Task running

trellis run fans a task out across workspace packages; trellis exec does the same for an arbitrary command. Both work from anywhere inside the workspace.

trellis run <task> [pkgs...] [--since <ref>] [--with-dependents]
                   [--target erlang|javascript|all] [--strict] [--check]
                   [--serial] [--keep-going] [--jobs N]
trellis exec [pkgs...] [--since <ref>] [--serial] [--keep-going] -- <command...>

Built-in tasks

Built-in tasks map 1:1 onto gleam verbs — no declaration needed:

Task	Runs
build	gleam build. --strict adds --warnings-as-errors.
test	gleam test
check	gleam check — type check without building.
format	gleam format. --check verifies instead of writing.
docs	gleam docs build
deps	gleam deps download
clean	gleam clean

--target erlang|javascript selects the compile target; --target all runs the task once per target.

Custom tasks

Custom tasks live under [tools.trellis.tasks] in the root manifest and run through trellis run <name> exactly like built-ins — same scheduling, same package selection:

gleam.toml

# Custom tasks for `trellis run <name>`. Built-in verbs need no declaration;
# a task with a built-in's name overrides it.
[tools.trellis.tasks.lint]
command = "gleam run -m glinter"
needs_deps = true            # run `gleam deps download` first if not cached

Any built-in or custom task can omit packages through a same-named key under exclude — see package exclusions.

Scheduling

Scheduling is graph-parallel by default: a package runs as soon as its workspace dependencies have finished, up to --jobs N at once (default: CPU count). Output is streamed live with a package prefix, and a summary table names any failures:

$ trellis run test
lat_core ▏ $ gleam test
lat_core ▏ Compiling lat_core
lat_core ▏ ...
lat_mid  ▏ $ gleam test
lat_cli  ▏ $ gleam test

package   status    time
lat_core  ok        3.2s
lat_mid   ok        2.8s
lat_cli   FAILED    1.4s  `gleam test` failed

The exit code is non-zero when any package fails. --serial runs one package at a time in dependency order; --keep-going continues scheduling after a failure instead of stopping at the first one.

Selecting packages

Name packages explicitly (trellis run test lat_core) or select them from git history. --since <ref> filters to packages owning changed files — committed, uncommitted, and untracked — and --with-dependents adds the reverse-dependency closure:

# Only test what a PR touched: packages owning changed files,
# plus everything that depends on them.
trellis run test --since origin/main --with-dependents

Arbitrary commands

trellis exec runs any command in each package directory, with the same selection and scheduling flags:

trellis exec -- gleam deps update
trellis exec lat_core lat_mid -- rm -rf build

Trellis is not a general task runner: compound flows stay in just as one-liners. Recipes become delegations that keep just --list discoverability while deleting the loops:

justfile

# justfile — recipes become one-line delegations
test *ARGS:
    trellis run test {{ARGS}}

ci:
    trellis run format --check
    trellis run check
    trellis run lint
    trellis run test
    trellis run build --strict