diff --git a/graphile/graphile-test/src/context.ts b/graphile/graphile-test/src/context.ts
index be26f3c32..f16e7c8ab 100644
--- a/graphile/graphile-test/src/context.ts
+++ b/graphile/graphile-test/src/context.ts
@@ -10,13 +10,15 @@ import type {
 import { parse, print, Kind } from 'graphql';
 import type { GraphileConfig } from 'graphile-config';
 import { execute } from 'grafast';
-import { withPgClientFromPgService } from 'graphile-build-pg';
 import { makePgService } from 'postgraphile/adaptors/pg';
-import type { Client, Pool } from 'pg';
+import type { Client, Pool, QueryConfig } from 'pg';
 import type { GetConnectionOpts, GetConnectionResult } from 'pgsql-test';
 
 import type { GetConnectionsInput } from './types';
 
+const EMPTY_ARRAY: readonly PgNotice[] = Object.freeze([]);
+const $$queue = Symbol('withPgClientQueue');
+
 /**
  * V4-compatible error format (plain object, not GraphQLError class)
  */
@@ -176,6 +178,204 @@ function normalizeResult<T>(result: ExecutionResult, document?: DocumentNode): T
   return normalized as T;
 }
 
+interface PgNotice {
+  severity: string;
+  message: string;
+  code?: string;
+  detail?: string;
+  hint?: string;
+  position?: number;
+  internalPosition?: number;
+  internalQuery?: string;
+  where?: string;
+  schema?: string;
+  table?: string;
+  column?: string;
+  dataType?: string;
+  constraint?: string;
+  file?: string;
+  line?: number;
+  routine?: string;
+}
+
+interface PgQueryResult {
+  rows: unknown[];
+  rowCount: number | null;
+  notices: readonly PgNotice[];
+}
+
+interface AdaptedPgClient {
+  rawClient: Client;
+  withTransaction(callback: (client: AdaptedPgClient) => Promise<unknown>): Promise<unknown>;
+  query(opts: { text: string; values?: unknown[]; arrayMode?: boolean }): Promise<PgQueryResult>;
+}
+
+function convertNotice(n: Record<string, unknown>): PgNotice {
+  return {
+    severity: (n.severity as string) ?? 'NOTICE',
+    message: (n.message as string) ?? '',
+    code: n.code as string | undefined,
+    detail: n.detail as string | undefined,
+    hint: n.hint as string | undefined,
+    position: n.position != null ? parseInt(String(n.position), 10) : undefined,
+    internalPosition: n.internalPosition != null ? parseInt(String(n.internalPosition), 10) : undefined,
+    internalQuery: n.internalQuery as string | undefined,
+    where: n.where as string | undefined,
+    schema: n.schema as string | undefined,
+    table: n.table as string | undefined,
+    column: n.column as string | undefined,
+    dataType: n.dataType as string | undefined,
+    constraint: n.constraint as string | undefined,
+    file: n.file as string | undefined,
+    line: n.line != null ? parseInt(String(n.line), 10) : undefined,
+    routine: n.routine as string | undefined,
+  };
+}
+
+async function pgClientQuery(pgClient: Client, queryObj: QueryConfig): Promise<PgQueryResult> {
+  let notices: PgNotice[] | null = null;
+  const addNotice = (n: Record<string, unknown>) => {
+    const converted = convertNotice(n);
+    if (notices === null) {
+      notices = [converted];
+    } else {
+      notices.push(converted);
+    }
+  };
+  pgClient.addListener('notice', addNotice);
+  try {
+    const { rows, rowCount } = await pgClient.query(queryObj);
+    return { rows, rowCount, notices: notices ?? EMPTY_ARRAY };
+  } finally {
+    pgClient.removeListener('notice', addNotice);
+  }
+}
+
+function newNodePostgresPgClient(
+  pgClient: Client,
+  txLevel: number,
+  alwaysQueue: boolean,
+  alreadyInTransaction: boolean
+): AdaptedPgClient {
+  let queue: Promise<unknown> | null = null;
+  const addToQueue = <T>(callback: () => Promise<T>): Promise<T> => {
+    const result = queue ? queue.then(callback) : callback();
+    const clearIfSame = () => {
+      if (queue === newQueue) {
+        queue = null;
+      }
+    };
+    const newQueue = result.then(clearIfSame, clearIfSame);
+    queue = newQueue;
+    return result;
+  };
+  return {
+    rawClient: pgClient,
+    withTransaction(callback) {
+      return addToQueue(async () => {
+        if (txLevel === 0 && !alreadyInTransaction) {
+          await pgClient.query({ text: 'begin' });
+        } else {
+          await pgClient.query({
+            text: `savepoint tx${txLevel === 0 ? '' : txLevel}`,
+          });
+        }
+        try {
+          const newClient = newNodePostgresPgClient(pgClient, txLevel + 1, alwaysQueue, alreadyInTransaction);
+          const innerResult = await callback(newClient);
+          if (txLevel === 0 && !alreadyInTransaction) {
+            await pgClient.query({ text: 'commit' });
+          } else {
+            await pgClient.query({
+              text: `release savepoint tx${txLevel === 0 ? '' : txLevel}`,
+            });
+          }
+          return innerResult;
+        } catch (e) {
+          try {
+            if (txLevel === 0 && !alreadyInTransaction) {
+              await pgClient.query({ text: 'rollback' });
+            } else {
+              await pgClient.query({
+                text: `rollback to savepoint tx${txLevel === 0 ? '' : txLevel}`,
+              });
+            }
+          } catch (_e2) {
+            console.error(`Error occurred whilst rolling back: ${e}`);
+          }
+          throw e;
+        }
+      });
+    },
+    query(opts) {
+      if (queue || alwaysQueue) {
+        return addToQueue(doIt);
+      } else {
+        return doIt();
+      }
+      function doIt() {
+        const { text, values, arrayMode } = opts;
+        const queryObj: QueryConfig = arrayMode
+          ? { text, values, rowMode: 'array' as const } as QueryConfig
+          : { text, values };
+        return pgClientQuery(pgClient, queryObj);
+      }
+    },
+  };
+}
+
+async function makeNodePostgresWithPgClient_inner<T>(
+  pgClient: Client & { [key: symbol]: Promise<unknown> | null },
+  pgSettings: Record<string, string> | null,
+  callback: (client: AdaptedPgClient) => T | Promise<T>,
+  alwaysQueue: boolean,
+  alreadyInTransaction: boolean
+): Promise<T> {
+  const pgSettingsEntries: [string, string][] = [];
+  if (pgSettings != null) {
+    for (const [key, value] of Object.entries(pgSettings)) {
+      if (value == null) continue;
+      pgSettingsEntries.push([key, '' + value]);
+    }
+  }
+  while (pgClient[$$queue]) {
+    await pgClient[$$queue];
+  }
+  return (pgClient[$$queue] = (async () => {
+    try {
+      if (pgSettingsEntries.length > 0) {
+        await pgClient.query({
+          text: alreadyInTransaction ? 'savepoint tx' : 'begin',
+        });
+        try {
+          await pgClient.query({
+            text: 'select set_config(el->>0, el->>1, true) from json_array_elements($1::json) el',
+            values: [JSON.stringify(pgSettingsEntries)],
+          });
+          const client = newNodePostgresPgClient(pgClient, 1, alwaysQueue, alreadyInTransaction);
+          const result = await callback(client);
+          await pgClient.query({
+            text: alreadyInTransaction ? 'release savepoint tx' : 'commit',
+          });
+          return result;
+        } catch (e) {
+          await pgClient.query({
+            text: alreadyInTransaction
+              ? 'rollback to savepoint tx'
+              : 'rollback',
+          });
+          throw e;
+        }
+      } else {
+        const client = newNodePostgresPgClient(pgClient, 0, alwaysQueue, alreadyInTransaction);
+        return await callback(client);
+      }
+    } finally {
+      pgClient[$$queue] = null;
+    }
+  })()) as Promise<T>;
+}
+
 interface PgSettings {
   [key: string]: string;
 }
@@ -262,23 +462,34 @@ export const runGraphQLInContext = async <T = ExecutionResult>({
     ),
   };
 
-  // Provide a custom withPgClient function that uses the test client
+  // Provide a custom withPgClient function that uses the test client.
   // This ensures GraphQL operations run within the test transaction
-  // instead of getting a new connection from the pool
+  // instead of getting a new connection from the pool.
+  //
+  // Uses the full adapted client from @dataplan/pg with:
+  // - Query queuing to serialize concurrent calls
+  // - Proper pgSettings handling with savepoint wrapping
+  // - arrayMode → rowMode translation for pg client compatibility
+  const isInTransaction = !input.useRoot;
   const withPgClientKey = pgService.withPgClientKey ?? 'withPgClient';
-  contextValue[withPgClientKey] = async <T>(
-    _pgSettings: Record<string, string> | null,
-    callback: (client: Client) => T | Promise<T>
-  ): Promise<T> => {
-    // Simply use the test client - it's already in a transaction
-    // The pgSettings have already been applied above via setContextOnClient
-    return callback(pgClient);
+  const adaptedWithPgClient = async (
+    callerPgSettings: Record<string, string> | null,
+    callback: (client: AdaptedPgClient) => unknown
+  ) => {
+    return makeNodePostgresWithPgClient_inner(
+      pgClient as Client & { [key: symbol]: Promise<unknown> | null },
+      callerPgSettings,
+      callback,
+      true,
+      isInTransaction
+    );
   };
-
-  // Check if we're in a transaction by looking at the test client's transaction state
-  // When useRoot is true, we might not be in a transaction
-  // pgsql-test's `db` client is in a transaction, but `pg` (root) client may not be
-  const isInTransaction = !input.useRoot;
+  let released = false;
+  (adaptedWithPgClient as unknown as { release: () => void }).release = () => {
+    if (released) return;
+    released = true;
+  };
+  contextValue[withPgClientKey] = adaptedWithPgClient;
 
   // Wrap the entire query execution in a savepoint if we're in a transaction
   // This matches v4 PostGraphile behavior where each mutation is wrapped in a savepoint
@@ -297,6 +508,7 @@ export const runGraphQLInContext = async <T = ExecutionResult>({
     rawResult = await execute({
       schema,
       document,
+      middleware: null,
       variableValues: variables ?? undefined,
       contextValue,
       resolvedPreset,