Harbingerx403-HARBINGER/1.0
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Last print is freeThe join is still 403Come back — the tape does not sleepLast print is freeThe join is still 403Come back — the tape does not sleepLast print is freeThe join is still 403Come back — the tape does not sleepLast print is freeThe join is still 403Come back — the tape does not sleepLast print is freeThe join is still 403Come back — the tape does not sleepLast print is freeThe join is still 403Come back — the tape does not sleepLast print is freeThe join is still 403Come back — the tape does not sleepLast print is freeThe join is still 403Come back — the tape does not sleep

X403-HP-1 · urn:x403:harbinger:1.0

Harbinger: Agent Grant and Notification Protocol

HTTP-native. One agent charges another for a ping the instant named prints line up. Unpaid callers receive 403. This is not pay-for-a-resource.

Designation

x403-HARBINGER/1.0

Status

403 Forbidden until grant

Media

application/vnd.x403.harbinger+json

3. Status-code binding

Harbinger binds to HTTP 403. 401 is authentication. 402 is payment-for-a-resource. Implementations MUST NOT speak HTTP 402 on Harbinger endpoints.

Status: real-move ping

The stream and hooks wait for a post-start threshold move on the watch's legs. firedAt is the quote time. One-leg correlation is null. If the window ends with no move, the result is no-move and the grant is not consumed (Nic, 10 Oct 2026). AgentMail send stays paused. Do not pay for that rail.

4–5. Grants and handshake

A grant is a bearer token of the form hp1.<payload>. Demo grant hp1.demo.

  1. GET /v1/stream with X-Harbinger-Watch.
  2. Edge answers 403 with grant-required, price, event, advantage window.
  3. Retry with X-Harbinger-Grant.
  4. 202 pending. Poll until one ping, or no-move with the grant unspent.

14. AgentMail rail

AgentMail is an optional delivery adapter. It is not the protocol. A mailbox API key is not a grant. SSE remains the hot path.