fix: restore pre-3400 OpenRouter billing semantics

[seefs001]

fix #3433

Summary by CodeRabbit

• Tests

  • Added tests covering OpenRouter/Claude token billing, cached token handling, and quota calculations.

• Bug Fixes

  • Corrected OpenRouter Claude billing so cached read/creation tokens and discount ratios are applied correctly to quotas.

• Refactor

  • Response conversion now uses a shared helper to ensure usage and cache-related token counts are populated consistently.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 336b283a-0256-4bfe-9196-77d31a3293f4

📥 Commits

Reviewing files that changed from the base of the PR and between d4a470a and 926e178.

📒 Files selected for processing (1)

• service/convert.go

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Walkthrough

Introduced an explicit boolean (isOpenRouterClaudeBilling) to gate OpenRouter+Claude-specific billing adjustments in token quota calculation; updated conversion of OpenAI usage to Claude usage via a helper; added tests covering OpenRouter/Claude token billing semantics.

Changes

Cohort / File(s)	Summary
Token Quota Billing Logic service/text_quota.go	Added isOpenRouterClaudeBilling to combine the OpenRouter channel check with Claude semantic usage; guarded prompt token adjustments, cached-token subtraction, and possible recomputation of CacheCreationTokens with this condition.
Token Quota Tests service/text_quota_test.go	Added OpenRouter-specific test cases validating prompt token/quota splits, cached read tokens, cached creation tokens, and Claude semantic behavior across relay formats.
Usage Conversion Helper service/convert.go	Changed ResponseOpenAI2Claude to build Claude usage via buildClaudeUsageFromOpenAIUsage(&openAIResponse.Usage) to centralize population of usage fields (including cache-related tokens).

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• fix: restore pre-3400 OpenRouter billing semantics #3438: Implements the same change introducing isOpenRouterClaudeBilling and adds matching tests for OpenRouter/Claude billing.
• refactor: optimize billing flow for OpenAI-to-Anthropic convert #3400: Related changes to OpenRouter/Claude billing and token handling, including usage propagation and quota computation.
• fix: openrouter claude cache usage #2811: Modifies Claude/OpenRouter cache-related token handling and preservation of cached token fields used in billing.

Poem

🐰 I nibble tokens, soft and bright,

OpenRouter and Claude in sight,
Cache and prompt now sort their dues,
Tests hop in to check the clues,
Hooray—billing bunnies dance tonight! 🥕✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'fix: restore pre-3400 OpenRouter billing semantics' directly relates to the main change, which restores OpenRouter billing behavior by introducing a condition that combines OpenRouter channel detection with Claude usage semantics.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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