diff --git a/.changeset/preserve-legacy-json-percent-sequences.md b/.changeset/preserve-legacy-json-percent-sequences.md
new file mode 100644
index 0000000000..4d5b6a7197
--- /dev/null
+++ b/.changeset/preserve-legacy-json-percent-sequences.md
@@ -0,0 +1,5 @@
+---
+'@hyperdx/app': patch
+---
+
+Preserve literal percent sequences in legacy JSON URL parameters.
diff --git a/packages/app/src/utils/__tests__/queryParsers.test.ts b/packages/app/src/utils/__tests__/queryParsers.test.ts
index ff1bf66873..9a0e7529dc 100644
--- a/packages/app/src/utils/__tests__/queryParsers.test.ts
+++ b/packages/app/src/utils/__tests__/queryParsers.test.ts
@@ -69,6 +69,16 @@ describe('parseAsJsonEncoded', () => {
       expect(jsonParser.parse(raw)).toEqual([{ key: 'hello world' }]);
     });
 
+    it.each(['%2F', '%20', '%25'])(
+      'preserves literal %s text in legacy JSON',
+      sequence => {
+        const raw = JSON.stringify([{ query: `path${sequence}segment` }]);
+        expect(jsonParser.parse(raw)).toEqual([
+          { query: `path${sequence}segment` },
+        ]);
+      },
+    );
+
     it('returns null for malformed JSON after successful URI decode', () => {
       // A valid percent-sequence that decodes to something that is not JSON.
       expect(jsonParser.parse('not-json')).toBeNull();
diff --git a/packages/app/src/utils/queryParsers.ts b/packages/app/src/utils/queryParsers.ts
index 5e165eda2c..b3b6b83705 100644
--- a/packages/app/src/utils/queryParsers.ts
+++ b/packages/app/src/utils/queryParsers.ts
@@ -36,10 +36,9 @@ export const parseAsStringEncoded = createParser<string>({
  * Same double-encoding protection as parseAsStringEncoded, but wraps
  * JSON.stringify / JSON.parse around the value.
  *
- * Backward compatible: old URLs where nuqs wrote raw JSON (with '+' for
- * spaces, unencoded '[', ']', etc.) are handled via a fallback to plain
- * JSON.parse after the decodeURIComponent step naturally resolves '%22' →
- * '"', '+' → ' ', etc. via URLSearchParams.get().
+ * Backward compatible: old URLs where nuqs wrote raw JSON are parsed before
+ * URI decoding, so literal '%XX' text inside JSON strings is preserved. New
+ * URLs are decoded before JSON.parse so their encoded structure still works.
  *
  * Optional `validate`: a guard that either returns the (narrowed) value or
  * throws / returns `null` for a shape mismatch. A stale, hand-edited, or
@@ -67,22 +66,15 @@ export function parseAsJsonEncoded<T>(validate?: (value: unknown) => T) {
 
   return createParser<T>({
     parse: value => {
-      let decoded: string;
       try {
-        decoded = decodeURIComponent(value);
+        return finalize(JSON.parse(value));
       } catch {
-        // Malformed URI sequence — value is likely old-format plain JSON.
-        try {
-          return finalize(JSON.parse(value));
-        } catch {
-          return null;
-        }
+        // New-format values are percent-encoded, so they cannot be parsed as
+        // raw JSON. Fall through to the decoded representation.
       }
-      // URI decoded successfully; parse the decoded string as JSON.
-      // This handles both new-format (double-encoded) and old-format URLs,
-      // since decodeURIComponent is a no-op on plain JSON strings.
+
       try {
-        return finalize(JSON.parse(decoded));
+        return finalize(JSON.parse(decodeURIComponent(value)));
       } catch {
         return null;
       }