diff --git a/apps/website/content/docs/ag-ui/api/api-docs.json b/apps/website/content/docs/ag-ui/api/api-docs.json
index 85cbb5322..7be9fe93b 100644
--- a/apps/website/content/docs/ag-ui/api/api-docs.json
+++ b/apps/website/content/docs/ag-ui/api/api-docs.json
@@ -8,7 +8,7 @@
         "name": "opts",
         "type": "object",
         "description": "",
-        "optional": false
+        "optional": true
       }
     ],
     "examples": [],
@@ -588,7 +588,7 @@
         "name": "config",
         "type": "FakeAgentConfig",
         "description": "",
-        "optional": false
+        "optional": true
       }
     ],
     "returns": {
@@ -613,7 +613,7 @@
         "name": "options",
         "type": "ToAgentOptions",
         "description": "",
-        "optional": false
+        "optional": true
       }
     ],
     "returns": {
diff --git a/apps/website/content/docs/chat/api/api-docs.json b/apps/website/content/docs/chat/api/api-docs.json
index 1b4293563..dac1fb041 100644
--- a/apps/website/content/docs/chat/api/api-docs.json
+++ b/apps/website/content/docs/chat/api/api-docs.json
@@ -7151,7 +7151,7 @@
         "name": "opts",
         "type": "MockAgentOptions",
         "description": "",
-        "optional": false
+        "optional": true
       }
     ],
     "returns": {
diff --git a/apps/website/content/docs/langgraph/api/api-docs.json b/apps/website/content/docs/langgraph/api/api-docs.json
index 0870ce31d..b6232ddd0 100644
--- a/apps/website/content/docs/langgraph/api/api-docs.json
+++ b/apps/website/content/docs/langgraph/api/api-docs.json
@@ -38,7 +38,7 @@
         "name": "config",
         "type": "FakeAgentConfig",
         "description": "",
-        "optional": false
+        "optional": true
       }
     ],
     "examples": [],
@@ -420,7 +420,7 @@
             "name": "metadata",
             "type": "Record<string, unknown>",
             "description": "",
-            "optional": false
+            "optional": true
           }
         ]
       },
@@ -563,7 +563,7 @@
         "name": "script",
         "type": "StreamEvent[][]",
         "description": "Array of event batches. Each batch is emitted as a group.",
-        "optional": false
+        "optional": true
       }
     ],
     "examples": [
@@ -2366,7 +2366,7 @@
         "name": "initial",
         "type": "MockAgentOptions & { hasValue?: boolean; isThreadLoading?: boolean; langGraphMessages?: BaseMessage<MessageStructure<MessageToolSet>, MessageType>[] }",
         "description": "",
-        "optional": false
+        "optional": true
       }
     ],
     "returns": {
@@ -2404,7 +2404,7 @@
         "name": "config",
         "type": "FakeAgentConfig",
         "description": "",
-        "optional": false
+        "optional": true
       }
     ],
     "returns": {
diff --git a/apps/website/content/docs/render/api/api-docs.json b/apps/website/content/docs/render/api/api-docs.json
index 3b34c44e4..21b47069f 100644
--- a/apps/website/content/docs/render/api/api-docs.json
+++ b/apps/website/content/docs/render/api/api-docs.json
@@ -624,7 +624,7 @@
         "name": "initialState",
         "type": "StateModel",
         "description": "",
-        "optional": false
+        "optional": true
       }
     ],
     "returns": {
diff --git a/apps/website/content/docs/telemetry/api/api-docs.json b/apps/website/content/docs/telemetry/api/api-docs.json
index a0893a4a2..dc96404b4 100644
--- a/apps/website/content/docs/telemetry/api/api-docs.json
+++ b/apps/website/content/docs/telemetry/api/api-docs.json
@@ -42,7 +42,7 @@
         "name": "env",
         "type": "ProcessEnv<>",
         "description": "",
-        "optional": false
+        "optional": true
       }
     ],
     "returns": {
@@ -61,7 +61,7 @@
         "name": "env",
         "type": "ProcessEnv<>",
         "description": "",
-        "optional": false
+        "optional": true
       }
     ],
     "returns": {
@@ -233,7 +233,7 @@
         "name": "properties",
         "type": "Record<string, unknown>",
         "description": "",
-        "optional": false
+        "optional": true
       }
     ],
     "returns": {
@@ -460,7 +460,7 @@
         "name": "maxLength",
         "type": "number",
         "description": "",
-        "optional": false
+        "optional": true
       }
     ],
     "returns": {
diff --git a/apps/website/scripts/generate-api-docs.ts b/apps/website/scripts/generate-api-docs.ts
index 07cc01a88..04e4460b1 100644
--- a/apps/website/scripts/generate-api-docs.ts
+++ b/apps/website/scripts/generate-api-docs.ts
@@ -78,7 +78,10 @@ function extractParams(sig: any): ApiParam[] {
     name: `${p.flags?.isRest ? '...' : ''}${p.name}`,
     type: extractType(p.type),
     description: extractDescription(p.comment),
-    optional: p.flags?.isOptional ?? false,
+    // A parameter is optional if explicitly marked `?` OR it has a default
+    // value (e.g. `opts: MockAgentOptions = {}`) — TypeDoc only sets the
+    // `isOptional` flag for the former, so check `defaultValue` for the latter.
+    optional: (p.flags?.isOptional ?? false) || p.defaultValue !== undefined,
   }));
 }