Summary

The fetch adapter does not set a User-Agent header, causing requests to appear with Node.js's default node user agent instead of axios/<version>. The HTTP adapter correctly sets this header.

Content-Length, Accept-Encoding, Host, and Connection are intentionally not added — these are forbidden headers managed automatically by the Fetch API (see maintainer feedback on #10633).

Fixes #7494

Changes

• lib/adapters/fetch.js: set User-Agent: axios/<version> header, mirroring the HTTP adapter, with a no-override guard for user-supplied values

Checklist

• Code follows axios style conventions
• Tests added/updated
• Conventional commit message used

Summary by cubic

Sets the fetch adapter’s default User-Agent to axios/<version> to match the Node HTTP adapter and avoid Node’s default node UA. Keeps any user-provided User-Agent intact.

Description

• Summary of changes
  • Set User-Agent: axios/<version> in the fetch adapter with a no-override guard.
  • Merged latest v1.x into the branch; no behavior changes.
• Reasoning
  • Aligns behavior with the HTTP adapter and fixes requests showing Node’s default node UA. Fixes Fetch Adapter: Content length header is missing in POST request #7494.
• Additional context
  • Did not add Content-Length, Accept-Encoding, Host, or Connection (managed by Fetch and forbidden to set).

Docs

• Update /docs/ to document the fetch adapter’s default User-Agent, how to override it, and parity with the HTTP adapter.

Testing

• Added unit tests:
  • Sets User-Agent to axios/<version> by default.
  • Does not override a user-provided User-Agent.
• No further tests needed.

Semantic version impact

• Patch: bug fix aligning adapter behavior without breaking the API.

^{Written for commit d7e0817. Summary will update on new commits.}