feat(core): allow guardian prompt overrides from model metadata

Co-authored-by: Codex <noreply@openai.com>

codex-rs/app-server/tests/common/models_cache.rs

@@ -29,6 +29,7 @@ fn preset_to_info(preset: &ModelPreset, priority: i32) -> ModelInfo {
         priority,
         upgrade: preset.upgrade.as_ref().map(|u| u.into()),
         base_instructions: "base instructions".to_string(),
+        guardian_developer_instructions: None,
         model_messages: None,
         supports_reasoning_summaries: false,
         default_reasoning_summary: ReasoningSummary::Auto,

codex-rs/codex-api/tests/models_integration.rs

@@ -77,6 +77,7 @@ async fn models_client_hits_models_endpoint() {
             priority: 1,
             upgrade: None,
             base_instructions: "base instructions".to_string(),
+            guardian_developer_instructions: None,
             model_messages: None,
             supports_reasoning_summaries: false,
             default_reasoning_summary: ReasoningSummary::Auto,

codex-rs/core/src/guardian.rs

@@ -538,11 +538,19 @@ async fn run_guardian_subagent(
         };
         (turn.model_info.slug.clone(), reasoning_effort)
     };
+    let guardian_model_info = session
+        .services
+        .models_manager
+        .get_model_info(&guardian_model, turn.config.as_ref())
+        .await;
     let guardian_config = build_guardian_subagent_config(
         turn.config.as_ref(),
         live_network_config,
         guardian_model.as_str(),
         guardian_reasoning_effort,
+        guardian_model_info
+            .guardian_developer_instructions
+            .as_deref(),
     )?;
 
     // Reuse the standard interactive subagent runner so we can seed inherited
@@ -608,11 +616,12 @@ fn build_guardian_subagent_config(
     live_network_config: Option<codex_network_proxy::NetworkProxyConfig>,
     active_model: &str,
     reasoning_effort: Option<codex_protocol::openai_models::ReasoningEffort>,
+    guardian_prompt_override: Option<&str>,
 ) -> anyhow::Result<Config> {
     let mut guardian_config = parent_config.clone();
     guardian_config.model = Some(active_model.to_string());
     guardian_config.model_reasoning_effort = reasoning_effort;
-    guardian_config.developer_instructions = Some(guardian_policy_prompt());
+    guardian_config.developer_instructions = Some(guardian_policy_prompt(guardian_prompt_override));
     guardian_config.permissions.approval_policy = Constrained::allow_only(AskForApproval::Never);
     guardian_config.permissions.sandbox_policy =
         Constrained::allow_only(SandboxPolicy::new_read_only_policy());
@@ -818,8 +827,10 @@ fn guardian_output_contract_prompt() -> &'static str {
 /// Keep the prompt in a dedicated markdown file so reviewers can audit prompt
 /// changes directly without diffing through code. The output contract is
 /// appended from code so it stays near `guardian_output_schema()`.
-fn guardian_policy_prompt() -> String {
-    let prompt = include_str!("guardian_prompt.md").trim_end();
+fn guardian_policy_prompt(prompt_override: Option<&str>) -> String {
+    let prompt = prompt_override
+        .unwrap_or(include_str!("guardian_prompt.md"))
+        .trim_end();
     format!("{prompt}\n\n{}\n", guardian_output_contract_prompt())
 }
 

codex-rs/core/src/guardian_tests.rs

@@ -232,6 +232,7 @@ fn guardian_subagent_config_preserves_parent_network_proxy() {
         None,
         "parent-active-model",
         Some(codex_protocol::openai_models::ReasoningEffort::Low),
+        None,
     )
     .expect("guardian config");
 
@@ -278,6 +279,7 @@ fn guardian_subagent_config_uses_live_network_proxy_state() {
         Some(live_network.clone()),
         "active-model",
         None,
+        None,
     )
     .expect("guardian config");
 
@@ -308,7 +310,7 @@ fn guardian_subagent_config_rejects_pinned_collab_feature() {
     )
     .expect("managed features");
 
-    let err = build_guardian_subagent_config(&parent_config, None, "active-model", None)
+    let err = build_guardian_subagent_config(&parent_config, None, "active-model", None, None)
         .expect_err("guardian config should fail when collab is pinned on");
 
     assert!(
@@ -323,8 +325,27 @@ fn guardian_subagent_config_uses_parent_active_model_instead_of_hardcoded_slug()
     parent_config.model = Some("configured-model".to_string());
 
     let guardian_config =
-        build_guardian_subagent_config(&parent_config, None, "active-model", None)
+        build_guardian_subagent_config(&parent_config, None, "active-model", None, None)
             .expect("guardian config");
 
     assert_eq!(guardian_config.model, Some("active-model".to_string()));
 }
+
+#[test]
+fn guardian_subagent_config_prefers_model_prompt_override() {
+    let guardian_config = build_guardian_subagent_config(
+        &test_config(),
+        None,
+        "active-model",
+        None,
+        Some("override prompt"),
+    )
+    .expect("guardian config");
+
+    let instructions = guardian_config
+        .developer_instructions
+        .expect("guardian instructions");
+
+    assert!(instructions.starts_with("override prompt"));
+    assert!(instructions.contains("\"risk_level\": \"low\" | \"medium\" | \"high\""));
+}

codex-rs/core/src/models_manager/model_info.rs

@@ -73,6 +73,7 @@ pub(crate) fn model_info_from_slug(slug: &str) -> ModelInfo {
         availability_nux: None,
         upgrade: None,
         base_instructions: BASE_INSTRUCTIONS.to_string(),
+        guardian_developer_instructions: None,
         model_messages: local_personality_messages_for_slug(slug),
         supports_reasoning_summaries: false,
         default_reasoning_summary: ReasoningSummary::Auto,

codex-rs/core/tests/suite/model_switching.rs

@@ -58,6 +58,7 @@ fn test_model_info(
         priority: 1,
         upgrade: None,
         base_instructions: "base instructions".to_string(),
+        guardian_developer_instructions: None,
         model_messages: None,
         supports_reasoning_summaries: false,
         default_reasoning_summary: ReasoningSummary::Auto,
@@ -678,6 +679,7 @@ async fn model_switch_to_smaller_model_updates_token_context_window() -> Result<
         priority: 1,
         upgrade: None,
         base_instructions: "base instructions".to_string(),
+        guardian_developer_instructions: None,
         model_messages: None,
         supports_reasoning_summaries: false,
         default_reasoning_summary: ReasoningSummary::Auto,

codex-rs/core/tests/suite/models_cache_ttl.rs

@@ -335,6 +335,7 @@ fn test_remote_model(slug: &str, priority: i32) -> ModelInfo {
         priority,
         upgrade: None,
         base_instructions: "base instructions".to_string(),
+        guardian_developer_instructions: None,
         model_messages: None,
         supports_reasoning_summaries: false,
         default_reasoning_summary: ReasoningSummary::Auto,

codex-rs/core/tests/suite/personality.rs

@@ -633,6 +633,7 @@ async fn remote_model_friendly_personality_instructions_with_feature() -> anyhow
         priority: 1,
         upgrade: None,
         base_instructions: "base instructions".to_string(),
+        guardian_developer_instructions: None,
         model_messages: Some(ModelMessages {
             instructions_template: Some("Base instructions\n{{ personality }}\n".to_string()),
             instructions_variables: Some(ModelInstructionsVariables {
@@ -748,6 +749,7 @@ async fn user_turn_personality_remote_model_template_includes_update_message() -
         priority: 1,
         upgrade: None,
         base_instructions: "base instructions".to_string(),
+        guardian_developer_instructions: None,
         model_messages: Some(ModelMessages {
             instructions_template: Some("Base instructions\n{{ personality }}\n".to_string()),
             instructions_variables: Some(ModelInstructionsVariables {

codex-rs/core/tests/suite/remote_models.rs

@@ -294,6 +294,7 @@ async fn remote_models_remote_model_uses_unified_exec() -> Result<()> {
         priority: 1,
         upgrade: None,
         base_instructions: "base instructions".to_string(),
+        guardian_developer_instructions: None,
         model_messages: None,
         supports_reasoning_summaries: false,
         default_reasoning_summary: ReasoningSummary::Auto,
@@ -536,6 +537,7 @@ async fn remote_models_apply_remote_base_instructions() -> Result<()> {
         priority: 1,
         upgrade: None,
         base_instructions: remote_base.to_string(),
+        guardian_developer_instructions: None,
         model_messages: None,
         supports_reasoning_summaries: false,
         default_reasoning_summary: ReasoningSummary::Auto,
@@ -1002,6 +1004,7 @@ fn test_remote_model_with_policy(
         priority,
         upgrade: None,
         base_instructions: "base instructions".to_string(),
+        guardian_developer_instructions: None,
         model_messages: None,
         supports_reasoning_summaries: false,
         default_reasoning_summary: ReasoningSummary::Auto,

codex-rs/core/tests/suite/rmcp_client.rs

@@ -400,6 +400,7 @@ async fn stdio_image_responses_are_sanitized_for_text_only_model() -> anyhow::Re
                 priority: 1,
                 upgrade: None,
                 base_instructions: "base instructions".to_string(),
+                guardian_developer_instructions: None,
                 model_messages: None,
                 supports_reasoning_summaries: false,
                 default_reasoning_summary: ReasoningSummary::Auto,

codex-rs/core/tests/suite/view_image.rs

@@ -996,6 +996,7 @@ async fn view_image_tool_returns_unsupported_message_for_text_only_model() -> an
         priority: 1,
         upgrade: None,
         base_instructions: "base instructions".to_string(),
+        guardian_developer_instructions: None,
         model_messages: None,
         supports_reasoning_summaries: false,
         default_reasoning_summary: ReasoningSummary::Auto,

codex-rs/protocol/src/openai_models.rs

@@ -246,6 +246,8 @@ pub struct ModelInfo {
     pub upgrade: Option<ModelInfoUpgrade>,
     pub base_instructions: String,
     #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub guardian_developer_instructions: Option<String>,
+    #[serde(default, skip_serializing_if = "Option::is_none")]
     pub model_messages: Option<ModelMessages>,
     pub supports_reasoning_summaries: bool,
     #[serde(default)]
@@ -521,6 +523,7 @@ mod tests {
             availability_nux: None,
             upgrade: None,
             base_instructions: "base".to_string(),
+            guardian_developer_instructions: None,
             model_messages: spec,
             supports_reasoning_summaries: false,
             default_reasoning_summary: ReasoningSummary::Auto,