fix(tui): reflow scrollback on terminal resize (#18575)

Fixes multiple scrollback and terminal resize issues: #5538, #5576,
#8352, #12223, #16165, and #15380.

## Why

Codex writes finalized transcript output into terminal scrollback after
wrapping it for the current viewport width. A later terminal resize
could leave that scrollback shaped for the old width, so wider windows
kept narrow output and narrower windows could show stale wrapping
artifacts until enough new output replaced the visible area.

This is also the foundation PR for responsive markdown tables. Table
rendering needs finalized transcript content to be width-sensitive after
insertion, not only while content is first streaming. Markdown table
rendering itself stays in #18576.

## Stack

- PR1: resize backlog reflow and interrupt cleanup
- #18576: markdown table support

## What Changed

- Rebuild source-backed transcript history when the terminal width
changes. `terminal_resize_reflow` is introduced through the experimental
feature system, but is enabled by default for this rollout so we can
validate behavior across real terminals.
- Preserve assistant and plan stream source so finalized streaming
output can participate in resize reflow after consolidation.
- Debounce resize work, but force a final source-backed reflow when a
resize happened during active or unconsolidated streaming output.
- Clear stale pending history lines on resize so old-width wrapped
output is not emitted just before rebuilt scrollback.
- Bound replay work with `[tui.terminal_resize_reflow].max_rows`:
omitted uses terminal-specific defaults, `0` keeps all rendered rows,
and a positive value sets an explicit cap. The cap applies both while
initially replaying a resumed transcript into scrollback and when
rebuilding scrollback after terminal resize.
- Consolidate interrupted assistant streams before cleanup, then clear
pending stream output and active-tail state consistently.
- Move resize reflow and thread event buffering helpers out of `app.rs`
into dedicated TUI modules.
- Add focused coverage for resize reflow, feature-gated behavior,
streaming source preservation, interrupted output cleanup,
unicode-neutral text, terminal-specific row caps, and composer/layout
stability.

## Runtime Bounds

Resize reflow keeps only the most recent rendered rows when a row cap is
active. The default is `auto`, which maps to the detected terminal's
default scrollback size where Codex can identify it: VS Code `1000`,
Windows Terminal `9001`, WezTerm `3500`, and Alacritty `10000`.
Terminals without a dedicated mapping use the conservative fallback of
`1000` rows. Users can override this with `[tui.terminal_resize_reflow]
max_rows = N`, or set `max_rows = 0` to disable row limiting.

## Validation

- `just fmt`
- `git diff --check`
- `cargo test --manifest-path codex-rs/Cargo.toml -p codex-tui reflow`
- `cargo test --manifest-path codex-rs/Cargo.toml -p codex-tui
transcript_reflow`
- `just fix -p codex-tui`
- PR CI in progress on the squashed branch

codex-rs/tui/src/chatwidget.rs

@@ -2034,12 +2034,25 @@ impl ChatWidget {
     }
 
     fn flush_answer_stream_with_separator(&mut self) {
-        if let Some(mut controller) = self.stream_controller.take()
-            && let Some(cell) = controller.finalize()
-        {
-            self.add_boxed_history(cell);
+        let had_stream_controller = self.stream_controller.is_some();
+        if let Some(mut controller) = self.stream_controller.take() {
+            let (cell, source) = controller.finalize();
+            if let Some(cell) = cell {
+                self.add_boxed_history(cell);
+            }
+            // Consolidate the run of streaming AgentMessageCells into a single AgentMarkdownCell
+            // that can re-render from source on resize.
+            if let Some(source) = source {
+                self.app_event_tx.send(AppEvent::ConsolidateAgentMessage {
+                    source,
+                    cwd: self.config.cwd.to_path_buf(),
+                });
+            }
         }
         self.adaptive_chunking.reset();
+        if had_stream_controller && self.stream_controllers_idle() {
+            self.app_event_tx.send(AppEvent::StopCommitAnimation);
+        }
     }
 
     fn stream_controllers_idle(&self) -> bool {
@@ -2626,7 +2639,7 @@ impl ChatWidget {
 
         if self.plan_stream_controller.is_none() {
             self.plan_stream_controller = Some(PlanStreamController::new(
-                self.last_rendered_width.get().map(|w| w.saturating_sub(4)),
+                self.current_stream_width(/*reserved_cols*/ 4),
                 &self.config.cwd,
             ));
         }
@@ -2656,18 +2669,25 @@ impl ChatWidget {
         self.plan_delta_buffer.clear();
         self.plan_item_active = false;
         self.saw_plan_item_this_turn = true;
-        let finalized_streamed_cell =
+        let (finalized_streamed_cell, consolidated_plan_source) =
             if let Some(mut controller) = self.plan_stream_controller.take() {
                 controller.finalize()
             } else {
-                None
+                (None, None)
             };
         if let Some(cell) = finalized_streamed_cell {
             self.add_boxed_history(cell);
             // TODO: Replace streamed output with the final plan item text if plan streaming is
             // removed or if we need to reconcile mismatches between streamed and final content.
+            if let Some(source) = consolidated_plan_source {
+                self.app_event_tx
+                    .send(AppEvent::ConsolidateProposedPlan(source));
+            }
         } else if !plan_text.is_empty() {
             self.add_to_history(history_cell::new_proposed_plan(plan_text, &self.config.cwd));
+        } else if let Some(source) = consolidated_plan_source {
+            self.app_event_tx
+                .send(AppEvent::ConsolidateProposedPlan(source));
         }
         if should_restore_after_stream {
             self.pending_status_indicator_restore = true;
@@ -2785,10 +2805,15 @@ impl ChatWidget {
         self.saw_copy_source_this_turn = false;
         // If a stream is currently active, finalize it.
         self.flush_answer_stream_with_separator();
-        if let Some(mut controller) = self.plan_stream_controller.take()
-            && let Some(cell) = controller.finalize()
-        {
-            self.add_boxed_history(cell);
+        if let Some(mut controller) = self.plan_stream_controller.take() {
+            let (cell, source) = controller.finalize();
+            if let Some(cell) = cell {
+                self.add_boxed_history(cell);
+            }
+            if let Some(source) = source {
+                self.app_event_tx
+                    .send(AppEvent::ConsolidateProposedPlan(source));
+            }
         }
         self.flush_unified_exec_wait_streak();
         if !from_replay {
@@ -5042,7 +5067,7 @@ impl ChatWidget {
                 self.needs_final_message_separator = false;
             }
             self.stream_controller = Some(StreamController::new(
-                self.last_rendered_width.get().map(|w| w.saturating_sub(2)),
+                self.current_stream_width(/*reserved_cols*/ 2),
                 &self.config.cwd,
             ));
         }
@@ -11377,6 +11402,52 @@ impl ChatWidget {
         self.bottom_pane.is_task_running() || self.is_review_mode
     }
 
+    /// Return the markdown body width available to an active stream.
+    ///
+    /// Streaming controllers render only the message body, while history cells add bullets,
+    /// gutters, or plan padding around that body. Callers pass the reserved columns for that
+    /// wrapper so live output uses the same width that finalized cells will use during reflow.
+    fn current_stream_width(&self, reserved_cols: usize) -> Option<usize> {
+        self.last_rendered_width.get().and_then(|width| {
+            if width == 0 {
+                None
+            } else {
+                Some(crate::width::usable_content_width(width, reserved_cols).unwrap_or(1))
+            }
+        })
+    }
+
+    /// Update resize-sensitive chat widget state after the terminal width changes.
+    ///
+    /// The app calls this even when terminal resize reflow is disabled so live stream wrapping
+    /// remains consistent with the current viewport. Finalized transcript rebuilding stays gated at
+    /// the app layer.
+    pub(crate) fn on_terminal_resize(&mut self, width: u16) {
+        let had_rendered_width = self.last_rendered_width.get().is_some();
+        self.last_rendered_width.set(Some(width as usize));
+        let stream_width = self.current_stream_width(/*reserved_cols*/ 2);
+        let plan_stream_width = self.current_stream_width(/*reserved_cols*/ 4);
+        if let Some(controller) = self.stream_controller.as_mut() {
+            controller.set_width(stream_width);
+        }
+        if let Some(controller) = self.plan_stream_controller.as_mut() {
+            controller.set_width(plan_stream_width);
+        }
+        if !had_rendered_width {
+            self.request_redraw();
+        }
+    }
+
+    /// Whether an agent message stream is active (not a plan stream).
+    pub(crate) fn has_active_agent_stream(&self) -> bool {
+        self.stream_controller.is_some()
+    }
+
+    /// Whether a proposed-plan stream is active.
+    pub(crate) fn has_active_plan_stream(&self) -> bool {
+        self.plan_stream_controller.is_some()
+    }
+
     fn is_plan_streaming_in_tui(&self) -> bool {
         self.plan_stream_controller.is_some()
     }
@@ -11503,6 +11574,7 @@ impl ChatWidget {
         T: Into<AppCommand>,
     {
         let op: AppCommand = op.into();
+        self.prepare_local_op_submission(&op);
         if op.is_review() && !self.bottom_pane.is_task_running() {
             self.bottom_pane.set_task_running(/*running*/ true);
         }
@@ -11521,6 +11593,20 @@ impl ChatWidget {
         true
     }
 
+    pub(crate) fn prepare_local_op_submission(&mut self, op: &AppCommand) {
+        if matches!(op.view(), crate::app_command::AppCommandView::Interrupt)
+            && self.agent_turn_running
+        {
+            if let Some(controller) = self.stream_controller.as_mut() {
+                controller.clear_queue();
+            }
+            if let Some(controller) = self.plan_stream_controller.as_mut() {
+                controller.clear_queue();
+            }
+            self.request_redraw();
+        }
+    }
+
     #[cfg(test)]
     fn on_list_mcp_tools(&mut self, ev: McpListToolsResponseEvent) {
         self.add_to_history(history_cell::new_mcp_tools_output(
@@ -11652,6 +11738,7 @@ impl ChatWidget {
         self.config.config_layer_stack = config.config_layer_stack.clone();
         self.config.realtime = config.realtime.clone();
         self.config.memories = config.memories.clone();
+        self.config.terminal_resize_reflow = config.terminal_resize_reflow;
     }
 
     pub(crate) fn open_review_popup(&mut self) {