server: honour per-request reasoning_budget_tokens in chat completions (#23116)

• server: honour per-request reasoning_budget_tokens in chat completions

The reasoning-budget block in oaicompat_chat_params_parse read only the server-level default (opt.reasoning_budget, typically -1) and the Anthropic-style alias thinking_budget_tokens, but never the canonical reasoning_budget_tokens field from the request body. Because the key was then written into llama_params before the generic body-copy loop ran, the copy loop found the key already present and silently skipped the caller-supplied value. Any per-request override (e.g. 0 to suppress thinking entirely) was therefore discarded.

Fix: read reasoning_budget_tokens from the request body first, so the value that reaches the sampling layer is the one the caller intended.

Add a unit test in test-chat.cpp that exercises this path via oaicompat_chat_params_parse with a Qwen3 template (which the autoparser detects as a thinking-capable model) and asserts the returned llama_params carries reasoning_budget_tokens == 0.

• server: honour per-request reasoning_budget_message in chat completions

The reasoning-budget block in oaicompat_chat_params_parse wrote reasoning_budget_message into llama_params straight from the server-level default (opt.reasoning_budget_message) and never read the canonical reasoning_budget_message field from the request body. Because the key was written before the generic body-copy loop ran, that loop found the key already present and silently skipped the caller-supplied value. Any per-request override of the message injected before the end tag when the budget is exhausted was therefore discarded, even though server-task.cpp already reads reasoning_budget_message from that data.

This mirrors the reasoning_budget_tokens bug fixed in the previous commit.

Fix: read reasoning_budget_message from the request body first, falling back to the server default, so the value that reaches the sampling layer is the one the caller intended.

While here, collapse the adjacent reasoning_budget_tokens override to a single json_value() call; json_value already falls back to the default on a missing/null/wrong-type key, so the explicit body.contains() guard was redundant. No behavioral change.

Add a unit test in test-chat.cpp that exercises this path via oaicompat_chat_params_parse with a Qwen3 template (which the autoparser detects as a thinking-capable model) and asserts the returned llama_params carries the per-request reasoning_budget_message rather than the server default.

• cleanup

Co-authored-by: Xuan Son Nguyen [email protected]