Lexicons #

SCN Chat's record types use the network.sharedcomputer.chat domain. Each conversation is stored in its own atproto space, written in the conversation owner's repo.

Spaces #

Space type	Key	Holds
`conversation`	TID	`info`, `message`
`settings`	`self`	`preferences`, `conversationRef`

Each conversation's URI is at://{ownerDid}/space/network.sharedcomputer.chat.conversation/{tid}. Sharing is done via the space's read policy.

Each conversation has a conversationRef in the settings space. This is the user's chat index. The title in the conversation's info record is authoritative, and the entry contains a copy for the listing.

The system prompt for a conversation is built from the user's custom instructions followed by the conversation system prompt.

Writing a conversation by hand #

A conversation can be held by writing records directly to the PDS without interacting with an appview.

Write a message with role: "user", a TID key, and a generation object to ask for a reply. Messages without generation won't trigger a reply.
After changing a conversation, put its conversationRef with a new updatedAt. Its record key is the conversation's space key. The app watches the chat index, so this is how it notices the change.
A client can call network.sharedcomputer.chat.requestSync on the app with service auth from its PDS, to have the app sync immediately. Minting that token needs an rpc:network.sharedcomputer.chat.requestSync permission for the app's DID in the client's own OAuth scope.
The reply is written with the key {userMessageKey}.r{attempt}, where attempt comes from the generation object and defaults to 0.
To regenerate, update the user message with attempt raised by one. Earlier replies stay as siblings. Order them by attempt number, since .r10 sorts before .r2.
When the app picks up a turn, it first writes the reply with status: "pending" and empty content, then updates it when generation ends. The write fails if the key already exists, so only one generation runs per attempt.
Only messages authored by the space owner trigger replies.
The default model is the model last used in the chat, or the user's default if this is the first message.
generation.tools lists the tools the model may use for this turn. Defaults to the tools the user has switched on.
parent holds the key of the previous message. Two messages with the same parent are an edit or a regeneration.

Example #

A user message asking for a reply, written with the key 3lzmxqvzwnk2a:

{
  "$type": "network.sharedcomputer.chat.message",
  "role": "user",
  "content": {
    "$type": "network.sharedcomputer.chat.defs#plainContent",
    "parts": [
      { "$type": "network.sharedcomputer.chat.defs#textPart", "text": "What's the weather in Vancouver?" }
    ]
  },
  "generation": {
    "model": { "provider": "anthropic", "id": "claude-opus-5-5" },
    "effort": "high",
    "tools": ["web_search"]
  },
  "createdAt": "2026-09-26T17:00:00.000Z"
}

The finished reply, at the key 3lzmxqvzwnk2a.r0:

{
  "$type": "network.sharedcomputer.chat.message",
  "role": "assistant",
  "parent": "3lzmxqvzwnk2a",
  "content": {
    "$type": "network.sharedcomputer.chat.defs#plainContent",
    "parts": [
      { "$type": "network.sharedcomputer.chat.defs#toolCallPart", "callId": "c1", "tool": "web_search", "input": "{\"query\":\"vancouver weather\"}" },
      { "$type": "network.sharedcomputer.chat.defs#toolResultPart", "callId": "c1", "output": "Rain, 12C" },
      { "$type": "network.sharedcomputer.chat.defs#textPart", "text": "Rainy, around 12C." }
    ]
  },
  "model": { "provider": "anthropic", "id": "claude-opus-5-5" },
  "effort": "high",
  "status": "complete",
  "usage": { "inputTokens": 412, "outputTokens": 38 },
  "createdAt": "2026-09-26T17:00:04.000Z"
}

Publishing #

These lexicons must be resolvable by the PDS to grant their permissions, no one will be able to sign in if they're not published.

pnpm publish-lexicons <handle> writes all lexicons to the sharedcomputer.network PDS. It signs in with an app password from LEXICON_APP_PASSWORD or a prompt.