Shield Wrappers

Reference for TypeScript Shield wrappers, including prompt, tool, tool response, model response, and generic wrap patterns.

Use Shield wrappers when you want guardrails to run automatically around your functions.

import { Highflame, Shield } from "@highflame/sdk";

const client = new Highflame({ apiKey: "hf_sk_..." });
const shield = new Shield(client);

shield.prompt(fn, options?)

Guards a prompt input before the function runs. If denied, fn is never called.

const chat = shield.prompt(async (message: string) => llm.complete(message));

const guardedChat = shield.prompt(
  async (context: string, userMessage: string) => llm.complete(context, userMessage),
  { contentArg: 1 },
);

const monitoredChat = shield.prompt(async (msg: string) => llm.complete(msg), {
  mode: "monitor",
  sessionId: "sess_user_abc",
});

Option	Type	Default	Description
mode	"enforce" | "monitor" | "alert"	"enforce"	Enforcement mode
contentArg	number	0	Zero-based index of the argument to guard
sessionId	string	—	Session ID for cross-turn tracking

shield.tool(fn, options?)

Guards a tool call before the function runs. If denied, fn is never called. All function arguments are forwarded as tool-call context.

const shell = shield.tool(async function shell(cmd: string) {
  return exec(cmd);
});

const runQuery = shield.tool(async function runSql(query: string, db: string) {
  return database.query(query, db);
});

const deleteFile = shield.tool(async (path: string) => fs.unlink(path), {
  toolName: "delete_file",
});

Option	Type	Default	Description
mode	"enforce" | "monitor" | "alert"	"enforce"	Enforcement mode
toolName	string	fn.name	Override the tool name
sessionId	string	—	Session ID

shield.toolResponse(fn, options?)

Guards a tool's return value after the function runs. The function always executes first; the return value is blocked if denied.

const fetchPage = shield.toolResponse(async function fetchPage(url: string) {
  return http.get(url);
});

const readRecord = shield.toolResponse(
  async function readRecord(id: string) {
    return db.find(id);
  },
  { mode: "alert", sessionId: "sess_abc" },
);

Option	Type	Default	Description
mode	"enforce" | "monitor" | "alert"	"enforce"	Enforcement mode
toolName	string	fn.name	Tool name included in the request
sessionId	string	—	Session ID

shield.modelResponse(fn, options?)

Guards a model's output before returning it to the caller. The function always executes first; its return value is blocked if denied.

const generate = shield.modelResponse(async (prompt: string) => {
  return openai.chat.completions.create({ ... });
});

const trackedGenerate = shield.modelResponse(
  async (prompt: string) => llm.complete(prompt),
  { sessionId: "sess_user_xyz" },
);

Option	Type	Default	Description
mode	"enforce" | "monitor" | "alert"	"enforce"	Enforcement mode
sessionId	string	—	Session ID

shield.wrap(options)

Generic wrapper for content types and actions not covered by the named shorthands.

const writeConfig = shield.wrap({
  contentType: "file",
  action: "write_file",
  contentArg: 1,
})(async (path: string, content: string) => fs.writeFile(path, content));

const fileGuard = shield.wrap({ contentType: "file", action: "read_file" });
const readKey = fileGuard(async (path: string) => fs.readFile(path, "utf8"));
const readCert = fileGuard(async (path: string) => fs.readFile(path, "utf8"));

Option	Type	Default	Description
contentType	"prompt" | "response" | "tool_call" | "file"	required	Content type
action	"process_prompt" | "call_tool" | "read_file" | "write_file" | "connect_server"	required	Cedar action
contentArg	number	0	Zero-based argument index to use as content
mode	"enforce" | "monitor" | "alert"	"enforce"	Enforcement mode
sessionId	string	—	Session ID

Related Topics

• Low-Level Client for direct request and response control

• Advanced Topics for streaming, sessions, logging, and advanced request options