Example 23: Checkpoint Store

What It Is

Checkpoint Store is the persistence boundary for resumable DAGs. The Archivist captures a parked run, writes the checkpoint outside process memory, recalls it later, restores state and stores, and resumes from the recorded cursor.

The demo uses browser and memory-backed stores, but the contract is the same for Postgres, Redis, S3, IndexedDB, or any application store that implements CheckpointStore.

How It Works

Checkpoint.capture creates a JSON-serializable checkpoint from an interrupted result. ckpt.persist(store, key) writes it through the CheckpointStore interface. Checkpoint.recall(store, key) loads and validates it. The caller restores state and stores, then resumes the same DAG from the captured cursor.

The checkpoint store does not execute the DAG and does not know application state classes. It persists the checkpoint payload; the dispatcher registry and restore adapter reconstruct executable state when the application resumes.

Diagrams, Examples, and Outputs

DAG registration and diagram

The graph is the live Archivist DAG; persistence is the checkpoint store used between park and resume. The browser session persists parked checkpoints and restores state plus memory before resuming.

Archivist checkpoint-store DAG

55 placements

DAG JSON-LD registered with the dispatcher

{
  "@context": {
    "@version": 1.1,
    "name": {
      "@id": "https://noocodec.dev/ontology/dag/name"
    },
    "version": {
      "@id": "https://noocodec.dev/ontology/dag/version"
    },
    "entrypoints": {
      "@id": "https://noocodec.dev/ontology/dag/entrypoints",
      "@container": "@index"
    },
    "nodes": {
      "@id": "https://noocodec.dev/ontology/dag/nodes",
      "@container": "@set"
    },
    "outputs": {
      "@id": "https://noocodec.dev/ontology/dag/outputs"
    },
    "node": {
      "@id": "https://noocodec.dev/ontology/dag/node"
    },
    "dag": {
      "@id": "https://noocodec.dev/ontology/dag/dag"
    },
    "body": {
      "@id": "https://noocodec.dev/ontology/dag/body"
    },
    "source": {
      "@id": "https://noocodec.dev/ontology/dag/source"
    },
    "sources": {
      "@id": "https://noocodec.dev/ontology/dag/sources",
      "@container": "@index"
    },
    "itemKey": {
      "@id": "https://noocodec.dev/ontology/dag/itemKey"
    },
    "execution": {
      "@id": "https://noocodec.dev/ontology/dag/execution"
    },
    "concurrency": {
      "@id": "https://noocodec.dev/ontology/dag/concurrency"
    },
    "throttle": {
      "@id": "https://noocodec.dev/ontology/dag/throttle"
    },
    "reservoir": {
      "@id": "https://noocodec.dev/ontology/dag/reservoir"
    },
    "gather": {
      "@id": "https://noocodec.dev/ontology/dag/gather"
    },
    "dagReference": {
      "@id": "https://noocodec.dev/ontology/dag/dagReference",
      "@type": "@id"
    },
    "DagReference": {
      "@id": "https://noocodec.dev/ontology/dag/DagReference"
    },
    "from": {
      "@id": "https://noocodec.dev/ontology/dag/from"
    },
    "path": {
      "@id": "https://noocodec.dev/ontology/dag/path"
    },
    "candidates": {
      "@id": "https://noocodec.dev/ontology/dag/candidates",
      "@container": "@set"
    },
    "candidateDag": {
      "@id": "https://noocodec.dev/ontology/dag/candidateDag",
      "@type": "@id"
    },
    "selectedDag": {
      "@id": "https://noocodec.dev/ontology/dag/selectedDag",
      "@type": "@id"
    },
    "resultField": {
      "@id": "https://noocodec.dev/ontology/dag/resultField"
    },
    "policy": {
      "@id": "https://noocodec.dev/ontology/dag/policy"
    },
    "reducer": {
      "@id": "https://noocodec.dev/ontology/dag/reducer"
    },
    "outcome": {
      "@id": "https://noocodec.dev/ontology/dag/outcome"
    },
    "phase": {
      "@id": "https://noocodec.dev/ontology/dag/phase"
    },
    "stateMapping": {
      "@id": "https://noocodec.dev/ontology/dag/stateMapping"
    },
    "container": {
      "@id": "https://noocodec.dev/ontology/dag/container"
    },
    "DAG": {
      "@id": "https://noocodec.dev/ontology/dag/DAG"
    },
    "Placement": {
      "@id": "https://noocodec.dev/ontology/dag/Placement"
    },
    "SingleNode": {
      "@id": "https://noocodec.dev/ontology/dag/SingleNode"
    },
    "ScatterNode": {
      "@id": "https://noocodec.dev/ontology/dag/ScatterNode"
    },
    "EmbeddedDAGNode": {
      "@id": "https://noocodec.dev/ontology/dag/EmbeddedDAGNode"
    },
    "GatherNode": {
      "@id": "https://noocodec.dev/ontology/dag/GatherNode"
    },
    "TerminalNode": {
      "@id": "https://noocodec.dev/ontology/dag/TerminalNode"
    },
    "PhaseNode": {
      "@id": "https://noocodec.dev/ontology/dag/PhaseNode"
    }
  },
  "@id": "urn:noocodec:dag:the-archivist",
  "@type": "DAG",
  "name": "the-archivist",
  "version": "6.0",
  "entrypoints": {
    "main": "urn:noocodec:dag:the-archivist/node/park-for-input"
  },
  "nodes": [
    {
      "@id": "urn:noocodec:dag:the-archivist/node/setup",
      "@type": "PhaseNode",
      "name": "setup",
      "node": "urn:noocodec:node:pre-run-setup",
      "phase": "pre"
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/park-for-input",
      "@type": "SingleNode",
      "name": "park-for-input",
      "node": "urn:noocodec:node:park-for-input",
      "outputs": {
        "parked": "urn:noocodec:dag:the-archivist/node/park-for-input",
        "resumed": "urn:noocodec:dag:the-archivist/node/recall-context"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/recall-context",
      "@type": "SingleNode",
      "name": "recall-context",
      "node": "urn:noocodec:node:recall-context",
      "outputs": {
        "recalled": "urn:noocodec:dag:the-archivist/node/classify-intent"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/classify-intent",
      "@type": "SingleNode",
      "name": "classify-intent",
      "node": "urn:noocodec:node:classify-intent",
      "outputs": {
        "lookup-author": "urn:noocodec:dag:the-archivist/node/author-search",
        "find-reviews": "urn:noocodec:dag:the-archivist/node/reviews-extract",
        "describe-book": "urn:noocodec:dag:the-archivist/node/describe-extract",
        "recommend-similar": "urn:noocodec:dag:the-archivist/node/recommend-similar",
        "recall-memories": "urn:noocodec:dag:the-archivist/node/memory-recall",
        "on-topic": "urn:noocodec:dag:the-archivist/node/on-topic-search",
        "recommend-top-rated": "urn:noocodec:dag:the-archivist/node/recommend-extract",
        "off-topic": "urn:noocodec:dag:the-archivist/node/decline-off-topic",
        "retry": "urn:noocodec:dag:the-archivist/node/classify-intent",
        "salvage": "urn:noocodec:dag:the-archivist/node/classify-intent-salvage"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/classify-intent-salvage",
      "@type": "SingleNode",
      "name": "classify-intent-salvage",
      "node": "urn:noocodec:node:classify-intent-salvage",
      "outputs": {
        "done": "urn:noocodec:dag:the-archivist/node/on-topic-search"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/on-topic-search",
      "@type": "EmbeddedDAGNode",
      "name": "on-topic-search",
      "outputs": {
        "success": "urn:noocodec:dag:the-archivist/node/compose-loop",
        "error": "urn:noocodec:dag:the-archivist/node/compose-empty"
      },
      "dag": "urn:noocodec:dag:book-search-scatter",
      "stateMapping": {
        "output": {
          "terms": "terms",
          "toolPlan": "toolPlan",
          "candidates": "candidates",
          "shortlist": "shortlist",
          "priorContext": "priorContext",
          "failureCause": "failureCause"
        }
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/author-search",
      "@type": "EmbeddedDAGNode",
      "name": "author-search",
      "outputs": {
        "success": "urn:noocodec:dag:the-archivist/node/group-by-year",
        "error": "urn:noocodec:dag:the-archivist/node/compose-empty"
      },
      "dag": "urn:noocodec:dag:book-search-scatter",
      "stateMapping": {
        "output": {
          "terms": "terms",
          "toolPlan": "toolPlan",
          "candidates": "candidates",
          "shortlist": "shortlist",
          "priorContext": "priorContext",
          "failureCause": "failureCause"
        }
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/group-by-year",
      "@type": "SingleNode",
      "name": "group-by-year",
      "node": "urn:noocodec:node:group-by-year",
      "outputs": {
        "ordered": "urn:noocodec:dag:the-archivist/node/compose-loop"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/reviews-extract",
      "@type": "SingleNode",
      "name": "reviews-extract",
      "node": "urn:noocodec:node:extract-query",
      "outputs": {
        "success": "urn:noocodec:dag:the-archivist/node/reviews-decide-tools",
        "retry": "urn:noocodec:dag:the-archivist/node/reviews-extract",
        "salvage": "urn:noocodec:dag:the-archivist/node/reviews-extract-salvage"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/reviews-extract-salvage",
      "@type": "SingleNode",
      "name": "reviews-extract-salvage",
      "node": "urn:noocodec:node:extract-query-salvage",
      "outputs": {
        "done": "urn:noocodec:dag:the-archivist/node/reviews-decide-tools"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/reviews-decide-tools",
      "@type": "SingleNode",
      "name": "reviews-decide-tools",
      "node": "urn:noocodec:node:decide-tools",
      "outputs": {
        "tools": "urn:noocodec:dag:the-archivist/node/reviews-build-worksets",
        "no-tools": "urn:noocodec:dag:the-archivist/node/reviews-build-worksets",
        "retry": "urn:noocodec:dag:the-archivist/node/reviews-decide-tools",
        "salvage": "urn:noocodec:dag:the-archivist/node/reviews-decide-tools-salvage"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/reviews-decide-tools-salvage",
      "@type": "SingleNode",
      "name": "reviews-decide-tools-salvage",
      "node": "urn:noocodec:node:decide-tools-salvage",
      "outputs": {
        "done": "urn:noocodec:dag:the-archivist/node/reviews-build-worksets"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/reviews-build-worksets",
      "@type": "SingleNode",
      "name": "reviews-build-worksets",
      "node": "urn:noocodec:node:build-book-worksets",
      "outputs": {
        "ready": "urn:noocodec:dag:the-archivist/node/reviews-scatter"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/reviews-scatter",
      "@type": "ScatterNode",
      "name": "reviews-scatter",
      "source": "bookWorksets",
      "body": {
        "dag": {
          "@type": "DagReference",
          "from": "item",
          "path": "dagIri",
          "candidates": [
            "urn:noocodec:tool:web_search_books",
            "urn:noocodec:tool:google_books_search",
            "urn:noocodec:tool:subject_search",
            "urn:noocodec:tool:wikipedia_summary"
          ]
        }
      },
      "outputs": {
        "success": "urn:noocodec:dag:the-archivist/node/reviews-gather",
        "error": "urn:noocodec:dag:the-archivist/node/reviews-gather",
        "empty": "urn:noocodec:dag:the-archivist/node/reviews-rank"
      },
      "itemKey": "currentItem",
      "reducer": "any-success",
      "execution": {
        "mode": "item",
        "concurrency": 4
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/reviews-gather",
      "@type": "GatherNode",
      "name": "reviews-gather",
      "sources": {
        "urn:noocodec:dag:the-archivist/node/reviews-scatter": {}
      },
      "gather": {
        "strategy": "tool-candidate-merge"
      },
      "outputs": {
        "success": "urn:noocodec:dag:the-archivist/node/reviews-rank",
        "error": "urn:noocodec:dag:the-archivist/node/reviews-rank",
        "empty": "urn:noocodec:dag:the-archivist/node/reviews-rank"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/reviews-rank",
      "@type": "SingleNode",
      "name": "reviews-rank",
      "node": "urn:noocodec:node:rank-by-rating",
      "outputs": {
        "ranked": "urn:noocodec:dag:the-archivist/node/reviews-merge"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/reviews-merge",
      "@type": "SingleNode",
      "name": "reviews-merge",
      "node": "urn:noocodec:node:merge-candidates",
      "outputs": {
        "ranked": "urn:noocodec:dag:the-archivist/node/reviews-record",
        "empty": "urn:noocodec:dag:the-archivist/node/compose-empty"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/reviews-record",
      "@type": "SingleNode",
      "name": "reviews-record",
      "node": "urn:noocodec:node:record-findings",
      "outputs": {
        "recorded": "urn:noocodec:dag:the-archivist/node/reviews-gate"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/reviews-gate",
      "@type": "SingleNode",
      "name": "reviews-gate",
      "node": "urn:noocodec:node:has-citations-gate",
      "outputs": {
        "pass": "urn:noocodec:dag:the-archivist/node/reviews-recall",
        "fail": "urn:noocodec:dag:the-archivist/node/compose-empty"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/reviews-recall",
      "@type": "SingleNode",
      "name": "reviews-recall",
      "node": "urn:noocodec:node:recall-past-visits",
      "outputs": {
        "recalled": "urn:noocodec:dag:the-archivist/node/compose-loop"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/recommend-extract",
      "@type": "SingleNode",
      "name": "recommend-extract",
      "node": "urn:noocodec:node:extract-query",
      "outputs": {
        "success": "urn:noocodec:dag:the-archivist/node/recommend-decide-tools",
        "retry": "urn:noocodec:dag:the-archivist/node/recommend-extract",
        "salvage": "urn:noocodec:dag:the-archivist/node/recommend-extract-salvage"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/recommend-extract-salvage",
      "@type": "SingleNode",
      "name": "recommend-extract-salvage",
      "node": "urn:noocodec:node:extract-query-salvage",
      "outputs": {
        "done": "urn:noocodec:dag:the-archivist/node/recommend-decide-tools"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/recommend-decide-tools",
      "@type": "SingleNode",
      "name": "recommend-decide-tools",
      "node": "urn:noocodec:node:decide-tools",
      "outputs": {
        "tools": "urn:noocodec:dag:the-archivist/node/recommend-build-worksets",
        "no-tools": "urn:noocodec:dag:the-archivist/node/recommend-build-worksets",
        "retry": "urn:noocodec:dag:the-archivist/node/recommend-decide-tools",
        "salvage": "urn:noocodec:dag:the-archivist/node/recommend-decide-tools-salvage"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/recommend-decide-tools-salvage",
      "@type": "SingleNode",
      "name": "recommend-decide-tools-salvage",
      "node": "urn:noocodec:node:decide-tools-salvage",
      "outputs": {
        "done": "urn:noocodec:dag:the-archivist/node/recommend-build-worksets"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/recommend-build-worksets",
      "@type": "SingleNode",
      "name": "recommend-build-worksets",
      "node": "urn:noocodec:node:build-book-worksets",
      "outputs": {
        "ready": "urn:noocodec:dag:the-archivist/node/recommend-scatter"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/recommend-scatter",
      "@type": "ScatterNode",
      "name": "recommend-scatter",
      "source": "bookWorksets",
      "body": {
        "dag": {
          "@type": "DagReference",
          "from": "item",
          "path": "dagIri",
          "candidates": [
            "urn:noocodec:tool:web_search_books",
            "urn:noocodec:tool:google_books_search",
            "urn:noocodec:tool:subject_search",
            "urn:noocodec:tool:wikipedia_summary"
          ]
        }
      },
      "outputs": {
        "success": "urn:noocodec:dag:the-archivist/node/recommend-gather",
        "error": "urn:noocodec:dag:the-archivist/node/recommend-gather",
        "empty": "urn:noocodec:dag:the-archivist/node/recommend-rank"
      },
      "itemKey": "currentItem",
      "reducer": "any-success",
      "execution": {
        "mode": "item",
        "concurrency": 4
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/recommend-gather",
      "@type": "GatherNode",
      "name": "recommend-gather",
      "sources": {
        "urn:noocodec:dag:the-archivist/node/recommend-scatter": {}
      },
      "gather": {
        "strategy": "tool-candidate-merge"
      },
      "outputs": {
        "success": "urn:noocodec:dag:the-archivist/node/recommend-rank",
        "error": "urn:noocodec:dag:the-archivist/node/recommend-rank",
        "empty": "urn:noocodec:dag:the-archivist/node/recommend-rank"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/recommend-rank",
      "@type": "SingleNode",
      "name": "recommend-rank",
      "node": "urn:noocodec:node:rank-by-rating",
      "outputs": {
        "ranked": "urn:noocodec:dag:the-archivist/node/recommend-merge"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/recommend-merge",
      "@type": "SingleNode",
      "name": "recommend-merge",
      "node": "urn:noocodec:node:merge-candidates",
      "outputs": {
        "ranked": "urn:noocodec:dag:the-archivist/node/recommend-record",
        "empty": "urn:noocodec:dag:the-archivist/node/compose-empty"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/recommend-record",
      "@type": "SingleNode",
      "name": "recommend-record",
      "node": "urn:noocodec:node:record-findings",
      "outputs": {
        "recorded": "urn:noocodec:dag:the-archivist/node/recommend-gate"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/recommend-gate",
      "@type": "SingleNode",
      "name": "recommend-gate",
      "node": "urn:noocodec:node:has-citations-gate",
      "outputs": {
        "pass": "urn:noocodec:dag:the-archivist/node/recommend-recall",
        "fail": "urn:noocodec:dag:the-archivist/node/compose-empty"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/recommend-recall",
      "@type": "SingleNode",
      "name": "recommend-recall",
      "node": "urn:noocodec:node:recall-past-visits",
      "outputs": {
        "recalled": "urn:noocodec:dag:the-archivist/node/compose-loop"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/describe-extract",
      "@type": "SingleNode",
      "name": "describe-extract",
      "node": "urn:noocodec:node:extract-query",
      "outputs": {
        "success": "urn:noocodec:dag:the-archivist/node/describe-decide-tools",
        "retry": "urn:noocodec:dag:the-archivist/node/describe-extract",
        "salvage": "urn:noocodec:dag:the-archivist/node/describe-extract-salvage"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/describe-extract-salvage",
      "@type": "SingleNode",
      "name": "describe-extract-salvage",
      "node": "urn:noocodec:node:extract-query-salvage",
      "outputs": {
        "done": "urn:noocodec:dag:the-archivist/node/describe-decide-tools"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/describe-decide-tools",
      "@type": "SingleNode",
      "name": "describe-decide-tools",
      "node": "urn:noocodec:node:decide-tools",
      "outputs": {
        "tools": "urn:noocodec:dag:the-archivist/node/describe-build-worksets",
        "no-tools": "urn:noocodec:dag:the-archivist/node/describe-build-worksets",
        "retry": "urn:noocodec:dag:the-archivist/node/describe-decide-tools",
        "salvage": "urn:noocodec:dag:the-archivist/node/describe-decide-tools-salvage"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/describe-decide-tools-salvage",
      "@type": "SingleNode",
      "name": "describe-decide-tools-salvage",
      "node": "urn:noocodec:node:decide-tools-salvage",
      "outputs": {
        "done": "urn:noocodec:dag:the-archivist/node/describe-build-worksets"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/describe-build-worksets",
      "@type": "SingleNode",
      "name": "describe-build-worksets",
      "node": "urn:noocodec:node:build-book-worksets",
      "outputs": {
        "ready": "urn:noocodec:dag:the-archivist/node/describe-scatter"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/describe-scatter",
      "@type": "ScatterNode",
      "name": "describe-scatter",
      "source": "bookWorksets",
      "body": {
        "dag": {
          "@type": "DagReference",
          "from": "item",
          "path": "dagIri",
          "candidates": [
            "urn:noocodec:tool:web_search_books",
            "urn:noocodec:tool:google_books_search",
            "urn:noocodec:tool:subject_search",
            "urn:noocodec:tool:wikipedia_summary"
          ]
        }
      },
      "outputs": {
        "success": "urn:noocodec:dag:the-archivist/node/describe-gather",
        "error": "urn:noocodec:dag:the-archivist/node/compose-empty",
        "empty": "urn:noocodec:dag:the-archivist/node/compose-empty"
      },
      "itemKey": "currentItem",
      "reducer": "any-success",
      "execution": {
        "mode": "item",
        "concurrency": 4
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/describe-gather",
      "@type": "GatherNode",
      "name": "describe-gather",
      "sources": {
        "urn:noocodec:dag:the-archivist/node/describe-scatter": {}
      },
      "gather": {
        "strategy": "tool-candidate-merge"
      },
      "outputs": {
        "success": "urn:noocodec:dag:the-archivist/node/describe-pick",
        "error": "urn:noocodec:dag:the-archivist/node/compose-empty",
        "empty": "urn:noocodec:dag:the-archivist/node/compose-empty"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/describe-pick",
      "@type": "SingleNode",
      "name": "describe-pick",
      "node": "urn:noocodec:node:pick-best-match",
      "outputs": {
        "picked": "urn:noocodec:dag:the-archivist/node/describe-merge"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/describe-merge",
      "@type": "SingleNode",
      "name": "describe-merge",
      "node": "urn:noocodec:node:merge-candidates",
      "outputs": {
        "ranked": "urn:noocodec:dag:the-archivist/node/describe-record",
        "empty": "urn:noocodec:dag:the-archivist/node/compose-empty"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/describe-record",
      "@type": "SingleNode",
      "name": "describe-record",
      "node": "urn:noocodec:node:record-findings",
      "outputs": {
        "recorded": "urn:noocodec:dag:the-archivist/node/describe-gate"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/describe-gate",
      "@type": "SingleNode",
      "name": "describe-gate",
      "node": "urn:noocodec:node:has-citations-gate",
      "outputs": {
        "pass": "urn:noocodec:dag:the-archivist/node/describe-recall",
        "fail": "urn:noocodec:dag:the-archivist/node/compose-empty"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/describe-recall",
      "@type": "SingleNode",
      "name": "describe-recall",
      "node": "urn:noocodec:node:recall-past-visits",
      "outputs": {
        "recalled": "urn:noocodec:dag:the-archivist/node/compose-loop"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/recommend-similar",
      "@type": "SingleNode",
      "name": "recommend-similar",
      "node": "urn:noocodec:node:recommend-similar",
      "outputs": {
        "seeded": "urn:noocodec:dag:the-archivist/node/similar-search",
        "empty": "urn:noocodec:dag:the-archivist/node/compose-empty"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/similar-search",
      "@type": "EmbeddedDAGNode",
      "name": "similar-search",
      "outputs": {
        "success": "urn:noocodec:dag:the-archivist/node/compose-loop",
        "error": "urn:noocodec:dag:the-archivist/node/compose-empty"
      },
      "dag": "urn:noocodec:dag:book-search-scatter",
      "stateMapping": {
        "output": {
          "terms": "terms",
          "toolPlan": "toolPlan",
          "candidates": "candidates",
          "shortlist": "shortlist",
          "priorContext": "priorContext",
          "failureCause": "failureCause"
        }
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/compose-loop",
      "@type": "EmbeddedDAGNode",
      "name": "compose-loop",
      "outputs": {
        "success": "urn:noocodec:dag:the-archivist/node/respond-to-visitor",
        "error": "urn:noocodec:dag:the-archivist/node/compose-empty"
      },
      "dag": "urn:noocodec:dag:compose-retry-loop",
      "stateMapping": {
        "output": {
          "draft": "draft",
          "approvalState": "approvalState"
        }
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/respond-to-visitor",
      "@type": "SingleNode",
      "name": "respond-to-visitor",
      "node": "urn:noocodec:node:respond-to-visitor",
      "outputs": {
        "success": "urn:noocodec:dag:the-archivist/node/end"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/memory-recall",
      "@type": "SingleNode",
      "name": "memory-recall",
      "node": "urn:noocodec:node:recall-memories",
      "outputs": {
        "recalled": "urn:noocodec:dag:the-archivist/node/compose-memory-recall"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/compose-memory-recall",
      "@type": "SingleNode",
      "name": "compose-memory-recall",
      "node": "urn:noocodec:node:compose-memory-response",
      "outputs": {
        "drafted": "urn:noocodec:dag:the-archivist/node/respond-to-visitor",
        "retry": "urn:noocodec:dag:the-archivist/node/compose-memory-recall",
        "salvage": "urn:noocodec:dag:the-archivist/node/compose-memory-salvage"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/compose-memory-salvage",
      "@type": "SingleNode",
      "name": "compose-memory-salvage",
      "node": "urn:noocodec:node:compose-memory-salvage",
      "outputs": {
        "done": "urn:noocodec:dag:the-archivist/node/respond-to-visitor"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/decline-off-topic",
      "@type": "SingleNode",
      "name": "decline-off-topic",
      "node": "urn:noocodec:node:decline-off-topic",
      "outputs": {
        "success": "urn:noocodec:dag:the-archivist/node/end"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/compose-empty",
      "@type": "SingleNode",
      "name": "compose-empty",
      "node": "urn:noocodec:node:compose-empty",
      "outputs": {
        "drafted": "urn:noocodec:dag:the-archivist/node/respond-to-visitor",
        "retry": "urn:noocodec:dag:the-archivist/node/compose-empty",
        "salvage": "urn:noocodec:dag:the-archivist/node/compose-empty-salvage"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/compose-empty-salvage",
      "@type": "SingleNode",
      "name": "compose-empty-salvage",
      "node": "urn:noocodec:node:compose-empty-salvage",
      "outputs": {
        "done": "urn:noocodec:dag:the-archivist/node/respond-to-visitor"
      }
    },
    {
      "@id": "urn:noocodec:dag:the-archivist/node/end",
      "@type": "TerminalNode",
      "name": "end",
      "outcome": "completed"
    }
  ]
}

Mermaid generated from the same DAG

Mermaid source

%%{init: {"flowchart":{"nodeSpacing":92,"rankSpacing":104,"padding":28}}}%%
flowchart TB
  %% the-archivist (v6.0)
  entry_main(["main"])
  entry_main --> urn_noocodec_dag_the-archivist/node/park-for-input
  urn_noocodec_dag_the-archivist/node/setup(["setup (pre)"])
  urn_noocodec_dag_the-archivist/node/park-for-input["park-for-input"]
  urn_noocodec_dag_the-archivist/node/park-for-input -->|parked| urn_noocodec_dag_the-archivist/node/park-for-input
  urn_noocodec_dag_the-archivist/node/park-for-input -->|resumed| urn_noocodec_dag_the-archivist/node/recall-context
  urn_noocodec_dag_the-archivist/node/recall-context["recall-context"]
  urn_noocodec_dag_the-archivist/node/recall-context -->|recalled| urn_noocodec_dag_the-archivist/node/classify-intent
  urn_noocodec_dag_the-archivist/node/classify-intent["classify-intent"]
  urn_noocodec_dag_the-archivist/node/classify-intent -->|lookup-author| urn_noocodec_dag_the-archivist/node/author-search
  urn_noocodec_dag_the-archivist/node/classify-intent -->|find-reviews| urn_noocodec_dag_the-archivist/node/reviews-extract
  urn_noocodec_dag_the-archivist/node/classify-intent -->|describe-book| urn_noocodec_dag_the-archivist/node/describe-extract
  urn_noocodec_dag_the-archivist/node/classify-intent -->|recommend-similar| urn_noocodec_dag_the-archivist/node/recommend-similar
  urn_noocodec_dag_the-archivist/node/classify-intent -->|recall-memories| urn_noocodec_dag_the-archivist/node/memory-recall
  urn_noocodec_dag_the-archivist/node/classify-intent -->|on-topic| urn_noocodec_dag_the-archivist/node/on-topic-search
  urn_noocodec_dag_the-archivist/node/classify-intent -->|recommend-top-rated| urn_noocodec_dag_the-archivist/node/recommend-extract
  urn_noocodec_dag_the-archivist/node/classify-intent -->|off-topic| urn_noocodec_dag_the-archivist/node/decline-off-topic
  urn_noocodec_dag_the-archivist/node/classify-intent -->|retry| urn_noocodec_dag_the-archivist/node/classify-intent
  urn_noocodec_dag_the-archivist/node/classify-intent -->|salvage| urn_noocodec_dag_the-archivist/node/classify-intent-salvage
  urn_noocodec_dag_the-archivist/node/classify-intent-salvage["classify-intent-salvage"]
  urn_noocodec_dag_the-archivist/node/classify-intent-salvage -->|done| urn_noocodec_dag_the-archivist/node/on-topic-search
  urn_noocodec_dag_the-archivist/node/on-topic-search[["on-topic-search"]]
  urn_noocodec_dag_the-archivist/node/on-topic-search -->|success| urn_noocodec_dag_the-archivist/node/compose-loop
  urn_noocodec_dag_the-archivist/node/on-topic-search -->|error| urn_noocodec_dag_the-archivist/node/compose-empty
  urn_noocodec_dag_the-archivist/node/author-search[["author-search"]]
  urn_noocodec_dag_the-archivist/node/author-search -->|success| urn_noocodec_dag_the-archivist/node/group-by-year
  urn_noocodec_dag_the-archivist/node/author-search -->|error| urn_noocodec_dag_the-archivist/node/compose-empty
  urn_noocodec_dag_the-archivist/node/group-by-year["group-by-year"]
  urn_noocodec_dag_the-archivist/node/group-by-year -->|ordered| urn_noocodec_dag_the-archivist/node/compose-loop
  urn_noocodec_dag_the-archivist/node/reviews-extract["reviews-extract"]
  urn_noocodec_dag_the-archivist/node/reviews-extract -->|success| urn_noocodec_dag_the-archivist/node/reviews-decide-tools
  urn_noocodec_dag_the-archivist/node/reviews-extract -->|retry| urn_noocodec_dag_the-archivist/node/reviews-extract
  urn_noocodec_dag_the-archivist/node/reviews-extract -->|salvage| urn_noocodec_dag_the-archivist/node/reviews-extract-salvage
  urn_noocodec_dag_the-archivist/node/reviews-extract-salvage["reviews-extract-salvage"]
  urn_noocodec_dag_the-archivist/node/reviews-extract-salvage -->|done| urn_noocodec_dag_the-archivist/node/reviews-decide-tools
  urn_noocodec_dag_the-archivist/node/reviews-decide-tools["reviews-decide-tools"]
  urn_noocodec_dag_the-archivist/node/reviews-decide-tools -->|tools| urn_noocodec_dag_the-archivist/node/reviews-build-worksets
  urn_noocodec_dag_the-archivist/node/reviews-decide-tools -->|no-tools| urn_noocodec_dag_the-archivist/node/reviews-build-worksets
  urn_noocodec_dag_the-archivist/node/reviews-decide-tools -->|retry| urn_noocodec_dag_the-archivist/node/reviews-decide-tools
  urn_noocodec_dag_the-archivist/node/reviews-decide-tools -->|salvage| urn_noocodec_dag_the-archivist/node/reviews-decide-tools-salvage
  urn_noocodec_dag_the-archivist/node/reviews-decide-tools-salvage["reviews-decide-tools-salvage"]
  urn_noocodec_dag_the-archivist/node/reviews-decide-tools-salvage -->|done| urn_noocodec_dag_the-archivist/node/reviews-build-worksets
  urn_noocodec_dag_the-archivist/node/reviews-build-worksets["reviews-build-worksets"]
  urn_noocodec_dag_the-archivist/node/reviews-build-worksets -->|ready| urn_noocodec_dag_the-archivist/node/reviews-scatter
  urn_noocodec_dag_the-archivist/node/reviews-scatter[/"reviews-scatter"/]
  urn_noocodec_dag_the-archivist/node/reviews-scatter -->|success| urn_noocodec_dag_the-archivist/node/reviews-gather
  urn_noocodec_dag_the-archivist/node/reviews-scatter -->|error| urn_noocodec_dag_the-archivist/node/reviews-gather
  urn_noocodec_dag_the-archivist/node/reviews-scatter -->|empty| urn_noocodec_dag_the-archivist/node/reviews-rank
  urn_noocodec_dag_the-archivist/node/reviews-gather{"reviews-gather"}
  urn_noocodec_dag_the-archivist/node/reviews-gather -->|success| urn_noocodec_dag_the-archivist/node/reviews-rank
  urn_noocodec_dag_the-archivist/node/reviews-gather -->|error| urn_noocodec_dag_the-archivist/node/reviews-rank
  urn_noocodec_dag_the-archivist/node/reviews-gather -->|empty| urn_noocodec_dag_the-archivist/node/reviews-rank
  urn_noocodec_dag_the-archivist/node/reviews-rank["reviews-rank"]
  urn_noocodec_dag_the-archivist/node/reviews-rank -->|ranked| urn_noocodec_dag_the-archivist/node/reviews-merge
  urn_noocodec_dag_the-archivist/node/reviews-merge["reviews-merge"]
  urn_noocodec_dag_the-archivist/node/reviews-merge -->|ranked| urn_noocodec_dag_the-archivist/node/reviews-record
  urn_noocodec_dag_the-archivist/node/reviews-merge -->|empty| urn_noocodec_dag_the-archivist/node/compose-empty
  urn_noocodec_dag_the-archivist/node/reviews-record["reviews-record"]
  urn_noocodec_dag_the-archivist/node/reviews-record -->|recorded| urn_noocodec_dag_the-archivist/node/reviews-gate
  urn_noocodec_dag_the-archivist/node/reviews-gate["reviews-gate"]
  urn_noocodec_dag_the-archivist/node/reviews-gate -->|pass| urn_noocodec_dag_the-archivist/node/reviews-recall
  urn_noocodec_dag_the-archivist/node/reviews-gate -->|fail| urn_noocodec_dag_the-archivist/node/compose-empty
  urn_noocodec_dag_the-archivist/node/reviews-recall["reviews-recall"]
  urn_noocodec_dag_the-archivist/node/reviews-recall -->|recalled| urn_noocodec_dag_the-archivist/node/compose-loop
  urn_noocodec_dag_the-archivist/node/recommend-extract["recommend-extract"]
  urn_noocodec_dag_the-archivist/node/recommend-extract -->|success| urn_noocodec_dag_the-archivist/node/recommend-decide-tools
  urn_noocodec_dag_the-archivist/node/recommend-extract -->|retry| urn_noocodec_dag_the-archivist/node/recommend-extract
  urn_noocodec_dag_the-archivist/node/recommend-extract -->|salvage| urn_noocodec_dag_the-archivist/node/recommend-extract-salvage
  urn_noocodec_dag_the-archivist/node/recommend-extract-salvage["recommend-extract-salvage"]
  urn_noocodec_dag_the-archivist/node/recommend-extract-salvage -->|done| urn_noocodec_dag_the-archivist/node/recommend-decide-tools
  urn_noocodec_dag_the-archivist/node/recommend-decide-tools["recommend-decide-tools"]
  urn_noocodec_dag_the-archivist/node/recommend-decide-tools -->|tools| urn_noocodec_dag_the-archivist/node/recommend-build-worksets
  urn_noocodec_dag_the-archivist/node/recommend-decide-tools -->|no-tools| urn_noocodec_dag_the-archivist/node/recommend-build-worksets
  urn_noocodec_dag_the-archivist/node/recommend-decide-tools -->|retry| urn_noocodec_dag_the-archivist/node/recommend-decide-tools
  urn_noocodec_dag_the-archivist/node/recommend-decide-tools -->|salvage| urn_noocodec_dag_the-archivist/node/recommend-decide-tools-salvage
  urn_noocodec_dag_the-archivist/node/recommend-decide-tools-salvage["recommend-decide-tools-salvage"]
  urn_noocodec_dag_the-archivist/node/recommend-decide-tools-salvage -->|done| urn_noocodec_dag_the-archivist/node/recommend-build-worksets
  urn_noocodec_dag_the-archivist/node/recommend-build-worksets["recommend-build-worksets"]
  urn_noocodec_dag_the-archivist/node/recommend-build-worksets -->|ready| urn_noocodec_dag_the-archivist/node/recommend-scatter
  urn_noocodec_dag_the-archivist/node/recommend-scatter[/"recommend-scatter"/]
  urn_noocodec_dag_the-archivist/node/recommend-scatter -->|success| urn_noocodec_dag_the-archivist/node/recommend-gather
  urn_noocodec_dag_the-archivist/node/recommend-scatter -->|error| urn_noocodec_dag_the-archivist/node/recommend-gather
  urn_noocodec_dag_the-archivist/node/recommend-scatter -->|empty| urn_noocodec_dag_the-archivist/node/recommend-rank
  urn_noocodec_dag_the-archivist/node/recommend-gather{"recommend-gather"}
  urn_noocodec_dag_the-archivist/node/recommend-gather -->|success| urn_noocodec_dag_the-archivist/node/recommend-rank
  urn_noocodec_dag_the-archivist/node/recommend-gather -->|error| urn_noocodec_dag_the-archivist/node/recommend-rank
  urn_noocodec_dag_the-archivist/node/recommend-gather -->|empty| urn_noocodec_dag_the-archivist/node/recommend-rank
  urn_noocodec_dag_the-archivist/node/recommend-rank["recommend-rank"]
  urn_noocodec_dag_the-archivist/node/recommend-rank -->|ranked| urn_noocodec_dag_the-archivist/node/recommend-merge
  urn_noocodec_dag_the-archivist/node/recommend-merge["recommend-merge"]
  urn_noocodec_dag_the-archivist/node/recommend-merge -->|ranked| urn_noocodec_dag_the-archivist/node/recommend-record
  urn_noocodec_dag_the-archivist/node/recommend-merge -->|empty| urn_noocodec_dag_the-archivist/node/compose-empty
  urn_noocodec_dag_the-archivist/node/recommend-record["recommend-record"]
  urn_noocodec_dag_the-archivist/node/recommend-record -->|recorded| urn_noocodec_dag_the-archivist/node/recommend-gate
  urn_noocodec_dag_the-archivist/node/recommend-gate["recommend-gate"]
  urn_noocodec_dag_the-archivist/node/recommend-gate -->|pass| urn_noocodec_dag_the-archivist/node/recommend-recall
  urn_noocodec_dag_the-archivist/node/recommend-gate -->|fail| urn_noocodec_dag_the-archivist/node/compose-empty
  urn_noocodec_dag_the-archivist/node/recommend-recall["recommend-recall"]
  urn_noocodec_dag_the-archivist/node/recommend-recall -->|recalled| urn_noocodec_dag_the-archivist/node/compose-loop
  urn_noocodec_dag_the-archivist/node/describe-extract["describe-extract"]
  urn_noocodec_dag_the-archivist/node/describe-extract -->|success| urn_noocodec_dag_the-archivist/node/describe-decide-tools
  urn_noocodec_dag_the-archivist/node/describe-extract -->|retry| urn_noocodec_dag_the-archivist/node/describe-extract
  urn_noocodec_dag_the-archivist/node/describe-extract -->|salvage| urn_noocodec_dag_the-archivist/node/describe-extract-salvage
  urn_noocodec_dag_the-archivist/node/describe-extract-salvage["describe-extract-salvage"]
  urn_noocodec_dag_the-archivist/node/describe-extract-salvage -->|done| urn_noocodec_dag_the-archivist/node/describe-decide-tools
  urn_noocodec_dag_the-archivist/node/describe-decide-tools["describe-decide-tools"]
  urn_noocodec_dag_the-archivist/node/describe-decide-tools -->|tools| urn_noocodec_dag_the-archivist/node/describe-build-worksets
  urn_noocodec_dag_the-archivist/node/describe-decide-tools -->|no-tools| urn_noocodec_dag_the-archivist/node/describe-build-worksets
  urn_noocodec_dag_the-archivist/node/describe-decide-tools -->|retry| urn_noocodec_dag_the-archivist/node/describe-decide-tools
  urn_noocodec_dag_the-archivist/node/describe-decide-tools -->|salvage| urn_noocodec_dag_the-archivist/node/describe-decide-tools-salvage
  urn_noocodec_dag_the-archivist/node/describe-decide-tools-salvage["describe-decide-tools-salvage"]
  urn_noocodec_dag_the-archivist/node/describe-decide-tools-salvage -->|done| urn_noocodec_dag_the-archivist/node/describe-build-worksets
  urn_noocodec_dag_the-archivist/node/describe-build-worksets["describe-build-worksets"]
  urn_noocodec_dag_the-archivist/node/describe-build-worksets -->|ready| urn_noocodec_dag_the-archivist/node/describe-scatter
  urn_noocodec_dag_the-archivist/node/describe-scatter[/"describe-scatter"/]
  urn_noocodec_dag_the-archivist/node/describe-scatter -->|success| urn_noocodec_dag_the-archivist/node/describe-gather
  urn_noocodec_dag_the-archivist/node/describe-scatter -->|error| urn_noocodec_dag_the-archivist/node/compose-empty
  urn_noocodec_dag_the-archivist/node/describe-scatter -->|empty| urn_noocodec_dag_the-archivist/node/compose-empty
  urn_noocodec_dag_the-archivist/node/describe-gather{"describe-gather"}
  urn_noocodec_dag_the-archivist/node/describe-gather -->|success| urn_noocodec_dag_the-archivist/node/describe-pick
  urn_noocodec_dag_the-archivist/node/describe-gather -->|error| urn_noocodec_dag_the-archivist/node/compose-empty
  urn_noocodec_dag_the-archivist/node/describe-gather -->|empty| urn_noocodec_dag_the-archivist/node/compose-empty
  urn_noocodec_dag_the-archivist/node/describe-pick["describe-pick"]
  urn_noocodec_dag_the-archivist/node/describe-pick -->|picked| urn_noocodec_dag_the-archivist/node/describe-merge
  urn_noocodec_dag_the-archivist/node/describe-merge["describe-merge"]
  urn_noocodec_dag_the-archivist/node/describe-merge -->|ranked| urn_noocodec_dag_the-archivist/node/describe-record
  urn_noocodec_dag_the-archivist/node/describe-merge -->|empty| urn_noocodec_dag_the-archivist/node/compose-empty
  urn_noocodec_dag_the-archivist/node/describe-record["describe-record"]
  urn_noocodec_dag_the-archivist/node/describe-record -->|recorded| urn_noocodec_dag_the-archivist/node/describe-gate
  urn_noocodec_dag_the-archivist/node/describe-gate["describe-gate"]
  urn_noocodec_dag_the-archivist/node/describe-gate -->|pass| urn_noocodec_dag_the-archivist/node/describe-recall
  urn_noocodec_dag_the-archivist/node/describe-gate -->|fail| urn_noocodec_dag_the-archivist/node/compose-empty
  urn_noocodec_dag_the-archivist/node/describe-recall["describe-recall"]
  urn_noocodec_dag_the-archivist/node/describe-recall -->|recalled| urn_noocodec_dag_the-archivist/node/compose-loop
  urn_noocodec_dag_the-archivist/node/recommend-similar["recommend-similar"]
  urn_noocodec_dag_the-archivist/node/recommend-similar -->|seeded| urn_noocodec_dag_the-archivist/node/similar-search
  urn_noocodec_dag_the-archivist/node/recommend-similar -->|empty| urn_noocodec_dag_the-archivist/node/compose-empty
  urn_noocodec_dag_the-archivist/node/similar-search[["similar-search"]]
  urn_noocodec_dag_the-archivist/node/similar-search -->|success| urn_noocodec_dag_the-archivist/node/compose-loop
  urn_noocodec_dag_the-archivist/node/similar-search -->|error| urn_noocodec_dag_the-archivist/node/compose-empty
  urn_noocodec_dag_the-archivist/node/compose-loop[["compose-loop"]]
  urn_noocodec_dag_the-archivist/node/compose-loop -->|success| urn_noocodec_dag_the-archivist/node/respond-to-visitor
  urn_noocodec_dag_the-archivist/node/compose-loop -->|error| urn_noocodec_dag_the-archivist/node/compose-empty
  urn_noocodec_dag_the-archivist/node/respond-to-visitor["respond-to-visitor"]
  urn_noocodec_dag_the-archivist/node/respond-to-visitor -->|success| urn_noocodec_dag_the-archivist/node/end
  urn_noocodec_dag_the-archivist/node/memory-recall["memory-recall"]
  urn_noocodec_dag_the-archivist/node/memory-recall -->|recalled| urn_noocodec_dag_the-archivist/node/compose-memory-recall
  urn_noocodec_dag_the-archivist/node/compose-memory-recall["compose-memory-recall"]
  urn_noocodec_dag_the-archivist/node/compose-memory-recall -->|drafted| urn_noocodec_dag_the-archivist/node/respond-to-visitor
  urn_noocodec_dag_the-archivist/node/compose-memory-recall -->|retry| urn_noocodec_dag_the-archivist/node/compose-memory-recall
  urn_noocodec_dag_the-archivist/node/compose-memory-recall -->|salvage| urn_noocodec_dag_the-archivist/node/compose-memory-salvage
  urn_noocodec_dag_the-archivist/node/compose-memory-salvage["compose-memory-salvage"]
  urn_noocodec_dag_the-archivist/node/compose-memory-salvage -->|done| urn_noocodec_dag_the-archivist/node/respond-to-visitor
  urn_noocodec_dag_the-archivist/node/decline-off-topic["decline-off-topic"]
  urn_noocodec_dag_the-archivist/node/decline-off-topic -->|success| urn_noocodec_dag_the-archivist/node/end
  urn_noocodec_dag_the-archivist/node/compose-empty["compose-empty"]
  urn_noocodec_dag_the-archivist/node/compose-empty -->|drafted| urn_noocodec_dag_the-archivist/node/respond-to-visitor
  urn_noocodec_dag_the-archivist/node/compose-empty -->|retry| urn_noocodec_dag_the-archivist/node/compose-empty
  urn_noocodec_dag_the-archivist/node/compose-empty -->|salvage| urn_noocodec_dag_the-archivist/node/compose-empty-salvage
  urn_noocodec_dag_the-archivist/node/compose-empty-salvage["compose-empty-salvage"]
  urn_noocodec_dag_the-archivist/node/compose-empty-salvage -->|done| urn_noocodec_dag_the-archivist/node/respond-to-visitor
  urn_noocodec_dag_the-archivist/node/end((("end")))

Full checkpoint-store lifecycle in the browser runner:

1. Execute the Archivist DAG until it parks for HITL.
2. Capture the parked result as a Checkpoint, including the memory store.
3. Persist the checkpoint under the parked correlation key.
4. Recall the checkpoint when the user provides the resume input.
5. Restore ArchivistState and stores.
6. Resume from the parked cursor.

The CLI uses MemoryCheckpointStore; the browser runner uses an IndexedDB-backed checkpoint store through the same CheckpointStore contract.

Run

npm run docs:dev

What It Lets You Do

Checkpoint stores let applications persist resumable DAG state outside process memory. Use this when a browser tab, serverless invocation, worker process, or queue worker may stop before the DAG finishes and another host must resume later.

This is the piece that turns checkpoint/resume from an in-memory trick into an application lifecycle feature: park now, persist under a correlation key, resume wherever the user or infrastructure shows up next.

Code Samples

The browser snippets show capture and restore around a parked Archivist session. The CLI snippet shows the same lifecycle against MemoryCheckpointStore.

const ckpt = await Checkpoint.capture(event.dagName, event.execution, { 'stores': { 'memory': this.store } });
await ckpt.persist(this.#ckptStore, event.execution.parked.correlationKey);

const recalled = await Checkpoint.recall(this.#ckptStore, pendingKey);
if (recalled === null) {
  this.appendErrorLine(`Checkpoint '${pendingKey}' not found in store.`);
  return;
}
await recalled.restoreStores({ 'memory': this.store });
const { dagName, state, cursor } = recalled.restoreState(
  CheckpointRestoreAdapter.wrap((snap) => ArchivistState.restore(snap)),
);
state.query = humanText;
this.#dom.hitlInput.value = '';
ConversationView.pushVisitor(this.#dom.conversationEl, humanText);
await this.resumeRun(humanText, dagName, state, cursor);

if (cancelResult.cursor !== null) {
  const store = new MemoryCheckpointStore();
  const ckpt = await Checkpoint.capture(ARCHIVIST_DAG_IRI, cancelResult, { 'stores': { 'memory': services.memory } });
  await ckpt.persist(store, `archivist:${cancelVisitor.query}`);

  const recalled = await Checkpoint.recall(store, `archivist:${cancelVisitor.query}`);
  if (recalled !== null) {
    const freshMemory = new MemoryStore();
    await recalled.restoreStores({ 'memory': freshMemory });
    const { dagName, state, cursor } = recalled.restoreState(
      CheckpointRestoreAdapter.wrap((snap) => ArchivistState.restore(snap)),
    );
    const resumeResult = await dispatcher.resume(dagName, state, cursor);
    logger.result(`resumed draft=${resumeResult.state.draft}`);
    logger.result(`resumed lifecycle=${resumeResult.state.lifecycle.variant}`);
    logger.result(`resumed memory triples=${String(freshMemory.size)}`);
  }
} else {
  logger.result('cancellation-run completed before cursor; no checkpoint needed');
}

Details for Nerds

• Checkpoint.capture(dagName, result). Produces a Checkpoint instance for an in-progress parked flow.
• ckpt.persist(store, key). Serialises the checkpoint and passes it to store.save(key, json).
• Checkpoint.recall(store, key). Reads from the store, deserialises, and returns a Checkpoint or null.
• ckpt.restoreState(adapter). Calls adapter(snapshot) to reconstruct the domain state from the serialised snapshot. The adapter is the restoreState function registered on the dispatcher.
• dispatcher.resume(dagName, state, cursor). Starts from the recalled cursor instead of the DAG's entrypoint. Only the remaining nodes execute; completed stages before the cursor are not re-run.
• MemoryCheckpointStore. In-process reference implementation. Swap with any CheckpointStore (Postgres, Redis, S3) without changing the calling code.

Related Concepts

• Example 08: Checkpoint and Resume - checkpoint mechanics in The Archivist
• Checkpoint guide - Checkpoint.capture, restore, cursor semantics
• Persistence guide - Postgres, Redis, and S3 CheckpointStore examples
• Example 16: Scatter resume - durable inbox: resumability across a scatter abort
• Reference: Checkpoint