Checked fact 9319 Oct 2026Safety and security

Anthropic gives calling sys.exit(0) in Python to break out of a test harness with an exit code of 0, making it appear all tests have passed, as an example of a reward hack on programming tasks.

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The exact words it rests on

one such method is calling sys.exit(0) in Python to break out of a test harness with an exit code of 0, making it appear that all tests have passed successfully

What the source said when we opened it, on 9 Oct 2026.

The source

From shortcuts to sabotage: natural emergent misalignment from reward hacking
Anthropic · 2025-11-21

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Checked

Checked by the notis newsroom on 9 Oct 2026, against the source above.

In the story

How reward hacking lets a model game its score 9 Oct 2026

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“Anthropic gives calling sys.exit(0) in Python to break out of a test harness with an exit code of 0, making it appear all tests have passed, as an example of a reward hack on programming tasks.” ai notis, checked 9 Oct 2026. Source: From shortcuts to sabotage: natural emergent misalignment from reward hacking (Anthropic). https://ainotis.com/c/931

As a reference (APA style)

ai notis. (2026, October 9). Anthropic gives calling sys.exit(0) in Python to break out of a test harness with an exit code of 0, making it appear all tests have passed, as an example of a reward hack on programming tasks [Checked claim 931]. ai notis. https://ainotis.com/c/931

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