Summary

NATS consumer names must not contain . (dots) or spaces. This is enforced by the NATS server because dots are the subject token delimiter in NATS subject-based addressing (e.g. orders.us.east). Allowing dots in consumer names would create ambiguity with the subject namespace. The NATS server rejects any js_PullSubscribe call with a consumer name containing . with an Invalid Argument error.

The auto-generated consumer name in Proton uses the format proton-{query_id}. For materialized views, the query ID contains dots (e.g. .mv-95861997-136d-4030-8298-f68745e50f04), producing names like:

proton-.mv-95861997-136d-4030-8298-f68745e50f04
       ^
       dot -- rejected by NATS server

This causes CREATE MATERIALIZED VIEW against a NATS JetStream external stream to fail with:

Code: 2629. DB::Exception: Failed to create JetStream pull subscription:
  subject='orders.>' stream='ORDERS'
  consumer='proton-.mv-95861997-136d-4030-8298-f68745e50f04': Invalid Argument.

Fix: Sanitize the auto-generated consumer name by replacing . and spaces with - before passing it to the NATS C client. This applies to both user-specified and auto-generated consumer names. The sanitized name proton--mv-95861997-136d-4030-8298-f68745e50f04 is valid and works correctly.

Reference: NATS naming conventions -- consumer names follow the same rules as stream names: alphanumeric, -, _, no . or spaces.

Test plan

• CREATE MATERIALIZED VIEW ... FROM nats_jetstream_stream succeeds without explicit consumer_name
• MV correctly consumes all messages and routes to target Proton stream
• Live INSERT via HTTP -> NATS -> MV -> archive stream works end-to-end
• Explicit consumer_name with dots (e.g. my.consumer) is also sanitized