diff --git a/Sources/OpenAI/Public/ResponseModels/Response/OutputItem.swift b/Sources/OpenAI/Public/ResponseModels/Response/OutputItem.swift
index 8ee434f..7bae3b1 100644
--- a/Sources/OpenAI/Public/ResponseModels/Response/OutputItem.swift
+++ b/Sources/OpenAI/Public/ResponseModels/Response/OutputItem.swift
@@ -281,8 +281,16 @@ public enum OutputItem: Decodable {
   public struct WebSearchToolCall: Decodable {
     /// Action taken in web search
     public struct Action: Decodable {
-      // Action properties will use AnyCodable for flexibility
-      // as different action types (search, open_page, find) have different structures
+      /// The action performed: search, open_page, or find_in_page.
+      public let type: String?
+      /// The search query returned by older responses.
+      public let query: String?
+      /// The search queries performed by the tool.
+      public let queries: [String]?
+      /// The URL opened or searched within.
+      public let url: String?
+      /// The pattern searched for within a page.
+      public let pattern: String?
     }
 
     /// An object describing the specific action taken in this web search call
@@ -487,9 +495,12 @@ public enum OutputItem: Decodable {
     public let status: String?
     /// The type of the image generation call. Always "image_generation_call"
     public let type: String
+    /// The output format used for generation: png, webp, or jpeg.
+    public let outputFormat: String?
 
     enum CodingKeys: String, CodingKey {
       case id, result, status, type
+      case outputFormat = "output_format"
     }
   }
 
diff --git a/Sources/OpenAI/Public/ResponseModels/Response/ResponseModel.swift b/Sources/OpenAI/Public/ResponseModels/Response/ResponseModel.swift
index 28b3f0e..f8709b6 100644
--- a/Sources/OpenAI/Public/ResponseModels/Response/ResponseModel.swift
+++ b/Sources/OpenAI/Public/ResponseModels/Response/ResponseModel.swift
@@ -110,7 +110,7 @@ public struct ResponseModel: Decodable {
   /// Set of 16 key-value pairs that can be attached to an object.
   /// This can be useful for storing additional information about the object in a structured format, and querying for objects via API or the dashboard.
   /// Keys are strings with a maximum length of 64 characters. Values are strings with a maximum length of 512 characters.
-  public let metadata: [String: String]
+  public let metadata: [String: String]?
 
   /// Model ID used to generate the response, like gpt-4o or o1.
   /// OpenAI offers a wide range of models with different capabilities, performance characteristics, and price points.
diff --git a/Tests/OpenAITests/ResponseModelValidationTests.swift b/Tests/OpenAITests/ResponseModelValidationTests.swift
index dba2a5b..4f0ee1d 100644
--- a/Tests/OpenAITests/ResponseModelValidationTests.swift
+++ b/Tests/OpenAITests/ResponseModelValidationTests.swift
@@ -60,7 +60,7 @@ final class ResponseModelValidationTests: XCTestCase {
     XCTAssertEqual(responseModel.topP, 1.0)
     XCTAssertEqual(responseModel.truncation, "disabled")
     XCTAssertNil(responseModel.user)
-    XCTAssertTrue(responseModel.metadata.isEmpty)
+    XCTAssertEqual(responseModel.metadata, [:])
 
     // Validate usage
     XCTAssertNotNil(responseModel.usage)
diff --git a/Tests/OpenAITests/ResponseSchemaRegressionTests.swift b/Tests/OpenAITests/ResponseSchemaRegressionTests.swift
new file mode 100644
index 0000000..05958a5
--- /dev/null
+++ b/Tests/OpenAITests/ResponseSchemaRegressionTests.swift
@@ -0,0 +1,116 @@
+#if compiler(>=6.0)
+import Foundation
+import SwiftOpenAI
+import Testing
+
+@Suite("Responses schema regressions")
+struct ResponseSchemaRegressionTests {
+  @Test("A response accepts explicitly null metadata")
+  func nullMetadata() throws {
+    let data = Data(
+      #"{"id":"r","object":"response","created_at":1,"model":"test","output":[],"parallel_tool_calls":true,"metadata":null}"#
+        .utf8)
+    let response = try JSONDecoder().decode(ResponseModel.self, from: data)
+    #expect(response.metadata == nil)
+  }
+
+  @Test("Documented web-search fields survive decoding")
+  func searchFields() throws {
+    let data = Data(
+      #"{"id":"w","type":"web_search_call","status":"completed","action":{"type":"search","query":"weather","queries":["weather","forecast"]}}"#
+        .utf8)
+    let item = try JSONDecoder().decode(OutputItem.self, from: data)
+    guard case .webSearchCall(let search) = item else {
+      Issue.record("Expected web search")
+      return
+    }
+    let action = try #require(search.action)
+    #expect(action.type == "search")
+    #expect(action.queries == ["weather", "forecast"])
+    #expect(action.query == "weather")
+    let event = try JSONDecoder().decode(ResponseStreamEvent.self, from: Data(
+      (#"{"type":"response.output_item.done","output_index":0,"item":"# + String(decoding: data, as: UTF8.self) + "}").utf8))
+    guard case .outputItemDone(let done) = event, case .webSearchCall(let streamed) = done.item else {
+      Issue.record("Expected streamed web search")
+      return
+    }
+    #expect(streamed.action?.queries == ["weather", "forecast"])
+  }
+
+  @Test("Documented generated-image format survives decoding", arguments: ["png", "jpeg", "webp"])
+  func imageFormat(format: String) throws {
+    let data = Data(
+      #"{"id":"i","type":"image_generation_call","status":"completed","result":"aW1hZ2U=","output_format":"\#(format)"}"#
+        .utf8)
+    let item = try JSONDecoder().decode(OutputItem.self, from: data)
+    guard case .imageGenerationCall(let image) = item else {
+      Issue.record("Expected generated image")
+      return
+    }
+    #expect(image.outputFormat == format)
+    #expect(image.result == "aW1hZ2U=")
+    let streamed = try JSONDecoder().decode(StreamOutputItem.self, from: data)
+    guard case .imageGenerationCall(let streamImage) = streamed else {
+      Issue.record("Expected streamed generated image")
+      return
+    }
+    #expect(streamImage.outputFormat == format)
+  }
+
+  @Test("Web search preserves page and find actions")
+  func pageActions() throws {
+    for type in ["open_page", "find_in_page"] {
+      let data = Data(#"{"type":"\#(type)","url":"https://example.com/","pattern":"forecast"}"#.utf8)
+      let action = try JSONDecoder().decode(OutputItem.WebSearchToolCall.Action.self, from: data)
+      #expect(action.type == type)
+      #expect(action.url == "https://example.com/")
+      #expect(action.pattern == "forecast")
+      #expect(action.queries == nil)
+    }
+  }
+
+  @Test("Optional tool fields may be absent or null")
+  func optionalToolFields() throws {
+    for body in ["{}", #"{"type":null,"query":null,"queries":null,"url":null,"pattern":null}"#] {
+      let action = try JSONDecoder().decode(OutputItem.WebSearchToolCall.Action.self, from: Data(body.utf8))
+      #expect(action.query == nil)
+      #expect(action.queries == nil)
+    }
+    for extra in ["", #", "output_format":null"#] {
+      let body = #"{"id":"i","type":"image_generation_call"\#(extra)}"#
+      let image = try JSONDecoder().decode(OutputItem.ImageGenerationCall.self, from: Data(body.utf8))
+      #expect(image.outputFormat == nil)
+    }
+  }
+
+  @Test("Wrong field types remain decoding errors")
+  func invalidFieldTypes() {
+    #expect(throws: DecodingError.self) {
+      try JSONDecoder().decode(OutputItem.WebSearchToolCall.Action.self, from: Data(#"{"queries":17}"#.utf8))
+    }
+    #expect(throws: DecodingError.self) {
+      try JSONDecoder().decode(
+        OutputItem.ImageGenerationCall.self,
+        from: Data(#"{"id":"i","type":"image_generation_call","output_format":17}"#.utf8))
+    }
+  }
+
+  @Test(
+    "Accepting null metadata does not relax other required response fields",
+    arguments: ["id", "object", "created_at", "model", "output", "parallel_tool_calls"])
+  func requiredResponseFields(field: String) throws {
+    var json: [String: Any] = [
+      "id": "r",
+      "object": "response",
+      "created_at": 1,
+      "model": "test",
+      "output": [],
+      "parallel_tool_calls": true,
+      "metadata": NSNull(),
+    ]
+    json.removeValue(forKey: field)
+    let data = try JSONSerialization.data(withJSONObject: json)
+    #expect(throws: DecodingError.self) { try JSONDecoder().decode(ResponseModel.self, from: data) }
+  }
+}
+#endif