PR #2101 swapped the openclaw runtime adapter from reading --json on
stderr to stdout. That fixed openclaw 2026.5+ but inverted the breakage
for pre-2026.5 builds — those still write JSON to stderr, so the
adapter now sees an empty stdout and falls through to the same
"openclaw returned no parseable output" failure that 2026.5+ users
saw before #2101.
Add a per-task version gate inside openclawBackend.Execute that runs
`openclaw --version`, parses the dotted version, and rejects anything
below 2026.5.5 with a hardcoded upgrade hint:
openclaw <detected> is below the minimum supported version 2026.5.5.
Run `openclaw update` to upgrade and try again.
The check is intentionally per-task and uncached so users who upgrade
do not need to restart the daemon — the next task automatically
re-checks. ~20ms per task is negligible vs. the typical run.
Co-authored-by: multica-agent <github@multica.ai>