diff --git a/FirebaseAI/CHANGELOG.md b/FirebaseAI/CHANGELOG.md
index 8a923e651e4..6a265d51932 100644
--- a/FirebaseAI/CHANGELOG.md
+++ b/FirebaseAI/CHANGELOG.md
@@ -1,4 +1,6 @@
 # 12.7.0
+- [feature] Added support for configuring thinking levels with Gemini 3 series
+  mdels and onwards. (#15557)
 - [fixed] Fixed support for API keys with iOS+ app
   [Bundle ID restrictions](https://docs.cloud.google.com/docs/authentication/api-keys#adding-application-restrictions)
   by setting the `x-ios-bundle-identifier` header. (#15475)
diff --git a/FirebaseAI/Sources/Types/Public/ThinkingConfig.swift b/FirebaseAI/Sources/Types/Public/ThinkingConfig.swift
index a339f8fa1d1..bf7ab4e4f58 100644
--- a/FirebaseAI/Sources/Types/Public/ThinkingConfig.swift
+++ b/FirebaseAI/Sources/Types/Public/ThinkingConfig.swift
@@ -14,9 +14,10 @@
 
 /// Configuration for controlling the "thinking" behavior of compatible Gemini models.
 ///
-/// Certain models, like Gemini 2.5 Flash and Pro, utilize a thinking process before generating a
-/// response. This allows them to reason through complex problems and plan a more coherent and
-/// accurate answer.
+/// Gemini 2.5 series models and newer utilize a thinking process before generating a response. This
+/// allows them to reason through complex problems and plan a more coherent and accurate answer.
+/// See the [thinking documentation](https://firebase.google.com/docs/ai-logic/thinking) for more
+/// details.
 public struct ThinkingConfig: Sendable {
   /// The thinking budget in tokens.
   ///
@@ -27,16 +28,13 @@ public struct ThinkingConfig: Sendable {
   /// If you don't specify a budget (`nil`), the model will automatically determine the appropriate
   /// amount of thinking based on the complexity of the prompt.
   ///
-  /// **Model-Specific Behavior:**
-  /// - **Gemini 2.5 Flash:** The budget can range from `0` to `24576`. Setting the budget to `0`
-  ///   disables the thinking process, which prioritizes the lowest latency and cost.
-  /// - **Gemini 2.5 Pro:** The budget must be an integer between `128` and `32768`. Thinking cannot
-  ///   be disabled for this model.
-  ///
   /// An error will be thrown if you set a thinking budget for a model that does not support this
   /// feature or if the specified budget is not within the model's supported range.
   let thinkingBudget: Int?
 
+  /// The level of thoughts tokens that the model should generate.
+  let thinkingLevel: ThinkingLevel?
+
   /// Whether summaries of the model's "thoughts" are included in responses.
   ///
   /// When `includeThoughts` is set to `true`, the model will return a summary of its internal
@@ -51,13 +49,66 @@ public struct ThinkingConfig: Sendable {
   ///
   /// - Parameters:
   ///   - thinkingBudget: The maximum number of tokens to be used for the model's thinking process.
+  ///     The range of [supported thinking budget values
+  ///     ](https://firebase.google.com/docs/ai-logic/thinking#supported-thinking-budget-values)
+  ///     depends on the model.
+  ///       - To use the default thinking budget or thinking level for a model, set this value to
+  ///         `nil` or omit it.
+  ///       - To disable thinking, when supported by the model, set this value to `0`.
+  ///       - To use dynamic thinking, allowing the model to decide on the thinking budget based on
+  ///         the task, set this value to `-1`.
   ///   - includeThoughts: If true, summaries of the model's "thoughts" are included in responses.
   public init(thinkingBudget: Int? = nil, includeThoughts: Bool? = nil) {
     self.thinkingBudget = thinkingBudget
+    thinkingLevel = nil
+    self.includeThoughts = includeThoughts
+  }
+
+  /// Initializes a `ThinkingConfig` with a ``ThinkingLevel``.
+  ///
+  /// If you don't specify a thinking level, Gemini will use the model's default dynamic thinking
+  /// level.
+  ///
+  /// > Important: Gemini 2.5 series models do not support thinking levels; use
+  /// > ``init(thinkingBudget:includeThoughts:)`` to set a thinking budget instead.
+  ///
+  /// - Parameters:
+  ///   - thinkingLevel: A preset that controls the model's "thinking" process. Use
+  ///     ``ThinkingLevel/low`` for faster responses on less complex tasks, and
+  ///     ``ThinkingLevel/high`` for better reasoning on more complex tasks.
+  ///   - includeThoughts: If true, summaries of the model's "thoughts" are included in responses.
+  public init(thinkingLevel: ThinkingLevel, includeThoughts: Bool? = nil) {
+    thinkingBudget = nil
+    self.thinkingLevel = thinkingLevel
     self.includeThoughts = includeThoughts
   }
 }
 
+public extension ThinkingConfig {
+  /// A preset that balances the trade-off between reasoning quality and response speed for a
+  /// model's "thinking" process.
+  struct ThinkingLevel: EncodableProtoEnum, Equatable {
+    enum Kind: String {
+      case low = "LOW"
+      case high = "HIGH"
+    }
+
+    /// A low thinking level optimized for speed and efficiency.
+    ///
+    /// This level is suitable for tasks that are less complex and do not require deep reasoning. It
+    /// provides a faster response time and lower computational cost.
+    public static let low = ThinkingLevel(kind: .low)
+
+    /// A high thinking level designed for complex tasks that require deep reasoning and planning.
+    ///
+    /// This level may result in higher quality, more coherent, and accurate responses, but with
+    /// increased latency and computational cost.
+    public static let high = ThinkingLevel(kind: .high)
+
+    var rawValue: String
+  }
+}
+
 // MARK: - Codable Conformances
 
 extension ThinkingConfig: Encodable {}