fix(ccusage): add flat pricing for Opus 4.6 / Sonnet 4.6 to fix inflated costs

[MumuTW]

Summary

• Fixes inflated cost calculation for Claude Opus 4.6 since Claude Code enabled 1M context in v2.1.75
• Claude Opus 4.6 and Sonnet 4.6 use flat pricing across the full 1M context window — no premium for requests exceeding 200k input tokens (docs)
• LiteLLM's dataset only has Bedrock entries (anthropic.claude-opus-4-6-v1) which include *_above_200k_tokens tiered pricing fields; when ccusage falls back to substring matching it picks up the Bedrock entry and incorrectly applies tiered pricing
• Fix: inject entries keyed by the exact Anthropic API model names (claude-opus-4-6, claude-sonnet-4-6) with correct flat pricing so direct lookup succeeds before the substring fallback fires

Test plan

• All 252 existing ccusage tests pass
• All 9 internal pricing tests pass
• Verify with a real Claude Code session that Opus 4.6 costs are no longer inflated

Fixes #891

Summary by CodeRabbit

• Bug Fixes
  • Improved pricing accuracy for Claude Opus 4.6 and Claude Sonnet 4.6 models when using direct Anthropic API.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: af3a6b60-f539-4a93-8b90-9203f389d611

📥 Commits

Reviewing files that changed from the base of the PR and between b81913f and b2de7c8.

📒 Files selected for processing (1)

• apps/ccusage/src/_macro.ts

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📝 Walkthrough

Walkthrough

Introduces flat pricing mappings for direct Anthropic API models (claude-opus-4-6 and claude-sonnet-4-6) and updates the prefetch logic to prioritize these direct API pricing lookups before falling back to Bedrock substring-based pricing resolution.

Changes

Cohort / File(s)	Summary
Anthropic API Flat Pricing apps/ccusage/src/_macro.ts	Added ANTHROPIC_API_FLAT_PRICING mapping for direct Anthropic API models with explicit token costs (input/output/cache) and max token limits; updated prefetchClaudePricing to inject these entries into the filtered dataset to ensure direct API models are resolved before Bedrock pricing fallback.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• fix(ccusage): support Opus 4.5 pricing from Bedrock-prefixed models #743: Updates model detection logic to expand isClaudeModel recognition for Bedrock-prefixed names, complementing this PR's pricing-entry injection for direct API model resolution.
• fix(internal): fix context size bug by using max_input_tokens instead of max_tokens #650: Modifies Claude pricing data and token limit handling by adjusting max_input_tokens vs max_tokens usage, which relates to the max token fields being set in the new flat pricing mappings.

Suggested reviewers

• ryoppippi

Poem

🐰 Hop hop, the prices now align,
Flat and true for Claude's design,
No more Bedrock's weary string,
Direct API gets its pricing! ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 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 (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically describes the main change: adding flat pricing entries for Opus 4.6 and Sonnet 4.6 models to resolve inflated cost calculation issues.
Linked Issues check	✅ Passed	The PR directly addresses issue #891 by implementing flat pricing for Anthropic API models (claude-opus-4-6, claude-sonnet-4-6) to fix inflated cost calculations caused by incorrect tiered-pricing fallback from Bedrock entries.
Out of Scope Changes check	✅ Passed	All changes are tightly scoped to fixing the cost calculation issue: introducing ANTHROPIC_API_FLAT_PRICING mapping and updating prefetchClaudePricing to use it, with no unrelated modifications.

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📝 Coding Plan

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