fix(providers): replay DeepSeek reasoning for opencode-zen (#994)

src/providers/registry.ts

@@ -1649,7 +1649,22 @@ export const PROVIDER_REGISTRY: readonly ProviderRegistryEntry[] = [
     autoToolChoiceOnlyModels: KIMI_AUTO_TOOL_CHOICE_ONLY_MODELS,
     preserveReasoningContentModels: KIMI_THINKING_MODELS,
   },
-  { id: "opencode-zen", label: "opencode zen", baseUrl: "https://opencode.ai/zen/v1", adapter: "openai-chat", authKind: "key", dashboardUrl: "https://opencode.ai/auth" },
+  {
+    id: "opencode-zen", label: "opencode zen", baseUrl: "https://opencode.ai/zen/v1", adapter: "openai-chat", authKind: "key", dashboardUrl: "https://opencode.ai/auth",
+    // Same opencode.ai/zen/v1 gateway as `opencode-free` (keyed tier): DeepSeek thinking mode
+    // requires the assistant's original reasoning_content to be replayed on tool-call
+    // continuations, or the gateway answers HTTP 400 (issues #950/#994). Mirror the DeepSeek
+    // reasoning + thinking metadata so `opencode-zen/deepseek-v4-flash-free` — and the other
+    // Zen DeepSeek thinking models — never serialize a bare tool-call turn.
+    modelReasoningEfforts: Object.fromEntries(
+      [...DEEPSEEK_THINKING_MODELS, ...OPENCODE_FREE_DEEPSEEK_MODELS].map(id => [id, DEEPSEEK_THINKING_EFFORTS]),
+    ),
+    modelReasoningEffortMap: Object.fromEntries(
+      [...DEEPSEEK_THINKING_MODELS, ...OPENCODE_FREE_DEEPSEEK_MODELS].map(id => [id, DEEPSEEK_THINKING_REASONING_MAP]),
+    ),
+    preserveReasoningContentModels: [...DEEPSEEK_THINKING_MODELS, ...OPENCODE_FREE_DEEPSEEK_MODELS],
+    noVisionModels: [...DEEPSEEK_THINKING_MODELS, ...OPENCODE_FREE_DEEPSEEK_MODELS],
+  },
   { id: "vercel-ai-gateway", label: "Vercel AI Gateway", baseUrl: "https://ai-gateway.vercel.sh/v1", adapter: "openai-chat", authKind: "key", dashboardUrl: "https://vercel.com/dashboard" },
   {
     id: "opencode-free",

tests/opencode-zen-deepseek-reasoning.test.ts

@@ -0,0 +1,96 @@
+import { describe, expect, test } from "bun:test";
+import { createOpenAIChatAdapter } from "../src/adapters/openai-chat";
+import { routeModel } from "../src/router";
+import type { OcxConfig } from "../src/types";
+
+function configFor(modelId: string): OcxConfig {
+  return {
+    port: 10110,
+    defaultProvider: "opencode-zen",
+    providers: {
+      "opencode-zen": {
+        adapter: "openai-chat",
+        baseUrl: "https://opencode.ai/zen/v1",
+        apiKey: "key",
+        models: [modelId],
+      },
+    },
+  };
+}
+
+function buildToolCallBody(modelId: string, reasoning?: string): {
+  reasoning_effort?: string;
+  messages: Record<string, unknown>[];
+} {
+  const route = routeModel(configFor(modelId), `opencode-zen/${modelId}`);
+  const req = createOpenAIChatAdapter(route.provider).buildRequest({
+    modelId: route.modelId,
+    context: {
+      messages: [
+        { role: "user", content: "inspect the repo", timestamp: 0 },
+        { role: "assistant", timestamp: 1, content: [
+          { type: "thinking", thinking: "I need to inspect files before answering." },
+          { type: "toolCall", id: "call_1", name: "read_file", arguments: { path: "README.md" } },
+        ] },
+        {
+          role: "toolResult",
+          toolCallId: "call_1",
+          toolName: "read_file",
+          content: "contents",
+          isError: false,
+          timestamp: 2,
+        },
+      ],
+    },
+    stream: true,
+    options: { reasoning: reasoning ?? "max" },
+  });
+
+  return JSON.parse(req.body as string) as {
+    reasoning_effort?: string;
+    messages: Record<string, unknown>[];
+  };
+}
+
+describe("opencode-zen DeepSeek thinking mode", () => {
+  test.each(["deepseek-v4-flash-free", "deepseek-v4-flash", "deepseek-v4-pro"])(
+    "%s replays tool-call reasoning_content and maps Codex efforts (issue #950/#994)",
+    modelId => {
+      const body = buildToolCallBody(modelId, "xhigh");
+
+      expect(body.reasoning_effort).toBe("max");
+      expect(body.messages[1].reasoning_content).toBe("I need to inspect files before answering.");
+      expect(body.messages[1]).toMatchObject({
+        role: "assistant",
+        content: "",
+        tool_calls: [{
+          id: "call_1",
+          type: "function",
+          function: { name: "read_file", arguments: JSON.stringify({ path: "README.md" }) },
+        }],
+      });
+    },
+  );
+
+  test("non-DeepSeek opencode-zen models do not replay reasoning_content", () => {
+    const body = buildToolCallBody("minimax-m2.7");
+
+    expect(body.messages[1].reasoning_content).toBeUndefined();
+    expect(body.messages[1]).toHaveProperty("tool_calls");
+  });
+
+  test.each(["deepseek-v4-flash-free", "deepseek-v4-flash", "deepseek-v4-pro"])(
+    "%s is listed in opencode-zen noVisionModels for the vision sidecar",
+    modelId => {
+      const route = routeModel(configFor(modelId), `opencode-zen/${modelId}`);
+
+      expect(route.provider.noVisionModels).toContain(modelId);
+    },
+  );
+
+  test("non-DeepSeek opencode-zen models stay out of noVisionModels", () => {
+    const route = routeModel(configFor("minimax-m2.7"), "opencode-zen/minimax-m2.7");
+
+    expect(route.provider.noVisionModels).not.toContain("minimax-m2.7");
+  });
+});