feat: add commits fees

[GabrielePicco]

Description

Add and apply commits fees

Summary by CodeRabbit

• New Features

  • Introduced standardized fee structure for commits and delegation sessions.

• Chores

  • Updated fee handling and distribution mechanism during undelegation to route fees through dedicated vaults.
  • Added test coverage for fee processing on undelegation.

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[snawaz]

Looks good to me!

Posted one question and couple of nits.

[snawaz]

The simplification looks awesome. I found a subtle bug though, once that is fixed, we can merge it.

[coderabbitai]

Actionable comments posted: 0

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

src/processor/fast/utils/pda.rs (1)

87-116: Well-structured fee distribution logic.

The refactored function cleanly handles:

• Proportional fee extraction from available lamports
• Protocol/validator fee splitting (10%/90%)
• Remainder reimbursement to rent payer

One minor robustness consideration on line 101: while the current domain constraints make overflow impossible (fees are capped by PDA rents which are tiny fractions of u64::MAX), using a u128 intermediate as suggested in past reviews would add defense-in-depth:

♻️ Optional: Use u128 intermediate for overflow safety

-        let protocol_fee = fee_taken * PROTOCOL_FEES_PERCENTAGE as u64 / 100;
+        let protocol_fee = ((fee_taken as u128 * PROTOCOL_FEES_PERCENTAGE as u128) / 100) as u64;

This matches the pattern suggested in past reviews and guards against any future changes that might increase fee magnitudes.

📜 Review details

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between adddad7 and 63c634e.

📒 Files selected for processing (5)

• src/consts.rs
• src/processor/fast/undelegate.rs
• src/processor/fast/utils/pda.rs
• tests/fixtures/accounts.rs
• tests/test_commit_fees_on_undelegation.rs

🧰 Additional context used

🧠 Learnings (1)

📚 Learning: 2025-10-15T11:45:25.802Z

Learnt from: snawaz
Repo: magicblock-labs/delegation-program PR: 107
File: src/entrypoint.rs:141-144
Timestamp: 2025-10-15T11:45:25.802Z
Learning: In the delegation-program codebase, prefer using `log!` (from pinocchio_log) over `msg!` for error and panic scenarios in the entrypoint code, as per maintainer preference.

Applied to files:

• src/processor/fast/undelegate.rs

🧬 Code graph analysis (2)

tests/fixtures/accounts.rs (1)

src/state/delegation_metadata.rs (1)

• seeds (35-35)

src/processor/fast/undelegate.rs (1)

src/processor/fast/utils/pda.rs (1)

• close_pda_with_fees (87-116)

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (1)

• GitHub Check: test

🔇 Additional comments (10)

src/consts.rs (1)

10-14: LGTM!

The new fee constants are well-documented and appropriately typed. The values (0.0001 SOL per commit, 0.0003 SOL per session) are reasonable for micropayments on Solana.

tests/fixtures/accounts.rs (1)

107-138: LGTM!

Good refactoring approach - the existing create_delegation_metadata_data now delegates to the new parameterized function, maintaining backward compatibility while enabling nonce-aware test scenarios.

tests/test_commit_fees_on_undelegation.rs (2)

22-69: LGTM!

The test correctly validates the fee calculation logic:

• Sets nonce to 101, implying 100 commits (101 - 1 = 100)
• Calculates expected fees using the same formula as the implementation
• Verifies the protocol fee vault receives 10% of total fees

The fee calculation at line 40-41 correctly caps fees at available lamports, matching the min() logic in process_delegation_cleanup.

---

71-165: LGTM!

Comprehensive test setup that properly initializes all required accounts for the undelegation flow. The high nonce (101) effectively tests the commit fee calculation path.

src/processor/fast/undelegate.rs (5)

14-14: LGTM!

Correctly imports the new fee constants for use in the cleanup logic.

---

134-134: LGTM!

Extracts the nonce before dropping the borrow, enabling its use in the cleanup logic.

---

165-172: LGTM!

Correctly passes delegation_last_update_nonce to the cleanup function for the empty-data fast path.

---

221-228: LGTM!

Correctly passes delegation_last_update_nonce to the cleanup function for the CPI path.

---

336-367: LGTM!

The fee calculation logic is correct:

• saturating_sub(1) safely handles zero nonce (first commit not charged, as clarified in past reviews)
• checked_mul protects against overflow in commit fee calculation
• min() ensures fees never exceed available lamports from the PDAs
• Shared mutable fee_remaining correctly distributes fees across both PDA closures

src/processor/fast/utils/pda.rs (1)

10-10: LGTM!

Correctly imports the protocol fee percentage constant for fee routing calculations.

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