Dockerfile Stage Dependency Inspector

How to use Dockerfile Stage Dependency Inspector

Trace literal build-stage dependencies and a selected target in a restricted Dockerfile, without building images. Find which declared stages feed FROM and COPY --from references. Inspect the target dependency closure, external source tokens and a concrete cycle witness while keeping every command inert.

1. Provide dockerfile: literal from/copy profile, optional target stage name or zero-based index.
2. Choose the supported mode and run the tool. Review its assumptions and any reported errors.
3. Copy the result or download a separate output; reset to clear the current form.

Good to know

• 100 KB UTF-8, 3,000 physical lines, 1,500 instructions, 50 stages and 500 stage-reference instructions. A logical instruction is at most 10,000 characters. Standard LF/CRLF and top-of-file backslash/backtick escape directives are supported. Continuation follows the inspected BuildKit boundary: only SP/TAB may follow a terminal escape, and an immediately preceding escape prevents joining, even in odd runs of three or more.
• Selected literal-stage profile only. FROM bases/platforms and COPY --from targets cannot use build-argument expansion. Here-documents, ONBUILD, RUN --mount and custom frontends/instructions are refused instead of guessing dependency behavior.
• FROM may inherit a previously named stage; COPY --from may name any declared stage or zero-based stage index. Unmatched literal COPY sources are reported as external images or named contexts without assuming which exists.
• Shell bodies and most instruction arguments remain opaque text. COPY JSON path arrays receive structural checks, but file existence, path/glob expansion, image reference syntax and complete Dockerfile validity are not established.
• The default target is the last stage. A closure is structural input, not a predicted cache hit, execution order, image size or successful build. Commands, files, images, registries and external contexts are never accessed.
• Inputs are processed on this device and are not automatically saved or uploaded.