diff --git a/UPGRADING.INTERNALS b/UPGRADING.INTERNALS
index b5f75747ef73..bf38a489139e 100644
--- a/UPGRADING.INTERNALS
+++ b/UPGRADING.INTERNALS
@@ -14,6 +14,12 @@ PHP 8.7 INTERNALS UPGRADE NOTES
 1. Internal API changes
 ========================
 
+- Added zend_module_entry.child_init_func, an optional void callback invoked by
+  php_child_init() in the child process after core child initialization. It runs
+  in module dependency order for started modules and may run before a request
+  starts or during an active request. Initialize it with a designated
+  initializer such as `.child_init_func = callback` after
+  STANDARD_MODULE_PROPERTIES_EX.
 - Removed the ZEND_LOG_XOR() macro.
 - Removed the ZEND_TRUTH() macro.
 - Removed zend_execute_scripts(). Manually call zend_execute_script() in a loop
diff --git a/Zend/zend_modules.h b/Zend/zend_modules.h
index bb3050927992..018ad5bbc147 100644
--- a/Zend/zend_modules.h
+++ b/Zend/zend_modules.h
@@ -45,7 +45,12 @@
 
 #define ZEND_MODULE_BUILD_ID "API" ZEND_TOSTR(ZEND_MODULE_API_NO) ZEND_BUILD_TS ZEND_BUILD_DEBUG ZEND_BUILD_SYSTEM ZEND_BUILD_EXTRA
 
-#define STANDARD_MODULE_PROPERTIES_EX 0, 0, NULL, 0, ZEND_MODULE_BUILD_ID
+#define STANDARD_MODULE_PROPERTIES_EX \
+	.module_started = 0, \
+	.type = 0, \
+	.handle = NULL, \
+	.module_number = 0, \
+	.build_id = ZEND_MODULE_BUILD_ID
 
 #define NO_MODULE_GLOBALS 0, NULL, NULL, NULL
 
@@ -91,6 +96,7 @@ struct _zend_module_entry {
 	void (*globals_ctor)(void *global);
 	void (*globals_dtor)(void *global);
 	zend_result (*post_deactivate_func)(void);
+	void (*child_init_func)(void);
 	int module_started;
 	unsigned char type;
 	void *handle;
diff --git a/ext/session/php_session.h b/ext/session/php_session.h
index ee36eb291e52..7711d9432dc3 100644
--- a/ext/session/php_session.h
+++ b/ext/session/php_session.h
@@ -183,8 +183,6 @@ typedef struct _php_ps_globals {
 	bool mod_user_is_open;
 	bool mod_user_uses_object_methods_as_handlers;
 	bool use_trans_sid; /* contains the INI value of whether to use trans-sid */
-	bool random_seeded;
-
 	bool in_rfc1867_update;    /* php_session_rfc1867_update() is running */
 } php_ps_globals;
 
diff --git a/ext/session/session.c b/ext/session/session.c
index 702b56020ae9..c15941b74523 100644
--- a/ext/session/session.c
+++ b/ext/session/session.c
@@ -409,18 +409,6 @@ static zend_long php_session_gc(bool immediate)
 	if ((PS(mod_data) || PS(mod_user_implemented))) {
 		/* Use probability-based GC if not forced and probability is configured */
 		if (!collect && PS(gc_probability) > 0) {
-			/* Seed lazily on first GC draw per process. */
-			if (UNEXPECTED(!PS(random_seeded))) {
-				php_random_uint128_t seed;
-				if (php_random_bytes_silent(&seed, sizeof(seed)) == FAILURE) {
-					seed = php_random_uint128_constant(
-						php_random_generate_fallback_seed(),
-						php_random_generate_fallback_seed()
-					);
-				}
-				php_random_pcgoneseq128xslrr64_seed128(PS(random).state, seed);
-				PS(random_seeded) = true;
-			}
 			collect = php_random_range(PS(random), 0, PS(gc_divisor) - 1) < PS(gc_probability);
 		}
 
@@ -3019,7 +3007,15 @@ static PHP_GINIT_FUNCTION(ps)
 		.algo = &php_random_algo_pcgoneseq128xslrr64,
 		.state = &ps_globals->random_state,
 	};
-	ps_globals->random_seeded = false;
+
+	php_random_uint128_t seed;
+	if (php_random_bytes_silent(&seed, sizeof(seed)) == FAILURE) {
+		seed = php_random_uint128_constant(
+			php_random_generate_fallback_seed(),
+			php_random_generate_fallback_seed()
+		);
+	}
+	php_random_pcgoneseq128xslrr64_seed128(ps_globals->random.state, seed);
 }
 
 /* Interfaces extending the given one are not flattened into ce->interfaces before they are
@@ -3454,6 +3450,13 @@ static zend_result php_session_rfc1867_callback(unsigned int event, void *event_
 	return retval;
 }
 
+PHP_CINIT_FUNCTION(session)
+{
+	/* Give each child a distinct, widely separated GC sequence without requesting new entropy. */
+	uint64_t advance = (uint64_t) getpid() << 32;
+	php_random_pcgoneseq128xslrr64_advance(PS(random).state, advance);
+}
+
 zend_module_entry session_module_entry = {
 	STANDARD_MODULE_HEADER,
 	"session",
@@ -3466,7 +3469,8 @@ zend_module_entry session_module_entry = {
 	PHP_GINIT(ps),
 	NULL,
 	NULL,
-	STANDARD_MODULE_PROPERTIES_EX
+	STANDARD_MODULE_PROPERTIES_EX,
+	.child_init_func = PHP_CINIT(session)
 };
 
 #ifdef COMPILE_DL_SESSION
diff --git a/ext/session/tests/gh22616.phpt b/ext/session/tests/gh22616.phpt
new file mode 100644
index 000000000000..13235dede567
--- /dev/null
+++ b/ext/session/tests/gh22616.phpt
@@ -0,0 +1,99 @@
+--TEST--
+GH-22616: Session GC randomness is independent after a fork
+--EXTENSIONS--
+session
+pcntl
+--INI--
+session.gc_probability=1
+session.gc_divisor=2
+session.use_cookies=0
+session.cache_limiter=
+--FILE--
+<?php
+$handler = new class implements SessionHandlerInterface, SessionIdInterface, SessionUpdateTimestampHandlerInterface {
+    public bool $collected = false;
+
+    public function create_sid(): string { return 'gh22616'; }
+    public function validateId(string $id): bool { return true; }
+    public function updateTimestamp(string $id, string $data): bool { return true; }
+    public function open(string $path, string $name): bool { return true; }
+    public function close(): bool { return true; }
+    public function read(string $id): string|false { return ''; }
+    public function write(string $id, string $data): bool { return true; }
+    public function destroy(string $id): bool { return true; }
+    public function gc(int $max_lifetime): int|false {
+        $this->collected = true;
+        return 0;
+    }
+};
+session_set_save_handler($handler);
+session_id('gh22616');
+
+function sequence(): string {
+    global $handler;
+    if (session_status() === PHP_SESSION_ACTIVE) {
+        session_write_close();
+    }
+    $result = '';
+    for ($i = 0; $i < 256; $i++) {
+        $handler->collected = false;
+        session_start();
+        session_write_close();
+        $result .= (int) $handler->collected;
+    }
+    return $result;
+}
+
+$results = [];
+foreach (['unseeded', 'seeded', 'active'] as $state) {
+    if ($state === 'active') {
+        session_start();
+    }
+    $file1 = tempnam(sys_get_temp_dir(), 'gh22616');
+    $pid1 = pcntl_fork();
+    if ($pid1 === -1) {
+        throw new Exception('fork failed');
+    }
+    if ($pid1 === 0) {
+        file_put_contents($file1, sequence());
+        exit;
+    }
+
+    $file2 = tempnam(sys_get_temp_dir(), 'gh22616');
+    $pid2 = pcntl_fork();
+    if ($pid2 === -1) {
+        throw new Exception('fork failed');
+    }
+    if ($pid2 === 0) {
+        file_put_contents($file2, sequence());
+        exit;
+    }
+
+    $parent = sequence();
+    pcntl_waitpid($pid1, $status1);
+    pcntl_waitpid($pid2, $status2);
+    $child1 = file_get_contents($file1);
+    $child2 = file_get_contents($file2);
+    unlink($file1);
+    unlink($file2);
+    $results[$state] = pcntl_wifexited($status1)
+        && pcntl_wexitstatus($status1) === 0
+        && pcntl_wifexited($status2)
+        && pcntl_wexitstatus($status2) === 0
+        && strlen($child1) === 256
+        && strlen($child2) === 256
+        && $parent !== $child1
+        && $parent !== $child2
+        && $child1 !== $child2;
+}
+var_dump($results);
+?>
+--EXPECT--
+array(3) {
+  ["unseeded"]=>
+  bool(true)
+  ["seeded"]=>
+  bool(true)
+  ["active"]=>
+  bool(true)
+}
diff --git a/ext/zend_test/php_test.h b/ext/zend_test/php_test.h
index db6feede7caf..34f6d7c30bfe 100644
--- a/ext/zend_test/php_test.h
+++ b/ext/zend_test/php_test.h
@@ -29,6 +29,7 @@ ZEND_TSRMLS_CACHE_EXTERN()
 #endif
 
 ZEND_BEGIN_MODULE_GLOBALS(zend_test)
+	zend_long child_init_count;
 	int observer_enabled;
 	int observer_show_output;
 	int observer_observe_all;
diff --git a/ext/zend_test/test.c b/ext/zend_test/test.c
index f3a8076a456b..307ec19bbe5e 100644
--- a/ext/zend_test/test.c
+++ b/ext/zend_test/test.c
@@ -1669,6 +1669,13 @@ static PHP_INI_MH(OnUpdateZendTestObserveOplineInZendMM)
 	return OnUpdateBool(entry, new_value, mh_arg1, mh_arg2, mh_arg3, stage);
 }
 
+static ZEND_FUNCTION(zend_test_child_init_count)
+{
+	ZEND_PARSE_PARAMETERS_NONE();
+
+	RETURN_LONG(ZT_G(child_init_count));
+}
+
 static ZEND_FUNCTION(zend_test_fill_packed_array)
 {
 	HashTable *parameter;
@@ -2609,6 +2616,11 @@ PHP_MINFO_FUNCTION(zend_test)
 	DISPLAY_INI_ENTRIES();
 }
 
+static void zend_test_child_init(void)
+{
+	ZT_G(child_init_count)++;
+}
+
 zend_module_entry zend_test_module_entry = {
 	STANDARD_MODULE_HEADER,
 	"zend_test",
@@ -2623,7 +2635,8 @@ zend_module_entry zend_test_module_entry = {
 	PHP_GINIT(zend_test),
 	PHP_GSHUTDOWN(zend_test),
 	NULL,
-	STANDARD_MODULE_PROPERTIES_EX
+	STANDARD_MODULE_PROPERTIES_EX,
+	.child_init_func = zend_test_child_init
 };
 
 #ifdef COMPILE_DL_ZEND_TEST
diff --git a/ext/zend_test/test.stub.php b/ext/zend_test/test.stub.php
index 96f4a599e3d2..87ad8c9b93c8 100644
--- a/ext/zend_test/test.stub.php
+++ b/ext/zend_test/test.stub.php
@@ -282,6 +282,8 @@ function zend_test_nodiscard(): int {}
     #[\NoDiscard(message: "custom message 2")]
     function zend_test_deprecated_nodiscard(): int {}
 
+    function zend_test_child_init_count(): int {}
+
     /** @alias zend_test_void_return */
     function zend_test_aliased(): void {}
 
diff --git a/ext/zend_test/test_arginfo.h b/ext/zend_test/test_arginfo.h
index 9ad59954eae7..314d66a2799a 100644
--- a/ext/zend_test/test_arginfo.h
+++ b/ext/zend_test/test_arginfo.h
@@ -1,5 +1,5 @@
 /* This is a generated file, edit test.stub.php instead.
- * Stub hash: 9d0e693b29e9e11d82404d486c9b2c2dc81ca1c7
+ * Stub hash: 64eb27c89a9a5a378385e5f778cd17cfd67caed8
  * Has decl header: yes */
 
 #include "zend_attributes.h"
@@ -41,6 +41,8 @@ ZEND_END_ARG_INFO()
 
 #define arginfo_zend_test_deprecated_nodiscard arginfo_zend_test_nodiscard
 
+#define arginfo_zend_test_child_init_count arginfo_zend_test_nodiscard
+
 #define arginfo_zend_test_aliased arginfo_zend_test_void_return
 
 #define arginfo_zend_test_deprecated_aliased arginfo_zend_test_void_return
@@ -479,6 +481,7 @@ static ZEND_FUNCTION(zend_test_deprecated);
 static ZEND_FUNCTION(zend_test_deprecated_attr);
 static ZEND_FUNCTION(zend_test_nodiscard);
 static ZEND_FUNCTION(zend_test_deprecated_nodiscard);
+static ZEND_FUNCTION(zend_test_child_init_count);
 static ZEND_FUNCTION(zend_create_unterminated_string);
 static ZEND_FUNCTION(zend_terminate_string);
 static ZEND_FUNCTION(zend_leak_variable);
@@ -656,6 +659,7 @@ static const zend_function_entry ext_functions[] = {
 #else
 	ZEND_RAW_FENTRY("zend_test_deprecated_nodiscard", zif_zend_test_deprecated_nodiscard, arginfo_zend_test_deprecated_nodiscard, ZEND_ACC_DEPRECATED)
 #endif
+	ZEND_FE(zend_test_child_init_count, arginfo_zend_test_child_init_count)
 #if (PHP_VERSION_ID >= 80400)
 	ZEND_RAW_FENTRY("zend_test_aliased", zif_zend_test_void_return, arginfo_zend_test_aliased, 0, NULL, NULL)
 #else
diff --git a/ext/zend_test/test_decl.h b/ext/zend_test/test_decl.h
index b38ffe98827d..494e097fa576 100644
--- a/ext/zend_test/test_decl.h
+++ b/ext/zend_test/test_decl.h
@@ -1,8 +1,8 @@
 /* This is a generated file, edit test.stub.php instead.
- * Stub hash: 9d0e693b29e9e11d82404d486c9b2c2dc81ca1c7 */
+ * Stub hash: 64eb27c89a9a5a378385e5f778cd17cfd67caed8 */
 
-#ifndef ZEND_TEST_DECL_9d0e693b29e9e11d82404d486c9b2c2dc81ca1c7_H
-#define ZEND_TEST_DECL_9d0e693b29e9e11d82404d486c9b2c2dc81ca1c7_H
+#ifndef ZEND_TEST_DECL_64eb27c89a9a5a378385e5f778cd17cfd67caed8_H
+#define ZEND_TEST_DECL_64eb27c89a9a5a378385e5f778cd17cfd67caed8_H
 
 typedef enum zend_enum_ZendTestUnitEnum {
 	ZEND_ENUM_ZendTestUnitEnum_Foo = 1,
@@ -27,4 +27,4 @@ typedef enum zend_enum_ZendTestEnumWithInterface {
 	ZEND_ENUM_ZendTestEnumWithInterface_Bar = 2,
 } zend_enum_ZendTestEnumWithInterface;
 
-#endif /* ZEND_TEST_DECL_9d0e693b29e9e11d82404d486c9b2c2dc81ca1c7_H */
+#endif /* ZEND_TEST_DECL_64eb27c89a9a5a378385e5f778cd17cfd67caed8_H */
diff --git a/ext/zend_test/test_legacy_arginfo.h b/ext/zend_test/test_legacy_arginfo.h
index ef7de4d062fd..f941cf44c573 100644
--- a/ext/zend_test/test_legacy_arginfo.h
+++ b/ext/zend_test/test_legacy_arginfo.h
@@ -1,5 +1,5 @@
 /* This is a generated file, edit test.stub.php instead.
- * Stub hash: 9d0e693b29e9e11d82404d486c9b2c2dc81ca1c7
+ * Stub hash: 64eb27c89a9a5a378385e5f778cd17cfd67caed8
  * Has decl header: yes */
 
 #include "zend_constants.h"
@@ -36,6 +36,8 @@ ZEND_END_ARG_INFO()
 
 #define arginfo_zend_test_deprecated_nodiscard arginfo_zend_trigger_bailout
 
+#define arginfo_zend_test_child_init_count arginfo_zend_trigger_bailout
+
 #define arginfo_zend_test_aliased arginfo_zend_trigger_bailout
 
 #define arginfo_zend_test_deprecated_aliased arginfo_zend_trigger_bailout
@@ -403,6 +405,7 @@ static ZEND_FUNCTION(zend_test_deprecated);
 static ZEND_FUNCTION(zend_test_deprecated_attr);
 static ZEND_FUNCTION(zend_test_nodiscard);
 static ZEND_FUNCTION(zend_test_deprecated_nodiscard);
+static ZEND_FUNCTION(zend_test_child_init_count);
 static ZEND_FUNCTION(zend_create_unterminated_string);
 static ZEND_FUNCTION(zend_terminate_string);
 static ZEND_FUNCTION(zend_leak_variable);
@@ -552,6 +555,7 @@ static const zend_function_entry ext_functions[] = {
 	ZEND_FE(zend_test_deprecated_attr, arginfo_zend_test_deprecated_attr)
 	ZEND_FE(zend_test_nodiscard, arginfo_zend_test_nodiscard)
 	ZEND_FE(zend_test_deprecated_nodiscard, arginfo_zend_test_deprecated_nodiscard)
+	ZEND_FE(zend_test_child_init_count, arginfo_zend_test_child_init_count)
 #if (PHP_VERSION_ID >= 80400)
 	ZEND_RAW_FENTRY("zend_test_aliased", zif_zend_test_void_return, arginfo_zend_test_aliased, 0, NULL, NULL)
 #else
diff --git a/ext/zend_test/tests/child_init.phpt b/ext/zend_test/tests/child_init.phpt
new file mode 100644
index 000000000000..60fd93ff8101
--- /dev/null
+++ b/ext/zend_test/tests/child_init.phpt
@@ -0,0 +1,39 @@
+--TEST--
+GH-22616: Extension child initialization runs once per fork in the child
+--EXTENSIONS--
+zend_test
+pcntl
+--FILE--
+<?php
+var_dump(zend_test_child_init_count());
+$pid = pcntl_fork();
+if ($pid === -1) {
+    throw new Exception('fork failed');
+}
+if ($pid === 0) {
+    var_dump(zend_test_child_init_count());
+    $pid = pcntl_fork();
+    if ($pid === -1) {
+        throw new Exception('fork failed');
+    }
+    if ($pid === 0) {
+        var_dump(zend_test_child_init_count());
+        exit;
+    }
+    pcntl_waitpid($pid, $status);
+    var_dump(pcntl_wifexited($status) && pcntl_wexitstatus($status) === 0);
+    var_dump(zend_test_child_init_count());
+    exit;
+}
+pcntl_waitpid($pid, $status);
+var_dump(pcntl_wifexited($status) && pcntl_wexitstatus($status) === 0);
+var_dump(zend_test_child_init_count());
+?>
+--EXPECT--
+int(0)
+int(1)
+int(2)
+bool(true)
+int(1)
+bool(true)
+int(0)
diff --git a/main/main.c b/main/main.c
index a8cdff9ff688..9029aab26e22 100644
--- a/main/main.c
+++ b/main/main.c
@@ -1847,6 +1847,12 @@ PHPAPI void php_child_init(void)
 	refresh_memory_manager();
 	zend_max_execution_timer_init();
 	php_clear_stat_cache(true, NULL, 0);
+
+	ZEND_HASH_MAP_FOREACH_PTR(&module_registry, zend_module_entry *module) {
+		if (module->module_started && module->child_init_func) {
+			module->child_init_func();
+		}
+	} ZEND_HASH_FOREACH_END();
 }
 
 /* {{{ php_request_startup */
diff --git a/main/php.h b/main/php.h
index 2b72f04d604f..3195ce77c07e 100644
--- a/main/php.h
+++ b/main/php.h
@@ -369,6 +369,7 @@ END_EXTERN_C()
 #define PHP_MINFO		ZEND_MODULE_INFO_N
 #define PHP_GINIT		ZEND_GINIT
 #define PHP_GSHUTDOWN	ZEND_GSHUTDOWN
+#define PHP_CINIT(module)		php_##module##_child_init
 
 #define PHP_MINIT_FUNCTION		ZEND_MODULE_STARTUP_D
 #define PHP_MSHUTDOWN_FUNCTION	ZEND_MODULE_SHUTDOWN_D
@@ -377,6 +378,7 @@ END_EXTERN_C()
 #define PHP_MINFO_FUNCTION		ZEND_MODULE_INFO_D
 #define PHP_GINIT_FUNCTION		ZEND_GINIT_FUNCTION
 #define PHP_GSHUTDOWN_FUNCTION	ZEND_GSHUTDOWN_FUNCTION
+#define PHP_CINIT_FUNCTION(module)	static void php_##module##_child_init(void)
 
 #define PHP_MODULE_GLOBALS		ZEND_MODULE_GLOBALS
 
diff --git a/sapi/fpm/tests/gh22616-child-init.phpt b/sapi/fpm/tests/gh22616-child-init.phpt
new file mode 100644
index 000000000000..e9acab083950
--- /dev/null
+++ b/sapi/fpm/tests/gh22616-child-init.phpt
@@ -0,0 +1,43 @@
+--TEST--
+GH-22616: Extension child initialization runs before FPM requests
+--EXTENSIONS--
+zend_test
+--SKIPIF--
+<?php include "skipif.inc"; ?>
+--FILE--
+<?php
+require_once "tester.inc";
+
+$cfg = <<<EOT
+[global]
+error_log = {{FILE:LOG}}
+[unconfined]
+listen = {{ADDR}}
+pm = static
+pm.max_children = 1
+pm.max_requests = 2
+EOT;
+
+$code = <<<'EOT'
+<?php
+echo zend_test_child_init_count();
+EOT;
+
+$tester = new FPM\Tester($cfg, $code);
+$tester->start(extensions: ['zend_test']);
+$tester->expectLogStartNotices();
+for ($i = 0; $i < 5; $i++) {
+    $tester->request()->expectBody('1');
+}
+$tester->terminate();
+$tester->expectLogTerminatingNotices();
+$tester->close();
+?>
+Done
+--EXPECT--
+Done
+--CLEAN--
+<?php
+require_once "tester.inc";
+FPM\Tester::clean();
+?>