diff --git a/codex-rs/core/src/agents_md_tests.rs b/codex-rs/core/src/agents_md_tests.rs
index f5dd78977f..a68079ab20 100644
--- a/codex-rs/core/src/agents_md_tests.rs
+++ b/codex-rs/core/src/agents_md_tests.rs
@@ -2,6 +2,7 @@ use super::*;
 use crate::config::ConfigBuilder;
 use crate::config::PermissionProfileSnapshot;
 use crate::context::ContextualUserFragment;
+use crate::environment_selection::EnvironmentConfigOrigin;
 use crate::environment_selection::TurnEnvironmentSnapshot;
 use crate::environment_selection::TurnEnvironmentState;
 use crate::session::turn_context::TurnEnvironment;
@@ -338,20 +339,20 @@ fn resolved_local_environments<const N: usize>(
                         environment_id: environment_id.to_string(),
                         cwd: PathUri::from_abs_path(&cwd),
                         workspace_roots: Vec::new(),
-                        config: EnvironmentConfigState::FromThread,
+                        config: EnvironmentConfigState::Ready(EnvironmentConfig {
+                            allow_login_shell: true,
+                            permission_profile: PermissionProfileSnapshot::legacy(
+                                PermissionProfile::read_only(),
+                            ),
+                            selected_capability_roots: Vec::new(),
+                        }),
                     },
+                    EnvironmentConfigOrigin::Thread,
                     Arc::new(
                         Environment::create_for_tests(/*exec_server_url*/ None)
                             .expect("local environment"),
                     ),
                     /*shell*/ None,
-                    EnvironmentConfig {
-                        allow_login_shell: true,
-                        permission_profile: PermissionProfileSnapshot::legacy(
-                            PermissionProfile::read_only(),
-                        ),
-                        selected_capability_roots: Vec::new(),
-                    },
                 ))
             })
             .collect(),
diff --git a/codex-rs/core/src/environment_selection.rs b/codex-rs/core/src/environment_selection.rs
index d256bd03f4..c52b66903d 100644
--- a/codex-rs/core/src/environment_selection.rs
+++ b/codex-rs/core/src/environment_selection.rs
@@ -34,6 +34,26 @@ use crate::session::turn_context::TurnEnvironment;
 use crate::shell::Shell;
 use crate::shell_snapshot::ShellSnapshot;
 
+/// Records whether a normalized config should follow later thread setting updates.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub(crate) enum EnvironmentConfigOrigin {
+    Thread,
+    Owner,
+}
+
+impl EnvironmentConfigOrigin {
+    /// Reconstructs the input form so another attachment boundary preserves config ownership.
+    pub(crate) fn into_input_selection(
+        self,
+        mut selection: TurnEnvironmentSelection,
+    ) -> TurnEnvironmentSelection {
+        if self == Self::Thread {
+            selection.config = EnvironmentConfigState::FromThread;
+        }
+        selection
+    }
+}
+
 pub(crate) fn default_thread_environment_selections(
     environment_manager: &EnvironmentManager,
     cwd: &AbsolutePathBuf,
@@ -66,7 +86,7 @@ struct ResolvedEnvironment {
 #[derive(Clone)]
 struct SelectedTurnEnvironment {
     selection: TurnEnvironmentSelection,
-    config: EnvironmentConfig,
+    config_origin: EnvironmentConfigOrigin,
     environment: Arc<Environment>,
     // Selection clones share one listener; the final handle drop aborts it.
     connection_events_task: Option<Arc<AbortOnDropHandle<()>>>,
@@ -76,24 +96,33 @@ struct SelectedTurnEnvironment {
 #[derive(Clone)]
 pub(crate) struct StartingTurnEnvironment {
     pub(crate) selection: TurnEnvironmentSelection,
-    config: EnvironmentConfig,
+    config_origin: EnvironmentConfigOrigin,
     resolution: TurnEnvironmentResolution,
 }
 
+/// Resolves config once at the attachment boundary and records who owns future updates.
+fn resolve_selection_config(
+    mut selection: TurnEnvironmentSelection,
+    thread_config: &EnvironmentConfig,
+) -> (TurnEnvironmentSelection, EnvironmentConfigOrigin) {
+    let (config, origin) = match selection.config {
+        EnvironmentConfigState::FromThread => {
+            (thread_config.clone(), EnvironmentConfigOrigin::Thread)
+        }
+        EnvironmentConfigState::Ready(config) => (config, EnvironmentConfigOrigin::Owner),
+        EnvironmentConfigState::Pending => {
+            unreachable!("pending environment configuration is not supported yet")
+        }
+    };
+    selection.config = EnvironmentConfigState::Ready(config);
+    (selection, origin)
+}
+
 impl SelectedTurnEnvironment {
-    fn apply_configuration(
-        &mut self,
-        selection_config: EnvironmentConfigState,
-        thread_config: &EnvironmentConfig,
-    ) {
-        self.config = match &selection_config {
-            EnvironmentConfigState::FromThread => thread_config.clone(),
-            EnvironmentConfigState::Ready(config) => config.clone(),
-            EnvironmentConfigState::Pending => {
-                unreachable!("pending environment configuration is not supported yet")
-            }
-        };
-        self.selection.config = selection_config;
+    fn refresh_thread_config(&mut self, config: &EnvironmentConfig) {
+        if self.config_origin == EnvironmentConfigOrigin::Thread {
+            self.selection.config = EnvironmentConfigState::Ready(config.clone());
+        }
     }
 }
 
@@ -139,9 +168,9 @@ impl ThreadEnvironments {
                 let TurnEnvironmentState::Ready(environment) = environment else {
                     return None;
                 };
-                let selection = environment.selection();
+                let selection = environment.selection;
+                let config_origin = environment.config_origin;
                 let selected_environment = Arc::clone(&environment.environment);
-                let inherited_config = environment.config;
                 let resolution: TurnEnvironmentResolution =
                     futures::future::ready(Ok(ResolvedEnvironment {
                         environment: environment.environment,
@@ -152,17 +181,13 @@ impl ThreadEnvironments {
                     .shared();
                 let mut inherited_environment = SelectedTurnEnvironment {
                     selection,
-                    config: inherited_config,
+                    config_origin,
                     environment: selected_environment,
                     connection_events_task: None,
                     resolution,
                 };
-                // Child threads get their own settings, but inherit any
-                // environment-owned policy that was already installed.
-                inherited_environment.apply_configuration(
-                    inherited_environment.selection.config.clone(),
-                    &thread_environment_config,
-                );
+                // Child threads re-infer thread-owned config while preserving owner config.
+                inherited_environment.refresh_thread_config(&thread_environment_config);
                 Some(inherited_environment)
             })
             .collect();
@@ -188,6 +213,8 @@ impl ThreadEnvironments {
             if !seen_environment_ids.insert(selected_environment.environment_id.as_str()) {
                 continue;
             }
+            let (selected_environment, config_origin) =
+                resolve_selection_config(selected_environment.clone(), thread_environment_config);
             if let Some(environment) = previous.iter().find(|environment| {
                 let previous = &environment.selection;
                 previous.environment_id == selected_environment.environment_id
@@ -196,10 +223,8 @@ impl ThreadEnvironments {
             }) && !matches!(environment.resolution.clone().now_or_never(), Some(Err(_)))
             {
                 let mut environment = environment.clone();
-                environment.apply_configuration(
-                    selected_environment.config.clone(),
-                    thread_environment_config,
-                );
+                environment.selection = selected_environment;
+                environment.config_origin = config_origin;
                 next.push(environment);
                 continue;
             }
@@ -235,17 +260,13 @@ impl ThreadEnvironments {
             .remote_handle();
             drop(tokio::spawn(resolution_task));
             let resolution = resolution.boxed().shared();
-            let mut selected = SelectedTurnEnvironment {
-                selection: selected_environment.clone(),
-                config: thread_environment_config.clone(),
+            let selected = SelectedTurnEnvironment {
+                selection: selected_environment,
+                config_origin,
                 environment,
                 connection_events_task,
                 resolution,
             };
-            selected.apply_configuration(
-                selected_environment.config.clone(),
-                thread_environment_config,
-            );
             next.push(selected);
         }
         let removed_connection_tasks = previous
@@ -267,11 +288,16 @@ impl ThreadEnvironments {
         }
     }
 
+    /// Projects canonical selections back to caller input form without losing config ownership.
     pub(crate) fn selections(&self) -> Vec<TurnEnvironmentSelection> {
         self.environments
             .load()
             .iter()
-            .map(|environment| environment.selection.clone())
+            .map(|environment| {
+                environment
+                    .config_origin
+                    .into_input_selection(environment.selection.clone())
+            })
             .collect()
     }
 
@@ -299,14 +325,15 @@ impl ThreadEnvironments {
             .unwrap_or_default()
     }
 
-    pub(crate) fn update_environment_configs(&self, config: &EnvironmentConfig) {
+    /// Refreshes attachments whose configuration is inferred from the thread.
+    pub(crate) fn update_thread_config(&self, config: &EnvironmentConfig) {
         let environments = self
             .environments
             .load()
             .iter()
             .map(|environment| {
                 let mut environment = environment.clone();
-                environment.apply_configuration(environment.selection.config.clone(), config);
+                environment.refresh_thread_config(config);
                 environment
             })
             .collect();
@@ -331,8 +358,8 @@ impl ThreadEnvironments {
             )));
         };
 
-        let thread_config = environment.config.clone();
-        environment.apply_configuration(EnvironmentConfigState::Ready(config), &thread_config);
+        environment.selection.config = EnvironmentConfigState::Ready(config);
+        environment.config_origin = EnvironmentConfigOrigin::Owner;
         self.environments.store(Arc::new(environments));
         Ok(())
     }
@@ -346,8 +373,10 @@ impl ThreadEnvironments {
         let environments = self.environments.load();
         let mut selected_capability_roots = thread_selected_capability_roots.to_vec();
         for environment in environments.iter() {
-            selected_capability_roots
-                .extend(environment.config.selected_capability_roots.iter().cloned());
+            let EnvironmentConfigState::Ready(config) = &environment.selection.config else {
+                unreachable!("selected environments always carry resolved configuration")
+            };
+            selected_capability_roots.extend(config.selected_capability_roots.iter().cloned());
         }
         let mut seen_root_ids = HashSet::with_capacity(selected_capability_roots.len());
         selected_capability_roots.retain(|root| seen_root_ids.insert(root.id.clone()));
@@ -491,7 +520,7 @@ impl ThreadEnvironments {
             if let Some(environment) = TurnEnvironmentState::from_resolution(
                 StartingTurnEnvironment {
                     selection: environment.selection.clone(),
-                    config: environment.config.clone(),
+                    config_origin: environment.config_origin,
                     resolution: environment.resolution.clone(),
                 },
                 resolved,
@@ -522,9 +551,9 @@ impl TurnEnvironmentState {
             Some(Ok(environment)) => {
                 let mut turn_environment = TurnEnvironment::new(
                     starting.selection,
+                    starting.config_origin,
                     environment.environment,
                     environment.shell,
-                    starting.config,
                 );
                 turn_environment.shell_snapshot = environment.shell_snapshot;
                 Some(Self::Ready(turn_environment))
@@ -897,7 +926,7 @@ url = "ws://127.0.0.1:8765"
         let environment = snapshot.primary().expect("local environment");
 
         assert_eq!(environment.shell.as_ref(), Some(&local_shell));
-        assert_eq!(environment.config, expected_config);
+        assert_eq!(environment.config(), &expected_config);
     }
 
     #[tokio::test]
@@ -1107,6 +1136,10 @@ url = "ws://127.0.0.1:8765"
         turn_environments.update_selections(&[remote.clone(), local.clone()], &expected_config);
 
         let starting = turn_environments.snapshot().await;
+        let resolved_remote = TurnEnvironmentSelection {
+            config: EnvironmentConfigState::Ready(expected_config.clone()),
+            ..remote.clone()
+        };
         assert_eq!(
             starting
                 .turn_environments()
@@ -1117,7 +1150,7 @@ url = "ws://127.0.0.1:8765"
         assert_eq!(
             starting
                 .turn_environments()
-                .map(|environment| environment.config.clone())
+                .map(|environment| environment.config().clone())
                 .collect::<Vec<_>>(),
             vec![expected_config.clone()]
         );
@@ -1126,13 +1159,13 @@ url = "ws://127.0.0.1:8765"
                 .starting()
                 .map(|environment| environment.selection.clone())
                 .collect::<Vec<_>>(),
-            vec![remote.clone()]
+            vec![resolved_remote.clone()]
         );
         assert_eq!(starting.to_selections(), vec![local.clone()]);
         assert!(starting.single_local_environment().is_none());
 
         let next_config = test_environment_config();
-        turn_environments.update_environment_configs(&next_config);
+        turn_environments.update_thread_config(&next_config);
         let next_starting = turn_environments.snapshot().await;
 
         let server = tokio::spawn(serve_environment_info(listener));
@@ -1161,7 +1194,7 @@ url = "ws://127.0.0.1:8765"
         assert_eq!(
             attached
                 .turn_environments()
-                .map(|environment| environment.config.clone())
+                .map(|environment| environment.config().clone())
                 .collect::<Vec<_>>(),
             vec![expected_config.clone(), expected_config]
         );
@@ -1170,7 +1203,7 @@ url = "ws://127.0.0.1:8765"
             next_starting
                 .refresh_readiness()
                 .turn_environments()
-                .map(|environment| environment.config.clone())
+                .map(|environment| environment.config().clone())
                 .collect::<Vec<_>>(),
             vec![next_config.clone(), next_config]
         );
@@ -1240,7 +1273,7 @@ url = "ws://127.0.0.1:8765"
             allow_login_shell: false,
             ..test_environment_config()
         };
-        environments.update_environment_configs(&next_config);
+        environments.update_thread_config(&next_config);
         assert!(
             failed_resolution.ptr_eq(&environments.environments.load()[0].resolution),
             "updating environment config must not retry a failed environment"
@@ -1252,7 +1285,14 @@ url = "ws://127.0.0.1:8765"
             .starting()
             .next()
             .expect("expected the replacement environment to be starting");
-        assert_eq!(replacement.selection, selection);
+        assert_eq!(
+            replacement.selection,
+            TurnEnvironmentSelection {
+                config: EnvironmentConfigState::Ready(next_config),
+                ..selection.clone()
+            }
+        );
+        assert_eq!(environments.selections(), vec![selection]);
         assert!(!failed_resolution.ptr_eq(&replacement.resolution));
     }
 
@@ -1373,10 +1413,13 @@ url = "ws://127.0.0.1:8765"
                 .expect("inherited environment"),
         );
         let inherited = TurnEnvironment::new(
-            selection.clone(),
+            TurnEnvironmentSelection {
+                config: EnvironmentConfigState::Ready(test_environment_config()),
+                ..selection.clone()
+            },
+            EnvironmentConfigOrigin::Thread,
             Arc::clone(&inherited_environment),
             /*shell*/ None,
-            test_environment_config(),
         );
         let manager = Arc::new(environment_manager_without_environments());
         manager
@@ -1411,7 +1454,7 @@ url = "ws://127.0.0.1:8765"
 
         let inherited = snapshot.primary().expect("inherited environment");
         assert!(Arc::ptr_eq(&inherited.environment, &inherited_environment));
-        assert_eq!(inherited.config, child_config);
+        assert_eq!(inherited.config(), &child_config);
     }
 
     #[tokio::test]
@@ -1448,6 +1491,16 @@ url = "ws://127.0.0.1:8765"
             ),
             ..test_environment_config()
         };
+        parent.update_thread_config(&child_thread_config);
+        assert_eq!(
+            parent
+                .snapshot()
+                .await
+                .primary()
+                .expect("owner-configured environment")
+                .config(),
+            &parent_owner_config
+        );
         let child = ThreadEnvironments::new(
             manager,
             crate::shell::default_user_shell(),
@@ -1471,10 +1524,10 @@ url = "ws://127.0.0.1:8765"
             cleared_snapshot
                 .primary()
                 .expect("environment with cleared roots")
-                .config,
-            cleared_parent_owner_config
+                .config(),
+            &cleared_parent_owner_config
         );
-        assert_eq!(child_environment.config, parent_owner_config);
+        assert_eq!(child_environment.config(), &parent_owner_config);
 
         let changed_selection = TurnEnvironmentSelection {
             cwd: PathUri::from_abs_path(&cwd.join("changed")),
@@ -1484,7 +1537,7 @@ url = "ws://127.0.0.1:8765"
         parent.update_selections(std::slice::from_ref(&changed_selection), &new_thread_config);
         let changed_snapshot = parent.snapshot().await;
         let changed_environment = changed_snapshot.primary().expect("changed environment");
-        assert_eq!(changed_environment.config, new_thread_config);
+        assert_eq!(changed_environment.config(), &new_thread_config);
     }
 
     #[tokio::test]
@@ -1514,11 +1567,11 @@ url = "ws://127.0.0.1:8765"
                     environment_id: REMOTE_ENVIRONMENT_ID.to_string(),
                     cwd: remote_cwd_uri.clone(),
                     workspace_roots: Vec::new(),
-                    config: EnvironmentConfigState::FromThread,
+                    config: EnvironmentConfigState::Ready(test_environment_config()),
                 },
+                EnvironmentConfigOrigin::Thread,
                 remote_environment.clone(),
                 /*shell*/ None,
-                test_environment_config(),
             ))],
         };
         let multiple = TurnEnvironmentSnapshot {
@@ -1528,11 +1581,11 @@ url = "ws://127.0.0.1:8765"
                         environment_id: REMOTE_ENVIRONMENT_ID.to_string(),
                         cwd: remote_cwd_uri,
                         workspace_roots: Vec::new(),
-                        config: EnvironmentConfigState::FromThread,
+                        config: EnvironmentConfigState::Ready(test_environment_config()),
                     },
+                    EnvironmentConfigOrigin::Thread,
                     remote_environment,
                     /*shell*/ None,
-                    test_environment_config(),
                 )),
                 TurnEnvironmentState::Ready(local.primary().expect("local environment").clone()),
             ],
@@ -1555,9 +1608,9 @@ url = "ws://127.0.0.1:8765"
                     environment_id: LOCAL_ENVIRONMENT_ID.to_string(),
                     cwd: PathUri::from_abs_path(&cwd),
                     workspace_roots: Vec::new(),
-                    config: EnvironmentConfigState::FromThread,
+                    config: EnvironmentConfigState::Ready(test_environment_config()),
                 },
-                config: test_environment_config(),
+                config_origin: EnvironmentConfigOrigin::Thread,
                 resolution: futures::future::pending().boxed().shared(),
             })],
         };
diff --git a/codex-rs/core/src/guardian/review_session.rs b/codex-rs/core/src/guardian/review_session.rs
index 9d548e5867..0d3691d8a9 100644
--- a/codex-rs/core/src/guardian/review_session.rs
+++ b/codex-rs/core/src/guardian/review_session.rs
@@ -1057,18 +1057,22 @@ async fn run_review_on_session(
         .permissions
         .permission_profile_state()
         .snapshot();
-    let mut parent_turn_environments = params.parent_context.environments().to_selections();
-    // FromThread inherits the Guardian profile below. Once Core normalizes FromThread
-    // to Ready(config), every selection will carry explicit config and this conditional can be
-    // removed.
-    for selection in &mut parent_turn_environments {
-        if let EnvironmentConfigState::Ready(config) = &mut selection.config {
+    // Guardian must receive read-only permissions for every inherited environment.
+    let parent_turn_environments = params
+        .parent_context
+        .environments()
+        .turn_environments()
+        .map(|environment| {
+            let mut selection = environment.selection();
+            let mut config = environment.config().clone();
             config.permission_profile =
                 PermissionProfileSnapshot::legacy(read_only_guardian_permission_profile(
                     config.permission_profile.permission_profile(),
                 ));
-        }
-    }
+            selection.config = EnvironmentConfigState::Ready(config);
+            selection
+        })
+        .collect();
     // TODO(anp): Migrate guardian review thread settings to a PathUri fallback cwd so foreign
     // parent environments do not fall back to the host-native config cwd.
     let parent_turn_legacy_fallback_cwd = params
diff --git a/codex-rs/core/src/guardian/tests.rs b/codex-rs/core/src/guardian/tests.rs
index c421c94dff..b83419ad22 100644
--- a/codex-rs/core/src/guardian/tests.rs
+++ b/codex-rs/core/src/guardian/tests.rs
@@ -628,7 +628,7 @@ async fn build_guardian_prompt_includes_parent_turn_denied_reads() -> anyhow::Re
     let TurnEnvironmentState::Ready(environment) = &mut turn.environments.environments[0] else {
         panic!("parent environment should be ready");
     };
-    environment.config.permission_profile =
+    environment.config_mut().permission_profile =
         PermissionProfileSnapshot::legacy(environment_permission_profile);
     environment.selection.workspace_roots = vec![
         PathUri::from_abs_path(&workspace_root),
diff --git a/codex-rs/core/src/mcp_openai_file.rs b/codex-rs/core/src/mcp_openai_file.rs
index c6f3d37eb1..e0a0cda2d0 100644
--- a/codex-rs/core/src/mcp_openai_file.rs
+++ b/codex-rs/core/src/mcp_openai_file.rs
@@ -367,7 +367,7 @@ mod tests {
             .primary()
             .expect("ready primary environment");
         let selection = environment.selection();
-        let environment_config = environment.config.clone();
+        let environment_config = environment.config().clone();
         let environments = crate::environment_selection::ThreadEnvironments::new(
             session.services.turn_environments.environment_manager(),
             crate::shell::default_user_shell(),
diff --git a/codex-rs/core/src/mcp_tool_call_tests.rs b/codex-rs/core/src/mcp_tool_call_tests.rs
index 7195ebb7b2..2160515213 100644
--- a/codex-rs/core/src/mcp_tool_call_tests.rs
+++ b/codex-rs/core/src/mcp_tool_call_tests.rs
@@ -1,6 +1,7 @@
 use super::*;
 use crate::config::ConfigBuilder;
 use crate::config::ManagedFeatures;
+use crate::environment_selection::EnvironmentConfigOrigin;
 use crate::environment_selection::TurnEnvironmentState;
 use crate::session::step_context::StepContext;
 use crate::session::tests::make_session_and_context;
@@ -1112,19 +1113,19 @@ async fn mcp_sandbox_cwd_uses_matching_server_environment_uri() -> anyhow::Resul
                 environment_id: "remote".to_string(),
                 cwd: secondary_cwd.clone(),
                 workspace_roots: Vec::new(),
-                config: EnvironmentConfigState::FromThread,
+                config: EnvironmentConfigState::Ready(EnvironmentConfig {
+                    allow_login_shell: true,
+                    permission_profile: turn_context
+                        .config
+                        .permissions
+                        .permission_profile_state()
+                        .snapshot(),
+                    selected_capability_roots: Vec::new(),
+                }),
             },
+            EnvironmentConfigOrigin::Thread,
             environment,
             /*shell*/ None,
-            EnvironmentConfig {
-                allow_login_shell: true,
-                permission_profile: turn_context
-                    .config
-                    .permissions
-                    .permission_profile_state()
-                    .snapshot(),
-                selected_capability_roots: Vec::new(),
-            },
         )));
 
     let step_context = StepContext::for_test(Arc::new(turn_context));
diff --git a/codex-rs/core/src/session/mcp.rs b/codex-rs/core/src/session/mcp.rs
index cfddb30f17..e12857e65d 100644
--- a/codex-rs/core/src/session/mcp.rs
+++ b/codex-rs/core/src/session/mcp.rs
@@ -448,7 +448,7 @@ impl Session {
             .chain(
                 environments
                     .turn_environments()
-                    .flat_map(|environment| environment.config.selected_capability_roots.clone()),
+                    .flat_map(|environment| environment.config().selected_capability_roots.clone()),
             )
             .enumerate()
         {
diff --git a/codex-rs/core/src/session/mod.rs b/codex-rs/core/src/session/mod.rs
index 33af3adc42..9bb00c2d0a 100644
--- a/codex-rs/core/src/session/mod.rs
+++ b/codex-rs/core/src/session/mod.rs
@@ -1596,7 +1596,7 @@ impl Session {
             } else if state.session_configuration.turn_environment_config() != environment_config {
                 self.services
                     .turn_environments
-                    .update_environment_configs(&environment_config);
+                    .update_thread_config(&environment_config);
             }
             state.session_configuration = updated;
             let new_config = notify_config_contributors
diff --git a/codex-rs/core/src/session/tests.rs b/codex-rs/core/src/session/tests.rs
index 46f351e0bb..beb48f4a38 100644
--- a/codex-rs/core/src/session/tests.rs
+++ b/codex-rs/core/src/session/tests.rs
@@ -7,6 +7,7 @@ use crate::config::ConfigOverrides;
 use crate::config::test_config;
 use crate::context::ContextualUserFragment;
 use crate::context::TurnAborted;
+use crate::environment_selection::EnvironmentConfigOrigin;
 use crate::environment_selection::ThreadEnvironments;
 use crate::environment_selection::TurnEnvironmentState;
 use crate::function_tool::FunctionCallError;
@@ -5450,7 +5451,7 @@ async fn permission_profile_updates_apply_to_next_turn_environment() {
             .environments
             .primary()
             .expect("active turn environment")
-            .config
+            .config()
             .clone();
         let profile_root = active_turn.config.cwd.join("profile-root");
         let active_profile = ActivePermissionProfile::read_only();
@@ -5485,14 +5486,14 @@ async fn permission_profile_updates_apply_to_next_turn_environment() {
                 vec![profile_root],
             );
 
-        assert_eq!(next_environment.config, expected_environment_config);
+        assert_eq!(next_environment.config(), &expected_environment_config);
         assert_eq!(
             active_turn
                 .environments
                 .primary()
                 .expect("active turn environment")
-                .config,
-            active_environment_config
+                .config(),
+            &active_environment_config
         );
     }
 }
@@ -6639,17 +6640,18 @@ async fn request_permissions_tool_resolves_relative_paths_against_selected_envir
         .primary()
         .expect("primary environment")
         .clone();
+    let current_environment_config = current_environment.config().clone();
     turn_context_mut.environments.environments[0] =
         TurnEnvironmentState::Ready(TurnEnvironment::new(
             TurnEnvironmentSelection {
                 environment_id: "remote".to_string(),
                 cwd: PathUri::from_abs_path(&environment_cwd),
                 workspace_roots: Vec::new(),
-                config: EnvironmentConfigState::FromThread,
+                config: EnvironmentConfigState::Ready(current_environment_config),
             },
+            current_environment.config_origin,
             current_environment.environment,
             current_environment.shell,
-            current_environment.config,
         ));
 
     let call_id = "call-1".to_string();
@@ -7237,6 +7239,7 @@ async fn primary_environment_uses_first_turn_environment() {
     #[allow(deprecated)]
     let second_cwd = turn_context.cwd.join("second");
     let second_cwd_uri = codex_utils_path_uri::PathUri::from_abs_path(&second_cwd);
+    let first_environment_config = first_environment.config().clone();
     turn_context
         .environments
         .environments
@@ -7245,11 +7248,11 @@ async fn primary_environment_uses_first_turn_environment() {
                 environment_id: "second".to_string(),
                 cwd: second_cwd_uri.clone(),
                 workspace_roots: Vec::new(),
-                config: EnvironmentConfigState::FromThread,
+                config: EnvironmentConfigState::Ready(first_environment_config),
             },
+            first_environment.config_origin,
             Arc::clone(&first_environment.environment),
             /*shell*/ None,
-            first_environment.config.clone(),
         )));
 
     assert_eq!(
@@ -8624,7 +8627,7 @@ async fn conflicting_ready_environment_root_ids_keep_first_location() {
             environment_id,
             ..
         } = &selected_root.location;
-        let mut environment_config = local_environment.config.clone();
+        let mut environment_config = local_environment.config().clone();
         environment_config.selected_capability_roots = vec![selected_root.clone()];
         turn_environments.push(TurnEnvironment::new(
             TurnEnvironmentSelection {
@@ -8633,12 +8636,12 @@ async fn conflicting_ready_environment_root_ids_keep_first_location() {
                 workspace_roots: local_environment.workspace_roots().to_vec(),
                 config: EnvironmentConfigState::Ready(environment_config.clone()),
             },
+            EnvironmentConfigOrigin::Owner,
             Arc::new(
                 codex_exec_server::Environment::create_for_tests(/*exec_server_url*/ None)
                     .expect("create test environment"),
             ),
             local_environment.shell.clone(),
-            environment_config,
         ));
     }
     let environments = TurnEnvironmentSnapshot {
@@ -8691,7 +8694,7 @@ async fn capability_discovery_uses_environment_permission_profile() {
         access: FileSystemAccessMode::Deny,
         missing_path_behavior: None,
     });
-    environment.config.permission_profile =
+    environment.config_mut().permission_profile =
         PermissionProfileSnapshot::legacy(PermissionProfile::from_runtime_permissions(
             &file_system_policy,
             NetworkSandboxPolicy::Restricted,
@@ -8888,17 +8891,18 @@ async fn record_context_updates_emits_environment_item_for_cwd_changes() {
         .primary()
         .expect("primary environment")
         .clone();
+    let environment_config = environment.config().clone();
     current_context.environments.environments[0] =
         TurnEnvironmentState::Ready(TurnEnvironment::new(
             TurnEnvironmentSelection {
                 environment_id: environment.selection.environment_id,
                 cwd: PathUri::from_abs_path(&cwd),
                 workspace_roots: Vec::new(),
-                config: EnvironmentConfigState::FromThread,
+                config: EnvironmentConfigState::Ready(environment_config),
             },
+            environment.config_origin,
             environment.environment,
             environment.shell,
-            environment.config,
         ));
 
     let update_items =
@@ -8927,7 +8931,7 @@ async fn record_context_updates_use_environment_permission_profile_and_workspace
         .primary()
         .expect("primary environment")
         .clone();
-    previous_environment.config.permission_profile =
+    previous_environment.config_mut().permission_profile =
         PermissionProfileSnapshot::legacy(PermissionProfile::Disabled);
     previous_context.environments.environments[0] =
         TurnEnvironmentState::Ready(previous_environment);
@@ -8945,7 +8949,7 @@ async fn record_context_updates_use_environment_permission_profile_and_workspace
         .clone();
     let cwd = environment.cwd().clone();
     let workspace_root = current_context.config.cwd.join("selected-workspace");
-    let mut environment_config = environment.config;
+    let mut environment_config = environment.config().clone();
     environment_config.permission_profile =
         PermissionProfileSnapshot::legacy(PermissionProfile::workspace_write());
     current_context.environments.environments[0] =
@@ -8954,11 +8958,11 @@ async fn record_context_updates_use_environment_permission_profile_and_workspace
                 environment_id: environment.selection.environment_id,
                 cwd,
                 workspace_roots: vec![PathUri::from_abs_path(&workspace_root)],
-                config: EnvironmentConfigState::FromThread,
+                config: EnvironmentConfigState::Ready(environment_config),
             },
+            environment.config_origin,
             environment.environment,
             environment.shell,
-            environment_config,
         ));
 
     let update_items =
@@ -9024,17 +9028,18 @@ async fn record_context_updates_omits_environment_item_when_disabled() {
         .primary()
         .expect("primary environment")
         .clone();
+    let environment_config = environment.config().clone();
     current_context.environments.environments[0] =
         TurnEnvironmentState::Ready(TurnEnvironment::new(
             TurnEnvironmentSelection {
                 environment_id: environment.selection.environment_id,
                 cwd: PathUri::from_abs_path(&test_path_buf("/new-repo").abs()),
                 workspace_roots: Vec::new(),
-                config: EnvironmentConfigState::FromThread,
+                config: EnvironmentConfigState::Ready(environment_config),
             },
+            environment.config_origin,
             environment.environment,
             environment.shell,
-            environment.config,
         ));
 
     let update_items =
@@ -9497,16 +9502,17 @@ async fn turn_context_item_stores_local_cwd() {
         .expect("primary environment")
         .clone();
     let cwd = PathUri::parse("file:///C:/windows").expect("Windows cwd URI");
+    let environment_config = environment.config().clone();
     turn_context.environments.environments[0] = TurnEnvironmentState::Ready(TurnEnvironment::new(
         TurnEnvironmentSelection {
             environment_id: "remote".to_string(),
             cwd,
             workspace_roots: Vec::new(),
-            config: EnvironmentConfigState::FromThread,
+            config: EnvironmentConfigState::Ready(environment_config),
         },
+        environment.config_origin,
         environment.environment,
         environment.shell,
-        environment.config,
     ));
 
     #[allow(deprecated)]
diff --git a/codex-rs/core/src/session/tests/guardian_tests.rs b/codex-rs/core/src/session/tests/guardian_tests.rs
index 12ccbf92d0..dd0efd1857 100644
--- a/codex-rs/core/src/session/tests/guardian_tests.rs
+++ b/codex-rs/core/src/session/tests/guardian_tests.rs
@@ -349,7 +349,7 @@ async fn guardian_allows_shell_command_additional_permissions_requests_past_poli
     else {
         panic!("primary environment should be ready");
     };
-    environment.config.permission_profile =
+    environment.config_mut().permission_profile =
         config.permissions.permission_profile_state().snapshot();
     config.codex_linux_sandbox_exe = codex_linux_sandbox_exe_or_skip!();
     config
@@ -471,7 +471,7 @@ async fn strict_auto_review_turn_grant_forces_guardian_for_shell_command_policy_
     else {
         panic!("primary environment should be ready");
     };
-    environment.config.permission_profile =
+    environment.config_mut().permission_profile =
         config.permissions.permission_profile_state().snapshot();
     config.approvals_reviewer = ApprovalsReviewer::User;
     config.model_provider.base_url = Some(format!("{}/v1", server.uri()));
diff --git a/codex-rs/core/src/session/turn_context.rs b/codex-rs/core/src/session/turn_context.rs
index a11bef12f4..03f204c75a 100644
--- a/codex-rs/core/src/session/turn_context.rs
+++ b/codex-rs/core/src/session/turn_context.rs
@@ -1,4 +1,5 @@
 use super::*;
+use crate::environment_selection::EnvironmentConfigOrigin;
 use crate::environment_selection::TurnEnvironmentSnapshot;
 use crate::exec_policy::AllowPrefixRules;
 use crate::shell_snapshot::ShellSnapshotFile;
@@ -15,6 +16,7 @@ use codex_protocol::models::AdditionalPermissionProfile;
 use codex_protocol::openai_models::MODEL_SPECIALTY_CYBER;
 use codex_protocol::openai_models::ModelInfo;
 use codex_protocol::protocol::EnvironmentConfig;
+use codex_protocol::protocol::EnvironmentConfigState;
 use codex_protocol::protocol::ErrorEvent;
 use codex_protocol::protocol::MultiAgentVersion;
 use codex_protocol::protocol::ThreadHistoryMode;
@@ -34,28 +36,44 @@ pub(crate) type ShellSnapshotTask = Shared<BoxFuture<'static, Option<Arc<ShellSn
 #[derive(Clone)]
 pub(crate) struct TurnEnvironment {
     pub(crate) selection: TurnEnvironmentSelection,
+    pub(crate) config_origin: EnvironmentConfigOrigin,
     pub(crate) environment: Arc<Environment>,
     pub(crate) shell: Option<shell::Shell>,
-    pub(crate) config: EnvironmentConfig,
     pub(crate) shell_snapshot: ShellSnapshotTask,
 }
 
 impl TurnEnvironment {
     pub(crate) fn new(
         selection: TurnEnvironmentSelection,
+        config_origin: EnvironmentConfigOrigin,
         environment: Arc<Environment>,
         shell: Option<shell::Shell>,
-        config: EnvironmentConfig,
     ) -> Self {
+        debug_assert!(matches!(selection.config, EnvironmentConfigState::Ready(_)));
         Self {
             selection,
+            config_origin,
             environment,
             shell,
-            config,
             shell_snapshot: futures::future::ready(None).boxed().shared(),
         }
     }
 
+    pub(crate) fn config(&self) -> &EnvironmentConfig {
+        let EnvironmentConfigState::Ready(config) = &self.selection.config else {
+            unreachable!("ready turn environments always carry resolved configuration")
+        };
+        config
+    }
+
+    #[cfg(test)]
+    pub(crate) fn config_mut(&mut self) -> &mut EnvironmentConfig {
+        let EnvironmentConfigState::Ready(config) = &mut self.selection.config else {
+            unreachable!("ready turn environments always carry resolved configuration")
+        };
+        config
+    }
+
     pub(crate) fn shell_snapshot(&self, cwd: &AbsolutePathBuf) -> Option<AbsolutePathBuf> {
         if self.selection.cwd != PathUri::from_abs_path(cwd) {
             return None;
@@ -75,11 +93,11 @@ impl TurnEnvironment {
     }
 
     pub(crate) fn permission_profile(&self) -> &PermissionProfile {
-        self.config.permission_profile.permission_profile()
+        self.config().permission_profile.permission_profile()
     }
 
     pub(crate) fn active_permission_profile(&self) -> Option<ActivePermissionProfile> {
-        self.config.permission_profile.active_permission_profile()
+        self.config().permission_profile.active_permission_profile()
     }
 
     pub(crate) fn permission_profile_with_workspace_roots(&self) -> PermissionProfile {
@@ -94,7 +112,8 @@ impl TurnEnvironment {
     }
 
     pub(crate) fn selection(&self) -> TurnEnvironmentSelection {
-        self.selection.clone()
+        self.config_origin
+            .into_input_selection(self.selection.clone())
     }
 }
 
@@ -106,7 +125,8 @@ impl std::fmt::Debug for TurnEnvironment {
             .field("cwd", &self.selection.cwd)
             .field("workspace_roots", &self.selection.workspace_roots)
             .field("shell", &self.shell)
-            .field("config", &self.config)
+            .field("config", self.config())
+            .field("config_origin", &self.config_origin)
             .finish_non_exhaustive()
     }
 }
@@ -690,7 +710,7 @@ impl Session {
                     {
                         self.services
                             .turn_environments
-                            .update_environment_configs(&environment_config);
+                            .update_thread_config(&environment_config);
                     }
                     if mcp_inputs_changed {
                         self.mark_mcp_runtime_dirty();
diff --git a/codex-rs/core/src/tools/handlers/multi_agents_tests.rs b/codex-rs/core/src/tools/handlers/multi_agents_tests.rs
index c18e2ae016..93a6d92aa9 100644
--- a/codex-rs/core/src/tools/handlers/multi_agents_tests.rs
+++ b/codex-rs/core/src/tools/handlers/multi_agents_tests.rs
@@ -2298,7 +2298,7 @@ async fn spawn_agent_reapplies_runtime_sandbox_after_role_config() {
     else {
         panic!("parent environment should be ready");
     };
-    environment.config.permission_profile =
+    environment.config_mut().permission_profile =
         PermissionProfileSnapshot::legacy(expected_permission_profile.clone());
     assert_ne!(
         role_config.permissions.effective_permission_profile(),
@@ -4572,7 +4572,7 @@ async fn build_agent_resume_config_clears_base_instructions() {
     else {
         panic!("parent environment should be ready");
     };
-    environment.config.permission_profile =
+    environment.config_mut().permission_profile =
         PermissionProfileSnapshot::legacy(environment_permission_profile.clone());
 
     let config =
diff --git a/codex-rs/core/src/tools/handlers/shell/shell_command.rs b/codex-rs/core/src/tools/handlers/shell/shell_command.rs
index 257e678da8..04d3011c3e 100644
--- a/codex-rs/core/src/tools/handlers/shell/shell_command.rs
+++ b/codex-rs/core/src/tools/handlers/shell/shell_command.rs
@@ -101,8 +101,10 @@ impl ShellCommandHandler {
             .shell
             .as_ref()
             .unwrap_or(session_shell.as_ref());
-        let use_login_shell =
-            Self::resolve_use_login_shell(params.login, turn_environment.config.allow_login_shell)?;
+        let use_login_shell = Self::resolve_use_login_shell(
+            params.login,
+            turn_environment.config().allow_login_shell,
+        )?;
         let command = Self::base_command(shell, &params.command, use_login_shell);
 
         let mut env = create_env(
diff --git a/codex-rs/core/src/tools/handlers/shell_tests.rs b/codex-rs/core/src/tools/handlers/shell_tests.rs
index 1a7fed0194..600888eec5 100644
--- a/codex-rs/core/src/tools/handlers/shell_tests.rs
+++ b/codex-rs/core/src/tools/handlers/shell_tests.rs
@@ -6,6 +6,7 @@ use codex_protocol::models::ShellCommandToolCallParams;
 use pretty_assertions::assert_eq;
 
 use crate::config::PermissionProfileSnapshot;
+use crate::environment_selection::EnvironmentConfigOrigin;
 use crate::exec_env::CODEX_PERMISSION_PROFILE_ENV_VAR;
 use crate::exec_env::create_env;
 use crate::exec_env::inject_permission_profile_env;
@@ -109,8 +110,16 @@ async fn shell_command_handler_to_exec_params_uses_selected_environment() {
             environment_id: "selected-environment".to_string(),
             cwd: PathUri::from_abs_path(&selected_cwd),
             workspace_roots: Vec::new(),
-            config: EnvironmentConfigState::FromThread,
+            config: EnvironmentConfigState::Ready(EnvironmentConfig {
+                allow_login_shell: true,
+                permission_profile: PermissionProfileSnapshot::active(
+                    permission_profile,
+                    active_permission_profile.clone(),
+                ),
+                selected_capability_roots: Vec::new(),
+            }),
         },
+        EnvironmentConfigOrigin::Thread,
         Arc::clone(
             &turn_context
                 .environments
@@ -119,14 +128,6 @@ async fn shell_command_handler_to_exec_params_uses_selected_environment() {
                 .environment,
         ),
         Some(selected_shell),
-        EnvironmentConfig {
-            allow_login_shell: true,
-            permission_profile: PermissionProfileSnapshot::active(
-                permission_profile,
-                active_permission_profile.clone(),
-            ),
-            selected_capability_roots: Vec::new(),
-        },
     );
     let mut expected_env = create_env(
         &turn_context.config.permissions.shell_environment_policy,
@@ -210,7 +211,7 @@ async fn shell_command_handler_defaults_to_non_login_when_disallowed() {
         .primary()
         .expect("primary environment")
         .clone();
-    turn_environment.config.allow_login_shell = false;
+    turn_environment.config_mut().allow_login_shell = false;
     let cwd = turn_environment
         .cwd()
         .to_abs_path()
diff --git a/codex-rs/core/src/tools/handlers/unified_exec/exec_command.rs b/codex-rs/core/src/tools/handlers/unified_exec/exec_command.rs
index e4e5624ee0..f7a24e86d4 100644
--- a/codex-rs/core/src/tools/handlers/unified_exec/exec_command.rs
+++ b/codex-rs/core/src/tools/handlers/unified_exec/exec_command.rs
@@ -233,7 +233,7 @@ impl ExecCommandHandler {
             &args,
             shell,
             &shell_mode,
-            turn_environment.config.allow_login_shell,
+            turn_environment.config().allow_login_shell,
         )
         .map_err(FunctionCallError::RespondToModel)?;
         let command = resolved_command.command;
diff --git a/codex-rs/core/src/tools/handlers/unified_exec_tests.rs b/codex-rs/core/src/tools/handlers/unified_exec_tests.rs
index 626bb90414..eee95fd43a 100644
--- a/codex-rs/core/src/tools/handlers/unified_exec_tests.rs
+++ b/codex-rs/core/src/tools/handlers/unified_exec_tests.rs
@@ -183,7 +183,7 @@ async fn exec_command_rejects_login_when_selected_environment_disallows_it() {
     else {
         panic!("primary environment should be ready");
     };
-    environment.config.allow_login_shell = false;
+    environment.config_mut().allow_login_shell = false;
 
     let turn = Arc::new(turn);
     let invocation = ToolInvocation {
diff --git a/codex-rs/core/src/tools/handlers/view_image.rs b/codex-rs/core/src/tools/handlers/view_image.rs
index 075460de7c..5e6bf3b0b4 100644
--- a/codex-rs/core/src/tools/handlers/view_image.rs
+++ b/codex-rs/core/src/tools/handlers/view_image.rs
@@ -290,9 +290,9 @@ mod tests {
         selection.workspace_roots.clear();
         turn.environments.environments[0] = TurnEnvironmentState::Ready(TurnEnvironment::new(
             selection,
+            current.config_origin,
             current.environment,
             current.shell,
-            current.config,
         ));
     }
 
@@ -358,7 +358,7 @@ mod tests {
         else {
             panic!("primary environment should be ready");
         };
-        environment.config.permission_profile =
+        environment.config_mut().permission_profile =
             PermissionProfileSnapshot::legacy(PermissionProfile::read_only());
         let turn = Arc::new(turn);
 
@@ -430,7 +430,7 @@ mod tests {
         else {
             panic!("primary environment should be ready");
         };
-        environment.config.permission_profile =
+        environment.config_mut().permission_profile =
             PermissionProfileSnapshot::legacy(PermissionProfile::Disabled);
         let turn = Arc::new(turn);
 
@@ -467,7 +467,7 @@ mod tests {
         else {
             panic!("primary environment should be ready");
         };
-        environment.config.permission_profile =
+        environment.config_mut().permission_profile =
             PermissionProfileSnapshot::legacy(PermissionProfile::Disabled);
         let turn = Arc::new(turn);
 
diff --git a/codex-rs/core/src/tools/runtimes/apply_patch_tests.rs b/codex-rs/core/src/tools/runtimes/apply_patch_tests.rs
index b62882c471..0b4fe66c55 100644
--- a/codex-rs/core/src/tools/runtimes/apply_patch_tests.rs
+++ b/codex-rs/core/src/tools/runtimes/apply_patch_tests.rs
@@ -1,5 +1,6 @@
 use super::*;
 use crate::config::PermissionProfileSnapshot;
+use crate::environment_selection::EnvironmentConfigOrigin;
 use crate::tools::sandboxing::SandboxAttempt;
 use codex_protocol::config_types::WindowsSandboxLevel;
 use codex_protocol::models::AdditionalPermissionProfile;
@@ -24,15 +25,17 @@ fn test_turn_environment(environment_id: &str) -> crate::session::turn_context::
             environment_id: environment_id.to_string(),
             cwd: PathUri::from_abs_path(&std::env::temp_dir().abs()),
             workspace_roots: Vec::new(),
-            config: EnvironmentConfigState::FromThread,
+            config: EnvironmentConfigState::Ready(EnvironmentConfig {
+                allow_login_shell: true,
+                permission_profile: PermissionProfileSnapshot::legacy(
+                    PermissionProfile::read_only(),
+                ),
+                selected_capability_roots: Vec::new(),
+            }),
         },
+        EnvironmentConfigOrigin::Thread,
         std::sync::Arc::new(codex_exec_server::Environment::default_for_tests()),
         /*shell*/ None,
-        EnvironmentConfig {
-            allow_login_shell: true,
-            permission_profile: PermissionProfileSnapshot::legacy(PermissionProfile::read_only()),
-            selected_capability_roots: Vec::new(),
-        },
     )
 }
 
diff --git a/codex-rs/core/src/tools/runtimes/shell_tests.rs b/codex-rs/core/src/tools/runtimes/shell_tests.rs
index a336983a53..04301bf669 100644
--- a/codex-rs/core/src/tools/runtimes/shell_tests.rs
+++ b/codex-rs/core/src/tools/runtimes/shell_tests.rs
@@ -1,5 +1,6 @@
 use super::*;
 use crate::config::PermissionProfileSnapshot;
+use crate::environment_selection::EnvironmentConfigOrigin;
 use crate::tools::approvals::ApprovalCacheKey;
 use codex_exec_server::Environment;
 use codex_protocol::models::PermissionProfile;
@@ -21,17 +22,17 @@ async fn approval_key_uses_path_uri_and_includes_environment_id() {
                 environment_id: "remote".to_string(),
                 cwd: PathUri::from_abs_path(&cwd),
                 workspace_roots: Vec::new(),
-                config: EnvironmentConfigState::FromThread,
+                config: EnvironmentConfigState::Ready(EnvironmentConfig {
+                    allow_login_shell: true,
+                    permission_profile: PermissionProfileSnapshot::legacy(
+                        PermissionProfile::read_only(),
+                    ),
+                    selected_capability_roots: Vec::new(),
+                }),
             },
+            EnvironmentConfigOrigin::Thread,
             Arc::new(Environment::default_for_tests()),
             /*shell*/ None,
-            EnvironmentConfig {
-                allow_login_shell: true,
-                permission_profile: PermissionProfileSnapshot::legacy(
-                    PermissionProfile::read_only(),
-                ),
-                selected_capability_roots: Vec::new(),
-            },
         ),
         shell_type: None,
         hook_command: "echo hello".to_string(),
diff --git a/codex-rs/core/src/tools/runtimes/unified_exec.rs b/codex-rs/core/src/tools/runtimes/unified_exec.rs
index b49843feba..1daebe95d2 100644
--- a/codex-rs/core/src/tools/runtimes/unified_exec.rs
+++ b/codex-rs/core/src/tools/runtimes/unified_exec.rs
@@ -514,6 +514,7 @@ impl<'a> ToolRuntime<UnifiedExecRequest, UnifiedExecAttempt> for UnifiedExecRunt
 mod tests {
     use super::*;
     use crate::config::PermissionProfileSnapshot;
+    use crate::environment_selection::EnvironmentConfigOrigin;
     use crate::exec::DEFAULT_EXEC_COMMAND_TIMEOUT_MS;
     use crate::tools::sandboxing::ToolRuntime;
     use codex_exec_server::Environment;
@@ -536,17 +537,17 @@ mod tests {
                 environment_id: LOCAL_ENVIRONMENT_ID.to_string(),
                 cwd,
                 workspace_roots: Vec::new(),
-                config: EnvironmentConfigState::FromThread,
+                config: EnvironmentConfigState::Ready(EnvironmentConfig {
+                    allow_login_shell: true,
+                    permission_profile: PermissionProfileSnapshot::legacy(
+                        PermissionProfile::read_only(),
+                    ),
+                    selected_capability_roots: Vec::new(),
+                }),
             },
+            EnvironmentConfigOrigin::Thread,
             Arc::new(Environment::default_for_tests()),
             /*shell*/ None,
-            EnvironmentConfig {
-                allow_login_shell: true,
-                permission_profile: PermissionProfileSnapshot::legacy(
-                    PermissionProfile::read_only(),
-                ),
-                selected_capability_roots: Vec::new(),
-            },
         )
     }
 
diff --git a/codex-rs/core/src/tools/spec_plan.rs b/codex-rs/core/src/tools/spec_plan.rs
index e094213a23..3da01c0023 100644
--- a/codex-rs/core/src/tools/spec_plan.rs
+++ b/codex-rs/core/src/tools/spec_plan.rs
@@ -954,7 +954,7 @@ fn tool_environment_mode(environments: &TurnEnvironmentSnapshot) -> ToolEnvironm
 fn any_environment_allows_login_shell(environments: &TurnEnvironmentSnapshot) -> bool {
     environments
         .turn_environments()
-        .any(|environment| environment.config.allow_login_shell)
+        .any(|environment| environment.config().allow_login_shell)
 }
 
 #[instrument(level = "trace", skip_all)]
diff --git a/codex-rs/core/src/tools/spec_plan_tests.rs b/codex-rs/core/src/tools/spec_plan_tests.rs
index 8eca4327aa..97b3c9e7d4 100644
--- a/codex-rs/core/src/tools/spec_plan_tests.rs
+++ b/codex-rs/core/src/tools/spec_plan_tests.rs
@@ -699,7 +699,7 @@ async fn login_shell_parameter_follows_selected_environment() {
                 else {
                     panic!("primary environment should be ready");
                 };
-                environment.config.allow_login_shell = allow_login_shell;
+                environment.config_mut().allow_login_shell = allow_login_shell;
                 if guardian {
                     turn.session_source = codex_protocol::protocol::SessionSource::SubAgent(
                         codex_protocol::protocol::SubAgentSource::Other(
@@ -731,7 +731,7 @@ async fn login_shell_parameter_is_available_when_any_environment_allows_it() {
             let TurnEnvironmentState::Ready(environment) = environment else {
                 panic!("environment should be ready");
             };
-            environment.config.allow_login_shell = index == 1;
+            environment.config_mut().allow_login_shell = index == 1;
         }
     })
     .await;
@@ -908,8 +908,19 @@ async fn zsh_fork_unified_exec_keeps_shell_parameter_when_remote_environment_ava
                         environment_id: "remote".to_string(),
                         cwd: remote_cwd,
                         workspace_roots: Vec::new(),
-                        config: EnvironmentConfigState::FromThread,
+                        config: EnvironmentConfigState::Ready(
+                            codex_protocol::protocol::EnvironmentConfig {
+                                allow_login_shell: true,
+                                permission_profile: turn
+                                    .config
+                                    .permissions
+                                    .permission_profile_state()
+                                    .snapshot(),
+                                selected_capability_roots: Vec::new(),
+                            },
+                        ),
                     },
+                    crate::environment_selection::EnvironmentConfigOrigin::Thread,
                     Arc::new(
                         codex_exec_server::Environment::create_for_tests(Some(
                             "ws://127.0.0.1:1/remote-exec-server".to_string(),
@@ -917,15 +928,6 @@ async fn zsh_fork_unified_exec_keeps_shell_parameter_when_remote_environment_ava
                         .expect("remote test environment"),
                     ),
                     /*shell*/ None,
-                    codex_protocol::protocol::EnvironmentConfig {
-                        allow_login_shell: true,
-                        permission_profile: turn
-                            .config
-                            .permissions
-                            .permission_profile_state()
-                            .snapshot(),
-                        selected_capability_roots: Vec::new(),
-                    },
                 ),
             ));
     })
diff --git a/codex-rs/core/tests/suite/remote_env.rs b/codex-rs/core/tests/suite/remote_env.rs
index 69604aab33..1b31111a7d 100644
--- a/codex-rs/core/tests/suite/remote_env.rs
+++ b/codex-rs/core/tests/suite/remote_env.rs
@@ -437,8 +437,9 @@ async fn explicit_remote_shell_runs_in_remote_cwd() -> Result<()> {
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
-async fn ready_environment_permissions_override_thread_permissions() -> Result<()> {
-    const CALL_ID: &str = "attachment-specific-permissions";
+async fn environment_permissions_follow_configuration_ownership() -> Result<()> {
+    const THREAD_CONFIG_CALL_ID: &str = "thread-config-permissions";
+    const OWNER_CONFIG_CALL_ID: &str = "owner-config-permissions";
     const FILE_NAME: &str = "attachment-read-only-marker.txt";
 
     skip_if_target_windows!(
@@ -459,13 +460,8 @@ async fn ready_environment_permissions_override_thread_permissions() -> Result<(
             .expect("thread should allow workspace writes");
     });
     let test = builder.build_with_auto_env(&server).await?;
-    let mut selection = test.executor_environment().selection().clone();
+    let selection = test.executor_environment().selection().clone();
     let marker = selection.cwd.join(FILE_NAME)?;
-    selection.config = EnvironmentConfigState::Ready(EnvironmentConfig {
-        allow_login_shell: test.config.permissions.allow_login_shell,
-        permission_profile: PermissionProfileSnapshot::legacy(PermissionProfile::read_only()),
-        selected_capability_roots: Vec::new(),
-    });
 
     let (shell, command) = match test_target_os() {
         TestTargetOs::Linux => (
@@ -499,7 +495,7 @@ async fn ready_environment_permissions_override_thread_permissions() -> Result<(
         vec![
             sse(vec![
                 ev_response_created("resp-1"),
-                ev_function_call(CALL_ID, "exec_command", &arguments),
+                ev_function_call(THREAD_CONFIG_CALL_ID, "exec_command", &arguments),
                 ev_completed("resp-1"),
             ]),
             sse(vec![
@@ -507,17 +503,77 @@ async fn ready_environment_permissions_override_thread_permissions() -> Result<(
                 ev_assistant_message("msg-1", "done"),
                 ev_completed("resp-2"),
             ]),
+            sse(vec![
+                ev_response_created("resp-3"),
+                ev_function_call(OWNER_CONFIG_CALL_ID, "exec_command", &arguments),
+                ev_completed("resp-3"),
+            ]),
+            sse(vec![
+                ev_response_created("resp-4"),
+                ev_assistant_message("msg-2", "done"),
+                ev_completed("resp-4"),
+            ]),
         ],
     )
     .await;
 
-    test.submit_turn_with_environments("try to write a file", Some(vec![selection]))
+    submit_thread_settings(
+        &test.codex,
+        ThreadSettingsOverrides {
+            permission_profile: Some(PermissionProfile::read_only()),
+            ..Default::default()
+        },
+    )
+    .await?;
+    test.submit_text_turn("try to write a file with thread-owned permissions")
         .await?;
 
     let output = response_mock
         .last_request()
         .context("model should receive the command output")?
-        .function_call_output_text(CALL_ID)
+        .function_call_output_text(THREAD_CONFIG_CALL_ID)
+        .context("shell tool result should be present")?;
+    assert!(
+        output.contains("WRITE_DENIED"),
+        "unexpected output: {output}"
+    );
+    assert!(!output.contains("WRITE_SUCCEEDED"));
+
+    submit_thread_settings(
+        &test.codex,
+        ThreadSettingsOverrides {
+            environments: Some(TurnEnvironmentSelections::new(
+                test.config.cwd.clone(),
+                vec![TurnEnvironmentSelection {
+                    config: EnvironmentConfigState::Ready(EnvironmentConfig {
+                        allow_login_shell: test.config.permissions.allow_login_shell,
+                        permission_profile: PermissionProfileSnapshot::legacy(
+                            PermissionProfile::read_only(),
+                        ),
+                        selected_capability_roots: Vec::new(),
+                    }),
+                    ..selection
+                }],
+            )),
+            ..Default::default()
+        },
+    )
+    .await?;
+    submit_thread_settings(
+        &test.codex,
+        ThreadSettingsOverrides {
+            permission_profile: Some(PermissionProfile::workspace_write()),
+            ..Default::default()
+        },
+    )
+    .await?;
+    test.submit_text_turn("try to write a file with owner-provided permissions")
+        .await?;
+
+    let output = response_mock
+        .last_request()
+        .context("model should receive the command output")?
+        .function_call_output_text(OWNER_CONFIG_CALL_ID)
         .context("shell tool result should be present")?;
     assert!(
         output.contains("WRITE_DENIED"),