fix(billing): release the reporting prefix lease once its prefix is stored

[waleedlatif1]

Summary

• The reporting-usage prefix refresh lease was never released after a successful refresh, so when an epoch bump discarded the stored prefix inside the lease window, every reader on every process summed the whole reporting window until the lease expired
• The lease now holds a per-acquisition token and is released through the existing compare-and-delete releaseLock once the new prefix is stored, so the next read refreshes the prefix once
• A failed prefix sum or write keeps the lease until expiry as before, as a backoff; a lease that expired and was taken by another process is never deleted by the old holder

Type of Change

• Bug fix

Testing

• New integration case in reporting-usage-cache.integration.ts (real Postgres/Redis): after a top-up discards the prefix, two reads sum the window twice in total instead of three times; it fails on the current code, where the lease is never released
• Ran biome on both files; lint, check:audits, type-check and the integration suite run in CI

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing (new tests pass the test-audit authoring gate)
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Actions	Updated
docs	Skipped		Oct 16, 2026 4:46am UTC

[cubic-dev-ai]

No issues found across 2 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{Turn on auto-fix | Re-trigger cubic}

[greptile-apps]

Confidence Score: 5/5

[Critical impact] The PR appears safe to merge.

Summary

Releases the reporting prefix lease after Redis stores the refreshed prefix.

• A refreshed reporting prefix frees its lease for the next read.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart TD
  A[Prefix needs refresh] --> B{Lease acquired?}
  B -->|No| C[Use stored prefix or sum whole window]
  B -->|Yes| D[Sum new prefix]
  D -->|Success| E[Store prefix in Redis]
  E -->|Success| F[Release lease only if token matches]
  D -->|Failure| G[Lease expires naturally]
  E -->|Failure| G

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_{Reviews (1) · Last reviewed commit: "fix(billing): release the reporting pref..." · Reviewed by Greptile}