fix: report safe M0 publish HTTP status

Co-Authored-By: Codex <noreply@openai.com>

Author: Pigbibi

python/scripts/build_m0_research_publisher_envelope.py

@@ -340,7 +340,11 @@ def publish_m0_research_publisher_envelope(
     try:
         with urllib.request.urlopen(request, timeout=15) as response:  # nosec B310 - URL is HTTPS validated above.
             status = response.getcode()
-    except (urllib.error.HTTPError, urllib.error.URLError, OSError) as exc:
+    except urllib.error.HTTPError as exc:
+        # The status code is sufficient for operational diagnosis and cannot
+        # disclose a token, request body, or arbitrary response content.
+        raise M0ResearchPublisherEnvelopeError(f"m0_publish_http_{exc.code}") from exc
+    except (urllib.error.URLError, OSError) as exc:
         raise M0ResearchPublisherEnvelopeError("m0_publish_failed") from exc
     if not isinstance(status, int) or status < 200 or status >= 300:
         raise M0ResearchPublisherEnvelopeError("m0_publish_failed")

python/tests/test_build_m0_research_publisher_envelope.py

@@ -7,6 +7,7 @@
 import sys
 import tempfile
 import unittest
+import urllib.error
 from contextlib import redirect_stdout
 from pathlib import Path
 from unittest.mock import patch
@@ -283,6 +284,32 @@ def fake_urlopen(request, timeout):
                 },
             )
 
+    def test_publish_reports_only_http_status_for_a_rejected_request(self):
+        envelope = publisher.build_m0_research_publisher_envelope(
+            source_snapshot=self._snapshot(),
+            source_artifact=self._artifact("f" * 64),
+            producer_repository="QuantStrategyLab/QuantRuntimeSettings",
+            producer_revision="e" * 40,
+            now="2026-08-21T12:00:00Z",
+        )
+        rejected = urllib.error.HTTPError(
+            "https://research-console.example/api/internal/sync-m0-research-ledger",
+            409,
+            "Conflict",
+            hdrs=None,
+            fp=io.BytesIO(b'{"error":"must-not-be-exposed"}'),
+        )
+        with patch.object(publisher.urllib.request, "urlopen", side_effect=rejected):
+            with self.assertRaisesRegex(publisher.M0ResearchPublisherEnvelopeError, "m0_publish_http_409") as caught:
+                publisher.publish_m0_research_publisher_envelope(
+                    envelope,
+                    environ={
+                        publisher.PUBLISH_URL_ENV: "https://research-console.example/api/internal/sync-m0-research-ledger",
+                        publisher.PUBLISH_TOKEN_ENV: "dedicated-publisher-token",
+                    },
+                )
+        self.assertNotIn("must-not-be-exposed", str(caught.exception))
+
 
 if __name__ == "__main__":
     unittest.main()