Peg Stability Module (PSM)

Overview

The Peg Stability Module (PSM) is a foundational stability mechanism in Sky Protocol (formerly MakerDAO) that enables users to swap stablecoins like USDC directly for USDS or DAI at a fixed 1:1 exchange rate, maintaining the critical dollar peg for Sky's decentralized stablecoins. ^[1] Unlike traditional vault-based collateralization where users borrow against overcollateralized assets, the PSM allows direct instantaneous swaps with minimal or zero fees, creating powerful arbitrage opportunities that automatically correct any deviation from the $1 peg. ^[2]

The PSM represents one of the most significant innovations in DeFi stablecoin design, transforming how decentralized protocols maintain price stability. ^[3] Launched in December 2020 following strong governance approval in November 2020, the PSM has evolved through multiple iterations, culminating in the gas-optimized LitePSM deployed in 2024. ^[4] As of January 2026, the PSM manages billions in stablecoin liquidity and serves as a core component of Sky Protocol's Actively Stabilizing Collateral (ASC) framework, directly influencing monetary policy through the Base Rate adjustment mechanism. ^[5]

The module's importance extends beyond simple peg maintenance. The PSM functions as the primary interface between Sky Protocol and centralized stablecoin liquidity, enabling deep integration with DeFi protocols and providing critical infrastructure for Prime Agents in the Sky ecosystem. ^[6] However, this central role has also generated ongoing debates about centralization risk, USDC concentration, and the protocol's exposure to external stablecoin issuers like Circle. ^[7]

How the PSM Works

The PSM operates through a deceptively simple mechanism: users deposit one stablecoin and receive another at a fixed 1:1 rate, with optional fees. This directness creates powerful arbitrage incentives that keep USDS and DAI tightly pegged to $1, while the underlying smart contract architecture manages debt accounting, buffer systems, and dynamic debt ceilings to scale with demand.

Core Mechanics

A Peg Stability Module operates similarly to a vault with a zero stability fee and a 100% liquidation ratio that can only be accessed through specialized smart contracts containing swap functions. ^[8] Unlike regular vaults where users retain ownership of their collateral and take on debt, PSM users permanently swap their stablecoin assets directly for USDS or DAI at a fixed exchange rate. ^[9]

The fundamental architecture consists of several interconnected components:

Gem Join Adapter — Manages the incoming stablecoin deposits (the "gem" collateral type like USDC)
PSM Core Contract — Handles the swap logic, fee calculations, and debt accounting
Pocket/Buffer System — Maintains pre-minted USDS/DAI for immediate swap fulfillment
Debt Ceiling Instant Access Module (DC-IAM) — Dynamically manages debt ceiling parameters

When a user deposits 100 USDC into the PSM, the module mints 100 USDS (minus any applicable fees) and transfers it to the user, while the USDC remains pooled in the PSM vault at 100% collateralization. ^[10] Conversely, when users swap USDS back to USDC, the USDS is burned and USDC is released from the pool. ^[11] This bidirectional mechanism creates the foundation for automated peg stabilization through market arbitrage.

Arbitrage Mechanism for Peg Stability

The PSM's effectiveness stems from its creation of risk-free arbitrage opportunities that automatically correct price deviations from the $1 peg. ^[12] The mechanism works differently depending on the direction of the depeg:

When USDS trades above $1.00

If market demand pushes USDS price above $1, arbitrageurs can deposit 1 USDC into the PSM to mint 1 USDS (minus tin fee) and immediately sell that USDS on the open market for more than $1. ^[13] This profitable trade increases USDS supply in the market, applying downward price pressure until USDS returns to $1. The arbitrageur captures the spread between $1 and the market price, minus any PSM fees.

When USDS trades below $1.00

Conversely, if USDS falls below $1, arbitrageurs can purchase discounted USDS on the open market, deposit it into the PSM, and receive 1 USDC (minus tout fee) per USDS. ^[14] This profitable trade reduces USDS supply from the market, applying upward price pressure. The arbitrageur profits from the difference between the purchase price and the $1 redemption value.

This direct swap mechanism acts as a highly efficient arbitrage tool with essentially zero slippage at any scale within the debt ceiling limits, enabling instant peg correction. ^[15] Unlike conventional DAI generation via overcollateralized vaults which charges stability fees and requires liquidation risk management, the PSM provides frictionless entry and exit with minimal fees, making arbitrage highly attractive at even small price deviations. ^[16]

Fee Structure: Tin and Tout

The PSM employs two fee parameters that governance can adjust to optimize protocol revenue and peg stability:

tin (Fee In) — A percentage fee applied when trading collateral stablecoins into the PSM in exchange for USDS or DAI ^[17]
tout (Fee Out) — A percentage fee applied when trading USDS or DAI into the PSM in exchange for collateral stablecoins ^[18]

These fees create an asymmetric arbitrage band around the $1 peg. For example, with tin at 0.1% and tout at 0.1%, arbitrage becomes profitable when USDS trades above $1.001 or below $0.999, creating a 20 basis point band where the peg can float without triggering arbitrage. ^[19] Governance can widen this band by increasing fees (generating more revenue but allowing larger price deviations) or narrow it by decreasing fees (tightening the peg but reducing protocol income).

As of January 2026, the LitePSM parameters are set at tin: 0% and tout: 0%, meaning the PSM currently charges no fees for swaps, enabling arbitrage at any price deviation and maximizing peg stability. ^[20] This zero-fee configuration reflects Sky Protocol's prioritization of stablecoin stability over PSM fee revenue generation.

Debt Ceiling and Buffer Management

The PSM employs sophisticated debt management through the Debt Ceiling Instant Access Module (DC-IAM) to balance liquidity provision with risk exposure:

DC-IAM line — The maximum amount of debt the LitePSM can accrue (currently 10,000,000,000 USDS) ^[21]
DC-IAM gap — The target gap between debt usage and the debt ceiling (currently 400,000,000 USDS) ^[22]
DC-IAM ttl — The time interval for debt ceiling adjustments (currently 43,200 seconds or 12 hours) ^[23]
buf (buffer) — A fixed-sized amount of pre-minted USDS maintained for immediate swap fulfillment (currently 400,000,000 USDS) ^[24]

The buffer system represents a key innovation in the LitePSM architecture. Rather than minting USDS on-demand during each swap (which is gas-intensive), the LitePSM maintains a pool of pre-minted USDS equal to the buf parameter. ^[25] Background keeper operations replenish this buffer by minting additional USDS when depleted or burning excess USDS when the buffer grows too large. ^[26] This design significantly reduces gas costs for end users while maintaining the same economic functionality as the original PSM.

History and Evolution

The PSM's development was driven by the persistent inability of traditional stability mechanisms to keep DAI at its $1 peg during the DeFi boom of 2020. What began as an emergency response to the peg crisis that followed Black Thursday in March 2020 evolved into a permanent protocol fixture, surviving its own existential stress test during the SVB collapse and ultimately being reimplemented as the gas-optimized LitePSM in 2024.

Launch: November-December 2020

The Peg Stability Module emerged from a critical need in late 2020 when DAI demand consistently outstripped supply, causing DAI to trade persistently above $1. ^[27] Traditional stability mechanisms like stability fee adjustments proved too slow to respond to rapid market dynamics, and the protocol needed a faster, more direct intervention tool.

Sam MacPherson authored MIP29: Peg Stability Module on November 9, 2020, proposing a smart contract implementation to address the peg stability challenge. ^[28] The proposal outlined a special vault type with 100% collateralization ratio, zero stability fees, and permissioned gemJoin adapters that would enable direct stablecoin swaps rather than debt-based borrowing. ^[29]

On November 23, 2020, MakerDAO governance voted on a poll to accelerate the PSM launch, with the community strongly supporting rapid deployment. ^[30] The proposal called for Domain Teams to prioritize PSM development, targeting a tentative launch date of December 18, 2020, beginning with USDC support and potentially expanding to other stablecoins. ^[31]

The PSM launched on December 24, 2020, representing one of the fastest major protocol additions in MakerDAO history. ^[32] Initial parameters set tin at 1%, with plans to reduce it linearly to 0.1% over 7 days to maximize early fee collection while testing the system. ^[33] The launch immediately demonstrated effectiveness, with the DAI peg stabilizing quickly as arbitrageurs utilized the new mechanism.

MIP29 was formally ratified on January 30, 2021, cementing the PSM as a permanent fixture of the protocol architecture. ^[34] The module's success in maintaining the DAI peg validated the innovative approach of direct stablecoin swaps as a stability mechanism.

Early Parameter Evolution: 2021-2022

Following successful deployment, governance began expanding PSM support beyond USDC to create redundancy and diversify stablecoin exposure:

August 2021 — PSM-PAX-A (Paxos Standard) onboarded with initial debt ceiling parameters ^[35]
February 2022 — PSM-GUSD-A (Gemini Dollar) debt ceiling increased from 10 million to 60 million DAI ^[36]
November 2021 — Critical policy shift: tin fees reduced to 0% for PSM-USDC-A and PSM-USDP-A, eliminating fees on deposits and significantly tightening the arbitrage band ^[37]

The removal of deposit fees represented a strategic decision to prioritize peg stability over fee revenue. With tin at 0%, arbitrageurs could profitably correct any upward deviation from $1, no matter how small, ensuring DAI remained tightly pegged during periods of high demand. This policy remained largely consistent through 2022 as the PSM grew to become the dominant collateral type in the protocol.

By mid-2022, PSM holdings had grown dramatically, with USDC in the PSM representing over 50% of DAI's backing collateral. ^[38] This concentration prompted increasing governance discussion about centralization risks and the protocol's exposure to Circle's USDC.

March 2023 Crisis: USDC Depeg and Emergency Response

The PSM faced its most severe stress test in March 2023 during the Silicon Valley Bank collapse and subsequent USDC depeg event. On March 10, 2023, California regulators closed Silicon Valley Bank following a bank run that had accelerated the previous day. ^[39] Circle, the issuer of USDC, revealed it had approximately $3.3 billion (roughly 8% of its $40 billion reserves) tied up in the failed bank. ^[40]

Over the weekend of March 11-12, 2023, USDC depegged dramatically, falling to as low as $0.87-$0.88 as markets feared Circle might not recover its SVB deposits. ^[41] The PSM, designed to maintain the peg, ironically became a transmission mechanism for contagion. DAI's PSMs were rapidly drained of liquidity as users rushed to exit USDC exposure, withdrawing over 400 million USDP from the PSM-USDP-A module (representing over half of USDP's total outstanding supply) and causing USDP to depeg to approximately $0.91. ^[42]

MakerDAO governance convened emergency sessions and passed multiple urgent executive votes:

March 11, 2023 — Emergency parameter changes to reduce PSM exposure ^[43]
March 14, 2023 — Further emergency PSM parameter adjustments ^[44]
March 20, 2023 — PSM parameter normalization after crisis resolution ^[45]

Key emergency actions included reducing PSM-USDC-A gap from higher levels to 250 million DAI and temporarily increasing tin to 1% to discourage further USDC deposits while the situation stabilized. ^[46]

The crisis resolved on March 12, 2023, when the FDIC, Treasury Department, and Federal Reserve jointly announced that all SVB depositors would be fully protected, enabling Circle to access its funds and USDC to begin repegging by March 13. ^[47] The incident exposed fundamental risks in the PSM design, particularly the protocol's vulnerability to centralized stablecoin issuer problems and the PSM's role in amplifying rather than dampening external shocks.

Post-Crisis Adjustments: 2023-2024

Following the March 2023 crisis, governance undertook systematic efforts to reduce USDC concentration and diversify collateral:

May 2023 — PSM-USDP-A debt ceiling reduced from 500 million DAI to 0 DAI ^[48]
June 2023 — PSM-GUSD-A debt ceiling decreased from 500 million to 110 million DAI ^[49]
November 2023 — PSM-GUSD-A debt ceiling set to zero and removed from AutoLine ^[50]
January 2024 — PSM-PAX-A debt ceiling set to zero and removed from AutoLine ^[51]

By May 2023, USDC backing DAI had decreased from over 50% in August 2022 to approximately 23.6%, representing a significant diversification away from PSM-USDC dominance. ^[52] However, the lion's share of DAI's backing remained centralized assets, with approximately 55% in stablecoins and 25% in Real World Assets (primarily U.S. Treasury bills). ^[53]

LitePSM Migration: July-October 2024

The most significant technical evolution came with the LitePSM upgrade, a complete reimplementation focused on gas efficiency and integration with the Endgame architecture. The migration occurred in three carefully orchestrated phases:

Phase 1: July 25, 2024

Phase 1 initiated the test period, onboarding the new LitePSM contracts while maintaining the legacy PSM-USDC-A in parallel. ^[54] Key technical actions included:

Onboarding MCD_LITE_PSM_USDC_A at 0xf6e72Db5454dd049d0788e411b06CfAF16853042
Onboarding MCD_LITE_PSM_USDC_A_POCKET at 0x37305B1cD40574E4C5Ce33f8e8306Be057fD7341
Setting buf (buffer) to 20 million DAI for initial testing
Migrating 20 million USDC from PSM-USDC-A to LITE-PSM-USDC-A
Activating LITE_PSM_MOM GSM Delay Exception for emergency response capability
Decreasing GSM Pause Delay from 30 hours to 16 hours
Increasing ESM Minimum Threshold from 150,000 MKR to 300,000 MKR ^[55]

The reduced GSM delay and increased ESM threshold reflected heightened security consciousness following the March 2023 crisis, enabling faster emergency response while requiring greater consensus for emergency shutdown.

Phase 2: August 22, 2024

Phase 2 represented the major migration, moving the bulk of liquidity from the legacy PSM to LitePSM. The buf parameter increased significantly to support production-scale usage, and keeper networks began actively managing the buffer to optimize gas costs for users. ^[56]

Phase 3: October 4, 2024

Phase 3 completed the migration, with final parameter adjustments and the return to zero-fee operations (tin and tout both reduced from 0.01% to 0%). ^[57] The legacy PSM-USDC-A was effectively deprecated, with all new swap activity routing through the LitePSM architecture.

The completed LitePSM achieved its primary design goals: significant gas cost reductions for user swaps by replacing on-chain mint/burn operations with simple ERC-20 transfers from a pre-minted buffer, compatibility with Endgame's authorized party requirements (enabling fee-free swaps for Prime Agents), and maintained economic equivalence with the original PSM design. ^[58]

September 2024: Sky Protocol Launch Integration

The LitePSM upgrade coincided with MakerDAO's rebrand to Sky Protocol and the launch of USDS as an upgraded stablecoin alongside DAI. In September 2024, Sky Protocol deployed the LitePSMWrapper-USDS-USDC, enabling both USDS and DAI holders to swap with USDC through a unified contract. ^[59]

The wrapper routes all USDS-to-USDC and USDC-to-USDS swaps through the existing LitePSM-DAI-USDC by converting USDS to DAI internally, allowing the protocol to share USDC liquidity between both stablecoins and avoid fragmentation. ^[60] This design decision maintained deep liquidity pools while supporting the dual-token ecosystem during the transition period.

Technical Architecture

The LitePSM represents a ground-up reimplementation of the original PSM design, optimizing for gas efficiency through a pre-minted buffer system while maintaining economic equivalence. The architecture consists of core swap contracts, a pocket-based buffer mechanism, governance emergency controls, and keeper infrastructure that together enable low-cost stablecoin swaps at any scale within debt ceiling limits.

Smart Contract Structure

The LitePSM architecture consists of several interconnected smart contracts deployed on Ethereum mainnet:

Core Contracts

LitePSM Core (0xf6e72Db5454dd049d0788e411b06CfAF16853042) — Main swap logic and fee calculations ^[61] ^[63]
LitePSM Pocket (0x37305B1cD40574E4C5Ce33f8e8306Be057fD7341) — Buffer management for pre-minted USDS ^[62]
LitePSMWrapper-USDS-USDC — Wrapper enabling USDS swaps via internal DAI conversion ^[64]

Governance and Emergency Contracts

LITE_PSM_MOM (0x467b32b0407Ad764f56304420Cddaa563bDab425) — Manages the breaker mechanism for halting swaps during emergencies ^[65]
ESM Integration — Emergency Shutdown Module authorized on LitePSM input conduit ^[66]

The breaker mechanism represents a critical safety feature, allowing governance to halt all PSM swaps through an expedited governance proposal without the standard delay periods. ^[67] This capability provides a key tool for managing extreme events, enabling rapid emergency response without waiting for the standard GSM Pause Delay.

Public Swap Functions

The LitePSM exposes four primary user-facing functions:

sellGem(address usr, uint256 gemAmt)

Deposits gem collateral (e.g., USDC) and mints USDS/DAI for the specified user, applying the tin fee if non-zero. ^[68] The function validates that the debt ceiling has not been exceeded, transfers the gem from the caller, calculates the tin fee, and transfers the net USDS/DAI amount to the recipient. All accounting updates occur atomically within the transaction.

buyGem(address usr, uint256 gemAmt)

Burns USDS/DAI and releases gem collateral to the specified user, applying the tout fee if non-zero. ^[69] The function validates sufficient gem liquidity exists in the PSM, calculates the required USDS/DAI amount including the tout fee, burns the USDS/DAI from the caller, and transfers the gem to the recipient.

sellGemNoFee(address usr, uint256 gemAmt)

Authorized-party-only function for depositing gem and minting USDS/DAI without paying tin fees, even if fees are active. ^[70] This function supports Endgame's requirement for Prime Agents to access PSM liquidity without fee overhead, enabling efficient allocation system operations.

buyGemNoFee(address usr, uint256 gemAmt)

Authorized-party-only function for burning USDS/DAI and receiving gem without paying tout fees. ^[71] Only addresses explicitly authorized by governance can call the no-fee functions, with authorization lists managed through governance proposals.

Buffer and Keeper System

The LitePSM's gas efficiency derives from its buffer mechanism, which fundamentally changes how USDS/DAI is minted and burned during swaps. ^[72] Rather than calling the Vat (core accounting system) to mint/burn on every swap, the LitePSM maintains a pocket of pre-minted USDS/DAI equal to the buf parameter.

When users call sellGem, they receive USDS/DAI from this pre-minted buffer through a simple ERC-20 transfer, avoiding expensive mint operations. Conversely, when users call buyGem, their USDS/DAI is transferred into the pocket, temporarily increasing the buffer size beyond buf. ^[73]

Authorized keepers monitor the buffer state and perform maintenance operations:

fill() — Called when the buffer is depleted below buf, mints additional USDS/DAI to restore the buffer to its target size
trim() — Called when the buffer exceeds buf (typically after buyGem operations), burns excess USDS/DAI to restore the buffer to its target size
chug() — Performs both fill and trim operations in a single transaction when appropriate ^[74]

Keeper operations are gas-intensive, but their cost is amortized across many user swaps. MakerDAO and its keeper ecosystem absorb these maintenance costs, while end users benefit from the dramatically reduced gas costs of simple ERC-20 transfers. ^[75] This design represents a clever optimization that maintains economic equivalence with the original PSM while improving user experience.

DC-IAM Integration

The Debt Ceiling Instant Access Module (DC-IAM) provides dynamic debt ceiling management without requiring governance votes for routine adjustments. ^[76] The module tracks three key parameters:

line — Absolute maximum debt ceiling (10 billion USDS)
gap — Target buffer of available debt capacity (400 million USDS)
ttl — Minimum time between automatic debt ceiling increases (12 hours)

As PSM debt approaches the current debt ceiling, the DC-IAM automatically increases the ceiling (up to the line maximum) to maintain the gap buffer, but only after ttl has elapsed since the last increase. ^[77] This mechanism allows the PSM to scale dynamically during periods of high demand without waiting for governance action, while the ttl parameter prevents rapid ceiling increases that could accumulate excessive risk.

If debt approaches the line parameter or if rapid increases trigger concerns, governance must intervene through executive votes to adjust parameters. Decreases in debt ceiling can occur immediately without ttl restrictions, enabling rapid risk reduction when needed.

PSM Variants and Deployments

Sky Protocol has operated multiple PSM variants across different stablecoins and networks since 2020. On Ethereum mainnet, the protocol has cycled through PSMs for USDC, GUSD, and USDP before consolidating into the single LitePSM-USDC-A. More recently, PSM3 contracts have extended PSM functionality to Layer 2 networks through the Spark Liquidity Layer, enabling multi-chain peg stability.

Ethereum Mainnet PSMs

PSM-USDC-A (Legacy, Deprecated)

The original PSM implementation launched December 2020, now deprecated following the LitePSM migration. Contract address: 0x89B78CfA322F6C5dE0aBcEecab66Aee45393cC5A ^[78]

At its peak, PSM-USDC-A held billions in USDC and represented the dominant collateral type in MakerDAO, comprising over 50% of DAI backing in 2022. ^[79] The module operated continuously from December 2020 through October 2024, processing hundreds of billions in cumulative swap volume and generating significant fee revenue during periods when tin/tout were non-zero.

LITE-PSM-USDC-A (Active)

The gas-optimized LitePSM implementation launched July 2024 and completed migration October 2024. Core contract: 0xf6e72Db5454dd049d0788e411b06CfAF16853042 ^[80]

Current parameters as of January 2026:

tin: 0%
tout: 0%
DC-IAM line: 10,000,000,000 USDS
DC-IAM gap: 400,000,000 USDS
DC-IAM ttl: 43,200 seconds (12 hours)
buf: 400,000,000 USDS
Authorized Parties: None (as specified in Atlas, though operational integrations may have authorization) ^[81]

The zero-fee configuration prioritizes peg stability over fee revenue, enabling arbitrage at any price deviation. The 10 billion USDS debt ceiling provides substantial headroom for the PSM to scale during demand surges.

LitePSMWrapper-USDS-USDC

Deployed September 2024 as part of Sky Protocol launch, this wrapper contract enables USDS holders to access PSM liquidity seamlessly. ^[82] The wrapper internally converts USDS to DAI, routes through LITE-PSM-USDC-A, and converts back as needed, sharing liquidity between the two stablecoin ecosystems without fragmentation.

This architecture avoids the need for separate USDS and DAI PSM pools, which would dilute liquidity and potentially create arbitrage opportunities between the pools. Instead, both USDS and DAI users access the same deep USDC liquidity pool through different entry points.

PSM-GUSD-A (Offboarded)

Gemini Dollar PSM variant active from 2021-2023. Debt ceiling peaked at 500 million DAI in June 2023 before reduction to 110 million, then final offboarding to 0 DAI in November 2023. ^[83]

The PSM-GUSD-A served as a diversification mechanism during periods of USDC concentration concern, offering an alternative centralized stablecoin path. However, limited GUSD liquidity and demand led to its eventual deprecation.

PSM-PAX-A / PSM-USDP-A (Offboarded)

Pax Dollar PSM variant, technically identified as PSM-PAX-A in MakerDAO's system. Paxos rebranded its PAX stablecoin to USDP in August 2021, but the vault identifier remained PSM-PAX-A. Onboarded August 2021, the vault's debt ceiling was reduced from 500 million DAI to 0 DAI through a governance poll in May 2023, ^[84] with formal offboarding and removal from the DC-IAM completed in January 2024. ^[86]

The PSM-PAX-A played a critical role during the March 2023 crisis, experiencing over 400 million USDP withdrawals as users sought to exit USDC exposure. ^[85] The rapid drain contributed to USDP's depeg to approximately $0.91, demonstrating the PSM's potential to transmit rather than contain external shocks when collateral assets themselves depeg.

The phasing out of multiple PSM variants between 2023-2024 reflects a strategic shift toward consolidating liquidity in the USDC PSM while diversifying the broader collateral portfolio away from stablecoins and toward RWAs, crypto collateral, and other asset types.

Layer 2 Deployments: PSM3

Sky Protocol has extended PSM functionality to Layer 2 networks through the PSM3 contract, part of the Spark Liquidity Layer infrastructure. ^[87] PSM3 deployments facilitate cross-chain liquidity for USDS and DAI, enabling users on L2s to access Sky Protocol features without bridging to mainnet for every transaction.

Supported Networks

Base — PSM3 deployed with rate limits managed through governance proposals ^[88]
Arbitrum One — Onboarded to Spark Liquidity Layer with initial PSM3 support ^[89]
Optimism — Onboarded to Spark Liquidity Layer in June 2025 ^[90]
Unichain — Onboarded to Spark Liquidity Layer in June 2025 ^[91]

The PSM3 architecture enables end users on L2s to tap into Sky Protocol features via Sky Ecosystem projects' rails, with the Sky.money web app and Spark providing bridging infrastructure between Ethereum mainnet and the growing number of supported L2 networks. ^[92]

Rate limits on L2 PSM3 contracts prevent rapid drawdowns that could strain cross-chain bridge capacity, with governance adjusting limits based on bridge security, demand patterns, and risk appetite. The multi-chain expansion represents Sky Protocol's recognition of L2's growing importance in the Ethereum ecosystem and the need to meet users where they operate.

Role in the Sky Ecosystem

The PSM's significance extends far beyond simple stablecoin swaps. Within the Sky ecosystem, PSM holdings serve as Actively Stabilizing Collateral, satisfy Demand Absorption Buffer requirements, influence monetary policy through the Base Rate, provide infrastructure for Prime Agent operations, and generate a framework for Peg Defense Event responses. The PSM sits at the intersection of stability, governance, and capital allocation.

Actively Stabilizing Collateral (ASC)

The PSM serves as a key source of Actively Stabilizing Collateral in Sky Protocol's Asset Liability Management framework. ^[93] ASC is defined as collateral that actively supports the USDS peg by providing buy support at a price close to 1 USD per USDS through market-making activities. ^[94]

Specifically, Resting Actively Stabilizing Collateral must provide buy support at a price of at least 0.999 USD per USDS (10bps downside spread), and cash stablecoins held in PSMs qualify as Resting ASC. ^[95] The USDC held in the LitePSM therefore directly counts toward Sky Protocol's ASC requirements, serving a dual role as both stability mechanism and regulatory framework compliance.

The level of ASC in the PSM relative to total collateral (PSM ASC percentage) serves as a key input to monetary policy decisions, specifically Base Rate adjustments. ^[96] According to Atlas guidance for Core Executor Agents:

PSM ASC above 30% → Consider decreasing Base Rate by ~2%
PSM ASC 28-30% → Consider decreasing Base Rate by ~1%
PSM ASC 26-28% → Consider decreasing Base Rate by ~0.3%
PSM ASC 24-26% → Maintain Base Rate at current level
PSM ASC 22-24% → Consider increasing Base Rate by ~0.3%
PSM ASC 20-22% → Consider increasing Base Rate by ~1%
PSM ASC below 20% → Consider increasing Base Rate by ~2% ^[97]

This framework creates a feedback loop: high PSM ASC indicates strong stability but potentially excessive reliance on centralized stablecoins, prompting lower Base Rates to make vault borrowing more attractive and diversify collateral. Conversely, low PSM ASC suggests insufficient stability reserves, prompting higher Base Rates to increase protocol revenue and build ASC through natural market dynamics.

In addition to Resting ASC, the framework defines Latent ASC — cash stablecoins that do not qualify as Resting ASC but can be converted into Resting ASC within 15 minutes under normal market conditions through a fully automated process. Latent ASC includes cash stablecoins in SparkLend, Aave, Morpho, and DEX positions not paired with USDS. Critically, Latent ASC may not exceed 25% of total ASC, ensuring that the majority of stability reserves remain immediately available through mechanisms like the PSM. ^[95]

Demand Absorption Buffer (DAB)

Alongside ASC's buy-side support, the PSM fulfills a complementary sell-side function through the Demand Absorption Buffer. Every Prime Agent must maintain a DAB equal to 25% of their required ASC. ^[101] The DAB consists of USDS that is available for sale at a price of at most 1.001 USD per USDS, providing sell-side liquidity during periods of excess demand that push USDS above its peg.

USDS and DAI held in PSMs directly qualify as DAB, since the PSM's 1:1 swap mechanism ensures USDS can always be sold for USDC at par (or USDC swapped for USDS at par). This means the PSM simultaneously serves both the buy-side (ASC, via USDC reserves enabling USDS purchases below peg) and the sell-side (DAB, via USDS/DAI reserves enabling USDS sales above peg) of the peg stability framework.

Integration with Prime Agents

The PSM plays a critical operational role for Prime Agents (Spark, Grove, Keel) managing liquidity across the Sky ecosystem. ^[98] The authorized party functionality in LitePSM enables Prime Agents to access PSM liquidity without paying tin/tout fees, supporting efficient rebalancing operations for the Allocation System.

Prime Agents utilize PSM functions for several key operations:

Spark Liquidity Layer

The Spark Liquidity Layer relies on PSM3 contracts on L2 networks to bridge liquidity between mainnet and supported chains. ^[99] Minted USDS is swapped for USDC through the Sky Peg Stability Module and then bridged to other networks. The Spark PSM enables swapping between USDS, sUSDS, and USDC with no slippage or fee beyond network fees, using hardcoded pricing for USDS/USDC at 1.00 USD with an exchange rate oracle for sUSDS.

These mechanisms enable Spark to dynamically manage liquidity distribution across chains, responding to demand patterns by moving funds into or out of L2 PSMs as needed.

Grove Liquidity Layer

The PSM relationship extends to Grove's planned takeover of PSM management from Sky Core, with control transitioning to Grove as part of the Endgame organizational structure. ^[100] Grove's infrastructure includes PSM interaction capabilities for managing collateral composition and responding to Peg Defense Events.

Keel and Other Agents

Keel and other Prime Agents are expected to incorporate similar PSM integration patterns as they launch, utilizing the authorized party functionality for fee-free PSM access.

The fee-free access for authorized Prime Agents ensures that internal protocol operations don't incur friction costs that would reduce capital efficiency, while public users continue to pay fees if/when governance sets tin/tout above zero.

Peg Defense Events

The PSM serves as one of the key tools available for satisfying Peg Defense Event obligations when USDS trades significantly off peg. ^[101] A Peg Defense Event triggers when the average price of USDS on LayerZero-connected DEXes falls below 0.999 USD per USDS. During such events, all Prime Agents must immediately begin buying USDS at a rate of at least 6.25% of their ASC requirement every 6 hours. ^[102]

Prime Agents can fulfill peg defense obligations through multiple methods: selling other collateral for USDS directly, or using USDS as collateral to borrow USDC/USDT on lending protocols like Aave and then buying USDS on the open market. The PSM provides critical infrastructure for these operations by enabling rapid USDC-to-USDS conversion. Penalty schedules for failing to fulfill Peg Defense obligations are to be specified in a future Atlas iteration.

Treasury Management and Revenue

LitePSM income (fees generated from tin/tout when non-zero) flows into Sky Protocol's treasury management allocation process as "Other Income." ^[103] While current parameters set fees at 0%, historical periods with positive fees generated meaningful protocol revenue, particularly during the initial launch phase when tin was 1% and during emergency periods when fees were temporarily increased.

The trade-off between fee revenue and peg stability remains an ongoing governance consideration. Higher fees generate income and may discourage excessive PSM reliance, but wider arbitrage bands allow greater peg volatility. The current zero-fee policy reflects a judgment that peg stability takes priority over PSM revenue extraction, particularly given the protocol's substantial income from other sources (stability fees, RWA yields, etc.).

Risks and Criticisms

Despite its effectiveness at maintaining the peg, the PSM has drawn persistent criticism for the centralization trade-offs it introduces. Holding billions in USDC creates direct dependency on Circle, generates opportunity costs from idle reserves, and proved during the March 2023 SVB crisis that the PSM can transmit rather than contain external shocks. These risks have shaped governance strategy around diversification and the eventual transition to a more distributed ASC framework.

USDC Concentration and Centralization

The PSM's most significant and persistent criticism centers on USDC concentration and the resulting centralization of what is meant to be a decentralized stablecoin system. ^[104] At its peak in 2022, approximately 80% of DAI was backed by centralized stablecoins held in PSMs, with USDC comprising the vast majority. ^[105] This concentration creates several interconnected risks:

Circle Blacklist Risk

Circle, as the issuer of USDC, maintains the technical capability to blacklist or freeze USDC addresses without notice or appeal, as evidenced by its compliance with OFAC sanctions and law enforcement requests. ^[106] If Circle were to blacklist the PSM contract addresses, it could indefinitely freeze billions in collateral backing a substantial portion of USDS/DAI supply, triggering an existential crisis for the protocol. ^[107]

A 2022 governance forum discussion framed this as an existential risk: the protocol became dependent on a single centralized entity (Circle) for its core stability mechanism, undermining the decentralization thesis that originally motivated DAI's creation. ^[108]

Regulatory Risk

Circle operates under U.S. regulatory oversight and must comply with evolving financial regulations. Regulatory action targeting Circle (whether related to stablecoin legislation, sanctions enforcement, or other policy objectives) could impair USDC functionality and cascade into Sky Protocol through the PSM dependency. ^[109]

The March 2023 SVB crisis illustrated this dynamic: Circle's banking relationships (inherently subject to regulatory intervention) directly impacted USDC reliability, which immediately transmitted to DAI through the PSM mechanism.

Contagion Amplification

Rather than insulating DAI from external shocks, the PSM can amplify contagion from the underlying collateral stablecoin. ^[110] When USDC depegged in March 2023, the PSM became a liquidity drain as users rushed to exit, depleting PSM reserves and transmitting instability to connected stablecoins like USDP. ^[111]

The PSM creates a guaranteed conversion mechanism, which provides stability under normal conditions but guarantees transmission of problems during crises. Users can always exit USDS for USDC at $1 (minus fees) through the PSM, but if USDC itself trades below $1, this guarantee becomes a vector for value destruction rather than protection.

Efforts to Reduce Concentration

Following the March 2023 crisis, governance undertook concrete steps to reduce USDC concentration:

Offboarding alternative PSM variants (GUSD, USDP, PAX) to consolidate liquidity while reducing stablecoin exposure overall
Increasing RWA vault debt ceilings to diversify toward U.S. Treasury-backed collateral
Growing crypto collateral vaults (ETH, wBTC, stETH, etc.) to increase decentralized collateral percentage
Implementing ASC monitoring frameworks to track concentration metrics ^[112]

By May 2023, USDC backing had decreased from over 50% to approximately 23.6% of total DAI backing. ^[113] However, the protocol's collateral remained majority-centralized, with approximately 55% in stablecoins overall and 25% in RWAs. ^[114] The shift reduced direct USDC exposure but replaced it largely with other centralized assets (Treasury bills, alternative stablecoins), maintaining fundamental centralization even if concentration in any single asset declined.

As of January 2026, Sky Protocol aims to maintain approximately 25% of USDS collateral backing in cash reserves (primarily USDC in PSMs), providing a buffer for users to exit even during large redemption events while limiting concentration risk. ^[115] This target balance reflects the ongoing tension between stability requirements (which favor liquid, reliable collateral like USDC) and decentralization goals (which favor crypto-native and diverse collateral).

Security Concerns: EOA Control Controversy

In late 2024, Sky Protocol faced scrutiny over its use of an externally owned account (EOA) to manage approximately $756 million in USDC reserves within the LitePSM during the migration period. ^[116] Security researchers and community members raised alarms that the EOA account holder had unrestricted access to withdraw funds at any time, posing significant risks to asset safety. ^[117]

Sky co-founder Rune Christensen clarified that the EOA was part of a multi-party computation (MPC) account and that the private keys needed to reconstitute the MPC account were destroyed, eliminating the risk of a compromised private key enabling unauthorized withdrawals. ^[118] The clarification addressed immediate security concerns, but the episode highlighted the challenges of managing large-scale DeFi infrastructure during transition periods and the scrutiny applied to custody arrangements for significant protocol assets.

The incident underscores a broader tension in DeFi between operational flexibility (which may require trusted parties or expedited processes during upgrades) and trustless security (which demands all operations occur through audited, time-locked smart contracts). The LitePSM migration ultimately completed successfully without security incidents, but the controversy demonstrated the community's heightened sensitivity to custody risks following various DeFi exploits and hacks in 2022-2024.

Opportunity Cost and Capital Efficiency

A subtler criticism involves the opportunity cost of holding billions in USDC within PSMs earning zero yield. ^[119] Unlike RWA vaults that generate 4-5% yields on Treasury bill backing, or stability fees on crypto vaults that produce ongoing income, USDC sitting idle in PSMs produces no direct return (aside from tin/tout fees when active).

Governance discussions have explored whether PSM USDC could be productively deployed while maintaining liquidity for peg stability operations. ^[120] Proposals have included:

Deploying PSM USDC to yield-bearing protocols (e.g., Yearn Finance, with a $100 million deployment approved in January 2023) ^[121]
Using PSM reserves to back RWA lending operations
Implementing partial reserve systems where only a fraction of PSM USDC remains immediately liquid

These approaches face significant trade-offs: yield-bearing deployments introduce smart contract risk, liquidity risk (assets may not be withdrawable immediately during peg defense needs), and complexity that could impair the PSM's core stability function. The current approach of maintaining full reserves reflects a conservative posture that prioritizes reliability over yield optimization.

PSM Breaker and Emergency Response

The PSM includes a breaker mechanism (managed by LITE_PSM_MOM contract) enabling governance to halt all swaps through expedited proposals without standard delay periods. ^[122] While essential for emergency response, the breaker also represents a centralized point of control that could be exploited through governance attacks or used to freeze user access during critical moments.

The March 2023 crisis demonstrated the need for rapid parameter adjustment capabilities, but it also showed that emergency measures (like rapidly increasing fees or reducing debt ceilings) can exacerbate user panic if perceived as signs of protocol distress. Governance must balance the need for responsive risk management against the risk that emergency actions themselves trigger or worsen crisis dynamics.

Current State: January 2026

As of January 2026, the PSM operates in a mature, zero-fee configuration following the completed LitePSM migration. Sky Protocol's financial performance continues to strengthen, with the PSM providing foundational stability infrastructure even as the ecosystem diversifies collateral and expands to Layer 2 networks. The ongoing transition of PSM management from Sky Core to Grove represents the next major structural evolution.

Operational Metrics

As of January 2026, the PSM continues to serve as Sky Protocol's primary stability mechanism and one of the largest sources of stablecoin liquidity in DeFi:

Total Value Locked — Sky Protocol's overall TVL reached $4 billion across all products, with substantial PSM holdings contributing to liquidity infrastructure ^[123]
USDS/DAI Supply — Combined supply increased by 86% to $9.86 billion, indicating strong demand for Sky stablecoins ^[124]
ASC Composition — PSM USDC represents a significant portion of Sky's Actively Stabilizing Collateral, with the protocol targeting approximately 25% of USDS backing in cash reserves ^[125]
Fee Revenue — With tin and tout at 0%, the PSM currently generates no direct fee revenue, prioritizing peg stability over income extraction ^[126]

The LitePSM operates smoothly following the completed migration, with keeper networks successfully managing the buffer mechanism and users benefiting from reduced gas costs. Integration with the Spark Liquidity Layer enables seamless multi-chain operations, with PSM3 contracts on Base, Arbitrum, and other L2s facilitating cross-chain liquidity access.

Performance and Stability

The USDS and DAI stablecoins maintain tight peg stability, with the zero-fee PSM configuration enabling arbitrage at any price deviation. Market prices for USDS and DAI remain tightly pegged to $1, demonstrating the PSM's continued effectiveness at its core mission. ^[127]

The protocol has not experienced significant peg stress events since the March 2023 crisis, with improved collateral diversification and RWA growth providing greater resilience against centralized stablecoin issues. However, the fundamental dependency on USDC (and by extension Circle and the U.S. banking system) remains unchanged, even if the degree of concentration has decreased.

Financial Performance

Sky Protocol reported strong financial performance for 2025:

Annualized operational profits — Rose 24.4% to $168 million ^[128]
Annualized SKY buybacks — Totaled $92.2 million ^[129]
Annualized operational expenses — Reduced 61.5% to $43.6 million ^[130]

While the PSM itself generates minimal direct revenue under current zero-fee parameters, it enables the broader ecosystem stability that supports vault growth, RWA deployment, and other revenue-generating activities. The PSM's value lies primarily in its infrastructure role rather than direct income contribution.

Governance Oversight and Future Direction

Control of the LitePSM is transitioning from Sky Core to Grove as part of the Endgame organizational restructuring. ^[131] Until the transition completes, Sky Core continues to manage the LitePSM subject to Atlas requirements for Asset Liability Management. ^[132] Post-transition, Grove will manage the LitePSM as an ASC asset pursuant to Prime Program Accord terms. ^[133]

The transition carries significant economic implications. Grove will be required to pay the Base Rate on all assets within the PSM, with the Base Rate aligned to the Sky Savings Rate and expected to fluctuate between Aave and Ethena rates. ^[133] To offset this cost, Grove earns yield through Coinbase Custody on USDC holdings within the PSM, enabling potential positive carry when custody yield exceeds the Base Rate. USDC in the PSM is treated as uniquely capital-efficient for peg liquidity — unlike alternative deployments that may require risk capital, PSM USDC has no capital requirement.

In the longer term, the PSM's role may diminish as the ASC system matures into the primary liquidity management framework. Grove retains the flexibility to reduce or wind down the PSM entirely if ASC requirements can be fulfilled through other mechanisms such as Uniswap or Curve positions that also qualify as Resting ASC.

Looking ahead to 2026 and beyond, Sky Protocol plans to launch additional Prime Agents (up to 10 new Sky Agents anticipated starting Q1 2026), expanding the ecosystem and potentially creating new use cases for PSM infrastructure in cross-agent liquidity management. ^[134] The fundamental PSM architecture is likely to remain central to Sky Protocol's stability framework for the foreseeable future, even as specific parameters, authorized parties, and operational control evolve.

USDS — Sky Protocol's upgraded decentralized stablecoin that the PSM helps stabilize
Actively Stabilizing Collateral — The asset classification framework within which PSM holdings are measured and monitored
Sky Vaults — Alternative collateral mechanisms that compete with and complement the PSM for backing USDS/DAI
DAI — The original MakerDAO stablecoin that the PSM was initially designed to stabilize
Spark — Prime Agent operating the Spark Liquidity Layer which relies on PSM3 for multi-chain stability
Grove — Prime Agent assuming operational control of the LitePSM from Sky Core

Data Freshness

This article reflects information current as of January 12, 2026. Key data points subject to frequent change:

PSM parameters (tin, tout, debt ceilings, buffer size) — Can be adjusted through governance votes; verify current values at Sky governance portal
USDC holdings and PSM utilization — Real-time data available at info.sky.money
ASC percentages and collateral composition — Updated monthly in Sky Protocol analytics
Governance discussions and proposals — Ongoing at forum.sky.money

Historical information (launch dates, crisis events, migration timeline) remains accurate, but parameter values, addresses, and operational details should be verified against current protocol state before relying on them for critical decisions.