fix(knowledge): make the conversation content hash collision-resistant

Greptile P1. The hash was `memory:{id}:{updatedAt}`, and updatedAt only has
millisecond resolution. Appends landing in the same millisecond as the value
already indexed hashed identically, so classifyExternalDoc called the
transcript unchanged and the new messages stayed out of the knowledge base
until some later write moved the clock.

messageCount closes the reported path — an append always increments it — and
approxBytes covers a same-count replacement. Both were already selected for
the listing, so neither costs an extra query. Mutation-checked: reverting to
the timestamp-only hash fails three tests.

Also switches the sim auth arm's line comment to TSDoc per the repo rule
(Greptile P2).

Author: mzxchandra

apps/sim/app/workspace/[workspaceId]/knowledge/[id]/components/add-connector-modal/add-connector-modal.tsx

@@ -246,7 +246,7 @@ export function AddConnectorModal({
   const renderAuthField = (auth: ConnectorAuthConfig) => {
     switch (auth.mode) {
       case 'sim':
-        // Nothing to collect: the connector reads this workspace directly.
+        /** Nothing to collect: the connector reads this workspace directly. */
         return null
 
       case 'apiKey':

apps/sim/connectors/sim-conversations/sim-conversations.test.ts

@@ -212,7 +212,7 @@ describe('conversationToStub', () => {
 
   it('hashes on the update watermark, which moves whenever a message is appended', () => {
     const base = conversationToStub(BASE_ROW).contentHash
-    expect(base).toBe('memory:mem-1:2026-01-02T00:00:00.000Z')
+    expect(base).toBe('memory:mem-1:2026-01-02T00:00:00.000Z:6:1024')
 
     const appended = conversationToStub({
       ...BASE_ROW,
@@ -227,6 +227,30 @@ describe('conversationToStub', () => {
       conversationToStub({ ...BASE_ROW }).contentHash
     )
   })
+
+  /**
+   * `updatedAt` is only millisecond-resolution, so appends landing in the same
+   * millisecond as the indexed value would otherwise hash identically and the sync
+   * engine would call the transcript unchanged — leaving the new messages out of
+   * the knowledge base until some later write moved the clock.
+   */
+  it('distinguishes appends that share a millisecond with the indexed value', () => {
+    const indexed = conversationToStub(BASE_ROW).contentHash
+    const appendedSameMs = conversationToStub({
+      ...BASE_ROW,
+      messageCount: BASE_ROW.messageCount + 2,
+      approxBytes: BASE_ROW.approxBytes + 180,
+    }).contentHash
+
+    expect(appendedSameMs).not.toBe(indexed)
+  })
+
+  /** A same-count replacement still moves the byte size. */
+  it('distinguishes a same-millisecond, same-count content replacement', () => {
+    expect(
+      conversationToStub({ ...BASE_ROW, approxBytes: BASE_ROW.approxBytes + 40 }).contentHash
+    ).not.toBe(conversationToStub(BASE_ROW).contentHash)
+  })
 })
 
 describe('cursor', () => {

apps/sim/connectors/sim-conversations/sim-conversations.ts

@@ -164,8 +164,16 @@ export function renderTranscript(
  * Builds the listing stub for one conversation.
  *
  * Single source of truth for `contentHash`, used by both listing and hydration.
- * `updatedAt` is the right watermark here: `Memory.appendMessage` bumps it on every
- * appended message, so it moves exactly when the transcript changes.
+ *
+ * `updatedAt` is the primary watermark — `Memory.appendMessage` bumps it on every
+ * appended message — but it only has millisecond resolution, so two appends landing
+ * in the same millisecond as the previously indexed value would hash identically and
+ * `classifyExternalDoc` would call the transcript unchanged, leaving the new messages
+ * out of the knowledge base until some later write moved the clock.
+ *
+ * `messageCount` closes that: an append always increments it. `approxBytes` covers
+ * the rarer case of a same-count replacement. Both are already selected for the
+ * listing, so neither costs an extra query.
  */
 export function conversationToStub(row: ConversationRow): ExternalDocument {
   return {
@@ -175,7 +183,7 @@ export function conversationToStub(row: ConversationRow): ExternalDocument {
     contentDeferred: true,
     mimeType: 'text/plain',
     // No sourceUrl: conversations have no page of their own in the app.
-    contentHash: `memory:${row.id}:${row.updatedAt.toISOString()}`,
+    contentHash: `memory:${row.id}:${row.updatedAt.toISOString()}:${row.messageCount}:${row.approxBytes}`,
     metadata: {
       conversationId: row.key,
       messageCount: row.messageCount,