fix(runtime): compact context inside worker

tests/unit/context-compaction-worker.test.ts

@@ -0,0 +1,66 @@
+import type { AgentMessage } from "@mariozechner/pi-agent-core";
+import { describe, expect, it, vi } from "vitest";
+import { buildAgentHooks } from "../../src/main/agent-runtime/agent-hooks";
+import type { WorkerRpcClient } from "../../src/main/worker/entry/rpc";
+
+function createRpc() {
+  return {
+    invoke: vi.fn(async () => ({ ok: true, result: undefined })),
+  } as unknown as WorkerRpcClient & { invoke: ReturnType<typeof vi.fn> };
+}
+
+function largeTranscript(): AgentMessage[] {
+  const messages: AgentMessage[] = [];
+  for (let i = 0; i < 46; i += 1) {
+    const role = i % 2 === 0 ? "user" : "assistant";
+    messages.push({
+      role,
+      content: [{
+        type: "text",
+        text: `${role} turn ${i}\n${"context ".repeat(6_000)}`,
+      }],
+      timestamp: i,
+    } as AgentMessage);
+  }
+  return messages;
+}
+
+describe("worker-side context compaction", () => {
+  it("compacts inside the worker without transformContext RPC", async () => {
+    const rpc = createRpc();
+    const onContextCompaction = vi.fn();
+    const hooks = buildAgentHooks({
+      runId: "8b3f07b2-841a-4e16-9d1c-9d2a27c3c2ad",
+      rpc,
+      onContextCompaction,
+    });
+
+    const messages = largeTranscript();
+    const transformed = await hooks.transformContext(messages);
+
+    expect(rpc.invoke).not.toHaveBeenCalledWith(
+      expect.any(String),
+      "transformContext",
+      expect.anything(),
+    );
+    expect(transformed.length).toBeLessThan(messages.length);
+    expect(transformed[0]).toMatchObject({ role: "user" });
+    expect(onContextCompaction).toHaveBeenCalledWith(expect.objectContaining({
+      runId: "8b3f07b2-841a-4e16-9d1c-9d2a27c3c2ad",
+      originalMessageCount: messages.length,
+      compactedMessageCount: transformed.length,
+    }));
+  });
+
+  it("propagates compaction failures instead of returning the original transcript", async () => {
+    const rpc = createRpc();
+    const hooks = buildAgentHooks({
+      runId: "b9f6aa93-0db7-4f39-8f28-2d87742ef414",
+      rpc,
+    });
+
+    await expect(hooks.transformContext(null as unknown as AgentMessage[])).rejects.toThrow(
+      "transformContext compaction failed",
+    );
+  });
+});