feat(llm-providers): add Opper as a named LLM provider

[Felixkw12]

Summary

Adds Opper as a named provider in Settings → LLM Providers. Opper is an EU-hosted AI gateway with 700+ models from 50+ providers behind one OpenAI-compatible API and one key. The entry follows the OpenRouter and Cheaper Inference entries and only adds configuration on top of the existing OpenAI-compatible transport, with no new dependency.

Changes

• backend/services/llm_providers.py: new opper provider after Cheaper Inference.
  • base URL https://api.opper.ai/v3/compat, default model claude-sonnet-4-6
  • OPPER_API_KEY and OPPER_MODEL, sign-up link https://platform.opper.ai
  • no base_url_env. Opper's own SDKs and examples read OPPER_BASE_URL as the API root (https://api.opper.ai), not the OpenAI-compatible path, so a user who already exports it would otherwise get a broken endpoint. The URL can still be changed in Settings.
• docs/dubbing/translation-engines.md: Opper in the supported list, a setup paragraph, and the LLM_DEFAULT_PROVIDER ids.
• electron/src/shared/components/settings/settingsCategories.jsx: opper search keyword.
• tests/test_llm_providers.py: registry id plus a contract test for the defaults, the env overrides, and that OPPER_BASE_URL does not replace the endpoint.

Type

• ✨ New feature

Testing

• python3 -m py_compile on both changed Python files.
• claude-sonnet-4-6 and gpt-5.4-mini are pooled models in Opper's public catalogue (GET https://api.opper.ai/v3/models).
• Not run: the pytest suites and bun run check:electron. The new contract test was checked by reading resolve_api_key, resolve_model and resolve_base_url, not by running it.

Checklist

• I've tested this locally
• Every commit author has signed the CLA (the CLA check tells you how)
• I've updated relevant documentation (if applicable)
• No local machine paths, logs, or personal env details in this PR
• Maintained version files are in sync (not applicable, no version bump)
• Regression fixture at tests/fixtures/omnivoice_data/ (not applicable, no change to the voice runtime)

Closes #2667

Disclosure: Opper is my startup.

Adds Opper as a named OpenAI-compatible LLM provider with a default endpoint and model, OPPER_API_KEY and OPPER_MODEL support, documentation, a Settings search keyword, and tests. This lets users select Opper without manually configuring the Custom provider; the endpoint remains editable in Settings and does not use OPPER_BASE_URL. The pytest suites and bun run check:electron were not run.

[github-actions]

All contributors on this pull request have signed the VoiceStudio CLA. Thank you!

[Felixkw12]

I have read the VoiceStudio CLA 1.0 and I hereby sign it.

[greptile-apps]

[Medium risk] Adds Opper as an optional LLM provider choice.

The PR appears safe to merge; no actionable issue remains.

Summary

Adds Opper through the existing OpenAI-compatible provider registry.

• Includes configuration docs, a search keyword, and contract tests.
• The previous contributor-credit finding is fixed.
• No new actionable findings.

_{Reviews (3) · Last reviewed commit: "feat(llm-providers): add Opper as a name..." · Reviewed by Greptile}

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: Repository: debpalash/VoiceStudio/.coderabbit.yaml
• Review profile: CHILL
• Plan: Advanced
• Run ID: c57cd242-dcf6-4e66-926a-ea62d10522e7

📥 Commits

Reviewing files that changed from the base of the PR and between 6b6e208 and f111224.

📒 Files selected for processing (2)

• CHANGELOG.md
• backend/services/llm_providers.py

🚧 Files skipped from review as they are similar to previous changes (1)

• CHANGELOG.md

Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 9 remain after this review.

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📝 Walkthrough

Walkthrough

The provider registry now includes Opper with a compatibility endpoint, default model, environment-variable settings, and signup URL. Tests cover its configuration. Documentation, settings search, and the changelog include Opper.

Changes

Opper provider support

Layer / File(s)	Summary
Provider configuration and contract tests backend/services/llm_providers.py, tests/test_llm_providers.py	The registry defines Opper’s compatibility endpoint, default model, API-key and model environment variables, and signup URL. Tests verify these settings and confirm that OPPER_BASE_URL does not replace the endpoint.
Provider discovery and documentation docs/dubbing/translation-engines.md, electron/src/shared/components/settings/settingsCategories.jsx, CHANGELOG.md	Documentation lists Opper and describes its configuration. Settings search includes opper, and the Unreleased changelog lists Opper as an optional LLM provider.

Priority: ➖ Normal

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

Change: Feature · Severity of issue fixed: Medium

Suggested reviewers: fenjufu

Merge Risk: ⚪ Minimal · up to f1112

Users can configure Opper through the existing provider settings, and the reviewed changes align with its documented endpoint and credentials. No actionable merge-blocking mismatch was found.

🚥 Pre-merge checks | ✅ 8 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 functions across 3 files. (1 skipped: 1 …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (8 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title uses Conventional Commit format with the llm-providers scope and accurately describes the provider addition. Issue #2667 is referenced in the pull request body.
Description check	✅ Passed	The description includes the required Summary, Changes, Type, Testing, Checklist, and Release cadence sections. It documents the unrun test suites and links the change to issue #2667.
Linked Issues check	✅ Passed	[#2667] The PR adds the named opper provider with the requested endpoint, default model, OPPER_API_KEY and OPPER_MODEL overrides, no OPPER_BASE_URL override, and the requested sign-up link. It…
Out of Scope Changes check	✅ Passed	The reviewed changes support the configuration, documentation, discovery, test, and changelog requirements in [#2667]. The available whole-PR summary shows no unrelated change.
Cross-Platform Default Parity	✅ Passed	The PR adds a provider definition and shared documentation only. Opper is not selected by default without explicit configuration: active-provider auto-selection requires an OPPER_API_KEY, and users …
I18n Completeness (21 Locales)	✅ Passed	No new or changed t('...') key appears in the Electron diff. The only Electron addition is the internal searchable keyword 'opper' in settingsCategories.jsx; it is not rendered user-facing text …
Local-First Guarantee	✅ Passed	No local-first violation is introduced. The changed backend adds only an Opper entry to the existing provider registry; its module states that configuration resolution does not contact providers, and …
Backward Compatibility	✅ Passed	The pull request changes only the LLM provider registry, documentation, a Settings search keyword, changelog text, and tests. It adds no database schema, migration, voice/project/settings storage form…

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 functions across 3 files. (1 skipped: 1 unsupported.)

• Fix all pre-merge checks with AI

• Autopilot · Keep fixing CodeRabbit findings and required CI, and resolving merge conflicts

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[Felixkw12]

Rebased on main after the 0.5.7 release. The changelog line now sits under Unreleased with the contributor credit Greptile asked for.