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

# Flowker webhook and external API header contract

> Flowker documentation now clarifies webhook accepted headers and fail-closed external API requirements.

<Badge stroke icon="calendar-days" iconType="regular">August 21, 2026</Badge> <Badge stroke icon="file-code" iconType="regular">Documentation correction</Badge> <Badge color="red" size="lg" stroke icon="triangle-exclamation" iconType="regular">Action required</Badge>

## Affects

***

Teams that configure Flowker webhook triggers or external OpenAPI integrations.

## What changed

***

Webhook triggers can declare `accepted_headers`; credential headers remain excluded from that immutable configuration. The documentation also clarifies the header-ingestion rules exposed through `_webhook.headers`.

External OpenAPI integrations support static `config.headers` and fail closed when required headers or query parameters are absent. The documented validation outcomes are `FLK-0954` for missing required inputs, `FLK-0955` for malformed static headers, and `FLK-0957` for invalid accepted webhook headers.

This is a documentation correction of implemented contracts. It does not announce a runtime release.

## Impact

***

**Classification: Action required.** A webhook or external API configuration based on the former rules can fail validation or omit required request inputs.

## What you need to do

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<Steps>
  <Step>Review webhook `accepted_headers` and downstream use of `_webhook.headers`.</Step>
  <Step>Confirm static headers and every required header and query parameter for external OpenAPI integrations.</Step>
  <Step>Handle the documented validation outcomes before the next workflow deployment.</Step>
</Steps>

### Deadline

Complete the review before the next affected workflow deployment.

## Resources

***

* [Configuring a webhook trigger](/en/products/flowker/configuring-a-webhook-trigger)
* [Connecting your own API](/en/products/flowker/connecting-your-own-api)
* [Flowker error list](/en/reference/products/flowker/flowker-error-list)