diff --git a/codex-rs/Cargo.lock b/codex-rs/Cargo.lock
index 523347d5db4..a949ce94e9e 100644
--- a/codex-rs/Cargo.lock
+++ b/codex-rs/Cargo.lock
@@ -837,7 +837,6 @@ dependencies = [
  "codex-login",
  "codex-protocol",
  "codex-rmcp-client",
- "codex-utils-absolute-path",
  "codex-utils-json-to-toml",
  "core_test_support",
  "mcp-types",
@@ -1887,6 +1886,7 @@ dependencies = [
  "base64",
  "codex-core",
  "codex-protocol",
+ "codex-utils-absolute-path",
  "notify",
  "regex-lite",
  "serde_json",
diff --git a/codex-rs/app-server/Cargo.toml b/codex-rs/app-server/Cargo.toml
index 211902d4acc..cb3f51bb821 100644
--- a/codex-rs/app-server/Cargo.toml
+++ b/codex-rs/app-server/Cargo.toml
@@ -27,7 +27,6 @@ codex-protocol = { workspace = true }
 codex-app-server-protocol = { workspace = true }
 codex-feedback = { workspace = true }
 codex-rmcp-client = { workspace = true }
-codex-utils-absolute-path = { workspace = true }
 codex-utils-json-to-toml = { workspace = true }
 chrono = { workspace = true }
 serde = { workspace = true, features = ["derive"] }
diff --git a/codex-rs/app-server/tests/common/lib.rs b/codex-rs/app-server/tests/common/lib.rs
index a095a713a05..f3950595be9 100644
--- a/codex-rs/app-server/tests/common/lib.rs
+++ b/codex-rs/app-server/tests/common/lib.rs
@@ -14,6 +14,9 @@ pub use core_test_support::format_with_current_shell;
 pub use core_test_support::format_with_current_shell_display;
 pub use core_test_support::format_with_current_shell_display_non_login;
 pub use core_test_support::format_with_current_shell_non_login;
+pub use core_test_support::test_path_buf_with_windows;
+pub use core_test_support::test_tmp_path;
+pub use core_test_support::test_tmp_path_buf;
 pub use mcp_process::McpProcess;
 pub use mock_model_server::create_mock_chat_completions_server;
 pub use mock_model_server::create_mock_chat_completions_server_unchecked;
diff --git a/codex-rs/app-server/tests/suite/config.rs b/codex-rs/app-server/tests/suite/config.rs
index 41d9e8d68a3..84b268a3c2b 100644
--- a/codex-rs/app-server/tests/suite/config.rs
+++ b/codex-rs/app-server/tests/suite/config.rs
@@ -1,5 +1,6 @@
 use anyhow::Result;
 use app_test_support::McpProcess;
+use app_test_support::test_tmp_path;
 use app_test_support::to_response;
 use codex_app_server_protocol::GetUserSavedConfigResponse;
 use codex_app_server_protocol::JSONRPCResponse;
@@ -14,7 +15,6 @@ use codex_protocol::config_types::ReasoningSummary;
 use codex_protocol::config_types::SandboxMode;
 use codex_protocol::config_types::Verbosity;
 use codex_protocol::openai_models::ReasoningEffort;
-use codex_utils_absolute_path::AbsolutePathBuf;
 use pretty_assertions::assert_eq;
 use std::collections::HashMap;
 use std::path::Path;
@@ -24,11 +24,7 @@ use tokio::time::timeout;
 const DEFAULT_READ_TIMEOUT: std::time::Duration = std::time::Duration::from_secs(10);
 
 fn create_config_toml(codex_home: &Path) -> std::io::Result<()> {
-    let writable_root = if cfg!(windows) {
-        r"C:\Users\codex\AppData\Local\Temp"
-    } else {
-        "/tmp"
-    };
+    let writable_root = test_tmp_path();
     let config_toml = codex_home.join("config.toml");
     std::fs::write(
         config_toml,
@@ -84,12 +80,7 @@ async fn get_config_toml_parses_all_fields() -> Result<()> {
     .await??;
 
     let config: GetUserSavedConfigResponse = to_response(resp)?;
-    let writable_root = if cfg!(windows) {
-        r"C:\Users\codex\AppData\Local\Temp"
-    } else {
-        "/tmp"
-    };
-    let writable_root = AbsolutePathBuf::from_absolute_path(writable_root)?;
+    let writable_root = test_tmp_path();
     let expected = GetUserSavedConfigResponse {
         config: UserSavedConfig {
             approval_policy: Some(AskForApproval::OnRequest),
diff --git a/codex-rs/app-server/tests/suite/v2/config_rpc.rs b/codex-rs/app-server/tests/suite/v2/config_rpc.rs
index 9b974773cbc..199d2f88e64 100644
--- a/codex-rs/app-server/tests/suite/v2/config_rpc.rs
+++ b/codex-rs/app-server/tests/suite/v2/config_rpc.rs
@@ -1,5 +1,7 @@
 use anyhow::Result;
 use app_test_support::McpProcess;
+use app_test_support::test_path_buf_with_windows;
+use app_test_support::test_tmp_path_buf;
 use app_test_support::to_response;
 use codex_app_server_protocol::AskForApproval;
 use codex_app_server_protocol::ConfigBatchWriteParams;
@@ -18,7 +20,6 @@ use codex_app_server_protocol::ToolsV2;
 use codex_app_server_protocol::WriteStatus;
 use pretty_assertions::assert_eq;
 use serde_json::json;
-use std::path::PathBuf;
 use tempfile::TempDir;
 use tokio::time::timeout;
 
@@ -135,11 +136,8 @@ view_image = false
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn config_read_includes_system_layer_and_overrides() -> Result<()> {
     let codex_home = TempDir::new()?;
-    let (user_dir, system_dir) = if cfg!(windows) {
-        (r"C:\Users\user", r"C:\System")
-    } else {
-        ("/user", "/system")
-    };
+    let user_dir = test_path_buf_with_windows("/user", Some(r"C:\Users\user"));
+    let system_dir = test_path_buf_with_windows("/system", Some(r"C:\System"));
     write_config(
         &codex_home,
         &format!(
@@ -167,7 +165,7 @@ approval_policy = "never"
 [sandbox_workspace_write]
 writable_roots = [{}]
 "#,
-            serde_json::json!(system_dir)
+            serde_json::json!(system_dir.clone())
         ),
     )?;
 
@@ -218,7 +216,7 @@ writable_roots = [{}]
         .sandbox_workspace_write
         .as_ref()
         .expect("sandbox workspace write");
-    assert_eq!(sandbox.writable_roots, vec![PathBuf::from(system_dir)]);
+    assert_eq!(sandbox.writable_roots, vec![system_dir]);
     assert_eq!(
         origins
             .get("sandbox_workspace_write.writable_roots.0")
@@ -361,11 +359,7 @@ async fn config_batch_write_applies_multiple_edits() -> Result<()> {
     let mut mcp = McpProcess::new(codex_home.path()).await?;
     timeout(DEFAULT_READ_TIMEOUT, mcp.initialize()).await??;
 
-    let writable_root = if cfg!(windows) {
-        r"C:\Users\codex\AppData\Local\Temp"
-    } else {
-        "/tmp"
-    };
+    let writable_root = test_tmp_path_buf();
     let batch_id = mcp
         .send_config_batch_write_request(ConfigBatchWriteParams {
             file_path: Some(codex_home.path().join("config.toml").display().to_string()),
@@ -378,7 +372,7 @@ async fn config_batch_write_applies_multiple_edits() -> Result<()> {
                 ConfigEdit {
                     key_path: "sandbox_workspace_write".to_string(),
                     value: json!({
-                        "writable_roots": [writable_root],
+                        "writable_roots": [writable_root.clone()],
                         "network_access": false
                     }),
                     merge_strategy: MergeStrategy::Replace,
@@ -420,7 +414,7 @@ async fn config_batch_write_applies_multiple_edits() -> Result<()> {
         .sandbox_workspace_write
         .as_ref()
         .expect("sandbox workspace write");
-    assert_eq!(sandbox.writable_roots, vec![PathBuf::from(writable_root)]);
+    assert_eq!(sandbox.writable_roots, vec![writable_root]);
     assert!(!sandbox.network_access);
 
     Ok(())
diff --git a/codex-rs/core/src/config/mod.rs b/codex-rs/core/src/config/mod.rs
index 95a9894ac03..df46a5fdd55 100644
--- a/codex-rs/core/src/config/mod.rs
+++ b/codex-rs/core/src/config/mod.rs
@@ -1315,6 +1315,7 @@ mod tests {
     use crate::features::Feature;
 
     use super::*;
+    use core_test_support::test_absolute_path;
     use pretty_assertions::assert_eq;
 
     use std::time::Duration;
@@ -1413,11 +1414,7 @@ network_access = true  # This should be ignored.
             }
         );
 
-        let writable_root = if cfg!(windows) {
-            "C:\\my\\workspace"
-        } else {
-            "/my/workspace"
-        };
+        let writable_root = test_absolute_path("/my/workspace");
         let sandbox_workspace_write = format!(
             r#"
 sandbox_mode = "workspace-write"
@@ -1429,7 +1426,7 @@ writable_roots = [
 exclude_tmpdir_env_var = true
 exclude_slash_tmp = true
 "#,
-            serde_json::json!(writable_root.to_string_lossy())
+            serde_json::json!(writable_root)
         );
 
         let sandbox_workspace_write_cfg = toml::from_str::<ConfigToml>(&sandbox_workspace_write)
@@ -1453,7 +1450,7 @@ exclude_slash_tmp = true
                 resolution,
                 SandboxPolicyResolution {
                     policy: SandboxPolicy::WorkspaceWrite {
-                        writable_roots: vec!["/my/workspace".try_into().unwrap()],
+                        writable_roots: vec![writable_root.clone()],
                         network_access: false,
                         exclude_tmpdir_env_var: true,
                         exclude_slash_tmp: true,
@@ -1477,7 +1474,7 @@ exclude_slash_tmp = true
 [projects."/tmp/test"]
 trust_level = "trusted"
 "#,
-            serde_json::json!(writable_root.to_string_lossy())
+            serde_json::json!(writable_root)
         );
 
         let sandbox_workspace_write_cfg = toml::from_str::<ConfigToml>(&sandbox_workspace_write)
@@ -1501,10 +1498,7 @@ trust_level = "trusted"
                 resolution,
                 SandboxPolicyResolution {
                     policy: SandboxPolicy::WorkspaceWrite {
-                        writable_roots: vec![
-                            AbsolutePathBuf::from_absolute_path("/my/workspace")
-                                .expect("absolute path")
-                        ],
+                        writable_roots: vec![writable_root],
                         network_access: false,
                         exclude_tmpdir_env_var: true,
                         exclude_slash_tmp: true,
diff --git a/codex-rs/core/src/environment_context.rs b/codex-rs/core/src/environment_context.rs
index b0ae385c1da..fc4ae174dfa 100644
--- a/codex-rs/core/src/environment_context.rs
+++ b/codex-rs/core/src/environment_context.rs
@@ -192,6 +192,8 @@ mod tests {
     use crate::shell::ShellType;
 
     use super::*;
+    use core_test_support::test_path_buf;
+    use core_test_support::test_tmp_path_buf;
     use pretty_assertions::assert_eq;
 
     fn fake_shell() -> Shell {
@@ -216,12 +218,19 @@ mod tests {
 
     #[test]
     fn serialize_workspace_write_environment_context() {
-        let cwd = if cfg!(windows) { "C:\\repo" } else { "/repo" };
-        let writable_root = if cfg!(windows) { "C:\\tmp" } else { "/tmp" };
+        let cwd = test_path_buf("/repo");
+        let writable_root = test_tmp_path_buf();
+        let cwd_str = cwd.to_str().expect("cwd is valid utf-8");
+        let writable_root_str = writable_root
+            .to_str()
+            .expect("writable root is valid utf-8");
         let context = EnvironmentContext::new(
-            Some(PathBuf::from(cwd)),
+            Some(cwd.clone()),
             Some(AskForApproval::OnRequest),
-            Some(workspace_write_policy(vec![cwd, writable_root], false)),
+            Some(workspace_write_policy(
+                vec![cwd_str, writable_root_str],
+                false,
+            )),
             fake_shell(),
         );
 
@@ -236,7 +245,9 @@ mod tests {
     <root>{writable_root}</root>
   </writable_roots>
   <shell>bash</shell>
-</environment_context>"#
+</environment_context>"#,
+            cwd = cwd.display(),
+            writable_root = writable_root.display(),
         );
 
         assert_eq!(context.serialize_to_xml(), expected);
diff --git a/codex-rs/core/tests/common/Cargo.toml b/codex-rs/core/tests/common/Cargo.toml
index 09da4bc7016..95ea788b4c6 100644
--- a/codex-rs/core/tests/common/Cargo.toml
+++ b/codex-rs/core/tests/common/Cargo.toml
@@ -13,6 +13,7 @@ assert_cmd = { workspace = true }
 base64 = { workspace = true }
 codex-core = { workspace = true, features = ["test-support"] }
 codex-protocol = { workspace = true }
+codex-utils-absolute-path = { workspace = true }
 notify = { workspace = true }
 regex-lite = { workspace = true }
 serde_json = { workspace = true }
diff --git a/codex-rs/core/tests/common/lib.rs b/codex-rs/core/tests/common/lib.rs
index 7b3c53cd300..61bac30cb17 100644
--- a/codex-rs/core/tests/common/lib.rs
+++ b/codex-rs/core/tests/common/lib.rs
@@ -6,7 +6,9 @@ use codex_core::CodexConversation;
 use codex_core::config::Config;
 use codex_core::config::ConfigOverrides;
 use codex_core::config::ConfigToml;
+use codex_utils_absolute_path::AbsolutePathBuf;
 use regex_lite::Regex;
+use std::path::PathBuf;
 
 #[cfg(target_os = "linux")]
 use assert_cmd::cargo::cargo_bin;
@@ -25,6 +27,49 @@ pub fn assert_regex_match<'s>(pattern: &str, actual: &'s str) -> regex_lite::Cap
         .unwrap_or_else(|| panic!("regex {pattern:?} did not match {actual:?}"))
 }
 
+pub fn test_path_buf_with_windows(unix_path: &str, windows_path: Option<&str>) -> PathBuf {
+    if cfg!(windows) {
+        if let Some(windows) = windows_path {
+            PathBuf::from(windows)
+        } else {
+            let mut path = PathBuf::from(r"C:\");
+            path.extend(
+                unix_path
+                    .trim_start_matches('/')
+                    .split('/')
+                    .filter(|segment| !segment.is_empty()),
+            );
+            path
+        }
+    } else {
+        PathBuf::from(unix_path)
+    }
+}
+
+pub fn test_path_buf(unix_path: &str) -> PathBuf {
+    test_path_buf_with_windows(unix_path, None)
+}
+
+pub fn test_absolute_path_with_windows(
+    unix_path: &str,
+    windows_path: Option<&str>,
+) -> AbsolutePathBuf {
+    AbsolutePathBuf::from_absolute_path(test_path_buf_with_windows(unix_path, windows_path))
+        .expect("test path should be absolute")
+}
+
+pub fn test_absolute_path(unix_path: &str) -> AbsolutePathBuf {
+    test_absolute_path_with_windows(unix_path, None)
+}
+
+pub fn test_tmp_path() -> AbsolutePathBuf {
+    test_absolute_path_with_windows("/tmp", Some(r"C:\Users\codex\AppData\Local\Temp"))
+}
+
+pub fn test_tmp_path_buf() -> PathBuf {
+    test_tmp_path().into_path_buf()
+}
+
 /// Returns a default `Config` whose on-disk state is confined to the provided
 /// temporary directory. Using a per-test directory keeps tests hermetic and
 /// avoids clobbering a developer’s real `~/.codex`.