Shifty appears with for an interview with Furrowed Brow to push the impeachment narrative etc.  Within the interview Shifty talks about lengthy coordination and careful planning with Robert Mueller for a scripted July appearance.
[Prompted to 05:38 just hit play]

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Shifty, Pelosi and Nadler have to be very careful with Mueller to avoid exposing the coordinated enterprise behind the two-year Rosenstein, Weissmann and Mueller scheme.  It will be interesting to see how they plan it out. [If Ever]
Likely they will only bring Mueller under VERY carefully control; and they’d probably prefer a panel approach where scripted Mueller confidants can bookend him during any questioning.  It’s highly unlikely Schiff would attempt to use Robert Mueller as a stand alone witness in a public hearing.