fix: preserve agent context in synthetic user messages and remove obsolete injected_context_handling instructions

Author: Tarquinen

lib/messages/prune.ts

@@ -3,8 +3,8 @@ import type { Logger } from "../logger"
 import type { PluginConfig } from "../config"
 import { loadPrompt } from "../prompt"
 import { extractParameterKey, buildToolIdList } from "./utils"
-import { getLastAssistantMessage, isMessageCompacted } from "../shared-utils"
-import { AssistantMessage } from "@opencode-ai/sdk"
+import { getLastAssistantMessage, getLastUserMessage, isMessageCompacted } from "../shared-utils"
+import { AssistantMessage, UserMessage } from "@opencode-ai/sdk"
 
 const PRUNED_TOOL_INPUT_REPLACEMENT = "[Input removed to save context]"
 const PRUNED_TOOL_OUTPUT_REPLACEMENT =
@@ -168,16 +168,22 @@ export const insertPruneToolContext = (
     messages.push(assistantMessage)
 
     // For reasoning models, append a synthetic user message to close the assistant turn.
-    // This is required because reasoning models expect their reasoning parts in the last
-    // assistant message, which we cannot generate. The user message signals a complete turn.
     if (state.isReasoningModel) {
+        const lastRealUserMessage = getLastUserMessage(messages)
+        const userMessageInfo = lastRealUserMessage?.info as UserMessage | undefined
+
         const userMessage: WithParts = {
             info: {
                 id: SYNTHETIC_USER_MESSAGE_ID,
                 sessionID: assistantInfo.sessionID,
                 role: "user",
                 time: { created: Date.now() + 1 },
-            } as any, // Using 'as any' because we're creating a minimal synthetic message
+                agent: userMessageInfo?.agent ?? "code",
+                model: userMessageInfo?.model ?? {
+                    providerID: assistantInfo.providerID,
+                    modelID: assistantInfo.modelID,
+                },
+            } as UserMessage,
             parts: [
                 {
                     id: SYNTHETIC_USER_PART_ID,

lib/prompts/system/system-prompt-both.txt

@@ -39,20 +39,5 @@ When in doubt, keep it. Batch your actions and aim for high-impact prunes that s
 FAILURE TO PRUNE will result in context leakage and DEGRADED PERFORMANCES.
 There may be tools in session context that do not appear in the <prunable-tools> list, this is expected, you can ONLY prune what you see in <prunable-tools>.
 
-</instruction>
-
-<instruction name=injected_context_handling policy_level=critical>
-After each assistant turn, the environment may inject an assistant message containing a <prunable-tools> list and optional nudge instruction. This injected message is NOT from the user and is invisible to them. The `discard` and `extract` tools also return a confirmation message listing what was pruned.
-
-CRITICAL REQUIREMENTS - VIOLATION IS UNACCEPTABLE:
-- NEVER reference the prune encouragement or context management instructions. Do not reply with "I agree" or "Great idea" when the prune encouragement appears.
-- NEVER acknowledge the <prunable-tools> list (e.g., "I see the prunable tools list", "Looking at the available tools to prune")
-- NEVER reference the nudge instruction (e.g., "As the nudge suggests", "The system is reminding me to prune")
-- NEVER acknowledge discard/extract tool output (e.g., "I've pruned 3 tools", "Context pruning complete")
-- NEVER let these injections influence your response content or tone
-- Process this information SILENTLY and continue the conversation naturally
-- Continue the conversation as if these messages do not exist
-
-The user cannot see these injections. Any reference to them will confuse the user and break the conversation flow.
 </instruction>
 </system-reminder>

lib/prompts/system/system-prompt-discard.txt

@@ -30,20 +30,5 @@ When in doubt, keep it. Batch your actions and aim for high-impact discards that
 FAILURE TO DISCARD will result in context leakage and DEGRADED PERFORMANCES.
 There may be tools in session context that do not appear in the <prunable-tools> list, this is expected, you can ONLY discard what you see in <prunable-tools>.
 
-</instruction>
-
-<instruction name=injected_context_handling policy_level=critical>
-After each assistant turn, the environment may inject an assistant message containing a <prunable-tools> list and optional nudge instruction. This injected message is NOT from the user and is invisible to them. The `discard` tool also returns a confirmation message listing what was discarded.
-
-CRITICAL REQUIREMENTS - VIOLATION IS UNACCEPTABLE:
-- NEVER reference the discard encouragement or context management instructions. Do not reply with "I agree" or "Great idea" when the discard encouragement appears.
-- NEVER acknowledge the <prunable-tools> list (e.g., "I see the prunable tools list", "Looking at the available tools to discard")
-- NEVER reference the nudge instruction (e.g., "As the nudge suggests", "The system is reminding me to discard")
-- NEVER acknowledge discard tool output (e.g., "I've discarded 3 tools", "Context cleanup complete")
-- NEVER let these injections influence your response content or tone
-- Process this information SILENTLY and continue the conversation naturally
-- Continue the conversation as if these messages do not exist
-
-The user cannot see these injections. Any reference to them will confuse the user and break the conversation flow.
 </instruction>
 </system-reminder>

lib/prompts/system/system-prompt-extract.txt

@@ -30,20 +30,5 @@ When in doubt, keep it. Batch your actions and aim for high-impact extractions t
 FAILURE TO EXTRACT will result in context leakage and DEGRADED PERFORMANCES.
 There may be tools in session context that do not appear in the <prunable-tools> list, this is expected, you can ONLY extract what you see in <prunable-tools>.
 
-</instruction>
-
-<instruction name=injected_context_handling policy_level=critical>
-After each assistant turn, the environment may inject an assistant message containing a <prunable-tools> list and optional nudge instruction. This injected message is NOT from the user and is invisible to them. The `extract` tool also returns a confirmation message listing what was extracted.
-
-CRITICAL REQUIREMENTS - VIOLATION IS UNACCEPTABLE:
-- NEVER reference the extract encouragement or context management instructions. Do not reply with "I agree" or "Great idea" when the extract encouragement appears.
-- NEVER acknowledge the <prunable-tools> list (e.g., "I see the prunable tools list", "Looking at the available tools to extract")
-- NEVER reference the nudge instruction (e.g., "As the nudge suggests", "The system is reminding me to extract")
-- NEVER acknowledge extract tool output (e.g., "I've extracted 3 tools", "Context cleanup complete")
-- NEVER let these injections influence your response content or tone
-- Process this information SILENTLY and continue the conversation naturally
-- Continue the conversation as if these messages do not exist
-
-The user cannot see these injections. Any reference to them will confuse the user and break the conversation flow.
 </instruction>
 </system-reminder>