USDC-only configuration

[sean-kuzco]

Summary

Add protocol support for operating in "USDC-only" mode.

Details

This adds the following two new fields to the PoolOverview account:

pub is_token_mint_usdc: bool,
pub token_rewards_enabled: bool,

• These fields must be set when the PoolOverview is created and cannot be updated.
• If is_token_mint_usdc is true, the protocol will enforce that the native token mint equals the USDC mint.
• If token_rewards_enabled is false, staking for delegators and other reward functionality will be disabled. Operator pool commission rates must be 100%, and token amounts in reward payouts must be zero.

Testing

All existing tests, and one new test suite for the USDC-only behavior, pass.

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Note

Introduce USDC-only mode with new PoolOverview flags that disable token rewards and delegator staking, updating instruction constraints, emissions, IDL, and tests.

• Protocol/State
  • Add immutable PoolOverview flags: is_token_mint_usdc and token_rewards_enabled.
  • Enforce USDC-only mode: if is_token_mint_usdc, mint must equal USDC mint; if !token_rewards_enabled, disable token rewards and delegator staking.
• Instruction Changes/Validation
  • create_pool_overview now takes args; wire-through in program and IDL.
  • create_operator_pool/update_operator_pool: require 100% commission when rewards disabled; validate USDC mint in USDC mode.
  • create_staking_record/stake: block delegators when rewards disabled (operators only).
  • create_reward_record/accrue_reward: require zero token rewards when disabled; update emissions check signature to accept PoolOverview.
• Emissions
  • get_expected_reward_emissions_for_epoch(epoch, &PoolOverview) returns 0 when rewards disabled; tests updated.
• Errors
  • New codes: TokenRewardsDisabled, DelegatorStakingDisabled, InvalidMintForUsdcMode, InvalidCommissionRateForDisabledRewards.
• SDK/IDL
  • Update IDL types, accounts, and args (notably createPoolOverviewArgs; add poolOverview to createStakingRecord).
• Tests/Tooling
  • Add tests/usdc-only-mode.test.ts; update existing tests to pass new args/accounts.
  • Extend scripts/test-all.sh and Anchor configs to include USDC-only test.
• Docs
  • README: clarify protocol description and add "USDC-only mode" to features.

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