Anthropic's Claude went down for about an hour on Tuesday, the 13th incident logged on its status page this month, according to Unite.ai.
Spotify, the music-streaming service, suffered its own disruption at the same time, though there is no sign the two were linked.
Neither company has said what went wrong.
What happened at Claude
Problems began at 7am Pacific time, or 3pm UK time, and lasted until just before 8am, Anthropic's status page shows.
The outage hit the Claude app on web, desktop and mobile, as well as Claude Code, its coding tool, Claude Cowork and the Claude API, which developers use to build Claude into their own products.
Users saw failed requests, errors loading conversations and prompts to sign in again.
Anthropic applied a fix within about 36 minutes, but a second fault then blocked many users from signing in, 9to5Google reported.
Single sign-on and Sign in with Apple stopped working, along with new chats, voice conversations, purchases and file uploads.
Anthropic told signed-in users not to log out.
Services were back to normal by 7:59am Pacific time, and Anthropic has since marked the incident resolved.
Reports on Downdetector, the outage-tracking site, topped 10,000 around 10:25am Eastern time before falling below 100, Reuters reported.
A difficult month
Claude also had partial outages on 11, 15 and 22 September, according to 9to5Google.
On 3 September it went down at the same time as ChatGPT and Grok in a wider AI disruption.
Claude's website recorded uptime of 99.70% in September, up from 99.59% in August and 99.01% in July, Unite.ai reported.
That still means hours of downtime a month for a service increasingly used for business-critical work.
What happened at Spotify
Spotify's problems began around 9:30am Eastern time, with Downdetector reports peaking above 19,000, according to Reuters.
Users struggled to log in and stream music, mainly on the mobile app, TechRadar reported.
Spotify posted from its main X account rather than its support channels, saying it was working to resolve the issues.
It gave TechRadar no cause and no estimate for a fix.
Two outages, no link
User reports for ChatGPT and Gemini also rose during the morning, but OpenAI and Google did not confirm any problems, 9to5Google noted.
Downdetector counts user-submitted reports, so the figures do not show how many people were actually affected.
