GitHub · Pull requests · Issues REST API · Checked October 27, 2026

GitHub: a label or an assignee is not added to a pull request

Labels and assignees of a pull request are set from its right sidebar (Labels, Assignees), and in the REST API through the Issues endpoints: every pull request is an issue, so the actions both share, such as managing assignees, labels and milestones, are provided there (GitHub's REST API endpoints for labels, checked October 27, 2026). Applying a label takes triage access to the repository, and only users with push access can add assignees: from anyone else, the assignees are silently ignored.

POST /repos/OWNER/REPO/issues/NUMBER/labels      {"labels": ["bug"]}
POST /repos/OWNER/REPO/issues/NUMBER/assignees   {"assignees": ["octocat"]}
GET  /repos/OWNER/REPO/assignees/octocat         204, or 404

Why a label is not added

Access: anyone with triage access to a repository can apply and dismiss labels; creating, editing and deleting labels takes write access (GitHub's managing labels).
Another repository: a label is applied in the repository it was created in, and a change to labels in one repository has no effect on the labels of another. Organization owners can customize the default labels of new repositories.
The REST answers: adding labels to an issue answers 200, 404 (resource not found), 410 (gone), or 422 when validation failed or the endpoint has been spammed. Removing one label answers 404 if that label does not exist.
Added or replaced: POST adds to the existing labels; PUT sets the labels and replaces the existing ones, and an empty array removes them all.

Why an assignee is not added

Who can be assigned: yourself, anyone who has commented on the issue or pull request, anyone with write permissions to the repository, and organization members with read permissions to it (GitHub's assigning issues and pull requests).
The limit: an issue or a pull request takes up to 10 assignees. Adding them in the REST API does not replace those already assigned.
No push access: only users with push access can add or remove assignees; otherwise the assignees are silently ignored (GitHub's REST API endpoints for issue assignees).
Check first: GET /repos/OWNER/REPO/assignees/USERNAME answers 204 when the user can be assigned to issues in the repository, and 404 otherwise; GET /repos/OWNER/REPO/issues/NUMBER/assignees/USERNAME asks the same for one issue or pull request.

What to do

Ask for access: triage access to apply labels, push access to assign people with the REST API.
Create the label in this repository: with write access, create it, then apply it.
Read the result: after adding assignees, look at the assignees in the answer: an assignee who is not there was ignored.
Labels in a compare URL: the labels query parameter on the compare page needs permission to add labels. See pull request templates.

In IntelliJ IDEA: it sends the whole list, not one label or assignee

How the GitHub support built into IntelliJ IDEA changes the labels and assignees of a pull request, in its source (checked October 31, 2026; IntelliJ IDEA: GHPRDetailsServiceImpl.kt, GithubApiRequests.kt, GHPRRepositoryDataServiceImpl.kt):

It replaces the whole list, not with the POST endpoints above: labels with PUT /repos/OWNER/REPO/issues/NUMBER/labels and assignees with PATCH /repos/OWNER/REPO/issues/NUMBER (assignees), each carrying every label or assignee the pull request is to have after your change. GitHub then sets exactly that list.
What it offers: the labels from GET /repos/OWNER/REPO/labels, and the people from GET /repos/OWNER/REPO/assignees, the users GitHub lists as available assignees for the repository.
When GitHub refuses, the source writes the error to the IDE's log as an error (refusals of other pull request changes are logged as information).

GitHub pull requests in IntelliJ IDEA

Pull Request Inbox for GitHub, a plugin by Lesstep for JetBrains IDEs 2024.1 or later, shows a pull request's reviews, checks and conversations next to the diff, and merges it with the methods the target branch allows. It does not add labels or assignees: set them on the pull request's page on GitHub, which Open in Browser opens. The review inbox, diffs and conversations are free; approving, commenting, resolving and merging are Pro (US$1.50 a month, with a 30-day trial).

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