diff --git a/packages/coding-agent/src/modes/controllers/command-controller.ts b/packages/coding-agent/src/modes/controllers/command-controller.ts
index 0af272c0c..1f9b080e9 100644
--- a/packages/coding-agent/src/modes/controllers/command-controller.ts
+++ b/packages/coding-agent/src/modes/controllers/command-controller.ts
@@ -1368,10 +1368,12 @@ function formatUnlimitedReportLabel(report: UsageReport, index: number): string
 }
 
 function formatResetShort(limit: UsageLimit, nowMs: number): string | undefined {
-	if (limit.window?.resetsAt !== undefined) {
-		return formatDuration(limit.window.resetsAt - nowMs);
-	}
-	return undefined;
+	const resetsAt = limit.window?.resetsAt;
+	if (resetsAt === undefined) return undefined;
+	// Codex returns the prior window's reset_at until a new request opens a fresh window —
+	// rendering a negative delta is meaningless, so drop the suffix in that case.
+	if (resetsAt <= nowMs) return undefined;
+	return formatDuration(resetsAt - nowMs);
 }
 
 function formatAccountHeaderRow(
diff --git a/packages/coding-agent/src/slash-commands/helpers/usage-report.ts b/packages/coding-agent/src/slash-commands/helpers/usage-report.ts
index 9d737ce9f..bbef96730 100644
--- a/packages/coding-agent/src/slash-commands/helpers/usage-report.ts
+++ b/packages/coding-agent/src/slash-commands/helpers/usage-report.ts
@@ -56,7 +56,9 @@ function renderUsageReports(reports: UsageReport[], nowMs: number): string {
 				lines.push(`- ${limit.label}${tier}${window ? ` — ${window}` : ""}`);
 				lines.push(`  ${formatUsageReportAccount(report, limit, index)}: ${formatUsageAmount(limit)}`);
 				lines.push(`  ${renderAsciiBar(limit.amount.usedFraction)}`);
-				if (limit.window?.resetsAt) lines.push(`  resets in ${formatDuration(limit.window.resetsAt - nowMs)}`);
+				if (limit.window?.resetsAt && limit.window.resetsAt > nowMs) {
+					lines.push(`  resets in ${formatDuration(limit.window.resetsAt - nowMs)}`);
+				}
 				if (limit.notes && limit.notes.length > 0) lines.push(`  ${limit.notes.join(" • ")}`);
 			}
 		}
diff --git a/packages/utils/src/format.ts b/packages/utils/src/format.ts
index 8e6a83a22..7e294e8a6 100644
--- a/packages/utils/src/format.ts
+++ b/packages/utils/src/format.ts
@@ -8,6 +8,7 @@ const DAY = 24 * HOUR;
  * Examples: "123ms", "1.5s", "30m15s", "2h30m", "3d2h"
  */
 export function formatDuration(ms: number): string {
+	if (!Number.isFinite(ms) || ms <= 0) return "0ms";
 	if (ms < SEC) return `${ms}ms`;
 	if (ms < MIN) return `${(ms / SEC).toFixed(1)}s`;
 	if (ms < HOUR) {
diff --git a/packages/utils/test/format.test.ts b/packages/utils/test/format.test.ts
new file mode 100644
index 000000000..ab81942a0
--- /dev/null
+++ b/packages/utils/test/format.test.ts
@@ -0,0 +1,26 @@
+import { describe, expect, it } from "bun:test";
+import { formatDuration } from "../src/format";
+
+describe("formatDuration", () => {
+	// Codex's wham/usage endpoint returns the prior window's reset_at until the
+	// next request opens a fresh window, so the `resetsAt - now` delta can land
+	// in the recent past. The util must defend against that — older builds
+	// rendered "-612090ms", which leaked straight into the /usage TUI.
+	it("clamps non-positive, NaN, and Infinity inputs to 0ms", () => {
+		expect(formatDuration(-612_090)).toBe("0ms");
+		expect(formatDuration(-1)).toBe("0ms");
+		expect(formatDuration(0)).toBe("0ms");
+		expect(formatDuration(Number.NaN)).toBe("0ms");
+		expect(formatDuration(Number.POSITIVE_INFINITY)).toBe("0ms");
+		expect(formatDuration(Number.NEGATIVE_INFINITY)).toBe("0ms");
+	});
+
+	it("formats sub-second, sub-minute, sub-hour, sub-day, and multi-day ranges", () => {
+		expect(formatDuration(500)).toBe("500ms");
+		expect(formatDuration(1_500)).toBe("1.5s");
+		expect(formatDuration(90_000)).toBe("1m30s");
+		expect(formatDuration(3_600_000)).toBe("1h");
+		expect(formatDuration(3_660_000)).toBe("1h1m");
+		expect(formatDuration(2 * 86_400_000 + 3_600_000)).toBe("2d1h");
+	});
+});