app-server: reload config for Windows thread forks

git-stack-id: aaron/app-server-in-memory-config---4ivokd7wtu-snl
git-stack-title: app-server: add in-memory config layer

codex-rs/app-server/src/request_processors/thread_processor.rs

@@ -3188,23 +3188,7 @@ impl ThreadRequestProcessor {
             })?;
         let history_cwd = Some(source_thread.cwd.clone());
 
-        // Persist Windows sandbox mode.
-        let mut cli_overrides = cli_overrides.unwrap_or_default();
-        if cfg!(windows) {
-            match WindowsSandboxLevel::from_config(&self.config) {
-                WindowsSandboxLevel::Elevated => {
-                    cli_overrides
-                        .insert("windows.sandbox".to_string(), serde_json::json!("elevated"));
-                }
-                WindowsSandboxLevel::RestrictedToken => {
-                    cli_overrides.insert(
-                        "windows.sandbox".to_string(),
-                        serde_json::json!("unelevated"),
-                    );
-                }
-                WindowsSandboxLevel::Disabled => {}
-            }
-        }
+        let cli_overrides = cli_overrides.unwrap_or_default();
         let request_overrides = if cli_overrides.is_empty() {
             None
         } else {

codex-rs/app-server/tests/suite/v2/thread_fork.rs

@@ -10,6 +10,8 @@ use codex_app_server_protocol::JSONRPCError;
 use codex_app_server_protocol::JSONRPCMessage;
 use codex_app_server_protocol::JSONRPCResponse;
 use codex_app_server_protocol::RequestId;
+#[cfg(windows)]
+use codex_app_server_protocol::SandboxPolicy;
 use codex_app_server_protocol::ServerNotification;
 use codex_app_server_protocol::SessionSource;
 use codex_app_server_protocol::ThreadForkParams;
@@ -674,6 +676,54 @@ async fn thread_fork_surfaces_cloud_config_bundle_load_errors() -> Result<()> {
     Ok(())
 }
 
+#[cfg(windows)]
+#[tokio::test]
+async fn thread_fork_reloads_windows_sandbox_config_instead_of_startup_snapshot() -> Result<()> {
+    let codex_home = TempDir::new()?;
+    std::fs::write(
+        codex_home.path().join("config.toml"),
+        "[windows]\nsandbox = \"elevated\"\n",
+    )?;
+
+    let mut mcp = TestAppServer::new(codex_home.path()).await?;
+    timeout(DEFAULT_READ_TIMEOUT, mcp.initialize()).await??;
+
+    let start_id = mcp
+        .send_thread_start_request(ThreadStartParams::default())
+        .await?;
+    let start_response: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(start_id)),
+    )
+    .await??;
+    let start_response: ThreadStartResponse = to_response(start_response)?;
+    assert!(
+        matches!(start_response.sandbox, SandboxPolicy::WorkspaceWrite { .. }),
+        "elevated Windows sandbox config should select workspace-write defaults"
+    );
+
+    std::fs::write(codex_home.path().join("config.toml"), "")?;
+
+    let fork_id = mcp
+        .send_thread_fork_request(ThreadForkParams {
+            thread_id: start_response.thread.id,
+            ..Default::default()
+        })
+        .await?;
+    let fork_response: JSONRPCResponse = timeout(
+        DEFAULT_READ_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(fork_id)),
+    )
+    .await??;
+    let fork_response: ThreadForkResponse = to_response(fork_response)?;
+    assert!(
+        matches!(fork_response.sandbox, SandboxPolicy::ReadOnly { .. }),
+        "fork should resolve the updated config.toml instead of pinning startup Windows sandbox state"
+    );
+
+    Ok(())
+}
+
 #[tokio::test]
 async fn thread_fork_ephemeral_remains_pathless_and_omits_listing() -> Result<()> {
     let server = create_mock_responses_server_repeating_assistant("Done").await;