fix: harden backtest contract boundaries

tests/test_backtest_contracts.py

@@ -16,6 +16,7 @@ import pytest
 from quant_engine.artifact import (
     BacktestEvidenceManifest,
     EvidenceQualification,
+    RESEARCH_ARTIFACT_SCHEMA_VERSION,
     ResearchRunArtifact,
     build_backtest_evidence_manifest,
     build_legacy_backtest_evidence_manifest,
@@ -310,6 +311,50 @@ def test_backtest_run_ref_rejects_unclosed_upstream_and_unsafe_scalars() -> None
     _assert_error(factor_type, BacktestContractErrorCode.TYPE_ERROR, "$.factor_set")
 
 
+def test_run_ref_rejects_aliases_locators_unsafe_integers_and_invalid_text() -> None:
+    with pytest.raises(BacktestContractError) as mutable_alias:
+        _run_ref(strategy_id="latest")
+    _assert_error(
+        mutable_alias,
+        BacktestContractErrorCode.INVALID_FORMAT,
+        "$.strategy_id",
+    )
+    with pytest.raises(BacktestContractError) as physical_uri:
+        _run_ref(execution_model_version="s3://model-bucket/current")
+    _assert_error(
+        physical_uri,
+        BacktestContractErrorCode.INVALID_FORMAT,
+        "$.execution_model_version",
+    )
+    with pytest.raises(BacktestContractError) as unsafe_seed:
+        _run_ref(random_seed=2**53)
+    _assert_error(
+        unsafe_seed,
+        BacktestContractErrorCode.INVALID_VALUE,
+        "$.random_seed",
+    )
+    with pytest.raises(BacktestContractError) as invalid_unicode:
+        _run_ref(strategy_id="\ud800")
+    _assert_error(
+        invalid_unicode,
+        BacktestContractErrorCode.INVALID_FORMAT,
+        "$.strategy_id",
+    )
+
+    run_ref = _run_ref()
+    mixed_keys = run_ref.to_dict()
+    mixed_keys[1] = "not-a-contract-key"  # type: ignore[index]
+    snapshot, foundation, factor_set = _accepted_authorities()
+    with pytest.raises(BacktestContractError) as invalid_key:
+        BacktestRunRef.from_dict(
+            mixed_keys,
+            dataset_snapshot=snapshot,
+            foundation=foundation,
+            factor_set=factor_set,
+        )
+    _assert_error(invalid_key, BacktestContractErrorCode.TYPE_ERROR, "$")
+
+
 def test_replay_lineage_is_acyclic_and_cannot_claim_changed_inputs() -> None:
     parent = _run_ref()
     replay = _run_ref(
@@ -462,6 +507,50 @@ def test_manifest_rejects_missing_mismatched_or_duplicate_evidence() -> None:
     )
 
 
+def test_manifest_binds_supported_schema_and_has_collision_free_cell_encoding() -> None:
+    run_ref = _run_ref()
+    artifact = _artifact(run_ref)
+
+    with pytest.raises(BacktestContractError) as unsupported_schema:
+        build_backtest_evidence_manifest(
+            run_ref,
+            replace(artifact, schema_version="999.0.0"),
+            artifact_available_at="2026-01-08T02:05:00Z",
+        )
+    _assert_error(
+        unsupported_schema,
+        BacktestContractErrorCode.INVALID_VALUE,
+        "$.artifact.schema_version",
+    )
+
+    identities: set[str] = set()
+    for value in (float("nan"), float("inf"), float("-inf")):
+        performance = artifact.performance
+        performance.loc[0, "alpha"] = value
+        manifest = build_backtest_evidence_manifest(
+            run_ref,
+            replace(artifact, _performance=performance),
+            artifact_available_at="2026-01-08T02:05:00Z",
+        )
+        assert manifest.artifact_schema_version == RESEARCH_ARTIFACT_SCHEMA_VERSION
+        identities.add(manifest.manifest_id)
+    assert len(identities) == 3
+
+    unsupported = artifact.performance.astype(object)
+    unsupported.loc[0, "alpha"] = object()
+    with pytest.raises(BacktestContractError) as unsupported_cell:
+        build_backtest_evidence_manifest(
+            run_ref,
+            replace(artifact, _performance=unsupported),
+            artifact_available_at="2026-01-08T02:05:00Z",
+        )
+    _assert_error(
+        unsupported_cell,
+        BacktestContractErrorCode.TYPE_ERROR,
+        "$.artifact.tables.performance.rows[0].alpha",
+    )
+
+
 def test_legacy_bridge_is_explicit_and_cannot_be_contract_qualified() -> None:
     run_ref = _run_ref()
     legacy_run = BacktestRun(