fix(events): run NATS handlers once per event, keep Kafka internal topics out of wildcards

[intech]

Summary

Three wildcard-subscription defects found by a live run against real brokers: @connectum/events-nats ran the handler once per matching pattern of a subscription (3 times for user.created with the routes user.created, user.*, user.>); @connectum/events-kafka subscribed Kafka's internal __consumer_offsets for a catch-all >, and never consumed a topic created after the subscription.

• NATS. Every pattern keeps its own durable consumer, exactly as in earlier versions: same names, same filters, same positions. A message matched by several patterns reaches the adapter once per consumer; the handler runs for the delivery of the most specific pattern among those whose consumer delivers it (an order derived from the pattern text, equal on every replica), and the other deliveries are acknowledged without running it. Upgrading and rolling back need no action and no queue is replaced.
• NATS never writes to the broker. The adapter reads the consumers it finds and never changes their configuration, so rolling back to 1.2 keeps working (verified with the published @connectum/events-nats@1.2.0 on nats-server 2.9.25, 2.10.29 and 2.15.0), and consumers provisioned by an operator need only read and pull permissions (verified with a user that cannot create consumers). Replicas compute where each consumer starts from what the server reports; a delivery below the delivering consumer's own bound always runs the handler, so replicas that disagree can duplicate a handler run, never skip one.
• NATS, also fixed. An unacknowledged delivery of an existing consumer used to be acknowledged away without running the handler when a wider route was added (found while reviewing this change; reproduced on all three servers, red before and green after). A failing subscribe() used to delete a consumer of the same group that existed before the call (present on main); it now deletes only the consumers of an auto-generated group, and leaves those of a named group for the next start. An existing consumer made with another ackWait, maxDeliver or deliverPolicy is kept and reported with one warning per consumer. Two replicas racing to create one consumer are handled.
• Kafka. A pattern that opens with a wildcard no longer matches topics starting with __ (exactly the topics Kafka and Redpanda mark internal; Redpanda's _schemas is not internal and is still received by >). New consumerOptions.topicDiscoveryInterval (number | false), on by default at 300 000 ms (false turns it off), picks up topics created after the subscription and logs each discovery with the topic names. In a group of several members a new topic is read completely after the longest interval among the members (KafkaJS assigns partitions only from the group leader's topic list); nothing is lost meanwhile.
• Redis. The rejection of wildcard patterns is documented and pinned by a test.
• CI. A NATS JetStream job runs the NATS integration tests on nats-server 2.9.25 (the oldest supported line), 2.10.29 and 2.15.0 for the first time.

Docs companion: Connectum-Framework/docs, branch docs/events-adapters-wildcard-defects.

Decisions

• Kafka discovery is on by default. The repository rule is that behaviour-changing defaults are opt-in, with an exception for a silent loss of data, and this loss was measured by the independent review and re-measured by the implementer on a live broker (6 runs each on apache/kafka 4.2.0 and Redpanda v25.3.10, identical in all 12): a topic created after the subscription, five messages published to it, the service restarted, a sixth message published. Discovery off, restart after 5 s: the group handled only the sixth (5 of 6 never handled, no line in the log), because a restart reads a new topic from its end. Discovery 1000 ms, restart after 8 s: all 6 handled, the first run having handled and committed 5. Discovery 60 000 ms, restart after 3 s (before the first check): the same 5 lost. So with discovery on, the loss is gone unless the service restarts inside one interval before a check has seen the topic; that window is a property of Kafka (a group without a committed offset starts at the end) and is documented. The three measurements are permanent integration tests. Cost: one metadata request per wildcard subscription every five minutes on one extra admin connection per adapter, and a group rebalance when a matching topic appears. false restores the fixed list of earlier versions. The changeset and the highlights say it changes a default.
• NATS: no write to the broker. The first design recorded the start sequence in consumer metadata (connectum.start_seq). Measured: after that write the published 1.2.0 cannot subscribe on nats-server 2.10.29 and 2.15.0 (consumer already exists, API error 10148), which breaks a rollback and the restart of a 1.2 replica during a rollout. The write was removed; the bounds are read only, and the delivery rule above makes the replicas safe whatever bounds they hold.
• NATS: duplicates, not losses. While a service is rolled out with a route added to a broader pattern, an event can be handled by both the old and the new replicas (measured: replicas [user.>] and [user.created, user.>], 30 events, 0 lost, 15 handled twice). The same can happen when replicas attach at different times while a wider consumer still lags behind a narrower one, and when a consumer holds a delivery that was never acknowledged. This is the at-least-once contract; handlers must tolerate redelivery.
• NATS: network copies remain. The server still sends one copy per matching pattern (as before); only the handler runs once.
• NATS: consumers of removed routes stay on the broker as before and keep growing; they are not deleted automatically because deleting a consumer under a running replica silently stops its delivery (measured and pinned by a test). The cleanup command is documented.
• Kafka: __ rule has no switch. Anyone who relied on a catch-all to read __consumer_offsets loses it; a pattern that spells the prefix out and literal topic names still work.
• Kafka integration tests: topic readiness. The branch includes the commit that waits for topic metadata instead of trusting waitForLeaders (also proposed separately): without it the suite on apache/kafka 4.2.0 failed a different test on each run with "This server does not host this topic-partition".

Type of change

• Bug fix (non-breaking)
• New feature (changes the default behaviour of Kafka wildcard subscriptions; false restores the old behaviour)
• Breaking change (documented in migration guide)
• Documentation / chore / internal

Test plan

• pnpm --filter @connectum/reflection build:proto, pnpm --filter @connectum/cli build:proto, pnpm turbo run build (20/20), then pnpm turbo run typecheck test (50/50, 0 type errors; events-nats 32 and events-kafka 90 unit tests; most other tasks replayed from the turbo cache)
• pnpm exec biome check . after the full build: exit 0, no warnings; pnpm lint:rules 5/5; TypeDoc (--emit none) exit 0; pnpm release:gate PASS; pnpm test:bun and pnpm test:esbuild 35/35 tasks each
• Red before, green after: the scenarios "attaching leaves the configuration untouched, so the earlier version can create it again", "an unacknowledged delivery of an existing consumer is handled after a wider route is added" and the unit tests of the own-bound rule, of the Kafka default and of the discovery log fail on the previous sources and pass on the new ones
• NATS integration 26/26 and 0 skipped on nats-server 2.9.25, 2.10.29 and 2.15.0; the NATS suites also pass under Bun (2.10.29, 5 suites)
• Rollback with the published @connectum/events-nats@1.2.0: this version attaches to consumers made by 1.2.0 and handles events, then 1.2.0 subscribes again and handles events, on 2.9.25, 2.10.29 and 2.15.0; the consumers' metadata stays empty. Before: a metadata write made 1.2.0 fail with 10148 on 2.10.29 and 2.15.0
• Least privilege: consumers made beforehand, a user without $JS.API.CONSUMER.CREATE.>: subscribe() succeeds and the events are handled
• Mutations, each fails the intended tests: ownership disabled, own-bound clause removed, the metadata write put back, rollback deleting every durable, the "already exists" branch removed, Kafka default turned off, false not recognised, __ guard removed, discovery not started, discovered topic not read from the beginning
• Kafka integration 30/30 on apache/kafka 4.2.0 and on Redpanda v25.3.10 (including the skewed-interval scenario); the suites also pass under Bun on Kafka; Redis 13/13 on redis 6.2 and valkey 9.1.1; AMQP 14/14 on rabbitmq 4.3.6
• Examples with tarballs packed from this branch (md5 of dist/index.js equal to the tarball, lockfiles restored): with-events-dlq (NATS) 5/5, with-events-kafka 5/5, with-events-redpanda 5/5, with-events-valkey 5/5, hris 36/36, car-sharing 49/49; scaffold:check --combo events-nats ok. with-events-amqp passes 5/5 in some runs and 4/5 in others ("multiple orders processed correctly": the order service handles InventoryReserved before it stores the order); with the published packages from the committed lockfile it fails the same test in 3 of 5 runs, so it is a race in the example, not in the adapter, and events-amqp is not changed here
• Not measured: whether ack_floor moves past a message that exhausted max_deliver (affects the number of duplicates only); a Kafka group mixing members with and without discovery; the size of the metadata answer on a cluster with thousands of topics

Parity coverage

• Parity coverage added
• Parity N/A: the change concerns event-bus adapter subscriptions (NATS, Kafka) and documentation; it does not change observable RPC behaviour and does not touch the HTTP/2 or in-process transports.

Related issues / changes

Related: #329 (AMQP > semantics, not touched here; the docs companion points the AMQP row to the AMQP page because AMQP > matches zero segments on main until #329 merges). Docs PRs #123/#126 edit the same pages as the docs companion (custom-topics.md conflicts with #126). Before merging: the new CI check NATS JetStream (nats-2.9.25) has never run on GitHub.

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Docs companion: Connectum-Framework/docs#128

Summary by CodeRabbit

• New Features
  • Kafka wildcard subscriptions exclude internal topics from broad matches and discover newly created matching topics every five minutes by default. Discovery can be disabled.
  • NATS subscriptions run handlers only for the most-specific matching pattern, reducing duplicate event handling.
• Bug Fixes
  • Redis subscriptions with unsupported wildcard patterns now fail with a clear error instead of silently receiving no events.

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📒 Files selected for processing (5)

• .github/RELEASE_HIGHLIGHTS.md
• packages/events-kafka/README.md
• packages/events-kafka/src/KafkaAdapter.ts
• packages/events-kafka/tests/integration/DiscoverySeed.integration.test.ts
• packages/events-kafka/tests/integration/KafkaAdapter.integration.test.ts

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🚧 Files skipped from review as they are similar to previous changes (1)

• .github/RELEASE_HIGHLIGHTS.md

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📝 Walkthrough

Walkthrough

The pull request adds periodic discovery and internal-topic filtering for Kafka wildcard subscriptions, single-handler delivery for overlapping NATS patterns, and documentation and integration tests for Redis wildcard rejection. It also adds NATS JetStream integration tests to CI across three server versions.

Changes

Kafka wildcard discovery

Layer / File(s)	Summary
Wildcard matching and discovery options packages/events-kafka/src/types.ts, packages/events-kafka/src/KafkaAdapter.ts, packages/events-kafka/tests/unit/KafkaAdapter.test.ts, packages/events-kafka/README.md, .changeset/kafka-wildcard-internal-topics-and-discovery.md, .github/RELEASE_HIGHLIGHTS.md	The adapter excludes __ topics from patterns beginning with * or >. It adds consumerOptions.topicDiscoveryInterval, defaulting to 300,000 ms, and accepts false to disable discovery. Unit tests and documentation cover the option and matching rules.
Discovery lifecycle and consumer restart packages/events-kafka/src/KafkaAdapter.ts, packages/events-kafka/src/topicDiscovery.ts, packages/events-kafka/tests/unit/topicDiscovery.test.ts	Wildcard subscriptions list existing topics before subscribing. A polling loop subscribes to newly matching topics and restarts consumption. Unsubscribe and disconnect stop discovery.
Broker-backed discovery validation packages/events-kafka/tests/integration/*	Integration tests cover initial topic-listing failures, discovery seeding, new topics, disabled discovery, group-member timing, restart behavior, and internal-topic filtering.

NATS overlapping-pattern delivery

Layer / File(s)	Summary
Consumer setup and pattern ownership packages/events-nats/src/consumerSetup.ts, packages/events-nats/src/patternOwner.ts, packages/events-nats/tests/unit/*, packages/events-nats/tests/integration/ConsumerSetup.integration.test.ts	Consumer setup handles existing durables, configuration differences, and consumer API errors. Pattern matching and ordering select an eligible owner using consumer start sequences. Unit and integration tests cover setup and ownership behavior.
Subscription delivery and durable lifecycle packages/events-nats/src/NatsAdapter.ts, packages/events-nats/tests/integration/*, packages/events-nats/README.md, packages/events-nats/package.json, .changeset/nats-overlapping-patterns-one-delivery.md, .github/workflows/ci.yml	The adapter prepares consumers before starting delivery loops and acknowledges deliveries that do not own a message. It preserves named-group durables during cleanup. Integration coverage and documentation describe overlapping patterns, route changes, redelivery, and cleanup. CI runs the NATS integration suite against three JetStream versions and checks that tests did not skip.

Redis wildcard rejection

Layer / File(s)	Summary
Document and verify wildcard rejection packages/events-redis/README.md, packages/events-redis/tests/integration/wildcard-rejection.test.ts, .changeset/redis-wildcard-rejection-documented.md	The README documents rejection of * and > subscription patterns. Integration tests check the error for direct subscriptions and EventBus startup.

Priority: ➖ Normal

Estimated code review effort: 4 (Complex) | ~45 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant KafkaAdapter
  participant KafkaAdmin
  participant KafkaConsumer
  participant startTopicDiscovery
  KafkaAdapter->>KafkaAdmin: List topics before wildcard subscription
  KafkaAdapter->>KafkaConsumer: Subscribe and start consumption
  startTopicDiscovery->>KafkaAdmin: Poll broker topic names
  startTopicDiscovery->>KafkaConsumer: Subscribe to newly matching topics
  startTopicDiscovery->>KafkaConsumer: Stop and restart consumption
  KafkaAdapter->>startTopicDiscovery: Stop discovery on unsubscribe or disconnect

Loading

sequenceDiagram
  participant NatsAdapter
  participant ensureConsumer
  participant JetStream
  participant consumeLoop
  participant EventHandler
  NatsAdapter->>ensureConsumer: Prepare durable and obtain start sequence
  ensureConsumer->>JetStream: Get or create durable consumer
  JetStream->>consumeLoop: Deliver message subject and sequence
  consumeLoop->>consumeLoop: Select eligible owning pattern
  consumeLoop->>JetStream: Acknowledge non-owning delivery
  consumeLoop->>EventHandler: Dispatch owning delivery

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Merge Risk: ⚪ Minimal · up to 02007

Wildcard subscriptions fail when their required initial metadata listing fails, rather than risking replay of existing messages. No merge-blocking issue is established.

Pre-merge checks | 4 | 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 56.60% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 53 functions across 20 files. (2 skipped:…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check		The title clearly identifies the two primary changes: single handler execution for overlapping NATS patterns and exclusion of Kafka internal topics from wildcard subscriptions.
Description check		The description includes all required sections, explains the NATS, Kafka, and Redis changes, documents decisions and risks, lists extensive test coverage, states parity is not applicable with justific…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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Full details: Docstring Coverage

Explanation

Docstring coverage is 56.60% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 53 functions across 20 files. (2 skipped: 2 unsupported.)

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commit: 02007d3

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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
Review comments at @packages/events-kafka/src/KafkaAdapter.ts:
- Around line 289-293: In the initial topic discovery block guarded by
topicDiscoveryInterval and wildcards, handle getAdmin().listTopics() failures
without aborting subscribe(); keep the known topics collected on success and
allow periodic discovery to retry after a failure.

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📒 Files selected for processing (28)

• .changeset/kafka-wildcard-internal-topics-and-discovery.md
• .changeset/nats-overlapping-patterns-one-delivery.md
• .changeset/redis-wildcard-rejection-documented.md
• .github/RELEASE_HIGHLIGHTS.md
• .github/workflows/ci.yml
• packages/events-kafka/README.md
• packages/events-kafka/src/KafkaAdapter.ts
• packages/events-kafka/src/topicDiscovery.ts
• packages/events-kafka/src/types.ts
• packages/events-kafka/tests/integration/DiscoverySkew.integration.test.ts
• packages/events-kafka/tests/integration/EventBusStop.integration.test.ts
• packages/events-kafka/tests/integration/KafkaAdapter.integration.test.ts
• packages/events-kafka/tests/integration/createTopic.ts
• packages/events-kafka/tests/unit/KafkaAdapter.test.ts
• packages/events-kafka/tests/unit/topicDiscovery.test.ts
• packages/events-nats/README.md
• packages/events-nats/package.json
• packages/events-nats/src/NatsAdapter.ts
• packages/events-nats/src/consumerSetup.ts
• packages/events-nats/src/patternOwner.ts
• packages/events-nats/tests/integration/ConsumerSetup.integration.test.ts
• packages/events-nats/tests/integration/LegacyConsumers.integration.test.ts
• packages/events-nats/tests/integration/OverlappingPatterns.integration.test.ts
• packages/events-nats/tests/integration/PatternOwnership.integration.test.ts
• packages/events-nats/tests/unit/consumerSetup.test.ts
• packages/events-nats/tests/unit/patternOwner.test.ts
• packages/events-redis/README.md
• packages/events-redis/tests/integration/wildcard-rejection.test.ts

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[intech]

@coderabbitai please read my reply in the thread on KafkaAdapter.ts (the first listTopics() failure): your suggestion is declined with measurements on Kafka 4.2.0 and Redpanda v25.3.10 (an empty known makes every existing topic a new one and re-reads its history). The behaviour is pinned by DiscoverySeed.integration.test.ts in f851b69. Please take it into account in further reviews of this PR.

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🧩 Analysis chain

🏁 Script executed:

#!/bin/bash
set -euo pipefail
gh api --paginate repos/Connectum-Framework/connectum/pulls/332/comments --jq '.[] | select(.path == "packages/events-kafka/src/KafkaAdapter.ts") | {id, in_reply_to_id, user: .user.login, body, html_url}'
fd -t f '^(KafkaAdapter\.ts|DiscoverySeed\.integration\.test\.ts|topicDiscovery\.ts)$'
ast-grep outline packages/events-kafka/src/KafkaAdapter.ts --items all
ast-grep outline packages/events-kafka/src/topicDiscovery.ts --items all
fd -t f '^DiscoverySeed\.integration\.test\.ts$' --exec ast-grep outline {} --items all
sed -n '230,380p' packages/events-kafka/src/KafkaAdapter.ts
sed -n '1,160p' packages/events-kafka/src/topicDiscovery.ts
fd -t f '^DiscoverySeed\.integration\.test\.ts$' --exec sed -n '1,260p' {}

Length of output: 26557

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@intech, I read your thread reply and inspected KafkaAdapter.ts, topicDiscovery.ts, and DiscoverySeed.integration.test.ts.

Your rejection is correct. My fallback suggestion was unsafe, and I withdraw it. An empty known set makes existing matching topics appear new. Discovery then subscribes with fromBeginning: true, which can replay history for groups without committed offsets.

The regression tests cover the seeded case, the empty-seed replay, and subscription failure when the initial listing fails. I did not run the tests.

The retrieved learning already captures this distinction: the initial listing must succeed; periodic discovery failures can retry. No duplicate learning is needed.

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🧠 Learnings used

Learnt from: intech
Repo: Connectum-Framework/connectum PR: 332
File: packages/events-kafka/src/KafkaAdapter.ts:293-297
Timestamp: 2026-10-09T10:06:25.158Z
Learning: In packages/events-kafka/src/KafkaAdapter.ts, wildcard topic discovery must seed known with the initial topic listing before starting periodic discovery. Do not swallow an initial getAdmin().listTopics() failure and continue with an empty known set. Discovery in packages/events-kafka/src/topicDiscovery.ts subscribes newly discovered topics with fromBeginning: true, so an empty seed misclassifies existing topics as new and can replay their history for groups without committed offsets despite consumerOptions.fromBeginning: false. Initial-listing failure and periodic-discovery retry are distinct cases.

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