Language versions

With no pin, your app gets the install’s default version. To choose, declare a range in toft.toml — or, for Go, in go.mod.

toft.toml

[runtime]
python = ">=3.12,<3.14"
node   = "22"
r      = ">=4.5"

Toft picks the highest installed version that satisfies the range.

How to write a range

Language	Compared on	Examples
Python, R	major.minor	3.13, >=3.12,<3.14
Node	major	22, >=20

• Operators are >=, <=, >, < and ==. A bare version means exactly that version. A comma means AND.
• One wildcard is accepted: a trailing .* after ==, as in python = "==3.13.*", which means the 3.13 line — the same as 3.13.
• ^, ~, ~=, ||, != and any other * are refused, each with the range to write instead.
• Extra components are refused, not truncated: 3.12.4 for Python, 22.4 for Node.

To stay on an older version, give an upper bound or an exact version (python = "3.13"). A bare >= floor always takes the newest.

Node’s engines and .nvmrc

Toft does not read engines.node in package.json, .nvmrc or .node-version. A tree that states its Node version only there builds on the install’s default, and toft check and the deploy say so with a node_version_unread warning naming the version it got. Pin it in toft.toml instead: [runtime] node = "22".

Python’s requires-python

With no [runtime] python pin, Toft uses the install’s default Python unless requires-python in pyproject.toml rules it out. In that case it builds with the newest installed version that requires-python allows, and the build log and toft check say so. If no installed version is allowed, the deploy is refused and the error lists the versions the install has.

A lower bound such as >=3.8 never changes the version, because the default already satisfies it. To choose a version yourself, pin it with [runtime] python.

Go

Go reads the go line in go.mod as a minimum — go 1.25 means 1.25 or newer. If no installed toolchain meets it, the go command either downloads one or fails, depending on your install. See Go.

When no version matches

The deploy is refused before anything builds, and the error lists the versions the install has. Toft never substitutes a different version.

Which versions exist

Your administrator decides. The published Toft image ships three of each language, Go included, with the newest as the default:

Language	Versions
Python	3.15, 3.14, 3.13
Node	24, 22, 20
R	4.6, 4.5, 4.4

Your install may differ.

What’s running

Your app’s Settings tab, under Runtime, shows the exact version the serving deployment runs on. A restart keeps it.

If your administrator removes a version, running apps keep it. Your next deploy re-resolves and is refused if the pin no longer matches — that’s your cue to update the pin.