@@ -47,7 +47,9 @@ export async function startFleetSync(request: FleetSyncRequest, sender: WebConte
       // A bucket is not a fleet host: refuse it on its own row.
       const target = await resolveConnection(destId)
       if (isS3Connection(target)) throw new Error(`${target.name} is an S3 bucket; Fleet Sync pushes to servers.`)
-      const built = await buildPlan(req)
+      // The same path rarely exists on every host already: create it (--mkpath,
+      // dropped with a warning by the planner when either rsync is older than 3.2.3).
+      const built = await buildPlan(req, { mkpath: true })
       cleanup = built.cleanup
       const handle = runPlan(built.plan)
       cancels.set(destId, handle.cancel)
 
@@ -1,10 +1,11 @@
 'use client'
 
 import { useCallback, useEffect, useMemo, useState } from 'react'
-import { CircleAlert, CircleCheck, CircleDashed, HardDriveDownload, Loader2, Play, Square } from 'lucide-react'
+import { CircleAlert, CircleCheck, CircleDashed, Copy, HardDriveDownload, Loader2, Play, Square } from 'lucide-react'
 import { Button } from '@/components/ui/button'
 import { Checkbox } from '@/components/ui/checkbox'
 import { PathInput, type PathSource } from '@/components/path-input'
+import { destinationFor, errorReport } from '@/lib/fleet-sync'
 import { ScrollArea } from '@/components/ui/scroll-area'
 import { api, unwrap, type Connection, type FleetSyncEvent } from '@/lib/api'
 
@@ -18,7 +19,19 @@ import { api, unwrap, type Connection, type FleetSyncEvent } from '@/lib/api'
  */
 
 type DestState = 'pending' | 'running' | 'done' | 'error'
-type DestView = { id: string; name: string; host: string; state: DestState; percent: number; message: string }
+type DestView = {
+  id: string
+  name: string
+  host: string
+  state: DestState
+  percent: number
+  /** The last line worth showing on the row while it runs, then the outcome. */
+  message: string
+  /** rsync's own stderr, kept so a failure shows its real cause, not just the summary. */
+  log: string[]
+}
+
+const LOG_LINES = 30
 
 const STATE_ICON: Record<DestState, React.ReactNode> = {
   pending: <CircleDashed className="size-3.5 text-faint" />,
@@ -61,7 +74,10 @@ export function FleetSyncPanel() {
         else if (e.type === 'progress') {
           next.state = 'running'
           next.percent = Math.max(0, Math.min(100, Math.round(e.progress.percent)))
-        } else if (e.type === 'stderr') next.message = e.line
+        } else if (e.type === 'stderr') {
+          next.message = e.line
+          next.log = [...cur.log, e.line].slice(-LOG_LINES)
+        }
         else if (e.type === 'error') {
           next.state = 'error'
           next.message = e.message
@@ -100,7 +116,7 @@ export function FleetSyncPanel() {
     const initial: Record<string, DestView> = {}
     for (const id of ids) {
       const s = servers.find((x) => x.id === id)
-      initial[id] = { id, name: s?.name ?? id, host: s?.host ?? '', state: 'pending', percent: 0, message: '' }
+      initial[id] = { id, name: s?.name ?? id, host: s?.host ?? '', state: 'pending', percent: 0, message: '', log: [] }
     }
     setDests(initial)
 
@@ -113,14 +129,25 @@ export function FleetSyncPanel() {
       api()?.fleet.sync({
         source,
         destinationConnectionIds: ids,
-        destinationPath: destPath.trim() || sourcePath.trim(),
+        destinationPath: destinationFor(sourcePath, destPath),
         options: {},
         concurrency: 4,
       }),
     )
     setSyncId(res?.syncId ?? null)
   }, [selected, sourceId, sourcePath, destPath, servers])
 
+  const [copied, setCopied] = useState<string | null>(null)
+  const copyError = useCallback(async (d: DestView) => {
+    try {
+      await navigator.clipboard.writeText(errorReport(d))
+      setCopied(d.id)
+      setTimeout(() => setCopied((cur) => (cur === d.id ? null : cur)), 1500)
+    } catch {
+      // The text stays selectable in the block, so a refused clipboard is not a dead end.
+    }
+  }, [])
+
   const cancel = useCallback(async () => {
     if (syncId) await api()?.fleet.cancelSync(syncId)
   }, [syncId])
@@ -203,17 +230,41 @@ export function FleetSyncPanel() {
       <ScrollArea className="min-h-0 flex-1 rounded-md border border-line">
         <div className="flex flex-col">
           {Object.values(dests).map((d) => (
-            <div key={d.id} className="flex items-center gap-2 px-2 py-1.5 text-[12px]">
-              {STATE_ICON[d.state]}
-              <span className="w-40 truncate">{d.name}</span>
-              <div className="h-1.5 flex-1 overflow-hidden rounded bg-secondary">
-                <div
-                  className={`h-full ${d.state === 'error' ? 'bg-destructive' : 'bg-primary'}`}
-                  style={{ width: `${d.percent}%` }}
-                />
+            <div key={d.id} className="border-b border-line last:border-b-0">
+              <div className="flex items-center gap-2 px-2 py-1.5 text-[12px]">
+                {STATE_ICON[d.state]}
+                <span className="w-40 truncate">{d.name}</span>
+                <div className="h-1.5 flex-1 overflow-hidden rounded bg-secondary">
+                  <div
+                    className={`h-full ${d.state === 'error' ? 'bg-destructive' : 'bg-primary'}`}
+                    style={{ width: `${d.percent}%` }}
+                  />
+                </div>
+                <span className="w-10 text-right text-faint">{d.percent}%</span>
+                {d.message && d.state !== 'error' ? <span className="max-w-[40%] truncate text-faint">{d.message}</span> : null}
               </div>
-              <span className="w-10 text-right text-faint">{d.percent}%</span>
-              {d.message ? <span className="max-w-[40%] truncate text-faint">{d.message}</span> : null}
+              {d.state === 'error' ? (
+                <div className="mx-2 mb-2 rounded-md border border-destructive/40 bg-destructive/5 p-2 text-[12px]" role="alert">
+                  <div className="flex items-start gap-2">
+                    <p className="flex-1 font-medium text-destructive selectable">{d.message || 'The transfer failed.'}</p>
+                    <Button
+                      variant="outline"
+                      size="sm"
+                      onClick={() => void copyError(d)}
+                      className="h-7 shrink-0 gap-1.5 text-[11px]"
+                      aria-label={`Copy the error for ${d.name}`}
+                    >
+                      <Copy className="size-3" />
+                      {copied === d.id ? 'Copied' : 'Copy error'}
+                    </Button>
+                  </div>
+                  {d.log.length ? (
+                    <pre className="mt-2 max-h-40 overflow-auto rounded bg-background/60 p-2 font-mono text-[11px] leading-relaxed whitespace-pre-wrap text-faint selectable">
+                      {d.log.join('\n')}
+                    </pre>
+                  ) : null}
+                </div>
+              ) : null}
             </div>
           ))}
           {Object.keys(dests).length === 0 ? (
 
@@ -0,0 +1,38 @@
+import { describe, expect, it } from 'vitest'
+import { destinationFor, errorReport } from './fleet-sync'
+
+describe('errorReport', () => {
+  it('is the summary, the host, and rsync\'s own lines: what a person pastes', () => {
+    const text = errorReport({
+      name: 'dev2',
+      host: 'dev2.profullstack.com',
+      message: 'The destination folder /home/anthony/x could not be created',
+      log: ['rsync: [Receiver] mkdir "/home/anthony/x" failed: No such file or directory (2)', 'rsync error: error in file IO (code 11)'],
+    })
+    expect(text).toBe(
+      'Fleet Sync to dev2 (dev2.profullstack.com) failed: The destination folder /home/anthony/x could not be created\n\n' +
+        'rsync: [Receiver] mkdir "/home/anthony/x" failed: No such file or directory (2)\nrsync error: error in file IO (code 11)',
+    )
+  })
+
+  it('stands alone when rsync said nothing', () => {
+    expect(errorReport({ name: 'web1', host: '', message: 'Connection refused', log: [] })).toBe('Fleet Sync to web1 failed: Connection refused')
+  })
+})
+
+describe('destinationFor', () => {
+  it('lands the same path at the same path when the destination is left empty', () => {
+    // rsync would otherwise nest the folder: ~/Desktop/me/ideas/ideas.
+    expect(destinationFor('~/Desktop/me/ideas', '')).toBe('~/Desktop/me/')
+    expect(destinationFor('/srv/app/releases', '  ')).toBe('/srv/app/')
+    expect(destinationFor('~/Desktop/me/ideas', '~/Desktop/me/ideas')).toBe('~/Desktop/me/')
+  })
+
+  it('keeps a trailing-slash source as is: its contents go to the same folder', () => {
+    expect(destinationFor('~/Desktop/me/ideas/', '')).toBe('~/Desktop/me/ideas/')
+  })
+
+  it('never rewrites a destination the user typed', () => {
+    expect(destinationFor('~/Desktop/me/ideas', '/backup/ideas')).toBe('/backup/ideas')
+  })
+})
@@ -0,0 +1,29 @@
+/**
+ * Fleet Sync's pure helpers, kept out of the component so they are tested
+ * without the app's module aliases.
+ */
+
+export type FailedDestination = { name: string; host: string; message: string; log: string[] }
+
+/** The text a person pastes into an issue or a chat: what failed, where, and rsync's own words. */
+export function errorReport(d: FailedDestination): string {
+  return [`Fleet Sync to ${d.name}${d.host ? ` (${d.host})` : ''} failed: ${d.message}`, ...(d.log.length ? ['', ...d.log] : [])].join('\n')
+}
+
+/**
+ * Where the source lands when the destination box is empty (or says the same
+ * path): the same path on every host. rsync copies a folder named without a
+ * trailing slash INTO its destination, so sending `~/a/ideas` to `~/a/ideas`
+ * would make `~/a/ideas/ideas`. Sending it to the parent, `~/a/`, makes
+ * `~/a/ideas`, and works for a single file too. A path the user typed that
+ * differs from the source is theirs and goes through untouched.
+ */
+export function destinationFor(sourcePath: string, destPath: string): string {
+  const source = sourcePath.trim()
+  const dest = destPath.trim()
+  if (dest && dest !== source) return dest
+  if (source.endsWith('/')) return source
+  const slash = source.lastIndexOf('/')
+  if (slash === -1) return '.'
+  return source.slice(0, slash + 1)
+}
@@ -56,3 +56,17 @@ describe('humanizeStderr', () => {
     expect(humanizeStderr('some unrecognised failure')).toBeNull()
   })
 })
+
+describe('a destination folder that cannot be created', () => {
+  it('names the folder and the real cause, not a full disk', () => {
+    const stderr = 'rsync: [Receiver] mkdir "/home/anthony/Desktop/me/ideas" failed: No such file or directory (2)\nrsync error: error in file IO (code 11) at main.c(800) [Receiver=3.4.1]'
+    const message = humanizeStderr(stderr)
+    expect(message).toContain('/home/anthony/Desktop/me/ideas')
+    expect(message).toContain('a folder above it does not exist')
+    expect(message).not.toMatch(/full|read-only/)
+  })
+
+  it('no longer guesses "full or read-only" for a bare code 11', () => {
+    expect(interpretExit(11).message).not.toMatch(/full|read-only/)
+  })
+})
@@ -22,7 +22,7 @@ const MESSAGES: Record<number, { message: string; resumable?: boolean; ok?: bool
   10: { message: 'Connection interrupted (socket I/O error). This transfer can be resumed.', resumable: true },
   11: {
     message:
-      'File I/O error. The destination filesystem may be full or read-only. Partial transfer data was preserved where possible.',
+      'rsync hit a file I/O error on one side (code 11). The rsync output says which path and why. Partial transfer data was preserved where possible.',
     resumable: true,
   },
   12: { message: 'The rsync data stream failed, usually because the connection dropped. This transfer can be resumed.', resumable: true },
@@ -67,6 +67,13 @@ export function interpretExit(code: number, signal: NodeJS.Signals | null = null
 
 /** Recognises the common stderr shapes worth rewriting before a user sees them. */
 export function humanizeStderr(stderr: string): string | null {
+  // Checked before the disk-full and permission cases: it is the commonest code-11
+  // failure, and the old generic wording ("filesystem full or read-only") sent people
+  // looking in the wrong place.
+  const mkdir = /mkdir "([^"]+)" failed: No such file or directory/i.exec(stderr)
+  if (mkdir) {
+    return `The destination folder ${mkdir[1]} could not be created because a folder above it does not exist on that side. Create it first, or let DiskPush create the whole path (Fleet Sync does, with --mkpath, on rsync 3.2.3 or newer).`
+  }
   if (/No space left on device/i.test(stderr)) {
     return 'Transfer stopped because the destination filesystem is out of space. Partial transfer data was preserved where possible.'
   }