# C902 — Recover whole source-pair families from span and placement

## Question

Does the endpoint-coordinate basis reconstruct all supplied pairs exactly?

## Inputs

```json
{}
```

## Sources

```json
[
  "C892 complete six",
  "C831 Actual/Rounded weighted bridge"
]
```

## Opened utc

2026-09-28T02:54:22.325714+00:00

## Results

```json
{
  "recovery": {
    "path": "model/endpoint_basis_recovery.json",
    "sha256": "db5f0def0e97416526798219789a2f562c5cecb648b744c5c98d3ed0d1fddf39",
    "bytes": 1504
  },
  "weighted_rows": [
    {
      "id": "Actual_weighted",
      "lambda": "4/5",
      "D": 9890,
      "W": 12026,
      "recovered_C": 14004,
      "recovered_R": 4114,
      "source_C": 14004,
      "source_R": 4114
    },
    {
      "id": "Rounded_weighted",
      "lambda": "4/5",
      "D": 9900,
      "W": 12026,
      "recovered_C": 14006,
      "recovered_R": 4106,
      "source_C": 14006,
      "source_R": 4106
    }
  ]
}
```

## Finding

All six macro pairs and both weighted Creation pairs are recovered exactly. The Actual and Rounded weighted coordinates both equal12026, but their different spans9890 and9900 recover different original pairs. A shared coordinate alone does not merge them.

## Reassessment

Compare whole-frame motion with source-fixed anchor changes across the new modules.

## Checks

```json
{
  "all_recovered": true,
  "weighted_equal": true,
  "spans_differ": true
}
```

## Closed utc

2026-09-28T02:54:22.326480+00:00

## Record provenance

Exact record hash: `00cc4f983c89c77c16600c84caed260c23465fa6481502c83b6451e0565a0c31`

Source journal: `Research_Cycles/C0832_C0931/journal.json`