diff --git a/Sources/AnyLanguageModel/Models/OllamaLanguageModel.swift b/Sources/AnyLanguageModel/Models/OllamaLanguageModel.swift
index 82be5cc7..b7a11635 100644
--- a/Sources/AnyLanguageModel/Models/OllamaLanguageModel.swift
+++ b/Sources/AnyLanguageModel/Models/OllamaLanguageModel.swift
@@ -26,11 +26,16 @@ public struct OllamaLanguageModel: LanguageModel {
     /// Available options are model-specific and defined in the model's Modelfile.
     /// Common options include `seed`, `repeat_penalty`, `stop`, and others.
     ///
+    /// Keys that Ollama defines as top-level chat request parameters
+    /// (`think` and `keep_alive`) are sent at the top level of the request
+    /// body instead of inside `options`.
+    ///
     /// ```swift
     /// var options = GenerationOptions(temperature: 0.7)
     /// options[custom: OllamaLanguageModel.self] = [
     ///     "seed": 42,
-    ///     "repeat_penalty": 1.2
+    ///     "repeat_penalty": 1.2,
+    ///     "think": true
     /// ]
     /// ```
     ///
@@ -100,7 +105,8 @@ public struct OllamaLanguageModel: LanguageModel {
             options: ollamaOptions,
             stream: false,
             images: ollamaImages.isEmpty ? nil : ollamaImages,
-            format: ollamaFormat
+            format: ollamaFormat,
+            parameters: extractTopLevelChatParameters(options)
         )
 
         let url = baseURL.appendingPathComponent("api/chat")
@@ -191,7 +197,8 @@ public struct OllamaLanguageModel: LanguageModel {
                         options: ollamaOptions,
                         stream: true,
                         images: (ollamaImages.isEmpty ? nil : ollamaImages),
-                        format: ollamaFormat
+                        format: ollamaFormat,
+                        parameters: extractTopLevelChatParameters(options)
                     )
                     let body = try JSONEncoder().encode(params)
 
@@ -375,7 +382,7 @@ private func resolveToolCalls(
 
 // MARK: - Conversions
 
-private func convertOptions(_ options: GenerationOptions) -> [String: JSONValue]? {
+func convertOptions(_ options: GenerationOptions) -> [String: JSONValue]? {
     var ollamaOptions: [String: JSONValue] = [:]
 
     // Handle temperature
@@ -415,7 +422,7 @@ private func convertOptions(_ options: GenerationOptions) -> [String: JSONValue]
 
     // Merge custom Ollama options
     if let customOptions: [String: JSONValue] = options[custom: OllamaLanguageModel.self] {
-        for (key, value) in customOptions {
+        for (key, value) in customOptions where !topLevelChatParameterKeys.contains(key) {
             ollamaOptions[key] = value
         }
     }
@@ -423,6 +430,18 @@ private func convertOptions(_ options: GenerationOptions) -> [String: JSONValue]
     return ollamaOptions.isEmpty ? nil : ollamaOptions
 }
 
+/// Custom option keys that Ollama's `/api/chat` endpoint reads from the top level
+/// of the request body rather than from `options`.
+private let topLevelChatParameterKeys: Set<String> = ["think", "keep_alive"]
+
+func extractTopLevelChatParameters(_ options: GenerationOptions) -> [String: JSONValue]? {
+    guard let customOptions: [String: JSONValue] = options[custom: OllamaLanguageModel.self] else {
+        return nil
+    }
+    let parameters = customOptions.filter { topLevelChatParameterKeys.contains($0.key) }
+    return parameters.isEmpty ? nil : parameters
+}
+
 private func convertToolToOllamaFormat(_ tool: any Tool) throws -> [String: JSONValue] {
     let resolvedSchema = tool.parameters.withResolvedRoot() ?? tool.parameters
     return [
@@ -448,14 +467,15 @@ private func toGeneratedContent(_ value: JSONValue?) throws -> GeneratedContent
     return try GeneratedContent(json: json)
 }
 
-private func createChatParams(
+func createChatParams(
     model: String,
     messages: [OllamaMessage],
     tools: [[String: JSONValue]]?,
     options: [String: JSONValue]?,
     stream: Bool,
     images: [String]?,
-    format: JSONValue?
+    format: JSONValue?,
+    parameters: [String: JSONValue]? = nil
 ) throws -> [String: JSONValue] {
     var params: [String: JSONValue] = [
         "model": .string(model),
@@ -479,12 +499,18 @@ private func createChatParams(
         params["format"] = format
     }
 
+    if let parameters {
+        for (key, value) in parameters where params[key] == nil {
+            params[key] = value
+        }
+    }
+
     return params
 }
 
 // MARK: - Supporting Types
 
-private struct OllamaMessage: Hashable, Codable, Sendable {
+struct OllamaMessage: Hashable, Codable, Sendable {
     enum Role: String, Hashable, Codable, Sendable {
         case system
         case user
diff --git a/Tests/AnyLanguageModelTests/OllamaLanguageModelTests.swift b/Tests/AnyLanguageModelTests/OllamaLanguageModelTests.swift
index 5a8911f0..357dcf5c 100644
--- a/Tests/AnyLanguageModelTests/OllamaLanguageModelTests.swift
+++ b/Tests/AnyLanguageModelTests/OllamaLanguageModelTests.swift
@@ -174,3 +174,50 @@ struct OllamaLanguageModelTests {
         #expect(!response.content.isEmpty)
     }
 }
+
+@Suite("Ollama top-level chat parameters")
+struct OllamaTopLevelChatParametersTests {
+    @Test func routesThinkToTheTopLevelOfTheRequest() throws {
+        var options = GenerationOptions()
+        options[custom: OllamaLanguageModel.self] = [
+            "think": .bool(true),
+            "repeat_penalty": .double(1.2),
+        ]
+
+        let params = try createChatParams(
+            model: "qwen3:8b",
+            messages: [OllamaMessage(role: .user, content: "Hello")],
+            tools: nil,
+            options: convertOptions(options),
+            stream: false,
+            images: nil,
+            format: nil,
+            parameters: extractTopLevelChatParameters(options)
+        )
+
+        #expect(params["think"] == .bool(true))
+
+        guard case .object(let requestOptions)? = params["options"] else {
+            Issue.record("Expected options to encode as an object")
+            return
+        }
+        #expect(requestOptions["think"] == nil)
+        #expect(requestOptions["repeat_penalty"] == .double(1.2))
+    }
+
+    @Test func topLevelParametersDoNotOverrideReservedKeys() throws {
+        let params = try createChatParams(
+            model: "gpt-oss:20b",
+            messages: [OllamaMessage(role: .user, content: "Hello")],
+            tools: nil,
+            options: nil,
+            stream: false,
+            images: nil,
+            format: nil,
+            parameters: ["model": .string("injected"), "think": .string("high")]
+        )
+
+        #expect(params["model"] == .string("gpt-oss:20b"))
+        #expect(params["think"] == .string("high"))
+    }
+}