fix(trigger): allow on_comment when thread root @mentions assignee agent (#382)

When a member-started thread root @mentions the assignee agent, replies
in that thread should trigger on_comment — the thread is a conversation
with the agent, not a member-to-member chat.

Previously isReplyToMemberThread only checked the reply content for
assignee mentions. Now it also checks the parent (thread root) content.
This fixes a gap where path 1 (on_comment) suppressed the trigger and
path 2 (on_mention) skipped the assignee, leaving no trigger path.

server/cmd/server/comment_trigger_integration_test.go

@@ -230,6 +230,20 @@ func TestCommentTriggerOnComment(t *testing.T) {
 			t.Errorf("expected 1 pending task (assignee mentioned in member thread), got %d", n)
 		}
 	})
+
+	t.Run("reply to member thread that @mentioned assignee triggers without re-mention", func(t *testing.T) {
+		clearTasks(t, issueID)
+		// Member starts a thread that @mentions the assignee agent.
+		content := fmt.Sprintf("[@Agent](mention://agent/%s) can you review this?", agentID)
+		threadID := postComment(t, issueID, content, nil)
+		// Clear the task created by the top-level mention.
+		clearTasks(t, issueID)
+		// Reply in the thread WITHOUT re-mentioning the assignee.
+		postComment(t, issueID, "Here is more context for you", strPtr(threadID))
+		if n := countPendingTasks(t, issueID); n != 1 {
+			t.Errorf("expected 1 pending task (assignee mentioned in thread root), got %d", n)
+		}
+	})
 }
 
 // TestCommentTriggerAtAllSuppression verifies that @all mentions do not

server/internal/handler/comment.go

@@ -227,6 +227,8 @@ func (h *Handler) commentMentionsOthersButNotAssignee(content string, issue db.I
 // continuing a human conversation — not requesting work from the assigned agent.
 // Replying to an agent-started thread, or explicitly @mentioning the assignee
 // in the reply, still triggers on_comment as expected.
+// If the parent (thread root) itself @mentions the assignee, the thread is
+// considered a conversation with the agent, so replies are allowed to trigger.
 func (h *Handler) isReplyToMemberThread(parent *db.Comment, content string, issue db.Issue) bool {
 	if parent == nil {
 		return false // Not a reply — normal top-level comment
@@ -235,14 +237,22 @@ func (h *Handler) isReplyToMemberThread(parent *db.Comment, content string, issu
 		return false // Thread started by an agent — allow trigger
 	}
 	// Thread was started by a member. Suppress on_comment unless the reply
-	// explicitly @mentions the assignee agent.
+	// or the parent explicitly @mentions the assignee agent.
 	if !issue.AssigneeID.Valid {
 		return true // No assignee to mention
 	}
 	assigneeID := uuidToString(issue.AssigneeID)
+	// Check current comment mentions.
 	for _, m := range util.ParseMentions(content) {
 		if m.ID == assigneeID {
-			return false // Assignee explicitly mentioned — allow trigger
+			return false // Assignee explicitly mentioned in reply — allow trigger
+		}
+	}
+	// Check parent (thread root) mentions — if the thread was started by
+	// mentioning the assignee, replies continue that conversation.
+	for _, m := range util.ParseMentions(parent.Content) {
+		if m.ID == assigneeID {
+			return false // Assignee mentioned in thread root — allow trigger
 		}
 	}
 	return true // Reply to member thread without mentioning agent — suppress

server/internal/handler/trigger_test.go

@@ -117,8 +117,20 @@ func TestIsReplyToMemberThread(t *testing.T) {
 	h := &Handler{}
 	issue := issueWithAgentAssignee()
 
-	memberParent := &db.Comment{AuthorType: "member", AuthorID: testUUID(memberID)}
-	agentParent := &db.Comment{AuthorType: "agent", AuthorID: testUUID(agentAssigneeID)}
+	memberParent := &db.Comment{AuthorType: "member", AuthorID: testUUID(memberID), Content: "plain thread starter"}
+	agentParent := &db.Comment{AuthorType: "agent", AuthorID: testUUID(agentAssigneeID), Content: "agent thread starter"}
+	// Member-started thread root that @mentions the assignee agent.
+	memberParentMentioningAssignee := &db.Comment{
+		AuthorType: "member",
+		AuthorID:   testUUID(memberID),
+		Content:    fmt.Sprintf("[@Agent](mention://agent/%s) can you look at this?", agentAssigneeID),
+	}
+	// Member-started thread root that @mentions a non-assignee agent.
+	memberParentMentioningOther := &db.Comment{
+		AuthorType: "member",
+		AuthorID:   testUUID(memberID),
+		Content:    fmt.Sprintf("[@Other](mention://agent/%s) what do you think?", otherAgentID),
+	}
 
 	tests := []struct {
 		name    string
@@ -168,6 +180,18 @@ func TestIsReplyToMemberThread(t *testing.T) {
 			content: fmt.Sprintf("[@Other](mention://agent/%s) take a look", otherAgentID),
 			want:    true,
 		},
+		{
+			name:    "reply to member thread that @mentioned assignee, no re-mention → allow",
+			parent:  memberParentMentioningAssignee,
+			content: "here is more context for you",
+			want:    false,
+		},
+		{
+			name:    "reply to member thread that @mentioned other agent, no re-mention → suppress",
+			parent:  memberParentMentioningOther,
+			content: "here is more context",
+			want:    true, // parent mentioned other agent, not assignee — still suppress on_comment
+		},
 	}
 
 	for _, tt := range tests {
@@ -188,8 +212,13 @@ func TestOnCommentTriggerDecision(t *testing.T) {
 	h := &Handler{}
 	issue := issueWithAgentAssignee()
 
-	memberParent := &db.Comment{AuthorType: "member", AuthorID: testUUID(memberID)}
-	agentParent := &db.Comment{AuthorType: "agent", AuthorID: testUUID(agentAssigneeID)}
+	memberParent := &db.Comment{AuthorType: "member", AuthorID: testUUID(memberID), Content: "plain thread starter"}
+	agentParent := &db.Comment{AuthorType: "agent", AuthorID: testUUID(agentAssigneeID), Content: "agent thread starter"}
+	memberParentMentioningAssignee := &db.Comment{
+		AuthorType: "member",
+		AuthorID:   testUUID(memberID),
+		Content:    fmt.Sprintf("[@Agent](mention://agent/%s) help me", agentAssigneeID),
+	}
 
 	// Simulates the combined check from CreateComment:
 	//   !commentMentionsOthersButNotAssignee && !isReplyToMemberThread
@@ -213,6 +242,7 @@ func TestOnCommentTriggerDecision(t *testing.T) {
 		{"reply member thread, no mention", memberParent, "agreed", false},
 		{"reply member thread, mention other member", memberParent, fmt.Sprintf("[@Bob](mention://member/%s) ok", memberID), false},
 		{"reply member thread, mention assignee", memberParent, fmt.Sprintf("[@Agent](mention://agent/%s) help", agentAssigneeID), true},
+		{"reply member thread that @mentioned assignee, no re-mention", memberParentMentioningAssignee, "here is more info", true},
 		{"top-level, @all broadcast", nil, "[@All](mention://all/all) heads up team", false},
 		{"reply agent thread, @all broadcast", agentParent, "[@All](mention://all/all) update for everyone", false},
 		{"reply member thread, @all broadcast", memberParent, "[@All](mention://all/all) fyi", false},