diff --git a/open-sse/providers/registry/opencode.js b/open-sse/providers/registry/opencode.js
index 0914f431..b0705066 100644
--- a/open-sse/providers/registry/opencode.js
+++ b/open-sse/providers/registry/opencode.js
@@ -17,6 +17,7 @@ export default {
     headers: {
       "x-opencode-client": "desktop",
     },
+    forceStream: true,
     noAuth: true,
     quirks: {
       forceAutoToolChoiceModels: ["muse-spark-1.3-contributor-free"],
diff --git a/tests/unit/opencode-session.test.js b/tests/unit/opencode-session.test.js
index 89e06a8f..3e50b9fe 100644
--- a/tests/unit/opencode-session.test.js
+++ b/tests/unit/opencode-session.test.js
@@ -311,4 +311,9 @@ describe("OpenCode Stable Session Reuse (429 follow-up)", () => {
     expect(chatFull.tools.length).toBe(2);
     expect(chatFull.tools[0].function.description).toBe("existing");
   });
+
+  it("declares forceStream on the opencode transport so chatCore serves SSE upstream", async () => {
+    const { PROVIDERS } = await import("../../open-sse/config/providers.js");
+    expect(PROVIDERS.opencode?.forceStream).toBe(true);
+  });
 });