# convert

Convert an existing index's evidence representation in place, between exact, approximate, and hybrid.

```bash
obikmer convert INDEX (--exact-evidence | --approx-evidence BITS | --hybrid-evidence) [OPTIONS]
```

## Arguments

| Argument | Description |
|---|---|
| `INDEX` | Index directory to convert (modified in place) |

## Options

Exactly one of the first three is required:

| Option | Description |
|---|---|
| `--exact-evidence` | Convert to exact evidence (zero false positives) |
| `--approx-evidence BITS` | Convert to approximate (fingerprint-only) evidence; `BITS` = fingerprint bits per slot (b) |
| `--hybrid-evidence` | Convert to hybrid evidence (both exact and approximate bundles kept) |
| `--evidence-bits BITS` | Fingerprint bits per slot (b) — required with `--hybrid-evidence` when the source index is currently exact; rejected otherwise (the source already fixes `b`) |
| `-z, --findere-z Z` | Findere z parameter: number of consecutive stored kmers that must all match to confirm a hit. This does not shorten the indexed kmer length (fixed forever at `index` build time) — it extends the effective match window: on a k=31 index, `z=2` requires 32 consecutive matching bases, not 30 |
| `--fp FP` | Target false-positive rate per z-window (e.g. `0.01`); derives `b` or `z` when one of them isn't given directly |
| `--block-size N` | Block size for exact evidence's on-disk index (unitigs per block). Ignored when converting to pure approximate evidence. Default `1` |

See [`index`](index_command.md#exact-vs-approximate-evidence) for the exact/approximate trade-off and the underlying false-positive model, and [`estimate`](estimate.md) to explore parameters beforehand. The index directory is locked for exclusive access during conversion.