fix(tui/plan): defer PlanUpdate history while streaming to prevent interleaving between reasoning headings and content; queue and flush after stream finalization.

codex-rs/tui/src/chatwidget.rs

@@ -3149,8 +3149,14 @@ impl ChatWidget<'_> {
                 self.on_error(message);
             }
             EventMsg::PlanUpdate(update) => {
-                // Commit plan updates directly to history (no status-line preview).
-                self.add_to_history(history_cell::new_plan_update(update));
+                // Avoid interleaving plan updates inside streaming sections.
+                // If a stream is active, defer until the stream finalizes so
+                // the plan block doesn't split a heading and its content.
+                if self.is_write_cycle_active() {
+                    self.interrupts.push_plan_update(update);
+                } else {
+                    self.add_to_history(history_cell::new_plan_update(update));
+                }
             }
             EventMsg::ExecApprovalRequest(ev) => {
                 let id2 = id.clone();

codex-rs/tui/src/chatwidget/interrupts.rs

@@ -7,6 +7,7 @@ use codex_core::protocol::ExecCommandEndEvent;
 use codex_core::protocol::McpToolCallBeginEvent;
 use codex_core::protocol::McpToolCallEndEvent;
 use codex_core::protocol::PatchApplyEndEvent;
+use codex_protocol::plan_tool::UpdatePlanArgs;
 
 use super::ChatWidget;
 
@@ -19,6 +20,7 @@ pub(crate) enum QueuedInterrupt {
     McpBegin(McpToolCallBeginEvent),
     McpEnd(McpToolCallEndEvent),
     PatchEnd(PatchApplyEndEvent),
+    PlanUpdate(UpdatePlanArgs),
 }
 
 #[derive(Default)]
@@ -67,6 +69,10 @@ impl InterruptManager {
         self.queue.push_back(QueuedInterrupt::PatchEnd(ev));
     }
 
+    pub(crate) fn push_plan_update(&mut self, ev: UpdatePlanArgs) {
+        self.queue.push_back(QueuedInterrupt::PlanUpdate(ev));
+    }
+
     pub(crate) fn flush_all(&mut self, chat: &mut ChatWidget<'_>) {
         while let Some(q) = self.queue.pop_front() {
             match q {
@@ -79,6 +85,7 @@ impl InterruptManager {
                 QueuedInterrupt::McpBegin(ev) => chat.handle_mcp_begin_now(ev),
                 QueuedInterrupt::McpEnd(ev) => chat.handle_mcp_end_now(ev),
                 QueuedInterrupt::PatchEnd(ev) => chat.handle_patch_apply_end_now(ev),
+                QueuedInterrupt::PlanUpdate(ev) => chat.add_to_history(crate::history_cell::new_plan_update(ev)),
             }
         }
     }