> For the complete documentation index, see [llms.txt](https://docs.syndromics.xyz/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.syndromics.xyz/protocol/idle-capital.md).

# Idle capital

A limit-order book only works if lenders are willing to leave capital available. Capital sitting in a wallet earning nothing is a cost, and lenders will not leave much of it there. Syndromics solves this the way Morpho Optimizer did for Aave and Compound: park the unmatched capital in a pooled market and withdraw it just in time when a match happens.

## How it works

1. A lender sets the `parkIdle` flag on their offers and approves the `IdleCapitalAdapter`.
2. The adapter deposits the lender's USDG into a **whitelisted Morpho Blue USDG vault** on Robinhood Chain. The vault shares are held for the lender's account; Syndromics has an allowance, not custody.
3. The lender's standing offers remain live. The relayer treats vault balance as available capacity.
4. When an offer is matched, `LoanSettlement` calls the adapter to withdraw exactly the fill amount from the vault and forward it to the borrower in the same transaction.
5. When the loan is repaid, proceeds return to the vault automatically if the lender still has `parkIdle` set.

Lenders earn the vault's pool rate while waiting and the peer-to-peer rate once matched.

## Whitelisting

Only vaults approved through the ParamController can be used. The whitelist is a single, well-established USDG vault with a conservative curator. Adding a vault is a timelocked parameter change with a published rationale. See [Parameter governance](/transparency/governance.md).

## Risks the lender takes on

Parking is opt-in because it adds risks that are not part of the core protocol:

* **Vault risk.** The lender is exposed to the Morpho vault's own markets and curator decisions while capital is parked.
* **Withdrawal liquidity.** If the vault is fully utilised at the moment of a match, the just-in-time withdrawal fails and the fill reverts for that slice. The relayer monitors vault liquidity and will not propose a slice it cannot fund.
* **Composability surface.** The adapter is an additional contract in the settlement path. It is small and allowance-based, and it is in scope for every audit.

## Fees

The idle-capital yield share (5% of vault yield) is scheduled on the fee page and is applied once it is switched on through the timelock; until then no fee applies to parking.

## What the adapter never does

* It never moves capital anywhere other than the whitelisted vault or a settlement.
* It never rehypothecates vault shares.
* It cannot be pointed at a new vault without a timelocked, publicly logged change.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.syndromics.xyz/protocol/idle-capital.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.