Claude Sonnet 5 delegated to a lesser agent to perform a code review

Describe the bug

I asked Claude Sonnet 5 to perform a code review. I specifically chose Claude Sonnet 5 for deep reasoning. The agent proceeded to review the structure of my project and then delegate to a lesser agent:

"Good, all directories exist. I'll launch a general-purpose agent to perform this code review, since it involves reading through before/after/project directories, comparing changes, and producing a structured markdown report — genuinely multi-step work."

"General-purpose(gpt-5.4) Perform code review for issue 44206"

The code review produced was of little use. I corrected the agent and requested Sonnet 5 to perform the review itself:

"I would like to start this code review over. I see that you delegated to gpt-5.4 and I do not want a weaker model doing the review. Please execute the review prompt in file 44206-review-prompt2.txt."

Sonnet replied "I'll perform this review myself directly (no sub-agent delegation this time). Let me examine the before/after directories to identify actual changed files."

Sonnet completed the review the second time and the quality was as expected.

Affected version

GitHub Copilot CLI 1.0.75

Steps to reproduce the behavior

No response

Expected behavior

I expected that when selecting the agent that it perform the work itself.

Additional context

No response

GitHub Copilot CLI 1.0.75 で、レビューシナリオと 44206-review-prompt2.txt プロンプトを使い、before、after、project ディレクトリを比較して動作を再現する。選択されたエージェントがどこで委譲を判断するのかを追跡し、その後、Sonnet が意図しない下位エージェントへの引き渡しを行わずに、要求されたレビューを自ら実行することを確認する。