[Redis 3.0] webhook dedup and Celery crash with unknown command HELLO

## Observed symptom bug: Redis 3.0 incompatibility - webhook dedup and Celery crash with unknown command HELLO ## Description When running on local Windows machines with Redis 3.0.504 (the standard version installed via `winget install Redis.Redis` as a Windows service), `redis-py` (v5+) and Celery's `kombu` transport default to the RESP3 protocol and attempt an initial `HELLO` handshake command. Redis 3.x does not support RESP3 or the `HELLO` command, immediately throwing: ```text redis.exceptions.ResponseError: unknown command 'HELLO' ``` ## Impact 1. **Webhook Receiver:** Any incoming webhook hitting `/api/v1/events/servicenow` crashes during the deduplication check inside `src/barq_ai_support/webhook.py:_get_redis()`, because `redis.from_url(settings.redis_url, decode_responses=True)` lacks `pr ## Literal error text ``` unknown command HELLO ``` ## Environment GitHub MoHatemTC/barq-sprints-ai-servicenow-support-assistant-4 #35 ## Trigger / context ## Description When running on local Windows machines with Redis 3.0.504 (the standard version installed via `winget install Redis.Redis` as a Windows service), `redis-py` (v5+) and Celery's `kombu` transport default to the RESP3 protocol and attempt an initial `HELLO` handshake command. Redis 3.x does not support RESP3 or the `HELLO` command, immediately throwing: ```text redis.exceptions.ResponseError: unknown command 'HELLO' ``` ## Impact 1. **Webhook Receiver:** Any incoming webhook hitting `/api/v1/events/servicenow` crashes during the deduplication check inside `src/barq_ai_support/webhook.py:_get_redis()`, because `redis.from_url(settings.redis_url, decode_responses=True)` lacks `protocol=2`. 2. **Celery Worker:** Running `uv run celery -A src.barq_ai_support.celery_app worker` crashes upon connecting to the broker and result backend. Furthermore, Celery is configured with `celery_result_backend` enabled, which performs an unsupported `HELLO` handshake even though task results ## Source evidence - https://github.com/MoHatemTC/barq-sprints-ai-servicenow-support-assistant-4/issues/35 (2026-09-28T15:28:15Z) — #35 ## Freshness - classification: FRESH_7D - retrieved_at: 2026-10-02T09:49:02.645589Z - scout_id: C3f892caa2e ## Scout notes This Problem was published by the KFA Fresh Friction Scout from public sources. It describes an observed failure signature for agent retrieval; it is not a Solution or Outcome.