{"record":{"id":"b4ee4fa07b661e5d","repo":"JuliusBrussee/caveman","slug":"where-representative-trace-names-a-variant-that","errorCode":null,"errorMessage":"${where} representative trace names a variant that is not that arm's variant","messagePattern":"(.+?) representative trace names a variant that is not that arm's variant","errorType":"exception","errorClass":"Error","httpStatus":null,"severity":"error","filePath":"packages/shared/contracts/scripts/validate-continuous-improvement.mjs","lineNumber":161,"sourceCode":"    if (roles.join(\",\") !== \"baseline,alternative\") throw new Error(`${where} cohort arms are not baseline then alternative`);\n    const armVariants = new Map();\n    let comparedUnits = 0;\n    for (const arm of item.cohort.arms) {\n      const variant = variantsByID.get(arm.variant_id);\n      if (!variant) throw new Error(`${where} cohort arm ${arm.role} references a workflow variant that is not in this report`);\n      if (variant.task_family_id !== family.id) throw new Error(`${where} cohort arm ${arm.role} uses a variant of another task family`);\n      armVariants.set(arm.role, variant);\n      comparedUnits += arm.unit_count;\n    }\n    const excluded = item.cohort.excluded_units.reduce((total, exclusion) => total + exclusion.unit_count, 0);\n    if (comparedUnits + excluded !== item.cohort.family_unit_count) {\n      throw new Error(`${where} cohort arms (${comparedUnits}) plus exclusions (${excluded}) do not account for its ${item.cohort.family_unit_count} family units`);\n    }\n\n    const selectedPerArm = new Map();\n    for (const trace of item.representative_traces) {\n      const variant = armVariants.get(trace.arm);\n      if (!variant || variant.id !== trace.variant_id) throw new Error(`${where} representative trace names a variant that is not that arm's variant`);\n      if (!unitsByID.has(trace.analysis_unit_id)) throw new Error(`${where} representative trace ${trace.analysis_unit_id} is not an analysis unit of this report`);\n      if (!familyUnits.has(trace.analysis_unit_id)) throw new Error(`${where} representative trace ${trace.analysis_unit_id} is not a member of the cohort's task family`);\n      if (!variant.analysis_unit_ids.includes(trace.analysis_unit_id)) throw new Error(`${where} representative trace ${trace.analysis_unit_id} did not run that arm's workflow variant`);\n      selectedPerArm.set(trace.arm, (selectedPerArm.get(trace.arm) ?? 0) + 1);\n    }\n    for (const [arm, count] of selectedPerArm) {\n      if (count > 3) throw new Error(`${where} arm ${arm} carries ${count} representative traces, more than three`);\n    }\n\n    const slice = item.causal_slice;\n    const sliceVariant = variantsByID.get(slice.variant_id);\n    if (!sliceVariant) throw new Error(`${where} causal slice references a workflow variant that is not in this report`);\n    if (sliceVariant.id !== armVariants.get(\"baseline\").id) throw new Error(`${where} causal slice is not taken from the baseline arm's variant`);\n    const sliceNodes = new Set(sliceVariant.nodes.map((node) => node.id));\n    if (slice.manifestation_node_id !== \"\" && !sliceNodes.has(slice.manifestation_node_id)) {\n      throw new Error(`${where} manifestation node ${slice.manifestation_node_id} is not a node of variant ${sliceVariant.id}`);\n    }\n    if (item.diagnosis.manifestation.node_id !== slice.manifestation_node_id) {","sourceCodeStart":143,"sourceCodeEnd":179,"githubUrl":"https://github.com/JuliusBrussee/caveman/blob/766dce6b1394ebb56a3090748d5a0240a5aefb36/packages/shared/contracts/scripts/validate-continuous-improvement.mjs#L143-L179","documentation":"Every representative trace declares the arm it was selected from and the variant it ran; the validator resolves trace.arm in the arm-to-variant map and requires trace.variant_id to equal that arm's variant id (validate-continuous-improvement.mjs:159-161). A trace naming another variant — or an arm role that is not baseline/alternative, which makes the lookup miss — fails here.","triggerScenarios":"A trace was copied from the other arm without updating variant_id; trace.arm is misspelled ('base', 'alt') so armVariants.get(trace.arm) returns undefined; an arm's variant_id was changed after the traces were written.","commonSituations":"Duplicating a trace entry to pad a fixture; editing cohort arms in a refactor while leaving traces untouched; generator emitting traces from a variant snapshot taken before arms were finalized.","solutions":["Set trace.variant_id to the named arm's current variant_id.","Fix trace.arm to be exactly \"baseline\" or \"alternative\".","If the arm's variant changed, re-select traces from units that actually ran the new variant, then re-run the validator."],"exampleFix":"// before — baseline arm's variant is wf-build-01\n{ \"arm\": \"baseline\", \"variant_id\": \"wf-build-02\", \"analysis_unit_id\": \"unit-901\" }\n// after\n{ \"arm\": \"baseline\", \"variant_id\": \"wf-build-01\", \"analysis_unit_id\": \"unit-901\" }","handlingStrategy":"validation","validationCode":"const traceVariantDrift = (report) =>\n  report.cases.flatMap((c) => {\n    const armVariant = new Map(c.cohort.arms.map((a) => [a.role, a.variant_id]));\n    return c.representative_traces\n      .filter((t) => armVariant.get(t.arm) !== t.variant_id)\n      .map((t) => `${c.id}:${t.analysis_unit_id}`);\n  });","typeGuard":null,"tryCatchPattern":"try {\n  execFileSync(process.execPath, [VALIDATOR, reportPath, spansPath]);\n} catch (err) {\n  if (/not that arm's variant/.test(err.message)) {\n    failCI(`trace/arm variant mismatch — align variant_id with the arm: ${err.message}`);\n  } else throw err;\n}","preventionTips":["Emit trace.variant_id from the arm lookup in the generator instead of writing it by hand.","Use exactly \"baseline\"/\"alternative\" for trace.arm.","When changing an arm's variant, re-select its traces in the same edit."],"tags":["fixtures","cross-validation","representative-trace","arms","cross-field"],"backgroundTag":"cross-field-mismatch","analyzedSha":"766dce6b1394ebb56a3090748d5a0240a5aefb36","analyzedAt":"2026-08-18T03:14:35.516Z","contentChangedAt":"2026-08-18T03:14:35.516Z","schemaVersion":2},"datasetVersion":"2026-09-14T05:17:10.506Z"}