If upload deltas are disabled on the snap store servers, snapcraft fails like this when trying to upload a delta (easy way to ensure it's a delta upload: push two revisions of the same snap, one after the other). After pushing, an attempt will be made to release to 'edge' Preparing to push '/home/ubuntu/minisnap/hello-roadmr-1_2018-07-09-02_amd64.snap' to the store. Found cached source snap /home/ubuntu/.cache/snapcraft/projects/hello-roadmr-1/snap_hashes/amd64/81d67619708155032388f69f382e0975d7c9dbdce6ec25590c1e6faf844b155ca307966c9c1af8e6b29ebfe44dcc0c68. Generating xdelta3 delta for hello-roadmr-1_2018-07-09-02_amd64.snap. Pushing delta /home/ubuntu/minisnap/hello-roadmr-1_2018-07-09-02_amd64.snap.xdelta3. Pushing hello-roadmr-1_2018-07-09-02_amd64.snap.xdelta3 [==========================================] 100% The Snap Store encountered an error while processing your request: not implemented (code 501). The operational status of the Snap Store can be checked at https://status.snapcraft.io/ > snapcraft --version snapcraft, version 2.42.1+18.4 > lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 18.04 LTS Release: 18.04 Codename: bionic this regressed in 2.42.1, because with 2.42 things work well, snapcraft gets the same 501 code from the store (which means deltas are not available/not implemented) and falls back to a full-snap upload (with a nice error saying delta support is disabled): Pushing hello-roadmr-1_2018-07-09-02_amd64.snap After pushing, an attempt will be made to release to 'edge' Preparing to push '/home/ubuntu/minisnap/hello-roadmr-1_2018-07-09-02_amd64.snap' to the store. Found cached source snap /home/ubuntu/.cache/snapcraft/projects/hello-roadmr-1/snap_hashes/amd64/81d67619708155032388f69f382e0975d7c9dbdce6ec25590c1e6faf844b155ca307966c9c1af8e6b29ebfe44dcc0c68. Generating xdelta3 delta for hello-roadmr-1_2018-07-09-02_amd64.snap. Pushing delta /home/ubuntu/minisnap/hello-roadmr-1_2018-07-09-02_amd64.snap.xdelta3. Pushing hello-roadmr-1_2018-07-09-02_amd64.snap.xdelta3 [==========================================] 100% Unable to push delta to store: The delta upload support is currently disabled. Falling back to pushing full snap... Pushing hello-roadmr-1_2018-07-09-02_amd64.snap [==================================================] 100% Processing...| Ready to release! Revision 51 of 'hello-roadmr-1' created. Track Arch Channel Version Revision Expires at latest amd64 stable 2018-06-08-01 47 candidate ^ ^ beta ^ ^ edge 2018-07-09-02 51 stable/mybranch 2018-06-08-01 47 2018-07-15T21:44:58.667374 We think the commit that regressed here was: https://github.com/snapcore/snapcraft/commit/c6500ca0ed3cf4fe564a15adfb0a46ff0a3a787f storeapi: handle 5xx error codes for all store endpoints (#2116) Currently, the snapcraft CLI handles a 500 response when releasing a snap. Make this more robust, and nicely handle 5xx codes for all endpoints. As reference, the response when deltas are disabled is that 501 HTTP status code with this payload: {"error_list": [{"message": "The delta upload support is currently disabled.", "code": "feature-disabled"}]}