Add minimal evidence filtering and persist minimal evidence.json

gateway/handlers.py

@@ -0,0 +1,21 @@
+"""Gateway handlers for evidence persistence."""
+
+from __future__ import annotations
+
+import json
+from pathlib import Path
+from typing import Mapping
+
+from hc_agent.core.evidence import build_min_evidence
+
+
+def write_evidence_json(evidence: Mapping[str, object], output_dir: str | Path) -> Path:
+    """Write minimal evidence payload to evidence.json and return its path."""
+    output_path = Path(output_dir) / "evidence.json"
+    minimal_evidence = build_min_evidence(evidence)
+
+    output_path.write_text(
+        json.dumps(minimal_evidence, indent=2, sort_keys=True) + "\n",
+        encoding="utf-8",
+    )
+    return output_path

hc_agent/core/evidence.py

@@ -0,0 +1,29 @@
+"""Evidence filtering helpers."""
+
+from __future__ import annotations
+
+from typing import Mapping
+
+ALLOWED_EVIDENCE_KEYS: tuple[str, ...] = (
+    "service",
+    "endpoint",
+    "method",
+    "path",
+    "status",
+    "request_id",
+    "duration_ms",
+    "signature_sha256",
+)
+
+
+def build_min_evidence(evidence: Mapping[str, object] | None) -> dict[str, object]:
+    """Return a minimal evidence payload containing only allowed keys."""
+    if not evidence:
+        return {}
+
+    return {
+        key: evidence[key]
+        for key in ALLOWED_EVIDENCE_KEYS
+        if key in evidence
+    }
+