failed to solve: target stage "builder" could not be found

TL;DR: The --target name does not match any FROM ... AS [name] in the Dockerfile. List your stage aliases (grep -n "^FROM" Dockerfile) and fix the typo or the renamed stage. Stage names are case-sensitive and must match exactly.

The error

failed to solve: target stage "builder" could not be found

Fix it

1. List the stages actually defined:

grep -n "^FROM" Dockerfile Expected: lines like FROM node:20 AS build showing the real alias.

1. Fix the mismatch, either the build command:

docker build --target build . or the Dockerfile alias: FROM node:20 AS builder

1. Rebuild.

When this applies

• docker build --target [name] with a misspelled or stale stage name
• Dockerfiles refactored to rename stages without updating CI scripts

When this does NOT apply

• COPY --from=[name] failing (that names the source stage in the Dockerfile itself; check the alias there)
• "failed to read dockerfile" (file missing, earlier failure)

Versions

All BuildKit versions; classic builder says "failed to find stage" variants.

Why it happens

--target selects which stage to build up to. BuildKit resolves the name against the AS aliases parsed from the Dockerfile; anything else is an error, and the message quotes the name you passed so you can diff it against the file.

Edge cases

• Stage names are case-sensitive: AS Builder is not --target builder.
• A stage defined AFTER the target in file order is fine; order does not matter, only the name.
• docker buildx bake targets are defined in the bake file, not the Dockerfile; a bake target typo produces a different error.