Troubleshooting

Who this is for: Developers and integrators debugging quote/swap failures, SDK or RPC issues, deployment/verification problems, or rebalancing with Mento V3. For end-user issues (getting stables, swap failed in app), see User troubleshooting.

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Quick reference: why did my swap or quote revert?

The pool (and Router) can revert for these reasons. Check your revert message or transaction trace first:

Revert / cause	Meaning	What to do
ReserveValueDecreased	Swap would decrease pool value at oracle after fees (value-protection check failed).	Usually means quote was stale or fee/rate changed; re-quote and retry with a fresh amount.
TradingSuspended	Circuit breaker has tripped for this feed; trading is halted.	Wait until breakers are reset; check BreakerBox / OracleAdapter for the feed’s trading mode.
NoRecentRate	Oracle report is older than the configured expiry (stale).	Wait for a new oracle update or check SortedOracles / Chainlink relay for the feed.
FXMarketClosed	FX market-hours breaker says the market is closed for this feed.	Trade during configured market hours, or use a pool that does not gate on market hours.
TradingLimitsV2 (limit exceeded)	Net flow for a token in the 5-minute or 1-day window would exceed the pool’s limit.	Use a smaller amount, wait for the rolling window to expire, or try again later.
Insufficient liquidity (Router)	Router/pool has no liquidity for the requested output.	Check pool reserves and that the pool exists for the pair.
Expired (Router)	Transaction submitted after the deadline passed.	Increase deadline (e.g. block.timestamp + 300) and resubmit.
Insufficient output (Router)	Output was less than amountOutMin (slippage).	Re-quote and raise amountOutMin slightly or accept a lower minimum.

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Swap and quote

Swap reverted: value protection, limits, or oracle

Every swap is checked in this order:

1. Oracle rate — The pool calls oracleAdapter.getFXRateIfValid(referenceRateFeedID). If the adapter reverts, the swap reverts with TradingSuspended, NoRecentRate, or FXMarketClosed. So: ensure the feed is recent, trading is allowed, and (if applicable) FX market is open.

2. Value protection — After the swap, the pool’s reserve value at the oracle must not decrease (after crediting fees). If it would, the pool reverts with ReserveValueDecreased. This can happen if the quote was computed with an older rate or different fee.

3. TradingLimitsV2 — After the swap, per-token net flow in the 5-minute and 1-day windows must stay within the pool’s configured limits. If a limit would be exceeded, the swap reverts.

Practical steps: Re-fetch a quote immediately before sending the transaction. Use the same pool and rate feed the pool uses. If the revert is ReserveValueDecreased, your executed rate/fee differed from the one used for the quote. If the revert is from TradingLimitsV2, reduce size or wait. See TradingLimitsV2 and BreakerBox.

Quote doesn’t match execution

Quotes are valid only at the current block’s oracle rate and fee. If the user sends the tx later, the rate may have changed or the oracle may have become invalid. Always re-fetch the quote right before building the transaction, and use a small slippage tolerance (e.g. amountOutMin = quote * 99 / 100) if needed.

getAmountOut or Router getAmountsOut fails

• Invalid pair or pool: Ensure the pool exists for the token pair (use FPMMFactory getPool(token0, token1) or Router poolFor). Tokens must be sorted by address (token0 < token1).

• Oracle invalid: getAmountOut calls the same getFXRateIfValid as the swap. If the oracle is suspended, stale, or market closed, the call reverts. Use adapter.getRate(rateFeedID) (no revert) to inspect tradingMode, isRecent, and isFXMarketOpen before quoting.

• Wrong rate feed ID: The pool’s referenceRateFeedID must match a feed that the OracleAdapter and BreakerBox know. Check OracleAdapter and Addresses for the correct adapter and feed setup per chain.

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Router vs direct pool calls

• Router: Use the Router for exact-input swaps and for mint/burn so it handles transfers and pool calls. Approve the Router for the input token(s). The Router reverts if the pool reverts (oracle, limits, value protection) or if output < amountOutMin or deadline has passed.

• Direct pool: The pool’s swap(amount0Out, amount1Out, to, data) is output-specified and requires the caller to supply the input tokens (e.g. via IFPMMCallee hook). Prefer the Router for simple flows. See FPMM and Router.

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Mint and burn (liquidity)

Symptom	Cause	Fix
Mint reverted	Wrong ratio or approval	You must transfer both tokens to the pool in the current reserve ratio. Use pool.quoteMint(amount0, amount1) or Router quoteAddLiquidity to get the required amounts. Approve the pool (or Router) for both tokens.
Burn reverted	Wrong LP amount or approval	Transfer the LP tokens to the pool first, then call burn(to). Approve the pool (or Router) for the LP tokens. Ensure you are not burning more than the pool’s total supply.
“Insufficient liquidity” on mint	First mint must meet minimum	The first mint uses sqrt(amount0*amount1) - MINIMUM_LIQUIDITY; ensure amounts are large enough.

See FPMM — Mint and burn and Router for exact signatures.

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Rebalancing (keepers / strategies)

If you are calling rebalance on a pool or a liquidity strategy:

Revert	Meaning	Fix
NotLiquidityStrategy	Caller is not allowlisted on the pool.	Only addresses set via setLiquidityStrategy(addr, true) can call rebalance.
PriceDifferenceTooSmall	Reserve price deviation from oracle is below the pool’s threshold.	Check getRebalancingState(); only rebalance when priceDifference >= rebalanceThreshold.
PriceDifferenceNotImproved / PriceDifferenceMovedInWrongDirection / PriceDifferenceMovedTooFarFromThresholds	Rebalance did not meet post-rebalance checks (direction preserved, no overshoot).	Strategy must return the other token in the right amount so the new deviation is still ≥ threshold and in the same direction.
InsufficientAmount0In / InsufficientAmount1In	Strategy did not send back enough of the other token (minimum repayment / incentive cap).	Strategy must return at least the minimum required by the pool’s rebalance incentive cap.

Use pool.getRebalancingState() to decide if and how much to rebalance. See Liquidity strategies and FPMM — Rebalance.

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Oracle and circuit breakers

• TradingSuspended: The BreakerBox has set the feed’s trading mode to suspended (e.g. MedianDeltaBreaker or ValueDeltaBreaker tripped). No swaps or quotes using that feed succeed until the breaker is reset and the cooldown has passed.

• NoRecentRate: The median report timestamp for the rate feed is older than reportExpiry. Relayers must submit a fresh price; check SortedOracles or the Chainlink relayer for that feed.

• FXMarketClosed: The pool uses getFXRateIfValid, which checks FX market hours. Use a feed without market-hours gating or wait until the market is open.

To inspect without reverting: call oracleAdapter.getRate(rateFeedID) and check tradingMode, isRecent, isFXMarketOpen. See OracleAdapter and BreakerBox.

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SDK and integration

Symptom	Cause	Fix
SDK returns wrong network or pairs	Using V2 Broker instead of V3 FPMM	V3 uses FPMM pools and the Router for quotes and swaps, not the legacy Broker. Point the SDK at the V3 factory, Router, and pool addresses; see Mento SDK and Deployments.
Wrong or stale quote	Caching or wrong pool	Ensure you are querying the correct pool for the token pair and re-fetch quotes before sending a transaction.
RPC or provider errors	Wrong RPC URL or chain	Use a supported chain (e.g. Celo, Monad) and a valid RPC endpoint. See Deployments and Addresses.

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Contracts and deployments

Symptom	Cause	Fix
Wrong pool or router address	Outdated or wrong chain	Use Deployments → Addresses for the chain you are on; verify factory, Router, and pool on a block explorer.
Pool not found for pair	Pool not deployed or wrong token order	Factory returns getPool(token0, token1) with tokens sorted by address. Ensure the pool is deployed for that pair on the correct factory.
Verification failed on explorer	Source or constructor args	Follow Verification for the correct compiler settings and constructor arguments.

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More

• Integration — How to integrate stables and oracles.

• Smart contracts — FPMM, Router, OracleAdapter, TradingLimitsV2, BreakerBox.

• Deployments — Addresses, verification, parameters.

• User troubleshooting — End-user issues (getting stables, swap in app, CDP).