diff --git a/run_agent.py b/run_agent.py
index 125f7dff119..1cb1f91d92d 100644
--- a/run_agent.py
+++ b/run_agent.py
@@ -292,6 +292,31 @@ def _qwen_portal_headers() -> dict:
     }
 
 
+def _safe_session_filename_component(session_id: str) -> str:
+    """Return a stable, path-safe filename component for a session ID.
+
+    Session IDs can originate from untrusted input (e.g. the
+    ``X-Hermes-Session-Id`` API header) and are otherwise interpolated raw
+    into on-disk artifact filenames under ``~/.hermes/sessions/``.  Without
+    sanitization, a traversal-shaped ID such as ``../../../../etc/pwned``
+    would let a caller write the session snapshot / request dump outside the
+    sessions directory.  This collapses every non ``[A-Za-z0-9_-]`` character
+    to ``_`` (so no path separators or ``.`` survive), caps the length, and —
+    when sanitization changed the string — appends a short content hash so two
+    distinct IDs that sanitize to the same component don't collide.  The
+    result is always a single, traversal-free path segment.
+    """
+    raw = str(session_id or "").strip()
+    sanitized = re.sub(r"[^\w-]", "_", raw).strip("._")
+    sanitized = sanitized[:96] or "session"
+    if raw and sanitized == raw:
+        return sanitized
+    digest = hashlib.sha256(
+        raw.encode("utf-8", errors="surrogatepass")
+    ).hexdigest()[:12]
+    return f"{sanitized}_{digest}"
+
+
 class _StreamErrorEvent(Exception):
     """Synthesized provider error surfaced from a Responses ``error`` SSE frame.