test: retain real OMP ACP provider ID collision reproduction

Reproduce #3178 through configuration parsing, provider registry resolution, and real session creation. The unique omp-acp ID succeeds, while omp keeps the built-in RPC runtime despite extends: acp and times out. This is an opt-in diagnosis test, with no production behavior changes.

Co-authored-by: Lorenzo Fiore <fiorelorenzo.fl@gmail.com>

packages/server/src/server/agent/provider-id-collision.local.e2e.test.ts

@@ -0,0 +1,52 @@
+import { mkdtemp, mkdir, rm } from "node:fs/promises";
+import path from "node:path";
+import { expect, test } from "vitest";
+import { ProviderOverridesSchema } from "@getpaseo/protocol/provider-config";
+import { createTestLogger } from "../../test-utils/test-logger.js";
+import { buildProviderRegistry } from "./provider-registry.js";
+import type { AgentSession } from "./agent-sdk-types.js";
+
+// Retained reproduction for #3178, awaiting the built-in ID configuration decision.
+// Requires OMP on PATH (or OMP_COMMAND). Uses no model calls or existing provider state.
+const runReproduction = process.env.OMP_PROVIDER_COLLISION_REPRO === "1";
+
+for (const providerId of ["omp-acp", "omp"]) {
+  test.skipIf(!runReproduction)(
+    `explicit ACP configuration creates an ACP session under '${providerId}'`,
+    async () => {
+      const cwd = await mkdtemp(path.join(process.cwd(), ".provider-collision-"));
+      const agentDir = path.join(cwd, "agent");
+      await mkdir(agentDir);
+      const providerOverrides = ProviderOverridesSchema.parse({
+        [providerId]: {
+          extends: "acp",
+          label: "Oh My Pi ACP",
+          command: [process.env.OMP_COMMAND ?? "omp", "acp"],
+          enabled: true,
+          env: {
+            PI_CODING_AGENT_DIR: agentDir,
+            OMP_PROFILE: "default",
+            PI_PROFILE: "default",
+            XDG_CONFIG_HOME: path.join(cwd, "config"),
+            XDG_DATA_HOME: path.join(cwd, "data"),
+            XDG_CACHE_HOME: path.join(cwd, "cache"),
+            XDG_STATE_HOME: path.join(cwd, "state"),
+          },
+        },
+      });
+      const logger = createTestLogger();
+      const registry = buildProviderRegistry(logger, { providerOverrides });
+      const client = registry[providerId]!.createClient(logger);
+      let session: AgentSession | undefined;
+      try {
+        session = await client.createSession({ provider: providerId, cwd });
+        expect(session.provider).toBe(providerId);
+      } finally {
+        await session?.close();
+        await client.shutdown?.();
+        await rm(cwd, { recursive: true, force: true });
+      }
+    },
+    30_000,
+  );
+}