LaTeX Architect

LaTeX conventions for documents you control — papers, reports, theses, preprints. Targets TeX Live 2026 with pdfLaTeX as the default engine and latexmk as the only build entry point. Full skeletons (project tree, .latexmkrc, preamble, CI workflow, .gitignore) live in RECIPES.md; pinned versions in STACK.md.

Venue-specific formatting (page limits, anonymization, conference style files) is not this skill's job — see ml-conference-paper-architect.

1. Scope & defaults

Decision	Default	Switch when
Distribution	TeX Live 2026	Never for CI. Use Tectonic for hermetic/reproducible builds where package coverage allows
Engine	pdflatex	lualatex when you need system fonts, real Unicode input, or microtype-heavy typography. xelatex only for legacy font pipelines
Build driver	latexmk	Never
Bibliography	biblatex + biber	Venue templates that ship natbib — see §8
Document classes	article, report, book, institutional thesis classes	—

Never hand-run pdflatex twice. Rerun logic (cross-refs, bibliography, ToC convergence) is exactly what latexmk exists to solve. A build recipe that calls pdflatex && biber && pdflatex && pdflatex is a bug waiting to happen — it silently under-runs on the documents that need a fourth pass.

2. Project layout

One file per chapter or section, assembled by \input from a thin root file. The root holds the preamble and the \input list and nothing else — this keeps merge conflicts confined and lets you comment out a chapter with one line while drafting.

• main.tex — documentclass, preamble, \input list only.
• sections/ (or chapters/) — one .tex per unit, no preamble, no \documentclass.
• figures/ — source images. tables/ if tables are large enough to warrant their own files.
• refs.bib — one bibliography database. Split only past ~200 entries.
• preamble/ — split the preamble into packages.tex + macros.tex once it passes ~100 lines.

Rules that make this survive collaborators:

• \input over \include unless you specifically need \includeonly and per-chapter .aux files (long theses). \include forces a page break; \input does not.
• No file extensions in \includegraphics — \includegraphics{figures/plot} lets the engine pick .pdf over .png. Hardcoding .png locks you out of vector output.
• Forward slashes and relative paths only. C:\Users\... or \graphicspath with absolute paths breaks every other machine, including CI.
• Vector figures (PDF/EPS) for anything plotted. Raster only for photographs, at 300 dpi minimum.

Tree and root-file skeleton in RECIPES §1.

3. Build

.latexmkrc committed at the repo root is the contract — it encodes the engine, the bibliography backend, and the output directory so that latexmk alone reproduces the build on any machine and in CI. Nobody should need to remember flags.

• Build into build/ ($out_dir), never the source tree. Keeps git status clean and makes cleanup a directory delete.
• Set $pdf_mode and $bibtex_use explicitly rather than relying on latexmk's defaults.
• latexmk -C for a full clean; -c leaves the PDF.
• Commit .latexmkrc; gitignore build/ and every generated artifact (.aux, .bbl, .fls, .synctex.gz, …). Exception: journals that demand a .bbl in the submission tarball — generate it at submission time, don't track it.

.latexmkrc and .gitignore in RECIPES §2.

4. Preamble discipline

Package order is load-bearing, not stylistic. The canonical order:

1. Encoding/font: fontenc (T1) + lmodern, or fontspec under lua/xelatex.
2. Layout: geometry, setspace.
3. Math: amsmath, amssymb, then mathtools (which patches amsmath and must follow it).
4. Content: graphicx, booktabs, siunitx, listings/minted.
5. Bibliography: biblatex.
6. hyperref second-to-last — it redefines a large surface of internal commands and must see the final versions.
7. cleveref last — it must load after hyperref. This one ordering constraint causes more silent breakage than any other.

Additional rules:

• microtype always. One line, measurably better justification and fewer overfull boxes. There is no reason to skip it.
• Define semantic macros, not visual ones. \newcommand{\model}{\textsc{Orion}} survives a rename; \newcommand{\bs}{\boldsymbol} just aliases a primitive and buys nothing.
• \newcommand over \def — it errors on redefinition instead of silently clobbering a package's internals.
• No \usepackage{times}, {mathptmx}, {pslatex} — obsolete font packages. Use newtxtext/newtxmath if a Times clone is mandated.
• Don't load inputenc under LuaLaTeX/XeLaTeX (UTF-8 is native), and don't load subfigure ever — it has been deprecated for two decades in favor of subcaption.

Preamble skeleton in RECIPES §3.

5. Semantic markup

The rule underneath all of these: write meaning, let packages render it. Anything you type as literal formatting becomes a manual-update liability when the document is restructured.

• \cref/\Cref (cleveref) over hand-written Figure~\ref{...}. The package emits the right word and the right capitalization, and \cref{fig:a,fig:b} handles ranges and lists automatically. Never write the word "Figure" next to a \ref by hand.
• \label immediately after \caption, never before — a label placed before the caption picks up the enclosing section's counter instead of the float's, producing references to the wrong number with no error.
• Label prefixes by type: fig:, tab:, eq:, sec:, alg:, app:. Makes \cref misuse visible on sight.
• siunitx for every number with a unit — \SI{9.8}{\meter\per\second\squared}, \num{1e-3}. Consistent spacing, correct minus signs, and one place to switch decimal separator.
• booktabs rules only (\toprule, \midrule, \bottomrule). No \hline, no vertical rules — vertical rules in tables are a typographic error, not a preference.
• ~ before every reference and citation (Figure~\ref, Smith~\cite{x}) to prevent a line break between the word and its number.
• Quotes: `single' and ``double'' `` — never the"` character, which renders as two right-quotes.
• Dashes: - hyphen, -- numeric range, --- em dash.

6. Floats

• Placement specifier [t] or [tb]. Never [h] alone (LaTeX may ignore it entirely) and never [H] unless float is loaded and you have a real reason — forcing exact placement fights the algorithm and produces half-empty pages.
• Reference every float in the text before it appears. A float nothing points to has no defined position in the reading order.
• Caption above tables, below figures. This is convention, not taste; follow it unless a venue's style file overrides.
• One \centering inside the float environment, not \begin{center} — the latter adds vertical space that misaligns the float.
• Fighting float placement at draft stage is wasted effort. Write first; place at the end, when the text is final.

7. Math

• \[ ... \] or equation/align. Never $$ — plain-TeX $$ breaks amsmath spacing and fleqn.
• eqnarray is banned — broken spacing, known bug. Use align.
• align for multi-line, split inside equation for one numbered equation across lines, gather for unrelated centered lines.
• Don't number equations you never reference. Use the starred forms (align*, equation*).
• \text{} (amsmath) for words inside math, not \mbox or bare italics.
• Operator names: \newcommand{\argmax}{\operatorname*{arg\,max}}, not \text{argmax} — spacing and limit placement differ.

8. Bibliography

Default: biblatex + biber. Unicode-correct sorting, real field handling, \autocite and friends, no .bst archaeology. Set backend=biber explicitly.

• One .bib file, entries keyed consistently (author-year-keyword), exported from a manager (Zotero/JabRef) rather than hand-typed.
• Clean the exported entries. Publisher exports carry wrong-cased titles, missing DOIs, and arXiv preprints for papers that were later published in a venue — cite the published version.
• Protect capitals with braces in titles: {B}ayesian, {L}aTeX. Style files that lowercase titles will mangle proper nouns otherwise.
• \autocite for the common case; \textcite when the author is part of the sentence.

natbib carve-out. Conference and journal templates ship their own .sty with natbib wired in and a matching .bst. Do not convert them to biblatex — you break the venue's citation rendering and risk desk rejection. In that case: keep natbib, use \citep/\citet, and run bibtex (set $bibtex_use = 2 in .latexmkrc). The rule is scoped by ownership: your document, biblatex; their template, whatever it ships. See ml-conference-paper-architect for the venue side.

biblatex config and both .latexmkrc variants in RECIPES §4.

9. Quality gates

• chktex — lints for the mechanical errors above (missing ~, $$, bad quotes, space after abbreviations). Run it in CI; suppress specific warnings with a committed .chktexrc, never by disabling the tool.
• latexindent — deterministic formatting. Commit .latexindent.yaml and run in pre-commit so diffs stay reviewable.
• Zero tolerance for Overfull \hbox over ~5pt in the final pass. Fix by rewording, not by \sloppy.
• \usepackage[l2tabu, orthodox]{nag} while drafting — warns on obsolete commands directly during compilation. Remove before submission.
• CI builds the PDF on every push and uploads it as an artifact. A LaTeX repo where main doesn't compile is worse than useless, and it's a 20-line workflow.
• One sentence per line in source. Line-level diffs become sentence-level diffs, making review and merges tractable. Never reflow paragraphs — it produces diffs nobody can read.

CI workflow and latexindent config in RECIPES §5.

10. Banned constructs

Each of these has a correct replacement and no legitimate use in a new document:

Never	Instead	Why
\\ to end a paragraph	blank line	\\ breaks the line without paragraph spacing or indentation logic
$$ ... $$	\[ ... \]	Breaks amsmath spacing
eqnarray	align	Known-broken spacing
\hline in tables	booktabs rules	Cramped, no vertical padding control
subfigure	subcaption	Deprecated, conflicts with caption
\bf, \it, \rm, \sc	\textbf, \textit, …	LaTeX 2.09 syntax; doesn't nest
\vspace / \hspace for layout	fix the underlying spacing	Hand-tuned space breaks on any reflow
\centerline	\centering	Plain TeX; ignores paragraph parameters
\sloppy to fix overfull boxes	reword the sentence	Trades one visible defect for worse inter-word spacing
Absolute paths in \includegraphics	relative paths	Breaks on every other machine

11. Out of scope

• Venue formatting (page limits, anonymization, camera-ready toggles, conference .sty files) → ml-conference-paper-architect
• Presentations / beamer → demo-presentation-architect for deck content design, reveal-js-architect for HTML decks
• URU institutional formats (Word-targeted .md specs) → uru-thesis-architect, uru-scientific-paper-architect
• Repo tooling (task runner, pre-commit wiring, version pinning) → repo-tooling-architect
• CI pipeline design beyond the build job → ci-cd-architect