Raise Anthropic default max tokens

server/tests/chat-tools-streaming.test.ts

@@ -140,6 +140,94 @@ test("plain Chat Completions stream does not send Sybil-managed tools", async ()
   assert.equal(events.at(-1)?.type === "done" ? events.at(-1)?.result.text : null, "Hi");
 });
 
+test("Messages API defaults max_tokens to the Anthropic model maximum", async () => {
+  let requestBody: any = null;
+  let retrievedModel: string | null = null;
+  const client = {
+    models: {
+      retrieve: async (model: string) => {
+        retrievedModel = model;
+        return { id: model, max_tokens: 128000 };
+      },
+    },
+    messages: {
+      create: async (body: any) => {
+        requestBody = body;
+        return {
+          content: [{ type: "text", text: "Done" }],
+          usage: { input_tokens: 1, output_tokens: 1 },
+        };
+      },
+    },
+  };
+
+  const result = await completeWithMessagesApi({
+    client: client as any,
+    model: "claude-max-default-test",
+    messages: [{ role: "user", content: "Say done" }],
+  });
+
+  assert.equal(retrievedModel, "claude-max-default-test");
+  assert.equal(requestBody?.max_tokens, 128000);
+  assert.equal(result.text, "Done");
+});
+
+test("Messages API preserves explicit maxTokens", async () => {
+  let requestBody: any = null;
+  let didRetrieveModel = false;
+  const client = {
+    models: {
+      retrieve: async () => {
+        didRetrieveModel = true;
+        return { max_tokens: 128000 };
+      },
+    },
+    messages: {
+      create: async (body: any) => {
+        requestBody = body;
+        return streamFrom([
+          {
+            type: "message_start",
+            message: {
+              usage: { input_tokens: 1, output_tokens: 0 },
+            },
+          },
+          {
+            type: "content_block_start",
+            index: 0,
+            content_block: { type: "text", text: "" },
+          },
+          {
+            type: "content_block_delta",
+            index: 0,
+            delta: { type: "text_delta", text: "Done" },
+          },
+          { type: "content_block_stop", index: 0 },
+          {
+            type: "message_delta",
+            delta: { stop_reason: "end_turn", stop_sequence: null },
+            usage: { output_tokens: 1 },
+          },
+          { type: "message_stop" },
+        ]);
+      },
+    },
+  };
+
+  const events = await collectEvents(
+    streamWithMessagesApi({
+      client: client as any,
+      model: "claude-explicit-max-test",
+      messages: [{ role: "user", content: "Say done" }],
+      maxTokens: 4096,
+    })
+  );
+
+  assert.equal(didRetrieveModel, false);
+  assert.equal(requestBody?.max_tokens, 4096);
+  assert.equal(events.at(-1)?.type === "done" ? events.at(-1)?.result.text : null, "Done");
+});
+
 test("fetch_url sends browser-like navigation headers", async () => {
   const originalFetch = globalThis.fetch;
   const fetchCalls: Array<{ input: RequestInfo | URL; init?: RequestInit }> = [];