diff --git a/plugins/platforms/photon/plugin.yaml b/plugins/platforms/photon/plugin.yaml
index 388bfc72dc5..562318520e1 100644
--- a/plugins/platforms/photon/plugin.yaml
+++ b/plugins/platforms/photon/plugin.yaml
@@ -63,8 +63,8 @@ optional_env:
     prompt: "Group mention patterns"
     password: false
   - name: PHOTON_HOME_CHANNEL
-    description: "Default Spectrum space id for cron / notification delivery"
-    prompt: "Home space id"
+    description: "Default Photon target for cron / notification delivery: Spectrum space id, DM GUID, or bare E.164 phone number"
+    prompt: "Home Photon target"
     password: false
   - name: PHOTON_HOME_CHANNEL_NAME
     description: "Human label for the home channel"
diff --git a/plugins/platforms/photon/sidecar/index.mjs b/plugins/platforms/photon/sidecar/index.mjs
index 5371a683d9a..52db54e6d5e 100644
--- a/plugins/platforms/photon/sidecar/index.mjs
+++ b/plugins/platforms/photon/sidecar/index.mjs
@@ -55,6 +55,9 @@ const sharedToken = process.env.PHOTON_SIDECAR_TOKEN;
 // single NDJSON line. Override via PHOTON_MAX_INLINE_ATTACHMENT_BYTES.
 const MAX_INLINE_ATTACHMENT_BYTES =
   Number(process.env.PHOTON_MAX_INLINE_ATTACHMENT_BYTES) || 20 * 1024 * 1024;
+const DM_CHAT_GUID_RE = /^any;-;(\+\d{6,})$/;
+const E164_RE = /^\+\d{6,}$/;
+const MAX_KNOWN_SPACES = 2048;
 
 if (!projectId || !projectSecret || !sharedToken) {
   console.error(
@@ -91,6 +94,34 @@ const app = await Spectrum({
 // At most one Python consumer is attached at a time (the gateway adapter).
 let consumerRes = null;
 let consumerWaiters = [];
+const knownSpaces = new Map();
+
+function rememberKnownSpace(id, space) {
+  if (!id || typeof id !== "string" || !space) return;
+  if (knownSpaces.has(id)) knownSpaces.delete(id);
+  knownSpaces.set(id, space);
+  if (knownSpaces.size > MAX_KNOWN_SPACES) {
+    const oldest = knownSpaces.keys().next().value;
+    if (oldest) knownSpaces.delete(oldest);
+  }
+}
+
+function phoneTargetFromSpaceId(spaceId) {
+  if (typeof spaceId !== "string") return null;
+  if (E164_RE.test(spaceId)) return spaceId;
+  const dmGuid = spaceId.match(DM_CHAT_GUID_RE);
+  return dmGuid ? dmGuid[1] : null;
+}
+
+function rememberInboundSpace(space, message) {
+  const msgSpace = message?.space || {};
+  const ids = [space?.id, msgSpace.id];
+  for (const id of ids) {
+    rememberKnownSpace(id, space);
+    const phone = phoneTargetFromSpaceId(id);
+    if (phone) rememberKnownSpace(phone, space);
+  }
+}
 
 function waitForConsumer() {
   if (consumerRes) return Promise.resolve();
@@ -215,6 +246,7 @@ async function normalizeEvent(space, message) {
       if (message && message.direction && message.direction !== "inbound") {
         continue;
       }
+      rememberInboundSpace(space, message);
       const event = await normalizeEvent(space, message);
       if (!event) continue;
       await deliver(JSON.stringify(event));
@@ -303,17 +335,26 @@ function handleInbound(req, res) {
 }
 
 async function resolveSpace(spaceId) {
+  const cached = knownSpaces.get(spaceId);
+  if (cached) return cached;
+
+  const phoneTarget = phoneTargetFromSpaceId(spaceId);
   // A bare E.164 phone number addresses a DM. Resolve the user, then the (DM)
   // space — `imessage(app).user(phone)` -> `im.space(user)` — so callers can
   // pass just "+1..." (e.g. PHOTON_HOME_CHANNEL for cron delivery) instead of
-  // an opaque inbound space id. Real inbound space ids never match this shape,
-  // so this only kicks in for phone-addressed sends.
-  if (typeof spaceId === "string" && /^\+\d{6,}$/.test(spaceId) && imessage) {
+  // an opaque inbound space id. Photon also represents DM chat ids as
+  // `any;-;+1...`; normalize those through the same path so replies to inbound
+  // DMs still resolve after Python stores the inbound `space.id`.
+  if (phoneTarget && imessage) {
     try {
       const im = imessage(app);
       if (typeof im.user === "function" && typeof im.space === "function") {
-        const user = await im.user(spaceId);
-        return await im.space(user);
+        const user = await im.user(phoneTarget);
+        const space = await im.space(user);
+        rememberKnownSpace(spaceId, space);
+        rememberKnownSpace(phoneTarget, space);
+        rememberKnownSpace(space?.id, space);
+        return space;
       }
     } catch (e) {
       console.error(
@@ -327,16 +368,25 @@ async function resolveSpace(spaceId) {
   // narrowed helpers; we fall back through a few accessor shapes to
   // tolerate small SDK API drift.
   if (typeof app.space === "function") {
-    return await app.space(spaceId);
+    const space = await app.space(spaceId);
+    rememberKnownSpace(spaceId, space);
+    rememberKnownSpace(space?.id, space);
+    return space;
   }
   if (app.spaces && typeof app.spaces.get === "function") {
-    return await app.spaces.get(spaceId);
+    const space = await app.spaces.get(spaceId);
+    rememberKnownSpace(spaceId, space);
+    rememberKnownSpace(space?.id, space);
+    return space;
   }
   if (imessage) {
     const im = imessage(app);
     if (typeof im.space === "function") {
       try {
-        return await im.space({ id: spaceId });
+        const space = await im.space({ id: spaceId });
+        rememberKnownSpace(spaceId, space);
+        rememberKnownSpace(space?.id, space);
+        return space;
       } catch {
         /* fall through */
       }
diff --git a/tests/tools/test_send_message_target_parse.py b/tests/tools/test_send_message_target_parse.py
new file mode 100644
index 00000000000..c3ad24576fb
--- /dev/null
+++ b/tests/tools/test_send_message_target_parse.py
@@ -0,0 +1,20 @@
+"""Parser-only tests for send_message targets.
+
+These stay separate from ``test_send_message_tool.py`` because that module
+skips wholesale when optional Telegram dependencies are not installed.
+"""
+
+from tools.send_message_tool import _parse_target_ref
+
+
+def test_photon_e164_target_is_explicit() -> None:
+    chat_id, thread_id, is_explicit = _parse_target_ref("photon", "+15551234567")
+
+    assert chat_id == "+15551234567"
+    assert thread_id is None
+    assert is_explicit is True
+
+
+def test_e164_target_still_requires_phone_platform() -> None:
+    assert _parse_target_ref("matrix", "+15551234567")[2] is False
+
diff --git a/tests/tools/test_send_message_tool.py b/tests/tools/test_send_message_tool.py
index 63f45e1e75c..d1afb6c4669 100644
--- a/tests/tools/test_send_message_tool.py
+++ b/tests/tools/test_send_message_tool.py
@@ -1199,6 +1199,11 @@ class TestParseTargetRefE164:
         assert chat_id == "+15551234567"
         assert is_explicit is True
 
+    def test_photon_e164_is_explicit(self):
+        chat_id, _, is_explicit = _parse_target_ref("photon", "+15551234567")
+        assert chat_id == "+15551234567"
+        assert is_explicit is True
+
     def test_signal_bare_digits_still_work(self):
         """Bare digit strings continue to match the generic numeric branch."""
         chat_id, _, is_explicit = _parse_target_ref("signal", "15551234567")
diff --git a/tools/send_message_tool.py b/tools/send_message_tool.py
index 83608044330..afa473e384b 100644
--- a/tools/send_message_tool.py
+++ b/tools/send_message_tool.py
@@ -38,7 +38,7 @@ _NUMERIC_TOPIC_RE = _TELEGRAM_TOPIC_TARGET_RE
 # below and falls through to channel-name resolution, which has no way to
 # resolve a raw phone number. Keeping the '+' preserves the E.164 form that
 # downstream adapters (signal, etc.) expect.
-_PHONE_PLATFORMS = frozenset({"signal", "sms", "whatsapp"})
+_PHONE_PLATFORMS = frozenset({"photon", "signal", "sms", "whatsapp"})
 _E164_TARGET_RE = re.compile(r"^\s*\+(\d{7,15})\s*$")
 # Email addresses — a valid email like "user@domain.com" should be treated as
 # an explicit target for the email platform, not fall through to channel-name