diff --git a/src/cmcp_gateway/tee/base.py b/src/cmcp_gateway/tee/base.py
index b301f28f..4b4e5620 100644
--- a/src/cmcp_gateway/tee/base.py
+++ b/src/cmcp_gateway/tee/base.py
@@ -7,6 +7,14 @@
 from dataclasses import dataclass
 from datetime import UTC, datetime
 
+_ALLOWED_PROVIDERS: frozenset[str] = frozenset({
+    "sev-snp",
+    "tdx",
+    "opaque",
+    "tpm",
+    "software-only",
+})
+
 
 @dataclass
 class AttestationReport:
@@ -20,6 +28,14 @@ class AttestationReport:
     attestation_validity_seconds: int
     measurement_note: str | None = None  # e.g. "sha1-bank-fallback"
 
+    def __post_init__(self) -> None:
+        if self.provider not in _ALLOWED_PROVIDERS:
+            raise ValueError(
+                f"AttestationReport.provider '{self.provider}' is not in the allowed set "
+                f"{sorted(_ALLOWED_PROVIDERS)}. "
+                "Custom TEE providers must use one of the allowed provider names."
+            )
+
 
 class TEEProvider(ABC):
     """Abstract interface all TEE provider implementations satisfy."""
diff --git a/tests/unit/test_tee.py b/tests/unit/test_tee.py
index 3ec6e8b3..4669f199 100644
--- a/tests/unit/test_tee.py
+++ b/tests/unit/test_tee.py
@@ -129,3 +129,37 @@ def test_detect_explicit_software_only_with_dev_mode(dev_config):
     dev_config.attestation.provider = TEEProviderEnum.SOFTWARE_ONLY
     provider = detect_provider(dev_config)
     assert isinstance(provider, SoftwareOnlyProvider)
+
+
+# ── HW-001: AttestationReport provider validation ────────────────────────────
+
+def test_attestation_report_unknown_provider_raises():
+    """HW-001: unknown provider string must be rejected at AttestationReport construction."""
+    from datetime import timezone
+
+    from cmcp_gateway.tee.base import AttestationReport
+    with pytest.raises(ValueError, match="not in the allowed set"):
+        AttestationReport(
+            provider="unknown-cloud-magic",
+            measurement="sha256:" + "a" * 64,
+            report_data="aa" * 32,
+            raw_evidence=None,
+            attestation_generated_at=datetime.now(tz=timezone.utc),
+            attestation_validity_seconds=86400,
+        )
+
+
+def test_attestation_report_known_providers_accepted():
+    """HW-001: all known providers must be accepted."""
+    from datetime import timezone
+
+    from cmcp_gateway.tee.base import AttestationReport, _ALLOWED_PROVIDERS
+    for provider in _ALLOWED_PROVIDERS:
+        AttestationReport(
+            provider=provider,
+            measurement="sha256:" + "a" * 64,
+            report_data="aa" * 32,
+            raw_evidence=None,
+            attestation_generated_at=datetime.now(tz=timezone.utc),
+            attestation_validity_seconds=86400,
+        )