Any files which end in *.snap are not copied to the part/x/src directory, as can be seen from this minimal example: snapcraft.yaml: name: my-snap-name base: core22 version: '0.1' summary: Single-line elevator pitch for your amazing snap description: Test grade: devel confinement: devmode parts: my-part: plugin: nil source: test override-build: | cp ${CRAFT_PART_SRC}/test.snap ${CRAFT_PART_INSTALL}/test.snap --- Snapcraft output: itrue@lxc-jammy:~/tmp/test-snap$ sudo snapcraft --verbose --destructive-mode Starting Snapcraft 7.1.3 Logging execution to '/root/.cache/snapcraft/log/snapcraft-20220919-153058.032639.log' Running on amd64 for amd64 Initializing parts lifecycle Executing parts lifecycle... Executing parts lifecycle: skip pull my-part (already ran) Executing action Executed: skip pull my-part (already ran) Executing parts lifecycle: skip overlay my-part (already ran) Executing action Executed: skip overlay my-part (already ran) Executing parts lifecycle: build my-part Executing action :: + cp /home/itrue/tmp/test-snap/parts/my-part/src/test.snap /home/itrue/tmp/test-snap/parts/my-part/install/test.snap :: cp: cannot stat '/home/itrue/tmp/test-snap/parts/my-part/src/test.snap': No such file or directory 'override-build' in part 'my-part' failed with code 1. Review the scriptlet and make sure it's correct. Full execution log: '/root/.cache/snapcraft/log/snapcraft-20220919-153058.032639.log' --- Source folder contents: itrue@lxc-jammy:~/tmp/test-snap$ ls test test.notasnap test.snap --- parts src folder contents: itrue@lxc-jammy:~/tmp/test-snap$ ls parts/my-part/src/ test.notasnap --- Please either copy all files in the source directory, or at least add a warning to say that these files are not being copied, rather than silently not doing it.