---
title: "Jira / Atlassian Cloud Search REST API returns 400 for invalid custom JQL function queries: 2026-10-08 | Harbyn"
description: "Jira / Atlassian Cloud Search REST API returns 400 for invalid custom JQL function queries, announced Oct 8, 2026."
canonical: "https://harbyn.com/changes/atlassian-jira/2026-10-08-direct-validation-of-custom-jql-functions-in-search-rest-api"
last-updated: 2026-10-08
---

# Jira / Atlassian Cloud Search REST API returns 400 for invalid custom JQL function queries

Markdown version of <https://harbyn.com/changes/atlassian-jira/2026-10-08-direct-validation-of-custom-jql-functions-in-search-rest-api>.

Behavior change - Jira / Atlassian Cloud. low severity. In effect.

The Search REST API now validates queries containing custom JQL functions and returns HTTP 400 Bad Request with detailed errors for invalid or unsupported functions or arguments. Native JQL queries and other uses of the endpoint are unaffected.

## Facts

| Fact | Value |
| --- | --- |
| Vendor | [Jira / Atlassian Cloud](https://harbyn.com/vendors/atlassian-jira.md) |
| Kind | Behavior change |
| Severity | low |
| Status | In effect |
| Announced | Oct 8, 2026 |
| Added to Harbyn | Oct 8, 2026 |
| Lead time | No dated deadline |
| Endpoints | `ANY /rest/api/3/search/jql` |
| Review | Reviewed by a person, extracted by a model |

## Find it in your code

```sh
npx harbyn scan
```

The scanner reads your repository on your machine and reports every file and line that uses the identifiers above. Nothing leaves your machine.

## Sources

Where this event comes from: the page we read, when we read it, and the hash of that snapshot.

- <https://developer.atlassian.com/cloud/jira/platform/changelog/> (changelog, fetched 2026-10-08 06:13 UTC, sha256 `96eb6902119f45a3ad06bf09f402232e0110c9633cc2772089e46ac523c4f6a6`)

## Related changes

### More from Jira / Atlassian Cloud

- [JQL user entity property searches on voter, watcher and creator are deprecated](https://harbyn.com/changes/atlassian-jira/2026-10-07-deprecating-user-entity-property-searches-for-voters-watchers-and-creators.md) (Deprecation, effective Nov 16, 2026)
- [Atlaskit and Forge UI Kit tag, lozenge and badge use the refreshed look by default](https://harbyn.com/changes/atlassian-jira/2026-10-07-refreshed-labelling-system-available-by-default.md) (Behavior change, announced Oct 7, 2026)
- [Forge client fetch permissions allow regional remote URLs](https://harbyn.com/changes/atlassian-jira/2026-10-07-regional-remote-urls-supported-in-client-fetch-permissions.md) (Behavior change, announced Oct 7, 2026)
- [JQL text-field queries with =, IN and NOT IN now match the phrase anywhere in the field](https://harbyn.com/changes/atlassian-jira/2026-10-06-jira-text-queries-using-in-or-not-in-now-use-exact-phrase-search.md) (Behavior change, announced Oct 6, 2026)

### Changes at other vendors

- [Amazon Selling Partner API: ORDER\_CHANGE notifications add PreFulfillmentStatusChange for Amazon Autos](https://harbyn.com/changes/amazon-sp-api/2026-10-14-sp-api-updates-new-listings-items-api-ivp-values-in-eu5-jp-and-ca-stores-oct-3.md) (effective Oct 28, 2026)
- [BigCommerce: 301 redirects will apply only to storefront channels](https://harbyn.com/changes/bigcommerce/2026-10-07-301-redirects-now-apply-to-storefront-channels-only.md) (effective Nov 10, 2026)
- [GitHub: Secret scanning audit log business field changes to enterprise slug](https://harbyn.com/changes/github/2026-10-20-updates-to-github-secret-scanning-7.md) (effective Nov 12, 2026)
- [Let's Encrypt: Default certificate lifetime changes to 64 days](https://harbyn.com/changes/letsencrypt/2026-10-07-64-day-certificate-lifetimes-coming-feb-2027.md) (effective Feb 10, 2027)

[All upcoming deadlines](https://harbyn.com/deadlines.md)