> ## Documentation Index
> Fetch the complete documentation index at: https://digraphsas-docs-pricing.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Delta, Market, and fallback modes

> Choose between mode=DELTA, mode=MARKET, and mode=ALL on Velora's /v2/quote endpoint: when to pick each, and how fallback responses work.

The `mode` query parameter on [`GET /v2/quote`](/api-reference/market/quote) tells Velora which execution path to consider: `DELTA`, `MARKET`, or `ALL`.

`mode=ALL` is the default for clients that don't want to commit upfront. Velora evaluates both paths server-side, picks the winner, and returns **one** response shape: either a `delta` block or a `market` block, never both. Clients must branch on which block is present, not on the mode they requested.

## Delta vs Market

|                    | Delta intent                                                                                       | Normal swap (Market API)               |
| ------------------ | -------------------------------------------------------------------------------------------------- | -------------------------------------- |
| User signs         | An EIP-712 order (off-chain message)                                                               | A transaction (on-chain tx)            |
| User pays gas      | No                                                                                                 | Yes                                    |
| MEV exposure       | Private solver auction                                                                             | Public mempool, sandwichable           |
| Crosschain         | One signature, multi-chain settlement                                                              | Separate tx per chain                  |
| Price improvements | Solvers compete in an auction to improve the quoted price                                          | Best-effort routing across DEXs        |
| Failure mode       | Revert-protection: failed settlements cost no gas; order expires or is rejected with no funds lost | Tx reverts; gas spent on a failed call |

Pick `mode=DELTA` when:

* The user can wait a few seconds for solver competition (gasless settlement, MEV-protected fills).
* The trade is large enough that solver competition beats AMM routing.
* The wallet has no native gas balance and would otherwise need an approval + ETH, typical of mobile, social, and wallet-onboarding flows.
* The swap is crosschain: one signed Delta order resolves across chains via bridge-aware solvers.

Pick `mode=MARKET` when:

* The user needs synchronous, on-chain settlement (for example, composing with another contract in the same transaction).
* The trade is small and AMM liquidity is the better route.
* Latency matters more than slippage savings.

<Warning>
  **Fallback envelope.** Fallback runs in one direction only, and only under `mode=ALL`: when Delta can't price the trade, the response carries a `market` block plus a `fallbackReason` (`errorType`, `details`) explaining why Delta was skipped. A `mode=DELTA` request never falls back; with no Delta route it fails with a `400` carrying that same `errorType` and `details`. A `mode=MARKET` request never returns a `delta` block, and when Market pricing fails (including crosschain pairs, which Market doesn't serve) you get a `400` with body `{"errorType":"PricingError","details":"Error getting price data"}`. Branch on which block is present and handle the `400` explicitly.
</Warning>