feat(macos): support agent environment hints

refs https://github.com/ogulcancelik/herdr/discussions/679

1 files changed, 32 insertions, 1 deletions

diff --git a/src/platform/mod.rs b/src/platform/mod.rs
index e396966b..3583df5e 100644
--- a/src/platform/mod.rs
+++ b/src/platform/mod.rs
@@ -148,11 +148,22 @@ mod fallback;
 #[cfg(not(any(target_os = "linux", target_os = "macos", target_os = "windows")))]
 pub use fallback::*;
 
-#[cfg(not(target_os = "linux"))]
+#[cfg(not(any(target_os = "linux", target_os = "macos")))]
 pub fn process_agent_hint(_pid: u32) -> Option<crate::detect::Agent> {
     None
 }
 
+#[cfg(any(target_os = "linux", target_os = "macos"))]
+pub(crate) fn parse_agent_env_hint(environ: &[u8]) -> Option<crate::detect::Agent> {
+    for record in environ.split(|&byte| byte == 0) {
+        let Some(value) = record.strip_prefix(b"HERDR_AGENT=") else {
+            continue;
+        };
+        return crate::detect::parse_agent_label(std::str::from_utf8(value).ok()?);
+    }
+    None
+}
+
 #[cfg(not(target_os = "macos"))]
 #[derive(Debug)]
 pub(crate) struct InputSourceRestore;
@@ -229,6 +240,26 @@ mod tests {
         );
     }
 
+    #[cfg(any(target_os = "linux", target_os = "macos"))]
+    #[test]
+    fn parse_agent_env_hint_accepts_known_agents() {
+        assert_eq!(
+            parse_agent_env_hint(b"PATH=/bin\0HERDR_AGENT=claude\0TERM=xterm\0"),
+            Some(crate::detect::Agent::Claude)
+        );
+        assert_eq!(
+            parse_agent_env_hint(b"HERDR_AGENT=codex"),
+            Some(crate::detect::Agent::Codex)
+        );
+    }
+
+    #[cfg(any(target_os = "linux", target_os = "macos"))]
+    #[test]
+    fn parse_agent_env_hint_ignores_missing_or_unknown_agents() {
+        assert_eq!(parse_agent_env_hint(b"PATH=/bin\0TERM=xterm\0"), None);
+        assert_eq!(parse_agent_env_hint(b"HERDR_AGENT=not-an-agent\0"), None);
+    }
+
     #[test]
     fn read_limited_reader_returns_complete_data_under_limit() {
         let input = std::io::Cursor::new(b"image".to_vec());