diff --git a/CHANGELOG.md b/CHANGELOG.md
index 70e2f57c..9233c011 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,22 @@
 All notable changes to `plotjuggler_sdk` are recorded here. Versioning policy is in
 [`CLAUDE.md`](./CLAUDE.md) → "Release Versioning".
 
+## [0.34.0]
+
+Host contract: extended: PJ_DATA_PROCESSOR_FLAG_HISTORY_EXEMPT (floor 0.34.0).
+
+- Add `PJ_DATA_PROCESSOR_FLAG_HISTORY_EXEMPT` to `create_data_processor`'s
+  `flags` bitset: the node is persisted in the layout file like any other
+  processor, but the host's undo/redo history never restores, recreates or
+  removes it — history has no authority over it. Orthogonal to
+  `PJ_DATA_PROCESSOR_FLAG_EPHEMERAL` (never persisted at all, so this bit is
+  irrelevant on it). Supporting hosts return the boolean `history_exempt`
+  through `data_processor_config` for transforms and markers. Only a returned
+  `true` confirms protection: older hosts may silently ignore unknown bits.
+  Conforming hosts reject unknown flags under the reserved-bits rule, allowing
+  a deliberate retry without the bit. A missing/false config property or a
+  failed config read also requires disclosing that protection is unavailable.
+
 ## [0.33.0]
 
 Host contract: unchanged (no floor impact) — this release adds the floor
diff --git a/VERSION b/VERSION
index be386c9e..85e60ed1 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-0.33.0
+0.34.0
diff --git a/pj_base/feature_floors.json b/pj_base/feature_floors.json
index 92c8c77b..70d5dd84 100644
--- a/pj_base/feature_floors.json
+++ b/pj_base/feature_floors.json
@@ -11,6 +11,9 @@
     },
     "0.32.0": {
       "setDatasetMetadata": "PJ_data_source_runtime_host_vtable_t::set_dataset_metadata"
+    },
+    "0.34.0": {
+      "PJ_DATA_PROCESSOR_FLAG_HISTORY_EXEMPT": ""
     }
   },
   "baseline": [
diff --git a/pj_base/include/pj_base/plugin_data_api.h b/pj_base/include/pj_base/plugin_data_api.h
index 6e1a4caa..5ee65d51 100644
--- a/pj_base/include/pj_base/plugin_data_api.h
+++ b/pj_base/include/pj_base/plugin_data_api.h
@@ -939,7 +939,10 @@ typedef struct {
  *                   {"scope":"all"} makes a global node publish across EVERY dataset;
  *                   absent = active dataset.
  *   - flags       : bitset; PJ_DATA_PROCESSOR_FLAG_EPHEMERAL marks a preview (never
- *                   persisted, dropped on remove). Reserved bits must be 0.
+ *                   persisted, dropped on remove). PJ_DATA_PROCESSOR_FLAG_HISTORY_EXEMPT
+ *                   marks a node the host's undo/redo history has no authority over
+ *                   (still persisted like any other node; history never restores,
+ *                   recreates or removes it). Reserved bits must be 0.
  *
  * DATASET-QUALIFIED NAMES — a series' full identity is (dataset, topic, field); a
  * bare "topic/field" name is an abbreviation that stops being unique the moment
@@ -974,6 +977,14 @@ typedef struct {
 
 /* create_data_processor flags. */
 #define PJ_DATA_PROCESSOR_FLAG_EPHEMERAL (1u << 0) /* preview: never persisted, dropped on remove_data_processor */
+/* Persisted in the layout file like any other processor, but the host's undo/redo
+ * history never restores, recreates or removes it -- history has no authority over
+ * it. Orthogonal to EPHEMERAL: an EPHEMERAL processor is never persisted at all, so
+ * this bit is irrelevant on it. A conforming host rejects unknown flag bits.
+ * To confirm protection even on a host that silently ignores unknown bits,
+ * read data_processor_config after creation: only history_exempt=true confirms
+ * the property. A missing/false property or failed read does not confirm it. */
+#define PJ_DATA_PROCESSOR_FLAG_HISTORY_EXEMPT (1u << 1)
 
 typedef struct PJ_data_processors_host_vtable_t {
   uint32_t protocol_version;  // = 1
@@ -1010,7 +1021,10 @@ typedef struct PJ_data_processors_host_vtable_t {
   /* [main-thread] Read a node's full recipe as JSON
    * {"kind":"...","language":"...","inputs":[...],"outputs":[...],"params":{...}} for
    * re-edit (e.g. after a session reload). *out_recipe_json is borrowed, valid only
-   * until the next call on this vtable. An unknown id is an error. */
+   * until the next call on this vtable. An unknown id is an error.
+   * Hosts supporting PJ_DATA_PROCESSOR_FLAG_HISTORY_EXEMPT include the boolean
+   * "history_exempt" for transforms and markers, reflecting the node's actual
+   * property. Callers must not infer support from a successful create alone. */
   bool (*data_processor_config)(
       void* ctx, PJ_string_view_t id, PJ_string_view_t* out_recipe_json, PJ_error_t* out_error) PJ_NOEXCEPT;
 
diff --git a/pj_base/include/pj_base/sdk/plugin_data_api.hpp b/pj_base/include/pj_base/sdk/plugin_data_api.hpp
index 5e18d964..a1df513c 100644
--- a/pj_base/include/pj_base/sdk/plugin_data_api.hpp
+++ b/pj_base/include/pj_base/sdk/plugin_data_api.hpp
@@ -1517,7 +1517,9 @@ class DataProcessorsHostView {
 
   /// Create or replace (upsert by id) a data processor of `kind` ("transform" or
   /// "markers"). `outputs` may be empty for an ephemeral preview (flags &
-  /// PJ_DATA_PROCESSOR_FLAG_EPHEMERAL), in which case the host names the sink(s).
+  /// PJ_DATA_PROCESSOR_FLAG_EPHEMERAL), in which case the host names the sink(s);
+  /// flags & PJ_DATA_PROCESSOR_FLAG_HISTORY_EXEMPT instead marks a persisted node the
+  /// host's undo/redo history has no authority over.
   /// Returns the resolved physical output topic name(s) (owned copies) so the caller
   /// can read results back through the kind's read surface. `params_json` is forwarded
   /// verbatim to the script. Input names MAY carry the dataset qualifier
diff --git a/tools/feature_floors/host_surfaces.snapshot b/tools/feature_floors/host_surfaces.snapshot
index 8ed8d06d..9834fc27 100644
--- a/tools/feature_floors/host_surfaces.snapshot
+++ b/tools/feature_floors/host_surfaces.snapshot
@@ -1,4 +1,5 @@
 PJ_DATA_PROCESSOR_FLAG_EPHEMERAL
+PJ_DATA_PROCESSOR_FLAG_HISTORY_EXEMPT
 PJ_DESCRIPTOR_IMPORT_START_FLAGS_V1_MASK
 PJ_DESCRIPTOR_IMPORT_START_FLAG_NONE
 PJ_INGEST_COMPLETION_FLAGS_V1_MASK