feat(contracts): add TWAP deviation guard for settlement price validation (#1762)

[frammawiliansyah]

Description

Resolves #1762.

Adds a TWAP deviation guard for open-market settlement to prevent last-block price manipulation attacks via large spot swaps.

Key Changes

• Settlement Helper (contracts/open-market/src/liquidity.rs & lib.rs):
  • Implemented validate_settlement_price(env, market_id, outcome, window):
    • Calculates the TWAP over the specified window and compares it with the current spot reserve price.
    • Reverts with PriceDeviationTooHigh if the spot vs. TWAP price deviation exceeds the configured threshold.
    • Reverts with TwapInsufficientHistory if the retained history does not cover the window (without silently truncating).
• Configuration (contracts/open-market/src/config.rs):
  • Added twap_max_deviation_bps to contract Config (defaults to 1000 bps / 10%).
  • Added admin-guarded setter set_twap_max_deviation_bps (validating range 1..=10000 bps) and getter get_twap_max_deviation_bps.
• Error Codes (contracts/open-market/src/errors.rs & ARCHITECTURE.md):
  • Registered PriceDeviationTooHigh = 113.
• Unit Tests (contracts/open-market/tests/twap_validation_tests.rs):
  • Added 5 new regression tests verifying rejection of manipulated spot prices outside the deviation band, acceptance of normal prices within the band, configurable thresholds, administrative checks, and window insufficiency reverts.

Verification

• cargo test --test twap_validation_tests passed (14 tests passed).
• cargo test across contracts/open-market passed with 0 errors.

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Project	Deployment	Actions	Updated
insight-arena-4rll	Error		Oct 3, 2026 3:37am UTC