diff --git a/src/pds.js b/src/pds.js
index 4978ded..65fb19e 100644
--- a/src/pds.js
+++ b/src/pds.js
@@ -1,3 +1,12 @@
+// === CONSTANTS ===
+// CBOR primitive markers (RFC 8949)
+const CBOR_FALSE = 0xf4
+const CBOR_TRUE = 0xf5
+const CBOR_NULL = 0xf6
+
+// DAG-CBOR CID link tag
+const CBOR_TAG_CID = 42
+
 // === CID WRAPPER ===
 // Explicit CID type for DAG-CBOR encoding (avoids fragile heuristic detection)
 
@@ -18,11 +27,11 @@ export function cborEncode(value) {
 
   function encode(val) {
     if (val === null) {
-      parts.push(0xf6) // null
+      parts.push(CBOR_NULL)
     } else if (val === true) {
-      parts.push(0xf5) // true
+      parts.push(CBOR_TRUE)
     } else if (val === false) {
-      parts.push(0xf4) // false
+      parts.push(CBOR_FALSE)
     } else if (typeof val === 'number') {
       encodeInteger(val)
     } else if (typeof val === 'string') {
@@ -82,11 +91,11 @@ function cborEncodeDagCbor(value) {
 
   function encode(val) {
     if (val === null) {
-      parts.push(0xf6) // null
+      parts.push(CBOR_NULL)
     } else if (val === true) {
-      parts.push(0xf5) // true
+      parts.push(CBOR_TRUE)
     } else if (val === false) {
-      parts.push(0xf4) // false
+      parts.push(CBOR_FALSE)
     } else if (typeof val === 'number') {
       if (Number.isInteger(val) && val >= 0) {
         encodeHead(0, val)
@@ -99,7 +108,7 @@ function cborEncodeDagCbor(value) {
       parts.push(...bytes)
     } else if (val instanceof CID) {
       // CID - encode with CBOR tag 42 + 0x00 prefix
-      parts.push(0xd8, 42) // tag(42)
+      parts.push(0xd8, CBOR_TAG_CID)
       encodeHead(2, val.bytes.length + 1) // +1 for 0x00 prefix
       parts.push(0x00) // multibase identity prefix
       parts.push(...val.bytes)
@@ -569,12 +578,12 @@ function cborEncodeMstNode(node) {
 
   function encode(val) {
     if (val === null || val === undefined) {
-      parts.push(0xf6) // null
+      parts.push(CBOR_NULL)
     } else if (typeof val === 'number') {
       encodeHead(0, val) // unsigned int
     } else if (val instanceof CID) {
       // CID - encode with CBOR tag 42 + 0x00 prefix (DAG-CBOR CID link)
-      parts.push(0xd8, 42) // tag 42
+      parts.push(0xd8, CBOR_TAG_CID)
       encodeHead(2, val.bytes.length + 1) // +1 for 0x00 prefix
       parts.push(0x00) // multibase identity prefix
       parts.push(...val.bytes)