diff --git a/docs/reference/create-client.txt b/docs/reference/create-client.txt
index 56a69df192..b5b15ebca1 100644
--- a/docs/reference/create-client.txt
+++ b/docs/reference/create-client.txt
@@ -619,8 +619,9 @@ Ruby Options
      -  ``{ :mode => :primary }``
 
    * - ``:read_concern``
-     - Specifies the read concern options. The only valid key is ``level``, for which the valid
-       values are ``:local``, ``:majority``, and ``:snapshot``.
+     - Specifies the read concern options. The only valid key is ``level``,
+       for which the valid values are ``:local``, ``:majority``, and
+       ``:snapshot``.
      - ``Hash``
      - none
 
diff --git a/lib/mongo/client.rb b/lib/mongo/client.rb
index 34fe7da4ae..0464fbbfca 100644
--- a/lib/mongo/client.rb
+++ b/lib/mongo/client.rb
@@ -887,6 +887,7 @@ def reconnect
     #
     #   See https://docs.mongodb.com/manual/reference/command/listDatabases/
     #   for more information and usage.
+    # @option opts [ Session ] :session The session to use.
     #
     # @return [ Array<String> ] The names of the databases.
     #
@@ -910,6 +911,7 @@ def database_names(filter = {}, opts = {})
     #
     #   See https://docs.mongodb.com/manual/reference/command/listDatabases/
     #   for more information and usage.
+    # @option opts [ Session ] :session The session to use.
     #
     # @return [ Array<Hash> ] The info for each database.
     #
@@ -930,6 +932,8 @@ def list_databases(filter = {}, name_only = false, opts = {})
     # @param [ Hash ] filter The filter criteria for getting a list of databases.
     # @param [ Hash ] opts The command options.
     #
+    # @option opts [ Session ] :session The session to use.
+    #
     # @return [ Array<Mongo::Database> ] The list of database objects.
     #
     # @since 2.5.0
diff --git a/lib/mongo/database.rb b/lib/mongo/database.rb
index a907758bf6..1db2a69908 100644
--- a/lib/mongo/database.rb
+++ b/lib/mongo/database.rb
@@ -253,12 +253,12 @@ def read_command(operation, opts = {})
 
       client.send(:with_session, opts) do |session|
         read_with_retry(session, preference) do |server|
-          Operation::Command.new({
-            :selector => operation.dup,
-            :db_name => name,
-            :read => preference,
-            :session => session
-          }).execute(server, context: Operation::Context.new(client: client, session: session))
+          Operation::Command.new(
+            selector: operation.dup,
+            db_name: name,
+            read: preference,
+            session: session,
+          ).execute(server, context: Operation::Context.new(client: client, session: session))
         end
       end
     end
diff --git a/lib/mongo/database/view.rb b/lib/mongo/database/view.rb
index 32492439e1..03076dec4c 100644
--- a/lib/mongo/database/view.rb
+++ b/lib/mongo/database/view.rb
@@ -57,6 +57,7 @@ class View
       #
       #   See https://docs.mongodb.com/manual/reference/command/listCollections/
       #   for more information and usage.
+      # @option options [ Session ] :session The session to use.
       #
       # @return [ Array<String> ] The names of all non-system collections.
       #
@@ -100,12 +101,13 @@ def collection_names(options = {})
       #
       #   See https://docs.mongodb.com/manual/reference/command/listCollections/
       #   for more information and usage.
+      # @option options [ Session ] :session The session to use.
       #
       # @return [ Array<Hash> ] Info for each collection in the database.
       #
       # @since 2.0.5
       def list_collections(options = {})
-        session = client.send(:get_session)
+        session = client.send(:get_session, options)
         collections_info(session, ServerSelector.primary, options)
       end
 
diff --git a/lib/mongo/error.rb b/lib/mongo/error.rb
index 62826ecf62..1a63311185 100644
--- a/lib/mongo/error.rb
+++ b/lib/mongo/error.rb
@@ -223,6 +223,8 @@ def add_label(label)
 require 'mongo/error/no_srv_records'
 require 'mongo/error/session_ended'
 require 'mongo/error/sessions_not_supported'
+require 'mongo/error/snapshot_session_invalid_server_version'
+require 'mongo/error/snapshot_session_transaction_prohibited'
 require 'mongo/error/operation_failure'
 require 'mongo/error/pool_closed_error'
 require 'mongo/error/raise_original_error'
diff --git a/lib/mongo/error/snapshot_session_invalid_server_version.rb b/lib/mongo/error/snapshot_session_invalid_server_version.rb
new file mode 100644
index 0000000000..e8a14c2d62
--- /dev/null
+++ b/lib/mongo/error/snapshot_session_invalid_server_version.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+# encoding: utf-8
+
+# Copyright (C) 2021 MongoDB Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+module Mongo
+  class Error
+
+    # Exception raised if an operation using a snapshot session is
+    # directed to a pre-5.0 server.
+    class SnapshotSessionInvalidServerVersion < Error
+
+      # Instantiate the new exception.
+      def initialize
+        super("Snapshot reads require MongoDB 5.0 or later")
+      end
+    end
+  end
+end
diff --git a/lib/mongo/error/snapshot_session_transaction_prohibited.rb b/lib/mongo/error/snapshot_session_transaction_prohibited.rb
new file mode 100644
index 0000000000..93fd5e6a1f
--- /dev/null
+++ b/lib/mongo/error/snapshot_session_transaction_prohibited.rb
@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+# encoding: utf-8
+
+# Copyright (C) 2021 MongoDB Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+module Mongo
+  class Error
+
+    # Exception raised if a transaction is attempted on a snapshot session.
+    class SnapshotSessionTransactionProhibited < Error
+
+      # Instantiate the new exception.
+      def initialize
+        super("Transactions are not supported in snapshot sessions")
+      end
+    end
+  end
+end
diff --git a/lib/mongo/operation/result.rb b/lib/mongo/operation/result.rb
index d31ceac3a5..953bd39e6a 100644
--- a/lib/mongo/operation/result.rb
+++ b/lib/mongo/operation/result.rb
@@ -429,6 +429,12 @@ def write_concern_error?
         !!(first_document && first_document['writeConcernError'])
       end
 
+      def snapshot_timestamp
+        if doc = reply.documents.first
+          doc['cursor']&.[]('atClusterTime') || doc['atClusterTime']
+        end
+      end
+
       private
 
       def aggregate_returned_count
diff --git a/lib/mongo/operation/shared/executable.rb b/lib/mongo/operation/shared/executable.rb
index abe8dbfc4f..7bc04a3100 100644
--- a/lib/mongo/operation/shared/executable.rb
+++ b/lib/mongo/operation/shared/executable.rb
@@ -43,6 +43,10 @@ def do_execute(connection, context, options = {})
                       session.pin_to_service(connection.service_id)
                     end
                   end
+
+                  if session.snapshot? && !session.snapshot_timestamp
+                    session.snapshot_timestamp = result.snapshot_timestamp
+                  end
                 end
                 process_result(result, connection)
               end
diff --git a/lib/mongo/operation/shared/sessions_supported.rb b/lib/mongo/operation/shared/sessions_supported.rb
index d2328e642d..1a00c5cfa1 100644
--- a/lib/mongo/operation/shared/sessions_supported.rb
+++ b/lib/mongo/operation/shared/sessions_supported.rb
@@ -224,6 +224,17 @@ def apply_session_options(sel, connection)
         then
           sel[:recoveryToken] = session.recovery_token
         end
+
+        if session.snapshot?
+          unless connection.description.server_version_gte?('5.0')
+            raise Error::SnapshotSessionInvalidServerVersion
+          end
+
+          sel[:readConcern] = {level: 'snapshot'}
+          if session.snapshot_timestamp
+            sel[:readConcern][:atClusterTime] = session.snapshot_timestamp
+          end
+        end
       end
 
       def build_message(connection, context)
diff --git a/lib/mongo/session.rb b/lib/mongo/session.rb
index 99a805497f..b695c5c87c 100644
--- a/lib/mongo/session.rb
+++ b/lib/mongo/session.rb
@@ -56,10 +56,16 @@ class Session
     #   - *:mode* -- the read preference as a string or symbol; valid values are
     #     *:primary*, *:primary_preferred*, *:secondary*, *:secondary_preferred*
     #     and *:nearest*.
+    # @option options [ true | false ] :snapshot Set up the session for
+    #   snapshot reads.
     #
     # @since 2.5.0
     # @api private
     def initialize(server_session, client, options = {})
+      if options[:causal_consistency] && options[:snapshot]
+        raise ArgumentError, ':causal_consistency and :snapshot options cannot be both set on a session'
+      end
+
       @server_session = server_session
       options = options.dup
 
@@ -83,6 +89,12 @@ def cluster
       @client.cluster
     end
 
+    # @return [ true | false ] Whether the session is configured for snapshot
+    #   reads.
+    def snapshot?
+      !!options[:snapshot]
+    end
+
     # @return [ BSON::Timestamp ] The latest seen operation time for this session.
     #
     # @since 2.5.0
@@ -506,6 +518,10 @@ def start_transaction(options = nil)
 =end
       end
 
+      if snapshot?
+        raise Mongo::Error::SnapshotSessionTransactionProhibited
+      end
+
       check_if_ended!
 
       if within_states?(STARTING_TRANSACTION_STATE, TRANSACTION_IN_PROGRESS_STATE)
@@ -1024,6 +1040,9 @@ def txn_num
       @server_session.txn_num
     end
 
+    # @api private
+    attr_accessor :snapshot_timestamp
+
     private
 
     # Get the read concern the session will use when starting a transaction.
diff --git a/spec/runners/unified/crud_operations.rb b/spec/runners/unified/crud_operations.rb
index 1c734b7960..535492cfb6 100644
--- a/spec/runners/unified/crud_operations.rb
+++ b/spec/runners/unified/crud_operations.rb
@@ -29,7 +29,11 @@ def find(op)
     def count_documents(op)
       collection = entities.get(:collection, op.use!('object'))
       use_arguments(op) do |args|
-        collection.find(args.use!('filter')).count_documents
+        opts = {}
+        if session = args.use('session')
+          opts[:session] = entities.get(:session, session)
+        end
+        collection.find(args.use!('filter')).count_documents(**opts)
       end
     end
 
@@ -47,7 +51,11 @@ def estimated_document_count(op)
     def distinct(op)
       collection = entities.get(:collection, op.use!('object'))
       use_arguments(op) do |args|
-        req = collection.find(args.use!('filter')).distinct(args.use!('fieldName'))
+        opts = {}
+        if session = args.use('session')
+          opts[:session] = entities.get(:session, session)
+        end
+        req = collection.find(args.use!('filter'), **opts).distinct(args.use!('fieldName'), **opts)
         result = req.to_a
       end
     end
@@ -61,6 +69,9 @@ def find_one_and_update(op)
         if return_document = args.use('returnDocument')
           opts[:return_document] = return_document.downcase.to_sym
         end
+        if session = args.use('session')
+          opts[:session] = entities.get(:session, session)
+        end
         collection.find_one_and_update(filter, update, **opts)
       end
     end
@@ -70,7 +81,11 @@ def find_one_and_replace(op)
       use_arguments(op) do |args|
         filter = args.use!('filter')
         update = args.use!('replacement')
-        collection.find_one_and_replace(filter, update)
+        opts = {}
+        if session = args.use('session')
+          opts[:session] = entities.get(:session, session)
+        end
+        collection.find_one_and_replace(filter, update, **opts)
       end
     end
 
@@ -78,7 +93,11 @@ def find_one_and_delete(op)
       collection = entities.get(:collection, op.use!('object'))
       use_arguments(op) do |args|
         filter = args.use!('filter')
-        collection.find_one_and_delete(filter)
+        opts = {}
+        if session = args.use('session')
+          opts[:session] = entities.get(:session, session)
+        end
+        collection.find_one_and_delete(filter, **opts)
       end
     end
 
@@ -96,18 +115,25 @@ def insert_one(op)
     def insert_many(op)
       collection = entities.get(:collection, op.use!('object'))
       use_arguments(op) do |args|
-        options = {}
+        opts = {}
         unless (ordered = args.use('ordered')).nil?
-          options[:ordered] = ordered
+          opts[:ordered] = ordered
+        end
+        if session = args.use('session')
+          opts[:session] = entities.get(:session, session)
         end
-        collection.insert_many(args.use!('documents'), **options)
+        collection.insert_many(args.use!('documents'), **opts)
       end
     end
 
     def update_one(op)
       collection = entities.get(:collection, op.use!('object'))
       use_arguments(op) do |args|
-        collection.update_one(args.use!('filter'), args.use!('update'))
+        opts = {}
+        if session = args.use('session')
+          opts[:session] = entities.get(:session, session)
+        end
+        collection.update_one(args.use!('filter'), args.use!('update'), **opts)
       end
     end
 
@@ -132,7 +158,11 @@ def replace_one(op)
     def delete_one(op)
       collection = entities.get(:collection, op.use!('object'))
       use_arguments(op) do |args|
-        collection.delete_one(args.use!('filter'))
+        opts = {}
+        if session = args.use('session')
+          opts[:session] = entities.get(:session, session)
+        end
+        collection.delete_one(args.use!('filter'), **opts)
       end
     end
 
@@ -157,6 +187,20 @@ def bulk_write(op)
       end
     end
 
+    def aggregate(op)
+      obj = entities.get_any(op.use!('object'))
+      args = op.use!('arguments')
+      pipeline = args.use!('pipeline')
+      opts = {}
+      if session = args.use('session')
+        opts[:session] = entities.get(:session, session)
+      end
+      unless args.empty?
+        raise NotImplementedError, "Unhandled spec keys: #{args} in #{test_spec}"
+      end
+      obj.aggregate(pipeline, **opts).to_a
+    end
+
     private
 
     def convert_bulk_write_spec(spec)
@@ -192,15 +236,5 @@ def convert_bulk_write_spec(spec)
       end
       {Utils.underscore(op) =>out}
     end
-
-    def aggregate(op)
-      obj = entities.get_any(op.use!('object'))
-      args = op.use!('arguments')
-      pipeline = args.use!('pipeline')
-      unless args.empty?
-        raise NotImplementedError, "Unhandled spec keys: #{test_spec}"
-      end
-      obj.aggregate(pipeline).to_a
-    end
   end
 end
diff --git a/spec/runners/unified/ddl_operations.rb b/spec/runners/unified/ddl_operations.rb
index dae9ad9966..59f66e308c 100644
--- a/spec/runners/unified/ddl_operations.rb
+++ b/spec/runners/unified/ddl_operations.rb
@@ -7,7 +7,13 @@ module DdlOperations
 
     def list_databases(op)
       client = entities.get(:client, op.use!('object'))
-      client.list_databases
+      use_arguments(op) do |args|
+        opts = {}
+        if session = args.use('session')
+          opts[:session] = entities.get(:session, session)
+        end
+        client.list_databases({}, false, **opts)
+      end
     end
 
     def create_collection(op)
@@ -28,6 +34,17 @@ def create_collection(op)
       end
     end
 
+    def list_collections(op)
+      database = entities.get(:database, op.use!('object'))
+      use_arguments(op) do |args|
+        opts = {}
+        if session = args.use('session')
+          opts[:session] = entities.get(:session, session)
+        end
+        database.list_collections(**opts)
+      end
+    end
+
     def drop_collection(op)
       database = entities.get(:database, op.use!('object'))
       use_arguments(op) do |args|
@@ -58,6 +75,17 @@ def assert_collection_not_exists(op)
       assert_collection_exists(op, false)
     end
 
+    def list_indexes(op)
+      collection = entities.get(:collection, op.use!('object'))
+      use_arguments(op) do |args|
+        opts = {}
+        if session = args.use('session')
+          opts[:session] = entities.get(:session, session)
+        end
+        collection.indexes(**opts).to_a
+      end
+    end
+
     def create_index(op)
       collection = entities.get(:collection, op.use!('object'))
       use_arguments(op) do |args|
diff --git a/spec/runners/unified/entity_map.rb b/spec/runners/unified/entity_map.rb
index c0725a1b43..503aa2e644 100644
--- a/spec/runners/unified/entity_map.rb
+++ b/spec/runners/unified/entity_map.rb
@@ -3,6 +3,8 @@
 
 module Unified
   class EntityMap
+    extend Forwardable
+
     def initialize
       @map = {}
     end
@@ -35,8 +37,6 @@ def get_any(id)
       raise Error::EntityMissing, "There is no #{id} known"
     end
 
-    def [](type)
-      @map[type]
-    end
+    def_delegators :@map, :[], :fetch
   end
 end
diff --git a/spec/runners/unified/support_operations.rb b/spec/runners/unified/support_operations.rb
index f713a103a6..f13cf4e2c1 100644
--- a/spec/runners/unified/support_operations.rb
+++ b/spec/runners/unified/support_operations.rb
@@ -13,7 +13,12 @@ def run_command(op)
 
         cmd = args.use!('command')
 
-        database.command(cmd)
+        opts = {}
+        if session = args.use('session')
+          opts[:session] = entities.get(:session, session)
+        end
+
+        database.command(cmd, **opts)
       end
     end
 
diff --git a/spec/runners/unified/test.rb b/spec/runners/unified/test.rb
index 69b7f58563..dc5dbe9b7b 100644
--- a/spec/runners/unified/test.rb
+++ b/spec/runners/unified/test.rb
@@ -195,7 +195,8 @@ def create_entities
     def set_initial_data
       @spec['initialData']&.each do |entity_spec|
         spec = UsingHash[entity_spec]
-        collection = root_authorized_client.use(spec.use!('databaseName'))[spec.use!('collectionName')]
+        collection = root_authorized_client.with(write_concern: {w: :majority}).
+          use(spec.use!('databaseName'))[spec.use!('collectionName')]
         collection.drop
         docs = spec.use!('documents')
         if docs.any?
@@ -268,7 +269,7 @@ def execute_operation(op)
         end
         if expected_error = op.use('expectError')
           begin
-            send(method_name, op)
+            public_send(method_name, op)
           rescue Mongo::Error, BSON::String::IllegalKey => e
             if expected_error.use('isClientError')
               # isClientError doesn't actually mean a client error.
diff --git a/spec/spec_tests/data/sessions_unified/snapshot-sessions-not-supported-client-error.yml b/spec/spec_tests/data/sessions_unified/snapshot-sessions-not-supported-client-error.yml
new file mode 100644
index 0000000000..b57344ce94
--- /dev/null
+++ b/spec/spec_tests/data/sessions_unified/snapshot-sessions-not-supported-client-error.yml
@@ -0,0 +1,69 @@
+description: snapshot-sessions-not-supported-client-error
+
+schemaVersion: "1.0"
+
+runOnRequirements:
+  - minServerVersion: "3.6"
+    maxServerVersion: "4.4.99"
+
+createEntities:
+  - client:
+      id: &client0 client0
+      observeEvents: [ commandStartedEvent, commandFailedEvent ]
+  - database:
+      id: &database0Name database0
+      client: *client0
+      databaseName: *database0Name
+  - collection:
+      id: &collection0Name collection0
+      database: *database0Name
+      collectionName: *collection0Name
+  - session:
+      id: session0
+      client: client0
+      sessionOptions:
+        snapshot: true
+
+initialData:
+  - collectionName: *collection0Name
+    databaseName: *database0Name
+    documents:
+      - { _id: 1, x: 11 }
+
+tests:
+- description: Client error on find with snapshot
+  operations:
+  - name: find
+    object: collection0
+    arguments:
+      session: session0
+      filter: {}
+    expectError:
+      isClientError: true
+      errorContains: Snapshot reads require MongoDB 5.0 or later
+  expectEvents: []
+
+- description: Client error on aggregate with snapshot
+  operations:
+  - name: aggregate
+    object: collection0
+    arguments:
+      session: session0
+      pipeline: []
+    expectError:
+      isClientError: true
+      errorContains: Snapshot reads require MongoDB 5.0 or later
+  expectEvents: []
+
+- description: Client error on distinct with snapshot
+  operations:
+  - name: distinct
+    object: collection0
+    arguments:
+      fieldName: x
+      filter: {}
+      session: session0
+    expectError:
+      isClientError: true
+      errorContains: Snapshot reads require MongoDB 5.0 or later
+  expectEvents: []
diff --git a/spec/spec_tests/data/sessions_unified/snapshot-sessions-not-supported-server-error.yml b/spec/spec_tests/data/sessions_unified/snapshot-sessions-not-supported-server-error.yml
new file mode 100644
index 0000000000..4953dbcbe5
--- /dev/null
+++ b/spec/spec_tests/data/sessions_unified/snapshot-sessions-not-supported-server-error.yml
@@ -0,0 +1,102 @@
+description: snapshot-sessions-not-supported-server-error
+
+schemaVersion: "1.0"
+
+runOnRequirements:
+  - minServerVersion: "5.0"
+    topologies: [ single ]
+
+createEntities:
+  - client:
+      id: &client0 client0
+      observeEvents: [ commandStartedEvent, commandFailedEvent ]
+  - database:
+      id: &database0Name database0
+      client: *client0
+      databaseName: *database0Name
+  - collection:
+      id: &collection0Name collection0
+      database: *database0Name
+      collectionName: *collection0Name
+  - session:
+      id: session0
+      client: client0
+      sessionOptions:
+        snapshot: true
+
+initialData:
+  - collectionName: *collection0Name
+    databaseName: *database0Name
+    documents:
+      - { _id: 1, x: 11 }
+
+tests:
+- description: Server returns an error on find with snapshot
+  operations:
+  - name: find
+    object: collection0
+    arguments:
+      session: session0
+      filter: {}
+    expectError:
+      isError: true
+      isClientError: false
+  expectEvents:
+  - client: client0
+    events:
+    - commandStartedEvent:
+        command:
+          find: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandFailedEvent:
+        commandName: find
+
+- description: Server returns an error on aggregate with snapshot
+  operations:
+  - name: aggregate
+    object: collection0
+    arguments:
+      session: session0
+      pipeline: []
+    expectError:
+      isError: true
+      isClientError: false
+  expectEvents:
+  - client: client0
+    events:
+    - commandStartedEvent:
+        command:
+          aggregate: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandFailedEvent:
+        commandName: aggregate
+
+- description: Server returns an error on distinct with snapshot
+  operations:
+  - name: distinct
+    object: collection0
+    arguments:
+      fieldName: x
+      filter: {}
+      session: session0
+    expectError:
+      isError: true
+      isClientError: false
+  expectEvents:
+  - client: client0
+    events:
+    - commandStartedEvent:
+        command:
+          distinct: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandFailedEvent:
+        commandName: distinct
diff --git a/spec/spec_tests/data/sessions_unified/snapshot-sessions-unsupported-ops.yml b/spec/spec_tests/data/sessions_unified/snapshot-sessions-unsupported-ops.yml
new file mode 100644
index 0000000000..1d5dce8933
--- /dev/null
+++ b/spec/spec_tests/data/sessions_unified/snapshot-sessions-unsupported-ops.yml
@@ -0,0 +1,258 @@
+description: snapshot-sessions-unsupported-ops
+
+schemaVersion: "1.0"
+
+runOnRequirements:
+  - minServerVersion: "5.0"
+    topologies: [replicaset, sharded-replicaset]
+
+createEntities:
+  - client:
+      id: &client0 client0
+      observeEvents: [ commandStartedEvent, commandFailedEvent ]
+  - database:
+      id: &database0Name database0
+      client: *client0
+      databaseName: *database0Name
+  - collection:
+      id: &collection0Name collection0
+      database: *database0Name
+      collectionName: *collection0Name
+  - session:
+      id: session0
+      client: client0
+      sessionOptions:
+        snapshot: true
+
+initialData:
+  - collectionName: *collection0Name
+    databaseName: *database0Name
+    documents:
+      - { _id: 1, x: 11 }
+
+tests:
+- description: Server returns an error on insertOne with snapshot
+  # Skip on sharded clusters due to SERVER-58176.
+  runOnRequirements:
+    - topologies: [replicaset]
+  operations:
+  - name: insertOne
+    object: collection0
+    arguments:
+      session: session0
+      document:
+        _id: 22
+        x: 22
+    expectError:
+      isError: true
+      isClientError: false
+  expectEvents:
+  - client: client0
+    events:
+    - commandStartedEvent:
+        command:
+          insert: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandFailedEvent:
+        commandName: insert
+
+- description: Server returns an error on insertMany with snapshot
+  # Skip on sharded clusters due to SERVER-58176.
+  runOnRequirements:
+    - topologies: [replicaset]
+  operations:
+  - name: insertMany
+    object: collection0
+    arguments:
+      session: session0
+      documents:
+        - _id: 22
+          x: 22
+        - _id: 33
+          x: 33
+    expectError:
+      isError: true
+      isClientError: false
+  expectEvents:
+  - client: client0
+    events:
+    - commandStartedEvent:
+        command:
+          insert: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandFailedEvent:
+        commandName: insert
+
+- description: Server returns an error on deleteOne with snapshot
+  # Skip on sharded clusters due to SERVER-58176.
+  runOnRequirements:
+    - topologies: [replicaset]
+  operations:
+  - name: deleteOne
+    object: collection0
+    arguments:
+      session: session0
+      filter: {}
+    expectError:
+      isError: true
+      isClientError: false
+  expectEvents:
+  - client: client0
+    events:
+    - commandStartedEvent:
+        command:
+          delete: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandFailedEvent:
+        commandName: delete
+
+- description: Server returns an error on updateOne with snapshot
+  # Skip on sharded clusters due to SERVER-58176.
+  runOnRequirements:
+    - topologies: [replicaset]
+  operations:
+  - name: updateOne
+    object: collection0
+    arguments:
+      session: session0
+      filter: { _id: 1 }
+      update: { $inc: { x: 1 } }
+    expectError:
+      isError: true
+      isClientError: false
+  expectEvents:
+  - client: client0
+    events:
+    - commandStartedEvent:
+        command:
+          update: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandFailedEvent:
+        commandName: update
+
+- description: Server returns an error on findOneAndUpdate with snapshot
+  operations:
+  - name: findOneAndUpdate
+    object: collection0
+    arguments:
+      session: session0
+      filter: { _id: 1 }
+      update: { $inc: { x: 1 } }
+    expectError:
+      isError: true
+      isClientError: false
+  expectEvents:
+  - client: client0
+    events:
+    - commandStartedEvent:
+        command:
+          findAndModify: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandFailedEvent:
+        commandName: findAndModify
+
+- description: Server returns an error on listDatabases with snapshot
+  operations:
+  - name: listDatabases
+    object: client0
+    arguments:
+      session: session0
+    expectError:
+      isError: true
+      isClientError: false
+  expectEvents:
+  - client: client0
+    events:
+    - commandStartedEvent:
+        command:
+          listDatabases: 1
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandFailedEvent:
+        commandName: listDatabases
+
+- description: Server returns an error on listCollections with snapshot
+  operations:
+  - name: listCollections
+    object: database0
+    arguments:
+      session: session0
+    expectError:
+      isError: true
+      isClientError: false
+  expectEvents:
+  - client: client0
+    events:
+    - commandStartedEvent:
+        command:
+          listCollections: 1
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandFailedEvent:
+        commandName: listCollections
+
+- description: Server returns an error on listIndexes with snapshot
+  operations:
+  - name: listIndexes
+    object: collection0
+    arguments:
+      session: session0
+    expectError:
+      isError: true
+      isClientError: false
+  expectEvents:
+  - client: client0
+    events:
+    - commandStartedEvent:
+        command:
+          listIndexes: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandFailedEvent:
+        commandName: listIndexes
+
+- description: Server returns an error on runCommand with snapshot
+  operations:
+  - name: runCommand
+    object: database0
+    arguments:
+      session: session0
+      commandName: listCollections
+      command:
+        listCollections: 1
+    expectError:
+      isError: true
+      isClientError: false
+  expectEvents:
+  - client: client0
+    events:
+    - commandStartedEvent:
+        command:
+          listCollections: 1
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandFailedEvent:
+        commandName: listCollections
diff --git a/spec/spec_tests/data/sessions_unified/snapshot-sessions.yml b/spec/spec_tests/data/sessions_unified/snapshot-sessions.yml
new file mode 100644
index 0000000000..2f5fc23125
--- /dev/null
+++ b/spec/spec_tests/data/sessions_unified/snapshot-sessions.yml
@@ -0,0 +1,482 @@
+description: snapshot-sessions
+
+schemaVersion: "1.0"
+
+runOnRequirements:
+  - minServerVersion: "5.0"
+    topologies: [replicaset, sharded-replicaset]
+
+createEntities:
+  - client:
+      id: &client0 client0
+      observeEvents: [ commandStartedEvent]
+      ignoreCommandMonitoringEvents: [ findAndModify, insert, update ]
+  - database:
+      id: &database0 database0
+      client: *client0
+      databaseName: &database0Name database0
+  - collection:
+      id: &collection0 collection0
+      database: *database0
+      collectionName: &collection0Name collection0
+      collectionOptions:
+        writeConcern: { w: majority }
+  - session:
+      id: session0
+      client: client0
+      sessionOptions:
+        snapshot: true
+  - session:
+      id: session1
+      client: client0
+      sessionOptions:
+        snapshot: true
+
+initialData:
+  - collectionName: *collection0Name
+    databaseName: *database0Name
+    documents:
+      - { _id: 1, x: 11 }
+      - { _id: 2, x: 11 }
+
+tests:
+- description: Find operation with snapshot
+  operations:
+  - name: find
+    object: collection0
+    arguments:
+      session: session0
+      filter: { _id: 1 }
+    expectResult:
+      - {_id: 1, x: 11}
+  - name: findOneAndUpdate
+    object: collection0
+    arguments:
+      filter: { _id: 1 }
+      update: { $inc: { x: 1 } }
+      returnDocument: After
+    expectResult: { _id: 1, x: 12 }
+  - name: find
+    object: collection0
+    arguments:
+      session: session1
+      filter: { _id: 1 }
+    expectResult:
+      - { _id: 1, x: 12 }
+  - name: findOneAndUpdate
+    object: collection0
+    arguments:
+      filter: { _id: 1 }
+      update: { $inc: { x: 1 } }
+      returnDocument: After
+    expectResult: { _id: 1, x: 13 }
+  - name: find
+    object: collection0
+    arguments:
+      filter: { _id: 1 }
+    expectResult:
+    - { _id: 1, x: 13 }
+  - name: find
+    object: collection0
+    arguments:
+      session: session0
+      filter: { _id: 1 }
+    expectResult:
+    - {_id: 1, x: 11}
+  - name: find
+    object: collection0
+    arguments:
+      session: session1
+      filter: { _id: 1 }
+    expectResult:
+    - {_id: 1, x: 12}
+  expectEvents:
+  - client: client0
+    events:
+    - commandStartedEvent:
+        command:
+          find: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandStartedEvent:
+        command:
+          find: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandStartedEvent:
+        command:
+          find: collection0
+          readConcern:
+            "$$exists": false
+    - commandStartedEvent:
+        command:
+          find: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": true
+    - commandStartedEvent:
+        command:
+          find: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": true
+
+- description: Distinct operation with snapshot
+  operations:
+  - name: distinct
+    object: collection0
+    arguments:
+      fieldName: x
+      filter: {}
+      session: session0
+    expectResult:
+    - 11
+  - name: findOneAndUpdate
+    object: collection0
+    arguments:
+      filter: { _id: 2 }
+      update: { $inc: { x: 1 } }
+      returnDocument: After
+    expectResult: { _id: 2, x: 12 }
+  - name: distinct
+    object: collection0
+    arguments:
+      fieldName: x
+      filter: {}
+      session: session1
+    expectResult: [11, 12]
+  - name: findOneAndUpdate
+    object: collection0
+    arguments:
+      filter: { _id: 2 }
+      update: { $inc: { x: 1 } }
+      returnDocument: After
+    expectResult: { _id: 2, x: 13 }
+  - name: distinct
+    object: collection0
+    arguments:
+      fieldName: x
+      filter: {}
+    expectResult: [ 11, 13 ]
+  - name: distinct
+    object: collection0
+    arguments:
+      fieldName: x
+      filter: {}
+      session: session0
+    expectResult: [ 11 ]
+  - name: distinct
+    object: collection0
+    arguments:
+      fieldName: x
+      filter: {}
+      session: session1
+    expectResult: [ 11, 12 ]
+  expectEvents:
+  - client: client0
+    events:
+    - commandStartedEvent:
+        command:
+          distinct: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandStartedEvent:
+        command:
+          distinct: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandStartedEvent:
+        command:
+          distinct: collection0
+          readConcern:
+            "$$exists": false
+    - commandStartedEvent:
+        command:
+          distinct: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": true
+    - commandStartedEvent:
+        command:
+          distinct: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": true
+
+- description: Aggregate operation with snapshot
+  operations:
+  - name: aggregate
+    object: collection0
+    arguments:
+      pipeline:
+      - "$match": { _id: 1 }
+      session: session0
+    expectResult:
+    - { _id: 1, x: 11 }
+  - name: findOneAndUpdate
+    object: collection0
+    arguments:
+      filter: { _id: 1 }
+      update: { $inc: { x: 1 } }
+      returnDocument: After
+    expectResult: { _id: 1, x: 12 }
+  - name: aggregate
+    object: collection0
+    arguments:
+      pipeline:
+      - "$match":
+          _id: 1
+      session: session1
+    expectResult:
+    - {_id: 1, x: 12}
+  - name: findOneAndUpdate
+    object: collection0
+    arguments:
+      filter: { _id: 1 }
+      update: { $inc: { x: 1 } }
+      returnDocument: After
+    expectResult: { _id: 1, x: 13 }
+  - name: aggregate
+    object: collection0
+    arguments:
+      pipeline:
+      - "$match": { _id: 1 }
+    expectResult:
+    - { _id: 1, x: 13 }
+  - name: aggregate
+    object: collection0
+    arguments:
+      pipeline:
+      - "$match":
+          _id: 1
+      session: session0
+    expectResult:
+    - { _id: 1, x: 11 }
+  - name: aggregate
+    object: collection0
+    arguments:
+      pipeline:
+      - "$match": { _id: 1 }
+      session: session1
+    expectResult:
+    - { _id: 1, x: 12 }
+  expectEvents:
+  - client: client0
+    events:
+    - commandStartedEvent:
+        command:
+          aggregate: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandStartedEvent:
+        command:
+          aggregate: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandStartedEvent:
+        command:
+          aggregate: collection0
+          readConcern:
+            "$$exists": false
+    - commandStartedEvent:
+        command:
+          aggregate: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": true
+    - commandStartedEvent:
+        command:
+          aggregate: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": true
+
+- description: countDocuments operation with snapshot
+  operations:
+  - name: countDocuments
+    object: collection0
+    arguments:
+      filter: {}
+      session: session0
+    expectResult: 2
+  - name: countDocuments
+    object: collection0
+    arguments:
+      filter: {}
+      session: session0
+    expectResult: 2
+  expectEvents:
+  - client: client0
+    events:
+    - commandStartedEvent:
+        command:
+          aggregate: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandStartedEvent:
+        command:
+          aggregate: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": true
+
+- description: Mixed operation with snapshot
+  operations:
+  - name: find
+    object: collection0
+    arguments:
+      session: session0
+      filter: { _id: 1 }
+    expectResult:
+    - { _id: 1, x: 11 }
+  - name: findOneAndUpdate
+    object: collection0
+    arguments:
+      filter: { _id: 1 }
+      update: { $inc: { x: 1 } }
+      returnDocument: After
+    expectResult: { _id: 1, x: 12 }
+  - name: find
+    object: collection0
+    arguments:
+      filter: { _id: 1 }
+    expectResult:
+    - { _id: 1, x: 12 }
+  - name: aggregate
+    object: collection0
+    arguments:
+      pipeline:
+      - "$match":
+          _id: 1
+      session: session0
+    expectResult:
+    - { _id: 1, x: 11 }
+  - name: distinct
+    object: collection0
+    arguments:
+      fieldName: x
+      filter: {}
+      session: session0
+    expectResult: [ 11 ] 
+  expectEvents:
+  - client: client0
+    events:
+    - commandStartedEvent:
+        command:
+          find: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandStartedEvent:
+        command:
+          find: collection0
+          readConcern:
+            "$$exists": false
+    - commandStartedEvent:
+        command:
+          aggregate: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": true
+    - commandStartedEvent:
+        command:
+          distinct: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": true
+
+- description: Write commands with snapshot session do not affect snapshot reads
+  operations:
+  - name: find
+    object: collection0
+    arguments:
+      filter: {}
+      session: session0
+  - name: insertOne
+    object: collection0
+    arguments:
+      document:
+        _id: 22
+        x: 33
+  - name: updateOne
+    object: collection0
+    arguments:
+      filter: { _id: 1 }
+      update: { $inc: { x: 1 } }
+  - name: find
+    object: collection0
+    arguments:
+      filter: { _id: 1 }
+      session: session0
+    expectResult:
+    - {_id: 1, x: 11}
+  expectEvents:
+  - client: client0
+    events:
+    - commandStartedEvent:
+        command:
+          find: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+    - commandStartedEvent:
+        command:
+          find: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": true
+
+- description: First snapshot read does not send atClusterTime
+  operations:
+  - name: find
+    object: collection0
+    arguments:
+      filter: {}
+      session: session0
+  expectEvents:
+  - client: client0
+    events:
+    - commandStartedEvent:
+        command:
+          find: collection0
+          readConcern:
+            level: snapshot
+            atClusterTime:
+              "$$exists": false
+        commandName: find
+        databaseName: database0
+
+- description: StartTransaction fails in snapshot session
+  operations:
+  - name: startTransaction
+    object: session0
+    expectError:
+      isError: true
+      isClientError: true
+      errorContains: Transactions are not supported in snapshot sessions
diff --git a/spec/spec_tests/sessions_unified_spec.rb b/spec/spec_tests/sessions_unified_spec.rb
new file mode 100644
index 0000000000..8217299205
--- /dev/null
+++ b/spec/spec_tests/sessions_unified_spec.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+# encoding: utf-8
+
+require 'spec_helper'
+
+require 'runners/unified'
+
+base = "#{CURRENT_PATH}/spec_tests/data/sessions_unified"
+SESSIONS_UNIFIED_TESTS = Dir.glob("#{base}/**/*.yml").sort
+
+describe 'Sessions unified spec tests' do
+  define_unified_spec_tests(base, SESSIONS_UNIFIED_TESTS)
+end