Introduction

• 1: What is Eventboat?
• 2: Architecture

1 - What is Eventboat?

Eventboat routes events through directed acyclic graphs (DAGs) of transforms — from sources (Kafka, HTTP, cron, SQL, files) to sinks (Kafka, HTTP, files), with at-least-once delivery, dead-lettering, and replay.

It is agent-native: every capability is accessible through MCP (Model Context Protocol), CLI, and a language server — so AI agents can write, verify, deploy, and operate pipelines autonomously.

What makes it different

The one-line pitch

Eventboat lets AI agents build and run event pipelines that don’t lose messages — because machines verify every step before it goes live.

2 - Architecture

Three-layer model

YAML (+overlay) → Config (typed) → Static IR → Runtime Engine
                                          ↓
                              Source → Transform → Sink plugins

• Config layer: YAML parsing, strict schema validation, variable substitution
• Static IR: validated DAG + precompiled CEL programs + Starlark programs + schema
• Runtime: spool + settle + checkpoint engine, consuming only the IR

Reliability model

source → [spool: append-only durable queue] → in-memory DAG → sinks
                │                                  │
                └── checkpoint ←── settle tracker ←── terminal states

• Spool: every message hits SQLite before the DAG sees it (invariant 1)
• Settle: each message settles when all branches reach terminal state
• Checkpoint: advances only over settled prefix (invariant 2)
• Crash recovery: kill -9 → restart → replay from checkpoint, never lose (invariant 3)
• Dead letters: exhausted retries → DLQ store with query + replay CLI

Seven invariant tests

Each has a dedicated test that must pass in CI:

1. Spool before visible
2. Checkpoint advances only after settle
3. Kill -9 replay covers all unsettled
4. Dead-letter write failure blocks settle
5. required: false edges don’t block siblings
6. Redelivery keeps message ID stable
7. Cursor watermark never exceeds settled

Four machine gates