diff --git a/crates/catalogd/src/bin/parity_subject_audit.rs b/crates/catalogd/src/bin/parity_subject_audit.rs
index a867d52..f0d8afe 100644
--- a/crates/catalogd/src/bin/parity_subject_audit.rs
+++ b/crates/catalogd/src/bin/parity_subject_audit.rs
@@ -2,9 +2,11 @@
 //!
 //! Specification: docs/specs/SUBJECT_MANIFESTS_ON_CATALOGD.md §5 Step 8.
 //!
-//! This binary is consumed by scripts/cutover/parity/subject_audit_parity.sh
-//! (which lives in /home/profit/golangLAKEHOUSE/scripts/cutover/parity/).
-//! Its Go counterpart is at golangLAKEHOUSE/scripts/cutover/parity/subject_audit_helper/main.go.
+//! This binary is consumed by the Go-repo's
+//! scripts/cutover/parity/subject_audit_parity.sh.
+//! Go counterpart: scripts/cutover/parity/subject_audit_helper/main.go
+//! (in the Go repo). Both helpers are kept in lockstep by the parity
+//! script's byte-equality assertions — change one, change both.
 //!
 //! Both helpers MUST produce byte-identical output for the same inputs.
 //! Divergence here is a parity break — a SubjectManifest written by Rust
@@ -88,6 +90,15 @@ fn deterministic_key() -> Vec<u8> {
     (0u8..32).collect()
 }
 
+/// Print to stderr + exit(2). Never returns. Used in place of `.expect()`
+/// on argv / file reads so failures produce a clean usage error rather
+/// than a Rust panic backtrace that the parity script would mistake
+/// for a parity break.
+fn die(msg: &str) -> ! {
+    eprintln!("error: {msg}");
+    std::process::exit(2);
+}
+
 #[derive(Serialize)]
 struct KnownAnswerOut {
     mode: &'static str,
@@ -141,6 +152,10 @@ async fn main() {
     let mut audit_path: Option<PathBuf> = None;
     let mut key_path: Option<PathBuf> = None;
 
+    // Argv parsing fails via stderr+exit, never via panic. The parity
+    // script captures stdout for byte-comparison; a Rust panic backtrace
+    // would land in stdout (the script merges 2>&1) and read as a parity
+    // break instead of a usage error. (Caught 2026-05-03 opus scrum WARN.)
     let mut i = 1;
     while i < argv.len() {
         match argv[i].as_str() {
@@ -149,13 +164,13 @@ async fn main() {
                 i += 1;
             }
             "--verify" => {
-                audit_path = Some(PathBuf::from(
-                    argv.get(i + 1).expect("--verify needs path"),
-                ));
+                let p = argv.get(i + 1).unwrap_or_else(|| die("--verify needs a path"));
+                audit_path = Some(PathBuf::from(p));
                 i += 2;
             }
             "--key" => {
-                key_path = Some(PathBuf::from(argv.get(i + 1).expect("--key needs path")));
+                let p = argv.get(i + 1).unwrap_or_else(|| die("--key needs a path"));
+                key_path = Some(PathBuf::from(p));
                 i += 2;
             }
             "-h" | "--help" => {
@@ -175,15 +190,15 @@ async fn main() {
         return;
     }
 
-    let audit_path = audit_path.expect("need --known-answer OR --verify ... --key ...");
-    let key_path = key_path.expect("--verify also needs --key");
+    let audit_path = audit_path.unwrap_or_else(|| die("need --known-answer OR --verify <path> --key <path>"));
+    let key_path = key_path.unwrap_or_else(|| die("--verify also needs --key"));
 
-    let key = std::fs::read(&key_path).expect("read key file");
+    let key = std::fs::read(&key_path).unwrap_or_else(|e| die(&format!("read key file: {e}")));
     let candidate_id = audit_path
         .file_name()
         .and_then(|s| s.to_str())
         .and_then(|s| s.strip_suffix(".audit.jsonl"))
-        .expect("audit log path must end with <candidate_id>.audit.jsonl")
+        .unwrap_or_else(|| die("audit log path must end with <candidate_id>.audit.jsonl"))
         .to_string();
 
     // Stand up an in-memory object store, seed it with the audit log