fix(agents): strip transcript marker from model context

steipete · steipete · commit 616440a5ed9b · 2026-05-27T23:45:35.000+01:00
diff --git a/src/agents/embedded-agent-runner/tool-result-context-guard.test.ts b/src/agents/embedded-agent-runner/tool-result-context-guard.test.ts
@@ -8,6 +8,7 @@ import {
   formatContextLimitTruncationNotice,
   installContextEngineLoopHook,
   installToolResultContextGuard,
+  markTranscriptPromptText,
   PREEMPTIVE_CONTEXT_OVERFLOW_MESSAGE,
 } from "./tool-result-context-guard.js";
 
@@ -669,6 +670,34 @@ describe("installContextEngineLoopHook", () => {
     });
   });
 
+  it("projects marked model prompts for ingest without leaking the marker to assembly", async () => {
+    const agent = makeGuardableAgent();
+    const engine = makeMockEngine();
+    installHook(agent, engine, 0);
+
+    const modelPrompt = makeUser("model-only hook context\n\nvisible prompt");
+    markTranscriptPromptText(modelPrompt, "visible prompt");
+    const messages = [modelPrompt, makeToolResult("call_1", "result")];
+    const transformed = await callTransform(agent, messages);
+
+    const afterTurnMessage = (recordMockArg(engine.afterTurn).messages as AgentMessage[])[0];
+    const assembleMessage = (recordMockArg(engine.assemble).messages as AgentMessage[])[0];
+    const transformedMessage = (transformed as AgentMessage[])[0];
+
+    expect(afterTurnMessage).toMatchObject({ role: "user", content: "visible prompt" });
+    expect(JSON.stringify(afterTurnMessage)).not.toContain("__openclawTranscriptPromptText");
+    expect(assembleMessage).toMatchObject({
+      role: "user",
+      content: "model-only hook context\n\nvisible prompt",
+    });
+    expect(JSON.stringify(assembleMessage)).not.toContain("__openclawTranscriptPromptText");
+    expect(transformedMessage).toMatchObject({
+      role: "user",
+      content: "model-only hook context\n\nvisible prompt",
+    });
+    expect(JSON.stringify(transformedMessage)).not.toContain("__openclawTranscriptPromptText");
+  });
+
   it("calls afterTurn and assemble when new messages are appended after the first call", async () => {
     const agent = makeGuardableAgent();
     const engine = makeMockEngine();
diff --git a/src/agents/embedded-agent-runner/tool-result-context-guard.ts b/src/agents/embedded-agent-runner/tool-result-context-guard.ts
@@ -102,6 +102,15 @@ function restoreTranscriptPromptText(
   return restoredMessage;
 }
 
+function stripTranscriptPromptMarker(message: AgentMessage): AgentMessage {
+  if (getTranscriptPromptText(message) === undefined) {
+    return message;
+  }
+  const { [TRANSCRIPT_PROMPT_TEXT_KEY]: _transcriptPromptText, ...messageRest } =
+    message as unknown as Record<string, unknown>;
+  return messageRest as unknown as AgentMessage;
+}
+
 function projectTranscriptPromptMessages(
   messages: AgentMessage[],
   cache: WeakMap<AgentMessage, AgentMessage>,
@@ -115,6 +124,16 @@ function projectTranscriptPromptMessages(
   return changed ? projected : messages;
 }
 
+function stripTranscriptPromptMarkers(messages: AgentMessage[]): AgentMessage[] {
+  let changed = false;
+  const stripped = messages.map((message) => {
+    const next = stripTranscriptPromptMarker(message);
+    changed ||= next !== message;
+    return next;
+  });
+  return changed ? stripped : messages;
+}
+
 function truncateTextToBudget(text: string, maxChars: number): string {
   if (text.length <= maxChars) {
     return text;
@@ -329,6 +348,7 @@ export function installContextEngineLoopHook(params: {
       sourceMessages,
       transcriptProjectionCache,
     );
+    const providerMessages = stripTranscriptPromptMarkers(sourceMessages);
     const checkedPrefixLength =
       lastSeenLength == null ? 0 : Math.min(lastSeenLength, transcriptMessages.length);
     const sourceHistoryChanged =
@@ -359,7 +379,7 @@ export function installContextEngineLoopHook(params: {
     if (!hasNewMessages) {
       lastSeenLength = prePromptMessageCount;
       lastSourceMessages = transcriptMessages;
-      return lastAssembledView ?? sourceMessages;
+      return lastAssembledView ?? providerMessages;
     }
     try {
       if (typeof contextEngine.afterTurn === "function") {
@@ -401,11 +421,15 @@ export function installContextEngineLoopHook(params: {
       const assembled = await contextEngine.assemble({
         sessionId,
         sessionKey,
-        messages: sourceMessages,
+        messages: providerMessages,
         tokenBudget,
         model: modelId,
       });
-      if (assembled && Array.isArray(assembled.messages) && assembled.messages !== sourceMessages) {
+      if (
+        assembled &&
+        Array.isArray(assembled.messages) &&
+        assembled.messages !== providerMessages
+      ) {
         lastAssembledView = assembled.messages;
         return assembled.messages;
       }
@@ -418,7 +442,7 @@ export function installContextEngineLoopHook(params: {
       lastSourceMessages = transcriptMessages;
     }
 
-    return sourceMessages;
+    return providerMessages;
   }) as GuardableTransformContext;
 
   return () => {
