Claude Code login: `Authorization failed: Redirect URI http:/localhost:<port>/callback is not supported by client` (URL broken when copied from the terminal)

Context

Source(s): https://github.com/anthropics/claude-code/issues/36215 Status: reported working by source, not reproduced by us (workaround only; root fix not confirmed).

Problem

claude → /login opens (or prints) the sign-in link; after you sign in with a Pro/Max account, the browser shows the error above and login never completes. Reported on macOS, Linux, Windows and WSL, commenters think usually when Claude Code runs on a remote machine over SSH and the link is copied from the terminal instead of clicked.

Error (redacted / normalized)

Authorization failed
Redirect URI http:/localhost:<port>/callback is not supported by client.

Authorization failed Redirect URI https:/platform.claude.com/oauth/code/callback is not supported by client

Applies when

Claude Code CLI (versions from 2.1.20 up to 2.1.2xx in the thread), terminal emulators such as iTerm2 and Warp, SSH sessions and remote VPS terminals, March to October 2026.

Confirm it is this problem

1. Look at the redirect in the error: it shows a single slash (http:/localhost or https:/platform...) → expect: a mangled URL, not a server-side rejection (our inference from the commenters' fixes).
2. Paste the copied sign-in link into a text editor → expect: stray spaces or line breaks where the terminal wrapped the long link (for example oauth split into o auth).

Not this when / boundary

The error names https://platform.claude.com/oauth/code/callback with a correct // and the link was not copied by hand: one commenter on WSL with a university single-sign-on account kept getting it after cleaning the cache and updating, and the thread has no fix for that case.

Root cause

Several commenters found the long sign-in URL gets broken when it is copied from a wrapped terminal line: each line break turns into a space (or + once URL-encoded) inside the URL. Several reports also show the // after the scheme as a single /, which two commenters fixed by hand; the thread does not explain why (our note). The broken redirect URI then doesn't match what the login server accepts. (Maintainers did not comment; the issue was auto-closed as inactive.)

Fix

1. Copy the sign-in link into a text editor, remove every space and line break inside it, and open the cleaned link. → expect: a commenter confirmed this fixed login; others reported the same stray spaces or line breaks (one from a 3-line URL) and said to clean the link in a text editor.
2. If the error page still shows http:/localhost:<port>/callback, correct it to http://localhost:<port>/callback and retry the request. → expect: two commenters confirmed login then worked.
3. Easier way to avoid the wrapping (commenter): shrink the terminal font or widen the window so the whole link fits on one line before copying it.
4. For a remote server: connect with VS Code's Remote SSH extension and run claude in its integrated terminal, then click the link. VS Code forwards the localhost port for you. → expect: a commenter confirmed this fixed it.

How to verify

The browser shows a success page and the terminal session finishes /login without the error.

What did not work

Updating Claude Code, removing the Claude Code cache, logging out and retrying, and forceLoginMethod settings did not help the commenters who tried them.

Risks

A commenter fell back to an API key, which bills separately from a Pro/Max plan.

Verified scope

Claude Code CLI as of October 2026.

Becomes obsolete when

Claude Code changes how it prints or copies the login link.