diff --git a/app/api/admin/sites/route.ts b/app/api/admin/sites/route.ts
index 1dcd3a0..a2d8a1d 100644
--- a/app/api/admin/sites/route.ts
+++ b/app/api/admin/sites/route.ts
@@ -1,17 +1,7 @@
 export const dynamic = 'force-dynamic'
 
 import { NextRequest, NextResponse } from 'next/server'
-import { createClient } from '@/lib/supabase/server'
-
-async function requireAdmin() {
-  const supabase = await createClient()
-  const { data: { user }, error } = await supabase.auth.getUser()
-  if (error || !user) return { supabase, user: null }
-  const { data: profile } = await supabase
-    .from('users').select('role').eq('id', user.id).single()
-  if (!profile || profile.role !== 'admin') return { supabase, user: null }
-  return { supabase, user }
-}
+import { requireAdmin } from '@/lib/auth/require-admin'
 
 export async function POST(request: NextRequest) {
   const { supabase, user } = await requireAdmin()
diff --git a/app/api/admin/users/route.ts b/app/api/admin/users/route.ts
index 9b3b368..d45e278 100644
--- a/app/api/admin/users/route.ts
+++ b/app/api/admin/users/route.ts
@@ -1,19 +1,9 @@
 export const dynamic = 'force-dynamic'
 
 import { NextRequest, NextResponse } from 'next/server'
-import { createClient } from '@/lib/supabase/server'
 import { createAdminClient } from '@/lib/supabase/admin'
 import { isValidRole } from '@/lib/auth/roles'
-
-async function requireAdmin() {
-  const supabase = await createClient()
-  const { data: { user }, error } = await supabase.auth.getUser()
-  if (error || !user) return { supabase, user: null }
-  const { data: profile } = await supabase
-    .from('users').select('role').eq('id', user.id).single()
-  if (!profile || profile.role !== 'admin') return { supabase, user: null }
-  return { supabase, user }
-}
+import { requireAdmin } from '@/lib/auth/require-admin'
 
 export async function GET() {
   const { supabase, user } = await requireAdmin()
@@ -108,6 +98,7 @@ export async function PATCH(request: NextRequest) {
 
   const { data: before } = await supabase
     .from('users').select('role, site_id, active, department').eq('id', body.id).single()
+  if (!before) return NextResponse.json({ error: 'User not found' }, { status: 404 })
 
   const { error } = await supabase.from('users').update(update).eq('id', body.id)
   if (error) return NextResponse.json({ error: 'Update failed' }, { status: 500 })
diff --git a/app/api/dashboard/export/route.ts b/app/api/dashboard/export/route.ts
index b007602..5558420 100644
--- a/app/api/dashboard/export/route.ts
+++ b/app/api/dashboard/export/route.ts
@@ -2,21 +2,7 @@ export const dynamic = 'force-dynamic'
 
 import { NextRequest, NextResponse } from 'next/server'
 import { createClient } from '@/lib/supabase/server'
-
-function escapeCsv(value: string | number | null | undefined): string {
-  if (value === null || value === undefined) return ''
-  const str = String(value)
-  if (str.includes(',') || str.includes('"') || str.includes('\n')) {
-    return `"${str.replace(/"/g, '""')}"`
-  }
-  return str
-}
-
-function rowsToCsv(headers: string[], rows: string[][]): string {
-  const lines = [headers.map(escapeCsv).join(',')]
-  for (const row of rows) lines.push(row.map(escapeCsv).join(','))
-  return lines.join('\r\n')
-}
+import { rowsToCsv } from '@/lib/csv'
 
 export async function GET(request: NextRequest) {
   const supabase = await createClient()
diff --git a/app/api/incidents/[id]/addenda/route.ts b/app/api/incidents/[id]/addenda/route.ts
index 78a8210..ab9f369 100644
--- a/app/api/incidents/[id]/addenda/route.ts
+++ b/app/api/incidents/[id]/addenda/route.ts
@@ -41,6 +41,8 @@ export async function POST(
   const body: { body?: string } = await request.json().catch(() => ({}))
   const text = (body.body ?? '').trim()
   if (!text) return NextResponse.json({ error: 'body required' }, { status: 422 })
+  if (text.length > 5000)
+    return NextResponse.json({ error: 'body must be 5000 characters or fewer' }, { status: 422 })
 
   const { data: addendum, error } = await supabase
     .from('incident_addenda')
@@ -54,7 +56,7 @@ export async function POST(
     p_table_name: 'incident_addenda',
     p_record_id: addendum.id,
     p_action: 'INSERT',
-    p_new_value: { incident_id: id, author: user.id },
+    p_new_value: { incident_id: id, author: user.id, body: text },
   })
 
   return NextResponse.json({ id: addendum.id }, { status: 201 })
diff --git a/app/api/incidents/[id]/similar/route.ts b/app/api/incidents/[id]/similar/route.ts
index 666b22c..af34058 100644
--- a/app/api/incidents/[id]/similar/route.ts
+++ b/app/api/incidents/[id]/similar/route.ts
@@ -22,12 +22,12 @@ export async function GET(
 
   const { data: incident } = await supabase
     .from('incidents')
-    .select('id, description, embedding')
+    .select('id, description, embedding, status')
     .eq('id', id)
     .single()
   if (!incident) return NextResponse.json({ error: 'Not found' }, { status: 404 })
 
-  const inc = incident as { id: string; description: string; embedding: string | null }
+  const inc = incident as { id: string; description: string; embedding: string | null; status: string }
 
   let embeddingVec: number[]
   try {
@@ -35,9 +35,14 @@ export async function GET(
       embeddingVec = JSON.parse(inc.embedding) as number[]
     } else {
       embeddingVec = await embedText(inc.description, voyageKey)
-      await supabase.from('incidents').update({
-        embedding: `[${embeddingVec.join(',')}]` as unknown as string,
-      }).eq('id', id)
+      // Closed incidents are locked at the DB level — the trigger would reject
+      // this backfill. The vector still serves the similarity query below.
+      if (inc.status !== 'closed') {
+        const { error: persistError } = await supabase.from('incidents').update({
+          embedding: `[${embeddingVec.join(',')}]` as unknown as string,
+        }).eq('id', id)
+        if (persistError) console.error('embedding backfill error:', persistError)
+      }
     }
   } catch {
     return NextResponse.json({ error: 'Embedding service unavailable' }, { status: 503 })
diff --git a/lib/auth/require-admin.ts b/lib/auth/require-admin.ts
new file mode 100644
index 0000000..bb2612e
--- /dev/null
+++ b/lib/auth/require-admin.ts
@@ -0,0 +1,18 @@
+import { createClient } from '@/lib/supabase/server'
+import type { SupabaseClient } from '@supabase/supabase-js'
+import type { User } from '@supabase/supabase-js'
+
+// Shared guard for /api/admin/* routes: resolves the session and requires
+// the admin role. Returns user: null when the caller must respond 403.
+export async function requireAdmin(): Promise<{
+  supabase: SupabaseClient
+  user: User | null
+}> {
+  const supabase = await createClient()
+  const { data: { user }, error } = await supabase.auth.getUser()
+  if (error || !user) return { supabase, user: null }
+  const { data: profile } = await supabase
+    .from('users').select('role').eq('id', user.id).single()
+  if (!profile || profile.role !== 'admin') return { supabase, user: null }
+  return { supabase, user }
+}
diff --git a/lib/csv.ts b/lib/csv.ts
new file mode 100644
index 0000000..4a6a579
--- /dev/null
+++ b/lib/csv.ts
@@ -0,0 +1,14 @@
+export function escapeCsv(value: string | number | null | undefined): string {
+  if (value === null || value === undefined) return ''
+  const str = String(value)
+  if (str.includes(',') || str.includes('"') || str.includes('\n')) {
+    return `"${str.replace(/"/g, '""')}"`
+  }
+  return str
+}
+
+export function rowsToCsv(headers: string[], rows: string[][]): string {
+  const lines = [headers.map(escapeCsv).join(',')]
+  for (const row of rows) lines.push(row.map(escapeCsv).join(','))
+  return lines.join('\r\n')
+}
diff --git a/lib/reports/jkkp8.ts b/lib/reports/jkkp8.ts
index c95712b..b452851 100644
--- a/lib/reports/jkkp8.ts
+++ b/lib/reports/jkkp8.ts
@@ -1,4 +1,5 @@
 import { computeDoshObligation } from '@/lib/incidents/dosh'
+import { escapeCsv } from '@/lib/csv'
 
 export interface Jkkp8Incident {
   reference_no: string | null
@@ -73,15 +74,6 @@ export const JKKP8_HEADERS = [
   'Description', 'Medical Status', 'Lost Days', 'NADOPOD Obligation', 'DOSH Filing Status',
 ]
 
-export function escapeCsv(value: string | number | null | undefined): string {
-  if (value === null || value === undefined) return ''
-  const str = String(value)
-  if (str.includes(',') || str.includes('"') || str.includes('\n')) {
-    return `"${str.replace(/"/g, '""')}"`
-  }
-  return str
-}
-
 export function jkkp8Csv(rows: Jkkp8Row[]): string {
   const lines = [JKKP8_HEADERS.map(escapeCsv).join(',')]
   for (const r of rows) {