diff --git a/strix/tools/reporting/tool.py b/strix/tools/reporting/tool.py
index c490e47c..2d245b69 100644
--- a/strix/tools/reporting/tool.py
+++ b/strix/tools/reporting/tool.py
@@ -1496,38 +1496,46 @@ async def update_vulnerability_report(
             default=str,
         )
 
+    fields = {
+        "title": title,
+        "description": description,
+        "impact": impact,
+        "target": target,
+        "technical_analysis": technical_analysis,
+        "poc_description": poc_description,
+        "poc_script_code": poc_script_code,
+        "remediation_steps": remediation_steps,
+        "evidence": evidence,
+        "assumptions": assumptions,
+        "counterevidence": counterevidence,
+        "confidence": confidence,
+        "confidence_rationale": confidence_rationale,
+        "severity_change_conditions": severity_change_conditions,
+        "fix_effort": fix_effort,
+        "cvss_breakdown": cvss_breakdown,
+        "endpoint": endpoint,
+        "method": method,
+        "cve": cve,
+        "cwe": cwe,
+        "code_locations": code_locations,
+        "http_exchange_ids": http_exchange_ids,
+        "fix_verification": fix_verification,
+        "fix_pr_body": fix_pr_body,
+        "contextual_cvss_reasoning": contextual_cvss_reasoning,
+    }
+    if http_exchange_warning and all(value is None for value in fields.values()):
+        return json.dumps(
+            {"success": False, "error": http_exchange_warning, "report_id": report_id},
+            ensure_ascii=False,
+            default=str,
+        )
+
     agent_id, agent_name = _caller_identity(ctx)
     result = await asyncio.to_thread(
         _do_update,
         report_id=report_id,
         update_reason=update_reason,
-        fields={
-            "title": title,
-            "description": description,
-            "impact": impact,
-            "target": target,
-            "technical_analysis": technical_analysis,
-            "poc_description": poc_description,
-            "poc_script_code": poc_script_code,
-            "remediation_steps": remediation_steps,
-            "evidence": evidence,
-            "assumptions": assumptions,
-            "counterevidence": counterevidence,
-            "confidence": confidence,
-            "confidence_rationale": confidence_rationale,
-            "severity_change_conditions": severity_change_conditions,
-            "fix_effort": fix_effort,
-            "cvss_breakdown": cvss_breakdown,
-            "endpoint": endpoint,
-            "method": method,
-            "cve": cve,
-            "cwe": cwe,
-            "code_locations": code_locations,
-            "http_exchange_ids": http_exchange_ids,
-            "fix_verification": fix_verification,
-            "fix_pr_body": fix_pr_body,
-            "contextual_cvss_reasoning": contextual_cvss_reasoning,
-        },
+        fields=fields,
         agent_id=agent_id,
         agent_name=agent_name,
     )
diff --git a/tests/test_reporting_fields.py b/tests/test_reporting_fields.py
index 4a62a90d..aaac7582 100644
--- a/tests/test_reporting_fields.py
+++ b/tests/test_reporting_fields.py
@@ -2,9 +2,11 @@
 
 from __future__ import annotations
 
+import json
 from typing import TYPE_CHECKING, Any, cast
 
 import pytest
+from agents.tool_context import ToolContext
 
 from strix.report.dedupe import (
     _check_dependency_duplicate,
@@ -1501,6 +1503,46 @@ async def test_create_reports_persistence_failure_as_tool_error(
     assert report_state.vulnerability_reports == []
 
 
+async def test_evidence_only_update_reports_proxy_outage_as_retryable(
+    report_state: ReportState,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    _seed_weak_report(report_state)
+    original = dict(report_state.vulnerability_reports[0])
+
+    async def existing_request_ids(
+        _ctx: Any,
+        _request_ids: list[str],
+    ) -> set[str]:
+        raise RuntimeError("Caido client is not available")
+
+    monkeypatch.setattr(reporting_tool, "existing_request_ids", existing_request_ids)
+
+    ctx = ToolContext(
+        context={"agent_id": "root"},
+        tool_name="update_vulnerability_report",
+        tool_call_id="call-1",
+        tool_arguments="{}",
+    )
+    raw = await update_vulnerability_report.on_invoke_tool(
+        ctx,
+        json.dumps(
+            {
+                "report_id": "vuln-0009",
+                "update_reason": "A replay produced a clearer proving exchange.",
+                "http_exchange_ids": ["204"],
+            }
+        ),
+    )
+    result = json.loads(raw)
+
+    assert result["success"] is False
+    assert "No fields to update" not in result["error"]
+    assert "update_vulnerability_report" in result["error"]
+    assert result["report_id"] == "vuln-0009"
+    assert report_state.vulnerability_reports[0] == original
+
+
 def test_update_reports_persistence_failure_as_tool_error(report_state: ReportState) -> None:
     _seed_weak_report(report_state)
     original = dict(report_state.vulnerability_reports[0])