fix(hashline): accepted spaces in edit paths

Parsed hashline section headers by recognizing only a trailing #TAG as the snapshot delimiter, allowing whitespace inside valid paths.

Updated recovery parsing and grammar docs to match the runtime parser, and added regression coverage for canonical and recovered headers with spaces.

Fixes #1634

packages/hashline/src/grammar.lark

@@ -5,7 +5,7 @@ end_patch:   "*** End Patch" LF?
 file_patch: file_header hunk+
 file_header: "¶" filename "#" file_hash LF
 file_hash: /[0-9A-F]{4}/
-filename: /[^\s#]+/
+filename: /[^#\r\n]+/
 
 hunk: replace_hunk | replace_block_hunk | insert_hunk | delete_hunk | delete_block_hunk
 replace_hunk: replace_anchor LF emit_op*

packages/hashline/src/input.ts

@@ -50,14 +50,14 @@ function stripApplyPatchPathNoise(pathText: string): string {
  * Best-effort recovery for `¶`-prefixed lines the strict tokenizer
  * rejects. Strips apply_patch keyword noise (`Update File:`, `Update:`,
  * etc.) and an extra leading `***` (some models emit a hybrid `¶***foo.ts`
- * shape), then expects `PATH(#HASH)?` with no embedded whitespace.
+ * shape), then expects `PATH(#HASH)?`.
  * Returns `null` when no clean path can be salvaged.
  */
 function tryParseRecoveryHeader(line: string, cwd?: string): RawSection | null {
 	if (!line.startsWith(HL_FILE_PREFIX)) return null;
 	const body = stripApplyPatchPathNoise(line.slice(HL_FILE_PREFIX.length).trim());
 	if (body.length === 0) return null;
-	const match = new RegExp(`^(\\S+?)(?:#([0-9A-Fa-f]{${HL_FILE_HASH_LENGTH}}))?\\s*$`).exec(body);
+	const match = new RegExp(`^(.+?)(?:#([0-9A-Fa-f]{${HL_FILE_HASH_LENGTH}}))?\\s*$`).exec(body);
 	if (match === null) return null;
 	const path = normalizeHashlinePath(match[1], cwd);
 	if (path.length === 0) return null;

packages/hashline/src/tokenizer.ts

@@ -312,28 +312,22 @@ function tryParseHunkHeader(line: string): ParsedHunkHeader | null {
 function tryParseHeader(line: string): { path: string; fileHash?: string } | null {
 	if (!line.startsWith(HL_FILE_PREFIX)) return null;
 	const end = trimEndIndex(line);
-	let index = FILE_PREFIX_LENGTH;
-	if (index >= end) return null;
-	const pathStart = index;
-	while (index < end) {
-		const code = line.charCodeAt(index);
-		if (code === CHAR_HASH || code === CHAR_SPACE || code === CHAR_TAB) break;
-		index++;
-	}
-	if (index === pathStart) return null;
-	const path = line.slice(pathStart, index);
+	if (FILE_PREFIX_LENGTH >= end) return null;
+
+	let pathEnd = end;
 	let fileHash: string | undefined;
-	if (index < end && line.charCodeAt(index) === CHAR_HASH) {
-		const hashStart = index + 1;
-		const hashEnd = hashStart + HL_FILE_HASH_LENGTH;
-		if (hashEnd > end) return null;
-		for (let probe = hashStart; probe < hashEnd; probe++) {
+	const hashStart = end - HL_FILE_HASH_LENGTH - 1;
+	if (hashStart >= FILE_PREFIX_LENGTH && line.charCodeAt(hashStart) === CHAR_HASH) {
+		const tagStart = hashStart + 1;
+		for (let probe = tagStart; probe < end; probe++) {
 			if (!isHexDigitCode(line.charCodeAt(probe))) return null;
 		}
-		fileHash = line.slice(hashStart, hashEnd).toUpperCase();
-		index = hashEnd;
+		pathEnd = hashStart;
+		fileHash = line.slice(tagStart, end).toUpperCase();
 	}
-	if (skipWhitespace(line, index, end) !== end) return null;
+
+	if (pathEnd === FILE_PREFIX_LENGTH) return null;
+	const path = line.slice(FILE_PREFIX_LENGTH, pathEnd);
 	return fileHash !== undefined ? { path, fileHash } : { path };
 }
 

packages/hashline/test/leniency.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from "bun:test";
-import { applyEdits, parsePatch } from "@oh-my-pi/hashline";
+import { applyEdits, Patch, parsePatch } from "@oh-my-pi/hashline";
 
 function applyPatch(text: string, diff: string): string {
 	return applyEdits(text, parsePatch(diff).edits).text;
@@ -7,6 +7,24 @@ function applyPatch(text: string, diff: string): string {
 
 const FILE = "a\nb\nc\nd\ne";
 
+describe("hashline section headers", () => {
+	it("accepts paths with spaces in anchored section headers", () => {
+		const section = Patch.parseSingle("¶dir with spaces/file.ts#1a2b\nreplace 1..1:\n+after");
+
+		expect(section.path).toBe("dir with spaces/file.ts");
+		expect(section.fileHash).toBe("1A2B");
+		expect(section.applyTo("before").text).toBe("after");
+	});
+
+	it("recovers apply_patch-contaminated headers whose paths contain spaces", () => {
+		const section = Patch.parseSingle("¶*** Update File: dir with spaces/file.ts#1A2B\nreplace 1..1:\n+after");
+
+		expect(section.path).toBe("dir with spaces/file.ts");
+		expect(section.fileHash).toBe("1A2B");
+		expect(section.applyTo("before").text).toBe("after");
+	});
+});
+
 describe("hashline core — verb header forms", () => {
 	it("rejects a bare single-number hunk header with verb guidance", () => {
 		expect(() => parsePatch("2\n+B")).toThrow(/hunk headers need a verb/);