"loading phase" is 20g a day. It's well tolerated as long as you drink adequate water

5g/day is the upper limit for known positive benefits specifically around muscle strength and recovery. Theres some studies seeming to show 10g+ is useful for additional cognitive benefits.

I’m not aware of any limit that results in toxicity.

I've never heard of taking more than 10g, or 20g for that matter, as being unsafe. It's the same amino acid you get form eating a steak, just isolated.