The free web debugging proxy for any browser, system or platform.
Would be helpful for debugging SAML issues. (May not be feasible due to encryption but I don't know the guts of SAML so this is just a guess)
I think a few folks have created SAML extensions over the years, but I haven't used any of them myself (see e.g. http://tech-turf.blogspot.com/2015/09/viewing-samlfederation-response-in.html)
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