override instructions using ModelInfo (#7754)

Making sure we can override base instructions

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

@@ -77,6 +77,7 @@ async fn models_client_hits_models_endpoint() {
             supported_in_api: true,
             priority: 1,
             upgrade: None,
+            base_instructions: None,
         }],
         etag: String::new(),
     };

codex-rs/core/src/openai_models/model_family.rs

@@ -102,6 +102,7 @@ impl ModelFamily {
             if model.slug == self.slug {
                 self.default_reasoning_effort = Some(model.default_reasoning_level);
                 self.shell_type = model.shell_type;
+                self.base_instructions = model.base_instructions.unwrap_or(self.base_instructions);
             }
         }
         self
@@ -357,6 +358,7 @@ mod tests {
             supported_in_api: true,
             priority: 1,
             upgrade: None,
+            base_instructions: None,
         }
     }
 

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

@@ -216,6 +216,7 @@ mod tests {
             "supported_in_api": true,
             "priority": priority,
             "upgrade": null,
+            "base_instructions": null,
         }))
         .expect("valid model")
     }

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

@@ -25,6 +25,7 @@ use core_test_support::responses::ev_completed;
 use core_test_support::responses::ev_function_call;
 use core_test_support::responses::ev_response_created;
 use core_test_support::responses::mount_models_once;
+use core_test_support::responses::mount_sse_once;
 use core_test_support::responses::mount_sse_sequence;
 use core_test_support::responses::sse;
 use core_test_support::skip_if_no_network;
@@ -67,6 +68,7 @@ async fn remote_models_remote_model_uses_unified_exec() -> Result<()> {
         supported_in_api: true,
         priority: 1,
         upgrade: None,
+        base_instructions: None,
     };
 
     let models_mock = mount_models_once(
@@ -167,6 +169,105 @@ async fn remote_models_remote_model_uses_unified_exec() -> Result<()> {
     Ok(())
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn remote_models_apply_remote_base_instructions() -> Result<()> {
+    skip_if_no_network!(Ok(()));
+    skip_if_sandbox!(Ok(()));
+
+    let server = MockServer::builder()
+        .body_print_limit(BodyPrintLimit::Limited(80_000))
+        .start()
+        .await;
+
+    let model = "test-gpt-5-remote";
+
+    let remote_base = "Use the remote base instructions only.";
+    let remote_model = ModelInfo {
+        slug: model.to_string(),
+        display_name: "Parallel Remote".to_string(),
+        description: Some("A remote model with custom instructions".to_string()),
+        default_reasoning_level: ReasoningEffort::Medium,
+        supported_reasoning_levels: vec![ReasoningEffortPreset {
+            effort: ReasoningEffort::Medium,
+            description: ReasoningEffort::Medium.to_string(),
+        }],
+        shell_type: ConfigShellToolType::ShellCommand,
+        visibility: ModelVisibility::List,
+        minimal_client_version: ClientVersion(0, 1, 0),
+        supported_in_api: true,
+        priority: 1,
+        upgrade: None,
+        base_instructions: Some(remote_base.to_string()),
+    };
+    mount_models_once(
+        &server,
+        ModelsResponse {
+            models: vec![remote_model],
+            etag: String::new(),
+        },
+    )
+    .await;
+
+    let response_mock = mount_sse_once(
+        &server,
+        sse(vec![
+            ev_response_created("resp-1"),
+            ev_assistant_message("msg-1", "done"),
+            ev_completed("resp-1"),
+        ]),
+    )
+    .await;
+
+    let mut builder = test_codex().with_config(|config| {
+        config.features.enable(Feature::RemoteModels);
+        config.model = "gpt-5.1".to_string();
+    });
+
+    let TestCodex {
+        codex,
+        cwd,
+        conversation_manager,
+        ..
+    } = builder.build(&server).await?;
+
+    let models_manager = conversation_manager.get_models_manager();
+    wait_for_model_available(&models_manager, model).await;
+
+    codex
+        .submit(Op::OverrideTurnContext {
+            cwd: None,
+            approval_policy: None,
+            sandbox_policy: None,
+            model: Some(model.to_string()),
+            effort: None,
+            summary: None,
+        })
+        .await?;
+
+    codex
+        .submit(Op::UserTurn {
+            items: vec![UserInput::Text {
+                text: "hello remote".into(),
+            }],
+            final_output_json_schema: None,
+            cwd: cwd.path().to_path_buf(),
+            approval_policy: AskForApproval::Never,
+            sandbox_policy: SandboxPolicy::DangerFullAccess,
+            model: model.to_string(),
+            effort: None,
+            summary: ReasoningSummary::Auto,
+        })
+        .await?;
+
+    wait_for_event(&codex, |event| matches!(event, EventMsg::TaskComplete(_))).await;
+
+    let body = response_mock.single_request().body_json();
+    let instructions = body["instructions"].as_str().unwrap();
+    assert_eq!(instructions, remote_base);
+
+    Ok(())
+}
+
 async fn wait_for_model_available(manager: &Arc<ModelsManager>, slug: &str) -> ModelPreset {
     let deadline = Instant::now() + Duration::from_secs(2);
     loop {

codex-rs/protocol/src/openai_models.rs

@@ -135,6 +135,8 @@ pub struct ModelInfo {
     pub priority: i32,
     #[serde(default)]
     pub upgrade: Option<String>,
+    #[serde(default)]
+    pub base_instructions: Option<String>,
 }
 
 /// Response wrapper for `/models`.