diff --git a/custom_components/localthings/registry/capabilities/airconditioner.py b/custom_components/localthings/registry/capabilities/airconditioner.py
index 2bc5cce..d231c52 100644
--- a/custom_components/localthings/registry/capabilities/airconditioner.py
+++ b/custom_components/localthings/registry/capabilities/airconditioner.py
@@ -555,9 +555,9 @@ CLIMATE = Capability(
         ),
         # Filter time in tenths of an hour, counting UP since last filter
         # reset; scale and direction confirmed against the Samsung app and
-        # the /alarms/vs/0 threshold crossing (500h). No reset entity: no
-        # local write path has been found -- see
-        # docs/investigations/ac-filter-reset.md for what's been tried.
+        # the /alarms/vs/0 threshold crossing (500h). Resettable via the
+        # FilterCleanAlarm_Clear trigger token below -- see
+        # docs/investigations/ac-filter-reset.md for how that was found.
         SensorDesc(
             key="filter_time",
             rep_fn=_option_token_num("FilterTime", divisor=10),
@@ -567,6 +567,26 @@ CLIMATE = Capability(
             state_class="measurement",
             icon="mdi:air-filter",
         ),
+        # Resets the counter above via the FilterCleanAlarm_Clear token, the
+        # same single-token options merge as every other /mode/vs/0 setting.
+        # It's a trigger, not a stored setting -- the board zeroes the
+        # counter on receipt and never reports this token back, which is why
+        # it doesn't show up in exists_fn like the others. Confirmed on an
+        # ARTIK051_KRAC_18K: FilterTime_95 -> FilterTime_0, stable across a
+        # fresh DTLS session and every poll after (see the investigation doc
+        # for why this was believed cloud-only until now).
+        ButtonDesc(
+            key="filter_time_reset",
+            field="",
+            payload="FilterCleanAlarm_Clear",
+            icon="mdi:restart",
+            entity_category="config",
+            exists_fn=_has_option_token("FilterTime"),
+            write_fn=lambda p, rep, href=None: (
+                ["mode", "vs", "0"],
+                {"x.com.samsung.da.options": [p]},
+            ),
+        ),
         # FilterTime_'s threshold, exposed as a static 4-way radio
         # (180/300/500/700h, matching the app) since options[] tokens carry
         # no supported-values list to read from, unlike air_filter_threshold
diff --git a/custom_components/localthings/translations/cs.json b/custom_components/localthings/translations/cs.json
index aeece88..83e5b72 100644
--- a/custom_components/localthings/translations/cs.json
+++ b/custom_components/localthings/translations/cs.json
@@ -120,6 +120,9 @@
       "auto_clean_stop": {
         "name": "Zastavit samočištění"
       },
+      "filter_time_reset": {
+        "name": "Vynulovat počítadlo filtru"
+      },
       "pause": {
         "name": "Pozastavit"
       },
diff --git a/custom_components/localthings/translations/en.json b/custom_components/localthings/translations/en.json
index 545e8c0..d403e24 100644
--- a/custom_components/localthings/translations/en.json
+++ b/custom_components/localthings/translations/en.json
@@ -120,6 +120,9 @@
       "auto_clean_stop": {
         "name": "Stop auto clean"
       },
+      "filter_time_reset": {
+        "name": "Reset filter time"
+      },
       "pause": {
         "name": "Pause"
       },
diff --git a/custom_components/localthings/translations/es.json b/custom_components/localthings/translations/es.json
index 729b853..ec8e6a0 100644
--- a/custom_components/localthings/translations/es.json
+++ b/custom_components/localthings/translations/es.json
@@ -242,6 +242,9 @@
       "auto_clean_stop": {
         "name": "Detener la autolimpieza"
       },
+      "filter_time_reset": {
+        "name": "Restablecer el contador del filtro"
+      },
       "pause": {
         "name": "Pausar"
       },
diff --git a/custom_components/localthings/translations/it.json b/custom_components/localthings/translations/it.json
index ecdb604..be69d02 100644
--- a/custom_components/localthings/translations/it.json
+++ b/custom_components/localthings/translations/it.json
@@ -120,6 +120,9 @@
       "auto_clean_stop": {
         "name": "Arresta autopulizia"
       },
+      "filter_time_reset": {
+        "name": "Azzera il contatore del filtro"
+      },
       "pause": {
         "name": "Pausa"
       },
diff --git a/custom_components/localthings/translations/ko.json b/custom_components/localthings/translations/ko.json
index 625a81a..7a86ba4 100644
--- a/custom_components/localthings/translations/ko.json
+++ b/custom_components/localthings/translations/ko.json
@@ -120,6 +120,9 @@
       "auto_clean_stop": {
         "name": "자동 청소 정지"
       },
+      "filter_time_reset": {
+        "name": "필터 사용 시간 초기화"
+      },
       "pause": {
         "name": "일시정지"
       },
diff --git a/custom_components/localthings/translations/nl.json b/custom_components/localthings/translations/nl.json
index e6658e9..09e15db 100644
--- a/custom_components/localthings/translations/nl.json
+++ b/custom_components/localthings/translations/nl.json
@@ -120,6 +120,9 @@
       "auto_clean_stop": {
         "name": "Zelfreiniging stoppen"
       },
+      "filter_time_reset": {
+        "name": "Filterteller op nul zetten"
+      },
       "pause": {
         "name": "Pauzeren"
       },
diff --git a/docs/investigations/ac-filter-reset.md b/docs/investigations/ac-filter-reset.md
index 858b049..e9c35e1 100644
--- a/docs/investigations/ac-filter-reset.md
+++ b/docs/investigations/ac-filter-reset.md
@@ -1,20 +1,28 @@
-# AC filter-time counter reset: not solved
+# AC filter-time counter reset: solved
 
 `registry/capabilities/airconditioner.py`'s `filter_time` sensor
-(`FilterTime_<N>` option token, tenths of an hour) has no reset entity. This
-is where the failed attempts to find one are kept, so the next attempt starts
-from the evidence instead of from scratch. Not finding a mechanism is not the
-same as it not existing.
+(`FilterTime_<N>` option token, tenths of an hour) has a reset entity now
+(`filter_time_reset`, issue-tracked as PR #289): a single-token options write
+of `FilterCleanAlarm_Clear` to `/mode/vs/0`, the same merge every other
+setting on that href uses. Measured on an ARTIK051_KRAC_18K: `FilterTime_95`
+(9h30m) → `FilterTime_0`, still zero on a fresh DTLS session and every poll
+after; none of the other 17 tokens moved and the `/alarms/vs/0` entries
+stayed `Deleted`.
+
+The rest of this file is kept as-is: the failed attempts below are still the
+best record of what *doesn't* work on this generation, and the reasoning
+that follows them explains why the reset looked cloud-only for as long as it
+did — a genuine trap worth knowing about before the next reset-adjacent
+mystery on this board family.
 
 ## What the reset actually is
 
-Samsung models it as a **command**, not a value write: capability
+A **command**, not a value write. Samsung's cloud models it as capability
 `custom.dustFilter`, command `resetDustFilter`, no arguments (implemented in
-several SmartThings HA forks; not in the core integration). That reframes
-every attempt below — nothing changes the counter by writing to it, because
-the board zeroes it itself on receiving a command.
+several SmartThings HA forks; not in the core integration) — that command
+name is real, but see below for why POSTing it directly went nowhere.
 
-## Tried, all against a live unit, all failed
+## Tried, all against a live unit, all failed (before the token above was found)
 
 - `FilterTime_0` via the single-token options merge that works for every
   other setting on this href — accepted with no error, then discarded. Tried
@@ -50,7 +58,18 @@ on `/rm/state/vs/0` was accepted (2.04 Changed, value held, restored
 afterwards), and `FilterAlarmTime_` is written through the very same options
 merge and kept. Writes work; this one value just isn't driven that way.
 
-## Where to look next
+## The token, and why the dead ends below missed it
+
+`FilterCleanAlarm_Clear` is not derived from anything in this file's earlier
+attempts — how it was originally identified isn't recorded here. What is
+recorded is why the standard technique (diff the appliance's reported state
+before/after triggering the action in Samsung's app) couldn't have found it
+on its own: the token is a trigger, never stored and never echoed back in
+`x.com.samsung.da.options`, so a before/after diff of stored state shows
+only the *effects* (counter zeroing, alarm clearing) and never the token
+that caused them.
+
+## Dead ends tried before the token was known (kept for the next unrelated mystery)
 
 - The `/actions/vs/0` action vocabulary from an independent source (a
   firmware image, or a capture of what the cloud sends the device).
diff --git a/tests/test_airconditioner_artik051_krac.py b/tests/test_airconditioner_artik051_krac.py
index 1034c94..5738b9e 100644
--- a/tests/test_airconditioner_artik051_krac.py
+++ b/tests/test_airconditioner_artik051_krac.py
@@ -261,6 +261,28 @@ def test_auto_clean_stop_stays_off_boards_without_the_token():
     assert "auto_clean_progress_legacy" not in _state("airconditioner_tp1x_rac")
 
 
+def test_filter_time_reset_writes_the_appliance_s_own_trigger_token():
+    """FilterCleanAlarm_Clear, measured on hardware: 2.04 Changed and
+    FilterTime_95 -> FilterTime_0, still zero on a fresh session and every poll
+    after. The token is a trigger the board acts on rather than a value it
+    stores -- it never appears in options[] -- so the button is gated on the
+    counter's own token being present, which is what says this board has a
+    filter timer at all."""
+    desc = _desc(_load_device(FIXTURE), "filter_time_reset")
+    assert desc is not None
+    assert desc.write_fn(desc.payload, {}) == (
+        ["mode", "vs", "0"],
+        {"x.com.samsung.da.options": ["FilterCleanAlarm_Clear"]},
+    )
+
+
+def test_filter_time_reset_stays_off_boards_without_the_counter():
+    """No FilterTime_ token, no counter to reset. Newer boards report filter
+    usage through their own resource and would need a different mechanism, so
+    offering a button that writes a legacy token there would be a guess."""
+    assert _desc(_load_device("airconditioner_tp1x_rac"), "filter_time_reset") is None
+
+
 def test_filter_alarm_time_stays_off_boards_with_a_real_threshold_resource():
     """Newer boards carry air_filter_threshold off supportedFilterDesiredUsage;
     two thresholds on one device would be a coin flip for the user.