diff --git a/cmd/mnemonic/main.go b/cmd/mnemonic/main.go
index 3c219e03..ecf65236 100644
--- a/cmd/mnemonic/main.go
+++ b/cmd/mnemonic/main.go
@@ -911,9 +911,18 @@ func serveCommand(configPath string) {
 
 	if cfg.Perception.Enabled {
 		if cfg.Perception.Filesystem.Enabled {
+			// Auto-detect noisy app directories and merge with configured exclusions
+			autoExclusions := fswatcher.DetectNoisyApps(log)
+			allExclusions := cfg.Perception.Filesystem.ExcludePatterns
+			for _, pattern := range autoExclusions {
+				if !fswatcher.MatchesExcludePattern(pattern, allExclusions) {
+					allExclusions = append(allExclusions, pattern)
+				}
+			}
+
 			fsw, err := fswatcher.NewFilesystemWatcher(fswatcher.Config{
 				WatchDirs:       cfg.Perception.Filesystem.WatchDirs,
-				ExcludePatterns: cfg.Perception.Filesystem.ExcludePatterns,
+				ExcludePatterns: allExclusions,
 				MaxContentBytes: cfg.Perception.Filesystem.MaxContentBytes,
 			}, log)
 			if err != nil {
diff --git a/internal/watcher/filesystem/autodetect.go b/internal/watcher/filesystem/autodetect.go
new file mode 100644
index 00000000..ad7436f5
--- /dev/null
+++ b/internal/watcher/filesystem/autodetect.go
@@ -0,0 +1,139 @@
+package filesystem
+
+import (
+	"log/slog"
+	"os"
+	"path/filepath"
+	"runtime"
+)
+
+// knownNoisyApp maps a directory name (found under XDG/Library base dirs)
+// to a human-readable description of why it's noisy.
+type knownNoisyApp struct {
+	Dir         string // directory name to match (e.g., "Code", "google-chrome")
+	Description string // why it's noisy
+}
+
+// Registry of known noisy applications. These write high-frequency internal
+// state to disk that is never useful as developer memories.
+var knownNoisyApps = []knownNoisyApp{
+	// Browsers
+	{Dir: "google-chrome", Description: "Chrome browser storage"},
+	{Dir: "chromium", Description: "Chromium browser storage"},
+	{Dir: "BraveSoftware", Description: "Brave browser storage"},
+	{Dir: "firefox", Description: "Firefox browser storage"},
+	{Dir: "vivaldi", Description: "Vivaldi browser storage"},
+	{Dir: "opera", Description: "Opera browser storage"},
+
+	// Editors/IDEs
+	{Dir: "Code", Description: "VS Code internal state"},
+	{Dir: "Code - Insiders", Description: "VS Code Insiders internal state"},
+	{Dir: "Cursor", Description: "Cursor editor internal state"},
+	{Dir: "JetBrains", Description: "JetBrains IDE state"},
+
+	// Communication
+	{Dir: "Slack", Description: "Slack desktop state"},
+	{Dir: "discord", Description: "Discord desktop state"},
+	{Dir: "Signal", Description: "Signal messenger state"},
+	{Dir: "teams", Description: "MS Teams state"},
+	{Dir: "Microsoft Teams", Description: "MS Teams state"},
+	{Dir: "Telegram Desktop", Description: "Telegram state"},
+	{Dir: "zoom.us", Description: "Zoom state"},
+
+	// Media/Desktop
+	{Dir: "spotify", Description: "Spotify cache"},
+	{Dir: "Spotify", Description: "Spotify cache"},
+	{Dir: "vlc", Description: "VLC media player state"},
+
+	// Desktop environments
+	{Dir: "gnome-shell", Description: "GNOME shell temp files"},
+	{Dir: "plasma", Description: "KDE Plasma state"},
+	{Dir: "xfce4", Description: "XFCE desktop state"},
+	{Dir: "cinnamon", Description: "Cinnamon desktop state"},
+
+	// System services
+	{Dir: "dconf", Description: "GNOME settings backend"},
+	{Dir: "gconf", Description: "legacy GNOME settings"},
+	{Dir: "pulse", Description: "PulseAudio state"},
+	{Dir: "pipewire", Description: "PipeWire audio state"},
+
+	// Package managers / runtimes
+	{Dir: "yarn", Description: "Yarn package cache"},
+	{Dir: "pnpm", Description: "pnpm package cache"},
+	{Dir: "Docker Desktop", Description: "Docker Desktop state"},
+
+	// Cloud sync / misc
+	{Dir: "Dropbox", Description: "Dropbox sync state"},
+	{Dir: "OneDrive", Description: "OneDrive sync state"},
+	{Dir: "obsidian", Description: "Obsidian vault metadata"},
+	{Dir: "1Password", Description: "1Password state"},
+}
+
+// linuxBaseDirs returns the XDG base directories to scan on Linux.
+func linuxBaseDirs(home string) []string {
+	return []string{
+		filepath.Join(home, ".config"),
+		filepath.Join(home, ".local", "share"),
+	}
+}
+
+// darwinBaseDirs returns the base directories to scan on macOS.
+func darwinBaseDirs(home string) []string {
+	return []string{
+		filepath.Join(home, "Library", "Application Support"),
+		filepath.Join(home, "Library", "Caches"),
+	}
+}
+
+// DetectNoisyApps scans known base directories for installed applications
+// that are known to produce high-frequency filesystem noise. Returns
+// exclusion patterns for any that are found.
+func DetectNoisyApps(log *slog.Logger) []string {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		log.Warn("auto-detect: could not determine home directory", "error", err)
+		return nil
+	}
+
+	var baseDirs []string
+	switch runtime.GOOS {
+	case "linux":
+		baseDirs = linuxBaseDirs(home)
+	case "darwin":
+		baseDirs = darwinBaseDirs(home)
+	default:
+		log.Debug("auto-detect: unsupported platform, skipping", "os", runtime.GOOS)
+		return nil
+	}
+
+	// Build a lookup set from existing config patterns so we don't duplicate
+	var detected []string
+
+	for _, baseDir := range baseDirs {
+		for _, app := range knownNoisyApps {
+			candidate := filepath.Join(baseDir, app.Dir)
+			if info, err := os.Stat(candidate); err == nil && info.IsDir() {
+				// Use the path relative to home for the exclusion pattern,
+				// with trailing slash to match the substring convention
+				relPattern := "." + candidate[len(home):]
+				if relPattern[len(relPattern)-1] != '/' {
+					relPattern += "/"
+				}
+				detected = append(detected, relPattern)
+				log.Info("auto-detected noisy app",
+					"path", candidate,
+					"pattern", relPattern,
+					"description", app.Description,
+				)
+			}
+		}
+	}
+
+	if len(detected) > 0 {
+		log.Info("auto-detect complete", "exclusions_found", len(detected))
+	} else {
+		log.Debug("auto-detect: no additional noisy apps found")
+	}
+
+	return detected
+}
diff --git a/internal/watcher/filesystem/autodetect_test.go b/internal/watcher/filesystem/autodetect_test.go
new file mode 100644
index 00000000..5d6c0121
--- /dev/null
+++ b/internal/watcher/filesystem/autodetect_test.go
@@ -0,0 +1,93 @@
+package filesystem
+
+import (
+	"log/slog"
+	"os"
+	"path/filepath"
+	"runtime"
+	"testing"
+)
+
+func testLogger() *slog.Logger {
+	return slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelWarn}))
+}
+
+func TestDetectNoisyApps(t *testing.T) {
+	// DetectNoisyApps scans real system directories, so results vary by machine.
+	// We just verify it runs without error and returns valid patterns.
+	detected := DetectNoisyApps(testLogger())
+
+	for _, pattern := range detected {
+		if pattern == "" {
+			t.Error("detected empty exclusion pattern")
+		}
+		if pattern[0] != '.' {
+			t.Errorf("pattern should start with '.': got %q", pattern)
+		}
+		if pattern[len(pattern)-1] != '/' {
+			t.Errorf("pattern should end with '/': got %q", pattern)
+		}
+	}
+}
+
+func TestDetectNoisyApps_FindsKnownDirs(t *testing.T) {
+	if runtime.GOOS != "linux" && runtime.GOOS != "darwin" {
+		t.Skip("test only runs on Linux/macOS")
+	}
+
+	home, err := os.UserHomeDir()
+	if err != nil {
+		t.Fatalf("could not get home dir: %v", err)
+	}
+
+	// Create a fake noisy app dir in a temp location, then verify it would be detected
+	// We can't mock os.Stat in the real function, so instead create a real dir
+	// under the actual XDG path if it exists.
+	var baseDir string
+	if runtime.GOOS == "linux" {
+		baseDir = filepath.Join(home, ".config")
+	} else {
+		baseDir = filepath.Join(home, "Library", "Application Support")
+	}
+
+	if _, err := os.Stat(baseDir); os.IsNotExist(err) {
+		t.Skipf("base dir %s does not exist", baseDir)
+	}
+
+	// Check if any known noisy app is actually installed
+	detected := DetectNoisyApps(testLogger())
+	t.Logf("detected %d noisy app exclusions on this system", len(detected))
+	for _, pattern := range detected {
+		t.Logf("  %s", pattern)
+	}
+}
+
+func TestDetectNoisyApps_NoDuplicatesWithExisting(t *testing.T) {
+	// Verify that using MatchesExcludePattern to deduplicate works
+	existing := []string{".config/Code/", ".config/google-chrome/"}
+	detected := []string{".config/Code/", ".config/discord/", ".config/google-chrome/"}
+
+	var merged []string
+	merged = append(merged, existing...)
+	for _, pattern := range detected {
+		if !MatchesExcludePattern(pattern, merged) {
+			merged = append(merged, pattern)
+		}
+	}
+
+	// Should have existing 2 + 1 new = 3
+	if len(merged) != 3 {
+		t.Errorf("expected 3 merged patterns, got %d: %v", len(merged), merged)
+	}
+
+	// discord should be the new one
+	found := false
+	for _, p := range merged {
+		if p == ".config/discord/" {
+			found = true
+		}
+	}
+	if !found {
+		t.Error("expected .config/discord/ in merged patterns")
+	}
+}