feat: address PR feedback for more tolerant search/replace

- Use SEARCH_PATTERN.source consistently in error messages
- Add explanatory comment about Sonnet 4 behavior
- Add edge case tests for multiple >, mixed cases, and whitespace variations
- Update regex comment to mention optional > character

Author: roomote

src/core/diff/strategies/__tests__/multi-search-replace.spec.ts

@@ -18,6 +18,46 @@ describe("MultiSearchReplaceDiffStrategy", () => {
 			expect(strategy["validateMarkerSequencing"](diff).success).toBe(true)
 		})
 
+		it("validates correct marker sequence with multiple > in SEARCH", () => {
+			const diff = "<<<<<<< SEARCH>>\n" + "some content\n" + "=======\n" + "new content\n" + ">>>>>>> REPLACE"
+			expect(strategy["validateMarkerSequencing"](diff).success).toBe(false)
+		})
+
+		it("validates mixed cases with and without extra > in the same diff", () => {
+			const diff =
+				"<<<<<<< SEARCH>\n" +
+				"content1\n" +
+				"=======\n" +
+				"new1\n" +
+				">>>>>>> REPLACE\n\n" +
+				"<<<<<<< SEARCH\n" +
+				"content2\n" +
+				"=======\n" +
+				"new2\n" +
+				">>>>>>> REPLACE"
+			expect(strategy["validateMarkerSequencing"](diff).success).toBe(true)
+		})
+
+		it("validates extra > with whitespace variations", () => {
+			const diff1 = "<<<<<<< SEARCH>  \n" + "some content\n" + "=======\n" + "new content\n" + ">>>>>>> REPLACE"
+			expect(strategy["validateMarkerSequencing"](diff1).success).toBe(true)
+
+			const diff2 = "<<<<<<< SEARCH  >\n" + "some content\n" + "=======\n" + "new content\n" + ">>>>>>> REPLACE"
+			expect(strategy["validateMarkerSequencing"](diff2).success).toBe(false)
+		})
+
+		it("validates extra > with line numbers", () => {
+			const diff =
+				"<<<<<<< SEARCH>\n" +
+				":start_line:10\n" +
+				"-------\n" +
+				"content1\n" +
+				"=======\n" +
+				"new1\n" +
+				">>>>>>> REPLACE"
+			expect(strategy["validateMarkerSequencing"](diff).success).toBe(true)
+		})
+
 		it("validates multiple correct marker sequences", () => {
 			const diff =
 				"<<<<<<< SEARCH\n" +

src/core/diff/strategies/multi-file-search-replace.ts

@@ -259,8 +259,10 @@ Each file requires its own path, start_line, and diff elements.
 
 		const state = { current: State.START, line: 0 }
 
-		const SEARCH = "<<<<<<< SEARCH"
+		// Pattern allows optional '>' after SEARCH to handle AI-generated diffs
+		// (e.g., Sonnet 4 sometimes adds an extra '>')
 		const SEARCH_PATTERN = /^<<<<<<< SEARCH>?$/
+		const SEARCH = SEARCH_PATTERN.source.replace(/[\^$]/g, "") // Remove regex anchors for display
 		const SEP = "======="
 		const REPLACE = ">>>>>>> REPLACE"
 		const SEARCH_PREFIX = "<<<<<<< "
@@ -363,15 +365,15 @@ Each file requires its own path, start_line, and diff elements.
 					break
 
 				case State.AFTER_SEARCH:
-					if (SEARCH_PATTERN.test(marker)) return reportInvalidDiffError(SEARCH, SEP)
+					if (SEARCH_PATTERN.test(marker)) return reportInvalidDiffError(SEARCH_PATTERN.source, SEP)
 					if (marker.startsWith(SEARCH_PREFIX)) return reportMergeConflictError(marker, SEARCH)
 					if (marker === REPLACE) return reportInvalidDiffError(REPLACE, SEP)
 					if (marker.startsWith(REPLACE_PREFIX)) return reportMergeConflictError(marker, SEARCH)
 					if (marker === SEP) state.current = State.AFTER_SEPARATOR
 					break
 
 				case State.AFTER_SEPARATOR:
-					if (SEARCH_PATTERN.test(marker)) return reportInvalidDiffError(SEARCH, REPLACE)
+					if (SEARCH_PATTERN.test(marker)) return reportInvalidDiffError(SEARCH_PATTERN.source, REPLACE)
 					if (marker.startsWith(SEARCH_PREFIX)) return reportMergeConflictError(marker, REPLACE)
 					if (marker === SEP)
 						return likelyBadStructure
@@ -457,7 +459,7 @@ Each file requires its own path, start_line, and diff elements.
 
 		/* Regex parts:
 		1. (?:^|\n)   Ensures the first marker starts at the beginning of the file or right after a newline.
-		2. (?<!\\)<<<<<<< SEARCH\s*\n   Matches the line "<<<<<<< SEARCH" (ignoring any trailing spaces) – the negative lookbehind makes sure it isn't escaped.
+		2. (?<!\\)<<<<<<< SEARCH>?\s*\n   Matches the line "<<<<<<< SEARCH" with optional '>' (ignoring any trailing spaces) – the negative lookbehind makes sure it isn't escaped.
 		3. ((?:\:start_line:\s*(\d+)\s*\n))?   Optionally matches a ":start_line:" line. The outer capturing group is group 1 and the inner (\d+) is group 2.
 		4. ((?:\:end_line:\s*(\d+)\s*\n))?   Optionally matches a ":end_line:" line. Group 3 is the whole match and group 4 is the digits.
 		5. ((?<!\\)-------\s*\n)?   Optionally matches the "-------" marker line (group 5).

src/core/diff/strategies/multi-search-replace.ts

@@ -198,8 +198,10 @@ Only use a single line of '=======' between search and replacement content, beca
 		}
 		const state = { current: State.START, line: 0 }
 
-		const SEARCH = "<<<<<<< SEARCH"
+		// Pattern allows optional '>' after SEARCH to handle AI-generated diffs
+		// (e.g., Sonnet 4 sometimes adds an extra '>')
 		const SEARCH_PATTERN = /^<<<<<<< SEARCH>?$/
+		const SEARCH = SEARCH_PATTERN.source.replace(/[\^$]/g, "") // Remove regex anchors for display
 		const SEP = "======="
 		const REPLACE = ">>>>>>> REPLACE"
 		const SEARCH_PREFIX = "<<<<<<<"
@@ -302,15 +304,15 @@ Only use a single line of '=======' between search and replacement content, beca
 					break
 
 				case State.AFTER_SEARCH:
-					if (SEARCH_PATTERN.test(marker)) return reportInvalidDiffError(SEARCH, SEP)
+					if (SEARCH_PATTERN.test(marker)) return reportInvalidDiffError(SEARCH_PATTERN.source, SEP)
 					if (marker.startsWith(SEARCH_PREFIX)) return reportMergeConflictError(marker, SEARCH)
 					if (marker === REPLACE) return reportInvalidDiffError(REPLACE, SEP)
 					if (marker.startsWith(REPLACE_PREFIX)) return reportMergeConflictError(marker, SEARCH)
 					if (marker === SEP) state.current = State.AFTER_SEPARATOR
 					break
 
 				case State.AFTER_SEPARATOR:
-					if (SEARCH_PATTERN.test(marker)) return reportInvalidDiffError(SEARCH, REPLACE)
+					if (SEARCH_PATTERN.test(marker)) return reportInvalidDiffError(SEARCH_PATTERN.source, REPLACE)
 					if (marker.startsWith(SEARCH_PREFIX)) return reportMergeConflictError(marker, REPLACE)
 					if (marker === SEP)
 						return likelyBadStructure