# Slack Web API conversations.replies rate limit new cohort limit thread backfill 429

Status: search-observed
Product: Slack Web API
Last verified: 2026-06-25
Canonical HTML: https://gitdocs.org/fix/slack-web-api-conversations-replies-rate-limit-new-cohort-limit-thread-backfill-429
Machine JSON: https://gitdocs.org/api/fixes/slack-web-api-conversations-replies-rate-limit-new-cohort-limit-thread-backfill-429.json

## Exact Symptom

See the observed Codex queries below.

## Diagnosis

The code can work for existing/internal installations yet fail for newly created or unlisted apps; account cohort and current service policy are external.

## Fix

```
Verifier checks backoff, pagination completeness, and installation-aware behavior under the current limits. Verify complete synchronization under each cohort without hard-coding one global throttle.
```

## Avoid

- Changing local code without checking the current external contract.
- Retrying the same install, build, or API call with no version/source change.
- Applying a broad unsafe bypass when a narrow compatibility fix is available.

## Observed Codex Queries

- Slack Web API conversations.replies rate limit new cohort limit thread backfill 429
- site:docs.slack.dev conversations.replies rate limit 1 request per minute 15 messages
- Slack conversations.replies rate limit 1 request per minute 15 messages 2025
- https://docs.slack.dev/reference/methods/conversations.replies

## Sources

- Slack rate limit changes for non-Marketplace apps: https://docs.slack.dev/changelog/2025/05/29/rate-limit-changes-for-non-marketplace-apps/
- Official reference opened by Codex: https://docs.slack.dev/reference/methods/conversations.replies