Qdrant Vector Store node: "fetch failed" / UND_ERR_INVALID_ARG when loading collections dropdown (undici dispatcher version mismatch)

[bestillcat]

Bug Description

The Qdrant Vector Store node's collection dropdown fails with a generic fetch failed error and no usable diagnostic info. Root cause isolated by calling @qdrant/js-client-rest directly inside the n8n container:

Failed to obtain server version. Unable to check client-server compatibility.
CLIENT ERROR: TypeError: fetch failed
at Object.processResponse (node:internal/deps/undici/undici:13720:20)
...
[cause]: InvalidArgumentError: invalid onError method
at Agent.dispatch (.../undici@6.28.0/node_modules/undici/lib/dispatcher/dispatcher-base.js:189:15)
...
code: 'UND_ERR_INVALID_ARG'

This is a known class of bug where a dispatcher created by one undici instance (the standalone undici@6.28.0 npm package bundled as a dependency of @qdrant/js-client-rest@1.16.2) is passed to a different undici instance backing global fetch (Node's built-in undici), and the two versions' internal dispatcher handler interfaces are incompatible.

To Reproduce

1. Confirmed Qdrant instance is reachable and API key is valid — direct fetch() and curl calls with the same URL/key from inside the n8n container succeed with 200.
2. n8n's built-in Qdrant credential test (generic HTTP request helper) succeeds.
3. Reproduced the failure directly by requiring @qdrant/js-client-rest from n8n's own node_modules and calling client.getCollections() — throws the error above every time.

Expected behavior

Collections dropdown populates normally; underlying client library should not throw a dispatcher compatibility error.

Debug Info

Debug info

core

• n8nVersion: 2.37.10
• platform: docker (self-hosted)
• nodeJsVersion: 26.5.1
• nodeEnv: production
• database: postgres
• executionMode: regular
• concurrency: -1
• license: enterprise (production)
• consumerId: 253ef39d-3ec0-4294-9620-35943ee44bb5

storage

• success: all
• error: all
• progress: false
• manual: true
• binaryMode: filesystem

pruning

• enabled: true
• maxAge: 336 hours
• maxCount: 10000 executions

client

• userAgent: mozilla/5.0 (windows nt 10.0; win64; x64) applewebkit/537.36 (khtml, like gecko) chrome/152.0.0.0 safari/537.36
• isTouchDevice: false

security

• secureCookie: false

cluster

• instanceCount: 1
• versions: 2.37.10
• instances:
  • instanceKey: 1198cb9b-93b8-493e-91ed-6def97573fd2, hostId: main-fb46d8e5a77b, instanceType: main, instanceRole: leader, version: 2.37.10
• checks:
  • check: hostid-clash, status: succeeded, warnings: -
  • check: lifecycle, status: succeeded, warnings: -
  • check: split-brain, status: succeeded, warnings: -
  • check: version-mismatch, status: succeeded, warnings: -

Generated at: 2026-09-05T03:44:00.252Z

Operating System

Rocky Linux 10.2

n8n Version

n8n version: 2.37.10 (self-hosted, Podman/Quadlet)

Node.js Version

v26.5.1

Database

PostgreSQL

Execution mode

main (default)

Hosting

self hosted

[n8n-assistant]

Hey @bestillcat,

Thank you for reaching out! We’ve received your issue and are looking into it. To help us track this internally, we’ve created a Linear ticket with the reference: "GHC-9418".

We’ll keep you updated as we make progress, but if you have any additional details or context to share, feel free to add them here - it’s always helpful!

Thanks for your patience and for bringing this to our attention.

---

For INTERNAL use only: GHC-9418

[bestillcat]

Update — this is not limited to the collection dropdown. Manually entering the collection name (bypassing the list-search/resource-locator dropdown) also fails with the same error during actual node execution. This confirms the entire node is broken for this Qdrant client/undici combination, not just the UI helper — the node cannot connect to Qdrant at all in this configuration.

[steinthomas]

I can confirm the problem described above. The Qdrant Vector Store node still works without issues in n8n version 2.36.9 (released 2026-08-31), whereas all newer/later versions fail with the following error message: "TypeError: fetch failed".

[Atomic1024]

I can confirm the issue described above. In n8n version 2.36.9 (released on 2026-08-31), the Qdrant vector storage node still works normally, but all updated versions will show the following error message: "TypeError: fetch failed".