June 2026: Delivered a high-impact correctness fix for Subagent History Reconstruction in langgraphjs, improving the accuracy of subagent conversations across completed tasks and preventing stale data from affecting results. Implemented a two-phase namespace resolution to first gather direct mappings from completed task results and then apply positional fallbacks only for unmapped calls. This change eliminates wrong subgraph lookups and stabilizes multi-agent workflows without requiring backend changes. Key outcomes include added regression coverage for fetchSubagentHistory namespace resolution, a robust test that failed before the fix and passes now, and a clean SDK/test ecosystem with strong validation that the change preserves backward compatibility while improving reliability. Overall impact: higher reliability and predictability of multi-agent interactions, reduced debugging time for history reconstruction, and clear business value through improved accuracy and user trust. Technologies/skills demonstrated include TypeScript, SDK-level refactoring, namespace-aware data resolution, regression testing (Vitest), static analysis and linting (oxlint/oxfmt), and cross-team collaboration.