@azure/functions-extensions-servicebus does not work with @azure/functions version 4.9.0

[kamaz]

@azure/functions-extensions-servicebus does not work with @azure/functions version 4.9.0, when starting function following errors is being thrown:

[2025-12-19T13:35:13.429Z] Executed 'Functions.serviceBusTrigger' (Failed, Id=b4becf29-6453-4d45-82a0-29b52102c64f, Duration=2ms)
[2025-12-19T13:35:13.429Z] System.Private.CoreLib: Exception while executing function: Functions.serviceBusTrigger. System.Private.CoreLib: Result: Failure
[2025-12-19T13:35:13.429Z] Exception: Unable to create client. Please register the extensions library with your function app. Error: Factory for type "AzureServiceBusReceivedMessage" is not registered. Register a factory implementation before creating clients.
[2025-12-19T13:35:13.429Z] Stack: Error: Unable to create client. Please register the extensions library with your function app. Error: Factory for type "AzureServiceBusReceivedMessage" is not registered. Register a factory implementation before creating clients.
[2025-12-19T13:35:13.429Z]     at fromRpcTypedData (file:///pnpm-esbuild-exponential-backoff/dist/dist/src/functions/index.mjs:57207:25)
[2025-12-19T13:35:13.429Z]     at InvocationModel.<anonymous> (file:///pnpm-esbuild-exponential-backoff/dist/dist/src/functions/index.mjs:56595:73)
[2025-12-19T13:35:13.429Z]     at Generator.next (<anonymous>)
[2025-12-19T13:35:13.429Z]     at file:///pnpm-esbuild-exponential-backoff/dist/dist/src/functions/index.mjs:56470:79
[2025-12-19T13:35:13.429Z]     at new Promise (<anonymous>)
[2025-12-19T13:35:13.429Z]     at __awaiter2 (file:///pnpm-esbuild-exponential-backoff/dist/dist/src/functions/index.mjs:56449:22)
[2025-12-19T13:35:13.429Z]     at InvocationModel.getArguments (file:///pnpm-esbuild-exponential-backoff/dist/dist/src/functions/index.mjs:56570:24)
[2025-12-19T13:35:13.429Z]     at y.<anonymous> (/opt/homebrew/Cellar/azure-functions-core-tools@4/4.2.2/workers/node/dist/src/worker-bundle.js:2:38523)
[2025-12-19T13:35:13.429Z]     at Generator.next (<anonymous>)
[2025-12-19T13:35:13.429Z]     at o (/opt/homebrew/Cellar/azure-functions-core-tools@4/4.2.2/workers/node/dist/src/worker-bundle.js:2:36540).

If you downgrade @azure/functions version to 4.7.4-preview all works as expected.

This can be replicated by upgrading package version in the https://github.com/swapnil-nagar/msft-azure-service-bus-batch/blob/swapnil/serviceBusMessageSettlementFix/pnpm-esbuild-exponential-backoff/package.json.

[swapnil-nagar]

Can you try the latest preview version of the @azure/Functions-extenstion-service to 0.3.6-preview.

You can try this sample for reference
https://github.com/Azure/azure-functions-nodejs-extensions/blob/main/azure-functions-nodejs-extensions-servicebus/samples/serviceBusTriggerExponentialBackOff/package.json

[kamaz]

@swapnil-nagar Thanks for the update, yes it resolves the issue in the example application, but the problem still persists in our codebase.

After further investigation, we traced this to the ResourceFactoryResolver singleton being used across @azure/functions-extensions-base and @azure/functions.

Minimal reproduction:

• @azure/functions is marked as external in esbuild
• @azure/functions-extensions-base is bundled
• Both packages reference ResourceFactoryResolver

At runtime, this results in two separate module instances, which means the singleton is instantiated twice.

As you know we have to keep @azure/functions external for OpenTelemetry to work correctly. At the same time, we bundle @azure/functions-extensions-base to reduce package size and limit cold-start impact.

Given these constraints in a Node ESM + esbuild setup, the only reliable way to ensure a shared singleton between bundled and non-bundled code is to store the singleton on globalThis (for example, using a Symbol.for(...) key), ensuring both module instances reference the same object to support bundlers.

[swapnil-nagar]

Instead of this you can try following solutions.

1. PublicHoistPattern in your package.json. https://pnpm.io/settings#publichoistpattern

{
  "pnpm": {
    "publicHoistPattern": ["@azure/functions-extensions-base"]
  }
}

2. If not then can we mark the base and serviceBus package as external as well and test.

// esbuild.config.ts
import { build } from "esbuild";

build({
  entryPoints: ["src/index.ts"],
  ....
  ....
  external: ["@azure/functions-extensions-base"], // ← key
});

If none of the above solution works for you, I will discuss globalThis solution in our sync.

[swapnil-nagar]

Let me know if the issue persists? Else I will mark it as closed.