diff --git a/CHANGELOG.md b/CHANGELOG.md
index f92231a73..090d67b4a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -22,6 +22,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - Clarify UDF documentation on required function type annotations. ([#757](https://github.com/Open-EO/openeo-python-client/issues/757))
+- `OidcProviderInfo` no longer drops requested OIDC scopes (including the "offline_access" scope used for refresh tokens) that are not listed in the provider's `scopes_supported` discovery field, which made it impossible to authenticate against such providers. ([#930](https://github.com/Open-EO/openeo-python-client/issues/930))
 
 ## [0.51.0] - 2026-07-16
 
diff --git a/openeo/rest/auth/oidc.py b/openeo/rest/auth/oidc.py
index 5120d5f37..d65abdab1 100644
--- a/openeo/rest/auth/oidc.py
+++ b/openeo/rest/auth/oidc.py
@@ -279,10 +279,12 @@ def __init__(
         except Exception as e:
             raise OidcException(f"Failed to obtain OIDC discovery document from {self.discovery_url!r}: {e!r}") from e
         self.issuer = issuer or self.config["issuer"]
-        # Minimal set of scopes to request
-        self._supported_scopes = self.config.get("scopes_supported", ["openid"])
-        self._scopes = {"openid"}.union(scopes or []).intersection(self._supported_scopes)
-        log.debug(f"Scopes: provider supported {self._supported_scopes} & backend desired {scopes} -> {self._scopes}")
+        # Note: we don't filter requested scopes against the discovery document's
+        # `scopes_supported`: it's only a RECOMMENDED discovery field (RFC 8414 section 2),
+        # and some providers (e.g. Microsoft Entra ID) report a fixed, incomplete list there
+        # regardless of which scopes they actually accept.
+        self._scopes = {"openid"}.union(scopes or [])
+        log.debug(f"Scopes: backend desired {scopes} -> {self._scopes}")
         self.default_clients = default_clients
         self.authorization_parameters = authorization_parameters or {}
 
@@ -301,12 +303,12 @@ def get_scopes_string(self, request_refresh_token: bool = False) -> str:
         """
         Build "scope" string for authentication request.
 
-        :param request_refresh_token: include "offline_access" scope (if supported),
+        :param request_refresh_token: include "offline_access" scope,
             which some OIDC providers require in order to return refresh token
         :return: space separated scope listing as single string
         """
         scopes = self._scopes
-        if request_refresh_token and "offline_access" in self._supported_scopes:
+        if request_refresh_token:
             scopes = scopes | {"offline_access"}
         log.debug("Using scopes: {s}".format(s=scopes))
         return " ".join(sorted(scopes))
diff --git a/tests/rest/auth/test_cli.py b/tests/rest/auth/test_cli.py
index 7870ca09d..32950ea7a 100644
--- a/tests/rest/auth/test_cli.py
+++ b/tests/rest/auth/test_cli.py
@@ -362,7 +362,7 @@ def test_oidc_auth_device_flow(auth_config, refresh_token_store, requests_mock,
         expected_grant_type="urn:ietf:params:oauth:grant-type:device_code",
         expected_client_id=client_id,
         oidc_issuer="https://authit.test",
-        expected_fields={"scope": "openid", "client_secret": client_secret},
+        expected_fields={"scope": "offline_access openid", "client_secret": client_secret},
         state={"device_code_callback_timeline": ["authorization_pending", "great success"]},
         scopes_supported=["openid"],
     )
@@ -421,7 +421,7 @@ def test_oidc_auth_device_flow_default_client(
         expected_grant_type="urn:ietf:params:oauth:grant-type:device_code",
         expected_client_id=default_client_id,
         oidc_issuer="https://authit.test",
-        expected_fields={"scope": "openid", "code_verifier": True, "code_challenge": True},
+        expected_fields={"scope": "offline_access openid", "code_verifier": True, "code_challenge": True},
         state={"device_code_callback_timeline": ["authorization_pending", "great success"]},
         scopes_supported=["openid"],
     )
@@ -479,7 +479,7 @@ def test_oidc_auth_device_flow_no_config_all_defaults(
         expected_grant_type="urn:ietf:params:oauth:grant-type:device_code",
         expected_client_id=default_client_id,
         oidc_issuer="https://authit.test",
-        expected_fields={"scope": "openid", "code_verifier": True, "code_challenge": True},
+        expected_fields={"scope": "offline_access openid", "code_verifier": True, "code_challenge": True},
         state={"device_code_callback_timeline": ["authorization_pending", "great success"]},
         scopes_supported=["openid"],
     )
@@ -529,7 +529,7 @@ def test_oidc_auth_auth_code_flow(auth_config, refresh_token_store, requests_moc
         requests_mock=requests_mock,
         expected_grant_type="authorization_code",
         expected_client_id=client_id,
-        expected_fields={"scope": "openid"},
+        expected_fields={"scope": "offline_access openid"},
         oidc_issuer="https://authit.test",
         scopes_supported=["openid"],
     )
diff --git a/tests/rest/auth/test_oidc.py b/tests/rest/auth/test_oidc.py
index 3d0cc73dd..6d49c07e0 100644
--- a/tests/rest/auth/test_oidc.py
+++ b/tests/rest/auth/test_oidc.py
@@ -148,6 +148,23 @@ def test_provider_info_scopes(requests_mock):
     ).get_scopes_string()
 
 
+def test_provider_info_scopes_not_in_scopes_supported(requests_mock):
+    """
+    Requested scopes should be preserved even when the provider's `scopes_supported`
+    discovery field does not list them (e.g. Microsoft Entra ID, which reports a fixed
+    tenant-wide list there regardless of which custom scopes it actually accepts).
+    https://github.com/Open-EO/openeo-python-client/issues/930
+    """
+    requests_mock.get(
+        "https://authit.test/.well-known/openid-configuration",
+        json={"scopes_supported": ["openid", "profile", "email", "offline_access"]},
+    )
+    provider = OidcProviderInfo(
+        issuer="https://authit.test", scopes=["openid", "profile", "email", "api://client-id/openeo"]
+    )
+    assert provider.get_scopes_string() == "api://client-id/openeo email openid profile"
+
+
 def test_provider_info_default_client_none(requests_mock):
     requests_mock.get("https://authit.test/.well-known/openid-configuration", json={})
     info = OidcProviderInfo(issuer="https://authit.test")
@@ -221,18 +238,23 @@ def test_provider_info_default_client_invalid_grants(requests_mock, caplog):
 
 
 @pytest.mark.parametrize(
-    ["scopes_supported", "expected"], [
-        (["openid", "email"], "openid"),
-        (["openid", "email", "offline_access"], "offline_access openid"),
+    "scopes_supported",
+    [
+        ["openid", "email"],
+        ["openid", "email", "offline_access"],
     ])
-def test_provider_info_get_scopes_string_refresh_token_offline_access(requests_mock, scopes_supported, expected):
+def test_provider_info_get_scopes_string_refresh_token_offline_access(requests_mock, scopes_supported):
+    """
+    "offline_access" should be requested when a refresh token is desired,
+    regardless of whether the provider's `scopes_supported` discovery field lists it.
+    """
     requests_mock.get(
         "https://authit.test/.well-known/openid-configuration",
         json={"scopes_supported": scopes_supported}
     )
     p = OidcProviderInfo(issuer="https://authit.test")
     assert p.get_scopes_string() == "openid"
-    assert p.get_scopes_string(request_refresh_token=True) == expected
+    assert p.get_scopes_string(request_refresh_token=True) == "offline_access openid"
     assert p.get_scopes_string() == "openid"
 
 
diff --git a/tests/rest/test_connection.py b/tests/rest/test_connection.py
index e59d88176..2e1bb10be 100644
--- a/tests/rest/test_connection.py
+++ b/tests/rest/test_connection.py
@@ -988,7 +988,7 @@ def test_authenticate_oidc_authorization_code_100_multiple_success(requests_mock
     [
         (False, ["openid", "email"], "openid"),
         (False, ["openid", "email", "offline_access"], "openid"),
-        (True, ["openid", "email"], "openid"),
+        (True, ["openid", "email"], "offline_access openid"),
         (True, ["openid", "email", "offline_access"], "offline_access openid"),
     ]
 )
@@ -1364,7 +1364,7 @@ def test_authenticate_oidc_resource_owner_password_credentials_client_from_confi
     [
         (False, ["openid", "email"], "openid"),
         (False, ["openid", "email", "offline_access"], "openid"),
-        (True, ["openid", "email"], "openid"),
+        (True, ["openid", "email"], "offline_access openid"),
         (True, ["openid", "email", "offline_access"], "offline_access openid"),
     ]
 )
@@ -1774,9 +1774,7 @@ def test_authenticate_oidc_device_flow_pkce_store_refresh_token(requests_mock, o
         ]
     })
 
-    expected_fields = {
-        "scope": "openid", "code_verifier": True, "code_challenge": True
-    }
+    expected_fields = {"scope": "offline_access openid", "code_verifier": True, "code_challenge": True}
     oidc_issuer = "https://auth.test"
     oidc_mock = OidcMock(
         requests_mock=requests_mock,
@@ -1971,7 +1969,7 @@ def test_authenticate_oidc_auto_no_existing_refresh_token(
         oidc_issuer=issuer,
         expected_fields={
             "refresh_token": "unkn0wn",
-            "scope": "openid",
+            "scope": "offline_access openid",
             "code_verifier": True if expect_pkce else ABSENT,
             "code_challenge": True if expect_pkce else ABSENT,
         }
@@ -2016,7 +2014,7 @@ def test_authenticate_oidc_auto_expired_refresh_token(
         oidc_issuer=issuer,
         expected_fields={
             "refresh_token": "unkn0wn",
-            "scope": "openid",
+            "scope": "offline_access openid",
             "code_verifier": True if expect_pkce else ABSENT,
             "code_challenge": True if expect_pkce else ABSENT,
         }
@@ -2225,7 +2223,7 @@ def test_authenticate_oidc_auto_renew_expired_access_token_initial_device_code(
         expected_client_id=client_id,
         oidc_issuer=oidc_issuer,
         expected_fields={
-            "scope": "openid",
+            "scope": "offline_access openid",
             "code_verifier": True,
             "code_challenge": True,
         },
@@ -2323,7 +2321,7 @@ def test_authenticate_oidc_auto_renew_expired_access_token_invalid_refresh_token
         expected_client_id=client_id,
         oidc_issuer=oidc_issuer,
         expected_fields={
-            "scope": "openid",
+            "scope": "offline_access openid",
             "code_verifier": True,
             "code_challenge": True,
         },
@@ -2664,7 +2662,7 @@ def test_try_access_token_refresh_initial_device_code(
         expected_client_id=client_id,
         oidc_issuer=oidc_issuer,
         expected_fields={
-            "scope": "openid",
+            "scope": "offline_access openid",
             "code_verifier": True,
             "code_challenge": True,
         },
@@ -4931,11 +4929,7 @@ def test_connect_auto_auth_from_config_oidc_device_code(
             },
         )
 
-    expected_fields = {
-        "scope": "openid",
-        "code_verifier": True,
-        "code_challenge": True
-    }
+    expected_fields = {"scope": "offline_access openid", "code_verifier": True, "code_challenge": True}
     oidc_mock = OidcMock(
         requests_mock=requests_mock,
         expected_grant_type="urn:ietf:params:oauth:grant-type:device_code",