## TL;DR

Fix: Maintainer timvisee's guidance: with no incoming writes, upgrade each node in isolation (cluster comms not needed), then use the --reinit flag (added in 1.12.2 via PR #(5265) on the final upgrade; always snapshot/back up the cluster first. A community member posted a verified step-by-step upgrade path in the thread.

## The error

```text
Upgrading clusters 1.10.0 -> 1.11.x consistently breaks cluster communication with 'h2 protocol error: http2 error: stream error received: frame with invalid size', rendering many operations non-functional.
```

## Fix

1. Maintainer timvisee's guidance: with no incoming writes, upgrade each node in isolation (cluster comms not needed), then use the --reinit flag (added in 1.12.2 via PR #(5265) on the final upgrade; always snapshot/back up the cluster first.
2. A community member posted a verified step-by-step upgrade path in the thread.

Success check: the symptom above is gone and the original operation completes.

## When to use

- You hit this exact symptom in qdrant.
- You want the verified fix without digging through the thread.

## When not to use

- A different error in qdrant, even a similar-looking one.
- General qdrant setup or credential questions.

## Compatibility

- Qdrant (qdrant/qdrant)

## Variant phrasings

- How to fix "upgrade from 1.10.0 to 1.11.0 consistently fail with h2 protocol error" in qdrant
- qdrant: upgrade from 1.10.0 to 1.11.0 consistently fail with h2 protocol error
- upgrade from 1.10.0 to 1.11.0 consistently fail with h2 protocol problem

## Source

- https://github.com/qdrant/qdrant/issues/6541

---

## Vectle citations

- Exact version: <https://vectle.com/skills/skl_UXTUlNJNN_3f-MNjBWZaLw/versions/skv_lwHW1vJKYDpPh7fycLeARQ>
- Canonical HTML skill page: <https://vectle.com/skills/skl_UXTUlNJNN_3f-MNjBWZaLw>
- Current Markdown URL: <https://vectle.com/skills/skl_UXTUlNJNN_3f-MNjBWZaLw/markdown>

## Selected public attribution and original notices/references

```json
{
  "author": "issueatlas",
  "client": null,
  "notices_and_references": [
    "https://github.com/qdrant/qdrant/issues/6541"
  ]
}
```