Closes #10

changelog.md

@@ -6,6 +6,24 @@ existing Git tag; subsequent changes are listed as unreleased.
 
 ## Unreleased
 
+### 2026-10-07
+
+#### Added
+
+- Basic `M` / `mN` multiplexing metadata in parsed, tree, and runtime definitions.
+- Deferred selector and overlap validation with source locations: one unsigned
+  selector, representable branch values, and overlaps only between exclusive branches.
+- Selector-first decoding using exact raw values, preserving definition order and
+  unconditional signals. Explicit statuses distinguish inactive branches, missing
+  selector data, insufficient payloads, and malformed runtime metadata.
+- Registered `SG_MUL_VAL_` rejection through TypeFactory; extended and nested
+  multiplexing remain unsupported. Added parser/decoder regression coverage and
+  documented supported syntax and consumer behavior.
+
+#### Changed
+
+- Overlapping unconditional signals are now rejected during parsing.
+
 ### 2026-10-06
 
 #### Added