[rit3sh-x]

Problem

Randomness requests fail with UnbalancedTransaction inside an ephemeral rollup for every oracle queue except DEFAULT_EPHEMERAL_QUEUE.

The rollup reports:

Program log: Feepayer <requester> was modified without being delegated
Confined account <queue> has been illegally modified

The fee flow causes the failure:

• request_randomness transfers lamports from the requester to the queue.
• provide_randomness and purge_expired_requests pay fees from the queue.

Ephemeral rollups cannot modify accounts they do not hold, such as the requester's wallet, or confined accounts, such as a delegated queue. These transfers therefore make the transaction invalid.

fees::is_fee_exempt_ephemeral_queue currently exempts only DEFAULT_EPHEMERAL_QUEUE. As a result, queues delegated through DelegateOracleQueue cannot serve randomness requests inside an ephemeral rollup.

The example's Do Roll Dice Delegated! passes in CI only because mb-stack preloads a build with the ephemeral-test-queue feature, which also exempts the local test queue. The same example fails against the production build.

Fix

• Track delegation: Add ephemeral: u8 to Queue, reusing a byte of its existing padding. Like paused, this preserves the account layout. Existing zero-initialized accounts default to not delegated.
• Mark before delegation: DelegateOracleQueue sets the flag before delegating, ensuring the rollup's clone carries it. Delegation is one-way on main, so the flag does not need to be cleared.
• Exempt delegated queues: Update is_fee_exempt_ephemeral_queue to exempt queues marked as ephemeral, while retaining the exemption for DEFAULT_EPHEMERAL_QUEUE.
• Update fee checks: Request, provide, and purge read the flag within their existing account borrows.

Test

delegated_queue_requests_move_no_fee verifies the behavior using an unused queue (queue 0, accepted by the test callback program).

The test:

1. Delegates the queue and verifies the ephemeral flag.
2. Returns the queue as the rollup's clone.
3. Requests randomness and fulfils the request.
4. Verifies that the queue's lamport balance remains unchanged.

The test fails at the flag assertion when run with only the field and test changes, without the program logic update.

Verification

• All 11 program tests pass.
• End-to-end testing with MagicBlock's ephemeral validator v1.0.2 and magicblock-engine-examples at e8393c6 confirms that Do Roll Dice Delegated! passes against the updated production build but fails with UnbalancedTransaction against the current mainnet build.
• The callback executes in the rollup 51 ms after the request.

Summary by CodeRabbit

• New Features
  • Delegated ephemeral queues are now identified as fee-exempt when requesting randomness or removing expired requests.
• Bug Fixes
  • Randomness requests and fulfillments on delegated ephemeral queues preserve the queue’s lamports.

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⚙️ Run configuration

• Configuration used: Organization UI
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📥 Commits

Reviewing files that changed from the base of the PR and between e6910a3 and 7f63220.

📒 Files selected for processing: 1

• program/tests/test.rs

Walkthrough

The queue header now records ephemeral delegation. Fee-exemption checks use this marker across randomness requests, fulfillment, and expired-request processing. An integration test covers delegation and randomness operations on an ephemeral queue.

Changes

Ephemeral Queue Fee Exemption

Layer / File(s)	Summary
Queue marker and delegation api/src/state/queue.rs, program/src/delegate_oracle_queue.rs	Queue gains an ephemeral field. Delegation sets it to 1 after the existing unused-queue checks pass.
Fee-exemption checks program/src/fees.rs, program/src/request_randomness.rs, program/src/provide_randomness.rs, program/src/purge_expired_requests.rs	The exemption function now accepts the queue header. Randomness request, fulfillment, and expired-request processing use the queue key and header to determine whether to transfer fees.
Delegated queue integration test program/tests/test.rs	The test checks the ephemeral marker and verifies that requesting and fulfilling randomness empties the queue without changing its lamports.

Priority: ⬆️ High

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Suggested reviewers: gabrielepicco, jonasxchen

Merge Risk: ⚪ Minimal · up to e6910

The change exempts all delegated queues from the request fee, which is the intended fix. No merge-blocking risk was found.

Pre-merge checks: 5

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: exempting delegated queues from request fees.
Docstring Coverage		Docstring coverage is 88.89% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 9 functions across 7 files.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 1

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• 🪄 Fix comments: Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
Review comments at @program/tests/test.rs:
- Around line 598-601: Extend the test containing the lamports assertion to
cover the delegated-queue purge fee gate: add another request, advance the clock
beyond QUEUE_TTL_SECONDS, purge the expired request, and assert the queue is
empty and its lamports are unchanged.

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⚙️ Run configuration

• Configuration used: Organization UI
• Review profile: ASSERTIVE
• Plan: Advanced
• Run ID: 3e675b48-860a-49d7-b617-19c288f5fbc4

📥 Commits

Reviewing files that changed from the base of the PR and between 4c6c97d and e6910a3.

📒 Files selected for processing: 7

• api/src/state/queue.rs
• program/src/delegate_oracle_queue.rs
• program/src/fees.rs
• program/src/provide_randomness.rs
• program/src/purge_expired_requests.rs
• program/src/request_randomness.rs
• program/tests/test.rs

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[rit3sh-x]

@GabrielePicco @jonasXchen, could either of you review this when you get a chance?

[GabrielePicco]

Hey @rit3sh-x, this is expected, vrf requests are sponsored only when using the default queue. Otherwise, you can use a delegate feepayer to interact with other queues (which will charge the fees correctly)