Just Monad Skill

Justfile as Free Monad for compositional task orchestration

Trit: 0 (ERGODIC)
Color: #49EE54 (Green)
Role: Coordinator/Orchestrator

Core Concept

The Just Monad treats

just

data JustF next
  = Recipe String [String] next     -- name, deps, continuation
  | Shell String next               -- command, continuation
  | Parallel [JustF next] next      -- concurrent recipes

type Just = Free JustF

Universal Property:

Just

Monad Laws in Justfiles

# Left identity: just (pure a) >>= f  ≡  f a
pure-then-use: other
    @echo "Equivalent to just running 'other'"

# Right identity: m >>= pure  ≡  m
action-then-pure: action
    # Returns result of action unchanged

# Associativity: (m >>= f) >>= g  ≡  m >>= (λx. f x >>= g)
a-then-b-then-c: a b c
    # Order doesn't matter for composition

Pattern: Dependency as Bind

# Pure: no dependencies
leaf:
    @echo "I am a leaf node"

# Bind: depends on other recipes
branch: leaf
    @echo "I depend on leaf"

# Nested bind
root: branch
    @echo "I depend on branch (transitively on leaf)"

Execution order:

leaf

branch

root

The Three Arrows (α/β/γ)

From Narya structural diffing:

test:

build:

deploy:

# α: Verify behavior hasn't changed
test:
    julia --project -e 'using Test; @testset "all" begin include("test/runtests.jl") end'

# β: Transform structure
build: test
    julia --project -e 'using Pkg; Pkg.build()'

# γ: Bridge to production (coherence check)
deploy: build
    @echo "Deploying if tests pass and build succeeds"

GF(3): (−1) + 0 + (+1) = 0 ✓ CONSERVED

Parallel Composition (Applicative)

# Parallel: independent recipes can run concurrently
parallel-test:
    just test-unit &
    just test-integration &
    wait

# Applicative: f <*> x
apply-all: build
    just deploy-a &
    just deploy-b &
    just deploy-c &
    wait

Justfile Random Walk

Navigate justfiles via deterministic random walk:

# Find all justfiles
find ~/worlds -name "justfile" | shuf -n 3

# Extract recipes
just --list --justfile /path/to/justfile

# Run random recipe
just --justfile /path/to/justfile $(just --list | shuf -n 1 | awk '{print $1}')

Skill Graph Rewilding

When adding a new skill that uses justfiles:

1. α-diff: Does the new recipe preserve existing test behavior?
2. β-diff: Does the recipe structure fit the existing graph?
3. γ-diff: Is there a bridge connecting new ↔ existing recipes?

# Verify transitivity when adding skill C between A and B
verify-transitivity a b c:
    @echo "Checking: {{a}} → {{c}} → {{b}}"
    just {{a}}
    just {{c}}
    just {{b}}
    @echo "Transitivity verified if all pass"

TeglonLabs Justfile Patterns

Found across TeglonLabs repos:

Cofree Comonad Dual

The dual of

Just

data Cojust a = a :< JustF (Cojust a)
-- Infinite stream of possible continuations

Cojust represents:

• The environment/context in which recipes run
• The history of all past executions
• The space of possible futures

End-of-Skill Interface

Commands

# List all recipes
just --list

# Run with variables
just test seed=1069

# Dry run (show commands)
just --dry-run build

# Evaluate expression
just --evaluate '{{arch()}}'

# Export as shell script
just --dump --format=just

Integration with Gay.jl

# Just Monad in Julia
struct JustMonad{A}
    recipe::String
    deps::Vector{String}
    action::Function
end

function just_pure(recipe, action)
    JustMonad{Any}(recipe, String[], action)
end

function just_bind(m::JustMonad, recipe, action)
    JustMonad{Any}(recipe, [m.recipe; m.deps], action)
end

# Color each recipe by trit
function just_color(m::JustMonad, seed::UInt64)
    idx = hash(m.recipe) % 1000
    gay_color_at(seed, idx)
end

GF(3) Triads

narya-proofs (-1) ⊗ just-monad (0) ⊗ free-monad-gen (+1) = 0 ✓
three-match (-1) ⊗ just-monad (0) ⊗ gay-mcp (+1) = 0 ✓
temporal-coalgebra (-1) ⊗ just-monad (0) ⊗ topos-generate (+1) = 0 ✓

References

• Just Manual
• Swierstra, "Data Types à la Carte"
• Kiselyov & Ishii, "Freer Monads"
• ALIFE 2025, "Structural Rewilding via Diffs"

Autopoietic Marginalia

The interaction IS the skill improving itself.

Every use of this skill is an opportunity for worlding:

• MEMORY (-1): Record what was learned
• REMEMBERING (0): Connect patterns to other skills
• WORLDING (+1): Evolve the skill based on use

Add Interaction Exemplars here as the skill is used.