diff --git a/src/calva-fmt/src/config.ts b/src/calva-fmt/src/config.ts
index 9fcaee15f..6f72b58da 100644
--- a/src/calva-fmt/src/config.ts
+++ b/src/calva-fmt/src/config.ts
@@ -90,11 +90,5 @@ function _updateConfig(): FormatConfig {
 export function onConfigurationChanged(e: vscode.ConfigurationChangeEvent) {
     if (e.affectsConfiguration("calva.fmt")) {
         updateConfig();
-        if (e.affectsConfiguration("calva.fmt.experimental.inferParensAsYouType")) {
-            const parinferOn = getConfig()['infer-parens-as-you-type'];
-            docMirror.getDocuments().forEach((doc: docMirror.MirroredDocument, _key: any) => {
-                doc.model.performInferParens = parinferOn;
-            });
-        }
     }
 }
\ No newline at end of file
diff --git a/src/cursor-doc/model.ts b/src/cursor-doc/model.ts
index e7ddf2371..28813ad82 100644
--- a/src/cursor-doc/model.ts
+++ b/src/cursor-doc/model.ts
@@ -99,7 +99,6 @@ export interface EditableModel {
      */
     edit: (edits: ModelEdit[], options: ModelEditOptions) => Thenable<boolean>;
     parinferReadiness: parinfer.ParinferReadiness,
-    performInferParens: boolean;
     isWritable: boolean;
     getText: (start: number, end: number, mustBeWithin?: boolean) => string;
     getLineText: (line: number) => string;
@@ -487,3 +486,48 @@ export class LineInputModel implements EditableModel {
 }
 
 
+export class StringDocument implements EditableDocument {
+    constructor(contents: string) {
+        this.insertString(contents);
+    }
+
+    selectionLeft: number;
+    selectionRight: number;
+
+    get selection() {
+        return new ModelEditSelection(this.selectionLeft, this.selectionRight);
+    }
+
+    set selection(sel: ModelEditSelection) {
+        this.selectionLeft = sel.anchor;
+        this.selectionRight = sel.active;
+    }
+
+    model: LineInputModel = new LineInputModel(1, this);
+
+    selectionStack: ModelEditSelection[] = [];
+
+    getTokenCursor(offset?: number, previous?: boolean): LispTokenCursor {
+        return this.model.getTokenCursor(offset);
+    };
+
+    insertString(text: string) {
+        this.model.insertString(0, text);
+    };
+
+    getSelectionText: () => string;
+
+    delete() {
+        const p = this.selectionLeft;
+        return this.model.edit([
+            new ModelEdit('deleteRange', [p, 1])
+        ], { selection: new ModelEditSelection(p) });
+    };
+
+    backspace() {
+        const p = this.selectionLeft;
+        return this.model.edit([
+            new ModelEdit('deleteRange', [p - 1, 1])
+        ], { selection: new ModelEditSelection(p - 1) });
+    };
+}
\ No newline at end of file
diff --git a/src/doc-mirror/index.ts b/src/doc-mirror/index.ts
index 34e9fbafd..49c17f56c 100644
--- a/src/doc-mirror/index.ts
+++ b/src/doc-mirror/index.ts
@@ -3,7 +3,7 @@ import * as vscode from "vscode"
 import * as utilities from '../utilities';
 import * as formatter from '../calva-fmt/src/format';
 import { LispTokenCursor } from "../cursor-doc/token-cursor";
-import { ModelEdit, EditableDocument, EditableModel, ModelEditOptions, LineInputModel, ModelEditSelection } from "../cursor-doc/model";
+import { ModelEdit, EditableDocument, EditableModel, ModelEditOptions, LineInputModel, ModelEditSelection, StringDocument } from "../cursor-doc/model";
 import * as parinfer from "../calva-fmt/src/infer";
 import * as formatConfig from '../calva-fmt/src/config';
 import statusbar from '../statusbar';
@@ -29,8 +29,6 @@ export class DocumentModel implements EditableModel {
         this._parinferReadiness = readiness;
     }
 
-    performInferParens = formatConfig.getConfig()["infer-parens-as-you-type"];
-
     isWritable = false;
 
     constructor(private document: MirroredDocument) {
@@ -43,9 +41,6 @@ export class DocumentModel implements EditableModel {
         const undoStopBefore = !!options.undoStopBefore;
         return editor.edit(builder => {
             for (const modelEdit of modelEdits) {
-                if (!options.performInferParens) {
-                    this.document.model.performInferParens = false;
-                }
                 switch (modelEdit.editFn) {
                     case 'insertString':
                         this.insertEdit.apply(this, [builder, ...modelEdit.args]);
@@ -116,6 +111,9 @@ export class DocumentModel implements EditableModel {
 export class MirroredDocument implements EditableDocument {
     constructor(public document: vscode.TextDocument) { }
 
+    parensInferred = false;
+    rangeFormatted = false;
+
     get selectionLeft(): number {
         return this.document.offsetAt(vscode.window.activeTextEditor.selection.anchor);
     }
@@ -180,7 +178,7 @@ function processChanges(event: vscode.TextDocumentChangeEvent) {
         const parinferOn = formatConfig.getConfig()["infer-parens-as-you-type"];
         const formatAsYouTypeOn = formatConfig.getConfig()["format-as-you-type"];
         const performFormatAsYouType = formatAsYouTypeOn && event.reason != vscode.TextDocumentChangeReason.Undo;
-        const performInferParens = parinferOn && event.reason != vscode.TextDocumentChangeReason.Undo && model.performInferParens;
+        const performInferParens = parinferOn && event.reason != vscode.TextDocumentChangeReason.Undo && !mirroredDoc.parensInferred;
         let performHealthCheck = !performFormatAsYouType;
         const edits: ModelEdit[] = event.contentChanges.map(change => {
             // vscode may have a \r\n marker, so it's line offsets are all wrong.
@@ -192,13 +190,19 @@ function processChanges(event: vscode.TextDocumentChangeEvent) {
             performInferParens: !vscode.TextDocumentChangeReason.Undo
         }).then(async _v => {
             if (event.document === vscode.window.activeTextEditor?.document) {
-                if (performFormatAsYouType) {
+                if (performFormatAsYouType && !mirroredDoc.rangeFormatted) {
                     if (event.contentChanges.length === 1 && event.contentChanges[0].text.match(/[\[\](){}]/)) {
                         const change = event.contentChanges[0];
                         const start = event.document.offsetAt(change.range.start);
                         const formatForwardIndex = formatter.indexForFormatForward(mirroredDoc);
                         const end = formatForwardIndex !== mirroredDoc.selection.active ? formatForwardIndex + 1 : mirroredDoc.selection.active;
-                        await formatter.formatRangeEditableDoc(mirroredDoc, [start, end], true);
+                        const checkDoc = new StringDocument(mirroredDoc.model.getText(start, end));
+                        if (parinfer.getParinferReadiness(checkDoc).isStructureHealthy) {
+                            await formatter.formatRangeEditableDoc(mirroredDoc, [start, end], true);
+                        } else {
+                            await formatter.formatForward(mirroredDoc);
+                        }
+                        mirroredDoc.rangeFormatted = true;
                     } else {
                         await formatter.formatForward(mirroredDoc);
                     }
@@ -206,6 +210,7 @@ function processChanges(event: vscode.TextDocumentChangeEvent) {
                 }
                 if ((mirroredDoc.model.parinferReadiness.isIndentationHealthy || performHealthCheck) && performInferParens) {
                     await parinfer.inferParens(mirroredDoc);
+                    mirroredDoc.parensInferred = true;
                 }
                 if (!performFormatAsYouType) {
                     performHealthCheck = true;
@@ -216,9 +221,8 @@ function processChanges(event: vscode.TextDocumentChangeEvent) {
                 statusBar.update(vscode.window.activeTextEditor?.document);
             }
         });
-        if (event.contentChanges.length > 0) {
-            model.performInferParens = formatConfig.getConfig()["infer-parens-as-you-type"];
-        }
+        mirroredDoc.parensInferred = false;
+        mirroredDoc.rangeFormatted = false;
         model.lineInputModel.flushChanges()
 
         // we must clear out the repaint cache data, since we don't use it. 
diff --git a/src/extension-test/unit/common/mock.ts b/src/extension-test/unit/common/mock.ts
index 21bcf542c..4a464ce47 100644
--- a/src/extension-test/unit/common/mock.ts
+++ b/src/extension-test/unit/common/mock.ts
@@ -4,8 +4,6 @@ import { LispTokenCursor } from '../../../cursor-doc/token-cursor'
 model.initScanner(20000);
 
 export class MockDocument implements model.EditableDocument {
-    isIndentationHealthy = true;
-    isStructureHealthy = true;
     selectionLeft: number;
     selectionRight: number;