[arian-gogani]

Problem

SplitLineHierarchy.SumNetAmount sums persisted prior-line Amount, which is gross, while the caller treats it as net spend when evaluating commitments. The split-line history introduced in #5341 carries gross amount and charges but omits DiscountsTotal, even though the persisted invoice line has that field. A prior line with 100 in gross amount and 40 in discounts therefore contributes 100 where the function promises 60.

This carries DiscountsTotal into the history model and subtracts it in SumNetAmount. #5297 established the net-of-discounts calculation for the separate delta engine; this change addresses the legacy history path.

Verification

• Focused billing test: before the subtraction, expected 60 and got 100 (exit 1); after, it passes (exit 0).
• Adapter test: a persisted line with 100 gross and 40 discounts maps to 40 in DiscountsTotal, and SumNetAmount returns 60. Passed.
• go test ./openmeter/billing/... passed.
• go vet ./openmeter/billing/... ./test/... passed.

This demonstrates the history sum and adapter mapping. I did not run a database-backed invoice flow or independently execute the maximum-spend commitment path.

Summary by CodeRabbit

• Bug Fixes
  • Minimum and maximum spend commitments now account for discounts when calculating previously billed amounts across invoice periods, helping ensure charges and minimum-spend top-ups reflect the correct net amount.
• Documentation
  • Clarified how spend commitments use prior usage after discounts and before taxes and credits.

Confidence Score: 5/5

The PR appears safe to merge; no actionable issue remains.

Summary

The PR makes legacy commitment history count prior spend after discounts.

• Progressive commitments count earlier invoice slices after discounts.

No new actionable issues or repository-rule violations were found. Tests were not run during this review.

_{Reviews (5) · Last reviewed commit: "test(billing): mirror progressive commit..." · Reviewed by Greptile}

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• Source mode: Auto
• Repository: openmeterio/openmeter
• Branch: main
• File: .coderabbit.yaml
• Commit: 813b0fa
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• Run ID: 8442651e-7fcc-48ea-ad32-c70349dc5eeb

Commits

Reviewing files that changed from the base of the PR and between 5b1f76f and 5f13ca1.

Files selected for processing: 2

• test/billing/discount_test.go
• test/credits_billing_compat/discount_test.go

Included review availability: This review used your included allowance. Your plan provides up to 8 included reviews per hour; 7 remain after this review.

Walkthrough

Split-line history now retains discounts from database invoice lines. SumNetAmount subtracts those discounts from eligible child amounts before optionally adding charges. Tests cover discount-aware totals and minimum and maximum spend commitments across progressive invoice slices.

Changes: Discounted split-line history

Layer / File(s)	Summary
Preserve discounts in history openmeter/billing/invoicelinesplitgroup.go, openmeter/billing/adapter/invoicelinesplitgroup.go	SplitLineHierarchyLine adds DiscountsTotal. The database mapping copies this value into the hierarchy line.
Subtract discounts from prior net amounts openmeter/billing/invoicelinesplitgroup.go, openmeter/billing/splitlinehierarchy_test.go, test/billing/discount_test.go, test/credits_billing_compat/discount_test.go, openmeter/billing/README.md	SumNetAmount subtracts discounts from eligible child amounts and still adds charges when requested. Tests cover discounted totals and progressive minimum and maximum spend commitments. The README describes how discounts and commitment amounts are counted across slices.

Priority: Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Possibly related PRs

• openmeterio/openmeter#5333: Introduced the persisted split-line history model and traversal used by SumNetAmount.
• openmeterio/openmeter#5356: Changed legacy calculations to resolve persisted split-line history.
• openmeterio/openmeter#5341: Routed prior-spend calculations through SplitLineHierarchy.SumNetAmount.

Suggested reviewers: turip, borosr

Merge Risk: Minimal · up to 5f13c

The change appears mergeable after normal checks; the database-backed invoice flows have not been independently run.

Pre-merge checks: 4

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: applying prior split discounts when calculating net billing history for legacy commitments.
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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[turip]

Thank you!