diff --git a/.github/workflows/ci-go-cover.yml b/.github/workflows/ci-go-cover.yml
index 6043df48..f011bbbe 100644
--- a/.github/workflows/ci-go-cover.yml
+++ b/.github/workflows/ci-go-cover.yml
@@ -51,5 +51,5 @@ jobs:
     - name: Go Coverage
       run: |
         go version
-        go test -short -cover | grep "^.*coverage:.*of statements$" | python -c "import os,re,sys; cover_rpt = sys.stdin.read(); print(cover_rpt) if len(cover_rpt) != 0 and len(cover_rpt.splitlines()) == 1 else sys.exit(1); min_cover = float(re.findall(r'\d*\.\d+|\d+', os.environ['GITHUB_WORKFLOW'])[0]); cover = float(re.findall(r'\d*\.\d+|\d+', cover_rpt)[0]); sys.exit(1) if (cover > 100) or (cover < min_cover) else sys.exit(0)"
+        go test -short -cover | grep "^.*coverage:.*of statements$" | python -c "import os,re,sys; cover_rpt = sys.stdin.read(); print(cover_rpt) if len(cover_rpt) != 0 and len(cover_rpt.splitlines()) == 1 else sys.exit(1); min_cover = float(re.findall(r'\d*\.\d+|\d+', os.environ['GITHUB_WORKFLOW'])[0]); cover = float(re.findall(r'coverage:\s*(\d+(?:\.\d+)?)', cover_rpt)[0]); sys.exit(1) if (cover > 100) or (cover < min_cover) else sys.exit(0)"
       shell: bash
diff --git a/README.md b/README.md
index f9ae78ec..1d1e902f 100644
--- a/README.md
+++ b/README.md
@@ -683,7 +683,7 @@ because RFC 8949 treats CBOR data item with remaining bytes as malformed.
 Other useful functions: 
 - `Diagnose`, `DiagnoseFirst` produce human-readable [Extended Diagnostic Notation](https://www.rfc-editor.org/rfc/rfc8610.html#appendix-G) from CBOR data.
 - `UnmarshalFirst` decodes first CBOR data item and return any remaining bytes.
-- `Wellformed` returns true if the CBOR data item is well-formed.
+- `Wellformed` returns nil error if the CBOR data item is well-formed.
 
 Interfaces identical or comparable to Go `encoding` packages include:  
 `Marshaler`, `Unmarshaler`, `BinaryMarshaler`, and `BinaryUnmarshaler`.
diff --git a/decode.go b/decode.go
index 03fd7f8b..1d3e63d0 100644
--- a/decode.go
+++ b/decode.go
@@ -2263,7 +2263,7 @@ func (d *decoder) applyByteStringTextConversion(
 		default:
 			// If this happens, there is a bug: the decoder has pushed an invalid
 			// "expected later encoding" tag to the stack.
-			panic(fmt.Sprintf("unrecognized expected later encoding tag: %d", d.expectedLaterEncodingTags))
+			panic(fmt.Sprintf("unrecognized expected later encoding tag: %d", d.expectedLaterEncodingTags[len(d.expectedLaterEncodingTags)-1]))
 		}
 
 	case reflect.Slice:
diff --git a/doc.go b/doc.go
index c758b737..e4c1d27b 100644
--- a/doc.go
+++ b/doc.go
@@ -56,20 +56,30 @@ modes won't accidentally change at runtime after they're created.
 
 Modes are intended to be reused and are safe for concurrent use.
 
-EncMode and DecMode Interfaces
+EncMode, UserBufferEncMode, and DecMode Interfaces
 
 	// EncMode interface uses immutable options and is safe for concurrent use.
 	type EncMode interface {
-		Marshal(v interface{}) ([]byte, error)
+		Marshal(v any) ([]byte, error)
 		NewEncoder(w io.Writer) *Encoder
-		EncOptions() EncOptions  // returns copy of options
+		EncOptions() EncOptions
+	}
+
+	// UserBufferEncMode extends EncMode with MarshalToBuffer, which supports
+	// user specified buffer rather than encoding into the built-in buffer pool.
+	type UserBufferEncMode interface {
+		EncMode
+		MarshalToBuffer(v any, buf *bytes.Buffer) error
 	}
 
 	// DecMode interface uses immutable options and is safe for concurrent use.
 	type DecMode interface {
-		Unmarshal(data []byte, v interface{}) error
+		Unmarshal(data []byte, v any) error
+		UnmarshalFirst(data []byte, v any) (rest []byte, err error)
+		Valid(data []byte) error          // Deprecated: use Wellformed instead.
+		Wellformed(data []byte) error
 		NewDecoder(r io.Reader) *Decoder
-		DecOptions() DecOptions  // returns copy of options
+		DecOptions() DecOptions
 	}
 
 Using Default Encoding Mode
diff --git a/encode_test.go b/encode_test.go
index 2daa8ae1..4b12fb53 100644
--- a/encode_test.go
+++ b/encode_test.go
@@ -142,6 +142,14 @@ var marshalTestCases = []marshalTestCase{
 		wantData: mustHexDecode("3affffffff"),
 		values:   []any{int64(-4294967296)},
 	},
+	{
+		wantData: mustHexDecode("3b0000000100000000"),
+		values:   []any{int64(-4294967297)},
+	},
+	{
+		wantData: mustHexDecode("3b7fffffffffffffff"),
+		values:   []any{int64(math.MinInt64)},
+	},
 
 	// byte string
 	{