diff --git a/lib/admin.js b/lib/admin.js
index ff4b8157ca..01c96ffc7a 100644
--- a/lib/admin.js
+++ b/lib/admin.js
@@ -89,11 +89,12 @@ define.classMethod('command', { callback: true, promise: true });
  */
 Admin.prototype.buildInfo = function(options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
 
   const cmd = { buildinfo: 1 };
   return executeOperation(this.s.db.s.topology, this.s.db.executeDbAdminCommand.bind(this.s.db), [
     cmd,
-    undefined,
+    options,
     callback
   ]);
 };
@@ -111,6 +112,7 @@ define.classMethod('buildInfo', { callback: true, promise: true });
  */
 Admin.prototype.serverInfo = function(options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
 
   const cmd = { buildinfo: 1 };
   return executeOperation(this.s.db.s.topology, this.s.db.executeDbAdminCommand.bind(this.s.db), [
@@ -132,6 +134,8 @@ define.classMethod('serverInfo', { callback: true, promise: true });
  */
 Admin.prototype.serverStatus = function(options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
   return executeOperation(this.s.db.s.topology, serverStatus, [this, options, callback]);
 };
 
@@ -158,6 +162,7 @@ define.classMethod('serverStatus', { callback: true, promise: true });
  */
 Admin.prototype.ping = function(options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
 
   const cmd = { ping: 1 };
   return executeOperation(this.s.db.s.topology, this.s.db.executeDbAdminCommand.bind(this.s.db), [
@@ -272,13 +277,15 @@ define.classMethod('removeUser', { callback: true, promise: true });
  * @return {Promise} returns Promise if no callback passed
  */
 Admin.prototype.validateCollection = function(collectionName, options, callback) {
-  var args = Array.prototype.slice.call(arguments, 1);
-  callback = typeof args[args.length - 1] === 'function' ? args.pop() : undefined;
-
-  options = args.length ? args.shift() : {};
+  if (typeof options === 'function') (callback = options), (options = {});
   options = options || {};
 
-  return executeOperation(this.s.db.s.topology, validateCollection, [this, collectionName, options, callback]);
+  return executeOperation(this.s.db.s.topology, validateCollection, [
+    this,
+    collectionName,
+    options,
+    callback
+  ]);
 };
 
 var validateCollection = function(self, collectionName, options, callback) {
@@ -287,12 +294,12 @@ var validateCollection = function(self, collectionName, options, callback) {
 
   // Decorate command with extra options
   for (var i = 0; i < keys.length; i++) {
-    if (options.hasOwnProperty(keys[i])) {
+    if (options.hasOwnProperty(keys[i]) && keys[i] !== 'session') {
       command[keys[i]] = options[keys[i]];
     }
   }
 
-  self.s.db.command(command, function(err, doc) {
+  self.s.db.command(command, options, function(err, doc) {
     if (err != null) return callback(err, null);
 
     if (doc.ok === 0) return callback(new Error('Error with validate command'), null);
@@ -343,6 +350,8 @@ define.classMethod('listDatabases', { callback: true, promise: true });
  */
 Admin.prototype.replSetGetStatus = function(options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
   return executeOperation(this.s.db.s.topology, replSetGetStatus, [this, options, callback]);
 };
 
diff --git a/lib/authenticate.js b/lib/authenticate.js
index f645c55e19..1a7003965c 100644
--- a/lib/authenticate.js
+++ b/lib/authenticate.js
@@ -81,6 +81,8 @@ var authenticate = function(client, username, password, options, callback) {
 
 module.exports = function(self, username, password, options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
   // Shallow copy the options
   options = shallowClone(options);
 
diff --git a/lib/bulk/ordered.js b/lib/bulk/ordered.js
index 66401faaa4..129ca70ca7 100644
--- a/lib/bulk/ordered.js
+++ b/lib/bulk/ordered.js
@@ -429,7 +429,7 @@ Object.defineProperty(OrderedBulkOperation.prototype, 'length', {
 
 //
 // Execute next write command in a chain
-var executeCommands = function(self, callback) {
+var executeCommands = function(self, options, callback) {
   if (self.s.batches.length === 0) {
     return handleCallback(callback, null, new BulkWriteResult(self.s.bulkResult));
   }
@@ -484,10 +484,10 @@ var executeCommands = function(self, callback) {
     }
 
     // Execute the next command in line
-    executeCommands(self, callback);
+    executeCommands(self, options, callback);
   };
 
-  var finalOptions = { ordered: true };
+  var finalOptions = Object.assign({ ordered: true }, options);
   if (self.s.writeConcern != null) {
     finalOptions.writeConcern = self.s.writeConcern;
   }
@@ -563,7 +563,10 @@ var executeCommands = function(self, callback) {
  * @throws {MongoError}
  * @return {Promise} returns Promise if no callback passed
  */
-OrderedBulkOperation.prototype.execute = function(_writeConcern, callback) {
+OrderedBulkOperation.prototype.execute = function(_writeConcern, options, callback) {
+  if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
   if (this.s.executed) {
     var executedError = toError('batch cannot be re-executed');
     return typeof callback === 'function'
@@ -588,7 +591,7 @@ OrderedBulkOperation.prototype.execute = function(_writeConcern, callback) {
       : this.s.promiseLibrary.reject(emptyBatchError);
   }
 
-  return executeOperation(this.s.topology, executeCommands, [this, callback]);
+  return executeOperation(this.s.topology, executeCommands, [this, options, callback]);
 };
 
 define.classMethod('execute', { callback: true, promise: false });
diff --git a/lib/bulk/unordered.js b/lib/bulk/unordered.js
index 06333142af..ca9e36bb6f 100644
--- a/lib/bulk/unordered.js
+++ b/lib/bulk/unordered.js
@@ -436,8 +436,8 @@ UnorderedBulkOperation.prototype.raw = function(op) {
 
 //
 // Execute the command
-var executeBatch = function(self, batch, callback) {
-  var finalOptions = { ordered: false };
+var executeBatch = function(self, batch, options, callback) {
+  var finalOptions = Object.assign({ ordered: false }, options);
   if (self.s.writeConcern != null) {
     finalOptions.writeConcern = self.s.writeConcern;
   }
@@ -506,11 +506,11 @@ var executeBatch = function(self, batch, callback) {
 
 //
 // Execute all the commands
-var executeBatches = function(self, callback) {
+var executeBatches = function(self, options, callback) {
   var numberOfCommandsToExecute = self.s.batches.length;
   // Execute over all the batches
   for (var i = 0; i < self.s.batches.length; i++) {
-    executeBatch(self, self.s.batches[i], function(err) {
+    executeBatch(self, self.s.batches[i], options, function(err) {
       // Count down the number of commands left to execute
       numberOfCommandsToExecute = numberOfCommandsToExecute - 1;
 
@@ -575,7 +575,10 @@ var executeBatches = function(self, callback) {
  * @throws {MongoError}
  * @return {Promise} returns Promise if no callback passed
  */
-UnorderedBulkOperation.prototype.execute = function(_writeConcern, callback) {
+UnorderedBulkOperation.prototype.execute = function(_writeConcern, options, callback) {
+  if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
   if (this.s.executed) {
     var executedError = toError('batch cannot be re-executed');
     return typeof callback === 'function'
@@ -602,7 +605,7 @@ UnorderedBulkOperation.prototype.execute = function(_writeConcern, callback) {
       : this.s.promiseLibrary.reject(emptyBatchError);
   }
 
-  return executeOperation(this.s.topology, executeBatches, [this, callback]);
+  return executeOperation(this.s.topology, executeBatches, [this, options, callback]);
 };
 
 define.classMethod('execute', { callback: true, promise: false });
diff --git a/lib/collection.js b/lib/collection.js
index 0913374db2..51d0273146 100644
--- a/lib/collection.js
+++ b/lib/collection.js
@@ -889,6 +889,7 @@ define.classMethod('insert', { callback: true, promise: true });
  */
 Collection.prototype.updateOne = function(filter, update, options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
 
   var err = checkForAtomicOperators(update);
   if (err) {
@@ -1013,6 +1014,7 @@ define.classMethod('replaceOne', { callback: true, promise: true });
  */
 Collection.prototype.updateMany = function(filter, update, options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
 
   var err = checkForAtomicOperators(update);
   if (err) {
@@ -1119,13 +1121,22 @@ var updateDocuments = function(self, selector, document, options, callback) {
  * @deprecated use updateOne, updateMany or bulkWrite
  */
 Collection.prototype.update = function(selector, document, options, callback) {
+  if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
   // Add ignoreUndfined
   if (this.s.options.ignoreUndefined) {
     options = shallowClone(options);
     options.ignoreUndefined = this.s.options.ignoreUndefined;
   }
 
-  return executeOperation(this.s.topology, updateDocuments, [this, selector, document, options, callback]);
+  return executeOperation(this.s.topology, updateDocuments, [
+    this,
+    selector,
+    document,
+    options,
+    callback
+  ]);
 };
 
 define.classMethod('update', { callback: true, promise: true });
@@ -1498,13 +1509,13 @@ define.classMethod('drop', { callback: true, promise: true });
  */
 Collection.prototype.options = function(opts, callback) {
   if (typeof opts === 'function') (callback = opts), (opts = {});
+  opts = opts || {};
 
   return executeOperation(this.s.topology, options, [this, opts, callback]);
 };
 
 var options = function(self, opts, callback) {
-  opts = assign({}, { name: self.s.name }, opts);
-  self.s.db.listCollections(opts).toArray(function(err, collections) {
+  self.s.db.listCollections({ name: self.s.name }, opts).toArray(function(err, collections) {
     if (err) return handleCallback(callback, err);
     if (collections.length === 0) {
       return handleCallback(
@@ -1530,6 +1541,7 @@ define.classMethod('options', { callback: true, promise: true });
  */
 Collection.prototype.isCapped = function(options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
 
   return executeOperation(this.s.topology, isCapped, [this, options, callback]);
 };
@@ -1596,6 +1608,7 @@ define.classMethod('createIndex', { callback: true, promise: true });
  */
 Collection.prototype.createIndexes = function(indexSpecs, options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
 
   return executeOperation(this.s.topology, createIndexes, [this, indexSpecs, options, callback]);
 };
@@ -1842,6 +1855,7 @@ define.classMethod('ensureIndex', { callback: true, promise: true });
  */
 Collection.prototype.indexExists = function(indexes, options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
 
   return executeOperation(this.s.topology, indexExists, [this, indexes, options, callback]);
 };
@@ -1939,8 +1953,9 @@ var count = function(self, query, options, callback) {
   if (hint) cmd.hint = hint;
 
   options = shallowClone(options);
+
   // Ensure we have the right read preference inheritance
-  options = getReadPreference(self, options, self.s.db, self);
+  options = getReadPreference(self, options, self.s.db);
 
   // Do we have a readConcern specified
   if (self.s.readConcern) {
@@ -1977,7 +1992,13 @@ Collection.prototype.distinct = function(key, query, options, callback) {
   var queryOption = args.length ? args.shift() || {} : {};
   var optionsOption = args.length ? args.shift() || {} : {};
 
-  return executeOperation(this.s.topology, distinct, [this, key, queryOption, optionsOption, callback]);
+  return executeOperation(this.s.topology, distinct, [
+    this,
+    key,
+    queryOption,
+    optionsOption,
+    callback
+  ]);
 };
 
 var distinct = function(self, key, query, options, callback) {
@@ -2025,6 +2046,7 @@ define.classMethod('distinct', { callback: true, promise: true });
  */
 Collection.prototype.indexes = function(options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
 
   return executeOperation(this.s.topology, indexes, [this, options, callback]);
 };
@@ -2148,7 +2170,13 @@ Collection.prototype.findOneAndReplace = function(filter, replacement, options,
   if (replacement == null || typeof replacement !== 'object')
     throw toError('replacement parameter must be an object');
 
-  return executeOperation(this.s.topology, findOneAndReplace, [this, filter, replacement, options, callback]);
+  return executeOperation(this.s.topology, findOneAndReplace, [
+    this,
+    filter,
+    replacement,
+    options,
+    callback
+  ]);
 };
 
 var findOneAndReplace = function(self, filter, replacement, options, callback) {
@@ -2192,7 +2220,13 @@ Collection.prototype.findOneAndUpdate = function(filter, update, options, callba
   if (update == null || typeof update !== 'object')
     throw toError('update parameter must be an object');
 
-  return executeOperation(this.s.topology, findOneAndUpdate, [this, filter, update, options, callback]);
+  return executeOperation(this.s.topology, findOneAndUpdate, [
+    this,
+    filter,
+    update,
+    options,
+    callback
+  ]);
 };
 
 var findOneAndUpdate = function(self, filter, update, options, callback) {
@@ -2241,7 +2275,14 @@ Collection.prototype.findAndModify = function(query, sort, doc, options, callbac
   // Force read preference primary
   options.readPreference = ReadPreference.PRIMARY;
 
-  return executeOperation(this.s.topology, findAndModify, [this, query, sort, doc, options, callback]);
+  return executeOperation(this.s.topology, findAndModify, [
+    this,
+    query,
+    sort,
+    doc,
+    options,
+    callback
+  ]);
 };
 
 var findAndModify = function(self, query, sort, doc, options, callback) {
@@ -2679,7 +2720,8 @@ var geoNear = function(self, x, y, point, options, callback) {
   var exclude = {
     readPreference: true,
     geoNear: true,
-    near: true
+    near: true,
+    session: true
   };
 
   // Filter out any excluded objects
@@ -2736,7 +2778,7 @@ var geoHaystackSearch = function(self, x, y, options, callback) {
   };
 
   // Remove read preference from hash if it exists
-  commandObject = decorateCommand(commandObject, options, { readPreference: true });
+  commandObject = decorateCommand(commandObject, options, { readPreference: true, session: true });
 
   options = shallowClone(options);
   // Ensure we have the right read preference inheritance
@@ -3014,7 +3056,7 @@ var mapReduce = function(self, map, reduce, options, callback) {
   };
 
   // Exclusion list
-  var exclusionList = ['readPreference'];
+  var exclusionList = ['readPreference', 'session'];
 
   // Add any other options passed in
   for (var n in options) {
diff --git a/lib/cursor.js b/lib/cursor.js
index 672b919f25..625817a43d 100644
--- a/lib/cursor.js
+++ b/lib/cursor.js
@@ -208,7 +208,9 @@ var define = (Cursor.define = new Define('Cursor', Cursor, true));
  * @return {Promise} returns Promise if no callback passed
  */
 Cursor.prototype.hasNext = function(callback) {
-  return executeOperation(this.s.topology, hasNext, [this, callback]);
+  return executeOperation(this.s.topology, hasNext, [this, callback], {
+    skipSessions: true
+  });
 };
 
 const hasNext = (self, callback) => {
@@ -235,7 +237,9 @@ define.classMethod('hasNext', { callback: true, promise: true });
  * @return {Promise} returns Promise if no callback passed
  */
 Cursor.prototype.next = function(callback) {
-  return executeOperation(this.s.topology, next, [this, callback]);
+  return executeOperation(this.s.topology, next, [this, callback], {
+    skipSessions: true
+  });
 };
 
 const next = (self, callback) => {
@@ -909,7 +913,9 @@ Cursor.prototype.toArray = function(callback) {
     });
   }
 
-  return executeOperation(this.s.topology, toArray, [this, callback]);
+  return executeOperation(this.s.topology, toArray, [this, callback], {
+    skipSessions: true
+  });
 };
 
 var toArray = function(self, callback) {
@@ -979,7 +985,9 @@ Cursor.prototype.count = function(applySkipLimit, opts, callback) {
   if (typeof opts === 'function') (callback = opts), (opts = {});
   opts = opts || {};
 
-  return executeOperation(this.s.topology, count, [this, applySkipLimit, opts, callback]);
+  return executeOperation(this.s.topology, count, [this, applySkipLimit, opts, callback], {
+    skipSessions: true
+  });
 };
 
 var count = function(self, applySkipLimit, opts, callback) {
@@ -1128,7 +1136,9 @@ Cursor.prototype.explain = function(callback) {
     delete this.s.cmd['readConcern'];
   }
 
-  return executeOperation(this.s.topology, this._next.bind(this), [callback]);
+  return executeOperation(this.s.topology, this._next.bind(this), [callback], {
+    skipSessions: true
+  });
 };
 
 define.classMethod('explain', { callback: true, promise: true });
diff --git a/lib/db.js b/lib/db.js
index 6c273e82fd..bbc73f338f 100644
--- a/lib/db.js
+++ b/lib/db.js
@@ -58,7 +58,8 @@ var illegalCommandFields = [
   'serializeFunctions',
   'pkFactory',
   'raw',
-  'readPreference'
+  'readPreference',
+  'session'
 ];
 
 /**
@@ -494,11 +495,13 @@ var createCollection = function(self, name, options, callback) {
   // Get the write concern options
   var finalOptions = writeConcern(shallowClone(options), self, options);
   // Did the user destroy the topology
-  if (self.serverConfig && self.serverConfig.isDestroyed())
+  if (self.serverConfig && self.serverConfig.isDestroyed()) {
     return callback(new MongoError('topology was destroyed'));
+  }
+
   // Check if we have the name
   self
-    .listCollections({ name: name })
+    .listCollections({ name: name }, finalOptions)
     .setReadPreference(ReadPreference.PRIMARY)
     .toArray(function(err, collections) {
       if (err != null) return handleCallback(callback, err, null);
@@ -932,12 +935,14 @@ define.classMethod('dropDatabase', { callback: true, promise: true });
  */
 Db.prototype.collections = function(options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
   return executeOperation(this.s.topology, collections, [this, options, callback]);
 };
 
 var collections = function(self, options, callback) {
   // Let's get the collection names
-  self.listCollections(options).toArray(function(err, documents) {
+  self.listCollections({}, options).toArray(function(err, documents) {
     if (err != null) return handleCallback(callback, err, null);
     // Filter collections removing any illegal ones
     documents = documents.filter(function(doc) {
@@ -983,7 +988,12 @@ Db.prototype.executeDbAdminCommand = function(selector, options, callback) {
     options.readPreference = convertReadPreference(options.readPreference);
   }
 
-  return executeOperation(this.s.topology, executeDbAdminCommand, [this, selector, options, callback]);
+  return executeOperation(this.s.topology, executeDbAdminCommand, [
+    this,
+    selector,
+    options,
+    callback
+  ]);
 };
 
 const executeDbAdminCommand = (self, selector, options, callback) => {
@@ -1032,7 +1042,13 @@ Db.prototype.createIndex = function(name, fieldOrSpec, options, callback) {
   // Shallow clone the options
   options = shallowClone(options);
 
-  return executeOperation(this.s.topology, createIndex, [this, name, fieldOrSpec, options, callback]);
+  return executeOperation(this.s.topology, createIndex, [
+    this,
+    name,
+    fieldOrSpec,
+    options,
+    callback
+  ]);
 };
 
 var createIndex = function(self, name, fieldOrSpec, options, callback) {
@@ -1117,7 +1133,13 @@ Db.prototype.ensureIndex = function(name, fieldOrSpec, options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
   options = options || {};
 
-  return executeOperation(this.s.topology, ensureIndex, [this, name, fieldOrSpec, options, callback]);
+  return executeOperation(this.s.topology, ensureIndex, [
+    this,
+    name,
+    fieldOrSpec,
+    options,
+    callback
+  ]);
 };
 
 var ensureIndex = function(self, name, fieldOrSpec, options, callback) {
@@ -1321,6 +1343,8 @@ define.classMethod('addUser', { callback: true, promise: true });
 
 var _executeAuthRemoveUserCommand = function(self, username, options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
   // Did the user destroy the topology
   if (self.serverConfig && self.serverConfig.isDestroyed())
     return callback(new MongoError('topology was destroyed'));
@@ -1413,6 +1437,8 @@ Db.prototype.removeUser = function(username, options, callback) {
  */
 Db.prototype.setProfilingLevel = function(level, options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
   return executeOperation(this.s.topology, setProfilingLevel, [this, level, options, callback]);
 };
 
@@ -1454,6 +1480,8 @@ define.classMethod('setProfilingLevel', { callback: true, promise: true });
  */
 Db.prototype.profilingInfo = function(options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
   return executeOperation(this.s.topology, profilingInfo, [this, options, callback]);
 };
 
@@ -1461,7 +1489,7 @@ var profilingInfo = function(self, options, callback) {
   try {
     self
       .collection('system.profile')
-      .find({}, options)
+      .find({}, null, options)
       .toArray(callback);
   } catch (err) {
     return callback(err, null);
@@ -1480,6 +1508,8 @@ define.classMethod('profilingInfo', { callback: true, promise: true });
  */
 Db.prototype.profilingLevel = function(options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
   return executeOperation(this.s.topology, profilingLevel, [this, options, callback]);
 };
 
@@ -1600,17 +1630,19 @@ var createIndexUsingCreateIndexes = function(self, name, fieldOrSpec, options, c
   // Set up the index
   var indexes = [{ name: indexName, key: indexParameters.fieldHash }];
   // merge all the options
-  var keysToOmit = Object.keys(indexes[0]);
+  var keysToOmit = Object.keys(indexes[0]).concat([
+    'w',
+    'wtimeout',
+    'j',
+    'fsync',
+    'readPreference',
+    'session'
+  ]);
+
   for (var optionName in options) {
     if (keysToOmit.indexOf(optionName) === -1) {
       indexes[0][optionName] = options[optionName];
     }
-
-    // Remove any write concern operations
-    var removeKeys = ['w', 'wtimeout', 'j', 'fsync', 'readPreference'];
-    for (var i = 0; i < removeKeys.length; i++) {
-      delete indexes[0][removeKeys[i]];
-    }
   }
 
   // Get capabilities
diff --git a/lib/gridfs/grid_store.js b/lib/gridfs/grid_store.js
index 266e696884..0e14ccfd4d 100644
--- a/lib/gridfs/grid_store.js
+++ b/lib/gridfs/grid_store.js
@@ -661,16 +661,17 @@ define.classMethod('collection', { callback: true, promise: false, returns: [Col
  * @return {Promise} returns Promise if no callback passed
  * @deprecated Use GridFSBucket API instead
  */
-GridStore.prototype.readlines = function(separator, callback) {
+GridStore.prototype.readlines = function(separator, options, callback) {
   var args = Array.prototype.slice.call(arguments, 0);
   callback = typeof args[args.length - 1] === 'function' ? args.pop() : undefined;
   separator = args.length ? args.shift() : '\n';
   separator = separator || '\n';
+  options = args.length ? args.shift() : {};
 
-  return executeOperation(this.db.s.topology, readlines, [this, separator, callback]);
+  return executeOperation(this.db.s.topology, readlines, [this, separator, options, callback]);
 };
 
-var readlines = function(self, separator, callback) {
+var readlines = function(self, separator, options, callback) {
   self.read(function(err, data) {
     if (err) return callback(err);
 
@@ -758,16 +759,17 @@ define.classMethod('rewind', { callback: true, promise: true });
  * @return {Promise} returns Promise if no callback passed
  * @deprecated Use GridFSBucket API instead
  */
-GridStore.prototype.read = function(length, buffer, callback) {
+GridStore.prototype.read = function(length, buffer, options, callback) {
   var args = Array.prototype.slice.call(arguments, 0);
   callback = typeof args[args.length - 1] === 'function' ? args.pop() : undefined;
   length = args.length ? args.shift() : null;
   buffer = args.length ? args.shift() : null;
+  options = args.length ? args.shift() : {};
 
-  return executeOperation(this.db.s.topology, read, [this, length, buffer, callback]);
+  return executeOperation(this.db.s.topology, read, [this, length, buffer, options, callback]);
 };
 
-var read = function(self, length, buffer, callback) {
+var read = function(self, length, buffer, options, callback) {
   // The data is a c-terminated string and thus the length - 1
   var finalLength = length == null ? self.length - self.position : length;
   var finalBuffer = buffer == null ? new Buffer(finalLength) : buffer;
@@ -872,15 +874,22 @@ define.classMethod('tell', { callback: true, promise: true });
  * @return {Promise} returns Promise if no callback passed
  * @deprecated Use GridFSBucket API instead
  */
-GridStore.prototype.seek = function(position, seekLocation, callback) {
+GridStore.prototype.seek = function(position, seekLocation, options, callback) {
   var args = Array.prototype.slice.call(arguments, 1);
   callback = typeof args[args.length - 1] === 'function' ? args.pop() : undefined;
   seekLocation = args.length ? args.shift() : null;
+  options = args.length ? args.shift() : {};
 
-  return executeOperation(this.db.s.topology, seek, [this, position, seekLocation, callback]);
+  return executeOperation(this.db.s.topology, seek, [
+    this,
+    position,
+    seekLocation,
+    options,
+    callback
+  ]);
 };
 
-var seek = function(self, position, seekLocation, callback) {
+var seek = function(self, position, seekLocation, options, callback) {
   // Seek only supports read mode
   if (self.mode !== 'r') {
     return callback(
diff --git a/lib/topologies/topology_base.js b/lib/topologies/topology_base.js
index 65b02f388b..c0efc4f4da 100644
--- a/lib/topologies/topology_base.js
+++ b/lib/topologies/topology_base.js
@@ -306,7 +306,7 @@ class TopologyBase extends EventEmitter {
   }
 
   startSession(options) {
-    return new ClientSession(this.s.coreTopology, this.s.sessionPool, options);
+    return new ClientSession(this, this.s.sessionPool, options);
   }
 
   // Server capabilities
diff --git a/lib/utils.js b/lib/utils.js
index 3f785a6e96..5acbd82632 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -126,6 +126,7 @@ var checkCollectionName = function checkCollectionName(collectionName) {
 var handleCallback = function(callback, err, value1, value2) {
   try {
     if (callback == null) return;
+
     if (callback) {
       return value2 ? callback(err, value1, value2) : callback(err, value1);
     }
@@ -405,12 +406,31 @@ const executeOperation = (topology, operation, args, options) => {
   let resultMutator = options.resultMutator;
   let callback = args[args.length - 1];
 
+  // The driver sessions spec mandates that we implicitly create sessions for operations
+  // that are not explicitly provided with a session.
+
+  let session;
+  if (!options.skipSessions) {
+    const opOptions = args[args.length - 2];
+    if (opOptions == null || opOptions.session == null) {
+      session = topology.startSession();
+      assign(args[args.length - 2], { session: session });
+    }
+  }
+
   // Execute using callback
   if (typeof callback === 'function') {
     callback = args.pop();
     args.push((err, result) => {
-      if (err) return callback(err, null);
-      return resultMutator ? callback(null, resultMutator(result)) : callback(null, result);
+      if (session) {
+        session.endSession(() => {
+          if (err) return callback(err, null);
+          return resultMutator ? callback(null, resultMutator(result)) : callback(null, result);
+        });
+      } else {
+        if (err) return callback(err, null);
+        return resultMutator ? callback(null, resultMutator(result)) : callback(null, result);
+      }
     });
 
     return operation.apply(null, args);
@@ -424,9 +444,17 @@ const executeOperation = (topology, operation, args, options) => {
 
   return new Promise(function(resolve, reject) {
     args[args.length - 1] = (err, r) => {
-      if (err) return reject(err);
-      if (resultMutator) return resolve(resultMutator(r));
-      resolve(r);
+      if (session) {
+        session.endSession(() => {
+          if (err) return reject(err);
+          if (resultMutator) return resolve(resultMutator(r));
+          resolve(r);
+        });
+      } else {
+        if (err) return reject(err);
+        if (resultMutator) return resolve(resultMutator(r));
+        resolve(r);
+      }
     };
 
     operation.apply(null, args);
diff --git a/test/functional/apm_tests.js b/test/functional/apm_tests.js
index 02529a0aeb..73803bba85 100644
--- a/test/functional/apm_tests.js
+++ b/test/functional/apm_tests.js
@@ -993,6 +993,7 @@ describe('APM', function() {
       return setupDatabase(this.configuration);
     });
 
+    var filterSessionsCommands = x => x.filter(y => y.commandName !== 'endSessions');
     var validateExpecations = function(expectation, results) {
       var obj, databaseName, commandName, reply, result;
       if (expectation.command_started_event) {
@@ -1043,6 +1044,7 @@ describe('APM', function() {
         commandName = obj.command_name;
 
         // Get the result
+        results.failures = filterSessionsCommands(results.failures);
         result = results.failures.shift();
 
         // Validate the test
diff --git a/test/functional/buffering_proxy_tests.js b/test/functional/buffering_proxy_tests.js
index 3134bf0d07..8bc761e7ee 100644
--- a/test/functional/buffering_proxy_tests.js
+++ b/test/functional/buffering_proxy_tests.js
@@ -146,6 +146,8 @@ describe.skip('Buffering Proxy', function() {
               request.reply({ ok: 1, n: 1 });
             } else if (doc.aggregate) {
               request.reply({ ok: 1, n: 1 });
+            } else if (doc.endSessions) {
+              request.reply({ ok: 1 });
             }
           }
         });
@@ -158,6 +160,8 @@ describe.skip('Buffering Proxy', function() {
           } else {
             if (doc.ismaster) {
               request.reply(firstSecondary[currentIsMasterIndex]);
+            } else if (doc.endSessions) {
+              request.reply({ ok: 1 });
             }
           }
         });
@@ -170,6 +174,8 @@ describe.skip('Buffering Proxy', function() {
           } else {
             if (doc.ismaster) {
               request.reply(secondSecondary[currentIsMasterIndex]);
+            } else if (doc.endSessions) {
+              request.reply({ ok: 1 });
             }
           }
         });
@@ -362,6 +368,8 @@ describe.skip('Buffering Proxy', function() {
           } else {
             if (doc.ismaster) {
               request.reply(primary[currentIsMasterIndex]);
+            } else if (doc.endSessions) {
+              request.reply({ ok: 1 });
             }
           }
         });
@@ -378,6 +386,8 @@ describe.skip('Buffering Proxy', function() {
               request.reply({ ok: 1, n: 10 });
             } else if (doc.find) {
               request.reply({ ok: 1, n: 10 });
+            } else if (doc.endSessions) {
+              request.reply({ ok: 1 });
             }
           }
         });
@@ -394,6 +404,8 @@ describe.skip('Buffering Proxy', function() {
               request.reply({ ok: 1, n: 10 });
             } else if (doc.find) {
               request.reply({ ok: 1, n: 10 });
+            } else if (doc.endSessions) {
+              request.reply({ ok: 1 });
             }
           }
         });
diff --git a/test/functional/change_stream_tests.js b/test/functional/change_stream_tests.js
index 0b642d2792..99382e20f4 100644
--- a/test/functional/change_stream_tests.js
+++ b/test/functional/change_stream_tests.js
@@ -778,6 +778,8 @@ describe('Change Streams', function() {
                 defaultFields
               )
             );
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
           // Do not respond to other requests
         });
@@ -900,6 +902,8 @@ describe('Change Streams', function() {
             request.reply(changeDoc, {
               cursorId: new Long(1407, 1407)
             });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
       });
@@ -1356,6 +1360,8 @@ describe('Change Streams', function() {
             request.reply(changeDoc, {
               cursorId: new Long(1407, 1407)
             });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
       });
diff --git a/test/functional/collations_tests.js b/test/functional/collations_tests.js
index d1c6568726..113ba91532 100644
--- a/test/functional/collations_tests.js
+++ b/test/functional/collations_tests.js
@@ -37,12 +37,13 @@ describe('Collation', function() {
         const singleServer = yield mock.createServer();
         singleServer.setMessageHandler(request => {
           var doc = request.document;
-
           if (doc.ismaster) {
             request.reply(primary[0]);
           } else if (doc.findandmodify) {
             commandResult = doc;
             request.reply({ ok: 1, result: {} });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -93,6 +94,8 @@ describe('Collation', function() {
           } else if (doc.count) {
             commandResult = doc;
             request.reply({ ok: 1, result: { n: 1 } });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -137,6 +140,8 @@ describe('Collation', function() {
           } else if (doc.aggregate) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -186,6 +191,8 @@ describe('Collation', function() {
           } else if (doc.distinct) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -232,6 +239,8 @@ describe('Collation', function() {
           } else if (doc.geoNear) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -280,6 +289,8 @@ describe('Collation', function() {
           } else if (doc.group) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -336,6 +347,8 @@ describe('Collation', function() {
           } else if (doc.mapreduce) {
             commandResult = doc;
             request.reply({ ok: 1, result: 'tempCollection' });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -390,6 +403,8 @@ describe('Collation', function() {
           } else if (doc.delete) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -434,6 +449,8 @@ describe('Collation', function() {
           } else if (doc.update) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -482,6 +499,8 @@ describe('Collation', function() {
           } else if (doc.find) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -529,6 +548,8 @@ describe('Collation', function() {
           } else if (doc.find) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -577,6 +598,8 @@ describe('Collation', function() {
           } else if (doc.find) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -633,6 +656,8 @@ describe('Collation', function() {
           } else if (doc.create) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -676,6 +701,8 @@ describe('Collation', function() {
             request.reply(primary[0]);
           } else if (doc.find) {
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -718,6 +745,8 @@ describe('Collation', function() {
             request.reply(primary[0]);
           } else if (doc.find) {
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -761,6 +790,8 @@ describe('Collation', function() {
             request.reply({ ok: 1 });
           } else if (doc.delete) {
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -817,6 +848,8 @@ describe('Collation', function() {
             request.reply(primary[0]);
           } else if (doc.update) {
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -925,6 +958,8 @@ describe('Collation', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(firstSecondary[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -932,6 +967,8 @@ describe('Collation', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(arbiter[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -988,6 +1025,8 @@ describe('Collation', function() {
           } else if (doc.createIndexes) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -1039,6 +1078,8 @@ describe('Collation', function() {
             request.reply(primary[0]);
           } else if (doc.createIndexes) {
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -1082,6 +1123,8 @@ describe('Collation', function() {
             request.reply(primary[0]);
           } else if (doc.createIndexes) {
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
diff --git a/test/functional/command_write_concern_tests.js b/test/functional/command_write_concern_tests.js
index 44d9a97d28..e71343b16d 100644
--- a/test/functional/command_write_concern_tests.js
+++ b/test/functional/command_write_concern_tests.js
@@ -89,6 +89,8 @@ describe('Command Write Concern', function() {
           } else if (doc.aggregate) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -96,6 +98,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(firstSecondary[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -103,6 +107,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(arbiter[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -211,6 +217,8 @@ describe('Command Write Concern', function() {
           } else if (doc.create) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -218,6 +226,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(firstSecondary[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -225,6 +235,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(arbiter[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -319,6 +331,8 @@ describe('Command Write Concern', function() {
           } else if (doc.createIndexes) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -326,6 +340,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(firstSecondary[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -333,6 +349,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(arbiter[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -432,6 +450,8 @@ describe('Command Write Concern', function() {
           } else if (doc.drop) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -439,6 +459,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(firstSecondary[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -446,6 +468,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(arbiter[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -543,6 +567,8 @@ describe('Command Write Concern', function() {
           } else if (doc.dropDatabase) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -550,6 +576,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(firstSecondary[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -557,6 +585,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(arbiter[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -656,6 +686,8 @@ describe('Command Write Concern', function() {
           } else if (doc.dropIndexes) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -663,6 +695,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(firstSecondary[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -670,6 +704,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(arbiter[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -768,6 +804,8 @@ describe('Command Write Concern', function() {
           } else if (doc.mapreduce) {
             commandResult = doc;
             request.reply({ ok: 1, result: 'tempCollection' });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -775,6 +813,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(firstSecondary[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -782,6 +822,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(arbiter[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -887,6 +929,8 @@ describe('Command Write Concern', function() {
           } else if (doc.createUser) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -894,6 +938,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(firstSecondary[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -901,6 +947,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(arbiter[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -994,6 +1042,8 @@ describe('Command Write Concern', function() {
           } else if (doc.dropUser) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -1001,6 +1051,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(firstSecondary[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -1008,6 +1060,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(arbiter[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -1101,6 +1155,8 @@ describe('Command Write Concern', function() {
           } else if (doc.findandmodify) {
             commandResult = doc;
             request.reply({ ok: 1, result: {} });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -1108,6 +1164,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(firstSecondary[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -1115,6 +1173,8 @@ describe('Command Write Concern', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(arbiter[0]);
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
diff --git a/test/functional/connection_tests.js b/test/functional/connection_tests.js
index 7055c8e6e0..635908972e 100644
--- a/test/functional/connection_tests.js
+++ b/test/functional/connection_tests.js
@@ -283,7 +283,7 @@ describe('Connection', function() {
         configuration.url(),
         { auto_reconnect: true, poolSize: 4 },
         connectionTester(configuration, 'testConnectServerOptions', function(client) {
-          test.equal(1, client.topology.poolSize);
+          test.equal(2, client.topology.poolSize);
           test.equal(4, client.topology.s.coreTopology.s.pool.size);
           test.equal(true, client.topology.autoReconnect);
           client.close();
diff --git a/test/functional/max_staleness_tests.js b/test/functional/max_staleness_tests.js
index ebad18dbc5..e9fee82fd3 100644
--- a/test/functional/max_staleness_tests.js
+++ b/test/functional/max_staleness_tests.js
@@ -35,6 +35,8 @@ describe('Max Staleness', function() {
             },
             ok: 1
           });
+        } else if (doc.endSessions) {
+          request.reply({ ok: 1 });
         }
       });
     });
diff --git a/test/functional/mongo_client_options_tests.js b/test/functional/mongo_client_options_tests.js
index 65ca1afa87..45215f399c 100644
--- a/test/functional/mongo_client_options_tests.js
+++ b/test/functional/mongo_client_options_tests.js
@@ -23,7 +23,7 @@ describe('MongoClient Options', function() {
         configuration.url(),
         { autoReconnect: true, poolSize: 4 },
         connectionTester(configuration, 'testConnectServerOptions', function(client) {
-          test.equal(1, client.topology.poolSize);
+          test.equal(2, client.topology.poolSize);
           test.equal(4, client.topology.s.coreTopology.s.pool.size);
           test.equal(true, client.topology.autoReconnect);
           client.close();
@@ -48,7 +48,7 @@ describe('MongoClient Options', function() {
         configuration.url(),
         { autoReconnect: true, poolSize: 4 },
         connectionTester(configuration, 'testConnectServerOptions', function(client) {
-          test.equal(1, client.topology.poolSize);
+          test.equal(2, client.topology.poolSize);
           test.equal(4, client.topology.s.coreTopology.s.pool.size);
           test.equal(true, client.topology.autoReconnect);
           client.close();
diff --git a/test/functional/readpreference_tests.js b/test/functional/readpreference_tests.js
index 9701df9eab..26dae73d67 100644
--- a/test/functional/readpreference_tests.js
+++ b/test/functional/readpreference_tests.js
@@ -32,7 +32,10 @@ describe('ReadPreference', function() {
         // Set up our checker method
         client.topology.command = function() {
           var args = Array.prototype.slice.call(arguments, 0);
-          test.equal(ReadPreference.SECONDARY_PREFERRED, args[2].readPreference.preference);
+          if (args[0] === 'integration_tests.$cmd') {
+            test.equal(ReadPreference.SECONDARY_PREFERRED, args[2].readPreference.preference);
+          }
+
           return command.apply(db.serverConfig, args);
         };
 
@@ -74,7 +77,10 @@ describe('ReadPreference', function() {
         // Set up our checker method
         client.topology.command = function() {
           var args = Array.prototype.slice.call(arguments, 0);
-          test.equal(ReadPreference.SECONDARY_PREFERRED, args[2].readPreference.preference);
+          if (args[0] === 'integration_tests.$cmd') {
+            test.equal(ReadPreference.SECONDARY_PREFERRED, args[2].readPreference.preference);
+          }
+
           return command.apply(db.serverConfig, args);
         };
 
@@ -162,7 +168,10 @@ describe('ReadPreference', function() {
         // Set up our checker method
         client.topology.command = function() {
           var args = Array.prototype.slice.call(arguments, 0);
-          test.equal(ReadPreference.SECONDARY_PREFERRED, args[2].readPreference.preference);
+          if (args[0] === 'integration_tests.$cmd') {
+            test.equal(ReadPreference.SECONDARY_PREFERRED, args[2].readPreference.preference);
+          }
+
           return command.apply(db.serverConfig, args);
         };
 
@@ -205,7 +214,10 @@ describe('ReadPreference', function() {
         // Set up our checker method
         client.topology.command = function() {
           var args = Array.prototype.slice.call(arguments, 0);
-          test.equal(ReadPreference.SECONDARY_PREFERRED, args[2].readPreference.preference);
+          if (args[0] === 'integration_tests.$cmd') {
+            test.equal(ReadPreference.SECONDARY_PREFERRED, args[2].readPreference.preference);
+          }
+
           return command.apply(db.serverConfig, args);
         };
 
@@ -250,7 +262,10 @@ describe('ReadPreference', function() {
         // Set up our checker method
         client.topology.command = function() {
           var args = Array.prototype.slice.call(arguments, 0);
-          test.equal(ReadPreference.SECONDARY_PREFERRED, args[2].readPreference.preference);
+          if (args[0] === 'integration_tests.$cmd') {
+            test.equal(ReadPreference.SECONDARY_PREFERRED, args[2].readPreference.preference);
+          }
+
           return command.apply(db.serverConfig, args);
         };
 
@@ -305,7 +320,10 @@ describe('ReadPreference', function() {
           // Set up our checker method
           client.topology.command = function() {
             var args = Array.prototype.slice.call(arguments, 0);
-            test.equal(ReadPreference.SECONDARY_PREFERRED, args[2].readPreference.preference);
+            if (args[0] === 'integration_tests.$cmd') {
+              test.equal(ReadPreference.SECONDARY_PREFERRED, args[2].readPreference.preference);
+            }
+
             return command.apply(db.serverConfig, args);
           };
 
@@ -400,7 +418,10 @@ describe('ReadPreference', function() {
         // Set up our checker method
         client.topology.command = function() {
           var args = Array.prototype.slice.call(arguments, 0);
-          test.equal(ReadPreference.SECONDARY_PREFERRED, args[2].readPreference.preference);
+          if (args[0] === 'integration_tests.$cmd') {
+            test.equal(ReadPreference.SECONDARY_PREFERRED, args[2].readPreference.preference);
+          }
+
           return command.apply(db.serverConfig, args);
         };
 
@@ -461,7 +482,10 @@ describe('ReadPreference', function() {
         // Set up our checker method
         client.topology.command = function() {
           var args = Array.prototype.slice.call(arguments, 0);
-          test.equal(ReadPreference.SECONDARY_PREFERRED, args[2].readPreference.preference);
+          if (args[0] === 'integration_tests.$cmd') {
+            test.equal(ReadPreference.SECONDARY_PREFERRED, args[2].readPreference.preference);
+          }
+
           return command.apply(db.serverConfig, args);
         };
 
@@ -496,7 +520,10 @@ describe('ReadPreference', function() {
         // Set up our checker method
         client.topology.command = function() {
           var args = Array.prototype.slice.call(arguments, 0);
-          test.equal(ReadPreference.SECONDARY, args[2].readPreference.preference);
+          if (args[0] === 'integration_tests.$cmd') {
+            test.equal(ReadPreference.SECONDARY, args[2].readPreference.preference);
+          }
+
           return command.apply(db.serverConfig, args);
         };
 
@@ -505,7 +532,10 @@ describe('ReadPreference', function() {
 
           client.topology.command = function() {
             var args = Array.prototype.slice.call(arguments, 0);
-            test.equal(ReadPreference.SECONDARY_PREFERRED, args[2].readPreference.preference);
+            if (args[0] === 'integration_tests.$cmd') {
+              test.equal(ReadPreference.SECONDARY_PREFERRED, args[2].readPreference.preference);
+            }
+
             return command.apply(db.serverConfig, args);
           };
 
diff --git a/test/functional/replicaset_mock_tests.js b/test/functional/replicaset_mock_tests.js
index f70d7fc20c..119c7e16bd 100644
--- a/test/functional/replicaset_mock_tests.js
+++ b/test/functional/replicaset_mock_tests.js
@@ -35,6 +35,8 @@ describe('ReplSet (mocks)', function() {
           request.reply(serverIsMaster[0]);
         } else if (doc.insert) {
           request.reply({ ok: 1, n: doc.documents, lastOp: new Date() });
+        } else if (doc.endSessions) {
+          request.reply({ ok: 1 });
         }
       });
 
@@ -44,6 +46,8 @@ describe('ReplSet (mocks)', function() {
           request.reply(serverIsMaster[1]);
         } else if (doc.insert) {
           request.reply({ ok: 1, n: doc.documents, lastOp: new Date() });
+        } else if (doc.endSessions) {
+          request.reply({ ok: 1 });
         }
       });
     });
diff --git a/test/functional/view_tests.js b/test/functional/view_tests.js
index 7584fe5e98..468da6a94f 100644
--- a/test/functional/view_tests.js
+++ b/test/functional/view_tests.js
@@ -39,6 +39,8 @@ describe('Views', function() {
           } else if (doc.create) {
             commandResult = doc;
             request.reply({ ok: 1 });
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
diff --git a/test/unit/sessions/client_tests.js b/test/unit/sessions/client_tests.js
index ad252c68e6..82950b8ca4 100644
--- a/test/unit/sessions/client_tests.js
+++ b/test/unit/sessions/client_tests.js
@@ -22,6 +22,8 @@ describe('Sessions', function() {
           var doc = request.document;
           if (doc.ismaster) {
             request.reply(assign({}, mock.DEFAULT_ISMASTER));
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
@@ -49,6 +51,8 @@ describe('Sessions', function() {
                 logicalSessionTimeoutMinutes: 10
               })
             );
+          } else if (doc.endSessions) {
+            request.reply({ ok: 1 });
           }
         });
 
diff --git a/yarn.lock b/yarn.lock
index 68cf33e3fe..a643f1dadc 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -47,13 +47,13 @@ ajv@^4.7.0:
     json-stable-stringify "^1.0.1"
 
 ajv@^5.1.0, ajv@^5.2.0, ajv@^5.2.3:
-  version "5.2.3"
-  resolved "https://registry.yarnpkg.com/ajv/-/ajv-5.2.3.tgz#c06f598778c44c6b161abafe3466b81ad1814ed2"
+  version "5.3.0"
+  resolved "https://registry.yarnpkg.com/ajv/-/ajv-5.3.0.tgz#4414ff74a50879c208ee5fdc826e32c303549eda"
   dependencies:
     co "^4.6.0"
     fast-deep-equal "^1.0.0"
+    fast-json-stable-stringify "^2.0.0"
     json-schema-traverse "^0.3.0"
-    json-stable-stringify "^1.0.1"
 
 align-text@^0.1.1, align-text@^0.1.3:
   version "0.1.4"
@@ -75,14 +75,14 @@ ampersand-events@^2.0.1:
     lodash "^4.6.1"
 
 ampersand-state@^5.0.1:
-  version "5.0.2"
-  resolved "https://registry.yarnpkg.com/ampersand-state/-/ampersand-state-5.0.2.tgz#16830def866c644ecd21da8c8ba8717aa2b8d23c"
+  version "5.0.3"
+  resolved "https://registry.yarnpkg.com/ampersand-state/-/ampersand-state-5.0.3.tgz#33402ea604375af64a249f664a0312c1160da475"
   dependencies:
     ampersand-events "^2.0.1"
     ampersand-version "^1.0.0"
     array-next "~0.0.1"
     key-tree-store "^1.3.0"
-    lodash "^4.11.1"
+    lodash "^4.12.0"
 
 ampersand-version@^1.0.0, ampersand-version@^1.0.2:
   version "1.0.2"
@@ -313,8 +313,8 @@ babylon@^6.18.0:
   resolved "https://registry.yarnpkg.com/babylon/-/babylon-6.18.0.tgz#af2f3b88fa6f5c1e4c634d1a0f8eac4f55b395e3"
 
 babylon@~7.0.0-beta.19:
-  version "7.0.0-beta.27"
-  resolved "https://registry.yarnpkg.com/babylon/-/babylon-7.0.0-beta.27.tgz#b6edd30ef30619e2f630eb52585fdda84e6542cd"
+  version "7.0.0-beta.29"
+  resolved "https://registry.yarnpkg.com/babylon/-/babylon-7.0.0-beta.29.tgz#6a3e0e6287390385a36f5511e7f94db8618574ae"
 
 balanced-match@^1.0.0:
   version "1.0.0"
@@ -483,8 +483,8 @@ chalk@^1.1.1, chalk@^1.1.3:
     supports-color "^2.0.0"
 
 chalk@^2.0.0, chalk@^2.1.0:
-  version "2.1.0"
-  resolved "https://registry.yarnpkg.com/chalk/-/chalk-2.1.0.tgz#ac5becf14fa21b99c6c92ca7a7d7cfd5b17e743e"
+  version "2.3.0"
+  resolved "https://registry.yarnpkg.com/chalk/-/chalk-2.3.0.tgz#b5ea48efc9c1793dccc9b4767c93914d3f2d52ba"
   dependencies:
     ansi-styles "^3.1.0"
     escape-string-regexp "^1.0.5"
@@ -943,8 +943,8 @@ eslint-scope@^3.7.1:
     estraverse "^4.1.1"
 
 eslint@^4.5.0:
-  version "4.8.0"
-  resolved "https://registry.yarnpkg.com/eslint/-/eslint-4.8.0.tgz#229ef0e354e0e61d837c7a80fdfba825e199815e"
+  version "4.9.0"
+  resolved "https://registry.yarnpkg.com/eslint/-/eslint-4.9.0.tgz#76879d274068261b191fe0f2f56c74c2f4208e8b"
   dependencies:
     ajv "^5.2.0"
     babel-code-frame "^6.22.0"
@@ -1085,6 +1085,10 @@ fast-diff@^1.1.1:
   version "1.1.2"
   resolved "https://registry.yarnpkg.com/fast-diff/-/fast-diff-1.1.2.tgz#4b62c42b8e03de3f848460b639079920695d0154"
 
+fast-json-stable-stringify@^2.0.0:
+  version "2.0.0"
+  resolved "https://registry.yarnpkg.com/fast-json-stable-stringify/-/fast-json-stable-stringify-2.0.0.tgz#d5142c0caee6b1189f87d3a76111064f86c8bbf2"
+
 fast-levenshtein@~2.0.4:
   version "2.0.6"
   resolved "https://registry.yarnpkg.com/fast-levenshtein/-/fast-levenshtein-2.0.6.tgz#3d8a5c66883a16a30ca8643e851f19baa7797917"
@@ -1343,8 +1347,8 @@ growl@1.9.2:
   resolved "https://registry.yarnpkg.com/growl/-/growl-1.9.2.tgz#0ea7743715db8d8de2c5ede1775e1b45ac85c02f"
 
 handlebars@^4.0.1:
-  version "4.0.10"
-  resolved "https://registry.yarnpkg.com/handlebars/-/handlebars-4.0.10.tgz#3d30c718b09a3d96f23ea4cc1f403c4d3ba9ff4f"
+  version "4.0.11"
+  resolved "https://registry.yarnpkg.com/handlebars/-/handlebars-4.0.11.tgz#630a35dfe0294bc281edae6ffc5d329fc7982dcc"
   dependencies:
     async "^1.4.0"
     optimist "^0.6.1"
@@ -1477,8 +1481,8 @@ ieee754@^1.1.4:
   resolved "https://registry.yarnpkg.com/ieee754/-/ieee754-1.1.8.tgz#be33d40ac10ef1926701f6f08a2d86fbfd1ad3e4"
 
 ignore@^3.3.3:
-  version "3.3.5"
-  resolved "https://registry.yarnpkg.com/ignore/-/ignore-3.3.5.tgz#c4e715455f6073a8d7e5dae72d2fc9d71663dba6"
+  version "3.3.7"
+  resolved "https://registry.yarnpkg.com/ignore/-/ignore-3.3.7.tgz#612289bfb3c220e186a58118618d5be8c1bab021"
 
 imurmurhash@^0.1.4:
   version "0.1.4"
@@ -1533,8 +1537,8 @@ is-arrayish@^0.2.1:
   resolved "https://registry.yarnpkg.com/is-arrayish/-/is-arrayish-0.2.1.tgz#77c99840527aa8ecb1a8ba697b80645a7a926a9d"
 
 is-buffer@^1.1.5:
-  version "1.1.5"
-  resolved "https://registry.yarnpkg.com/is-buffer/-/is-buffer-1.1.5.tgz#1f3b26ef613b214b88cbca23cc6c01d87961eecc"
+  version "1.1.6"
+  resolved "https://registry.yarnpkg.com/is-buffer/-/is-buffer-1.1.6.tgz#efaa2ea9daa0d7ab2ea13a97b2b8ad51fefbe8be"
 
 is-builtin-module@^1.0.0:
   version "1.0.0"
@@ -1971,7 +1975,7 @@ lodash.transform@^4.6.0:
   version "4.6.0"
   resolved "https://registry.yarnpkg.com/lodash.transform/-/lodash.transform-4.6.0.tgz#12306422f63324aed8483d3f38332b5f670547a0"
 
-lodash@^4.0.0, lodash@^4.11.1, lodash@^4.14.0, lodash@^4.17.4, lodash@^4.3.0, lodash@^4.6.1:
+lodash@^4.0.0, lodash@^4.12.0, lodash@^4.14.0, lodash@^4.17.4, lodash@^4.3.0, lodash@^4.6.1:
   version "4.17.4"
   resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.4.tgz#78203a4d1c328ae1d86dca6460e369b57f4055ae"
 
@@ -2001,10 +2005,10 @@ lru-cache@^4.0.1:
     yallist "^2.1.2"
 
 make-dir@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/make-dir/-/make-dir-1.0.0.tgz#97a011751e91dd87cfadef58832ebb04936de978"
+  version "1.1.0"
+  resolved "https://registry.yarnpkg.com/make-dir/-/make-dir-1.1.0.tgz#19b4369fe48c116f53c2af95ad102c0e39e85d51"
   dependencies:
-    pify "^2.3.0"
+    pify "^3.0.0"
 
 map-stream@~0.1.0:
   version "0.1.0"
@@ -2026,7 +2030,11 @@ metamocha@^1.2.5:
   dependencies:
     mocha "^3.5.3"
 
-mime-db@^1.28.0, mime-db@~1.30.0:
+mime-db@^1.28.0:
+  version "1.31.0"
+  resolved "https://registry.yarnpkg.com/mime-db/-/mime-db-1.31.0.tgz#a49cd8f3ebf3ed1a482b60561d9105ad40ca74cb"
+
+mime-db@~1.30.0:
   version "1.30.0"
   resolved "https://registry.yarnpkg.com/mime-db/-/mime-db-1.30.0.tgz#74c643da2dd9d6a45399963465b26d5ca7d71f01"
 
@@ -2098,7 +2106,7 @@ mongodb-core@2.1.17:
 
 mongodb-core@mongodb-js/mongodb-core#3.0.0:
   version "2.1.90"
-  resolved "https://codeload.github.com/mongodb-js/mongodb-core/tar.gz/d92efecfabd8774df6ff46b7fcabdd4ddcc83aed"
+  resolved "https://codeload.github.com/mongodb-js/mongodb-core/tar.gz/1bf9864cc427e95eccb4fcebb7334b684df61956"
   dependencies:
     bson "~1.0.4"
     require_optional "^1.0.1"
@@ -2703,8 +2711,8 @@ sntp@1.x.x:
     hoek "2.x.x"
 
 sntp@2.x.x:
-  version "2.0.2"
-  resolved "https://registry.yarnpkg.com/sntp/-/sntp-2.0.2.tgz#5064110f0af85f7cfdb7d6b67a40028ce52b4b2b"
+  version "2.1.0"
+  resolved "https://registry.yarnpkg.com/sntp/-/sntp-2.1.0.tgz#2c6cec14fedc2222739caf9b5c3d85d1cc5a2cc8"
   dependencies:
     hoek "4.x.x"
 
@@ -2832,8 +2840,8 @@ strip-bom@^3.0.0:
   resolved "https://registry.yarnpkg.com/strip-bom/-/strip-bom-3.0.0.tgz#2334c18e9c759f7bdd56fdef7e9ae3d588e68ed3"
 
 strip-dirs@^2.0.0:
-  version "2.0.0"
-  resolved "https://registry.yarnpkg.com/strip-dirs/-/strip-dirs-2.0.0.tgz#610cdb2928200da0004f41dcb90fc95cd919a0b6"
+  version "2.1.0"
+  resolved "https://registry.yarnpkg.com/strip-dirs/-/strip-dirs-2.1.0.tgz#4987736264fc344cf20f6c34aca9d13d1d4ed6c5"
   dependencies:
     is-natural-number "^4.0.1"
 
@@ -2868,8 +2876,8 @@ supports-color@^3.1.0:
     has-flag "^1.0.0"
 
 supports-color@^4.0.0:
-  version "4.4.0"
-  resolved "https://registry.yarnpkg.com/supports-color/-/supports-color-4.4.0.tgz#883f7ddabc165142b2a61427f3352ded195d1a3e"
+  version "4.5.0"
+  resolved "https://registry.yarnpkg.com/supports-color/-/supports-color-4.5.0.tgz#be7a0de484dec5c5cddf8b3d59125044912f635b"
   dependencies:
     has-flag "^2.0.0"