diff --git a/AGENTS.md b/AGENTS.md
index cc7994efbe1..50c10b1da1f 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -75,6 +75,7 @@ If you don’t have the tool:
 
 - Tests should use pretty_assertions::assert_eq for clearer diffs. Import this at the top of the test module if it isn't already.
 - Prefer deep equals comparisons whenever possible. Perform `assert_eq!()` on entire objects, rather than individual fields.
+- Avoid mutating process environment in tests; prefer passing environment-derived flags or dependencies from above.
 
 ### Integration tests (core)
 
diff --git a/codex-rs/core/src/config/service.rs b/codex-rs/core/src/config/service.rs
index 6f9d0e4d602..958044eafde 100644
--- a/codex-rs/core/src/config/service.rs
+++ b/codex-rs/core/src/config/service.rs
@@ -7,6 +7,7 @@ use crate::config_loader::ConfigLayerStack;
 use crate::config_loader::LoaderOverrides;
 use crate::config_loader::load_config_layers_state;
 use crate::config_loader::merge_toml_values;
+use crate::path_utils;
 use codex_app_server_protocol::Config as ApiConfig;
 use codex_app_server_protocol::ConfigBatchWriteParams;
 use codex_app_server_protocol::ConfigLayerMetadata;
@@ -470,9 +471,10 @@ fn validate_config(value: &TomlValue) -> Result<(), toml::de::Error> {
 }
 
 fn paths_match(expected: &Path, provided: &Path) -> bool {
-    if let (Ok(expanded_expected), Ok(expanded_provided)) =
-        (expected.canonicalize(), provided.canonicalize())
-    {
+    if let (Ok(expanded_expected), Ok(expanded_provided)) = (
+        path_utils::normalize_for_path_comparison(expected),
+        path_utils::normalize_for_path_comparison(provided),
+    ) {
         return expanded_expected == expanded_provided;
     }
 
diff --git a/codex-rs/core/src/lib.rs b/codex-rs/core/src/lib.rs
index 11b49c78c41..f78c19328f0 100644
--- a/codex-rs/core/src/lib.rs
+++ b/codex-rs/core/src/lib.rs
@@ -41,6 +41,7 @@ mod mcp_tool_call;
 mod message_history;
 mod model_provider_info;
 pub mod parse_command;
+pub mod path_utils;
 pub mod powershell;
 pub mod sandboxing;
 mod stream_events_utils;
diff --git a/codex-rs/core/src/path_utils.rs b/codex-rs/core/src/path_utils.rs
new file mode 100644
index 00000000000..9a7007e4f10
--- /dev/null
+++ b/codex-rs/core/src/path_utils.rs
@@ -0,0 +1,116 @@
+use std::path::Path;
+use std::path::PathBuf;
+
+use crate::env;
+
+pub fn normalize_for_path_comparison(path: &Path) -> std::io::Result<PathBuf> {
+    let canonical = path.canonicalize()?;
+    Ok(normalize_for_wsl(canonical))
+}
+
+fn normalize_for_wsl(path: PathBuf) -> PathBuf {
+    normalize_for_wsl_with_flag(path, env::is_wsl())
+}
+
+fn normalize_for_wsl_with_flag(path: PathBuf, is_wsl: bool) -> PathBuf {
+    if !is_wsl {
+        return path;
+    }
+
+    if !is_wsl_case_insensitive_path(&path) {
+        return path;
+    }
+
+    lower_ascii_path(path)
+}
+
+fn is_wsl_case_insensitive_path(path: &Path) -> bool {
+    #[cfg(target_os = "linux")]
+    {
+        use std::os::unix::ffi::OsStrExt;
+        use std::path::Component;
+
+        let mut components = path.components();
+        let Some(Component::RootDir) = components.next() else {
+            return false;
+        };
+        let Some(Component::Normal(mnt)) = components.next() else {
+            return false;
+        };
+        if !ascii_eq_ignore_case(mnt.as_bytes(), b"mnt") {
+            return false;
+        }
+        let Some(Component::Normal(drive)) = components.next() else {
+            return false;
+        };
+        let drive_bytes = drive.as_bytes();
+        drive_bytes.len() == 1 && drive_bytes[0].is_ascii_alphabetic()
+    }
+    #[cfg(not(target_os = "linux"))]
+    {
+        let _ = path;
+        false
+    }
+}
+
+#[cfg(target_os = "linux")]
+fn ascii_eq_ignore_case(left: &[u8], right: &[u8]) -> bool {
+    left.len() == right.len()
+        && left
+            .iter()
+            .zip(right)
+            .all(|(lhs, rhs)| lhs.to_ascii_lowercase() == *rhs)
+}
+
+#[cfg(target_os = "linux")]
+fn lower_ascii_path(path: PathBuf) -> PathBuf {
+    use std::ffi::OsString;
+    use std::os::unix::ffi::OsStrExt;
+    use std::os::unix::ffi::OsStringExt;
+
+    // WSL mounts Windows drives under /mnt/<drive>, which are case-insensitive.
+    let bytes = path.as_os_str().as_bytes();
+    let mut lowered = Vec::with_capacity(bytes.len());
+    for byte in bytes {
+        lowered.push(byte.to_ascii_lowercase());
+    }
+    PathBuf::from(OsString::from_vec(lowered))
+}
+
+#[cfg(not(target_os = "linux"))]
+fn lower_ascii_path(path: PathBuf) -> PathBuf {
+    path
+}
+
+#[cfg(test)]
+mod tests {
+    #[cfg(target_os = "linux")]
+    mod wsl {
+        use super::super::normalize_for_wsl_with_flag;
+        use pretty_assertions::assert_eq;
+        use std::path::PathBuf;
+
+        #[test]
+        fn wsl_mnt_drive_paths_lowercase() {
+            let normalized = normalize_for_wsl_with_flag(PathBuf::from("/mnt/C/Users/Dev"), true);
+
+            assert_eq!(normalized, PathBuf::from("/mnt/c/users/dev"));
+        }
+
+        #[test]
+        fn wsl_non_drive_paths_unchanged() {
+            let path = PathBuf::from("/mnt/cc/Users/Dev");
+            let normalized = normalize_for_wsl_with_flag(path.clone(), true);
+
+            assert_eq!(normalized, path);
+        }
+
+        #[test]
+        fn wsl_non_mnt_paths_unchanged() {
+            let path = PathBuf::from("/home/Dev");
+            let normalized = normalize_for_wsl_with_flag(path.clone(), true);
+
+            assert_eq!(normalized, path);
+        }
+    }
+}
diff --git a/codex-rs/tui/src/resume_picker.rs b/codex-rs/tui/src/resume_picker.rs
index f2c6a3269dd..7f3665d563d 100644
--- a/codex-rs/tui/src/resume_picker.rs
+++ b/codex-rs/tui/src/resume_picker.rs
@@ -10,6 +10,7 @@ use codex_core::ConversationsPage;
 use codex_core::Cursor;
 use codex_core::INTERACTIVE_SESSION_SOURCES;
 use codex_core::RolloutRecorder;
+use codex_core::path_utils;
 use codex_protocol::items::TurnItem;
 use color_eyre::eyre::Result;
 use crossterm::event::KeyCode;
@@ -670,7 +671,10 @@ fn extract_session_meta_from_head(head: &[serde_json::Value]) -> (Option<PathBuf
 }
 
 fn paths_match(a: &Path, b: &Path) -> bool {
-    if let (Ok(ca), Ok(cb)) = (a.canonicalize(), b.canonicalize()) {
+    if let (Ok(ca), Ok(cb)) = (
+        path_utils::normalize_for_path_comparison(a),
+        path_utils::normalize_for_path_comparison(b),
+    ) {
         return ca == cb;
     }
     a == b
diff --git a/codex-rs/tui2/src/resume_picker.rs b/codex-rs/tui2/src/resume_picker.rs
index f2c6a3269dd..7f3665d563d 100644
--- a/codex-rs/tui2/src/resume_picker.rs
+++ b/codex-rs/tui2/src/resume_picker.rs
@@ -10,6 +10,7 @@ use codex_core::ConversationsPage;
 use codex_core::Cursor;
 use codex_core::INTERACTIVE_SESSION_SOURCES;
 use codex_core::RolloutRecorder;
+use codex_core::path_utils;
 use codex_protocol::items::TurnItem;
 use color_eyre::eyre::Result;
 use crossterm::event::KeyCode;
@@ -670,7 +671,10 @@ fn extract_session_meta_from_head(head: &[serde_json::Value]) -> (Option<PathBuf
 }
 
 fn paths_match(a: &Path, b: &Path) -> bool {
-    if let (Ok(ca), Ok(cb)) = (a.canonicalize(), b.canonicalize()) {
+    if let (Ok(ca), Ok(cb)) = (
+        path_utils::normalize_for_path_comparison(a),
+        path_utils::normalize_for_path_comparison(b),
+    ) {
         return ca == cb;
     }
     a == b