Index: ext/misc/json1.c
==================================================================
--- ext/misc/json1.c
+++ ext/misc/json1.c
@@ -1818,11 +1818,11 @@
   pStr = (JsonString*)sqlite3_aggregate_context(ctx, sizeof(*pStr));
   if( pStr ){
     if( pStr->zBuf==0 ){
       jsonInit(pStr, ctx);
       jsonAppendChar(pStr, '[');
-    }else{
+    }else if( pStr->nUsed>1 ){
       jsonAppendChar(pStr, ',');
       pStr->pCtx = ctx;
     }
     jsonAppendValue(pStr, argv[0]);
   }
@@ -1868,11 +1868,13 @@
   int argc,
   sqlite3_value **argv
 ){
   int i;
   int inStr = 0;
+  int nNest = 0;
   char *z;
+  char c;
   JsonString *pStr;
   UNUSED_PARAM(argc);
   UNUSED_PARAM(argv);
   pStr = (JsonString*)sqlite3_aggregate_context(ctx, 0);
 #ifdef NEVER
@@ -1879,16 +1881,22 @@
   /* pStr is always non-NULL since jsonArrayStep() or jsonObjectStep() will
   ** always have been called to initalize it */
   if( NEVER(!pStr) ) return;
 #endif
   z = pStr->zBuf;
-  for(i=1; z[i]!=',' || inStr; i++){
-    assert( i<pStr->nUsed );
-    if( z[i]=='"' ){
+  for(i=1; (c = z[i])!=',' || inStr || nNest; i++){
+    if( i>=pStr->nUsed ){
+      pStr->nUsed = 1;
+      return;
+    }
+    if( c=='"' ){
       inStr = !inStr;
-    }else if( z[i]=='\\' ){
+    }else if( c=='\\' ){
       i++;
+    }else if( !inStr ){
+      if( c=='{' || c=='[' ) nNest++;
+      if( c=='}' || c==']' ) nNest--;
     }
   }
   pStr->nUsed -= i;      
   memmove(&z[1], &z[i+1], (size_t)pStr->nUsed-1);
 }
@@ -1914,11 +1922,11 @@
   pStr = (JsonString*)sqlite3_aggregate_context(ctx, sizeof(*pStr));
   if( pStr ){
     if( pStr->zBuf==0 ){
       jsonInit(pStr, ctx);
       jsonAppendChar(pStr, '{');
-    }else{
+    }else if( pStr->nUsed>1 ){
       jsonAppendChar(pStr, ',');
       pStr->pCtx = ctx;
     }
     z = (const char*)sqlite3_value_text(argv[0]);
     n = (u32)sqlite3_value_bytes(argv[0]);

Index: test/windowB.test
==================================================================
--- test/windowB.test
+++ test/windowB.test
@@ -81,15 +81,15 @@
 
 #-------------------------------------------------------------------------
 ifcapable json1 {
   reset_db
   do_execsql_test 3.0 {
-    CREATE TABLE testjson(id INTEGER PRIMARY KEY, j TEXT);
-    INSERT INTO testjson VALUES(1, '{"a":1}');
-    INSERT INTO testjson VALUES(2, '{"b":2}');
-    INSERT INTO testjson VALUES(3, '{"c":3}');
-    INSERT INTO testjson VALUES(4, '{"d":4}');
+    CREATE TABLE testjson(id INTEGER PRIMARY KEY, j TEXT, x TEXT);
+    INSERT INTO testjson VALUES(1, '{"a":1}', 'a');
+    INSERT INTO testjson VALUES(2, '{"b":2}', 'b');
+    INSERT INTO testjson VALUES(3, '{"c":3}', 'c');
+    INSERT INTO testjson VALUES(4, '{"d":4}', 'd');
   }
   
   do_execsql_test 3.1 {
     SELECT json_group_array(json(j)) FROM testjson;
   } {
@@ -105,11 +105,12 @@
     {[{"a":1},{"b":2},{"c":3},{"d":4}]}
   }
   
   do_execsql_test 3.3 {
     SELECT json_group_array(json(j)) OVER (
-      ORDER BY id RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW EXCLUDE TIES
+      ORDER BY id RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
+      EXCLUDE TIES
     ) FROM testjson;
   } {
     {[{"a":1}]}
     {[{"a":1},{"b":2}]}
     {[{"a":1},{"b":2},{"c":3}]}
@@ -136,39 +137,69 @@
     {[{"a":1}]}
     {[{"a":1},{"b":2}]}
     {[{"b":2},{"c":3}]}
   }
   
-  if 0 {
-  
-  do_execsql_test 3.5 {
+  do_execsql_test 3.5a {
+    UPDATE testjson SET j = replace(j,char(125),',"e":9'||char(125));
+    SELECT j FROM testjson;
+  } {
+    {{"a":1,"e":9}}
+    {{"b":2,"e":9}}
+    {{"c":3,"e":9}}
+    {{"d":4,"e":9}}
+  }
+  do_execsql_test 3.5b {
+    SELECT group_concat(x,'') OVER (
+      ORDER BY id ROWS BETWEEN 1 FOLLOWING AND 2 FOLLOWING
+    ) FROM testjson ORDER BY id;
+  } {bc cd d {}}
+  do_execsql_test 3.5c {
     SELECT json_group_array(json(j)) OVER (
       ORDER BY id ROWS BETWEEN 1 FOLLOWING AND 2 FOLLOWING
     ) FROM testjson;
   } {
-    {[]}
-    {[{"a":1}]}
-    {[{"a":1},{"b":2}]}
-    {[{"b":2},{"c":3}]}
-  }
-  
-  explain_i {
-    SELECT json_group_array(json(j)) FILTER (WHERE id!=2) OVER (
-      ORDER BY id ROWS BETWEEN 2 PRECEDING AND 1 PRECEDING
-    ) FROM testjson;
-  }
-  do_execsql_test 3.7 {
-  PRAGMA vdbe_trace = 1;
-    SELECT json_group_array(json(j)) FILTER (WHERE id!=2) OVER (
-      ORDER BY id ROWS BETWEEN 2 PRECEDING AND 1 PRECEDING
-    ) FROM testjson;
-  } {
-    {[]}
-    {[{"a":1}]}
-    {[{"a":1}]}
-    {[{"c":3}]}
-  }
-  
+    {[{"b":2,"e":9},{"c":3,"e":9}]}
+    {[{"c":3,"e":9},{"d":4,"e":9}]}
+    {[{"d":4,"e":9}]}
+    {[]}
+  }
+  do_execsql_test 3.5d {
+    SELECT json_group_object(x,json(j)) OVER (
+      ORDER BY id ROWS BETWEEN 1 FOLLOWING AND 2 FOLLOWING
+    ) FROM testjson;
+  } {
+    {{"b":{"b":2,"e":9},"c":{"c":3,"e":9}}}
+    {{"c":{"c":3,"e":9},"d":{"d":4,"e":9}}}
+    {{"d":{"d":4,"e":9}}}
+    {{}}
+  }
+  
+  do_execsql_test 3.7b {
+    SELECT group_concat(x,'') FILTER (WHERE id!=2) OVER (
+      ORDER BY id ROWS BETWEEN 2 PRECEDING AND 1 PRECEDING
+    ) FROM testjson;
+  } {{} a a c}
+
+  do_execsql_test 3.7c {
+    SELECT json_group_array(json(j)) FILTER (WHERE id!=2) OVER (
+      ORDER BY id ROWS BETWEEN 2 PRECEDING AND 1 PRECEDING
+    ) FROM testjson
+  } {
+    {[]}
+    {[{"a":1,"e":9}]}
+    {[{"a":1,"e":9}]}
+    {[{"c":3,"e":9}]}
+  }
+  do_execsql_test 3.7d {
+    SELECT json_group_object(x,json(j)) FILTER (WHERE id!=2) OVER (
+      ORDER BY id ROWS BETWEEN 2 PRECEDING AND 1 PRECEDING
+    ) FROM testjson
+  } {
+    {{}}
+    {{"a":{"a":1,"e":9}}}
+    {{"a":{"a":1,"e":9}}}
+    {{"c":{"c":3,"e":9}}}
   }
 }
 
 finish_test