> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cowboy.inc/llms.txt
> Use this file to discover all available pages before exploring further.

# E1817 — Event payload schema does not match the declared schema

> Event payload schema does not match the declared schema

# E1817 — Event payload schema does not match the declared schema

| Property | Value |
| - | - |
| **Code** | `1817` |
| **Slug** | `E1817` |
| **Category** | `runtime` (Runtime) |
| **CIP** | CIP-29 |

## What happened

Event payload schema does not match the declared schema.

This is the receipt's `what` text, produced by the host-call result `HostError::EventSchemaMismatch`.

## Why it happened

The node rejected the operation with `E1817` (category `runtime`, Runtime). The receipt's `why` field carries the specific cause and `context` carries structured details, when the emitter attaches any.

The normative rule is in CIP-29.

## How to fix

Use the same payload schema identifier for the emitter and subscriber, or omit the optional declaration for opaque payloads.

## Receipt example

```json theme={null}
{
  "code": 1817,
  "slug": "E1817",
  "category": "runtime",
  "what": "event payload schema does not match the declared schema",
  "fix": "Use the same payload schema identifier for the emitter and subscriber, or omit the optional declaration for opaque payloads.",
  "docs_url": "https://docs.cowboy.inc/errors/E1817"
}
```

***

> [card] [All Error Codes](https://docs.cowboy.inc/errors/overview.md)
>
> View the complete error code reference


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