diff --git a/src/server/static-react/src/api/core/errors.ts b/src/server/static-react/src/api/core/errors.ts
index 7df0a01d..ea2605a4 100644
--- a/src/server/static-react/src/api/core/errors.ts
+++ b/src/server/static-react/src/api/core/errors.ts
@@ -68,11 +68,21 @@ export class ApiError extends Error {
     if (this.isNetworkError) {
       return ERROR_MESSAGES.NETWORK_ERROR;
     }
-    
+
     if (this.isTimeoutError) {
       return ERROR_MESSAGES.TIMEOUT_ERROR;
     }
 
+    // Prefer the server-supplied descriptive message over the generic constant
+    // for HTTP errors. ErrorFactory.fromResponse fills `this.message` with
+    // `errorData.message` / `errorData.error` (e.g. structured 400 payloads
+    // like "Field 'title' not on schema 'X'", or a 404 body's "schema not
+    // found") — that text is what the user can actually act on. The synthetic
+    // `HTTP <status>` fallback is filtered out so we don't surface "HTTP 404".
+    if (this.message && this.status > 0 && !/^HTTP \d+$/.test(this.message)) {
+      return this.message;
+    }
+
     switch (this.status) {
       case HTTP_STATUS_CODES.UNAUTHORIZED:
         return ERROR_MESSAGES.AUTHENTICATION_ERROR;
diff --git a/src/server/static-react/src/components/StatusSection.tsx b/src/server/static-react/src/components/StatusSection.tsx
index 59110e7c..86dea759 100644
--- a/src/server/static-react/src/components/StatusSection.tsx
+++ b/src/server/static-react/src/components/StatusSection.tsx
@@ -4,6 +4,8 @@ import { systemClient } from '../api/clients/systemClient'
 import { ingestionClient } from '../api/clients'
 import type { IngestionProgress } from '../api/clients/ingestionClient'
 import { usePolling } from '../hooks/usePolling'
+import { isNetworkError } from '../api/core/errors'
+import { toErrorMessage } from '../utils/schemaUtils'
 
 type ProgressJob = IngestionProgress & { job_type?: string }
 
@@ -76,8 +78,11 @@ function StatusSection() {
         setIsResetting(false)
       }
     } catch (error) {
-      const msg = error instanceof Error ? error.message : String(error)
-      setResetResult({ type: 'error', message: `Network error: ${msg}` })
+      const msg = toErrorMessage(error)
+      setResetResult({
+        type: 'error',
+        message: isNetworkError(error) ? `Network error: ${msg}` : msg,
+      })
       setShowConfirmDialog(false)
       setIsResetting(false)
     }
diff --git a/src/server/static-react/src/components/tabs/DataBrowserTab.tsx b/src/server/static-react/src/components/tabs/DataBrowserTab.tsx
index aa13bbab..bc5c7df2 100644
--- a/src/server/static-react/src/components/tabs/DataBrowserTab.tsx
+++ b/src/server/static-react/src/components/tabs/DataBrowserTab.tsx
@@ -15,7 +15,7 @@ import { FieldsTable } from '../StructuredResults'
 import SchemaName from '../shared/SchemaName'
 import ShareRecordModal from '../ShareRecordModal'
 import { ArrowUpTrayIcon } from '@heroicons/react/24/outline'
-import { getFieldNames, toggleSetItem } from '../../utils/schemaUtils'
+import { getFieldNames, toErrorMessage, toggleSetItem } from '../../utils/schemaUtils'
 import {
   keyId,
   keyLabel,
@@ -186,7 +186,7 @@ export default function DataBrowserTab() {
           setSchemaErrors((p) => ({ ...p, [name]: res.error || 'Failed to fetch keys' }))
         }
       } catch (e) {
-        setSchemaErrors((p) => ({ ...p, [name]: (e instanceof Error ? e.message : String(e)) || 'Network error' }))
+        setSchemaErrors((p) => ({ ...p, [name]: toErrorMessage(e) || 'Failed to fetch keys' }))
       } finally {
         setSchemaLoading((p) => ({ ...p, [name]: false }))
       }
diff --git a/src/server/static-react/src/components/tabs/DiscoveryBrowseTab.tsx b/src/server/static-react/src/components/tabs/DiscoveryBrowseTab.tsx
index c498cc33..36a55efd 100644
--- a/src/server/static-react/src/components/tabs/DiscoveryBrowseTab.tsx
+++ b/src/server/static-react/src/components/tabs/DiscoveryBrowseTab.tsx
@@ -47,7 +47,7 @@ function ProfileCard({ result, onConnect }: ProfileCardProps) {
         onConnect({ error: res.error || 'Connect failed' })
       }
     } catch (e) {
-      onConnect({ error: toErrorMessage(e) || 'Network error' })
+      onConnect({ error: toErrorMessage(e) || 'Connect failed' })
     } finally {
       setSending(false)
     }
@@ -235,7 +235,7 @@ export default function DiscoveryBrowseTab({ onResult }: DiscoveryBrowseTabProps
         setSearchError(res.error || 'Search failed')
       }
     } catch (e) {
-      setSearchError(toErrorMessage(e) || 'Network error')
+      setSearchError(toErrorMessage(e) || 'Search failed')
     } finally {
       setSearching(false)
     }
diff --git a/src/server/static-react/src/components/tabs/FeedTab.tsx b/src/server/static-react/src/components/tabs/FeedTab.tsx
index 08a07c72..a124a2c2 100644
--- a/src/server/static-react/src/components/tabs/FeedTab.tsx
+++ b/src/server/static-react/src/components/tabs/FeedTab.tsx
@@ -2,6 +2,7 @@ import { useState, useCallback } from 'react'
 import { useAppSelector } from '../../store/hooks'
 import { createApiClient } from '../../api/core/client'
 import { API_ENDPOINTS } from '../../api/endpoints'
+import { toErrorMessage } from '../../utils/schemaUtils'
 
 const apiClient = createApiClient()
 
@@ -78,7 +79,7 @@ export default function FeedTab() {
       setTotal(data?.total || 0)
       setFetched(true)
     } catch (err) {
-      setError((err instanceof Error ? err.message : null) || 'Network error')
+      setError(toErrorMessage(err) || 'Failed to fetch feed')
     } finally {
       setLoading(false)
     }
diff --git a/src/server/static-react/src/components/tabs/MyProfileTab.tsx b/src/server/static-react/src/components/tabs/MyProfileTab.tsx
index 248aa4ba..1538cf17 100644
--- a/src/server/static-react/src/components/tabs/MyProfileTab.tsx
+++ b/src/server/static-react/src/components/tabs/MyProfileTab.tsx
@@ -342,7 +342,7 @@ export default function MyProfileTab({ onResult }: MyProfileTabProps) {
         onResult?.({ error: res.error || 'Detection failed' })
       }
     } catch (e) {
-      onResult?.({ error: toErrorMessage(e) || 'Network error' })
+      onResult?.({ error: toErrorMessage(e) || 'Detection failed' })
     } finally {
       setDetecting(false)
     }
@@ -358,7 +358,7 @@ export default function MyProfileTab({ onResult }: MyProfileTabProps) {
         onResult?.({ error: res.error || 'Toggle failed' })
       }
     } catch (e) {
-      onResult?.({ error: toErrorMessage(e) || 'Network error' })
+      onResult?.({ error: toErrorMessage(e) || 'Toggle failed' })
     } finally {
       setToggling(false)
     }
diff --git a/src/server/static-react/src/components/tabs/NativeIndexTab.tsx b/src/server/static-react/src/components/tabs/NativeIndexTab.tsx
index 7275de73..7ec45cb1 100644
--- a/src/server/static-react/src/components/tabs/NativeIndexTab.tsx
+++ b/src/server/static-react/src/components/tabs/NativeIndexTab.tsx
@@ -154,9 +154,9 @@ export default function NativeIndexTab({ onResult }: NativeIndexTabProps) {
         onResult({ error: res.error || 'Search failed', status: res.status })
       }
     } catch (e) {
-      const msg = toErrorMessage(e)
-      setError(msg || 'Network error')
-      onResult({ error: msg || 'Network error' })
+      const msg = toErrorMessage(e) || 'Search failed'
+      setError(msg)
+      onResult({ error: msg })
     } finally {
       setIsSearching(false)
     }
diff --git a/src/server/static-react/src/components/tabs/WordGraphTab.tsx b/src/server/static-react/src/components/tabs/WordGraphTab.tsx
index d6a78111..2fb5da12 100644
--- a/src/server/static-react/src/components/tabs/WordGraphTab.tsx
+++ b/src/server/static-react/src/components/tabs/WordGraphTab.tsx
@@ -154,7 +154,7 @@ export default function WordGraphTab() {
         setError(res.error || 'Search failed')
       }
     } catch (e) {
-      setError(toErrorMessage(e) || 'Network error')
+      setError(toErrorMessage(e) || 'Search failed')
     } finally {
       setIsSearching(false)
     }
diff --git a/src/server/static-react/src/components/tabs/discovery/ConnectionRequestsPanel.tsx b/src/server/static-react/src/components/tabs/discovery/ConnectionRequestsPanel.tsx
index f088247b..48147776 100644
--- a/src/server/static-react/src/components/tabs/discovery/ConnectionRequestsPanel.tsx
+++ b/src/server/static-react/src/components/tabs/discovery/ConnectionRequestsPanel.tsx
@@ -67,7 +67,7 @@ export default function ConnectionRequestsPanel({ onResult }: ConnectionRequests
         onResult({ error: res.error || `Failed to ${action}` })
       }
     } catch (e) {
-      onResult({ error: toErrorMessage(e) || 'Network error' })
+      onResult({ error: toErrorMessage(e) || 'Failed to respond' })
     } finally {
       setResponding(null)
     }
diff --git a/src/server/static-react/src/components/tabs/discovery/FaceSearchPanel.tsx b/src/server/static-react/src/components/tabs/discovery/FaceSearchPanel.tsx
index 21f3b627..ae90aa97 100644
--- a/src/server/static-react/src/components/tabs/discovery/FaceSearchPanel.tsx
+++ b/src/server/static-react/src/components/tabs/discovery/FaceSearchPanel.tsx
@@ -117,9 +117,9 @@ export default function FaceSearchPanel({ onResult }: FaceSearchPanelProps) {
         onResult({ error: res.error || 'Face search failed' })
       }
     } catch (e) {
-      const msg = toErrorMessage(e)
-      setError(msg || 'Network error')
-      onResult({ error: msg || 'Network error' })
+      const msg = toErrorMessage(e) || 'Face search failed'
+      setError(msg)
+      onResult({ error: msg })
     } finally {
       setSearching(false)
     }
@@ -138,7 +138,7 @@ export default function FaceSearchPanel({ onResult }: FaceSearchPanelProps) {
         onResult({ error: res.error || 'Connect failed' })
       }
     } catch (e) {
-      onResult({ error: toErrorMessage(e) || 'Network error' })
+      onResult({ error: toErrorMessage(e) || 'Connect failed' })
     }
   }
 
diff --git a/src/server/static-react/src/components/tabs/discovery/InterestsPanel.tsx b/src/server/static-react/src/components/tabs/discovery/InterestsPanel.tsx
index 6cead256..40e85d69 100644
--- a/src/server/static-react/src/components/tabs/discovery/InterestsPanel.tsx
+++ b/src/server/static-react/src/components/tabs/discovery/InterestsPanel.tsx
@@ -25,7 +25,7 @@ export default function InterestsPanel({ onResult }: InterestsPanelProps) {
         setLoadError(res.error || 'Failed to load interests')
       }
     } catch (e) {
-      setLoadError(toErrorMessage(e) || 'Network error')
+      setLoadError(toErrorMessage(e) || 'Failed to load interests')
     } finally {
       setLoading(false)
     }
@@ -42,7 +42,7 @@ export default function InterestsPanel({ onResult }: InterestsPanelProps) {
         onResult({ error: res.error || 'Toggle failed' })
       }
     } catch (e) {
-      onResult({ error: toErrorMessage(e) || 'Network error' })
+      onResult({ error: toErrorMessage(e) || 'Toggle failed' })
     }
   }
 
@@ -57,7 +57,7 @@ export default function InterestsPanel({ onResult }: InterestsPanelProps) {
         onResult({ error: res.error || 'Detection failed' })
       }
     } catch (e) {
-      onResult({ error: toErrorMessage(e) || 'Network error' })
+      onResult({ error: toErrorMessage(e) || 'Detection failed' })
     } finally {
       setDetecting(false)
     }
diff --git a/src/server/static-react/src/components/tabs/discovery/PeopleLikeYouPanel.tsx b/src/server/static-react/src/components/tabs/discovery/PeopleLikeYouPanel.tsx
index a71d7b2c..b765e874 100644
--- a/src/server/static-react/src/components/tabs/discovery/PeopleLikeYouPanel.tsx
+++ b/src/server/static-react/src/components/tabs/discovery/PeopleLikeYouPanel.tsx
@@ -40,7 +40,7 @@ export default function PeopleLikeYouPanel({ onResult }: PeopleLikeYouPanelProps
         }
       }
     } catch (e) {
-      const msg = toErrorMessage(e) || 'Network error'
+      const msg = toErrorMessage(e) || 'Failed to load similar profiles'
       setError(msg)
       if (isLocalModeError(msg)) {
         localModeRef.current = true
@@ -74,7 +74,7 @@ export default function PeopleLikeYouPanel({ onResult }: PeopleLikeYouPanelProps
         onResult({ error: res.error || 'Connect failed' })
       }
     } catch (e) {
-      onResult({ error: toErrorMessage(e) || 'Network error' })
+      onResult({ error: toErrorMessage(e) || 'Connect failed' })
     }
   }
 
diff --git a/src/server/static-react/src/components/tabs/discovery/SearchPanel.tsx b/src/server/static-react/src/components/tabs/discovery/SearchPanel.tsx
index 4ed767c7..d4954896 100644
--- a/src/server/static-react/src/components/tabs/discovery/SearchPanel.tsx
+++ b/src/server/static-react/src/components/tabs/discovery/SearchPanel.tsx
@@ -55,9 +55,9 @@ export default function SearchPanel({ onResult }: SearchPanelProps) {
         onResult({ error: res.error || 'Search failed' })
       }
     } catch (e) {
-      const msg = toErrorMessage(e)
-      setError(msg || 'Network error')
-      onResult({ error: msg || 'Network error' })
+      const msg = toErrorMessage(e) || 'Search failed'
+      setError(msg)
+      onResult({ error: msg })
     } finally {
       setSearching(false)
     }
@@ -76,7 +76,7 @@ export default function SearchPanel({ onResult }: SearchPanelProps) {
         onResult({ error: res.error || 'Connect failed' })
       }
     } catch (e) {
-      onResult({ error: toErrorMessage(e) || 'Network error' })
+      onResult({ error: toErrorMessage(e) || 'Connect failed' })
     }
   }
 
diff --git a/src/server/static-react/src/components/tabs/discovery/SharedEventsPanel.tsx b/src/server/static-react/src/components/tabs/discovery/SharedEventsPanel.tsx
index f1902839..89fe3927 100644
--- a/src/server/static-react/src/components/tabs/discovery/SharedEventsPanel.tsx
+++ b/src/server/static-react/src/components/tabs/discovery/SharedEventsPanel.tsx
@@ -36,7 +36,7 @@ export default function SharedEventsPanel({ onResult }: SharedEventsPanelProps)
         setError(statusRes.error || 'Failed to load calendar sharing status')
       }
     } catch (e) {
-      setError(toErrorMessage(e) || 'Network error')
+      setError(toErrorMessage(e) || 'Failed to load calendar sharing status')
     } finally {
       setLoading(false)
     }
@@ -65,7 +65,7 @@ export default function SharedEventsPanel({ onResult }: SharedEventsPanelProps)
         onResult({ error: res.error || 'Failed to toggle calendar sharing' })
       }
     } catch (e) {
-      onResult({ error: toErrorMessage(e) || 'Network error' })
+      onResult({ error: toErrorMessage(e) || 'Failed to toggle calendar sharing' })
     } finally {
       setToggling(false)
     }
diff --git a/src/server/static-react/src/components/tabs/personas/ImportedIdentitiesPanel.tsx b/src/server/static-react/src/components/tabs/personas/ImportedIdentitiesPanel.tsx
index 11e95019..cee9e1da 100644
--- a/src/server/static-react/src/components/tabs/personas/ImportedIdentitiesPanel.tsx
+++ b/src/server/static-react/src/components/tabs/personas/ImportedIdentitiesPanel.tsx
@@ -1,5 +1,6 @@
 import { useCallback, useEffect, useState } from 'react'
 import { listIdentities, type IdentityAuditRow } from '../../../api/clients/fingerprintsClient'
+import { toErrorMessage } from '../../../utils/schemaUtils'
 
 /**
  * "Identities" audit panel — surfaces every Identity record on this
@@ -29,7 +30,7 @@ export default function ImportedIdentitiesPanel() {
         setError(res.error ?? 'Failed to load identities')
       }
     } catch (e) {
-      setError((e as Error)?.message ?? 'Network error')
+      setError(toErrorMessage(e) || 'Failed to load identities')
     } finally {
       setLoading(false)
     }
diff --git a/src/server/static-react/src/components/tabs/personas/IngestionErrorsPanel.tsx b/src/server/static-react/src/components/tabs/personas/IngestionErrorsPanel.tsx
index 4ae4803f..38c58567 100644
--- a/src/server/static-react/src/components/tabs/personas/IngestionErrorsPanel.tsx
+++ b/src/server/static-react/src/components/tabs/personas/IngestionErrorsPanel.tsx
@@ -4,6 +4,7 @@ import {
   resolveIngestionError,
   type IngestionErrorView,
 } from '../../../api/clients/fingerprintsClient'
+import { toErrorMessage } from '../../../utils/schemaUtils'
 
 /**
  * Failed records panel. Renders unresolved IngestionError rows so the
@@ -33,7 +34,7 @@ export default function IngestionErrorsPanel() {
         setError(res.error ?? 'Failed to load ingestion errors')
       }
     } catch (e) {
-      setError((e as Error)?.message ?? 'Network error')
+      setError(toErrorMessage(e) || 'Failed to load ingestion errors')
     } finally {
       setLoading(false)
     }
@@ -63,7 +64,7 @@ export default function IngestionErrorsPanel() {
           setError(res.error ?? `Failed to ${resolved ? 'dismiss' : 'restore'}`)
         }
       } catch (e) {
-        setError((e as Error)?.message ?? 'Network error')
+        setError(toErrorMessage(e) || 'Failed to update ingestion error')
       } finally {
         setBusyId(null)
       }
diff --git a/src/server/static-react/src/components/tabs/personas/MyIdentityCardPanel.tsx b/src/server/static-react/src/components/tabs/personas/MyIdentityCardPanel.tsx
index 8bab91b7..8aef0b47 100644
--- a/src/server/static-react/src/components/tabs/personas/MyIdentityCardPanel.tsx
+++ b/src/server/static-react/src/components/tabs/personas/MyIdentityCardPanel.tsx
@@ -8,6 +8,7 @@ import {
   type MyIdentityCardResponse,
 } from '../../../api/clients/fingerprintsClient'
 import { listContacts, type Contact } from '../../../api/clients/trustClient'
+import { toErrorMessage } from '../../../utils/schemaUtils'
 
 type AttachStage = 'idle' | 'camera' | 'detecting' | 'saving'
 
@@ -93,7 +94,7 @@ export default function MyIdentityCardPanel() {
         setError(res.error ?? 'Failed to load identity card')
       }
     } catch (e) {
-      setError((e as Error)?.message ?? 'Network error')
+      setError(toErrorMessage(e) || 'Failed to load identity card')
     } finally {
       setLoading(false)
     }
@@ -134,7 +135,7 @@ export default function MyIdentityCardPanel() {
         setSaveError(res.error ?? 'Failed to reissue identity card')
       }
     } catch (e) {
-      setSaveError((e as Error)?.message ?? 'Network error')
+      setSaveError(toErrorMessage(e) || 'Failed to reissue identity card')
     } finally {
       setSaving(false)
     }
diff --git a/src/server/static-react/src/components/tabs/personas/PersonasPanel.tsx b/src/server/static-react/src/components/tabs/personas/PersonasPanel.tsx
index 71d80ff0..5c017623 100644
--- a/src/server/static-react/src/components/tabs/personas/PersonasPanel.tsx
+++ b/src/server/static-react/src/components/tabs/personas/PersonasPanel.tsx
@@ -16,6 +16,7 @@ import {
   type ResolveDiagnostics,
 } from '../../../api/clients/fingerprintsClient'
 import { ErrorMessage } from '../../shared/ErrorMessage'
+import { toErrorMessage } from '../../../utils/schemaUtils'
 
 type SortMode = 'recent' | 'name_asc' | 'mentions_desc' | 'trust_tier_desc'
 
@@ -160,7 +161,7 @@ export default function PersonasPanel() {
         setError(res.error ?? 'Failed to load personas')
       }
     } catch (e) {
-      setError((e as Error)?.message ?? 'Network error')
+      setError(toErrorMessage(e) || 'Failed to load personas')
     } finally {
       setLoading(false)
     }
@@ -190,7 +191,7 @@ export default function PersonasPanel() {
       })
       .catch((e: unknown) => {
         if (!cancelled) {
-          setDetailError((e as Error)?.message ?? 'Network error')
+          setDetailError(toErrorMessage(e) || 'Failed to load persona')
           setDetail(null)
         }
       })
diff --git a/src/server/static-react/src/components/tabs/personas/ReceivedCardsPanel.tsx b/src/server/static-react/src/components/tabs/personas/ReceivedCardsPanel.tsx
index baadeffa..b1e1db03 100644
--- a/src/server/static-react/src/components/tabs/personas/ReceivedCardsPanel.tsx
+++ b/src/server/static-react/src/components/tabs/personas/ReceivedCardsPanel.tsx
@@ -5,6 +5,7 @@ import {
   listReceivedCards,
   type ReceivedCardView,
 } from '../../../api/clients/fingerprintsClient'
+import { toErrorMessage } from '../../../utils/schemaUtils'
 
 type ActionFlag = 'accept' | 'dismiss' | null
 
@@ -52,7 +53,7 @@ export default function ReceivedCardsPanel() {
         setError(res.error ?? 'Failed to load received cards')
       }
     } catch (e) {
-      setError((e as Error)?.message ?? 'Network error')
+      setError(toErrorMessage(e) || 'Failed to load received cards')
     } finally {
       setLoading(false)
     }
diff --git a/src/server/static-react/src/components/tabs/personas/SuggestedPersonasPanel.tsx b/src/server/static-react/src/components/tabs/personas/SuggestedPersonasPanel.tsx
index 5a7e7a0a..81ec188d 100644
--- a/src/server/static-react/src/components/tabs/personas/SuggestedPersonasPanel.tsx
+++ b/src/server/static-react/src/components/tabs/personas/SuggestedPersonasPanel.tsx
@@ -5,6 +5,7 @@ import {
   RELATIONSHIP_OPTIONS,
   type SuggestedPersonaView,
 } from '../../../api/clients/fingerprintsClient'
+import { toErrorMessage } from '../../../utils/schemaUtils'
 
 /**
  * localStorage key used to persist the set of dismissed suggestion
@@ -78,7 +79,7 @@ export default function SuggestedPersonasPanel() {
         setError(res.error ?? 'Failed to load suggestions')
       }
     } catch (e) {
-      setError((e as Error)?.message ?? 'Network error')
+      setError(toErrorMessage(e) || 'Failed to load suggestions')
     } finally {
       setLoading(false)
     }
diff --git a/src/server/static-react/src/components/tabs/sharing/CrossUserSharingPanel.tsx b/src/server/static-react/src/components/tabs/sharing/CrossUserSharingPanel.tsx
index a6352ecb..9e10c5db 100644
--- a/src/server/static-react/src/components/tabs/sharing/CrossUserSharingPanel.tsx
+++ b/src/server/static-react/src/components/tabs/sharing/CrossUserSharingPanel.tsx
@@ -13,6 +13,7 @@ import {
 } from '../../../api/clients/sharingClient'
 import { listContacts, type Contact } from '../../../api/clients/trustClient'
 import { getAllSchemasWithState } from '../../../api/clients/schemaClient'
+import { toErrorMessage } from '../../../utils/schemaUtils'
 
 type ScopeKind = 'AllSchemas' | 'Schema' | 'SchemaField'
 
@@ -81,7 +82,7 @@ export default function CrossUserSharingPanel() {
         setRulesError(res.error ?? 'Failed to load share rules')
       }
     } catch (e) {
-      setRulesError((e as Error)?.message ?? 'Network error')
+      setRulesError(toErrorMessage(e) || 'Failed to load share rules')
     } finally {
       setRulesLoading(false)
     }
@@ -98,7 +99,7 @@ export default function CrossUserSharingPanel() {
         setPendingError(res.error ?? 'Failed to load pending invites')
       }
     } catch (e) {
-      setPendingError((e as Error)?.message ?? 'Network error')
+      setPendingError(toErrorMessage(e) || 'Failed to load pending invites')
     } finally {
       setPendingLoading(false)
     }
@@ -181,7 +182,7 @@ export default function CrossUserSharingPanel() {
               setToast(res.error ?? 'Failed to generate invite')
             }
           } catch (e) {
-            setToast((e as Error)?.message ?? 'Network error')
+            setToast(toErrorMessage(e) || 'Failed to generate invite')
           }
         }}
         onDeactivate={async (rule: ShareRule) => {
@@ -197,7 +198,7 @@ export default function CrossUserSharingPanel() {
               setToast(res.error ?? 'Failed to deactivate')
             }
           } catch (e) {
-            setToast((e as Error)?.message ?? 'Network error')
+            setToast(toErrorMessage(e) || 'Failed to deactivate')
           }
         }}
       />
@@ -219,7 +220,7 @@ export default function CrossUserSharingPanel() {
               setToast(res.error ?? 'Failed to accept invite')
             }
           } catch (e) {
-            setToast((e as Error)?.message ?? 'Network error')
+            setToast(toErrorMessage(e) || 'Failed to accept invite')
           }
         }}
       />
@@ -289,7 +290,7 @@ function CreateRuleForm({ contacts, schemas, onCreated }: CreateRuleFormProps) {
         setError(res.error ?? 'Failed to create share rule')
       }
     } catch (err) {
-      setError((err as Error)?.message ?? 'Network error')
+      setError(toErrorMessage(err) || 'Failed to create share rule')
     } finally {
       setSubmitting(false)
     }
diff --git a/src/server/static-react/src/utils/schemaUtils.ts b/src/server/static-react/src/utils/schemaUtils.ts
index bf7f2296..4f3725f1 100644
--- a/src/server/static-react/src/utils/schemaUtils.ts
+++ b/src/server/static-react/src/utils/schemaUtils.ts
@@ -9,6 +9,8 @@
  * - Query-by-key record fetching
  */
 
+import { isApiError } from '../api/core/errors'
+
 export interface SchemaLike {
   name?: string;
   descriptive_name?: string;
@@ -81,8 +83,13 @@ export function toggleSetItem<T>(set: Iterable<T>, item: T): Set<T> {
   return next
 }
 
-/** Convert an unknown error value to a string message. */
+/**
+ * Convert an unknown error value to a user-friendly message.
+ * For ApiError, defers to toUserMessage() so HTTP 4xx/5xx responses surface
+ * the server-supplied message instead of a generic "Network error" fallback.
+ */
 export function toErrorMessage(error: unknown): string {
+  if (isApiError(error)) return error.toUserMessage()
   if (error instanceof Error) return error.message
   return String(error)
 }