Previous value: -"What this line costs per unit, in the calculation's currency."New value: +"What this line costs per unit, in the calculation's currency, as shown: a tier adds up exactly to the line above it."

Added value: +{
+  "anyOf": [
+    {
+      "type": "number"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "This line's amount before it was rounded for display; a per-lot figure is it times the lot, rounded once."
+}

Added value: +"uuid"

Added value: +{
+  "default": "summary",
+  "description": "'summary' (the default): the headline before and after, the change per cost category and only the cost lines that moved. 'full': the whole previewed cost sheet in cost_lines instead.",
+  "enum": [
+    "summary",
+    "full"
+  ],
+  "type": "string"
+}

Added value: +{
+  "description": "One cost line whose amount the what-if moved.",
+  "properties": {
+    "after": {
+      "anyOf": [
+        {
+          "type": "number"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "default": null,
+      "description": "Amount per part under the what-if; null when the line is gone."
+    },
+    "before": {
+      "anyOf": [
+        {
+          "type": "number"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "default": null,
+      "description": "Amount per part in the priced calculation; null when the line is new."
+    },
+    "delta": {
+      "default": 0,
+      "description": "after minus before.",
+      "type": "number"
+    },
+    "label_id": {
+      "anyOf": [
+        {
+          "type": "string"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "default": null,
+      "description": "Message id for this line's name."
+    },
+    "label_params": {
+      "additionalProperties": true,
+      "description": "Values the label refers to, e.g. the machine name.",
+      "type": "object"
+    },
+    "path": {
+      "description": "Bucket slugs from the top-level category down to this line, so the line can be found in get_cost_breakdown's tree.",
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    }
+  },
+  "type": "object"
+}

Added value: +{
+  "description": "One side of a what-if's headline, in the calculation's currency.",
+  "properties": {
+    "lot_size": {
+      "anyOf": [
+        {
+          "type": "integer"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "default": null,
+      "description": "Lot size this side is priced at."
+    },
+    "offer_price": {
+      "anyOf": [
+        {
+          "type": "number"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "default": null,
+      "description": "Offer price per part: every top-level cost line, the surcharges and mark-up included."
+    },
+    "total_cost": {
+      "anyOf": [
+        {
+          "type": "number"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "default": null,
+      "description": "unit_cost times lot_size."
+    },
+    "unit_cost": {
+      "anyOf": [
+        {
+          "type": "number"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "default": null,
+      "description": "Manufacturing cost per part, on the basis of the calculation's own unit cost."
+    }
+  },
+  "type": "object"
+}

Added value: +{
+  "anyOf": [
+    {
+      "type": "integer"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "How many lines sit beneath this one that `max_depth` left out: ask again with a larger `max_depth`, or null, to see them. Absent when nothing beneath this line was left out."
+}

Added value: +{
+  "anyOf": [
+    {
+      "$ref": "#/$defs/CostPreviewHeadline"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "detail='summary' only: the headline under the what-if."
+}

Added value: +{
+  "anyOf": [
+    {
+      "$ref": "#/$defs/CostPreviewHeadline"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "detail='summary' only: the priced calculation's headline."
+}

Previous value: -"The previewed cost sheet as a tree, same shape as get_cost_breakdown's."New value: +"The previewed cost sheet as a tree, same shape as get_cost_breakdown's. Empty under detail='summary'."

Added value: +{
+  "anyOf": [
+    {
+      "items": {
+        "$ref": "#/$defs/CostLineMove"
+      },
+      "type": "array"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "detail='summary' only: every cost line, at any depth, whose amount moved, each with its path in the tree. Top-level lines only when the calculation recorded no itemised sheet to compare."
+}

Added value: +"The factors to move, as {factor_key: new_value}. The keys are the ones get_cost_breakdown shows on each cost line. Omit to re-price at another lot_size only."

Added value: +"Id of a calculation, as upload_and_quote, quote_part or list_calculations return it."

Added value: +"Lot size to price the what-if at. Omit to keep the calculation's own lot size."

Previous value: -"Adjustable factors that move this line, by name — the keys get_cost_factors publishes and preview_cost accepts. A factor is listed only where this line carries what is needed to work it out, so an empty list does not mean the line is fixed."New value: +"Adjustable factors that move this line, by name: the keys preview_cost accepts. A factor is listed only where this line carries what is needed to work it out, so an empty list does not mean the line is fixed."