README.md

[mcm-jyl]

NOTE: You can only open one mbtiles file at a time, it seems, most likely because mbtiles will open an sqlite database file for you, and you won't be able to open multiple ones simultaneously. Please correct me if I'm wrong, however.

So I'm correcting you ;-). With Tessera I'm using several MBtiles to create a bigger MBtiles (zoom level 0-10 and zoom level 11 are blended to simulate a zoom level range 0-11).
I had to set the min and max zoom levels in the .mbtiles if I remember right.
Observed on a Linux machine (or Linux in a vagrant virtual machine on Windows).

  "/": {
    "source": {
      "protocol": "blend:",
      "query": {
        "layers": [
          {
            "source": "mbtiles:///home/mbtiles/osmfr-z0-z10.mbtiles"
          },
          {
            "source": "mbtiles:///home/mbtiles/osmfr-z11-z11.mbtiles"
          }
        ],
        "format": "png32:z=1"
      }
    }
  }
}