Unified API Update: Enhanced Idempotency Handling

At the core of any robust API integration is idempotency—a mechanism that ensures retrying a request does not result in unintended side effects.

To provide greater visibility into how your requests are handled, we’ve introduced a small but impactful enhancement to our response headers.

This update applies to all services powered by the Unified API — currently SIGN IT, SIGN FR, and E-INVOICE.

The Challenge: "Was This a Replay?"

When a request is retried using the same X-Idempotency-Key, our API correctly returns the cached response from the original operation. This behavior prevents duplicate processing and is fundamental to reliable integrations.

However, this can make debugging more challenging. In certain situations—especially when investigating edge cases—it may not be immediately clear whether a response was freshly generated or served from the idempotency cache.

The Solution: X-Idempotency-Replayed

With the latest Unified API release on 18 Mar 2026, all POST and PATCH responses now include a new header: X-Idempotency-Replayed.

This header explicitly indicates whether a response was replayed from the idempotency cache:

X-Idempotency-Replayed: "true"
The request was identified as a retry, and the response was returned from the cache.

X-Idempotency-Replayed: "false"
The request was processed as a new operation, and the response was generated normally.

With this update, idempotency behavior becomes more transparent—reducing debugging time and helping you build more reliable integrations.