doxygen graphviz "Problems running dot" class diagram

TL;DR

Install Graphviz so the dot executable is on PATH, or point DOT_PATH at it. Doxygen shells out to dot for every diagram; a missing binary fails them all.

Error

Problems running dot: exit code=1, command='dot', arguments='...'

Steps

1. Check dot directly: run dot -V in the same environment as the Doxygen run. Expected: a version string, or "command not found" telling you it is missing.
2. Install Graphviz via your OS package manager, or download it for the build machine. Expected: dot -V now prints a version.
3. If dot lives outside PATH, set DOT_PATH in the Doxyfile to the directory containing it. Expected: Doxygen finds the binary without PATH changes.
4. Re-run doxygen Doxyfile. Expected: class diagrams render and the dot warnings disappear.

When to use

• Doxygen logs "Problems running dot"
• Diagrams are blank or missing in the output
• CI or Docker builds lack Graphviz while local builds work

When not to use

• You do not want diagrams at all (set HAVE_DOT = NO instead)
• dot runs but a specific diagram errors (check that diagram's input)
• The failure is a Doxygen crash, not a dot failure

Tool compatibility

Doxygen 1.9 through 1.12 with Graphviz 2.4x through 10.x.

Variant phrasings

dot found but diagrams still fail

The dot version may be too old for the output format. Upgrade Graphviz or set DOTIMAGEFORMAT to a supported type.

problems running dot only in CI

Install graphviz in the CI image; developer laptops usually have it, containers usually do not.

Why it happens

HAVE_DOT defaults to YES, so Doxygen attempts diagrams on every run. The dependency is external and often absent from minimal build environments, and Doxygen reports the failure per diagram rather than once.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_pvxXhLNEMfdkqhY7LI3GQw