When does auto mode become the default?

Auto mode becomes the default setting for new Claude Code sessions starting August 14th for Pro, Max, and Team plans.

What did the safety tests show?

In a test of 1,053 paid testers where a permission prompt was replaced with a dangerous command, only 13.6% of humans refused the harmful action while auto mode would have blocked 89% of those actions. Trajectory Labs also tested 720 indirect prompt injection scenarios against Claude Fable 5, Opus 5, and Sonnet 5 running auto mode, reporting none of the attacks succeeded.

AI Coding AssistantsAI Safety & AlignmentSimon Willison's WeblogAug 9, 2026Aug 9, 2026, 10:00 JST

Claude Code auto mode now default for Pro, Max, Team plans

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3 Key Points

What happened
Anthropic is making auto mode the default setting for new Claude Code sessions starting August 14th across Pro, Max, and Team plans. The company commissioned an evaluation from Trajectory Labs testing prompt injection attacks, reporting that none of 720 attack attempts succeeded against Claude Fable 5, Opus 5, or Sonnet 5 running auto mode.
Why it matters
Auto mode automatically approves or blocks code actions without requiring manual confirmation at each step. In Anthropic's test of 1,053 paid testers, when a harmless permission prompt was swapped for a dangerous command, only 13.6% of humans refused it while auto mode would have blocked 89% of those actions. This suggests auto mode may be more reliable than human judgment, which suffers from confirmation fatigue.
What to watch
Auto mode still left 11% of potentially harmful actions unblocked in the human test. Independent security researchers have raised concerns about whether auto mode can defend against sophisticated attacks such as malicious third-party packages that hide data exfiltration instructions in seemingly legitimate development workflows.

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FAQ

When does auto mode become the default?: Auto mode becomes the default setting for new Claude Code sessions starting August 14th for Pro, Max, and Team plans.
What did the safety tests show?: In a test of 1,053 paid testers where a permission prompt was replaced with a dangerous command, only 13.6% of humans refused the harmful action while auto mode would have blocked 89% of those actions. Trajectory Labs also tested 720 indirect prompt injection scenarios against Claude Fable 5, Opus 5, and Sonnet 5 running auto mode, reporting none of the attacks succeeded.

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