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Nexus exposes a Python-first API for trace logging.

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Core modules

  • NexusClient and Span for manual instrumentation.
  • PrintingHandler for LangChain callback instrumentation.
  • config helpers for DB and trigger URLs.

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Data model written to storage

Both manual spans and LangChain callbacks map to rows with these key fields:
  • run_id
  • user_id
  • trace_id
  • parent_run_id
  • event_type
  • name
  • input
  • output
  • error

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Reference pages

NexusClient + Span

Constructor behavior, span lifecycle, flush, and tree helpers.

PrintingHandler

Callback hooks, event mapping, and root-chain trigger behavior.