diff --git a/src/__tests__/tokscale.test.ts b/src/__tests__/tokscale.test.ts
index d039d70..d092bea 100644
--- a/src/__tests__/tokscale.test.ts
+++ b/src/__tests__/tokscale.test.ts
@@ -29,6 +29,7 @@ import {
   versionAtLeast,
   reportToStats,
   resetDetectionCache,
+  TokscaleNotFoundError,
 } from "../tokscale"
 
 const mockExecFile = vi.mocked(execFile)
@@ -282,6 +283,26 @@ describe("fetchPeriodStats", () => {
     mockExecFileError(error)
     await expect(fetchPeriodStats("today")).rejects.toThrow()
   })
+
+  it("throws TokscaleNotFoundError and resets detection cache on ENOENT", async () => {
+    // Prime cache as installed
+    mockDetectSequence("tokscale 4.0.5")
+    await detectTokscale()
+    vi.clearAllMocks()
+
+    // Now simulate binary gone (ENOENT)
+    const error = Object.assign(new Error("spawn tokscale ENOENT"), {
+      code: "ENOENT" as unknown as number,
+    })
+    mockExecFileError(error)
+
+    await expect(fetchPeriodStats("today")).rejects.toThrow(TokscaleNotFoundError)
+
+    // Detection cache should be reset — next detectTokscale() must re-probe
+    mockExecFileError(Object.assign(new Error("not found"), { code: 1 }))
+    const result = await detectTokscale()
+    expect(result).toBe(false)
+  })
 })
 
 describe("parseModelReport", () => {
diff --git a/src/tokscale.ts b/src/tokscale.ts
index 36d606e..64528b1 100644
--- a/src/tokscale.ts
+++ b/src/tokscale.ts
@@ -4,6 +4,13 @@ import { PERIOD_FLAGS } from "./types"
 
 type SemVer = readonly [number, number, number]
 
+export class TokscaleNotFoundError extends Error {
+  constructor() {
+    super("tokscale binary not found")
+    this.name = "TokscaleNotFoundError"
+  }
+}
+
 let cachedDetection: boolean | null = null
 let cachedVersion: SemVer | null = null
 
@@ -70,6 +77,11 @@ export function fetchPeriodStats(
       { timeout: 15000, maxBuffer: 1024 * 1024 },
       (error, stdout) => {
         if (error) {
+          if ((error as NodeJS.ErrnoException).code === "ENOENT") {
+            resetDetectionCache()
+            reject(new TokscaleNotFoundError())
+            return
+          }
           reject(new Error(`tokscale CLI failed: ${error.message}`))
           return
         }
diff --git a/src/tui.tsx b/src/tui.tsx
index d4bd00c..7714c5f 100644
--- a/src/tui.tsx
+++ b/src/tui.tsx
@@ -4,7 +4,7 @@ import { createSignal } from "solid-js"
 import type { TimePeriod, PeriodState, TokscalePluginOptions } from "./types"
 import { TIME_PERIODS, PERIOD_LABELS } from "./types"
 import { formatTokens, formatCost } from "./format"
-import { detectTokscale, fetchPeriodStats } from "./tokscale"
+import { detectTokscale, fetchPeriodStats, TokscaleNotFoundError } from "./tokscale"
 
 const TOKSCALE_BLUE = "#0073FF"
 
@@ -45,6 +45,13 @@ const tui: TuiPlugin = async (api, options, _meta) => {
             })
             setState({ status: "success", stats, error: null })
           } catch (e) {
+            if (e instanceof TokscaleNotFoundError) {
+              setInstalled(false)
+              for (const p of TIME_PERIODS) {
+                signals[p][1]({ status: "not-installed", stats: null, error: null })
+              }
+              return
+            }
             setState({ status: "error", stats: signals[period][0]().stats, error: String(e) })
           }
         })