Retell AI API
outbound_agent_id body parameter removal on PATCH /update-phone-number/{id}
Stopped workingSubscribe to Retell AI APIShare
Calls to PATCH /update-phone-number/{id}, body parameter outbound_agent_id on Retell AI API stopped working on March 31, 2026.
Calls it hits
PATCH /update-phone-number/{id}body parameter outbound_agent_id
What to use instead of these calls
Send outbound_agents instead as a list of {agent_id, agent_version, weight} entries whose weights sum to 1. For a single agent, set the weight to 1.
In Retell AI API's words
After 03/31/2026, the deprecated single-agent fields will no longer be supported.
Facts
- API
- Retell AI API
api.retellai.com - Kind
- Parameter removal
- Takes effect
- March 31, 2026
- Calls after that day
- Fail
- Source
- Announcement
- Last updated
- Verified
- , against Retell AI API's own pages
Questions
When does this change take effect?
Calls to PATCH /update-phone-number/{id}, body parameter outbound_agent_id on Retell AI API stopped working on March 31, 2026.
What happens to calls after March 31, 2026?
They have failed since March 31, 2026.
How do I find the calls this hits in my code?
Okapi reads your repository, finds the calls this change hits and opens a pull request with the fix. It never commits to your branches: every change comes as a pull request you review.
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You fixed this one by hand.
Okapi opens the pull request with the fix before the next breaking change reaches your code.