fix(videos): allow up to 9 reference images on Seedance 2.0

[steebchen]

Summary

A user reported that Seedance 2.0 Fast only accepted up to 3 reference images, while ByteDance's official Seedance 2.0 omni-reference documentation states it supports up to 9 reference images (alongside up to 3 reference videos and 3 reference audio clips).

This was not Fast-specific: the shared reference_images request schema in apps/gateway/src/videos/videos.ts was hard-capped at .max(3) for every video model, so all three Seedance 2.0 variants (seedance-2-0, seedance-2-0-fast, seedance-2-0-mini) were affected.

Changes

• Raise the shared videoReferenceImagesSchema cap from 3 → 9 (the maximum any model supports).
• Enforce the real per-provider limits in getVideoProviderConstraintReasons:
  • bytedance Seedance 2.0 → up to 9 reference images
  • all other providers (google-vertex / avalanche Veo, etc.) → keep the previous cap of 3 (no behavior change)
• Update the reference_images OpenAPI description to reflect the new range.
• Extend the mock server to capture ByteDance reference_image content items so forwarding can be asserted.

Tests

New tests in videos.spec.ts:

• Seedance 2.0 Fast forwards all 9 reference images.
• Seedance 2.0 Fast rejects 10 (schema cap).
• Veo rejects more than 3 reference images (per-provider cap preserved).

The reference videos/audios .max(3) caps already matched the docs and were left unchanged. Full videos.spec.ts suite (45 tests) passes.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Support up to nine reference images for Seedance 2.0 Fast video generation.
  • Updated reference-image guidance to reflect provider-specific limits.

• Bug Fixes

  • Added validation to reject requests exceeding supported reference-image limits.
  • Other video providers now allow up to three reference images, with clear error messages when exceeded.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 54d42982-9e1c-42fd-a9d2-807c106c72dc

📥 Commits

Reviewing files that changed from the base of the PR and between 9177a84 and ef4acd3.

📒 Files selected for processing (3)

• apps/gateway/src/test-utils/mock-openai-server.ts
• apps/gateway/src/videos/videos.spec.ts
• apps/gateway/src/videos/videos.ts

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Walkthrough

Changes

The gateway now supports provider-specific reference image limits: up to 9 for Seedance 2.0 and up to 3 for other providers. Tests cover acceptance and rejection cases, while the mock upstream server parses and stores reference images.

Reference image limits

Layer / File(s)	Summary
Provider-specific image limits and validation apps/gateway/src/videos/videos.ts, apps/gateway/src/videos/videos.spec.ts	Schemas, OpenAPI text, routing constraints, and tests now enforce Seedance’s 9-image limit and the 3-image default limit.
Mock upstream reference image parsing apps/gateway/src/test-utils/mock-openai-server.ts	Reference-image content entries are parsed from data URLs and stored on MockVideoJobState when present.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Possibly related PRs

• theopenco/llmgateway#2082: Updates related Vertex model eligibility in the same provider constraint logic.
• theopenco/llmgateway#2538: Extends the Seedance reference-image request path using reference_image content entries.
• theopenco/llmgateway#2699: Adds related Seedance frame handling and mock parsing in the same areas.

Suggested reviewers: copilot

🚥 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 matches the main change: increasing Seedance 2.0 reference-image support to 9.
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
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🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/seedance-2-reference-images

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