diff --git a/pm/install.py b/pm/install.py
index a1316de627..fbea7b9d7d 100644
--- a/pm/install.py
+++ b/pm/install.py
@@ -542,6 +542,22 @@ def _member_inputs(plugins: PluginInput | None) -> dict:
     raise TypeError(f"{type(plugins).__name__} changes plugin state; only a sync may carry it")
 
 
+def _still_declared(package, recorded: list[str]) -> list[str]:
+    """The recorded extras this tree still declares.
+
+    An extra the source removed (``hindsight``) would otherwise ride the ledger
+    into every later ``uv sync`` and fail it with "Extra is not defined". Only
+    recorded extras are pruned; an explicitly requested unknown extra still fails.
+    """
+    from pm.features import declared_extras
+
+    root = package.project_root()
+    if not (root / "pyproject.toml").is_file():
+        return list(recorded)
+    declared = set(declared_extras(root))
+    return [extra for extra in recorded if extra in declared]
+
+
 def venv_is_current(*, extras: list[str] | None = None, plugins: Members | Candidates | None = None,
                     project_root: Path | None = None) -> bool:
     """Probe the requested union without changing recorded dependency state."""
@@ -559,7 +575,7 @@ def venv_is_current(*, extras: list[str] | None = None, plugins: Members | Candi
             or not isinstance(fact.get("extras"), list)
             or any(not isinstance(extra, str) for extra in fact["extras"])):
         raise ValueError("invalid recorded dependency state")
-    enabled = sorted(set(fact["extras"]) | set(extras or []))
+    enabled = sorted(set(_still_declared(package, fact["extras"])) | set(extras or []))
     stamp = package.expected_stamp(enabled, **_member_inputs(plugins))
     return _runtime_state_matches(fact, stamp, project_root=root)
 
@@ -651,7 +667,7 @@ def _target_selection(package, fact: dict, *, extras, inputs: dict, repair: bool
         return enabled, stamp, {"repair": True}
     # The first writable generation replaces, rather than layers on,
     # the payload. Retain its extras until a recorded selection owns them.
-    enabled = sorted(set(fact.get("extras", shipped or [])) | set(extras or []))
+    enabled = sorted(set(_still_declared(package, fact.get("extras", shipped or []))) | set(extras or []))
     return enabled, package.expected_stamp(enabled, **inputs), inputs
 
 
diff --git a/tests/hermes_cli/test_venv_sync_currency.py b/tests/hermes_cli/test_venv_sync_currency.py
index 0b43195e74..b103f659fa 100644
--- a/tests/hermes_cli/test_venv_sync_currency.py
+++ b/tests/hermes_cli/test_venv_sync_currency.py
@@ -59,6 +59,10 @@ def test_check_uses_real_pm_selection_and_keeps_invalid_evidence(admission_env,
     config.write_bytes(old_config)
     check('current')
 
+    # A recorded extra only counts while the tree still declares it.
+    pyproject = core / 'pyproject.toml'
+    pyproject.write_text(pyproject.read_text(encoding='utf-8')
+                         + '[project.optional-dependencies]\nchanged-extra = []\n', encoding='utf-8')
     altered = json.loads(pristine)
     altered['packages']['venv']['extras'] = ['changed-extra']
     facts_path.write_text(json.dumps(altered), encoding='utf-8')
diff --git a/tests/pm/test_source_update_launch.py b/tests/pm/test_source_update_launch.py
index 7f8ecb0386..0bd0a36a02 100644
--- a/tests/pm/test_source_update_launch.py
+++ b/tests/pm/test_source_update_launch.py
@@ -329,6 +329,24 @@ def test_failed_real_sync_preserves_previous_selection_and_retries(source_launch
     assert not any(marker.exists() for marker in markers)
 
 
+@pytest.mark.platforms("posix")
+def test_source_update_that_removes_a_recorded_extra_still_syncs(source_launch):
+    """A dropped extra (hindsight, 73c598e319) must not brick every later sync."""
+    root, store_python, _ = source_launch
+    pm.sync_venv(["all", "launch-extra"], explicit=True, project_root=root)
+    assert _fact(root)["extras"] == ["all", "launch-extra"]
+
+    pyproject = root / "pyproject.toml"
+    pyproject.write_text(pyproject.read_text(encoding="utf-8").replace("launch-extra = []\n", ""),
+                         encoding="utf-8")
+    pm.lock_project(root, offline=True, explicit=True)
+    assert not pm.venv_is_current(project_root=root)
+
+    assert venv_sync.prepare_launch(root, []) == store_python
+    assert _fact(root)["extras"] == ["all"]
+    assert pm.venv_is_current(project_root=root)
+
+
 @pytest.mark.platforms("posix")
 @pytest.mark.parametrize("mode", ["script", "module", "command"])
 def test_real_bootstrap_reexecs_before_app_imports(source_launch, tmp_path, isolated_python, mode):