diff --git a/.evergreen/config.yml b/.evergreen/config.yml
index d64b5ba485..4f9b4fb876 100644
--- a/.evergreen/config.yml
+++ b/.evergreen/config.yml
@@ -914,10 +914,10 @@ axes:
         display_name: ruby-dev
         variables:
           RVM_RUBY: "ruby-dev"
-      - id: "ruby-3.5"
-        display_name: ruby-3.5
+      - id: "ruby-4.0"
+        display_name: ruby-4.0
         variables:
-          RVM_RUBY: "ruby-3.5"
+          RVM_RUBY: "ruby-4.0"
       - id: "ruby-3.4"
         display_name: ruby-3.4
         variables:
@@ -946,10 +946,6 @@ axes:
         display_name: ruby-2.7
         variables:
           RVM_RUBY: "ruby-2.7"
-      - id: "jruby-10"
-        display_name: jruby-10
-        variables:
-          RVM_RUBY: "jruby-10"
       - id: "jruby-9.4"
         display_name: jruby-9.4
         variables:
@@ -1170,9 +1166,19 @@ axes:
         display_name: No
 
 buildvariants:
+  - matrix_name: "ruby-dev"
+    matrix_spec:
+      ruby: "ruby-dev"
+      mongodb-version: ["8.0", "7.0"]
+      topology: "replica-set"
+      os: ubuntu2404
+    display_name: "${mongodb-version} ${os} ${topology} ${auth-and-ssl} ${ruby}"
+    tasks:
+      - name: "run-main-test-suite"
+
   - matrix_name: DriverBench
     matrix_spec:
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       mongodb-version: "8.0"
       topology: standalone
       os: ubuntu2204
@@ -1183,41 +1189,45 @@ buildvariants:
   - matrix_name: "auth/ssl"
     matrix_spec:
       auth-and-ssl: ["auth-and-ssl", "noauth-and-nossl"]
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       mongodb-version: ["8.0", "7.0"]
       topology: ["standalone", "replica-set", "sharded-cluster"]
       os: ubuntu2204
     display_name: ${auth-and-ssl} ${ruby} db-${mongodb-version} ${topology}
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
   - matrix_name: "mongo-recent"
     matrix_spec:
-      ruby: ["ruby-3.3", "ruby-3.2", "jruby-9.4"]
+      ruby: ["ruby-4.0", "ruby-3.4", "ruby-3.3", "ruby-3.2", "jruby-9.4"]
       mongodb-version: ["8.0", "7.0"]
       topology: ["standalone", "replica-set", "sharded-cluster"]
       os: ubuntu2204
     display_name: "${mongodb-version} ${os} ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
   - matrix_name: "mongo-8-arm"
     matrix_spec:
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       mongodb-version: [ '8.0' ]
       topology: ["standalone", "replica-set", "sharded-cluster"]
       os: ubuntu2404-arm
     display_name: "${mongodb-version} ${os} ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
   - matrix_name: "mongo-5.x"
     matrix_spec:
-      ruby: ["ruby-3.3", "ruby-3.2"]
+      ruby: ["ruby-4.0", "ruby-3.4"]
       mongodb-version: ['5.0']
       topology: ["standalone", "replica-set", "sharded-cluster"]
       os: ubuntu2004
     display_name: "${mongodb-version} ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
@@ -1228,88 +1238,96 @@ buildvariants:
       topology: ["standalone", "replica-set", "sharded-cluster"]
       os: ubuntu1804
     display_name: "${mongodb-version} ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
   - matrix_name: "single-lb"
     matrix_spec:
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       mongodb-version: "8.0"
       topology: load-balanced
       single-mongos: single-mongos
       os: ubuntu2204
     display_name: "${mongodb-version} ${topology} single-lb ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-mlaunch"
 
   - matrix_name: "mongo-api-version"
     matrix_spec:
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       mongodb-version: '7.0'
       topology: standalone
       api-version-required: yes
       os: ubuntu2204
     display_name: "${mongodb-version} api-version-required ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-mlaunch"
 
   - matrix_name: "single-mongos"
     matrix_spec:
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       mongodb-version: "8.0"
       topology: "sharded-cluster"
       single-mongos: single-mongos
       os: ubuntu2204
     display_name: "${mongodb-version} ${topology} single-mongos ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-mlaunch"
 
   - matrix_name: CSOT
     matrix_spec:
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       mongodb-version: "8.0"
       topology: replica-set-single-node
       os: ubuntu2204
     display_name: "CSOT - ${mongodb-version}"
+    tags: ["pr"]
     tasks:
       - name: test-csot
 
   - matrix_name: OTel
     matrix_spec:
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       mongodb-version: "8.0"
       topology: replica-set-single-node
       os: ubuntu2204
     display_name: "OTel - ${mongodb-version}"
+    tags: ["pr"]
     tasks:
       - name: test-otel
 
   - matrix_name: "no-retry-reads"
     matrix_spec:
       retry-reads: no-retry-reads
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       mongodb-version: "8.0"
       topology: ["standalone", "replica-set", "sharded-cluster"]
       os: ubuntu2204
     display_name: "${mongodb-version} ${topology} ${retry-reads} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-mlaunch"
 
   - matrix_name: "no-retry-writes"
     matrix_spec:
       retry-writes: no-retry-writes
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       mongodb-version: "8.0"
       topology: [replica-set, sharded-cluster]
       os: ubuntu2204
     display_name: "${mongodb-version} ${topology} ${retry-writes} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-mlaunch"
 
   - matrix_name: "lint"
     matrix_spec:
       lint: on
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       mongodb-version: "8.0"
       topology: ["standalone", "replica-set", "sharded-cluster"]
       os: ubuntu2204
@@ -1320,7 +1338,7 @@ buildvariants:
   - matrix_name: "fork"
     matrix_spec:
       fork: on
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       mongodb-version: "8.0"
       topology: ["standalone", "replica-set", "sharded-cluster"]
       os: ubuntu2204
@@ -1331,7 +1349,7 @@ buildvariants:
   - matrix_name: "solo"
     matrix_spec:
       solo: on
-      ruby: ["ruby-3.3", "ruby-3.2", "ruby-3.1"]
+      ruby: ["ruby-4.0", "ruby-3.4", "ruby-3.3", "ruby-3.2", "ruby-3.1"]
       mongodb-version: "8.0"
       topology: ["standalone", "replica-set", "sharded-cluster"]
       os: ubuntu2204
@@ -1353,7 +1371,7 @@ buildvariants:
   - matrix_name: "stress"
     matrix_spec:
       stress: on
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       mongodb-version: ["8.0", "7.0"]
       topology: replica-set
       os: ubuntu2204
@@ -1364,7 +1382,7 @@ buildvariants:
 #  - matrix_name: "x509-tests"
 #    matrix_spec:
 #      auth-and-ssl: "x509"
-#      ruby: "ruby-3.3"
+#      ruby: "ruby-4.0"
 #      mongodb-version: "8.0"
 #      topology: standalone
 #      os: ubuntu2204
@@ -1380,30 +1398,33 @@ buildvariants:
       topology: ["standalone", "replica-set", "sharded-cluster"]
       os: ubuntu2204
     display_name: "${mongodb-version} ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
-  - matrix_name: zlib-"ruby-3.3"
+  - matrix_name: zlib-"ruby-4.0"
     matrix_spec:
       auth-and-ssl: [ "auth-and-ssl", "noauth-and-nossl" ]
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       mongodb-version: "8.0"
       topology: "replica-set"
       compressor: 'zlib'
       os: ubuntu2204
     display_name: "${compressor} ${mongodb-version} ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
-  - matrix_name: snappy-"ruby-3.3"
+  - matrix_name: snappy-"ruby-4.0"
     matrix_spec:
       auth-and-ssl: [ "auth-and-ssl", "noauth-and-nossl" ]
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       mongodb-version: "8.0"
       topology: "replica-set"
       compressor: 'snappy'
       os: ubuntu2204
     display_name: "${compressor} ${mongodb-version} ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
@@ -1411,37 +1432,40 @@ buildvariants:
   # apparently a zstd-jni gem for JRuby that we could investigate here; if
   # this test is ever supported to support jruby, the `sample_mri_rubies`
   # reference should be replaced with `sample_rubies`.
-  - matrix_name: zstd-auth-"ruby-3.3"
+  - matrix_name: zstd-auth-"ruby-4.0"
     matrix_spec:
       auth-and-ssl: [ "auth-and-ssl", "noauth-and-nossl" ]
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       mongodb-version: "8.0"
       topology: "replica-set"
       compressor: 'zstd'
       os: ubuntu2204
     display_name: "${compressor} ${mongodb-version} ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
-  - matrix_name: activesupport-"ruby-3.3"
+  - matrix_name: activesupport-"ruby-4.0"
     matrix_spec:
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       mongodb-version: "8.0"
       topology: replica-set
       as: as
       os: ubuntu2204
     display_name: "AS ${mongodb-version} ${topology} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-mlaunch"
 
-  - matrix_name: bson-"ruby-3.3"
+  - matrix_name: bson-"ruby-4.0"
     matrix_spec:
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       mongodb-version: "8.0"
       topology: replica-set
       bson: "*"
       os: ubuntu2204
     display_name: "bson-${bson} ${mongodb-version} ${topology} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-mlaunch"
   - matrix_name: zlib-"ruby-2.7"
@@ -1453,6 +1477,7 @@ buildvariants:
       compressor: 'zlib'
       os: ubuntu2004
     display_name: "${compressor} ${mongodb-version} ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
@@ -1465,6 +1490,7 @@ buildvariants:
       compressor: 'snappy'
       os: ubuntu2004
     display_name: "${compressor} ${mongodb-version} ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
@@ -1481,6 +1507,7 @@ buildvariants:
       compressor: 'zstd'
       os: ubuntu2004
     display_name: "${compressor} ${mongodb-version} ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
@@ -1492,6 +1519,7 @@ buildvariants:
       as: as
       os: ubuntu2004
     display_name: "AS ${mongodb-version} ${topology} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-mlaunch"
 
@@ -1503,32 +1531,26 @@ buildvariants:
       bson: "*"
       os: ubuntu2004
     display_name: "bson-${bson} ${mongodb-version} ${topology} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-mlaunch"
 
   - matrix_name: "fle above 4.4"
     matrix_spec:
       auth-and-ssl: "noauth-and-nossl"
-      ruby: ["ruby-3.3", "ruby-3.2", "ruby-3.1"]
+      ruby: ["ruby-4.0", "ruby-3.4", "ruby-3.3", "ruby-3.2", "ruby-3.1"]
       topology: [replica-set, sharded-cluster]
       mongodb-version: [ '6.0', '7.0', '8.0' ]
       os: ubuntu2204
       fle: helper
     display_name: "FLE: ${mongodb-version} ${topology} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-fle"
-  # kerberos integration tests are broken (RUBY-3266)
-  # - matrix_name: "kerberos-integration"
-  #   matrix_spec:
-  #     ruby: ["ruby-3.3", "ruby-2.7", "jruby-9.4"]
-  #     os: rhel8
-  #   display_name: "Kerberos integration ${os} ${ruby}"
-  #   tasks:
-  #     - name: "test-kerberos-integration"
 
   - matrix_name: "kerberos-unit"
     matrix_spec:
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       mongodb-version: "8.0"
       topology: standalone
       os: ubuntu2204
@@ -1556,11 +1578,12 @@ buildvariants:
       # auth-and-ssl: [ aws-regular, aws-assume-role, aws-ecs, aws-web-identity ]
       # https://jira.mongodb.org/browse/RUBY-3659
       auth-and-ssl: [ aws-regular, aws-assume-role, aws-web-identity ]
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       topology: standalone
       mongodb-version: "8.0"
       os: ubuntu2204
     display_name: "AWS ${auth-and-ssl} ${mongodb-version} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-aws-auth"
 
@@ -1568,11 +1591,12 @@ buildvariants:
     matrix_spec:
       ocsp-verifier: true
       # No JRuby due to https://github.com/jruby/jruby-openssl/issues/210
-      ruby: ["ruby-3.3", "ruby-3.2", "ruby-3.1"]
+      ruby: ["ruby-4.0", "ruby-3.4", "ruby-3.3", "ruby-3.2", "ruby-3.1"]
       topology: standalone
       mongodb-version: "8.0"
       os: ubuntu2204
     display_name: "OCSP verifier: ${mongodb-version} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: test-mlaunch
 
@@ -1581,7 +1605,7 @@ buildvariants:
       ocsp-algorithm: ecdsa
       ocsp-must-staple: on
       ocsp-delegate: on
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       topology: standalone
       mongodb-version: "8.0"
       os: ubuntu2204
@@ -1594,7 +1618,7 @@ buildvariants:
     matrix_spec:
       ocsp-algorithm: rsa
       ocsp-status: unknown
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       topology: standalone
       mongodb-version: "8.0"
       os: ubuntu2204
@@ -1610,11 +1634,12 @@ buildvariants:
       ocsp-delegate: '*'
       ocsp-connectivity: pass
       extra-uri-options: "none"
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       topology: standalone
       mongodb-version: "8.0"
       os: ubuntu2204
     display_name: "OCSP connectivity: ${ocsp-algorithm} ${ocsp-status} ${ocsp-delegate} ${extra-uri-options} ${mongodb-version} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: test-mlaunch
   - matrix_name: ocsp-connectivity
@@ -1624,11 +1649,12 @@ buildvariants:
       ocsp-delegate: '*'
       ocsp-connectivity: pass
       extra-uri-options: "none"
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       topology: standalone
       mongodb-version: "8.0"
       os: ubuntu2204
     display_name: "OCSP connectivity: ${ocsp-algorithm} ${ocsp-status} ${ocsp-delegate} ${extra-uri-options} ${mongodb-version} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: test-mlaunch
   - matrix_name: ocsp-connectivity
@@ -1638,11 +1664,12 @@ buildvariants:
       ocsp-delegate: '*'
       ocsp-connectivity: fail
       extra-uri-options: "none"
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       topology: standalone
       mongodb-version: "8.0"
       os: ubuntu2204
     display_name: "OCSP connectivity: ${ocsp-algorithm} ${ocsp-status} ${ocsp-delegate} ${extra-uri-options} ${mongodb-version} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: test-mlaunch
   - matrix_name: ocsp-connectivity
@@ -1652,11 +1679,12 @@ buildvariants:
       ocsp-delegate: '*'
       ocsp-connectivity: pass
       extra-uri-options: "tlsInsecure=true"
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       topology: standalone
       mongodb-version: "8.0"
       os: ubuntu2204
     display_name: "OCSP connectivity: ${ocsp-algorithm} ${ocsp-status} ${ocsp-delegate} ${extra-uri-options} ${mongodb-version} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: test-mlaunch
   - matrix_name: ocsp-connectivity
@@ -1666,11 +1694,12 @@ buildvariants:
       ocsp-delegate: '*'
       ocsp-connectivity: pass
       extra-uri-options: "tlsInsecure=true"
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       topology: standalone
       mongodb-version: "8.0"
       os: ubuntu2204
     display_name: "OCSP connectivity: ${ocsp-algorithm} ${ocsp-status} ${ocsp-delegate} ${extra-uri-options} ${mongodb-version} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: test-mlaunch
   - matrix_name: ocsp-connectivity
@@ -1680,11 +1709,12 @@ buildvariants:
       ocsp-delegate: '*'
       ocsp-connectivity: pass
       extra-uri-options: "tlsInsecure=true"
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       topology: standalone
       mongodb-version: "8.0"
       os: ubuntu2204
     display_name: "OCSP connectivity: ${ocsp-algorithm} ${ocsp-status} ${ocsp-delegate} ${extra-uri-options} ${mongodb-version} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: test-mlaunch
   - matrix_name: ocsp-connectivity
@@ -1694,11 +1724,12 @@ buildvariants:
       ocsp-delegate: '*'
       ocsp-connectivity: pass
       extra-uri-options: "tlsAllowInvalidCertificates=true"
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       topology: standalone
       mongodb-version: "8.0"
       os: ubuntu2204
     display_name: "OCSP connectivity: ${ocsp-algorithm} ${ocsp-status} ${ocsp-delegate} ${extra-uri-options} ${mongodb-version} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: test-mlaunch
   - matrix_name: ocsp-connectivity
@@ -1708,11 +1739,12 @@ buildvariants:
       ocsp-delegate: '*'
       ocsp-connectivity: pass
       extra-uri-options: "tlsAllowInvalidCertificates=true"
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       topology: standalone
       mongodb-version: "8.0"
       os: ubuntu2204
     display_name: "OCSP connectivity: ${ocsp-algorithm} ${ocsp-status} ${ocsp-delegate} ${extra-uri-options} ${mongodb-version} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: test-mlaunch
   - matrix_name: ocsp-connectivity
@@ -1722,11 +1754,12 @@ buildvariants:
       ocsp-delegate: '*'
       ocsp-connectivity: pass
       extra-uri-options: "tlsAllowInvalidCertificates=true"
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       topology: standalone
       mongodb-version: "8.0"
       os: ubuntu2204
     display_name: "OCSP connectivity: ${ocsp-algorithm} ${ocsp-status} ${ocsp-delegate} ${extra-uri-options} ${mongodb-version} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: test-mlaunch
 
@@ -1747,13 +1780,14 @@ buildvariants:
       mongodb-version: "8.0"
       os: ubuntu2204
     display_name: "OCSP connectivity: ${ocsp-algorithm} ${ocsp-status} ${ocsp-delegate} ${mongodb-version} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: test-mlaunch
 
   # https://jira.mongodb.org/browse/RUBY-3540
   #- matrix_name: testgcpkms-variant
   #  matrix_spec:
-  #    ruby: "ruby-3.3"
+  #    ruby: "ruby-4.0"
   #    fle: helper
   #    topology: standalone
   #    os: ubuntu2204
@@ -1778,7 +1812,7 @@ buildvariants:
 
   - matrix_name: atlas-full
     matrix_spec:
-      ruby: "ruby-3.3"
+      ruby: "ruby-4.0"
       os: ubuntu2204
     display_name: "Atlas (Full)"
     tasks:
@@ -1786,9 +1820,10 @@ buildvariants:
 
   - matrix_name: "atlas"
     matrix_spec:
-      ruby: ["ruby-3.3", "ruby-3.2", "ruby-3.1"]
+      ruby: ["ruby-4.0", "ruby-3.4", "ruby-3.3", "ruby-3.2", "ruby-3.1"]
       os: ubuntu2204
     display_name: "Atlas  connectivity tests ${ruby}"
+    tags: ["pr"]
     tasks:
        - name: test-atlas
 
diff --git a/.evergreen/config/axes.yml.erb b/.evergreen/config/axes.yml.erb
index 3bd44c95ea..66f1ec5f9b 100644
--- a/.evergreen/config/axes.yml.erb
+++ b/.evergreen/config/axes.yml.erb
@@ -139,10 +139,10 @@ axes:
         display_name: ruby-dev
         variables:
           RVM_RUBY: "ruby-dev"
-      - id: "ruby-3.5"
-        display_name: ruby-3.5
+      - id: "ruby-4.0"
+        display_name: ruby-4.0
         variables:
-          RVM_RUBY: "ruby-3.5"
+          RVM_RUBY: "ruby-4.0"
       - id: "ruby-3.4"
         display_name: ruby-3.4
         variables:
@@ -171,10 +171,6 @@ axes:
         display_name: ruby-2.7
         variables:
           RVM_RUBY: "ruby-2.7"
-      - id: "jruby-10"
-        display_name: jruby-10
-        variables:
-          RVM_RUBY: "jruby-10"
       - id: "jruby-9.4"
         display_name: jruby-9.4
         variables:
diff --git a/.evergreen/config/standard.yml.erb b/.evergreen/config/standard.yml.erb
index 6118d1bb99..3479edd631 100644
--- a/.evergreen/config/standard.yml.erb
+++ b/.evergreen/config/standard.yml.erb
@@ -3,28 +3,22 @@
 
   # latest_ruby = the most recently released, stable version of Ruby
   #    (make sure this version is being built by 10gen/mongo-ruby-toolchain)
-  latest_ruby = "ruby-3.3".inspect # so it gets quoted as a string
+  latest_ruby = "ruby-4.0".inspect # so it gets quoted as a string
 
   # these are used for testing against a few recent ruby versions
-  recent_rubies = %w( ruby-3.3 ruby-3.2 jruby-9.4 )
+  recent_rubies = %w( ruby-4.0 ruby-3.4 ruby-3.3 ruby-3.2 jruby-9.4 )
 
-  recent_mri_rubies = %w( ruby-3.3 ruby-3.2 )
-
-  # this is a list of the most recent 3.x and 2.x MRI ruby versions
-  sample_mri_rubies = %w( ruby-3.3 ruby-2.7 )
-
-  # as above, but including the most recent JRuby release
-  sample_rubies = sample_mri_rubies + %w( jruby-9.4 )
+  recent_mri_rubies = %w( ruby-4.0 ruby-3.4 )
 
   # older Ruby versions provided by 10gen/mongo-ruby-toolchain
   older_rubies = %w( ruby-3.0 ruby-2.7  )
 
   # all supported JRuby versions provided by 10gen/mongo-ruby-toolchain
-  jrubies = %w( jruby-9.4 jruby-9.3 )
+  jrubies = %w( jruby-9.4 )
 
-  supported_mri_rubies_3 = %w( ruby-3.3 ruby-3.2 ruby-3.1 ruby-3.0 )
+  supported_mri_rubies_3 = %w( ruby-4.0 ruby-3.4 ruby-3.3 ruby-3.2 ruby-3.1 ruby-3.0 )
 
-  supported_mri_rubies_3_ubuntu = %w( ruby-3.3 ruby-3.2 ruby-3.1 )
+  supported_mri_rubies_3_ubuntu = %w( ruby-4.0 ruby-3.4 ruby-3.3 ruby-3.2 ruby-3.1 )
 
   supported_mri_ruby_2 = "ruby-2.7".inspect
 
@@ -40,6 +34,16 @@
 %>
 
 buildvariants:
+  - matrix_name: "ruby-dev"
+    matrix_spec:
+      ruby: "ruby-dev"
+      mongodb-version: <%= recent_mdb %>
+      topology: "replica-set"
+      os: ubuntu2404
+    display_name: "${mongodb-version} ${os} ${topology} ${auth-and-ssl} ${ruby}"
+    tasks:
+      - name: "run-main-test-suite"
+
   - matrix_name: DriverBench
     matrix_spec:
       ruby: <%= latest_ruby %>
@@ -58,6 +62,7 @@ buildvariants:
       topology: <%= topologies %>
       os: ubuntu2204
     display_name: ${auth-and-ssl} ${ruby} db-${mongodb-version} ${topology}
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
@@ -68,6 +73,7 @@ buildvariants:
       topology: <%= topologies %>
       os: ubuntu2204
     display_name: "${mongodb-version} ${os} ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
@@ -78,6 +84,7 @@ buildvariants:
       topology: <%= topologies %>
       os: ubuntu2404-arm
     display_name: "${mongodb-version} ${os} ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
@@ -88,6 +95,7 @@ buildvariants:
       topology: <%= topologies %>
       os: ubuntu2004
     display_name: "${mongodb-version} ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
@@ -98,6 +106,7 @@ buildvariants:
       topology: <%= topologies %>
       os: ubuntu1804
     display_name: "${mongodb-version} ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
@@ -109,6 +118,7 @@ buildvariants:
       single-mongos: single-mongos
       os: ubuntu2204
     display_name: "${mongodb-version} ${topology} single-lb ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-mlaunch"
 
@@ -120,6 +130,7 @@ buildvariants:
       api-version-required: yes
       os: ubuntu2204
     display_name: "${mongodb-version} api-version-required ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-mlaunch"
 
@@ -131,6 +142,7 @@ buildvariants:
       single-mongos: single-mongos
       os: ubuntu2204
     display_name: "${mongodb-version} ${topology} single-mongos ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-mlaunch"
 
@@ -141,6 +153,7 @@ buildvariants:
       topology: replica-set-single-node
       os: ubuntu2204
     display_name: "CSOT - ${mongodb-version}"
+    tags: ["pr"]
     tasks:
       - name: test-csot
 
@@ -151,6 +164,7 @@ buildvariants:
       topology: replica-set-single-node
       os: ubuntu2204
     display_name: "OTel - ${mongodb-version}"
+    tags: ["pr"]
     tasks:
       - name: test-otel
 
@@ -162,6 +176,7 @@ buildvariants:
       topology: <%= topologies %>
       os: ubuntu2204
     display_name: "${mongodb-version} ${topology} ${retry-reads} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-mlaunch"
 
@@ -173,6 +188,7 @@ buildvariants:
       topology: [replica-set, sharded-cluster]
       os: ubuntu2204
     display_name: "${mongodb-version} ${topology} ${retry-writes} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-mlaunch"
 
@@ -250,6 +266,7 @@ buildvariants:
       topology: <%= topologies %>
       os: ubuntu2204
     display_name: "${mongodb-version} ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
@@ -267,6 +284,7 @@ buildvariants:
       compressor: 'zlib'
       os: <%= distro %>
     display_name: "${compressor} ${mongodb-version} ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
@@ -279,6 +297,7 @@ buildvariants:
       compressor: 'snappy'
       os: <%= distro %>
     display_name: "${compressor} ${mongodb-version} ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
@@ -295,6 +314,7 @@ buildvariants:
       compressor: 'zstd'
       os: <%= distro %>
     display_name: "${compressor} ${mongodb-version} ${topology} ${auth-and-ssl} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "run-main-test-suite"
 
@@ -306,6 +326,7 @@ buildvariants:
       as: as
       os: <%= distro %>
     display_name: "AS ${mongodb-version} ${topology} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-mlaunch"
 
@@ -317,6 +338,7 @@ buildvariants:
       bson: "*"
       os: <%= distro %>
     display_name: "bson-${bson} ${mongodb-version} ${topology} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-mlaunch"
   <% end %>
@@ -330,16 +352,9 @@ buildvariants:
       os: ubuntu2204
       fle: helper
     display_name: "FLE: ${mongodb-version} ${topology} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-fle"
-  # kerberos integration tests are broken (RUBY-3266)
-  # - matrix_name: "kerberos-integration"
-  #   matrix_spec:
-  #     ruby: <%= sample_rubies %>
-  #     os: rhel8
-  #   display_name: "Kerberos integration ${os} ${ruby}"
-  #   tasks:
-  #     - name: "test-kerberos-integration"
 
   - matrix_name: "kerberos-unit"
     matrix_spec:
@@ -376,6 +391,7 @@ buildvariants:
       mongodb-version: <%= latest_stable_mdb %>
       os: ubuntu2204
     display_name: "AWS ${auth-and-ssl} ${mongodb-version} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: "test-aws-auth"
 
@@ -388,6 +404,7 @@ buildvariants:
       mongodb-version: <%= latest_stable_mdb %>
       os: ubuntu2204
     display_name: "OCSP verifier: ${mongodb-version} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: test-mlaunch
 
@@ -444,6 +461,7 @@ buildvariants:
       mongodb-version: <%= latest_stable_mdb %>
       os: ubuntu2204
     display_name: "OCSP connectivity: ${ocsp-algorithm} ${ocsp-status} ${ocsp-delegate} ${extra-uri-options} ${mongodb-version} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: test-mlaunch
   <% end %>
@@ -465,6 +483,7 @@ buildvariants:
       mongodb-version: <%= latest_stable_mdb %>
       os: ubuntu2204
     display_name: "OCSP connectivity: ${ocsp-algorithm} ${ocsp-status} ${ocsp-delegate} ${mongodb-version} ${ruby}"
+    tags: ["pr"]
     tasks:
       - name: test-mlaunch
 
@@ -507,6 +526,7 @@ buildvariants:
       ruby: <%= supported_mri_rubies_3_ubuntu %>
       os: ubuntu2204
     display_name: "Atlas  connectivity tests ${ruby}"
+    tags: ["pr"]
     tasks:
        - name: test-atlas
 
diff --git a/gemfiles/standard.rb b/gemfiles/standard.rb
index d03b9ec7f3..3a8f01ff96 100644
--- a/gemfiles/standard.rb
+++ b/gemfiles/standard.rb
@@ -41,6 +41,8 @@ def standard_dependencies
         gem 'ruby-debug-ide'
       end
     end
+
+    gem 'ostruct' if RUBY_VERSION >= '3.4'
   end
 
   group :testing do
diff --git a/spec/mongo/client_construction_spec.rb b/spec/mongo/client_construction_spec.rb
index 48f4039b4a..e1331f1dea 100644
--- a/spec/mongo/client_construction_spec.rb
+++ b/spec/mongo/client_construction_spec.rb
@@ -1666,21 +1666,23 @@
           require_no_linting
 
           it 'rejects bogus read preference as symbol' do
+            read = BSON::Document.new({ mode: :bogus })
             expect do
-              new_local_client_nmio(SINGLE_CLIENT, read: { mode: :bogus })
+              new_local_client_nmio(SINGLE_CLIENT, read: read)
             end.to raise_error(
               Mongo::Error::InvalidReadOption,
-              'Invalid read preference value: {"mode"=>:bogus}: ' \
+              "Invalid read preference value: #{read}: " \
               'mode bogus is not one of recognized modes'
             )
           end
 
           it 'rejects bogus read preference as string' do
+            read = BSON::Document.new({ mode: 'bogus' })
             expect do
-              new_local_client_nmio(SINGLE_CLIENT, read: { mode: 'bogus' })
+              new_local_client_nmio(SINGLE_CLIENT, read: read)
             end.to raise_error(
               Mongo::Error::InvalidReadOption,
-              'Invalid read preference value: {"mode"=>"bogus"}: mode bogus is not one of recognized modes'
+              "Invalid read preference value: #{read}: mode bogus is not one of recognized modes"
             )
           end
 
diff --git a/spec/mongo/monitoring/event/cmap/pool_created_spec.rb b/spec/mongo/monitoring/event/cmap/pool_created_spec.rb
index 637c46ba18..cf9a1d980f 100644
--- a/spec/mongo/monitoring/event/cmap/pool_created_spec.rb
+++ b/spec/mongo/monitoring/event/cmap/pool_created_spec.rb
@@ -30,7 +30,7 @@
     end
 
     it 'renders correctly' do
-      expect(event.summary).to eq("#<PoolCreated address=127.0.0.1:27017 options={:wait_queue_timeout=>3, :min_pool_size=>5} pool=0x#{pool.object_id}>")
+      expect(event.summary).to eq("#<PoolCreated address=127.0.0.1:27017 options=#{options} pool=0x#{pool.object_id}>")
     end
   end
 end