[sanmipaul]

Summary

Comprehensive implementation of issues #32 (XDR decoding performance) and #33 (sequence-number race detection).

Issue #33: Detect and warn about sequence-number races

Problem: Read-only tools reporting sequence numbers can show stale values if the account submits another transaction in between.

Solution:

• Added timestamps/ledger info to every sequence-number display
• Implemented refresh action in sequence-inspector with state tracking
• Added consistent advisory copy across all features displaying sequences
• Created comprehensive documentation explaining staleness risk

Features updated:

• ✅ sequence-inspector (with manual refresh button)
• ✅ xdr-inspector (advisory for encoded sequence)
• ✅ preconditions-explainer (advisory for envelope sequence)
• ✅ fee-bump-inspector (advisory for inner transaction sequence)

Issue #32: Profile and optimize XDR decoding performance

Problem: Large transactions (100+ operations) could block the main thread during decoding.

Solution:

• Created benchmark suite measuring 100-operation transaction decoding
• Implemented optimized decoding path with Web Worker support
• Threshold-based approach: synchronous for small envelopes (<2KB), worker for larger
• Graceful fallback: falls back to sync if worker initialization fails or times out

Implementation:

• xdrInspector.optimized.ts - Smart routing between sync/worker paths
• xdrInspector.worker.ts - Web Worker for off-main-thread decoding
• xdrInspector.benchmark.ts - Performance test suite with frame-budget validation

Acceptance Criteria (Both Issues)

Issue #32:

• ✅ Documented benchmark for 100-operation and large-ScVal fixtures
• ✅ Decoding moves off-thread if threshold exceeded
• ✅ Small transactions not penalized by worker overhead
• ✅ Errors from off-thread decoding surface same way

Issue #33:

• ✅ Every sequence display labeled with ledger/time retrieved
• ✅ Manual refresh available for decoding-preview features
• ✅ Advisory copy consistent across all slices
• ✅ Documentation explaining freshness limitations

Test Plan

• Manual: Inspect a sequence number, verify timestamp/ledger shown
• Manual: Click refresh button, verify re-fetch with new timestamp
• Manual: Paste 100-op XDR in xdr-inspector, verify no main-thread blocking
• Manual: Review advisory copy across sequence-inspector, xdr-inspector, preconditions-explainer, fee-bump-inspector
• Run: npm run test -- xdrInspector.benchmark to verify performance targets

Documentation

Added two new docs:

• docs/SEQUENCE_FRESHNESS.md - Complete guide to sequence staleness and user best practices
• docs/XDR_DECODING_PERFORMANCE.md - Architecture and optimization strategy

closes #27
closes #29
closes #32
closes #33

[drips-wave]

@sanmipaul Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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