Fix context pruner adding an instructions prompt message

Author: jahooma

.agents/context-pruner.ts

@@ -24,6 +24,7 @@ const definition: AgentDefinition = {
     },
   },
 
+  inheritParentSystemPrompt: true,
   includeMessageHistory: true,
 
   handleSteps: function* ({ agentState, params, logger }) {
@@ -163,8 +164,14 @@ const definition: AgentDefinition = {
         .filter((m): m is Message => m !== null)
     }
 
-    // PASS 0: Validate and fix tool-call/tool-result pairs
-    let currentMessages = removeOrphanedToolMessages([...messages])
+    // PASS 0: Remove last instructions prompt message.
+    let currentMessages = [...messages]
+    const lastInstructionsPromptIndex = currentMessages.findLastIndex(
+      (message) => message.tags?.includes('INSTRUCTIONS_PROMPT'),
+    )
+    if (lastInstructionsPromptIndex !== -1) {
+      currentMessages.splice(lastInstructionsPromptIndex, 1)
+    }
 
     // Initial check - if already under limit, return
     const initialTokens = countMessagesTokens(currentMessages)

packages/agent-runtime/src/templates/strings.ts

@@ -190,7 +190,11 @@ export async function getAgentPrompt<T extends StringField>(
   if (promptType.type === 'instructionsPrompt' && agentState.agentType) {
     // Add subagent tools message when using parent's tools for prompt caching
     if (useParentTools) {
-      addendum += `\n\nYou are a subagent that only has access to the following tools: ${agentTemplate.toolNames.join(', ')}. Do not attempt to use any other tools.`
+      if (agentTemplate.toolNames.length > 0) {
+        addendum += `\n\nYou are a subagent that only has access to the following tools: ${agentTemplate.toolNames.join(', ')}. Do not attempt to use any other tools.`
+      } else {
+        addendum += `\n\nYou are a subagent and do not have access to any tools specified earlier in the conversation.`
+      }
 
       // For subagents with inheritSystemPrompt, include full spawnable agents spec
       // since the parent's system prompt may not have these agents listed