From 2fce6bfee7cd31fcd78282e696f586a3eeb1f810 Mon Sep 17 00:00:00 2001
From: Mauro Deryckere <mauro.deryckere@gmail.com>
Date: Thu, 26 Mar 2026 09:03:56 +0100
Subject: [PATCH] fix(rewrite): skip cat rewrite when incompatible flags are
 present
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

cat flags like -v, -A, -e, -t, -s have different semantics than
rtk read flags (-v means verbose, -n means line numbers). Blindly
forwarding flags caused incorrect behavior (e.g. cat -A file →
rtk read -A file which fails).

Only skip rewrite for incompatible flags. cat -n (line numbers) maps
correctly to rtk read -n, so it is still rewritten for token savings.
Plain `cat file` continues to rewrite to `rtk read file` as before.
---
 src/discover/registry.rs | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/src/discover/registry.rs b/src/discover/registry.rs
index cc975b3b..f8d37c31 100644
--- a/src/discover/registry.rs
+++ b/src/discover/registry.rs
@@ -615,6 +615,16 @@ fn rewrite_segment(seg: &str, excluded: &[String]) -> Option<String> {
         return rewrite_tail_lines(cmd_part).map(|r| format!("{}{}", r, redirect_suffix));
     }
 
+    // Most cat flags (-v, -A, -e, -t, -s, -b, --show-all, etc.) have different
+    // semantics than rtk read or no equivalent at all. Only `-n` (line numbers)
+    // maps correctly to `rtk read -n`. Skip rewrite for any other flag.
+    if cmd_part.starts_with("cat ") {
+        let args = cmd_part["cat ".len()..].trim_start();
+        if args.starts_with('-') && !args.starts_with("-n ") && !args.starts_with("-n\t") {
+            return None;
+        }
+    }
+
     // Use classify_command for correct ignore/prefix handling
     let rtk_equivalent = match classify_command(cmd_part) {
         Classification::Supported { rtk_equivalent, .. } => {
@@ -1165,6 +1175,26 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_rewrite_cat_with_incompatible_flags_skipped() {
+        // cat flags with different semantics than rtk read — skip rewrite
+        assert_eq!(rewrite_command("cat -A file.cpp", &[]), None);
+        assert_eq!(rewrite_command("cat -v file.txt", &[]), None);
+        assert_eq!(rewrite_command("cat -e file.txt", &[]), None);
+        assert_eq!(rewrite_command("cat -t file.txt", &[]), None);
+        assert_eq!(rewrite_command("cat -s file.txt", &[]), None);
+        assert_eq!(rewrite_command("cat --show-all file.txt", &[]), None);
+    }
+
+    #[test]
+    fn test_rewrite_cat_with_compatible_flags() {
+        // cat -n (line numbers) maps to rtk read -n — allow rewrite
+        assert_eq!(
+            rewrite_command("cat -n file.txt", &[]),
+            Some("rtk read -n file.txt".into())
+        );
+    }
+
     #[test]
     fn test_rewrite_rg_pattern() {
         assert_eq!(