feat(providers): add Volcengine Ark (火山引擎) / BytePlus as built-in provider

[fuleinist]

Summary

Adds Volcengine Ark (火山引擎) / BytePlus — ByteDance's unified AI model platform — as a first-class built-in provider. Users can discover and configure it directly from Settings → Providers.

Settings → Providers → "Volcengine Ark / BytePlus (火山引擎)" → paste ARK_API_KEY → done

What's included

plugins/model-providers/volcengine-ark/__init__.py — ProviderProfile subclass + plugin.yaml manifest

• Anthropic-compatible /api/coding endpoint via api_mode="anthropic_messages"
• Overrides fetch_models() to return the maintained text-model list (11 models) — Ark's /models endpoint returns 124+ stale model IDs
• Aliases: ark, volcengine, volcano, bytedance, byteplus
• Display name includes Chinese (火山引擎) for discoverability
• Supports both China mainland (ark.cn-beijing.volces.com) and International/BytePlus (ark.ap-southeast.bytepluses.com) endpoints
• default_aux_model="doubao-seed-2.0-lite" — cheapest model that caches at the lowest prefix threshold (~4k)

agent/agent_runtime_helpers.py — Prompt-caching enablement

Ark serves non-Claude model families (deepseek-v4, glm-5.2, doubao-seed, kimi-k2, minimax-m3), so the blanket is_claude gate excluded them → 0% cache hits, re-billing the full prefix every turn. This adds an explicit Ark allowlist branch (provider id / host) returning native Anthropic layout — same class and fix as MiniMax's allowlist.

tests/run_agent/test_anthropic_prompt_cache_policy.py — Test coverage

• TestVolcengineArkAnthropicWire: 6 test cases covering provider id, short alias, BytePlus alias, custom provider host match (both regions), and OpenAI-wire exclusion

Related issues

Closes #29331 — feat: add Volcengine (火山引擎) as built-in provider
Closes #40195 — Feature Request: Add official ByteDance / BytePlus ModelArk provider
Closes #51319 — Feature Request: 新增豆包 (Doubao/Volcano Engine) 作为原生 Provider

Provenance

This PR builds on #52836 (feat: add Volcengine Ark (火山引擎) as built-in provider by @david-bowiegxw), with the BytePlus (international) endpoint support added on top. The commit carries Co-authored-by: david-bowiegxw <834563048@qq.com>.

Notes

• Follows the same pattern as the existing Fireworks AI and Vertex AI providers — plugin-native, self-contained
• Per-model prompt-caching data is documented inline in the model list (empirical measurements from 2026-06-26)
• Requires fix(providers): honor plugin ProviderProfile.api_mode at runtime (#53054) #53055 (fix: honor plugin ProviderProfile.api_mode at runtime) for correct anthropic_messages routing — without it, plugins whose endpoint isn't URL-self-describing degrade to chat_completions

[alt-glitch]

This was generated by AI during triage.

Related to #14070: both add Volcengine/BytePlus support, but this PR uses a plugin plus the Anthropic /api/coding prompt-cache policy while #14070 is a broader direct-provider integration. Maintainers should choose or consolidate the architecture.

[tonydwb]

Code Review Summary

Verdict: Approved (LGTM)

Overview

Adds Volcengine Ark (火山引擎) / BytePlus as a built-in provider. +199/0, 4 files.

Security

• No hardcoded secrets or credentials

Code Quality

• Clean provider integration
• Proper API key/credential handling for the new provider

Looks Good

• Well-scoped provider addition
• Consistent with existing provider patterns

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Reviewed by Hermes Agent

[david-bowiegxw]

Glad to see continued interest in getting Ark support landed — and the BytePlus/International endpoint is a genuinely useful addition. That said, this PR needs an attribution fix before it goes further:

This diff is my patch from #52836, opened 2026-06-26 and closed 2026-07-15 by the automated sweeper (appeal pending in that thread). Apart from the BytePlus layer — the byteplus alias, the ark.ap-southeast.bytepluses.com host, a few docstring lines, and two tests following the same pattern — the two patches are line-for-line identical. That includes the 102-line provider profile, the prompt-cache allowlist hunk in agent_runtime_helpers.py, the test suite, the per-model cache annotations from my 2026-06-26 empirical measurements, and the default_aux_model selection rationale. Anyone can verify:

gh pr diff 52836 > a.patch && gh pr diff 66266 > b.patch && diff a.patch b.patch

@fuleinist you commented "+1 on this" on #52836, so you know the provenance — but this PR's single commit carries only your authorship, with no Co-authored-by and no reference to #52836 anywhere. MIT permits reuse; contributor norms still require credit. Please:

1. Add to the commit message: Co-authored-by: david-bowiegxw <834563048@qq.com>
2. Note in the PR body that this builds on feat: add Volcengine Ark (火山引擎) as built-in provider #52836, with the BytePlus support added on top.

I have no objection to this PR carrying the work forward with that fixed — shipping the feature matters more than who opens the PR, and the BytePlus extension is a real improvement.

One heads-up for maintainers: #52836 was closed under the in-tree-provider-integration policy, and this PR is the same in-tree shape, so it presumably faces the same call. My appeal in #52836 argues that policy doesn't cover model providers (AGENTS.md's own text plus the post-policy Vertex #56363 and Fireworks merges). It would make sense to resolve the policy question and this PR together rather than separately — whichever way it goes, the authorship record should reflect where the patch came from.

[fuleinist]

@david-bowiegxw — thank you for the call-out, I've fixed both issues:

1. Commit amended with Co-authored-by: david-bowiegxw <834563048@qq.com> — the commit message now carries proper attribution for the feat: add Volcengine Ark (火山引擎) as built-in provider #52836 patch.
2. PR body updated with a Provenance section explicitly noting this builds on feat: add Volcengine Ark (火山引擎) as built-in provider #52836 with BytePlus support added on top.

The diff now shows the correct author email (noreply.github.com) and the Co-authored-by trailer. Apologies for the oversight — the BytePlus extension was the delta I should have highlighted from the start, and I should have carried the attribution forward when branching from your work.

[teknium1]

Thanks for carrying forward the Ark work, adding the BytePlus endpoint, and preserving the prior contributor attribution.

This automated hermes-sweeper review is closing this under the standing in-tree-provider-integration policy:

• The PR adds a new third-party LLM provider under plugins/model-providers/volcengine-ark/ (commit 82f1e3c903b36624623df40b7cc41cb083035d23).
• The policy requires vendor/provider integrations of this kind to ship as standalone plugins installed into ~/.hermes/plugins/, rather than adding an in-tree provider plugin.
• The standalone plugin can retain the provider profile, model catalog, BytePlus endpoint support, and cache-policy work, while avoiding a permanent core-tree maintenance commitment.

Please consider publishing the provider as a standalone plugin repository and sharing it in #plugins-skills-and-skins.

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Closed as not-planned per standing maintainer policy (in-tree-provider-integration). This is a design-direction decision, not a code-quality judgment — see the Contribution Rubric in AGENTS.md for what the project is looking for. If you believe this policy was misapplied to your change, comment here and a maintainer will take a look.