diff --git a/packages/coding-agent/src/commit/agentic/tools/split-commit.ts b/packages/coding-agent/src/commit/agentic/tools/split-commit.ts
index 43985d0c6..137dde24a 100644
--- a/packages/coding-agent/src/commit/agentic/tools/split-commit.ts
+++ b/packages/coding-agent/src/commit/agentic/tools/split-commit.ts
@@ -68,6 +68,7 @@ export function createSplitCommitTool(
 			const errors: string[] = [];
 			const warnings: string[] = [];
 			const diffText = await git.diff(cwd, { cached: true });
+			const validateHunksForDiff = git.createHunkSelectionValidator(diffText);
 
 			const commits: SplitCommitGroup[] = params.commits.map((commit, index) => {
 				const scope = commit.scope?.trim() || null;
@@ -102,7 +103,7 @@ export function createSplitCommitTool(
 				}
 				warnings.push(...summaryValidation.warnings.map(warning => `Commit ${index + 1}: ${warning}`));
 				warnings.push(...typeValidation.warnings.map(warning => `Commit ${index + 1}: ${warning}`));
-				const hunkValidation = validateHunkSelectors(index, changes, files, diffText);
+				const hunkValidation = validateHunkSelectors(index, changes, files, validateHunksForDiff);
 				warnings.push(...hunkValidation.warnings);
 				errors.push(...hunkValidation.errors);
 				errors.push(...validateDependencies(index, dependencies, params.commits.length));
@@ -186,7 +187,7 @@ function validateHunkSelectors(
 	commitIndex: number,
 	changes: SplitCommitGroup["changes"],
 	files: string[],
-	diffText: string,
+	validateHunksForDiff: (changes: SplitCommitGroup["changes"]) => git.HunkSelectionValidationError[],
 ): { errors: string[]; warnings: string[] } {
 	const errors: string[] = [];
 	const warnings: string[] = [];
@@ -217,7 +218,7 @@ function validateHunkSelectors(
 		}
 	}
 	if (errors.length === 0) {
-		for (const error of git.validateHunkSelections(diffText, changes)) {
+		for (const error of validateHunksForDiff(changes)) {
 			errors.push(`${prefix}: ${error.message}`);
 		}
 	}
diff --git a/packages/coding-agent/src/utils/git.ts b/packages/coding-agent/src/utils/git.ts
index cea9f4f86..31779e5ed 100644
--- a/packages/coding-agent/src/utils/git.ts
+++ b/packages/coding-agent/src/utils/git.ts
@@ -682,12 +682,17 @@ function selectHunks(file: FileHunks, selector: HunkSelection["hunks"]): FileHun
 	return file.hunks;
 }
 
-export function validateHunkSelections(
+export function createHunkSelectionValidator(
 	rawDiff: string,
+): (selections: readonly HunkSelection[]) => HunkSelectionValidationError[] {
+	const fileDiffMap = new Map(parseFileDiffs(rawDiff).map(entry => [entry.filename, entry]));
+	return selections => validateHunkSelectionsFromMap(fileDiffMap, selections);
+}
+
+function validateHunkSelectionsFromMap(
+	fileDiffMap: ReadonlyMap<string, FileDiff>,
 	selections: readonly HunkSelection[],
 ): HunkSelectionValidationError[] {
-	const fileDiffs = parseFileDiffs(rawDiff);
-	const fileDiffMap = new Map(fileDiffs.map(entry => [entry.filename, entry]));
 	const errors: HunkSelectionValidationError[] = [];
 
 	for (const selection of selections) {
@@ -707,6 +712,13 @@ export function validateHunkSelections(
 	return errors;
 }
 
+export function validateHunkSelections(
+	rawDiff: string,
+	selections: readonly HunkSelection[],
+): HunkSelectionValidationError[] {
+	return createHunkSelectionValidator(rawDiff)(selections);
+}
+
 function parseStatusPorcelain(text: string): GitStatusSummary {
 	let staged = 0;
 	let unstaged = 0;