> For the complete documentation index, see [llms.txt](https://docs.paragon.trade/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.paragon.trade/markets/equities/off-hours-and-fallback.md).

# Off Hours & Fallback

Equity perpetuals trade on Hyperliquid around the clock, but their external price feeds only run during covered [sessions](/markets/equities/external-pricing.md). When the underlying market is closed — overnight gaps, weekends, and holidays — Paragon switches to an internal pricing mechanism, then snaps back to the external feed once it returns.

With no live feed to track, the oracle steps forward from its last value by a fraction of the order book's **impact price difference (IPD)** — a read on where resting liquidity sits relative to the current oracle price `S`:

$$
\text{IPD} = \max(P\_{\text{impactBid}} - S,\ 0) - \max(S - P\_{\text{impactAsk}},\ 0)
$$

`P_impactBid` and `P_impactAsk` are the average fill prices for a fixed impact notional swept across the bid and ask sides of the book.

The oracle advances as a continuous-time exponentially weighted moving average with time constant **τ = 30 minutes**, which keeps it stable across irregular updates and halts:

$$
S\_t = \beta\_t, S\_{t^-} + (1 - \beta\_t), x\_t, \qquad \beta\_t = \exp!\left(-\frac{\Delta t^{\*}}{\tau}\right), \qquad x\_t = S\_{t^-} + \text{IPD}\_t
$$

where $$\Delta t = t - t\_{\text{prev}}$$, $$\Delta t^{*} = \min(\Delta t,\ c\tau)$$, and $$c = 0.1$$. Capping $$\Delta t^{*}$$ holds any single step to at most $$1 - e^{-0.1} \approx 9.5%$$ of the move toward $$x\_t$$, so long gaps between updates can't jolt the oracle.

When coverage drops, the mechanism seeds from the last external price; when it resumes, the oracle reverts to the external value on the next tick.

## Bounds

Off-hours, the mark is hard-capped to the market's [Bounds](/trading/bounds-and-anchors.md), measured from the last on-hours price. Per-market values are listed in the [Contract Specifications](/resources/specifications.md#market-specifications).


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