Parameters

Every number in Fyber is one of three things (Rule R-12.7.1, principle P7):

• Fixed — an immutable or constant set in the deployment transaction, validated by a constructor assertion, and never changed afterwards by anybody.
• Formula — computed on-chain at every read from protocol state, time, or an external reference.
• Dated tier — a frozen table indexed by elapsed time, sometimes gated by an on-chain condition.

There is a fourth category that does not exist: a parameter somebody can set. forge inspect storage-layout is run at deployment to assert that no storage variable holds a risk constant (Rule R-16.5.1).

Values marked [F] were estimated rather than measured when the specification was frozen and are recalibrated before deployment from 28 days of feed logs and 30 days of depth measurements. After deployment there is no correction: freezing the specification is freezing the constants (Rule R-16.5.2).

Tier assignment: Tier 1 is SPY, QQQ, the third ETF and mega caps; Tier 2 is GLD and IWM. Tier 3 does not exist in version 1.

Values marked [P] are the founder working values of 7 September 2026 and are pending confirmation by specification v0.5. They are printed here so the site states one set of numbers, and they are the only figures on this page that a constructor assertion does not yet validate.

Headline values

Protocol-wide: minimum debt 100 fyUSD, mint fee 7 days of interest, PSM entry fee 0.05%, PSM exit fee 0.20%, PSM cap 30%, redemption fee floor 0.5%, Stability Pool share of interest 90% in regime 1, Closer expiry 365 days.

Per branch, by tier

Global constants

Dated tiers

Activation criteria for the dormant branches

Date (day 90 for the third ETF and GLD, day 150 for IWM); d2P25 at least 1.0 M USD for Tier 1 and 500 k for Tier 2; depth buffer at least 84 of 168 slots; at least two reference pools at 250 k or more; on-chain market capitalisation at least 8 M (A) or 4 M (B); the adapter deployed at least 90 days with no degraded episode longer than 24 hours; regime LIVE with no pending corporate action; and, for Tier 2 only, the sum of active Stability Pools at least 40% of the fyUSD supply. Full detail: Branches and versions.

Constructor assertions

A configuration that violates any of these cannot be deployed, and a configuration that is wrong cannot be corrected (Rule R-12.7.1):

MCR                       ≥ 110%
CR_mint                   > MCR / (1 − BAND_BASE)    // the band alone never liquidates a fresh position
CR_mint / (1 − H_MAX)     ≤ 250% (tier 1), ≤ 310% (tier 2)
MCR × (1 − BAND_BASE)     > 1 + B_BASE + 300 bps     // a sale at the bottom of the band is still solvent
U_MAX                     ≥ BAND_BASE                // "band full" and "confidence zero" coincide
B_MIN                     < B_BASE ≤ 15%
DROP_TRIGGER              ≤ BAND_BASE / 2
PERSIST_SINGLE_H          ≥ 2 h
CONFIRM_LIVE < SESSION_EDGE_S < FLAG_TTL_LIVE ≤ CONFIRM_DRIFT < FLAG_TTL_DRIFT
LIQ_TX_CAP_DRIFT ≤ LIQ_TX_CAP_LIVE ≤ BUCKET_DRIFT_HOURLY
ETHUSD_AVG_MAX_ROUNDS     ≥ 2
CLOSER_LIQ_FREEZE_GAP     ≥ 24 h
sequencerFeed == 0, or latestRoundData() is readable
floorFixed                ≥ 0.5%
rateMax                   ≤ 100%
k × rMax                  ≤ 10%
treasury share            ≤ 20% in every regime
capShare                  ≤ 50% outside Sunset
τ_live regular ≤ extended ≤ overnight < HEARTBEAT_MISS
CLOSED_MAX_H              > 80 h
W_REGULAR ≥ W_EXTENDED ≥ W_OVERNIGHT ≥ W_CLOSED > 0
C_abs tiers increasing
at least one price pool per branch, each v2 or v3
EXPIRES_AT                == DEPLOY_TS + 365 days
all cross-addresses non-zero and mutually consistent
no two branches share a token
fyUSD minters             == exactly the five branches and the PSM

Two further assertions of specification v0.4, CR_mint ≥ MCR + 20 pts and SCR ∈ [100%, MCR − 20 pts], are omitted above because the ratios marked [P] do not satisfy them. They return once v0.5 settles the thresholds.

What is no longer here

MCR_closed, CR_withdraw_closed, HardFloor, the fixed out-of-session band, graceOpen, the Monday grace, the sweep bonus adjustment, the relief-valve parameters and the long out-of-session staleness thresholds went with the closed-market design. Nothing replaced them one for one: the single MCR, the haircut, the recognition band and the open sale together do the work all nine used to do.

Version 0.4 removed four more. BAND_RATE and BAND_MAX, because the band no longer widens. RETURN_RAMP, replaced by SESSION_EDGE_S, which stops the Stability Pool executing for ten minutes instead of interpolating a price nobody trades at. And the ETH/USD sequencer substitute, whose 7 200-second threshold would have blinded every branch at once on a quiet night. Confirmation of a fall by the basket of other equity branches went with them.

Last reviewed: 2026-09-07 · Spec v0.4