diff --git a/pkgs/servers/sql/postgresql/ext/citus.nix b/pkgs/servers/sql/postgresql/ext/citus.nix
index 2b197e70719f..7dd9874a2821 100644
--- a/pkgs/servers/sql/postgresql/ext/citus.nix
+++ b/pkgs/servers/sql/postgresql/ext/citus.nix
@@ -66,7 +66,14 @@ postgresqlBuildExtension (finalAttrs: {
     # "Our soft policy for Postgres version compatibility is to support Citus'
     # latest release with Postgres' 3 latest releases."
     # https://www.citusdata.com/updates/v12-0/#deprecated_features
-    broken = lib.versionOlder postgresql.version "15";
+    broken =
+      lib.versionOlder postgresql.version "15"
+      ||
+        # PostgreSQL 18 support issue upstream: https://github.com/citusdata/citus/issues/7978
+        # Check after next package update.
+        lib.warnIf (finalAttrs.version != "13.0.3") "Is postgresql18Packages.citus still broken?" (
+          lib.versionAtLeast postgresql.version "18"
+        );
     description = "Distributed PostgreSQL as an extension";
     homepage = "https://www.citusdata.com/";
     changelog = "https://github.com/citusdata/citus/blob/${finalAttrs.src.rev}/CHANGELOG.md";
diff --git a/pkgs/servers/sql/postgresql/ext/lantern.nix b/pkgs/servers/sql/postgresql/ext/lantern.nix
index 8cd89a145bde..449be22a31ec 100644
--- a/pkgs/servers/sql/postgresql/ext/lantern.nix
+++ b/pkgs/servers/sql/postgresql/ext/lantern.nix
@@ -51,6 +51,11 @@ postgresqlBuildExtension (finalAttrs: {
   };
 
   meta = {
+    # PostgreSQL 18 support issue upstream: https://github.com/lanterndata/lantern/issues/375
+    # Check after next package update.
+    broken = lib.warnIf (
+      finalAttrs.version != "0.5.0"
+    ) "Is postgresql18Packages.lantern still broken?" (lib.versionAtLeast postgresql.version "18");
     description = "PostgreSQL vector database extension for building AI applications";
     homepage = "https://lantern.dev/";
     changelog = "https://github.com/lanterndata/lantern/blob/${finalAttrs.src.rev}/CHANGELOG.md";
diff --git a/pkgs/servers/sql/postgresql/ext/pg_auto_failover.nix b/pkgs/servers/sql/postgresql/ext/pg_auto_failover.nix
index 3bf237c88b45..4cc2eb58e73d 100644
--- a/pkgs/servers/sql/postgresql/ext/pg_auto_failover.nix
+++ b/pkgs/servers/sql/postgresql/ext/pg_auto_failover.nix
@@ -19,6 +19,11 @@ postgresqlBuildExtension (finalAttrs: {
   buildInputs = postgresql.buildInputs;
 
   meta = {
+    # PostgreSQL 18 support issue upstream: https://github.com/hapostgres/pg_auto_failover/issues/1083
+    # Check after next package update.
+    broken =
+      lib.warnIf (finalAttrs.version != "2.2") "Is postgresql18Packages.pg_auto_failover still broken?"
+        (lib.versionAtLeast postgresql.version "18");
     description = "PostgreSQL extension and service for automated failover and high-availability";
     mainProgram = "pg_autoctl";
     homepage = "https://github.com/citusdata/pg_auto_failover";
diff --git a/pkgs/servers/sql/postgresql/ext/pg_bigm.nix b/pkgs/servers/sql/postgresql/ext/pg_bigm.nix
index 9db198216bb6..f4ed12e2f902 100644
--- a/pkgs/servers/sql/postgresql/ext/pg_bigm.nix
+++ b/pkgs/servers/sql/postgresql/ext/pg_bigm.nix
@@ -19,6 +19,11 @@ postgresqlBuildExtension (finalAttrs: {
   makeFlags = [ "USE_PGXS=1" ];
 
   meta = {
+    # PostgreSQL 18 support issue upstream: https://github.com/pgbigm/pg_bigm/issues/28
+    # Check after next package update.
+    broken = lib.warnIf (
+      finalAttrs.version != "1.2-20240606"
+    ) "Is postgresql18Packages.pg_bigm still broken?" (lib.versionAtLeast postgresql.version "18");
     description = "Text similarity measurement and index searching based on bigrams";
     homepage = "https://pgbigm.osdn.jp/";
     maintainers = [ ];
diff --git a/pkgs/servers/sql/postgresql/ext/pg_cron.nix b/pkgs/servers/sql/postgresql/ext/pg_cron.nix
index 1345dc4b1051..ef019030ddb1 100644
--- a/pkgs/servers/sql/postgresql/ext/pg_cron.nix
+++ b/pkgs/servers/sql/postgresql/ext/pg_cron.nix
@@ -17,6 +17,12 @@ postgresqlBuildExtension (finalAttrs: {
   };
 
   meta = {
+    # PostgreSQL 18 support issue upstream: https://github.com/citusdata/pg_cron/issues/396
+    # Note: already fixed on `main` branch.
+    # Check after next package update.
+    broken = lib.warnIf (
+      finalAttrs.version != "1.6.5"
+    ) "Is postgresql18Packages.pg_cron still broken?" (lib.versionAtLeast postgresql.version "18");
     description = "Run Cron jobs through PostgreSQL";
     homepage = "https://github.com/citusdata/pg_cron";
     changelog = "https://github.com/citusdata/pg_cron/releases/tag/v${finalAttrs.version}";
diff --git a/pkgs/servers/sql/postgresql/ext/pg_ivm.nix b/pkgs/servers/sql/postgresql/ext/pg_ivm.nix
index 4e2e3c3d3776..1c57b2502482 100644
--- a/pkgs/servers/sql/postgresql/ext/pg_ivm.nix
+++ b/pkgs/servers/sql/postgresql/ext/pg_ivm.nix
@@ -23,6 +23,14 @@ postgresqlBuildExtension (finalAttrs: {
     maintainers = with lib.maintainers; [ ivan ];
     platforms = postgresql.meta.platforms;
     license = lib.licenses.postgresql;
-    broken = lib.versionOlder postgresql.version "13";
+    broken =
+      lib.versionOlder postgresql.version "13"
+      ||
+        # PostgreSQL 18 support issue upstream: https://github.com/sraoss/pg_ivm/issues/133
+        # Note: already fixed on `main` branch.
+        # Check after next package update.
+        lib.warnIf (finalAttrs.version != "1.11") "Is postgresql18Packages.pg_ivm still broken?" (
+          lib.versionAtLeast postgresql.version "18"
+        );
   };
 })
diff --git a/pkgs/servers/sql/postgresql/ext/pg_tle.nix b/pkgs/servers/sql/postgresql/ext/pg_tle.nix
index 20355bc0bda0..ea1fbcbcfe4c 100644
--- a/pkgs/servers/sql/postgresql/ext/pg_tle.nix
+++ b/pkgs/servers/sql/postgresql/ext/pg_tle.nix
@@ -19,6 +19,11 @@ postgresqlBuildExtension rec {
   buildInputs = postgresql.buildInputs;
 
   meta = {
+    # PostgreSQL 18 support issue upstream: https://github.com/aws/pg_tle/issues/302
+    # Check after next package update.
+    broken = lib.warnIf (version != "1.5.1") "Is postgresql18Packages.pg_tle still broken?" (
+      lib.versionAtLeast postgresql.version "18"
+    );
     description = "Framework for building trusted language extensions for PostgreSQL";
     homepage = "https://github.com/aws/pg_tle";
     changelog = "https://github.com/aws/pg_tle/releases/tag/v${version}";
diff --git a/pkgs/servers/sql/postgresql/ext/pgroonga.nix b/pkgs/servers/sql/postgresql/ext/pgroonga.nix
index c365aea52bae..82611345c418 100644
--- a/pkgs/servers/sql/postgresql/ext/pgroonga.nix
+++ b/pkgs/servers/sql/postgresql/ext/pgroonga.nix
@@ -34,6 +34,11 @@ postgresqlBuildExtension (finalAttrs: {
   ];
 
   meta = {
+    # PostgreSQL 18 support issue upstream: https://github.com/pgroonga/pgroonga/issues/708
+    # Check after next package update.
+    broken = lib.warnIf (
+      finalAttrs.version != "4.0.1"
+    ) "Is postgresql18Packages.pgroonga still broken?" (lib.versionAtLeast postgresql.version "18");
     description = "PostgreSQL extension to use Groonga as the index";
     longDescription = ''
       PGroonga is a PostgreSQL extension to use Groonga as the index.
diff --git a/pkgs/servers/sql/postgresql/ext/pgvector.nix b/pkgs/servers/sql/postgresql/ext/pgvector.nix
index 36789689bae0..3b440e537ffc 100644
--- a/pkgs/servers/sql/postgresql/ext/pgvector.nix
+++ b/pkgs/servers/sql/postgresql/ext/pgvector.nix
@@ -17,6 +17,12 @@ postgresqlBuildExtension (finalAttrs: {
   };
 
   meta = {
+    # PostgreSQL 18 support issue upstream: https://github.com/pgvector/pgvector/issues/869
+    # Note: already fixed on `master` branch.
+    # Check after next package update.
+    broken = lib.warnIf (
+      finalAttrs.version != "0.8.0"
+    ) "Is postgresql18Packages.pgvector still broken?" (lib.versionAtLeast postgresql.version "18");
     description = "Open-source vector similarity search for PostgreSQL";
     homepage = "https://github.com/pgvector/pgvector";
     changelog = "https://github.com/pgvector/pgvector/raw/v${finalAttrs.version}/CHANGELOG.md";
diff --git a/pkgs/servers/sql/postgresql/ext/pgvectorscale/package.nix b/pkgs/servers/sql/postgresql/ext/pgvectorscale/package.nix
index ffc2f2682d52..8da7420f3bea 100644
--- a/pkgs/servers/sql/postgresql/ext/pgvectorscale/package.nix
+++ b/pkgs/servers/sql/postgresql/ext/pgvectorscale/package.nix
@@ -65,6 +65,11 @@ buildPgrxExtension (finalAttrs: {
   };
 
   meta = {
+    # PostgreSQL 18 support issue upstream: https://github.com/timescale/pgvectorscale/issues/249
+    # Check after next package update.
+    broken =
+      lib.warnIf (finalAttrs.version != "0.7.0") "Is postgresql18Packages.pgvectorscale still broken?"
+        (lib.versionAtLeast postgresql.version "18");
     homepage = "https://github.com/timescale/pgvectorscale";
     teams = [ lib.teams.flyingcircus ];
     description = "Complement to pgvector for high performance, cost efficient vector search on large workloads";
diff --git a/pkgs/servers/sql/postgresql/ext/pgx_ulid.nix b/pkgs/servers/sql/postgresql/ext/pgx_ulid.nix
index d1a7ed141f96..456d7bca4efa 100644
--- a/pkgs/servers/sql/postgresql/ext/pgx_ulid.nix
+++ b/pkgs/servers/sql/postgresql/ext/pgx_ulid.nix
@@ -40,7 +40,15 @@ buildPgrxExtension (finalAttrs: {
 
   meta = {
     # Support for PostgreSQL 13 was removed in 0.2.0: https://github.com/pksunkara/pgx_ulid/blob/084778c3e2af08d16ec5ec3ef4e8f345ba0daa33/CHANGELOG.md?plain=1#L6
-    broken = lib.versionOlder postgresql.version "14";
+    broken =
+      lib.versionOlder postgresql.version "14"
+      ||
+        # PostgreSQL 18 support issue upstream: https://github.com/pksunkara/pgx_ulid/issues/65
+        # Note: already fixed on `master` branch.
+        # Check after next package update.
+        lib.warnIf (finalAttrs.version != "0.2.0") "Is postgresql18Packages.pgx_ulid still broken?" (
+          lib.versionAtLeast postgresql.version "18"
+        );
     description = "ULID Postgres extension written in Rust";
     homepage = "https://github.com/pksunkara/pgx_ulid";
     changelog = "https://github.com/pksunkara/pgx_ulid/blob/v${finalAttrs.version}/CHANGELOG.md";
diff --git a/pkgs/servers/sql/postgresql/ext/rum.nix b/pkgs/servers/sql/postgresql/ext/rum.nix
index bc93ff3b76a6..99f0d336d525 100644
--- a/pkgs/servers/sql/postgresql/ext/rum.nix
+++ b/pkgs/servers/sql/postgresql/ext/rum.nix
@@ -29,6 +29,11 @@ postgresqlBuildExtension (finalAttrs: {
   };
 
   meta = {
+    # PostgreSQL 18 support issue upstream: https://github.com/postgrespro/rum/issues/156
+    # Check after next package update.
+    broken = lib.warnIf (finalAttrs.version != "1.3.14") "Is postgresql18Packages.rum still broken?" (
+      lib.versionAtLeast postgresql.version "18"
+    );
     description = "Full text search index method for PostgreSQL";
     homepage = "https://github.com/postgrespro/rum";
     license = lib.licenses.postgresql;
diff --git a/pkgs/servers/sql/postgresql/ext/sqlite_fdw.nix b/pkgs/servers/sql/postgresql/ext/sqlite_fdw.nix
index 1ade4b6e90fa..dd5da727beee 100644
--- a/pkgs/servers/sql/postgresql/ext/sqlite_fdw.nix
+++ b/pkgs/servers/sql/postgresql/ext/sqlite_fdw.nix
@@ -22,6 +22,12 @@ postgresqlBuildExtension (finalAttrs: {
   makeFlags = [ "USE_PGXS=1" ];
 
   meta = {
+    # PostgreSQL 18 support issue upstream: https://github.com/pgspider/sqlite_fdw/issues/117
+    # Note: already fixed on `master` branch.
+    # Check after next package update.
+    broken = lib.warnIf (
+      finalAttrs.version != "2.5.0"
+    ) "Is postgresql18Packages.sqlite_fdw still broken?" (lib.versionAtLeast postgresql.version "18");
     description = "SQLite Foreign Data Wrapper for PostgreSQL";
     homepage = "https://github.com/pgspider/sqlite_fdw";
     changelog = "https://github.com/pgspider/sqlite_fdw/releases/tag/v${finalAttrs.version}";
diff --git a/pkgs/servers/sql/postgresql/ext/tds_fdw.nix b/pkgs/servers/sql/postgresql/ext/tds_fdw.nix
index e89acc14811e..f6a4ba6f9607 100644
--- a/pkgs/servers/sql/postgresql/ext/tds_fdw.nix
+++ b/pkgs/servers/sql/postgresql/ext/tds_fdw.nix
@@ -20,6 +20,11 @@ postgresqlBuildExtension (finalAttrs: {
   };
 
   meta = {
+    # PostgreSQL 18 support issue upstream: https://github.com/tds-fdw/tds_fdw/issues/384
+    # Check after next package update.
+    broken = lib.warnIf (
+      finalAttrs.version != "2.0.4"
+    ) "Is postgresql18Packages.tds_fdw still broken?" (lib.versionAtLeast postgresql.version "18");
     description = "PostgreSQL foreign data wrapper to connect to TDS databases (Sybase and Microsoft SQL Server)";
     homepage = "https://github.com/tds-fdw/tds_fdw";
     changelog = "https://github.com/tds-fdw/tds_fdw/releases/tag/v${finalAttrs.version}";
diff --git a/pkgs/servers/sql/postgresql/ext/timescaledb.nix b/pkgs/servers/sql/postgresql/ext/timescaledb.nix
index 2fe5cf171589..ea60aa516889 100644
--- a/pkgs/servers/sql/postgresql/ext/timescaledb.nix
+++ b/pkgs/servers/sql/postgresql/ext/timescaledb.nix
@@ -101,6 +101,13 @@ postgresqlBuildExtension (finalAttrs: {
     maintainers = with lib.maintainers; [ kirillrdy ];
     platforms = postgresql.meta.platforms;
     license = with lib.licenses; if enableUnfree then tsl else asl20;
-    broken = lib.versionOlder postgresql.version "15";
+    broken =
+      lib.versionOlder postgresql.version "15"
+      ||
+        # PostgreSQL 18 support issue upstream: https://github.com/timescale/timescaledb/issues/8233
+        # Check after next package update.
+        lib.warnIf (finalAttrs.version != "2.21.1") "Is postgresql18Packages.timescaledb still broken?" (
+          lib.versionAtLeast postgresql.version "18"
+        );
   };
 })
diff --git a/pkgs/servers/sql/postgresql/ext/vectorchord/package.nix b/pkgs/servers/sql/postgresql/ext/vectorchord/package.nix
index 2217c9b0d275..eeb3bcef1e3e 100644
--- a/pkgs/servers/sql/postgresql/ext/vectorchord/package.nix
+++ b/pkgs/servers/sql/postgresql/ext/vectorchord/package.nix
@@ -123,6 +123,12 @@ buildPgrxExtension (finalAttrs: {
   };
 
   meta = {
+    # PostgreSQL 18 is not yet supported
+    # Will be supported in the next release (likely 0.5.0), as it's already supported in the main branch
+    # Check after next package update.
+    broken = lib.warnIf (
+      finalAttrs.version != "0.4.2"
+    ) "Is postgresql18Packages.vectorchord still broken?" (lib.versionAtLeast postgresql.version "18");
     changelog = "https://github.com/tensorchord/VectorChord/releases/tag/${finalAttrs.version}";
     description = "Scalable, fast, and disk-friendly vector search in Postgres, the successor of pgvecto.rs";
     homepage = "https://github.com/tensorchord/VectorChord";