feat(ollama): add reasoning model detection with config overrides

- Auto-detect reasoning models (qwen3, phi4, gemma3, llama3, deepseek, qwq, gpt-oss)
- Add config support to force reasoning ON/OFF via capabilities.reasoning
- Enable interleaved with reasoning_content field for reasoning models
- Increase token limits (context: 200k, output: 32k) for reasoning models
- Add default reasoningEffort: medium for reasoning models
- Add think parameter support for Ollama API (true/false or low/medium/high for GPT-OSS)

Author: Kory Boyd

packages/opencode/src/provider/provider.ts

@@ -1024,6 +1024,23 @@ export namespace Provider {
       mergeProvider(providerID, partial)
     }
 
+    // Patterns to detect reasoning-capable Ollama models
+    const OLLAMA_REASONING_PATTERNS = [
+      /qwen[_\-]?3/i, // qwen3, qwen-3, qwen_3
+      /phi[_\-]?4/i, // phi4, phi-4
+      /gemma[_\-]?3/i, // gemma3, gemma-3
+      /llama[_\-]?3/i, // llama3, llama-3
+      /r1$/i, // deepseek-r1, etc.
+      /qwq/i, // QwQ
+      /deepseek/i, // DeepSeek family
+      /gpt-?oss/i, // GPT-OSS
+    ]
+
+    function isOllamaReasoningModel(modelName: string, family?: string, families?: string[]): boolean {
+      const searchText = `${modelName} ${family ?? ""} ${families?.join(" ") ?? ""}`
+      return OLLAMA_REASONING_PATTERNS.some(pattern => pattern.test(searchText))
+    }
+
     // Auto-detect Ollama if not already configured
     const ollamaConfigured = providers["ollama"] || configProviders.some(([id]) => id === "ollama")
     if (!ollamaConfigured) {
@@ -1035,6 +1052,19 @@ export namespace Provider {
         for (const ollamaModel of ollama.models) {
           const { model, tag } = parseModelName(ollamaModel.name)
           const modelID = tag ? `${model}:${tag}` : model
+
+          // Detect if this is a reasoning model based on patterns
+          const isReasoning = isOllamaReasoningModel(
+            model,
+            ollamaModel.details?.family,
+            ollamaModel.details?.families,
+          )
+
+          // Check for config overrides - allow forcing reasoning on/off
+          const configModel = config.provider?.ollama?.models?.[modelID]
+          const configForceReasoning = configModel?.capabilities?.reasoning // undefined = auto, true = force on, false = force off
+          const finalReasoning = configForceReasoning !== undefined ? configForceReasoning : isReasoning
+
           ollamaModels[modelID] = {
             id: modelID,
             providerID: ollamaProviderID,
@@ -1048,18 +1078,25 @@ export namespace Provider {
             status: "active",
             capabilities: {
               temperature: true,
-              reasoning: ollamaModel.details?.family?.includes("reasoning") ?? false,
+              reasoning: finalReasoning,
               attachment: false,
               toolcall: true,
               input: { text: true, audio: false, image: false, video: false, pdf: false },
               output: { text: true, audio: false, image: false, video: false, pdf: false },
-              interleaved: false,
+              interleaved: finalReasoning
+                ? configModel?.capabilities?.interleaved ?? { field: "reasoning_content" }
+                : false,
             },
             cost: { input: 0, output: 0, cache: { read: 0, write: 0 } },
-            options: {},
+            options:
+              finalReasoning
+                ? { reasoningEffort: configModel?.options?.reasoningEffort ?? "medium", ...configModel?.options }
+                : {},
             limit: {
-              context: ollamaModel.details?.parameter_size ? 128000 : 8192,
-              output: 8192,
+              context:
+                configModel?.limit?.context ??
+                (finalReasoning ? 200000 : ollamaModel.details?.parameter_size ? 128000 : 8192),
+              output: configModel?.limit?.output ?? (finalReasoning ? 32768 : 8192),
             },
             headers: {},
             release_date: "",

packages/opencode/src/provider/transform.ts

@@ -756,6 +756,28 @@ export namespace ProviderTransform {
       result["enable_thinking"] = true
     }
 
+    // Enable thinking for Ollama reasoning models via the "think" parameter
+    // Ollama supports thinking for: DeepSeek R1, DeepSeek v3.1, Qwen 3, GPT-OSS
+    // Most models accept true/false, GPT-OSS accepts low/medium/high
+    if (
+      input.model.providerID === "ollama" &&
+      input.model.capabilities.reasoning &&
+      input.model.api.npm === "@ai-sdk/openai-compatible"
+    ) {
+      // Check if it's a GPT-OSS model (supports thinking levels)
+      if (input.model.id.toLowerCase().includes("gpt-oss")) {
+        result["think"] = input.model.options?.reasoningEffort ?? "medium"
+      } else {
+        // For most models, enable thinking when not disabled
+        const effort = input.model.options?.reasoningEffort
+        if (effort === "none") {
+          result["think"] = false
+        } else {
+          result["think"] = true
+        }
+      }
+    }
+
     if (input.model.api.id.includes("gpt-5") && !input.model.api.id.includes("gpt-5-chat")) {
       if (!input.model.api.id.includes("gpt-5-pro")) {
         result["reasoningEffort"] = "medium"