diff --git a/pyatlan/errors.py b/pyatlan/errors.py
index efc42d3a3..2a51e279d 100644
--- a/pyatlan/errors.py
+++ b/pyatlan/errors.py
@@ -689,6 +689,13 @@ class ErrorCode(Enum):
         "Ensure the file path does not point to a blocked location (system files, credential directories, or paths defined in PYATLAN_UPLOAD_FILE_BLOCKED_PATHS).",
         InvalidRequestError,
     )
+    INVALID_CONNECTION_QN = (
+        400,
+        "ATLAN-PYTHON-400-079",
+        "Invalid connectorType slug '{0}' for connection qualifiedName: must match pattern '^[a-z0-9-]+$' (lower-case alphanumerics and hyphens only).",
+        "Replace any underscores with hyphens (e.g. 'dev_cmdr' -> 'dev-cmdr'). Underscores, dots, uppercase letters, whitespace, and other characters are not permitted because the Atlan platform's asset-import path rejects them at ingestion time, leaving phantom Connection rows in Atlas. Mirrors the Java SDK constraint (atlan-java ErrorCode.INVALID_CONNECTION_QN).",
+        InvalidRequestError,
+    )
     AUTHENTICATION_PASSTHROUGH = (
         401,
         "ATLAN-PYTHON-401-000",
diff --git a/pyatlan/model/assets/connection.py b/pyatlan/model/assets/connection.py
index c4969a01d..334b1e33e 100644
--- a/pyatlan/model/assets/connection.py
+++ b/pyatlan/model/assets/connection.py
@@ -4,12 +4,14 @@
 
 from __future__ import annotations
 
+import re
 from datetime import datetime
 from typing import TYPE_CHECKING, ClassVar, Dict, List, Optional, Set
 from warnings import warn
 
 from pydantic.v1 import Field, validator
 
+from pyatlan.errors import ErrorCode
 from pyatlan.model.enums import (
     AtlanConnectorType,
     ConnectionDQEnvironmentSetupStatus,
@@ -31,6 +33,41 @@
     from pyatlan.client.atlan import AtlanClient
 
 
+#: Allowed characters for the connector-type slug embedded in
+#: ``connectionQualifiedName`` (the ``{slug}`` in
+#: ``default/{slug}/{epoch}``). Lower-case alphanumerics and hyphens
+#: only — mirrors the Java SDK constraint and the Atlan platform's
+#: server-side ``RAB`` (Reading Asset Bulk) / asset-import validation.
+#: Tightening pyatlan to this pattern at creation time (BLDX-1294)
+#: closes a gap where users could create connections with underscores
+#: (or other characters) via pyatlan only to discover them rejected
+#: by RAB at import time — leaving phantom Connection rows in Atlas.
+_CONNECTOR_TYPE_VALUE_PATTERN: re.Pattern = re.compile(r"^[a-z0-9-]+$")
+
+
+def _validate_connector_type_value(connector_type: AtlanConnectorType) -> None:
+    """Reject ``connector_type`` values that wouldn't survive RAB / asset-import
+    validation server-side. See ``_CONNECTOR_TYPE_VALUE_PATTERN``.
+
+    Built-in :class:`AtlanConnectorType` members are all kebab-case and
+    therefore always pass; this guard exists for custom types created
+    via :meth:`AtlanConnectorType.CREATE_CUSTOM` where the caller-
+    supplied ``value`` could otherwise contain underscores, dots,
+    uppercase letters, or other characters that the platform rejects
+    later in the pipeline.
+
+    Raises:
+        InvalidRequestError: With error code
+            ``ATLAN-PYTHON-400-079`` (``INVALID_CONNECTION_QN``) when the
+            slug fails the pattern check. Mirrors the Java SDK's
+            ``ErrorCode.INVALID_CONNECTION_QN`` so cross-SDK error
+            reporting stays consistent.
+    """
+    value = connector_type.value
+    if not _CONNECTOR_TYPE_VALUE_PATTERN.match(value):
+        raise ErrorCode.INVALID_CONNECTION_QN.exception_with_parameters(value)
+
+
 class Connection(Asset, type_name="Connection"):
     """Description"""
 
@@ -51,6 +88,7 @@ def creator(
         validate_required_fields(
             ["client", "name", "connector_type"], [client, name, connector_type]
         )
+        _validate_connector_type_value(connector_type)
         if not admin_users and not admin_groups and not admin_roles:
             raise ValueError(
                 "One of admin_user, admin_groups or admin_roles is required"
@@ -102,6 +140,7 @@ async def creator_async(
         validate_required_fields(
             ["client", "name", "connector_type"], [client, name, connector_type]
         )
+        _validate_connector_type_value(connector_type)
         if not admin_users and not admin_groups and not admin_roles:
             raise ValueError(
                 "One of admin_user, admin_groups or admin_roles is required"
diff --git a/pyatlan/test_utils/__init__.py b/pyatlan/test_utils/__init__.py
index 01f485090..bc69c7814 100644
--- a/pyatlan/test_utils/__init__.py
+++ b/pyatlan/test_utils/__init__.py
@@ -32,14 +32,36 @@
 
 
 class TestId:
+    # Slug-safe alphabet (lower-case alphanumerics only). Together with
+    # the hyphen separators in ``make_unique``, this guarantees every
+    # generated id matches ``^[a-z0-9-]+$`` — the same pattern the
+    # platform's asset-import (RAB) validator enforces for the
+    # connectorType segment of ``connectionQualifiedName``. Tests can
+    # therefore feed ``TestId.make_unique(...)`` directly into
+    # ``AtlanConnectorType.CREATE_CUSTOM(value=...)`` without tripping
+    # ``ErrorCode.INVALID_CONNECTION_QN`` (ATLAN-PYTHON-400-079, see
+    # BLDX-1294). The previous mixed-case + underscore-separated form
+    # caused every integration test that built a custom connector slug
+    # from ``MODULE_NAME`` to fail at fixture setup.
     session_id = generate_nanoid(
-        alphabet="1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ",
+        alphabet="1234567890abcdefghijklmnopqrstuvwxyz",
         size=5,
     )
 
     @classmethod
     def make_unique(cls, input: str):
-        return f"psdk_{input}_{cls.session_id}"
+        """Return a slug-safe, run-unique id of the form
+        ``psdk-<input>-<session>`` where every segment matches
+        ``^[a-z0-9-]+$``.
+
+        Input is lower-cased and any underscores are converted to
+        hyphens, so callers don't need to remember to slug-format the
+        input themselves. Backward-compat note for searches keyed on
+        the old ``psdk_`` prefix: switch to ``psdk-`` or strip the
+        separator entirely.
+        """
+        slug = input.lower().replace("_", "-")
+        return f"psdk-{slug}-{cls.session_id}"
 
 
 def get_random_connector():
@@ -57,7 +79,14 @@ def delete_token(client: AtlanClient, token: Optional[ApiToken] = None):
         delete_tokens = [
             token
             for token in tokens
-            if token.display_name and "psdk_Requests" in token.display_name
+            # Match both pre-BLDX-1294 (``psdk_Requests``) and current
+            # (``psdk-requests``) display-name shapes so cleanup works
+            # across runs.
+            if token.display_name
+            and (
+                "psdk_Requests" in token.display_name
+                or "psdk-requests" in token.display_name
+            )
         ]
         for token in delete_tokens:
             assert token and token.guid  # noqa: S101
diff --git a/pyatlan_v9/model/assets/_overlays/connection.py b/pyatlan_v9/model/assets/_overlays/connection.py
index 95f815543..bbf47d956 100644
--- a/pyatlan_v9/model/assets/_overlays/connection.py
+++ b/pyatlan_v9/model/assets/_overlays/connection.py
@@ -1,5 +1,6 @@
 # STDLIB_IMPORT: from typing import TYPE_CHECKING, List, Optional
 # IMPORT: from pyatlan.model.enums import AtlanConnectorType
+# INTERNAL_IMPORT: from pyatlan.model.assets.connection import _validate_connector_type_value
 # INTERNAL_IMPORT: from pyatlan.utils import init_guid, validate_required_fields
 
     @classmethod
@@ -38,6 +39,7 @@ def creator(
         validate_required_fields(
             ["client", "name", "connector_type"], [client, name, connector_type]
         )
+        _validate_connector_type_value(connector_type)
         if not admin_users and not admin_groups and not admin_roles:
             raise ValueError(
                 "One of admin_user, admin_groups or admin_roles is required"
@@ -92,6 +94,7 @@ async def creator_async(
         validate_required_fields(
             ["client", "name", "connector_type"], [client, name, connector_type]
         )
+        _validate_connector_type_value(connector_type)
         if not admin_users and not admin_groups and not admin_roles:
             raise ValueError(
                 "One of admin_user, admin_groups or admin_roles is required"
diff --git a/pyatlan_v9/model/assets/connection.py b/pyatlan_v9/model/assets/connection.py
index 4976accd2..07b312028 100644
--- a/pyatlan_v9/model/assets/connection.py
+++ b/pyatlan_v9/model/assets/connection.py
@@ -20,6 +20,7 @@
 import msgspec
 from msgspec import UNSET, UnsetType
 
+from pyatlan.model.assets.connection import _validate_connector_type_value
 from pyatlan.model.enums import AtlanConnectorType
 from pyatlan_v9.model.conversion_utils import (
     categorize_relationships,
@@ -439,6 +440,7 @@ def creator(
         validate_required_fields(
             ["client", "name", "connector_type"], [client, name, connector_type]
         )
+        _validate_connector_type_value(connector_type)
         if not admin_users and not admin_groups and not admin_roles:
             raise ValueError(
                 "One of admin_user, admin_groups or admin_roles is required"
@@ -493,6 +495,7 @@ async def creator_async(
         validate_required_fields(
             ["client", "name", "connector_type"], [client, name, connector_type]
         )
+        _validate_connector_type_value(connector_type)
         if not admin_users and not admin_groups and not admin_roles:
             raise ValueError(
                 "One of admin_user, admin_groups or admin_roles is required"
diff --git a/tests/integration/aio/test_connection.py b/tests/integration/aio/test_connection.py
index 2cf409e3b..ab661a025 100644
--- a/tests/integration/aio/test_connection.py
+++ b/tests/integration/aio/test_connection.py
@@ -39,7 +39,7 @@ async def custom_connection(
 ) -> AsyncGenerator[Connection, None]:
     CUSTOM_CONNECTOR_TYPE = AtlanConnectorType.CREATE_CUSTOM(
         name=f"{MODULE_NAME}_NAME",
-        value=f"{MODULE_NAME}_type",
+        value=f"{MODULE_NAME}-type",
         category=AtlanConnectionCategory.API,
     )
     result = await create_connection_async(
@@ -52,7 +52,7 @@ async def custom_connection(
 
 async def test_custom_connection(custom_connection: Connection):
     assert custom_connection.name == MODULE_NAME
-    assert custom_connection.connector_name == f"{MODULE_NAME.lower()}_type"
+    assert custom_connection.connector_name == f"{MODULE_NAME.lower()}-type"
     assert custom_connection.qualified_name
     assert custom_connection.category == AtlanConnectionCategory.API
 
@@ -68,4 +68,4 @@ async def test_custom_connection_qualified_name(
     )
     assert found
     assert found.name == MODULE_NAME
-    assert found.connector_name == f"{MODULE_NAME.lower()}_type"
+    assert found.connector_name == f"{MODULE_NAME.lower()}-type"
diff --git a/tests/integration/aio/test_index_search.py b/tests/integration/aio/test_index_search.py
index 9cb26e964..d7fd19115 100644
--- a/tests/integration/aio/test_index_search.py
+++ b/tests/integration/aio/test_index_search.py
@@ -404,8 +404,12 @@ async def _assert_search_results(
 @patch.object(LOGGER, "debug")
 async def test_search_pagination(mock_logger, client: AsyncAtlanClient):
     # Avoid testing on integration tests objects
+    # Match both legacy ``psdk_*`` (pre-BLDX-1294, underscore separator)
+    # and current ``psdk-*`` (slug-safe hyphen separator) test-asset
+    # names so older runs' artifacts aren't accidentally pulled in.
     exclude_sdk_terms = [
         Asset.NAME.wildcard("psdk_*"),
+        Asset.NAME.wildcard("psdk-*"),
         Asset.NAME.wildcard("jsdk_*"),
         Asset.NAME.wildcard("gsdk_*"),
     ]
diff --git a/tests/integration/aio/utils.py b/tests/integration/aio/utils.py
index 095ed1639..dbabd3998 100644
--- a/tests/integration/aio/utils.py
+++ b/tests/integration/aio/utils.py
@@ -40,7 +40,13 @@ async def delete_token_async(
         delete_tokens = [
             token
             for token in tokens
-            if token.display_name and "psdk_async" in token.display_name
+            # Match both pre-BLDX-1294 (``psdk_async``) and current
+            # (``psdk-async``) display-name shapes so cleanup works
+            # across runs.
+            if token.display_name
+            and (
+                "psdk_async" in token.display_name or "psdk-async" in token.display_name
+            )
         ]
         for token in delete_tokens:
             assert token and token.guid
diff --git a/tests/integration/client.py b/tests/integration/client.py
index 4762863b7..6623a576e 100644
--- a/tests/integration/client.py
+++ b/tests/integration/client.py
@@ -13,16 +13,23 @@
 
 
 class TestId:
+    # Mirrors :class:`pyatlan.test_utils.TestId` — kept in sync so a
+    # value passed to ``AtlanConnectorType.CREATE_CUSTOM`` matches the
+    # platform's ``^[a-z0-9-]+$`` connectorType slug rule (BLDX-1294 /
+    # ATLAN-PYTHON-400-079). Lowercase alphanumeric session_id + hyphen
+    # separators + lowercased+hyphenated input.
     from nanoid import generate as generate_nanoid  # type: ignore
 
     session_id = generate_nanoid(
-        alphabet="1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ",
+        alphabet="1234567890abcdefghijklmnopqrstuvwxyz",
         size=5,
     )
 
     @classmethod
     def make_unique(cls, input: str):
-        return f"psdk_{input}_{cls.session_id}"
+        """See :meth:`pyatlan.test_utils.TestId.make_unique`."""
+        slug = input.lower().replace("_", "-")
+        return f"psdk-{slug}-{cls.session_id}"
 
 
 @pytest.fixture(scope="module")
diff --git a/tests/integration/connection_test.py b/tests/integration/connection_test.py
index 8fc2329dd..92aab7939 100644
--- a/tests/integration/connection_test.py
+++ b/tests/integration/connection_test.py
@@ -33,7 +33,7 @@ def create_connection(
 def custom_connection(client: AtlanClient) -> Generator[Connection, None, None]:
     CUSTOM_CONNECTOR_TYPE = AtlanConnectorType.CREATE_CUSTOM(
         name=f"{MODULE_NAME}_NAME",
-        value=f"{MODULE_NAME}_type",
+        value=f"{MODULE_NAME}-type",
         category=AtlanConnectionCategory.API,
     )
     result = create_connection(
@@ -46,11 +46,11 @@ def custom_connection(client: AtlanClient) -> Generator[Connection, None, None]:
 
 def test_custom_connection(custom_connection: Connection):
     assert custom_connection.name == MODULE_NAME
-    assert custom_connection.connector_name == f"{MODULE_NAME.lower()}_type"
+    assert custom_connection.connector_name == f"{MODULE_NAME.lower()}-type"
     assert custom_connection.qualified_name
-    assert f"default/{MODULE_NAME.lower()}_type" in custom_connection.qualified_name
+    assert f"default/{MODULE_NAME.lower()}-type" in custom_connection.qualified_name
     assert (
-        AtlanConnectorType[f"{MODULE_NAME}_NAME"].value == f"{MODULE_NAME.lower()}_type"
+        AtlanConnectorType[f"{MODULE_NAME}_NAME"].value == f"{MODULE_NAME.lower()}-type"
     )
 
 
diff --git a/tests/integration/requests_test.py b/tests/integration/requests_test.py
index f4a059b10..ea573fd44 100644
--- a/tests/integration/requests_test.py
+++ b/tests/integration/requests_test.py
@@ -26,7 +26,16 @@ def delete_token(token_client: AtlanClient, token: Optional[ApiToken] = None):
         delete_tokens = [
             token
             for token in tokens
-            if token.display_name and "psdk_Requests" in token.display_name
+            # Match both pre-BLDX-1294 (``psdk_Requests``, mixed-case
+            # underscore-separated) and current (``psdk-requests``,
+            # lower-case hyphen-separated) display-name shapes — so a
+            # cleanup that catches partial failures from older sessions
+            # still works.
+            if token.display_name
+            and (
+                "psdk_Requests" in token.display_name
+                or "psdk-requests" in token.display_name
+            )
         ]
         for token in delete_tokens:
             assert token and token.guid
diff --git a/tests/integration/test_index_search.py b/tests/integration/test_index_search.py
index 0b9c02ccd..59cda5a97 100644
--- a/tests/integration/test_index_search.py
+++ b/tests/integration/test_index_search.py
@@ -385,8 +385,12 @@ def _assert_search_results(results, expected_sorts, size, TOTAL_ASSETS, bulk=Fal
 @patch.object(LOGGER, "debug")
 def test_search_pagination(mock_logger, client: AtlanClient):
     # Avoid testing on integration tests objects
+    # Match both legacy ``psdk_*`` (pre-BLDX-1294, underscore separator)
+    # and current ``psdk-*`` (slug-safe hyphen separator) test-asset
+    # names so older runs' artifacts aren't accidentally pulled in.
     exclude_sdk_terms = [
         Asset.NAME.wildcard("psdk_*"),
+        Asset.NAME.wildcard("psdk-*"),
         Asset.NAME.wildcard("jsdk_*"),
         Asset.NAME.wildcard("gsdk_*"),
     ]
diff --git a/tests/unit/model/connection_test.py b/tests/unit/model/connection_test.py
index 495c460e9..ea19bbac9 100644
--- a/tests/unit/model/connection_test.py
+++ b/tests/unit/model/connection_test.py
@@ -5,6 +5,7 @@
 
 from pyatlan.client.atlan import AtlanClient
 from pyatlan.client.token import TokenClient
+from pyatlan.errors import InvalidRequestError
 from pyatlan.model.assets import Connection
 from pyatlan.model.enums import AtlanConnectionCategory, AtlanConnectorType
 from tests.unit.model.constants import CONNECTION_NAME, CONNECTION_QUALIFIED_NAME
@@ -321,3 +322,127 @@ def test_validation_of_admin_not_done_when_constructed_from_json(
     mock_role_cache.validate_idstrs.assert_not_called()
     mock_group_cache.validate_aliases.assert_not_called()
     mock_user_cache.validate_names.assert_not_called()
+
+
+# ---------------------------------------------------------------------------
+# BLDX-1294 — connector-type value regex validation in Connection.creator
+# ---------------------------------------------------------------------------
+
+
+@pytest.mark.parametrize(
+    "bad_value",
+    [
+        "dev_cmdr",  # underscore — the original reported case
+        "dev.cmdr",  # dot
+        "dev cmdr",  # whitespace
+        "dev/cmdr",  # slash
+        "dev@cmdr",  # special char
+        "dev_",  # trailing underscore
+    ],
+)
+def test_creator_rejects_invalid_connector_type_value(
+    client: AtlanClient,
+    bad_value: str,
+    mock_role_cache,
+    mock_user_cache,
+    mock_group_cache,
+):
+    """BLDX-1294: Connection.creator() must reject custom connector_type values
+    whose slug doesn't match the platform's [a-z0-9-]+ pattern. Without this,
+    callers create Connections via pyatlan that the server-side asset-import
+    path later rejects, leaving phantom Connection rows in Atlas."""
+    custom = AtlanConnectorType.CREATE_CUSTOM(
+        name=bad_value.upper().replace("-", "_") or "EMPTY",
+        value=bad_value,
+        category=AtlanConnectionCategory.CUSTOM,
+    )
+
+    with pytest.raises(InvalidRequestError) as exc_info:
+        Connection.creator(
+            client=client,
+            name=CONNECTION_NAME,
+            connector_type=custom,
+            admin_users=["ernest"],
+        )
+    # Match the Java SDK convention — typed error with code
+    # ATLAN-PYTHON-400-079 (INVALID_CONNECTION_QN) and the bad slug
+    # surfaced in the message.
+    assert "ATLAN-PYTHON-400-079" in str(exc_info.value)
+    assert bad_value in str(exc_info.value)
+
+
+@pytest.mark.parametrize(
+    "good_value",
+    [
+        "dev-cmdr",  # hyphen — the recommended replacement
+        "snowflake",  # built-in-like slug
+        "amazon-msk",  # hyphenated multi-word
+        "a",  # single-char
+        "abc123",  # alphanumerics
+        "123-abc-456",  # mixed digit + alpha + hyphen
+    ],
+)
+def test_creator_accepts_valid_connector_type_value(
+    client: AtlanClient,
+    good_value: str,
+    mock_role_cache,
+    mock_user_cache,
+    mock_group_cache,
+):
+    """Valid lowercase-alphanumeric-and-hyphen slugs continue to work."""
+    custom = AtlanConnectorType.CREATE_CUSTOM(
+        name="CUSTOM",
+        value=good_value,
+        category=AtlanConnectionCategory.CUSTOM,
+    )
+
+    sut = Connection.creator(
+        client=client,
+        name=CONNECTION_NAME,
+        connector_type=custom,
+        admin_users=["ernest"],
+    )
+    assert sut.name == CONNECTION_NAME
+    assert sut.qualified_name.startswith(f"default/{good_value}/")
+
+
+def test_creator_accepts_builtin_connector_types(
+    client: AtlanClient,
+    mock_role_cache,
+    mock_user_cache,
+    mock_group_cache,
+):
+    """Built-in AtlanConnectorType members have always-valid slugs.
+    Regression pin — the new BLDX-1294 validator must not break them."""
+    sut = Connection.creator(
+        client=client,
+        name=CONNECTION_NAME,
+        connector_type=AtlanConnectorType.SNOWFLAKE,
+        admin_users=["ernest"],
+    )
+    assert sut.qualified_name.startswith("default/snowflake/")
+
+
+@pytest.mark.asyncio
+async def test_creator_async_rejects_invalid_connector_type_value(
+    client: AtlanClient,
+    mock_role_cache,
+    mock_user_cache,
+    mock_group_cache,
+):
+    """Same validation must apply to the async creator path."""
+    bad = AtlanConnectorType.CREATE_CUSTOM(
+        name="DEV_CMDR",
+        value="dev_cmdr",
+        category=AtlanConnectionCategory.CUSTOM,
+    )
+
+    with pytest.raises(InvalidRequestError) as exc_info:
+        await Connection.creator_async(
+            client=client,
+            name=CONNECTION_NAME,
+            connector_type=bad,
+            admin_users=["ernest"],
+        )
+    assert "ATLAN-PYTHON-400-079" in str(exc_info.value)
+    assert "dev_cmdr" in str(exc_info.value)
diff --git a/tests_v9/integration/aio/test_connection.py b/tests_v9/integration/aio/test_connection.py
index c36271b5e..131aa8197 100644
--- a/tests_v9/integration/aio/test_connection.py
+++ b/tests_v9/integration/aio/test_connection.py
@@ -39,7 +39,7 @@ async def custom_connection(
 ) -> AsyncGenerator[Connection, None]:
     CUSTOM_CONNECTOR_TYPE = AtlanConnectorType.CREATE_CUSTOM(
         name=f"{MODULE_NAME}_NAME",
-        value=f"{MODULE_NAME}_type",
+        value=f"{MODULE_NAME}-type",
         category=AtlanConnectionCategory.API,
     )
     result = await create_connection_async(
@@ -52,7 +52,7 @@ async def custom_connection(
 
 async def test_custom_connection(custom_connection: Connection):
     assert custom_connection.name == MODULE_NAME
-    assert custom_connection.connector_name == f"{MODULE_NAME.lower()}_type"
+    assert custom_connection.connector_name == f"{MODULE_NAME.lower()}-type"
     assert custom_connection.qualified_name
     assert custom_connection.category == AtlanConnectionCategory.API
 
@@ -68,4 +68,4 @@ async def test_custom_connection_qualified_name(
     )
     assert found
     assert found.name == MODULE_NAME
-    assert found.connector_name == f"{MODULE_NAME.lower()}_type"
+    assert found.connector_name == f"{MODULE_NAME.lower()}-type"
diff --git a/tests_v9/integration/aio/test_index_search.py b/tests_v9/integration/aio/test_index_search.py
index 2cf094ea2..cb9e52919 100644
--- a/tests_v9/integration/aio/test_index_search.py
+++ b/tests_v9/integration/aio/test_index_search.py
@@ -405,6 +405,7 @@ async def test_search_pagination(mock_logger, client: AsyncAtlanClient):
     # Avoid testing on integration tests objects
     exclude_sdk_terms = [
         Asset.NAME.wildcard("psdkv9_*"),
+        Asset.NAME.wildcard("psdkv9-*"),
         Asset.NAME.wildcard("jsdk_*"),
         Asset.NAME.wildcard("gsdk_*"),
     ]
diff --git a/tests_v9/integration/aio/utils.py b/tests_v9/integration/aio/utils.py
index cf4231264..d78edab98 100644
--- a/tests_v9/integration/aio/utils.py
+++ b/tests_v9/integration/aio/utils.py
@@ -44,7 +44,14 @@ async def delete_token_async(
         delete_tokens = [
             token
             for token in tokens
-            if token.display_name and "psdkv9_Async" in token.display_name
+            # Match both pre-BLDX-1294 (``psdkv9_Async``) and current
+            # (``psdkv9-async``) display-name shapes so cleanup works
+            # across runs.
+            if token.display_name
+            and (
+                "psdkv9_Async" in token.display_name
+                or "psdkv9-async" in token.display_name
+            )
         ]
         for token in delete_tokens:
             assert token and token.guid
diff --git a/tests_v9/integration/client.py b/tests_v9/integration/client.py
index e8c4864cb..198e05d16 100644
--- a/tests_v9/integration/client.py
+++ b/tests_v9/integration/client.py
@@ -15,16 +15,22 @@
 
 
 class TestId:
+    # Mirrors :class:`tests.integration.client.TestId` — kept in sync so
+    # a value passed to ``AtlanConnectorType.CREATE_CUSTOM`` matches the
+    # platform's ``^[a-z0-9-]+$`` connectorType slug rule (BLDX-1294 /
+    # ATLAN-PYTHON-400-079). Lowercase alphanumeric session_id + hyphen
+    # separators + lowercased+hyphenated input.
     from nanoid import generate as generate_nanoid  # type: ignore
 
     session_id = generate_nanoid(
-        alphabet="1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ",
+        alphabet="1234567890abcdefghijklmnopqrstuvwxyz",
         size=5,
     )
 
     @classmethod
     def make_unique(cls, input: str):
-        return f"psdkv9_{input}_{cls.session_id}"
+        slug = input.lower().replace("_", "-")
+        return f"psdkv9-{slug}-{cls.session_id}"
 
 
 @pytest.fixture(scope="module")
diff --git a/tests_v9/integration/connection_test.py b/tests_v9/integration/connection_test.py
index e80d706d3..2a22a9a06 100644
--- a/tests_v9/integration/connection_test.py
+++ b/tests_v9/integration/connection_test.py
@@ -33,7 +33,7 @@ def create_connection(
 def custom_connection(client: AtlanClient) -> Generator[Connection, None, None]:
     CUSTOM_CONNECTOR_TYPE = AtlanConnectorType.CREATE_CUSTOM(
         name=f"{MODULE_NAME}_NAME",
-        value=f"{MODULE_NAME}_type",
+        value=f"{MODULE_NAME}-type",
         category=AtlanConnectionCategory.API,
     )
     result = create_connection(
@@ -46,11 +46,11 @@ def custom_connection(client: AtlanClient) -> Generator[Connection, None, None]:
 
 def test_custom_connection(custom_connection: Connection):
     assert custom_connection.name == MODULE_NAME
-    assert custom_connection.connector_name == f"{MODULE_NAME.lower()}_type"
+    assert custom_connection.connector_name == f"{MODULE_NAME.lower()}-type"
     assert custom_connection.qualified_name
-    assert f"default/{MODULE_NAME.lower()}_type" in custom_connection.qualified_name
+    assert f"default/{MODULE_NAME.lower()}-type" in custom_connection.qualified_name
     assert (
-        AtlanConnectorType[f"{MODULE_NAME}_NAME"].value == f"{MODULE_NAME.lower()}_type"
+        AtlanConnectorType[f"{MODULE_NAME}_NAME"].value == f"{MODULE_NAME.lower()}-type"
     )
 
 
diff --git a/tests_v9/integration/requests_test.py b/tests_v9/integration/requests_test.py
index 1dc77468b..19389643e 100644
--- a/tests_v9/integration/requests_test.py
+++ b/tests_v9/integration/requests_test.py
@@ -26,7 +26,14 @@ def delete_token(token_client: AtlanClient, token: Optional[ApiToken] = None):
         delete_tokens = [
             token
             for token in tokens
-            if token.display_name and "psdkv9_Requests" in token.display_name
+            # Match both pre-BLDX-1294 (``psdkv9_Requests``) and current
+            # (``psdkv9-requests``) display-name shapes so cleanup works
+            # across runs.
+            if token.display_name
+            and (
+                "psdkv9_Requests" in token.display_name
+                or "psdkv9-requests" in token.display_name
+            )
         ]
         for token in delete_tokens:
             assert token and token.guid
diff --git a/tests_v9/integration/test_index_search.py b/tests_v9/integration/test_index_search.py
index 9f4be2eea..8ee870f57 100644
--- a/tests_v9/integration/test_index_search.py
+++ b/tests_v9/integration/test_index_search.py
@@ -386,6 +386,7 @@ def test_search_pagination(mock_logger, client: AtlanClient):
     # Avoid testing on integration tests objects
     exclude_sdk_terms = [
         Asset.NAME.wildcard("psdkv9_*"),
+        Asset.NAME.wildcard("psdkv9-*"),
         Asset.NAME.wildcard("jsdk_*"),
         Asset.NAME.wildcard("gsdk_*"),
     ]
diff --git a/tests_v9/unit/model/connection_test.py b/tests_v9/unit/model/connection_test.py
index ff7639051..aa208e9c2 100644
--- a/tests_v9/unit/model/connection_test.py
+++ b/tests_v9/unit/model/connection_test.py
@@ -9,6 +9,7 @@
 import pytest
 from msgspec import UNSET
 
+from pyatlan.errors import InvalidRequestError
 from pyatlan_v9.client.atlan import AtlanClient
 from pyatlan_v9.model import Connection
 from pyatlan_v9.model.enums import AtlanConnectionCategory, AtlanConnectorType
@@ -390,3 +391,68 @@ def test_type_name_defaults():
     """Test that type_name defaults to 'Connection'."""
     conn = Connection(name=CONNECTION_NAME, qualified_name=CONNECTION_QUALIFIED_NAME)
     assert conn.type_name == "Connection"
+
+
+# ---------------------------------------------------------------------------
+# BLDX-1294 — connector-type value regex validation (mirrors pyatlan)
+# ---------------------------------------------------------------------------
+
+
+@pytest.mark.parametrize(
+    "bad_value",
+    [
+        "dev_cmdr",  # underscore — the original reported case
+        "dev.cmdr",  # dot
+        "dev cmdr",  # whitespace
+        "dev/cmdr",  # slash
+        "dev@cmdr",  # special char
+        "dev_",  # trailing underscore
+    ],
+)
+def test_creator_rejects_invalid_connector_type_value_v9(
+    client: AtlanClient,
+    bad_value: str,
+    mock_role_cache,
+    mock_user_cache,
+    mock_group_cache,
+):
+    """BLDX-1294: pyatlan_v9 Connection.creator() must enforce the same
+    [a-z0-9-]+ slug rule as pyatlan to keep parity with the platform's
+    asset-import / RAB validation."""
+    custom = AtlanConnectorType.CREATE_CUSTOM(
+        name=bad_value.upper().replace("-", "_") or "BADNAME",
+        value=bad_value,
+        category=AtlanConnectionCategory.CUSTOM,
+    )
+
+    with pytest.raises(InvalidRequestError) as exc_info:
+        Connection.creator(
+            client=client,
+            name=CONNECTION_NAME,
+            connector_type=custom,
+            admin_users=["ernest"],
+        )
+    assert "ATLAN-PYTHON-400-079" in str(exc_info.value)
+    assert bad_value in str(exc_info.value)
+
+
+def test_creator_accepts_valid_connector_type_value_v9(
+    client: AtlanClient,
+    mock_role_cache,
+    mock_user_cache,
+    mock_group_cache,
+):
+    """Valid slugs (hyphen-only) continue to work in v9."""
+    custom = AtlanConnectorType.CREATE_CUSTOM(
+        name="DEV_CMDR",
+        value="dev-cmdr",
+        category=AtlanConnectionCategory.CUSTOM,
+    )
+
+    sut = Connection.creator(
+        client=client,
+        name=CONNECTION_NAME,
+        connector_type=custom,
+        admin_users=["ernest"],
+    )
+    assert sut.qualified_name.startswith("default/dev-cmdr/")