diff --git a/core/test/memory-search-edge.test.js b/core/test/memory-search-edge.test.js
new file mode 100644
index 000000000..ea0d37ba9
--- /dev/null
+++ b/core/test/memory-search-edge.test.js
@@ -0,0 +1,48 @@
+// Edge cases for the semantic recall merged in #478: CJK, stem matching across a whole word,
+// determinism, and a [[topic]] graph with a cycle, a self-link and no link. Test only.
+import assert from 'node:assert/strict'
+import { test } from 'node:test'
+import { buildGraph, buildIndex, relatedOf, searchIndex, termsOf, topicNode } from '../src/host/memory-search.js'
+
+test('a Chinese query finds a Chinese entry, with no word split', () => {
+  const index = buildIndex([
+    { key: 'seat', ref: '用户喜欢靠窗的座位' },
+    { key: 'ship', ref: 'The user ships on Friday' },
+  ])
+  assert.equal(searchIndex(index, '靠窗座位')[0]?.doc.key, 'seat')
+  // A query that shares a term still matches; an unrelated one does not.
+  assert.ok(searchIndex(index, '座位').some(hit => hit.doc.key === 'seat'))
+  assert.ok(!searchIndex(index, 'noodles').some(hit => hit.doc.key === 'seat'))
+})
+
+test('a word stem matches across endings, and ranking is deterministic', () => {
+  const docs = [{ key: 'a', ref: 'The user books flights' }, { key: 'b', ref: 'Likes strong coffee' }]
+  const first = searchIndex(buildIndex(docs), 'flight bookings').map(hit => hit.doc.key)
+  assert.deepEqual(first, ['a'])
+  // The same index and query give the same order every time.
+  const index = buildIndex(docs)
+  assert.deepEqual(searchIndex(index, 'flight bookings').map(hit => hit.doc.key), searchIndex(index, 'flight bookings').map(hit => hit.doc.key))
+})
+
+test('an empty query, and a tokenization with nothing to keep, return no hits', () => {
+  const index = buildIndex([{ key: 'a', ref: 'x' }])
+  assert.deepEqual(searchIndex(index, ''), [])
+  assert.deepEqual(searchIndex(index, '  '), [])
+  assert.deepEqual([...termsOf('- - -').keys()], [])
+})
+
+test('a two-way [[topic]] link does not loop, and a self-link is ignored', () => {
+  const graph = buildGraph([
+    { topic: 'a', entries: [{ text: 'see [[b]] and [[a]]', meta: {} }] },
+    { topic: 'b', entries: [{ text: 'see [[a]]', meta: {} }] },
+  ])
+  const near = relatedOf(graph, topicNode('a'), { hops: 3 }).neighbours
+  assert.deepEqual(near.map(node => node.name), ['b'], 'b once, a itself never')
+  assert.equal(graph.edges.some(edge => edge.from === edge.to), false, 'the self-link is dropped')
+})
+
+test('an unknown start is empty, and a topic with no link has no neighbours', () => {
+  const graph = buildGraph([{ topic: 'lonely', entries: [{ text: 'no links here', meta: {} }] }])
+  assert.deepEqual(relatedOf(graph, topicNode('nope')).neighbours, [])
+  assert.deepEqual(relatedOf(graph, topicNode('lonely')).neighbours, [])
+})
diff --git a/patches/ds-bot/files/test/memory-search-edge.test.js b/patches/ds-bot/files/test/memory-search-edge.test.js
new file mode 100644
index 000000000..ea0d37ba9
--- /dev/null
+++ b/patches/ds-bot/files/test/memory-search-edge.test.js
@@ -0,0 +1,48 @@
+// Edge cases for the semantic recall merged in #478: CJK, stem matching across a whole word,
+// determinism, and a [[topic]] graph with a cycle, a self-link and no link. Test only.
+import assert from 'node:assert/strict'
+import { test } from 'node:test'
+import { buildGraph, buildIndex, relatedOf, searchIndex, termsOf, topicNode } from '../src/host/memory-search.js'
+
+test('a Chinese query finds a Chinese entry, with no word split', () => {
+  const index = buildIndex([
+    { key: 'seat', ref: '用户喜欢靠窗的座位' },
+    { key: 'ship', ref: 'The user ships on Friday' },
+  ])
+  assert.equal(searchIndex(index, '靠窗座位')[0]?.doc.key, 'seat')
+  // A query that shares a term still matches; an unrelated one does not.
+  assert.ok(searchIndex(index, '座位').some(hit => hit.doc.key === 'seat'))
+  assert.ok(!searchIndex(index, 'noodles').some(hit => hit.doc.key === 'seat'))
+})
+
+test('a word stem matches across endings, and ranking is deterministic', () => {
+  const docs = [{ key: 'a', ref: 'The user books flights' }, { key: 'b', ref: 'Likes strong coffee' }]
+  const first = searchIndex(buildIndex(docs), 'flight bookings').map(hit => hit.doc.key)
+  assert.deepEqual(first, ['a'])
+  // The same index and query give the same order every time.
+  const index = buildIndex(docs)
+  assert.deepEqual(searchIndex(index, 'flight bookings').map(hit => hit.doc.key), searchIndex(index, 'flight bookings').map(hit => hit.doc.key))
+})
+
+test('an empty query, and a tokenization with nothing to keep, return no hits', () => {
+  const index = buildIndex([{ key: 'a', ref: 'x' }])
+  assert.deepEqual(searchIndex(index, ''), [])
+  assert.deepEqual(searchIndex(index, '  '), [])
+  assert.deepEqual([...termsOf('- - -').keys()], [])
+})
+
+test('a two-way [[topic]] link does not loop, and a self-link is ignored', () => {
+  const graph = buildGraph([
+    { topic: 'a', entries: [{ text: 'see [[b]] and [[a]]', meta: {} }] },
+    { topic: 'b', entries: [{ text: 'see [[a]]', meta: {} }] },
+  ])
+  const near = relatedOf(graph, topicNode('a'), { hops: 3 }).neighbours
+  assert.deepEqual(near.map(node => node.name), ['b'], 'b once, a itself never')
+  assert.equal(graph.edges.some(edge => edge.from === edge.to), false, 'the self-link is dropped')
+})
+
+test('an unknown start is empty, and a topic with no link has no neighbours', () => {
+  const graph = buildGraph([{ topic: 'lonely', entries: [{ text: 'no links here', meta: {} }] }])
+  assert.deepEqual(relatedOf(graph, topicNode('nope')).neighbours, [])
+  assert.deepEqual(relatedOf(graph, topicNode('lonely')).neighbours, [])
+})