Command \circledR already defined.

[dhicks]

I'm starting to work on my first JOSS submission, and encountering this cryptic latex error when trying to build the paper:

Error producing PDF.
! LaTeX Error: Command \circledR already defined.
               Or name \end... illegal, see p.192 of the manual.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              
                                                  
l.601 \newcommand{\circledR}{Ⓡ}

Pandoc is current (3.9.0.2). I use tinytex; I've tried uninstalling and reinstalling, and filling in the missing dependencies as they cause errors. So I suppose maybe that's what's going on? In 25 years I don't think I've encountered a missing latex dependency that caused a definition collision error, though.

[dhicks]

After banging away at it for a while, Claude was able to give a diagnosis:

Template line 67: \usepackage{amssymb,amsmath} — amsfonts checks @ifundefined{circledR}, finds it undefined, and defines it
Template line 224: \usepackage{fontsetup} — inputs fspdefault.tex, which at its line 601 does \newcommand{\circledR}{Ⓡ} → FAILS (already defined)
The "l.601" in the error is fontsetup's internal file (fspdefault.tex), not input.tex.

The underlying bug: fontsetup 2.5.0 (dated 2026-04-30, very new) uses \newcommand instead of \providecommand for \circledR. The fix is to patch the three fontsetup files in your local TinyTeX to use \providecommand — which is semantically correct here ("define only if not already defined"):

/Users/danhicks/Library/TinyTeX/texmf-dist/tex/latex/fontsetup/fspdefault.tex line 601
/Users/danhicks/Library/TinyTeX/texmf-dist/tex/latex/fontsetup/fspolddefault.tex line 604
/Users/danhicks/Library/TinyTeX/texmf-dist/tex/latex/fontsetup/fspsansdefault.tex line 645
Each needs \newcommand{\circledR}{Ⓡ} → \providecommand{\circledR}{Ⓡ}.

I'm going to look for a solution that doesn't require editing local copies of text files 🙄