fix: prevent agent message template feedback (#20042)

internal/service/agent.go

@@ -2310,7 +2310,7 @@ func (s *AgentService) buildRunFunc(canvasID string, versionRow *entity.UserCanv
 				return state, err
 			}
 			if shouldTreatAsCompletedLoopRun(err, answer) {
-				appendAssistantHistory(state, assistantOutput)
+				appendAssistantHistory(state, partialAssistantOutput(answer, downloads, attachment))
 				if persistErr := s.persistAgentRunSession(ctx, canvasID, userID, sessionID, messageID, userInput, answer, thinking, referencePayload, dsl, state, true); persistErr != nil {
 					s.markRunFailed(ctx2, runID, "persist session: "+persistErr.Error())
 					return nil, canvas.NewInternalRunError(
@@ -2331,7 +2331,7 @@ func (s *AgentService) buildRunFunc(canvasID string, versionRow *entity.UserCanv
 
 				wfPayload := map[string]interface{}{
 					"inputs":       map[string]any{"query": userInput},
-					"outputs":      workflowOutputs(answer, downloads, attachment),
+					"outputs":      workflowOutputsFromTerminal(assistantOutput),
 					"elapsed_time": now - startedAt,
 					"created_at":   now,
 				}
@@ -2370,8 +2370,11 @@ func (s *AgentService) buildRunFunc(canvasID string, versionRow *entity.UserCanv
 			return nil, canvasInvokeError(err)
 		}
 
-		// Emit message + message_end (mirrors Python's ans dict).
-		appendAssistantHistory(state, assistantOutput)
+		// Persist the Agent answer for subsequent Agent prompts. The terminal
+		// Message output is presentation data and may wrap the answer with
+		// template literals; retaining it in the prompt history makes the model
+		// reproduce and amplify those literals on later turns.
+		appendAssistantHistory(state, partialAssistantOutput(answer, downloads, attachment))
 		if persistErr := s.persistAgentRunSession(ctx, canvasID, userID, sessionID, messageID, userInput, answer, thinking, referencePayload, dsl, state, true); persistErr != nil {
 			s.markRunFailed(ctx2, runID, "persist session: "+persistErr.Error())
 			return nil, canvas.NewInternalRunError(
@@ -2394,7 +2397,7 @@ func (s *AgentService) buildRunFunc(canvasID string, versionRow *entity.UserCanv
 		// per-run token usage across all LLM calls in this turn.
 		wfPayload := map[string]interface{}{
 			"inputs":       map[string]any{"query": userInput},
-			"outputs":      workflowOutputs(answer, downloads, attachment),
+			"outputs":      workflowOutputsFromTerminal(assistantOutput),
 			"elapsed_time": now - startedAt,
 			"created_at":   now,
 		}
@@ -2506,6 +2509,17 @@ func workflowOutputs(content string, downloads, attachment any) any {
 	return out
 }
 
+// workflowOutputsFromTerminal preserves the terminal component's complete
+// visible content in workflow_finished while retaining the established compact
+// string shape when it has no downloads or attachment.
+func workflowOutputsFromTerminal(output map[string]any) any {
+	if len(output) == 0 {
+		return ""
+	}
+	content, _ := output["content"].(string)
+	return workflowOutputs(content, output["downloads"], output["attachment"])
+}
+
 // emptyAttachmentValue reports whether an attachment descriptor is
 // absent or empty (nil or an empty map), matching the omitempty
 // semantics of the message_end frame.

internal/service/agent_run_e2e_test.go

@@ -327,8 +327,8 @@ func TestRunAgent_SessionHistoryFeedsSysHistoryAndPersists(t *testing.T) {
 	}
 	if !strings.HasPrefix(secondHistory[0], "assistant: ") ||
 		!strings.Contains(secondHistory[0], `'content': '["user: hi"]'`) ||
-		!strings.Contains(secondHistory[0], `'downloads': []`) {
-		t.Fatalf("assistant history entry = %q, want persisted Message content and downloads", secondHistory[0])
+		strings.Contains(secondHistory[0], `'downloads': []`) {
+		t.Fatalf("assistant history entry = %q, want raw Agent output without Message presentation fields", secondHistory[0])
 	}
 	if secondHistory[1] != "user: again" || secondHistory[2] != "user: hi" {
 		t.Fatalf("sorted user history = %#v, want [user: again, user: hi]", secondHistory[1:])

internal/service/agent_test.go

@@ -407,6 +407,33 @@ func TestWorkflowOutputs_WithAttachment(t *testing.T) {
 	}
 }
 
+func TestWorkflowOutputsFromTerminalUsesMessageContent(t *testing.T) {
+	output := map[string]any{
+		"content":   "****\nvisible answer\n++++",
+		"downloads": []any{},
+	}
+	if got := workflowOutputsFromTerminal(output); got != "****\nvisible answer\n++++" {
+		t.Fatalf("workflowOutputsFromTerminal = %#v, want complete Message content", got)
+	}
+}
+
+func TestPartialAssistantOutputExcludesMessagePresentation(t *testing.T) {
+	state := canvas.NewCanvasState("run-history", "session-history")
+	appendAssistantHistory(state, partialAssistantOutput("model answer", nil, nil))
+
+	history := state.SnapshotHistory()
+	if len(history) != 1 {
+		t.Fatalf("history length = %d, want 1", len(history))
+	}
+	if history[0]["content"] != "model answer" {
+		t.Fatalf("history content = %#v, want raw Agent answer", history[0]["content"])
+	}
+	payload, _ := history[0]["payload"].(map[string]any)
+	if _, ok := payload["downloads"]; ok {
+		t.Fatalf("history payload unexpectedly contains Message presentation fields: %#v", payload)
+	}
+}
+
 // TestGetVersion_Success verifies getting a specific version by ID.
 func TestGetVersion_Success(t *testing.T) {
 	testDB := setupServiceTestDB(t)