fix: encoder silent row drop, negative/non-decimal array lengths, trailing delimiter, colon re-search

packages/toon/src/decode/decoders.ts

@@ -194,9 +194,10 @@ function* decodeKeyValueSync(
   }
 
   // Regular key-value pair
-  const { key, isQuoted } = withLine(line, () => parseKeyToken(content, 0))
-  const colonIndex = content.indexOf(COLON, key.length)
-  const rest = colonIndex >= 0 ? content.slice(colonIndex + 1).trim() : ''
+  // Use `end` from parseKeyToken directly — it already points to the character
+  // after the colon separator, avoiding a fragile secondary indexOf search.
+  const { key, end, isQuoted } = withLine(line, () => parseKeyToken(content, 0))
+  const rest = content.slice(end).trim()
 
   yield isQuoted ? { type: 'key', key, wasQuoted: true } : { type: 'key', key }
 
@@ -616,9 +617,10 @@ async function* decodeKeyValueAsync(
   }
 
   // Regular key-value pair
-  const { key, isQuoted } = withLine(line, () => parseKeyToken(content, 0))
-  const colonIndex = content.indexOf(COLON, key.length)
-  const rest = colonIndex >= 0 ? content.slice(colonIndex + 1).trim() : ''
+  // Use `end` from parseKeyToken directly — it already points to the character
+  // after the colon separator, avoiding a fragile secondary indexOf search.
+  const { key, end, isQuoted } = withLine(line, () => parseKeyToken(content, 0))
+  const rest = content.slice(end).trim()
 
   yield isQuoted ? { type: 'key', key, wasQuoted: true } : { type: 'key', key }
 

packages/toon/src/decode/parser.ts

@@ -136,8 +136,14 @@ export function parseBracketSegment(
     content = content.slice(0, -1)
   }
 
+  // Reject non-decimal-integer strings: hex (0x…), floats (3.7), leading
+  // junk, etc.  parseInt is too permissive — it accepts all of these.
+  if (!/^-?\d+$/.test(content)) {
+    throw new TypeError(`Invalid array length: ${seg}`)
+  }
+
   const length = Number.parseInt(content, 10)
-  if (Number.isNaN(length)) {
+  if (Number.isNaN(length) || length < 0) {
     throw new TypeError(`Invalid array length: ${seg}`)
   }
 
@@ -191,8 +197,10 @@ export function parseDelimitedValues(input: string, delimiter: Delimiter): strin
     i++
   }
 
-  // Add last value
-  if (valueBuffer || values.length > 0) {
+  // Add last value only when there is actual content or a non-trailing
+  // delimiter was seen.  A trailing delimiter (e.g. "a,b,") must not produce
+  // a spurious empty final element.
+  if (valueBuffer.trim() || values.length === 0) {
     values.push(valueBuffer.trim())
   }
 

packages/toon/src/encode/encoders.ts

@@ -183,6 +183,11 @@ export function* encodeArrayOfArraysAsListItemsLines(
       const arrayLine = encodeInlineArrayLine(arr, options.delimiter)
       yield indentedListItem(depth + 1, arrayLine, options.indent)
     }
+    else {
+      // Non-primitive sub-arrays fall back to the mixed/expanded path so no
+      // rows are silently dropped from the declared header count.
+      yield* encodeMixedArrayAsListItemsLines(undefined, arr, depth + 1, options)
+    }
   }
 }