# 012 — SLURP Idempotency, Backpressure, and DLQ

- Area: `pkg/integration/slurp_client.go`, `pkg/integration/slurp_events.go`, config
- Priority: High

## Background
SLURP event delivery has retries and batching but lacks idempotency keys, circuit-breaking/backpressure, and a dead-letter queue (DLQ). Under failure/load this can produce duplicates or data loss.

## Scope / Deliverables
- Idempotency:
  - Generate a stable idempotency key per event (e.g., hash of {discussion_id, event_type, timestamp bucket}).
  - Send via header `Idempotency-Key` and include in body for server-side dedupe (if supported).
- Backpressure & Circuit-breaker:
  - Add exponential backoff with jitter and max retry window.
  - Implement a circuit-breaker that opens on consecutive failures, stops sending for a cooldown, then half-open probes.
- DLQ & Replay:
  - Persist failed events (JSONL or lightweight queue) with reason and next-attempt time.
  - Add a background replay worker with rate limiting and visibility into backlog.
- Metrics & Logging:
  - Prometheus counters/gauges: events_generated, sent, failed, deduped, dlq_depth, circuit_state; latency histograms.
  - Structured logs for failures with keys.

## Acceptance Criteria / Tests
- Under induced 5xx or timeouts, client opens breaker, stops flooding, writes to DLQ, then recovers and drains when service returns.
- Idempotent resubmissions do not create duplicates (server returns success with same id), counters reflect dedupe.
- Unit tests for backoff, breaker state transitions, DLQ persistence, and replay.

## Notes
- Keep DLQ pluggable (file-based default); allow disabling via config.