fix(usage): price Cursor cache savings by base model

[Yash-Singh1]

What Changed

Cursor usage records now map tiered model names to their base model rate key. Cost and cache savings use that rate while provider-reported costs remain unchanged.

Why

Cursor model names include tier and speed suffixes that do not match the pricing table keys. Mapping them to the base model lets cache savings use the correct rate.

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes
• I included a video for animation/interaction changes

Summary by CodeRabbit

• Bug Fixes
  • Cursor usage costs and cache savings now use matching base-model rates for recognized Claude and Grok variants, including names with tier or speed suffixes.
  • When a provider reports a cost for a model variant, that reported cost is used. Models without a matching rate continue to show no cache savings.

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This focused server change remaps Cursor’s tiered model names to base pricing keys and changes displayed usage pricing and cache-savings calculations. Because it directly affects production usage metering/pricing, it requires human review despite its limited scope.

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[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	13.5 KiB	13.5 KiB	−15 B (−0.1%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.1 KiB	7.1 KiB	−4 B (−0.1%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.4 KiB	6.4 KiB	−11 B (−0.2%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	56.2 KiB	56.2 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	9	9	0 (0.0%)	21	✅
Claude	Total thread wire	13.5 KiB	13.5 KiB	−4 B (−0.0%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.1 KiB	7.1 KiB	−3 B (−0.0%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.4 KiB	6.4 KiB	−1 B (−0.0%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	57.0 KiB	57.0 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	9	9	0 (0.0%)	21	✅

Baseline: ed809f7 · PR result: 5c77e7d · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 114.0 KiB
• Claude decoded thread snapshot: 114.7 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.

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ℹ️ Recent review info

⚙️ Run configuration

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Run ID: c2eef35d-37c7-4867-b174-3d6ee8f94bca

📥 Commits

Reviewing files that changed from the base of the PR and between ed809f7 and 5c77e7d.

📒 Files selected for processing (4)

• apps/server/src/usage/cursorUsageReader.ts
• apps/server/src/usage/usagePricing.test.ts
• apps/server/src/usage/usagePricing.ts
• apps/server/src/usage/usageTranscripts.ts

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📝 Walkthrough

Walkthrough

Cursor usage records now include a normalized rate-model key. Pricing and cache-savings calculations use that key for rate-table lookups when it is present, and otherwise use the displayed model name.

Changes

Cursor rate-model pricing

Layer / File(s)	Summary
Define and populate rateModel apps/server/src/usage/usageTranscripts.ts, apps/server/src/usage/cursorUsageReader.ts	UsageRecord adds an optional rateModel. Cursor records populate it with a normalized model name.
Use rateModel for pricing lookups apps/server/src/usage/usagePricing.ts, apps/server/src/usage/usagePricing.test.ts	Rate-table lookups for usage pricing and cache savings use rateModel when present, otherwise model. Tests cover Cursor model variants, cache savings, and provider-reported cost precedence.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Suggested reviewers: t3dotgg

Merge Risk: ⚪ Minimal · up to 5c77e

Cursor usage pricing is ready to merge after normal checks; no actionable pricing regression was established.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 6 functions across 4 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the primary change: pricing Cursor cache savings by the base model.
Description check	✅ Passed	The description explains what changed and why, confirms the PR is focused, and does not require UI details because the changes are server-side.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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