From ad355d4c9641953bb85c242c92f72f924edd4687 Mon Sep 17 00:00:00 2001
From: Eric Traut <etraut@openai.com>
Date: Tue, 2 Jun 2026 12:42:42 -0700
Subject: [PATCH] Fix Windows running thread resume path normalization (#25509)

## Why

Fixes #24944.

On Windows, app-server resume could reject an active running thread when
the requested session path used normal `C:\...` form and the
already-running path used verbatim `\\?\C:\...` form. The paths point at
the same JSONL file, but the resume stale-path guard compared raw
`PathBuf`s, so desktop resume and heartbeat flows could fail with a
mismatched-path error.

## What Changed

- Compare requested and active rollout paths with
`path_utils::paths_match_after_normalization`.
- Extend the existing running-thread mismatched-path test with a
Windows-only same-file resume case before the stale-path rejection.

## Verification

- `just test -p codex-app-server
thread_resume_rejects_mismatched_path_for_running_thread_id`
---
 .../request_processors/thread_processor.rs    |  2 +-
 .../tests/suite/v2/thread_resume.rs           | 30 +++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/codex-rs/app-server/src/request_processors/thread_processor.rs b/codex-rs/app-server/src/request_processors/thread_processor.rs
index 32dfb1eeb..b26c2e4df 100644
--- a/codex-rs/app-server/src/request_processors/thread_processor.rs
+++ b/codex-rs/app-server/src/request_processors/thread_processor.rs
@@ -2766,7 +2766,7 @@ impl ThreadRequestProcessor {
                 .as_ref()
                 .or(source_thread.rollout_path.as_ref());
             if let (Some(requested_path), Some(active_path)) = (params.path.as_ref(), active_path)
-                && requested_path != active_path
+                && !path_utils::paths_match_after_normalization(requested_path, active_path)
             {
                 return Err(invalid_request(format!(
                     "cannot resume running thread {existing_thread_id} with stale path: requested `{}`, active `{}`",
diff --git a/codex-rs/app-server/tests/suite/v2/thread_resume.rs b/codex-rs/app-server/tests/suite/v2/thread_resume.rs
index c016b3882..3073b382a 100644
--- a/codex-rs/app-server/tests/suite/v2/thread_resume.rs
+++ b/codex-rs/app-server/tests/suite/v2/thread_resume.rs
@@ -2410,6 +2410,36 @@ async fn thread_resume_rejects_mismatched_path_for_running_thread_id() -> Result
     )
     .await??;
 
+    #[cfg(windows)]
+    {
+        let active_path = thread.path.as_ref().expect("thread should have path");
+        let active_path_display = active_path.as_os_str().to_string_lossy();
+        let equivalent_path = if let Some(path) = active_path_display.strip_prefix(r"\\?\UNC\") {
+            PathBuf::from(format!(r"\\{path}"))
+        } else if let Some(path) = active_path_display.strip_prefix(r"\\?\") {
+            PathBuf::from(path)
+        } else if let Some(path) = active_path_display.strip_prefix(r"\\") {
+            PathBuf::from(format!(r"\\?\UNC\{path}"))
+        } else {
+            PathBuf::from(format!(r"\\?\{active_path_display}"))
+        };
+        let normalized_resume_id = primary
+            .send_thread_resume_request(ThreadResumeParams {
+                thread_id: thread_id.clone(),
+                path: Some(equivalent_path),
+                ..Default::default()
+            })
+            .await?;
+        let normalized_resume_resp: JSONRPCResponse = timeout(
+            DEFAULT_READ_TIMEOUT,
+            primary.read_stream_until_response_message(RequestId::Integer(normalized_resume_id)),
+        )
+        .await??;
+        let ThreadResumeResponse { thread, .. } =
+            to_response::<ThreadResumeResponse>(normalized_resume_resp)?;
+        assert_eq!(thread.id, thread_id);
+    }
+
     let stale_thread_id = Uuid::new_v4().to_string();
     let stale_path = rollout_path(codex_home.path(), "2025-01-01T00-00-00", &stale_thread_id);
     std::fs::create_dir_all(stale_path.parent().expect("stale path parent"))?;