diff --git a/src/backend/bootstrap/bootstrap.c b/src/backend/bootstrap/bootstrap.c
index 3766d8231ac..63378ab3d8c 100644
--- a/src/backend/bootstrap/bootstrap.c
+++ b/src/backend/bootstrap/bootstrap.c
@@ -363,6 +363,8 @@ BootstrapModeMain(int argc, char *argv[], bool check_only)
 	SetProcessingMode(BootstrapProcessing);
 	IgnoreSystemIndexes = true;
 
+	RegisterBuiltinShmemCallbacks();
+
 	InitializeMaxBackends();
 
 	/*
diff --git a/src/backend/postmaster/launch_backend.c b/src/backend/postmaster/launch_backend.c
index 0973010b7dc..ed0f4f2d234 100644
--- a/src/backend/postmaster/launch_backend.c
+++ b/src/backend/postmaster/launch_backend.c
@@ -664,6 +664,8 @@ SubPostmasterMain(int argc, char *argv[])
 	 */
 	LocalProcessControlFile(false);
 
+	RegisterBuiltinShmemCallbacks();
+
 	/*
 	 * Reload any libraries that were preloaded by the postmaster.  Since we
 	 * exec'd this process, those libraries didn't come along with us; but we
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 7a8ee19bdaf..a2de96a9a8e 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -922,6 +922,11 @@ PostmasterMain(int argc, char *argv[])
 	 */
 	ApplyLauncherRegister();
 
+	/*
+	 * Register the shared memory needs of all core subsystems.
+	 */
+	RegisterBuiltinShmemCallbacks();
+
 	/*
 	 * process any libraries that should be preloaded at postmaster start
 	 */
diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c
index 24422a80ab3..e4a6a52f12d 100644
--- a/src/backend/storage/ipc/ipci.c
+++ b/src/backend/storage/ipc/ipci.c
@@ -52,6 +52,7 @@
 #include "storage/procsignal.h"
 #include "storage/shmem_internal.h"
 #include "storage/sinvaladt.h"
+#include "storage/subsystems.h"
 #include "utils/guc.h"
 #include "utils/injection_point.h"
 #include "utils/wait_event.h"
@@ -252,6 +253,26 @@ CreateSharedMemoryAndSemaphores(void)
 		shmem_startup_hook();
 }
 
+/*
+ * Early initialization of various subsystems, giving them a chance to
+ * register their shared memory needs before the shared memory segment is
+ * allocated.
+ */
+void
+RegisterBuiltinShmemCallbacks(void)
+{
+	/*
+	 * Call RegisterShmemCallbacks(...) on each subsystem listed in
+	 * subsystemslist.h
+	 */
+#define PG_SHMEM_SUBSYSTEM(subsystem_callbacks) \
+	RegisterShmemCallbacks(&(subsystem_callbacks));
+
+#include "storage/subsystemlist.h"
+
+#undef PG_SHMEM_SUBSYSTEM
+}
+
 /*
  * Initialize various subsystems, setting up their data structures in
  * shared memory.
diff --git a/src/backend/storage/ipc/shmem.c b/src/backend/storage/ipc/shmem.c
index e1724b0358d..51d974523d4 100644
--- a/src/backend/storage/ipc/shmem.c
+++ b/src/backend/storage/ipc/shmem.c
@@ -77,8 +77,10 @@
  *			);
  *	}
  *
- * Register the callbacks by calling RegisterShmemCallbacks(&MyShmemCallbacks)
- * in the extension's _PG_init() function.
+ * In builtin PostgreSQL code, add the callbacks to the list in
+ * src/include/storage/subsystemlist.h.  In an add-in module, you can register
+ * the callbacks by calling RegisterShmemCallbacks(&MyShmemCallbacks) in the
+ * extension's _PG_init() function.
  *
  * Lifecycle
  * ---------
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 93851269e43..6a9ff3ad225 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -4138,6 +4138,9 @@ PostgresSingleUserMain(int argc, char *argv[],
 	/* read control file (error checking and contains config ) */
 	LocalProcessControlFile(false);
 
+	/* Register the shared memory needs of all core subsystems. */
+	RegisterBuiltinShmemCallbacks();
+
 	/*
 	 * process any libraries that should be preloaded at postmaster start
 	 */
diff --git a/src/include/storage/ipc.h b/src/include/storage/ipc.h
index da32787ab51..b205b00e7a1 100644
--- a/src/include/storage/ipc.h
+++ b/src/include/storage/ipc.h
@@ -77,6 +77,7 @@ extern void check_on_shmem_exit_lists_are_empty(void);
 /* ipci.c */
 extern PGDLLIMPORT shmem_startup_hook_type shmem_startup_hook;
 
+extern void RegisterBuiltinShmemCallbacks(void);
 extern Size CalculateShmemSize(void);
 extern void CreateSharedMemoryAndSemaphores(void);
 #ifdef EXEC_BACKEND
diff --git a/src/include/storage/subsystemlist.h b/src/include/storage/subsystemlist.h
new file mode 100644
index 00000000000..ed43c90bcc3
--- /dev/null
+++ b/src/include/storage/subsystemlist.h
@@ -0,0 +1,23 @@
+/*---------------------------------------------------------------------------
+ * subsystemlist.h
+ *
+ * List of initialization callbacks of built-in subsystems. This is kept in
+ * its own source file for possible use by automatic tools.
+ * PG_SHMEM_SUBSYSTEM is defined in the callers depending on how the list is
+ * used.
+ *
+ * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/storage/subsystemlist.h
+ *---------------------------------------------------------------------------
+ */
+
+/* there is deliberately not an #ifndef SUBSYSTEMLIST_H here */
+
+/*
+ * Note: there are some inter-dependencies between these, so the order of some
+ * of these matter.
+ */
+
+/* TODO: empty for now */
diff --git a/src/include/storage/subsystems.h b/src/include/storage/subsystems.h
new file mode 100644
index 00000000000..38b735bec67
--- /dev/null
+++ b/src/include/storage/subsystems.h
@@ -0,0 +1,30 @@
+/*-------------------------------------------------------------------------
+ *
+ * subsystems.h
+ *	  Provide extern declarations for all the built-in subsystem callbacks
+ *
+ *
+ * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/storage/subsystems.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SUBSYSTEMS_H
+#define SUBSYSTEMS_H
+
+#include "storage/shmem.h"
+
+/*
+ * Extern declarations of all the built-in subsystem callbacks
+ *
+ * The actual list is in subsystemlist.h, so that the same list can be used
+ * for other purposes.
+ */
+#define PG_SHMEM_SUBSYSTEM(callbacks) \
+	extern const ShmemCallbacks callbacks;
+#include "storage/subsystemlist.h"
+#undef PG_SHMEM_SUBSYSTEM
+
+#endif							/* SUBSYSTEMS_H */
diff --git a/src/tools/pginclude/headerscheck b/src/tools/pginclude/headerscheck
index 14c466cc237..24f7416185e 100755
--- a/src/tools/pginclude/headerscheck
+++ b/src/tools/pginclude/headerscheck
@@ -131,6 +131,7 @@ do
 	test "$f" = src/include/postmaster/proctypelist.h && continue
 	test "$f" = src/include/regex/regerrs.h && continue
 	test "$f" = src/include/storage/lwlocklist.h && continue
+	test "$f" = src/include/storage/subsystemlist.h && continue
 	test "$f" = src/include/tcop/cmdtaglist.h && continue
 	test "$f" = src/interfaces/ecpg/preproc/c_kwlist.h && continue
 	test "$f" = src/interfaces/ecpg/preproc/ecpg_kwlist.h && continue