Support offline tectonic use

[krokosik]

I have a project that I build the Tectonic, mostly due to limited disk space. All the dependencies are properly cached and texpresso launches instantly when I start it (side note, this project is pure magic, thank you so much for creating this!).

I need to do some writing during travels as well, so I need offline support. While I can run tectonic -X compile <path> when the Wifi is disconnected, texpresso gives the following output:

2026-05-26 13:30:49.585 [info] texpresso logo: 412x412
2026-05-26 13:30:49.626 [info] sh: line 1: kpsewhich: command not found
2026-05-26 13:30:49.631 [info] note: "version 2" Tectonic command-line interface activated
2026-05-26 13:30:49.680 [info] Sent command: ["theme",[0.9019607843137255,0.9058823529411765,0.9294117647058824],[0.20392156862745098,0.23137254901960785,0.34901960784313724]]
2026-05-26 13:30:59.670 [info] tectonic bundle: indexing succeeded (0 entries)
2026-05-26 13:30:59.681 [info] note: "version 2" Tectonic command-line interface activated
2026-05-26 13:31:09.797 [info] [fatal] cannot find tectonic nor kpsewhich (texlive)(please make sure at least one of them is installed and visible in PATH)

It's quite puzzling that tectonic runs, yet texpresso claims it's missing. I'm not that familiar with either codebase, but it seems this might be something fixable on the texpresso side, especially given that standalone tectonic compiles the project.

[let-def]

Try the direct-tectonic-cache branch (#139). I reimplemented tectonic support to bypass Tectonic command when files are already in cache. It should be faster and don't need internet access for cached files.

[let-def]

It's quite puzzling that tectonic runs, yet texpresso claims it's missing. I'm not that familiar with either codebase, but it seems this might be something fixable on the texpresso side, especially given that standalone tectonic compiles the project.

Yes, I am abusing Tectonic CLI a bit 😅, it was not really designed to let other tools access its repository efficiently.

[krokosik]

Yess, works perfect! Thank you so much

[let-def]

I have updated the branch. The issue is that my fast path worked only with Tectonic 0.16. I added back the previous code to support older Tectonic and switch dynamically if the new version is not available.
Please just check that the latest version still solves your problem.

[krokosik]

Still works (with tectonic 0.16 on Arch)

[let-def]

Thank you for testing.