My MCP Tool's Audit Log Was Built So a Bad Write Would Leave a Trace. The Log Itself Leaves None.

A few days ago I fixed update_article , one of the tools in this repo's MCP server, because it had a nasty shape: it took a bare integer article_id , PUT whatever fields you gave it straight to the DEV.to API, and if the id was wrong or hallucinated, it would silently overwrite a live published post with nothing left behind to show it had happened. The fix added a fetch-before-write diff and a JSONL audit log: _ARTICLE_UPDATE_LOG = " logs/article_updates.jsonl " def _log_article_update ( article_id , before , fields_changed , after ): os . makedirs ( os . path . dirname ( _ARTICLE_UPDATE_LOG ), exist_ok = True ) entry = { " article_id " : article_id , " fields_changed " : sorted ( fields_changed ), " url " : after . get ( " url " )} for field in fields_changed : entry [ f " { field } _before " ] = before . get ( field ) entry [ f " { field } _after " ] = after . get ( field ) with open ( _ARTICLE_UPDATE_LOG , " a " ) as f : f . write ( json . dumps ( entry ) + " \n " ) The whole point of that function is durability. "Zero trace" was the bug; a JSONL file that records before/after state on every write was the fix. I verified the logging logic itself with an offline unit test against fake before/after states and moved on, same as the diff field. What I never checked is whether logs/article_updates.jsonl outlives the process that writes it. Checking whether the trace actually exists anywhere logs/ isn't in .gitignore — I checked, it's not there. So nothing is actively hiding it. But not-hidden isn't the same as tracked: $ git log --all --oneline -- 'logs/*' $ ls logs/ ls: cannot access 'logs/': No such file or directory Empty output from the first command, across every branch and every commit this repo has ever had (50 commits, not a shallow clone — git rev-parse --is-shallow-repository is false ). Nothing has ever touched logs/ . The directory doesn't even exist right now. Not because anything deleted it — because nothing has ever run update_article in an environment