Require absolute cwd in thread settings (#26532)

## Why

Thread settings cwd overrides are expected to be resolved before they
enter core. Keeping this boundary as a plain `PathBuf` made it easy for
core/session code to keep fallback normalization and relative-path
resolution logic in places that should only receive an already-resolved
cwd.

This is intentionally the absolute-cwd-only slice: it does not change
environment selection stickiness or cwd-to-default-environment fallback
behavior.

## What changed

- Changes `ThreadSettingsOverrides.cwd`,
`CodexThreadSettingsOverrides.cwd`, and `SessionSettingsUpdate.cwd` to
use `AbsolutePathBuf`.
- Removes core-side cwd normalization/resolution from session settings
updates.
- Updates affected core/app-server test helpers and callsites to pass
existing absolute cwd values or use `abs()` helpers.

## Validation

Opening as draft so CI can start while local validation continues.

codex-rs/core/src/codex_thread.rs

@@ -127,7 +127,7 @@ impl ThreadConfigSnapshot {
 /// Thread settings overrides that app-server validates before starting a turn.
 #[derive(Clone, Default)]
 pub struct CodexThreadSettingsOverrides {
-    pub cwd: Option<PathBuf>,
+    pub cwd: Option<AbsolutePathBuf>,
     pub workspace_roots: Option<Vec<AbsolutePathBuf>>,
     pub profile_workspace_roots: Option<Vec<AbsolutePathBuf>>,
     pub approval_policy: Option<AskForApproval>,

codex-rs/core/src/guardian/review_session.rs

@@ -733,7 +733,7 @@ async fn run_review_on_session(
             additional_context: Default::default(),
             thread_settings: codex_protocol::protocol::ThreadSettingsOverrides {
                 #[allow(deprecated)]
-                cwd: Some(params.parent_turn.cwd.to_path_buf()),
+                cwd: Some(params.parent_turn.cwd.clone()),
                 approval_policy: Some(AskForApproval::Never),
                 sandbox_policy: None,
                 permission_profile: Some(guardian_permission_profile),

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

@@ -32,7 +32,6 @@ use crate::default_skill_metadata_budget;
 use crate::environment_selection::ResolvedTurnEnvironments;
 use crate::exec_policy::ExecPolicyManager;
 use crate::parse_turn_item;
-use crate::path_utils::normalize_for_native_workdir;
 use crate::realtime_conversation::RealtimeConversationManager;
 use crate::session_prefix::format_subagent_notification_message;
 use crate::skills::SkillRenderSideEffects;

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

@@ -251,19 +251,7 @@ impl SessionConfiguration {
             next_configuration.windows_sandbox_level = windows_sandbox_level;
         }
 
-        let absolute_cwd = updates
-            .cwd
-            .as_ref()
-            .map(|cwd| {
-                AbsolutePathBuf::relative_to_current_dir(normalize_for_native_workdir(
-                    cwd.as_path(),
-                ))
-                .unwrap_or_else(|e| {
-                    warn!("failed to normalize update cwd: {cwd:?}: {e}");
-                    self.cwd.clone()
-                })
-            })
-            .unwrap_or_else(|| self.cwd.clone());
+        let absolute_cwd = updates.cwd.clone().unwrap_or_else(|| self.cwd.clone());
 
         let cwd_changed = absolute_cwd.as_path() != self.cwd.as_path();
         next_configuration.cwd = absolute_cwd;
@@ -415,7 +403,7 @@ impl SessionConfiguration {
 
 #[derive(Default, Clone)]
 pub(crate) struct SessionSettingsUpdate {
-    pub(crate) cwd: Option<PathBuf>,
+    pub(crate) cwd: Option<AbsolutePathBuf>,
     pub(crate) workspace_roots: Option<Vec<AbsolutePathBuf>>,
     pub(crate) profile_workspace_roots: Option<Vec<AbsolutePathBuf>>,
     pub(crate) approval_policy: Option<AskForApproval>,

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

@@ -3932,6 +3932,7 @@ async fn session_configuration_apply_preserves_profile_file_system_policy_on_cwd
     let original_cwd = project_root.join("subdir");
     let docs_dir = original_cwd.join("docs");
     std::fs::create_dir_all(&docs_dir).expect("create docs dir");
+    let project_root = project_root.abs();
     let docs_dir = docs_dir.abs();
 
     session_configuration.cwd = original_cwd.abs();
@@ -4152,7 +4153,7 @@ async fn session_configuration_apply_retargets_implicit_workspace_root_on_cwd_up
 
     let updated = session_configuration
         .apply(&SessionSettingsUpdate {
-            cwd: Some(new_root.to_path_buf()),
+            cwd: Some(new_root.clone()),
             ..Default::default()
         })
         .expect("cwd-only update should succeed");
@@ -4391,7 +4392,7 @@ async fn session_configuration_apply_retargets_legacy_workspace_root_on_cwd_upda
 
     let updated = session_configuration
         .apply(&SessionSettingsUpdate {
-            cwd: Some(project_root.to_path_buf()),
+            cwd: Some(project_root.clone()),
             ..Default::default()
         })
         .expect("cwd-only update should succeed");
@@ -4420,6 +4421,7 @@ async fn session_configuration_apply_preserves_absolute_cwd_write_root_on_cwd_up
     std::fs::create_dir_all(&original_cwd).expect("create original cwd");
     std::fs::create_dir_all(&next_cwd).expect("create next cwd");
     let original_cwd = original_cwd.abs();
+    let next_cwd = next_cwd.abs();
 
     session_configuration.cwd = original_cwd.clone();
     let file_system_sandbox_policy = FileSystemSandboxPolicy::restricted(vec![
@@ -4480,7 +4482,7 @@ async fn session_update_settings_does_not_rewrite_sticky_environment_cwds() {
 
     session
         .update_settings(SessionSettingsUpdate {
-            cwd: Some(PathBuf::from("project")),
+            cwd: Some(updated_cwd.clone()),
             ..Default::default()
         })
         .await
@@ -4516,7 +4518,7 @@ async fn relative_cwd_update_without_environments_resolves_under_session_cwd() {
 
     session
         .update_settings(SessionSettingsUpdate {
-            cwd: Some(PathBuf::from("project")),
+            cwd: Some(updated_cwd.clone()),
             ..Default::default()
         })
         .await
@@ -4545,7 +4547,7 @@ async fn cwd_update_does_not_rewrite_sticky_environment_cwd() {
 
     session
         .update_settings(SessionSettingsUpdate {
-            cwd: Some(PathBuf::from("project")),
+            cwd: Some(updated_cwd.clone()),
             ..Default::default()
         })
         .await
@@ -4572,7 +4574,7 @@ async fn absolute_cwd_update_with_turn_environment_is_allowed() {
         .new_turn_with_sub_id(
             "sub-1".to_string(),
             SessionSettingsUpdate {
-                cwd: Some(absolute_cwd.to_path_buf()),
+                cwd: Some(absolute_cwd.clone()),
                 environments: Some(vec![TurnEnvironmentSelection {
                     environment_id: codex_exec_server::LOCAL_ENVIRONMENT_ID.to_string(),
                     cwd: absolute_cwd.clone(),
@@ -5989,7 +5991,7 @@ async fn user_turn_updates_approvals_reviewer() {
             responsesapi_client_metadata: None,
             additional_context: Default::default(),
             thread_settings: codex_protocol::protocol::ThreadSettingsOverrides {
-                cwd: Some(config.cwd.to_path_buf()),
+                cwd: Some(config.cwd.clone()),
                 approval_policy: Some(config.permissions.approval_policy.value()),
                 approvals_reviewer: Some(codex_config::types::ApprovalsReviewer::AutoReview),
                 sandbox_policy: Some(config.legacy_sandbox_policy()),