diff --git a/contracts/seats/mesh-wants/fixtures/events.json b/contracts/seats/mesh-wants/fixtures/events.json
new file mode 100644
index 00000000..70fbc77c
--- /dev/null
+++ b/contracts/seats/mesh-wants/fixtures/events.json
@@ -0,0 +1,170 @@
+[
+  {
+    "name": "an assignment graph revision kept",
+    "of": "event:assignment-revision",
+    "subject": "mesh.seat.mesh-wants.event.assignment-revision",
+    "given": {
+      "v": 1,
+      "revision": 40,
+      "kind": "trunk",
+      "catalogs": [
+        {
+          "branch": "main",
+          "revision": 12,
+          "source": 3589
+        }
+      ],
+      "cause": "placement-changed",
+      "at": "2026-11-09T19:00:00Z"
+    }
+  },
+  {
+    "name": "a difference worked out",
+    "of": "event:difference",
+    "subject": "mesh.seat.mesh-wants.event.difference",
+    "given": {
+      "v": 1,
+      "from": 40,
+      "to": 41,
+      "source": 3589,
+      "changes": 1,
+      "nodes": [
+        "n1"
+      ]
+    }
+  },
+  {
+    "name": "an entry wanted from a trunk revision",
+    "of": "event:wanted",
+    "subject": "mesh.seat.mesh-wants.event.wanted",
+    "given": {
+      "v": 1,
+      "node": "n1",
+      "module": "xclip",
+      "fp": "src2:b427bdde1f100e2f52490cfa9df0c5112dd3700226b4892349f0c14a15a4af56",
+      "revision": 40,
+      "source": 3589,
+      "at": "2026-11-09T19:00:00Z"
+    }
+  },
+  {
+    "name": "a composing wait held with its bound",
+    "of": "event:wait-held",
+    "subject": "mesh.seat.mesh-wants.event.wait-held",
+    "given": {
+      "step": "compose",
+      "part": "node-engine",
+      "version": "src2:7dd0db8e98224f46121a5ae05c0b9c5a430eff531a5120aa40b1a59237853a3f",
+      "node": "n1",
+      "module": "xclip",
+      "fp": "src2:b427bdde1f100e2f52490cfa9df0c5112dd3700226b4892349f0c14a15a4af56",
+      "since": "2026-11-09T19:00:00Z",
+      "bound": "30m"
+    }
+  },
+  {
+    "name": "a wait ended, released by hand",
+    "of": "event:wait-ended",
+    "subject": "mesh.seat.mesh-wants.event.wait-ended",
+    "given": {
+      "step": "compose",
+      "part": "node-engine",
+      "version": "src2:7dd0db8e98224f46121a5ae05c0b9c5a430eff531a5120aa40b1a59237853a3f",
+      "node": "n1",
+      "module": "xclip",
+      "fp": "src2:b427bdde1f100e2f52490cfa9df0c5112dd3700226b4892349f0c14a15a4af56",
+      "since": "2026-11-09T19:00:00Z",
+      "bound": "30m",
+      "how": "released",
+      "by": "lead@shanks: the node is away"
+    }
+  },
+  {
+    "name": "the store past 80 % of its cap",
+    "of": "event:filling",
+    "subject": "mesh.seat.mesh-wants.event.filling",
+    "given": {
+      "store": "assignment-revisions",
+      "bytes": 450000000,
+      "cap": 536870912,
+      "at": "2026-11-09T19:00:00Z"
+    }
+  },
+  {
+    "name": "the store full, keeping its last revision",
+    "of": "event:full",
+    "subject": "mesh.seat.mesh-wants.event.full",
+    "given": {
+      "store": "assignment-revisions",
+      "bytes": 536870912,
+      "cap": 536870912,
+      "at": "2026-11-09T19:00:00Z",
+      "refused": "the next revision; no new want is written"
+    }
+  },
+  {
+    "name": "the store back below its cap",
+    "of": "event:room",
+    "subject": "mesh.seat.mesh-wants.event.room",
+    "given": {
+      "store": "assignment-revisions",
+      "bytes": 300000000,
+      "cap": 536870912,
+      "at": "2026-11-09T19:00:00Z"
+    }
+  },
+  {
+    "name": "the composition step ended passed on the assigner's node, a node asleep warned",
+    "of": "event:step-ended",
+    "subject": "mesh.seat.mesh-wants.event.step-ended.novox",
+    "given": {
+      "v": 1,
+      "id": "m2kx9a1b3c4d6a",
+      "pipeline": "main.12.nats",
+      "step": "composition",
+      "module": "nats",
+      "commit": "0123456789abcdef0123456789abcdef01234567",
+      "fingerprint": "fp-0123",
+      "node": "novox",
+      "outcome": "passed",
+      "warnings": [
+        "g14 asleep: composed from its last capabilities"
+      ],
+      "started": "2026-11-10T10:00:00Z",
+      "ended": "2026-11-10T10:01:00Z"
+    }
+  },
+  {
+    "name": "the composition step failed, two modules owning one path",
+    "of": "event:step-ended",
+    "subject": "mesh.seat.mesh-wants.event.step-ended.novox",
+    "given": {
+      "v": 1,
+      "id": "m2kx9a1b3c4d6b",
+      "pipeline": "main.12.nats",
+      "step": "composition",
+      "module": "nats",
+      "commit": "0123456789abcdef0123456789abcdef01234567",
+      "fingerprint": "fp-0123",
+      "node": "novox",
+      "outcome": "failed",
+      "said": "nats and xclip both own /etc/nats.conf on ace"
+    }
+  },
+  {
+    "name": "a version delivered with the machines away",
+    "of": "event:version-delivered",
+    "subject": "mesh.seat.mesh-wants.event.version-delivered",
+    "given": {
+      "v": 1,
+      "module": "mesh-sdk",
+      "version": "0.1.15",
+      "parts": {
+        "mesh-sdk:go": "sha256:0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef"
+      },
+      "away": [
+        "laptop"
+      ]
+    }
+  }
+]
diff --git a/contracts/seats/mesh-wants/fixtures/states.json b/contracts/seats/mesh-wants/fixtures/states.json
index cb38a399..818850d5 100644
--- a/contracts/seats/mesh-wants/fixtures/states.json
+++ b/contracts/seats/mesh-wants/fixtures/states.json
@@ -43,5 +43,100 @@
       "heads": "0123456789ab",
       "state": "pass"
     }
+  },
+  {
+    "name": "a trunk assignment graph revision naming its inputs",
+    "of": "state:assignment-revisions/trunk.<revision>",
+    "given": {
+      "v": 1,
+      "revision": 40,
+      "kind": "trunk",
+      "catalogs": [
+        {
+          "branch": "main",
+          "revision": 12,
+          "source": 3589
+        }
+      ],
+      "placements": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+      "capabilities": [
+        {
+          "node": "n1",
+          "digest": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+        }
+      ],
+      "cause": "catalog-revision",
+      "at": "2026-11-09T19:00:00Z",
+      "entries": [
+        {
+          "node": "n1",
+          "module": "xclip",
+          "digest": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+        }
+      ]
+    }
+  },
+  {
+    "name": "a candidate's assignment graph revision",
+    "of": "state:assignment-revisions/candidate.<group>.<heads>",
+    "given": {
+      "v": 1,
+      "revision": 41,
+      "kind": "candidate",
+      "catalogs": [
+        {
+          "branch": "main",
+          "revision": 13,
+          "source": 3589
+        }
+      ],
+      "placements": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+      "capabilities": [
+        {
+          "node": "n1",
+          "digest": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+        }
+      ],
+      "cause": "catalog-revision",
+      "at": "2026-11-09T19:00:00Z",
+      "entries": [
+        {
+          "node": "n1",
+          "module": "xclip",
+          "digest": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+        }
+      ],
+      "group": "feat/47-G",
+      "heads": "0123456789ab"
+    }
+  },
+  {
+    "name": "an assignment entry with an acting edge and a provisioning edge",
+    "of": "state:assignment-revisions/entry.<digest>",
+    "given": {
+      "v": 1,
+      "node": "n1",
+      "module": "xclip",
+      "branch": "main",
+      "fp": "src2:b427bdde1f100e2f52490cfa9df0c5112dd3700226b4892349f0c14a15a4af56",
+      "catalog": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+      "edges": [
+        {
+          "kind": "acting",
+          "node": "n1",
+          "module": "node-engine",
+          "fp": "src2:7dd0db8e98224f46121a5ae05c0b9c5a430eff531a5120aa40b1a59237853a3f",
+          "seat": "node-engine",
+          "step": "compose",
+          "bound": "30m"
+        },
+        {
+          "kind": "provisioning",
+          "node": "n2",
+          "module": "postgres",
+          "provision": "database"
+        }
+      ]
+    }
   }
 ]
diff --git a/contracts/seats/mesh-wants/fixtures/verbs.json b/contracts/seats/mesh-wants/fixtures/verbs.json
new file mode 100644
index 00000000..3a50a8c5
--- /dev/null
+++ b/contracts/seats/mesh-wants/fixtures/verbs.json
@@ -0,0 +1,173 @@
+[
+  {
+    "name": "revision asks the trunk's newest",
+    "of": "verb:revision.input",
+    "given": {}
+  },
+  {
+    "name": "revision asks a candidate's",
+    "of": "verb:revision.input",
+    "given": {
+      "group": "feat/47-G",
+      "heads": "0123456789ab"
+    }
+  },
+  {
+    "name": "revision answers one revision naming its inputs",
+    "of": "verb:revision.answer",
+    "given": {
+      "revision": {
+        "v": 1,
+        "revision": 40,
+        "kind": "trunk",
+        "catalogs": [
+          {
+            "branch": "main",
+            "revision": 12,
+            "source": 3589
+          }
+        ],
+        "placements": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+        "capabilities": [
+          {
+            "node": "n1",
+            "digest": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+          }
+        ],
+        "cause": "catalog-revision",
+        "at": "2026-11-09T19:00:00Z",
+        "entries": [
+          {
+            "node": "n1",
+            "module": "xclip",
+            "digest": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+          }
+        ]
+      }
+    }
+  },
+  {
+    "name": "entry asks by node and module in a revision",
+    "of": "verb:entry.input",
+    "given": {
+      "revision": 40,
+      "node": "n1",
+      "module": "xclip"
+    }
+  },
+  {
+    "name": "entry answers the entry with its edges",
+    "of": "verb:entry.answer",
+    "given": {
+      "digest": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+      "entry": {
+        "v": 1,
+        "node": "n1",
+        "module": "xclip",
+        "branch": "main",
+        "fp": "src2:b427bdde1f100e2f52490cfa9df0c5112dd3700226b4892349f0c14a15a4af56",
+        "catalog": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
+        "edges": [
+          {
+            "kind": "acting",
+            "node": "n1",
+            "module": "node-engine",
+            "fp": "src2:7dd0db8e98224f46121a5ae05c0b9c5a430eff531a5120aa40b1a59237853a3f",
+            "seat": "node-engine",
+            "step": "compose",
+            "bound": "30m"
+          },
+          {
+            "kind": "provisioning",
+            "node": "n2",
+            "module": "postgres",
+            "provision": "database"
+          }
+        ]
+      }
+    }
+  },
+  {
+    "name": "difference asks a candidate's against trunk",
+    "of": "verb:difference.input",
+    "given": {
+      "group": "feat/47-G",
+      "heads": "0123456789ab"
+    }
+  },
+  {
+    "name": "difference answers the changes and their order",
+    "of": "verb:difference.answer",
+    "given": {
+      "from": 40,
+      "to": 41,
+      "group": "feat/47-G",
+      "heads": "0123456789ab",
+      "changes": [
+        {
+          "node": "n1",
+          "module": "xclip",
+          "from": "src2:b427bdde1f100e2f52490cfa9df0c5112dd3700226b4892349f0c14a15a4af56",
+          "to": "src2:7dd0db8e98224f46121a5ae05c0b9c5a430eff531a5120aa40b1a59237853a3f"
+        }
+      ],
+      "nodes": [
+        "n1"
+      ],
+      "tiers": [
+        [
+          {
+            "node": "n1",
+            "module": "xclip",
+            "digest": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
+          }
+        ]
+      ]
+    }
+  },
+  {
+    "name": "difference refuses a changed fingerprint with no difference, by name",
+    "of": "verb:difference.answer",
+    "given": {
+      "from": 40,
+      "to": 41,
+      "changes": [],
+      "refused": [
+        {
+          "module": "xclip",
+          "why": "its fingerprint changed and its difference is empty"
+        }
+      ]
+    }
+  },
+  {
+    "name": "a composition step asked by the runner",
+    "of": "accept:step",
+    "subject": "mesh.seat.mesh-wants.accept.step",
+    "given": {
+      "pipeline": "main.12.nats",
+      "step": "composition",
+      "module": "nats",
+      "branch": "main",
+      "commit": "0123456789abcdef0123456789abcdef01234567",
+      "revision": 12,
+      "source": 3589,
+      "fingerprint": "fp-0123"
+    }
+  },
+  {
+    "name": "input asks a composition step's input by digest",
+    "of": "verb:input.input",
+    "given": {
+      "digest": "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef"
+    }
+  },
+  {
+    "name": "input answers the exact bytes",
+    "of": "verb:input.answer",
+    "given": {
+      "digest": "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef",
+      "input": "eyJ2IjoxfQ=="
+    }
+  }
+]
diff --git a/contracts/seats/mesh-wants/seat.json b/contracts/seats/mesh-wants/seat.json
index a8834526..e002258b 100644
--- a/contracts/seats/mesh-wants/seat.json
+++ b/contracts/seats/mesh-wants/seat.json
@@ -51,6 +51,160 @@
         "type": "object",
         "description": "what a bus upgrade would do, read only"
       }
+    },
+    {
+      "name": "revision",
+      "description": "The assignment half of the revision view (ADR 0656 \u00a76): one assignment graph revision, named by its own number and naming its inputs, with its entries' digests; the trunk's newest when none is named, or a candidate's for its group and heads. Reads only.",
+      "input": {
+        "type": "object",
+        "properties": {
+          "revision": {
+            "type": "integer",
+            "description": "a kept revision; absent: the newest of trunk, or of the candidate named"
+          },
+          "group": {
+            "type": "string",
+            "description": "a candidate's group"
+          },
+          "heads": {
+            "type": "string",
+            "description": "a candidate's heads"
+          }
+        }
+      },
+      "answer": {
+        "type": "object",
+        "properties": {
+          "revision": {
+            "$ref": "#/defs/AssignmentRevision"
+          }
+        },
+        "required": [
+          "revision"
+        ]
+      },
+      "class": "read"
+    },
+    {
+      "name": "entry",
+      "description": "One entry of an assignment graph revision whole, by its digest or by its node and module in a revision, with the seat rule that gave each edge. Reads only.",
+      "input": {
+        "type": "object",
+        "properties": {
+          "revision": {
+            "type": "integer",
+            "description": "a kept revision; absent: the newest of trunk, or of the candidate named"
+          },
+          "group": {
+            "type": "string",
+            "description": "a candidate's group"
+          },
+          "heads": {
+            "type": "string",
+            "description": "a candidate's heads"
+          },
+          "digest": {
+            "type": "string"
+          },
+          "node": {
+            "type": "string"
+          },
+          "module": {
+            "type": "string"
+          }
+        }
+      },
+      "answer": {
+        "type": "object",
+        "properties": {
+          "digest": {
+            "type": "string"
+          },
+          "entry": {
+            "$ref": "#/defs/AssignmentEntry"
+          }
+        },
+        "required": [
+          "digest",
+          "entry"
+        ]
+      },
+      "class": "read"
+    },
+    {
+      "name": "difference",
+      "description": "A change's graph difference, which is its delivery: two kept revisions compared, or a candidate's newest against trunk's newest, with the changed module versions, the touched nodes and the order as tiers. Reads only.",
+      "input": {
+        "type": "object",
+        "properties": {
+          "from": {
+            "type": "integer"
+          },
+          "to": {
+            "type": "integer"
+          },
+          "group": {
+            "type": "string"
+          },
+          "heads": {
+            "type": "string"
+          }
+        }
+      },
+      "answer": {
+        "$ref": "#/defs/Difference"
+      },
+      "class": "read"
+    },
+    {
+      "name": "input",
+      "class": "read",
+      "callers": [
+        "seat:node-build-go",
+        "seat:node-build-node",
+        "seat:node-build-image"
+      ],
+      "description": "A step's input by its digest, as the assigner keeps it for the composition step it asked a build seat to run (design 47 G section 354).",
+      "input": {
+        "type": "object",
+        "properties": {
+          "digest": {
+            "type": "string",
+            "description": "the input's sha256"
+          }
+        },
+        "required": [
+          "digest"
+        ]
+      },
+      "answer": {
+        "type": "object",
+        "properties": {
+          "digest": {
+            "type": "string",
+            "description": "the input's sha256"
+          },
+          "input": {
+            "type": "string",
+            "description": "the input's exact bytes, base64"
+          }
+        },
+        "required": [
+          "digest",
+          "input"
+        ]
+      }
+    }
+  ],
+  "accepts": [
+    {
+      "name": "step",
+      "body": {
+        "$ref": "#/defs/StepRun"
+      },
+      "callers": [
+        "seat:mesh-pipeline-runner"
+      ]
     }
   ],
   "events": [
@@ -59,6 +213,220 @@
       "body": {
         "type": "object"
       }
+    },
+    {
+      "name": "assignment-revision",
+      "body": {
+        "type": "object",
+        "description": "an assignment graph revision kept",
+        "properties": {
+          "v": {
+            "type": "integer"
+          },
+          "revision": {
+            "type": "integer"
+          },
+          "kind": {
+            "type": "string"
+          },
+          "cause": {
+            "type": "string"
+          },
+          "group": {
+            "type": "string"
+          },
+          "heads": {
+            "type": "string"
+          },
+          "catalogs": {
+            "type": "array",
+            "items": {
+              "$ref": "#/defs/CatalogOf"
+            },
+            "minItems": 1,
+            "description": "the catalog graph revision of each watched branch a placement names, which the entries come from"
+          },
+          "at": {
+            "type": "string",
+            "format": "date-time"
+          }
+        },
+        "required": [
+          "v",
+          "revision",
+          "kind",
+          "catalogs"
+        ]
+      }
+    },
+    {
+      "name": "difference",
+      "body": {
+        "type": "object",
+        "description": "a difference worked out between two revisions",
+        "properties": {
+          "v": {
+            "type": "integer"
+          },
+          "from": {
+            "type": "integer"
+          },
+          "to": {
+            "type": "integer"
+          },
+          "source": {
+            "type": "integer"
+          },
+          "group": {
+            "type": "string"
+          },
+          "heads": {
+            "type": "string"
+          },
+          "changes": {
+            "type": "integer",
+            "description": "how many module versions it changes"
+          },
+          "nodes": {
+            "type": "array",
+            "items": {
+              "type": "string"
+            }
+          }
+        },
+        "required": [
+          "v",
+          "from",
+          "to"
+        ]
+      }
+    },
+    {
+      "name": "wanted",
+      "body": {
+        "type": "object",
+        "description": "an entry written as a want, from a trunk revision only",
+        "properties": {
+          "v": {
+            "type": "integer"
+          },
+          "node": {
+            "type": "string"
+          },
+          "module": {
+            "type": "string"
+          },
+          "fp": {
+            "type": "string"
+          },
+          "revision": {
+            "type": "integer"
+          },
+          "source": {
+            "type": "integer"
+          },
+          "at": {
+            "type": "string",
+            "format": "date-time"
+          }
+        },
+        "required": [
+          "v",
+          "node",
+          "module",
+          "fp",
+          "revision"
+        ]
+      }
+    },
+    {
+      "name": "wait-held",
+      "body": {
+        "$ref": "#/defs/Wait"
+      }
+    },
+    {
+      "name": "wait-ended",
+      "body": {
+        "$ref": "#/defs/Wait"
+      }
+    },
+    {
+      "name": "filling",
+      "body": {
+        "$ref": "#/defs/Fill"
+      }
+    },
+    {
+      "name": "full",
+      "body": {
+        "$ref": "#/defs/Fill"
+      }
+    },
+    {
+      "name": "room",
+      "body": {
+        "$ref": "#/defs/Fill"
+      }
+    },
+    {
+      "name": "step-ended",
+      "subject": "step-ended.<node>",
+      "body": {
+        "$ref": "#/defs/StepEnded"
+      },
+      "keep": {
+        "max-age-days": 90,
+        "max-mib": 32
+      }
+    },
+    {
+      "name": "version-delivered",
+      "keep": {
+        "max-age-days": 90,
+        "max-mib": 64
+      },
+      "body": {
+        "type": "object",
+        "description": "a version delivered to every present machine that places it, and healthy (design 47 G section 376)",
+        "properties": {
+          "v": {
+            "type": "integer"
+          },
+          "module": {
+            "type": "string",
+            "description": "the module"
+          },
+          "version": {
+            "type": "string",
+            "description": "MAJOR.MINOR.PATCH"
+          },
+          "parts": {
+            "type": "object",
+            "additionalProperties": {
+              "type": "string"
+            },
+            "description": "the digest of each of its parts, by artifact reference"
+          },
+          "away": {
+            "type": "array",
+            "items": {
+              "type": "string"
+            },
+            "description": "the machines away when it was said"
+          },
+          "at": {
+            "type": "string",
+            "format": "date-time"
+          }
+        },
+        "required": [
+          "v",
+          "module",
+          "version",
+          "parts"
+        ]
+      }
     }
   ],
   "family": {
@@ -120,6 +488,17 @@
               },
               "self": {
                 "type": "boolean"
+              },
+              "version": {
+                "type": "string",
+                "description": "the module's released version, for people; none for a build of another watched branch (design 47 G section 379)"
+              },
+              "parts": {
+                "type": "object",
+                "additionalProperties": {
+                  "type": "string"
+                },
+                "description": "the digest of each of the module's parts, by artifact reference; the node-engine fetches and checks each part by it (design 47 G section 379)"
               }
             }
           },
@@ -279,6 +658,577 @@
       ],
       "history": 5,
       "description": "composition verdicts of a group's check; the checker reads them"
+    },
+    {
+      "name": "assignment-revisions",
+      "template": "objects",
+      "description": "the assignment graph revisions, each a list of its entries' digests naming its inputs, and each entry once by its digest; a revision is kept while a delivery record pins it or it is current (design 47)",
+      "key-forms": [
+        {
+          "key": "trunk.<revision>",
+          "value": {
+            "$ref": "#/defs/AssignmentRevision"
+          },
+          "description": "a trunk revision"
+        },
+        {
+          "key": "candidate.<group>.<heads>",
+          "value": {
+            "$ref": "#/defs/AssignmentRevision"
+          },
+          "description": "a candidate's newest revision, dropped on heads-replaced"
+        },
+        {
+          "key": "entry.<digest>",
+          "value": {
+            "$ref": "#/defs/AssignmentEntry"
+          },
+          "description": "an entry, written once, removed when no kept revision lists it"
+        }
+      ]
+    },
+    {
+      "name": "inputs",
+      "template": "state",
+      "history": 1,
+      "description": "a step's input, named by its write time and its sha256 (design 47 G section 354)",
+      "key-forms": [
+        {
+          "key": "<time>.<digest>",
+          "value": {
+            "type": "string",
+            "description": "the input's bytes, base64"
+          },
+          "description": "one input"
+        }
+      ]
+    }
+  ],
+  "defs": {
+    "Edge": {
+      "type": "object",
+      "description": "an edge from one module version on a node to another: provisioning, contribution, or an acting part's version that is to act on it in a step (ADR 0656)",
+      "properties": {
+        "kind": {
+          "type": "string",
+          "description": "provisioning, contribution or acting"
+        },
+        "node": {
+          "type": "string"
+        },
+        "module": {
+          "type": "string"
+        },
+        "fp": {
+          "type": "string",
+          "description": "the other end's fingerprint"
+        },
+        "provision": {
+          "type": "string",
+          "description": "for provisioning, the provision"
+        },
+        "seat": {
+          "type": "string",
+          "description": "for contribution, the seat it contributes to; for acting, the seat whose rule gave the edge"
+        },
+        "step": {
+          "type": "string",
+          "description": "for acting, the step: take-in, validate, check, build, compose, grant or place"
+        },
+        "bound": {
+          "type": "string",
+          "description": "for acting, how long the new version may take before it acts"
+        }
+      },
+      "required": [
+        "kind",
+        "node",
+        "module"
+      ]
+    },
+    "AssignmentEntry": {
+      "type": "object",
+      "description": "one module version on a node of an assignment graph revision, stored once by its digest (ADR 0656)",
+      "properties": {
+        "v": {
+          "type": "integer",
+          "description": "the layout version"
+        },
+        "node": {
+          "type": "string"
+        },
+        "module": {
+          "type": "string"
+        },
+        "branch": {
+          "type": "string",
+          "description": "the watched branch its placement names, whose catalog graph the entry comes from (design 47 lines 523-525)"
+        },
+        "fp": {
+          "type": "string",
+          "description": "the fingerprint it is to run"
+        },
+        "catalog": {
+          "type": "string",
+          "description": "the digest of its catalog graph entry"
+        },
+        "edges": {
+          "type": "array",
+          "items": {
+            "$ref": "#/defs/Edge"
+          }
+        }
+      },
+      "required": [
+        "node",
+        "module",
+        "branch",
+        "fp",
+        "catalog"
+      ]
+    },
+    "NodeEntryRef": {
+      "type": "object",
+      "properties": {
+        "node": {
+          "type": "string"
+        },
+        "module": {
+          "type": "string"
+        },
+        "digest": {
+          "type": "string",
+          "description": "the entry's digest, its object's name"
+        }
+      },
+      "required": [
+        "node",
+        "module",
+        "digest"
+      ]
+    },
+    "AssignmentRevision": {
+      "type": "object",
+      "description": "an assignment graph revision: the list of its entries' digests and the inputs it was computed from, so it can be computed again and compared",
+      "properties": {
+        "v": {
+          "type": "integer",
+          "description": "the layout version"
+        },
+        "revision": {
+          "type": "integer",
+          "description": "counted by its holder"
+        },
+        "kind": {
+          "type": "string",
+          "description": "trunk or candidate"
+        },
+        "group": {
+          "type": "string"
+        },
+        "heads": {
+          "type": "string"
+        },
+        "catalogs": {
+          "type": "array",
+          "items": {
+            "$ref": "#/defs/CatalogOf"
+          },
+          "minItems": 1,
+          "description": "the catalog graph revision of each watched branch a placement names, which the entries come from"
+        },
+        "placements": {
+          "type": "string",
+          "description": "the digest of the placements it was computed from"
+        },
+        "capabilities": {
+          "type": "array",
+          "items": {
+            "type": "object",
+            "properties": {
+              "node": {
+                "type": "string"
+              },
+              "digest": {
+                "type": "string",
+                "description": "the digest of the node's capability reading"
+              }
+            },
+            "required": [
+              "node",
+              "digest"
+            ]
+          }
+        },
+        "cause": {
+          "type": "string",
+          "description": "what made it: catalog-revision, placement-changed or capabilities-changed"
+        },
+        "at": {
+          "type": "string",
+          "format": "date-time"
+        },
+        "entries": {
+          "type": "array",
+          "items": {
+            "$ref": "#/defs/NodeEntryRef"
+          }
+        }
+      },
+      "required": [
+        "revision",
+        "kind",
+        "catalogs",
+        "placements",
+        "entries"
+      ]
+    },
+    "Change": {
+      "type": "object",
+      "description": "one module on a node whose version differs between two revisions",
+      "properties": {
+        "node": {
+          "type": "string"
+        },
+        "module": {
+          "type": "string"
+        },
+        "from": {
+          "type": "string",
+          "description": "the fingerprint before; absent when it is new there"
+        },
+        "to": {
+          "type": "string",
+          "description": "the fingerprint after; absent when it goes"
+        },
+        "edges": {
+          "type": "array",
+          "items": {
+            "$ref": "#/defs/Edge"
+          },
+          "description": "the edges that moved"
+        }
+      },
+      "required": [
+        "node",
+        "module"
+      ]
+    },
+    "Difference": {
+      "type": "object",
+      "description": "two assignment graph revisions compared: a change's delivery, with its order read off the edges and no plan stored (ADR 0656)",
+      "properties": {
+        "from": {
+          "type": "integer",
+          "description": "the revision compared from"
+        },
+        "to": {
+          "type": "integer",
+          "description": "the revision compared to"
+        },
+        "group": {
+          "type": "string"
+        },
+        "heads": {
+          "type": "string"
+        },
+        "changes": {
+          "type": "array",
+          "items": {
+            "$ref": "#/defs/Change"
+          }
+        },
+        "nodes": {
+          "type": "array",
+          "items": {
+            "type": "string"
+          },
+          "description": "the nodes it touches"
+        },
+        "tiers": {
+          "type": "array",
+          "items": {
+            "type": "array",
+            "items": {
+              "$ref": "#/defs/NodeEntryRef"
+            }
+          },
+          "description": "the order as a view: each tier the changes whose acting parts acted in the tiers before it (ADR 0603 \u00a76 as ADR 0656 changes it)"
+        },
+        "refused": {
+          "type": "array",
+          "items": {
+            "type": "object",
+            "properties": {
+              "module": {
+                "type": "string"
+              },
+              "why": {
+                "type": "string"
+              }
+            },
+            "required": [
+              "module",
+              "why"
+            ]
+          },
+          "description": "a module whose fingerprint changed while the difference is empty, refused by name"
+        }
+      },
+      "required": [
+        "from",
+        "to",
+        "changes"
+      ]
+    },
+    "Wait": {
+      "type": "object",
+      "description": "a step's wait the assigner holds: placing, wanting or composing until an acting part's new version runs",
+      "properties": {
+        "step": {
+          "type": "string"
+        },
+        "part": {
+          "type": "string",
+          "description": "the acting part waited for"
+        },
+        "version": {
+          "type": "string",
+          "description": "its new version's fingerprint"
+        },
+        "node": {
+          "type": "string"
+        },
+        "module": {
+          "type": "string",
+          "description": "the entry that waits"
+        },
+        "fp": {
+          "type": "string"
+        },
+        "since": {
+          "type": "string",
+          "format": "date-time"
+        },
+        "bound": {
+          "type": "string",
+          "description": "a duration such as 30m"
+        },
+        "how": {
+          "type": "string",
+          "description": "on wait-ended: ran or released"
+        },
+        "by": {
+          "type": "string",
+          "description": "on a release, who released it and why"
+        }
+      },
+      "required": [
+        "step",
+        "part",
+        "version",
+        "module",
+        "since"
+      ]
+    },
+    "Fill": {
+      "type": "object",
+      "description": "a store's fill against its cap",
+      "properties": {
+        "store": {
+          "type": "string",
+          "description": "the kept data, by its name in the holder's manifest"
+        },
+        "bytes": {
+          "type": "integer"
+        },
+        "cap": {
+          "type": "integer",
+          "description": "bytes"
+        },
+        "refused": {
+          "type": "string",
+          "description": "what full refuses"
+        },
+        "at": {
+          "type": "string",
+          "format": "date-time"
+        }
+      },
+      "required": [
+        "store",
+        "bytes",
+        "cap"
+      ]
+    },
+    "StepRun": {
+      "type": "object",
+      "description": "the composition step of one module's pipeline (design 47 *Pipeline steps and the policy*, *The pipeline makes the check*): the assigner composes each machine's declaration at the change's heads with the composer built from them, in the build seat's sandbox, and refuses a change in which two modules own one path",
+      "properties": {
+        "pipeline": {
+          "type": "string",
+          "description": "the runner's pipeline key, <branch>.<revision>.<module>, a branch escaped as a key's name is"
+        },
+        "step": {
+          "type": "string",
+          "enum": [
+            "composition"
+          ]
+        },
+        "module": {
+          "type": "string"
+        },
+        "branch": {
+          "type": "string",
+          "description": "the watched branch, or the branch of a run on request"
+        },
+        "commit": {
+          "type": "string",
+          "description": "the commit the step runs at"
+        },
+        "revision": {
+          "type": "integer",
+          "description": "the catalog graph revision of the branch the pipeline runs for"
+        },
+        "source": {
+          "type": "integer",
+          "description": "the source revision of the watched branch; absent for a run on request"
+        },
+        "fingerprint": {
+          "type": "string",
+          "description": "the module's build-input fingerprint at the commit"
+        },
+        "run": {
+          "type": "string",
+          "description": "the run on request's id: its composition writes no want (ADR 0666 section 18)"
+        },
+        "rerun": {
+          "type": "boolean",
+          "description": "the step is asked again by the runner's rerun"
+        },
+        "by": {
+          "type": "string",
+          "description": "for a rerun, the caller the runtime proved"
+        }
+      },
+      "required": [
+        "pipeline",
+        "step",
+        "module",
+        "branch",
+        "commit",
+        "fingerprint"
+      ]
+    },
+    "StepEnded": {
+      "type": "object",
+      "description": "the composition step's end, said by the assigner on the node it runs on (ADR 0666 sections 7, 21): the runner takes it only from that holder's account, naming the ask, the commit and the fingerprint it was asked at",
+      "properties": {
+        "v": {
+          "type": "integer",
+          "description": "the layout version"
+        },
+        "id": {
+          "type": "string",
+          "description": "the ask's id"
+        },
+        "pipeline": {
+          "type": "string"
+        },
+        "step": {
+          "type": "string",
+          "enum": [
+            "composition"
+          ]
+        },
+        "module": {
+          "type": "string"
+        },
+        "commit": {
+          "type": "string"
+        },
+        "fingerprint": {
+          "type": "string"
+        },
+        "node": {
+          "type": "string",
+          "description": "the node the assigner ran it on, as in the subject"
+        },
+        "outcome": {
+          "type": "string",
+          "enum": [
+            "passed",
+            "failed",
+            "nothing to run",
+            "could not run"
+          ],
+          "description": "never passed for a step that composed nothing"
+        },
+        "said": {
+          "type": "string",
+          "description": "why it failed or could not run: the two modules owning one path, the part not heard"
+        },
+        "warnings": {
+          "type": "array",
+          "items": {
+            "type": "string"
+          },
+          "description": "a node asleep, passed with a warning (ADR 0593 section 9)"
+        },
+        "rerun": {
+          "type": "boolean"
+        },
+        "by": {
+          "type": "string",
+          "description": "for a rerun, the caller the runtime proved"
+        },
+        "started": {
+          "type": "string",
+          "format": "date-time"
+        },
+        "ended": {
+          "type": "string",
+          "format": "date-time"
+        }
+      },
+      "required": [
+        "id",
+        "pipeline",
+        "step",
+        "module",
+        "commit",
+        "fingerprint",
+        "node",
+        "outcome"
+      ]
+    },
+    "CatalogOf": {
+      "type": "object",
+      "description": "one catalog graph revision of a watched branch the revision was computed from (design 47 lines 1416-1418)",
+      "properties": {
+        "branch": {
+          "type": "string",
+          "description": "the watched branch"
+        },
+        "revision": {
+          "type": "integer",
+          "description": "that branch's catalog graph revision"
+        },
+        "source": {
+          "type": "integer",
+          "description": "the source revision of that branch it carries"
+        }
+      },
+      "required": [
+        "branch",
+        "revision"
+      ]
+    }
+  },
+  "acts": [
+    {
+      "step": "place",
+      "on": "every"
     }
   ]
 }