Name the failing segment in extra-segment load errors

src/session/optimized-context-store.test.ts

@@ -398,6 +398,21 @@ describe("loadRecentTurns", () => {
 
     await expect(store.load()).rejects.toThrow(TURNS_FILE);
   });
+
+  test("reactor's load() stays strict and names an unrecoverable extra segment", async () => {
+    const dir = tempDir();
+    const store = await createOptimizedContextStore(dir);
+    const segmentName = segmentFileName(TURNS_FILE, 1);
+
+    fs.writeFileSync(path.join(dir, TURNS_FILE), jsonl([turn("a")]));
+    // Mid-file garbage that is neither null padding nor a torn tail — unrecoverable.
+    fs.writeFileSync(
+      path.join(dir, segmentName),
+      jsonl([turn("b")]) + "THIS IS NOT JSON\n" + jsonl([turn("c")]),
+    );
+
+    await expect(store.load()).rejects.toThrow(segmentName);
+  });
 });
 
 describe("createOptimizedContextStore checkpoint", () => {

src/session/optimized-context-store.ts

@@ -387,7 +387,11 @@ export async function createOptimizedContextStore(dir: string): Promise<ContextS
     if (extraTexts.length === 0) return baseTurns;
 
     const parsedExtras = extraTexts.map((text, index) =>
-      parseSegmentTurns(text, index === extraTexts.length - 1),
+      parseSegmentTurns(
+        text,
+        index === extraTexts.length - 1,
+        segmentFileName(TURNS_FILE, index + 1),
+      ),
     );
     const keepExtras = longestWellFormedExtraCount(baseTurns, parsedExtras);
 
@@ -466,7 +470,7 @@ export async function createOptimizedContextStore(dir: string): Promise<ContextS
       const parsedExtras: ConversationTurn[][] = [];
       for (const name of extraNames) {
         const text = await runGit(dir, ["show", `${hash}:${name}`]);
-        parsedExtras.push(parseSegmentTurns(text, false));
+        parsedExtras.push(parseSegmentTurns(text, false, name));
       }
       const keepExtras = longestWellFormedExtraCount(baseTurns, parsedExtras);
       if (keepExtras === 0) return baseTurns;