I was really excited to use this for automated fluid chains in Omnifactory. However, what I found when I was starting to set this up is that auto crafting will always prefer to assume liquid storage will fill the flask. If I have a chain of liquid recipes in say the chemical reactor with actual filled flask output meant to begin the next step in a process, automation will not allow this.

You may increase the priority of the interface with filled flask pattern, in order to encourage AE to use the pattern rather than the filler. However, if anything was missing in your chain of liquid recipes, making it impossible for AE to craft filled flask using your recipe, AE will use filler as a fallback.
Furthermore, priority of filler in 0.13 version was decreased to -1. Your interface with default priority 0 should be preferred.
Please leave a message if you insist on removing the fallback plan, or want the priority of filler configurable maybe.

既然实现了AE的流体合成链断裂后会自动采用filter进行合成，能不能使得Filter的优先级高于接口时，AE优先采用filter进行合成，直到库中流体无法合成时再通过接口进行合成？

@CSOLYOO This is the expected behavior. The Filler(I assume you mean "Filler" rather than "Filter") has a priority of -1. (But sadly it can't be changed now. Create a new issue if you need that.) If you set the priority of an Interface to -2 or any number below -1, the ME network will use Filler first and turn to Interface if the Filler cannot provide a recipe anymore.
The problem is, the Filler claims it can provide a 1000mB water Volumetric Flask even if there is only 500mB water in the ME network. The Filler just don't know the exact amount of water. Making Filler aware of this may cost performance issues like this #5.
Anyway, I'm still working on this. But if the amount of fluid in the ME network is always enough or ZERO in your circumstance, you can just adjust the priority of Interface to achieve your objective.