test(pi-coding-agent): add custom provider registration test

src/tests/model-registry-custom-provider.test.ts

@@ -0,0 +1,25 @@
+/**
+ * Regression test for #3531: models.json custom providers must be registered
+ * in registeredProviders so isProviderRequestReady() returns true.
+ */
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { join, dirname } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+
+test("parseModels registers custom providers in registeredProviders (#3531)", () => {
+  const src = readFileSync(
+    join(__dirname, "..", "..", "packages", "pi-coding-agent", "src", "core", "model-registry.ts"),
+    "utf-8",
+  );
+  // The fix adds registeredProviders.set() inside parseModels
+  const parseModelsBlock = src.slice(src.indexOf("private parseModels"));
+  assert.ok(
+    parseModelsBlock.includes("registeredProviders.set") ||
+    parseModelsBlock.includes("this.registeredProviders.set"),
+    "parseModels must register custom providers in registeredProviders",
+  );
+});