Chains

A chain runs several stages in order. When one stage stops, the next starts from the last checkpoint the previous stage saved, with a different signal source or domain. This is how a model is taught through a curriculum: for example, corpus first, then self-generation, then preference pairs.

Defining a chain

A chain has a name and at least two stages. Each stage is a full run definition plus the stop reasons that let the chain advance past it:

{
  "name": "notary-curriculum",
  "stages": [
    {
      "definition": { "...": "a run definition with a corpus signal source" },
      "advance_on": ["step_count", "loss_plateau"]
    },
    {
      "definition": { "...": "a run definition with a self-generation signal source" },
      "advance_on": ["test_threshold", "step_count"]
    }
  ]
}

Submit it with POST /api/v1/chains (the forge_create_chain MCP tool). Every stage is validated when the chain is created, so a mistake in stage four is found now, not three hours in. The graphics card is leased for the chain as a whole, and stage 0 starts.

Only stage 0 may use a model source other than loading. Every later stage must declare "mode": "load"; the chain fills in the path with the previous stage's last save, and keeps your stage definition as you wrote it.

When a chain advances, and when it halts

A stage may advance on step_count, test_threshold or loss_plateau. A chain never advances past:

• a retention-floor breach: the next stage would start from the checkpoint whose general ability had just collapsed, and push further in the same direction;
• your own stop: advancing would restart work you had just stopped;
• a failed stage: the next stage would start from a checkpoint nothing verified.

A configuration naming any of those as an advance reason is refused. When a stage ends for a reason that does not advance, the chain halts and records why.

A background sweep checks finished stages every two minutes and starts the next one.

Watching and stopping a chain

Action	Route	MCP tool
List chains	GET /api/v1/chains	forge_list_chains
One chain, with each stage's outcome and advance decision	GET /api/v1/chains/{chain_id}	forge_get_chain
Halt the chain and stop its running stage	POST /api/v1/chains/{chain_id}/stop	forge_stop_chain

Each stage is an ordinary run, so its run view, scores and checkpoints are where they always are.