DataDave said:

The useful checklist is about verifiability rather than presentation.

I disagree that testing history is decisive. It tells you what a supplier did when they were being watched. Continuity of behaviour under stress — a late shipment, a failed test, a complaint — is more predictive than any run of good results.

NauseaFreeNow said:

Eight months with one supplier, then a change in how they communicate that I noticed before I noticed anything about the product.

Vendor reputation tracking for vendor vetting: I maintain a personal spreadsheet with every order I've placed — date, vendor, batch number, Janoshik result, personal efficacy assessment (1-5 scale), and any issues.

After 22 orders across 4 vendors: average purity 97.6%, zero sterility concerns, 2 shipping issues (all resolved). This data gives me confidence in my current source and documentation if issues arise.

I encourage everyone to track their orders systematically. Community data aggregation makes us all safer.

DebRD_ATL said:

I disagree that testing history is decisive.

There is a second half to this that has not been said yet. If two explanations both fit, the useful question is which one predicts something the other does not. That is answerable; arguing about which sounds more plausible is not.

One thing that is still open after pam_stl’s answer:

What a vetting checklist should actually contain, as opposed to a list of things that are easy to fake?

OP back with an update, since a thread like this is useless without one.

Went back through my own correspondence with an earlier supplier and the warning signs were all there in the replies, weeks before the quality changed. I was reading the product and not the behaviour.