diff --git a/src/usage/log.ts b/src/usage/log.ts
index 7d7ed5ea11..7bca650964 100644
--- a/src/usage/log.ts
+++ b/src/usage/log.ts
@@ -1142,6 +1142,14 @@ export async function readUsageEntriesForManagement(): Promise<PersistedUsageEnt
   return (await readUsageSnapshotForManagement()).entries;
 }
 
+/** Keep legacy optional fields permissive, but reject rows that cannot be safely attributed. */
+function normalizePersistedUsageRow(value: unknown): PersistedUsageEntry | undefined {
+  if (value === null || typeof value !== "object" || Array.isArray(value)) return undefined;
+  const row = value as Record<string, unknown>;
+  if (typeof row.requestId !== "string" || typeof row.provider !== "string") return undefined;
+  return normalizeUsageEntry(row as unknown as PersistedUsageEntry);
+}
+
 export function readUsageEntries(): PersistedUsageEntry[] {
   const path = usageLogPath();
   if (!existsSync(path)) return [];
@@ -1150,10 +1158,8 @@ export function readUsageEntries(): PersistedUsageEntry[] {
   for (const line of lines) {
     if (!line.trim()) continue;
     try {
-      const parsed = JSON.parse(line) as PersistedUsageEntry;
-      if (parsed && typeof parsed === "object" && typeof parsed.requestId === "string") {
-        entries.push(normalizeUsageEntry(parsed));
-      }
+      const parsed = normalizePersistedUsageRow(JSON.parse(line));
+      if (parsed) entries.push(parsed);
     } catch {
       /* keep reading after a partially written or hand-edited line */
     }
@@ -1166,10 +1172,8 @@ function parseUsageLines(lines: string[]): PersistedUsageEntry[] {
   for (const line of lines) {
     if (!line.trim()) continue;
     try {
-      const parsed = JSON.parse(line) as PersistedUsageEntry;
-      if (parsed && typeof parsed === "object" && typeof parsed.requestId === "string") {
-        entries.push(normalizeUsageEntry(parsed));
-      }
+      const parsed = normalizePersistedUsageRow(JSON.parse(line));
+      if (parsed) entries.push(parsed);
     } catch {
       /* skip partial / hand-edited lines */
     }
diff --git a/tests/usage-log.test.ts b/tests/usage-log.test.ts
index 8414287b01..e22c7e84b3 100644
--- a/tests/usage-log.test.ts
+++ b/tests/usage-log.test.ts
@@ -226,7 +226,7 @@ describe("usage log", () => {
   test("usage byte-prefix truncation and entry-count truncation report independent metadata", async () => {
     writeFileSync(
       usageLogPath(),
-      `${Array.from({ length: 500_001 }, (_, index) => JSON.stringify({ requestId: String(index) })).join("\n")}\n`,
+      `${Array.from({ length: 500_001 }, (_, index) => JSON.stringify({ requestId: String(index), provider: "p" })).join("\n")}\n`,
     );
     const snapshot = await readUsageSnapshotForManagement();
     expect(snapshot.entries).toHaveLength(500_000);
@@ -739,14 +739,26 @@ describe("usage log", () => {
     }]);
   });
 
-  test("skips malformed JSONL lines while keeping valid entries", () => {
+  test("skips malformed JSONL and rows without string usage identities", async () => {
     writeFileSync(usageLogPath(), [
-      "{\"requestId\":\"a\",\"timestamp\":1,\"provider\":\"p\",\"model\":\"m\",\"status\":200,\"durationMs\":1,\"usageStatus\":\"unreported\"}",
+      persistedLine("a"),
       "{not-json",
-      "{\"requestId\":\"b\",\"timestamp\":2,\"provider\":\"p\",\"model\":\"m\",\"status\":200,\"durationMs\":1,\"usageStatus\":\"reported\",\"usage\":{\"inputTokens\":1,\"outputTokens\":2},\"totalTokens\":3}",
+      "null",
+      "42",
+      "[]",
+      "{}",
+      JSON.stringify({ provider: "p", timestamp: 2 }),
+      JSON.stringify({ requestId: 42, provider: "p", timestamp: 2 }),
+      JSON.stringify({ requestId: "missing-provider", timestamp: 2 }),
+      JSON.stringify({ requestId: "null-provider", provider: null, timestamp: 2 }),
+      JSON.stringify({ requestId: "number-provider", provider: 42, timestamp: 2 }),
+      JSON.stringify({ requestId: "object-provider", provider: {}, timestamp: 2 }),
+      JSON.stringify({ requestId: "array-provider", provider: [], timestamp: 2 }),
+      persistedLine("b"),
     ].join("\n"));
 
     expect(readUsageEntries().map(entry => entry.requestId)).toEqual(["a", "b"]);
+    expect((await readUsageEntriesForManagement()).map(entry => entry.requestId)).toEqual(["a", "b"]);
   });
 
   test("keeps missing usage distinct from zero usage", () => {