diff --git a/lib/Client.php b/lib/Client.php
index 9e6fe89..327d00e 100644
--- a/lib/Client.php
+++ b/lib/Client.php
@@ -256,6 +256,8 @@ public function getFeatureFlag(
                         $personProperties,
                         $groupProperties
                     );
+                } catch (RequiresServerEvaluationException $e) {
+                    $result = null;
                 } catch (InconclusiveMatchException $e) {
                     $result = null;
                 } catch (Exception $e) {
@@ -387,6 +389,8 @@ public function getAllFlags(
                         $personProperties,
                         $groupProperties
                     );
+                } catch (RequiresServerEvaluationException $e) {
+                    $fallbackToFlags = true;
                 } catch (InconclusiveMatchException $e) {
                     $fallbackToFlags = true;
                 } catch (Exception $e) {
diff --git a/lib/FeatureFlag.php b/lib/FeatureFlag.php
index 17e95ec..deb679d 100644
--- a/lib/FeatureFlag.php
+++ b/lib/FeatureFlag.php
@@ -103,7 +103,10 @@ public static function matchCohort($property, $propertyValues, $cohortProperties
     {
         $cohortId = strval($property["value"]);
         if (!array_key_exists($cohortId, $cohortProperties)) {
-            throw new InconclusiveMatchException("can't match cohort without a given cohort property value");
+            throw new RequiresServerEvaluationException(
+                "cohort {$cohortId} not found in local cohorts - " .
+                "likely a static cohort that requires server evaluation"
+            );
         }
 
         $propertyGroup = $cohortProperties[$cohortId];
@@ -141,6 +144,9 @@ public static function matchPropertyGroup($propertyGroup, $propertyValues, $coho
                             return true;
                         }
                     }
+                } catch (RequiresServerEvaluationException $err) {
+                    // Immediately propagate - this condition requires server-side data
+                    throw $err;
                 } catch (InconclusiveMatchException $err) {
                     $errorMatchingLocally = true;
                 }
@@ -183,6 +189,9 @@ public static function matchPropertyGroup($propertyGroup, $propertyValues, $coho
                             return true;
                         }
                     }
+                } catch (RequiresServerEvaluationException $err) {
+                    // Immediately propagate - this condition requires server-side data
+                    throw $err;
                 } catch (InconclusiveMatchException $err) {
                     // If this is a flag dependency error, preserve the original message
                     if ($propType === 'flag') {
@@ -402,6 +411,9 @@ function ($conditionA, $conditionB) {
                         return FeatureFlag::getMatchingVariant($flag, $distinctId) ?? true;
                     }
                 }
+            } catch (RequiresServerEvaluationException $e) {
+                // Immediately propagate - this condition requires server-side data
+                throw $e;
             } catch (InconclusiveMatchException $e) {
                 // If this is a flag dependency error, preserve the original message
                 if (
diff --git a/lib/RequiresServerEvaluationException.php b/lib/RequiresServerEvaluationException.php
new file mode 100644
index 0000000..b0ae805
--- /dev/null
+++ b/lib/RequiresServerEvaluationException.php
@@ -0,0 +1,14 @@
+<?php
+
+namespace PostHog;
+
+use Exception;
+
+class RequiresServerEvaluationException extends Exception
+{
+    public function errorMessage()
+    {
+        $errorMsg = 'Error on line ' . $this->getLine() . ' in ' . $this->getFile() . ': <b> Requires Server Evaluation:' . $this->getMessage() . '</b>'; //phpcs:ignore
+        return $errorMsg;
+    }
+}
diff --git a/test/FeatureFlagLocalEvaluationTest.php b/test/FeatureFlagLocalEvaluationTest.php
index 8fafa0f..b4a3114 100644
--- a/test/FeatureFlagLocalEvaluationTest.php
+++ b/test/FeatureFlagLocalEvaluationTest.php
@@ -3840,4 +3840,95 @@ public function testFeatureFlagsWithFlagDependencies(): void
         }
         $this->assertTrue($threwException, "Expected InconclusiveMatchException was not thrown");
     }
+
+    public function testFallsBackToAPIWhenFlagHasStaticCohort()
+    {
+        $this->http_client = new MockedHttpClient(
+            host: "app.posthog.com",
+            flagEndpointResponse: MockedResponses::LOCAL_EVALUATION_WITH_STATIC_COHORT,
+            flagsEndpointResponse: MockedResponses::FLAGS_WITH_STATIC_COHORT_RESPONSE
+        );
+
+        $this->client = new Client(
+            self::FAKE_API_KEY,
+            [
+                "debug" => true,
+            ],
+            $this->http_client,
+            "test"
+        );
+
+        $result = $this->client->getFeatureFlag(
+            'multi-condition-flag',
+            'test-user',
+            [],
+            ['$geoip_country_code' => 'DE']
+        );
+
+        // Should return 'set-1' from API, not 'set-8' from local evaluation
+        $this->assertEquals('set-1', $result);
+
+        $this->checkEmptyErrorLogs();
+    }
+
+    public function testFallsBackToAPIInGetAllFlagsWhenFlagHasStaticCohort()
+    {
+        $this->http_client = new MockedHttpClient(
+            host: "app.posthog.com",
+            flagEndpointResponse: MockedResponses::LOCAL_EVALUATION_WITH_STATIC_COHORT,
+            flagsEndpointResponse: MockedResponses::FLAGS_WITH_STATIC_COHORT_RESPONSE
+        );
+
+        $this->client = new Client(
+            self::FAKE_API_KEY,
+            [
+                "debug" => true,
+            ],
+            $this->http_client,
+            "test"
+        );
+
+        $result = $this->client->getAllFlags(
+            'test-user',
+            [],
+            ['$geoip_country_code' => 'DE']
+        );
+
+        // Should return flags from API
+        $this->assertEquals([
+            'multi-condition-flag' => 'set-1'
+        ], $result);
+
+        $this->checkEmptyErrorLogs();
+    }
+
+    public function testFallsBackToAPIInGetFeatureFlagPayloadWhenFlagHasStaticCohort()
+    {
+        $this->http_client = new MockedHttpClient(
+            host: "app.posthog.com",
+            flagEndpointResponse: MockedResponses::LOCAL_EVALUATION_WITH_STATIC_COHORT_FOR_PAYLOAD,
+            flagsEndpointResponse: MockedResponses::FLAGS_WITH_STATIC_COHORT_PAYLOAD_RESPONSE
+        );
+
+        $this->client = new Client(
+            self::FAKE_API_KEY,
+            [
+                "debug" => true,
+            ],
+            $this->http_client,
+            "test"
+        );
+
+        $result = $this->client->getFeatureFlagPayload(
+            'flag-with-payload',
+            'test-user'
+        );
+
+        // Should return payload from API, not local evaluation
+        $this->assertEquals([
+            'message' => 'from-api'
+        ], $result);
+
+        $this->checkEmptyErrorLogs();
+    }
 }
diff --git a/test/assests/MockedResponses.php b/test/assests/MockedResponses.php
index 69307d5..2082550 100644
--- a/test/assests/MockedResponses.php
+++ b/test/assests/MockedResponses.php
@@ -1429,4 +1429,100 @@ class MockedResponses
             ],
         ]
     ];
+
+    public const LOCAL_EVALUATION_WITH_STATIC_COHORT = [
+        'flags' => [
+            [
+                'id' => 1,
+                'key' => 'multi-condition-flag',
+                'filters' => [
+                    'groups' => [
+                        [
+                            'properties' => [
+                                [
+                                    'key' => 'id',
+                                    'value' => 999,
+                                    'type' => 'cohort'
+                                ]
+                            ],
+                            'rollout_percentage' => 100,
+                            'variant' => 'set-1'
+                        ],
+                        [
+                            'properties' => [
+                                [
+                                    'key' => '$geoip_country_code',
+                                    'operator' => 'exact',
+                                    'value' => ['DE'],
+                                    'type' => 'person'
+                                ]
+                            ],
+                            'rollout_percentage' => 100,
+                            'variant' => 'set-8'
+                        ]
+                    ],
+                    'multivariate' => [
+                        'variants' => [
+                            ['key' => 'set-1', 'rollout_percentage' => 50],
+                            ['key' => 'set-8', 'rollout_percentage' => 50]
+                        ]
+                    ],
+                    'payloads' => [
+                        'set-1' => '{"message": "local-payload-1"}',
+                        'set-8' => '{"message": "local-payload-8"}'
+                    ]
+                ],
+                'active' => true,
+                'is_simple_flag' => false
+            ]
+        ],
+        'cohorts' => []
+    ];
+
+    public const FLAGS_WITH_STATIC_COHORT_RESPONSE = [
+        'featureFlags' => [
+            'multi-condition-flag' => 'set-1'
+        ],
+        'featureFlagPayloads' => [
+            'multi-condition-flag' => '{"message": "from-api"}'
+        ]
+    ];
+
+    public const LOCAL_EVALUATION_WITH_STATIC_COHORT_FOR_PAYLOAD = [
+        'flags' => [
+            [
+                'id' => 2,
+                'key' => 'flag-with-payload',
+                'filters' => [
+                    'groups' => [
+                        [
+                            'properties' => [
+                                [
+                                    'key' => 'id',
+                                    'value' => 999,
+                                    'type' => 'cohort'
+                                ]
+                            ],
+                            'rollout_percentage' => 100
+                        ]
+                    ],
+                    'payloads' => [
+                        'true' => '{"message": "local-payload"}'
+                    ]
+                ],
+                'active' => true,
+                'is_simple_flag' => false
+            ]
+        ],
+        'cohorts' => []
+    ];
+
+    public const FLAGS_WITH_STATIC_COHORT_PAYLOAD_RESPONSE = [
+        'featureFlags' => [
+            'flag-with-payload' => true
+        ],
+        'featureFlagPayloads' => [
+            'flag-with-payload' => '{"message": "from-api"}'
+        ]
+    ];
 }