[codex] add s2.1 pro pricing and model guidance

[leng-yue]

Summary

• Add s2.1-pro and s2.1-pro-free to the models overview and pricing docs.
• Mark s2.1-pro as the recommended production model at the same TTS price as s2-pro.
• Describe s2.1-pro-free as the same model at $0 for testing, prototyping, development, and smaller businesses without TTFA or DPA guarantees.
• Keep related overview and text-to-speech pages consistent.

Validation

• git diff --check
• npm run check:openapi

Notes

• npm run validate is stale with the installed Mint CLI because mint validate is not a recognized command.
• npx mint broken-links reports pre-existing broken links under .mintlify/skills and temp, not in the edited files.

Summary by CodeRabbit

Release Notes

• Documentation
  • Introduced Fish Audio S2.1-Pro as the recommended production model with improved quality, latency, and throughput.
  • Added S2.1-Pro-free tier for development, testing, and prototyping at no cost (excludes TTFA/DPA guarantees).
  • Updated model selection guidance and pricing information across documentation.

[mintlify]

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Project	Status	Preview	Updated (UTC)
hanabiaiinc	🟢 Ready	View Preview	Jun 24, 2026, 12:52 AM

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[coderabbitai]

Caution

Review failed

Pull request was closed or merged during review

📝 Walkthrough

Walkthrough

Documentation across five MDX files is updated to introduce s2.1-pro as the new recommended production TTS model and s2.1-pro-free as a free testing/prototyping tier. The changes affect model overview cards, choosing-a-model guidance, pricing tables, TTS feature listings, and capability summaries, replacing prior s2-pro-first recommendations throughout.

Changes

S2.1-Pro Documentation Rollout

Layer / File(s)	Summary
Model overview cards and recommendation note developer-guide/models-pricing/models-overview.mdx	Replaces the S2-Pro recommended card with an S2.1-Pro production card, adds a new S2.1-Pro Free development card with TTFA/DPA guarantee notes, updates the recommendation note, adjusts the S2 summary paragraph to reference both S2.1-Pro and S2-Pro, and generalizes Natural Language Control wording and tip examples from S2-Pro to S2.1-Pro and S2-Pro.
Choosing-a-model guidance developer-guide/models-pricing/choosing-a-model.mdx	Replaces the prior S2-Pro blanket recommendation with updated guidance: use s2.1-pro for production with TTFA/DPA guarantees, and s2.1-pro-free for testing, prototyping, and smaller-scale use cases where guarantees are not required.
Pricing table expansion developer-guide/models-pricing/pricing-and-rate-limits.mdx	Adds s2.1-pro ($15.00/M UTF-8 bytes) and s2.1-pro-free ($0.00/M UTF-8 bytes) rows to the TTS pricing table, producing a full four-row table alongside the existing s2-pro and s1 entries.
TTS feature page and capabilities overview features/text-to-speech.mdx, overview/capabilities.mdx	Updates the TTS feature intro and Models section to list s2.1-pro and s2.1-pro-free alongside s2-pro; updates the capabilities Core features card model list and Models bulleted list with the same three-model lineup and TTFA/DPA notes for the free tier.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• fishaudio/docs#55: Updates the same choosing-a-model.mdx and models-overview.mdx files to switch the default recommended model to s2-pro, which this PR supersedes by switching to s2.1-pro.
• fishaudio/docs#56: Originally introduced the Natural Language Control section and model/pricing structure for s2-pro in the same models-overview.mdx that this PR extends to cover s2.1-pro.
• fishaudio/docs#59: Modified the same pricing-and-rate-limits.mdx TTS pricing table by removing a duplicate s2-pro row, directly adjacent to the table rows this PR restructures and expands.

Suggested reviewers

• twangodev

Poem

🐰 A hop and a skip through the model docs lane,
S2.1-Pro is here, leading the refrain!
The free tier joins in for testing delight,
TTFA and DPA shine oh so bright.
The pricing table grew, four rows now stand tall —
This bunny approves the best model of all! 🎉

🚥 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 accurately describes the main change: adding documentation for s2.1-pro pricing and model guidance across multiple documentation pages.
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.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/add-s21-pro-models

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