The HTTP backend has been migrated from httr to httr2. OAuth 1.0a signing and the interactive browser authentication flow are now implemented in-package; the user-facing setup is unchanged (set RTUMBLR_TOKEN="consumer_key;consumer_secret").
rtumblr_auth() is exported to (re-)run the OAuth flow explicitly. The access token is now cached under tools::R_user_dir("Rtumblr", "cache") instead of .httr-oauth, so you will be asked to authorize once after upgrading. Power users can supply a pre-issued access token via a four-field RTUMBLR_TOKEN ("consumer_key;consumer_secret;oauth_token;oauth_token_secret") to skip the browser.
The default limit for get_blog_posts() (and the following/followers helpers) is now 20, matching the Tumblr API maximum (the previous default of 50 was silently capped).