diff --git a/.evergreen/config.yml b/.evergreen/config.yml
index 6ec839c605..d4e48a29c0 100644
--- a/.evergreen/config.yml
+++ b/.evergreen/config.yml
@@ -777,6 +777,10 @@ axes:
   - id: "mongodb-version"
     display_name: MongoDB Version
     values:
+      - id: "rapid"
+        display_name: "Rapid"
+        variables:
+          MONGODB_VERSION: "rapid"
       - id: "8.0"
         display_name: "8.0"
         variables:
@@ -1245,7 +1249,7 @@ buildvariants:
   - matrix_name: "single-lb"
     matrix_spec:
       ruby: "ruby-4.0"
-      mongodb-version: "8.0"
+      mongodb-version: ["8.0", "rapid"]
       topology: load-balanced
       single-mongos: single-mongos
       os: ubuntu2204
@@ -1269,7 +1273,7 @@ buildvariants:
   - matrix_name: "single-mongos"
     matrix_spec:
       ruby: "ruby-4.0"
-      mongodb-version: "8.0"
+      mongodb-version: ["8.0", "rapid"]
       topology: "sharded-cluster"
       single-mongos: single-mongos
       os: ubuntu2204
@@ -1281,7 +1285,7 @@ buildvariants:
   - matrix_name: CSOT
     matrix_spec:
       ruby: "ruby-4.0"
-      mongodb-version: "8.0"
+      mongodb-version: ["8.0", "rapid"]
       topology: replica-set-single-node
       os: ubuntu2204
     display_name: "CSOT - ${mongodb-version}"
@@ -1304,7 +1308,7 @@ buildvariants:
     matrix_spec:
       retry-reads: no-retry-reads
       ruby: "ruby-4.0"
-      mongodb-version: "8.0"
+      mongodb-version: ["8.0", "rapid"]
       topology: ["standalone", "replica-set", "sharded-cluster"]
       os: ubuntu2204
     display_name: "${mongodb-version} ${topology} ${retry-reads} ${ruby}"
@@ -1316,7 +1320,7 @@ buildvariants:
     matrix_spec:
       retry-writes: no-retry-writes
       ruby: "ruby-4.0"
-      mongodb-version: "8.0"
+      mongodb-version: ["8.0", "rapid"]
       topology: [replica-set, sharded-cluster]
       os: ubuntu2204
     display_name: "${mongodb-version} ${topology} ${retry-writes} ${ruby}"
@@ -1406,7 +1410,7 @@ buildvariants:
     matrix_spec:
       auth-and-ssl: [ "auth-and-ssl", "noauth-and-nossl" ]
       ruby: "ruby-4.0"
-      mongodb-version: "8.0"
+      mongodb-version: ["8.0", "rapid"]
       topology: "replica-set"
       compressor: 'zlib'
       os: ubuntu2204
@@ -1419,7 +1423,7 @@ buildvariants:
     matrix_spec:
       auth-and-ssl: [ "auth-and-ssl", "noauth-and-nossl" ]
       ruby: "ruby-4.0"
-      mongodb-version: "8.0"
+      mongodb-version: ["8.0", "rapid"]
       topology: "replica-set"
       compressor: 'snappy'
       os: ubuntu2204
@@ -1436,7 +1440,7 @@ buildvariants:
     matrix_spec:
       auth-and-ssl: [ "auth-and-ssl", "noauth-and-nossl" ]
       ruby: "ruby-4.0"
-      mongodb-version: "8.0"
+      mongodb-version: ["8.0", "rapid"]
       topology: "replica-set"
       compressor: 'zstd'
       os: ubuntu2204
@@ -1448,7 +1452,7 @@ buildvariants:
   - matrix_name: activesupport-"ruby-4.0"
     matrix_spec:
       ruby: "ruby-4.0"
-      mongodb-version: "8.0"
+      mongodb-version: ["8.0", "rapid"]
       topology: replica-set
       as: as
       os: ubuntu2204
@@ -1460,7 +1464,7 @@ buildvariants:
   - matrix_name: bson-"ruby-4.0"
     matrix_spec:
       ruby: "ruby-4.0"
-      mongodb-version: "8.0"
+      mongodb-version: ["8.0", "rapid"]
       topology: replica-set
       bson: "*"
       os: ubuntu2204
@@ -1535,12 +1539,12 @@ buildvariants:
     tasks:
       - name: "test-mlaunch"
 
-  - matrix_name: "fle above 4.4"
+  - matrix_name: "fle"
     matrix_spec:
       auth-and-ssl: "noauth-and-nossl"
       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' ]
+      mongodb-version: [ '6.0', '7.0', '8.0', 'rapid' ]
       os: ubuntu2204
       fle: helper
     display_name: "FLE: ${mongodb-version} ${topology} ${ruby}"
@@ -1571,6 +1575,8 @@ buildvariants:
 #    tasks:
 #      - name: "test-fle"
 
+  # Runs specs against the latest server. This is not automatically run on PR's
+  # because we don't want to block PR's when the latest DB breaks something.
   - name: 'latest-server'
     activate: false
     display_name: 'Latest MongoDB Server'
@@ -1592,7 +1598,7 @@ buildvariants:
       auth-and-ssl: [ aws-regular, aws-assume-role, aws-web-identity ]
       ruby: "ruby-4.0"
       topology: standalone
-      mongodb-version: "8.0"
+      mongodb-version: ["8.0", "rapid"]
       os: ubuntu2204
     display_name: "AWS ${auth-and-ssl} ${mongodb-version} ${ruby}"
     tags: ["pr"]
diff --git a/.evergreen/config/axes.yml.erb b/.evergreen/config/axes.yml.erb
index 66f1ec5f9b..5219f22e87 100644
--- a/.evergreen/config/axes.yml.erb
+++ b/.evergreen/config/axes.yml.erb
@@ -2,6 +2,10 @@ axes:
   - id: "mongodb-version"
     display_name: MongoDB Version
     values:
+      - id: "rapid"
+        display_name: "Rapid"
+        variables:
+          MONGODB_VERSION: "rapid"
       - id: "8.0"
         display_name: "8.0"
         variables:
diff --git a/.evergreen/config/standard.yml.erb b/.evergreen/config/standard.yml.erb
index 83c0d404e1..db844c82bd 100644
--- a/.evergreen/config/standard.yml.erb
+++ b/.evergreen/config/standard.yml.erb
@@ -27,7 +27,10 @@
                      jrubies
 
   # The latest stable version of MongoDB
-  latest_stable_mdb = "8.0".inspect # so it gets quoted as a string
+  latest_stable_mdb_raw = "8.0"
+  latest_stable_mdb = latest_stable_mdb_raw.inspect # so it gets quoted as a string
+
+  stable_and_rapid = [ latest_stable_mdb_raw, "rapid" ]
 
   recent_mdb = %w( 8.0 7.0 )
 %>
@@ -112,7 +115,7 @@ buildvariants:
   - matrix_name: "single-lb"
     matrix_spec:
       ruby: <%= latest_ruby %>
-      mongodb-version: <%= latest_stable_mdb %>
+      mongodb-version: <%= stable_and_rapid %>
       topology: load-balanced
       single-mongos: single-mongos
       os: ubuntu2204
@@ -136,7 +139,7 @@ buildvariants:
   - matrix_name: "single-mongos"
     matrix_spec:
       ruby: <%= latest_ruby %>
-      mongodb-version: <%= latest_stable_mdb %>
+      mongodb-version: <%= stable_and_rapid %>
       topology: "sharded-cluster"
       single-mongos: single-mongos
       os: ubuntu2204
@@ -148,7 +151,7 @@ buildvariants:
   - matrix_name: CSOT
     matrix_spec:
       ruby: <%= latest_ruby %>
-      mongodb-version: <%= latest_stable_mdb %>
+      mongodb-version: <%= stable_and_rapid %>
       topology: replica-set-single-node
       os: ubuntu2204
     display_name: "CSOT - ${mongodb-version}"
@@ -171,7 +174,7 @@ buildvariants:
     matrix_spec:
       retry-reads: no-retry-reads
       ruby: <%= latest_ruby %>
-      mongodb-version: <%= latest_stable_mdb %>
+      mongodb-version: <%= stable_and_rapid %>
       topology: <%= topologies %>
       os: ubuntu2204
     display_name: "${mongodb-version} ${topology} ${retry-reads} ${ruby}"
@@ -183,7 +186,7 @@ buildvariants:
     matrix_spec:
       retry-writes: no-retry-writes
       ruby: <%= latest_ruby %>
-      mongodb-version: <%= latest_stable_mdb %>
+      mongodb-version: <%= stable_and_rapid %>
       topology: [replica-set, sharded-cluster]
       os: ubuntu2204
     display_name: "${mongodb-version} ${topology} ${retry-writes} ${ruby}"
@@ -270,7 +273,7 @@ buildvariants:
       - name: "run-main-test-suite"
 
  <% [
-      [latest_ruby, latest_stable_mdb, 'ubuntu2204'],
+      [latest_ruby, stable_and_rapid, 'ubuntu2204'],
       [supported_mri_ruby_2, '"6.0"', 'ubuntu2004']
     ].each do |rubies, mdb, distro|
  %>
@@ -342,12 +345,12 @@ buildvariants:
       - name: "test-mlaunch"
   <% end %>
 
-  - matrix_name: "fle above 4.4"
+  - matrix_name: "fle"
     matrix_spec:
       auth-and-ssl: "noauth-and-nossl"
       ruby: <%= supported_mri_rubies_3_ubuntu %>
       topology: [replica-set, sharded-cluster]
-      mongodb-version: [ '6.0', '7.0', '8.0' ]
+      mongodb-version: [ '6.0', '7.0', '8.0', 'rapid' ]
       os: ubuntu2204
       fle: helper
     display_name: "FLE: ${mongodb-version} ${topology} ${ruby}"
@@ -378,6 +381,8 @@ buildvariants:
 #    tasks:
 #      - name: "test-fle"
 
+  # Runs specs against the latest server. This is not automatically run on PR's
+  # because we don't want to block PR's when the latest DB breaks something.
   - name: 'latest-server'
     activate: false
     display_name: 'Latest MongoDB Server'
@@ -399,7 +404,7 @@ buildvariants:
       auth-and-ssl: [ aws-regular, aws-assume-role, aws-web-identity ]
       ruby: <%= latest_ruby %>
       topology: standalone
-      mongodb-version: <%= latest_stable_mdb %>
+      mongodb-version: <%= stable_and_rapid %>
       os: ubuntu2204
     display_name: "AWS ${auth-and-ssl} ${mongodb-version} ${ruby}"
     tags: ["pr"]
diff --git a/.evergreen/run-tests.sh b/.evergreen/run-tests.sh
index 27e02c3302..da94291800 100755
--- a/.evergreen/run-tests.sh
+++ b/.evergreen/run-tests.sh
@@ -61,6 +61,7 @@ prepare_server
 
 if test "$DOCKER_PRELOAD" != 1; then
   install_mlaunch_venv
+  pip3 install waitress
 fi
 
 # Make sure cmake is installed (in case we need to install the libmongocrypt
diff --git a/.mod/drivers-evergreen-tools b/.mod/drivers-evergreen-tools
index 9142b7055e..f3720c0b98 160000
--- a/.mod/drivers-evergreen-tools
+++ b/.mod/drivers-evergreen-tools
@@ -1 +1 @@
-Subproject commit 9142b7055ea5940e59ad41c4b069376f867031da
+Subproject commit f3720c0b98fb14a8b452670f7cda5ef8080e7eaf
diff --git a/spec/integration/client_side_encryption/kms_tls_options_spec.rb b/spec/integration/client_side_encryption/kms_tls_options_spec.rb
index a36b1d745b..ff1c1f4878 100644
--- a/spec/integration/client_side_encryption/kms_tls_options_spec.rb
+++ b/spec/integration/client_side_encryption/kms_tls_options_spec.rb
@@ -18,6 +18,13 @@
       )
     end
 
+    # 6.0 mongocrypt expects a JSON-compatible error message from the KMS, but
+    # the mock KMS server returns an HTML error page.
+    let(:affected_by_mock_kms_server_change) do
+      (kms_provider == 'azure' || kms_provider == 'gcp') &&
+        ClusterConfig.instance.server_version < '7.0'
+    end
+
     let(:client_encryption_no_client_cert) do
       Mongo::ClientEncryption.new(
         client,
@@ -314,7 +321,7 @@
         end
 
         it 'raises KmsError directly without wrapping CryptError' do
-          if should_raise_with_tls
+          if should_raise_with_tls && !affected_by_mock_kms_server_change
             begin
               client_encryption_with_tls.create_data_key(
                 kms_provider,
diff --git a/spec/support/crypt.rb b/spec/support/crypt.rb
index f6337eeb63..14b65720a1 100644
--- a/spec/support/crypt.rb
+++ b/spec/support/crypt.rb
@@ -23,6 +23,21 @@ module Crypt
 
   # For all FLE-related tests
   shared_context 'define shared FLE helpers' do
+    # SERVER-118428 -- mongocryptd rejects large messages
+    # DRIVERS-3382 -- once SERVER-118428 is fixed, remove these checks
+    before do
+      if extra_options[:mongocryptd_uri]
+        version = ClusterConfig.instance.server_version
+        bad_mongocryptd = case version
+          when /^8\.2/ then version >= '8.2.4'
+          when /^8\.0/ then version >= '8.0.18'
+          when /^7\.0/ then version >= '7.0.29'
+          else false
+          end
+        skip 'Bad mongocryptd version -- see DRIVERS-3382' if bad_mongocryptd
+      end
+    end
+
     # 96-byte binary string, base64-encoded local master key
     let(:local_master_key_b64) do
       Crypt::LOCAL_MASTER_KEY_B64