Docker "failed to solve: failed to load LLB" in CI

By Daniel Zoghalchali·Latchkey

BuildKit compiles your Dockerfile into a low-level build (LLB) graph before it executes anything. "failed to load LLB" means the builder received a definition it could not decode - a corrupted or truncated LLB blob, a frontend that emitted a malformed graph, or a build context that did not transfer cleanly.

What this error means

A docker buildx build aborts immediately with failed to solve: failed to load LLB, before any RUN step prints output. The Dockerfile itself looks valid.

ERROR: failed to solve: failed to load LLB: unexpected EOF

Common causes

A truncated or corrupt LLB definition

The frontend that compiles the Dockerfile emitted a graph the worker could not decode, often after a partial context transfer.

A mismatched or pinned Dockerfile frontend

A # syntax= line pinning a frontend image that is incompatible with the running BuildKit can produce LLB the worker rejects.

A stale or wedged builder instance

A buildx builder left in a bad state from a prior crashed build can fail to load fresh LLB until it is reset.

How to fix it

Recreate the buildx builder from scratch

1. Remove the existing builder and create a clean one.
2. A fresh builder loads the LLB graph without inherited corruption.

docker buildx rm mybuilder || true
docker buildx create --name mybuilder --use
docker buildx build -t myorg/api:ci .

Pin a compatible Dockerfile frontend

1. Set an explicit, current # syntax= line so the frontend matches your BuildKit.
2. Avoid floating :latest frontend tags that can drift ahead of the worker.

# syntax=docker/dockerfile:1.7
FROM alpine:3.20
RUN echo hello

How to prevent it

• Pin a concrete Dockerfile frontend version with # syntax=.
• Recreate ephemeral builders rather than reusing a wedged one across jobs.

Frequently asked questions

Related guides

References

• Docker documentation
• Docker build cache
• GitHub Actions documentation