Engine

The engine manages the upload state machine, scheduling, and side effects. All state changes go through the reducer, and all public events emit from a single transition layer.

State Machine

Scheduling

The scheduler continuously makes progress:

• Intent creation for items in the creating_intent phase
• Upload slots for queued items, respecting the configured concurrency limit
• Finalization for items in the completing phase

Event Emission

Public events are emitted by store.runtime.ts after transitions, not inside handlers. This prevents duplicates and ensures consistent semantics.

file.rejected is emitted during addFiles because rejected files never enter state.

Retry Model

retryDecision centralizes retry policy. Handlers only request a decision; they never hardcode retry logic. The default configuration allows up to 3 attempts with exponential backoff.