# Machine10 Origin fallback contract v1

Contract: public v1.

## Configure

The app must already have an installed Main Machine. An owner or delegated app
manager can enable or remove the global mapping with either equivalent route:

```text
PUT|DELETE https://jmpkit.com/api/apps/<appId>/origin10/fallback
PUT|DELETE https://<appHost>/api/origin10/fallback
```

The initial mapping is fixed:

```json
{"enabled":true,"match":"/**","on":"ziphost-miss","target":"machine-main"}
```

Reserved JMPKit paths stay Gateway-owned. `GET` and `HEAD` try Ziphost first;
only a static `404` wakes Machine. Other supported application methods go
directly to the mapped Machine.

## Request occurrence

Gateway creates an `origin.request` occurrence whose payload is:

```json
{
  "version": "origin10.request.v1",
  "requestId": "occ_...",
  "method": "GET",
  "url": "/path?mode=test",
  "headers": [["accept", "text/html"]],
  "bodyBase64": "",
  "client": {"ip": "...", "protocol": "https"}
}
```

The complete JSON payload, including base64 body and selected headers, must
fit the Main Machine's 32 KiB event limit. Treat all request content and client
metadata as untrusted.

## Response

Return this JSON envelope as the guest's response bytes:

```json
{
  "version": "origin10.response.v1",
  "status": 200,
  "headers": [["content-type", "text/plain; charset=utf-8"]],
  "bodyBase64": "aGVsbG8="
}
```

Gateway validates the exact occurrence, status, headers, canonical base64,
and bounds. It removes hop-by-hop and `x-jmpkit-*` response headers, makes
cookies host-only, and suppresses bodies for `HEAD`, `204`, and `304`.

A disconnected caller stops only the HTTP wait; an admitted durable turn may
still commit. Expect `413` for oversized request envelopes, `503` when Machine
cannot run, `504` at the response deadline, and `502` for failed turns or
malformed response envelopes.

Connected Origin may remain configured. The explicit Machine mapping wins
while enabled. Removing it restores connected Origin or ordinary Ziphost/404
behavior. Confirmed Main Machine deletion removes the mapping automatically.