diff --git a/dist/index.cjs b/dist/index.cjs
--- a/dist/index.cjs
+++ b/dist/index.cjs
@@ -245,10 +245,9 @@
 ];
 const ALPHA_NUMERALS = "abcdefghijklmnopqrstuvwxyz";
 /**
-* Marker segment for ordered list lines: numeric, roman, or 1–2 letter alpha.
-* Roman is matched before alpha so "iii" is roman; invalid romans like "aa" fall through to alpha.
+* Orca patch: ordered-list markers are digits only, as in CommonMark, so "Dr." and "A." stay prose.
 */
-const ORDERED_LIST_MARKER_PATTERN = String.raw`\d+|[ivxlcdmIVXLCDM]+|${"[a-zA-Z]{1,2}"}`;
+const ORDERED_LIST_MARKER_PATTERN = String.raw`\d+`;
 /**
 * Convert a number to lowercase roman numerals.
 * @example toRoman(1) // 'i'
@@ -897,6 +896,26 @@
 	};
 }
 /**
+* Orca patch: marker columns are counted without the delimiter, so trim() left later sibling tasks indented and
+* parseIndentedBlocks cut into them. Dedent by the first task; a task one column deeper is a sibling, and other
+* text at or within the first task's column stays nested under the task above.
+*/
+function dedentOrderedItemTaskBlock(blockLines) {
+	const isTaskLine = (line) => /^\s*[-+*]\s+\[[ xX]\][^\S\r\n]/.test(line);
+	const leadingWidth = (line) => line.length - line.trimStart().length;
+	const firstIndex = blockLines.findIndex((line) => line.trim() !== "");
+	if (firstIndex === -1 || !isTaskLine(blockLines[firstIndex])) return null;
+	const firstIndent = leadingWidth(blockLines[firstIndex]);
+	return blockLines.slice(firstIndex).map((line) => {
+		if (line.trim() === "") return "";
+		const indent = leadingWidth(line);
+		const depth = indent - firstIndent;
+		if (isTaskLine(line)) return depth === 1 ? line.trimStart() : line.slice(Math.min(indent, firstIndent));
+		if (depth > 0) return depth === 1 ? ` ${line.slice(firstIndent)}` : line.slice(firstIndent);
+		return indent > 0 ? `  ${line.trimStart()}` : line;
+	}).join("\n").trimEnd();
+}
+/**
 * Recursively builds a nested structure from a flat array of list items
 * based on their indentation levels. Creates proper markdown tokens with
 * nested lists where appropriate.
@@ -920,7 +939,7 @@
 				raw: mainText,
 				tokens: lexer.inlineTokens(mainText)
 			});
-			const additionalContent = blockLines.join("\n").trim();
+			const additionalContent = dedentOrderedItemTaskBlock(blockLines) ?? blockLines.join("\n").trim();
 			if (additionalContent) {
 				const blockTokens = lexer.blockTokens(additionalContent);
 				tokens.push(...blockTokens);
diff --git a/dist/index.js b/dist/index.js
--- a/dist/index.js
+++ b/dist/index.js
@@ -233,10 +233,9 @@
 ];
 const ALPHA_NUMERALS = "abcdefghijklmnopqrstuvwxyz";
 /**
-* Marker segment for ordered list lines: numeric, roman, or 1–2 letter alpha.
-* Roman is matched before alpha so "iii" is roman; invalid romans like "aa" fall through to alpha.
+* Orca patch: ordered-list markers are digits only, as in CommonMark, so "Dr." and "A." stay prose.
 */
-const ORDERED_LIST_MARKER_PATTERN = String.raw`\d+|[ivxlcdmIVXLCDM]+|${"[a-zA-Z]{1,2}"}`;
+const ORDERED_LIST_MARKER_PATTERN = String.raw`\d+`;
 /**
 * Convert a number to lowercase roman numerals.
 * @example toRoman(1) // 'i'
@@ -885,6 +884,26 @@
 	};
 }
 /**
+* Orca patch: marker columns are counted without the delimiter, so trim() left later sibling tasks indented and
+* parseIndentedBlocks cut into them. Dedent by the first task; a task one column deeper is a sibling, and other
+* text at or within the first task's column stays nested under the task above.
+*/
+function dedentOrderedItemTaskBlock(blockLines) {
+	const isTaskLine = (line) => /^\s*[-+*]\s+\[[ xX]\][^\S\r\n]/.test(line);
+	const leadingWidth = (line) => line.length - line.trimStart().length;
+	const firstIndex = blockLines.findIndex((line) => line.trim() !== "");
+	if (firstIndex === -1 || !isTaskLine(blockLines[firstIndex])) return null;
+	const firstIndent = leadingWidth(blockLines[firstIndex]);
+	return blockLines.slice(firstIndex).map((line) => {
+		if (line.trim() === "") return "";
+		const indent = leadingWidth(line);
+		const depth = indent - firstIndent;
+		if (isTaskLine(line)) return depth === 1 ? line.trimStart() : line.slice(Math.min(indent, firstIndent));
+		if (depth > 0) return depth === 1 ? ` ${line.slice(firstIndent)}` : line.slice(firstIndent);
+		return indent > 0 ? `  ${line.trimStart()}` : line;
+	}).join("\n").trimEnd();
+}
+/**
 * Recursively builds a nested structure from a flat array of list items
 * based on their indentation levels. Creates proper markdown tokens with
 * nested lists where appropriate.
@@ -908,7 +927,7 @@
 				raw: mainText,
 				tokens: lexer.inlineTokens(mainText)
 			});
-			const additionalContent = blockLines.join("\n").trim();
+			const additionalContent = dedentOrderedItemTaskBlock(blockLines) ?? blockLines.join("\n").trim();
 			if (additionalContent) {
 				const blockTokens = lexer.blockTokens(additionalContent);
 				tokens.push(...blockTokens);
diff --git a/dist/kit/index.cjs b/dist/kit/index.cjs
--- a/dist/kit/index.cjs
+++ b/dist/kit/index.cjs
@@ -233,10 +233,9 @@
 ];
 const ALPHA_NUMERALS = "abcdefghijklmnopqrstuvwxyz";
 /**
-* Marker segment for ordered list lines: numeric, roman, or 1–2 letter alpha.
-* Roman is matched before alpha so "iii" is roman; invalid romans like "aa" fall through to alpha.
+* Orca patch: ordered-list markers are digits only, as in CommonMark, so "Dr." and "A." stay prose.
 */
-const ORDERED_LIST_MARKER_PATTERN = String.raw`\d+|[ivxlcdmIVXLCDM]+|${"[a-zA-Z]{1,2}"}`;
+const ORDERED_LIST_MARKER_PATTERN = String.raw`\d+`;
 /**
 * Convert a number to lowercase roman numerals.
 * @example toRoman(1) // 'i'
@@ -839,6 +838,26 @@
 	};
 }
 /**
+* Orca patch: marker columns are counted without the delimiter, so trim() left later sibling tasks indented and
+* parseIndentedBlocks cut into them. Dedent by the first task; a task one column deeper is a sibling, and other
+* text at or within the first task's column stays nested under the task above.
+*/
+function dedentOrderedItemTaskBlock(blockLines) {
+	const isTaskLine = (line) => /^\s*[-+*]\s+\[[ xX]\][^\S\r\n]/.test(line);
+	const leadingWidth = (line) => line.length - line.trimStart().length;
+	const firstIndex = blockLines.findIndex((line) => line.trim() !== "");
+	if (firstIndex === -1 || !isTaskLine(blockLines[firstIndex])) return null;
+	const firstIndent = leadingWidth(blockLines[firstIndex]);
+	return blockLines.slice(firstIndex).map((line) => {
+		if (line.trim() === "") return "";
+		const indent = leadingWidth(line);
+		const depth = indent - firstIndent;
+		if (isTaskLine(line)) return depth === 1 ? line.trimStart() : line.slice(Math.min(indent, firstIndent));
+		if (depth > 0) return depth === 1 ? ` ${line.slice(firstIndent)}` : line.slice(firstIndent);
+		return indent > 0 ? `  ${line.trimStart()}` : line;
+	}).join("\n").trimEnd();
+}
+/**
 * Recursively builds a nested structure from a flat array of list items
 * based on their indentation levels. Creates proper markdown tokens with
 * nested lists where appropriate.
@@ -862,7 +881,7 @@
 				raw: mainText,
 				tokens: lexer.inlineTokens(mainText)
 			});
-			const additionalContent = blockLines.join("\n").trim();
+			const additionalContent = dedentOrderedItemTaskBlock(blockLines) ?? blockLines.join("\n").trim();
 			if (additionalContent) {
 				const blockTokens = lexer.blockTokens(additionalContent);
 				tokens.push(...blockTokens);
diff --git a/dist/kit/index.js b/dist/kit/index.js
--- a/dist/kit/index.js
+++ b/dist/kit/index.js
@@ -232,10 +232,9 @@
 ];
 const ALPHA_NUMERALS = "abcdefghijklmnopqrstuvwxyz";
 /**
-* Marker segment for ordered list lines: numeric, roman, or 1–2 letter alpha.
-* Roman is matched before alpha so "iii" is roman; invalid romans like "aa" fall through to alpha.
+* Orca patch: ordered-list markers are digits only, as in CommonMark, so "Dr." and "A." stay prose.
 */
-const ORDERED_LIST_MARKER_PATTERN = String.raw`\d+|[ivxlcdmIVXLCDM]+|${"[a-zA-Z]{1,2}"}`;
+const ORDERED_LIST_MARKER_PATTERN = String.raw`\d+`;
 /**
 * Convert a number to lowercase roman numerals.
 * @example toRoman(1) // 'i'
@@ -838,6 +837,26 @@
 	};
 }
 /**
+* Orca patch: marker columns are counted without the delimiter, so trim() left later sibling tasks indented and
+* parseIndentedBlocks cut into them. Dedent by the first task; a task one column deeper is a sibling, and other
+* text at or within the first task's column stays nested under the task above.
+*/
+function dedentOrderedItemTaskBlock(blockLines) {
+	const isTaskLine = (line) => /^\s*[-+*]\s+\[[ xX]\][^\S\r\n]/.test(line);
+	const leadingWidth = (line) => line.length - line.trimStart().length;
+	const firstIndex = blockLines.findIndex((line) => line.trim() !== "");
+	if (firstIndex === -1 || !isTaskLine(blockLines[firstIndex])) return null;
+	const firstIndent = leadingWidth(blockLines[firstIndex]);
+	return blockLines.slice(firstIndex).map((line) => {
+		if (line.trim() === "") return "";
+		const indent = leadingWidth(line);
+		const depth = indent - firstIndent;
+		if (isTaskLine(line)) return depth === 1 ? line.trimStart() : line.slice(Math.min(indent, firstIndent));
+		if (depth > 0) return depth === 1 ? ` ${line.slice(firstIndent)}` : line.slice(firstIndent);
+		return indent > 0 ? `  ${line.trimStart()}` : line;
+	}).join("\n").trimEnd();
+}
+/**
 * Recursively builds a nested structure from a flat array of list items
 * based on their indentation levels. Creates proper markdown tokens with
 * nested lists where appropriate.
@@ -861,7 +880,7 @@
 				raw: mainText,
 				tokens: lexer.inlineTokens(mainText)
 			});
-			const additionalContent = blockLines.join("\n").trim();
+			const additionalContent = dedentOrderedItemTaskBlock(blockLines) ?? blockLines.join("\n").trim();
 			if (additionalContent) {
 				const blockTokens = lexer.blockTokens(additionalContent);
 				tokens.push(...blockTokens);
diff --git a/dist/ordered-list/index.cjs b/dist/ordered-list/index.cjs
--- a/dist/ordered-list/index.cjs
+++ b/dist/ordered-list/index.cjs
@@ -19,10 +19,9 @@
 ];
 const ALPHA_NUMERALS = "abcdefghijklmnopqrstuvwxyz";
 /**
-* Marker segment for ordered list lines: numeric, roman, or 1–2 letter alpha.
-* Roman is matched before alpha so "iii" is roman; invalid romans like "aa" fall through to alpha.
+* Orca patch: ordered-list markers are digits only, as in CommonMark, so "Dr." and "A." stay prose.
 */
-const ORDERED_LIST_MARKER_PATTERN = String.raw`\d+|[ivxlcdmIVXLCDM]+|${"[a-zA-Z]{1,2}"}`;
+const ORDERED_LIST_MARKER_PATTERN = String.raw`\d+`;
 /**
 * Convert a number to lowercase roman numerals.
 * @example toRoman(1) // 'i'
@@ -333,6 +332,26 @@
 	};
 }
 /**
+* Orca patch: marker columns are counted without the delimiter, so trim() left later sibling tasks indented and
+* parseIndentedBlocks cut into them. Dedent by the first task; a task one column deeper is a sibling, and other
+* text at or within the first task's column stays nested under the task above.
+*/
+function dedentOrderedItemTaskBlock(blockLines) {
+	const isTaskLine = (line) => /^\s*[-+*]\s+\[[ xX]\][^\S\r\n]/.test(line);
+	const leadingWidth = (line) => line.length - line.trimStart().length;
+	const firstIndex = blockLines.findIndex((line) => line.trim() !== "");
+	if (firstIndex === -1 || !isTaskLine(blockLines[firstIndex])) return null;
+	const firstIndent = leadingWidth(blockLines[firstIndex]);
+	return blockLines.slice(firstIndex).map((line) => {
+		if (line.trim() === "") return "";
+		const indent = leadingWidth(line);
+		const depth = indent - firstIndent;
+		if (isTaskLine(line)) return depth === 1 ? line.trimStart() : line.slice(Math.min(indent, firstIndent));
+		if (depth > 0) return depth === 1 ? ` ${line.slice(firstIndent)}` : line.slice(firstIndent);
+		return indent > 0 ? `  ${line.trimStart()}` : line;
+	}).join("\n").trimEnd();
+}
+/**
 * Recursively builds a nested structure from a flat array of list items
 * based on their indentation levels. Creates proper markdown tokens with
 * nested lists where appropriate.
@@ -356,7 +375,7 @@
 				raw: mainText,
 				tokens: lexer.inlineTokens(mainText)
 			});
-			const additionalContent = blockLines.join("\n").trim();
+			const additionalContent = dedentOrderedItemTaskBlock(blockLines) ?? blockLines.join("\n").trim();
 			if (additionalContent) {
 				const blockTokens = lexer.blockTokens(additionalContent);
 				tokens.push(...blockTokens);
diff --git a/dist/ordered-list/index.js b/dist/ordered-list/index.js
--- a/dist/ordered-list/index.js
+++ b/dist/ordered-list/index.js
@@ -18,10 +18,9 @@
 ];
 const ALPHA_NUMERALS = "abcdefghijklmnopqrstuvwxyz";
 /**
-* Marker segment for ordered list lines: numeric, roman, or 1–2 letter alpha.
-* Roman is matched before alpha so "iii" is roman; invalid romans like "aa" fall through to alpha.
+* Orca patch: ordered-list markers are digits only, as in CommonMark, so "Dr." and "A." stay prose.
 */
-const ORDERED_LIST_MARKER_PATTERN = String.raw`\d+|[ivxlcdmIVXLCDM]+|${"[a-zA-Z]{1,2}"}`;
+const ORDERED_LIST_MARKER_PATTERN = String.raw`\d+`;
 /**
 * Convert a number to lowercase roman numerals.
 * @example toRoman(1) // 'i'
@@ -332,6 +331,26 @@
 	};
 }
 /**
+* Orca patch: marker columns are counted without the delimiter, so trim() left later sibling tasks indented and
+* parseIndentedBlocks cut into them. Dedent by the first task; a task one column deeper is a sibling, and other
+* text at or within the first task's column stays nested under the task above.
+*/
+function dedentOrderedItemTaskBlock(blockLines) {
+	const isTaskLine = (line) => /^\s*[-+*]\s+\[[ xX]\][^\S\r\n]/.test(line);
+	const leadingWidth = (line) => line.length - line.trimStart().length;
+	const firstIndex = blockLines.findIndex((line) => line.trim() !== "");
+	if (firstIndex === -1 || !isTaskLine(blockLines[firstIndex])) return null;
+	const firstIndent = leadingWidth(blockLines[firstIndex]);
+	return blockLines.slice(firstIndex).map((line) => {
+		if (line.trim() === "") return "";
+		const indent = leadingWidth(line);
+		const depth = indent - firstIndent;
+		if (isTaskLine(line)) return depth === 1 ? line.trimStart() : line.slice(Math.min(indent, firstIndent));
+		if (depth > 0) return depth === 1 ? ` ${line.slice(firstIndent)}` : line.slice(firstIndent);
+		return indent > 0 ? `  ${line.trimStart()}` : line;
+	}).join("\n").trimEnd();
+}
+/**
 * Recursively builds a nested structure from a flat array of list items
 * based on their indentation levels. Creates proper markdown tokens with
 * nested lists where appropriate.
@@ -355,7 +374,7 @@
 				raw: mainText,
 				tokens: lexer.inlineTokens(mainText)
 			});
-			const additionalContent = blockLines.join("\n").trim();
+			const additionalContent = dedentOrderedItemTaskBlock(blockLines) ?? blockLines.join("\n").trim();
 			if (additionalContent) {
 				const blockTokens = lexer.blockTokens(additionalContent);
 				tokens.push(...blockTokens);