diff --git a/.librarian/generator-input/client-post-processing/add-missing-dependencies-to-setup-py-constraints.yaml b/.librarian/generator-input/client-post-processing/add-missing-dependencies-to-setup-py-constraints.yaml
index 11644256a0ae..487d05b400e8 100644
--- a/.librarian/generator-input/client-post-processing/add-missing-dependencies-to-setup-py-constraints.yaml
+++ b/.librarian/generator-input/client-post-processing/add-missing-dependencies-to-setup-py-constraints.yaml
@@ -30,7 +30,7 @@ replacements:
           # Exclude incompatible versions of `google-auth`
           # See https://github.com/googleapis/google-cloud-python/issues/12364
           "google-auth >= 2.14.1, <3.0.0,!=2.24.0,!=2.25.0",
-          "grpc-google-iam-v1 >=0.12.4, <1.0.0",
+          "grpc-google-iam-v1 >=0.14.2, <1.0.0",
           "grpcio >= 1.59.0, < 2.0.0",
     count: 1
   - paths: [
@@ -49,7 +49,7 @@ replacements:
           # Exclude incompatible versions of `google-auth`
           # See https://github.com/googleapis/google-cloud-python/issues/12364
           "google-auth >= 2.14.1, <3.0.0,!=2.24.0,!=2.25.0",
-          "grpc-google-iam-v1 >=0.12.4, <1.0.0",
+          "grpc-google-iam-v1 >=0.14.2, <1.0.0",
           "grpcio >= 1.59.0, < 2.0.0",
     count: 1
   - paths: [
@@ -68,7 +68,7 @@ replacements:
           # Exclude incompatible versions of `google-auth`
           # See https://github.com/googleapis/google-cloud-python/issues/12364
           "google-auth >= 2.14.1, <3.0.0,!=2.24.0,!=2.25.0",
-          "grafeas >= 1.7.0, <2.0",
+          "grafeas >= 1.14.1, <2.0",
           "grpcio >= 1.59.0, < 2.0.0",
     count: 1
   - paths: [
@@ -87,7 +87,7 @@ replacements:
           # Exclude incompatible versions of `google-auth`
           # See https://github.com/googleapis/google-cloud-python/issues/12364
           "google-auth >= 2.14.1, <3.0.0,!=2.24.0,!=2.25.0",
-          "grpc-google-iam-v1 >=0.12.4, <1.0.0",
+          "grpc-google-iam-v1 >=0.14.2, <1.0.0",
           "grpcio >= 1.59.0, < 2.0.0",
     count: 1
   - paths: [
diff --git a/.librarian/generator-input/client-post-processing/containeranalysis-grafeas-integration.yaml b/.librarian/generator-input/client-post-processing/containeranalysis-grafeas-integration.yaml
index 880f20cc44fa..53b8769ddadb 100644
--- a/.librarian/generator-input/client-post-processing/containeranalysis-grafeas-integration.yaml
+++ b/.librarian/generator-input/client-post-processing/containeranalysis-grafeas-integration.yaml
@@ -30,7 +30,7 @@ replacements:
           # Exclude incompatible versions of `google-auth`
           # See https://github.com/googleapis/google-cloud-python/issues/12364
           "google-auth >= 2.14.1, <3.0.0,!=2.24.0,!=2.25.0",
-          "grafeas >=1.7.0, <2.0",
+          "grafeas >=1.14.1, <2.0",
           "grpcio >= 1.59.0, < 2.0.0",
     count: 1
   - paths: [
diff --git a/.librarian/generator-input/client-post-processing/logging-integration.yaml b/.librarian/generator-input/client-post-processing/logging-integration.yaml
index e7141bb85c20..a73953e305ad 100644
--- a/.librarian/generator-input/client-post-processing/logging-integration.yaml
+++ b/.librarian/generator-input/client-post-processing/logging-integration.yaml
@@ -41,7 +41,7 @@ replacements:
           "grpcio >= 1.59.0, < 2.0.0",
     after: |
       "google-auth >= 2.14.1, <3.0.0,!=2.24.0,!=2.25.0",
-          "google-cloud-appengine-logging>=0.1.3, <2.0.0",
+          "google-cloud-appengine-logging>=1.6.1, <2.0.0",
           "google-cloud-audit-log >= 0.3.2, < 1.0.0",
           "google-cloud-core >= 2.0.0, <3.0.0",
           "grpc-google-iam-v1 >=0.14.2, <1.0.0",
@@ -56,7 +56,7 @@ replacements:
       grpcio==1.59.0
     after: |
       google-auth==2.14.1
-      google-cloud-appengine-logging==0.1.3
+      google-cloud-appengine-logging==1.6.1
       google-cloud-audit-log==0.3.2
       google-cloud-core==2.0.0
       grpc-google-iam-v1==0.14.2
diff --git a/.librarian/generator-input/client-post-processing/storage-integration.yaml b/.librarian/generator-input/client-post-processing/storage-integration.yaml
index 248a2f91a8b6..6a4126f739a9 100644
--- a/.librarian/generator-input/client-post-processing/storage-integration.yaml
+++ b/.librarian/generator-input/client-post-processing/storage-integration.yaml
@@ -603,8 +603,8 @@ replacements:
               "grpcio-status >= 1.75.1, < 2.0.0; python_version >= '3.14'",
               "proto-plus >= 1.22.3, <2.0.0; python_version < '3.13'",
               "proto-plus >= 1.25.0, <2.0.0; python_version >= '3.13'",
-              "protobuf >= 4.25.8, < 8.0.0",
-              "grpc-google-iam-v1 >= 0.14.0, <1.0.0",
+              "protobuf >= 6.33.5, < 8.0.0",
+              "grpc-google-iam-v1 >= 0.14.2, <1.0.0",
           ],
           "protobuf": ["protobuf >= 3.20.2, < 7.0.0"],
           "tracing": [
@@ -656,8 +656,8 @@ replacements:
       grpcio==1.59.0
       grpcio-status==1.59.0
       proto-plus==1.22.3
-      protobuf==4.25.8
-      grpc-google-iam-v1==0.14.0
+      protobuf==6.33.5
+      grpc-google-iam-v1==0.14.2
       opentelemetry-api==1.1.0
       requests==2.22.0
       google-crc32c==1.6.0
diff --git a/packages/bigframes/setup.py b/packages/bigframes/setup.py
index 76b98b88d312..e2717fbe5e4b 100644
--- a/packages/bigframes/setup.py
+++ b/packages/bigframes/setup.py
@@ -42,9 +42,9 @@
     "google-cloud-bigquery[bqstorage,pandas] >=3.36.0",
     # 2.30 needed for arrow support.
     "google-cloud-bigquery-storage >= 2.30.0, < 3.0.0",
-    "google-cloud-functions >=1.12.0",
-    "google-cloud-bigquery-connection >=1.12.0",
-    "google-cloud-resource-manager >=1.10.3",
+    "google-cloud-functions >=1.20.2",
+    "google-cloud-bigquery-connection >=1.18.2",
+    "google-cloud-resource-manager >=1.14.2",
     "google-cloud-storage >=2.0.0",
     "google-crc32c >=1.0.0,<2.0.0",
     "grpc-google-iam-v1 >= 0.14.2",
@@ -73,8 +73,8 @@
     "tests": [
         "freezegun",
         "pytest-snapshot",
-        "google-cloud-bigtable >=2.24.0",
-        "google-cloud-pubsub >=2.21.4",
+        "google-cloud-bigtable >=2.30.0",
+        "google-cloud-pubsub >=2.29.0",
         "tzdata",
     ],
     # used for local engine
diff --git a/packages/bigframes/testing/constraints-3.10.txt b/packages/bigframes/testing/constraints-3.10.txt
index 0c76f1dda750..1dcdd64baa0a 100644
--- a/packages/bigframes/testing/constraints-3.10.txt
+++ b/packages/bigframes/testing/constraints-3.10.txt
@@ -4,13 +4,13 @@ fsspec==2023.3.0
 gcsfs==2023.3.0
 geopandas==0.12.2
 google-auth==2.15.0
-google-cloud-bigtable==2.24.0
-google-cloud-pubsub==2.21.4
+google-cloud-bigtable==2.30.0
+google-cloud-pubsub==2.29.0
 google-cloud-bigquery==3.36.0
-google-cloud-functions==1.12.0
-google-cloud-bigquery-connection==1.12.0
-google-cloud-iam==2.12.1
-google-cloud-resource-manager==1.10.3
+google-cloud-functions==1.20.2
+google-cloud-bigquery-connection==1.18.2
+google-cloud-iam==2.18.2
+google-cloud-resource-manager==1.14.2
 google-cloud-storage==2.0.0
 grpc-google-iam-v1==0.14.2
 numpy==1.24.0
@@ -95,7 +95,7 @@ pluggy==1.6.0
 prompt_toolkit==3.0.52
 propcache==0.4.1
 proto-plus==1.27.1
-protobuf==4.25.8
+protobuf==6.33.5
 psygnal==0.15.1
 ptyprocess==0.7.0
 pure_eval==0.2.3
diff --git a/packages/bigframes/testing/constraints-3.11.txt b/packages/bigframes/testing/constraints-3.11.txt
index 77645780b7b0..00a399fb514d 100644
--- a/packages/bigframes/testing/constraints-3.11.txt
+++ b/packages/bigframes/testing/constraints-3.11.txt
@@ -180,7 +180,7 @@ groovy==0.1.2
 grpc-google-iam-v1==0.14.2
 grpc-interceptor==0.15.4
 grpcio==1.74.0
-grpcio-status==1.71.2
+grpcio-status==1.72.1
 grpclib==0.4.8
 gspread==6.2.1
 gspread-dataframe==4.0.0
@@ -401,7 +401,7 @@ prompt_toolkit==3.0.51
 propcache==0.3.2
 prophet==1.1.7
 proto-plus==1.26.1
-protobuf==5.29.5
+protobuf==6.33.5
 psutil==5.9.5
 psycopg2==2.9.10
 psygnal==0.14.0
diff --git a/packages/gapic-generator/setup.py b/packages/gapic-generator/setup.py
index 39fb12e96f93..0150b72338e3 100644
--- a/packages/gapic-generator/setup.py
+++ b/packages/gapic-generator/setup.py
@@ -26,10 +26,10 @@
 release_status = "Development Status :: 5 - Production/Stable"
 dependencies = [
     # Ensure that the lower bounds of these dependencies match what we have in the
-    # templated setup.py.j2: https://github.com/googleapis/gapic-generator-python/blob/main/gapic/templates/setup.py.j2
+    # templated setup.py.j2: https://github.com/googleapis/google-cloud-python/blob/main/packages/gapic-generator/gapic/templates/setup.py.j2
     "click >= 6.7",
     "google-api-core[grpc] >= 2.25.0, < 3.0.0",
-    "googleapis-common-protos >= 1.55.0, < 2.0.0",
+    "googleapis-common-protos >= 1.69.2, < 2.0.0",
     "grpcio >= 1.59.0, < 2.0.0",
     # 2.11.0 is required which adds the `default` argument to `jinja-filters.map()`
     # https://jinja.palletsprojects.com/en/3.0.x/templates/#jinja-filters.map
diff --git a/packages/gcp-sphinx-docfx-yaml/tests/testdata/gapic-combo/setup.py b/packages/gcp-sphinx-docfx-yaml/tests/testdata/gapic-combo/setup.py
index 2ee5bcef45bb..1234383a55ed 100644
--- a/packages/gcp-sphinx-docfx-yaml/tests/testdata/gapic-combo/setup.py
+++ b/packages/gcp-sphinx-docfx-yaml/tests/testdata/gapic-combo/setup.py
@@ -32,7 +32,7 @@
     "google-api-core[grpc] >= 1.32.0, <3.0.0dev,!=2.0.*,!=2.1.*,!=2.2.*,!=2.3.*,!=2.4.*,!=2.5.*,!=2.6.*,!=2.7.*",
     "proto-plus >= 1.22.0, <2.0.0dev",
     "protobuf>=3.19.5,<5.0.0dev,!=3.20.0,!=3.20.1,!=4.21.0,!=4.21.1,!=4.21.2,!=4.21.3,!=4.21.4,!=4.21.5",
-    "grpc-google-iam-v1 >=0.12.4, <1.0.0dev",
+    "grpc-google-iam-v1 >=0.14.2, <1.0.0dev",
     "grpcio-status >= 1.59.0, < 2.0.0",
 ]
 extras = {"libcst": "libcst >= 0.3.10"}
diff --git a/packages/google-api-core/google/api_core/_python_package_support.py b/packages/google-api-core/google/api_core/_python_package_support.py
index e667620170db..a6c35d8c1804 100644
--- a/packages/google-api-core/google/api_core/_python_package_support.py
+++ b/packages/google-api-core/google/api_core/_python_package_support.py
@@ -35,7 +35,7 @@
 _PACKAGE_DEPENDENCY_WARNINGS = [
     DependencyConstraint(
         "google.protobuf",
-        minimum_fully_supported_version="4.25.8",
+        minimum_fully_supported_version="6.33.5",
         recommended_version="6.x",
     )
 ]
@@ -50,7 +50,7 @@
 def parse_version_to_tuple(version_string: str) -> ParsedVersion:
     """Safely converts a semantic version string to a comparable tuple of integers.
 
-    Example: "4.25.8" -> (4, 25, 8)
+    Example: "6.33.5" -> (6, 33, 5)
     Ignores non-numeric parts and handles common version formats.
 
     Args:
diff --git a/packages/google-api-core/noxfile.py b/packages/google-api-core/noxfile.py
index a696331a73bb..fca53607bdb2 100644
--- a/packages/google-api-core/noxfile.py
+++ b/packages/google-api-core/noxfile.py
@@ -307,51 +307,28 @@ def default(
 
 @nox.session(python=ALL_PYTHON)
 @nox.parametrize(
-    ["install_grpc", "install_async_rest", "python_versions", "legacy_proto"],
+    ["install_grpc", "install_async_rest", "python_versions"],
     [
-        (True, False, None, None),  # Run unit tests with grpcio installed
-        (False, False, None, None),  # Run unit tests without grpcio installed
+        (True, False, None),  # Run unit tests with grpcio installed
+        (False, False, None),  # Run unit tests without grpcio installed
         (
             True,
             True,
             None,
-            None,
         ),  # Run unit tests with grpcio and async rest installed
-        # TODO: Remove once we stop support for protobuf 4.x.
-        (
-            True,
-            False,
-            ["3.10", "3.11"],
-            4,
-        ),  # Run proto4 tests with grpcio/grpcio-gcp installed
     ],
 )
-def unit(
-    session, install_grpc, install_async_rest, python_versions=None, legacy_proto=None
-):
+def unit(session, install_grpc, install_async_rest, python_versions=None):
     """Run the unit test suite with the given configuration parameters.
 
     If `python_versions` is provided, the test suite only runs when the Python version (xx.yy) is
     one of the values in `python_versions`.
-
-    If `legacy_proto` is provided, this test suite will explicitly install the proto library at
-    that major version. Only a few values are supported at any one time; the intent is to test
-    deprecated but noyet abandoned versions.
     """
 
     if python_versions and session.python not in python_versions:
         session.log(f"Skipping session for Python {session.python}")
         session.skip()
 
-    match legacy_proto:
-        case 4:
-            # Pin protobuf to a 4.x version to ensure coverage for the legacy code path.
-            session.install("protobuf>=4.25.8,<5.0.0")
-        case None | False:
-            pass
-        case _:
-            assert False, f"Unknown legacy_proto: {legacy_proto}"
-
     default(
         session=session,
         install_grpc=install_grpc,
diff --git a/packages/google-api-core/pyproject.toml b/packages/google-api-core/pyproject.toml
index 1cc9a964348e..c759466861f5 100644
--- a/packages/google-api-core/pyproject.toml
+++ b/packages/google-api-core/pyproject.toml
@@ -43,7 +43,7 @@ classifiers = [
   "Topic :: Internet",
 ]
 dependencies = [
-  "googleapis-common-protos >= 1.63.2, < 2.0.0",
+  "googleapis-common-protos >= 1.69.2, < 2.0.0",
   "protobuf >= 5.29.6, < 8.0.0",
   "proto-plus >= 1.24.0, < 2.0.0",
   "proto-plus >= 1.25.0, < 2.0.0; python_version >= '3.13'",
diff --git a/packages/google-api-core/testing/constraints-3.10.txt b/packages/google-api-core/testing/constraints-3.10.txt
index b501dd49a4f4..d236a7d1d202 100644
--- a/packages/google-api-core/testing/constraints-3.10.txt
+++ b/packages/google-api-core/testing/constraints-3.10.txt
@@ -5,8 +5,8 @@
 #
 # e.g., if pyproject.toml has "foo >= 1.14.0, < 2.0.0dev",
 # Then this file should have foo==1.14.0
-googleapis-common-protos==1.63.2
-protobuf==5.29.6
+googleapis-common-protos==1.69.2
+protobuf==6.33.5
 google-auth==2.14.1
 requests==2.33.0
 grpcio==1.59.0
diff --git a/packages/google-api-core/testing/constraints-async-rest-3.10.txt b/packages/google-api-core/testing/constraints-async-rest-3.10.txt
index 557f4206e148..03ff593e654d 100644
--- a/packages/google-api-core/testing/constraints-async-rest-3.10.txt
+++ b/packages/google-api-core/testing/constraints-async-rest-3.10.txt
@@ -5,8 +5,8 @@
 #
 # e.g., if pyproject.toml has "foo >= 1.14.0, < 2.0.0dev",
 # Then this file should have foo==1.14.0
-googleapis-common-protos==1.63.2
-protobuf==5.29.6
+googleapis-common-protos==1.69.2
+protobuf==6.33.5
 google-auth==2.14.1
 requests==2.33.0
 grpcio==1.59.0
diff --git a/packages/google-cloud-access-context-manager/setup.py b/packages/google-cloud-access-context-manager/setup.py
index f4febf1d15c3..8fcba6d7eb80 100644
--- a/packages/google-cloud-access-context-manager/setup.py
+++ b/packages/google-cloud-access-context-manager/setup.py
@@ -29,8 +29,8 @@
 # 'Development Status :: 5 - Production/Stable'
 release_status = "Development Status :: 4 - Beta"
 dependencies = [
-    "google-api-core[grpc] >= 2.11.0, <3.0.0",
-    "protobuf >= 4.25.8, < 8.0.0",
+    "google-api-core[grpc] >= 2.25.0, <3.0.0",
+    "protobuf >= 6.33.5, < 8.0.0",
 ]
 
 # Setup boilerplate below this line.
diff --git a/packages/google-cloud-access-context-manager/testing/constraints-3.10.txt b/packages/google-cloud-access-context-manager/testing/constraints-3.10.txt
index 2b0e26586a65..58e7ed875ec4 100644
--- a/packages/google-cloud-access-context-manager/testing/constraints-3.10.txt
+++ b/packages/google-cloud-access-context-manager/testing/constraints-3.10.txt
@@ -5,5 +5,5 @@
 #
 # e.g., if setup.py has "foo >= 1.14.0, < 2.0.0dev",
 # Then this file should have foo==1.14.0
-protobuf==4.25.8
+protobuf==6.33.5
 google-api-core==2.11.0
diff --git a/packages/google-cloud-apigee-registry/setup.py b/packages/google-cloud-apigee-registry/setup.py
index a29d8f16ed7a..54df5cdceca1 100644
--- a/packages/google-cloud-apigee-registry/setup.py
+++ b/packages/google-cloud-apigee-registry/setup.py
@@ -44,7 +44,7 @@
     release_status = "Development Status :: 5 - Production/Stable"
 
 dependencies = [
-    "google-api-core[grpc] >= 2.24.2, <3.0.0",
+    "google-api-core[grpc] >= 2.25.0, <3.0.0",
     # Exclude incompatible versions of `google-auth`
     # See https://github.com/googleapis/google-cloud-python/issues/12364
     "google-auth >= 2.14.1, <3.0.0,!=2.24.0,!=2.25.0",
diff --git a/packages/google-cloud-apigee-registry/testing/constraints-3.10.txt b/packages/google-cloud-apigee-registry/testing/constraints-3.10.txt
index 3a84666fb90e..0ce4b3d6e6f5 100644
--- a/packages/google-cloud-apigee-registry/testing/constraints-3.10.txt
+++ b/packages/google-cloud-apigee-registry/testing/constraints-3.10.txt
@@ -4,7 +4,7 @@
 # pinning their versions to their lower bounds.
 # For example, if setup.py has "google-cloud-foo >= 1.14.0, < 2.0.0",
 # then this file should have google-cloud-foo==1.14.0
-google-api-core==2.24.2
+google-api-core==2.25.0
 google-auth==2.14.1
 grpcio==1.59.0
 proto-plus==1.26.1
diff --git a/packages/google-cloud-audit-log/setup.py b/packages/google-cloud-audit-log/setup.py
index de4e89c9d70c..ddb8fde443c4 100644
--- a/packages/google-cloud-audit-log/setup.py
+++ b/packages/google-cloud-audit-log/setup.py
@@ -23,8 +23,8 @@
 version = "0.6.0"
 release_status = "Development Status :: 4 - Beta"
 dependencies = [
-    "protobuf >= 4.25.8, < 8.0.0",
-    "googleapis-common-protos >= 1.56.2, < 2.0.0",
+    "protobuf >= 6.33.5, < 8.0.0",
+    "googleapis-common-protos >= 1.69.2, < 2.0.0",
 ]
 
 package_root = os.path.abspath(os.path.dirname(__file__))
diff --git a/packages/google-cloud-audit-log/testing/constraints-3.10.txt b/packages/google-cloud-audit-log/testing/constraints-3.10.txt
index 2cea8ffcdad0..c02063fef892 100644
--- a/packages/google-cloud-audit-log/testing/constraints-3.10.txt
+++ b/packages/google-cloud-audit-log/testing/constraints-3.10.txt
@@ -18,5 +18,5 @@
 # Pin the version to the lower bound.
 # e.g., if setup.py has "google-cloud-foo >= 1.14.0, < 2.0.0dev",
 # Then this file should have google-cloud-foo==1.14.0
-protobuf==4.25.8
-googleapis-common-protos==1.63.2
+protobuf==6.33.5
+googleapis-common-protos==1.69.2
diff --git a/packages/google-cloud-bigquery/testing/constraints-3.10.txt b/packages/google-cloud-bigquery/testing/constraints-3.10.txt
index 2636a7d07ff0..510a2d1b4ba5 100644
--- a/packages/google-cloud-bigquery/testing/constraints-3.10.txt
+++ b/packages/google-cloud-bigquery/testing/constraints-3.10.txt
@@ -24,4 +24,4 @@ opentelemetry-api==1.16.0
 opentelemetry-sdk==1.16.0
 opentelemetry-instrumentation==0.41b0
 proto-plus==1.22.3
-protobuf==4.25.8
+protobuf==6.33.5
\ No newline at end of file
diff --git a/packages/google-cloud-binary-authorization/setup.py b/packages/google-cloud-binary-authorization/setup.py
index 72441ef2b08e..5491a1c012e0 100644
--- a/packages/google-cloud-binary-authorization/setup.py
+++ b/packages/google-cloud-binary-authorization/setup.py
@@ -48,7 +48,7 @@
     # Exclude incompatible versions of `google-auth`
     # See https://github.com/googleapis/google-cloud-python/issues/12364
     "google-auth >= 2.14.1, <3.0.0,!=2.24.0,!=2.25.0",
-    "grafeas >= 1.7.0, <2.0",
+    "grafeas >= 1.14.1, <2.0",
     "grpcio >= 1.59.0, < 2.0.0",
     "grpcio >= 1.75.1, < 2.0.0; python_version >= '3.14'",
     "proto-plus >= 1.26.1, <2.0.0",
diff --git a/packages/google-cloud-build/setup.py b/packages/google-cloud-build/setup.py
index e106e092157e..5673153ac126 100644
--- a/packages/google-cloud-build/setup.py
+++ b/packages/google-cloud-build/setup.py
@@ -48,7 +48,7 @@
     # Exclude incompatible versions of `google-auth`
     # See https://github.com/googleapis/google-cloud-python/issues/12364
     "google-auth >= 2.14.1, <3.0.0,!=2.24.0,!=2.25.0",
-    "grpc-google-iam-v1 >=0.12.4, <1.0.0",
+    "grpc-google-iam-v1 >=0.14.2, <1.0.0",
     "grpcio >= 1.59.0, < 2.0.0",
     "grpcio >= 1.75.1, < 2.0.0; python_version >= '3.14'",
     "proto-plus >= 1.26.1, <2.0.0",
diff --git a/packages/google-cloud-containeranalysis/setup.py b/packages/google-cloud-containeranalysis/setup.py
index e9ae729e772a..2fde412b0b4e 100644
--- a/packages/google-cloud-containeranalysis/setup.py
+++ b/packages/google-cloud-containeranalysis/setup.py
@@ -50,7 +50,7 @@
     # Exclude incompatible versions of `google-auth`
     # See https://github.com/googleapis/google-cloud-python/issues/12364
     "google-auth >= 2.14.1, <3.0.0,!=2.24.0,!=2.25.0",
-    "grafeas >=1.7.0, <2.0",
+    "grafeas >=1.14.1, <2.0",
     "grpcio >= 1.59.0, < 2.0.0",
     "grpcio >= 1.75.1, < 2.0.0; python_version >= '3.14'",
     "proto-plus >= 1.26.1, <2.0.0",
diff --git a/packages/google-cloud-core/setup.py b/packages/google-cloud-core/setup.py
index ed6d9d2f2b72..138a821301b2 100644
--- a/packages/google-cloud-core/setup.py
+++ b/packages/google-cloud-core/setup.py
@@ -28,7 +28,7 @@
 # 'Development Status :: 5 - Production/Stable'
 release_status = "Development Status :: 5 - Production/Stable"
 dependencies = [
-    "google-api-core >= 2.11.0, <3.0.0",
+    "google-api-core >= 2.25.0, <3.0.0",
     "google-auth >= 2.14.1, <3.0.0,!=2.24.0,!=2.25.0",
 ]
 extras = {
diff --git a/packages/google-cloud-documentai-toolbox/setup.py b/packages/google-cloud-documentai-toolbox/setup.py
index f3c23347b6f1..59715a6b4660 100644
--- a/packages/google-cloud-documentai-toolbox/setup.py
+++ b/packages/google-cloud-documentai-toolbox/setup.py
@@ -53,17 +53,17 @@
         "google.cloud.documentai_toolbox": ["templates/*.xml.j2"],
     },
     install_requires=(
-        "google-api-core>=2.15.0, <3.0.0",
+        "google-api-core>=2.25.0, <3.0.0",
         "pandas[performance,gcp]>=2.0.0, <3.0.0",
         "pyarrow>=15.0.0, <23.0.0",
         "tabulate>=0.9.0, <1.0.0",
         "proto-plus>=1.22.3, <2.0.0",
         "proto-plus >= 1.25.0, <2.0.0; python_version>='3.13'",
-        "grpc-google-iam-v1>=0.12.6, <1.0.0",
+        "grpc-google-iam-v1>=0.14.2, <1.0.0",
         "google-cloud-bigquery>=3.14.0, <4.0.0",
-        "google-cloud-documentai>=2.29.2, <4.0.0",
+        "google-cloud-documentai>=3.2.1, <4.0.0",
         "google-cloud-storage>=2.3.0, <4.0.0",
-        "google-cloud-vision>=3.2.0, <4.0.0",
+        "google-cloud-vision>=3.10.1, <4.0.0",
         "numpy>=1.23.5, <3.0.0",
         "intervaltree>=3.0.0",
         "pikepdf>=8.0.0, <11.0.0",
diff --git a/packages/google-cloud-filestore/setup.py b/packages/google-cloud-filestore/setup.py
index 2b74f59b7473..ecdd1303e3d1 100644
--- a/packages/google-cloud-filestore/setup.py
+++ b/packages/google-cloud-filestore/setup.py
@@ -46,7 +46,7 @@
     # Exclude incompatible versions of `google-auth`
     # See https://github.com/googleapis/google-cloud-python/issues/12364
     "google-auth >= 2.14.1, <3.0.0,!=2.24.0,!=2.25.0",
-    "google-cloud-common >= 1.0.0, <2.0.0",
+    "google-cloud-common >= 1.5.1, <2.0.0",
     "grpcio >= 1.59.0, < 2.0.0",
     "grpcio >= 1.75.1, < 2.0.0; python_version >= '3.14'",
     "proto-plus >= 1.26.1, <2.0.0",
diff --git a/packages/google-cloud-gke-hub/google/cloud/gkehub_v1/rbacrolebindingactuation_v1/__init__.py b/packages/google-cloud-gke-hub/google/cloud/gkehub_v1/rbacrolebindingactuation_v1/__init__.py
index a32bd1358a3a..b29b84210f7f 100644
--- a/packages/google-cloud-gke-hub/google/cloud/gkehub_v1/rbacrolebindingactuation_v1/__init__.py
+++ b/packages/google-cloud-gke-hub/google/cloud/gkehub_v1/rbacrolebindingactuation_v1/__init__.py
@@ -69,7 +69,7 @@
 
         def parse_version_to_tuple(version_string: str):
             """Safely converts a semantic version string to a comparable tuple of integers.
-            Example: "4.25.8" -> (4, 25, 8)
+            Example: "6.33.5" -> (6, 33, 5)
             Ignores non-numeric parts and handles common version formats.
             Args:
                 version_string: Version string in the format "x.y.z" or "x.y.z<suffix>"
@@ -98,8 +98,8 @@ def _get_version(dependency_name):
                 return (None, "--")
 
         _dependency_package = "google.protobuf"
-        _next_supported_version = "4.25.8"
-        _next_supported_version_tuple = (4, 25, 8)
+        _next_supported_version = "6.33.5"
+        _next_supported_version_tuple = (6, 33, 5)
         _recommendation = " (we recommend 6.x)"
         (_version_used, _version_used_string) = _get_version(_dependency_package)
         if _version_used and _version_used < _next_supported_version_tuple:
diff --git a/packages/google-cloud-gke-hub/setup.py b/packages/google-cloud-gke-hub/setup.py
index 368abbe13103..dfd242d73cf2 100644
--- a/packages/google-cloud-gke-hub/setup.py
+++ b/packages/google-cloud-gke-hub/setup.py
@@ -46,7 +46,7 @@
     # Exclude incompatible versions of `google-auth`
     # See https://github.com/googleapis/google-cloud-python/issues/12364
     "google-auth >= 2.14.1, <3.0.0,!=2.24.0,!=2.25.0",
-    "grpc-google-iam-v1 >=0.12.4, <1.0.0",
+    "grpc-google-iam-v1 >=0.14.2, <1.0.0",
     "grpcio >= 1.59.0, < 2.0.0",
     "grpcio >= 1.75.1, < 2.0.0; python_version >= '3.14'",
     "proto-plus >= 1.26.1, <2.0.0",
diff --git a/packages/google-cloud-iam/setup.py b/packages/google-cloud-iam/setup.py
index ec778f190ae0..95be948d4453 100644
--- a/packages/google-cloud-iam/setup.py
+++ b/packages/google-cloud-iam/setup.py
@@ -46,7 +46,7 @@
     # Exclude incompatible versions of `google-auth`
     # See https://github.com/googleapis/google-cloud-python/issues/12364
     "google-auth >= 2.14.1, <3.0.0,!=2.24.0,!=2.25.0",
-    "grpc-google-iam-v1 >=0.12.4, <1.0.0",
+    "grpc-google-iam-v1 >=0.14.2, <1.0.0",
     "grpcio >= 1.59.0, < 2.0.0",
     "grpcio >= 1.75.1, < 2.0.0; python_version >= '3.14'",
     "proto-plus >= 1.26.1, <2.0.0",
diff --git a/packages/google-cloud-logging/constraints.txt b/packages/google-cloud-logging/constraints.txt
index 4eeb7ced651b..f779df6b579d 100644
--- a/packages/google-cloud-logging/constraints.txt
+++ b/packages/google-cloud-logging/constraints.txt
@@ -1,11 +1,11 @@
 google-api-core==2.17.1
 google-auth==2.14.1
-google-cloud-appengine-logging==0.1.3
+google-cloud-appengine-logging==1.6.1
 google-cloud-audit-log==0.3.1
 google-cloud-core==2.0.0
-grpc-google-iam-v1==0.12.4
+grpc-google-iam-v1==0.14.2
 grpcio==1.59.0
 opentelemetry-api==1.16.0
 proto-plus==1.22.3
 proto-plus==1.25.0
-protobuf==4.25.8
\ No newline at end of file
+protobuf==6.33.5
\ No newline at end of file
diff --git a/packages/google-cloud-logging/setup.py b/packages/google-cloud-logging/setup.py
index f1243f3e63b6..dbb0b22aecee 100644
--- a/packages/google-cloud-logging/setup.py
+++ b/packages/google-cloud-logging/setup.py
@@ -46,7 +46,7 @@
     # Exclude incompatible versions of `google-auth`
     # See https://github.com/googleapis/google-cloud-python/issues/12364
     "google-auth >= 2.14.1, <3.0.0,!=2.24.0,!=2.25.0",
-    "google-cloud-appengine-logging>=0.1.3, <2.0.0",
+    "google-cloud-appengine-logging>=1.6.1, <2.0.0",
     "google-cloud-audit-log >= 0.3.2, < 1.0.0",
     "google-cloud-core >= 2.0.0, <3.0.0",
     "grpc-google-iam-v1 >=0.14.2, <1.0.0",
diff --git a/packages/google-cloud-logging/testing/constraints-3.10.txt b/packages/google-cloud-logging/testing/constraints-3.10.txt
index 606ef2ec0697..5afdb28c39d9 100644
--- a/packages/google-cloud-logging/testing/constraints-3.10.txt
+++ b/packages/google-cloud-logging/testing/constraints-3.10.txt
@@ -6,7 +6,7 @@
 # then this file should have google-cloud-foo==1.14.0
 google-api-core==2.25.0
 google-auth==2.14.1
-google-cloud-appengine-logging==0.1.3
+google-cloud-appengine-logging==1.6.1
 google-cloud-audit-log==0.3.2
 google-cloud-core==2.0.0
 grpc-google-iam-v1==0.14.2
diff --git a/packages/google-cloud-ndb/setup.py b/packages/google-cloud-ndb/setup.py
index 8c22f5349b16..53ccb694d3ac 100644
--- a/packages/google-cloud-ndb/setup.py
+++ b/packages/google-cloud-ndb/setup.py
@@ -40,9 +40,9 @@ def main():
     with io.open(readme_filename, encoding="utf-8") as readme_file:
         readme = readme_file.read()
     dependencies = [
-        "google-api-core[grpc] >= 2.11.0, <3.0.0",
+        "google-api-core[grpc] >= 2.25.0, <3.0.0",
         "google-cloud-datastore >= 2.16.0, != 2.20.2, < 3.0.0",
-        "protobuf >= 4.25.8, < 8.0.0",
+        "protobuf >= 6.33.5, < 8.0.0",
         "pymemcache >= 2.1.0, < 5.0.0",
         "pytz >= 2022.1",
         "redis >= 3.0.0, < 8.0.0",
diff --git a/packages/google-cloud-ndb/testing/constraints-3.10.txt b/packages/google-cloud-ndb/testing/constraints-3.10.txt
index c4835683ad0a..1c249e72604a 100644
--- a/packages/google-cloud-ndb/testing/constraints-3.10.txt
+++ b/packages/google-cloud-ndb/testing/constraints-3.10.txt
@@ -7,7 +7,7 @@
 # Then this file should have foo==1.14.0
 google-cloud-datastore==2.16.0
 google-api-core==2.11.0
-protobuf==4.25.8
+protobuf==6.33.5
 pymemcache==2.1.0
 redis==3.0.0
 pytz==2022.1
diff --git a/packages/google-cloud-storage/setup.py b/packages/google-cloud-storage/setup.py
index 33d64bbb690c..e3b589fac2c0 100644
--- a/packages/google-cloud-storage/setup.py
+++ b/packages/google-cloud-storage/setup.py
@@ -67,10 +67,10 @@
         "grpcio-status >= 1.75.1, < 2.0.0; python_version >= '3.14'",
         "proto-plus >= 1.22.3, <2.0.0; python_version < '3.13'",
         "proto-plus >= 1.25.0, <2.0.0; python_version >= '3.13'",
-        "protobuf >= 4.25.8, < 8.0.0",
-        "grpc-google-iam-v1 >= 0.14.0, <1.0.0",
+        "protobuf >= 6.33.5, < 8.0.0",
+        "grpc-google-iam-v1 >= 0.14.2, <1.0.0",
     ],
-    "protobuf": ["protobuf >= 3.20.2, < 7.0.0"],
+    "protobuf": ["protobuf >= 6.33.5, < 8.0.0"],
     "tracing": [
         "opentelemetry-api >= 1.1.0, < 2.0.0",
     ],
diff --git a/packages/google-cloud-storage/testing/constraints-3.10.txt b/packages/google-cloud-storage/testing/constraints-3.10.txt
index e4294e2f1397..d55b8a54b9fd 100644
--- a/packages/google-cloud-storage/testing/constraints-3.10.txt
+++ b/packages/google-cloud-storage/testing/constraints-3.10.txt
@@ -13,8 +13,8 @@ google-resumable-media==2.7.2
 grpcio==1.59.0
 grpcio-status==1.59.0
 proto-plus==1.22.3
-protobuf==4.25.8
-grpc-google-iam-v1==0.14.0
+protobuf==6.33.5
+grpc-google-iam-v1==0.14.2
 opentelemetry-api==1.1.0
 requests==2.22.0
 google-crc32c==1.6.0
diff --git a/packages/googleapis-common-protos/noxfile.py b/packages/googleapis-common-protos/noxfile.py
index c4c87ce1c974..e43d6651c824 100644
--- a/packages/googleapis-common-protos/noxfile.py
+++ b/packages/googleapis-common-protos/noxfile.py
@@ -208,30 +208,16 @@ def install_unittest_dependencies(session, *constraints):
 @nox.session(python=UNIT_TEST_PYTHON_VERSIONS)
 @nox.parametrize(
     "protobuf_implementation",
-    ["python", "upb", "cpp"],
+    ["python", "upb"],
 )
 def unit(session, protobuf_implementation):
     # Install all test dependencies, then install this package in-place.
 
-    if protobuf_implementation == "cpp" and session.python in (
-        "3.11",
-        "3.12",
-        "3.13",
-        "3.14",
-    ):
-        session.skip("cpp implementation is not supported in python 3.11+")
-
     constraints_path = str(
         CURRENT_DIRECTORY / "testing" / f"constraints-{session.python}.txt"
     )
     install_unittest_dependencies(session, "-c", constraints_path)
 
-    # TODO(https://github.com/googleapis/synthtool/issues/1976):
-    # Remove the 'cpp' implementation once support for Protobuf 3.x is dropped.
-    # The 'cpp' implementation requires Protobuf<4.
-    if protobuf_implementation == "cpp":
-        session.install("protobuf<4")
-
     # Run py.test against the unit tests.
     session.run(
         "py.test",
@@ -421,7 +407,7 @@ def docfx(session):
 @nox.session(python=DEFAULT_PYTHON_VERSION)
 @nox.parametrize(
     "protobuf_implementation",
-    ["python", "upb", "cpp"],
+    ["python", "upb"],
 )
 def prerelease_deps(session, protobuf_implementation):
     """
@@ -431,14 +417,6 @@ def prerelease_deps(session, protobuf_implementation):
     `pip install --pre <package>`.
     """
 
-    if protobuf_implementation == "cpp" and session.python in (
-        "3.11",
-        "3.12",
-        "3.13",
-        "3.14",
-    ):
-        session.skip("cpp implementation is not supported in python 3.11+")
-
     # Install all dependencies
     session.install("-e", ".")
 
diff --git a/packages/googleapis-common-protos/pyproject.toml b/packages/googleapis-common-protos/pyproject.toml
index c95e4f9062c9..28c06f9ef283 100644
--- a/packages/googleapis-common-protos/pyproject.toml
+++ b/packages/googleapis-common-protos/pyproject.toml
@@ -39,7 +39,7 @@ classifiers = [
   "Topic :: Internet",
 ]
 dependencies = [
-  "protobuf >= 4.25.8, < 8.0.0",
+  "protobuf >= 6.33.5, < 8.0.0",
 ]
 
 [project.urls]
diff --git a/packages/googleapis-common-protos/testing/constraints-3.10-python-pubsub.txt b/packages/googleapis-common-protos/testing/constraints-3.10-python-pubsub.txt
deleted file mode 100644
index 0d45849ee764..000000000000
--- a/packages/googleapis-common-protos/testing/constraints-3.10-python-pubsub.txt
+++ /dev/null
@@ -1,9 +0,0 @@
-# This constraints file is used to check that lower bounds
-# are correct in setup.py
-# List *all* library dependencies and extras in this file.
-# Pin the version to the lower bound.
-#
-# e.g., if setup.py has "foo >= 1.14.0, < 2.0.0dev",
-# Then this file should have foo==1.14.0
-protobuf==4.25.8
-grpcio==1.59.0
\ No newline at end of file
diff --git a/packages/googleapis-common-protos/testing/constraints-3.10.txt b/packages/googleapis-common-protos/testing/constraints-3.10.txt
index e72cafcdd6f9..dcaf1f5238c3 100644
--- a/packages/googleapis-common-protos/testing/constraints-3.10.txt
+++ b/packages/googleapis-common-protos/testing/constraints-3.10.txt
@@ -5,5 +5,5 @@
 #
 # e.g., if setup.py has "foo >= 1.14.0, < 2.0.0dev",
 # Then this file should have foo==1.14.0
-protobuf==4.25.8
+protobuf==6.33.5
 grpcio==1.59.0
diff --git a/packages/grpc-google-iam-v1/noxfile.py b/packages/grpc-google-iam-v1/noxfile.py
index b22bedf724db..291eb1341764 100644
--- a/packages/grpc-google-iam-v1/noxfile.py
+++ b/packages/grpc-google-iam-v1/noxfile.py
@@ -208,30 +208,16 @@ def install_unittest_dependencies(session, *constraints):
 @nox.session(python=UNIT_TEST_PYTHON_VERSIONS)
 @nox.parametrize(
     "protobuf_implementation",
-    ["python", "upb", "cpp"],
+    ["python", "upb"],
 )
 def unit(session, protobuf_implementation):
     # Install all test dependencies, then install this package in-place.
 
-    if protobuf_implementation == "cpp" and session.python in (
-        "3.11",
-        "3.12",
-        "3.13",
-        "3.14",
-    ):
-        session.skip("cpp implementation is not supported in python 3.11+")
-
     constraints_path = str(
         CURRENT_DIRECTORY / "testing" / f"constraints-{session.python}.txt"
     )
     install_unittest_dependencies(session, "-c", constraints_path)
 
-    # TODO(https://github.com/googleapis/synthtool/issues/1976):
-    # Remove the 'cpp' implementation once support for Protobuf 3.x is dropped.
-    # The 'cpp' implementation requires Protobuf<4.
-    if protobuf_implementation == "cpp":
-        session.install("protobuf<4")
-
     # Run py.test against the unit tests.
     session.run(
         "py.test",
@@ -421,7 +407,7 @@ def docfx(session):
 @nox.session(python=DEFAULT_PYTHON_VERSION)
 @nox.parametrize(
     "protobuf_implementation",
-    ["python", "upb", "cpp"],
+    ["python", "upb"],
 )
 def prerelease_deps(session, protobuf_implementation):
     """
@@ -431,14 +417,6 @@ def prerelease_deps(session, protobuf_implementation):
     `pip install --pre <package>`.
     """
 
-    if protobuf_implementation == "cpp" and session.python in (
-        "3.11",
-        "3.12",
-        "3.13",
-        "3.14",
-    ):
-        session.skip("cpp implementation is not supported in python 3.11+")
-
     # Install all dependencies
     session.install("-e", ".")
 
diff --git a/packages/grpc-google-iam-v1/pyproject.toml b/packages/grpc-google-iam-v1/pyproject.toml
index e8975612f8f0..65d80436cfcf 100644
--- a/packages/grpc-google-iam-v1/pyproject.toml
+++ b/packages/grpc-google-iam-v1/pyproject.toml
@@ -40,8 +40,8 @@ classifiers = [
 ]
 dependencies = [
   "grpcio >= 1.59.0, < 2.0.0",
-  "googleapis-common-protos[grpc] >= 1.63.2, < 2.0.0",
-  "protobuf >= 4.25.8, < 8.0.0",
+  "googleapis-common-protos[grpc] >= 1.69.2, < 2.0.0",
+  "protobuf >= 6.33.5, < 8.0.0",
 ]
 
 [project.urls]
diff --git a/packages/grpc-google-iam-v1/testing/constraints-3.10-python-pubsub.txt b/packages/grpc-google-iam-v1/testing/constraints-3.10-python-pubsub.txt
index e72cafcdd6f9..dcaf1f5238c3 100644
--- a/packages/grpc-google-iam-v1/testing/constraints-3.10-python-pubsub.txt
+++ b/packages/grpc-google-iam-v1/testing/constraints-3.10-python-pubsub.txt
@@ -5,5 +5,5 @@
 #
 # e.g., if setup.py has "foo >= 1.14.0, < 2.0.0dev",
 # Then this file should have foo==1.14.0
-protobuf==4.25.8
+protobuf==6.33.5
 grpcio==1.59.0
diff --git a/packages/grpc-google-iam-v1/testing/constraints-3.10.txt b/packages/grpc-google-iam-v1/testing/constraints-3.10.txt
index e72cafcdd6f9..dcaf1f5238c3 100644
--- a/packages/grpc-google-iam-v1/testing/constraints-3.10.txt
+++ b/packages/grpc-google-iam-v1/testing/constraints-3.10.txt
@@ -5,5 +5,5 @@
 #
 # e.g., if setup.py has "foo >= 1.14.0, < 2.0.0dev",
 # Then this file should have foo==1.14.0
-protobuf==4.25.8
+protobuf==6.33.5
 grpcio==1.59.0
diff --git a/packages/pandas-gbq/setup.py b/packages/pandas-gbq/setup.py
index de65ff230c85..78e22dca2c4d 100644
--- a/packages/pandas-gbq/setup.py
+++ b/packages/pandas-gbq/setup.py
@@ -33,7 +33,7 @@
     # Note: google-api-core and google-auth are also included via transitive
     # dependency on google-cloud-bigquery, but this library also uses them
     # directly.
-    "google-api-core >= 2.15.0, <3.0.0",
+    "google-api-core >= 2.25.0, <3.0.0",
     "google-auth >=2.14.1",
     "google-auth-oauthlib >=0.7.0",
     # Please also update the minimum version in pandas_gbq/features.py to
diff --git a/packages/pandas-gbq/testing/constraints-3.10.txt b/packages/pandas-gbq/testing/constraints-3.10.txt
index 1a92652d1ba9..9e20c3801079 100644
--- a/packages/pandas-gbq/testing/constraints-3.10.txt
+++ b/packages/pandas-gbq/testing/constraints-3.10.txt
@@ -11,7 +11,7 @@ pandas==1.5.3
 psutil==5.9.8
 pyarrow==12.0.0
 pydata-google-auth==1.5.0
-google-api-core==2.15.0
+google-api-core==2.25.0
 google-auth==2.14.1
 google-auth-oauthlib==0.7.0
 google-cloud-bigquery==3.20.0
diff --git a/packages/proto-plus/noxfile.py b/packages/proto-plus/noxfile.py
index 047e6d9b2221..57a12b5eaa13 100644
--- a/packages/proto-plus/noxfile.py
+++ b/packages/proto-plus/noxfile.py
@@ -54,20 +54,10 @@
 
 
 @nox.session(python=PYTHON_VERSIONS)
-@nox.parametrize("implementation", ["cpp", "upb", "python"])
+@nox.parametrize("implementation", ["upb", "python"])
 def unit(session, implementation):
     """Run the unit test suite."""
 
-    # TODO(https://github.com/googleapis/gapic-generator-python/issues/2388):
-    # Remove this check once support for Protobuf 3.x is dropped.
-    if implementation == "cpp" and session.python in (
-        "3.11",
-        "3.12",
-        "3.13",
-        "3.14",
-    ):
-        session.skip("cpp implementation is not supported in python 3.11+")
-
     constraints_path = str(
         CURRENT_DIRECTORY / "testing" / f"constraints-{session.python}.txt"
     )
@@ -75,11 +65,6 @@ def unit(session, implementation):
     session.env["PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION"] = implementation
     session.install("coverage", "pytest", "pytest-cov", "pytz")
     session.install("-e", ".[testing]", "-c", constraints_path)
-    # TODO(https://github.com/googleapis/proto-plus-python/issues/389):
-    # Remove the 'cpp' implementation once support for Protobuf 3.x is dropped.
-    # The 'cpp' implementation requires Protobuf<4.
-    if implementation == "cpp":
-        session.install("protobuf<4")
 
     # TODO(https://github.com/googleapis/proto-plus-python/issues/403): re-enable `-W=error`
     # The warnings-as-errors flag `-W=error` was removed in
diff --git a/packages/proto-plus/pyproject.toml b/packages/proto-plus/pyproject.toml
index efe9a2a3b2ec..4f0c30439ba1 100644
--- a/packages/proto-plus/pyproject.toml
+++ b/packages/proto-plus/pyproject.toml
@@ -38,7 +38,7 @@ classifiers = [
   "Topic :: Software Development :: Code Generators",
   "Topic :: Software Development :: Libraries :: Python Modules",
 ]
-dependencies = ["protobuf >= 4.25.8, < 8.0.0"]
+dependencies = ["protobuf >= 6.33.5, < 8.0.0"]
 dynamic = ["version"]
 
 [project.urls]
@@ -47,7 +47,7 @@ Repository = "https://github.com/googleapis/google-cloud-python"
 Homepage = "https://github.com/googleapis/google-cloud-python/tree/main/packages/proto-plus"
 
 [project.optional-dependencies]
-testing = ["google-api-core >= 1.31.5"]
+testing = ["google-api-core >= 2.25.0"]
 
 [tool.setuptools.dynamic]
 version = { attr = "proto.version.__version__" }
diff --git a/packages/proto-plus/testing/constraints-3.10.txt b/packages/proto-plus/testing/constraints-3.10.txt
index 2aa3356da157..4781776b4626 100644
--- a/packages/proto-plus/testing/constraints-3.10.txt
+++ b/packages/proto-plus/testing/constraints-3.10.txt
@@ -5,5 +5,5 @@
 #
 # e.g., if setup.py has "foo >= 1.14.0, < 2.0.0dev",
 # Then this file should have foo==1.14.0
-google-api-core==2.11.0
-protobuf==4.25.8
+google-api-core==2.25.0
+protobuf==6.33.5
diff --git a/packages/proto-plus/tests/test_fields_enum.py b/packages/proto-plus/tests/test_fields_enum.py
index de1184b3979e..aa66dcfca444 100644
--- a/packages/proto-plus/tests/test_fields_enum.py
+++ b/packages/proto-plus/tests/test_fields_enum.py
@@ -12,9 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import os
 import proto
-import pytest
 import sys
 
 
@@ -357,25 +355,6 @@ class Task(proto.Message):
     assert t == t2
 
 
-if os.environ.get("PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION", "python") == "cpp":
-    # This test only works, and is only relevant, with the cpp runtime.
-    # Python just doesn't give a care and lets it work anyway.
-    def test_enum_alias_bad():
-        # Certain enums may shadow the different enum monikers with the same value.
-        # This is generally discouraged, and protobuf will object by default,
-        # but will explicitly allow this behavior if the enum is defined with
-        # the `allow_alias` option set.
-        with pytest.raises(TypeError):
-            # The wrapper message is a hack to avoid manifest wrangling to
-            # define the enum.
-            class BadMessage(proto.Message):
-                class BadEnum(proto.Enum):
-                    UNKNOWN = 0
-                    DEFAULT = 0
-
-                bad_dup_enum = proto.Field(proto.ENUM, number=1, enum=BadEnum)
-
-
 def test_enum_alias_good():
     # Have to split good and bad enum alias into two tests so that the generated
     # file descriptor is properly created.
diff --git a/packages/sqlalchemy-bigquery/noxfile.py b/packages/sqlalchemy-bigquery/noxfile.py
index b1e6b068c872..ea8d0281fb2e 100644
--- a/packages/sqlalchemy-bigquery/noxfile.py
+++ b/packages/sqlalchemy-bigquery/noxfile.py
@@ -267,20 +267,12 @@ def install_unittest_dependencies(session, *constraints):
 @nox.session(python=ALL_PYTHON)
 @nox.parametrize(
     "protobuf_implementation",
-    ["python", "upb", "cpp"],
+    ["python", "upb"],
 )
 @_calculate_duration
 def unit(session, protobuf_implementation, install_extras=True):
     # Install all test dependencies, then install this package in-place.
 
-    if protobuf_implementation == "cpp" and session.python in (
-        "3.11",
-        "3.12",
-        "3.13",
-        "3.14",
-    ):
-        session.skip("cpp implementation is not supported in python 3.11+")
-
     constraints_path = str(
         CURRENT_DIRECTORY / "testing" / f"constraints-{session.python}.txt"
     )
@@ -294,12 +286,6 @@ def unit(session, protobuf_implementation, install_extras=True):
         install_target = "."
     session.install("-e", install_target, "-c", constraints_path)
 
-    # TODO(https://github.com/googleapis/synthtool/issues/1976):
-    # Remove the 'cpp' implementation once support for Protobuf 3.x is dropped.
-    # The 'cpp' implementation requires Protobuf<4.
-    if protobuf_implementation == "cpp":
-        session.install("protobuf<4")
-
     session.run("python", "-m", "pip", "freeze")
 
     # Run py.test against the unit tests.
@@ -562,20 +548,12 @@ def docfx(session):
 @nox.session(python=DEFAULT_PYTHON_VERSION)
 @nox.parametrize(
     "protobuf_implementation",
-    ["python", "upb", "cpp"],
+    ["python", "upb"],
 )
 @_calculate_duration
 def prerelease_deps(session, protobuf_implementation):
     """Run all tests with prerelease versions of dependencies installed."""
 
-    if protobuf_implementation == "cpp" and session.python in (
-        "3.11",
-        "3.12",
-        "3.13",
-        "3.14",
-    ):
-        session.skip("cpp implementation is not supported in python 3.11+")
-
     # Install all dependencies
     session.install("-e", ".[all, tests]")
     unit_deps_all = UNIT_TEST_STANDARD_DEPENDENCIES + UNIT_TEST_EXTERNAL_DEPENDENCIES
diff --git a/packages/sqlalchemy-bigquery/setup.py b/packages/sqlalchemy-bigquery/setup.py
index bdfb262bf4c2..1c042d054f7e 100644
--- a/packages/sqlalchemy-bigquery/setup.py
+++ b/packages/sqlalchemy-bigquery/setup.py
@@ -111,10 +111,7 @@ def readme():
     ],
     platforms="Posix; MacOS X; Windows",
     install_requires=[
-        "google-api-core >= 2.11.1, <3.0.0,!=2.0.*,!=2.1.*,!=2.2.*,!=2.3.0",
-        # NOTE: Maintainers, please do not require google-auth>=2.x.x
-        # Until this issue is closed
-        # https://github.com/googleapis/google-cloud-python/issues/10566
+        "google-api-core >= 2.25.0, <3.0.0",
         "google-auth>=2.14.1,<3.0.0",
         "google-cloud-bigquery>=3.20.0,<4.0.0",
         "packaging",
diff --git a/packages/sqlalchemy-bigquery/testing/constraints-3.10.txt b/packages/sqlalchemy-bigquery/testing/constraints-3.10.txt
index 31dd91a92cb5..31e0294b8bc4 100644
--- a/packages/sqlalchemy-bigquery/testing/constraints-3.10.txt
+++ b/packages/sqlalchemy-bigquery/testing/constraints-3.10.txt
@@ -8,7 +8,7 @@ sqlalchemy==1.4.16
 google-auth==2.14.1
 google-cloud-bigquery==3.20.0
 google-cloud-bigquery-storage==2.18.0
-google-api-core==2.11.1
+google-api-core==2.25.0
 grpcio==1.47.0
 numpy==1.26.4
 alembic==1.7.7