fix: keep legacy transaction v computation in BigInt to avoid precision loss

[Sednaoui]

Fixes #128

Red/green verified: test/utils7702.test.js signs a legacy tx with chainId 4337433743374337433 (> 2^53) and parses it back with ethers; on pre-fix dev the recovered sender is wrong (1 failed), with the fix both chainId and sender recover exactly (2 passed).

Summary by CodeRabbit

• Bug Fixes

  • Fixed legacy transaction signing for very large chain IDs so transactions preserve correct chain ID and sender recovery.

• Tests

  • Added unit tests verifying signing and sender recovery for large and standard chain IDs.

• Documentation

  • Updated changelog with the bug fix entry.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Run ID: 14f17f53-afc9-469f-8f31-11b016a995dd

📥 Commits

Reviewing files that changed from the base of the PR and between 4ff3f2a and 436764b.

📒 Files selected for processing (1)

• CHANGELOG.md

✅ Files skipped from review due to trivial changes (1)

• CHANGELOG.md

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📝 Walkthrough

Walkthrough

Fixes a precision bug in createAndSignLegacyRawTransaction by computing legacy v using pure BigInt arithmetic; adds tests verifying chainId preservation and sender recovery for large (>2^53) and small chain IDs, and documents the change in CHANGELOG.md.

Changes

Legacy Transaction v Computation Fix

Layer / File(s)	Summary
BigInt v computation fix and validation src/utils7702.ts, test/utils7702.test.js	The legacy transaction signature v is computed with pure bigint arithmetic (BigInt(signature.yParity) + chainId * 2n + 35n) instead of converting chainId to Number. Tests sign and parse transactions to validate chainId preservation and sender recovery for very large and small chain IDs.
Changelog documentation CHANGELOG.md	Adds an UNRELEASED Bug Fix entry describing the switch from Number(chainId) to BigInt in createAndSignLegacyRawTransaction to prevent rounding errors in v computation.

🎯 3 (Moderate) | ⏱️ ~20 minutes

🐰 I hopped on bytes both large and small,
Switched to BigInt to catch them all,
No more rounding in the v we send,
Chain IDs safe from end to end,
A thump, a test, precision for all! 🥕

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (1 warning, 1 inconclusive)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.
Description check	❓ Inconclusive	The description provides issue reference, test verification details, and test results but lacks structured sections (Summary, Test, Risk/Compatibility) from the template.	Expand description to follow the template structure with explicit Summary, Test, and Risk/Compatibility sections for clarity.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: fixing legacy transaction v computation to use BigInt for precision handling with large chain IDs.
Linked Issues check	✅ Passed	The code changes fully address issue #128 by replacing Number(chainId) with pure BigInt arithmetic in createAndSignLegacyRawTransaction to prevent precision loss for large chain IDs.
Out of Scope Changes check	✅ Passed	All changes (CHANGELOG.md, src/utils7702.ts, test/utils7702.test.js) are directly scoped to fixing issue #128 with no unrelated modifications present.

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Update the built dist artifacts

This new regression test imports ../dist/index.cjs, but the commit only updates src/utils7702.ts; the checked-in dist/index.cjs still computes v with Number(chainId), while package.json also points main/exports at dist. In the current tree, npx jest --runTestsByPath test/utils7702.test.js --runInBand fails because the large-chainId case parses back as 4337433743374337518n, so CI and any consumers using the committed package entrypoint still get the old precision-loss behavior until the dist outputs are rebuilt and committed.

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[sherifahmed990]

LGTM