diff --git a/cmd/test_test.go b/cmd/test_test.go
index 8bf47173b6..1b601b8f25 100644
--- a/cmd/test_test.go
+++ b/cmd/test_test.go
@@ -83,10 +83,10 @@ func TestFilterTraceExplainFull(t *testing.T) {
 	p.explain.Set(explainModeFull)
 	expected := `Enter data.testing.test_p = _
 | Eval data.testing.test_p = _
-| Index data.testing.test_p = _ (matched 1 rule)
+| Index data.testing.test_p (matched 1 rule)
 | Enter data.testing.test_p
 | | Eval data.testing.p with data.x as "bar"
-| | Index data.testing.p with data.x as "bar" (matched 1 rule)
+| | Index data.testing.p (matched 1 rule)
 | | Enter data.testing.p
 | | | Eval data.testing.x
 | | | Index data.testing.x (matched 1 rule)
@@ -100,12 +100,12 @@ func TestFilterTraceExplainFull(t *testing.T) {
 | | | Eval trace("test test")
 | | | Note "test test"
 | | | Eval data.testing.q.foo
-| | | Index data.testing.q.foo (matched 1 rule)
+| | | Index data.testing.q (matched 1 rule)
 | | | Enter data.testing.q
 | | | | Eval trace("got this far")
 | | | | Note "got this far"
 | | | | Eval data.testing.r[x]
-| | | | Index data.testing.r[__local0__] (matched 1 rule)
+| | | | Index data.testing.r (matched 1 rule)
 | | | | Enter data.testing.r
 | | | | | Eval trace("got this far2")
 | | | | | Note "got this far2"
diff --git a/tester/reporter_test.go b/tester/reporter_test.go
index 565c211a28..b45508c98e 100644
--- a/tester/reporter_test.go
+++ b/tester/reporter_test.go
@@ -171,42 +171,43 @@ func TestJSONReporter(t *testing.T) {
     "name": "test_baz",
     "duration": 0,
     "trace": [
-		{
-		  "Op": "Fail",
-		  "Node": {
-			"index": 0,
-			"terms": [
-			  {
-				"type": "ref",
-				"value": [
-				  {
-					"type": "var",
-					"value": "eq"
-				  }
-				]
-			  },
-			  {
-				"type": "boolean",
-				"value": true
-			  },
-			  {
-				"type": "boolean",
-				"value": false
-			  }
-			]
-		  },
-		  "Location": {
-			"row": 1,
-			"col": 1,
-			"file": ""
-		  },
-		  "QueryID": 0,
-		  "ParentID": 0,
-		  "Locals": null,
-          "LocalMetadata": null,
-		  "Message": ""
-		}
-	  ]
+      {
+        "Op": "Fail",
+        "Node": {
+          "index": 0,
+          "terms": [
+            {
+              "type": "ref",
+              "value": [
+                {
+                  "type": "var",
+                  "value": "eq"
+                }
+              ]
+            },
+            {
+              "type": "boolean",
+              "value": true
+            },
+            {
+              "type": "boolean",
+              "value": false
+            }
+          ]
+        },
+        "Location": {
+          "file": "",
+          "row": 1,
+          "col": 1
+        },
+        "QueryID": 0,
+        "ParentID": 0,
+        "Locals": null,
+        "LocalMetadata": null,
+        "Message": "",
+        "Ref": null
+      }
+    ]
   },
   {
     "location": null,
@@ -215,42 +216,43 @@ func TestJSONReporter(t *testing.T) {
     "error": {},
     "duration": 0,
     "trace": [
-		{
-		  "Op": "Fail",
-		  "Node": {
-			"index": 0,
-			"terms": [
-			  {
-				"type": "ref",
-				"value": [
-				  {
-					"type": "var",
-					"value": "eq"
-				  }
-				]
-			  },
-			  {
-				"type": "boolean",
-				"value": true
-			  },
-			  {
-				"type": "boolean",
-				"value": false
-			  }
-			]
-		  },
-		  "Location": {
-			"row": 1,
-			"col": 1,
-			"file": ""
-		  },
-		  "QueryID": 0,
-		  "ParentID": 0,
-		  "Locals": null,
-		  "LocalMetadata": null,
-		  "Message": ""
-		}
-	  ]
+      {
+        "Op": "Fail",
+        "Node": {
+          "index": 0,
+          "terms": [
+            {
+              "type": "ref",
+              "value": [
+                {
+                  "type": "var",
+                  "value": "eq"
+                }
+              ]
+            },
+            {
+              "type": "boolean",
+              "value": true
+            },
+            {
+              "type": "boolean",
+              "value": false
+            }
+          ]
+        },
+        "Location": {
+          "file": "",
+          "row": 1,
+          "col": 1
+        },
+        "QueryID": 0,
+        "ParentID": 0,
+        "Locals": null,
+        "LocalMetadata": null,
+        "Message": "",
+        "Ref": null
+      }
+    ]
   },
   {
     "location": null,
@@ -259,42 +261,44 @@ func TestJSONReporter(t *testing.T) {
     "fail": true,
     "duration": 0,
     "trace": [
-		{
-		  "Op": "Fail",
-		  "Node": {
-			"index": 0,
-			"terms": [
-			  {
-				"type": "ref",
-				"value": [
-				  {
-					"type": "var",
-					"value": "eq"
-				  }
-				]
-			  },
-			  {
-				"type": "boolean",
-				"value": true
-			  },
-			  {
-				"type": "boolean",
-				"value": false
-			  }
-			]
-		  },
-		  "Location": {
-			"row": 1,
-			"col": 1,
-			"file": ""
-		  },
-		  "QueryID": 0,
-		  "ParentID": 0,
-		  "Locals": null,
-		  "LocalMetadata": null,
-		  "Message": ""
-		}
-	  ]  }
+      {
+        "Op": "Fail",
+        "Node": {
+          "index": 0,
+          "terms": [
+            {
+              "type": "ref",
+              "value": [
+                {
+                  "type": "var",
+                  "value": "eq"
+                }
+              ]
+            },
+            {
+              "type": "boolean",
+              "value": true
+            },
+            {
+              "type": "boolean",
+              "value": false
+            }
+          ]
+        },
+        "Location": {
+          "file": "",
+          "row": 1,
+          "col": 1
+        },
+        "QueryID": 0,
+        "ParentID": 0,
+        "Locals": null,
+        "LocalMetadata": null,
+        "Message": "",
+        "Ref": null
+      }
+    ]
+  }
 ]
 `))
 
diff --git a/topdown/eval.go b/topdown/eval.go
index 024011093d..50f2d30196 100644
--- a/topdown/eval.go
+++ b/topdown/eval.go
@@ -151,38 +151,38 @@ func (e *eval) unknown(x interface{}, b *bindings) bool {
 }
 
 func (e *eval) traceEnter(x ast.Node) {
-	e.traceEvent(EnterOp, x, "")
+	e.traceEvent(EnterOp, x, "", nil)
 }
 
 func (e *eval) traceExit(x ast.Node) {
-	e.traceEvent(ExitOp, x, "")
+	e.traceEvent(ExitOp, x, "", nil)
 }
 
 func (e *eval) traceEval(x ast.Node) {
-	e.traceEvent(EvalOp, x, "")
+	e.traceEvent(EvalOp, x, "", nil)
 }
 
 func (e *eval) traceFail(x ast.Node) {
-	e.traceEvent(FailOp, x, "")
+	e.traceEvent(FailOp, x, "", nil)
 }
 
 func (e *eval) traceRedo(x ast.Node) {
-	e.traceEvent(RedoOp, x, "")
+	e.traceEvent(RedoOp, x, "", nil)
 }
 
 func (e *eval) traceSave(x ast.Node) {
-	e.traceEvent(SaveOp, x, "")
+	e.traceEvent(SaveOp, x, "", nil)
 }
 
-func (e *eval) traceIndex(x ast.Node, msg string) {
-	e.traceEvent(IndexOp, x, msg)
+func (e *eval) traceIndex(x ast.Node, msg string, target *ast.Ref) {
+	e.traceEvent(IndexOp, x, msg, target)
 }
 
-func (e *eval) traceExternalResolve(x ast.Node) {
-	e.traceEvent(ExternalResolveOp, x, "")
+func (e *eval) traceWasm(x ast.Node, target *ast.Ref) {
+	e.traceEvent(WasmOp, x, "", target)
 }
 
-func (e *eval) traceEvent(op Op, x ast.Node, msg string) {
+func (e *eval) traceEvent(op Op, x ast.Node, msg string, target *ast.Ref) {
 
 	if !e.traceEnabled {
 		return
@@ -200,6 +200,7 @@ func (e *eval) traceEvent(op Op, x ast.Node, msg string) {
 		Node:     x,
 		Location: x.Loc(),
 		Message:  msg,
+		Ref:      target,
 	}
 
 	// Skip plugging the local variables, unless any of the tracers
@@ -1253,7 +1254,7 @@ func (e *eval) getRules(ref ast.Ref) (*ast.IndexResult, error) {
 		b.WriteString(" rules)")
 		msg = b.String()
 	}
-	e.traceIndex(e.query[e.index], msg)
+	e.traceIndex(e.query[e.index], msg, &ref)
 	return result, err
 }
 
@@ -1330,13 +1331,11 @@ func (e *eval) resolveReadFromStorage(ref ast.Ref, a ast.Value) (ast.Value, erro
 		return a, nil
 	}
 
-	v, err := e.external.Resolve(e.ctx, ref, e.input)
+	v, err := e.external.Resolve(e, ref)
 
 	if err != nil {
 		return nil, err
-	} else if v != nil {
-		e.traceExternalResolve(e.query[e.index])
-	} else {
+	} else if v == nil {
 
 		path, err := storage.NewPathForRef(ref)
 		if err != nil {
diff --git a/topdown/resolver.go b/topdown/resolver.go
index 0671a56f57..47af4cfd63 100644
--- a/topdown/resolver.go
+++ b/topdown/resolver.go
@@ -5,8 +5,6 @@
 package topdown
 
 import (
-	"context"
-
 	"github.com/open-policy-agent/opa/ast"
 	"github.com/open-policy-agent/opa/resolver"
 )
@@ -33,10 +31,10 @@ func (t *resolverTrie) Put(ref ast.Ref, r resolver.Resolver) {
 	node.r = r
 }
 
-func (t *resolverTrie) Resolve(ctx context.Context, ref ast.Ref, input *ast.Term) (ast.Value, error) {
+func (t *resolverTrie) Resolve(e *eval, ref ast.Ref) (ast.Value, error) {
 	in := resolver.Input{
 		Ref:   ref,
-		Input: input,
+		Input: e.input,
 	}
 	node := t
 	for i, t := range ref {
@@ -46,7 +44,8 @@ func (t *resolverTrie) Resolve(ctx context.Context, ref ast.Ref, input *ast.Term
 		}
 		node = child
 		if node.r != nil {
-			result, err := node.r.Eval(ctx, in)
+			e.traceWasm(e.query[e.index], &in.Ref)
+			result, err := node.r.Eval(e.ctx, in)
 			if err != nil {
 				return nil, err
 			}
@@ -56,12 +55,13 @@ func (t *resolverTrie) Resolve(ctx context.Context, ref ast.Ref, input *ast.Term
 			return result.Value.Find(ref[i+1:])
 		}
 	}
-	return node.mktree(ctx, in)
+	return node.mktree(e, in)
 }
 
-func (t *resolverTrie) mktree(ctx context.Context, in resolver.Input) (ast.Value, error) {
+func (t *resolverTrie) mktree(e *eval, in resolver.Input) (ast.Value, error) {
 	if t.r != nil {
-		result, err := t.r.Eval(ctx, in)
+		e.traceWasm(e.query[e.index], &in.Ref)
+		result, err := t.r.Eval(e.ctx, in)
 		if err != nil {
 			return nil, err
 		}
@@ -72,7 +72,7 @@ func (t *resolverTrie) mktree(ctx context.Context, in resolver.Input) (ast.Value
 	}
 	obj := ast.NewObject()
 	for k, child := range t.children {
-		v, err := child.mktree(ctx, resolver.Input{Ref: append(in.Ref, ast.NewTerm(k)), Input: in.Input})
+		v, err := child.mktree(e, resolver.Input{Ref: append(in.Ref, ast.NewTerm(k)), Input: in.Input})
 		if err != nil {
 			return nil, err
 		}
diff --git a/topdown/trace.go b/topdown/trace.go
index 906ba92143..2d4d5b76ee 100644
--- a/topdown/trace.go
+++ b/topdown/trace.go
@@ -51,9 +51,9 @@ const (
 	// matches.
 	IndexOp Op = "Index"
 
-	// ExternalResolveOp is emitted when resolving a ref using an external
+	// WasmOp is emitted when resolving a ref using an external
 	// Resolver.
-	ExternalResolveOp Op = "ExternalResolve"
+	WasmOp Op = "Wasm"
 )
 
 // VarMetadata provides some user facing information about
@@ -73,6 +73,7 @@ type Event struct {
 	Locals        *ast.ValueMap           // Contains local variable bindings from the query context. Nil if variables were not included in the trace event.
 	LocalMetadata map[ast.Var]VarMetadata // Contains metadata for the local variable bindings. Nil if variables were not included in the trace event.
 	Message       string                  // Contains message for Note events.
+	Ref           *ast.Ref                // Identifies the subject ref for the event. Only applies to Index and Wasm operations.
 }
 
 // HasRule returns true if the Event contains an ast.Rule.
@@ -242,16 +243,26 @@ func formatEvent(event *Event, depth int) string {
 	padding := formatEventPadding(event, depth)
 	if event.Op == NoteOp {
 		return fmt.Sprintf("%v%v %q", padding, event.Op, event.Message)
-	} else if event.Message != "" {
-		return fmt.Sprintf("%v%v %v %v", padding, event.Op, event.Node, event.Message)
-	} else {
-		switch node := event.Node.(type) {
-		case *ast.Rule:
-			return fmt.Sprintf("%v%v %v", padding, event.Op, node.Path())
-		default:
-			return fmt.Sprintf("%v%v %v", padding, event.Op, rewrite(event).Node)
-		}
 	}
+
+	var details interface{}
+	if node, ok := event.Node.(*ast.Rule); ok {
+		details = node.Path()
+	} else if event.Ref != nil {
+		details = event.Ref
+	} else {
+		details = rewrite(event).Node
+	}
+
+	template := "%v%v %v"
+	opts := []interface{}{padding, event.Op, details}
+
+	if event.Message != "" {
+		template += " %v"
+		opts = append(opts, event.Message)
+	}
+
+	return fmt.Sprintf(template, opts...)
 }
 
 func formatEventPadding(event *Event, depth int) string {
diff --git a/topdown/trace_test.go b/topdown/trace_test.go
index 651f040099..8a803b7baa 100644
--- a/topdown/trace_test.go
+++ b/topdown/trace_test.go
@@ -80,10 +80,10 @@ func TestPrettyTrace(t *testing.T) {
 
 	expected := `Enter data.test.p = _
 | Eval data.test.p = _
-| Index data.test.p = _ (matched 1 rule)
+| Index data.test.p (matched 1 rule)
 | Enter data.test.p
 | | Eval data.test.q[x]
-| | Index data.test.q[x] (matched 1 rule)
+| | Index data.test.q (matched 1 rule)
 | | Enter data.test.q
 | | | Eval x = data.a[_]
 | | | Exit data.test.q
@@ -173,10 +173,10 @@ func TestPrettyTraceWithLocation(t *testing.T) {
 
 	expected := `query:1     Enter data.test.p = _
 query:1     | Eval data.test.p = _
-query:1     | Index data.test.p = _ (matched 1 rule)
+query:1     | Index data.test.p (matched 1 rule)
 query:3     | Enter data.test.p
 query:3     | | Eval data.test.q[x]
-query:3     | | Index data.test.q[x] (matched 1 rule)
+query:3     | | Index data.test.q (matched 1 rule)
 query:4     | | Enter data.test.q
 query:4     | | | Eval x = data.a[_]
 query:4     | | | Exit data.test.q
@@ -275,10 +275,10 @@ func TestPrettyTraceWithLocationTruncatedPaths(t *testing.T) {
 
 	expected := `query:1                                                              Enter data.test.p = _
 query:1                                                              | Eval data.test.p = _
-query:1                                                              | Index data.test.p = _ (matched 1 rule)
+query:1                                                              | Index data.test.p (matched 1 rule)
 authz_bundle/...ternal/authz/policies/abac/v1/beta/policy.rego:6     | Enter data.test.p
 authz_bundle/...ternal/authz/policies/abac/v1/beta/policy.rego:6     | | Eval data.utils.q[x]
-authz_bundle/...ternal/authz/policies/abac/v1/beta/policy.rego:6     | | Index data.utils.q[x] (matched 1 rule)
+authz_bundle/...ternal/authz/policies/abac/v1/beta/policy.rego:6     | | Index data.utils.q (matched 1 rule)
 authz_bundle/...ternal/authz/policies/utils/utils.rego:4             | | Enter data.utils.q
 authz_bundle/...ternal/authz/policies/utils/utils.rego:4             | | | Eval x = data.a[_]
 authz_bundle/...ternal/authz/policies/utils/utils.rego:4             | | | Exit data.utils.q
@@ -426,7 +426,7 @@ query:1                                                              | Eval data
 query:1                                                              | Index data.example_rbac.allow (matched 1 rule)
 authz_bundle/...ternal/authz/policies/rbac/v1/beta/policy.rego:6     | Enter data.example_rbac.allow
 authz_bundle/...ternal/authz/policies/rbac/v1/beta/policy.rego:7     | | Eval data.utils.user_has_role[role_name]
-authz_bundle/...ternal/authz/policies/rbac/v1/beta/policy.rego:7     | | Index data.utils.user_has_role[role_name] (matched 1 rule)
+authz_bundle/...ternal/authz/policies/rbac/v1/beta/policy.rego:7     | | Index data.utils.user_has_role (matched 1 rule)
 authz_bundle/...ternal/authz/policies/utils/user.rego:4              | | Enter data.utils.user_has_role
 authz_bundle/...ternal/authz/policies/utils/user.rego:5              | | | Eval role_binding = data.bindings[_]
 authz_bundle/...ternal/authz/policies/utils/user.rego:6              | | | Eval role_binding.role = role_name
@@ -434,7 +434,7 @@ authz_bundle/...ternal/authz/policies/utils/user.rego:7              | | | Eval
 authz_bundle/...ternal/authz/policies/utils/user.rego:7              | | | Save "inspector-alice" = input.subject.user
 authz_bundle/...ternal/authz/policies/utils/user.rego:4              | | | Exit data.utils.user_has_role
 authz_bundle/...ternal/authz/policies/rbac/v1/beta/policy.rego:9     | | Eval data.utils.role_has_permission[role_name]
-authz_bundle/...ternal/authz/policies/rbac/v1/beta/policy.rego:9     | | Index data.utils.role_has_permission[role_name] (matched 1 rule)
+authz_bundle/...ternal/authz/policies/rbac/v1/beta/policy.rego:9     | | Index data.utils.role_has_permission (matched 1 rule)
 authz_bundle/...ternal/authz/policies/utils/user.rego:10             | | Enter data.utils.role_has_permission
 authz_bundle/...ternal/authz/policies/utils/user.rego:11             | | | Eval role = data.roles[_]
 authz_bundle/...ternal/authz/policies/utils/user.rego:12             | | | Eval role.name = role_name
@@ -464,7 +464,7 @@ authz_bundle/...ternal/authz/policies/utils/user.rego:7              | | | Eval
 authz_bundle/...ternal/authz/policies/utils/user.rego:7              | | | Save "maker-bob" = input.subject.user
 authz_bundle/...ternal/authz/policies/utils/user.rego:4              | | | Exit data.utils.user_has_role
 authz_bundle/...ternal/authz/policies/rbac/v1/beta/policy.rego:9     | | Eval data.utils.role_has_permission[role_name]
-authz_bundle/...ternal/authz/policies/rbac/v1/beta/policy.rego:9     | | Index data.utils.role_has_permission[role_name] (matched 1 rule)
+authz_bundle/...ternal/authz/policies/rbac/v1/beta/policy.rego:9     | | Index data.utils.role_has_permission (matched 1 rule)
 authz_bundle/...ternal/authz/policies/utils/user.rego:10             | | Enter data.utils.role_has_permission
 authz_bundle/...ternal/authz/policies/utils/user.rego:11             | | | Eval role = data.roles[_]
 authz_bundle/...ternal/authz/policies/utils/user.rego:12             | | | Eval role.name = role_name
@@ -556,10 +556,10 @@ func TestTraceNote(t *testing.T) {
 
 	expected := `Enter data.test.p = _
 | Eval data.test.p = _
-| Index data.test.p = _ (matched 1 rule)
+| Index data.test.p (matched 1 rule)
 | Enter data.test.p
 | | Eval data.test.q[x]
-| | Index data.test.q[x] (matched 1 rule)
+| | Index data.test.q (matched 1 rule)
 | | Enter data.test.q
 | | | Eval x = data.a[_]
 | | | Exit data.test.q
@@ -669,10 +669,10 @@ func TestTraceNoteWithLocation(t *testing.T) {
 
 	expected := `query:1     Enter data.test.p = _
 query:1     | Eval data.test.p = _
-query:1     | Index data.test.p = _ (matched 1 rule)
+query:1     | Index data.test.p (matched 1 rule)
 query:3     | Enter data.test.p
 query:3     | | Eval data.test.q[x]
-query:3     | | Index data.test.q[x] (matched 1 rule)
+query:3     | | Index data.test.q (matched 1 rule)
 query:4     | | Enter data.test.q
 query:4     | | | Eval x = data.a[_]
 query:4     | | | Exit data.test.q