Third-party coding agents - Claude defaulting to Fable 5 for every request

[hello-consumer]

🏷️ Discussion Type

Bug

💬 Feature/Topic Area

Copilot Cloud Agent

Body

I've been using Copilot Cloud Agent steadily for several months and have really enjoyed it, and I've been steadily using Third-party coding agents (https://docs.github.com/en/copilot/concepts/agents/about-third-party-coding-agents) for the last month or two.

Last night when routing an issue to Claude, I specified a branch to work off of but did not specify a model to use. To my disappointment, it seems like Fable 5 was auto-selected for the task, which ate my entire budget for the month. I had not previously selected Fable 5 for a task, so this default selection surprises me. This morning when assigning tasks, I'm no longer seeing the interstitial pop-up where I can choose the source branch and model when assigning tasks to Claude, and when running a simple test issue where I asked which model was being used, the agent reported:

This session is powered by Anthropic model claude-fable-5, running as Claude Code via the Claude Agent SDK (environment metadata notes the most recent frontier Claude model is Claude Opus 4.5, model ID claude-opus-4-5-20251101)

I understand third party agents are in public preview and I'm not entirely sure if this feedback is most appropriately routed to the Copilot Agent team or someone at Anthropic, and I can't find any other reports of this so I thought I'd start here and see if anyone has suggestions for me. Short term I can stop using the Claude assignee to avoid racking up cost.

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