agents >=0.25.0 changed what `loadCdpSpec` does. loadCdpSpec now includes command parameters and return types, so a model can see how to call a CDP method. Silent: code written for older versions still runs, without an error.

const fs = require("fs");
const path = require("path");
const W = "/w";
const nm = path.join(W, "node_modules");
// @cloudflare/codemode is an optional peer that loadCdpSpec does not use; stub it only if absent.
const cm = path.join(nm, "@cloudflare", "codemode");
if (!fs.existsSync(path.join(cm, "package.json"))) {
  fs.mkdirSync(cm, { recursive: true });
  fs.writeFileSync(path.join(cm, "package.json"), JSON.stringify({ name: "@cloudflare/codemode", type: "module", main: "index.js" }));
  fs.writeFileSync(path.join(cm, "index.js"), "export class CodemodeConnector {}\nexport class CodemodeRuntime {}\n");
}
const protocol = {
  domains: [{
    domain: "Page",
    description: "Page domain",
    types: [{ id: "FrameId", type: "string", description: "Frame id" }],
    commands: [{
      name: "navigate",
      description: "Navigates current page to the given URL.",
      parameters: [
        { name: "url", type: "string", description: "URL to navigate the page to." },
        { name: "frameId", $ref: "FrameId", optional: true }
      ],
      returns: [{ name: "frameId", $ref: "FrameId" }]
    }],
    events: []
  }]
};
const json = (body) => new Response(JSON.stringify(body), { status: 200, headers: { "content-type": "application/json" } });
const browser = {
  async fetch(url, init) {
    const u = String(url);
    if (init && init.method === "POST") return json({ sessionId: "s1" });
    if (init && init.method === "DELETE") return new Response("", { status: 200 });
    if (u.endsWith("/json/protocol")) return json(protocol);
    return new Response("not found", { status: 404 });
  }
};
const entry = path.join(W, "loadspec.mjs");
fs.writeFileSync(entry, "export * from 'agents/browser';\n");
const ver = JSON.parse(fs.readFileSync(path.join(nm, "agents", "package.json"), "utf8")).version;
(async () => {
  let mod;
  try {
    mod = await import(require("url").pathToFileURL(entry).href);
  } catch (e) {
    console.error("ERROR: cannot import agents/browser: " + e.message);
    process.exit(2);
  }
  if (typeof mod.loadCdpSpec !== "function") {
    console.error("ERROR: loadCdpSpec is not exported");
    process.exit(2);
  }
  let spec;
  try {
    spec = await mod.loadCdpSpec({ browser });
  } catch (e) {
    console.error("ERROR: loadCdpSpec threw: " + e.message);
    process.exit(2);
  }
  const page = spec && spec.domains && spec.domains.find((d) => d.name === "Page");
  const cmd = page && page.commands.find((c) => c.method === "Page.navigate");
  if (!cmd) {
    console.error("ERROR: Page.navigate missing from spec " + JSON.stringify(spec));
    process.exit(2);
  }
  const params = cmd.parameters;
  const returns = cmd.returns;
  if (params === undefined && returns === undefined) {
    console.error("FAIL: loadCdpSpec drops command parameters and returns (agents " + ver + ")");
    process.exit(1);
  }
  const url = Array.isArray(params) && params.find((p) => p.name === "url");
  const ret = Array.isArray(returns) && returns.find((r) => r.name === "frameId");
  if (url && url.type === "string" && ret && ret.$ref === "Page.FrameId") {
    console.log("OK: agents " + ver + " loadCdpSpec keeps Page.navigate parameters and returns: " + JSON.stringify({ parameters: params.map((p) => p.name), returns: returns.map((r) => r.$ref) }));
    process.exit(0);
  }
  console.error("ERROR: unexpected command shape " + JSON.stringify(cmd));
  process.exit(2);
})();

const fs = require("fs");
const path = require("path");
const W = "/w";
const nm = path.join(W, "node_modules");
// @cloudflare/codemode is an optional peer that loadCdpSpec does not use; stub it only if absent.
const cm = path.join(nm, "@cloudflare", "codemode");
if (!fs.existsSync(path.join(cm, "package.json"))) {
  fs.mkdirSync(cm, { recursive: true });
  fs.writeFileSync(path.join(cm, "package.json"), JSON.stringify({ name: "@cloudflare/codemode", type: "module", main: "index.js" }));
  fs.writeFileSync(path.join(cm, "index.js"), "export class CodemodeConnector {}\nexport class CodemodeRuntime {}\n");
}
const protocol = {
  domains: [{
    domain: "Page",
    description: "Page domain",
    types: [{ id: "FrameId", type: "string", description: "Frame id" }],
    commands: [{
      name: "navigate",
      description: "Navigates current page to the given URL.",
      parameters: [
        { name: "url", type: "string", description: "URL to navigate the page to." },
        { name: "frameId", $ref: "FrameId", optional: true }
      ],
      returns: [{ name: "frameId", $ref: "FrameId" }]
    }],
    events: []
  }]
};
const json = (body) => new Response(JSON.stringify(body), { status: 200, headers: { "content-type": "application/json" } });
const browser = {
  async fetch(url, init) {
    const u = String(url);
    if (init && init.method === "POST") return json({ sessionId: "s1" });
    if (init && init.method === "DELETE") return new Response("", { status: 200 });
    if (u.endsWith("/json/protocol")) return json(protocol);
    return new Response("not found", { status: 404 });
  }
};
const entry = path.join(W, "loadspec.mjs");
fs.writeFileSync(entry, "export * from 'agents/browser';\n");
const ver = JSON.parse(fs.readFileSync(path.join(nm, "agents", "package.json"), "utf8")).version;
(async () => {
  let mod;
  try {
    mod = await import(require("url").pathToFileURL(entry).href);
  } catch (e) {
    console.error("ERROR: cannot import agents/browser: " + e.message);
    process.exit(2);
  }
  if (typeof mod.loadCdpSpec !== "function") {
    console.error("ERROR: loadCdpSpec is not exported");
    process.exit(2);
  }
  let spec;
  try {
    spec = await mod.loadCdpSpec({ browser });
  } catch (e) {
    console.error("ERROR: loadCdpSpec threw: " + e.message);
    process.exit(2);
  }
  const page = spec && spec.domains && spec.domains.find((d) => d.name === "Page");
  const cmd = page && page.commands.find((c) => c.method === "Page.navigate");
  if (!cmd) {
    console.error("ERROR: Page.navigate missing from spec " + JSON.stringify(spec));
    process.exit(2);
  }
  const params = cmd.parameters;
  const returns = cmd.returns;
  if (params === undefined && returns === undefined) {
    console.error("FAIL: loadCdpSpec drops command parameters and returns (agents " + ver + ")");
    process.exit(1);
  }
  const url = Array.isArray(params) && params.find((p) => p.name === "url");
  const ret = Array.isArray(returns) && returns.find((r) => r.name === "frameId");
  if (url && url.type === "string" && ret && ret.$ref === "Page.FrameId") {
    console.log("OK: agents " + ver + " loadCdpSpec keeps Page.navigate parameters and returns: " + JSON.stringify({ parameters: params.map((p) => p.name), returns: returns.map((r) => r.$ref) }));
    process.exit(0);
  }
  console.error("ERROR: unexpected command shape " + JSON.stringify(cmd));
  process.exit(2);
})();