diff --git a/packages/bot-runner/tests/bot-runner-test.ts b/packages/bot-runner/tests/bot-runner-test.ts
index 872b8bd400a..2560eda7815 100644
--- a/packages/bot-runner/tests/bot-runner-test.ts
+++ b/packages/bot-runner/tests/bot-runner-test.ts
@@ -112,6 +112,7 @@ module('timeline handler', () => {
 
   dbAdapter = {
     kind: 'pg',
+    notify: async () => {},
     isClosed: false,
     execute: async (sql: string, opts?: ExecuteOptions) => {
       if (sql.includes('FROM bot_registrations br')) {
diff --git a/packages/bot-runner/tests/command-runner-test.ts b/packages/bot-runner/tests/command-runner-test.ts
index 7e9d82ca861..ab8193f7afe 100644
--- a/packages/bot-runner/tests/command-runner-test.ts
+++ b/packages/bot-runner/tests/command-runner-test.ts
@@ -84,6 +84,7 @@ module('command runner', () => {
     ]);
     let dbAdapter = {
       kind: 'pg',
+      notify: async () => {},
       isClosed: false,
       execute: async (sql: string, opts?: ExecuteOptions) => {
         if (sql.includes('FROM bot_commands WHERE bot_id =')) {
@@ -228,6 +229,7 @@ module('command runner', () => {
     ]);
     let dbAdapter = {
       kind: 'pg',
+      notify: async () => {},
       isClosed: false,
       execute: async (sql: string, opts?: ExecuteOptions) => {
         if (sql.includes('FROM bot_commands WHERE bot_id =')) {
@@ -440,6 +442,7 @@ module('command runner', () => {
     ]);
     let dbAdapter = {
       kind: 'pg',
+      notify: async () => {},
       isClosed: false,
       execute: async (sql: string, opts?: ExecuteOptions) => {
         if (sql.includes('FROM bot_commands WHERE bot_id =')) {
@@ -534,6 +537,7 @@ module('command runner', () => {
     ]);
     let dbAdapter = {
       kind: 'pg',
+      notify: async () => {},
       isClosed: false,
       execute: async (sql: string, opts?: ExecuteOptions) => {
         if (sql.includes('FROM bot_commands WHERE bot_id =')) {
@@ -671,6 +675,7 @@ module('command runner', () => {
     ]);
     let dbAdapter = {
       kind: 'pg',
+      notify: async () => {},
       isClosed: false,
       execute: async (sql: string, opts?: ExecuteOptions) => {
         if (sql.includes('FROM bot_commands WHERE bot_id =')) {
@@ -883,6 +888,7 @@ module('command runner', () => {
     ]);
     let dbAdapter = {
       kind: 'pg',
+      notify: async () => {},
       isClosed: false,
       execute: async (sql: string, opts?: ExecuteOptions) => {
         if (sql.includes('FROM bot_commands WHERE bot_id =')) {
@@ -1002,6 +1008,7 @@ module('command runner', () => {
     ]);
     let dbAdapter = {
       kind: 'pg',
+      notify: async () => {},
       isClosed: false,
       execute: async (sql: string, opts?: ExecuteOptions) => {
         if (sql.includes('FROM bot_commands WHERE bot_id =')) {
diff --git a/packages/host/app/lib/sqlite-adapter.ts b/packages/host/app/lib/sqlite-adapter.ts
index e611786a8ff..df8e599d1aa 100644
--- a/packages/host/app/lib/sqlite-adapter.ts
+++ b/packages/host/app/lib/sqlite-adapter.ts
@@ -53,6 +53,10 @@ export default class SQLiteAdapter implements DBAdapter {
     return await this.internalExecute(sql, opts);
   }
 
+  // SQLite has no pub/sub primitive and the host runs a single in-process
+  // realm with no peers to notify, so this is intentionally a no-op.
+  async notify(_channel: string, _payload: string): Promise<void> {}
+
   private async internalExecute(sql: string, opts?: ExecuteOptions) {
     sql = this.adjustSQL(sql);
     return await this.query(sql, opts);
diff --git a/packages/postgres/pg-adapter.ts b/packages/postgres/pg-adapter.ts
index f9256b9fa98..3e87102efe9 100644
--- a/packages/postgres/pg-adapter.ts
+++ b/packages/postgres/pg-adapter.ts
@@ -291,6 +291,12 @@ export class PgAdapter implements DBAdapter {
     }
   }
 
+  async notify(channel: string, payload: string): Promise<void> {
+    await this.execute('SELECT pg_notify($1, $2)', {
+      bind: [channel, payload],
+    });
+  }
+
   // @deprecated — prefer `subscribe(channel, handler)`. Each call to listen()
   // opens its own dedicated Client connection for the duration of `fn`, which
   // doesn't scale as the number of LISTEN-using callers grows. subscribe()
diff --git a/packages/realm-server/tests/prerender-proxy-test.ts b/packages/realm-server/tests/prerender-proxy-test.ts
index 2fe79955a57..a739a359b1e 100644
--- a/packages/realm-server/tests/prerender-proxy-test.ts
+++ b/packages/realm-server/tests/prerender-proxy-test.ts
@@ -20,6 +20,7 @@ module(basename(__filename), function () {
     function makeDbAdapter(rows: any[]): DBAdapter {
       return {
         kind: 'pg',
+        async notify() {},
         isClosed: false,
         async execute() {
           return rows;
diff --git a/packages/realm-server/tests/realm-file-changes-listener-test.ts b/packages/realm-server/tests/realm-file-changes-listener-test.ts
index 07ac461c844..9007d5d323a 100644
--- a/packages/realm-server/tests/realm-file-changes-listener-test.ts
+++ b/packages/realm-server/tests/realm-file-changes-listener-test.ts
@@ -2,7 +2,6 @@ import { module, test } from 'qunit';
 import { basename } from 'path';
 import type { PgAdapter } from '@cardstack/postgres';
 import type { Realm } from '@cardstack/runtime-common';
-import { query, param } from '@cardstack/runtime-common';
 import { setupDB } from './helpers';
 import {
   RealmFileChangesListener,
@@ -164,13 +163,10 @@ module(basename(__filename), function () {
       });
       await listener.start();
       try {
-        await query(dbAdapter, [
-          `SELECT pg_notify(`,
-          param('realm_file_changes'),
-          `,`,
-          param(`${realmUrl}:src/greeting.gts`),
-          `)`,
-        ]);
+        await dbAdapter.notify(
+          'realm_file_changes',
+          `${realmUrl}:src/greeting.gts`,
+        );
 
         const received = await waitFor(() =>
           invalidations.length > 0 ? invalidations : undefined,
@@ -194,13 +190,10 @@ module(basename(__filename), function () {
       });
       await listener.start();
       try {
-        await query(dbAdapter, [
-          `SELECT pg_notify(`,
-          param('realm_file_changes'),
-          `,`,
-          param(`http://x.test/not-mounted/:file.gts`),
-          `)`,
-        ]);
+        await dbAdapter.notify(
+          'realm_file_changes',
+          `http://x.test/not-mounted/:file.gts`,
+        );
 
         // Wait for the lookup to be recorded (proves the NOTIFY was received
         // and dispatched; the lookup miss then silently drops).
diff --git a/packages/realm-server/tests/screenshot-card-test.ts b/packages/realm-server/tests/screenshot-card-test.ts
index 7e8958a73fc..fd29f312f1f 100644
--- a/packages/realm-server/tests/screenshot-card-test.ts
+++ b/packages/realm-server/tests/screenshot-card-test.ts
@@ -24,6 +24,7 @@ module(basename(__filename), function () {
     function makeDbAdapter(): DBAdapter {
       return {
         kind: 'pg',
+        async notify() {},
         isClosed: false,
         async execute() {
           return [];
diff --git a/packages/runtime-common/db.ts b/packages/runtime-common/db.ts
index 7e92381cff7..9f327683a72 100644
--- a/packages/runtime-common/db.ts
+++ b/packages/runtime-common/db.ts
@@ -20,4 +20,9 @@ export interface DBAdapter {
   ) => Promise<Record<string, PgPrimitive>[]>;
   close: () => Promise<void>;
   getColumnNames: (tableName: string) => Promise<string[]>;
+  // Best-effort cross-instance broadcast on a named channel. Backends that
+  // don't support pub/sub (e.g. in-process SQLite) implement this as a no-op:
+  // the caller must treat it as fire-and-forget cache-coherency, never as
+  // delivery-guaranteed messaging.
+  notify: (channel: string, payload: string) => Promise<void>;
 }
diff --git a/packages/runtime-common/realm.ts b/packages/runtime-common/realm.ts
index ec3c5aea1ab..ffa8d83c5b1 100644
--- a/packages/runtime-common/realm.ts
+++ b/packages/runtime-common/realm.ts
@@ -1125,19 +1125,17 @@ export class Realm {
   // same path. Best-effort — failures are logged and swallowed because the
   // local write already succeeded and a missed NOTIFY is a bounded cache-
   // staleness window (see docs §9 "Cache-invalidation NOTIFY missed"), not
-  // a correctness failure.
+  // a correctness failure. Adapters without pub/sub (e.g. SQLite in the
+  // host/browser context) implement notify as a no-op.
   async #notifyFileChange(path: LocalPath): Promise<void> {
     try {
-      await query(this.#dbAdapter, [
-        `SELECT pg_notify(`,
-        param(REALM_FILE_CHANGES_CHANNEL),
-        `,`,
-        param(`${this.url}:${path}`),
-        `)`,
-      ]);
+      await this.#dbAdapter.notify(
+        REALM_FILE_CHANGES_CHANNEL,
+        `${this.url}:${path}`,
+      );
     } catch (err: unknown) {
       this.#log.warn(
-        `pg_notify ${REALM_FILE_CHANGES_CHANNEL} failed for ${this.url}:${path}: ${String(err)}`,
+        `notify ${REALM_FILE_CHANGES_CHANNEL} failed for ${this.url}:${path}: ${String(err)}`,
       );
     }
   }
diff --git a/packages/runtime-common/tests/run-command-task-shared-tests.ts b/packages/runtime-common/tests/run-command-task-shared-tests.ts
index 824eaaaab8e..3784a2f5f5b 100644
--- a/packages/runtime-common/tests/run-command-task-shared-tests.ts
+++ b/packages/runtime-common/tests/run-command-task-shared-tests.ts
@@ -15,6 +15,7 @@ function makeDBAdapter(
 ): DBAdapter {
   return {
     kind: 'pg',
+    notify: async () => {},
     isClosed: false,
     execute: async (sql: string, opts?: ExecuteOptions) => {
       assertion?.(sql, opts);