diff --git a/tests/api/v1/extauth/__init__.py b/tests/api/v1/extauth/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/api/v1/extauth/test_provider_helpers.py b/tests/api/v1/extauth/test_provider_helpers.py
new file mode 100644
index 0000000..6596110
--- /dev/null
+++ b/tests/api/v1/extauth/test_provider_helpers.py
@@ -0,0 +1,52 @@
+import pytest
+from gatehouse_app.utils.constants import AuthMethodType
+from gatehouse_app.services.external_auth.models import ExternalAuthError
+from gatehouse_app.api.v1.external_auth._helpers import (
+    get_provider_type,
+    _get_provider_endpoints,
+)
+
+
+class TestProviderType:
+    def test_google(self):
+        assert get_provider_type("google") == AuthMethodType.GOOGLE
+
+    def test_github(self):
+        assert get_provider_type("github") == AuthMethodType.GITHUB
+
+    def test_microsoft(self):
+        assert get_provider_type("microsoft") == AuthMethodType.MICROSOFT
+
+    def test_case_insensitive(self):
+        assert get_provider_type("GitHub") == AuthMethodType.GITHUB
+
+    def test_unknown_provider_raises(self):
+        with pytest.raises(ExternalAuthError) as exc_info:
+            get_provider_type("facebook")
+        assert exc_info.value.status_code == 400
+        assert "facebook" in exc_info.value.message.lower()
+
+
+class TestProviderEndpoints:
+    def test_google_endpoints(self):
+        auth, token, userinfo = _get_provider_endpoints(AuthMethodType.GOOGLE)
+        assert "accounts.google.com" in auth
+        assert "oauth2.googleapis.com" in token
+        assert "googleapis.com" in userinfo
+
+    def test_github_endpoints(self):
+        auth, token, userinfo = _get_provider_endpoints(AuthMethodType.GITHUB)
+        assert "github.com/login" in auth
+        assert "github.com/login/oauth/access_token" in token
+        assert "api.github.com/user" in userinfo
+
+    def test_microsoft_endpoints(self):
+        auth, token, userinfo = _get_provider_endpoints(AuthMethodType.MICROSOFT)
+        assert "login.microsoftonline.com" in auth
+        assert "login.microsoftonline.com" in token
+        assert "graph.microsoft.com" in userinfo
+
+    def test_unknown_type_raises(self):
+        with pytest.raises(ExternalAuthError) as exc_info:
+            _get_provider_endpoints("nonexistent")
+        assert exc_info.value.status_code == 400
diff --git a/tests/api/v1/organizations/__init__.py b/tests/api/v1/organizations/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/api/v1/organizations/test_system_ca_dict.py b/tests/api/v1/organizations/test_system_ca_dict.py
new file mode 100644
index 0000000..2780067
--- /dev/null
+++ b/tests/api/v1/organizations/test_system_ca_dict.py
@@ -0,0 +1,59 @@
+import pytest
+from gatehouse_app.api.v1.organizations._helpers import _get_system_ca_dict
+from gatehouse_app.config.ssh_ca_config import SSHCAConfig, reset_config_instance
+
+# Ed25519 key fixture data
+VALID_PRIVATE_KEY = (
+    "-----BEGIN OPENSSH PRIVATE KEY-----\n"
+    "b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtzc2gtZW\n"
+    "QyNTUxOQAAACCi+2CgIPgoFL5P6DZlNXztuHy3+TuS2shh/xIDkW89OgAAAJhDQd+ZQ0Hf\n"
+    "mQAAAAtzc2gtZWQyNTUxOQAAACCi+2CgIPgoFL5P6DZlNXztuHy3+TuS2shh/xIDkW89Og\n"
+    "AAAECMbnF+1E22w9Z1AOTUbUGspL8Pb0UyP+p8lSLpAwZSpaL7YKAg+CgUvk/oNmU1fO24\n"
+    "fLf5O5LayGH/EgORbz06AAAAD2NvcnlAbGFwdG9wLXZtMQECAwQFBg==\n"
+    "-----END OPENSSH PRIVATE KEY-----"
+)
+
+
+class FakeEmptyConfig(SSHCAConfig):
+    def get_str(self, key, default=""):
+        if key == "ca_key_path":
+            return ""
+        return default
+
+
+class BadConfig(SSHCAConfig):
+    def get_str(self, key, default=""):
+        raise RuntimeError("config error")
+
+
+class TestSystemCADict:
+
+    def test_no_key_available_returns_none(self, monkeypatch):
+        monkeypatch.delenv("SSH_CA_PRIVATE_KEY", raising=False)
+        reset_config_instance()
+        monkeypatch.setattr(
+            "gatehouse_app.config.ssh_ca_config.get_ssh_ca_config",
+            lambda: FakeEmptyConfig(),
+        )
+        result = _get_system_ca_dict()
+        assert result is None
+
+    def test_env_var_returns_dict(self, monkeypatch):
+        monkeypatch.setenv("SSH_CA_PRIVATE_KEY", VALID_PRIVATE_KEY)
+        result = _get_system_ca_dict()
+        assert result is not None
+        assert result["ca_type"] == "user"
+        assert result["is_system"] is True
+        assert "fingerprint" in result
+        assert result["public_key"]
+        assert result["public_key"].startswith("ssh-")
+
+    def test_exception_gracefully_returns_none(self, monkeypatch):
+        monkeypatch.delenv("SSH_CA_PRIVATE_KEY", raising=False)
+        reset_config_instance()
+        monkeypatch.setattr(
+            "gatehouse_app.config.ssh_ca_config.get_ssh_ca_config",
+            lambda: BadConfig(),
+        )
+        result = _get_system_ca_dict()
+        assert result is None
diff --git a/tests/api/v1/ssh/test_classify_key_material.py b/tests/api/v1/ssh/test_classify_key_material.py
new file mode 100644
index 0000000..ea34252
--- /dev/null
+++ b/tests/api/v1/ssh/test_classify_key_material.py
@@ -0,0 +1,92 @@
+import pytest
+from gatehouse_app.api.v1.ssh._helpers import _classify_ssh_key_material
+
+
+class TestClassifySSHKeyMaterial:
+    def test_classifies_certificate(self):
+        result = _classify_ssh_key_material("ssh-ed25519-cert-v01@openssh.com AAAA comment")
+        assert result == "certificate"
+
+    def test_classifies_ed25519_public_key(self):
+        result = _classify_ssh_key_material("ssh-ed25519 AAAAB3NzaC1lZDI1NTE5AAAAI... comment")
+        assert result == "public_key"
+
+    def test_classifies_rsa_public_key(self):
+        result = _classify_ssh_key_material("ssh-rsa AAAAB3NzaC1yc2E... comment")
+        assert result == "public_key"
+
+    def test_classifies_dss_public_key(self):
+        result = _classify_ssh_key_material("ssh-dss AAAAB3NzaC1kc3M... comment")
+        assert result == "public_key"
+
+    def test_classifies_ecdsa_nistp256_public_key(self):
+        result = _classify_ssh_key_material("ecdsa-sha2-nistp256 AAAAE2Vj... comment")
+        assert result == "public_key"
+
+    def test_classifies_ecdsa_nistp384_public_key(self):
+        result = _classify_ssh_key_material("ecdsa-sha2-nistp384 AAAAE2Vj... comment")
+        assert result == "public_key"
+
+    def test_classifies_ecdsa_nistp521_public_key(self):
+        result = _classify_ssh_key_material("ecdsa-sha2-nistp521 AAAAE2Vj... comment")
+        assert result == "public_key"
+
+    def test_classifies_sk_ed25519_public_key(self):
+        result = _classify_ssh_key_material(
+            "sk-ssh-ed25519@openssh.com AAAAGnNrLXNzaC1lZDI1NTE5... comment"
+        )
+        assert result == "public_key"
+
+    def test_classifies_openssh_private_key(self):
+        result = _classify_ssh_key_material(
+            "-----BEGIN OPENSSH PRIVATE KEY-----\n"
+            "base64data==\n"
+            "-----END OPENSSH PRIVATE KEY-----"
+        )
+        assert result == "private_key"
+
+    def test_classifies_rsa_private_key(self):
+        result = _classify_ssh_key_material(
+            "-----BEGIN RSA PRIVATE KEY-----\n"
+            "base64data==\n"
+            "-----END RSA PRIVATE KEY-----"
+        )
+        assert result == "private_key"
+
+    def test_unknown_for_empty_string(self):
+        result = _classify_ssh_key_material("")
+        assert result == "unknown"
+
+    def test_unknown_for_whitespace_string(self):
+        result = _classify_ssh_key_material("   \n  ")
+        assert result == "unknown"
+
+    def test_unknown_for_gibberish(self):
+        result = _classify_ssh_key_material("not a valid ssh key")
+        assert result == "unknown"
+
+    def test_unknown_for_unsupported_key_type(self):
+        result = _classify_ssh_key_material("ssh-nonsense AAAABogus...")
+        assert result == "unknown"
+
+    @pytest.mark.parametrize("raw,expected", [
+        ("ssh-rsa AAAAB3Nza... user@host", "public_key"),
+        ("ssh-ed25519 AAAAC3... john@laptop", "public_key"),
+        ("ecdsa-sha2-nistp256 AAAAE2Vj... me@box", "public_key"),
+        ("sk-ssh-ed25519@openssh.com AAAAGn...", "public_key"),
+        ("ssh-ed25519-cert-v01@openssh.com AAAAB3Nza cert for user", "certificate"),
+        (
+            "-----BEGIN OPENSSH PRIVATE KEY-----\n"
+            "abcdefghijklmnopqrstuvwxyz\n"
+            "-----END OPENSSH PRIVATE KEY-----",
+            "private_key",
+        ),
+        ("", "unknown"),
+        ("totally random garbage here", "unknown"),
+    ])
+    def test_parametrized_variants(self, raw, expected):
+        assert _classify_ssh_key_material(raw) == expected
+
+    def test_certificate_with_leading_whitespace(self):
+        raw = "  ssh-ed25519-cert-v01@openssh.com AAAAB3Nza extra words"
+        assert _classify_ssh_key_material(raw) == "certificate"
\ No newline at end of file
diff --git a/tests/api/v1/ssh/test_dept_cert_policy.py b/tests/api/v1/ssh/test_dept_cert_policy.py
new file mode 100644
index 0000000..0b90805
--- /dev/null
+++ b/tests/api/v1/ssh/test_dept_cert_policy.py
@@ -0,0 +1,275 @@
+import pytest
+from datetime import datetime, timezone
+from gatehouse_app.extensions import db
+from gatehouse_app.models.organization.department import (
+    Department,
+    DepartmentMembership,
+)
+from gatehouse_app.models.organization.department_cert_policy import DepartmentCertPolicy
+from gatehouse_app.api.v1.ssh._helpers import _get_merged_dept_cert_policy
+
+
+class TestDeptCertPolicy:
+    def test_no_departments_returns_none(self, app, test_user):
+        with app.app_context():
+            result = _get_merged_dept_cert_policy(test_user)
+            assert result is None
+
+    def test_department_without_policy_returns_none(self, app, test_user, test_org):
+        with app.app_context():
+            dept = Department(
+                organization_id=test_org,
+                name="No Policy Dept",
+            )
+            db.session.add(dept)
+            db.session.commit()
+
+            membership = DepartmentMembership(
+                user_id=test_user,
+                department_id=dept.id,
+            )
+            db.session.add(membership)
+            db.session.commit()
+
+            result = _get_merged_dept_cert_policy(test_user)
+            assert result is None
+
+    def test_single_department_policy(self, app, test_user, test_org):
+        with app.app_context():
+            dept = Department(
+                organization_id=test_org,
+                name="Engineering",
+            )
+            db.session.add(dept)
+            db.session.commit()
+
+            membership = DepartmentMembership(
+                user_id=test_user,
+                department_id=dept.id,
+            )
+            db.session.add(membership)
+            db.session.commit()
+
+            policy = DepartmentCertPolicy(
+                department_id=dept.id,
+                allow_user_expiry=True,
+                default_expiry_hours=4,
+                max_expiry_hours=48,
+                allowed_extensions=["permit-pty", "permit-agent-forwarding"],
+            )
+            db.session.add(policy)
+            db.session.commit()
+
+            result = _get_merged_dept_cert_policy(test_user)
+            assert result is not None
+            assert result["allow_user_expiry"] is True
+            assert result["default_expiry_hours"] == 4
+            assert result["max_expiry_hours"] == 48
+            assert set(result["extensions"]) == {"permit-pty", "permit-agent-forwarding"}
+
+    def test_both_departments_same_policies(self, app, test_user, test_org):
+        with app.app_context():
+            dept1 = Department(
+                organization_id=test_org,
+                name="Engineering",
+            )
+            dept2 = Department(
+                organization_id=test_org,
+                name="SRE",
+            )
+            db.session.add_all([dept1, dept2])
+            db.session.commit()
+
+            member1 = DepartmentMembership(user_id=test_user, department_id=dept1.id)
+            member2 = DepartmentMembership(user_id=test_user, department_id=dept2.id)
+            db.session.add_all([member1, member2])
+            db.session.commit()
+
+            policy1 = DepartmentCertPolicy(
+                department_id=dept1.id,
+                allow_user_expiry=True,
+                default_expiry_hours=4,
+                max_expiry_hours=48,
+                allowed_extensions=["permit-pty", "permit-agent-forwarding"],
+            )
+            policy2 = DepartmentCertPolicy(
+                department_id=dept2.id,
+                allow_user_expiry=True,
+                default_expiry_hours=4,
+                max_expiry_hours=48,
+                allowed_extensions=["permit-pty", "permit-agent-forwarding"],
+            )
+            db.session.add_all([policy1, policy2])
+            db.session.commit()
+
+            result = _get_merged_dept_cert_policy(test_user)
+            assert result["allow_user_expiry"] is True
+            assert result["default_expiry_hours"] == 4
+            assert result["max_expiry_hours"] == 48
+
+    def test_merges_min_expiry_across_departments(self, app, test_user, test_org):
+        with app.app_context():
+            dept1 = Department(
+                organization_id=test_org,
+                name="Engineering",
+            )
+            dept2 = Department(
+                organization_id=test_org,
+                name="SRE",
+            )
+            db.session.add_all([dept1, dept2])
+            db.session.commit()
+
+            member1 = DepartmentMembership(user_id=test_user, department_id=dept1.id)
+            member2 = DepartmentMembership(user_id=test_user, department_id=dept2.id)
+            db.session.add_all([member1, member2])
+            db.session.commit()
+
+            policy1 = DepartmentCertPolicy(
+                department_id=dept1.id,
+                allow_user_expiry=True,
+                default_expiry_hours=24,
+                max_expiry_hours=720,
+            )
+            policy2 = DepartmentCertPolicy(
+                department_id=dept2.id,
+                allow_user_expiry=True,
+                default_expiry_hours=1,
+                max_expiry_hours=72,
+            )
+            db.session.add_all([policy1, policy2])
+            db.session.commit()
+
+            result = _get_merged_dept_cert_policy(test_user)
+            assert result["default_expiry_hours"] == 1
+            assert result["max_expiry_hours"] == 72
+
+    def test_extends_intersection_across_departments(self, app, test_user, test_org):
+        with app.app_context():
+            dept1 = Department(
+                organization_id=test_org,
+                name="Engineering",
+            )
+            dept2 = Department(
+                organization_id=test_org,
+                name="SRE",
+            )
+            db.session.add_all([dept1, dept2])
+            db.session.commit()
+
+            member1 = DepartmentMembership(user_id=test_user, department_id=dept1.id)
+            member2 = DepartmentMembership(user_id=test_user, department_id=dept2.id)
+            db.session.add_all([member1, member2])
+            db.session.commit()
+
+            policy1 = DepartmentCertPolicy(
+                department_id=dept1.id,
+                allowed_extensions=["permit-pty", "permit-agent-forwarding"],
+            )
+            policy2 = DepartmentCertPolicy(
+                department_id=dept2.id,
+                allowed_extensions=["permit-pty", "permit-port-forwarding"],
+            )
+            db.session.add_all([policy1, policy2])
+            db.session.commit()
+
+            result = _get_merged_dept_cert_policy(test_user)
+            assert set(result["extensions"]) == {"permit-pty"}
+
+    def test_any_false_user_expiry_means_overall_false(
+        self, app, test_user, test_org
+    ):
+        with app.app_context():
+            dept1 = Department(
+                organization_id=test_org,
+                name="Engineering",
+            )
+            dept2 = Department(
+                organization_id=test_org,
+                name="SRE",
+            )
+            db.session.add_all([dept1, dept2])
+            db.session.commit()
+
+            member1 = DepartmentMembership(user_id=test_user, department_id=dept1.id)
+            member2 = DepartmentMembership(user_id=test_user, department_id=dept2.id)
+            db.session.add_all([member1, member2])
+            db.session.commit()
+
+            policy1 = DepartmentCertPolicy(
+                department_id=dept1.id,
+                allow_user_expiry=True,
+            )
+            policy2 = DepartmentCertPolicy(
+                department_id=dept2.id,
+                allow_user_expiry=False,
+            )
+            db.session.add_all([policy1, policy2])
+            db.session.commit()
+
+            result = _get_merged_dept_cert_policy(test_user)
+            assert result["allow_user_expiry"] is False
+
+    def test_deleted_department_filtered(self, app, test_user, test_org):
+        with app.app_context():
+            active_dept = Department(
+                organization_id=test_org,
+                name="Active Dept",
+            )
+            deleted_dept = Department(
+                organization_id=test_org,
+                name="Deleted Dept",
+                deleted_at=datetime.now(timezone.utc),
+            )
+            db.session.add_all([active_dept, deleted_dept])
+            db.session.commit()
+
+            active_member = DepartmentMembership(
+                user_id=test_user, department_id=active_dept.id
+            )
+            deleted_member = DepartmentMembership(
+                user_id=test_user,
+                department_id=deleted_dept.id,
+                deleted_at=datetime.now(timezone.utc),
+            )
+            db.session.add_all([active_member, deleted_member])
+            db.session.commit()
+
+            policy = DepartmentCertPolicy(
+                department_id=active_dept.id,
+                allow_user_expiry=True,
+                default_expiry_hours=12,
+                max_expiry_hours=96,
+            )
+            db.session.add(policy)
+            db.session.commit()
+
+            result = _get_merged_dept_cert_policy(test_user)
+            assert result is not None
+            assert result["default_expiry_hours"] == 12
+
+    def test_single_department_no_extensions(self, app, test_user, test_org):
+        with app.app_context():
+            dept = Department(
+                organization_id=test_org,
+                name="Minimal Dept",
+            )
+            db.session.add(dept)
+            db.session.commit()
+
+            membership = DepartmentMembership(
+                user_id=test_user, department_id=dept.id
+            )
+            db.session.add(membership)
+            db.session.commit()
+
+            policy = DepartmentCertPolicy(
+                department_id=dept.id,
+                allowed_extensions=[],
+            )
+            db.session.add(policy)
+            db.session.commit()
+
+            result = _get_merged_dept_cert_policy(test_user)
+            assert result is not None
+            assert result["extensions"] == []
\ No newline at end of file
diff --git a/tests/api/v1/ssh/test_org_ca_for_user.py b/tests/api/v1/ssh/test_org_ca_for_user.py
new file mode 100644
index 0000000..2e9832e
--- /dev/null
+++ b/tests/api/v1/ssh/test_org_ca_for_user.py
@@ -0,0 +1,118 @@
+import pytest
+from uuid import uuid4
+from datetime import datetime, timezone
+from gatehouse_app.extensions import db
+from gatehouse_app.models.user.user import User
+from gatehouse_app.models.organization.organization import Organization
+from gatehouse_app.models.organization.organization_member import OrganizationMember
+from gatehouse_app.models.ssh_ca.ca import CA, CaType, KeyType
+from gatehouse_app.api.v1.ssh._helpers import _get_org_ca_for_user
+from gatehouse_app.utils.constants import OrganizationRole
+
+
+class TestOrgCAForUser:
+    def test_organization_id_param_overrides_membership(self, app, test_user, test_org, test_ca, test_membership):
+        with app.app_context():
+            org2 = Organization(name="Org 2", slug="org-2")
+            db.session.add(org2)
+            db.session.commit()
+
+            ca2 = CA(
+                organization_id=org2.id,
+                name="Org 2 CA",
+                ca_type=CaType.USER,
+                key_type=KeyType.ED25519,
+                private_key="key2",
+                public_key="pubkey2",
+                fingerprint="sha256:org2...",
+                is_active=True,
+            )
+            db.session.add(ca2)
+            db.session.commit()
+
+            user = db.session.get(User, test_user)
+            result = _get_org_ca_for_user(user, ca_type="user", organization_id=test_org)
+            assert result is not None
+            assert result.organization_id == test_org
+
+    def test_multiple_orgs_returns_ca(self, app, test_user, test_org, test_ca, test_membership):
+        with app.app_context():
+            org2 = Organization(name="Org 2", slug="org-2")
+            db.session.add(org2)
+            db.session.commit()
+
+            user = db.session.get(User, test_user)
+            member2 = OrganizationMember(
+                user_id=test_user, organization_id=org2.id, role=OrganizationRole.MEMBER
+            )
+            db.session.add(member2)
+            db.session.commit()
+
+            result = _get_org_ca_for_user(user, ca_type="user")
+            assert result is not None
+
+    def test_user_with_no_memberships_returns_none(self, app):
+        with app.app_context():
+            user = User(email="lonely@test.com", full_name="Lonely User")
+            db.session.add(user)
+            db.session.commit()
+
+            result = _get_org_ca_for_user(user, ca_type="user")
+            assert result is None
+
+    def test_inactive_ca_not_returned(self, app, test_user, test_org, test_membership):
+        with app.app_context():
+            ca = CA(
+                organization_id=test_org,
+                name="Inactive CA",
+                ca_type=CaType.USER,
+                key_type=KeyType.ED25519,
+                private_key="key",
+                public_key="pubkey",
+                fingerprint="sha256:inactive123...",
+                is_active=False,
+            )
+            db.session.add(ca)
+            db.session.commit()
+
+            user = db.session.get(User, test_user)
+            result = _get_org_ca_for_user(user, ca_type="user")
+            assert result is None
+
+    def test_host_ca_not_returned_when_user_requested(self, app, test_user, test_org, test_membership):
+        with app.app_context():
+            ca = CA(
+                organization_id=test_org,
+                name="Host CA",
+                ca_type=CaType.HOST,
+                key_type=KeyType.ED25519,
+                private_key="key",
+                public_key="pubkey",
+                fingerprint="sha256:host123...",
+                is_active=True,
+            )
+            db.session.add(ca)
+            db.session.commit()
+
+            user = db.session.get(User, test_user)
+            result = _get_org_ca_for_user(user, ca_type="user")
+            assert result is None
+
+    def test_user_ca_not_returned_when_host_requested(self, app, test_user, test_org, test_membership):
+        with app.app_context():
+            ca = CA(
+                organization_id=test_org,
+                name="User CA",
+                ca_type=CaType.USER,
+                key_type=KeyType.ED25519,
+                private_key="key",
+                public_key="pubkey",
+                fingerprint="sha256:useronly...",
+                is_active=True,
+            )
+            db.session.add(ca)
+            db.session.commit()
+
+            user = db.session.get(User, test_user)
+            result = _get_org_ca_for_user(user, ca_type="host")
+            assert result is None
\ No newline at end of file
diff --git a/tests/api/v1/ssh/test_persist_certificate.py b/tests/api/v1/ssh/test_persist_certificate.py
new file mode 100644
index 0000000..7c9122e
--- /dev/null
+++ b/tests/api/v1/ssh/test_persist_certificate.py
@@ -0,0 +1,180 @@
+import pytest
+from uuid import uuid4
+from datetime import datetime, timezone, timedelta
+from gatehouse_app.extensions import db
+from gatehouse_app.models.user.user import User
+from gatehouse_app.models.ssh_ca.ca import CA, CaType, KeyType, CertType
+from gatehouse_app.models.ssh_ca.ssh_key import SSHKey
+from gatehouse_app.models.ssh_ca.ssh_certificate import SSHCertificate, CertificateStatus
+from gatehouse_app.services.ssh_ca_signing_service import SSHCertificateSigningResponse
+from gatehouse_app.api.v1.ssh._helpers import _persist_certificate
+
+
+class TestPersistCertificate:
+    def test_persists_valid_certificate(self, app, test_user, test_org):
+        with app.app_context():
+            ca = CA(
+                organization_id=test_org,
+                name="Signing CA",
+                ca_type=CaType.USER,
+                key_type=KeyType.ED25519,
+                private_key="enc_priv",
+                public_key="ssh-ed25519 AAAAB3Nza...",
+                fingerprint="sha256:abc123...",
+                is_active=True,
+            )
+            db.session.add(ca)
+            db.session.commit()
+
+            ssh_key = SSHKey(
+                user_id=test_user,
+                payload="ssh-ed25519 AAAAB3NzaC1lZDI1NTE5AAAAIKeyData comment",
+                fingerprint="sha256:keyfp123...",
+            )
+            db.session.add(ssh_key)
+            db.session.commit()
+
+            now = datetime.now(timezone.utc)
+            later = now + timedelta(hours=24)
+            response = SSHCertificateSigningResponse(
+                certificate="ssh-ed25519-cert-v01@openssh.com AAAACertData...",
+                serial="123456",
+                valid_after=now,
+                valid_before=later,
+                principals=["eng-prod"],
+            )
+
+            result = _persist_certificate(
+                user_id=test_user,
+                ssh_key_id=ssh_key.id,
+                ca=ca,
+                signing_response=response,
+                request_ip="10.0.0.1",
+                cert_type_str="user",
+                cert_identity="user@example.com",
+            )
+
+            assert result is not None
+            assert result.ca_id == ca.id
+            assert result.user_id == test_user
+            assert result.ssh_key_id == ssh_key.id
+            assert result.cert_type == CertType.USER
+            assert result.certificate == response.certificate
+            assert result.serial == response.serial
+            assert result.valid_after.replace(tzinfo=None) == now.replace(tzinfo=None)
+            assert result.valid_before.replace(tzinfo=None) == later.replace(tzinfo=None)
+            assert result.request_ip == "10.0.0.1"
+            assert result.key_id == "user@example.com"
+            assert sorted(result.principals) == ["eng-prod"]
+            assert result.revoked is False
+            assert result.status == CertificateStatus.ISSUED
+
+    def test_none_ca_returns_none(self, app, test_user):
+        with app.app_context():
+            now = datetime.now(timezone.utc)
+            response = SSHCertificateSigningResponse(
+                certificate="cert-data",
+                serial="1",
+                valid_after=now,
+                valid_before=now + timedelta(hours=1),
+            )
+            result = _persist_certificate(test_user, "keyid", None, response)
+            assert result is None
+
+    def test_invalid_cert_type_str_falls_back_to_user(self, app, test_user, test_org):
+        with app.app_context():
+            ca = CA(
+                organization_id=test_org,
+                name="Signing CA",
+                ca_type=CaType.USER,
+                key_type=KeyType.ED25519,
+                private_key="enc_priv",
+                public_key="ssh-ed25519 AAAAB3Nza...",
+                fingerprint="sha256:fallback123...",
+                is_active=True,
+            )
+            db.session.add(ca)
+            db.session.commit()
+
+            now = datetime.now(timezone.utc)
+            response = SSHCertificateSigningResponse(
+                certificate="cert-data",
+                serial="1",
+                valid_after=now,
+                valid_before=now + timedelta(hours=1),
+            )
+            result = _persist_certificate(
+                user_id=test_user,
+                ssh_key_id=None,
+                ca=ca,
+                signing_response=response,
+                cert_type_str="invalid_type",
+            )
+
+            assert result is not None
+            assert result.cert_type == CertType.USER
+
+    def test_none_ssh_key_id_defaults_to_host_cert_key_id(self, app, test_user, test_org):
+        with app.app_context():
+            ca = CA(
+                organization_id=test_org,
+                name="Host CA",
+                ca_type=CaType.HOST,
+                key_type=KeyType.ED25519,
+                private_key="enc_priv",
+                public_key="ssh-ed25519 AAAAB3Nza...",
+                fingerprint="sha256:hostca123...",
+                is_active=True,
+            )
+            db.session.add(ca)
+            db.session.commit()
+
+            now = datetime.now(timezone.utc)
+            response = SSHCertificateSigningResponse(
+                certificate="cert-data",
+                serial="1",
+                valid_after=now,
+                valid_before=now + timedelta(hours=1),
+            )
+            result = _persist_certificate(
+                user_id=test_user,
+                ssh_key_id=None,
+                ca=ca,
+                signing_response=response,
+            )
+
+            assert result is not None
+            assert result.key_id == "host-cert"
+
+    def test_request_ip_stored(self, app, test_user, test_org):
+        with app.app_context():
+            ca = CA(
+                organization_id=test_org,
+                name="Signing CA",
+                ca_type=CaType.USER,
+                key_type=KeyType.ED25519,
+                private_key="enc_priv",
+                public_key="ssh-ed25519 AAAAB3Nza...",
+                fingerprint="sha256:ip...",
+                is_active=True,
+            )
+            db.session.add(ca)
+            db.session.commit()
+
+            now = datetime.now(timezone.utc)
+            response = SSHCertificateSigningResponse(
+                certificate="cert-data",
+                serial="1",
+                valid_after=now,
+                valid_before=now + timedelta(hours=1),
+            )
+            result = _persist_certificate(
+                user_id=test_user,
+                ssh_key_id=None,
+                ca=ca,
+                signing_response=response,
+                request_ip="192.168.1.100",
+            )
+
+            assert result is not None
+            assert result.request_ip == "192.168.1.100"
\ No newline at end of file
diff --git a/tests/api/v1/ssh/test_ssh_key_service.py b/tests/api/v1/ssh/test_ssh_key_service.py
new file mode 100644
index 0000000..a9e41f2
--- /dev/null
+++ b/tests/api/v1/ssh/test_ssh_key_service.py
@@ -0,0 +1,78 @@
+import pytest
+from datetime import datetime, timezone
+from gatehouse_app.extensions import db
+from gatehouse_app.models.user.user import User
+from gatehouse_app.models.ssh_ca.ssh_key import SSHKey
+from gatehouse_app.services.ssh_key_service import SSHKeyService
+from gatehouse_app.exceptions import UserNotFoundError, SSHKeyError
+
+
+VALID_PUBLIC_KEY = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIKL7YKAg+CgUvk/oNmU1fO24fLf5O5LayGH/EgORbz06"
+
+
+class TestSSHKeyServiceAdd:
+
+    def test_add_new_key_returns_true(self, app, test_user):
+        with app.app_context():
+            service = SSHKeyService()
+            key, is_new = service.add_ssh_key(test_user, VALID_PUBLIC_KEY, "My laptop")
+            assert is_new is True
+            assert key.user_id == test_user
+            assert key.payload == VALID_PUBLIC_KEY
+            assert key.description == "My laptop"
+            assert key.verified is False
+            assert key.fingerprint is not None
+            assert key.key_type is not None
+
+    def test_add_duplicate_returns_existing(self, app, test_user):
+        with app.app_context():
+            service = SSHKeyService()
+            key1, _ = service.add_ssh_key(test_user, VALID_PUBLIC_KEY)
+            key2, is_new = service.add_ssh_key(test_user, VALID_PUBLIC_KEY)
+            assert is_new is False
+            assert key2.id == key1.id
+
+    def test_add_restores_soft_deleted_key(self, app, test_user):
+        with app.app_context():
+            service = SSHKeyService()
+            key1, _ = service.add_ssh_key(test_user, VALID_PUBLIC_KEY, "Original")
+
+            # Soft-delete the key
+            key1.deleted_at = datetime.now(timezone.utc)
+            db.session.commit()
+
+            # Re-add same key
+            key2, is_new = service.add_ssh_key(test_user, VALID_PUBLIC_KEY, "Restored")
+            assert is_new is False
+            assert key2.id == key1.id
+            assert key2.deleted_at is None
+            assert key2.description == "Restored"
+            assert key2.verified is False
+            assert key2.verified_at is None
+
+    def test_add_with_description(self, app, test_user):
+        with app.app_context():
+            service = SSHKeyService()
+            key, is_new = service.add_ssh_key(test_user, VALID_PUBLIC_KEY, "Work laptop")
+            assert is_new is True
+            assert key.description == "Work laptop"
+
+    def test_user_not_found_raises(self, app):
+        with app.app_context():
+            service = SSHKeyService()
+            with pytest.raises(UserNotFoundError):
+                service.add_ssh_key("nonexistent-user-id", VALID_PUBLIC_KEY)
+
+    def test_invalid_key_format_raises(self, app, test_user):
+        with app.app_context():
+            service = SSHKeyService()
+            with pytest.raises(SSHKeyError):
+                service.add_ssh_key(test_user, "not-a-valid-key")
+
+    def test_idempotent_second_call_no_error(self, app, test_user):
+        with app.app_context():
+            service = SSHKeyService()
+            service.add_ssh_key(test_user, VALID_PUBLIC_KEY)
+            key2, is_new = service.add_ssh_key(test_user, VALID_PUBLIC_KEY)
+            assert is_new is False
+            assert key2 is not None
diff --git a/tests/api/v1/test_cert_signing_request.py b/tests/api/v1/test_cert_signing_request.py
new file mode 100644
index 0000000..ffee864
--- /dev/null
+++ b/tests/api/v1/test_cert_signing_request.py
@@ -0,0 +1,148 @@
+import pytest
+from gatehouse_app.services.ssh_ca_signing_service import SSHCertificateSigningRequest
+
+
+VALID_PUBLIC_KEY = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIKL7YKAg+CgUvk/oNmU1fO24fLf5O5LayGH/EgORbz06"
+
+
+class TestCertSigningRequestValidate:
+
+    @pytest.fixture(autouse=True)
+    def patch_config(self, monkeypatch):
+        from gatehouse_app.config.ssh_ca_config import SSHCAConfig
+
+        class TestConfig(SSHCAConfig):
+            def get_int(self, key, default=0):
+                values = {
+                    "max_cert_validity_hours": 720,
+                    "max_principals_per_cert": 256,
+                    "max_key_id_length": 255,
+                }
+                return values.get(key, default)
+
+        monkeypatch.setattr(
+            "gatehouse_app.config.ssh_ca_config.get_ssh_ca_config",
+            lambda: TestConfig(),
+        )
+
+    def test_valid_request_no_errors(self):
+        req = SSHCertificateSigningRequest(
+            ssh_public_key=VALID_PUBLIC_KEY,
+            principals=["eng-prod"],
+            key_id="user@example.com",
+        )
+        errors = req.validate()
+        assert errors == []
+
+    def test_valid_host_cert_no_errors(self):
+        req = SSHCertificateSigningRequest(
+            ssh_public_key=VALID_PUBLIC_KEY,
+            principals=["host1.example.com"],
+            key_id="host-identity",
+            cert_type="host",
+        )
+        errors = req.validate()
+        assert errors == []
+
+    def test_invalid_cert_type(self):
+        req = SSHCertificateSigningRequest(
+            ssh_public_key=VALID_PUBLIC_KEY,
+            principals=["eng-prod"],
+            key_id="user@example.com",
+            cert_type="invalid",
+        )
+        errors = req.validate()
+        assert any("cert_type" in e.lower() for e in errors)
+
+    def test_missing_public_key(self):
+        req = SSHCertificateSigningRequest(
+            ssh_public_key="",
+            principals=["eng-prod"],
+            key_id="user@example.com",
+        )
+        errors = req.validate()
+        assert any("public key" in e.lower() for e in errors)
+
+    def test_malformed_public_key(self):
+        req = SSHCertificateSigningRequest(
+            ssh_public_key="not-a-key",
+            principals=["eng-prod"],
+            key_id="user@example.com",
+        )
+        errors = req.validate()
+        assert any("public key" in e.lower() for e in errors)
+
+    def test_no_principals(self):
+        req = SSHCertificateSigningRequest(
+            ssh_public_key=VALID_PUBLIC_KEY,
+            principals=[],
+            key_id="user@example.com",
+        )
+        errors = req.validate()
+        assert any("principal" in e.lower() for e in errors)
+
+    def test_too_many_principals(self):
+        req = SSHCertificateSigningRequest(
+            ssh_public_key=VALID_PUBLIC_KEY,
+            principals=[f"p{i}" for i in range(300)],
+            key_id="user@example.com",
+        )
+        errors = req.validate()
+        assert any("too many" in e.lower() for e in errors)
+
+    def test_missing_key_id(self):
+        req = SSHCertificateSigningRequest(
+            ssh_public_key=VALID_PUBLIC_KEY,
+            principals=["eng-prod"],
+            key_id="",
+        )
+        errors = req.validate()
+        assert any("key_id" in e.lower() for e in errors)
+
+    def test_key_id_too_short(self):
+        req = SSHCertificateSigningRequest(
+            ssh_public_key=VALID_PUBLIC_KEY,
+            principals=["eng-prod"],
+            key_id="ab",
+        )
+        errors = req.validate()
+        assert any("key_id" in e.lower() for e in errors)
+
+    def test_key_id_exceeds_max_length(self):
+        req = SSHCertificateSigningRequest(
+            ssh_public_key=VALID_PUBLIC_KEY,
+            principals=["eng-prod"],
+            key_id="x" * 300,
+        )
+        errors = req.validate()
+        assert any("key_id" in e.lower() for e in errors)
+
+    def test_non_positive_expiry(self):
+        req = SSHCertificateSigningRequest(
+            ssh_public_key=VALID_PUBLIC_KEY,
+            principals=["eng-prod"],
+            key_id="user@example.com",
+            expiry_hours=0,
+        )
+        errors = req.validate()
+        assert any("expiry" in e.lower() for e in errors)
+
+    def test_expiry_exceeds_max(self):
+        req = SSHCertificateSigningRequest(
+            ssh_public_key=VALID_PUBLIC_KEY,
+            principals=["eng-prod"],
+            key_id="user@example.com",
+            expiry_hours=99999,
+        )
+        errors = req.validate()
+        assert any("expiry" in e.lower() for e in errors)
+
+    def test_none_expiry_is_ok(self):
+        req = SSHCertificateSigningRequest(
+            ssh_public_key=VALID_PUBLIC_KEY,
+            principals=["eng-prod"],
+            key_id="user@example.com",
+            expiry_hours=None,
+        )
+        errors = req.validate()
+        assert errors == []
diff --git a/tests/api/v1/test_superadmin_schemas.py b/tests/api/v1/test_superadmin_schemas.py
new file mode 100644
index 0000000..36b7f88
--- /dev/null
+++ b/tests/api/v1/test_superadmin_schemas.py
@@ -0,0 +1,77 @@
+from gatehouse_app.api.v1.superadmin.organizations import (
+    ListOrganizationsSchema,
+    UpdateOrganizationSchema,
+)
+
+
+class TestListOrganizationsSchema:
+    def test_defaults_when_empty(self):
+        result = ListOrganizationsSchema.load({})
+        assert result["page"] == 1
+        assert result["per_page"] == 20
+        assert result["search"] is None
+        assert result["status"] is None
+        assert result["plan_slug"] is None
+
+    def test_normal_pagination(self):
+        result = ListOrganizationsSchema.load({"page": 3, "per_page": 10})
+        assert result["page"] == 3
+        assert result["per_page"] == 10
+
+    def test_page_zero_clamped_to_one(self):
+        result = ListOrganizationsSchema.load({"page": 0})
+        assert result["page"] == 1
+
+    def test_negative_per_page_clamped_to_one(self):
+        result = ListOrganizationsSchema.load({"per_page": -5})
+        assert result["per_page"] == 1
+
+    def test_per_page_exceeds_max_clamped_to_100(self):
+        result = ListOrganizationsSchema.load({"per_page": 200})
+        assert result["per_page"] == 100
+
+    def test_non_integer_values_fallback(self):
+        result = ListOrganizationsSchema.load({"page": "abc", "per_page": "xyz"})
+        assert result["page"] == 1
+        assert result["per_page"] == 20
+
+    def test_search_passthrough(self):
+        result = ListOrganizationsSchema.load({"search": "acme"})
+        assert result["search"] == "acme"
+
+    def test_status_passthrough(self):
+        result = ListOrganizationsSchema.load({"status": "active"})
+        assert result["status"] == "active"
+
+    def test_plan_slug_passthrough(self):
+        result = ListOrganizationsSchema.load({"plan_slug": "pro"})
+        assert result["plan_slug"] == "pro"
+
+
+class TestUpdateOrganizationSchema:
+    def test_all_fields(self):
+        result = UpdateOrganizationSchema.load({
+            "name": "New Name",
+            "description": "New Description",
+            "is_active": True,
+        })
+        assert result == {
+            "name": "New Name",
+            "description": "New Description",
+            "is_active": True,
+        }
+
+    def test_empty_dict(self):
+        result = UpdateOrganizationSchema.load({})
+        assert result == {}
+
+    def test_partial_data(self):
+        result = UpdateOrganizationSchema.load({"name": "Renamed Only"})
+        assert result == {"name": "Renamed Only"}
+
+    def test_is_active_coerced_to_bool(self):
+        result = UpdateOrganizationSchema.load({"is_active": "truthy"})
+        assert result["is_active"] is True
+
+        result = UpdateOrganizationSchema.load({"is_active": ""})
+        assert result["is_active"] is False