feat: add Synthetic LLM provider support

.changeset/add-synthetic-provider.md

@@ -0,0 +1,39 @@
+---
+"opencode-swarm-plugin": minor
+---
+
+## 🐝 Add Synthetic LLM Provider Support
+
+Adds support for **Synthetic** as a first-class LLM provider in swarm-tools.
+
+**New Models Available:**
+
+**Coordinator Models (Complex Tasks):**
+- `synthetic/hf:moonshotai/Kimi-K2.5` - Strong reasoning model
+- `synthetic/hf:deepseek-ai/DeepSeek-V3.2` - Advanced reasoning
+
+**Worker Models (Parallel Tasks):**
+- `synthetic/hf:moonshotai/Kimi-K2.5` - Strong reasoning
+- `synthetic/hf:MiniMaxAI/MiniMax-M2.1` - Fast and cost-effective
+- `synthetic/hf:Qwen/Qwen3-Coder-480B-A35B-Instruct` - Powerful coding model
+
+**Lite Models (Docs, Tests, Simple Edits):**
+- `synthetic/hf:MiniMaxAI/MiniMax-M2.1` - Fast and cost-effective
+- `synthetic/hf:Qwen/Qwen3-Coder-480B-A35B-Instruct` - Powerful coding model
+
+**Why it matters:**
+- Synthetic provides OpenAI-compatible API at `https://api.synthetic.new/openai/v1`
+- Enables users already configured with Synthetic in OpenCode to use swarm-tools
+- Cost-effective alternative for multi-agent workflows
+- Qwen3-Coder specialized for coding tasks
+
+**Usage:**
+```bash
+swarm setup  # Select Synthetic models during setup
+```
+
+**Requirements:**
+- Synthetic API access configured in OpenCode
+- No additional configuration needed in swarm-tools
+
+Refs: #148, #150

packages/opencode-swarm-plugin/bin/swarm.ts

@@ -313,6 +313,7 @@ interface ModelOption {
   hint: string;
 }
 
+/** Available coordinator models for orchestration and planning tasks */
 const COORDINATOR_MODELS: ModelOption[] = [
   {
     value: "anthropic/claude-sonnet-4-5",
@@ -339,8 +340,19 @@ const COORDINATOR_MODELS: ModelOption[] = [
     label: "Gemini 1.5 Pro",
     hint: "More capable, larger context",
   },
+  {
+    value: "synthetic/hf:moonshotai/Kimi-K2.5",
+    label: "Synthetic Kimi K2.5",
+    hint: "Strong reasoning model via Synthetic",
+  },
+  {
+    value: "synthetic/hf:deepseek-ai/DeepSeek-V3.2",
+    label: "Synthetic DeepSeek V3.2",
+    hint: "Advanced reasoning via Synthetic",
+  },
 ];
 
+/** Available worker models for parallel task execution */
 const WORKER_MODELS: ModelOption[] = [
   {
     value: "anthropic/claude-haiku-4-5",
@@ -362,6 +374,21 @@ const WORKER_MODELS: ModelOption[] = [
     label: "Gemini 2.0 Flash",
     hint: "Fast and capable",
   },
+  {
+    value: "synthetic/hf:moonshotai/Kimi-K2.5",
+    label: "Synthetic Kimi K2.5",
+    hint: "Strong reasoning via Synthetic",
+  },
+  {
+    value: "synthetic/hf:MiniMaxAI/MiniMax-M2.1",
+    label: "Synthetic MiniMax M2.1",
+    hint: "Fast and cost-effective via Synthetic",
+  },
+  {
+    value: "synthetic/hf:Qwen/Qwen3-Coder-480B-A35B-Instruct",
+    label: "Synthetic Qwen3 Coder 480B",
+    hint: "Powerful coding model via Synthetic",
+  },
 ];
 
 // ============================================================================
@@ -2419,6 +2446,16 @@ async function setup(forceReinstall = false, nonInteractive = false) {
           label: "Gemini 1.5 Pro",
           hint: "More capable",
         },
+        {
+          value: "synthetic/hf:moonshotai/Kimi-K2.5",
+          label: "Synthetic Kimi K2.5",
+          hint: "Strong reasoning model via Synthetic",
+        },
+        {
+          value: "synthetic/hf:deepseek-ai/DeepSeek-V3.2",
+          label: "Synthetic DeepSeek V3.2",
+          hint: "Advanced reasoning via Synthetic",
+        },
       ],
       initialValue: DEFAULT_COORDINATOR,
     });
@@ -2467,6 +2504,21 @@ async function setup(forceReinstall = false, nonInteractive = false) {
           label: "Gemini 1.5 Pro",
           hint: "More capable",
         },
+        {
+          value: "synthetic/hf:moonshotai/Kimi-K2.5",
+          label: "Synthetic Kimi K2.5",
+          hint: "Strong reasoning via Synthetic",
+        },
+        {
+          value: "synthetic/hf:MiniMaxAI/MiniMax-M2.1",
+          label: "Synthetic MiniMax M2.1",
+          hint: "Fast and cost-effective via Synthetic",
+        },
+        {
+          value: "synthetic/hf:Qwen/Qwen3-Coder-480B-A35B-Instruct",
+          label: "Synthetic Qwen3 Coder 480B",
+          hint: "Powerful coding model via Synthetic",
+        },
       ],
       initialValue: DEFAULT_WORKER,
     });
@@ -2501,6 +2553,16 @@ async function setup(forceReinstall = false, nonInteractive = false) {
           label: "Gemini 2.0 Flash",
           hint: "Fast and capable",
         },
+        {
+          value: "synthetic/hf:MiniMaxAI/MiniMax-M2.1",
+          label: "Synthetic MiniMax M2.1",
+          hint: "Fast and cost-effective via Synthetic",
+        },
+        {
+          value: "synthetic/hf:Qwen/Qwen3-Coder-480B-A35B-Instruct",
+          label: "Synthetic Qwen3 Coder 480B",
+          hint: "Powerful coding model via Synthetic",
+        },
       ],
       initialValue: DEFAULT_LITE,
     });

packages/opencode-swarm-plugin/src/model-selection.test.ts

@@ -185,4 +185,43 @@ describe("selectWorkerModel", () => {
     const result = selectWorkerModel(subtask, mockConfig);
     expect(result).toBe("anthropic/claude-haiku-4-5");
   });
+
+  test("uses Synthetic model when explicitly provided", () => {
+    const subtask: DecomposedSubtask & { model?: string } = {
+      title: "Complex reasoning task",
+      description: "Use advanced reasoning",
+      files: ["src/ai.ts"],
+      estimated_effort: "large",
+      model: "synthetic/hf:moonshotai/Kimi-K2.5",
+    };
+
+    const result = selectWorkerModel(subtask, mockConfig);
+    expect(result).toBe("synthetic/hf:moonshotai/Kimi-K2.5");
+  });
+
+  test("synthetic DeepSeek model is selectable", () => {
+    const subtask: DecomposedSubtask & { model?: string } = {
+      title: "Deep reasoning task",
+      description: "Deep analysis required",
+      files: ["src/deep.ts"],
+      estimated_effort: "large",
+      model: "synthetic/hf:deepseek-ai/DeepSeek-V3.2",
+    };
+
+    const result = selectWorkerModel(subtask, mockConfig);
+    expect(result).toBe("synthetic/hf:deepseek-ai/DeepSeek-V3.2");
+  });
+
+  test("synthetic MiniMax model is selectable for worker tasks", () => {
+    const subtask: DecomposedSubtask & { model?: string } = {
+      title: "Fast processing task",
+      description: "Process data quickly",
+      files: ["src/process.ts"],
+      estimated_effort: "small",
+      model: "synthetic/hf:MiniMaxAI/MiniMax-M2.1",
+    };
+
+    const result = selectWorkerModel(subtask, mockConfig);
+    expect(result).toBe("synthetic/hf:MiniMaxAI/MiniMax-M2.1");
+  });
 });