Revert "SERVER-32064 Requests from the shell should use an implicit session by default"

This reverts commit 3225e5f0784b8306c700a6280bbb986634129291.

77 files changed, 25 insertions, 599 deletions

diff --git a/buildscripts/resmokeconfig/suites/causally_consistent_jscore_passthrough_auth.yml b/buildscripts/resmokeconfig/suites/causally_consistent_jscore_passthrough_auth.yml
index e09d9791c5f..34218fa2665 100644
--- a/buildscripts/resmokeconfig/suites/causally_consistent_jscore_passthrough_auth.yml
+++ b/buildscripts/resmokeconfig/suites/causally_consistent_jscore_passthrough_auth.yml
@@ -157,17 +157,6 @@ selector:
   # sync source if the RestartCatalog command kills its oplog fetching cursor, which blocks
   # secondary majority reads.
   - jstests/core/restart_catalog.js
-
-  # These include operations the root user auth'd on the test database is not authorized to perform,
-  # e.g. dropping or creating system collections.
-  - jstests/core/cannot_create_system_dot_indexes.js
-  - jstests/core/list_collections_no_views.js
-  - jstests/core/rename8.js
-  - jstests/core/views/duplicate_ns.js
-  - jstests/core/views/invalid_system_views.js
-  - jstests/core/views/views_creation.js
-  - jstests/core/views/views_drop.js
-  - jstests/core/views/views_rename.js
   exclude_with_any_tags:
   - assumes_against_mongod_not_mongos
   ##
@@ -179,11 +168,7 @@ selector:
   # "Cowardly refusing to run test with overridden read preference when it reads from a
   #  non-replicated collection: ..."
   - assumes_read_preference_unchanged
-  # TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-  - creates_and_authenticates_user
   - requires_collstats
-  # This suite runs as the root user, but eval requires universal privileges with authentication on.
-  - requires_eval_command
 
 executor:
   archive:
@@ -207,7 +192,7 @@ executor:
           const res = db.runCommand({
               createUser: username,
               pwd: password,
-              roles: [{role: "root", db: jsTest.options().authenticationDatabase}]
+              roles: ["dbOwner"],
           });
 
           if (res.ok === 1) {
@@ -218,8 +203,7 @@ executor:
               assert.commandFailedWithCode(res, ErrorCodes.DuplicateKey);
           }
 
-          // Log out as the __system user and auth as the newly created user.
-          db.getSiblingDB(jsTest.options().authenticationDatabase).logout();
+          db.logout();
           db.auth(username, password);
         })();
         load("jstests/libs/override_methods/enable_causal_consistency.js");
diff --git a/buildscripts/resmokeconfig/suites/core_auth.yml b/buildscripts/resmokeconfig/suites/core_auth.yml
index d5290825547..0304de42ad2 100644
--- a/buildscripts/resmokeconfig/suites/core_auth.yml
+++ b/buildscripts/resmokeconfig/suites/core_auth.yml
@@ -20,9 +20,6 @@ selector:
   - jstests/core/**/*[aA]uth*.js
   # Commands using UUIDs are not compatible with name-based auth
   - jstests/core/commands_with_uuid.js
-  exclude_with_any_tags:
-  # TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-  - creates_and_authenticates_user
 
 executor:
   archive:
diff --git a/buildscripts/resmokeconfig/suites/jstestfuzz_replication.yml b/buildscripts/resmokeconfig/suites/jstestfuzz_replication.yml
index 6584273afa8..6c1c85d9014 100644
--- a/buildscripts/resmokeconfig/suites/jstestfuzz_replication.yml
+++ b/buildscripts/resmokeconfig/suites/jstestfuzz_replication.yml
@@ -13,10 +13,6 @@ executor:
   config:
     shell_options:
       readMode: commands
-      global_vars:
-        TestData:
-          # Other fuzzers test commands against replica sets with logical session ids.
-          disableImplicitSessions: true
   hooks:
   # The CheckReplDBHash hook waits until all operations have replicated to and have been applied
   # on the secondaries, so we run the ValidateCollections hook after it to ensure we're
diff --git a/buildscripts/resmokeconfig/suites/jstestfuzz_sharded.yml b/buildscripts/resmokeconfig/suites/jstestfuzz_sharded.yml
index 65b093116eb..394b0af4ff6 100644
--- a/buildscripts/resmokeconfig/suites/jstestfuzz_sharded.yml
+++ b/buildscripts/resmokeconfig/suites/jstestfuzz_sharded.yml
@@ -11,10 +11,6 @@ executor:
       - ValidateCollections
   config:
     shell_options:
-      global_vars:
-        TestData:
-          # Other fuzzers test commands against sharded clusters with logical session ids.
-          disableImplicitSessions: true
       readMode: commands
   hooks:
   - class: CheckReplDBHash
diff --git a/buildscripts/resmokeconfig/suites/replica_sets_multi_stmt_txn_jscore_passthrough.yml b/buildscripts/resmokeconfig/suites/replica_sets_multi_stmt_txn_jscore_passthrough.yml
index f5d2c288232..b0491cec3e9 100644
--- a/buildscripts/resmokeconfig/suites/replica_sets_multi_stmt_txn_jscore_passthrough.yml
+++ b/buildscripts/resmokeconfig/suites/replica_sets_multi_stmt_txn_jscore_passthrough.yml
@@ -223,9 +223,6 @@ selector:
   - jstests/core/json_schema/misc_validation.js
   - jstests/core/views/views_all_commands.js
 
-  # Fails with implicit sessions because it will use multiple sessions on the same Mongo connection.
-  - jstests/core/dropdb.js
-
   # Committing a transaction when the server is fsync locked fails.
   - jstests/core/fsync.js
 
diff --git a/jstests/auth/auth1.js b/jstests/auth/auth1.js
index 6eff329e341..183317414df 100644
--- a/jstests/auth/auth1.js
+++ b/jstests/auth/auth1.js
@@ -1,9 +1,6 @@
 // test read/write permissions
 // skip this test on 32-bit platforms
 
-// TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-TestData.disableImplicitSessions = true;
-
 function setupTest() {
     print("START auth1.js");
     baseName = "jstests_auth_auth1";
diff --git a/jstests/auth/authentication_restrictions.js b/jstests/auth/authentication_restrictions.js
index 1f08b3e6d6d..ad12fd33f35 100644
--- a/jstests/auth/authentication_restrictions.js
+++ b/jstests/auth/authentication_restrictions.js
@@ -6,9 +6,6 @@
 (function() {
     'use strict';
 
-    // TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-    TestData.disableImplicitSessions = true;
-
     function testConnection(
         conn, eventuallyConsistentConn, sleepUntilUserDataPropagated, sleepUntilUserDataRefreshed) {
         load("jstests/libs/host_ipaddr.js");
diff --git a/jstests/auth/authentication_restrictions_role.js b/jstests/auth/authentication_restrictions_role.js
index 3f23cfdcb92..41e3a133cab 100644
--- a/jstests/auth/authentication_restrictions_role.js
+++ b/jstests/auth/authentication_restrictions_role.js
@@ -6,9 +6,6 @@
 (function() {
     'use strict';
 
-    // TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-    TestData.disableImplicitSessions = true;
-
     function testRestrictionCreationAndEnforcement(
         conn, eventuallyConsistentConn, sleepUntilUserDataPropagated, sleepUntilUserDataRefreshed) {
         load("jstests/libs/host_ipaddr.js");
diff --git a/jstests/auth/basic_role_auth.js b/jstests/auth/basic_role_auth.js
index 81e1518152c..9f8abffae40 100644
--- a/jstests/auth/basic_role_auth.js
+++ b/jstests/auth/basic_role_auth.js
@@ -493,7 +493,7 @@ var runTests = function(conn) {
             testFunc.test(newConn);
         } catch (x) {
             failures.push(testFunc.name);
-            jsTestLog(tojson(x));
+            jsTestLog(x);
         }
     });
 
diff --git a/jstests/auth/commands_builtin_roles.js b/jstests/auth/commands_builtin_roles.js
index cee5957d354..93eef01bcd6 100644
--- a/jstests/auth/commands_builtin_roles.js
+++ b/jstests/auth/commands_builtin_roles.js
@@ -9,10 +9,6 @@ in jstests/auth/commands.js.
 
 */
 
-// TODO SERVER-35447: This test involves killing all sessions, which will not work as expected if
-// the kill command is sent with an implicit session.
-TestData.disableImplicitSessions = true;
-
 load("jstests/auth/lib/commands_lib.js");
 
 var roles = [
diff --git a/jstests/auth/commands_user_defined_roles.js b/jstests/auth/commands_user_defined_roles.js
index 034694c96bb..ad75b5e1d83 100644
--- a/jstests/auth/commands_user_defined_roles.js
+++ b/jstests/auth/commands_user_defined_roles.js
@@ -9,10 +9,6 @@ in jstests/auth/commands.js.
 
 */
 
-// TODO SERVER-35447: This test involves killing all sessions, which will not work as expected if
-// the kill command is sent with an implicit session.
-TestData.disableImplicitSessions = true;
-
 // constants
 var testUser = "userDefinedRolesTestUser";
 var testRole = "userDefinedRolesTestRole";
diff --git a/jstests/auth/copyauth.js b/jstests/auth/copyauth.js
index 9caa51a6e87..faf5badd5ff 100644
--- a/jstests/auth/copyauth.js
+++ b/jstests/auth/copyauth.js
@@ -195,10 +195,6 @@ function copydbBetweenClustersTest(configObj) {
     assert.eq(1, target.conn.getDB(baseName)[baseName].count());
     assert.eq(1, target.conn.getDB(baseName)[baseName].findOne().i);
 
-    if (configObj.isTargetUsingAuth) {
-        target.conn.getDB("admin").logout();
-    }
-
     // 4. Do any necessary cleanup
     source.stop();
     target.stop();
diff --git a/jstests/auth/getMore.js b/jstests/auth/getMore.js
index cbb84c4a687..999fa733be8 100644
--- a/jstests/auth/getMore.js
+++ b/jstests/auth/getMore.js
@@ -3,9 +3,6 @@
 (function() {
     "use strict";
 
-    // TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-    TestData.disableImplicitSessions = true;
-
     function runTest(conn) {
         let adminDB = conn.getDB("admin");
         let isMaster = adminDB.runCommand("ismaster");
diff --git a/jstests/auth/kill_cursors.js b/jstests/auth/kill_cursors.js
index 3264bbcc15b..2fd3d7054f8 100644
--- a/jstests/auth/kill_cursors.js
+++ b/jstests/auth/kill_cursors.js
@@ -3,9 +3,6 @@
 (function() {
     'use strict';
 
-    // TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-    TestData.disableImplicitSessions = true;
-
     function runTest(mongod) {
         /**
          * Open a cursor on `db` while authenticated as `authUsers`.
diff --git a/jstests/auth/kill_sessions.js b/jstests/auth/kill_sessions.js
index b07364bc0c2..b2090d28609 100644
--- a/jstests/auth/kill_sessions.js
+++ b/jstests/auth/kill_sessions.js
@@ -3,10 +3,6 @@ load("jstests/libs/kill_sessions.js");
 (function() {
     'use strict';
 
-    // TODO SERVER-35447: This test involves killing all sessions, which will not work as expected
-    // if the kill command is sent with an implicit session.
-    TestData.disableImplicitSessions = true;
-
     var forExec = MongoRunner.runMongod({nojournal: "", auth: ""});
     var forKill = new Mongo(forExec.host);
     var forVerify = new Mongo(forExec.host);
diff --git a/jstests/auth/list_all_local_sessions.js b/jstests/auth/list_all_local_sessions.js
index 3b7c19d1cbe..8e889feb4e2 100644
--- a/jstests/auth/list_all_local_sessions.js
+++ b/jstests/auth/list_all_local_sessions.js
@@ -5,10 +5,6 @@
     'use strict';
     load('jstests/aggregation/extras/utils.js');
 
-    // This test makes assertions about the number of sessions, which are not compatible with
-    // implicit sessions.
-    TestData.disableImplicitSessions = true;
-
     function runListAllLocalSessionsTest(mongod) {
         assert(mongod);
         const admin = mongod.getDB("admin");
diff --git a/jstests/auth/list_all_sessions.js b/jstests/auth/list_all_sessions.js
index 1337fc2e94c..35a4e3b3c06 100644
--- a/jstests/auth/list_all_sessions.js
+++ b/jstests/auth/list_all_sessions.js
@@ -5,10 +5,6 @@
     'use strict';
     load('jstests/aggregation/extras/utils.js');
 
-    // This test makes assertions about the number of sessions, which are not compatible with
-    // implicit sessions.
-    TestData.disableImplicitSessions = true;
-
     function runListAllSessionsTest(mongod) {
         assert(mongod);
         const admin = mongod.getDB("admin");
diff --git a/jstests/auth/list_local_sessions.js b/jstests/auth/list_local_sessions.js
index b943ba45955..4693d694666 100644
--- a/jstests/auth/list_local_sessions.js
+++ b/jstests/auth/list_local_sessions.js
@@ -4,10 +4,6 @@
     'use strict';
     load('jstests/aggregation/extras/utils.js');
 
-    // This test makes assertions about the number of sessions, which are not compatible with
-    // implicit sessions.
-    TestData.disableImplicitSessions = true;
-
     function runListLocalSessionsTest(mongod) {
         assert(mongod);
         const admin = mongod.getDB('admin');
diff --git a/jstests/auth/list_sessions.js b/jstests/auth/list_sessions.js
index 2b6c8a0f8f1..e6c14a11c4c 100644
--- a/jstests/auth/list_sessions.js
+++ b/jstests/auth/list_sessions.js
@@ -7,10 +7,6 @@
     'use strict';
     load('jstests/aggregation/extras/utils.js');
 
-    // This test makes assertions about the number of sessions, which are not compatible with
-    // implicit sessions.
-    TestData.disableImplicitSessions = true;
-
     function runListSessionsTest(mongod) {
         assert(mongod);
         const admin = mongod.getDB('admin');
diff --git a/jstests/auth/refresh_logical_session_cache_with_long_usernames.js b/jstests/auth/refresh_logical_session_cache_with_long_usernames.js
index e584a1b8345..d9bbed5324f 100644
--- a/jstests/auth/refresh_logical_session_cache_with_long_usernames.js
+++ b/jstests/auth/refresh_logical_session_cache_with_long_usernames.js
@@ -4,10 +4,6 @@
 (function() {
     'use strict';
 
-    // This test makes assertions about the number of sessions, which are not compatible with
-    // implicit sessions.
-    TestData.disableImplicitSessions = true;
-
     const mongod = MongoRunner.runMongod({auth: ""});
 
     const refresh = {refreshLogicalSessionCacheNow: 1};
diff --git a/jstests/auth/rename.js b/jstests/auth/rename.js
index 0ae3eac3113..a8120d22322 100644
--- a/jstests/auth/rename.js
+++ b/jstests/auth/rename.js
@@ -1,8 +1,5 @@
 // test renameCollection with auth
 
-// TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-TestData.disableImplicitSessions = true;
-
 var m = MongoRunner.runMongod({auth: ""});
 
 var db1 = m.getDB("foo");
@@ -45,4 +42,4 @@ assert.eq(db1.a.count(), 0);
 assert.eq(db1.b.count(), 0);
 assert.eq(db2.a.count(), 1);
 
-MongoRunner.stopMongod(m, null, {user: 'admin', pwd: 'password'});
+MongoRunner.stopMongod(m, null, {user: 'admin', pwd: 'password'});
\ No newline at end of file
diff --git a/jstests/auth/repl_auth.js b/jstests/auth/repl_auth.js
index fea8f227366..17a6e13bd4b 100644
--- a/jstests/auth/repl_auth.js
+++ b/jstests/auth/repl_auth.js
@@ -65,8 +65,4 @@ for (var x = 0; x < 20; x++) {
     assert.eq(1, explain.executionStats.nReturned);
 }
 
-admin.logout();
-fooDB0.logout();
-barDB1.logout();
-
 rsTest.stopSet();
diff --git a/jstests/auth/resource_pattern_matching.js b/jstests/auth/resource_pattern_matching.js
index ca3c9b50195..0fd30650982 100644
--- a/jstests/auth/resource_pattern_matching.js
+++ b/jstests/auth/resource_pattern_matching.js
@@ -3,11 +3,6 @@
  * @tags: [requires_replication, requires_sharding]
  */
 
-// TODO SERVER-35447: This test logs in users on the admin database, but doesn't log them out, which
-// can fail with implicit sessions and ReplSetTest when the fixture attempts to verify data hashes
-// at shutdown by authenticating as the __system user.
-TestData.disableImplicitSessions = true;
-
 function setup_users(granter) {
     var admindb = granter.getSiblingDB("admin");
     admindb.runCommand({
diff --git a/jstests/auth/secondary_invalidation.js b/jstests/auth/secondary_invalidation.js
index 16f2938ebbf..8500322751f 100644
--- a/jstests/auth/secondary_invalidation.js
+++ b/jstests/auth/secondary_invalidation.js
@@ -31,7 +31,4 @@ assert.doesNotThrow(function() {
     secondaryFoo.col.findOne();
 }, [], "Secondary read did not work with permissions");
 
-admin.logout();
-secondaryFoo.logout();
-
 rsTest.stopSet();
diff --git a/jstests/auth/views_authz.js b/jstests/auth/views_authz.js
index 080a4b2bfcd..e22dcf86cb6 100644
--- a/jstests/auth/views_authz.js
+++ b/jstests/auth/views_authz.js
@@ -6,9 +6,6 @@
 (function() {
     "use strict";
 
-    // TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-    TestData.disableImplicitSessions = true;
-
     function runTest(conn) {
         // Create the admin user.
         let adminDB = conn.getDB("admin");
diff --git a/jstests/core/auth1.js b/jstests/core/auth1.js
index 4f2a869ab44..05450d14ddc 100644
--- a/jstests/core/auth1.js
+++ b/jstests/core/auth1.js
@@ -1,9 +1,4 @@
-// @tags: [
-//   assumes_write_concern_unchanged,
-//   creates_and_authenticates_user,
-//   requires_auth,
-//   requires_non_retryable_commands,
-// ]
+// @tags: [requires_non_retryable_commands, requires_auth, assumes_write_concern_unchanged]
 
 var mydb = db.getSiblingDB('auth1_db');
 mydb.dropAllUsers();
diff --git a/jstests/core/connection_status.js b/jstests/core/connection_status.js
index 33d11149657..df1c59ab234 100644
--- a/jstests/core/connection_status.js
+++ b/jstests/core/connection_status.js
@@ -1,8 +1,7 @@
 // @tags: [
-//      assumes_write_concern_unchanged,
-//      creates_and_authenticates_user,
-//      requires_auth,
 //      requires_non_retryable_commands,
+//      requires_auth,
+//      assumes_write_concern_unchanged
 //      ]
 
 // Tests the connectionStatus command
diff --git a/jstests/core/evalb.js b/jstests/core/evalb.js
index 96f2bbd7358..92fbb81f31c 100644
--- a/jstests/core/evalb.js
+++ b/jstests/core/evalb.js
@@ -2,11 +2,10 @@
 // contents are logged in the profile log.
 //
 // @tags: [
-//   assumes_read_preference_unchanged,
-//   creates_and_authenticates_user,
 //   does_not_support_stepdowns,
 //   requires_eval_command,
 //   requires_non_retryable_commands,
+//   assumes_read_preference_unchanged
 // ]
 
 // Use a reserved database name to avoid a conflict in the parallel test suite.
diff --git a/jstests/core/profile1.js b/jstests/core/profile1.js
index 730bb91a33a..4109c3ac55d 100644
--- a/jstests/core/profile1.js
+++ b/jstests/core/profile1.js
@@ -1,9 +1,4 @@
-// @tags: [
-//   creates_and_authenticates_user,
-//   does_not_support_stepdowns,
-//   requires_collstats,
-//   requires_non_retryable_commands,
-// ]
+// @tags: [does_not_support_stepdowns, requires_non_retryable_commands, requires_collstats]
 
 (function() {
     "use strict";
diff --git a/jstests/core/profile3.js b/jstests/core/profile3.js
index f55256783ab..35e37d0917d 100644
--- a/jstests/core/profile3.js
+++ b/jstests/core/profile3.js
@@ -1,5 +1,4 @@
 // @tags: [
-//     creates_and_authenticates_user
 //     # profile command is not available on embedded
 //     incompatible_with_embedded,
 // ]
diff --git a/jstests/core/txns/multi_statement_transaction_command_args.js b/jstests/core/txns/multi_statement_transaction_command_args.js
index 8246d1030a5..fe139e2f16d 100644
--- a/jstests/core/txns/multi_statement_transaction_command_args.js
+++ b/jstests/core/txns/multi_statement_transaction_command_args.js
@@ -8,9 +8,6 @@
     "use strict";
     load('jstests/libs/uuid_util.js');
 
-    // Makes assertions on commands run without logical session ids.
-    TestData.disableImplicitSessions = true;
-
     const dbName = "test";
     const collName = "multi_statement_transaction_command_args";
     const testDB = db.getSiblingDB(dbName);
diff --git a/jstests/core/user_management_helpers.js b/jstests/core/user_management_helpers.js
index 3d3b1b49c68..6e3ee9187c0 100644
--- a/jstests/core/user_management_helpers.js
+++ b/jstests/core/user_management_helpers.js
@@ -1,8 +1,7 @@
 // @tags: [
-//      assumes_write_concern_unchanged,
-//      creates_and_authenticates_user,
-//      requires_auth,
 //      requires_non_retryable_commands,
+//      requires_auth,
+//      assumes_write_concern_unchanged
 //      ]
 
 // This test is a basic sanity check of the shell helpers for manipulating user objects
diff --git a/jstests/multiVersion/mixed_storage_version_replication.js b/jstests/multiVersion/mixed_storage_version_replication.js
index d9f2e880e0c..c67de845e77 100644
--- a/jstests/multiVersion/mixed_storage_version_replication.js
+++ b/jstests/multiVersion/mixed_storage_version_replication.js
@@ -4,11 +4,6 @@
  * storage engines, do a bunch of random work, and assert that it replicates the same way on all
  * nodes.
  */
-
-// This test randomly generates operations, which may include direct writes against
-// config.transactions, which are not allowed to run under a session.
-TestData.disableImplicitSessions = true;
-
 load('jstests/libs/parallelTester.js');
 load("jstests/replsets/rslib.js");
 
@@ -575,10 +570,6 @@ function assertSameData(primary, conns) {
  * function to pass to a thread to make it start doing random commands/CRUD operations.
  */
 function startCmds(randomOps, host) {
-    // This test randomly generates operations, which may include direct writes against
-    // config.transactions, which are not allowed to run under a session.
-    TestData = {disableImplicitSessions: true};
-
     var ops = [
         "insert",
         "remove",
@@ -605,10 +596,6 @@ function startCmds(randomOps, host) {
  * function to pass to a thread to make it start doing random CRUD operations.
  */
 function startCRUD(randomOps, host) {
-    // This test randomly generates operations, which may include direct writes against
-    // config.transactions, which are not allowed to run under a session.
-    TestData = {disableImplicitSessions: true};
-
     var m = new Mongo(host);
     var numOps = 500;
     Random.setRandomSeed();
diff --git a/jstests/noPassthrough/aggregation_cursor_invalidations.js b/jstests/noPassthrough/aggregation_cursor_invalidations.js
index ecc4fe160c9..e35598dc2dd 100644
--- a/jstests/noPassthrough/aggregation_cursor_invalidations.js
+++ b/jstests/noPassthrough/aggregation_cursor_invalidations.js
@@ -12,10 +12,6 @@
 (function() {
     'use strict';
 
-    // This test runs a getMore in a parallel shell, which will not inherit the implicit session of
-    // the cursor establishing command.
-    TestData.disableImplicitSessions = true;
-
     // The DocumentSourceCursor which wraps PlanExecutors will batch results internally. We use the
     // 'internalDocumentSourceCursorBatchSizeBytes' parameter to disable this behavior so that we
     // can easily pause a pipeline in a state where it will need to request more results from the
diff --git a/jstests/noPassthrough/count_helper_read_preference.js b/jstests/noPassthrough/count_helper_read_preference.js
index 619773c3563..63b5faed2ce 100644
--- a/jstests/noPassthrough/count_helper_read_preference.js
+++ b/jstests/noPassthrough/count_helper_read_preference.js
@@ -19,12 +19,7 @@
         commandsRan.push({db: db, cmd: cmd, opts: opts});
         return {ok: 1, n: 100};
     };
-
-    const mockMongo = new MockMongo();
-    var db = new DB(mockMongo, "test");
-
-    // Attach a dummy implicit session because the mock connection cannot create sessions.
-    db._session = new _DummyDriverSession(mockMongo);
+    var db = new DB(new MockMongo(), "test");
 
     assert.eq(commandsRan.length, 0);
 
diff --git a/jstests/noPassthrough/currentop_includes_await_time.js b/jstests/noPassthrough/currentop_includes_await_time.js
index a8ec126f6d7..0c34999a512 100644
--- a/jstests/noPassthrough/currentop_includes_await_time.js
+++ b/jstests/noPassthrough/currentop_includes_await_time.js
@@ -5,10 +5,6 @@
 (function() {
     "use test";
 
-    // This test runs a getMore in a parallel shell, which will not inherit the implicit session of
-    // the cursor establishing command.
-    TestData.disableImplicitSessions = true;
-
     const conn = MongoRunner.runMongod({});
     assert.neq(null, conn, "mongod was unable to start up");
     const testDB = conn.getDB("test");
diff --git a/jstests/noPassthrough/currentop_query.js b/jstests/noPassthrough/currentop_query.js
index b05e66d1af0..7d39fcaed21 100644
--- a/jstests/noPassthrough/currentop_query.js
+++ b/jstests/noPassthrough/currentop_query.js
@@ -6,10 +6,6 @@
 (function() {
     "use strict";
 
-    // This test runs manual getMores using different connections, which will not inherit the
-    // implicit session of the cursor establishing command.
-    TestData.disableImplicitSessions = true;
-
     load("jstests/libs/fixture_helpers.js");  // For FixtureHelpers.
 
     // Set up a 2-shard cluster. Configure 'internalQueryExecYieldIterations' on both shards such
diff --git a/jstests/noPassthrough/end_sessions_command.js b/jstests/noPassthrough/end_sessions_command.js
index e4ee14b8ecb..1ed1c471557 100644
--- a/jstests/noPassthrough/end_sessions_command.js
+++ b/jstests/noPassthrough/end_sessions_command.js
@@ -1,10 +1,6 @@
 (function() {
     "use script";
 
-    // This test makes assertions about the number of sessions, which are not compatible with
-    // implicit sessions.
-    TestData.disableImplicitSessions = true;
-
     var res;
     var refresh = {refreshLogicalSessionCacheNow: 1};
     var startSession = {startSession: 1};
diff --git a/jstests/noPassthrough/implicit_sessions.js b/jstests/noPassthrough/implicit_sessions.js
deleted file mode 100644
index 350571164b9..00000000000
--- a/jstests/noPassthrough/implicit_sessions.js
+++ /dev/null
@@ -1,265 +0,0 @@
-/**
- * Verifies behavior around implicit sessions in the mongo shell.
- */
-(function() {
-    "use strict";
-
-    /**
-     * Runs the given function, inspecting the outgoing command object and making assertions about
-     * its logical session id.
-     */
-    function inspectCommandForSessionId(func, {shouldIncludeId, expectedId, differentFromId}) {
-        const mongoRunCommandOriginal = Mongo.prototype.runCommand;
-
-        const sentinel = {};
-        let cmdObjSeen = sentinel;
-
-        Mongo.prototype.runCommand = function runCommandSpy(dbName, cmdObj, options) {
-            cmdObjSeen = cmdObj;
-            return mongoRunCommandOriginal.apply(this, arguments);
-        };
-
-        try {
-            assert.doesNotThrow(func);
-        } finally {
-            Mongo.prototype.runCommand = mongoRunCommandOriginal;
-        }
-
-        if (cmdObjSeen === sentinel) {
-            throw new Error("Mongo.prototype.runCommand() was never called: " + func.toString());
-        }
-
-        // If the command is in a wrapped form, then we look for the actual command object inside
-        // the query/$query object.
-        let cmdName = Object.keys(cmdObjSeen)[0];
-        if (cmdName === "query" || cmdName === "$query") {
-            cmdObjSeen = cmdObjSeen[cmdName];
-            cmdName = Object.keys(cmdObjSeen)[0];
-        }
-
-        if (shouldIncludeId) {
-            assert(cmdObjSeen.hasOwnProperty("lsid"),
-                   "Expected operation " + tojson(cmdObjSeen) + " to have a logical session id.");
-
-            if (expectedId) {
-                assert(bsonBinaryEqual(expectedId, cmdObjSeen.lsid),
-                       "The sent session id did not match the expected, sent: " +
-                           tojson(cmdObjSeen.lsid) + ", expected: " + tojson(expectedId));
-            }
-
-            if (differentFromId) {
-                assert(!bsonBinaryEqual(differentFromId, cmdObjSeen.lsid),
-                       "The sent session id was not different from the expected, sent: " +
-                           tojson(cmdObjSeen.lsid) + ", expected: " + tojson(differentFromId));
-            }
-
-        } else {
-            assert(
-                !cmdObjSeen.hasOwnProperty("lsid"),
-                "Expected operation " + tojson(cmdObjSeen) + " to not have a logical session id.");
-        }
-
-        return cmdObjSeen.lsid;
-    }
-
-    // Tests regular behavior of implicit sessions.
-    function runTest() {
-        const conn = MongoRunner.runMongod();
-
-        // Commands run on a database without an explicit session should use an implicit one.
-        const testDB = conn.getDB("test");
-        const coll = testDB.getCollection("foo");
-        const implicitId = inspectCommandForSessionId(function() {
-            assert.writeOK(coll.insert({x: 1}));
-        }, {shouldIncludeId: true});
-
-        assert(bsonBinaryEqual(testDB.getSession().getSessionId(), implicitId),
-               "Expected the id of the database's implicit session to match the one sent, sent: " +
-                   tojson(implicitId) + " db session id: " +
-                   tojson(testDB.getSession().getSessionId()));
-
-        // Implicit sessions are not causally consistent.
-        assert(!testDB.getSession().getOptions().isCausalConsistency(),
-               "Expected the database's implicit session to not be causally consistent");
-
-        // Further commands run on the same database should reuse the implicit session.
-        inspectCommandForSessionId(function() {
-            assert.writeOK(coll.insert({x: 1}));
-        }, {shouldIncludeId: true, expectedId: implicitId});
-
-        // New collections from the same database should inherit the implicit session.
-        const collTwo = testDB.getCollection("bar");
-        inspectCommandForSessionId(function() {
-            assert.writeOK(collTwo.insert({x: 1}));
-        }, {shouldIncludeId: true, expectedId: implicitId});
-
-        // Sibling databases should inherit the implicit session.
-        let siblingColl = testDB.getSiblingDB("foo").getCollection("bar");
-        inspectCommandForSessionId(function() {
-            assert.writeOK(siblingColl.insert({x: 1}));
-        }, {shouldIncludeId: true, expectedId: implicitId});
-
-        // A new database from the same connection should inherit the implicit session.
-        const newCollSameConn = conn.getDB("testTwo").getCollection("foo");
-        inspectCommandForSessionId(function() {
-            assert.writeOK(newCollSameConn.insert({x: 1}));
-        }, {shouldIncludeId: true, expectedId: implicitId});
-
-        // A new database from a new connection should use a different implicit session.
-        const newCollNewConn = new Mongo(conn.host).getDB("test").getCollection("foo");
-        inspectCommandForSessionId(function() {
-            assert.writeOK(newCollNewConn.insert({x: 1}));
-        }, {shouldIncludeId: true, differentFromId: implicitId});
-
-        // The original implicit session should still live on the first database.
-        inspectCommandForSessionId(function() {
-            assert.writeOK(coll.insert({x: 1}));
-        }, {shouldIncludeId: true, expectedId: implicitId});
-
-        // Databases created from an explicit session should override any implicit sessions.
-        const session = conn.startSession();
-        const sessionColl = session.getDatabase("test").getCollection("foo");
-        const explicitId = inspectCommandForSessionId(function() {
-            assert.writeOK(sessionColl.insert({x: 1}));
-        }, {shouldIncludeId: true, differentFromId: implicitId});
-
-        assert(bsonBinaryEqual(session.getSessionId(), explicitId),
-               "Expected the id of the explicit session to match the one sent, sent: " +
-                   tojson(explicitId) + " explicit session id: " + tojson(session.getSessionId()));
-        assert(bsonBinaryEqual(sessionColl.getDB().getSession().getSessionId(), explicitId),
-               "Expected id of the database's session to match the explicit session's id, sent: " +
-                   tojson(sessionColl.getDB().getSession().getSessionId()) +
-                   ", explicit session id: " + tojson(session.getSessionId()));
-
-        // The original implicit session should still live on the first database.
-        inspectCommandForSessionId(function() {
-            assert.writeOK(coll.insert({x: 1}));
-        }, {shouldIncludeId: true, expectedId: implicitId});
-
-        // New databases on the same connection as the explicit session should still inherit the
-        // original implicit session.
-        const newCollSameConnAfter = conn.getDB("testThree").getCollection("foo");
-        inspectCommandForSessionId(function() {
-            assert.writeOK(newCollSameConnAfter.insert({x: 1}));
-        }, {shouldIncludeId: true, expectedId: implicitId});
-
-        session.endSession();
-        MongoRunner.stopMongod(conn);
-    }
-
-    // Tests behavior when the test flag to disable implicit sessions is changed.
-    function runTestTransitionToDisabled() {
-        const conn = MongoRunner.runMongod();
-
-        // Existing implicit sessions should be erased when the disable flag is set.
-        const coll = conn.getDB("test").getCollection("foo");
-        const implicitId = inspectCommandForSessionId(function() {
-            assert.writeOK(coll.insert({x: 1}));
-        }, {shouldIncludeId: true});
-
-        TestData.disableImplicitSessions = true;
-
-        inspectCommandForSessionId(function() {
-            assert.writeOK(coll.insert({x: 1}));
-        }, {shouldIncludeId: false});
-
-        // After the flag is unset, databases using existing connections with implicit sessions will
-        // use the original implicit sessions again and new connections will create and use new
-        // implicit sessions.
-        TestData.disableImplicitSessions = false;
-
-        inspectCommandForSessionId(function() {
-            assert.writeOK(coll.insert({x: 1}));
-        }, {shouldIncludeId: true, expectedId: implicitId});
-
-        const newColl = conn.getDB("test").getCollection("foo");
-        inspectCommandForSessionId(function() {
-            assert.writeOK(newColl.insert({x: 1}));
-        }, {shouldIncludeId: true, expectedId: implicitId});
-
-        const newCollNewConn = new Mongo(conn.host).getDB("test").getCollection("foo");
-        inspectCommandForSessionId(function() {
-            assert.writeOK(newCollNewConn.insert({x: 1}));
-        }, {shouldIncludeId: true, differentFromId: implicitId});
-
-        // Explicit sessions should not be affected by the disable flag being set.
-        const session = conn.startSession();
-        const sessionColl = session.getDatabase("test").getCollection("foo");
-        const explicitId = inspectCommandForSessionId(function() {
-            assert.writeOK(sessionColl.insert({x: 1}));
-        }, {shouldIncludeId: true});
-
-        TestData.disableImplicitSessions = true;
-
-        inspectCommandForSessionId(function() {
-            assert.writeOK(sessionColl.insert({x: 1}));
-        }, {shouldIncludeId: true, expectedId: explicitId});
-
-        session.endSession();
-        MongoRunner.stopMongod(conn);
-    }
-
-    // Tests for the shell parameter, and the function that exposes it, for disabling implicit
-    // sessions.
-    function runTestGlobalFlag() {
-        const conn = MongoRunner.runMongod();
-        const testDB = conn.getDB("test");
-
-        // The native disabled function should return false in the mongo shell by default.
-        assert(_shouldUseImplicitSessions());
-
-        // Commands run in eval should never use implicit sessions.
-        const evalFunc = function() {
-            assert(!_shouldUseImplicitSessions(),
-                   "expected implicit sessions to be disabled inside eval");
-
-            inspectCommandForSessionId(function() {
-                assert.writeOK(db.foo.insert({x: 1}));
-            }, {shouldIncludeId: false});
-        };
-        testDB.eval("inspectCommandForSessionId = " + inspectCommandForSessionId.toString() +
-                    "; (" + evalFunc.toString() + ")()");
-
-        MongoRunner.stopMongod(conn);
-    }
-
-    // Tests behavior of implicit sessions when they are disabled via a test flag.
-    function runTestDisabled() {
-        const conn = MongoRunner.runMongod();
-
-        // Commands run without an explicit session should not use an implicit one.
-        const coll = conn.getDB("test").getCollection("foo");
-        inspectCommandForSessionId(function() {
-            assert.writeOK(coll.insert({x: 1}));
-        }, {shouldIncludeId: false});
-
-        // Explicit sessions should still include session ids.
-        const session = conn.startSession();
-        const sessionColl = session.getDatabase("test").getCollection("foo");
-        inspectCommandForSessionId(function() {
-            assert.writeOK(sessionColl.insert({x: 1}));
-        }, {shouldIncludeId: true});
-
-        // Commands run in a parallel shell inherit the disable flag.
-        TestData.inspectCommandForSessionId = inspectCommandForSessionId;
-        const awaitShell = startParallelShell(function() {
-            const parallelColl = db.getCollection("foo");
-            TestData.inspectCommandForSessionId(function() {
-                assert.writeOK(parallelColl.insert({x: 1}));
-            }, {shouldIncludeId: false});
-        }, conn.port);
-        awaitShell();
-
-        session.endSession();
-        MongoRunner.stopMongod(conn);
-    }
-
-    runTest();
-
-    runTestTransitionToDisabled();
-
-    runTestGlobalFlag();
-
-    TestData.disableImplicitSessions = true;
-    runTestDisabled();
-})();
diff --git a/jstests/noPassthrough/kill_pinned_cursor.js b/jstests/noPassthrough/kill_pinned_cursor.js
index e70f7f98dfb..d8ecd4998d2 100644
--- a/jstests/noPassthrough/kill_pinned_cursor.js
+++ b/jstests/noPassthrough/kill_pinned_cursor.js
@@ -12,11 +12,6 @@
 
 (function() {
     "use strict";
-
-    // This test runs manual getMores using different connections, which will not inherit the
-    // implicit session of the cursor establishing command.
-    TestData.disableImplicitSessions = true;
-
     load("jstests/libs/fixture_helpers.js");  // For "isMongos".
 
     const st = new ShardingTest({shards: 2});
diff --git a/jstests/noPassthrough/kill_sessions.js b/jstests/noPassthrough/kill_sessions.js
index 16cb100d31e..bd804fa4528 100644
--- a/jstests/noPassthrough/kill_sessions.js
+++ b/jstests/noPassthrough/kill_sessions.js
@@ -3,10 +3,6 @@ load("jstests/libs/kill_sessions.js");
 (function() {
     'use strict';
 
-    // TODO SERVER-35447: This test involves killing all sessions, which will not work as expected
-    // if the kill command is sent with an implicit session.
-    TestData.disableImplicitSessions = true;
-
     var conn = MongoRunner.runMongod({nojournal: ""});
     KillSessionsTestHelper.runNoAuth(conn, conn, [conn]);
     MongoRunner.stopMongod(conn);
diff --git a/jstests/noPassthrough/log_format_slowms_samplerate_loglevel.js b/jstests/noPassthrough/log_format_slowms_samplerate_loglevel.js
index 786f28c9d6b..37afb165dd8 100644
--- a/jstests/noPassthrough/log_format_slowms_samplerate_loglevel.js
+++ b/jstests/noPassthrough/log_format_slowms_samplerate_loglevel.js
@@ -7,10 +7,6 @@
 (function() {
     "use strict";
 
-    // This test looks for exact matches in log output, which does not account for implicit
-    // sessions.
-    TestData.disableImplicitSessions = true;
-
     load("jstests/libs/fixture_helpers.js");  // For FixtureHelpers.
     load("jstests/libs/check_log.js");        // For formatAsLogLine.
 
diff --git a/jstests/noPassthrough/refresh_logical_session_cache_now.js b/jstests/noPassthrough/refresh_logical_session_cache_now.js
index 59d181845fe..294a16043d2 100644
--- a/jstests/noPassthrough/refresh_logical_session_cache_now.js
+++ b/jstests/noPassthrough/refresh_logical_session_cache_now.js
@@ -1,10 +1,6 @@
 (function() {
     "use script";
 
-    // This test makes assertions about the number of sessions, which are not compatible with
-    // implicit sessions.
-    TestData.disableImplicitSessions = true;
-
     var res;
     var refresh = {refreshLogicalSessionCacheNow: 1};
     var startSession = {startSession: 1};
diff --git a/jstests/noPassthrough/refresh_sessions_command.js b/jstests/noPassthrough/refresh_sessions_command.js
index 1f7b1a4c301..80b249faca7 100644
--- a/jstests/noPassthrough/refresh_sessions_command.js
+++ b/jstests/noPassthrough/refresh_sessions_command.js
@@ -1,10 +1,6 @@
 (function() {
     "use strict";
 
-    // This test makes assertions about the number of sessions, which are not compatible with
-    // implicit sessions.
-    TestData.disableImplicitSessions = true;
-
     var conn;
     var admin;
     var result;
diff --git a/jstests/noPassthrough/sessions_collection_auto_healing.js b/jstests/noPassthrough/sessions_collection_auto_healing.js
index 21eb3d221a3..58c64561161 100644
--- a/jstests/noPassthrough/sessions_collection_auto_healing.js
+++ b/jstests/noPassthrough/sessions_collection_auto_healing.js
@@ -3,10 +3,6 @@ load('jstests/libs/sessions_collection.js');
 (function() {
     "use strict";
 
-    // This test makes assertions about the number of sessions, which are not compatible with
-    // implicit sessions.
-    TestData.disableImplicitSessions = true;
-
     var startSession = {startSession: 1};
     var conn = MongoRunner.runMongod({nojournal: ""});
 
diff --git a/jstests/noPassthrough/shell_can_use_read_concern.js b/jstests/noPassthrough/shell_can_use_read_concern.js
index 049e7cad818..65cf66c06cc 100644
--- a/jstests/noPassthrough/shell_can_use_read_concern.js
+++ b/jstests/noPassthrough/shell_can_use_read_concern.js
@@ -6,9 +6,6 @@
 (function() {
     "use strict";
 
-    // This test makes assertions on commands run without logical session ids.
-    TestData.disableImplicitSessions = true;
-
     const rst = new ReplSetTest({nodes: 1});
     rst.startSet();
     rst.initiate();
diff --git a/jstests/noPassthrough/snapshot_cursor_integrity.js b/jstests/noPassthrough/snapshot_cursor_integrity.js
index fa1a44a6699..d5d0678a641 100644
--- a/jstests/noPassthrough/snapshot_cursor_integrity.js
+++ b/jstests/noPassthrough/snapshot_cursor_integrity.js
@@ -4,9 +4,6 @@
 (function() {
     "use strict";
 
-    // This test makes assertions on commands run without logical session ids.
-    TestData.disableImplicitSessions = true;
-
     const dbName = "test";
     const collName = "coll";
 
diff --git a/jstests/noPassthrough/start_session_command.js b/jstests/noPassthrough/start_session_command.js
index bfdd053179d..4564cf5ab54 100644
--- a/jstests/noPassthrough/start_session_command.js
+++ b/jstests/noPassthrough/start_session_command.js
@@ -1,10 +1,5 @@
 (function() {
     'use strict';
-
-    // This test makes assertions about the number of sessions, which are not compatible with
-    // implicit sessions.
-    TestData.disableImplicitSessions = true;
-
     var conn;
     var admin;
     var foo;
diff --git a/jstests/noPassthrough/transaction_reaper.js b/jstests/noPassthrough/transaction_reaper.js
index 71a0977f972..cdf58ec481e 100644
--- a/jstests/noPassthrough/transaction_reaper.js
+++ b/jstests/noPassthrough/transaction_reaper.js
@@ -2,10 +2,6 @@
 (function() {
     'use strict';
 
-    // This test makes assertions about the number of sessions, which are not compatible with
-    // implicit sessions.
-    TestData.disableImplicitSessions = true;
-
     load("jstests/libs/retryable_writes_util.js");
 
     if (!RetryableWritesUtil.storageEngineSupportsRetryableWrites(jsTest.options().storageEngine)) {
diff --git a/jstests/noPassthrough/verify_session_cache_updates.js b/jstests/noPassthrough/verify_session_cache_updates.js
index 22674cb1ecb..0f4e6cb39c1 100644
--- a/jstests/noPassthrough/verify_session_cache_updates.js
+++ b/jstests/noPassthrough/verify_session_cache_updates.js
@@ -3,10 +3,6 @@
 (function() {
     'use strict';
 
-    // This test makes assertions about the number of sessions, which are not compatible with
-    // implicit sessions.
-    TestData.disableImplicitSessions = true;
-
     function runTest(conn) {
         for (var i = 0; i < 10; ++i) {
             conn.getDB("test").test.save({a: i});
diff --git a/jstests/noPassthroughWithMongod/tailable_getmore_does_not_timeout.js b/jstests/noPassthroughWithMongod/tailable_getmore_does_not_timeout.js
index 19a0452febb..0e8d05db09b 100644
--- a/jstests/noPassthroughWithMongod/tailable_getmore_does_not_timeout.js
+++ b/jstests/noPassthroughWithMongod/tailable_getmore_does_not_timeout.js
@@ -4,10 +4,6 @@
 (function() {
     "use strict";
 
-    // This test runs a getMore in a parallel shell, which will not inherit the implicit session of
-    // the cursor establishing command.
-    TestData.disableImplicitSessions = true;
-
     const coll = db.tailable_getmore_no_timeout;
     coll.drop();
 
diff --git a/jstests/replsets/auth1.js b/jstests/replsets/auth1.js
index 9a9f36939b2..81d3ddca816 100644
--- a/jstests/replsets/auth1.js
+++ b/jstests/replsets/auth1.js
@@ -6,11 +6,6 @@
 load("jstests/replsets/rslib.js");
 
 (function() {
-    "use strict";
-
-    // TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-    TestData.disableImplicitSessions = true;
-
     var name = "rs_auth1";
     var port = allocatePorts(5);
     var path = "jstests/libs/";
diff --git a/jstests/replsets/refresh_sessions_rs.js b/jstests/replsets/refresh_sessions_rs.js
index 9bd4527c7bf..307915d2faa 100644
--- a/jstests/replsets/refresh_sessions_rs.js
+++ b/jstests/replsets/refresh_sessions_rs.js
@@ -1,9 +1,6 @@
 (function() {
     "use strict";
 
-    // This test makes assertions about the number of logical session records.
-    TestData.disableImplicitSessions = true;
-
     var refresh = {refreshLogicalSessionCacheNow: 1};
     var startSession = {startSession: 1};
 
diff --git a/jstests/replsets/retryable_writes_direct_write_to_config_transactions.js b/jstests/replsets/retryable_writes_direct_write_to_config_transactions.js
index 0a89dcc7390..6739915ec56 100644
--- a/jstests/replsets/retryable_writes_direct_write_to_config_transactions.js
+++ b/jstests/replsets/retryable_writes_direct_write_to_config_transactions.js
@@ -2,9 +2,6 @@
 (function() {
     'use strict';
 
-    // Direct writes to config.transactions cannot be part of a session.
-    TestData.disableImplicitSessions = true;
-
     load("jstests/libs/retryable_writes_util.js");
 
     if (!RetryableWritesUtil.storageEngineSupportsRetryableWrites(jsTest.options().storageEngine)) {
diff --git a/jstests/replsets/rollback_auth.js b/jstests/replsets/rollback_auth.js
index 7d78484fdf1..e3b03ad40b2 100644
--- a/jstests/replsets/rollback_auth.js
+++ b/jstests/replsets/rollback_auth.js
@@ -20,9 +20,6 @@
     // TODO SERVER-32639: remove this flag.
     TestData.skipGossipingClusterTime = true;
 
-    // TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-    TestData.disableImplicitSessions = true;
-
     // helper function for verifying contents at the end of the test
     var checkFinalResults = function(db) {
         assert.commandWorked(db.runCommand({dbStats: 1}));
diff --git a/jstests/replsets/sessions_collection_auto_healing.js b/jstests/replsets/sessions_collection_auto_healing.js
index f4f147a5dd3..e77b99f4059 100644
--- a/jstests/replsets/sessions_collection_auto_healing.js
+++ b/jstests/replsets/sessions_collection_auto_healing.js
@@ -3,10 +3,6 @@ load('jstests/libs/sessions_collection.js');
 (function() {
     "use strict";
 
-    // This test makes assertions about the number of sessions, which are not compatible with
-    // implicit sessions.
-    TestData.disableImplicitSessions = true;
-
     var replTest = new ReplSetTest({name: 'refresh', nodes: 3});
     var nodes = replTest.startSet();
 
diff --git a/jstests/replsets/user_management_wc.js b/jstests/replsets/user_management_wc.js
index e24c4c74eae..a0796b4fcbf 100644
--- a/jstests/replsets/user_management_wc.js
+++ b/jstests/replsets/user_management_wc.js
@@ -10,10 +10,6 @@ load('jstests/multiVersion/libs/auth_helpers.js');
 
 (function() {
     "use strict";
-
-    // TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-    TestData.disableImplicitSessions = true;
-
     var replTest = new ReplSetTest(
         {name: 'UserManagementWCSet', nodes: 3, settings: {chainingAllowed: false}});
     replTest.startSet();
diff --git a/jstests/sharding/advance_cluster_time_action_type.js b/jstests/sharding/advance_cluster_time_action_type.js
index 1f3f00a2abb..fac7f803774 100644
--- a/jstests/sharding/advance_cluster_time_action_type.js
+++ b/jstests/sharding/advance_cluster_time_action_type.js
@@ -5,9 +5,6 @@
 (function() {
     "use strict";
 
-    // TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-    TestData.disableImplicitSessions = true;
-
     // TODO: Remove 'shardAsReplicaSet: false' when SERVER-32672 is fixed.
     let st = new ShardingTest({
         mongos: 1,
diff --git a/jstests/sharding/authCommands.js b/jstests/sharding/authCommands.js
index efd285869ab..8ad74f23db3 100644
--- a/jstests/sharding/authCommands.js
+++ b/jstests/sharding/authCommands.js
@@ -4,9 +4,6 @@
 (function() {
     'use strict';
 
-    // TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-    TestData.disableImplicitSessions = true;
-
     load("jstests/replsets/rslib.js");
 
     // Replica set nodes started with --shardsvr do not enable key generation until they are added
diff --git a/jstests/sharding/auth_repl.js b/jstests/sharding/auth_repl.js
index 0c8e976bd48..9e1ddb06873 100644
--- a/jstests/sharding/auth_repl.js
+++ b/jstests/sharding/auth_repl.js
@@ -1,6 +1,3 @@
-// TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-TestData.disableImplicitSessions = true;
-
 var replTest = new ReplSetTest({nodes: 3, useHostName: false, keyFile: 'jstests/libs/key1'});
 replTest.startSet({oplogSize: 10});
 replTest.initiate();
diff --git a/jstests/sharding/cleanup_orphaned_auth.js b/jstests/sharding/cleanup_orphaned_auth.js
index f32a66ee242..4943643c33d 100644
--- a/jstests/sharding/cleanup_orphaned_auth.js
+++ b/jstests/sharding/cleanup_orphaned_auth.js
@@ -5,9 +5,6 @@
 (function() {
     'use strict';
 
-    // TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-    TestData.disableImplicitSessions = true;
-
     function assertUnauthorized(res, msg) {
         if (assert._debug && msg)
             print("in assert for: " + msg);
diff --git a/jstests/sharding/commands_that_write_accept_wc_configRS.js b/jstests/sharding/commands_that_write_accept_wc_configRS.js
index ba2f3f559c6..1f436cc163b 100644
--- a/jstests/sharding/commands_that_write_accept_wc_configRS.js
+++ b/jstests/sharding/commands_that_write_accept_wc_configRS.js
@@ -17,10 +17,6 @@ load('jstests/multiVersion/libs/auth_helpers.js');
 
 (function() {
     "use strict";
-
-    // TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-    TestData.disableImplicitSessions = true;
-
     var st = new ShardingTest({
         shards: {
             rs0: {nodes: 3, settings: {chainingAllowed: false}},
diff --git a/jstests/sharding/kill_pinned_cursor.js b/jstests/sharding/kill_pinned_cursor.js
index d7e4017d273..417ed66817e 100644
--- a/jstests/sharding/kill_pinned_cursor.js
+++ b/jstests/sharding/kill_pinned_cursor.js
@@ -9,9 +9,6 @@
 (function() {
     "use strict";
 
-    // This test manually simulates a session, which is not compatible with implicit sessions.
-    TestData.disableImplicitSessions = true;
-
     const kFailPointName = "waitAfterPinningCursorBeforeGetMoreBatch";
     const kFailpointOptions = {shouldCheckForInterrupt: true};
 
diff --git a/jstests/sharding/kill_sessions.js b/jstests/sharding/kill_sessions.js
index a3ad23139a0..d5bb39213f1 100644
--- a/jstests/sharding/kill_sessions.js
+++ b/jstests/sharding/kill_sessions.js
@@ -3,10 +3,6 @@ load("jstests/libs/kill_sessions.js");
 (function() {
     'use strict';
 
-    // TODO SERVER-35447: This test involves killing all sessions, which will not work as expected
-    // if the kill command is sent with an implicit session.
-    TestData.disableImplicitSessions = true;
-
     function runTests(needAuth) {
         var other = {
             rs: true,
diff --git a/jstests/sharding/mongod_returns_no_cluster_time_without_keys.js b/jstests/sharding/mongod_returns_no_cluster_time_without_keys.js
index 8cb8fe8f7fb..b9ac2deda07 100644
--- a/jstests/sharding/mongod_returns_no_cluster_time_without_keys.js
+++ b/jstests/sharding/mongod_returns_no_cluster_time_without_keys.js
@@ -9,10 +9,6 @@
 (function() {
     "use strict";
 
-    // This test uses authentication and runs commands without authenticating, which is not
-    // compatible with implicit sessions.
-    TestData.disableImplicitSessions = true;
-
     load("jstests/multiVersion/libs/multi_rs.js");
 
     // TODO SERVER-32672: remove this flag.
@@ -50,7 +46,6 @@
     priRSConn.auth(rUser.username, rUser.password);
     const resWithKeys = priRSConn.runCommand({isMaster: 1});
     assertContainsValidLogicalTime(resWithKeys);
-    priRSConn.logout();
 
     // Enable the failpoint, remove all keys, and restart the config servers with the failpoint
     // still enabled to guarantee there are no keys.
@@ -65,7 +60,6 @@
     });
 
     assert(adminDB.system.keys.count() == 0, "expected there to be no keys on the config server");
-    adminDB.logout();
 
     st.configRS.stopSet(null /* signal */, true /* forRestart */);
     st.configRS.startSet(
@@ -78,7 +72,6 @@
     priRSConn = st.rs0.getPrimary().getDB("admin");
     priRSConn.auth(rUser.username, rUser.password);
     const resNoKeys = assert.commandWorked(priRSConn.runCommand({isMaster: 1}));
-    priRSConn.logout();
 
     assert.eq(resNoKeys.hasOwnProperty("$clusterTime"), false);
     assert.eq(resNoKeys.hasOwnProperty("operationTime"), false);
diff --git a/jstests/sharding/mongos_rs_auth_shard_failure_tolerance.js b/jstests/sharding/mongos_rs_auth_shard_failure_tolerance.js
index 5ce56f9f546..774c1d7dd01 100644
--- a/jstests/sharding/mongos_rs_auth_shard_failure_tolerance.js
+++ b/jstests/sharding/mongos_rs_auth_shard_failure_tolerance.js
@@ -24,9 +24,6 @@ TestData.skipCheckingUUIDsConsistentAcrossCluster = true;
 // TODO SERVER-32672: remove this flag.
 TestData.skipGossipingClusterTime = true;
 
-// TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-TestData.disableImplicitSessions = true;
-
 var options = {rs: true, rsOptions: {nodes: 2}, keyFile: "jstests/libs/key1"};
 
 var st = new ShardingTest({shards: 3, mongos: 1, other: options});
diff --git a/jstests/sharding/mrShardedOutputAuth.js b/jstests/sharding/mrShardedOutputAuth.js
index 0536c6a51b9..3dc02da7072 100644
--- a/jstests/sharding/mrShardedOutputAuth.js
+++ b/jstests/sharding/mrShardedOutputAuth.js
@@ -6,9 +6,6 @@
 
 (function() {
 
-    // TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-    TestData.disableImplicitSessions = true;
-
     function doMapReduce(connection, outputDb) {
         // clean output db and run m/r
         outputDb.numbers_out.drop();
diff --git a/jstests/sharding/refresh_sessions.js b/jstests/sharding/refresh_sessions.js
index ee4ee125db3..8199ffb4563 100644
--- a/jstests/sharding/refresh_sessions.js
+++ b/jstests/sharding/refresh_sessions.js
@@ -1,9 +1,6 @@
 (function() {
     "use strict";
 
-    // This test makes assumptions about the number of logical sessions.
-    TestData.disableImplicitSessions = true;
-
     var sessionsDb = "config";
     var refresh = {refreshLogicalSessionCacheNow: 1};
     var startSession = {startSession: 1};
diff --git a/jstests/sharding/sessions_collection_auto_healing.js b/jstests/sharding/sessions_collection_auto_healing.js
index 61271bd8dc5..5dcf6d66590 100644
--- a/jstests/sharding/sessions_collection_auto_healing.js
+++ b/jstests/sharding/sessions_collection_auto_healing.js
@@ -3,10 +3,6 @@ load('jstests/libs/sessions_collection.js');
 (function() {
     "use strict";
 
-    // This test makes assertions about the number of sessions, which are not compatible with
-    // implicit sessions.
-    TestData.disableImplicitSessions = true;
-
     var st = new ShardingTest({shards: 0});
     var configSvr = st.configRS.getPrimary();
     var configAdmin = configSvr.getDB("admin");
diff --git a/jstests/sharding/sharding_options.js b/jstests/sharding/sharding_options.js
index 190d78a1e94..8af7bf01c53 100644
--- a/jstests/sharding/sharding_options.js
+++ b/jstests/sharding/sharding_options.js
@@ -1,6 +1,3 @@
-// TODO SERVER-35447: Multiple users cannot be authenticated on one connection within a session.
-TestData.disableImplicitSessions = true;
-
 var baseName = "jstests_sharding_sharding_options";
 
 load('jstests/libs/command_line/test_parsed_options.js');
diff --git a/jstests/sharding/snapshot_aggregate_mongos.js b/jstests/sharding/snapshot_aggregate_mongos.js
index 43ce65a7672..b0480fc534c 100644
--- a/jstests/sharding/snapshot_aggregate_mongos.js
+++ b/jstests/sharding/snapshot_aggregate_mongos.js
@@ -3,10 +3,6 @@
 (function() {
     "use strict";
 
-    // This test intentionally runs commands without a logical session id, which is not compatible
-    // with implicit sessions.
-    TestData.disableImplicitSessions = true;
-
     load("jstests/libs/global_snapshot_reads_util.js");
 
     const dbName = "test";
diff --git a/jstests/sharding/snapshot_find_mongos.js b/jstests/sharding/snapshot_find_mongos.js
index 0c7bf4c59f4..92b5b679730 100644
--- a/jstests/sharding/snapshot_find_mongos.js
+++ b/jstests/sharding/snapshot_find_mongos.js
@@ -4,10 +4,6 @@
 (function() {
     "use strict";
 
-    // This test intentionally runs commands without a logical session id, which is not compatible
-    // with implicit sessions.
-    TestData.disableImplicitSessions = true;
-
     load("jstests/libs/global_snapshot_reads_util.js");
 
     const dbName = "test";
diff --git a/src/mongo/shell/mongo.js b/src/mongo/shell/mongo.js
index 0a78e9db761..bfb1e04f7cf 100644
--- a/src/mongo/shell/mongo.js
+++ b/src/mongo/shell/mongo.js
@@ -58,9 +58,7 @@ Mongo.prototype.getDB = function(name) {
 
 Mongo.prototype.getDBs = function(driverSession = this._getDefaultSession()) {
     var cmdObj = {listDatabases: 1};
-    if (driverSession._isExplicit || !jsTest.options().disableImplicitSessions) {
-        cmdObj = driverSession._serverSession.injectSessionId(cmdObj);
-    }
+    cmdObj = driverSession._serverSession.injectSessionId(cmdObj);
 
     var res = this.adminCommand(cmdObj);
     if (!res.ok)
@@ -77,9 +75,7 @@ Mongo.prototype.adminCommand = function(cmd) {
  */
 Mongo.prototype.getLogComponents = function(driverSession = this._getDefaultSession()) {
     var cmdObj = {getParameter: 1, logComponentVerbosity: 1};
-    if (driverSession._isExplicit || !jsTest.options().disableImplicitSessions) {
-        cmdObj = driverSession._serverSession.injectSessionId(cmdObj);
-    }
+    cmdObj = driverSession._serverSession.injectSessionId(cmdObj);
 
     var res = this.adminCommand(cmdObj);
     if (!res.ok)
@@ -110,9 +106,7 @@ Mongo.prototype.setLogLevel = function(
     }
 
     var cmdObj = {setParameter: 1, logComponentVerbosity: vDoc};
-    if (driverSession._isExplicit || !jsTest.options().disableImplicitSessions) {
-        cmdObj = driverSession._serverSession.injectSessionId(cmdObj);
-    }
+    cmdObj = driverSession._serverSession.injectSessionId(cmdObj);
 
     var res = this.adminCommand(cmdObj);
     if (!res.ok)
@@ -432,14 +426,11 @@ Mongo.prototype.startSession = function startSession(options = {}) {
 };
 
 Mongo.prototype._getDefaultSession = function getDefaultSession() {
-    // We implicitly associate a Mongo connection object with a real session so all requests include
-    // a logical session id. These implicit sessions are intentionally not causally consistent. If
-    // implicit sessions have been globally disabled, a dummy session is used instead of a real one.
+    // We implicitly associate a Mongo connection object with a DriverSession so that tests which
+    // call DB.prototype.getMongo() and then Mongo.prototype.getDB() to get a different DB instance
+    // are still causally consistent.
     if (!this.hasOwnProperty("_defaultSession")) {
-        this._defaultSession = _shouldUseImplicitSessions()
-            ? this.startSession({causalConsistency: false})
-            : new _DummyDriverSession(this);
-        this._defaultSession._isExplicit = false;
+        this._defaultSession = new _DummyDriverSession(this);
     }
     return this._defaultSession;
 };
diff --git a/src/mongo/shell/query.js b/src/mongo/shell/query.js
index 60785e4b417..fcbcd5a39b3 100644
--- a/src/mongo/shell/query.js
+++ b/src/mongo/shell/query.js
@@ -112,11 +112,10 @@ DBQuery.prototype._exec = function() {
             var cmdRes = this._db.runReadCommand(findCmd, null, this._options);
             this._cursor = new DBCommandCursor(this._db, cmdRes, this._batchSize);
         } else {
-            // The exhaust cursor option is disallowed under a session because it doesn't work as
-            // expected, but all requests from the shell use implicit sessions, so to allow users
-            // to continue using exhaust cursors through the shell, they are only disallowed with
-            // explicit sessions.
-            if (this._db.getSession()._isExplicit) {
+            // Note that depending on how SERVER-32064 is implemented, we may need to alter this
+            // check to account for implicit sessions, so that exhaust cursors can still be used in
+            // the shell.
+            if (this._db.getSession().getSessionId() !== null) {
                 throw new Error("Cannot run a legacy query on a session.");
             }
 
diff --git a/src/mongo/shell/session.js b/src/mongo/shell/session.js
index 07720d49047..b7e77d8e9f2 100644
--- a/src/mongo/shell/session.js
+++ b/src/mongo/shell/session.js
@@ -209,14 +209,7 @@ var {
         }
 
         function prepareCommandRequest(driverSession, cmdObj) {
-            if (serverSupports(kWireVersionSupportingLogicalSession) &&
-                // Always attach sessionId from explicit sessions.
-                (driverSession._isExplicit ||
-                 // Check that implicit sessions are not disabled. The client must be using read
-                 // commands because aggregations always use runCommand() to establish cursors but
-                 // may use OP_GET_MORE (and therefore not have a session id attached) to retrieve
-                 // subsequent batches.
-                 (!jsTest.options().disableImplicitSessions && client.useReadCommands()))) {
+            if (serverSupports(kWireVersionSupportingLogicalSession)) {
                 cmdObj = driverSession._serverSession.injectSessionId(cmdObj);
             }
 
@@ -843,8 +836,6 @@ var {
 
             this._serverSession = implMethods.createServerSession(client);
 
-            this._isExplicit = true;
-
             this.getClient = function getClient() {
                 return client;
             };
diff --git a/src/mongo/shell/shell_utils.cpp b/src/mongo/shell/shell_utils.cpp
index f441f0ba4ab..5a9742d3935 100644
--- a/src/mongo/shell/shell_utils.cpp
+++ b/src/mongo/shell/shell_utils.cpp
@@ -253,10 +253,6 @@ BSONObj shouldRetryWrites(const BSONObj&, void* data) {
     return BSON("" << shellGlobalParams.shouldRetryWrites);
 }
 
-BSONObj shouldUseImplicitSessions(const BSONObj&, void* data) {
-    return BSON("" << true);
-}
-
 BSONObj interpreterVersion(const BSONObj& a, void* data) {
     uassert(16453, "interpreterVersion accepts no arguments", a.nFields() == 0);
     return BSON("" << getGlobalScriptEngine()->getInterpreterVersionString());
@@ -294,7 +290,6 @@ void initScope(Scope& scope) {
     scope.injectNative("_writeMode", writeMode);
     scope.injectNative("_readMode", readMode);
     scope.injectNative("_shouldRetryWrites", shouldRetryWrites);
-    scope.injectNative("_shouldUseImplicitSessions", shouldUseImplicitSessions);
     scope.externalSetup();
     mongo::shell_utils::installShellUtils(scope);
     scope.execSetup(JSFiles::servers);
diff --git a/src/mongo/shell/utils.js b/src/mongo/shell/utils.js
index 79c5433b892..3820eac4f36 100644
--- a/src/mongo/shell/utils.js
+++ b/src/mongo/shell/utils.js
@@ -313,8 +313,7 @@ jsTestOptions = function() {
             skipCheckDBHashes: TestData.skipCheckDBHashes || false,
             traceExceptions: TestData.hasOwnProperty("traceExceptions") ? TestData.traceExceptions
                                                                         : true,
-            transactionLifetimeLimitSeconds: TestData.transactionLifetimeLimitSeconds,
-            disableImplicitSessions: TestData.disableImplicitSessions || false,
+            transactionLifetimeLimitSeconds: TestData.transactionLifetimeLimitSeconds
         });
     }
     return _jsTestOptions;
@@ -560,16 +559,6 @@ if (typeof _shouldRetryWrites === 'undefined') {
     };
 }
 
-if (typeof _shouldUseImplicitSessions === 'undefined') {
-    // We ensure the _shouldUseImplicitSessions() function is always defined, in case the JavaScript
-    // engine is being used from someplace other than the mongo shell (e.g. map-reduce). If the
-    // function was not defined, implicit sessions are disabled to prevent unnecessary sessions from
-    // being created.
-    _shouldUseImplicitSessions = function _shouldUseImplicitSessions() {
-        return false;
-    };
-}
-
 shellPrintHelper = function(x) {
     if (typeof(x) == "undefined") {
         // Make sure that we have a db var before we use it