate gaps, in order of how clear the fix is.

stop_words reaches no provider at all

ParametersConfig::stop_words is declared in jp_config::model::parameters, carries an append_vec merge strategy, has delta and fill coverage, and appears in four places in the config snapshots. Grepping crates/jp_llm/src for stop_words returns nothing: every hit in the workspace is in jp_config or its tests.

Every provider JP speaks to accepts a stop sequence list — stop for the OpenAI-compatible dialects, stop_sequences for Anthropic, stopSequences for Google, options.stop for Ollama. Either the field is wired to each of them, or it should be removed from ParametersConfig rather than left as configuration that does nothing.

top_k reaches three providers of nine

Forwarded by anthropic, google, ollama, and vllm. Not forwarded by openai, openrouter, cerebras, or llamacpp.

llama.cpp and vLLM serve the same dialect and the same locally-hosted models, so the split between them is the odd one: a Qwen3 deployment documents a top_k alongside its top_p, and which of the two servers is running decides whether it applies.

parameters.other is documented as a passthrough but is not one

The doc comment reads "Parameters JP does not model are collected into [Self::other], so a provider-specific key can be written directly in the parameter block." No provider forwards the map. Each reads named keys out of it: verbosity and reasoning_mode (openai.rs), keep_alive (ollama.rs), context_management (anthropic.rs). Anything else a user writes there is dropped in silence.

This one carries a decision rather than a fix. A generic passthrough sends a user's typo to the server as an unknown field, which some servers reject and others ignore; a curated allowlist means every provider-specific key costs code and the documented promise has to be narrowed to match. Settle that before touching the other two, since it decides whether min_p and friends are a provider's job or the map's.

Notes

Found while reviewing #1174, which added the vllm provider. top_k was wired there as part of that review; the rest is untouched and predates it.