wip: zen

4 files changed, 128 insertions, 5 deletions

diff --git a/packages/console/app/src/routes/zen/util/error.ts b/packages/console/app/src/routes/zen/util/error.ts
index a1393eb7f..a3a93d2ef 100644
--- a/packages/console/app/src/routes/zen/util/error.ts
+++ b/packages/console/app/src/routes/zen/util/error.ts
@@ -3,11 +3,13 @@ export class CreditsError extends Error {}
 export class MonthlyLimitError extends Error {}
 export class UserLimitError extends Error {}
 export class ModelError extends Error {}
-export class FreeUsageLimitError extends Error {}
-export class SubscriptionUsageLimitError extends Error {
+
+class LimitError extends Error {
   retryAfter?: number
   constructor(message: string, retryAfter?: number) {
     super(message)
     this.retryAfter = retryAfter
   }
 }
+export class FreeUsageLimitError extends LimitError {}
+export class SubscriptionUsageLimitError extends LimitError {}
diff --git a/packages/console/app/src/routes/zen/util/handler.ts b/packages/console/app/src/routes/zen/util/handler.ts
index a72435e68..9646cacd0 100644
--- a/packages/console/app/src/routes/zen/util/handler.ts
+++ b/packages/console/app/src/routes/zen/util/handler.ts
@@ -313,7 +313,7 @@ export async function handler(
 
     if (error instanceof FreeUsageLimitError || error instanceof SubscriptionUsageLimitError) {
       const headers = new Headers()
-      if (error instanceof SubscriptionUsageLimitError && error.retryAfter) {
+      if (error.retryAfter) {
         headers.set("retry-after", String(error.retryAfter))
       }
       return new Response(
diff --git a/packages/console/app/src/routes/zen/util/rateLimiter.ts b/packages/console/app/src/routes/zen/util/rateLimiter.ts
index fafbc06e9..5e4f31e67 100644
--- a/packages/console/app/src/routes/zen/util/rateLimiter.ts
+++ b/packages/console/app/src/routes/zen/util/rateLimiter.ts
@@ -28,17 +28,46 @@ export function createRateLimiter(limit: ZenData.RateLimit | undefined, rawIp: s
     check: async () => {
       const rows = await Database.use((tx) =>
         tx
-          .select({ count: IpRateLimitTable.count })
+          .select({ interval: IpRateLimitTable.interval, count: IpRateLimitTable.count })
           .from(IpRateLimitTable)
           .where(and(eq(IpRateLimitTable.ip, ip), inArray(IpRateLimitTable.interval, intervals))),
       )
       const total = rows.reduce((sum, r) => sum + r.count, 0)
       logger.debug(`rate limit total: ${total}`)
-      if (total >= limitValue) throw new FreeUsageLimitError(`Rate limit exceeded. Please try again later.`)
+      if (total >= limitValue)
+        throw new FreeUsageLimitError(
+          `Rate limit exceeded. Please try again later.`,
+          limit.period === "day" ? getRetryAfterDay(now) : getRetryAfterHour(rows, intervals, limitValue, now),
+        )
     },
   }
 }
 
+export function getRetryAfterDay(now: number) {
+  return Math.ceil((86_400_000 - (now % 86_400_000)) / 1000)
+}
+
+export function getRetryAfterHour(
+  rows: { interval: string; count: number }[],
+  intervals: string[],
+  limit: number,
+  now: number,
+) {
+  const counts = new Map(rows.map((r) => [r.interval, r.count]))
+  // intervals are ordered newest to oldest: [current, -1h, -2h]
+  // simulate dropping oldest intervals one at a time
+  let running = intervals.reduce((sum, i) => sum + (counts.get(i) ?? 0), 0)
+  for (let i = intervals.length - 1; i >= 0; i--) {
+    running -= counts.get(intervals[i]) ?? 0
+    if (running < limit) {
+      // interval at index i rolls out of the window (intervals.length - i) hours from the current hour start
+      const hours = intervals.length - i
+      return Math.ceil((hours * 3_600_000 - (now % 3_600_000)) / 1000)
+    }
+  }
+  return Math.ceil((3_600_000 - (now % 3_600_000)) / 1000)
+}
+
 function buildYYYYMMDD(timestamp: number) {
   return new Date(timestamp)
     .toISOString()
diff --git a/packages/console/app/test/rateLimiter.test.ts b/packages/console/app/test/rateLimiter.test.ts
new file mode 100644
index 000000000..864f907d6
--- /dev/null
+++ b/packages/console/app/test/rateLimiter.test.ts
@@ -0,0 +1,92 @@
+import { describe, expect, test } from "bun:test"
+import { getRetryAfterDay, getRetryAfterHour } from "../src/routes/zen/util/rateLimiter"
+
+describe("getRetryAfterDay", () => {
+  test("returns full day at midnight UTC", () => {
+    const midnight = Date.UTC(2026, 0, 15, 0, 0, 0, 0)
+    expect(getRetryAfterDay(midnight)).toBe(86_400)
+  })
+
+  test("returns remaining seconds until next UTC day", () => {
+    const noon = Date.UTC(2026, 0, 15, 12, 0, 0, 0)
+    expect(getRetryAfterDay(noon)).toBe(43_200)
+  })
+
+  test("rounds up to nearest second", () => {
+    const almost = Date.UTC(2026, 0, 15, 23, 59, 59, 500)
+    expect(getRetryAfterDay(almost)).toBe(1)
+  })
+})
+
+describe("getRetryAfterHour", () => {
+  // 14:30:00 UTC — 30 minutes into the current hour
+  const now = Date.UTC(2026, 0, 15, 14, 30, 0, 0)
+  const intervals = ["2026011514", "2026011513", "2026011512"]
+
+  test("waits 3 hours when all usage is in current hour", () => {
+    const rows = [{ interval: "2026011514", count: 10 }]
+    // only current hour has usage — it won't leave the window for 3 hours from hour start
+    // 3 * 3600 - 1800 = 9000s
+    expect(getRetryAfterHour(rows, intervals, 10, now)).toBe(9000)
+  })
+
+  test("waits 1 hour when dropping oldest interval is sufficient", () => {
+    const rows = [
+      { interval: "2026011514", count: 2 },
+      { interval: "2026011512", count: 10 },
+    ]
+    // total=12, drop oldest (-2h, count=10) -> 2 < 10
+    // hours = 3 - 2 = 1 -> 1 * 3600 - 1800 = 1800s
+    expect(getRetryAfterHour(rows, intervals, 10, now)).toBe(1800)
+  })
+
+  test("waits 2 hours when usage spans oldest two intervals", () => {
+    const rows = [
+      { interval: "2026011513", count: 8 },
+      { interval: "2026011512", count: 5 },
+    ]
+    // total=13, drop -2h (5) -> 8, 8 >= 8, drop -1h (8) -> 0 < 8
+    // hours = 3 - 1 = 2 -> 2 * 3600 - 1800 = 5400s
+    expect(getRetryAfterHour(rows, intervals, 8, now)).toBe(5400)
+  })
+
+  test("waits 1 hour when oldest interval alone pushes over limit", () => {
+    const rows = [
+      { interval: "2026011514", count: 1 },
+      { interval: "2026011513", count: 1 },
+      { interval: "2026011512", count: 10 },
+    ]
+    // total=12, drop -2h (10) -> 2 < 10
+    // hours = 3 - 2 = 1 -> 1800s
+    expect(getRetryAfterHour(rows, intervals, 10, now)).toBe(1800)
+  })
+
+  test("waits 2 hours when middle interval keeps total over limit", () => {
+    const rows = [
+      { interval: "2026011514", count: 4 },
+      { interval: "2026011513", count: 4 },
+      { interval: "2026011512", count: 4 },
+    ]
+    // total=12, drop -2h (4) -> 8, 8 >= 5, drop -1h (4) -> 4 < 5
+    // hours = 3 - 1 = 2 -> 5400s
+    expect(getRetryAfterHour(rows, intervals, 5, now)).toBe(5400)
+  })
+
+  test("rounds up to nearest second", () => {
+    const offset = Date.UTC(2026, 0, 15, 14, 30, 0, 500)
+    const rows = [
+      { interval: "2026011514", count: 2 },
+      { interval: "2026011512", count: 10 },
+    ]
+    // hours=1 -> 3_600_000 - 1_800_500 = 1_799_500ms -> ceil(1799.5) = 1800
+    expect(getRetryAfterHour(rows, intervals, 10, offset)).toBe(1800)
+  })
+
+  test("fallback returns time until next hour when rows are empty", () => {
+    // edge case: rows empty but function called (shouldn't happen in practice)
+    // loop drops all zeros, running stays 0 which is < any positive limit on first iteration
+    const rows: { interval: string; count: number }[] = []
+    // drop -2h (0) -> 0 < 1 -> hours = 3 - 2 = 1 -> 1800s
+    expect(getRetryAfterHour(rows, intervals, 1, now)).toBe(1800)
+  })
+})