diff --git a/src/agents/model-forward-compat.test.ts b/src/agents/model-forward-compat.test.ts
new file mode 100644
index 0000000000..b2017213e0
--- /dev/null
+++ b/src/agents/model-forward-compat.test.ts
@@ -0,0 +1,59 @@
+import type { Api, Model } from "@mariozechner/pi-ai";
+import { describe, expect, it } from "vitest";
+import { resolveForwardCompatModel } from "./model-forward-compat.js";
+import type { ModelRegistry } from "./pi-model-discovery.js";
+
+function createTemplateModel(provider: string, id: string): Model<Api> {
+  return {
+    id,
+    name: id,
+    provider,
+    api: "anthropic-messages",
+    input: ["text"],
+    reasoning: true,
+    cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+    contextWindow: 200_000,
+    maxTokens: 8_192,
+  } as Model<Api>;
+}
+
+function createRegistry(models: Record<string, Model<Api>>): ModelRegistry {
+  return {
+    find(provider: string, modelId: string) {
+      return models[`${provider}/${modelId}`] ?? null;
+    },
+  } as ModelRegistry;
+}
+
+describe("agents/model-forward-compat", () => {
+  it("resolves anthropic opus 4.6 via 4.5 template", () => {
+    const registry = createRegistry({
+      "anthropic/claude-opus-4-5": createTemplateModel("anthropic", "claude-opus-4-5"),
+    });
+    const model = resolveForwardCompatModel("anthropic", "claude-opus-4-6", registry);
+    expect(model?.id).toBe("claude-opus-4-6");
+    expect(model?.name).toBe("claude-opus-4-6");
+    expect(model?.provider).toBe("anthropic");
+  });
+
+  it("resolves anthropic sonnet 4.6 dot variant with suffix", () => {
+    const registry = createRegistry({
+      "anthropic/claude-sonnet-4.5-20260219": createTemplateModel(
+        "anthropic",
+        "claude-sonnet-4.5-20260219",
+      ),
+    });
+    const model = resolveForwardCompatModel("anthropic", "claude-sonnet-4.6-20260219", registry);
+    expect(model?.id).toBe("claude-sonnet-4.6-20260219");
+    expect(model?.name).toBe("claude-sonnet-4.6-20260219");
+    expect(model?.provider).toBe("anthropic");
+  });
+
+  it("does not resolve anthropic 4.6 fallback for other providers", () => {
+    const registry = createRegistry({
+      "anthropic/claude-opus-4-5": createTemplateModel("anthropic", "claude-opus-4-5"),
+    });
+    const model = resolveForwardCompatModel("openai", "claude-opus-4-6", registry);
+    expect(model).toBeUndefined();
+  });
+});