A refusal an agent can read

An agent that runs vx run build --format json reads stdout. When vx
refused the run, stdout used to be empty, and the reason sat on stderr
as prose. Now the refusal is on stdout too, as one JSON line:

$ vx run biuld --all --format json
{"ok":false,"error":{"code":"VX_E_UNKNOWN_TASK","message":"vx run: no projects declare task(s): biuld. Did you mean build?"}}

The exit code is still 1 and stderr still says it in words. The code
is the contract; the message may change.

Code	Means
VX_E_USAGE	A flag or argument vx does not take
VX_E_UNKNOWN_TASK	No project declares the task
VX_E_CONFIG	A config that does not load
VX_E_CYCLE	The task graph has a cycle
VX_E_NO_WORKSPACE	No workspace above the working directory
VX_E_REFUSED	Any other refusal
VX_E_INTERNAL	A bug in vx

schemas/error.json describes the line, and the full table is in the
CLI reference.

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Originally published on the vx blog. vx is an MIT task runner and build cache for JS monorepos: vznjs.github.io/vx · GitHub.

_{Written with AI assistance.}