diff --git a/packages/provider-bridge-acp/src/bridge/bridge.test.ts b/packages/provider-bridge-acp/src/bridge/bridge.test.ts
index 3649140..cc16ce7 100644
--- a/packages/provider-bridge-acp/src/bridge/bridge.test.ts
+++ b/packages/provider-bridge-acp/src/bridge/bridge.test.ts
@@ -581,6 +581,31 @@ afterEach(async () => {
 });
 
 describe("acp bridge", () => {
+  it.each([false, true])("issue 4154 preserves later model efforts (reject middle: %s)", async (rejectMiddle) => {
+    const log = join(workspaceDir, "probes.txt");
+    const modelListId = sendModelList({
+      agent: { command: process.execPath, args: [resolve(dirname(FAKE_AGENT_PATH), "issue-4154-agent.mjs")] },
+      envVars: { REPRO_REQUEST_LOG: log, REPRO_REJECT_MIDDLE: rejectMiddle ? "1" : "0" },
+    });
+    const response = await waitForResponse(modelListId);
+    const probed = readFileSync(log, "utf8").trim().split("\n");
+    console.error(JSON.stringify({ rejectMiddle, probed, response }));
+    expect(response.result).toMatchObject({
+      models: [
+        { id: "probe-a", supportedReasoningEfforts: [
+          { reasoningEffort: "low" }, { reasoningEffort: "medium" }, { reasoningEffort: "high" },
+        ] },
+        { id: "probe-b", supportedReasoningEfforts: rejectMiddle
+          ? [{ reasoningEffort: "medium" }]
+          : [{ reasoningEffort: "low" }, { reasoningEffort: "medium" }, { reasoningEffort: "high" }] },
+        { id: "probe-c", supportedReasoningEfforts: [
+          { reasoningEffort: "low" }, { reasoningEffort: "medium" }, { reasoningEffort: "high" },
+        ] },
+      ],
+    });
+    expect(probed).toEqual(["probe-a", "probe-b", "probe-c"]);
+  });
+
   it("answers initialize and lists grouped models without spawning an agent", async () => {
     const initializeId = sendRequest("initialize", {
       protocolVersion: PROVIDER_BRIDGE_PROTOCOL_VERSION,