[study] (2h) V4 return-delta hooks — BEFORE_SWAP_RETURN_DELTA, AFTER_SWAP_RETURN_DELTA

[ozpool]

Goal

Understand the advanced V4 feature PRISM avoids in v1.0 but may use in v1.1.

Time estimate

2h (single focused session)

Prerequisites

• [study] (2h) V4 IHooks callback interface — selectors, return shapes, sentinels #85 (F14) — V4 IHooks callback interface — selectors, return shapes, sentinels
• [study] (2h) V4 hook permission flag matrix — all 14 bits, PRISM's 4-of-14 choice #86 (F15) — V4 hook permission flag matrix — all 14 bits, PRISM's 4-of-14 choice

Study plan (in order)

1. [25 min] uniswap/v4-core: src/libraries/Hooks.sol — return-delta flags (bits 0–3)
2. [25 min] uniswap/v4-core: src/PoolManager.sol — how return-delta modifies pool accounting
3. [25 min] Use cases: custom fees, JIT-liquidity hooks, dynamic fee + delta combos
4. [20 min] Why PRISM v1.0 doesn't use return-delta (simpler security surface)
5. [25 min] Write outcomes from memory

Total: 120 min

After studying, you can

• Explain BEFORE_SWAP_RETURN_DELTA semantics (hook returns custom delta that adjusts swap)
• Explain AFTER_SWAP_RETURN_DELTA use cases
• Describe when returnDelta enables custom accounting
• Articulate why PRISM v1.0 avoids these flags

Tradeoff prompt for the architectural review

What would PRISM need return-delta hooks for in v1.1 MEV execution?

References

• uniswap/v4-core Hooks.sol
• uniswap/v4-core PoolManager.sol