Canvas is awesome, but if you try to use actions to load content into canvas and save from canvas, it goes through generation often replacing characters, and doing its generative magic. For example, if you use canvas to draft a letter to Santa, and have an action to send that letter, the content of the letter can be transformed before the email action is triggered, and you can’t be 100% sure if Santa will be sending you the gift that you thought you requested. With very very careful prompting you can force this to happen somewhat reliably, but even then, there is no reason to go through the full generation process just to pass the content of the canvas into the action parameter, it adds unnecessary delay.
Simple solution would be to indicate somehow in action parameter definition that it copies the content from the canvas, and vice versa, that action will return content that should be moved directly into canvas.