diff --git a/decode.go b/decode.go
index f02fc05..faac222 100644
--- a/decode.go
+++ b/decode.go
@@ -405,7 +405,14 @@ func (d *Decoder) nodeToValue(node ast.Node) (any, error) {
 			}
 			return nil, errors.ErrSyntax(fmt.Sprintf("cannot convert %q to boolean", fmt.Sprint(v)), n.Value.GetToken())
 		case token.StringTag:
-			return d.nodeToValue(n.Value)
+			v, err := d.nodeToValue(n.Value)
+			if err != nil {
+				return nil, err
+			}
+			if v == nil {
+				return "", nil
+			}
+			return fmt.Sprint(v), nil
 		case token.MappingTag:
 			return d.nodeToValue(n.Value)
 		default:
diff --git a/parser/parser.go b/parser/parser.go
index 20908f7..5173393 100644
--- a/parser/parser.go
+++ b/parser/parser.go
@@ -442,11 +442,18 @@ func (p *parser) parseMap(ctx *context) (*ast.MappingNode, error) {
 		tk = ctx.currentToken()
 	}
 	for tk.Column() == keyTk.Column() {
+		typ := tk.Type()
+		if ctx.isFlow && typ == token.SequenceEndType {
+			// [
+			// key: value
+			// ] <=
+			break
+		}
 		if !p.isMapToken(tk) {
 			return nil, errors.ErrSyntax("non-map value is specified", tk.RawToken())
 		}
 		cm := p.parseHeadComment(ctx)
-		if tk.Type() == token.MappingEndType {
+		if typ == token.MappingEndType {
 			// a: {
 			//  b: c
 			// } <=
@@ -644,6 +651,15 @@ func (p *parser) parseMapValue(ctx *context, key ast.MapKeyNode, colonTk *Token)
 	keyCol := key.GetToken().Position.Column
 	keyLine := key.GetToken().Position.Line
 
+	if tk.Column() != keyCol && tk.Line() == keyLine && (tk.GroupType() == TokenGroupMapKey || tk.GroupType() == TokenGroupMapKeyValue) {
+		// a: b:
+		//    ^
+		//
+		// a: b: c
+		//    ^
+		return nil, errors.ErrSyntax("mapping value is not allowed in this context", tk.RawToken())
+	}
+
 	if tk.Column() == keyCol && p.isMapToken(tk) {
 		// in this case,
 		// ----
@@ -673,9 +689,6 @@ func (p *parser) parseMapValue(ctx *context, key ast.MapKeyNode, colonTk *Token)
 	if tk.Column() <= keyCol && tk.GroupType() == TokenGroupAnchorName {
 		// key: <value does not defined>
 		// &anchor
-		//
-		//  key: <value does not defined>
-		// &anchor
 		return nil, errors.ErrSyntax("anchor is not allowed in this context", tk.RawToken())
 	}
 
@@ -932,17 +945,7 @@ func (p *parser) parseSequence(ctx *context) (*ast.SequenceNode, error) {
 		comment := p.parseHeadComment(ctx)
 		ctx.goNext() // skip sequence entry token
 
-		valueTk := ctx.currentToken()
-		if valueTk == nil {
-			node, err := newNullNode(ctx, ctx.createNullToken(seqTk))
-			if err != nil {
-				return nil, err
-			}
-			seqNode.Values = append(seqNode.Values, node)
-			break
-		}
-
-		value, err := p.parseToken(ctx.withIndex(uint(len(seqNode.Values))), valueTk)
+		value, err := p.parseSequenceValue(ctx.withIndex(uint(len(seqNode.Values))), seqTk)
 		if err != nil {
 			return nil, err
 		}
@@ -968,6 +971,83 @@ func (p *parser) parseSequence(ctx *context) (*ast.SequenceNode, error) {
 	return seqNode, nil
 }
 
+func (p *parser) parseSequenceValue(ctx *context, seqTk *Token) (ast.Node, error) {
+	tk := ctx.currentToken()
+	if tk == nil {
+		return newNullNode(ctx, ctx.insertNullToken(seqTk))
+	}
+
+	if ctx.isComment() {
+		tk = ctx.nextNotCommentToken()
+	}
+	seqCol := seqTk.Column()
+	seqLine := seqTk.Line()
+
+	if tk.Column() == seqCol && tk.Type() == token.SequenceEntryType {
+		// in this case,
+		// ----
+		// - <value does not defined>
+		// -
+		return newNullNode(ctx, ctx.insertNullToken(seqTk))
+	}
+
+	if tk.Line() == seqLine && tk.GroupType() == TokenGroupAnchorName &&
+		ctx.nextToken().Column() == seqCol && ctx.nextToken().Type() == token.SequenceEntryType {
+		// in this case,
+		// ----
+		// - &anchor
+		// -
+		group := &TokenGroup{
+			Type:   TokenGroupAnchor,
+			Tokens: []*Token{tk, ctx.createNullToken(tk)},
+		}
+		anchor, err := p.parseAnchor(ctx.withGroup(group), group)
+		if err != nil {
+			return nil, err
+		}
+		ctx.goNext()
+		return anchor, nil
+	}
+
+	if tk.Column() <= seqCol && tk.GroupType() == TokenGroupAnchorName {
+		// - <value does not defined>
+		// &anchor
+		return nil, errors.ErrSyntax("anchor is not allowed in this sequence context", tk.RawToken())
+	}
+
+	if tk.Column() < seqCol {
+		// in this case,
+		// ----
+		//   - <value does not defined>
+		// next
+		return newNullNode(ctx, ctx.insertNullToken(seqTk))
+	}
+
+	if tk.Line() == seqLine && tk.GroupType() == TokenGroupAnchorName &&
+		ctx.nextToken().Column() < seqCol {
+		// in this case,
+		// ----
+		//   - &anchor
+		// next
+		group := &TokenGroup{
+			Type:   TokenGroupAnchor,
+			Tokens: []*Token{tk, ctx.createNullToken(tk)},
+		}
+		anchor, err := p.parseAnchor(ctx.withGroup(group), group)
+		if err != nil {
+			return nil, err
+		}
+		ctx.goNext()
+		return anchor, nil
+	}
+
+	value, err := p.parseToken(ctx, ctx.currentToken())
+	if err != nil {
+		return nil, err
+	}
+	return value, nil
+}
+
 func (p *parser) parseDirective(ctx *context, g *TokenGroup) (*ast.DirectiveNode, error) {
 	node, err := newDirectiveNode(ctx, g.First())
 	if err != nil {
diff --git a/parser/token.go b/parser/token.go
index 2fd3127..c7bc5e8 100644
--- a/parser/token.go
+++ b/parser/token.go
@@ -630,6 +630,10 @@ func createDocumentTokens(tokens []*Token) ([]*Token, error) {
 }
 
 func isScalarType(tk *Token) bool {
+	switch tk.GroupType() {
+	case TokenGroupMapKey, TokenGroupMapKeyValue:
+		return false
+	}
 	typ := tk.Type()
 	return typ == token.AnchorType ||
 		typ == token.AliasType ||
diff --git a/scanner/context.go b/scanner/context.go
index 6d5e7eb..2529713 100644
--- a/scanner/context.go
+++ b/scanner/context.go
@@ -352,10 +352,25 @@ func (c *Context) bufferedToken(pos *token.Position) *token.Token {
 	} else {
 		tk = token.New(string(source), string(c.obuf), pos)
 	}
+	c.setTokenTypeByPrevTag(tk)
 	c.resetBuffer()
 	return tk
 }
 
+func (c *Context) setTokenTypeByPrevTag(tk *token.Token) {
+	lastTk := c.lastToken()
+	if lastTk == nil {
+		return
+	}
+	if lastTk.Type != token.TagType {
+		return
+	}
+	tag := token.ReservedTagKeyword(lastTk.Value)
+	if _, exists := token.ReservedTagKeywordMap[tag]; !exists {
+		tk.Type = token.StringType
+	}
+}
+
 func (c *Context) lastToken() *token.Token {
 	if len(c.tokens) != 0 {
 		return c.tokens[len(c.tokens)-1]
diff --git a/scanner/scanner.go b/scanner/scanner.go
index 428854a..bc2710f 100644
--- a/scanner/scanner.go
+++ b/scanner/scanner.go
@@ -515,8 +515,17 @@ func (s *Scanner) scanDoubleQuote(ctx *Context) (*token.Token, error) {
 }
 
 func (s *Scanner) validateDocumentSeparatorMarker(ctx *Context, src []rune) error {
+	if s.foundDocumentSeparatorMarker(src) {
+		return ErrInvalidToken(
+			token.Invalid("found unexpected document separator", string(ctx.obuf), s.pos()),
+		)
+	}
+	return nil
+}
+
+func (s *Scanner) foundDocumentSeparatorMarker(src []rune) bool {
 	if len(src) < 3 {
-		return nil
+		return false
 	}
 	var marker string
 	if len(src) == 3 {
@@ -526,12 +535,7 @@ func (s *Scanner) validateDocumentSeparatorMarker(ctx *Context, src []rune) erro
 			return r == ' ' || r == '\t' || r == '\n' || r == '\r'
 		})
 	}
-	if marker == "---" || marker == "..." {
-		return ErrInvalidToken(
-			token.Invalid("found unexpected document separator", string(ctx.obuf), s.pos()),
-		)
-	}
-	return nil
+	return marker == "---" || marker == "..."
 }
 
 func (s *Scanner) scanQuote(ctx *Context, ch rune) (bool, error) {
@@ -701,6 +705,14 @@ func (s *Scanner) scanDocument(ctx *Context, c rune) error {
 		ctx.addBuf(c)
 		ctx.updateDocumentNewLineState()
 		s.progressLine(ctx)
+		if ctx.next() {
+			if s.foundDocumentSeparatorMarker(ctx.src[ctx.idx:]) {
+				value := ctx.bufferedSrc()
+				ctx.addToken(token.String(string(value), string(ctx.obuf), s.pos()))
+				ctx.clear()
+				s.breakDocument(ctx)
+			}
+		}
 	} else if s.isFirstCharAtLine && c == ' ' {
 		ctx.addDocumentIndent(s.column)
 		s.progressColumn(ctx, 1)
@@ -1319,6 +1331,13 @@ func (s *Scanner) scan(ctx *Context) error {
 				return err
 			}
 		case '\t':
+			if ctx.existsBuffer() && s.lastDelimColumn == 0 {
+				// tab indent for plain text (yaml-test-suite's spec-example-7-12-plain-lines).
+				s.indentNum++
+				ctx.addOriginBuf(c)
+				s.progressColumn(ctx, 1)
+				continue
+			}
 			if err := s.scanTab(ctx, c); err != nil {
 				return err
 			}
diff --git a/yaml_test_suite_test.go b/yaml_test_suite_test.go
index 27782ba..eae8f16 100644
--- a/yaml_test_suite_test.go
+++ b/yaml_test_suite_test.go
@@ -17,9 +17,7 @@ var failureTestNames = []string{
 	"anchors-on-empty-scalars",          // no json.
 	"aliases-in-flow-objects",           // no json.
 	"aliases-in-explicit-block-mapping", // no json.
-	"aliases-in-implicit-block-mapping",
-	"bare-document-after-document-end-marker",
-	"block-mapping-with-missing-keys", // no json.
+	"block-mapping-with-missing-keys",   // no json.
 	"block-mapping-with-missing-values",
 	"block-mapping-with-multiline-scalars",
 	"block-scalar-with-more-spaces-than-first-content-line",
@@ -86,22 +84,14 @@ var failureTestNames = []string{
 	"spec-example-8-19-compact-block-mappings",         // no json.
 	"spec-example-6-19-secondary-tag-handle",
 	"spec-example-6-24-verbatim-tags",
-	"spec-example-6-28-non-specific-tags",
-	"spec-example-6-4-line-prefixes",
 	"spec-example-6-6-line-folding",
 	"spec-example-6-6-line-folding-1-3",
 	"spec-example-6-8-flow-folding",
-	"spec-example-7-12-plain-lines",
-	"spec-example-7-19-single-pair-flow-mappings",
-	"spec-example-7-20-single-pair-explicit-entry",
-	"spec-example-7-24-flow-nodes",
 	"spec-example-8-10-folded-lines-8-13-final-empty-lines",
-	"spec-example-8-15-block-sequence-entry-types",
 	"spec-example-8-17-explicit-block-mapping-entries",
 	"spec-example-8-2-block-indentation-indicator",
 	"spec-example-9-3-bare-documents",
 	"spec-example-9-4-explicit-documents",
-	"spec-example-9-5-directives-documents",
 	"spec-example-9-6-stream",
 	"spec-example-9-6-stream-1-3",
 	"syntax-character-edge-cases/00", // no json.