diff --git a/zcl/diagnostic_text.go b/zcl/diagnostic_text.go
index 1bdd39d..7a455b7 100644
--- a/zcl/diagnostic_text.go
+++ b/zcl/diagnostic_text.go
@@ -6,16 +6,15 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"strings"
 
 	wordwrap "github.com/mitchellh/go-wordwrap"
 )
 
 type diagnosticTextWriter struct {
-	sources map[string][]byte
-	wr      io.Writer
-	width   uint
-	color   bool
+	files map[string]*File
+	wr    io.Writer
+	width uint
+	color bool
 }
 
 // NewDiagnosticTextWriter creates a DiagnosticWriter that writes diagnostics
@@ -30,12 +29,12 @@ type diagnosticTextWriter struct {
 // If color is set to true, the output will include VT100 escape sequences to
 // color-code the severity indicators. It is suggested to turn this off if
 // the target writer is not a terminal.
-func NewDiagnosticTextWriter(wr io.Writer, sources map[string][]byte, width uint, color bool) DiagnosticWriter {
+func NewDiagnosticTextWriter(wr io.Writer, files map[string]*File, width uint, color bool) DiagnosticWriter {
 	return &diagnosticTextWriter{
-		sources: sources,
-		wr:      wr,
-		width:   width,
-		color:   color,
+		files: files,
+		wr:    wr,
+		width: width,
+		color: color,
 	}
 }
 
@@ -70,14 +69,14 @@ func (w *diagnosticTextWriter) WriteDiagnostic(diag *Diagnostic) error {
 
 	if diag.Subject != nil {
 
-		src := w.sources[diag.Subject.Filename]
-		if src == nil {
+		file := w.files[diag.Subject.Filename]
+		if file == nil || file.Bytes == nil {
 			fmt.Fprintf(w.wr, "  on %s line %d:\n  (source code not available)\n\n", diag.Subject.Filename, diag.Subject.Start.Line)
 		} else {
+			src := file.Bytes
 			r := bytes.NewReader(src)
 			sc := bufio.NewScanner(r)
 			sc.Split(bufio.ScanLines)
-			contextLine := ""
 
 			var startLine, endLine int
 			if diag.Context != nil {
@@ -88,17 +87,18 @@ func (w *diagnosticTextWriter) WriteDiagnostic(diag *Diagnostic) error {
 				endLine = diag.Subject.End.Line
 			}
 
+			var contextLine string
+			if diag.Subject != nil {
+				contextLine = contextString(file, diag.Subject.Start.Byte)
+				if contextLine != "" {
+					contextLine = ", in " + contextLine
+				}
+			}
+
 			li := 1
 			var ls string
 			for sc.Scan() {
 				ls = sc.Text()
-				if len(ls) > 0 && strings.Contains(ls, "{") && ls[0] != ' ' && ls[0] != '\t' && ls[0] != '#' && ls[0] != '/' && ls[0] != '{' {
-					// Keep track of the latest non-space-prefixed line we've
-					// seen, to use as context. This is a pretty sloppy way
-					// to do this, but it works well enough for most normal
-					// files. (In particular though, it doesn't work for JSON sources.)
-					contextLine = fmt.Sprintf(", in %s", strings.Replace(ls, " {", "", 1))
-				}
 
 				if li == startLine {
 					break
@@ -150,3 +150,14 @@ func (w *diagnosticTextWriter) WriteDiagnostics(diags Diagnostics) error {
 	}
 	return nil
 }
+
+func contextString(file *File, offset int) string {
+	type contextStringer interface {
+		ContextString(offset int) string
+	}
+
+	if cser, ok := file.Nav.(contextStringer); ok {
+		return cser.ContextString(offset)
+	}
+	return ""
+}
diff --git a/zcl/diagnostic_text_test.go b/zcl/diagnostic_text_test.go
index 6930bae..9d51731 100644
--- a/zcl/diagnostic_text_test.go
+++ b/zcl/diagnostic_text_test.go
@@ -31,7 +31,7 @@ func TestDiagnosticTextWriter(t *testing.T) {
 			},
 			`Error: Splines not reticulated
 
-  on  line 1:
+  on  line 1, in hardcoded-context:
    1: foo = 1
 
 All splines must be pre-reticulated.
@@ -56,7 +56,7 @@ All splines must be pre-reticulated.
 			},
 			`Error: Unsupported attribute
 
-  on  line 3:
+  on  line 3, in hardcoded-context:
    3: baz = 3
 
 "baz" is not a supported top-level
@@ -94,7 +94,7 @@ attribute. Did you mean "bam"?
 			},
 			`Error: Unsupported attribute
 
-  on  line 5, in block "party":
+  on  line 5, in hardcoded-context:
    4: block "party" {
    5:   pizza = "cheese"
    6: }
@@ -106,14 +106,17 @@ Did you mean "pizzetta"?
 		},
 	}
 
-	sources := map[string][]byte{
-		"": []byte(testDiagnosticTextWriterSource),
+	files := map[string]*File{
+		"": &File{
+			Bytes: []byte(testDiagnosticTextWriterSource),
+			Nav:   &diagnosticTestNav{},
+		},
 	}
 
 	for i, test := range tests {
 		t.Run(fmt.Sprintf("%02d", i), func(t *testing.T) {
 			bwr := &bytes.Buffer{}
-			dwr := NewDiagnosticTextWriter(bwr, sources, 40, false)
+			dwr := NewDiagnosticTextWriter(bwr, files, 40, false)
 			err := dwr.WriteDiagnostic(test.Input)
 			if err != nil {
 				t.Fatalf("unexpected error: %s", err)
@@ -133,3 +136,10 @@ block "party" {
   pizza = "cheese"
 }
 `
+
+type diagnosticTestNav struct {
+}
+
+func (tn *diagnosticTestNav) ContextString(offset int) string {
+	return "hardcoded-context"
+}
diff --git a/zcl/structure.go b/zcl/structure.go
index 1df01b0..d567052 100644
--- a/zcl/structure.go
+++ b/zcl/structure.go
@@ -8,6 +8,11 @@ import (
 type File struct {
 	Body  Body
 	Bytes []byte
+
+	// Nav is used to integrate with the "zcled" editor integration package,
+	// and with diagnostic information formatters. It is not for direct use
+	// by a calling application.
+	Nav interface{}
 }
 
 // Block represents a nested block within a Body.
diff --git a/zcled/doc.go b/zcled/doc.go
new file mode 100644
index 0000000..9e77fd1
--- /dev/null
+++ b/zcled/doc.go
@@ -0,0 +1,4 @@
+// Package zcled provides functionality intended to help an application
+// that embeds zcl to deliver relevant information to a text editor or IDE
+// for navigating around and analyzing configuration files.
+package zcled
diff --git a/zcled/navigation.go b/zcled/navigation.go
new file mode 100644
index 0000000..7190494
--- /dev/null
+++ b/zcled/navigation.go
@@ -0,0 +1,20 @@
+package zcled
+
+import (
+	"github.com/apparentlymart/go-zcl/zcl"
+)
+
+type contextStringer interface {
+	ContextString(offset int) string
+}
+
+// ContextString returns a string describing the context of the given byte
+// offset, if available. An empty string is returned if no such information
+// is available, or otherwise the returned string is in a form that depends
+// on the language used to write the referenced file.
+func ContextString(file *zcl.File, offset int) string {
+	if cser, ok := file.Nav.(contextStringer); ok {
+		return cser.ContextString(offset)
+	}
+	return ""
+}
diff --git a/zclparse/parser.go b/zclparse/parser.go
index 06c1234..360f921 100644
--- a/zclparse/parser.go
+++ b/zclparse/parser.go
@@ -65,3 +65,13 @@ func (p *Parser) Sources() map[string][]byte {
 	}
 	return ret
 }
+
+// Files returns a map from filenames to the File objects produced from them.
+// This is intended to be used, for example, to print diagnostics with
+// contextual information.
+//
+// The returned map and all of the objects it refers to directly or indirectly
+// must not be modified.
+func (p *Parser) Files() map[string]*zcl.File {
+	return p.files
+}