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Versioning & Migration

Sequences are versioned. Running instances are bound to the version that was active when they were created. New versions deploy without touching in-flight instances — they keep running on their original definition.

Version lifecycle

  • ✓Each sequence has a version field and a unique index on (tenant_id, name, version)
  • ✓New instances bind to the latest non-deprecated version at creation time
  • ✓Running instances complete on their original version — immutable binding
  • ✓Deprecate a version: POST /sequences/{id}/deprecate — blocks new instances on that version
  • ✓List all versions: GET /sequences/versions

Hot migration

Rebind a running instance to a new sequence version without stopping it. The new definition applies at the next step boundary.

POST /sequences/migrate-instance
{
  "instance_id": "<uuid>",
  "target_sequence_id": "<new-version-uuid>"
}

// Response
{
  "migrated": true,
  "instance_id": "<uuid>",
  "from_sequence_id": "<old-uuid>",
  "to_sequence_id": "<new-uuid>"
}

Only non-terminal instances (not Completed, Failed, or Cancelled) can be migrated. Terminal instances return a 422 error.

Dynamic step injection

Add blocks to a running instance at runtime. Injected blocks are stored in metadata._injected_blocks and executed after the current position in the sequence. Designed for AI agent workflows where the next step is determined dynamically.

POST /instances/{id}/inject-blocks
{
  "blocks": [
    {
      "type": "step",
      "id": "dynamic_followup",
      "handler": "send_email",
      "params": { "template": "agent-suggested-followup" }
    }
  ],
  "inject_after": "current"
}