E1501. Hook input was not JSON

Severity: WARNING. The hook fails open for this class.

What happened

The agent invoked the controlzero hook subprocess but the stdin payload could not be parsed as JSON. The hook fails open (allows the tool call) so the agent does not stall.

How to fix

Re-install the hook with controlzero install <agent> to fix any manual edits to the agent's settings file that may have corrupted the contract.

See also

• E1502 -- Hook timed out
• Coding assistant hooks guide
• Errors index