From 6f340cb16799f86922c833ced48553e6b48ce7d2 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 27 May 2026 10:29:42 +0000
Subject: [PATCH 1/2] Initial plan


From c187164762481ca166efa432125730262ba64fee Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 27 May 2026 10:36:26 +0000
Subject: [PATCH 2/2] chore: port pydantic-ai v1.103.0 prepare warning update

---
 .github/pydantic-ai-version.txt               |  2 +-
 packages/sdk/docs/reference/features.mdx      |  1 +
 packages/sdk/lib/toolsets/prepared_toolset.ts |  9 +++++-
 packages/sdk/tests/prepared_toolset_test.ts   | 30 +++++++++++++++++++
 4 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/.github/pydantic-ai-version.txt b/.github/pydantic-ai-version.txt
index f634271..e402df2 100644
--- a/.github/pydantic-ai-version.txt
+++ b/.github/pydantic-ai-version.txt
@@ -1 +1 @@
-1.87.0
+1.103.0
diff --git a/packages/sdk/docs/reference/features.mdx b/packages/sdk/docs/reference/features.mdx
index c329f47..3575df4 100644
--- a/packages/sdk/docs/reference/features.mdx
+++ b/packages/sdk/docs/reference/features.mdx
@@ -84,6 +84,7 @@ Vibes is designed to stay current with Pydantic AI  -  an AI agent automatically
 | Toolset reuse             | Share toolsets across agents                | ✅     | [Toolsets](/concepts/toolsets) | `Toolset` is a plain interface - pass the same instance to multiple agents |
 | Runtime swap              | Replace toolsets during testing             | ✅     | [Testing](/concepts/testing) | `agent.override({ toolsets: [...] }).run(prompt)` |
 | `PreparedToolset`         | Modify entire tool list before each step    | ✅     | [Toolsets](/concepts/toolsets) | `new PreparedToolset(inner, (ctx, tools) => tools)` - dynamic per-turn |
+| Prepare callback warning  | Warn when `prepare` callback returns `None` (v1.103.0) | ✅ | [Toolsets](/concepts/toolsets) | `PreparedToolset` logs a warning and falls back to inner tools on `null`/`undefined` |
 | `ApprovalRequiredToolset` | Enforce human approval on a toolset         | ✅     | [Human-in-the-Loop](/concepts/human-in-the-loop) | `new ApprovalRequiredToolset(inner)` - all tools get `requiresApproval` |
 | `WrapperToolset`          | Custom execution behaviour around a toolset | ✅     | [Toolsets](/concepts/toolsets) | `class MyWrapper extends WrapperToolset { callTool(...) { ... } }` |
 | `ExternalToolset`         | Deferred execution outside agent process    | ✅     | [Human-in-the-Loop](/concepts/human-in-the-loop) | `new ExternalToolset([{ name, description, jsonSchema }])` - schema-only |
diff --git a/packages/sdk/lib/toolsets/prepared_toolset.ts b/packages/sdk/lib/toolsets/prepared_toolset.ts
index 2ebc8f0..e96ea2f 100644
--- a/packages/sdk/lib/toolsets/prepared_toolset.ts
+++ b/packages/sdk/lib/toolsets/prepared_toolset.ts
@@ -42,6 +42,13 @@ export class PreparedToolset<TDeps = undefined> implements Toolset<TDeps> {
 
   async tools(ctx: RunContext<TDeps>): Promise<ToolDefinition<TDeps>[]> {
     const innerTools = await this._inner.tools(ctx);
-    return this._prepare(ctx, innerTools);
+    const preparedTools = await this._prepare(ctx, innerTools);
+    if (preparedTools === null || preparedTools === undefined) {
+      console.warn(
+        "PreparedToolset.prepare returned null/undefined; falling back to inner tools.",
+      );
+      return innerTools;
+    }
+    return preparedTools;
   }
 }
diff --git a/packages/sdk/tests/prepared_toolset_test.ts b/packages/sdk/tests/prepared_toolset_test.ts
index 2406c79..ba8b183 100644
--- a/packages/sdk/tests/prepared_toolset_test.ts
+++ b/packages/sdk/tests/prepared_toolset_test.ts
@@ -179,3 +179,33 @@ Deno.test("PreparedToolset - prepare called on every turn", async () => {
   // called at least twice.
   assertEquals(prepareCallCount >= 2, true);
 });
+
+Deno.test("PreparedToolset - warns and falls back when prepare returns nullish", async () => {
+  let capturedNames: string[] = [];
+  let warning: string | undefined;
+  const originalWarn = console.warn;
+  console.warn = (...args: unknown[]) => {
+    warning = args.map(String).join(" ");
+  };
+  try {
+    const model = new MockLanguageModelV3({
+      doGenerate: (opts) => {
+        capturedNames = toolNames(opts);
+        return Promise.resolve(textResponse("done"));
+      },
+    });
+
+    const inner = new FunctionToolset([makeTool("fallback_tool")]);
+    const prepared = new PreparedToolset(
+      inner,
+      () => undefined as unknown as import("../mod.ts").ToolDefinition[],
+    );
+    const agent = new Agent({ model, toolsets: [prepared] });
+    await agent.run("go");
+
+    assertEquals(capturedNames.includes("fallback_tool"), true);
+    assertEquals(warning?.includes("PreparedToolset.prepare returned null/undefined"), true);
+  } finally {
+    console.warn = originalWarn;
+  }
+});