# Volatility-Auction Reopening

`D12-F02-A05` · Matching Engines and Venue Logic → Auctions · archetype `record-transform` · difficulty 5/5 · verification **verified**

Full page: https://docs.thefintechbuilder.com/matching-engines-and-venue-logic/auctions/volatility-auction-reopening/
Agent skill: `npx skills add IslamBaraka90/Fintech-Algorithms-Library` — https://docs.thefintechbuilder.com/guides/agent-skill/

## Install and import

```bash
npm install fintech-algorithms
```

```ts
import { volatilityAuctionReopening } from "fintech-algorithms/matching-engines-and-venue-logic/auctions/volatility-auction-reopening";
```

## Signature

```ts
volatilityAuctionReopening(inputs)
```

Determines the reopening price after a volatility halt, including whether the auction may conclude at all or must be extended. An auction that reopens outside the band simply extends rather than printing.

## Parameters

| Name | Type | Required | Notes |
| --- | --- | --- | --- |
| `inputs` | `ReopeningInput` | yes | Auction orders with the halt reference, the permitted band, and the extension policy. |

## Returns

`{ status, price, extended, band, … }`

The reopening price, or an extension decision with the reason.

## Errors

- When the extension policy is unrecognised — throws

## Complexity

Time `O(orders log orders)`, space `O(prices)`.

## Worked example

Captured by running this function on the input its own test provides. Real output of real code — but not asserted against a published figure.

### Input

`inputs`:

```json
{
  "reference_price": 100,
  "dynamic_reference": 100,
  "dynamic_band_pct": 0.02,
  "static_reference": 98,
  "static_band_pct": 0.05,
  "potential_continuous_price": 103,
  "indicative_auction_price": 101.5,
  "extended_band_multiplier": 2,
  "executable_quantity": 500
}
```

### Call

```ts
volatilityAuctionReopening(inputs)
```

### Returns

object with 17 fields: model, reference_price, potential_continuous_price, dynamic_corridor, static_corridor, dynamic_breach, static_breach, triggered, …

```json
{
  "model": "dual-corridor-volatility-auction-reopening",
  "reference_price": 100,
  "potential_continuous_price": 103,
  "dynamic_corridor": [98, 102],
  "static_corridor": [93.1, 102.9],
  "dynamic_breach": true,
  "static_breach": true,
  "triggered": true,
  "indicative_auction_price": 101.5,
  "executable_quantity": 500,
  "expanded_dynamic_corridor": [96, 104],
  "expanded_static_corridor": [88.2, 107.80000000000001],
  "inside_reopening_corridor": true,
  "reopened": true
}
```

Showing 14 of 17 fields.

## Other exports

`maximumExecutableVolumeAuction`, `minimumImbalanceTieBreak`, `openingCrossPrice`, `closingCrossPrice`, `calculate`. Every module additionally exports `run` as an alias of its primary
function, and a `meta` object carrying its catalog id, domain, family, shape and article URL.

## Verification and provenance

Tier: **verified** (via D).

The worked example below is the figure published in this algorithm's article, replayed and asserted by the test suite on every build. The arithmetic cannot drift without the build failing.

Both tiers guarantee the signature. Full explanation: https://docs.thefintechbuilder.com/guides/verification/

Generated from the docs.json payload shipped inside fintech-algorithms@0.13.1.
The signature and parameter list are checked against the compiled implementation at build time,
so a description that contradicts the code fails the build rather than reaching this file.

## Links

- Article (how it works, step by step): https://thefintechbuilder.com/matching-engines-and-venue-logic/auctions/volatility-auction-reopening/
- Implementation source: https://github.com/IslamBaraka90/Fintech-Algorithms-Library/blob/main/src/matching-engines-and-venue-logic/auctions/volatility-auction-reopening/impl.ts
- Package on npm: https://www.npmjs.com/package/fintech-algorithms
- Domain index for agents: https://docs.thefintechbuilder.com/matching-engines-and-venue-logic/llms.txt