How do I include chapters?

[eduardz1]

In LaTeX, it's common to subdivide your work in chapters in a "chapters" folder, however using the standard "\include" syntax doesn't seem to work, it's like it's including an empty chapter. My project is structured in this way:

.
├── latex
│   ├── guide
│   │   ├── chapters
│   │   │   └── a.tex
│   │   └── guide.tex
│   └── lib
│        ├── _postamble.tex
│        └── _preamble.tex
└── Tectonic.toml

It looks a bit complicated but it makes sense in the entire repository context. In the Tectonic.toml file I wrote:

[doc]
name = "eta-kappa-notes"
bundle = "https://data1.fullyjustified.net/tlextras-2022.0r0.tar"
extra_paths = ["latex"]

[[output]]
name = "guide"
type = "pdf"
shell_escape = true
inputs = ["lib/_preamble.tex", "guide/guide.tex", "lib/_postamble.tex"]

A minimal reproducible example would be guide.tex containing:

\title{Guide}

\maketitle
\tableofcontents

\include{chapters/a}

a.tex containing

\chapter{A}

a

_preamble.tex with

\documentclass[a4paper,12pt]{book}
\begin{document}

and _postamble.tex with

\end{document}

The resulting PDF does not contain the "A" chapter

I am using the latest version, compiled with cargo with

cargo install --git https://github.com/tectonic-typesetting/tectonic tectonic

[eduardz1]

I'll open an issue instead