diff --git a/README.md b/README.md
index 121258a..23d097b 100644
--- a/README.md
+++ b/README.md
@@ -189,6 +189,10 @@ docker build -t cc2-spoolman-bridge:dev .        # Image
 python tools/mock_env.py --host mock --printers 2  # Mock: 2 Drucker (SSH :2222/2223, CC2 :8081/8082), Spoolman
 ```
 
+Einen Test-Container der Bridge gegen den Mock nur in einem Netz ohne Außenverbindung starten
+(`docker network create --internal …`) und mit `SPOOLMAN_URL=http://mock:7912`. Sonst spricht er bis zum Speichern
+der Einstellungen mit der voreingestellten echten Spoolman-Instanz.
+
 Die Tests decken ab: Tag-Kodierung gegen die verifizierte Vorlage, ID-Dekodierung, Palette und Materialvorschlag,
 Zuordnung bei verschwindender ID, Verbrauchs-Delta und Idempotenz (auch nach Abbruch), Dry-Run, mehrere Drucker
 (Umzug, Ausfall eines Druckers, Entfernen, Umbenennen), Spoolman-Ort und Zusatzfelder inkl. Korrektur von Hand-
diff --git a/app/bridge.py b/app/bridge.py
index a1f1586..34b27b5 100644
--- a/app/bridge.py
+++ b/app/bridge.py
@@ -948,6 +948,10 @@ class Bridge:
         ours.discard(self.settings.location_storage)
         return ours
 
+    def _our_printers(self) -> set[str]:
+        """Printer names this bridge runs or has written. Spoolman's "drucker" field naming anyone else is not ours."""
+        return set(self.state.data.get("written_printers", [])) | {w.name for w in self.workers.values()}
+
     def _ensure_fields(self) -> bool:
         if self.fields_ok or not self.settings.spoolman_fields:
             return True
@@ -979,14 +983,15 @@ class Bridge:
             if self.clock() - self.last_sync >= SYNC_SECONDS:
                 # Full comparison: the printer wins over manual edits in Spoolman.
                 ours = self._our_locations()
+                our_printers = self._our_printers()
                 for sp in self.spoolman.spools():
                     sid = int(sp["id"])
                     names[sid] = label(sp)
                     actual = self._actual(sp)
                     want = desired.get(sid)
                     if want is None:
-                        if actual["location"] not in ours and actual["printer"] is None:
-                            # a place of yours (e.g. a shelf): not ours to touch
+                        if actual["location"] not in ours and actual["printer"] not in our_printers:
+                            # a place of yours (e.g. a shelf), or a printer this bridge never ran: not ours to touch
                             targets.pop(sid, None)
                             applied.pop(str(sid), None)
                             continue
@@ -1016,6 +1021,9 @@ class Bridge:
                     if t["location"] != storage["location"]:
                         written = set(self.state.data["written_locations"]) | {t["location"]}
                         self.state.data["written_locations"] = sorted(written)
+                    if t.get("printer"):
+                        printers = set(self.state.data.get("written_printers", [])) | {t["printer"]}
+                        self.state.data["written_printers"] = sorted(printers)
         except SpoolmanError as e:
             self.fields_ok = False
             self._spoolman_error(str(e))
diff --git a/app/storage.py b/app/storage.py
index 2899bfd..9bdb59b 100644
--- a/app/storage.py
+++ b/app/storage.py
@@ -267,4 +267,6 @@ def migrate_state(data: dict, first_printer: str) -> dict:
         data["version"] = 2
     data.setdefault("applied", {})
     data.setdefault("written_locations", [])
+    if "written_printers" not in data:
+        data["written_printers"] = sorted({a["printer"] for a in data["applied"].values() if a.get("printer")})
     return data
diff --git a/tests/test_bridge.py b/tests/test_bridge.py
index 106810f..3d30cac 100644
--- a/tests/test_bridge.py
+++ b/tests/test_bridge.py
@@ -417,6 +417,7 @@ def test_stale_printer_locations_go_to_storage(env):
     env["sm"].add(3, location="Lager", extra={"drucker": '"Links"', "slot": "1"})
     env["sm"].add(4, location="Regal 1")
     env["bridge"].state.data["written_locations"] = ["CC2 Slot 2"]
+    env["bridge"].state.data["written_printers"] = ["Links"]  # a printer this bridge used to run
     poll(env)
     assert env["sm"].db[1]["location"] == "Lager"
     assert env["sm"].db[2]["location"] == "Lager"
@@ -773,3 +774,21 @@ def test_job_progress_only_read_while_printing(env):
     job = b.snapshot["printers"][0]["job"]
     assert job["file"] == "cube.gcode" and job["grams"] == 1.23 and job["slots"] == [{"slot": 1, "grams": 1.23}]
     assert job["progress"] == 40 and job["layer"] == 12 and job["layers"] == 30 and job["remaining"] == 600
+
+
+def test_fresh_bridge_leaves_other_bridges_spools_alone(env):
+    """A new instance (empty data volume, no printers yet) must not pull spools out of printers it never ran."""
+    env["settings"].save({"printers": []})
+    env["sm"].add(11, location="CC2 Links Slot 4", extra={"drucker": '"CC2 Links"', "slot": "4"})
+    env["sm"].add(1, location="CC2 Rechts Slot 2", extra={"drucker": '"CC2 Rechts"', "slot": "2"})
+    poll(env, 13)
+    assert env["sm"].db[11]["location"] == "CC2 Links Slot 4" and env["sm"].extra(11)["drucker"] == "CC2 Links"
+    assert env["sm"].db[1]["location"] == "CC2 Rechts Slot 2"
+    assert not [c for c in env["sm"].calls if c[0] in ("location", "extra")]
+
+
+def test_printer_names_written_are_remembered(env):
+    env["sm"].add(5)
+    insert(env, 0, 5)
+    poll(env)
+    assert env["bridge"].state.data["written_printers"] == ["Rechts"]