SERVER-68151 Add a required feature flag IDL parameter of shouldBeFCVGated

26 files changed, 239 insertions, 16 deletions

diff --git a/buildscripts/idl/idl/binder.py b/buildscripts/idl/idl/binder.py
index 51db4476b22..47ef2c02d40 100644
--- a/buildscripts/idl/idl/binder.py
+++ b/buildscripts/idl/idl/binder.py
@@ -1476,13 +1476,20 @@ def _bind_feature_flags(ctxt, param):
         ctxt.add_feature_flag_default_false_has_version(param)
         return None
 
-    # Feature flags that default to true are required to have a version
-    if param.default.literal == "true" and not param.version:
+    # Feature flags that default to true and should be FCV gated are required to have a version
+    if param.default.literal == "true" and param.shouldBeFCVGated.literal == "true" and not param.version:
         ctxt.add_feature_flag_default_true_missing_version(param)
         return None
 
+    # Feature flags that should not be FCV gated must not have a version
+    if param.shouldBeFCVGated.literal == "false" and param.version:
+        ctxt.add_feature_flag_fcv_gated_false_has_version(param)
+        return None
+
     expr = syntax.Expression(param.default.file_name, param.default.line, param.default.column)
-    expr.expr = '%s, "%s"_sd' % (param.default.literal, param.version if param.version else '')
+    expr.expr = '%s, "%s"_sd, %s' % (param.default.literal, param.version if
+                                     (param.shouldBeFCVGated.literal == "true"
+                                      and param.version) else '', param.shouldBeFCVGated.literal)
 
     ast_param.default = _bind_expression(expr)
     ast_param.default.export = False
diff --git a/buildscripts/idl/idl/errors.py b/buildscripts/idl/idl/errors.py
index c3b870e8fd7..677cf9eca8f 100644
--- a/buildscripts/idl/idl/errors.py
+++ b/buildscripts/idl/idl/errors.py
@@ -137,6 +137,7 @@ ERROR_ID_CANNOT_BE_LITERAL_AND_FIELDPATH = "ID0097"
 ERROR_ID_QUERY_SHAPE_FIELDPATH_CANNOT_BE_FALSE = "ID0098"
 ERROR_ID_STRICT_AND_DISABLE_CHECK_NOT_ALLOWED = "ID0099"
 ERROR_ID_INHERITANCE_AND_DISABLE_CHECK_NOT_ALLOWED = "ID0100"
+ERROR_ID_FEATURE_FLAG_SHOULD_BE_FCV_GATED_FALSE_HAS_VERSION = "ID0101"
 
 
 class IDLError(Exception):
@@ -843,9 +844,10 @@ class ParserContext(object):
 
     def add_feature_flag_default_true_missing_version(self, location):
         # type: (common.SourceLocation) -> None
-        """Add an error about a default flag with a default value of true but no version."""
-        self._add_error(location, ERROR_ID_FEATURE_FLAG_DEFAULT_TRUE_MISSING_VERSION,
-                        ("Missing 'version' required for feature flag that defaults to true"))
+        """Add an error about a default flag with a default value of true and should be FCV gated but no version."""
+        self._add_error(location, ERROR_ID_FEATURE_FLAG_DEFAULT_TRUE_MISSING_VERSION, (
+            "Missing 'version' required for feature flag that defaults to true and should be FCV gated"
+        ))
 
     def add_feature_flag_default_false_has_version(self, location):
         # type: (common.SourceLocation) -> None
@@ -854,6 +856,13 @@ class ParserContext(object):
             location, ERROR_ID_FEATURE_FLAG_DEFAULT_FALSE_HAS_VERSION,
             ("The 'version' attribute is not allowed for feature flag that defaults to false"))
 
+    def add_feature_flag_fcv_gated_false_has_version(self, location):
+        # type: (common.SourceLocation) -> None
+        """Add an error about a feature flag that should not be FCV gated but has a version."""
+        self._add_error(
+            location, ERROR_ID_FEATURE_FLAG_SHOULD_BE_FCV_GATED_FALSE_HAS_VERSION,
+            ("The 'version' attribute is not allowed for feature flag that should be FCV gated"))
+
     def add_reply_type_invalid_type(self, location, command_name, reply_type_name):
         # type: (common.SourceLocation, str, str) -> None
         """Add an error about a command whose reply_type refers to an unknown type."""
diff --git a/buildscripts/idl/idl/parser.py b/buildscripts/idl/idl/parser.py
index 3393d6681e7..349ef8ff64a 100644
--- a/buildscripts/idl/idl/parser.py
+++ b/buildscripts/idl/idl/parser.py
@@ -986,6 +986,9 @@ def _parse_feature_flag(ctxt, spec, name, node):
                           mapping_parser_func=_parse_expression),
             "version":
                 _RuleDesc('scalar'),
+            "shouldBeFCVGated":
+                _RuleDesc('scalar_or_mapping', _RuleDesc.REQUIRED,
+                          mapping_parser_func=_parse_expression),
         })
 
     spec.feature_flags.append(param)
diff --git a/buildscripts/idl/idl/syntax.py b/buildscripts/idl/idl/syntax.py
index 21f2e252ec8..cf23b4931c5 100644
--- a/buildscripts/idl/idl/syntax.py
+++ b/buildscripts/idl/idl/syntax.py
@@ -886,6 +886,8 @@ class FeatureFlag(common.SourceLocation):
         self.cpp_varname = None  # type: str
         self.default = None  # type: Expression
         self.version = None  # type: str
+        # pylint: disable=C0103
+        self.shouldBeFCVGated = None  # type: Expression
 
         super(FeatureFlag, self).__init__(file_name, line, column)
 
diff --git a/buildscripts/idl/tests/test_binder.py b/buildscripts/idl/tests/test_binder.py
index 8cf23521b0f..0118f38c7b9 100644
--- a/buildscripts/idl/tests/test_binder.py
+++ b/buildscripts/idl/tests/test_binder.py
@@ -2335,7 +2335,7 @@ class TestBinder(testcase.IDLTestcase):
         # type: () -> None
         """Test feature flag checks around version."""
 
-        # feature flag can default to false without a version
+        # feature flag can default to false without a version (shouldBeFCVGated can be true or false)
         self.assert_bind(
             textwrap.dedent("""
             feature_flags:
@@ -2343,9 +2343,20 @@ class TestBinder(testcase.IDLTestcase):
                     description: "Make toast"
                     cpp_varname: gToaster
                     default: false
+                    shouldBeFCVGated: false
             """))
 
-        # feature flag can default to true with a version
+        self.assert_bind(
+            textwrap.dedent("""
+            feature_flags:
+                featureFlagToaster:
+                    description: "Make toast"
+                    cpp_varname: gToaster
+                    default: false
+                    shouldBeFCVGated: true
+            """))
+
+        # if shouldBeFCVGated: true, feature flag can default to true with a version
         self.assert_bind(
             textwrap.dedent("""
             feature_flags:
@@ -2354,9 +2365,21 @@ class TestBinder(testcase.IDLTestcase):
                     cpp_varname: gToaster
                     default: true
                     version: 123
+                    shouldBeFCVGated: true
             """))
 
-        # true is only allowed with a version
+        # if shouldBeFCVGated: false, we do not need a version
+        self.assert_bind(
+            textwrap.dedent("""
+            feature_flags:
+                featureFlagToaster:
+                    description: "Make toast"
+                    cpp_varname: gToaster
+                    default: true
+                    shouldBeFCVGated: false
+            """))
+
+        # if shouldBeFCVGated: true and default: true, a version is required
         self.assert_bind_fail(
             textwrap.dedent("""
             feature_flags:
@@ -2364,9 +2387,10 @@ class TestBinder(testcase.IDLTestcase):
                     description: "Make toast"
                     cpp_varname: gToaster
                     default: true
+                    shouldBeFCVGated: true
             """), idl.errors.ERROR_ID_FEATURE_FLAG_DEFAULT_TRUE_MISSING_VERSION)
 
-        # false is not allowed with a version
+        # false is not allowed with a version and shouldBeFCVGated: true
         self.assert_bind_fail(
             textwrap.dedent("""
             feature_flags:
@@ -2375,8 +2399,33 @@ class TestBinder(testcase.IDLTestcase):
                     cpp_varname: gToaster
                     default: false
                     version: 123
+                    shouldBeFCVGated: true
             """), idl.errors.ERROR_ID_FEATURE_FLAG_DEFAULT_FALSE_HAS_VERSION)
 
+        # false is not allowed with a version and shouldBeFCVGated: false
+        self.assert_bind_fail(
+            textwrap.dedent("""
+            feature_flags:
+                featureFlagToaster:
+                    description: "Make toast"
+                    cpp_varname: gToaster
+                    default: false
+                    version: 123
+                    shouldBeFCVGated: false
+            """), idl.errors.ERROR_ID_FEATURE_FLAG_DEFAULT_FALSE_HAS_VERSION)
+
+        # if shouldBeFCVGated is false, a version is not allowed
+        self.assert_bind_fail(
+            textwrap.dedent("""
+            feature_flags:
+                featureFlagToaster:
+                    description: "Make toast"
+                    cpp_varname: gToaster
+                    default: true
+                    version: 123
+                    shouldBeFCVGated: false
+            """), idl.errors.ERROR_ID_FEATURE_FLAG_SHOULD_BE_FCV_GATED_FALSE_HAS_VERSION)
+
     def test_access_check(self):
         # type: () -> None
         """Test access check."""
diff --git a/buildscripts/idl/tests/test_parser.py b/buildscripts/idl/tests/test_parser.py
index 305d5fbbafd..91aa7d4ce2a 100644
--- a/buildscripts/idl/tests/test_parser.py
+++ b/buildscripts/idl/tests/test_parser.py
@@ -1591,6 +1591,17 @@ class TestParser(testcase.IDLTestcase):
                 featureFlagToaster:
                     description: "Make toast"
                     cpp_varname: gToaster
+                    shouldBeFCVGated: true
+            """), idl.errors.ERROR_ID_MISSING_REQUIRED_FIELD)
+
+        # Missing shouldBeFCVGated
+        self.assert_parse_fail(
+            textwrap.dedent("""
+            feature_flags:
+                featureFlagToaster:
+                    description: "Make toast"
+                    cpp_varname: gToaster
+                    default: false
             """), idl.errors.ERROR_ID_MISSING_REQUIRED_FIELD)
 
     def _test_field_list(self, field_list_name, should_forward_name):
diff --git a/src/mongo/crypto/encryption_fields.idl b/src/mongo/crypto/encryption_fields.idl
index 85b2ac77ebb..ef48242d030 100644
--- a/src/mongo/crypto/encryption_fields.idl
+++ b/src/mongo/crypto/encryption_fields.idl
@@ -61,10 +61,12 @@ feature_flags:
         version: 7.0
         cpp_varname: gFeatureFlagFLE2CompactForProtocolV2
         default: true
+        shouldBeFCVGated: true
     featureFlagFLE2CleanupCommand:
         description: "Enable support for the Cleanup Structured Encryption Data command"
         cpp_varname: gFeatureFlagFLE2CleanupCommand
         default: false
+        shouldBeFCVGated: true
 
 structs:
 
diff --git a/src/mongo/db/catalog_shard_feature_flag.idl b/src/mongo/db/catalog_shard_feature_flag.idl
index bcbef0063fd..e43d755c675 100644
--- a/src/mongo/db/catalog_shard_feature_flag.idl
+++ b/src/mongo/db/catalog_shard_feature_flag.idl
@@ -35,9 +35,11 @@ feature_flags:
         cpp_varname: gFeatureFlagCatalogShard
         default: true
         version: 7.0
+        shouldBeFCVGated: true
 
     featureFlagTransitionToCatalogShard:
         description: "Feature flag for transitioning a config server in and out of config shard mode"
         cpp_varname: gFeatureFlagTransitionToCatalogShard
         default: true
         version: 7.0
+        shouldBeFCVGated: true
diff --git a/src/mongo/db/feature_flag.cpp b/src/mongo/db/feature_flag.cpp
index b75892a9408..818df3bfdcc 100644
--- a/src/mongo/db/feature_flag.cpp
+++ b/src/mongo/db/feature_flag.cpp
@@ -35,8 +35,10 @@
 namespace mongo {
 
 // (Generic FCV reference): feature flag support
-FeatureFlag::FeatureFlag(bool enabled, StringData versionString)
-    : _enabled(enabled), _version(multiversion::GenericFCV::kLatest) {
+FeatureFlag::FeatureFlag(bool enabled, StringData versionString, bool shouldBeFCVGated)
+    : _enabled(enabled),
+      _version(multiversion::GenericFCV::kLatest),
+      _shouldBeFCVGated(shouldBeFCVGated) {
 
     // Verify the feature flag invariants. IDL binder verifies these hold but we add these checks to
     // prevent incorrect direct instantiation.
@@ -44,7 +46,7 @@ FeatureFlag::FeatureFlag(bool enabled, StringData versionString)
     // If default is true, then version should be present.
     // If default is false, then no version is allowed.
     if (kDebugBuild) {
-        if (enabled) {
+        if (enabled && shouldBeFCVGated) {
             dassert(!versionString.empty());
         } else {
             dassert(versionString.empty());
@@ -57,6 +59,12 @@ FeatureFlag::FeatureFlag(bool enabled, StringData versionString)
 }
 
 bool FeatureFlag::isEnabled(const ServerGlobalParams::FeatureCompatibility& fcv) const {
+    // If the feature flag is not FCV gated, return whether it is enabled.
+    if (!_shouldBeFCVGated) {
+        return _enabled;
+    }
+
+
     // If the FCV is not initialized yet, we check whether the feature flag is enabled on the last
     // LTS FCV, which is the lowest FCV we can have on this server. Because the version of a feature
     // flag is not supposed to change, we are sure that if the feature flag is enabled on the last
@@ -70,13 +78,27 @@ bool FeatureFlag::isEnabled(const ServerGlobalParams::FeatureCompatibility& fcv)
         return false;
     }
 
+    // If the feature flag is enabled, return whether the server's FCV is >= to the version the
+    // feature flag was enabled on.
     return fcv.isGreaterThanOrEqualTo(_version);
 }
 
+// isEnabledAndIgnoreFCVUnsafe should NOT be used in general, as it checks if the feature flag is
+// turned on, regardless of which FCV we are on. It can result in unsafe scenarios
+// where we enable a feature on an FCV where it is not supported or where the feature has not been
+// fully implemented yet. In order to use isEnabledAndIgnoreFCVUnsafe, you **must** add a comment
+// above that line starting with "(Ignore FCV check):" describing why we can safely ignore checking
+// the FCV here.
+// Note that if the feature flag does not have any upgrade/downgrade concerns, then shouldBeFCVGated
+// should be set to false and FeatureFlag::isEnabled() should be used instead of this function.
 bool FeatureFlag::isEnabledAndIgnoreFCVUnsafe() const {
     return _enabled;
 }
 
+// isEnabledAndIgnoreFCVUnsafeAtStartup should only be used on startup, if we want to check if the
+// feature flag if the feature flag is turned on, regardless of which FCV we are on.
+// Note that if the feature flag does not have any upgrade/downgrade concerns, then shouldBeFCVGated
+// should be set to false and FeatureFlag::isEnabled() should be used instead of this function.
 bool FeatureFlag::isEnabledAndIgnoreFCVUnsafeAtStartup() const {
     return _enabled;
 }
diff --git a/src/mongo/db/feature_flag.h b/src/mongo/db/feature_flag.h
index 746f14e41c5..d59407c2c2e 100644
--- a/src/mongo/db/feature_flag.h
+++ b/src/mongo/db/feature_flag.h
@@ -52,7 +52,7 @@ class FeatureFlag {
     friend class FeatureFlagServerParameter;
 
 public:
-    FeatureFlag(bool enabled, StringData versionString);
+    FeatureFlag(bool enabled, StringData versionString, bool shouldBeFCVGated);
 
     /**
      * Returns true if the flag is set to true and enabled for this FCV version.
@@ -126,6 +126,7 @@ private:
 private:
     bool _enabled;
     multiversion::FeatureCompatibilityVersion _version;
+    bool _shouldBeFCVGated;
 };
 
 /**
diff --git a/src/mongo/db/feature_flag_test.idl.tpl b/src/mongo/db/feature_flag_test.idl.tpl
index d83d2316aaf..5b5d6e8a0ed 100644
--- a/src/mongo/db/feature_flag_test.idl.tpl
+++ b/src/mongo/db/feature_flag_test.idl.tpl
@@ -42,11 +42,19 @@ feature_flags:
       description: "Create a feature flag"
       cpp_varname: gFeatureFlagToaster
       default: false
+      shouldBeFCVGated: true
 
     featureFlagFryer:
       description: "Create a feature flag"
       cpp_varname: gFeatureFlagFryer
       default: false
+      shouldBeFCVGated: true
+    
+    featureFlagFork:
+      description: "Create a feature flag that should not be FCV gated"
+      cpp_varname: gFeatureFlagFork
+      default: true
+      shouldBeFCVGated: false
 
 #def $ver_str(v): ${'{}.{}'.format(v.major, v.minor)}
     featureFlagBlender:
@@ -56,6 +64,7 @@ feature_flags:
       # The version should be a valid FCV not equal to GenericFCV::kLastLTS in
       # the generated 'releases.h' file.
       version: $ver_str(latest)
+      shouldBeFCVGated: true
 
     featureFlagSpoon:
       description: "Create a feature flag"
@@ -63,6 +72,7 @@ feature_flags:
       default: true
       # The version should match GenericFCV::kLastLTS in the generated 'releases.h' file.
       version: $ver_str(last_lts)
+      shouldBeFCVGated: true
 
 server_parameters:
     spTestNeedsFeatureFlagToaster:
diff --git a/src/mongo/db/internal_transactions_feature_flag.idl b/src/mongo/db/internal_transactions_feature_flag.idl
index 97b0bcd927a..9a38ed96d7f 100644
--- a/src/mongo/db/internal_transactions_feature_flag.idl
+++ b/src/mongo/db/internal_transactions_feature_flag.idl
@@ -39,13 +39,16 @@ feature_flags:
         description: Feature flag to enable always creating the config.transactions partial index on step up to primary even if the collection is not empty.
         cpp_varname: gFeatureFlagAlwaysCreateConfigTransactionsPartialIndexOnStepUp
         default: false
+        shouldBeFCVGated: true
 
     featureFlagUpdateDocumentShardKeyUsingTransactionApi:
         description: Feature flag to enable usage of the transaction api for update findAndModify and update commands that change a document's shard key.
         cpp_varname: gFeatureFlagUpdateDocumentShardKeyUsingTransactionApi
         default: false
+        shouldBeFCVGated: true
 
     featureFlagUpdateOneWithoutShardKey:
         description: Feature flag to enable updateOne, deleteOne, and findAndModify without a shard key or _id equality in their filter against a sharded collection.
         cpp_varname: gFeatureFlagUpdateOneWithoutShardKey
         default: false
+        shouldBeFCVGated: true
diff --git a/src/mongo/db/process_health/health_monitoring.idl b/src/mongo/db/process_health/health_monitoring.idl
index 88837981d8c..5c9a23e5bc5 100644
--- a/src/mongo/db/process_health/health_monitoring.idl
+++ b/src/mongo/db/process_health/health_monitoring.idl
@@ -40,3 +40,4 @@ feature_flags:
         cpp_varname: gFeatureFlagHealthMonitoring
         default: true
         version: 5.3
+        shouldBeFCVGated: true
diff --git a/src/mongo/db/query/query_feature_flags.idl b/src/mongo/db/query/query_feature_flags.idl
index 86d0622d385..c99596755a9 100644
--- a/src/mongo/db/query/query_feature_flags.idl
+++ b/src/mongo/db/query/query_feature_flags.idl
@@ -35,88 +35,104 @@ feature_flags:
       cpp_varname: gFeatureFlagChangeStreamsRewrite
       default: true
       version: 5.1
+      shouldBeFCVGated: true
 
     featureFlagShardedTimeSeries:
       description: "Feature flag for allowing sharding a Time Series collection"
       cpp_varname: gFeatureFlagShardedTimeSeries
       default: true
       version: 5.1
+      shouldBeFCVGated: true
 
     featureFlagShardedTimeSeriesUpdateDelete:
       description: "Feature flag for allowing update and delete operations on a sharded Time Series collection"
       cpp_varname: gFeatureFlagShardedTimeSeriesUpdateDelete
       default: true
       version: 5.1
+      shouldBeFCVGated: true
 
     featureFlagChangeStreamsFurtherEnrichedEvents:
       description: "Feature flag for enabling the reshardCollection and refineCollectionShardKey events, as well as enhancements to the updateDescription field for update events"
       cpp_varname: gFeatureFlagChangeStreamsFurtherEnrichedEvents
       default: true
       version: 6.1
+      shouldBeFCVGated: true
 
     featureFlagCommonQueryFramework:
       description: "Feature flag for allowing use of Cascades-based query optimizer"
       cpp_varname: gFeatureFlagCommonQueryFramework
       default: false
+      shouldBeFCVGated: true
 
     featureFlagBucketUnpackWithSort:
       description: "Enables a time-series optimization that allows for partially-blocking sort on time"
       cpp_varname: gFeatureFlagBucketUnpackWithSort
       default: true
       version: 6.0
+      shouldBeFCVGated: true
 
     featureFlagColumnstoreIndexes:
       description: "Enables creation of a new columnstore index type"
       cpp_varname: gFeatureFlagColumnstoreIndexes
       default: false
+      shouldBeFCVGated: true
 
     featureFlagServerlessChangeStreams:
       description: "Feature flag to enable reading change events from the change collection rather than the oplog"
       cpp_varname: gFeatureFlagServerlessChangeStreams
       default: false
+      shouldBeFCVGated: true
 
     featureFlagSbeFull:
       description: "Feature flag for SBE behaviors, features, or extensions that are not yet enabled
                     by default"
       cpp_varname: gFeatureFlagSbeFull
       default: false
+      shouldBeFCVGated: true
 
     featureFlagTelemetry:
       description: "Feature flag for enabling the telemetry store."
       cpp_varname: gFeatureFlagTelemetry
       default: false
+      shouldBeFCVGated: true
 
     featureFlagBitwiseAggOperators:
       description: "Feature flag for enabling support for bitwise operators in the aggregation language."
       cpp_varname: gFeatureFlagBitwise
       default: true
       version: 6.3
+      shouldBeFCVGated: true
 
     featureFlagCompoundWildcardIndexes:
       description: "Feature flag to enable compound wildcard indexes."
       cpp_varname: gFeatureFlagCompoundWildcardIndexes
       default: true
       version: 7.0
+      shouldBeFCVGated: true
 
     featureFlagShardedSearchCustomSort:
       description: "Feature flag to enable user specified sort for sharded $search queries."
       cpp_varname: gFeatureFlagShardedSearchCustomSort
       default: true
       version: 7.0
+      shouldBeFCVGated: true
 
     featureFlagUserRoles:
       description: "Feature flag to enable usage of $$USER_ROLES."
       cpp_varname: gFeatureFlagUserRoles
       default: true
       version: 7.0
+      shouldBeFCVGated: true
 
     featureFlagApproxPercentiles:
       description: "Feature flag to enable approximate $percentile accumulator/expression."
       cpp_varname: gFeatureFlagApproxPercentiles
       default: true
       version: 7.0
+      shouldBeFCVGated: true
 
     featureFlagSearchBatchSizeLimit:
       description: "Feature flag to enable the search batchsize and limit optimization."
       cpp_varname: gFeatureFlagSearchBatchSizeLimit
       default: false
+      shouldBeFCVGated: true
diff --git a/src/mongo/db/repl/FCV_AND_FEATURE_FLAG_README.md b/src/mongo/db/repl/FCV_AND_FEATURE_FLAG_README.md
index b5570f5206f..97381b12223 100644
--- a/src/mongo/db/repl/FCV_AND_FEATURE_FLAG_README.md
+++ b/src/mongo/db/repl/FCV_AND_FEATURE_FLAG_README.md
@@ -544,6 +544,7 @@ Feature flags are created by adding it to an IDL file:
      description: "Create a feature flag"
      cpp_varname: gFeatureFlagToaster
      default: false
+     shouldBeFCVGated: true
 ```
 
 A feature flag has the following properties:
@@ -569,6 +570,13 @@ A feature flag has the following properties:
 * Version: string - a string for the FCV version
     * Required field if default is true, Must be a string acceptable to 
     FeatureCompatibilityVersionParser.
+* shouldBeFCVGated: boolean
+    * This should usually be true in order to gate the feature flag based on the FCV.
+    * However, some feature flags should not be FCV gated (for example, if the feature only exists
+    on mongos, which doesn't have an FCV, or if the feature doesn't have any upgrade downgrade 
+    concerns and can be enabled as soon as the binary is upgraded/downgraded.
+    * When set to false, the feature flag won't require a version parameter, so it will only be
+    gated based on whether it is enabled by default on that binary version.
 
 To turn on a feature flag for testing when starting up a server, we would use the following command
 line (for the Toaster feature):
@@ -599,9 +607,12 @@ if(feature_flags::gFeatureFlagToaster.isEnabled(serverGlobalParams.featureCompat
 }
 ```
 
-Note that `isEnabled` checks if the feature flag is enabled on the input FCV, which is usually 
-the server's current FCV `serverGlobalParams.featureCompatibility`. If the FCV has not been 
+Note that `isEnabled` checks if the feature flag is enabled on the input FCV, which is usually
+the server's current FCV `serverGlobalParams.featureCompatibility`. If the FCV has not been
 initialized yet, it will check if the feature flag is enabled on the lastLTS FCV.
+If the feature flag has `shouldBeFCVGated` set to false, then `isEnabled` will simply return
+whether the feature flag is enabled.
+
 
 There are some places where we only want to check if the feature flag is turned on, regardless of
 which FCV we are on. For example, this could be the case if we need to perform the check in a spot
diff --git a/src/mongo/db/repl/repl_server_parameters.idl b/src/mongo/db/repl/repl_server_parameters.idl
index 4e2c0838e4d..620a4d08a29 100644
--- a/src/mongo/db/repl/repl_server_parameters.idl
+++ b/src/mongo/db/repl/repl_server_parameters.idl
@@ -769,17 +769,20 @@ feature_flags:
         cpp_varname: feature_flags::gFeatureFlagRetryableFindAndModify
         default: true
         version: 5.1
+        shouldBeFCVGated: true
 
     featureFlagShardMerge:
         description: When enabled, multitenant migration uses the "shard merge" protocol.
         cpp_varname: feature_flags::gShardMerge
         default: false
+        shouldBeFCVGated: true
 
     featureFlagShardSplit:
         description: When enabled, multitenant migration can use the shard split commands.
         cpp_varname: feature_flags::gShardSplit
         default: true
         version: 6.3
+        shouldBeFCVGated: true
 
     featureFlagDowngradingToUpgrading:
         description: When enabled, 
@@ -787,9 +790,11 @@ feature_flags:
         cpp_varname: feature_flags::gDowngradingToUpgrading
         default: true
         version: 7.0
+        shouldBeFCVGated: true
 
     featureFlagApplyPreparedTxnsInParallel:
         description: when enabled, secondaries will apply prepared transactions in parallel.
         cpp_varname: feature_flags::gApplyPreparedTxnsInParallel
         default: true
         version: 7.0
+        shouldBeFCVGated: true
diff --git a/src/mongo/db/server_feature_flags.idl b/src/mongo/db/server_feature_flags.idl
index d7324158ccd..57b34e36c89 100644
--- a/src/mongo/db/server_feature_flags.idl
+++ b/src/mongo/db/server_feature_flags.idl
@@ -34,6 +34,7 @@ feature_flags:
         description: "Enable parsing and handling of SecurityTokens in multitenancy mode"
         cpp_varname: gFeatureFlagSecurityToken
         default: false
+        shouldBeFCVGated: true
     featureFlagRequireTenantID:
         # Only available with the server parameter "multitenancySupport".
         description: >-
@@ -41,47 +42,57 @@ feature_flags:
             require tenantID to be a part of NamespaceString and TenantDatabase.
         cpp_varname: gFeatureFlagRequireTenantID
         default: false
+        shouldBeFCVGated: true
     featureFlagConnHealthMetrics:
         description: "Enable newly added cluster connection health metrics"
         cpp_varname: gFeatureFlagConnHealthMetrics
         default: true
         version: 6.3
+        shouldBeFCVGated: true
     featureFlagGlobalIndexes:
         description: "Enable support for global indexes"
         cpp_varname: gFeatureFlagGlobalIndexes
         default: false
+        shouldBeFCVGated: true
     featureFlagAdditionalParticipants:
         description: "Adding additional participants to existing transactions"
         cpp_varname: gFeatureFlagAdditionalParticipants
         default: false
+        shouldBeFCVGated: true
     featureFlagUseNewCompactStructuredEncryptionDataCoordinator:
         description: "Use the new 6.1 compact structured encryption data coordinator"
         cpp_varname: gFeatureFlagUseNewCompactStructuredEncryptionDataCoordinator
         default: true
         version: 6.1
+        shouldBeFCVGated: true
     featureFlagOIDC:
         description: "Feature flag for OIDC support"
         cpp_varname: gFeatureFlagOIDC
         default: true
         version: 7.0
+        shouldBeFCVGated: true
     featureFlagBulkWriteCommand:
         description: "Support for bulkWrite command and one-shot transactions"
         cpp_varname: gFeatureFlagBulkWriteCommand
         default: false
+        shouldBeFCVGated: true
     featureFlagAuditConfigClusterParameter:
         description: "Enable use of new auditConfig cluster server parameter"
         cpp_varname: feature_flags::gFeatureFlagAuditConfigClusterParameter
         default: false
+        shouldBeFCVGated: true
     featureFlagStreams:
         description: "Enable support for streams"
         cpp_varname: gFeatureFlagStreams
         default: false
+        shouldBeFCVGated: true
     featureFlagUseUnreplicatedTruncatesForDeletions:
         description: "Feature flag to enable pre-image collection and change collection maintenance
         using unreplicated truncates instead of normal document deletions replicated from the
         primary."
         cpp_varname: feature_flags::gFeatureFlagUseUnreplicatedTruncatesForDeletions
         default: false
+        shouldBeFCVGated: true
     featureFlagConfigurableX509ClusterAuthn:
         description: >- 
             Enable configurable parameters for detection of peer server nodes using X.509 
@@ -89,3 +100,4 @@ feature_flags:
         cpp_varname: gFeatureFlagConfigurableX509ClusterAuthn
         default: true
         version: 7.0
+        shouldBeFCVGated: true
diff --git a/src/mongo/db/storage/storage_engine_feature_flags.idl b/src/mongo/db/storage/storage_engine_feature_flags.idl
index d2ef38f4576..26052df419b 100644
--- a/src/mongo/db/storage/storage_engine_feature_flags.idl
+++ b/src/mongo/db/storage/storage_engine_feature_flags.idl
@@ -34,8 +34,10 @@ feature_flags:
     cpp_varname: feature_flags::gFeatureFlagExecutionControl
     default: true
     version: 7.0
+    shouldBeFCVGated: true
   featureFlagDeprioritizeLowPriorityOperations:
     description: Enables the deprioritization of low priority operations
     cpp_varname: feature_flags::gFeatureFlagDeprioritizeLowPriorityOperations
     default: true
     version: 7.0
+    shouldBeFCVGated: true
diff --git a/src/mongo/db/storage/storage_parameters.idl b/src/mongo/db/storage/storage_parameters.idl
index ea461827d05..b17ad345e71 100644
--- a/src/mongo/db/storage/storage_parameters.idl
+++ b/src/mongo/db/storage/storage_parameters.idl
@@ -171,55 +171,67 @@ feature_flags:
         cpp_varname: feature_flags::gTimeseriesMetricIndexes
         default: true
         version: 6.0
+        shouldBeFCVGated: true
     featureFlagCollModIndexUnique:
         description: "When enabled, collMod supports making an index unique"
         cpp_varname: feature_flags::gCollModIndexUnique
         default: true
         version: 6.0
+        shouldBeFCVGated: true
     featureFlagSelectiveBackup:
         description: "When enabled, support selective backups and restores on collections"
         cpp_varname: feature_flags::gSelectiveBackup
         default: true
         version: 6.0
+        shouldBeFCVGated: true
     featureFlagBatchMultiDeletes:
         description: "When enabled, support batching multi-document deletions"
         cpp_varname: feature_flags::gBatchMultiDeletes
         default: true
         version: 6.1
+        shouldBeFCVGated: true
     featureFlagDocumentSourceListCatalog:
         description: "When enabled, allow the use of the $listCatalog aggregation stage"
         cpp_varname: feature_flags::gDocumentSourceListCatalog
         default: true
         version: 6.0
+        shouldBeFCVGated: true
     featureFlagDerivedMetadata:
         description: "When enabled, support storing derived collection and index metadata"
         cpp_varname: feature_flags::gDerivedMetadata
         default: false
+        shouldBeFCVGated: true
     featureFlagTimeseriesScalabilityImprovements:
         description: "Enable scalability and usability improvements for time-series collections"
         cpp_varname: feature_flags::gTimeseriesScalabilityImprovements
         default: true
         version: 6.3
+        shouldBeFCVGated: true
     featureFlagExtendValidateCommand:
         description: "Enable checks on more types of inconsistencies for the validate command"
         cpp_varname: feature_flags::gExtendValidateCommand
         default: true
         version: 6.2
+        shouldBeFCVGated: true
     featureFlagInternalWritesAreReplicatedTransactionally:
         description: Feature flag to enable internal writes to use the transactionally replicated WriteUnitOfWork API by default.
         cpp_varname: gFeatureFlagInternalWritesAreReplicatedTransactionally
         default: false
+        shouldBeFCVGated: true
     featureFlagTimeseriesDeletesSupport:
         description: "Enable support for arbitrary deletes on time-series collections"
         cpp_varname: feature_flags::gTimeseriesDeletesSupport
         default: true
         version: 7.0
+        shouldBeFCVGated: true
     featureFlagTimeseriesUpdatesSupport:
         description: "Enable support for arbitrary updates on time-series collections"
         cpp_varname: feature_flags::gTimeseriesUpdatesSupport
         default: false
+        shouldBeFCVGated: true
     featureFlagIndexBuildGracefulErrorHandling:
         description: "Enable index build error handling improvements"
         cpp_varname: feature_flags::gIndexBuildGracefulErrorHandling
         default: true
         version: 7.1
+        shouldBeFCVGated: true
diff --git a/src/mongo/executor/network_interface_tl.idl b/src/mongo/executor/network_interface_tl.idl
index 03decc33c96..11226a554b9 100644
--- a/src/mongo/executor/network_interface_tl.idl
+++ b/src/mongo/executor/network_interface_tl.idl
@@ -34,6 +34,7 @@ feature_flags:
     description: Suppress network interface transport layer exceptions
     cpp_varname: gSuppressNetworkInterfaceTransportLayerExceptions
     default: false 
+    shouldBeFCVGated: true
 
 server_parameters:
   opportunisticSecondaryTargeting:
diff --git a/src/mongo/idl/cluster_server_parameter.idl b/src/mongo/idl/cluster_server_parameter.idl
index 8991e4f47f9..216193190c8 100644
--- a/src/mongo/idl/cluster_server_parameter.idl
+++ b/src/mongo/idl/cluster_server_parameter.idl
@@ -92,10 +92,12 @@ feature_flags:
         cpp_varname: gFeatureFlagClusterWideConfigM2
         default: true
         version: 6.1
+        shouldBeFCVGated: true
     featureFlagClusterWideToaster:
         description: Feature flag for testing use of feature flags with CW server params
         cpp_varname: gFeatureFlagClusterWideToaster
         default: false
+        shouldBeFCVGated: true
 
 server_parameters:
     testIntClusterParameter:
diff --git a/src/mongo/idl/feature_flag_test.cpp b/src/mongo/idl/feature_flag_test.cpp
index f0b43850b78..e0636f53d75 100644
--- a/src/mongo/idl/feature_flag_test.cpp
+++ b/src/mongo/idl/feature_flag_test.cpp
@@ -51,6 +51,7 @@ protected:
 protected:
     ServerParameter* _featureFlagBlender{nullptr};
     ServerParameter* _featureFlagSpoon{nullptr};
+    ServerParameter* _featureFlagFork{nullptr};
 };
 
 
@@ -199,6 +200,28 @@ TEST_F(FeatureFlagTest, RAIIFeatureFlagController) {
         feature_flags::gFeatureFlagBlender.isEnabled(serverGlobalParams.featureCompatibility));
 }
 
+// Test feature flags that should not be FCV Gated
+TEST_F(FeatureFlagTest, ShouldBeFCVGatedFalse) {
+    // Test that feature flag that is enabled and not FCV gated will return true for isEnabled.
+    // Test newest version
+    // (Generic FCV reference): feature flag test
+    serverGlobalParams.mutableFeatureCompatibility.setVersion(multiversion::GenericFCV::kLatest);
+
+    ASSERT_TRUE(feature_flags::gFeatureFlagFork.isEnabled(serverGlobalParams.featureCompatibility));
+
+    // Test oldest version
+    // (Generic FCV reference): feature flag test
+    serverGlobalParams.mutableFeatureCompatibility.setVersion(multiversion::GenericFCV::kLastLTS);
+
+    ASSERT_TRUE(feature_flags::gFeatureFlagFork.isEnabled(serverGlobalParams.featureCompatibility));
+
+    // Test uninitialized FCV
+    serverGlobalParams.mutableFeatureCompatibility.setVersion(
+        multiversion::FeatureCompatibilityVersion::kUnsetDefaultLastLTSBehavior);
+
+    ASSERT_TRUE(feature_flags::gFeatureFlagFork.isEnabled(serverGlobalParams.featureCompatibility));
+}
+
 
 }  // namespace
 }  // namespace mongo
diff --git a/src/mongo/s/analyze_shard_key_feature_flag.idl b/src/mongo/s/analyze_shard_key_feature_flag.idl
index 4e92dcac667..b995fe0430f 100644
--- a/src/mongo/s/analyze_shard_key_feature_flag.idl
+++ b/src/mongo/s/analyze_shard_key_feature_flag.idl
@@ -40,3 +40,4 @@ feature_flags:
         cpp_varname: gFeatureFlagAnalyzeShardKey
         default: true
         version: 7.0
+        shouldBeFCVGated: true
diff --git a/src/mongo/s/move_primary/move_primary_feature_flag.idl b/src/mongo/s/move_primary/move_primary_feature_flag.idl
index 61099c5cbdd..876715c7222 100644
--- a/src/mongo/s/move_primary/move_primary_feature_flag.idl
+++ b/src/mongo/s/move_primary/move_primary_feature_flag.idl
@@ -40,3 +40,4 @@ feature_flags:
         cpp_varname: gFeatureFlagOnlineMovePrimaryLifecycle
         default: true
         version: 7.0
+        shouldBeFCVGated: true
diff --git a/src/mongo/s/resharding/resharding_feature_flag.idl b/src/mongo/s/resharding/resharding_feature_flag.idl
index afdad3d093e..551bd8dcc81 100644
--- a/src/mongo/s/resharding/resharding_feature_flag.idl
+++ b/src/mongo/s/resharding/resharding_feature_flag.idl
@@ -40,3 +40,4 @@ feature_flags:
         cpp_varname: gFeatureFlagResharding
         default: true
         version: 5.0
+        shouldBeFCVGated: true
diff --git a/src/mongo/s/sharding_feature_flags.idl b/src/mongo/s/sharding_feature_flags.idl
index 339d9072d87..f084c5827fd 100644
--- a/src/mongo/s/sharding_feature_flags.idl
+++ b/src/mongo/s/sharding_feature_flags.idl
@@ -36,27 +36,32 @@ feature_flags:
     description: "Feature flag for enabling sharding catalog features for global indexes"
     cpp_varname: feature_flags::gGlobalIndexesShardingCatalog
     default: false
+    shouldBeFCVGated: true
   featureFlagRangeDeleterService:
     description: "Feature flag protecting instantiation and usages of the range deleter service"
     cpp_varname: feature_flags::gRangeDeleterService
     default: true
     version: 6.2
+    shouldBeFCVGated: true
   featureFlagCollModCoordinatorV3:
     description: "Feature for enabling new coll mod coordinator v3"
     cpp_varname: feature_flags::gCollModCoordinatorV3
     default: true
     version: 6.1
+    shouldBeFCVGated: true
   featureFlagCreateCollectionCoordinatorV3:
     description: "Feature for enabling new createCollection coordinator v3"
     cpp_varname: feature_flags::gCreateCollectionCoordinatorV3
     default: true
     version: 6.2
+    shouldBeFCVGated: true
   # TODO SERVER-68217 remove once 7.0 becomes last LTS
   featureFlagHistoricalPlacementShardingCatalog:
     description: "Feature flag for enabling the storage and access to historical placement data at shards granularity through the Sharding Catalog"
     cpp_varname: feature_flags::gHistoricalPlacementShardingCatalog
     default: true
     version: 7.0
+    shouldBeFCVGated: true
   featureFlagImplicitDDLTimeseriesNssTranslation:
     description: "When enabled, the logic to evaluate whether a DDL is targeting a Timeseries operation
                   will always be executed by the DDL Coordinator (VS doing the evaluation when the command is received by the primary shard).
@@ -64,40 +69,49 @@ feature_flags:
     cpp_varname: feature_flags::gImplicitDDLTimeseriesNssTranslation
     default: true
     version: 6.1
+    shouldBeFCVGated: true
   featureFlagConcurrencyInChunkMigration:
     description: "Feature flag for enabling concurrency within a chunk migration"
     cpp_varname: feature_flags::gConcurrencyInChunkMigration
     default: true
     version: 6.3
+    shouldBeFCVGated: true
   featureFlagStopUsingConfigVersion:
   # TODO SERVER-68889 remove once 7.0 becomes last LTS
     description: "Stop using deprecated config version fields to check metadata compatibility between different version"
     cpp_varname: feature_flags::gStopUsingConfigVersion
     default: true
     version: 6.2
+    shouldBeFCVGated: true
   featureFlagAutoMerger:
     description: "Feature flag for enabling auto-merging of contiguous chunks belonging to the same shard"
     cpp_varname: feature_flags::gAutoMerger
     default: true
     version: 7.0
+    shouldBeFCVGated: true
   # TODO (SERVER-70396): Remove once 7.0 becomes last LTS
   featureFlagCheckMetadataConsistency:
     description: "Feature flag for checking metadata consistency in the cluster, database or collection"
     cpp_varname: feature_flags::gCheckMetadataConsistency
     default: true
     version: 7.0
+    shouldBeFCVGated: true
   # TODO SERVER-73627: Remove once 7.0 becomes last LTS.
   featureFlagDropCollectionHoldingCriticalSection:
     description: "Feature flag for enabling the new implementation of the dropCollection DDL operation."
     cpp_varname: feature_flags::gDropCollectionHoldingCriticalSection
     default: true
     version: 7.0
+    shouldBeFCVGated: true
+
   featureFlagCheckForDirectShardOperations:
     description: "Feature flag for checking for direct shard operations."
     cpp_varname: feature_flags::gCheckForDirectShardOperations
     default: false
+    shouldBeFCVGated: true
   featureFlagClusterCardinalityParameter:
     description: "Feature flag for enabling the cluster parameter tracking cluster cardinality."
     cpp_varname: feature_flags::gClusterCardinalityParameter
     default: true
     version: 7.0
+    shouldBeFCVGated: true