diff --git a/tests/unit/opencode-executor.test.mjs b/tests/unit/opencode-executor.test.mjs
new file mode 100644
index 0000000000..45c0924d63
--- /dev/null
+++ b/tests/unit/opencode-executor.test.mjs
@@ -0,0 +1,124 @@
+import { beforeEach, describe, it } from "node:test";
+import assert from "node:assert/strict";
+
+const { OpencodeExecutor } = await import("../../open-sse/executors/opencode.ts");
+const { getModelTargetFormat } = await import("../../open-sse/config/providerModels.ts");
+
+function setRequestFormat(executor, provider, model, overrideFormat) {
+  executor._requestFormat = overrideFormat ?? getModelTargetFormat(provider, model);
+}
+
+describe("OpencodeExecutor", () => {
+  let zenExecutor;
+  let goExecutor;
+
+  beforeEach(() => {
+    zenExecutor = new OpencodeExecutor("opencode-zen");
+    goExecutor = new OpencodeExecutor("opencode-go");
+  });
+
+  describe("buildUrl", () => {
+    it("returns chat completions for opencode zen default models", () => {
+      setRequestFormat(zenExecutor, "opencode-zen", "minimax-m2.5-free");
+      assert.equal(
+        zenExecutor.buildUrl("minimax-m2.5-free", true),
+        "https://opencode.ai/zen/v1/chat/completions"
+      );
+
+      setRequestFormat(zenExecutor, "opencode-zen", "big-pickle");
+      assert.equal(
+        zenExecutor.buildUrl("big-pickle", true),
+        "https://opencode.ai/zen/v1/chat/completions"
+      );
+
+      setRequestFormat(zenExecutor, "opencode-zen", "gpt-5-nano");
+      assert.equal(
+        zenExecutor.buildUrl("gpt-5-nano", true),
+        "https://opencode.ai/zen/v1/chat/completions"
+      );
+    });
+
+    it("returns messages endpoint for claude target format models", () => {
+      setRequestFormat(goExecutor, "opencode-go", "minimax-m2.7");
+      assert.equal(
+        goExecutor.buildUrl("minimax-m2.7", true),
+        "https://opencode.ai/zen/go/v1/messages"
+      );
+
+      setRequestFormat(goExecutor, "opencode-go", "minimax-m2.5");
+      assert.equal(
+        goExecutor.buildUrl("minimax-m2.5", true),
+        "https://opencode.ai/zen/go/v1/messages"
+      );
+    });
+
+    it("returns responses endpoint for openai responses target format", () => {
+      setRequestFormat(zenExecutor, "opencode-zen", "gpt-5-nano", "openai-responses");
+      assert.equal(
+        zenExecutor.buildUrl("gpt-5-nano", true),
+        "https://opencode.ai/zen/v1/responses"
+      );
+    });
+
+    it("returns gemini streaming endpoint when stream is true", () => {
+      setRequestFormat(zenExecutor, "opencode-zen", "gemini-2.5-pro", "gemini");
+      assert.equal(
+        zenExecutor.buildUrl("gemini-2.5-pro", true),
+        "https://opencode.ai/zen/v1/models/gemini-2.5-pro:streamGenerateContent?alt=sse"
+      );
+    });
+
+    it("returns gemini non streaming endpoint when stream is false", () => {
+      setRequestFormat(zenExecutor, "opencode-zen", "gemini-2.5-pro", "gemini");
+      assert.equal(
+        zenExecutor.buildUrl("gemini-2.5-pro", false),
+        "https://opencode.ai/zen/v1/models/gemini-2.5-pro:generateContent"
+      );
+    });
+
+    it("falls back to chat completions for unknown models", () => {
+      setRequestFormat(zenExecutor, "opencode-zen", "unknown-model");
+      assert.equal(
+        zenExecutor.buildUrl("unknown-model", true),
+        "https://opencode.ai/zen/v1/chat/completions"
+      );
+    });
+  });
+
+  describe("buildHeaders", () => {
+    it("builds default headers for standard models", () => {
+      setRequestFormat(zenExecutor, "opencode-zen", "gpt-5-nano");
+      assert.deepEqual(zenExecutor.buildHeaders({ apiKey: "test-key" }), {
+        Authorization: "Bearer test-key",
+        "Content-Type": "application/json",
+        Accept: "text/event-stream",
+      });
+    });
+
+    it("adds anthropic version for claude target format", () => {
+      setRequestFormat(goExecutor, "opencode-go", "minimax-m2.7");
+      assert.deepEqual(goExecutor.buildHeaders({ apiKey: "claude-key" }), {
+        Authorization: "Bearer claude-key",
+        "Content-Type": "application/json",
+        "anthropic-version": "2023-06-01",
+        Accept: "text/event-stream",
+      });
+    });
+
+    it("omits accept header when stream is false", () => {
+      setRequestFormat(zenExecutor, "opencode-zen", "big-pickle");
+      assert.deepEqual(zenExecutor.buildHeaders({ apiKey: "test-key" }, false), {
+        Authorization: "Bearer test-key",
+        "Content-Type": "application/json",
+      });
+    });
+
+    it("omits authorization when credentials are missing", () => {
+      setRequestFormat(zenExecutor, "opencode-zen", "minimax-m2.5-free");
+      assert.deepEqual(zenExecutor.buildHeaders(null), {
+        "Content-Type": "application/json",
+        Accept: "text/event-stream",
+      });
+    });
+  });
+});