cua-driver 0.21 refuses a bare element_index:
click: bare element_index is not accepted; pass element_token,
or snapshot_id together with element_index
_maybe_attach_element_token gated solely on the trycua/cua#1961 capability
vocabulary. 0.21 stopped publishing per-tool capability sets — every tool
reports an empty set — while still accepting element_token in its input
schema. The gate therefore fails closed on 0.21.x and we send the bare
index, so the driver rejects the call.
The effect is total: every element-targeted click is refused, leaving
agents with only blind pixel coordinates. Observed against cua-driver
0.21.0 on X11, where a capture returned 762 elements with 762 tokens
cached and every subsequent click still failed with snapshot_id_required.
Check the live input schema first — supports_input_property() already
exists for exactly this, and its docstring notes it "deliberately inspects
tools/list rather than ... requiring a capability token the driver never
shipped". The capability check is retained as a fallback so drivers that
did ship the vocabulary are unaffected.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Jeff J Hunter
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