From 5355b476f67a6ccd17758ca41695b7c6648c2297 Mon Sep 17 00:00:00 2001
From: Aswin Sreenivas <awinsreenivas@gmail.com>
Date: Thu, 29 Jan 2026 22:20:28 +0800
Subject: [PATCH] fix(agent): sanitize messages after orphan user repair

When repairing orphaned trailing user messages, buildSessionContext()
was called but messages bypassed the sanitization pipeline. This could
cause tool_result blocks without matching tool_use blocks, leading to
Anthropic API "unexpected tool_use_id" errors.

Apply full sanitization (sanitizeSessionHistory, validateTurns,
limitHistoryTurns) to rebuilt messages.
---
 src/agents/pi-embedded-runner/run/attempt.ts | 23 +++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/agents/pi-embedded-runner/run/attempt.ts b/src/agents/pi-embedded-runner/run/attempt.ts
index 776525658..2c496eb50 100644
--- a/src/agents/pi-embedded-runner/run/attempt.ts
+++ b/src/agents/pi-embedded-runner/run/attempt.ts
@@ -709,7 +709,28 @@ export async function runEmbeddedAttempt(
             sessionManager.resetLeaf();
           }
           const sessionContext = sessionManager.buildSessionContext();
-          activeSession.agent.replaceMessages(sessionContext.messages);
+          // Re-sanitize the rebuilt messages to ensure tool_use/tool_result pairing is valid.
+          // Without this, Anthropic API rejects the request with "unexpected tool_use_id" errors.
+          const rebuiltSanitized = await sanitizeSessionHistory({
+            messages: sessionContext.messages,
+            modelApi: params.model.api,
+            modelId: params.modelId,
+            provider: params.provider,
+            sessionManager,
+            sessionId: params.sessionId,
+            policy: transcriptPolicy,
+          });
+          const rebuiltValidatedGemini = transcriptPolicy.validateGeminiTurns
+            ? validateGeminiTurns(rebuiltSanitized)
+            : rebuiltSanitized;
+          const rebuiltValidated = transcriptPolicy.validateAnthropicTurns
+            ? validateAnthropicTurns(rebuiltValidatedGemini)
+            : rebuiltValidatedGemini;
+          const rebuiltLimited = limitHistoryTurns(
+            rebuiltValidated,
+            getDmHistoryLimitFromSessionKey(params.sessionKey, params.config),
+          );
+          activeSession.agent.replaceMessages(rebuiltLimited);
           log.warn(
             `Removed orphaned user message to prevent consecutive user turns. ` +
               `runId=${params.runId} sessionId=${params.sessionId}`,