Fix version chain: bidirectional traversal so any node shows full chain

- Added childrenMap for forward traversal from parent to children
- getChain now walks backward to root AND forward to latest descendant
- Clicking v1 root node now shows the complete version chain UI
- Standalone v1 nodes (no children) still return null (no chain to show)
- Updated tests to reflect bidirectional behavior + added v1 root test

packages/memory-graph/src/__tests__/version-chain.test.ts

@@ -71,7 +71,7 @@ describe("VersionChainIndex", () => {
 		expect(chain!.map((e) => e.id)).toEqual(["m1", "m2", "m3"])
 	})
 
-	it("getChain from middle element walks back to root", () => {
+	it("getChain from middle element returns full chain (backward + forward)", () => {
 		const idx = new VersionChainIndex()
 		const doc = makeDoc("d1", [
 			makeMem({ id: "m1", version: 1 }),
@@ -90,12 +90,11 @@ describe("VersionChainIndex", () => {
 		])
 		idx.rebuild([doc])
 
-		// Query from m2 (version 2) — walks back m2->m1, reverses to [m1,m2]
-		// Note: it doesn't walk forward to m3, only backward
+		// Query from m2 (version 2) — walks back to m1, forward to m3
 		const chain = idx.getChain("m2")
 		expect(chain).not.toBeNull()
-		expect(chain!.length).toBe(2)
-		expect(chain!.map((e) => e.id)).toEqual(["m1", "m2"])
+		expect(chain!.length).toBe(3)
+		expect(chain!.map((e) => e.id)).toEqual(["m1", "m2", "m3"])
 	})
 
 	it("caches chain results for all entries in the chain", () => {
@@ -118,6 +117,32 @@ describe("VersionChainIndex", () => {
 		expect(chain2).toBe(chain1) // same reference
 	})
 
+	it("getChain from v1 root with children returns full chain", () => {
+		const idx = new VersionChainIndex()
+		const doc = makeDoc("d1", [
+			makeMem({ id: "m1", version: 1 }),
+			makeMem({
+				id: "m2",
+				parentMemoryId: "m1",
+				rootMemoryId: "m1",
+				version: 2,
+			}),
+			makeMem({
+				id: "m3",
+				parentMemoryId: "m2",
+				rootMemoryId: "m1",
+				version: 3,
+			}),
+		])
+		idx.rebuild([doc])
+
+		// Query from v1 root — walks forward to m2, m3
+		const chain = idx.getChain("m1")
+		expect(chain).not.toBeNull()
+		expect(chain!.length).toBe(3)
+		expect(chain!.map((e) => e.id)).toEqual(["m1", "m2", "m3"])
+	})
+
 	it("getChain returns null for unknown ID", () => {
 		const idx = new VersionChainIndex()
 		idx.rebuild([makeDoc("d1", [makeMem({ id: "m1", version: 1 })])])

packages/memory-graph/src/canvas/version-chain.ts

@@ -10,6 +10,7 @@ export interface ChainEntry {
 
 export class VersionChainIndex {
 	private memoryMap = new Map<string, GraphApiMemory>()
+	private childrenMap = new Map<string, string[]>()
 	private cache = new Map<string, ChainEntry[]>()
 	private lastDocs: GraphApiDocument[] | null = null
 
@@ -17,11 +18,20 @@ export class VersionChainIndex {
 		if (documents === this.lastDocs) return
 		this.lastDocs = documents
 		this.memoryMap.clear()
+		this.childrenMap.clear()
 		this.cache.clear()
 
 		for (const doc of documents) {
 			for (const m of doc.memories) {
 				this.memoryMap.set(m.id, m)
+				if (m.parentMemoryId) {
+					let children = this.childrenMap.get(m.parentMemoryId)
+					if (!children) {
+						children = []
+						this.childrenMap.set(m.parentMemoryId, children)
+					}
+					children.push(m.id)
+				}
 			}
 		}
 	}
@@ -31,26 +41,47 @@ export class VersionChainIndex {
 		if (cached) return cached
 
 		const mem = this.memoryMap.get(memoryId)
-		if (!mem || mem.version <= 1) return null
+		if (!mem) return null
 
-		const chain: ChainEntry[] = []
+		// Walk backward to root
+		const backward: GraphApiMemory[] = []
 		const visited = new Set<string>()
 		let current: GraphApiMemory | undefined = mem
 		while (current && !visited.has(current.id)) {
 			visited.add(current.id)
-			chain.push({
-				id: current.id,
-				version: current.version,
-				memory: current.memory,
-				isForgotten: current.isForgotten,
-				isLatest: current.isLatest,
-			})
+			backward.push(current)
 			current = current.parentMemoryId
 				? this.memoryMap.get(current.parentMemoryId)
 				: undefined
 		}
+		backward.reverse()
 
-		chain.reverse()
+		// Walk forward from the selected node to find descendants
+		const forward: GraphApiMemory[] = []
+		let tip: GraphApiMemory | undefined = mem
+		while (tip) {
+			const children = this.childrenMap.get(tip.id)
+			if (!children || children.length === 0) break
+			const child = this.memoryMap.get(children[0])
+			if (!child || visited.has(child.id)) break
+			visited.add(child.id)
+			forward.push(child)
+			tip = child
+		}
+
+		// Combine: backward (root..selected) + forward (selected+1..latest)
+		const all = [...backward, ...forward]
+
+		// A single-entry chain (standalone v1 with no children) is not useful
+		if (all.length <= 1) return null
+
+		const chain: ChainEntry[] = all.map((m) => ({
+			id: m.id,
+			version: m.version,
+			memory: m.memory,
+			isForgotten: m.isForgotten,
+			isLatest: m.isLatest,
+		}))
 
 		for (const entry of chain) {
 			this.cache.set(entry.id, chain)