decode diagram hash JSON: got closing token %v, want }

Error message

decode diagram hash JSON: got closing token %v, want }

What it means

While walking nested JSON arrays during stable hashing, each object must be closed with '}'. If the decoder returns a different token where the object close is expected, this error reports the offending token. It means the JSON structure is not a well-formed object at that position.

Source

Thrown at d2target/d2target.go:304

				stable, err := stableHashURL(raw)
				if err != nil {
					return err
				}
				valueEnd := int(dec.InputOffset())
				if valueEnd < valueStart || valueEnd > len(b) {
					return fmt.Errorf("decode icon URL for stable diagram hash: invalid offsets %d:%d", valueStart, valueEnd)
				}
				out.Write(b[lastWrite:valueStart])
				out.Write(stable)
				lastWrite = valueEnd
			}
			closeToken, err := dec.Token()
			if err != nil {
				return err
			}
			if closeToken != json.Delim('}') {
				return fmt.Errorf("decode diagram hash JSON: got closing token %v, want }", closeToken)
			}
		case '[':
			for dec.More() {
				if err := walkValue(); err != nil {
					return err
				}
			}
			closeToken, err := dec.Token()
			if err != nil {
				return err
			}
			if closeToken != json.Delim(']') {
				return fmt.Errorf("decode diagram hash JSON: got closing token %v, want ]", closeToken)
			}
		default:
			return fmt.Errorf("decode diagram hash JSON: unexpected delimiter %q", delim)
		}
		return nil

View on GitHub (pinned to 0d69dca6f5)

Solutions

Validate the JSON with json.Valid before hashing
Re-serialize the diagram from the compiled d2target.Diagram rather than editing serialized JSON
Fix the generator/editor that produced mismatched brackets

Example fix

// before
b = []byte(`{"icon": ["url"]`) // missing }
// after
b = []byte(`{"icon": ["url"]}`)

Defensive patterns

Strategy: validation

Validate before calling

if !json.Valid(b) {
	return errors.New("diagram JSON is malformed")
}

Prevention

Never patch serialized JSON with string/regex edits
Validate JSON before hashing
Regenerate from the source diagram instead of editing output

When it happens

Trigger: Stable-hashing JSON with mismatched brackets — e.g. an object terminated by ']' instead of '}' — usually from corrupted, truncated, or hand-edited diagram JSON.

Common situations: Manual string surgery on diagram JSON; partial reads from cache files; regex-based JSON rewriting that broke bracket pairing.

Related errors

AI-assisted analysis of d2lang/d2@0d69dca6f5 (2026-08-31). Data as JSON: /api/errors/39112584ed505df4. Report an issue: GitHub.