X_IMAGE_LIBC_MISMATCH
Means
the stage, stage index or external image any Dockerfile in the tree copies its runtime artifact from links a different C library than the runtime provides
Typical cause
a musl build base (alpine) under a glibc runtime (distroless/cc, debian, slim), or the reverse. The binary asks for a loader that is not there, every container exits exec …: no such file or directory, and docker build still succeeds — which is how a dead-on-arrival image shipped green. An image neither family pattern recognises is not reported: unknown is not broken
Fix
bun run scripts/image-contract.ts --json, then docker build -f docker/Dockerfile . — the fix names the stage whose FROM must change