diff --git a/CHANGELOG.md b/CHANGELOG.md
index e71f99a66f83..494096e61377 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -33,6 +33,7 @@ Docs: https://docs.openclaw.ai
 - **Small-context compaction:** cap the effective reserve against the known model context window so small local models do not enter compaction from the first token. (#100621) Thanks @vincentkoc.
 - **Plugin install diagnostics:** suppress the misleading hook-pack fallback after plugin install failures only when the hook manifest is absent, while preserving actionable malformed hook-pack errors. (#100554) Thanks @vincentkoc.
 - **Config validation diagnostics:** emit each unchanged sanitized validation-warning payload once per config path, reset deduplication after a clean validation, and preserve the warning fingerprint across transient invalid reads and failed refreshes. (#100569, #25574) Thanks @vincentkoc.
+- **Session usage logs:** normalize malformed transcript timestamps before sorting and Gateway serialization so invalid dates cannot surface as null usage-log times. (#99418) Thanks @sheyanmin.
 - **Config size-drop guard:** compare writes against canonical bytes for parseable object configs instead of raw BOM and indentation overhead, while preserving raw audit telemetry and the conservative malformed-input fallback. (#100591, #71865) Thanks @vincentkoc.
 - **Control UI coalesced updates:** show a clear queued-restart completion banner when an update joins an already-running Gateway restart. (#93082) Thanks @goutamadwant.
 - **Control UI connection errors:** preserve structured pairing and authentication failures for pending RPC callers while keeping generic disconnect behavior unchanged. (#54758) Thanks @ruanrrn.
diff --git a/src/infra/session-cost-usage.test.ts b/src/infra/session-cost-usage.test.ts
index 2c76ce22b41e..bd44f3c3d776 100644
--- a/src/infra/session-cost-usage.test.ts
+++ b/src/infra/session-cost-usage.test.ts
@@ -2919,6 +2919,45 @@ example
     expect(logs?.[0]?.content).toBe("hello there");
   });
 
+  it("normalizes malformed log timestamps with the transcript timestamp rules", async () => {
+    const root = await makeSessionCostRoot("logs-malformed-timestamp");
+    const sessionsDir = path.join(root, "agents", "main", "sessions");
+    await fs.mkdir(sessionsDir, { recursive: true });
+    const sessionFile = path.join(sessionsDir, "sess-malformed.jsonl");
+
+    await fs.writeFile(
+      sessionFile,
+      [
+        JSON.stringify({
+          type: "message",
+          timestamp: "not-a-valid-date-string",
+          message: { role: "user", content: "bad timestamp entry" },
+        }),
+        JSON.stringify({
+          type: "message",
+          timestamp: "still-not-a-valid-date-string",
+          message: {
+            role: "assistant",
+            content: "nested timestamp entry",
+            timestamp: Date.parse("2026-02-21T17:46:00.000Z"),
+          },
+        }),
+        JSON.stringify({
+          type: "message",
+          timestamp: "2026-02-21T17:47:00.000Z",
+          message: { role: "assistant", content: "valid timestamp entry" },
+        }),
+      ].join("\n"),
+      "utf-8",
+    );
+
+    const logs = await loadSessionLogs({ sessionFile });
+    expect(logs).toHaveLength(3);
+    expect(logs?.[0]?.timestamp).toBe(0);
+    expect(logs?.[1]?.timestamp).toBe(Date.parse("2026-02-21T17:46:00.000Z"));
+    expect(logs?.[2]?.timestamp).toBe(Date.parse("2026-02-21T17:47:00.000Z"));
+  });
+
   it("buckets hourly message counts into UTC quarter-hour slots", async () => {
     const root = await makeSessionCostRoot("cost-quarter");
     const sessionFile = path.join(root, "session.jsonl");
diff --git a/src/infra/session-cost-usage.ts b/src/infra/session-cost-usage.ts
index e2f4d41d26a7..517c6a32ce30 100644
--- a/src/infra/session-cost-usage.ts
+++ b/src/infra/session-cost-usage.ts
@@ -2740,15 +2740,9 @@ export async function loadSessionLogs(params: {
       }
 
       // Get timestamp
-      let timestamp = 0;
-      if (typeof parsed.timestamp === "string") {
-        timestamp = new Date(parsed.timestamp).getTime();
-        if (Number.isNaN(timestamp)) {
-          timestamp = 0;
-        }
-      } else if (typeof message.timestamp === "number") {
-        timestamp = message.timestamp;
-      }
+      // Keep detail logs on the usage-summary timestamp path, including nested
+      // fallback; direct Date parsing can leak NaN as null through Gateway JSON.
+      const timestamp = parseTimestamp(parsed)?.getTime() ?? 0;
 
       // Get usage for assistant messages
       let tokens: number | undefined;