diff --git a/codex-rs/core/src/shell_env_file.rs b/codex-rs/core/src/shell_env_file.rs
index 1511d7cfbf..88969e3364 100644
--- a/codex-rs/core/src/shell_env_file.rs
+++ b/codex-rs/core/src/shell_env_file.rs
@@ -7,6 +7,7 @@ use anyhow::Result;
 use anyhow::anyhow;
 use anyhow::bail;
 use codex_protocol::ThreadId;
+use codex_protocol::shell_environment::CLAUDE_ENV_FILE_ENV_VAR;
 use codex_protocol::shell_environment::CODEX_ENV_FILE_ENV_VAR;
 use codex_protocol::shell_environment::CODEX_THREAD_ID_ENV_VAR;
 use tempfile::TempPath;
@@ -52,11 +53,9 @@ impl ShellEnvFile {
     }
 
     pub(crate) fn insert_path_into_env(&self, env: &mut HashMap<String, String>) {
-        insert_env_var(
-            env,
-            CODEX_ENV_FILE_ENV_VAR.to_string(),
-            self.path().to_string_lossy().to_string(),
-        );
+        let path = self.path().to_string_lossy().to_string();
+        insert_env_var(env, CODEX_ENV_FILE_ENV_VAR.to_string(), path.clone());
+        insert_env_var(env, CLAUDE_ENV_FILE_ENV_VAR.to_string(), path);
     }
 
     /// Sources the hook-writable env file once and stores the resulting
@@ -65,8 +64,8 @@ impl ShellEnvFile {
     /// The temp file remains an input channel for SessionStart hooks, but later
     /// commands receive only captured variable changes. Running both a baseline
     /// environment dump and a sourced dump lets shell syntax such as command
-    /// substitution behave naturally without keeping `CODEX_ENV_FILE` available
-    /// after hook execution.
+    /// substitution behave naturally without keeping env-file path variables
+    /// available after hook execution.
     pub(crate) async fn capture_exports(
         &self,
         shell: &Shell,
@@ -79,6 +78,7 @@ impl ShellEnvFile {
 
         let mut capture_env = base_env.clone();
         remove_env_var(&mut capture_env, CODEX_ENV_FILE_ENV_VAR);
+        remove_env_var(&mut capture_env, CLAUDE_ENV_FILE_ENV_VAR);
         self.insert_path_into_env(&mut capture_env);
 
         let baseline = self
@@ -135,6 +135,7 @@ impl ShellEnvFile {
             insert_env_var(env, CODEX_THREAD_ID_ENV_VAR.to_string(), thread_id);
         }
         remove_env_var(env, CODEX_ENV_FILE_ENV_VAR);
+        remove_env_var(env, CLAUDE_ENV_FILE_ENV_VAR);
     }
 }
 
@@ -317,6 +318,7 @@ fn diff_env(
 fn ignored_capture_key(key: &str) -> bool {
     [
         CODEX_ENV_FILE_ENV_VAR,
+        CLAUDE_ENV_FILE_ENV_VAR,
         CODEX_THREAD_ID_ENV_VAR,
         "PWD",
         "OLDPWD",
diff --git a/codex-rs/core/src/shell_env_file_tests.rs b/codex-rs/core/src/shell_env_file_tests.rs
index 6fcff1d223..be03da5f2e 100644
--- a/codex-rs/core/src/shell_env_file_tests.rs
+++ b/codex-rs/core/src/shell_env_file_tests.rs
@@ -39,6 +39,7 @@ async fn shell_env_file_applies_exports_without_exposing_writable_path() -> Resu
 export CODEX_SESSION_START_TEST='from-session-start'
 export PATH=\"/plugin/bin:$PATH\"
 export CODEX_ENV_FILE='/tmp/poison'
+export CLAUDE_ENV_FILE='/tmp/poison'
 export CODEX_THREAD_ID='poisoned-thread'
 export EXPLICIT_OVERRIDE='from-hook'
 ",
@@ -53,6 +54,10 @@ export EXPLICIT_OVERRIDE='from-hook'
         CODEX_ENV_FILE_ENV_VAR.to_string(),
         env_file.path().display().to_string(),
     );
+    env.insert(
+        CLAUDE_ENV_FILE_ENV_VAR.to_string(),
+        env_file.path().display().to_string(),
+    );
     let explicit_env_overrides =
         HashMap::from([("EXPLICIT_OVERRIDE".to_string(), "from-policy".to_string())]);
 
@@ -181,6 +186,7 @@ Write-Output "hidden"
 $env:CODEX_SESSION_START_TEST = "from-session-start"
 $env:COMMAND_EXPRESSION = ("unsafe").ToUpperInvariant()
 $env:CODEX_ENV_FILE = "C:\poison"
+$env:CLAUDE_ENV_FILE = "C:\poison"
 $env:CODEX_THREAD_ID = "poisoned-thread"
 $env:EXPLICIT_OVERRIDE = "from-hook"
 Remove-Item Env:REMOVED_BY_HOOK -ErrorAction SilentlyContinue
@@ -196,6 +202,10 @@ Remove-Item Env:REMOVED_BY_HOOK -ErrorAction SilentlyContinue
         CODEX_ENV_FILE_ENV_VAR.to_string(),
         env_file.path().display().to_string(),
     );
+    env.insert(
+        CLAUDE_ENV_FILE_ENV_VAR.to_string(),
+        env_file.path().display().to_string(),
+    );
     let explicit_env_overrides =
         HashMap::from([("EXPLICIT_OVERRIDE".to_string(), "from-policy".to_string())]);
 
diff --git a/codex-rs/core/tests/suite/hooks.rs b/codex-rs/core/tests/suite/hooks.rs
index db72fe0445..c314ec0674 100644
--- a/codex-rs/core/tests/suite/hooks.rs
+++ b/codex-rs/core/tests/suite/hooks.rs
@@ -783,7 +783,7 @@ fn write_session_start_hook_exporting_env(home: &Path) -> Result<()> {
     let session_start_script = r#"import os
 from pathlib import Path
 
-env_file = Path(os.environ["CODEX_ENV_FILE"])
+env_file = Path(os.environ["CLAUDE_ENV_FILE"])
 with env_file.open("a", encoding="utf-8") as handle:
     handle.write("export CODEX_SESSION_START_TEST='from-session-start'\n")
 "#;
@@ -791,7 +791,7 @@ with env_file.open("a", encoding="utf-8") as handle:
     let pre_tool_use_script = r#"import os
 from pathlib import Path
 
-env_file = os.environ.get("CODEX_ENV_FILE")
+env_file = os.environ.get("CODEX_ENV_FILE") or os.environ.get("CLAUDE_ENV_FILE")
 if env_file:
     with Path(env_file).open("a", encoding="utf-8") as handle:
         handle.write("export CODEX_SESSION_START_TEST='leaked-to-pre-tool-use'\n")
@@ -2717,7 +2717,7 @@ async fn assert_session_start_env_file_reaches_bash_surface(
 
     let server = start_mock_server().await;
     let call_id = format!("session-start-env-file-{}", surface.slug());
-    let command = "printf '%s|%s' \"$CODEX_SESSION_START_TEST\" \"${CODEX_ENV_FILE:+configured}\"";
+    let command = "printf '%s|%s|%s' \"$CODEX_SESSION_START_TEST\" \"${CODEX_ENV_FILE:+configured}\" \"${CLAUDE_ENV_FILE:+configured}\"";
     let tool_call = match surface {
         BashRewriteSurface::ExecCommand => ev_function_call(
             &call_id,
@@ -2773,12 +2773,12 @@ async fn assert_session_start_env_file_reaches_bash_surface(
         "expected hook-exported value in {surface:?} output: {output}"
     );
     assert!(
-        output.contains("from-session-start|"),
-        "expected CODEX_ENV_FILE to stay hidden from {surface:?} command: {output}"
+        output.contains("from-session-start||"),
+        "expected env-file paths to stay hidden from {surface:?} command: {output}"
     );
     assert!(
         !output.contains("leaked-to-pre-tool-use"),
-        "PreToolUse should not receive CODEX_ENV_FILE: {output}"
+        "PreToolUse should not receive env-file paths: {output}"
     );
 
     Ok(())
@@ -2795,7 +2795,7 @@ async fn session_start_env_file_exports_reach_exec_command() -> Result<()> {
 }
 
 #[tokio::test]
-async fn shell_command_hides_codex_env_file_when_hooks_are_disabled() -> Result<()> {
+async fn shell_command_hides_env_file_paths_when_hooks_are_disabled() -> Result<()> {
     skip_if_no_network!(Ok(()));
     skip_if_windows!(Ok(()));
 
@@ -2810,7 +2810,7 @@ async fn shell_command_hides_codex_env_file_when_hooks_are_disabled() -> Result<
                     call_id,
                     "shell_command",
                     &serde_json::to_string(&serde_json::json!({
-                        "command": "printf '%s' \"${CODEX_ENV_FILE:+configured}\"",
+                        "command": "printf '%s|%s' \"${CODEX_ENV_FILE:+configured}\" \"${CLAUDE_ENV_FILE:+configured}\"",
                         "login": false,
                     }))?,
                 ),
diff --git a/codex-rs/hooks/src/engine/command_runner.rs b/codex-rs/hooks/src/engine/command_runner.rs
index 3eac1d0ecf..27fb1b3a1c 100644
--- a/codex-rs/hooks/src/engine/command_runner.rs
+++ b/codex-rs/hooks/src/engine/command_runner.rs
@@ -8,6 +8,7 @@ use tokio::process::Command;
 use tokio::time::timeout;
 
 use codex_protocol::protocol::HookEventName;
+use codex_protocol::shell_environment::CLAUDE_ENV_FILE_ENV_VAR;
 use codex_protocol::shell_environment::CODEX_ENV_FILE_ENV_VAR;
 
 use super::CommandShell;
@@ -116,8 +117,9 @@ fn build_command(shell: &CommandShell, handler: &ConfiguredHandler) -> Command {
         command.arg(&handler.command);
     }
     command.envs(&handler.env);
-    // Only SessionStart hooks receive CODEX_ENV_FILE.
+    // Only SessionStart hooks receive session env-file paths.
     command.env_remove(CODEX_ENV_FILE_ENV_VAR);
+    command.env_remove(CLAUDE_ENV_FILE_ENV_VAR);
     if handler.event_name == HookEventName::SessionStart {
         command.envs(&shell.env);
     }
@@ -153,6 +155,7 @@ mod tests {
     use pretty_assertions::assert_eq;
     use tokio::process::Command;
 
+    use super::CLAUDE_ENV_FILE_ENV_VAR;
     use super::CODEX_ENV_FILE_ENV_VAR;
     use super::CommandShell;
     use super::ConfiguredHandler;
@@ -162,10 +165,16 @@ mod tests {
         CommandShell {
             program: "hook-shell".to_string(),
             args: Vec::new(),
-            env: HashMap::from([(
-                CODEX_ENV_FILE_ENV_VAR.to_string(),
-                "session-owned-env-file".to_string(),
-            )]),
+            env: HashMap::from([
+                (
+                    CODEX_ENV_FILE_ENV_VAR.to_string(),
+                    "session-owned-env-file".to_string(),
+                ),
+                (
+                    CLAUDE_ENV_FILE_ENV_VAR.to_string(),
+                    "session-owned-env-file".to_string(),
+                ),
+            ]),
         }
     }
 
@@ -192,19 +201,24 @@ mod tests {
     }
 
     #[test]
-    fn non_session_start_hook_masks_inherited_codex_env_file() {
+    fn non_session_start_hook_masks_inherited_env_file_paths() {
         let command = build_command(&shell(), &handler(HookEventName::PreToolUse));
 
         assert_eq!(command_env(&command, CODEX_ENV_FILE_ENV_VAR), Some(None));
+        assert_eq!(command_env(&command, CLAUDE_ENV_FILE_ENV_VAR), Some(None));
     }
 
     #[test]
-    fn session_start_hook_receives_session_owned_codex_env_file() {
+    fn session_start_hook_receives_session_owned_env_file_paths() {
         let command = build_command(&shell(), &handler(HookEventName::SessionStart));
 
         assert_eq!(
             command_env(&command, CODEX_ENV_FILE_ENV_VAR),
             Some(Some(OsStr::new("session-owned-env-file")))
         );
+        assert_eq!(
+            command_env(&command, CLAUDE_ENV_FILE_ENV_VAR),
+            Some(Some(OsStr::new("session-owned-env-file")))
+        );
     }
 }
diff --git a/codex-rs/hooks/src/events/session_start.rs b/codex-rs/hooks/src/events/session_start.rs
index 18f17e7486..d3ed583771 100644
--- a/codex-rs/hooks/src/events/session_start.rs
+++ b/codex-rs/hooks/src/events/session_start.rs
@@ -7,6 +7,7 @@ use codex_protocol::protocol::HookOutputEntry;
 use codex_protocol::protocol::HookOutputEntryKind;
 use codex_protocol::protocol::HookRunStatus;
 use codex_protocol::protocol::HookRunSummary;
+use codex_protocol::shell_environment::CLAUDE_ENV_FILE_ENV_VAR;
 use codex_protocol::shell_environment::CODEX_ENV_FILE_ENV_VAR;
 use codex_utils_absolute_path::AbsolutePathBuf;
 
@@ -181,9 +182,10 @@ pub(crate) async fn run(
     };
 
     let results = if event_name == HookEventName::SessionStart
-        && shell.env.contains_key(CODEX_ENV_FILE_ENV_VAR)
+        && (shell.env.contains_key(CODEX_ENV_FILE_ENV_VAR)
+            || shell.env.contains_key(CLAUDE_ENV_FILE_ENV_VAR))
     {
-        // Serialize hooks that share CODEX_ENV_FILE to preserve configured order.
+        // Serialize hooks that share the session env file to preserve configured order.
         let mut results = Vec::with_capacity(matched.len());
         for (completion_order, handler) in matched.into_iter().enumerate() {
             let result = run_command(shell, &handler, &input_json, request.cwd.as_path()).await;
diff --git a/codex-rs/protocol/src/shell_environment.rs b/codex-rs/protocol/src/shell_environment.rs
index 89f3bf9ca5..00394e0b44 100644
--- a/codex-rs/protocol/src/shell_environment.rs
+++ b/codex-rs/protocol/src/shell_environment.rs
@@ -4,6 +4,7 @@ use crate::config_types::ShellEnvironmentPolicyInherit;
 use std::collections::HashMap;
 
 pub const CODEX_ENV_FILE_ENV_VAR: &str = "CODEX_ENV_FILE";
+pub const CLAUDE_ENV_FILE_ENV_VAR: &str = "CLAUDE_ENV_FILE";
 pub const CODEX_THREAD_ID_ENV_VAR: &str = "CODEX_THREAD_ID";
 
 /// Construct a shell environment from the supplied process environment and