fix: don't add synth instruction after DCP "ignored" summary messages - extract synth instruction to its own file

Author: spoons-and-mirrors

index.ts

@@ -5,6 +5,7 @@ import { Logger } from "./lib/logger"
 import { Janitor, type SessionStats } from "./lib/janitor"
 import { checkForUpdates } from "./lib/version-checker"
 import { loadPrompt } from "./lib/prompt"
+import { injectSynthInstruction } from "./lib/synth-instruction"
 
 async function isSubagentSession(client: any, sessionID: string): Promise<boolean> {
     try {
@@ -61,37 +62,6 @@ const plugin: Plugin = (async (ctx) => {
         }
     }
 
-    // Inject synthInstruction into the last user message
-    const injectSynthInstruction = (messages: any[]): boolean => {
-        // Find the last user message
-        for (let i = messages.length - 1; i >= 0; i--) {
-            const msg = messages[i]
-            if (msg.role === 'user') {
-                const instruction = TOOL_SYNTH_INSTRUCTION
-
-                // Avoid double-injecting the same instruction
-                if (typeof msg.content === 'string') {
-                    if (msg.content.includes(instruction)) {
-                        return false
-                    }
-                    msg.content = msg.content + '\n\n' + instruction
-                } else if (Array.isArray(msg.content)) {
-                    const alreadyInjected = msg.content.some(
-                        (part: any) => part?.type === 'text' && typeof part.text === 'string' && part.text.includes(instruction)
-                    )
-                    if (alreadyInjected) {
-                        return false
-                    }
-                    msg.content.push({
-                        type: 'text',
-                        text: instruction
-                    })
-                }
-                return true
-            }
-        }
-        return false
-    }
 
     // Global fetch wrapper - caches tool parameters, injects instructions, and performs pruning
     const originalGlobalFetch = globalThis.fetch
@@ -106,7 +76,7 @@ const plugin: Plugin = (async (ctx) => {
 
                     // Inject synthInstruction for the context_pruning tool
                     if (config.strategies.onTool.length > 0) {
-                        if (injectSynthInstruction(body.messages)) {
+                        if (injectSynthInstruction(body.messages, TOOL_SYNTH_INSTRUCTION)) {
                             logger.debug("fetch", "Injected synthInstruction")
                             modified = true
                         }

lib/synth-instruction.ts

@@ -0,0 +1,47 @@
+export function isIgnoredUserMessage(msg: any): boolean {
+    if (!msg || msg.role !== 'user') {
+        return false
+    }
+
+    if (msg.ignored || msg.info?.ignored) {
+        return true
+    }
+
+    if (Array.isArray(msg.content) && msg.content.length > 0) {
+        const allPartsIgnored = msg.content.every((part: any) => part?.ignored)
+        if (allPartsIgnored) {
+            return true
+        }
+    }
+
+    return false
+}
+
+export function injectSynthInstruction(messages: any[], instruction: string): boolean {
+    // Find the last user message that is not ignored
+    for (let i = messages.length - 1; i >= 0; i--) {
+        const msg = messages[i]
+        if (msg.role === 'user' && !isIgnoredUserMessage(msg)) {
+            // Avoid double-injecting the same instruction
+            if (typeof msg.content === 'string') {
+                if (msg.content.includes(instruction)) {
+                    return false
+                }
+                msg.content = msg.content + '\n\n' + instruction
+            } else if (Array.isArray(msg.content)) {
+                const alreadyInjected = msg.content.some(
+                    (part: any) => part?.type === 'text' && typeof part.text === 'string' && part.text.includes(instruction)
+                )
+                if (alreadyInjected) {
+                    return false
+                }
+                msg.content.push({
+                    type: 'text',
+                    text: instruction
+                })
+            }
+            return true
+        }
+    }
+    return false
+}