fix(mcp): fall back to root insert for phantom parent refs

A generated program that parents its first line onto a binding that was
never created used to ride into InsertAuthoredSubtree unvalidated; the
host's existence check then rejected the WHOLE otherwise-valid program
and the section was lost to retries. Insert at the document root instead
and surface a warning in the envelope.

Also: drop the ambiguous bare-word 'auto' sizing (schema default wins
instead of inverting intent), and recover word-based textGrowth
spellings (fixed_width_and_height and friends) instead of silently
removing them.

crates/op-mcp/src/batch_design.rs

@@ -705,10 +705,11 @@ fn normalize_layout_object(obj: &mut serde_json::Map<String, serde_json::Value>)
 
 /// `width` / `height` accept `fill_container` / `fit_content` / a number. A weak
 /// model sometimes appends a type-hint suffix (`fill_container_str` — a leaked
-/// variable name) or uses a CSS-ish spelling (`fill-container` / `hug` / `auto`),
-/// which fails the `Sizing` enum and drops the whole node. Map the known
-/// content-hug / fill spellings back to the canonical keyword; leave numbers,
-/// numeric strings, and already-valid / unrecognised values untouched.
+/// variable name) or uses a CSS-ish spelling (`fill-container` / `hug`), which
+/// fails the `Sizing` enum and drops the whole node. Map the known content-hug /
+/// fill spellings back to the canonical keyword; DROP the ambiguous `auto`
+/// (schema default wins); leave numbers, numeric strings, and already-valid /
+/// unrecognised values untouched.
 fn normalize_sizing_keyword(obj: &mut serde_json::Map<String, serde_json::Value>, key: &str) {
     let Some(serde_json::Value::String(raw)) = obj.get(key) else {
         return;
@@ -723,9 +724,17 @@ fn normalize_sizing_keyword(obj: &mut serde_json::Map<String, serde_json::Value>
     let normalized = match canon.as_str() {
         "fill_container" | "fillcontainer" | "fill" | "container" | "full" | "fill_width"
         | "fill_parent" => Some("fill_container"),
-        "fit_content" | "fitcontent" | "fit" | "hug" | "hug_content" | "auto" | "content" => {
+        "fit_content" | "fitcontent" | "fit" | "hug" | "hug_content" | "content" => {
             Some("fit_content")
         }
+        // CSS `auto` is AMBIGUOUS: for a block's width it usually means
+        // stretch/fill, for height it means hug — forcing either direction
+        // inverts the author's intent half the time. Drop the key so the node
+        // survives deserialization with the schema default instead.
+        "auto" => {
+            obj.remove(key);
+            return;
+        }
         _ => None,
     };
     if let Some(valid) = normalized {
@@ -777,6 +786,19 @@ fn normalize_text_growth(obj: &mut serde_json::Map<String, serde_json::Value>) {
         "fixed-width-height" | "fixed-width-and-height" | "fixed" => Some("fixed-width-height"),
         _ => None,
     };
+    // Unrecognized spellings: recover the intent from the words before falling
+    // back to removal ("fixed_width_and_height", "fixedWidth" and friends carry
+    // a clear meaning — silently reverting them to the default undoes a
+    // deliberate wrap request).
+    let normalized = normalized.or_else(|| {
+        if canon.contains("width") && canon.contains("height") {
+            Some("fixed-width-height")
+        } else if canon.contains("width") {
+            Some("fixed-width")
+        } else {
+            None
+        }
+    });
     match normalized {
         Some(valid) => {
             obj.insert(

crates/op-mcp/src/batch_design_result.rs

@@ -133,6 +133,21 @@ impl BatchDesign {
                 .collect();
             result["promoted"] = json!(notes);
         }
+        // A parent ref that is NEITHER a binding NOR a node in the snapshot
+        // (a weak model copies the `sec` example binding as its first line's
+        // parent) would fail the host's existence check and sink the WHOLE
+        // otherwise-valid program (measured: an orchestrator stats subtask
+        // retried its complete 4-card program away over a phantom `sec`).
+        // Insert at the root instead and say so — the section coalesce /
+        // finalize passes reparent stray roots anyway.
+        let mut parent_id = parent_id;
+        if parent_id.is_real() && !self.existing_ids.contains(&parent_id) {
+            result["warnings"] = json!([format!(
+                "parent '{}' does not exist — inserted at the document root instead",
+                parent_id.as_str()
+            )]);
+            parent_id = NodeId::NONE;
+        }
         ToolOutcome::OkJsonWithCommand(
             result.to_string(),
             EditorCommand::InsertAuthoredSubtree {

crates/op-mcp/src/batch_design_tests.rs

@@ -1081,3 +1081,66 @@ fn batch_insert_command_rejects_empty_items() {
         page_id: None,
     }));
 }
+
+#[test]
+fn batch_design_drops_ambiguous_auto_sizing_and_recovers_text_growth_words() {
+    // `width:"auto"` is ambiguous in CSS (fill for a block's width, hug for its
+    // height) — forcing either direction inverts intent half the time, so the
+    // key must be DROPPED (schema default wins) while the node itself survives.
+    // A misspelled `textGrowth` carrying clear words ("fixed_width_and_height")
+    // must recover its meaning instead of silently reverting to the default.
+    let tool = batch_design_snapshot(&sample());
+    let mut args = BTreeMap::new();
+    args.insert(
+        "operations".into(),
+        r##"root=I(null, {"type":"frame","name":"Block","width":"auto","height":"fit_content","children":[{"type":"text","name":"T","content":"hello","textGrowth":"fixed_width_and_height"}]})"##
+            .into(),
+    );
+    let ToolOutcome::OkJsonWithCommand(_, EditorCommand::InsertAuthoredSubtree { nodes, .. }) =
+        tool.call(&args)
+    else {
+        panic!("expected InsertSubtree command");
+    };
+    let value = serde_json::to_value(&nodes[0]).expect("node json");
+    assert!(
+        value.get("width").map(|w| !w.is_string()).unwrap_or(true),
+        "ambiguous auto width dropped, got {:?}",
+        value.get("width")
+    );
+    assert_eq!(value["height"], "fit_content", "valid keyword untouched");
+    let text = &value["children"][0];
+    assert_eq!(
+        text["textGrowth"], "fixed-width-height",
+        "word-based textGrowth spelling recovered"
+    );
+}
+
+#[test]
+fn batch_design_falls_back_to_root_for_phantom_parent_binding() {
+    // A weak model copies the `sec` example binding as its FIRST line's
+    // parent. The phantom parent used to ride into `InsertAuthoredSubtree`
+    // unvalidated and the host rejected the WHOLE otherwise-valid program
+    // (an orchestrator stats subtask retried its complete 4-card section
+    // away). The tool must fall back to a root insert and surface a warning.
+    let state = op_editor_core::EditorState::new();
+    let tool = batch_design_snapshot(&state);
+    let mut args = BTreeMap::new();
+    args.insert(
+        "operations".into(),
+        "row=I(sec, {\"type\":\"frame\",\"name\":\"Stat Row\",\"layout\":\"horizontal\",\"gap\":24})\nc1=I(row, {\"type\":\"frame\",\"name\":\"Card\",\"layout\":\"vertical\"})".to_string(),
+    );
+    let ToolOutcome::OkJsonWithCommand(json, cmd) = tool.call(&args) else {
+        panic!("expected a command outcome");
+    };
+    assert!(json.contains("warnings"), "phantom parent surfaced: {json}");
+    let mut s2 = op_editor_core::EditorState::new();
+    assert!(s2.apply(cmd), "root-fallback insert must apply cleanly");
+    assert_eq!(s2.active_children().len(), 1, "one root landed");
+    use op_editor_core::PenNodeExt;
+    let root = &s2.active_children()[0];
+    assert_eq!(
+        root.children().map(|c| c.len()),
+        Some(1),
+        "card nested in row"
+    );
+}