Remove resurrected /collab slash command (#22535)

## Summary
`/collab` was intentionally removed in
[#12012](https://github.com/openai/codex/pull/12012), but the
TUI/app-server migration accidentally brought that slash-command path
back. This restores the earlier product decision so the TUI no longer
advertises or dispatches `/collab`. This command was redundant because
it did the same thing as `/plan` but in a less-intuitive way.

## What Changed
- Remove `SlashCommand::Collab` from the TUI slash-command surface.
- Delete the picker and app-event plumbing that only existed to service
`/collab`.
- Remove obsolete TUI test coverage for the deleted picker flow.

codex-rs/tui/src/app/event_dispatch.rs

@@ -756,9 +756,6 @@ impl App {
             AppEvent::UpdateModel(model) => {
                 self.chat_widget.set_model(&model);
             }
-            AppEvent::UpdateCollaborationMode(mask) => {
-                self.chat_widget.set_collaboration_mask(mask);
-            }
             AppEvent::UpdatePersonality(personality) => {
                 self.on_update_personality(personality);
             }

codex-rs/tui/src/app_event.rs

@@ -608,9 +608,6 @@ pub(crate) enum AppEvent {
     /// Update the current model slug in the running app and widget.
     UpdateModel(String),
 
-    /// Update the active collaboration mask in the running app and widget.
-    UpdateCollaborationMode(CollaborationModeMask),
-
     /// Update the current personality in the running app and widget.
     UpdatePersonality(Personality),
 

codex-rs/tui/src/bottom_pane/command_popup.rs

@@ -419,7 +419,7 @@ mod tests {
     }
 
     #[test]
-    fn collab_command_hidden_when_collaboration_modes_disabled() {
+    fn plan_command_hidden_when_collaboration_modes_disabled() {
         let mut popup = CommandPopup::new(CommandPopupFlags::default(), Vec::new());
         popup.on_composer_text_change("/".to_string());
 
@@ -431,44 +431,12 @@ mod tests {
                 CommandItem::ServiceTier(command) => command.name,
             })
             .collect();
-        assert!(
-            !cmds.iter().any(|cmd| cmd == "collab"),
-            "expected '/collab' to be hidden when collaboration modes are disabled, got {cmds:?}"
-        );
         assert!(
             !cmds.iter().any(|cmd| cmd == "plan"),
             "expected '/plan' to be hidden when collaboration modes are disabled, got {cmds:?}"
         );
     }
 
-    #[test]
-    fn collab_command_visible_when_collaboration_modes_enabled() {
-        let mut popup = CommandPopup::new(
-            CommandPopupFlags {
-                collaboration_modes_enabled: true,
-                connectors_enabled: false,
-                plugins_command_enabled: false,
-                service_tier_commands_enabled: false,
-                goal_command_enabled: false,
-                personality_command_enabled: true,
-                realtime_conversation_enabled: false,
-                audio_device_selection_enabled: false,
-                windows_degraded_sandbox_active: false,
-                side_conversation_active: false,
-            },
-            Vec::new(),
-        );
-        popup.on_composer_text_change("/collab".to_string());
-
-        match popup.selected_item() {
-            Some(CommandItem::Builtin(cmd)) => assert_eq!(cmd.command(), "collab"),
-            Some(CommandItem::ServiceTier(command)) => {
-                panic!("expected collab command, got service tier {command:?}")
-            }
-            other => panic!("expected collab to be selected for exact match, got {other:?}"),
-        }
-    }
-
     #[test]
     fn plan_command_visible_when_collaboration_modes_enabled() {
         let mut popup = CommandPopup::new(

codex-rs/tui/src/bottom_pane/slash_commands.rs

@@ -72,10 +72,7 @@ pub(crate) fn builtins_for_input(flags: BuiltinCommandFlags) -> Vec<(&'static st
     built_in_slash_commands()
         .into_iter()
         .filter(|(_, cmd)| flags.allow_elevate_sandbox || *cmd != SlashCommand::ElevateSandbox)
-        .filter(|(_, cmd)| {
-            flags.collaboration_modes_enabled
-                || !matches!(*cmd, SlashCommand::Collab | SlashCommand::Plan)
-        })
+        .filter(|(_, cmd)| flags.collaboration_modes_enabled || *cmd != SlashCommand::Plan)
         .filter(|(_, cmd)| flags.connectors_enabled || *cmd != SlashCommand::Apps)
         .filter(|(_, cmd)| flags.plugins_command_enabled || *cmd != SlashCommand::Plugins)
         .filter(|(_, cmd)| flags.goal_command_enabled || *cmd != SlashCommand::Goal)

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

@@ -213,51 +213,6 @@ impl ChatWidget {
         });
     }
 
-    pub(crate) fn open_collaboration_modes_popup(&mut self) {
-        let presets = collaboration_modes::presets_for_tui(self.model_catalog.as_ref());
-        if presets.is_empty() {
-            self.add_info_message(
-                "No collaboration modes are available right now.".to_string(),
-                /*hint*/ None,
-            );
-            return;
-        }
-
-        let current_kind = self
-            .active_collaboration_mask
-            .as_ref()
-            .and_then(|mask| mask.mode)
-            .or_else(|| {
-                collaboration_modes::default_mask(self.model_catalog.as_ref())
-                    .and_then(|mask| mask.mode)
-            });
-        let items: Vec<SelectionItem> = presets
-            .into_iter()
-            .map(|mask| {
-                let name = mask.name.clone();
-                let is_current = current_kind == mask.mode;
-                let actions: Vec<SelectionAction> = vec![Box::new(move |tx| {
-                    tx.send(AppEvent::UpdateCollaborationMode(mask.clone()));
-                })];
-                SelectionItem {
-                    name,
-                    is_current,
-                    actions,
-                    dismiss_on_select: true,
-                    ..Default::default()
-                }
-            })
-            .collect();
-
-        self.bottom_pane.show_selection_view(SelectionViewParams {
-            title: Some("Select Collaboration Mode".to_string()),
-            subtitle: Some("Pick a collaboration preset.".to_string()),
-            footer_hint: Some(standard_popup_hint_line()),
-            items,
-            ..Default::default()
-        });
-    }
-
     fn model_selection_actions(
         model_for_action: String,
         effort_for_action: Option<ReasoningEffortConfig>,

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

@@ -238,16 +238,6 @@ impl ChatWidget {
                     );
                 }
             }
-            SlashCommand::Collab => {
-                if !self.collaboration_modes_enabled() {
-                    self.add_info_message(
-                        "Collaboration modes are disabled.".to_string(),
-                        Some("Enable collaboration modes to use /collab.".to_string()),
-                    );
-                    return;
-                }
-                self.open_collaboration_modes_popup();
-            }
             SlashCommand::Side => {
                 self.request_empty_side_conversation();
             }
@@ -965,7 +955,6 @@ impl ChatWidget {
             | SlashCommand::Personality
             | SlashCommand::Plan
             | SlashCommand::Goal
-            | SlashCommand::Collab
             | SlashCommand::Side
             | SlashCommand::Keymap
             | SlashCommand::Agent

codex-rs/tui/src/chatwidget/tests/plan_mode.rs

@@ -1367,63 +1367,6 @@ async fn mode_switch_surfaces_reasoning_change_notification_when_model_stays_sam
     );
 }
 
-#[tokio::test]
-async fn collab_slash_command_opens_picker_and_updates_mode() {
-    let (mut chat, mut rx, mut op_rx) = make_chatwidget_manual(/*model_override*/ None).await;
-    chat.thread_id = Some(ThreadId::new());
-    chat.set_feature_enabled(Feature::CollaborationModes, /*enabled*/ true);
-
-    chat.dispatch_command(SlashCommand::Collab);
-    let popup = render_bottom_popup(&chat, /*width*/ 80);
-    assert!(
-        popup.contains("Select Collaboration Mode"),
-        "expected collaboration picker: {popup}"
-    );
-
-    chat.handle_key_event(KeyEvent::from(KeyCode::Enter));
-    let selected_mask = match rx.try_recv() {
-        Ok(AppEvent::UpdateCollaborationMode(mask)) => mask,
-        other => panic!("expected UpdateCollaborationMode event, got {other:?}"),
-    };
-    chat.set_collaboration_mask(selected_mask);
-
-    chat.bottom_pane
-        .set_composer_text("hello".to_string(), Vec::new(), Vec::new());
-    chat.handle_key_event(KeyEvent::from(KeyCode::Enter));
-    match next_submit_op(&mut op_rx) {
-        Op::UserTurn {
-            collaboration_mode:
-                Some(CollaborationMode {
-                    mode: ModeKind::Default,
-                    ..
-                }),
-            personality: Some(Personality::Pragmatic),
-            ..
-        } => {}
-        other => {
-            panic!("expected Op::UserTurn with code collab mode, got {other:?}")
-        }
-    }
-
-    chat.bottom_pane
-        .set_composer_text("follow up".to_string(), Vec::new(), Vec::new());
-    chat.handle_key_event(KeyEvent::from(KeyCode::Enter));
-    match next_submit_op(&mut op_rx) {
-        Op::UserTurn {
-            collaboration_mode:
-                Some(CollaborationMode {
-                    mode: ModeKind::Default,
-                    ..
-                }),
-            personality: Some(Personality::Pragmatic),
-            ..
-        } => {}
-        other => {
-            panic!("expected Op::UserTurn with code collab mode, got {other:?}")
-        }
-    }
-}
-
 #[tokio::test]
 async fn plan_slash_command_switches_to_plan_mode() {
     let (mut chat, mut rx, _op_rx) = make_chatwidget_manual(/*model_override*/ None).await;

codex-rs/tui/src/collaboration_modes.rs

@@ -11,10 +11,6 @@ fn filtered_presets(_model_catalog: &ModelCatalog) -> Vec<CollaborationModeMask>
         .collect()
 }
 
-pub(crate) fn presets_for_tui(model_catalog: &ModelCatalog) -> Vec<CollaborationModeMask> {
-    filtered_presets(model_catalog)
-}
-
 pub(crate) fn default_mask(model_catalog: &ModelCatalog) -> Option<CollaborationModeMask> {
     let presets = filtered_presets(model_catalog);
     presets

codex-rs/tui/src/slash_command.rs

@@ -36,7 +36,6 @@ pub enum SlashCommand {
     Compact,
     Plan,
     Goal,
-    Collab,
     Agent,
     Side,
     Copy,
@@ -114,7 +113,6 @@ impl SlashCommand {
             SlashCommand::Settings => "configure realtime microphone/speaker",
             SlashCommand::Plan => "switch to Plan mode",
             SlashCommand::Goal => "set or view the goal for a long-running task",
-            SlashCommand::Collab => "change collaboration mode (experimental)",
             SlashCommand::Agent | SlashCommand::MultiAgents => "switch the active agent thread",
             SlashCommand::Side => "start a side conversation in an ephemeral fork",
             SlashCommand::Permissions => "choose what Codex is allowed to do",
@@ -224,7 +222,6 @@ impl SlashCommand {
             SlashCommand::TestApproval => true,
             SlashCommand::Realtime => true,
             SlashCommand::Settings => true,
-            SlashCommand::Collab => true,
             SlashCommand::Agent | SlashCommand::MultiAgents => true,
             SlashCommand::Theme | SlashCommand::Pets => false,
         }