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A tunable, spatially and spectrally coherent soft X-ray undulator branchline at the Advanced Light Source (ALS) is under operation. Using the third harmonic from an 8-cm period undulator, this branch delivers coherent soft X-rays with photon energies ranging from 200 to 1000 eV. Here, the beamline layout and characterization are presented. The characterization includes measurements of available coherent photon flux as well as a series of double-pinhole experiments to measure spatial coherence in the focal plane.