Exclude tool call errors from last_message and all_messages subagent output

Author: jahooma

packages/agent-runtime/src/tools/stream-parser.ts

@@ -114,11 +114,12 @@ export async function processStream(
         if (chunk.type === 'error') {
           hadToolCallError = true
           errorMessages.push(
-            userMessage(
-              withSystemTags(
+            userMessage({
+              content: withSystemTags(
                 `Error during tool call: ${chunk.message}. Please check the tool name and arguments and try again.`,
               ),
-            ),
+              tags: ['TOOL_CALL_ERROR'],
+            }),
           )
         }
       }
@@ -304,11 +305,12 @@ export async function processStream(
         onResponseChunk(chunk)
         hadToolCallError = true
         errorMessages.push(
-          userMessage(
-            withSystemTags(
+          userMessage({
+            content: withSystemTags(
               `Error during tool call: ${chunk.message}. Please check the tool name and arguments and try again.`,
             ),
-          ),
+            tags: ['TOOL_CALL_ERROR'],
+          }),
         )
       } else if (chunk.type === 'tool-call') {
       } else {

packages/agent-runtime/src/util/agent-output.ts

@@ -5,12 +5,29 @@ import type {
   AgentOutput,
 } from '@codebuff/common/types/session-state'
 
+/** Messages tagged with these tags are stripped from agent output. */
+const EXCLUDED_OUTPUT_TAGS = ['TOOL_CALL_ERROR'] as const
+
+function isExcludedFromOutput(message: Message): boolean {
+  return !!message.tags?.some((t) =>
+    (EXCLUDED_OUTPUT_TAGS as readonly string[]).includes(t),
+  )
+}
+
 /**
- * Get the last assistant turn messages, which includes the last assistant message
- * and any subsequent tool messages that are responses to its tool calls.
+ * Get the last assistant turn messages, which includes the last assistant
+ * message and any subsequent tool messages that are responses to its tool
+ * calls.
+ *
+ * Turn selection walks the raw `messageHistory` so that user-role messages
+ * (including synthesized TOOL_CALL_ERROR ones) correctly bound the turn —
+ * otherwise a failed attempt + its retry would get conflated into a single
+ * "turn". Exclusion filtering is applied *after* selection: TOOL_CALL_ERROR
+ * messages are user-role so they never enter `result` anyway (the role check
+ * below stops at user messages), but keeping the filter explicit documents
+ * the contract that no excluded tags leak into agent output.
  */
 function getLastAssistantTurnMessages(messageHistory: Message[]): Message[] {
-  // Find the index of the last assistant message
   let lastAssistantIndex = -1
   for (let i = messageHistory.length - 1; i >= 0; i--) {
     if (messageHistory[i].role === 'assistant') {
@@ -29,19 +46,18 @@ function getLastAssistantTurnMessages(messageHistory: Message[]): Message[] {
     return []
   }
 
-  // Collect the assistant message and all subsequent tool messages
   const result: Message[] = []
   for (let i = lastAssistantIndex; i < messageHistory.length; i++) {
     const message = messageHistory[i]
     if (message.role === 'assistant' || message.role === 'tool') {
       result.push(message)
     } else {
-      // Stop if we hit a user or system message
+      // Stop if we hit a user or system message.
       break
     }
   }
 
-  return result
+  return result.filter((m) => !isExcludedFromOutput(m))
 }
 
 export function getAgentOutput(
@@ -71,7 +87,9 @@ export function getAgentOutput(
   }
   if (agentTemplate.outputMode === 'all_messages') {
     // Remove the first message, which includes the previous conversation history.
-    const agentMessages = agentState.messageHistory.slice(1)
+    const agentMessages = agentState.messageHistory
+      .slice(1)
+      .filter((m) => !isExcludedFromOutput(m))
     return {
       type: 'allMessages',
       value: agentMessages,