From b9ddfda945d00da73b7d8a0843438ab716d5ff38 Mon Sep 17 00:00:00 2001
From: Eva <eva@100yen.org>
Date: Tue, 14 Jul 2026 03:20:54 +0700
Subject: [PATCH] fix(communities): canonicalize projection order

---
 .../src/core/ingestion/community-processor.ts | 10 +++++++++-
 .../test/unit/community-processor.test.ts     | 20 +++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/gitnexus/src/core/ingestion/community-processor.ts b/gitnexus/src/core/ingestion/community-processor.ts
index e5c85ef586..ff892ae73a 100644
--- a/gitnexus/src/core/ingestion/community-processor.ts
+++ b/gitnexus/src/core/ingestion/community-processor.ts
@@ -302,6 +302,7 @@ export const buildCommunityProjection = (knowledgeGraph: KnowledgeGraph): Commun
 
   const nodes: CommunityProjectionNode[] = [];
   const nodeIndexById = new Map<string, number>();
+  const eligibleNodes: GraphNode[] = [];
 
   knowledgeGraph.forEachNode((node) => {
     if (!isCommunitySymbol(node) || !connectedNodes.has(node.id)) return;
@@ -309,6 +310,12 @@ export const buildCommunityProjection = (knowledgeGraph: KnowledgeGraph): Commun
     // get absorbed into their single neighbor's community, but cost iteration time.
     if (isLarge && (nodeDegree.get(node.id) || 0) < 2) return;
 
+    eligibleNodes.push(node);
+  });
+
+  eligibleNodes.sort((left, right) => (left.id < right.id ? -1 : left.id > right.id ? 1 : 0));
+
+  for (const node of eligibleNodes) {
     nodeIndexById.set(node.id, nodes.length);
     nodes.push({
       id: node.id,
@@ -316,7 +323,7 @@ export const buildCommunityProjection = (knowledgeGraph: KnowledgeGraph): Commun
       filePath: node.properties.filePath,
       type: node.label,
     });
-  });
+  }
 
   const seenEdges = new Set<string>();
   const edges: Array<readonly [number, number]> = [];
@@ -338,6 +345,7 @@ export const buildCommunityProjection = (knowledgeGraph: KnowledgeGraph): Commun
     seenEdges.add(edgeKey);
     edges.push([a, b]);
   });
+  edges.sort(([leftA, leftB], [rightA, rightB]) => leftA - rightA || leftB - rightB);
 
   return { nodes, edges, symbolCount, isLarge };
 };
diff --git a/gitnexus/test/unit/community-processor.test.ts b/gitnexus/test/unit/community-processor.test.ts
index 7f62861d3e..c0e5ff14c0 100644
--- a/gitnexus/test/unit/community-processor.test.ts
+++ b/gitnexus/test/unit/community-processor.test.ts
@@ -102,6 +102,26 @@ describe('community-processor', () => {
       expect(projection.symbolCount).toBe(3);
     });
 
+    it('produces the same projection regardless of graph insertion order', () => {
+      const first = createKnowledgeGraph();
+      for (const id of ['fn:c', 'fn:a', 'fn:b']) {
+        first.addNode(makeNode(id, id.slice(3)));
+      }
+      first.addRelationship(makeRel('rel:ac', 'fn:a', 'fn:c'));
+      first.addRelationship(makeRel('rel:ab', 'fn:a', 'fn:b'));
+      first.addRelationship(makeRel('rel:bc', 'fn:b', 'fn:c'));
+
+      const second = createKnowledgeGraph();
+      for (const id of ['fn:b', 'fn:c', 'fn:a']) {
+        second.addNode(makeNode(id, id.slice(3)));
+      }
+      second.addRelationship(makeRel('rel:bc', 'fn:c', 'fn:b'));
+      second.addRelationship(makeRel('rel:ab', 'fn:b', 'fn:a'));
+      second.addRelationship(makeRel('rel:ac', 'fn:c', 'fn:a'));
+
+      expect(buildCommunityProjection(second)).toEqual(buildCommunityProjection(first));
+    });
+
     it('exports a deterministic undirected CSR adjacency', () => {
       const projection = {
         nodes: [