fix(coding-agent/eval): hardened eval parser against stray non-marker lines

- Updated parseEvalInput to verify begin-cell markers before dereferencing regex matches.
- Skipped stray non-marker lines between and after cells, preserving valid cells when model output is noisy.
- Added eval parse regression tests for stray content and trailing chatter, and kept abort-line handling explicit.

packages/agent/src/harmony-leak.ts

@@ -397,7 +397,7 @@ function truncateAtLineAndAppendSentinel(
 }
 
 function sha8(text: string): string {
-	return new Bun.CryptoHasher("sha256").update(text).digest("hex").slice(0, 8);
+	return Bun.sha(text, "hex").slice(0, 8);
 }
 
 const PREVIEW_KEEP_RE = new RegExp(`[${SCRIPT_CLASS}\\s】【”“…」「、。]`, "u");

packages/coding-agent/src/eval/parse.ts

@@ -148,7 +148,19 @@ export function parseEvalInput(input: string): ParsedEvalInput {
 	}
 
 	while (i < lines.length) {
-		const beginMatch = BEGIN_RE.exec(lines[i])!;
+		const beginMatch = BEGIN_RE.exec(lines[i]);
+		if (!beginMatch) {
+			// Stray content between/after cells (blank lines were already
+			// consumed). `*** Abort` here terminates parsing; anything else
+			// — typically a harmony-leak fragment or model garbage — is
+			// skipped rather than crashing the parser.
+			if (ABORT_RE.test(lines[i])) {
+				aborted = true;
+				break;
+			}
+			i++;
+			continue;
+		}
 		const langToken = beginMatch[1];
 		const explicitLanguage = resolveLang(langToken);
 		i++;

packages/coding-agent/test/eval/parse.test.ts

@@ -270,4 +270,35 @@ print(1)
 			expect(result.aborted).toBeUndefined();
 		});
 	});
+
+	it("does not crash on stray non-marker lines between cells", () => {
+		// Regression: prior to fix, the outer parse loop unconditionally ran
+		// `BEGIN_RE.exec(lines[i])!` on whatever followed a closed cell, so a
+		// stray line — common in harmony-leak fragments — threw
+		// "null is not an object (evaluating 'BEGIN_RE.exec(lines[i])[1]')".
+		const result = parseEvalInput(`*** Begin PY
+print("a")
+*** End PY
+stray junk that is not a marker
+*** Begin PY
+print("b")
+*** End PY
+`);
+		expect(result.aborted).toBeUndefined();
+		expect(result.cells).toHaveLength(2);
+		expect(result.cells[0].code).toBe('print("a")');
+		expect(result.cells[1].code).toBe('print("b")');
+	});
+
+	it("does not crash on trailing stray content after the final cell", () => {
+		const result = parseEvalInput(`*** Begin PY
+print(1)
+*** End PY
+leftover model chatter
+more junk
+`);
+		expect(result.aborted).toBeUndefined();
+		expect(result.cells).toHaveLength(1);
+		expect(result.cells[0].code).toBe("print(1)");
+	});
 });