Handle swap errors in chain buys

[gztensor]

Description

Chain buys may result in swap errors, in which case the TAO will be withdrawn from the subnet account and returned to the total imbalance.

Related Issue(s)

• Closes inject_and_maybe_swap silently strands TAO when swap_tao_for_alpha fails #2661

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please describe):

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have run ./scripts/fix_rust.sh to ensure my code is formatted and linted correctly
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[github-actions]

🛡️ AI Review — Skeptic (security review)

VERDICT: SAFE

BASELINE scrutiny: gztensor has repo write permission, established contribution history, no trusted Gittensor allowlist hit; branch fix/handle-chain-buy-swap-failures -> devnet-ready.

Static review only. The diff does not modify .github/ai-review/*, .github/copilot-instructions.md, dependencies, lockfiles, or build scripts. The runtime/pallet changes are limited to refunding failed chain-buy TAO deposits through the existing credit/recycle accounting path, handling ED dust in Subtensor TotalIssuance, updating tests, and bumping spec_version.

Findings

No findings.

Conclusion

No malicious behavior or security vulnerability was found. The failed swap path uses fallible withdrawal and preserves issuance/accounting without adding panic, origin-bypass, dependency, or build-time execution surfaces.

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🔍 AI Review — Auditor (domain review)

VERDICT: 👍

Author is LIKELY Gittensor by recent Subtensor-heavy contribution history, has repo write permission, and is not in the trusted allowlists.

PR body is substantive and matches the implementation. No duplicate-work blocker found; overlapping PRs touch nearby runtime or pallet files, but their scopes are adjacent accounting, root, governance, or cleanup work rather than a better candidate for this chain-buy swap-failure fix.

Spec-version auto-fix was not needed: the PR already bumps runtime/src/lib.rs from 424 to 426 for the devnet-ready target.

Auto-fix applied locally because this is not a fork: pallets/subtensor/src/tests/swap_hotkey_with_subnet.rs now removes the unused another_coldkey binding and restores an IsNetworkMember assertion for the already-registered hotkey setup.

Verification: git diff --check passed. I attempted the three focused cargo test --package pallet-subtensor --lib tests for the changed paths, but they could not start in this sandbox because rustup/cargo tried to write under read-only /home/runner/.rustup and /home/runner/.cargo.

Findings

No findings.

Prior-comment reconciliation

• 66ac1209: addressed — Fixed locally by removing the unused another_coldkey binding and adding assert!(IsNetworkMember::<Test>::get(new_hotkey, netuid)); before the swap assertion.

Conclusion

The failed dynamic chain-buy path now refunds the deposited subnet-account TAO back into remaining credit before the existing recycle path, with focused accounting coverage and the prior low-risk test issue fixed locally. I found no merge-blocking domain issues.

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📜 Previous run (superseded)

Sev	File	Finding	Status
LOW	pallets/subtensor/src/tests/swap_hotkey_with_subnet.rs:868	Restore the already-registered hotkey assertion	✅ Addressed Fixed locally by removing the unused another_coldkey binding and adding assert!(IsNetworkMember::<Test>::get(new_hotkey, netuid)); before the swap assertion.

[github-actions]

🔄 AI review updated — Skeptic: SAFE Auditor: 👍

[github-actions]

🔄 AI review updated — Skeptic: SAFE Auditor: 👍

[github-actions]

🔄 AI review updated — Skeptic: SAFE Auditor: 👍

[github-actions]

🔄 AI review updated — Skeptic: SAFE Auditor: 👍

[github-actions]

🔄 AI review updated — Skeptic: SAFE Auditor: 👍

[github-actions]

AI review — see the sticky summary comment for the verdict and the inline comments below for specific findings.

[github-actions]

🔄 AI review updated — Skeptic: SAFE Auditor: 👍

[github-actions]

🔄 AI review updated — Skeptic: SAFE Auditor: 👍