build: let infra containers builds fail individually

Signed-off-by: Jakob Borg <jakob@kastelo.net>

.github/workflows/build-infra-dockers.yaml

@@ -21,8 +21,8 @@ jobs:
     name: Build and push Docker images
     if: github.repository_owner == 'syncthing'
     runs-on: ubuntu-latest
-    environment: docker
     strategy:
+      fail-fast: false
       matrix:
         pkg:
           - stcrashreceiver

.github/workflows/build-syncthing.yaml

@@ -9,6 +9,11 @@ on:
   workflow_call:
   workflow_dispatch:
 
+permissions:
+  contents: read
+  issues: read
+  pull-requests: read
+
 env:
   # The go version to use for builds. We set check-latest to true when
   # installing, so we get the latest patch version that matches the
@@ -229,7 +234,6 @@ jobs:
   codesign-windows:
     name: Codesign for Windows
     if: github.repository_owner == 'syncthing' && (github.event_name == 'push' || github.event_name == 'workflow_dispatch') && (github.ref == 'refs/heads/release-nightly' || startsWith(github.ref, 'refs/tags/v'))
-    environment: release
     runs-on: windows-latest
     needs:
       - package-windows
@@ -402,7 +406,6 @@ jobs:
   package-macos:
     name: Package for macOS
     if: github.repository_owner == 'syncthing' && (github.event_name == 'push' || github.event_name == 'workflow_dispatch') && (github.ref == 'refs/heads/release-nightly' || startsWith(github.ref, 'refs/tags/v'))
-    environment: release
     runs-on: macos-latest
     needs:
       - facts
@@ -500,7 +503,6 @@ jobs:
   notarize-macos:
     name: Notarize for macOS
     if: github.repository_owner == 'syncthing' && (github.event_name == 'push' || github.event_name == 'workflow_dispatch') && (github.ref == 'refs/heads/release-nightly' || startsWith(github.ref, 'refs/tags/v'))
-    environment: release
     needs:
       - package-macos
     runs-on: macos-latest
@@ -641,7 +643,6 @@ jobs:
   sign-for-upgrade:
     name: Sign for upgrade
     if: github.repository_owner == 'syncthing' && (github.event_name == 'push' || github.event_name == 'workflow_dispatch') && (github.ref == 'refs/heads/release-nightly' || startsWith(github.ref, 'refs/tags/v'))
-    environment: release
     needs:
       - codesign-windows
       - package-linux
@@ -788,7 +789,6 @@ jobs:
   publish-nightly:
     name: Publish nightly build
     if: github.repository_owner == 'syncthing' && (github.event_name == 'push' || github.event_name == 'workflow_dispatch') && startsWith(github.ref, 'refs/heads/release-nightly')
-    environment: release
     needs:
       - sign-for-upgrade
       - facts
@@ -837,7 +837,6 @@ jobs:
   publish-release-files:
     name: Publish release files
     if: github.repository_owner == 'syncthing' && (github.event_name == 'push' || github.event_name == 'workflow_dispatch') && (github.ref == 'refs/heads/release' || startsWith(github.ref, 'refs/tags/v'))
-    environment: release
     permissions:
       contents: write
       id-token: write
@@ -948,7 +947,6 @@ jobs:
   publish-apt:
     name: Publish APT
     if: github.repository_owner == 'syncthing' && (github.event_name == 'push' || github.event_name == 'workflow_dispatch') && (github.ref == 'refs/heads/release-nightly' || startsWith(github.ref, 'refs/tags/v'))
-    environment: release
     needs:
       - package-debian
       - facts
@@ -1020,6 +1018,7 @@ jobs:
       VERSION: ${{ needs.facts.outputs.version }}
       RELEASE_KIND: ${{ needs.facts.outputs.release-kind }}
     strategy:
+      fail-fast: false
       matrix:
         pkg:
           - syncthing
@@ -1138,7 +1137,6 @@ jobs:
     runs-on: ubuntu-latest
     needs:
       - docker-ghcr
-    environment: docker
     env:
       DOCKERHUB_USERNAME: ${{ secrets.DOCKERHUB_USERNAME }}
       DOCKERHUB_TOKEN: ${{ secrets.DOCKERHUB_TOKEN }}

.github/workflows/mirrors.yaml

@@ -2,6 +2,9 @@ name: Mirrors
 
 on: [push, delete]
 
+permissions:
+  contents: read
+
 jobs:
   codeberg:
     name: Mirror to Codeberg

.github/workflows/release-syncthing.yaml

@@ -14,7 +14,6 @@ jobs:
     name: Create release tag
     if: github.repository_owner == 'syncthing'
     runs-on: ubuntu-latest
-    environment: release
     steps:
       - uses: actions/checkout@v5
         with:

.github/workflows/trigger-nightly.yaml

@@ -5,6 +5,9 @@ on:
     # Run nightly build at 01:00 UTC
     - cron: '00 01 * * *'
 
+permissions:
+  contents: write
+
 jobs:
 
   trigger-nightly:

.github/workflows/update-docs-translations.yaml

@@ -4,6 +4,9 @@ on:
   schedule:
     - cron: '42 3 * * 1'
 
+permissions:
+  contents: write
+
 jobs:
 
   update_transifex_docs:

cmd/infra/stcrashreceiver/_testdata/gcerror.log

@@ -0,0 +1,76 @@
+2026-05-21 10:03:01 INF syncthing v2.1.1-dev.9.gb3b7d228.dirty-morecrashrep "Hafnium Hornet" (go1.26.3 darwin-arm64) jb@jbo-m3wl72rv 2026-05-21 07:58:11 UTC [stnoupgrade] (log.pkg=main)
+2026-05-21 10:03:01 INF No automatic upgrades; STNOUPGRADE environment variable defined (log.pkg=main)
+2026-05-21 10:03:01 INF Calculated our device ID (device=I6KAH76-66SLLLB-5PFXSOA-UFJCDZC-YAOMLEK-CP2GB32-BV5RQST-3PSROAU log.pkg=syncthing)
+2026-05-21 10:03:01 INF Overall rate limit in use (send="is unlimited" recv="is unlimited" log.pkg=connections)
+2026-05-21 10:03:01 INF Using discovery mechanism (identity="IPv4 local broadcast discovery on port 21027" log.pkg=discover)
+2026-05-21 10:03:01 INF Using discovery mechanism (identity="IPv6 local multicast discovery on address [ff12::8384]:21027" log.pkg=discover)
+2026-05-21 10:03:01 INF TCP listener starting (address=127.0.0.1:22001 log.pkg=connections)
+2026-05-21 10:03:01 INF Ready to synchronize (folder.id=default folder.type=sendreceive log.pkg=model)
+2026-05-21 10:03:01 INF QUIC listener starting (address=127.0.0.1:22001 log.pkg=connections)
+2026-05-21 10:03:01 INF GUI and API listening (address=127.0.0.1:8081 log.pkg=api)
+...
+2026-05-21 10:03:01 INF Access the GUI via the following URL: http://127.0.0.1:8081/ (log.pkg=api)
+2026-05-21 10:03:01 INF Loaded configuration (name=s1 log.pkg=syncthing)
+2026-05-21 10:03:01 INF Loaded peer device configuration (device=MRIW7OK name=s2 address="[tcp://127.0.0.1:22002 quic://127.0.0.1:22002]" log.pkg=syncthing)
+2026-05-21 10:03:01 INF Completed initial scan (folder.id=default folder.type=sendreceive log.pkg=model)
+0xee9de1fe260
+2026-05-21 10:03:02 INF Measured hashing performance (perf="2789.71 MB/s" log.pkg=syncthing)
+Panic at 2026-05-21T10:03:02+02:00
+runtime: marked free object in span 0x108b34d20, elemsize=8 freeindex=34 (bad use of unsafe.Pointer or having race conditions? try -d=checkptr or -race)
+0xee9de1fe000 alloc marked
+0xee9de1fe008 alloc marked
+...
+0xee9de1fe250 free  unmarked
+0xee9de1fe258 free  unmarked
+0xee9de1fe260 free  marked   zombie
+                   7 6 5 4  3 2 1 0   f e d c  b a 9 8  0123456789abcdef
+00000ee9de1fe260: 00000000 00000000                     ........
+0xee9de1fe268 free  unmarked
+0xee9de1fe270 free  unmarked
+...
+0xee9de1fff60 free  unmarked
+0xee9de1fff68 free  unmarked
+0xee9de1fff70 free  unmarked
+0xee9de1fff78 free  unmarked
+fatal error: found pointer to free object
+
+runtime stack:
+runtime.throw({0x105881781?, 0x8?})
+	runtime/panic.go:1229 +0x38 fp=0x16bf82bb0 sp=0x16bf82b80 pc=0x104f0ca48
+runtime.(*mspan).reportZombies(0x108b34d20)
+	runtime/mgcsweep.go:893 +0x314 fp=0x16bf82c30 sp=0x16bf82bb0 pc=0x104ec10b4
+runtime.(*sweepLocked).sweep(0x16bf82d88?, 0x0)
+	runtime/mgcsweep.go:673 +0xbd0 fp=0x16bf82d50 sp=0x16bf82c30 pc=0x104ec0840
+runtime.(*mcentral).uncacheSpan(0x16bf82db8?, 0x104ea4954?)
+	runtime/mcentral.go:237 +0xbc fp=0x16bf82d80 sp=0x16bf82d50 pc=0x104eaac3c
+runtime.(*mcache).releaseAll(0x1089a85f0)
+	runtime/mcache.go:322 +0x188 fp=0x16bf82df0 sp=0x16bf82d80 pc=0x104eaa4e8
+runtime.(*mcache).prepareForSweep(0x1089a85f0)
+	runtime/mcache.go:366 +0x4c fp=0x16bf82e20 sp=0x16bf82df0 pc=0x104eaa61c
+runtime.gcMarkTermination.func4(0xee9de005808)
+	runtime/mgc.go:1546 +0x24 fp=0x16bf82e50 sp=0x16bf82e20 pc=0x104f076e4
+runtime.forEachPInternal(0x10656f798)
+	runtime/proc.go:2167 +0x178 fp=0x16bf82ee0 sp=0x16bf82e50 pc=0x104eda728
+runtime.gcMarkTermination.forEachP.func7()
+	runtime/proc.go:2126 +0x40 fp=0x16bf82f10 sp=0x16bf82ee0 pc=0x104eb3130
+runtime.systemstack(0x7fc000)
+	runtime/asm_arm64.s:399 +0x68 fp=0x16bf82f20 sp=0x16bf82f10 pc=0x104f12888
+
+goroutine 84 gp=0xee9de45c1e0 m=3 mp=0xee9de019008 [flushing proc caches]:
+runtime.systemstack_switch()
+	runtime/asm_arm64.s:347 +0x8 fp=0xee9de805c40 sp=0xee9de805c30 pc=0x104f12808
+runtime.forEachP(...)
+	runtime/proc.go:2112
+runtime.gcMarkTermination({0xc0?, 0x1331f928480ca?, 0xc?, 0x0?})
+	runtime/mgc.go:1545 +0x5f4 fp=0xee9de805e80 sp=0xee9de805c40 pc=0x104eb28c4
+runtime.gcMarkDone()
+	runtime/mgc.go:1173 +0x364 fp=0xee9de805f20 sp=0xee9de805e80 pc=0x104eb1bc4
+runtime.gcBgMarkWorker(0xee9de341810)
+	runtime/mgc.go:1912 +0x29c fp=0xee9de805fb0 sp=0xee9de805f20 pc=0x104eb372c
+runtime.gcBgMarkStartWorkers.gowrap1()
+	runtime/mgc.go:1695 +0x20 fp=0xee9de805fd0 sp=0xee9de805fb0 pc=0x104eb3470
+runtime.goexit({})
+	runtime/asm_arm64.s:1447 +0x4 fp=0xee9de805fd0 sp=0xee9de805fd0 pc=0x104f14a04
+created by runtime.gcBgMarkStartWorkers in goroutine 1
+	runtime/mgc.go:1695 +0x134
+

cmd/infra/stcrashreceiver/diskstore.go

@@ -136,15 +136,25 @@ func (d *diskStore) Exists(path string) bool {
 }
 
 func (d *diskStore) clean() {
-	for len(d.currentFiles) > 0 && (len(d.currentFiles) > d.maxFiles || d.currentSize > d.maxBytes) {
-		f := d.currentFiles[0]
+	numDeleted := 0
+	for idx := range d.currentFiles {
+		if len(d.currentFiles)-numDeleted < d.maxFiles && d.currentSize < d.maxBytes {
+			break
+		}
+
+		f := d.currentFiles[idx]
 		log.Println("Removing", f.path)
 		if err := os.Remove(f.path); err != nil {
 			log.Println("Failed to remove file:", err)
 		}
-		d.currentFiles = d.currentFiles[1:]
 		d.currentSize -= f.size
+		numDeleted = idx + 1
 	}
+
+	// Compact currentFiles
+	copy(d.currentFiles, d.currentFiles[numDeleted:])
+	d.currentFiles = d.currentFiles[:len(d.currentFiles)-numDeleted]
+
 	var oldest time.Duration
 	if len(d.currentFiles) > 0 {
 		oldest = time.Since(time.Unix(d.currentFiles[0].mtime, 0)).Truncate(time.Minute)
@@ -158,7 +168,7 @@ func (d *diskStore) clean() {
 }
 
 func (d *diskStore) inventory() error {
-	d.currentFiles = nil
+	d.currentFiles = d.currentFiles[:0]
 	d.currentSize = 0
 	err := filepath.Walk(d.dir, func(path string, info os.FileInfo, err error) error {
 		if err != nil {

cmd/infra/stcrashreceiver/main.go

@@ -20,6 +20,7 @@ import (
 	"io"
 	"log"
 	"net/http"
+	"net/http/pprof"
 	"os"
 	"path/filepath"
 	"regexp"
@@ -29,7 +30,7 @@ import (
 	raven "github.com/getsentry/raven-go"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/syncthing/syncthing/lib/build"
-	"github.com/syncthing/syncthing/lib/ur"
+	"github.com/syncthing/syncthing/lib/ur/contract"
 )
 
 const maxRequestSize = 1 << 20 // 1 MiB
@@ -89,6 +90,7 @@ func main() {
 	if params.MetricsListen != "" {
 		mmux := http.NewServeMux()
 		mmux.Handle("/metrics", promhttp.Handler())
+		mmux.HandleFunc("/debug/pprof/", pprof.Index)
 		go func() {
 			if err := http.ListenAndServe(params.MetricsListen, mmux); err != nil {
 				log.Fatalln("HTTP serve metrics:", err)
@@ -123,12 +125,13 @@ func handleFailureFn(dsn, failureDir string, ignore *ignorePatterns) func(w http
 			return
 		}
 
-		if ignore.match(bs) {
+		if pat, ok := ignore.match(bs); ok {
+			metricIgnoreMatchesTotal.WithLabelValues(pat).Inc()
 			result = "ignored"
 			return
 		}
 
-		var reports []ur.FailureReport
+		var reports []contract.FailureReport
 		err = json.Unmarshal(bs, &reports)
 		if err != nil {
 			http.Error(w, err.Error(), http.StatusBadRequest)
@@ -176,7 +179,7 @@ func handleFailureFn(dsn, failureDir string, ignore *ignorePatterns) func(w http
 	}
 }
 
-func saveFailureWithGoroutines(data ur.FailureData, failureDir string) (string, error) {
+func saveFailureWithGoroutines(data contract.FailureData, failureDir string) (string, error) {
 	bs := make([]byte, len(data.Description)+len(data.Goroutines))
 	copy(bs, data.Description)
 	copy(bs[len(data.Description):], data.Goroutines)
@@ -216,14 +219,14 @@ func loadIgnorePatterns(path string) (*ignorePatterns, error) {
 	return &ignorePatterns{patterns: patterns}, nil
 }
 
-func (i *ignorePatterns) match(report []byte) bool {
+func (i *ignorePatterns) match(report []byte) (string, bool) {
 	if i == nil {
-		return false
+		return "", false
 	}
 	for _, re := range i.patterns {
 		if re.Match(report) {
-			return true
+			return re.String(), true
 		}
 	}
-	return false
+	return "", false
 }

cmd/infra/stcrashreceiver/metrics.go

@@ -37,4 +37,24 @@ var (
 		Subsystem: "crashreceiver",
 		Name:      "diskstore_oldest_age_seconds",
 	})
+	metricSentryReportsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
+		Namespace: "syncthing",
+		Subsystem: "crashreceiver",
+		Name:      "sentry_reports_total",
+	}, []string{"result"})
+	metricIgnoreMatchesTotal = promauto.NewCounterVec(prometheus.CounterOpts{
+		Namespace: "syncthing",
+		Subsystem: "crashreceiver",
+		Name:      "ignore_matches_total",
+	}, []string{"pattern"})
+	metricSourceCodeLoadsTotal = promauto.NewCounterVec(prometheus.CounterOpts{
+		Namespace: "syncthing",
+		Subsystem: "crashreceiver",
+		Name:      "source_code_loads_total",
+	}, []string{"result"})
+	metricSourceCodeCacheSize = promauto.NewGauge(prometheus.GaugeOpts{
+		Namespace: "syncthing",
+		Subsystem: "crashreceiver",
+		Name:      "source_code_cache_size",
+	})
 )

cmd/infra/stcrashreceiver/sentry.go

@@ -10,6 +10,7 @@ import (
 	"bytes"
 	"context"
 	"errors"
+	"fmt"
 	"io"
 	"log"
 	"regexp"
@@ -52,11 +53,15 @@ func (s *sentryService) Serve(ctx context.Context) {
 			pkt, err := parseCrashReport(req.reportID, req.data)
 			if err != nil {
 				log.Println("Failed to parse crash report:", err)
+				metricSentryReportsTotal.WithLabelValues("parse_failure").Inc()
 				continue
 			}
 			if err := sendReport(s.dsn, pkt, req.userID); err != nil {
 				log.Println("Failed to send crash report:", err)
+				metricSentryReportsTotal.WithLabelValues("send_failure").Inc()
+				continue
 			}
+			metricSentryReportsTotal.WithLabelValues("success").Inc()
 
 		case <-ctx.Done():
 			return
@@ -69,6 +74,7 @@ func (s *sentryService) Send(reportID, userID string, data []byte) bool {
 	case s.inbox <- sentryRequest{reportID, userID, data}:
 		return true
 	default:
+		metricCrashReportsTotal.WithLabelValues("overflow").Inc()
 		return false
 	}
 }
@@ -108,11 +114,10 @@ func parseCrashReport(path string, report []byte) (*raven.Packet, error) {
 
 	version, err := build.ParseVersion(string(parts[0]))
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("%w in %q", err, parts[0])
 	}
 	report = parts[1]
 
-	foundPanic := false
 	var subjectLine []byte
 	for {
 		parts = bytes.SplitN(report, []byte("\n"), 2)
@@ -123,14 +128,9 @@ func parseCrashReport(path string, report []byte) (*raven.Packet, error) {
 		line := parts[0]
 		report = parts[1]
 
-		if foundPanic {
-			// The previous line was our "Panic at ..." header. We are now
-			// at the beginning of the real panic trace and this is our
-			// subject line.
+		if bytes.HasPrefix(line, []byte("panic:")) || bytes.HasPrefix(line, []byte("fatal error:")) {
 			subjectLine = line
 			break
-		} else if bytes.HasPrefix(line, []byte("Panic at")) {
-			foundPanic = true
 		}
 	}
 

cmd/infra/stcrashreceiver/sentry_test.go

@@ -9,26 +9,33 @@ package main
 import (
 	"fmt"
 	"os"
+	"path/filepath"
 	"testing"
 )
 
 func TestParseReport(t *testing.T) {
-	bs, err := os.ReadFile("_testdata/panic.log")
+	files, err := filepath.Glob("_testdata/*.log")
 	if err != nil {
 		t.Fatal(err)
 	}
+	for _, file := range files {
+		bs, err := os.ReadFile(file)
+		if err != nil {
+			t.Fatal(err)
+		}
 
-	pkt, err := parseCrashReport("1/2/345", bs)
-	if err != nil {
-		t.Fatal(err)
+		pkt, err := parseCrashReport("1/2/345", bs)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		bs, err = pkt.JSON()
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		fmt.Printf("%s\n", bs)
 	}
-
-	bs, err = pkt.JSON()
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	fmt.Printf("%s\n", bs)
 }
 
 func TestCrashReportFingerprint(t *testing.T) {

cmd/infra/stcrashreceiver/sourcecodeloader.go

@@ -15,23 +15,33 @@ import (
 	"strings"
 	"sync"
 	"time"
+
+	lru "github.com/hashicorp/golang-lru/v2"
 )
 
 const (
-	urlPrefix   = "https://raw.githubusercontent.com/syncthing/syncthing/"
-	httpTimeout = 10 * time.Second
+	urlPrefix       = "https://raw.githubusercontent.com/syncthing/syncthing/"
+	httpTimeout     = 10 * time.Second
+	maxCacheEntries = 1000
 )
 
+type cacheKey struct {
+	version string
+	file    string
+}
+
 type githubSourceCodeLoader struct {
 	mut     sync.Mutex
 	version string
-	cache   map[string]map[string][][]byte // version -> file -> lines
-	client  *http.Client
+
+	cache  *lru.TwoQueueCache[cacheKey, [][]byte] // version & file -> lines
+	client *http.Client
 }
 
 func newGithubSourceCodeLoader() *githubSourceCodeLoader {
+	cache, _ := lru.New2Q[cacheKey, [][]byte](maxCacheEntries)
 	return &githubSourceCodeLoader{
-		cache:  make(map[string]map[string][][]byte),
+		cache:  cache,
 		client: &http.Client{Timeout: httpTimeout},
 	}
 }
@@ -39,9 +49,6 @@ func newGithubSourceCodeLoader() *githubSourceCodeLoader {
 func (l *githubSourceCodeLoader) LockWithVersion(version string) {
 	l.mut.Lock()
 	l.version = version
-	if _, ok := l.cache[version]; !ok {
-		l.cache[version] = make(map[string][][]byte)
-	}
 }
 
 func (l *githubSourceCodeLoader) Unlock() {
@@ -50,11 +57,13 @@ func (l *githubSourceCodeLoader) Unlock() {
 
 func (l *githubSourceCodeLoader) Load(filename string, line, context int) ([][]byte, int) {
 	filename = filepath.ToSlash(filename)
-	lines, ok := l.cache[l.version][filename]
+	key := cacheKey{version: l.version, file: filename}
+	lines, ok := l.cache.Get(key)
 	if !ok {
 		// Cache whatever we managed to find (or nil if nothing, so we don't try again)
 		defer func() {
-			l.cache[l.version][filename] = lines
+			l.cache.Add(key, lines)
+			metricSourceCodeCacheSize.Set(float64(l.cache.Len()))
 		}()
 
 		knownPrefixes := []string{"/lib/", "/cmd/"}
@@ -73,19 +82,25 @@ func (l *githubSourceCodeLoader) Load(filename string, line, context int) ([][]b
 		resp, err := l.client.Get(url)
 		if err != nil {
 			fmt.Println("Loading source:", err)
+			metricSourceCodeLoadsTotal.WithLabelValues("failed").Inc()
 			return nil, 0
 		}
 		if resp.StatusCode != http.StatusOK {
 			fmt.Println("Loading source:", resp.Status)
+			metricSourceCodeLoadsTotal.WithLabelValues("failed").Inc()
 			return nil, 0
 		}
 		data, err := io.ReadAll(resp.Body)
 		_ = resp.Body.Close()
 		if err != nil {
 			fmt.Println("Loading source:", err.Error())
+			metricSourceCodeLoadsTotal.WithLabelValues("failed").Inc()
 			return nil, 0
 		}
 		lines = bytes.Split(data, []byte{'\n'})
+		metricSourceCodeLoadsTotal.WithLabelValues("loaded").Inc()
+	} else {
+		metricSourceCodeLoadsTotal.WithLabelValues("cached").Inc()
 	}
 
 	return getLineFromLines(lines, line, context)

cmd/infra/stcrashreceiver/stcrashreceiver.go

@@ -7,21 +7,18 @@
 package main
 
 import (
+	"bytes"
 	"io"
 	"log"
 	"net/http"
 	"path"
 	"strings"
-	"sync"
 )
 
 type crashReceiver struct {
 	store  *diskStore
 	sentry *sentryService
 	ignore *ignorePatterns
-
-	ignoredMut sync.RWMutex
-	ignored    map[string]struct{}
 }
 
 func (r *crashReceiver) ServeHTTP(w http.ResponseWriter, req *http.Request) {
@@ -69,12 +66,6 @@ func (r *crashReceiver) serveGet(reportID string, w http.ResponseWriter, _ *http
 // serveHead responds to HEAD requests by checking if the named report
 // already exists in the system.
 func (r *crashReceiver) serveHead(reportID string, w http.ResponseWriter, _ *http.Request) {
-	r.ignoredMut.RLock()
-	_, ignored := r.ignored[reportID]
-	r.ignoredMut.RUnlock()
-	if ignored {
-		return // found
-	}
 	if !r.store.Exists(reportID) {
 		http.Error(w, "Not found", http.StatusNotFound)
 	}
@@ -87,17 +78,7 @@ func (r *crashReceiver) servePut(reportID string, w http.ResponseWriter, req *ht
 		metricCrashReportsTotal.WithLabelValues(result).Inc()
 	}()
 
-	r.ignoredMut.RLock()
-	_, ignored := r.ignored[reportID]
-	r.ignoredMut.RUnlock()
-	if ignored {
-		result = "ignored_cached"
-		io.Copy(io.Discard, req.Body)
-		return // found
-	}
-
 	// Read at most maxRequestSize of report data.
-	log.Println("Receiving report", reportID)
 	lr := io.LimitReader(req.Body, maxRequestSize)
 	bs, err := io.ReadAll(lr)
 	if err != nil {
@@ -106,14 +87,12 @@ func (r *crashReceiver) servePut(reportID string, w http.ResponseWriter, req *ht
 		return
 	}
 
-	if r.ignore.match(bs) {
-		r.ignoredMut.Lock()
-		if r.ignored == nil {
-			r.ignored = make(map[string]struct{})
-		}
-		r.ignored[reportID] = struct{}{}
-		r.ignoredMut.Unlock()
+	first := string(bytes.TrimSpace(bytes.Split(bs, []byte("\n"))[0]))
+
+	if pat, ok := r.ignore.match(bs); ok {
+		metricIgnoreMatchesTotal.WithLabelValues(pat).Inc()
 		result = "ignored"
+		log.Printf("Ignored report %s, matched: %s (%s)", reportID[:8], pat, first)
 		return
 	}
 
@@ -121,13 +100,15 @@ func (r *crashReceiver) servePut(reportID string, w http.ResponseWriter, req *ht
 
 	// Store the report
 	if !r.store.Put(reportID, bs) {
-		log.Println("Failed to store report (queue full):", reportID)
+		log.Println("Failed to store report (queue full):", reportID[:8])
 		result = "queue_failure"
 	}
 
 	// Send the report to Sentry
 	if !r.sentry.Send(reportID, userIDFor(req), bs) {
-		log.Println("Failed to send report to sentry (queue full):", reportID)
+		log.Println("Failed to send report to sentry (queue full):", reportID[:8])
 		result = "sentry_failure"
 	}
+
+	log.Printf("Received report %s (%s)", reportID[:8], first)
 }

cmd/stdiscosrv/stats.go

@@ -7,6 +7,8 @@
 package main
 
 import (
+	"net/http"
+
 	"github.com/prometheus/client_golang/prometheus"
 )
 
@@ -113,14 +115,11 @@ var (
 )
 
 const (
-	dbOpGet             = "get"
-	dbOpPut             = "put"
-	dbOpMerge           = "merge"
-	dbOpDelete          = "delete"
-	dbResSuccess        = "success"
-	dbResNotFound       = "not_found"
-	dbResError          = "error"
-	dbResUnmarshalError = "unmarsh_err"
+	dbOpGet       = "get"
+	dbOpPut       = "put"
+	dbOpMerge     = "merge"
+	dbResSuccess  = "success"
+	dbResNotFound = "not_found"
 )
 
 func init() {
@@ -132,4 +131,24 @@ func init() {
 		databaseOperations, databaseOperationSeconds,
 		databaseWriteSeconds, databaseLastWritten,
 		retryAfterLevel)
+
+	// Prewarm important counters so they're available with zero values at
+	// startup
+
+	apiRequestsTotal.WithLabelValues(http.MethodGet, "200")
+	apiRequestsTotal.WithLabelValues(http.MethodGet, "404")
+	apiRequestsTotal.WithLabelValues(http.MethodPost, "204")
+	apiRequestsTotal.WithLabelValues(http.MethodPost, "400")
+	apiRequestsTotal.WithLabelValues(http.MethodPost, "403")
+
+	lookupRequestsTotal.WithLabelValues("success")
+	lookupRequestsTotal.WithLabelValues("not_found_ever")
+	lookupRequestsTotal.WithLabelValues("not_found_recent")
+
+	announceRequestsTotal.WithLabelValues("success")
+	announceRequestsTotal.WithLabelValues("bad_request")
+	announceRequestsTotal.WithLabelValues("no_certificate")
+
+	replicationSendsTotal.WithLabelValues("success")
+	replicationRecvsTotal.WithLabelValues("success")
 }

cmd/syncthing/main.go

@@ -915,10 +915,14 @@ func (u upgradeCmd) Run() error {
 		case err != nil && !os.IsNotExist(err):
 			slog.Error("Failed to lock for upgrade", slogutil.Error(err))
 			os.Exit(1)
-		case locked:
-			err = upgradeViaRest()
-		default:
+		case locked || os.IsNotExist(err):
+			// We got the lock, or the config directory didn't exist, so we
+			// can do a direct upgrade
 			err = upgrade.To(release)
+		default:
+			// We didn't get the lock, because Syncthing was running, so
+			// upgrade via REST.
+			err = upgradeViaRest()
 		}
 	}
 	if err != nil {

cmd/syncthing/monitor.go

@@ -233,7 +233,7 @@ func copyStderr(stderr io.Reader, dst io.Writer) {
 
 		dst.Write([]byte(line))
 
-		if panicFd == nil && (strings.HasPrefix(line, "panic:") || strings.HasPrefix(line, "fatal error:")) {
+		if panicFd == nil && (strings.HasPrefix(line, "panic:") || strings.HasPrefix(line, "fatal error:") || strings.HasPrefix(line, "runtime:")) {
 			panicFd, err = os.Create(locations.GetTimestamped(locations.PanicLog))
 			if err != nil {
 				slog.Error("Failed to create panic log", slogutil.Error(err))

go.mod

@@ -42,8 +42,8 @@ require (
 	github.com/wlynxg/anet v0.0.5
 	golang.org/x/crypto v0.51.0
 	golang.org/x/exp v0.0.0-20260508232706-74f9aab9d74a
-	golang.org/x/net v0.54.0
-	golang.org/x/sys v0.44.0
+	golang.org/x/net v0.55.0
+	golang.org/x/sys v0.45.0
 	golang.org/x/text v0.37.0
 	golang.org/x/time v0.15.0
 	google.golang.org/protobuf v1.36.11

go.sum

@@ -280,8 +280,8 @@ golang.org/x/net v0.0.0-20201021035429-f5854403a974/go.mod h1:sp8m0HH+o8qH0wwXwY
 golang.org/x/net v0.0.0-20210428140749-89ef3d95e781/go.mod h1:OJAsFXCWl8Ukc7SiCT/9KSuxbyM7479/AVlXFRxuMCk=
 golang.org/x/net v0.0.0-20220225172249-27dd8689420f/go.mod h1:CfG3xpIq0wQ8r1q4Su4UZFWDARRcnwPjda9FqA0JpMk=
 golang.org/x/net v0.0.0-20220607020251-c690dde0001d/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
-golang.org/x/net v0.54.0 h1:2zJIZAxAHV/OHCDTCOHAYehQzLfSXuf/5SoL/Dv6w/w=
-golang.org/x/net v0.54.0/go.mod h1:Sj4oj8jK6XmHpBZU/zWHw3BV3abl4Kvi+Ut7cQcY+cQ=
+golang.org/x/net v0.55.0 h1:bcvxaJn3e1U6InsFWt1JUq1aSjnRxLzT2rtD2KfkDF8=
+golang.org/x/net v0.55.0/go.mod h1:L5U2KuzuOe1lY7Z+aWVIKK6qEeJXnXV9yzGA+WCHJww=
 golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
@@ -309,8 +309,8 @@ golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBc
 golang.org/x/sys v0.0.0-20220908164124-27713097b956/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.1.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.44.0 h1:ildZl3J4uzeKP07r2F++Op7E9B29JRUy+a27EibtBTQ=
-golang.org/x/sys v0.44.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
+golang.org/x/sys v0.45.0 h1:dO4czNzziLiiXplLQgBCEpCvXQ3dnkn0SdaZSYdQ+FY=
+golang.org/x/sys v0.45.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
 golang.org/x/telemetry v0.0.0-20260508192327-42602be52be6 h1:HjU6IWBiAgRIdAJ9/y1rwCn+UELEmwV+VsTLzj/W4sE=
 golang.org/x/telemetry v0.0.0-20260508192327-42602be52be6/go.mod h1:Eqhaxk/wZsWEH8CRxLwj6xzEJbz7k1EFGqx7nyCoabE=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=

gui/default/assets/lang/lang-fr.json

@@ -50,7 +50,7 @@
     "Automatically create or share folders that this device advertises at the default path.": "Automatiquement créer dans le chemin par défaut les partages auxquels cet appareil vous propose de participer, ou accepter leur partage s'ils pré-existent.",
     "Available debug logging facilities:": "Outils de débogage disponibles :",
     "Be careful!": "Faites attention !",
-    "Block Indexing": "Indexation de blocs",
+    "Block Indexing": "Indexation des blocs",
     "Body:": "Corps du message :",
     "Bugs": "Bogues",
     "Cancel": "Annuler",
@@ -252,7 +252,7 @@
     "Log tailing paused. Scroll to the bottom to continue.": "Le défilement du journal est en pause. Faites défiler jusqu'en bas pour continuer.",
     "Login failed, see Syncthing logs for details.": "Échec de connexion, consultez les journaux de Syncthing pour les détails.",
     "Logs": "Journaux",
-    "Maintain an index of all blocks in the folder, enabling reuse of blocks from other files when syncing changes. Disable to reduce database size at the cost of not being able to reuse blocks across files.": "Entretient un index de tous les blocs du répertoire pour permettre leur réutilisation depuis d'autres fichiers lors de changements dans la synchronisation. Désactivez pour diminuer la taille de la base de donnée, au prix de téléchargements potentiellement plus long.",
+    "Maintain an index of all blocks in the folder, enabling reuse of blocks from other files when syncing changes. Disable to reduce database size at the cost of not being able to reuse blocks across files.": "Entretient un index de tous les blocs du répertoire pour permettre leur réutilisation depuis d'autres fichiers lors de changements dans la synchronisation. Désactivez pour diminuer la taille de la base de donnée, au prix de téléchargements potentiellement plus longs.",
     "Major Upgrade": "Mise à jour majeure",
     "Mass actions": "Actions multiples",
     "Maximum Age": "Ancienneté maximum",

gui/default/assets/lang/lang-ru.json

@@ -410,7 +410,7 @@
     "Syncthing is listening on the following network addresses for connection attempts from other devices:": "Syncthing ожидает подключения от других устройств на следующих сетевых адресах:",
     "Syncthing is not listening for connection attempts from other devices on any address.  Only outgoing connections from this device may work.": "Syncthing не ожидает попыток подключения ни на каких адресах. Только исходящие подключения могут работать на этом устройстве.",
     "Syncthing is restarting.": "Перезапуск Syncthing.",
-    "Syncthing is saving changes.": "Синхронизация это сохранение изменений.",
+    "Syncthing is saving changes.": "Syncthing сохраняет изменения.",
     "Syncthing is upgrading.": "Обновление Syncthing.",
     "Syncthing now supports automatically reporting crashes to the developers. This feature is enabled by default.": "Syncthing теперь поддерживает автоматическую отправку отчетов о сбоях разработчикам. Эта функция включена по умолчанию.",
     "Syncthing seems to be down, or there is a problem with your Internet connection. Retrying…": "Кажется, Syncthing не запущен или есть проблемы с подключением к Интернету. Переподключаюсь…",

lib/build/parse.go

@@ -16,7 +16,7 @@ import (
 // or, somewhere along the way the "+" in the version tag disappeared:
 // syncthing v1.23.7-dev.26.gdf7b56ae.dirty-stversionextra "Fermium Flea" (go1.20.5 darwin-arm64) jb@ok.kastelo.net 2023-07-12 06:55:26 UTC [Some Wrapper, purego, stnoupgrade]
 var (
-	longVersionRE = regexp.MustCompile(`syncthing\s+(v[^\s]+)\s+"([^"]+)"\s\(([^\s]+)\s+([^-]+)-([^)]+)\)\s+([^\s]+)[^\[]*(?:\[(.+)\])?$`)
+	longVersionRE = regexp.MustCompile(`syncthing\s+(v[^\s]+)\s+"([^"]+)"\s\(([^\s]+)\s+([^-]+)-([^)]+)\)\s+([^\s]+)[^\[]*(?:\[(.+)\])?`)
 	gitExtraRE    = regexp.MustCompile(`\.\d+\.g[0-9a-f]+`) // ".1.g6aaae618"
 	gitExtraSepRE = regexp.MustCompile(`[.-]`)              // dot or dash
 )

lib/build/parse_test.go

@@ -57,6 +57,20 @@ func TestParseVersion(t *testing.T) {
 				Extra:    []string{"Some Wrapper", "purego", "stnoupgrade"},
 			},
 		},
+		{
+			longVersion: `2026-05-18 14:53:32 INF syncthing v2.0.3 "Hafnium Hornet" (go1.25.0 darwin-amd64) builder@github.syncthing.net 2025-08-22 07:00:05 UTC [stnoupgrade] (log.pkg=main)`,
+			parsed: VersionParts{
+				Version:  "v2.0.3",
+				Tag:      "v2.0.3",
+				Commit:   "",
+				Codename: "Hafnium Hornet",
+				Runtime:  "go1.25.0",
+				GOOS:     "darwin",
+				GOARCH:   "amd64",
+				Builder:  "builder@github.syncthing.net",
+				Extra:    []string{"stnoupgrade"},
+			},
+		},
 	}
 
 	for _, tc := range cases {

lib/connections/tcp_listen.go

@@ -13,6 +13,7 @@ import (
 	"log/slog"
 	"net"
 	"net/url"
+	"slices"
 	"sync"
 	"time"
 
@@ -185,9 +186,10 @@ func (t *tcpListener) WANAddresses() []*url.URL {
 
 	t.mut.RUnlock()
 
-	// If we support ReusePort, add an unspecified zero port address, which will be resolved by the discovery server
-	// in hopes that TCP punch through works.
-	if dialer.SupportsReusePort {
+	// If we support ReusePort, and we are already announcing an unspecified
+	// address, add an unspecified zero port address, which will be resolved
+	// by the discovery server in hopes that TCP punch through works.
+	if dialer.SupportsReusePort && slices.ContainsFunc(uris, func(u *url.URL) bool { return u.Hostname() == "0.0.0.0" }) {
 		uri := *t.uri
 		uri.Host = "0.0.0.0:0"
 		uris = append([]*url.URL{&uri}, uris...)

lib/discover/global.go

@@ -289,7 +289,6 @@ func (c *globalClient) sendAnnouncement(ctx context.Context, timer *time.Timer)
 	resp.Body.Close()
 
 	if resp.StatusCode < 200 || resp.StatusCode > 299 {
-		slog.DebugContext(ctx, "announce POST", "server", c.server, "status", resp.Status)
 		c.setError(errors.New(resp.Status))
 
 		if h := resp.Header.Get("Retry-After"); h != "" {

lib/model/indexhandler.go

@@ -20,7 +20,7 @@ import (
 	"github.com/syncthing/syncthing/lib/events"
 	"github.com/syncthing/syncthing/lib/protocol"
 	"github.com/syncthing/syncthing/lib/svcutil"
-	"github.com/syncthing/syncthing/lib/ur"
+	"github.com/syncthing/syncthing/lib/ur/contract"
 )
 
 type indexHandler struct {
@@ -470,7 +470,7 @@ func (s *indexHandler) logSequenceAnomaly(msg string, extra map[string]any) {
 		extraStrs[k] = fmt.Sprint(v)
 	}
 
-	s.evLogger.Log(events.Failure, ur.FailureData{
+	s.evLogger.Log(events.Failure, contract.FailureData{
 		Description: msg,
 		Extra:       extraStrs,
 	})

lib/ur/contract/contract.go

@@ -282,3 +282,16 @@ func clear(v interface{}, since int) error {
 	}
 	return nil
 }
+
+type FailureReport struct {
+	FailureData
+
+	Count   int
+	Version string
+}
+
+type FailureData struct {
+	Description string
+	Goroutines  string
+	Extra       map[string]string
+}

lib/ur/failurereporting.go

@@ -23,6 +23,7 @@ import (
 	"github.com/syncthing/syncthing/lib/events"
 	"github.com/syncthing/syncthing/lib/svcutil"
 	"github.com/syncthing/syncthing/lib/tlsutil"
+	"github.com/syncthing/syncthing/lib/ur/contract"
 
 	"github.com/thejerf/suture/v4"
 )
@@ -39,23 +40,10 @@ var (
 	invalidEventDataType = "failure event data is not a string"
 )
 
-type FailureReport struct {
-	FailureData
-
-	Count   int
-	Version string
-}
-
-type FailureData struct {
-	Description string
-	Goroutines  string
-	Extra       map[string]string
-}
-
-func FailureDataWithGoroutines(description string) FailureData {
+func FailureDataWithGoroutines(description string) contract.FailureData {
 	var buf strings.Builder
 	pprof.Lookup("goroutine").WriteTo(&buf, 1)
-	return FailureData{
+	return contract.FailureData{
 		Description: description,
 		Goroutines:  buf.String(),
 		Extra:       make(map[string]string),
@@ -86,7 +74,7 @@ type failureHandler struct {
 type failureStat struct {
 	first, last time.Time
 	count       int
-	data        FailureData
+	data        contract.FailureData
 }
 
 func (h *failureHandler) Serve(ctx context.Context) error {
@@ -105,24 +93,24 @@ func (h *failureHandler) Serve(ctx context.Context) error {
 			if !ok {
 				// Just to be safe - shouldn't ever happen, as
 				// evChan is set to nil when unsubscribing.
-				h.addReport(FailureData{Description: evChanClosed}, time.Now())
+				h.addReport(contract.FailureData{Description: evChanClosed}, time.Now())
 				evChan = nil
 				continue
 			}
-			var data FailureData
+			var data contract.FailureData
 			switch d := e.Data.(type) {
 			case string:
 				data.Description = d
-			case FailureData:
+			case contract.FailureData:
 				data = d
 			default:
 				// Same here, shouldn't ever happen.
-				h.addReport(FailureData{Description: invalidEventDataType}, time.Now())
+				h.addReport(contract.FailureData{Description: invalidEventDataType}, time.Now())
 				continue
 			}
 			h.addReport(data, e.Time)
 		case <-timer.C:
-			reports := make([]FailureReport, 0, len(h.buf))
+			reports := make([]contract.FailureReport, 0, len(h.buf))
 			now := time.Now()
 			for descr, stat := range h.buf {
 				if now.Sub(stat.last) > minDelay || now.Sub(stat.first) > maxDelay {
@@ -152,7 +140,7 @@ func (h *failureHandler) Serve(ctx context.Context) error {
 	if sub != nil {
 		sub.Unsubscribe()
 		if len(h.buf) > 0 {
-			reports := make([]FailureReport, 0, len(h.buf))
+			reports := make([]contract.FailureReport, 0, len(h.buf))
 			for _, stat := range h.buf {
 				reports = append(reports, newFailureReport(stat))
 			}
@@ -179,7 +167,7 @@ func (h *failureHandler) applyOpts(opts config.OptionsConfiguration, sub events.
 	return url, nil, nil
 }
 
-func (h *failureHandler) addReport(data FailureData, evTime time.Time) {
+func (h *failureHandler) addReport(data contract.FailureData, evTime time.Time) {
 	if stat, ok := h.buf[data.Description]; ok {
 		stat.last = evTime
 		stat.count++
@@ -204,7 +192,7 @@ func (*failureHandler) String() string {
 	return "FailureHandler"
 }
 
-func sendFailureReports(ctx context.Context, reports []FailureReport, url string) {
+func sendFailureReports(ctx context.Context, reports []contract.FailureReport, url string) {
 	var b bytes.Buffer
 	if err := json.NewEncoder(&b).Encode(reports); err != nil {
 		panic(err)
@@ -235,8 +223,8 @@ func sendFailureReports(ctx context.Context, reports []FailureReport, url string
 	resp.Body.Close()
 }
 
-func newFailureReport(stat *failureStat) FailureReport {
-	return FailureReport{
+func newFailureReport(stat *failureStat) contract.FailureReport {
+	return contract.FailureReport{
 		FailureData: stat.data,
 		Count:       stat.count,
 		Version:     build.LongVersion,

lib/versioner/simple_test.go

@@ -15,6 +15,7 @@ import (
 
 	"github.com/syncthing/syncthing/lib/build"
 	"github.com/syncthing/syncthing/lib/config"
+	"github.com/syncthing/syncthing/lib/fs"
 )
 
 func TestTaggedFilename(t *testing.T) {
@@ -256,3 +257,57 @@ func TestArchiveFoldersCreationPermission(t *testing.T) {
 		t.Errorf("földer2 permissions %v, want %v", folder2VersionsInfo.Mode(), folder2Perms)
 	}
 }
+
+func TestDupDirTreeWritePermissions(t *testing.T) {
+	// The structure should be replicated, with user permission bits set along the way
+
+	srcFs := fs.NewFilesystem(fs.FilesystemTypeFake, "TestDupDirTreeWritePermissions/srcFs")
+	dstFs := fs.NewFilesystem(fs.FilesystemTypeFake, "TestDupDirTreeWritePermissions/dstFs")
+
+	// A source dir to duplicate
+	_ = srcFs.Mkdir("foo", 0o444)
+	_ = srcFs.Mkdir("foo/bar", 0o555)
+	_ = srcFs.Mkdir("foo/bar/baz", 0o000)
+
+	// Duplication should succeed
+	if err := dupDirTree(srcFs, dstFs, "foo/bar/baz"); err != nil {
+		t.Fatal(err)
+	}
+
+	// Permissions should be the same, but with read/write/execute bits for
+	// the user
+	if info, err := dstFs.Lstat("foo"); err != nil || info.Mode() != 0o744 {
+		t.Fatalf("foo: 0o%o", info.Mode())
+	}
+	if info, err := dstFs.Lstat("foo/bar"); err != nil || info.Mode() != 0o755 {
+		t.Fatalf("foo/bar: 0o%o", info.Mode())
+	}
+	if info, err := dstFs.Lstat("foo/bar/baz"); err != nil || info.Mode() != 0o700 {
+		t.Fatalf("foo/bar/baz: 0o%o", info.Mode())
+	}
+}
+
+func TestDupDirFastPath(t *testing.T) {
+	srcFs := fs.NewFilesystem(fs.FilesystemTypeFake, "TestDupDirFastPath/srcFs")
+	dstFs := fs.NewFilesystem(fs.FilesystemTypeFake, "TestDupDirFastPath/dstFs")
+
+	// A source dir to duplicate
+	_ = srcFs.Mkdir("foo", 0o444)
+	_ = srcFs.Mkdir("foo/bar", 0o555)
+	_ = srcFs.Mkdir("foo/bar/baz", 0o000)
+
+	// The destination exists, but with too few permission bits
+	_ = dstFs.MkdirAll("foo/bar/baz", 0o555)
+
+	// Duplication should succeed
+	if err := dupDirTree(srcFs, dstFs, "foo/bar/baz"); err != nil {
+		t.Fatal(err)
+	}
+
+	// Permissions for the destination should have been updated. (This
+	// differs from what would have been created by the duplication of the
+	// 0o000 dir in the src, because it already existed.)
+	if info, err := dstFs.Lstat("foo/bar/baz"); err != nil || info.Mode() != 0o755 {
+		t.Fatalf("foo/bar/baz: 0o%o", info.Mode())
+	}
+}

lib/versioner/util.go

@@ -192,48 +192,78 @@ func archiveFile(method fs.CopyRangeMethod, srcFs, dstFs fs.Filesystem, filePath
 	return err
 }
 
-func dupDirTree(srcFs, dstFs fs.Filesystem, folderPath string) error {
-	// Return early if the folder already exists.
-	_, err := dstFs.Stat(folderPath)
-	if err == nil || !fs.IsNotExist(err) {
-		return err
+// dupDirTree ensures folderPath exists in dstFs, copying permissions mostly
+// from srcFs. Permissions are altered to have the user read, write, and
+// execute bits set so that Syncthing file operations are possible within
+// the destination directory.
+//
+// We want to retain the source group and other bits so that we do not
+// inadvertently open up a directory for users who shouldn't have access to
+// it, but we do not consider it a security issue to open up the permissions
+// for the current user.
+//
+// This is based on os.MkdirAll with our srcFs adjustments.
+func dupDirTree(srcFs, dstFs fs.Filesystem, path string) error {
+	const (
+		allPerms    = 0o777
+		minDirPerms = 0o700
+	)
+
+	// Fast path: if we can tell whether path is a directory or file, stop with success or error.
+	if dir, err := dstFs.Lstat(path); err == nil {
+		if !dir.IsDir() {
+			return errors.New("destination exists but is not a directory")
+		}
+		if dir.Mode()&minDirPerms != minDirPerms {
+			// We want all the required permission bits set
+			_ = dstFs.Chmod(path, dir.Mode()&allPerms|minDirPerms)
+		}
+		return nil
 	}
-	hadParent := true
-	for i := range folderPath {
-		if os.IsPathSeparator(folderPath[i]) {
-			// If the parent folder didn't exist, then this folder doesn't exist
-			// so we can skip the check
-			if hadParent {
-				_, err := dstFs.Stat(folderPath[:i])
-				if err == nil {
-					continue
-				}
-				if !fs.IsNotExist(err) {
-					return err
-				}
-			}
-			hadParent = false
-			err := dupDirWithPerms(srcFs, dstFs, folderPath[:i])
-			if err != nil {
-				return err
-			}
+
+	// Slow path: make sure parent exists and then call Mkdir for path.
+
+	// Extract the parent folder from path by first removing any trailing
+	// path separator and then scanning backward until finding a path
+	// separator or reaching the beginning of the string.
+	i := len(path) - 1
+	for i >= 0 && os.IsPathSeparator(path[i]) {
+		i--
+	}
+	for i >= 0 && !os.IsPathSeparator(path[i]) {
+		i--
+	}
+	if i < 0 {
+		i = 0
+	}
+
+	// If there is a parent directory, and it is not the volume name,
+	// recurse to ensure parent directory exists.
+	if parent := path[:i]; len(parent) > len(filepath.VolumeName(path)) {
+		if err := dupDirTree(srcFs, dstFs, parent); err != nil {
+			return err
 		}
 	}
-	return dupDirWithPerms(srcFs, dstFs, folderPath)
-}
 
-func dupDirWithPerms(srcFs, dstFs fs.Filesystem, folderPath string) error {
-	srcStat, err := srcFs.Stat(folderPath)
-	if err != nil {
+	// Parent now exists; invoke Mkdir and use its result.
+	srcPerms := fs.FileMode(minDirPerms)
+	if srcDir, err := srcFs.Lstat(path); err == nil {
+		srcPerms = srcDir.Mode()&allPerms | minDirPerms
+	}
+	if err := dstFs.Mkdir(path, srcPerms); err != nil {
+		// Handle arguments like "foo/." by
+		// double-checking that directory doesn't exist.
+		dir, err1 := dstFs.Lstat(path)
+		if err1 == nil && dir.IsDir() {
+			return nil
+		}
 		return err
 	}
-	// If we call Mkdir with srcStat.Mode(), we won't get the expected perms because of umask
-	// So, we create the folder with 0700, and then change the perms to the srcStat.Mode()
-	err = dstFs.Mkdir(folderPath, 0o700)
-	if err != nil {
-		return err
-	}
-	return dstFs.Chmod(folderPath, srcStat.Mode())
+
+	// Extra chmod to ensure our permissions override umask
+	_ = dstFs.Chmod(path, srcPerms)
+
+	return nil
 }
 
 func restoreFile(method fs.CopyRangeMethod, src, dst fs.Filesystem, filePath string, versionTime time.Time, tagger fileTagger) error {

man/stdiscosrv.1

@@ -27,7 +27,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "STDISCOSRV" "1" "Apr 30, 2026" "v2.0.0" "Syncthing"
+.TH "STDISCOSRV" "1" "May 13, 2026" "v2.1.0" "Syncthing"
 .SH NAME
 stdiscosrv \- Syncthing Discovery Server
 .SH SYNOPSIS

man/strelaysrv.1

@@ -27,7 +27,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "STRELAYSRV" "1" "Apr 30, 2026" "v2.0.0" "Syncthing"
+.TH "STRELAYSRV" "1" "May 13, 2026" "v2.1.0" "Syncthing"
 .SH NAME
 strelaysrv \- Syncthing Relay Server
 .SH SYNOPSIS

man/syncthing-bep.7

@@ -28,7 +28,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "SYNCTHING-BEP" "7" "Apr 30, 2026" "v2.0.0" "Syncthing"
+.TH "SYNCTHING-BEP" "7" "May 13, 2026" "v2.1.0" "Syncthing"
 .SH NAME
 syncthing-bep \- Block Exchange Protocol v1
 .SH INTRODUCTION AND DEFINITIONS

man/syncthing-config.5

@@ -27,7 +27,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "SYNCTHING-CONFIG" "5" "Apr 30, 2026" "v2.0.0" "Syncthing"
+.TH "SYNCTHING-CONFIG" "5" "May 13, 2026" "v2.1.0" "Syncthing"
 .SH NAME
 syncthing-config \- Syncthing Configuration
 .SH OVERVIEW

man/syncthing-device-ids.7

@@ -27,7 +27,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "SYNCTHING-DEVICE-IDS" "7" "Apr 30, 2026" "v2.0.0" "Syncthing"
+.TH "SYNCTHING-DEVICE-IDS" "7" "May 13, 2026" "v2.1.0" "Syncthing"
 .SH NAME
 syncthing-device-ids \- Understanding Device IDs
 .sp

man/syncthing-event-api.7

@@ -27,7 +27,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "SYNCTHING-EVENT-API" "7" "Apr 30, 2026" "v2.0.0" "Syncthing"
+.TH "SYNCTHING-EVENT-API" "7" "May 13, 2026" "v2.1.0" "Syncthing"
 .SH NAME
 syncthing-event-api \- Event API
 .SH DESCRIPTION

man/syncthing-faq.7

@@ -27,7 +27,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "SYNCTHING-FAQ" "7" "Apr 30, 2026" "v2.0.0" "Syncthing"
+.TH "SYNCTHING-FAQ" "7" "May 13, 2026" "v2.1.0" "Syncthing"
 .SH NAME
 syncthing-faq \- Frequently Asked Questions
 .INDENT 0.0

man/syncthing-globaldisco.7

@@ -27,7 +27,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "SYNCTHING-GLOBALDISCO" "7" "Apr 30, 2026" "v2.0.0" "Syncthing"
+.TH "SYNCTHING-GLOBALDISCO" "7" "May 13, 2026" "v2.1.0" "Syncthing"
 .SH NAME
 syncthing-globaldisco \- Global Discovery Protocol v3
 .SH ANNOUNCEMENTS

man/syncthing-localdisco.7

@@ -27,7 +27,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "SYNCTHING-LOCALDISCO" "7" "Apr 30, 2026" "v2.0.0" "Syncthing"
+.TH "SYNCTHING-LOCALDISCO" "7" "May 13, 2026" "v2.1.0" "Syncthing"
 .SH NAME
 syncthing-localdisco \- Local Discovery Protocol v4
 .SH MODE OF OPERATION

man/syncthing-networking.7

@@ -27,7 +27,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "SYNCTHING-NETWORKING" "7" "Apr 30, 2026" "v2.0.0" "Syncthing"
+.TH "SYNCTHING-NETWORKING" "7" "May 13, 2026" "v2.1.0" "Syncthing"
 .SH NAME
 syncthing-networking \- Firewall Setup
 .SH ROUTER SETUP

man/syncthing-relay.7

@@ -28,7 +28,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "SYNCTHING-RELAY" "7" "Apr 30, 2026" "v2.0.0" "Syncthing"
+.TH "SYNCTHING-RELAY" "7" "May 13, 2026" "v2.1.0" "Syncthing"
 .SH NAME
 syncthing-relay \- Relay Protocol v1
 .SH WHAT IS A RELAY?

man/syncthing-rest-api.7

@@ -27,7 +27,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "SYNCTHING-REST-API" "7" "Apr 30, 2026" "v2.0.0" "Syncthing"
+.TH "SYNCTHING-REST-API" "7" "May 13, 2026" "v2.1.0" "Syncthing"
 .SH NAME
 syncthing-rest-api \- REST API
 .sp

man/syncthing-security.7

@@ -27,7 +27,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "SYNCTHING-SECURITY" "7" "Apr 30, 2026" "v2.0.0" "Syncthing"
+.TH "SYNCTHING-SECURITY" "7" "May 13, 2026" "v2.1.0" "Syncthing"
 .SH NAME
 syncthing-security \- Security Principles
 .sp

man/syncthing-stignore.5

@@ -27,7 +27,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "SYNCTHING-STIGNORE" "5" "Apr 30, 2026" "v2.0.0" "Syncthing"
+.TH "SYNCTHING-STIGNORE" "5" "May 13, 2026" "v2.1.0" "Syncthing"
 .SH NAME
 syncthing-stignore \- Prevent files from being synchronized to other nodes
 .SH SYNOPSIS

man/syncthing-versioning.7

@@ -27,7 +27,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "SYNCTHING-VERSIONING" "7" "Apr 30, 2026" "v2.0.0" "Syncthing"
+.TH "SYNCTHING-VERSIONING" "7" "May 13, 2026" "v2.1.0" "Syncthing"
 .SH NAME
 syncthing-versioning \- Keep automatic backups of deleted files by other nodes
 .sp

man/syncthing.1

@@ -27,7 +27,7 @@ level margin: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .\" new: \\n[rst2man-indent\\n[rst2man-indent-level]]
 .in \\n[rst2man-indent\\n[rst2man-indent-level]]u
 ..
-.TH "SYNCTHING" "1" "Apr 30, 2026" "v2.0.0" "Syncthing"
+.TH "SYNCTHING" "1" "May 13, 2026" "v2.1.0" "Syncthing"
 .SH NAME
 syncthing \- Syncthing
 .SH SYNOPSIS