### Check existing issues - [x] I've verified that this bug isn't described by any existing issues. ### Bug description Found together with @alesancor1 Rebuilding the same project after switching `base: ubuntu@26.04` to `base: bare` reuses stale state and packs a rock **silently** missing every file the previous base had provided. ### Steps to reproduce ```bash mkdir my-test-rock && cd my-test-rock # Two projects differing only in the base. cat > ubuntu-base.yaml <<'EOF' name: python base: ubuntu@26.04 version: "3.14" summary: Python3.14 rock description: Example of a Python rock license: Python-2.0 platforms: amd64: run-user: _daemon_ parts: install-python: plugin: nil stage-packages: - base-files - python3.14 EOF sed -e 's/^base: ubuntu@26.04$/base: bare\nbuild-base: ubuntu@26.04/' \ ubuntu-base.yaml > bare-base.yaml # 1. Build with the Ubuntu base. cp ubuntu-base.yaml rockcraft.yaml rockcraft pack mv python_3.14_amd64.rock 1-ubuntu.rock # 2. Swap to the bare base and rebuild WITHOUT cleaning. This succeeds. cp bare-base.yaml rockcraft.yaml rockcraft pack mv python_3.14_amd64.rock 2-bare-no-clean.rock # 3. Reference: the same bare project, built clean. rockcraft clean rockcraft pack mv python_3.14_amd64.rock 3-bare-clean.rock # 4. Compare the two bare rocks. They should be identical; they are not. list_rootfs() { d=$(mktemp -d) mkdir -p "$d/oci" "$d/fs" tar -xf "$1" -C "$d/oci" for l in $(find "$d/oci/blobs" -type f -size +100k); do tar -xzf "$l" -C "$d/fs" 2>/dev/null || tar -xf "$l" -C "$d/fs" 2>/dev/null || true done (cd "$d/fs" && find . | LC_ALL=C sort) rm -rf "$d" } list_rootfs 2-bare-no-clean.rock > no-clean.txt list_rootfs 3-bare-clean.rock > clean.txt wc -l no-clean.txt clean.txt comm -13 no-clean.txt clean.txt # files the no-clean build is missing ``` Step 2 exits 0 with no warning, but `2-bare-no-clean.rock` is a strict subset of `3-bare-clean.rock`, missing 520 files -- all of `base-files` and friends. ### Environment - Rockcraft 1.20.0 (snap, `latest/stable`, classic) - LXD provider, **not** destructive mode - Host: Ubuntu 24.04.4 LTS, amd64 (itself running as an LXD VM, but that does not matter. @alesancor1 reproduced this on metal host) - Build base: `ubuntu@26.04`, amd64 ### rockcraft.yaml ```yaml name: python base: ubuntu@26.04 version: "3.14" summary: Python3.14 rock description: Example of a Python rock license: Python-2.0 platforms: amd64: run-user: _daemon_ parts: install-python: plugin: nil stage-packages: - base-files - python3.14 ``` ### Log output ```shell n/a ```