feat: allow --comfy-api-base target ephemeral testenvs

[bigcat88]

Today the frontend only learns which backend to talk to at build time. This PR allows Frontend to read the comfy-api-base at runtime instead.

Supersedes: #14200

When you start ComfyUI with --comfy-api-base pointed at one of our non-production backends (staging, or a per-PR preview environment under *.testenvs.comfy.org), the server now includes that backend's URLs in its /features response.
The frontend reads them from there, so the same prebuilt UI can follow along without anyone rebuilding it.

Preview environments keep their friendly URL separate from the actual API host, so you can pass the friendly one (pr-N.testenvs.comfy.org) and let the server resolve the real host (pr-N-registry.testenvs.comfy.org) for you, both in what it tells the frontend and in where the API nodes send their calls.

Production and ordinary self-hosting are untouched: the server only adds this when you point it somewhere non-production, so everyone else sees exactly what they do today.

API Node PR Checklist

Scope

• Is API Node Change

Pricing & Billing

• Need pricing update
• No pricing update

If Need pricing update:

• Metronome rate cards updated
• Auto‑billing tests updated and passing

QA

• QA done
• QA not required

Comms

• Informed Kosinkadink

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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📥 Commits

Reviewing files that changed from the base of the PR and between 905a70d and e2dd7b4.

📒 Files selected for processing (5)

• comfy/comfy_api_env.py
• comfy_api/feature_flags.py
• comfy_api_nodes/util/_helpers.py
• server.py
• tests-unit/feature_flags_test.py

🚧 Files skipped from review as they are similar to previous changes (2)

• comfy_api_nodes/util/_helpers.py
• comfy/comfy_api_env.py

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📝 Walkthrough

Walkthrough

A new module comfy/comfy_api_env.py adds staging and testenv API host detection, testenv hostname rewriting, and frontend config overrides for staging-tier bases. get_frontend_features() now merges get_frontend_config() output into feature flags, and the /features route now returns those frontend features. default_base_url() now normalizes the configured API base URL. Tests were added for URL normalization, frontend config generation, and conditional feature flag overrides.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 35.29% 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
Title check	✅ Passed	The title clearly summarizes the main change: allowing --comfy-api-base to target ephemeral testenvs.
Description check	✅ Passed	The description is directly related to the changeset and explains the runtime backend URL behavior well.
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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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@comfy/comfy_api_env.py`:
- Around line 23-32: The normalize_comfy_api_base function only preserves the
scheme and hostname when rewriting the URL on line 32, but discards the original
URL's port, path, query parameters, and fragment. This can silently retarget
requests when the input includes a custom port or path prefix. To fix this,
preserve all URL components from the parsed object when reconstructing the URL:
either manually include parsed.port, parsed.path, parsed.query, and
parsed.fragment in the f-string, or use urlunparse to reconstruct the full URL
after modifying the hostname in the parsed URL object.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

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• Create a new PR with the fixes

---

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📥 Commits

Reviewing files that changed from the base of the PR and between dc3f8f3 and 7ed56ac.

📒 Files selected for processing (4)

• comfy/comfy_api_env.py
• comfy_api/feature_flags.py
• comfy_api_nodes/util/_helpers.py
• tests-unit/feature_flags_test.py

[christian-byrne]

Comfy-Org/ComfyUI_frontend#13054 (review)