fix network context removal

codex-rs/core/src/context/environment_context.rs

@@ -18,6 +18,7 @@ pub(crate) struct EnvironmentContext {
 
 #[derive(Debug, Clone, PartialEq, Eq, Default)]
 pub(crate) struct NetworkContext {
+    enabled: bool,
     allowed_domains: Vec<String>,
     denied_domains: Vec<String>,
 }
@@ -25,10 +26,19 @@ pub(crate) struct NetworkContext {
 impl NetworkContext {
     pub(crate) fn new(allowed_domains: Vec<String>, denied_domains: Vec<String>) -> Self {
         Self {
+            enabled: true,
             allowed_domains,
             denied_domains,
         }
     }
+
+    fn disabled() -> Self {
+        Self {
+            enabled: false,
+            allowed_domains: Vec::new(),
+            denied_domains: Vec::new(),
+        }
+    }
 }
 
 impl EnvironmentContext {
@@ -79,7 +89,10 @@ impl EnvironmentContext {
             _ => None,
         };
         let network = if before_network != after.network {
-            after.network.clone()
+            after
+                .network
+                .clone()
+                .or_else(|| Some(NetworkContext::disabled()))
         } else {
             before_network
         };
@@ -180,7 +193,7 @@ impl ContextualUserFragment for EnvironmentContext {
             lines.push(format!("  <timezone>{timezone}</timezone>"));
         }
         match &self.network {
-            Some(network) => {
+            Some(network) if network.enabled => {
                 lines.push("  <network enabled=\"true\">".to_string());
                 for allowed in &network.allowed_domains {
                     lines.push(format!("    <allowed>{allowed}</allowed>"));
@@ -190,6 +203,9 @@ impl ContextualUserFragment for EnvironmentContext {
                 }
                 lines.push("  </network>".to_string());
             }
+            Some(_) => {
+                lines.push("  <network enabled=\"false\" />".to_string());
+            }
             None => {
                 // TODO(mbolin): Include this line if it helps the model.
                 // lines.push("  <network enabled=\"false\" />".to_string());

codex-rs/core/src/context/environment_context_tests.rs

@@ -72,6 +72,31 @@ fn serialize_environment_context_with_network() {
     assert_eq!(context.render(), expected);
 }
 
+#[test]
+fn serialize_environment_context_with_disabled_network() {
+    let context = EnvironmentContext::new(
+        Some(test_path_buf("/repo")),
+        fake_shell_name(),
+        Some("2026-02-26".to_string()),
+        Some("America/Los_Angeles".to_string()),
+        Some(NetworkContext::disabled()),
+        /*subagents*/ None,
+    );
+
+    let expected = format!(
+        r#"<environment_context>
+  <cwd>{}</cwd>
+  <shell>bash</shell>
+  <current_date>2026-02-26</current_date>
+  <timezone>America/Los_Angeles</timezone>
+  <network enabled="false" />
+</environment_context>"#,
+        test_path_buf("/repo").display()
+    );
+
+    assert_eq!(context.render(), expected);
+}
+
 #[test]
 fn serialize_read_only_environment_context() {
     let context = EnvironmentContext::new(

codex-rs/core/src/session/tests.rs

@@ -4764,6 +4764,80 @@ async fn build_settings_update_items_emits_environment_item_for_network_changes(
     assert!(environment_update.contains("<denied>blocked.example.com</denied>"));
 }
 
+#[tokio::test]
+async fn build_settings_update_items_marks_network_disabled_when_network_is_removed() {
+    let (session, mut previous_context) = make_session_and_context().await;
+
+    let mut config = (*previous_context.config).clone();
+    let mut requirements = config.config_layer_stack.requirements().clone();
+    requirements.network = Some(Sourced::new(
+        NetworkConstraints {
+            domains: Some(NetworkDomainPermissionsToml {
+                entries: std::collections::BTreeMap::from([(
+                    "api.example.com".to_string(),
+                    NetworkDomainPermissionToml::Allow,
+                )]),
+            }),
+            ..Default::default()
+        },
+        RequirementSource::CloudRequirements,
+    ));
+    let layers = config
+        .config_layer_stack
+        .get_layers(
+            ConfigLayerStackOrdering::LowestPrecedenceFirst,
+            /*include_disabled*/ true,
+        )
+        .into_iter()
+        .cloned()
+        .collect();
+    config.config_layer_stack = ConfigLayerStack::new(
+        layers,
+        requirements,
+        config.config_layer_stack.requirements_toml().clone(),
+    )
+    .expect("rebuild previous config layer stack with network requirements");
+    previous_context.config = Arc::new(config);
+
+    let mut current_context = previous_context
+        .with_model(
+            previous_context.model_info.slug.clone(),
+            &session.services.models_manager,
+        )
+        .await;
+    let mut config = (*current_context.config).clone();
+    let mut requirements = config.config_layer_stack.requirements().clone();
+    requirements.network = None;
+    let layers = config
+        .config_layer_stack
+        .get_layers(
+            ConfigLayerStackOrdering::LowestPrecedenceFirst,
+            /*include_disabled*/ true,
+        )
+        .into_iter()
+        .cloned()
+        .collect();
+    config.config_layer_stack = ConfigLayerStack::new(
+        layers,
+        requirements,
+        config.config_layer_stack.requirements_toml().clone(),
+    )
+    .expect("rebuild current config layer stack without network requirements");
+    current_context.config = Arc::new(config);
+
+    let reference_context_item = previous_context.to_turn_context_item();
+    let update_items = session
+        .build_settings_update_items(Some(&reference_context_item), &current_context)
+        .await;
+
+    let environment_update = user_input_texts(&update_items)
+        .into_iter()
+        .find(|text| text.contains("<environment_context>"))
+        .expect("environment update item should be emitted");
+    assert!(environment_update.contains("<network enabled=\"false\" />"));
+    assert!(!environment_update.contains("<allowed>api.example.com</allowed>"));
+}
+
 #[tokio::test]
 async fn build_settings_update_items_emits_environment_item_for_time_changes() {
     let (session, previous_context) = make_session_and_context().await;