Fix /v1/images/edits routing for reference-conditioned models

[losewayy]

Summary

/v1/images/edits currently assigns the first uploaded image to both ref_images and init_image. For models that support reference-image conditioning, the implicit init_image can route the request through IMG2IMG and apply the default strength, interfering with reference-conditioned edits.

Add a model capability query and use it when building OpenAI edit requests so the first upload remains in ref_images without becoming an implicit init_image for reference-conditioned models. Preserve the existing init-image path for models that do not support reference conditioning, requests with a mask, or requests with an explicit strength override. Preserve explicit init_image overrides.

All uploaded images remain in ref_images in their original request order.

Related Issue / Discussion

Closes #1779

Related discussion: #1766

Additional Information

Built the CUDA sd-server on Windows and tested a real /v1/images/edits request with Qwen Image 2.1. The default request returned HTTP 200 and a nonblank 512×512 image; server logs show the upload handled through ref_images without an implicit init_image or IMG2IMG path.

Requests with an explicit strength=0.4, an explicit init_image, and a mask each returned HTTP 200 and followed the existing initialization path.

Pix2Pix runtime generation was not tested because no Pix2Pix weights were available locally; its routing was reviewed in the source.

git diff --check and formatting checks for changed lines passed.

Checklist

• I have read and confirmed this PR follows the contribution guidelines.

Summary by CodeRabbit

• New Features
  • Image edit requests now automatically route uploaded images as reference images when supported by the selected model and no mask or explicit strength setting is provided.
  • When reference conditioning is unavailable, references are absent, a mask is supplied, or strength is explicitly set, the uploaded image is used for image-to-image editing or inpainting.
  • Explicit initial-image, reference-image, mask, and strength settings take precedence over automatic routing.

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Reviewing files that changed from the base of the PR and between 401b538 and d85b57b.

📒 Files selected for processing: 4

• examples/server/api.md
• examples/server/openai_edit_policy.h
• examples/server/routes_openai.cpp
• src/model.h

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📝 Walkthrough

The /v1/images/edits endpoint now selects whether the first uploaded image initializes img2img or remains a reference. The selection uses model support for reference-image conditioning and request overrides. A public API reports the model capability.

Changes: Edit image routing

Layer / File(s)	Summary
Reference-image capability query src/model.h, include/stable-diffusion.h, src/stable-diffusion.cpp	The model-version helper identifies supported versions. The public context API returns whether the loaded model supports reference-image conditioning.
Edit request image selection examples/server/openai_edit_policy.h, examples/server/routes_openai.cpp, examples/server/api.md	The route parses image, mask, strength, and init-image overrides. The policy keeps, uses, or clears the init image. The API documentation describes the routing behavior.

Priority: ➖ Normal

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

Change: Bug fix · Severity of issue fixed: Medium

Sequence Diagram(s)

sequenceDiagram
  participant OpenAIEditRoute
  participant sd_ctx_supports_ref_image_conditioning
  participant apply_openai_edit_init_image_policy
  OpenAIEditRoute->>sd_ctx_supports_ref_image_conditioning: Query model conditioning support
  sd_ctx_supports_ref_image_conditioning-->>OpenAIEditRoute: Return support status
  OpenAIEditRoute->>apply_openai_edit_init_image_policy: Pass upload and override state
  apply_openai_edit_init_image_policy-->>OpenAIEditRoute: Select init-image action

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Suggested reviewers: fszontagh, leejet

Merge Risk: ⚪ Minimal · up to d85b5

No actionable merge-blocking risk remains in the reviewed changes.

Architecture risk: 🟡 Medium · up to d85b5

The change affects 3 systems.

Changed systems: examples, src, include

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

• observed — examples (service) was modified; 3 changed files map to changed impact.
• observed — src (service) was modified; 2 changed files map to changed impact.
• observed — include (service) was modified; 1 changed file maps to changed impact.

Before / after behavior

• observed — Modified behavior in include/stable-diffusion.h: Added the sd_ctx_supports_ref_image_conditioning API declaration and documentation describing the model capability it queries.
• observed — Modified behavior in src/stable-diffusion.cpp: Added sd_ctx_supports_ref_image_conditioning, which returns false for a null context or model and otherwise checks reference-image-conditioning support for the model version.
• observed — Modified behavior in examples/server/api.md: POST /v1/images/edits now documents conditional init-image selection and reference routing after applying sd_cpp_extra_args, including null/empty clearing semantics and explicit init_image precedence.
• observed — Modified behavior in examples/server/openai_edit_policy.h: Adds the include guard, SDImageOwner dependency, and the public OpenAIEditInitImageAction result enum.

Reliability and maintainability

• inferred — Risk-relevant change factors for examples: blast_radius_1; blast_radius_2; direct_dependents_1

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 10.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 10 functions across 5 files. (1 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Title check		The title clearly and concisely describes the main change: correcting /v1/images/edits routing for reference-conditioned models.
Description check		The description includes the required Summary, Related Issue / Discussion, Additional Information, and Checklist sections. It explains the change, scope, testing, known limitation, and linked issue.
Linked Issues check		Active direct issue #1779 requires /v1/images/edits to stop forcing every request through IMG2IMG. The change adds a model capability query and clears the implicit init_image for supported referen…
Out of Scope Changes check		The changed API query, model-version classification, edit policy, route integration, and routing documentation all support issue #1779 or preserve required existing behavior. No unrelated change is es…

Full details: Linked Issues check

Explanation

Active direct issue #1779 requires /v1/images/edits to stop forcing every request through IMG2IMG. The change adds a model capability query and clears the implicit init_image for supported reference-conditioned models. It preserves the uploaded-image init path for unsupported models, masks, explicit strength overrides, and explicit init overrides. The upload order remains unchanged. The linked issue has no separate automated-test requirement.

Full details: Out of Scope Changes check

Explanation

The changed API query, model-version classification, edit policy, route integration, and routing documentation all support issue #1779 or preserve required existing behavior. No unrelated change is established by the reviewed change summary.

Full details: Docstring Coverage

Explanation

Docstring coverage is 10.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 10 functions across 5 files. (1 skipped: 1 unsupported.)

Resolution

Write docstrings for the functions missing them to satisfy the coverage threshold.

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Actionable comments posted: 1

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Inline comments:
Review comments at @src/model.h:
- Around line 368-391: Remove VERSION_HIDREAM_O1 from
sd_version_supports_ref_image_conditioning so HiDream O1 is not advertised as
reference-image conditioned until its default path handles uploaded reference
images. Preserve the other supported-version checks unchanged.

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⚙️ Run configuration

• Configuration used: Repository UI
• Review profile: CHILL
• Plan: Advanced
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📥 Commits

Reviewing files that changed from the base of the PR and between b13a482 and c62a3be.

📒 Files selected for processing: 6

• examples/server/api.md
• examples/server/openai_edit_policy.h
• examples/server/routes_openai.cpp
• include/stable-diffusion.h
• src/model.h
• src/stable-diffusion.cpp

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[leejet]

Two routing issues should be addressed before merging:

1. The policy runs after from_json_str(), but does not check the resulting ref_images. For example, a FLUX.2 edit request with an uploaded image and "ref_images": [] in sd_cpp_extra_args previously used the upload for img2img. This change clears init_image as well, turning the request into text-to-image. Please preserve the uploaded init image when the final reference list is empty.

2. sd_version_is_flux() includes VERSION_CHROMA_RADIANCE, but forward_chroma_radiance() does not consume its ref_latents argument. The new capability query therefore incorrectly returns true and causes the route to clear init_image. Please exclude Chroma Radiance from this capability check, as was done for HiDream O1.

[losewayy]

Fixed both issues. Clearing ref_images now preserves the uploaded init-image fallback, and Chroma Radiance is excluded from the capability check.

I also updated routing to use the final mask state, so clearing an uploaded mask with mask_image: null no longer forces img2img. Request-parsing regression tests and the Windows Release server build pass.

[leejet]

Thanks.