fix(rss): deliver unseen items published before the last poll

[TheodoreSpeaks]

Summary

RSS polling advances lastCheckedTimestamp on every poll and rejects items published before that timestamp, even when their GUID has never been delivered. A feed that exposes a 21:25 article after a 23:26 poll therefore silently loses it. Staging native canaries exposed this while the poller itself continued reporting success.

Use the subscription's immutable webhook creation time as the historical cutoff and retain GUID deduplication. This accepts delayed feed entries without replaying known GUIDs or backfilling items published before subscription. This patch is limited to the timestamp filter; the separate attempted-versus-delivered bookkeeping issue is deferred.

Type of Change

• Bug fix

Testing

• New delayed-item regression test fails on the original implementation and passes with the fix.
• RSS, IMAP, and polling-state tests: 14 passed.
• App bun run type-check: passed.
• bun run check:api-validation: passed.
• Biome checks and git diff --check: passed.

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

1 Skipped Deployment

Project	Deployment	Actions	Updated
docs	Skipped		Sep 11, 2026 11:51pm UTC

[greptile-apps]

Confidence Score: 4/5

The PR should not merge until RSS deduplication remains effective for the full history admitted by the new subscription-time cutoff.

Findings

1.  Old Entries Can Replay ▶

Summary

• Retains GUID-based filtering for known entries.
• Adds regression coverage for delayed entries, changed publication dates, and pre-subscription history.
• The broader timestamp window can replay previously delivered entries after bounded GUID history and temporary idempotency records expire.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart TD
  A[Poll RSS feed] --> B{GUID in latest 500?}
  B -->|Yes| C[Skip item]
  B -->|No| D{Published after subscription?}
  D -->|No| C
  D -->|Yes| E{Idempotency record active?}
  E -->|Yes| C
  E -->|No| F[Deliver item]
  F --> G[Prepend GUID and truncate history to 500]
  G --> H[Older GUID may be evicted]
  H --> A

Loading

_{Reviews (1) · Last reviewed commit: "fix(rss): deliver unseen items published..."}

[greptile-apps]

Old Entries Can Replay

If a feed retains an item after its GUID falls out of the 500-entry lastSeenGuids window, this subscription-time cutoff allows that already-delivered item through again because its publication date remains after the subscription began. The idempotency key expires after three days, so feeds containing more than 500 retained items can cause old entries to be delivered repeatedly. Deduplication needs to remain durable for every item admitted by this broader timestamp window.