fix(ai): stop defaulting max token request caps

closes #4675

packages/ai/test/github-copilot-anthropic.test.ts

@@ -87,7 +87,7 @@ describe("Copilot Claude via Anthropic Messages", () => {
 		const params = mockState.createParams!;
 		expect(params.model).toBe("claude-sonnet-4.6");
 		expect(params.stream).toBe(true);
-		expect(params.max_tokens).toBeGreaterThan(0);
+		expect(params.max_tokens).toBe(model.maxTokens);
 		expect(Array.isArray(params.messages)).toBe(true);
 	});
 

packages/ai/test/openai-completions-empty-tools.test.ts

@@ -93,6 +93,40 @@ describe("openai-completions empty tools handling", () => {
 		expect("tools" in (params as object)).toBe(false);
 	});
 
+	it("does not send default max token fields", async () => {
+		const { compat: _compat, ...baseModel } = getModel("openai", "gpt-4o-mini")!;
+		const model = { ...baseModel, api: "openai-completions" } as const;
+
+		await streamSimple(
+			model,
+			{
+				messages: [{ role: "user", content: "hi", timestamp: Date.now() }],
+			},
+			{ apiKey: "test" },
+		).result();
+
+		const params = mockState.lastParams as { max_tokens?: number; max_completion_tokens?: number };
+		expect(params.max_tokens).toBeUndefined();
+		expect(params.max_completion_tokens).toBeUndefined();
+	});
+
+	it("sends explicit maxTokens", async () => {
+		const { compat: _compat, ...baseModel } = getModel("openai", "gpt-4o-mini")!;
+		const model = { ...baseModel, api: "openai-completions" } as const;
+
+		await streamSimple(
+			model,
+			{
+				messages: [{ role: "user", content: "hi", timestamp: Date.now() }],
+			},
+			{ apiKey: "test", maxTokens: 1234 },
+		).result();
+
+		const params = mockState.lastParams as { max_tokens?: number; max_completion_tokens?: number };
+		expect(params.max_tokens).toBeUndefined();
+		expect(params.max_completion_tokens).toBe(1234);
+	});
+
 	it("uses conservative OpenAI-compatible fields for Cloudflare AI Gateway /compat models", async () => {
 		process.env.CLOUDFLARE_ACCOUNT_ID = "account-id";
 		process.env.CLOUDFLARE_GATEWAY_ID = "gateway-id";
@@ -104,7 +138,7 @@ describe("openai-completions empty tools handling", () => {
 				systemPrompt: "You are helpful.",
 				messages: [{ role: "user", content: "hi", timestamp: Date.now() }],
 			},
-			{ apiKey: "test", reasoning: "high" },
+			{ apiKey: "test", maxTokens: 1234, reasoning: "high" },
 		).result();
 
 		const params = mockState.lastParams as {
@@ -115,7 +149,7 @@ describe("openai-completions empty tools handling", () => {
 			store?: boolean;
 		};
 		expect(params.messages[0].role).toBe("system");
-		expect(params.max_tokens).toBeDefined();
+		expect(params.max_tokens).toBe(1234);
 		expect(params.max_completion_tokens).toBeUndefined();
 		expect(params.reasoning_effort).toBeUndefined();
 		expect(params.store).toBeUndefined();