diff --git a/.jules/sentinel.md b/.jules/sentinel.md
index 1b18e6e83..1a9528255 100644
--- a/.jules/sentinel.md
+++ b/.jules/sentinel.md
@@ -2,6 +2,11 @@
 **Vulnerability:** The manual SVG sanitizer `apps/web/src/lib/sanitize-svg.ts` used an insufficient allowlist/blocklist. It allowed `<foreignObject>`, `<use>`, `<animate>`, `<set>`, `<image>`, and `<math>` which could lead to mutation XSS (mXSS) and other attack vectors when rendering untrusted Mermaid or Math blocks.
 **Learning:** Manual DOM tree sanitization is notoriously hard to get right because attackers can hide active elements (e.g. `<a>` tags with `javascript:` payloads) inside grandchild trees (like `<math><mtext><a>`) or use SVG-specific tricks (like `<animate href... values="javascript:...">`) which naive list-based cleaners overlook.
 **Prevention:** Rather than adding heavy third-party dependencies (like DOMPurify) against explicit project instructions, expanding the `BLOCKED` Set to include these structural injection vectors provides a robust, zero-dependency mitigation. Future expansions should verify nested elements carefully.
+## 2026-10-22 - [Bypass Command Parsing and Path Traversal fix]
+**Vulnerability:** The `validate_read_only` function in `crates/agent/src/tools/workdir_cmd.rs` allowed command parsing bypass (using quoted paths like `cat ".."/".."/etc/passwd`) which facilitated path traversal because the check only matched against the literal block string `../`.
+**Learning:** Checking for exact substrings against raw commands is highly fragile against obfuscation, such as Unix-style quotation.
+**Prevention:** Validation for string containment (such as blocking `..`) should run against the tokenized and normalized (i.e., lower-case without surrounding quotes) arguments, not the unparsed raw command line.
+
 ## 2023-10-25 - [Fix Masking of Secrets in Environment Variables]
 **Vulnerability:** The `mask_sensitive_env_key` function in `docker.rs` was not properly masking environment variables that contained sensitive keywords (like `AWS_SECRET_ACCESS_KEY`) because it only checked for exact matches or suffix matches (e.g., ends with `_SECRET`).
 **Learning:** Only matching for suffixes or exact values can leave secrets exposed when developers prefix or infix the sensitive word in the environment variable name.
diff --git a/crates/agent/src/tools/workdir_cmd.rs b/crates/agent/src/tools/workdir_cmd.rs
index 932065676..77426cbf8 100644
--- a/crates/agent/src/tools/workdir_cmd.rs
+++ b/crates/agent/src/tools/workdir_cmd.rs
@@ -35,6 +35,7 @@ fn validate_read_only(bin: &str, parts: &[String]) -> std::result::Result<(), St
         let l = a.to_ascii_lowercase();
         if a.starts_with('/')
             || a.starts_with('~')
+            || l.contains("..")
             || l.contains(".env")
             || l.contains("secret")
             || l.contains(".git/")
@@ -328,6 +329,7 @@ mod tests {
         assert!(validate_command("git -c x=y status").is_err());
         assert!(validate_command("cat .env").is_err());
         assert!(validate_command("cat /etc/passwd").is_err());
+        assert!(validate_command("cat \"..\"/\"..\"/etc/passwd").is_err());
         assert!(validate_command("git branch -D main").is_err());
     }