feat(llm): add Doubao (Volcengine Ark) as an LLM provider

[MackDing]

What

Adds Doubao (豆包 / ByteDance) via Volcengine Ark as a first-class LLM provider in Continue, following the existing pattern used for Moonshot, Deepseek, MiniMax, zAI, and SiliconFlow.

Doubao is one of the most-used LLM families in China; Volcengine Ark (火山方舟) is its official hosted platform and exposes an OpenAI-compatible /chat/completions surface at https://ark.cn-beijing.volces.com/api/v3/. Today users have to work around the gap by using the generic OpenAI provider with apiBase and model overrides — this PR makes provider: doubao just work.

Why

• Demand: Doubao is ByteDance's flagship LLM and is widely deployed in mainland-China-facing projects.
• No new surface area: Ark is OpenAI-compatible, so the adapter is a ~30-line OpenAI subclass. Registration is the same shape used by Moonshot / Deepseek / zAI.
• Closes an implicit feature gap that existing users of China-region models have been asking about (visible in several closed Qwen/Deepseek provider-error issues where users cite Doubao as the alternative).

Changes

File	Purpose
core/llm/llms/Doubao.ts	New Doubao extends OpenAI with Ark base URL
core/llm/llms/index.ts	Register in LLMClasses
core/llm/autodetect.ts	Add to PROVIDER_HANDLES_TEMPLATING (Ark handles chat templating server-side, same as Moonshot/Deepseek)
packages/openai-adapters/src/apis/Doubao.ts	Adapter wrapping OpenAIApi with ark.cn-beijing.volces.com/api/v3/
packages/openai-adapters/src/types.ts	DoubaoConfigSchema in the discriminated union
packages/openai-adapters/src/index.ts	constructLlmApi → DoubaoApi
packages/openai-adapters/src/apis/Doubao.test.ts	3 new tests (routing / default base URL / preserved OpenAI-chat surface)
core/llm/llms/OpenAI-compatible.vitest.ts	Doubao row in the shared subclass test matrix
docs/customize/model-providers/more/doubao.mdx	User-facing config docs

Diff: 9 files, +222 / −0.

Design notes

• No default model is set. Ark addresses models by either a date-stamped model ID (e.g. doubao-seed-1-6-251015, doubao-1-5-pro-32k-250115) or a user-provisioned endpoint ID (ep-20240xxx-xxxxx). A bare alias like doubao-1-5-pro-32k would silently 404, so the adapter intentionally requires the user to pick a valid ID. The docs link to the official Ark model list so users can copy a currently valid one.
• maxStopWords = 4 matches Ark's documented limit for OpenAI-compatible chat completions.
• No FIM override. Ark does not expose a public beta/completions FIM protocol today. If that changes, we can override fimStream the way Moonshot and Deepseek do.
• Not registered in packages/llm-info — consistent with Moonshot and Deepseek, which also rely solely on the LLMClasses + openai-adapters registration.

Testing

packages/openai-adapters$ npm test
Test Files  15 passed | 2 skipped (17)
     Tests  148 passed | 5 skipped (150)

3 of those 148 are new Doubao tests covering:

1. constructLlmApi({ provider: "doubao" }) returns a DoubaoApi instance.
2. Default apiBase is the Ark cn-beijing v3 URL.
3. Inherits the OpenAI-chat surface (chatCompletionStream / chatCompletionNonStream).

TypeScript check: tsc --noEmit on packages/openai-adapters → 0 errors.

References

• Volcengine Ark docs root: https://www.volcengine.com/docs/82379
• Ark model list (date-stamped IDs): https://www.volcengine.com/docs/82379/1330310
• Ark OpenAI-SDK compatibility notes: https://www.volcengine.com/docs/82379/1330626

---

Summary by cubic

Adds Doubao (ByteDance) via Volcengine Ark as a first-class LLM provider using the OpenAI-compatible /chat/completions API. Users can now set provider: doubao to use China-region Doubao models without workarounds.

• New Features

  • New doubao provider with default apiBase: https://ark.cn-beijing.volces.com/api/v3/.
  • Registered in LLMClasses and constructLlmApi; added DoubaoConfigSchema.
  • Autodetect updated so Doubao handles chat templating on the server.
  • Docs added for configuration; tests cover routing and API surface.

• Migration

  • No default model. Set a valid Ark model ID (e.g. doubao-seed-1-6-251015) or endpoint ID (e.g. ep-...) in model.
  • If you previously used provider: openai with Ark apiBase, switch to provider: doubao and keep the same model and apiKey.

^{Written for commit 27dd211. Summary will update on new commits.}

[github-actions]

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

[cubic-dev-ai]

2 issues found across 9 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="docs/customize/model-providers/more/doubao.mdx">

<violation number="1" location="docs/customize/model-providers/more/doubao.mdx:15">
P2: Configuration instructions are internally contradictory about using model aliases versus date-stamped model IDs/endpoint IDs, which can lead to invalid setup.</violation>
</file>

<file name="packages/openai-adapters/src/apis/Doubao.ts">

<violation number="1" location="packages/openai-adapters/src/apis/Doubao.ts:19">
P2: Subclass field initialization overwrites `config.apiBase` set by `OpenAIApi`, breaking custom base URL configuration.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review, or fix all with cubic.}

[cubic-dev-ai]

P2: Configuration instructions are internally contradictory about using model aliases versus date-stamped model IDs/endpoint IDs, which can lead to invalid setup.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At docs/customize/model-providers/more/doubao.mdx, line 15:

<comment>Configuration instructions are internally contradictory about using model aliases versus date-stamped model IDs/endpoint IDs, which can lead to invalid setup.</comment>

<file context>
@@ -0,0 +1,111 @@
+To use Doubao models:
+
+1. Create an API key on the [Volcengine Ark console](https://console.volcengine.com/ark/).
+2. Either deploy the model you want as an endpoint and copy its endpoint ID, or use a public model alias.
+3. Add the following configuration:
+
</file context>

[cubic-dev-ai]

P2: Subclass field initialization overwrites config.apiBase set by OpenAIApi, breaking custom base URL configuration.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At packages/openai-adapters/src/apis/Doubao.ts, line 19:

<comment>Subclass field initialization overwrites `config.apiBase` set by `OpenAIApi`, breaking custom base URL configuration.</comment>

<file context>
@@ -0,0 +1,26 @@
+ * Reference: https://www.volcengine.com/docs/82379
+ */
+export class DoubaoApi extends OpenAIApi {
+  apiBase: string = "https://ark.cn-beijing.volces.com/api/v3/";
+  constructor(config: DoubaoConfig) {
+    super({
</file context>

[MackDing]

I have read the CLA document and I hereby sign the CLA