diff --git a/src/lib/api/index.ts b/src/lib/api/index.ts
--- a/src/lib/api/index.ts
+++ b/src/lib/api/index.ts
@@ -59,6 +59,21 @@
   onStateChange?: (state: string) => void
   langs?: string[]
   omitViaField?: boolean
+  tidSuffix?: string
+}
+
+const MAX_TID_SUFFIX_LEN = 6
+
+function nextPostTid(prev: TID | undefined, tidSuffix?: string): TID {
+  if (prev) {
+    return TID.next(prev)
+  }
+  if (!tidSuffix) {
+    return TID.next(prev)
+  }
+  const suffix = tidSuffix.slice(0, MAX_TID_SUFFIX_LEN)
+  const next = TID.next(prev)
+  return TID.fromStr(next.toString().slice(0, -suffix.length) + suffix)
 }
 
 export async function post(
@@ -118,7 +133,7 @@
     // The sorting behavior for multiple posts sharing the same createdAt time is
     // undefined, so what we'll do here is increment the time by 1 for every post
     now.setMilliseconds(now.getMilliseconds() + 1)
-    tid = TID.next(tid)
+    tid = nextPostTid(tid, opts.tidSuffix)
     const rkey = tid.toString()
     const uri = `at://${did}/app.bsky.feed.post/${rkey}`
     uris.push(uri)
diff --git a/src/state/persisted/schema.ts b/src/state/persisted/schema.ts
--- a/src/state/persisted/schema.ts
+++ b/src/state/persisted/schema.ts
@@ -281,6 +281,7 @@
 
   autoLikeOnRepost: z.boolean().optional(),
   omitViaField: z.boolean().optional(),
+  tidSuffix: z.string().optional(),
 
   // settings sync
   settingsSyncEnabled: z.boolean().optional(),
@@ -417,6 +418,7 @@
 
   autoLikeOnRepost: false,
   omitViaField: false,
+  tidSuffix: undefined,
 
   settingsSyncEnabled: false,
   settingsSyncDraftId: undefined,
diff --git a/src/state/preferences/index.tsx b/src/state/preferences/index.tsx
--- a/src/state/preferences/index.tsx
+++ b/src/state/preferences/index.tsx
@@ -42,6 +42,7 @@
 import {MetricsDisplayPreferencesProvider} from './metrics-display-preference'
 import {Provider as NoDiscoverProvider} from './no-discover-fallback'
 import {Provider as OmitViaFieldProvider} from './omit-via-field'
+import {Provider as TidSuffixProvider} from './tid-suffix'
 import {Provider as OpenRouterProvider} from './openrouter'
 import {Provider as PdsLabelProvider} from './pds-label'
 import {Provider as PlcDirectoryProvider} from './plc-directory'
@@ -111,6 +112,7 @@
 export {useLabelDefinitions} from './label-defs'
 export {useLanguagePrefs, useLanguagePrefsApi} from './languages'
 export {useOmitViaField, useSetOmitViaField} from './omit-via-field'
+export {useTidSuffix, useSetTidSuffix} from './tid-suffix'
 export {
   useOpenRouterApiKey,
   useOpenRouterConfigured,
@@ -203,9 +205,11 @@
                                                                                                                       <DisableTopOfFeedButtonProvider>
                                                                                                                         <DiscoverContextEnabledProvider>
                                                                                                                           <OmitViaFieldProvider>
-                                                                                                                            {
-                                                                                                                              children
-                                                                                                                            }
+                                                                                                                            <TidSuffixProvider>
+                                                                                                                              {
+                                                                                                                                children
+                                                                                                                              }
+                                                                                                                            </TidSuffixProvider>
                                                                                                                           </OmitViaFieldProvider>
                                                                                                                         </DiscoverContextEnabledProvider>
                                                                                                                       </DisableTopOfFeedButtonProvider>
diff --git a/src/state/preferences/settings-sync.tsx b/src/state/preferences/settings-sync.tsx
--- a/src/state/preferences/settings-sync.tsx
+++ b/src/state/preferences/settings-sync.tsx
@@ -96,6 +96,7 @@
   'trendingVideoDisabled',
   'autoLikeOnRepost',
   'omitViaField',
+  'tidSuffix',
   'syncOpenRouterApiKey',
 ] as const satisfies readonly (keyof Schema)[]
 
diff --git a/src/state/preferences/tid-suffix.tsx b/src/state/preferences/tid-suffix.tsx
new file mode 100644
--- /dev/null
+++ b/src/state/preferences/tid-suffix.tsx
@@ -0,0 +1,52 @@
+import {
+  createContext,
+  type PropsWithChildren,
+  useCallback,
+  useContext,
+  useEffect,
+  useState,
+} from 'react'
+
+import * as persisted from '#/state/persisted'
+
+type StateContext = persisted.Schema['tidSuffix']
+type SetContext = (v: persisted.Schema['tidSuffix']) => void
+
+const stateContext = createContext<StateContext>(persisted.defaults.tidSuffix)
+const setContext = createContext<SetContext>(
+  (_: persisted.Schema['tidSuffix']) => {},
+)
+
+export function Provider({children}: PropsWithChildren<{}>) {
+  const [state, setState] = useState(persisted.get('tidSuffix'))
+
+  const setStateWrapped = useCallback(
+    (value: persisted.Schema['tidSuffix']) => {
+      setState(value)
+      persisted.write('tidSuffix', value)
+    },
+    [setState],
+  )
+
+  useEffect(() => {
+    return persisted.onUpdate('tidSuffix', next => {
+      setState(next)
+    })
+  }, [setStateWrapped])
+
+  return (
+    <stateContext.Provider value={state}>
+      <setContext.Provider value={setStateWrapped}>
+        {children}
+      </setContext.Provider>
+    </stateContext.Provider>
+  )
+}
+
+export function useTidSuffix() {
+  return useContext(stateContext)
+}
+
+export function useSetTidSuffix() {
+  return useContext(setContext)
+}
diff --git a/src/screens/Settings/RunesSettings/ExtraSettings.tsx b/src/screens/Settings/RunesSettings/ExtraSettings.tsx
--- a/src/screens/Settings/RunesSettings/ExtraSettings.tsx
+++ b/src/screens/Settings/RunesSettings/ExtraSettings.tsx
@@ -1,5 +1,8 @@
+import {useState} from 'react'
+import {View} from 'react-native'
 import {Trans, useLingui} from '@lingui/react/macro'
 
+import {usePalette} from '#/lib/hooks/usePalette'
 import {
   useAutoLikeOnRepost,
   useSetAutoLikeOnRepost,
@@ -20,15 +23,21 @@
   useOmitViaField,
   useSetOmitViaField,
 } from '#/state/preferences/omit-via-field'
+import {useTidSuffix, useSetTidSuffix} from '#/state/preferences/tid-suffix'
 import * as SettingsList from '#/screens/Settings/components/SettingsList'
 import {atoms as a} from '#/alf'
 import {Admonition} from '#/components/Admonition'
+import {Button, ButtonText} from '#/components/Button'
+import * as Dialog from '#/components/Dialog'
 import * as Toggle from '#/components/forms/Toggle'
 import {BellRinging_Stroke2_Corner0_Rounded as BellRingingIcon} from '#/components/icons/BellRinging'
 import {CodeBrackets_Stroke2_Corner2_Rounded as CodeBracketsIcon} from '#/components/icons/CodeBrackets'
 import {Explosion_Stroke2_Corner0_Rounded as ExplosionIcon} from '#/components/icons/Explosion'
 import {Eye_Stroke2_Corner0_Rounded as VisibilityIcon} from '#/components/icons/Eye'
 import {LikeRepost_Stroke2_Corner2_Rounded as LikeRepostIcon} from '#/components/icons/Heart2'
+import {Hashtag_Stroke2_Corner0_Rounded as HashtagIcon} from '#/components/icons/Hashtag'
+import {Text} from '#/components/Typography'
+import {IS_WEB} from '#/env'
 import {Lab_Stroke2_Corner0_Rounded as BeakerIcon} from '#/components/icons/Lab'
 import {useDevMode} from '#/storage/hooks/dev-mode'
 import {RunesScreenLayout} from './components/RunesScreenLayout'
@@ -50,6 +59,8 @@
 
   const omitViaField = useOmitViaField()
   const setOmitViaField = useSetOmitViaField()
+  const tidSuffix = useTidSuffix()
+  const setTidSuffixControl = Dialog.useDialogControl()
   const [devMode, setDevMode] = useDevMode()
 
   return (
@@ -127,6 +138,25 @@
           <Toggle.Platform />
         </SettingsList.Item>
       </Toggle.Item>
+      <SettingsList.Item>
+        <SettingsList.ItemIcon icon={HashtagIcon} />
+        <SettingsList.ItemText>
+          <Trans>Custom TID suffix for posts</Trans>
+        </SettingsList.ItemText>
+        <SettingsList.BadgeButton
+          label={tidSuffix ? l`Change` : l`Set`}
+          onPress={() => setTidSuffixControl.open()}
+        />
+      </SettingsList.Item>
+      <SettingsList.Item>
+        <Admonition type="info" style={[a.flex_1]}>
+          <Trans>
+            Replace the last characters of the first post in a thread's record
+            key with a custom suffix (up to 6 characters). Current:&nbsp;
+            <Text style={[a.font_bold]}>{tidSuffix || l`none`}</Text>
+          </Trans>
+        </Admonition>
+      </SettingsList.Item>
       <Toggle.Item
         name="dev_mode"
         label={l`Developer mode`}
@@ -148,6 +178,82 @@
           <Trans>Feature gates</Trans>
         </SettingsList.ItemText>
       </SettingsList.LinkItem>
+      <TidSuffixDialog control={setTidSuffixControl} />
     </RunesScreenLayout>
   )
+}
+
+const MAX_TID_SUFFIX_LEN = 6
+
+function TidSuffixDialog({control}: {control: Dialog.DialogControlProps}) {
+  const pal = usePalette('default')
+  const {t: l} = useLingui()
+
+  const tidSuffix = useTidSuffix()
+  const [suffix, setSuffix] = useState(tidSuffix ?? '')
+  const setTidSuffix = useSetTidSuffix()
+  const isReset = suffix.trim().length === 0
+
+  const submit = () => {
+    const trimmedSuffix = suffix.trim().slice(0, MAX_TID_SUFFIX_LEN)
+    control.close(() => {
+      setTidSuffix(trimmedSuffix || undefined)
+    })
+  }
+
+  return (
+    <Dialog.Outer
+      control={control}
+      nativeOptions={{preventExpansion: true}}
+      onClose={() => setSuffix(tidSuffix ?? '')}>
+      <Dialog.Handle />
+      <Dialog.ScrollableInner label={l`Custom TID suffix`}>
+        <View style={[a.gap_sm, a.pb_lg]}>
+          <Text style={[a.text_2xl, a.font_bold]}>
+            <Trans>Custom TID suffix</Trans>
+          </Text>
+        </View>
+
+        <View style={a.gap_lg}>
+          <Dialog.Input
+            label={l`TID suffix`}
+            autoFocus
+            style={[styles.textInput, pal.border, pal.text]}
+            onChangeText={text => setSuffix(text.slice(0, MAX_TID_SUFFIX_LEN))}
+            placeholder={l`e.g. abc`}
+            placeholderTextColor={pal.colors.textLight}
+            onSubmitEditing={submit}
+            accessibilityHint={l`Input up to 6 characters to use as a TID suffix`}
+            defaultValue={tidSuffix}
+            maxLength={MAX_TID_SUFFIX_LEN}
+          />
+
+          <View style={IS_WEB && [a.flex_row, a.justify_end]}>
+            <Button
+              label={isReset ? l`Reset` : l`Save`}
+              size="large"
+              onPress={() => void submit()}
+              variant="solid"
+              color={isReset ? 'secondary' : 'primary'}>
+              <ButtonText>
+                {isReset ? <Trans>Reset</Trans> : <Trans>Save</Trans>}
+              </ButtonText>
+            </Button>
+          </View>
+        </View>
+
+        <Dialog.Close />
+      </Dialog.ScrollableInner>
+    </Dialog.Outer>
+  )
+}
+
+const styles = {
+  textInput: {
+    borderWidth: 1,
+    borderRadius: 8,
+    paddingHorizontal: 14,
+    paddingVertical: 10,
+    fontSize: 16,
+  },
 }
diff --git a/src/view/com/composer/Composer.tsx b/src/view/com/composer/Composer.tsx
--- a/src/view/com/composer/Composer.tsx
+++ b/src/view/com/composer/Composer.tsx
@@ -103,6 +103,7 @@
   useLanguagePrefsApi,
 } from '#/state/preferences/languages'
 import {useOmitViaField} from '#/state/preferences/omit-via-field'
+import {useTidSuffix} from '#/state/preferences/tid-suffix'
 import {
   useOpenRouterApiKey,
   useOpenRouterConfigured,
@@ -310,6 +311,7 @@
   const {t: l, i18n} = useLingui()
   const requireAltTextEnabled = useRequireAltTextEnabled()
   const omitViaField = useOmitViaField()
+  const tidSuffix = useTidSuffix()
   const langPrefs = useLanguagePrefs()
   const setLangPrefs = useLanguagePrefsApi()
   const textInputRef = useRef<TextInputRef>(null)
@@ -1173,6 +1175,7 @@
           onStateChange: setPublishingStage,
           langs: currentLanguages,
             omitViaField,
+            tidSuffix,
         })
       ).uris[0]