diff --git a/.evergreen/config.yml b/.evergreen/config.yml
index d77769d3da..0b64eb0fe8 100644
--- a/.evergreen/config.yml
+++ b/.evergreen/config.yml
@@ -26,6 +26,11 @@ timeout:
       args: [ls, -la]
 
 functions:
+  assume-test-secrets-ec2-role: 
+    - command: ec2.assume_role
+      params:
+        role_arn: ${aws_test_secrets_role}
+
   setup-system:
     # Executes clone and applies the submitted patch, if any
     - command: git.get_project
@@ -109,9 +114,13 @@ functions:
         display_name: test_suite.tgz
 
   bootstrap-mongohoused:
+    - command: ec2.assume_role
+      params:
+        role_arn: ${aws_test_secrets_role}
     - command: subprocess.exec
       params:
         binary: bash
+        add_expansions_to_env: true
         args: 
           - ${DRIVERS_TOOLS}/.evergreen/atlas_data_lake/pull-mongohouse-image.sh
     - command: subprocess.exec
@@ -376,20 +385,6 @@ functions:
         binary: bash
         args: [*task-runner, evg-test-load-balancers]
 
-  run-serverless-tests:
-    - command: subprocess.exec
-      type: test
-      params:
-        binary: "bash"
-        env:
-          SERVERLESS: "serverless"
-        args: [*task-runner, setup-test]
-    - command: subprocess.exec
-      type: test
-      params:
-        binary: "bash"
-        args: [*task-runner, evg-test-serverless]
-
   run-atlas-data-lake-test:
     - command: subprocess.exec
       type: test
@@ -1606,14 +1601,6 @@ tasks:
       - func: start-cse-servers
       - func: run-retry-kms-requests
 
-  - name: "test-serverless"
-    tags: ["serverless"]
-    commands:
-      - func: start-cse-servers
-      - func: "run-serverless-tests"
-        vars:
-          MONGO_GO_DRIVER_COMPRESSOR: "snappy"
-
   - name: "testgcpkms-task"
     commands:
     - command: subprocess.exec
@@ -1636,20 +1623,24 @@ tasks:
 
   - name: "testawskms-task"
     commands:
+    - func: assume-test-secrets-ec2-role
     - command: subprocess.exec
       type: test
       params:
         binary: "bash"
+        add_expansions_to_env: true
         args: [*task-runner, test-awskms]
 
   - name: "testawskms-fail-task"
     # testawskms-fail-task runs without environment variables.
     # It is expected to fail to obtain credentials.
     commands:
+    - func: assume-test-secrets-ec2-role
     - command: subprocess.exec
       type: test
       params:
         binary: "bash"
+        add_expansions_to_env: true
         env: 
           EXPECT_ERROR: 'status=400'
         args: [*task-runner, test-awskms]
@@ -1660,16 +1651,19 @@ tasks:
       type: test
       params:
         binary: bash
+        add_expansions_to_env: true
         args: [*task-runner, test-azurekms]
 
   - name: "testazurekms-fail-task"
     # testazurekms-fail-task runs without environment variables.
     # It is expected to fail to obtain credentials.
     commands:
+    - func: assume-test-secrets-ec2-role
     - command: subprocess.exec
       type: test
       params:
         binary: bash
+        add_expansions_to_env: true
         env:
           EXPECT_ERROR: "1"
         args: [*task-runner, test-azurekms]
@@ -1681,10 +1675,6 @@ tasks:
 
   - name: "test-aws-lambda-deployed"
     commands:
-      - command: ec2.assume_role
-        params:
-          role_arn: ${LAMBDA_AWS_ROLE_ARN}
-          duration_seconds: 3600
       - command: subprocess.exec
         type: test
         params:
@@ -1896,49 +1886,17 @@ axes:
         variables:
           GO_DIST: "/opt/golang/go1.23"
 
-  - id: os-serverless
-    display_name: OS
-    values:
-      - id: "rhel87"
-        display_name: "RHEL 8.7"
-        run_on: rhel8.7-small
-        variables:
-          GO_DIST: "/opt/golang/go1.23"
-
 task_groups:
-  - name: serverless_task_group
-    setup_group_can_fail_task: true
-    setup_group_timeout_secs: 1800 # 30 minutes
-    setup_group:
-      - func: setup-system
-      - command: subprocess.exec
-        params:
-          binary: "bash"
-          args: 
-            - ${DRIVERS_TOOLS}/.evergreen/serverless/setup.sh
-      - command: expansions.update
-        params:
-          file: serverless-expansion.yml
-    teardown_group:
-      - command: subprocess.exec
-        params:
-          binary: "bash"
-          args:
-            - ${DRIVERS_TOOLS}/.evergreen/serverless/teardown.sh
-      - func: teardown
-      - func: handle-test-artifacts
-      
-    tasks:
-      - ".serverless"
-
   - name: testgcpkms_task_group
     setup_group_can_fail_task: true
     setup_group_timeout_secs: 1800 # 30 minutes
     setup_group:
       - func: setup-system
+      - func: assume-test-secrets-ec2-role
       - command: subprocess.exec
         params:
           binary: "bash"
+          add_expansions_to_env: true
           args: 
             - ${DRIVERS_TOOLS}/.evergreen/csfle/gcpkms/setup.sh
     teardown_group:
@@ -1958,9 +1916,11 @@ task_groups:
     setup_group_timeout_secs: 1800 # 30 minutes
     setup_group:
       - func: setup-system
+      - func: assume-test-secrets-ec2-role
       - command: subprocess.exec
         params:
           binary: bash
+          add_expansions_to_env: true
           env: 
             AZUREKMS_VMNAME_PREFIX: GODRIVER
           args:
@@ -2013,9 +1973,11 @@ task_groups:
     teardown_group_timeout_secs: 180 # 3 minutes (max allowed time)
     setup_group:
       - func: setup-system
+      - func: assume-test-secrets-ec2-role
       - command: subprocess.exec
         params:
           binary: bash
+          add_expansions_to_env: true
           env:
             AZUREOIDC_VMNAME_PREFIX: "GO_DRIVER"
           args:
@@ -2038,9 +2000,11 @@ task_groups:
     teardown_group_timeout_secs: 180 # 3 minutes (max allowed time)
     setup_group:
       - func: setup-system
+      - func: assume-test-secrets-ec2-role
       - command: subprocess.exec
         params:
           binary: bash
+          add_expansions_to_env: true
           env:
             AZUREOIDC_VMNAME_PREFIX: "GO_DRIVER"
           args:
@@ -2063,6 +2027,7 @@ task_groups:
     teardown_group_timeout_secs: 180 # 3 minutes (max allowed time)
     setup_group:
       - func: setup-system
+      - func: assume-test-secrets-ec2-role
       - command: subprocess.exec
         params:
           binary: bash
@@ -2083,10 +2048,12 @@ task_groups:
   - name: test-aws-lambda-task-group
     setup_group:
       - func: setup-system
+      - func: assume-test-secrets-ec2-role
       - command: subprocess.exec
         params:
           working_dir: src/go.mongodb.org/mongo-driver
           binary: bash
+          add_expansions_to_env: true
           env:
             LAMBDA_STACK_NAME: dbx-go-lambda
           args:
@@ -2340,13 +2307,6 @@ buildvariants:
     tasks:
       - name: ".load-balancer"
 
-  - matrix_name: "serverless"
-    tags: ["pullrequest"]
-    matrix_spec: { os-serverless: "*" }
-    display_name: "Serverless ${os-serverless}"
-    tasks:
-      - "serverless_task_group"
-
   - matrix_name: "kms-kmip-test"
     matrix_spec: { version: ["7.0"], os-ssl-40: ["rhel87-64"] }
     display_name: "KMS KMIP ${os-ssl-40}"
diff --git a/Taskfile.yml b/Taskfile.yml
index 6784d855c2..ab552205f5 100644
--- a/Taskfile.yml
+++ b/Taskfile.yml
@@ -165,24 +165,6 @@ tasks:
   evg-test-ocsp:
     - go test -v ./mongo -run TestOCSP ${OCSP_TLS_SHOULD_SUCCEED} >> test.suite
 
-  evg-test-serverless:
-    # Serverless should be tested with all unified tests as well as tests in the following components: CRUD, load balancer,
-    # retryable reads, retryable writes, sessions, transactions and cursor behavior.
-    - go test ${BUILD_TAGS} ./internal/integration -run TestWriteErrorsWithLabels -v -timeout {{.TEST_TIMEOUT}}s >> test.suite
-    - go test ${BUILD_TAGS} ./internal/integration -run TestWriteErrorsDetails -v -timeout {{.TEST_TIMEOUT}}s >> test.suite
-    - go test ${BUILD_TAGS} ./internal/integration -run TestHintErrors -v -timeout {{.TEST_TIMEOUT}}s >> test.suite
-    - go test ${BUILD_TAGS} ./internal/integration -run TestWriteConcernError -v -timeout {{.TEST_TIMEOUT}}s >> test.suite
-    - go test ${BUILD_TAGS} ./internal/integration -run TestErrorsCodeNamePropagated -v -timeout {{.TEST_TIMEOUT}}s >> test.suite
-    - go test ${BUILD_TAGS} ./internal/integration -run TestLoadBalancerSupport -v -timeout {{.TEST_TIMEOUT}}s >> test.suite
-    - go test ${BUILD_TAGS} ./internal/integration -run TestRetryableReadsProse -v -timeout {{.TEST_TIMEOUT}}s >> test.suite
-    - go test ${BUILD_TAGS} ./internal/integration -run TestRetryableWritesProse -v -timeout {{.TEST_TIMEOUT}}s >> test.suite
-    - go test ${BUILD_TAGS} ./internal/integration -run TestSessionsProse -v -timeout {{.TEST_TIMEOUT}}s >> test.suite
-    - go test ${BUILD_TAGS} ./internal/integration -run TestConvenientTransactions -v -timeout {{.TEST_TIMEOUT}}s >> test.suite
-    - go test ${BUILD_TAGS} ./internal/integration -run TestCursor -v -timeout {{.TEST_TIMEOUT}}s >> test.suite
-    - go test ${BUILD_TAGS} ./internal/integration/unified -run TestUnifiedSpec -v -timeout {{.TEST_TIMEOUT}}s >> test.suite
-    - go test -exec "env PKG_CONFIG_PATH=${PKG_CONFIG_PATH} LD_LIBRARY_PATH=${LD_LIBRARY_PATH} DYLD_LIBRARY_PATH=${MACOS_LIBRARY_PATH}" ${BUILD_TAGS} -v -timeout {{.TEST_TIMEOUT}}s ./internal/integration -run TestClientSideEncryptionSpec >> test.suite
-    - go test -exec "env PKG_CONFIG_PATH=${PKG_CONFIG_PATH} LD_LIBRARY_PATH=${LD_LIBRARY_PATH} DYLD_LIBRARY_PATH=${MACOS_LIBRARY_PATH}" ${BUILD_TAGS} -v -timeout {{.TEST_TIMEOUT}}s ./internal/integration -run TestClientSideEncryptionProse >> test.suite
-
   evg-test-versioned-api:
     # Versioned API related tests are in the mongo, integration and unified packages.
     - go test -exec "env PKG_CONFIG_PATH=${PKG_CONFIG_PATH} LD_LIBRARY_PATH=${LD_LIBRARY_PATH} DYLD_LIBRARY_PATH=${MACOS_LIBRARY_PATH}" ${BUILD_TAGS} -v -timeout {{.TEST_TIMEOUT}}s ./mongo >> test.suite
diff --git a/etc/run-awskms-test.sh b/etc/run-awskms-test.sh
index e37c27f57f..11c6adb953 100755
--- a/etc/run-awskms-test.sh
+++ b/etc/run-awskms-test.sh
@@ -10,9 +10,13 @@ task build-kms-test
 export MONGODB_URI="$ATLAS_FREE"
 
 if [ -z "${EXPECT_ERROR:-}" ]; then
-    . ${DRIVERS_TOOLS}/.evergreen/csfle/setup-secrets.sh
-    export AWS_SECRET_ACCESS_KEY=$FLE_AWS_SECRET_ACCESS_KEY
-    export AWS_ACCESS_KEY_ID=$FLE_AWS_ACCESS_KEY_ID
+  . ${DRIVERS_TOOLS}/.evergreen/csfle/setup-secrets.sh
+  export AWS_SECRET_ACCESS_KEY=$FLE_AWS_SECRET_ACCESS_KEY
+  export AWS_ACCESS_KEY_ID=$FLE_AWS_ACCESS_KEY_ID
 fi
 
+# AWS_SESSION_TOKEN is required to get credentials from the drivers/csfle vault
+# but interferes with the testkms binary causing UnrecognizedClientException.
+unset AWS_SESSION_TOKEN
+
 LD_LIBRARY_PATH=./install/libmongocrypt/lib64 PROVIDER='aws' ./testkms