diff --git a/README.md b/README.md
index e7bf778..d1849cd 100644
--- a/README.md
+++ b/README.md
@@ -17,7 +17,7 @@ CrewAI is Python. LangGraph makes you draw the graph by hand. `open-multi-agent`
 
 - **Goal to result in one call.** `runTeam(team, "Build a REST API")` kicks off a coordinator agent that decomposes the goal into a task DAG, resolves dependencies, runs independent tasks in parallel, and synthesizes the final output. No graph to draw, no tasks to wire up.
 - **TypeScript-native, three runtime dependencies.** `@anthropic-ai/sdk`, `openai`, `zod`. That is the whole runtime. Embed in Express, Next.js, serverless functions, or CI/CD pipelines. No Python runtime, no subprocess bridge, no cloud sidecar.
-- **Multi-model teams.** Claude, GPT, Gemini, Grok, MiniMax, Copilot, or any OpenAI-compatible local model (Ollama, vLLM, LM Studio, llama.cpp) in the same team. Run the architect on Opus 4.6, the developer on GPT-5.4, the reviewer on local Gemma 4, all in one `runTeam()` call. Gemini ships as an optional peer dependency: `npm install @google/genai` to enable.
+- **Multi-model teams.** Claude, GPT, Gemini, Grok, MiniMax, DeepSeek, Copilot, or any OpenAI-compatible local model (Ollama, vLLM, LM Studio, llama.cpp) in the same team. Run the architect on Opus 4.6, the developer on GPT-5.4, the reviewer on local Gemma 4, all in one `runTeam()` call. Gemini ships as an optional peer dependency: `npm install @google/genai` to enable.
 
 Other features (MCP integration, context strategies, structured output, task retry, human-in-the-loop, lifecycle hooks, loop detection, observability) live below the fold and in [`examples/`](./examples/).
 
@@ -74,6 +74,7 @@ Set the API key for your provider. Local models via Ollama require no API key 
 - `XAI_API_KEY` (for Grok)
 - `MINIMAX_API_KEY` (for MiniMax)
 - `MINIMAX_BASE_URL` (for MiniMax — optional, selects endpoint)
+- `DEEPSEEK_API_KEY` (for DeepSeek)
 - `GITHUB_TOKEN` (for Copilot)
 
 **CLI (`oma`).** For shell and CI, the package exposes a JSON-first binary. See [docs/cli.md](./docs/cli.md) for `oma run`, `oma task`, `oma provider`, exit codes, and file formats.
@@ -141,13 +142,14 @@ For MapReduce-style fan-out without task dependencies, use `AgentPool.runParalle
 
 ## Examples
 
-17 runnable scripts and 1 full-stack demo in [`examples/`](./examples/). Start with these:
+18 runnable scripts and 1 full-stack demo in [`examples/`](./examples/). Start with these:
 
 - [02 — Team Collaboration](examples/02-team-collaboration.ts): `runTeam()` coordinator pattern.
 - [06 — Local Model](examples/06-local-model.ts): Ollama and Claude in one pipeline via `baseURL`.
 - [09 — Structured Output](examples/09-structured-output.ts): any agent returns Zod-validated JSON.
 - [11 — Trace Observability](examples/11-trace-observability.ts): `onTrace` spans for LLM calls, tools, and tasks.
 - [17 — MiniMax](examples/17-minimax.ts): three-agent team using MiniMax M2.7.
+- [18 — DeepSeek](examples/18-deepseek.ts): three-agent team using DeepSeek Chat.
 - [with-vercel-ai-sdk](examples/with-vercel-ai-sdk/): Next.js app — OMA `runTeam()` + AI SDK `useChat` streaming.
 
 Run scripts with `npx tsx examples/02-team-collaboration.ts`.
@@ -187,6 +189,7 @@ Run scripts with `npx tsx examples/02-team-collaboration.ts`.
          │               │  - GeminiAdapter     │
          │               │  - GrokAdapter       │
          │               │  - MiniMaxAdapter    │
+         │               │  - DeepSeekAdapter   │
          │               └──────────────────────┘
 ┌────────▼──────────┐
 │  AgentRunner      │    ┌──────────────────────┐
@@ -288,6 +291,7 @@ Notes:
 | Grok (xAI)   | `provider: 'grok'` | `XAI_API_KEY` | Verified |
 | MiniMax (global) | `provider: 'minimax'` | `MINIMAX_API_KEY` | Verified |
 | MiniMax (China) | `provider: 'minimax'` + `MINIMAX_BASE_URL` | `MINIMAX_API_KEY` | Verified |
+| DeepSeek | `provider: 'deepseek'` | `DEEPSEEK_API_KEY` | Verified |
 | GitHub Copilot | `provider: 'copilot'` | `GITHUB_TOKEN` | Verified |
 | Gemini | `provider: 'gemini'` | `GEMINI_API_KEY` | Verified |
 | Ollama / vLLM / LM Studio | `provider: 'openai'` + `baseURL` | — | Verified |
@@ -297,7 +301,7 @@ Gemini requires `npm install @google/genai` (optional peer dependency).
 
 Verified local models with tool-calling: **Gemma 4** (see [example 08](examples/08-gemma4-local.ts)).
 
-Any OpenAI-compatible API should work via `provider: 'openai'` + `baseURL` (DeepSeek, Groq, Mistral, Qwen, etc.). **Grok and MiniMax now have first-class support** via `provider: 'grok'` and `provider: 'minimax'`.
+Any OpenAI-compatible API should work via `provider: 'openai'` + `baseURL` (Groq, Mistral, Qwen, etc.). **Grok, MiniMax, and DeepSeek now have first-class support** via `provider: 'grok'`, `provider: 'minimax'`, and `provider: 'deepseek'`.
 
 ### Local Model Tool-Calling
 
@@ -355,6 +359,17 @@ Set `MINIMAX_API_KEY`. The adapter selects the endpoint via `MINIMAX_BASE_URL`:
 
 You can also pass `baseURL` directly in `AgentConfig` to override the env var.
 
+```typescript
+const deepseekAgent: AgentConfig = {
+  name: 'deepseek-agent',
+  provider: 'deepseek',
+  model: 'deepseek-chat',
+  systemPrompt: 'You are a helpful assistant.',
+}
+```
+
+Set `DEEPSEEK_API_KEY`. Available models: `deepseek-chat` (DeepSeek-V3, recommended for coding) and `deepseek-reasoner` (thinking mode).
+
 ## Contributing
 
 Issues, feature requests, and PRs are welcome. Some areas where contributions would be especially valuable:
diff --git a/README_zh.md b/README_zh.md
index 2dc9d13..aa9c83e 100644
--- a/README_zh.md
+++ b/README_zh.md
@@ -17,7 +17,7 @@ CrewAI 是 Python。LangGraph 需要你自己画图。`open-multi-agent` 是你
 
 - **一次调用从目标到结果。** `runTeam(team, "构建一个 REST API")` 启动一个协调者 agent，把目标拆成任务 DAG，解析依赖，独立任务并行执行，最终合成输出。不需要画图，不需要手动连任务。
 - **TypeScript 原生，3 个运行时依赖。** `@anthropic-ai/sdk`、`openai`、`zod`。这就是全部运行时。可嵌入 Express、Next.js、Serverless 函数或 CI/CD 流水线。没有 Python 运行时，没有子进程桥接，没有云端 sidecar。
-- **多模型团队。** Claude、GPT、Gemini、Grok、MiniMax、Copilot，或任何 OpenAI 兼容的本地模型（Ollama、vLLM、LM Studio、llama.cpp）可以在同一个团队中使用。让架构师用 Opus 4.6，开发者用 GPT-5.4，评审用本地的 Gemma 4，一次 `runTeam()` 调用全部搞定。Gemini 作为 optional peer dependency 提供：使用前需 `npm install @google/genai`。
+- **多模型团队。** Claude、GPT、Gemini、Grok、MiniMax、DeepSeek、Copilot，或任何 OpenAI 兼容的本地模型（Ollama、vLLM、LM Studio、llama.cpp）可以在同一个团队中使用。让架构师用 Opus 4.6，开发者用 GPT-5.4，评审用本地的 Gemma 4，一次 `runTeam()` 调用全部搞定。Gemini 作为 optional peer dependency 提供：使用前需 `npm install @google/genai`。
 
 其他能力（MCP 集成、上下文策略、结构化输出、任务重试、人机协同、生命周期钩子、循环检测、可观测性）在下方章节和 [`examples/`](./examples/) 里。
 
@@ -74,6 +74,7 @@ npm install @jackchen_me/open-multi-agent
 - `XAI_API_KEY`（Grok）
 - `MINIMAX_API_KEY`（MiniMax）
 - `MINIMAX_BASE_URL`（MiniMax — 可选，用于选择接入端点）
+- `DEEPSEEK_API_KEY`（DeepSeek）
 - `GITHUB_TOKEN`（Copilot）
 
 三个智能体，一个目标——框架处理剩下的一切：
@@ -139,13 +140,14 @@ Tokens: 12847 output tokens
 
 ## 示例
 
-[`examples/`](./examples/) 里有 17 个可运行脚本和 1 个完整项目。推荐从这几个开始：
+[`examples/`](./examples/) 里有 18 个可运行脚本和 1 个完整项目。推荐从这几个开始：
 
 - [02 — 团队协作](examples/02-team-collaboration.ts)：`runTeam()` 协调者模式。
 - [06 — 本地模型](examples/06-local-model.ts)：通过 `baseURL` 把 Ollama 和 Claude 放在同一条管线。
 - [09 — 结构化输出](examples/09-structured-output.ts)：任意 agent 产出 Zod 校验过的 JSON。
 - [11 — 可观测性](examples/11-trace-observability.ts)：`onTrace` 回调，为 LLM 调用、工具、任务发出结构化 span。
 - [17 — MiniMax](examples/17-minimax.ts)：使用 MiniMax M2.7 的三智能体团队。
+- [18 — DeepSeek](examples/18-deepseek.ts)：使用 DeepSeek Chat 的三智能体团队。
 - [with-vercel-ai-sdk](examples/with-vercel-ai-sdk/)：Next.js 应用 — OMA `runTeam()` + AI SDK `useChat` 流式输出。
 
 用 `npx tsx examples/02-team-collaboration.ts` 运行脚本示例。
@@ -185,6 +187,7 @@ Tokens: 12847 output tokens
          │               │  - GeminiAdapter     │
          │               │  - GrokAdapter       │
          │               │  - MiniMaxAdapter    │
+         │               │  - DeepSeekAdapter   │
          │               └──────────────────────┘
 ┌────────▼──────────┐
 │  AgentRunner      │    ┌──────────────────────┐
@@ -262,6 +265,7 @@ const customAgent: AgentConfig = {
 | Grok (xAI)   | `provider: 'grok'` | `XAI_API_KEY` | 已验证 |
 | MiniMax（全球） | `provider: 'minimax'` | `MINIMAX_API_KEY` | 已验证 |
 | MiniMax（国内） | `provider: 'minimax'` + `MINIMAX_BASE_URL` | `MINIMAX_API_KEY` | 已验证 |
+| DeepSeek | `provider: 'deepseek'` | `DEEPSEEK_API_KEY` | 已验证 |
 | GitHub Copilot | `provider: 'copilot'` | `GITHUB_TOKEN` | 已验证 |
 | Gemini | `provider: 'gemini'` | `GEMINI_API_KEY` | 已验证 |
 | Ollama / vLLM / LM Studio | `provider: 'openai'` + `baseURL` | — | 已验证 |
@@ -271,7 +275,7 @@ Gemini 需要 `npm install @google/genai`（optional peer dependency）。
 
 已验证支持 tool-calling 的本地模型：**Gemma 4**（见[示例 08](examples/08-gemma4-local.ts)）。
 
-任何 OpenAI 兼容 API 均可通过 `provider: 'openai'` + `baseURL` 接入（DeepSeek、Groq、Mistral、Qwen 等）。**Grok 和 MiniMax 现已原生支持**，分别使用 `provider: 'grok'` 和 `provider: 'minimax'`。
+任何 OpenAI 兼容 API 均可通过 `provider: 'openai'` + `baseURL` 接入（Groq、Mistral、Qwen 等）。**Grok、MiniMax 和 DeepSeek 现已原生支持**，分别使用 `provider: 'grok'`、`provider: 'minimax'` 和 `provider: 'deepseek'`。
 
 ### 本地模型 Tool-Calling
 
@@ -329,6 +333,17 @@ const minimaxAgent: AgentConfig = {
 
 也可在 `AgentConfig` 中直接传入 `baseURL` 覆盖环境变量。
 
+```typescript
+const deepseekAgent: AgentConfig = {
+  name: 'deepseek-agent',
+  provider: 'deepseek',
+  model: 'deepseek-chat',
+  systemPrompt: '你是一个有用的助手。',
+}
+```
+
+设置 `DEEPSEEK_API_KEY`。可用模型：`deepseek-chat`（DeepSeek-V3，推荐用于编码任务）和 `deepseek-reasoner`（思考模式）。
+
 ## 参与贡献
 
 欢迎提 Issue、功能需求和 PR。以下方向的贡献尤其有价值：
diff --git a/docs/cli.md b/docs/cli.md
index 9fc6ccd..38a6522 100644
--- a/docs/cli.md
+++ b/docs/cli.md
@@ -55,7 +55,7 @@ Global flags: [`--pretty`](#output-flags), [`--include-messages`](#output-flags)
 Read-only helper for wiring JSON configs and env vars.
 
 - **`oma provider`** or **`oma provider list`** — Prints JSON: built-in provider ids, API key environment variable names, whether `baseURL` is supported, and short notes (e.g. OpenAI-compatible servers, Copilot in CI).
-- **`oma provider template <provider>`** — Prints a JSON object with example `orchestrator` and `agent` fields plus placeholder `env` entries. `<provider>` is one of: `anthropic`, `openai`, `gemini`, `grok`, `minimax`, `copilot`.
+- **`oma provider template <provider>`** — Prints a JSON object with example `orchestrator` and `agent` fields plus placeholder `env` entries. `<provider>` is one of: `anthropic`, `openai`, `gemini`, `grok`, `minimax`, `deepseek`, `copilot`.
 
 Supports `--pretty`.
 
diff --git a/examples/18-deepseek.ts b/examples/18-deepseek.ts
new file mode 100644
index 0000000..937b2ef
--- /dev/null
+++ b/examples/18-deepseek.ts
@@ -0,0 +1,158 @@
+/**
+ * Example 18 — Multi-Agent Team Collaboration with DeepSeek
+ *
+ * Three specialized agents (architect, developer, reviewer) collaborate via `runTeam()`
+ * to build a minimal Express.js REST API. Every agent uses DeepSeek's flagship model.
+ *
+ * Run:
+ *   npx tsx examples/18-deepseek.ts
+ *
+ * Prerequisites:
+ *   DEEPSEEK_API_KEY environment variable must be set.
+ *
+ * Available models:
+ *   deepseek-chat      — DeepSeek-V3 (non-thinking mode, recommended for coding tasks)
+ *   deepseek-reasoner  — DeepSeek-V3 (thinking mode, for complex reasoning)
+ */
+
+import { OpenMultiAgent } from '../src/index.js'
+import type { AgentConfig, OrchestratorEvent } from '../src/types.js'
+
+// ---------------------------------------------------------------------------
+// Agent definitions (all using deepseek-chat)
+// ---------------------------------------------------------------------------
+const architect: AgentConfig = {
+  name: 'architect',
+  model: 'deepseek-reasoner',
+  provider: 'deepseek',
+  systemPrompt: `You are a software architect with deep experience in Node.js and REST API design.
+Your job is to design clear, production-quality API contracts and file/directory structures.
+Output concise plans in markdown — no unnecessary prose.`,
+  tools: ['bash', 'file_write'],
+  maxTurns: 5,
+  temperature: 0.2,
+}
+
+const developer: AgentConfig = {
+  name: 'developer',
+  model: 'deepseek-chat',
+  provider: 'deepseek',
+  systemPrompt: `You are a TypeScript/Node.js developer. You implement what the architect specifies.
+Write clean, runnable code with proper error handling. Use the tools to write files and run tests.`,
+  tools: ['bash', 'file_read', 'file_write', 'file_edit'],
+  maxTurns: 12,
+  temperature: 0.1,
+}
+
+const reviewer: AgentConfig = {
+  name: 'reviewer',
+  model: 'deepseek-chat',
+  provider: 'deepseek',
+  systemPrompt: `You are a senior code reviewer. Review code for correctness, security, and clarity.
+Provide a structured review with: LGTM items, suggestions, and any blocking issues.
+Read files using the tools before reviewing.`,
+  tools: ['bash', 'file_read', 'grep'],
+  maxTurns: 5,
+  temperature: 0.3,
+}
+
+// ---------------------------------------------------------------------------
+// Progress tracking
+// ---------------------------------------------------------------------------
+const startTimes = new Map<string, number>()
+
+function handleProgress(event: OrchestratorEvent): void {
+  const ts = new Date().toISOString().slice(11, 23) // HH:MM:SS.mmm
+  switch (event.type) {
+    case 'agent_start':
+      startTimes.set(event.agent ?? '', Date.now())
+      console.log(`[${ts}] AGENT START → ${event.agent}`)
+      break
+    case 'agent_complete': {
+      const elapsed = Date.now() - (startTimes.get(event.agent ?? '') ?? Date.now())
+      console.log(`[${ts}] AGENT DONE ← ${event.agent} (${elapsed}ms)`)
+      break
+    }
+    case 'task_start':
+      console.log(`[${ts}] TASK START ↓ ${event.task}`)
+      break
+    case 'task_complete':
+      console.log(`[${ts}] TASK DONE ↑ ${event.task}`)
+      break
+    case 'message':
+      console.log(`[${ts}] MESSAGE • ${event.agent} → (team)`)
+      break
+    case 'error':
+      console.error(`[${ts}] ERROR ✗ agent=${event.agent} task=${event.task}`)
+      if (event.data instanceof Error) console.error(` ${event.data.message}`)
+      break
+  }
+}
+
+// ---------------------------------------------------------------------------
+// Orchestrate
+// ---------------------------------------------------------------------------
+const orchestrator = new OpenMultiAgent({
+  defaultModel: 'deepseek-chat',
+  defaultProvider: 'deepseek',
+  maxConcurrency: 1, // sequential for readable output
+  onProgress: handleProgress,
+})
+
+const team = orchestrator.createTeam('api-team', {
+  name: 'api-team',
+  agents: [architect, developer, reviewer],
+  sharedMemory: true,
+  maxConcurrency: 1,
+})
+
+console.log(`Team "${team.name}" created with agents: ${team.getAgents().map(a => a.name).join(', ')}`)
+console.log('\nStarting team run...\n')
+console.log('='.repeat(60))
+
+const goal = `Create a minimal Express.js REST API in /tmp/express-api/ with:
+- GET /health → { status: "ok" }
+- GET /users → returns a hardcoded array of 2 user objects
+- POST /users → accepts { name, email } body, logs it, returns 201
+- Proper error handling middleware
+- The server should listen on port 3001
+- Include a package.json with the required dependencies`
+
+const result = await orchestrator.runTeam(team, goal)
+
+console.log('\n' + '='.repeat(60))
+
+// ---------------------------------------------------------------------------
+// Results
+// ---------------------------------------------------------------------------
+console.log('\nTeam run complete.')
+console.log(`Success: ${result.success}`)
+console.log(`Total tokens — input: ${result.totalTokenUsage.input_tokens}, output: ${result.totalTokenUsage.output_tokens}`)
+
+console.log('\nPer-agent results:')
+for (const [agentName, agentResult] of result.agentResults) {
+  const status = agentResult.success ? 'OK' : 'FAILED'
+  const tools = agentResult.toolCalls.length
+  console.log(` ${agentName.padEnd(12)} [${status}] tool_calls=${tools}`)
+  if (!agentResult.success) {
+    console.log(` Error: ${agentResult.output.slice(0, 120)}`)
+  }
+}
+
+// Sample outputs
+const developerResult = result.agentResults.get('developer')
+if (developerResult?.success) {
+  console.log('\nDeveloper output (last 600 chars):')
+  console.log('─'.repeat(60))
+  const out = developerResult.output
+  console.log(out.length > 600 ? '...' + out.slice(-600) : out)
+  console.log('─'.repeat(60))
+}
+
+const reviewerResult = result.agentResults.get('reviewer')
+if (reviewerResult?.success) {
+  console.log('\nReviewer output:')
+  console.log('─'.repeat(60))
+  console.log(reviewerResult.output)
+  console.log('─'.repeat(60))
+}
diff --git a/src/cli/oma.ts b/src/cli/oma.ts
index 75a08b3..859d9d5 100644
--- a/src/cli/oma.ts
+++ b/src/cli/oma.ts
@@ -51,6 +51,7 @@ const PROVIDER_REFERENCE: ReadonlyArray<{
   { id: 'gemini', apiKeyEnv: ['GEMINI_API_KEY', 'GOOGLE_API_KEY'], baseUrlSupported: false },
   { id: 'grok', apiKeyEnv: ['XAI_API_KEY'], baseUrlSupported: true },
   { id: 'minimax', apiKeyEnv: ['MINIMAX_API_KEY'], baseUrlSupported: true, notes: 'Global endpoint: https://api.minimax.io/v1 (default). China endpoint: https://api.minimaxi.com/v1. Set MINIMAX_BASE_URL to choose, or pass baseURL in agent config.' },
+  { id: 'deepseek', apiKeyEnv: ['DEEPSEEK_API_KEY'], baseUrlSupported: true, notes: 'OpenAI-compatible endpoint at https://api.deepseek.com/v1. Models: deepseek-chat (V3), deepseek-reasoner (thinking).' },
   {
     id: 'copilot',
     apiKeyEnv: ['GITHUB_COPILOT_TOKEN', 'GITHUB_TOKEN'],
@@ -261,6 +262,7 @@ const DEFAULT_MODEL_HINT: Record<SupportedProvider, string> = {
   grok: 'grok-2-latest',
   copilot: 'gpt-4o',
   minimax: 'MiniMax-M2.7',
+  deepseek: 'deepseek-chat',
 }
 
 async function cmdProvider(sub: string | undefined, arg: string | undefined, pretty: boolean): Promise<number> {
diff --git a/src/llm/adapter.ts b/src/llm/adapter.ts
index 939a9eb..75426ef 100644
--- a/src/llm/adapter.ts
+++ b/src/llm/adapter.ts
@@ -38,7 +38,7 @@ import type { LLMAdapter } from '../types.js'
  * Additional providers can be integrated by implementing {@link LLMAdapter}
  * directly and bypassing this factory.
  */
-export type SupportedProvider = 'anthropic' | 'copilot' | 'grok' | 'minimax' | 'openai' | 'gemini'
+export type SupportedProvider = 'anthropic' | 'copilot' | 'deepseek' | 'grok' | 'minimax' | 'openai' | 'gemini'
 
 /**
  * Instantiate the appropriate {@link LLMAdapter} for the given provider.
@@ -50,6 +50,7 @@ export type SupportedProvider = 'anthropic' | 'copilot' | 'grok' | 'minimax' | '
  * - `gemini`    → `GEMINI_API_KEY` / `GOOGLE_API_KEY`
  * - `grok`      → `XAI_API_KEY`
  * - `minimax`   → `MINIMAX_API_KEY`
+ * - `deepseek`  → `DEEPSEEK_API_KEY`
  * - `copilot`   → `GITHUB_COPILOT_TOKEN` / `GITHUB_TOKEN`, or interactive
  *                  OAuth2 device flow if neither is set
  *
@@ -94,6 +95,10 @@ export async function createAdapter(
       const { MiniMaxAdapter } = await import('./minimax.js')
       return new MiniMaxAdapter(apiKey, baseURL)
     }
+    case 'deepseek': {
+      const { DeepSeekAdapter } = await import('./deepseek.js')
+      return new DeepSeekAdapter(apiKey, baseURL)
+    }
     default: {
       // The `never` cast here makes TypeScript enforce exhaustiveness.
       const _exhaustive: never = provider
diff --git a/src/llm/deepseek.ts b/src/llm/deepseek.ts
new file mode 100644
index 0000000..cb52a24
--- /dev/null
+++ b/src/llm/deepseek.ts
@@ -0,0 +1,29 @@
+/**
+ * @fileoverview DeepSeek adapter.
+ *
+ * Thin wrapper around OpenAIAdapter that hard-codes the official DeepSeek
+ * OpenAI-compatible endpoint and DEEPSEEK_API_KEY environment variable fallback.
+ */
+
+import { OpenAIAdapter } from './openai.js'
+
+/**
+ * LLM adapter for DeepSeek models (deepseek-chat, deepseek-reasoner, and future models).
+ *
+ * Thread-safe. Can be shared across agents.
+ *
+ * Usage:
+ *   provider: 'deepseek'
+ *   model: 'deepseek-chat' (or 'deepseek-reasoner' for the thinking model)
+ */
+export class DeepSeekAdapter extends OpenAIAdapter {
+  readonly name = 'deepseek'
+
+  constructor(apiKey?: string, baseURL?: string) {
+    // Allow override of baseURL (for proxies or future changes) but default to official DeepSeek endpoint.
+    super(
+      apiKey ?? process.env['DEEPSEEK_API_KEY'],
+      baseURL ?? 'https://api.deepseek.com/v1'
+    )
+  }
+}
diff --git a/tests/deepseek-adapter.test.ts b/tests/deepseek-adapter.test.ts
new file mode 100644
index 0000000..2d68427
--- /dev/null
+++ b/tests/deepseek-adapter.test.ts
@@ -0,0 +1,74 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+
+// ---------------------------------------------------------------------------
+// Mock OpenAI constructor (must be hoisted for Vitest)
+// ---------------------------------------------------------------------------
+const OpenAIMock = vi.hoisted(() => vi.fn())
+
+vi.mock('openai', () => ({
+  default: OpenAIMock,
+}))
+
+import { DeepSeekAdapter } from '../src/llm/deepseek.js'
+import { createAdapter } from '../src/llm/adapter.js'
+
+// ---------------------------------------------------------------------------
+// DeepSeekAdapter tests
+// ---------------------------------------------------------------------------
+
+describe('DeepSeekAdapter', () => {
+  beforeEach(() => {
+    OpenAIMock.mockClear()
+  })
+
+  it('has name "deepseek"', () => {
+    const adapter = new DeepSeekAdapter()
+    expect(adapter.name).toBe('deepseek')
+  })
+
+  it('uses DEEPSEEK_API_KEY by default', () => {
+    const original = process.env['DEEPSEEK_API_KEY']
+    process.env['DEEPSEEK_API_KEY'] = 'deepseek-test-key-123'
+
+    try {
+      new DeepSeekAdapter()
+      expect(OpenAIMock).toHaveBeenCalledWith(
+        expect.objectContaining({
+          apiKey: 'deepseek-test-key-123',
+          baseURL: 'https://api.deepseek.com/v1',
+        })
+      )
+    } finally {
+      if (original === undefined) {
+        delete process.env['DEEPSEEK_API_KEY']
+      } else {
+        process.env['DEEPSEEK_API_KEY'] = original
+      }
+    }
+  })
+
+  it('uses official DeepSeek baseURL by default', () => {
+    new DeepSeekAdapter('some-key')
+    expect(OpenAIMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        apiKey: 'some-key',
+        baseURL: 'https://api.deepseek.com/v1',
+      })
+    )
+  })
+
+  it('allows overriding apiKey and baseURL', () => {
+    new DeepSeekAdapter('custom-key', 'https://custom.endpoint/v1')
+    expect(OpenAIMock).toHaveBeenCalledWith(
+      expect.objectContaining({
+        apiKey: 'custom-key',
+        baseURL: 'https://custom.endpoint/v1',
+      })
+    )
+  })
+
+  it('createAdapter("deepseek") returns DeepSeekAdapter instance', async () => {
+    const adapter = await createAdapter('deepseek')
+    expect(adapter).toBeInstanceOf(DeepSeekAdapter)
+  })
+})