It acts as the right person, with their own secrets.

import { createHmac } from "crypto";

// Canonical JSON, byte-for-byte what Agentifys verifies against:
//   json.dumps(ctx, sort_keys=True, separators=(",", ":"))   # ensure_ascii=True by default
// Three things diverge if you hand-roll this with JSON.stringify:
//   1. every non-ASCII char must become \uXXXX (an Arabic name signs wrong otherwise),
//   2. keys sort by Unicode CODE POINT, not UTF-16 code unit (differs above the BMP),
//   3. only integers are safe (Python renders 1e-7 as 1e-07).
function enc(v) {
  return JSON.stringify(v).replace(/[^ -~]/g,
    c => "\\u" + c.charCodeAt(0).toString(16).padStart(4, "0"));
}
const codePoints = (s) => Array.from(s, (c) => c.codePointAt(0));
function byCodePoint(a, b) {
  const A = codePoints(a), B = codePoints(b);
  for (let i = 0; i < Math.min(A.length, B.length); i++) if (A[i] !== B[i]) return A[i] - B[i];
  return A.length - B.length;
}
function canonicalJson(v) {
  if (Array.isArray(v)) return "[" + v.map(canonicalJson).join(",") + "]";
  if (v && typeof v === "object") {
    return "{" + Object.keys(v).sort(byCodePoint)
      .map((k) => enc(k) + ":" + canonicalJson(v[k])).join(",") + "}";
  }
  if (typeof v === "number" && !Number.isInteger(v)) {
    throw new Error("Sign integers only: " + v + " formats differently in Python. Send it as a string.");
  }
  return enc(v);
}

// Add _ts (unix seconds), sign the context WITHOUT _sig, then send { ...identity, _ts, _sig }.
// Valid for 5 minutes, and re-checked on every /v1/chat call.
function signUserContext(identity, secret) {
  const ctx = { ...identity, _ts: Math.floor(Date.now() / 1000) };
  ctx._sig = createHmac("sha256", secret).update(canonicalJson(ctx)).digest("hex");
  return ctx;
}