Authoring GitHub Actions Workflows Safely GitHub Actions workflow files are YAML, but valid YAML is not the same as a valid workflow . A workflow can parse cleanly with (or a casual review) yet still be rejected by GitHub Actions at load time — producing the opaque failure "This run likely failed because of a workflow file issue" with zero jobs started . This skill teaches the YAML-vs-Actions traps (the -as-comment trap above all), how to quote expression scalars correctly, and how to validate with before merge. Scope: syntactic vs. semantic. This skill is about the syntactic and structural c…