Make Sonnet 5 pricing permanent

[mike1858]

Why

Anthropic initially described Claude Sonnet 5's $2 per million input token and $10 per million output token rates as introductory pricing. Splitrail therefore retained the previous $3/$15 Sonnet rates as the durable default and scheduled the introductory rates to expire on September 1, 2026.

Anthropic updated the Sonnet 5 launch announcement on August 10, 2026 to make the introductory rates permanent, and its current API pricing documentation reports the same rates. Without this update, Splitrail would overstate Sonnet 5 costs for usage on or after September 1.

What changed

• Make $2/MTok input and $10/MTok output the durable Sonnet 5 rates.
• Keep Anthropic prompt-cache pricing at $2.50/MTok for standard cache writes and $0.20/MTok for cache reads.
• Remove the obsolete dated override and September 1 transition to $3/$15 pricing.
• Update canonical and global-alias coverage to assert that Sonnet 5 has no dated pricing override.
• Update model and Claude Code analyzer boundary tests so August 31 and September 1 usage both calculate to $14.70 for one million input, output, cache-write, and cache-read tokens.

Validation

• TMPDIR=/var/tmp/splitrail-cargo cargo test --quiet claude_sonnet_5
• TMPDIR=/var/tmp/splitrail-cargo cargo test --quiet test_parse_jsonl_file_uses_sonnet_5_permanent_pricing
• TMPDIR=/var/tmp/splitrail-cargo cargo build --quiet
• TMPDIR=/var/tmp/splitrail-cargo cargo test --quiet — 413 passed; one unrelated existing TUI model-filter test failed
• TMPDIR=/var/tmp/splitrail-cargo cargo clippy --quiet -- -D warnings
• TMPDIR=/var/tmp/splitrail-cargo cargo doc --quiet
• cargo fmt --all --quiet
• git diff --check

Summary by CodeRabbit

• Bug Fixes
  • Updated Claude Sonnet 5 pricing to use consistent permanent rates.
  • Removed the outdated September 2026 pricing change.
  • Corrected Anthropic cache pricing and ensured totals remain consistent across the August–September boundary.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: f1d4bdcd-2159-4084-b4d0-388ea1950e29

📥 Commits

Reviewing files that changed from the base of the PR and between db3a592 and 5666b07.

📒 Files selected for processing (2)

• src/analyzers/tests/claude_code.rs
• src/models.rs

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📝 Walkthrough

Walkthrough

Claude Sonnet 5 now uses permanent $2/$10 pricing with Anthropic cache rates of $2.50/$0.20. Dated September 2026 pricing was removed, and tests verify stable boundary totals, alias resolution, and analyzer costs.

Changes

Sonnet 5 pricing

Layer / File(s)	Summary
Update permanent pricing src/models.rs	Claude Sonnet 5 now uses permanent input, output, cache-write, and cache-read rates without a dated override.
Validate pricing behavior src/models.rs, src/analyzers/tests/claude_code.rs	Tests verify permanent rates, consistent totals across the September boundary, global Anthropic alias resolution, and matching analyzer costs.

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

Possibly related PRs

• Piebald-AI/splitrail#193: Introduced the dated Sonnet 5 pricing tests that this change replaces.
• Piebald-AI/splitrail#142: Updated Anthropic Claude pricing and alias configuration in src/models.rs.
• Piebald-AI/splitrail#161: Modified Anthropic pricing and alias-resolution tests.

Suggested reviewers: jimyag, nickame03

Poem

I’m a rabbit with rates set bright,
Sonnet stays steady day and night.
No dated jump, no cost surprise,
Cache and aliases harmonize.
Hop, hop—the tests agree!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: making Sonnet 5 pricing permanent.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch make-sonnet-5-pricing-permanent

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