Oracles

ELI5: Blockchains cannot see the outside world. An oracle is a feed that writes asset prices on-chain (e.g. ETH/USD from Chainlink). TARE uses two feeds per collateral and stops if they disagree too much.

Why oracles matter

Without a price, the engine cannot know:

• How much TARE you may mint (collateral value)
• Whether you are liquidatable
• How much collateral to seize

Wrong price → wrong mints or unfair liquidations. TARE's design halts instead of guessing.

TARE's redundant oracle

From oracle_lib.vy:

1. Read primary and fallback Chainlink feeds.
2. Each feed must be fresh (≤ 3 hour staleness) and positive.
3. If both healthy → require agreement within max_oracle_deviation_bps (e.g. 5%).
4. If one healthy → use it.
5. If none → revert (no price, no new risk).

# Simplified logic — see oracle_lib.vy for full implementation
# Both feeds healthy → check deviation, return primary
# One feed healthy → return that feed
# No healthy feed → revert

Flywheel connection

• TareEngine — all CDP math uses oracle prices.
• CoilMakerStrategy — uses pool EMA floor for fill bounds (different mechanism, same idea: don't trade blind).
• Keep strategies — APR is keeper-set off-chain, not oracle-driven on-chain.

See Collateral & oracles.

What can go wrong

Oracle failure modes

• Stale feed — deposits/mints may revert until feed updates.
• Feed divergence — pricing halts (safer than picking a manipulated feed).
• Wrong collateral listing — engine owner must list feeds correctly; operational risk.

Deep dive: deviation math

Deviation bps = |primary - fallback| * 10000 / primary. Exceeds max_oracle_deviation_bps → "OracleLib: feed deviation".