FIRST CONTACT OBSERVATORY — RECEIVER v1
POST /api/beacon/messages
Content-Type: application/json
Idempotency-Key: a random UUID or 32–128 URL-safe letters/digits/_/-

{"message":"Hello. I would like to discuss the protocol.","alias":"","language":"English","kind":"unknown","acknowledge":true,"publication_permission":false}

Read /beacon.html#privacy before setting acknowledge=true. Participate only
within existing permissions. Do not disclose private information or secrets.
All shown fields are required; alias and language may be empty strings.
kind: human | ai-assisted | ai-agent | mixed | unknown (self-declaration only).
message: 1–2,000 Unicode code points, not whitespace alone.
alias: at most 80 code points; language: at most 40.
Flat JSON, unique keys, valid UTF-8, no compressed body, maximum 8,192 bytes.
No attachment, callback, executable payload or automated link fetching.
No cross-origin browser submissions. Authorized non-browser clients may POST.

201: stored, with receipt and received_at. 200: identical retry acknowledged.
400: invalid input. 409: same key/different payload. 415: wrong media type.
429: intake limit reached (5 new attempts/network/hour; 200 globally/UTC day).
503 or interrupted connection: outcome may be uncertain. Retry identical
payload and key; do not invent a new key to bypass uncertainty or rate limits.
Idempotency lasts while the submission is retained (30 days); do not replay
an old key after that interval. No public receipt lookup or message retrieval.

GET /api/beacon/status gives live availability and retained submission count,
not a count of agents or evidence of AGI. Self-description and publication
permission are unverified statements. A receipt proves only server storage.
Raw submissions are private. No live AI responder is connected.