fix: forward subscription updates that resolve pending fetches

[GabrielePicco]

Problem

A subscription update arriving for an account with a fetch in flight is consumed to resolve that fetch and never forwarded to the update pipeline — while submux dedup has already dropped every other copy. Correctness silently depends on the fetch caller cloning the result. Non-cloning callers (delegation-status reads via fetch_remote_accounts) and multi-stage resolutions that fail mid-churn discard it, permanently losing the freshest chain state. With a stale copy in the bank suppressing refetches, the account stays wedged until the next on-chain write — reproducible by delegating/undelegating in quick succession while anything polls the account.

#1507 fixed one consumer of this class (the slot-matching companion path); this fixes the class at its source.

Solution

Consumption is non-exclusive: the update resolves the fetch waiters and is forwarded like any other notification (one None → Some(update) at the arbitration site). Double-processing is benign via the existing non-advancing-slot gate.

Tests

• test_update_resolving_pending_fetch_is_also_forwarded — non-cloning fetch in flight, update consumed; red before, green after.
• Two existing tests updated from the old exclusive-consumption contract; exact global-metric asserts relaxed to lower bounds (concurrent tests share label sets).

Summary by CodeRabbit

• Bug Fixes

  • Subscription updates that resolve in-flight account fetches are now also forwarded to downstream consumers.
  • Redelegation updates are preserved and correctly applied when finalizing account state.
  • Consumed subscription updates are reliably replayed through the update pipeline.

• Tests

  • Expanded coverage for forwarded subscription updates and replay behavior.
  • Improved metric assertions to remain reliable during concurrent test execution.

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Review details

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📥 Commits

Reviewing files that changed from the base of the PR and between b8bd5ca and a8c3101.

📒 Files selected for processing (1)

• magicblock-chainlink/src/remote_account_provider/tests.rs

📝 Walkthrough

Walkthrough

Subscription updates that resolve in-flight account fetches are now forwarded into the main update pipeline while also resolving fetch waiters. Tests now verify forwarded redelegation and consumed updates, validate subscription-derived fetch results and forwarding, and use lower-bound assertions for shared companion-fetch attempt metrics.

Suggested reviewers: thlorenz, dodecahedr0x

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/forward-consumed-subscription-updates

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[chatgpt-codex-connector]

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Reviewed commit: b8bd5ca3a9

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[coderabbitai]

Actionable comments posted: 1

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Inline comments:
In `@magicblock-chainlink/src/remote_account_provider/tests.rs`:
- Around line 1663-1669: Update the paired histogram-sum assertion following
chainlink_companion_fetch_attempts_sample_count to require at least
attempts_sum_before + 1.0 instead of exactly that value, preserving
concurrency-safe behavior when same-label observations increase the sum.

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ℹ️ Review info

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Configuration used: Path: .coderabbit.yaml

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Run ID: 2200d86a-924e-448a-88a9-9fa1c2c104eb

📥 Commits

Reviewing files that changed from the base of the PR and between 1d9aa3e and b8bd5ca.

📒 Files selected for processing (3)

• magicblock-chainlink/src/chainlink/fetch_cloner/tests.rs
• magicblock-chainlink/src/remote_account_provider/mod.rs
• magicblock-chainlink/src/remote_account_provider/tests.rs