Hook output parsing tells you what was wrong with it / Claude Code v2.1.248

You'll notice

Useful4 Signal2

Hooks

Unparseable hook output now shows the failure kind, exit code and stderr.

What

When a hook prints something Claude Code cannot read as JSON, the message now says which failure it was and includes the hook's exit code and stderr.

Details

Parsing distinguishes plain text, valid JSON, several JSON documents run together, and output that looks like JSON but is not.
The last case advises using a real encoder: "Emit the payload with a JSON encoder (jq, ConvertTo-Json, json.dumps) rather than string concatenation so backslashes and quotes inside strings are escaped."

Evidence

Emit the payload with a JSON encoder (jq, ConvertTo-Json, json.dumps) rather than string concatenation so backslashes and quotes inside strings are escaped.

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.

v2.1.234 SessionEnd hooks lose the bypass_permissions_disabled reason
Both mention hook
v2.1.236 Hooks and Ctrl-C go quiet once shutdown has started
Both mention hook
v2.1.236 Shutdown seals transcript writes and gives SessionEnd hooks more time
Both mention hook

Hook output parsing tells you what was wrong with it

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