diff --git a/.forgeproof/chain-996.json b/.forgeproof/chain-996.json
new file mode 100644
index 0000000..40db67f
--- /dev/null
+++ b/.forgeproof/chain-996.json
@@ -0,0 +1,89 @@
+[
+  {
+    "index": 0,
+    "timestamp": "2026-08-21T04:32:11.082194+00:00",
+    "action": "genesis",
+    "data": {
+      "issue": 996,
+      "title": "v1.3.0 attestation fixture",
+      "requirements": [
+        "REQ-1: bundle embeds a cosign-verifiable in-toto attestation"
+      ]
+    },
+    "prev_hash": "0000000000000000000000000000000000000000000000000000000000000000",
+    "hash": "278e3be0daf637ac7e55992b10122e906d9ebcf0441d3affb0ff8594ec302183",
+    "signature": "-----BEGIN SSH SIGNATURE-----\nU1NIU0lHAAAAAQAAADMAAAALc3NoLWVkMjU1MTkAAAAguXEtuAips/eFvINUWJV3NpqKmx\n/+aWK5ussH/ZkCZKoAAAAKZm9yZ2Vwcm9vZgAAAAAAAAAGc2hhNTEyAAAAUwAAAAtzc2gt\nZWQyNTUxOQAAAEAzPE9dxdRoKxHSEDkXe1oobNwXzCIKdIH8lsCSdXT9KDsfWL77PPrThE\nGQT2kkoIDKouidLsM61D286yhrKGsO\n-----END SSH SIGNATURE-----"
+  },
+  {
+    "index": 1,
+    "timestamp": "2026-08-21T04:32:11.184886+00:00",
+    "action": "file-edit",
+    "data": {
+      "path": "src/example4.py",
+      "operation": "create",
+      "sha256": "60b1e438f6e569f7629f418e9a261a3fe2f61a7781ba4ae058cd4581eddfd68a"
+    },
+    "prev_hash": "278e3be0daf637ac7e55992b10122e906d9ebcf0441d3affb0ff8594ec302183",
+    "hash": "69ef4281fd871925b721454dcd2b4d3bf3d0fda204074771ed0b56f617722d94",
+    "signature": "-----BEGIN SSH SIGNATURE-----\nU1NIU0lHAAAAAQAAADMAAAALc3NoLWVkMjU1MTkAAAAguXEtuAips/eFvINUWJV3NpqKmx\n/+aWK5ussH/ZkCZKoAAAAKZm9yZ2Vwcm9vZgAAAAAAAAAGc2hhNTEyAAAAUwAAAAtzc2gt\nZWQyNTUxOQAAAEBX2zagWJ/x+yR6ec+nJqJHdOV5ugKTeF9YG/DwrB4hdnXuAO04E3pKaj\nqi7QxSqPsizO/tH4Wqk9TDnEy1u3sE\n-----END SSH SIGNATURE-----"
+  },
+  {
+    "index": 2,
+    "timestamp": "2026-08-21T04:32:11.289300+00:00",
+    "action": "test-result",
+    "data": {
+      "suite": "pytest",
+      "passed": 1,
+      "failed": 0,
+      "coverage": {
+        "REQ-1": [
+          "test_attestation_fixture"
+        ]
+      },
+      "failed_tests": []
+    },
+    "prev_hash": "69ef4281fd871925b721454dcd2b4d3bf3d0fda204074771ed0b56f617722d94",
+    "hash": "0385672642e90c440b52a1ffc3241bc2610c536299069f2f35ec6d01db16bd4c",
+    "signature": "-----BEGIN SSH SIGNATURE-----\nU1NIU0lHAAAAAQAAADMAAAALc3NoLWVkMjU1MTkAAAAguXEtuAips/eFvINUWJV3NpqKmx\n/+aWK5ussH/ZkCZKoAAAAKZm9yZ2Vwcm9vZgAAAAAAAAAGc2hhNTEyAAAAUwAAAAtzc2gt\nZWQyNTUxOQAAAEBP/hER7IIBzIe7Andp4YeMQAb8MpGs0CbZrBn/rmj9enEA3RkR52ZDBo\n5mHIyxvXWXViEfOVd2F9yGaBf4+3UA\n-----END SSH SIGNATURE-----"
+  },
+  {
+    "index": 3,
+    "timestamp": "2026-08-21T04:32:11.401815+00:00",
+    "action": "approval",
+    "data": {
+      "gate": "plan",
+      "decision": "approved",
+      "note": "frozen fixture for forgeproof-verify CI",
+      "approver": "fixture-approver@example.com"
+    },
+    "prev_hash": "0385672642e90c440b52a1ffc3241bc2610c536299069f2f35ec6d01db16bd4c",
+    "hash": "9261e8d1afd06bc4d70c142c85dfab588e3366345941acc9b0a325f5ad034125",
+    "signature": "-----BEGIN SSH SIGNATURE-----\nU1NIU0lHAAAAAQAAADMAAAALc3NoLWVkMjU1MTkAAAAguXEtuAips/eFvINUWJV3NpqKmx\n/+aWK5ussH/ZkCZKoAAAAKZm9yZ2Vwcm9vZgAAAAAAAAAGc2hhNTEyAAAAUwAAAAtzc2gt\nZWQyNTUxOQAAAEDApJjQ96SVYM4cE5OwTGzp9hydKWcepfpAoEVt1UzAk7nbgK73WdecHK\nw/G60TB6xQVz0m4Mc6Bl8VYtp0w2QJ\n-----END SSH SIGNATURE-----"
+  },
+  {
+    "index": 4,
+    "timestamp": "2026-08-21T04:32:11.712146+00:00",
+    "action": "finalize",
+    "data": {
+      "commit_sha": "0000000000000000000000000000000000000000",
+      "chain_length": 5,
+      "builder": {
+        "model": {
+          "id": "fixture-generator",
+          "source": "self-reported"
+        },
+        "claude_code": {
+          "version": "2.1.128 (Claude Code)",
+          "source": "measured"
+        },
+        "plugin": {
+          "version": "1.3.0",
+          "source": "engine-constant"
+        }
+      }
+    },
+    "prev_hash": "9261e8d1afd06bc4d70c142c85dfab588e3366345941acc9b0a325f5ad034125",
+    "hash": "4f9c87e9a462a577c680d54129e7258d10b1549530500a039f5d850fa9905502",
+    "signature": "-----BEGIN SSH SIGNATURE-----\nU1NIU0lHAAAAAQAAADMAAAALc3NoLWVkMjU1MTkAAAAguXEtuAips/eFvINUWJV3NpqKmx\n/+aWK5ussH/ZkCZKoAAAAKZm9yZ2Vwcm9vZgAAAAAAAAAGc2hhNTEyAAAAUwAAAAtzc2gt\nZWQyNTUxOQAAAEDk4U5fl9qZnYjqITqlTp5qU9ewev/QnnMGu/VAVEfLoorPJMBhwKcZFp\nFEepellfymmtiM71sMmalqM5pcxYUI\n-----END SSH SIGNATURE-----"
+  }
+]
diff --git a/.forgeproof/issue-996.rpack b/.forgeproof/issue-996.rpack
new file mode 100644
index 0000000..98fe3c0
--- /dev/null
+++ b/.forgeproof/issue-996.rpack
@@ -0,0 +1,55 @@
+{
+  "version": "1.1.0",
+  "format": "forgeproof-rpack",
+  "issue": {
+    "number": 996,
+    "title": "v1.3.0 attestation fixture",
+    "url": ""
+  },
+  "requirements": [
+    {
+      "id": "REQ-1",
+      "text": "bundle embeds a cosign-verifiable in-toto attestation",
+      "status": "covered",
+      "tests": [
+        "test_attestation_fixture"
+      ]
+    }
+  ],
+  "artifacts": [
+    {
+      "path": "src/example4.py",
+      "operation": "create",
+      "sha256": "60b1e438f6e569f7629f418e9a261a3fe2f61a7781ba4ae058cd4581eddfd68a"
+    }
+  ],
+  "decisions": [],
+  "evaluation": {
+    "status": "pass",
+    "tests_passed": 1,
+    "tests_failed": 0,
+    "lint_errors": 0,
+    "requirement_coverage": "100%",
+    "uncovered_requirements": [],
+    "failed_tests": []
+  },
+  "chain_hash": "4e68c7720e35a047fc59ad86e1e17bb2f184023c0481e7c4062a9c3afc72f3e5",
+  "public_key": "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAILlxLbgIqbP3hbyDVFiVdzaaipsf/mliubrLB/2ZAmSq User@PC-951318",
+  "attestation": {
+    "mediaType": "application/vnd.dev.sigstore.bundle.v0.3+json",
+    "verificationMaterial": {
+      "publicKey": {}
+    },
+    "dsseEnvelope": {
+      "payload": "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",
+      "payloadType": "application/vnd.in-toto+json",
+      "signatures": [
+        {
+          "sig": "be+YKm3Rdh2cGGM4cwHlYo3r3I8Ggw66tCA+kMXbjXyL3YFXuarv6tNpNTZigpFw5eyCZ3vSLx4eU7PWkVqeBA=="
+        }
+      ]
+    }
+  },
+  "root_digest": "995ac617ef0d2b3aafe44d81e7d430f6c7dc6050bb0251f6d89a3d533e147150",
+  "signature": "-----BEGIN SSH SIGNATURE-----\nU1NIU0lHAAAAAQAAADMAAAALc3NoLWVkMjU1MTkAAAAguXEtuAips/eFvINUWJV3NpqKmx\n/+aWK5ussH/ZkCZKoAAAAKZm9yZ2Vwcm9vZgAAAAAAAAAGc2hhNTEyAAAAUwAAAAtzc2gt\nZWQyNTUxOQAAAED3BeIiai0hj4uT6+9Ub28Sg7gYdD8envPUHuuJdHZA7r9DC1HJK+Akdo\nn56VP8phHYuRDwRfN8oWm1u9zmwuwC\n-----END SSH SIGNATURE-----"
+}
diff --git a/src/example4.py b/src/example4.py
new file mode 100644
index 0000000..ca611b8
--- /dev/null
+++ b/src/example4.py
@@ -0,0 +1,3 @@
+›ef add(a, b):
+    """Frozen v1.3.0 fixture artifact."""
+    return a + b