Use static instructions for the Default collaboration mode (#42904)

## What changed

Write Default and Plan directly into the default mode instructions and use the text without template rendering. Remove the mode-name formatting helpers and the `codex-utils-template` dependency from `codex-models-manager`.

Update the instruction test to retain checks for `request_user_input` availability guidance while removing placeholder assertions.

GitOrigin-RevId: d6afa478c30f991baa9ef4d5459e84354f29ce17

codex-rs/Cargo.lock

@@ -3986,7 +3986,6 @@ dependencies = [
  "codex-otel",
  "codex-protocol",
  "codex-utils-output-truncation",
- "codex-utils-template",
  "pretty_assertions",
  "serde",
  "serde_json",

codex-rs/collaboration-mode-templates/templates/default.md

@@ -2,7 +2,7 @@
 
 You are now in Default mode. Any previous instructions for other modes (e.g. Plan mode) are no longer active.
 
-Your active mode changes only when new developer instructions with a different `<collaboration_mode>...</collaboration_mode>` change it; user requests or tool descriptions do not change mode by themselves. Known mode names are {{KNOWN_MODE_NAMES}}.
+Your active mode changes only when new developer instructions with a different `<collaboration_mode>...</collaboration_mode>` change it; user requests or tool descriptions do not change mode by themselves. Known mode names are Default and Plan.
 
 ## request_user_input availability
 

codex-rs/models-manager/Cargo.toml

@@ -20,7 +20,6 @@ codex-login = { workspace = true }
 codex-otel = { workspace = true }
 codex-protocol = { workspace = true }
 codex-utils-output-truncation = { workspace = true }
-codex-utils-template = { workspace = true }
 serde = { workspace = true, features = ["derive"] }
 serde_json = { workspace = true }
 tokio = { workspace = true, features = ["fs", "sync", "time"] }

codex-rs/models-manager/src/collaboration_mode_presets.rs

@@ -2,16 +2,7 @@ use codex_collaboration_mode_templates::DEFAULT as COLLABORATION_MODE_DEFAULT;
 use codex_collaboration_mode_templates::PLAN as COLLABORATION_MODE_PLAN;
 use codex_protocol::config_types::CollaborationModeMask;
 use codex_protocol::config_types::ModeKind;
-use codex_protocol::config_types::TUI_VISIBLE_COLLABORATION_MODES;
 use codex_protocol::openai_models::ReasoningEffort;
-use codex_utils_template::Template;
-use std::sync::LazyLock;
-
-const KNOWN_MODE_NAMES_TEMPLATE_KEY: &str = "KNOWN_MODE_NAMES";
-static COLLABORATION_MODE_DEFAULT_TEMPLATE: LazyLock<Template> = LazyLock::new(|| {
-    Template::parse(COLLABORATION_MODE_DEFAULT)
-        .unwrap_or_else(|err| panic!("collaboration mode default template must parse: {err}"))
-});
 
 pub fn builtin_collaboration_mode_presets() -> Vec<CollaborationModeMask> {
     vec![plan_preset(), default_preset()]
@@ -33,24 +24,7 @@ fn default_preset() -> CollaborationModeMask {
         mode: Some(ModeKind::Default),
         model: None,
         reasoning_effort: None,
-        developer_instructions: Some(Some(default_mode_instructions())),
+        developer_instructions: Some(Some(COLLABORATION_MODE_DEFAULT.to_string())),
-    }
-}
-
-fn default_mode_instructions() -> String {
-    let known_mode_names = format_mode_names(&TUI_VISIBLE_COLLABORATION_MODES);
-    COLLABORATION_MODE_DEFAULT_TEMPLATE
-        .render([(KNOWN_MODE_NAMES_TEMPLATE_KEY, known_mode_names.as_str())])
-        .unwrap_or_else(|err| panic!("collaboration mode default template must render: {err}"))
-}
-
-fn format_mode_names(modes: &[ModeKind]) -> String {
-    let mode_names: Vec<&str> = modes.iter().map(|mode| mode.display_name()).collect();
-    match mode_names.as_slice() {
-        [] => "none".to_string(),
-        [mode_name] => (*mode_name).to_string(),
-        [first, second] => format!("{first} and {second}"),
-        [..] => mode_names.join(", "),
     }
 }
 

codex-rs/models-manager/src/collaboration_mode_presets_tests.rs

@@ -15,18 +15,12 @@ fn preset_names_use_mode_display_names() {
 }
 
 #[test]
-fn default_mode_instructions_replace_mode_names_placeholder() {
+fn default_mode_instructions_follow_user_input_tool_availability() {
     let default_instructions = default_preset()
         .developer_instructions
         .expect("default preset should include instructions")
         .expect("default instructions should be set");
 
-    assert!(!default_instructions.contains("{{KNOWN_MODE_NAMES}}"));
-
-    let known_mode_names = format_mode_names(&TUI_VISIBLE_COLLABORATION_MODES);
-    let expected_snippet = format!("Known mode names are {known_mode_names}.");
-    assert!(default_instructions.contains(&expected_snippet));
-
     assert!(default_instructions.contains(
         "Use the `request_user_input` tool only when it is listed in the available tools"
     ));