feat: add configuration for model, mode, and thought level

docs/sdk-overview.mdx

@@ -100,6 +100,25 @@ await restored.prompt([{ type: "text", text: "Continue from previous context." }
 await sdk.destroySession(restored.id);
 ```
 
+## Session configuration
+
+Set model, mode, or thought level at creation or on an existing session:
+
+```ts
+const session = await sdk.createSession({
+  agent: "codex",
+  model: "gpt-5.3-codex",
+});
+
+await session.setModel("gpt-5.2-codex");
+await session.setMode("plan");
+
+const options = await session.getConfigOptions();
+const modes = await session.getModes();
+```
+
+See [Agent Sessions](/agent-sessions) for full details on config options and error handling.
+
 ## Events
 
 Subscribe to live events:
@@ -171,13 +190,3 @@ Parameters:
 - `headers` (optional): Additional request headers
 - `fetch` (optional): Custom fetch implementation used by SDK HTTP and ACP calls
 
-## Types
-
-```ts
-import type {
-  AgentInfo,
-  HealthResponse,
-  SessionEvent,
-  SessionRecord,
-} from "sandbox-agent";
-```