server: honour per-request reasoning_budget_tokens in chat completions

tests/test-chat.cpp

@@ -5503,6 +5503,71 @@ static void test_developer_role_to_system_workaround() {
     }
 }
 
+static void test_reasoning_budget_tokens_per_request() {
+    LOG_DBG("%s\n", __func__);
+    // Use Qwen3 template which has <think>...</think> reasoning markers.
+    // The autoparser detects them and sets thinking_start/end_tag, which enables
+    // the reasoning-budget code path in oaicompat_chat_params_parse.
+    auto tmpls = read_templates("models/templates/Qwen-Qwen3-0.6B.jinja");
+
+    server_chat_params opt;
+    opt.tmpls            = std::move(tmpls);
+    opt.use_jinja        = true;
+    opt.enable_thinking  = true;
+    opt.reasoning_budget = -1;
+    opt.reasoning_format = COMMON_REASONING_FORMAT_NONE;
+
+    // Body with per-request reasoning_budget_tokens=0 (suppress thinking).
+    json body = {
+        {"messages", json::array({json{{"role", "user"}, {"content", "hello"}}})},
+        {"reasoning_budget_tokens", 0},
+    };
+    std::vector<raw_buffer> out_files;
+    auto llama_params = oaicompat_chat_params_parse(body, opt, out_files);
+
+    // The per-request value must win over the server default (-1).
+    if (!llama_params.contains("reasoning_budget_tokens")) {
+        throw std::runtime_error("reasoning_budget_tokens missing from llama_params (thinking_end_tag may be empty for this template)");
+    }
+    int got = llama_params["reasoning_budget_tokens"].get<int>();
+    if (got != 0) {
+        throw std::runtime_error(std::string("Expected reasoning_budget_tokens=0, got ") + std::to_string(got));
+    }
+}
+
+static void test_reasoning_budget_message_per_request() {
+    LOG_DBG("%s\n", __func__);
+    // Same code path as test_reasoning_budget_tokens_per_request: the Qwen3 template's
+    // <think>...</think> markers enable the reasoning-budget block in oaicompat_chat_params_parse.
+    auto tmpls = read_templates("models/templates/Qwen-Qwen3-0.6B.jinja");
+
+    server_chat_params opt;
+    opt.tmpls                   = std::move(tmpls);
+    opt.use_jinja               = true;
+    opt.enable_thinking         = true;
+    opt.reasoning_budget        = -1;
+    opt.reasoning_format        = COMMON_REASONING_FORMAT_NONE;
+    opt.reasoning_budget_message = "server default";
+
+    // Body with a per-request reasoning_budget_message override.
+    const std::string per_request_message = "per-request message";
+    json body = {
+        {"messages", json::array({json{{"role", "user"}, {"content", "hello"}}})},
+        {"reasoning_budget_message", per_request_message},
+    };
+    std::vector<raw_buffer> out_files;
+    auto llama_params = oaicompat_chat_params_parse(body, opt, out_files);
+
+    // The per-request value must win over the server default.
+    if (!llama_params.contains("reasoning_budget_message")) {
+        throw std::runtime_error("reasoning_budget_message missing from llama_params (thinking_end_tag may be empty for this template)");
+    }
+    std::string got = llama_params["reasoning_budget_message"].get<std::string>();
+    if (got != per_request_message) {
+        throw std::runtime_error("Expected reasoning_budget_message='" + per_request_message + "', got '" + got + "'");
+    }
+}
+
 static void test_msg_diffs_compute() {
     LOG_DBG("%s\n", __func__);
     {
@@ -5660,6 +5725,8 @@ int main(int argc, char ** argv) {
         test_convert_responses_to_chatcmpl();
         test_developer_role_to_system_workaround();
         test_template_generation_prompt();
+        test_reasoning_budget_tokens_per_request();
+        test_reasoning_budget_message_per_request();
         test_template_output_peg_parsers(detailed_debug);
         std::cout << "\n[chat] All tests passed!" << '\n';
     }

tools/server/server-common.cpp

@@ -1134,16 +1134,24 @@ json oaicompat_chat_params_parse(
 
     // Reasoning budget: pass parameters through to sampling layer
     {
-        int reasoning_budget = json_value(body, "thinking_budget_tokens", -1);
+        // Per-request overrides, read before writing to llama_params so the generic copy
+        // loop (which skips keys already present) won't clobber the caller-supplied values.
+        // Precedence: canonical reasoning_budget_tokens > Anthropic thinking_budget_tokens
+        // alias > server-level default.
+        int reasoning_budget = json_value(body, "reasoning_budget_tokens", -1);
+        if (reasoning_budget == -1) {
+            reasoning_budget = json_value(body, "thinking_budget_tokens", -1);
+        }
         if (reasoning_budget == -1) {
             reasoning_budget = opt.reasoning_budget;
         }
+        std::string reasoning_budget_message = json_value(body, "reasoning_budget_message", opt.reasoning_budget_message);
 
         if (!chat_params.thinking_end_tag.empty()) {
             llama_params["reasoning_budget_tokens"] = reasoning_budget;
             llama_params["reasoning_budget_start_tag"] = chat_params.thinking_start_tag;
             llama_params["reasoning_budget_end_tag"] = chat_params.thinking_end_tag;
-            llama_params["reasoning_budget_message"] = opt.reasoning_budget_message;
+            llama_params["reasoning_budget_message"] = reasoning_budget_message;
             llama_params["reasoning_control"] = json_value(body, "reasoning_control", false);
         }
     }