diff --git a/workspace/a2a_tools_delegation.py b/workspace/a2a_tools_delegation.py
index 5a40891b..c6416122 100644
--- a/workspace/a2a_tools_delegation.py
+++ b/workspace/a2a_tools_delegation.py
@@ -167,12 +167,19 @@ async def _delegate_sync_via_polling(
                 break
         if terminal:
             if (terminal.get("status") or "").lower() == "completed":
-                return terminal.get("response_preview") or ""
-            err = (
+                # OFFSEC-003: sanitize response_preview before returning so
+                # boundary markers injected by a malicious peer cannot escape
+                # the trust boundary.
+                return sanitize_a2a_result(terminal.get("response_preview") or "")
+            # OFFSEC-003: sanitize error_detail / summary before wrapping with
+            # the _A2A_ERROR_PREFIX sentinel so injected markers cannot appear
+            # inside the trusted error block returned to the agent.
+            err_raw = (
                 terminal.get("error_detail")
                 or terminal.get("summary")
                 or "delegation failed"
             )
+            err = sanitize_a2a_result(err_raw)
             return f"{_A2A_ERROR_PREFIX}{err}"
 
         await asyncio.sleep(_SYNC_POLL_INTERVAL_S)
@@ -408,12 +415,11 @@ async def tool_check_task_status(
                 # Filter by delegation_id
                 matching = [d for d in delegations if d.get("delegation_id") == task_id]
                 if matching:
-                    entry = dict(matching[0])
-                    # OFFSEC-003: sanitize peer-generated text fields
-                    for field in ("result", "response_preview"):
-                        if field in entry and entry[field]:
-                            entry[field] = sanitize_a2a_result(str(entry[field]))
-                    return json.dumps(entry)
+                    # OFFSEC-003: sanitize peer-supplied fields
+                    d = matching[0]
+                    d["summary"] = sanitize_a2a_result(d.get("summary", ""))
+                    d["response_preview"] = sanitize_a2a_result(d.get("response_preview", ""))
+                    return json.dumps(d)
                 return json.dumps({"status": "not_found", "delegation_id": task_id})
             # Return all recent delegations
             summary = []
@@ -425,7 +431,7 @@ async def tool_check_task_status(
                     "delegation_id": d.get("delegation_id", ""),
                     "target_id": d.get("target_id", ""),
                     "status": d.get("status", ""),
-                    "summary": d.get("summary", ""),
+                    "summary": sanitize_a2a_result(d.get("summary", "")),
                     "response_preview": preview,
                 })
             return json.dumps({"delegations": summary, "count": len(delegations)})