fix: prevent protected tools from being pruned

Author: Tarquinen

lib/messages/utils.ts

@@ -103,11 +103,24 @@ export function buildToolIdList(messages: WithParts[]): string[] {
     return toolIds
 }
 
-export function getPruneToolIds(numericToolIds: number[], toolIdList: string[]): string[] {
+export interface GetPruneToolIdsOptions {
+    numericToolIds: number[]
+    toolIdList: string[]
+    toolParameters: Map<string, { tool: string }>
+    protectedTools: string[]
+}
+
+export function getPruneToolIds(options: GetPruneToolIdsOptions): string[] {
+    const { numericToolIds, toolIdList, toolParameters, protectedTools } = options
     const pruneToolIds: string[] = []
     for (const index of numericToolIds) {
         if (!isNaN(index) && index >= 0 && index < toolIdList.length) {
-            pruneToolIds.push(toolIdList[index])
+            const id = toolIdList[index]
+            const metadata = toolParameters.get(id)
+            if (metadata && protectedTools.includes(metadata.tool)) {
+                continue
+            }
+            pruneToolIds.push(id)
         }
     }
     return pruneToolIds

lib/prompts/tool.txt

@@ -1,7 +1,7 @@
 Prunes tool outputs from context to manage conversation size and reduce noise.
 
 ## IMPORTANT: The Prunable List
-A `<prunable-tools>` list is injected into user messages showing available tool outputs you can prune. Each line has the format `ID: tool, parameter` (e.g., `20: read, /path/to/file.ts`). Use these numeric IDs to select which tools to prune.
+A `<prunable-tools>` list is injected into user messages showing available tool outputs you can prune. Each line has the format `ID: tool, parameter` (e.g., `20: read, /path/to/file.ts`). You MUST only use numeric IDs that appear in this list to select which tools to prune.
 
 ## CRITICAL: When and How to Prune
 

lib/strategies/prune-tool.ts

@@ -70,7 +70,12 @@ export function createPruneTool(
 
             const currentAgent: string | undefined = findCurrentAgent(messages)
             const toolIdList: string[] = buildToolIdList(messages)
-            const pruneToolIds: string[] = getPruneToolIds(numericToolIds, toolIdList)
+            const pruneToolIds: string[] = getPruneToolIds({
+                numericToolIds,
+                toolIdList,
+                toolParameters: state.toolParameters,
+                protectedTools: config.strategies.pruneTool.protectedTools
+            })
             state.prune.toolIds.push(...pruneToolIds)
 
             const toolMetadata = new Map<string, ToolParameterEntry>()