Effects and handlers

Chelis tracks effects explicitly. Pure tensor code stays pure; host interaction and randomness are surfaced in types and syntax.

Common effects

• Random
• IO
• device-selection handlers for compiled execution paths

Handler fragments

with seed(42) {
  sample_fn(x)
}

(with-handler {effect Random seed 42}
  (app {} (var {} sample_fn) (var {} x)))

Use fragment fences here because the book is teaching handler shape, not promising that this exact snippet is a full standalone program.

For the active effect semantics, use spec/07-concurrency.md and the effect-checking crates/tests.