Addresses egilewski (Codex) CR on PR #52351: the run_job() credential-exfil
backstop caught every exception around _validate_cron_base_url() and set
err = None, so an unexpected validator/import error let an unvetted stored
provider/base_url pair reach resolve_runtime_provider() — the very sink this
checkpoint exists to guard. A synthetic validator-exception probe with a
legacy custom:legit + off-host base_url job slipped through (validator_exception
ALLOW).
Now fail closed: if the validator raises and the job carries a base_url
override (the exfil precondition), refuse the run. A job with no base_url
override can't exfiltrate via this path — the validator would return None — so
it still runs, keeping the common no-override jobs from wedging on an unrelated
error. Operator fallback providers come from config, not the job, so they are
unaffected.
Adds two regressions: validator-exception + base_url -> blocked;
validator-exception without base_url -> still allowed.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
1b7e781d21