diff --git a/container/agent-runner/src/formatter.ts b/container/agent-runner/src/formatter.ts
index 590875c9e3..7b9f44a0aa 100644
--- a/container/agent-runner/src/formatter.ts
+++ b/container/agent-runner/src/formatter.ts
@@ -82,10 +82,11 @@ export function isRunnerCommand(msg: MessageInRow): boolean {
 function extractSenderId(msg: MessageInRow, content: any): string | null {
   const raw: string | null = content?.senderId || content?.author?.userId || null;
   if (!raw) return null;
-  // Already namespaced (e.g. "telegram:123") — use as-is.
-  if (raw.includes(':')) return raw;
-  // Raw platform id from chat-sdk serialization — prefix with channel type.
   if (!msg.channel_type) return raw;
+  // Already namespaced for this channel — use as-is. `includes(':')` would be
+  // wrong here: Teams Bot Framework user ids like `29:1abc...` natively
+  // contain a colon and would slip through unprefixed.
+  if (raw.startsWith(`${msg.channel_type}:`)) return raw;
   return `${msg.channel_type}:${raw}`;
 }
 
diff --git a/src/modules/permissions/index.ts b/src/modules/permissions/index.ts
index 67adfe771b..d6ca6909da 100644
--- a/src/modules/permissions/index.ts
+++ b/src/modules/permissions/index.ts
@@ -90,7 +90,11 @@ function extractAndUpsertUser(event: InboundEvent): string | null {
   const rawHandle = senderIdField ?? senderField ?? authorUserId;
   if (!rawHandle) return null;
 
-  const userId = rawHandle.includes(':') ? rawHandle : `${event.channelType}:${rawHandle}`;
+  // Namespace the handle as `<channel>:<handle>` unless it's already namespaced
+  // for this channel. `includes(':')` is wrong: Teams Bot Framework user ids
+  // like `29:1abc...` natively contain a colon, so that check would skip the
+  // prefix and produce `29:1abc...` instead of `teams:29:1abc...`.
+  const userId = rawHandle.startsWith(`${event.channelType}:`) ? rawHandle : `${event.channelType}:${rawHandle}`;
   if (!getUser(userId)) {
     upsertUser({
       id: userId,
@@ -227,11 +231,11 @@ async function handleSenderApprovalResponse(payload: ResponsePayload): Promise<b
   if (!row) return false;
 
   // payload.userId is the raw platform userId (e.g. "6037840640"); namespace it
-  // with the channel type so it matches users(id) format. Some platforms
-  // (e.g. Teams "29:xxx") already include a colon — mirror resolveOrCreateUser
-  // logic and only prefix when the raw id has no colon.
+  // with the channel type so it matches users(id) format. Teams ids like
+  // "29:xxx" natively contain a colon, so we can't use `includes(':')` as the
+  // "already namespaced" check — match by channel-type prefix instead.
   const clickerId = payload.userId
-    ? payload.userId.includes(':')
+    ? payload.userId.startsWith(`${payload.channelType}:`)
       ? payload.userId
       : `${payload.channelType}:${payload.userId}`
     : null;
@@ -312,7 +316,7 @@ async function handleChannelApprovalResponse(payload: ResponsePayload): Promise<
   if (!row) return false;
 
   const clickerId = payload.userId
-    ? payload.userId.includes(':')
+    ? payload.userId.startsWith(`${payload.channelType}:`)
       ? payload.userId
       : `${payload.channelType}:${payload.userId}`
     : null;
diff --git a/src/modules/permissions/sender-approval.test.ts b/src/modules/permissions/sender-approval.test.ts
index f037fa8486..1f63e39f03 100644
--- a/src/modules/permissions/sender-approval.test.ts
+++ b/src/modules/permissions/sender-approval.test.ts
@@ -143,7 +143,7 @@ function stranger(text: string) {
       id: `stranger-${Math.random().toString(36).slice(2, 8)}`,
       kind: 'chat' as const,
       content: JSON.stringify({
-        senderId: 'tg:stranger',
+        senderId: 'stranger-tg-id',
         senderName: 'Stranger',
         text,
       }),
@@ -220,7 +220,7 @@ describe('unknown-sender request_approval flow', () => {
     // Member row added for the stranger against the wired agent group.
     const member = getDb()
       .prepare('SELECT 1 AS x FROM agent_group_members WHERE user_id = ? AND agent_group_id = ?')
-      .get('tg:stranger', 'ag-1');
+      .get('telegram:stranger-tg-id', 'ag-1');
     expect(member).toBeDefined();
 
     // Pending row cleared.
@@ -258,7 +258,7 @@ describe('unknown-sender request_approval flow', () => {
     expect(count).toBe(0);
     const member = getDb()
       .prepare('SELECT 1 AS x FROM agent_group_members WHERE user_id = ? AND agent_group_id = ?')
-      .get('tg:stranger', 'ag-1');
+      .get('telegram:stranger-tg-id', 'ag-1');
     expect(member).toBeUndefined();
   });
 
@@ -292,7 +292,7 @@ describe('unknown-sender request_approval flow', () => {
     // No member added for the stranger.
     const member = getDb()
       .prepare('SELECT 1 AS x FROM agent_group_members WHERE user_id = ? AND agent_group_id = ?')
-      .get('tg:stranger', 'ag-1');
+      .get('telegram:stranger-tg-id', 'ag-1');
     expect(member).toBeUndefined();
 
     // Pending row is still there — a legitimate approver can still act on it.
@@ -338,7 +338,7 @@ describe('unknown-sender request_approval flow', () => {
     // Stranger admitted thanks to the admin's authority.
     const member = getDb()
       .prepare('SELECT 1 AS x FROM agent_group_members WHERE user_id = ? AND agent_group_id = ?')
-      .get('tg:stranger', 'ag-1');
+      .get('telegram:stranger-tg-id', 'ag-1');
     expect(member).toBeDefined();
   });
 });