Superstep Execution Model

Eko executes graphs in supersteps. Each superstep runs a batch of tasks in parallel, then merges results and advances to the next batch.

Superstep Loop

Superstep 1: [task_A, task_B]  ← parallel execution
    ↓ merge writes into channels
    ↓ save checkpoint
    ↓ resolve edges → collect next batch of tasks
Superstep 2: [task_C]
    ↓ ...
Done (no more tasks)

Key Properties

• Parallel within superstep: All tasks in a superstep execute concurrently.
• Batch merge: Writes to channels are merged after the superstep completes.
• Determinism: Results are independent of task completion order within a superstep.
• Checkpoint per superstep: State is persisted after each superstep for fault tolerance.

Flow

1. Execute – Run all tasks in the current batch in parallel.
2. Merge – Apply channel writes (reducers, last-write-wins, etc.).
3. Checkpoint – Persist graph state.
4. Resolve edges – Evaluate conditional edges and collect the next task batch.
5. Repeat – If tasks remain, start the next superstep; otherwise finish.