fix(telegram): grant in-chat members regardless of reported can_send

The CanSendMessages loop-guard skipped exactly the stuck case — a restricted
member whose chat_member event reports can_send=true yet who cannot actually
write. Replace it with a precise loop guard (skip only the bot's own restrict
action, i.e. the update whose performer is the bot) and grant any eligible
in-chat member (member or restricted) otherwise. Also log the new member's
can_send, is_member and the actor id for full visibility.

platform/telegram/internal/bot/bot.go

@@ -54,6 +54,9 @@ type Bot struct {
 	limiter *rate.Limiter
 	// chatID is the moderated discussion chat (0 disables gating).
 	chatID int64
+	// botID is the bot's own Telegram user id (resolved at startup); it skips the
+	// chat_member updates the bot's own restrict actions generate — the grant loop guard.
+	botID int64
 	// eligibility resolves a joining user's chat write eligibility; nil leaves a
 	// joiner muted (fail-closed) until it is wired.
 	eligibility EligibilityResolver
@@ -134,6 +137,7 @@ func (t *Bot) logChatAdminStatus(ctx context.Context) {
 		t.log.Warn("chat self-check: getMe failed", zap.Error(err))
 		return
 	}
+	t.botID = me.ID
 	m, err := t.api.GetChatMember(ctx, &tgbot.GetChatMemberParams{ChatID: t.chatID, UserID: me.ID})
 	if err != nil {
 		t.log.Warn("chat gating self-check failed: the bot cannot read the chat — is it added and is TELEGRAM_CHAT_ID the discussion group id?",
@@ -260,14 +264,19 @@ func (t *Bot) handleChatMember(ctx context.Context, cm *models.ChatMemberUpdated
 	if user != nil {
 		uid = user.ID
 	}
-	// Log every chat_member update the bot receives: this is the one place to see
-	// whether Telegram is delivering joins at all, for which chat, and the transition.
+	// Log every chat_member update the bot receives: the one place to see whether
+	// Telegram delivers joins, for which chat, the transition, who performed it, and the
+	// new member's send/membership state.
+	canSend, isMember := restrictedSendState(cm.NewChatMember)
 	t.log.Info("chat_member update",
 		zap.Int64("chat_id", cm.Chat.ID),
 		zap.Int64("configured_chat_id", t.chatID),
 		zap.Int64("user_id", uid),
+		zap.Int64("actor_id", cm.From.ID),
 		zap.String("old_status", string(cm.OldChatMember.Type)),
-		zap.String("new_status", string(cm.NewChatMember.Type)))
+		zap.String("new_status", string(cm.NewChatMember.Type)),
+		zap.Bool("new_can_send", canSend),
+		zap.Bool("new_is_member", isMember))
 
 	if t.chatID == 0 || cm.Chat.ID != t.chatID {
 		return
@@ -275,22 +284,19 @@ func (t *Bot) handleChatMember(ctx context.Context, cm *models.ChatMemberUpdated
 	if user == nil || user.IsBot {
 		return
 	}
-	// (Re)grant write to an eligible user who is in the chat but cannot yet send: a join
-	// into the default-deny chat (where a joined member appears `restricted`, sometimes
-	// `member`) or a restricted member still lacking send rights. A user who can already
-	// send is skipped — which also breaks the feedback loop from the bot's own grant,
-	// since restricting re-fires a chat_member event. Revoking a now-ineligible user is
-	// the chat-gate path's job (an admin block or chat_muted change), not this one.
+	// Loop guard: the bot's own restrict re-fires a chat_member update whose performer is
+	// the bot; skip those so a grant never re-triggers itself.
+	if t.botID != 0 && cm.From.ID == t.botID {
+		return
+	}
+	// Act only on a user who is in the chat (member or restricted) — a join into the
+	// default-deny chat appears as `restricted`, not `member`. Left/kicked and admins
+	// have nothing to grant here. An eligible user is (re)granted write; revoking a
+	// now-ineligible user is the chat-gate path's job (an admin block or chat_muted).
 	switch cm.NewChatMember.Type {
-	case models.ChatMemberTypeMember:
-		// A plain member follows the chat default; in the gated (default-deny) chat that
-		// denies sending, so (re)grant.
-	case models.ChatMemberTypeRestricted:
-		if cm.NewChatMember.Restricted.CanSendMessages {
-			return // already allowed to send
-		}
+	case models.ChatMemberTypeMember, models.ChatMemberTypeRestricted:
 	default:
-		return // left / kicked / administrator / owner — nothing to grant here
+		return
 	}
 	if t.eligibility == nil {
 		t.log.Warn("chat access: eligibility resolver not wired", zap.Int64("user_id", uid))
@@ -372,6 +378,16 @@ func chatWritePerms() models.ChatPermissions {
 	}
 }
 
+// restrictedSendState returns a restricted member's text-send permission and whether
+// they are currently a member of the chat; (false, false) for any non-restricted
+// status (the fields exist only on the restricted variant).
+func restrictedSendState(m models.ChatMember) (canSend, isMember bool) {
+	if m.Type == models.ChatMemberTypeRestricted && m.Restricted != nil {
+		return m.Restricted.CanSendMessages, m.Restricted.IsMember
+	}
+	return false, false
+}
+
 // chatMemberUser returns the user a ChatMember refers to across the union variants,
 // or nil for an unrecognised type.
 func chatMemberUser(m models.ChatMember) *models.User {

platform/telegram/internal/bot/chat_test.go

@@ -3,6 +3,7 @@ package bot
 import (
 	"context"
 	"encoding/json"
+	"fmt"
 	"io"
 	"net/http"
 	"net/http/httptest"
@@ -13,7 +14,10 @@ import (
 	"go.uber.org/zap"
 )
 
-const testChatID = 555
+const (
+	testChatID = 555
+	botSelfID  = 111111 // the bot's own id in tests (for the loop guard)
+)
 
 // chatAPI is a fake Bot API for the chat-gating tests: it answers getMe, returns a
 // scripted getChatMember status, and records restrictChatMember calls.
@@ -59,6 +63,7 @@ func newChatBot(t *testing.T, api *chatAPI) *Bot {
 	if err != nil {
 		t.Fatalf("new bot: %v", err)
 	}
+	b.botID = botSelfID // normally set at startup; the chat_member updates default actor 0 != this
 	return b
 }
 
@@ -109,14 +114,22 @@ func TestHandleChatMemberGrantsEligibleMemberJoin(t *testing.T) {
 }
 
 func TestHandleChatMemberGrantsRestrictedMember(t *testing.T) {
-	// A default-deny group reports a present member as restricted with no send right —
-	// the real-world case. Both a fresh join (left->restricted) and an already-present
-	// restricted member (restricted->restricted) must be granted when eligible.
-	for _, oldType := range []models.ChatMemberType{models.ChatMemberTypeLeft, models.ChatMemberTypeRestricted} {
-		t.Run(string(oldType), func(t *testing.T) {
+	// A default-deny group reports a present member as restricted — the real-world case.
+	// A fresh join (left->restricted) or an already-present restricted member
+	// (restricted->restricted), and regardless of the reported can_send (which can be
+	// misleading), an eligible member is granted.
+	for _, tc := range []struct {
+		old     models.ChatMemberType
+		canSend bool
+	}{
+		{models.ChatMemberTypeLeft, false},
+		{models.ChatMemberTypeRestricted, false},
+		{models.ChatMemberTypeRestricted, true},
+	} {
+		t.Run(fmt.Sprintf("%s_cansend=%v", tc.old, tc.canSend), func(t *testing.T) {
 			api := &chatAPI{}
 			b := eligibleBot(t, api, true, nil)
-			b.handleChatMember(context.Background(), restrictedUpdate(testChatID, 777, oldType, false))
+			b.handleChatMember(context.Background(), restrictedUpdate(testChatID, 777, tc.old, tc.canSend))
 			if len(api.restricts) != 1 || !api.restricts[0].canSend {
 				t.Fatalf("restricts = %+v, want one grant for a restricted member", api.restricts)
 			}
@@ -124,14 +137,16 @@ func TestHandleChatMemberGrantsRestrictedMember(t *testing.T) {
 	}
 }
 
-func TestHandleChatMemberSkipsAlreadyAllowed(t *testing.T) {
-	// The bot's own grant re-fires a chat_member event (restricted, can_send=true); it
-	// must not loop into another grant.
+func TestHandleChatMemberSkipsBotsOwnAction(t *testing.T) {
+	// The bot's own grant re-fires a chat_member update performed by the bot; it must be
+	// skipped so a grant never loops into another grant.
 	api := &chatAPI{}
 	b := eligibleBot(t, api, true, nil)
-	b.handleChatMember(context.Background(), restrictedUpdate(testChatID, 777, models.ChatMemberTypeRestricted, true))
+	upd := restrictedUpdate(testChatID, 777, models.ChatMemberTypeRestricted, false)
+	upd.From = models.User{ID: botSelfID}
+	b.handleChatMember(context.Background(), upd)
 	if len(api.restricts) != 0 {
-		t.Fatalf("restricts = %+v, want none for an already-allowed member (no loop)", api.restricts)
+		t.Fatalf("restricts = %+v, want none for the bot's own action (no loop)", api.restricts)
 	}
 }