fix: handle unjustified unknown selection ties

lib/graph/orchestrator.js

@@ -15,6 +15,7 @@ import {
 import { buildInitialGraph, describeGraph } from "./builder.js";
 import { applyValidatedProposal } from "./apply-proposal.js";
 import { buildGraphUpdatePrompt } from "./prompt-builder.js";
+import { formulateTieResolutionQuestion } from "./question-formulator.js";
 import { parseGraphUpdateProposal } from "./update-proposal.js";
 import {
   explainUnknownSelection,
@@ -53,6 +54,26 @@ function buildDiagnostics({
   };
 }
 
+function buildUnknownSelectionDiagnostics(
+  graph,
+  resolvedNodeIds = [],
+  selectedQuestion = null,
+) {
+  const explanation = explainUnknownSelection(graph, resolvedNodeIds);
+  if (explanation.status === "ambiguous") {
+    return {
+      ...explanation,
+      tieResolutionQuestion:
+        selectedQuestion?.selectionStatus === "ambiguous"
+          ? selectedQuestion.question
+          : formulateTieResolutionQuestion({ graph }).question,
+      alphabeticalUsedAsReasoning: false,
+    };
+  }
+
+  return explanation;
+}
+
 function buildUpdateDiagnostics({
   promptVersion,
   modelName,
@@ -119,14 +140,17 @@ export async function startCase(body) {
   });
 
   const currentSummary = describeGraph(initialGraph);
+  const deterministicSelection = selectActiveUnknownCandidate(
+    {
+      ...initialGraph,
+      resolvedNodeIds: [],
+    },
+    [],
+  );
   const activeUnknownNodeId =
-    selectActiveUnknownCandidate(
-      {
-        ...initialGraph,
-        resolvedNodeIds: [],
-      },
-      [],
-    )?.nodeId ?? null;
+    deterministicSelection?.status === "selected"
+      ? deterministicSelection.nodeId
+      : null;
 
   const situationGraph = makeGraph({
     centralStatement: scenario,
@@ -140,9 +164,18 @@ export async function startCase(body) {
   situationGraphSchema.parse(situationGraph);
 
   const graphReferenceValidation = validateGraphReferences(situationGraph);
-  const unknownSelectionExplanation = explainUnknownSelection(
+  const selectedQuestion =
+    deterministicSelection?.status === "ambiguous"
+      ? {
+          id: "q_tie_resolution",
+          ...formulateTieResolutionQuestion({ graph: situationGraph }),
+          tiedCandidateIds: deterministicSelection.tiedCandidateIds,
+        }
+      : (analysis.nextQuestion ?? null);
+  const unknownSelectionExplanation = buildUnknownSelectionDiagnostics(
     situationGraph,
     [],
+    selectedQuestion,
   );
   if (!graphReferenceValidation.valid) {
     return {
@@ -162,7 +195,7 @@ export async function startCase(body) {
   return {
     success: true,
     situationGraph,
-    selectedQuestion: analysis.nextQuestion ?? null,
+    selectedQuestion,
     diagnostics: buildDiagnostics({
       analysis,
       graph: situationGraph,
@@ -339,9 +372,10 @@ async function updateCaseWithDependencies(body, dependencies = {}) {
         graph: applicationResult.updatedSituationGraph,
         graphReferenceValidation: applicationResult.graphReferenceValidation,
         selectedQuestion: applicationResult.selectedQuestion,
-        unknownSelectionExplanation: explainUnknownSelection(
+        unknownSelectionExplanation: buildUnknownSelectionDiagnostics(
           applicationResult.updatedSituationGraph,
           applicationResult.updatedSituationGraph.resolvedNodeIds || [],
+          applicationResult.selectedQuestion,
         ),
       }),
     };
@@ -359,9 +393,10 @@ async function updateCaseWithDependencies(body, dependencies = {}) {
       graph: situationGraph,
       graphReferenceValidation,
       selectedQuestion: null,
-      unknownSelectionExplanation: explainUnknownSelection(
+      unknownSelectionExplanation: buildUnknownSelectionDiagnostics(
         situationGraph,
         situationGraph.resolvedNodeIds || [],
+        null,
       ),
     }),
   };