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Skill

span-coding

analyze and code Phoenix spans

Covers Tracing Observability LLM Debugging

Description

Open-code Phoenix spans with PXI-owned notes, recover those notes for axial coding, and promote stable categories into structured annotations. Load this when analyzing spans to discover failure patterns before a taxonomy exists.

SKILL.md

Span Coding

Open coding is the exploratory pass: inspect individual spans and write short, evidence-close notes about concrete behaviors before deciding what the categories are. Axial coding is the synthesis pass: recover those notes, group recurring patterns, name actionable categories, and promote stable categories into structured annotations.

The unit of analysis is always the span. Inspect spans first, avoid taxonomy labels while collecting open notes, and only write structured annotations after the categories have stabilized.

Source of Truth

PXI span notes in Phoenix are the durable source of truth for open codes.

  • Write open codes with write_span_note.
  • write_span_note always uses identifier pxi.
  • Each span has at most one current PXI open-coding note; repeated writes update it.
  • The tool is server-executed and does not require approval.

The virtual bash filesystem is scratch space, not the canonical note store. Use files under /home/user/workspace/.pxi/coding/ for sampled span lists, interim memos, grouping tables, or draft axial categories when that helps the analysis. Do not dual-write every note to a file by default; recover durable notes from Phoenix when you need to resume.

Open Coding

  1. Use the phoenix-graphql skill and phoenix-gql to inspect spans and surrounding trace context.
  2. Read the span input, output, status, attributes, exceptions, and nearby parent/child spans before writing.
  3. If the span shows a concrete failure or notable behavior, call write_span_note with:
    {"spanId": "<16-char OTel span id>", "note": "<specific observation>"}
    
  4. Write what you saw, not the category you think it belongs to. Good notes cite the observed behavior: "Retriever returned onboarding docs for a cancellation question." Weak notes jump straight to categories: "retrieval_failure".
  5. Skip correct spans. Open coding is a signal-building pass, not a requirement to annotate every span.

Do not use batch_span_annotate during open coding unless the user has already supplied a stable rubric. Free-form PXI notes come first; structured annotation comes later.

Recover PXI Span Notes

Recover PXI notes with a GraphQL query over Project.spans, then filter spanNotes locally to identifier == "pxi". There is no list_span_notes tool.

query RecoverPxiSpanNotes($projectId: ID!, $first: Int = 50, $after: String) {
  node(id: $projectId) {
    ... on Project {
      spans(first: $first, after: $after) {
        edges {
          node {
            spanId
            name
            trace { traceId }
            spanNotes {
              identifier
              explanation
              createdAt
              updatedAt
            }
          }
        }
        pageInfo {
          hasNextPage
          endCursor
        }
      }
    }
  }
}

Paginate until hasNextPage is false or the recovered sample is sufficient. Keep only notes whose identifier is exactly pxi. When a span has no PXI note, treat it as uncoded.

Axial Coding

Use recovered PXI notes as the raw material for axial coding.

  1. Group notes that describe the same underlying failure.
  2. Name categories for likely causes or fixes, not generic symptoms.
  3. Check project annotation configs before creating new structured labels.
  4. Use batch_span_annotate only after the categories and labels stabilize.
  5. Keep optional bash sidecars focused on analysis handoff: grouping tables, current counts, and draft taxonomies. The DB notes remain the durable open-coding record.

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