diff --git a/src/background.ts b/src/background.ts
index 0d8bdd6..dd1c7bc 100644
--- a/src/background.ts
+++ b/src/background.ts
@@ -5,8 +5,8 @@
 // {did, handle} into chrome.storage.local under `session` for the worker.
 
 import { listRecords, parseAtUri, resolveDid } from './lib/atproto'
-import { cached } from './lib/cache'
-import { detectPage } from './lib/detection'
+import { cached, dropAll } from './lib/cache'
+import { detectPage, dropProbes } from './lib/detection'
 import { type IconState, badgeFor, iconStateFor, titleFor } from './lib/icon'
 import { FOLLOWS_CAP, type FollowList, followingDids } from './lib/subscribers'
 import { welcomeUrl } from './lib/welcome'
@@ -235,6 +235,36 @@ async function computeState(
   return state
 }
 
+// --- dropping everything remembered (dev channel) ----------------------------
+
+/**
+ * Everything the extension has remembered about what it fetched: the scoped
+ * caches (src/lib/cache.ts), detection's well-known probe answers
+ * (src/lib/detection.ts), and the per-tab detection states above.
+ *
+ * In the worker rather than in the popup because two thirds of that is the
+ * worker's. The tab states go through `setTabState`, so every badge drops back
+ * to idle as its state does instead of leaving a green dot standing for
+ * something no longer stored anywhere — which is also what makes the drop
+ * visible without opening the popup again.
+ *
+ * The account mirror and the stored reader choice are deliberately untouched:
+ * dropping a cache is not signing out, and not a factory reset.
+ */
+async function dropCaches(): Promise<{ dropped: number }> {
+  const all = await chrome.storage.session.get(null)
+  const tabIds = Object.keys(all)
+    .filter((k) => k.startsWith('tab:'))
+    .map((k) => Number(k.slice(4)))
+  await Promise.all(tabIds.map((tabId) => setTabState(tabId, undefined)))
+  const [entries, probes] = await Promise.all([dropAll(), dropProbes()])
+  console.debug(
+    `[substandard] dropped ${entries} cache entr(ies), ${probes} probe answer(s)`,
+    `and ${tabIds.length} tab state(s)`,
+  )
+  return { dropped: entries + probes + tabIds.length }
+}
+
 function isHttpUrl(url: string | undefined): url is string {
   return !!url && /^https?:\/\//.test(url)
 }
@@ -279,6 +309,9 @@ async function handle(msg: Msg, sender: chrome.runtime.MessageSender): Promise<u
       // src/signin.ts finish the flow after the popup is gone.
       return startSignIn(msg.handle)
     }
+    case 'drop-caches': {
+      return dropCaches()
+    }
     case 'follows': {
       // Cosmetic on both sides — a face in the subscriber row, a line on the
       // owner card — so a failed walk is an absent answer, not an error the
diff --git a/src/lib/types.ts b/src/lib/types.ts
index 881a827..88a0e6a 100644
--- a/src/lib/types.ts
+++ b/src/lib/types.ts
@@ -108,6 +108,8 @@ export type Msg =
   | { type: 'get-state'; tabId: number; refresh?: boolean }
   | { type: 'signin'; handle: string }
   | { type: 'follows'; refresh?: boolean }
+  /** Dev channel only: forget every cached read. Answers `{dropped}`. */
+  | { type: 'drop-caches' }
 
 /**
  * Messages from the worker to the offscreen document that hosts the OAuth