fix(agents): reuse memoized prompt projections

vincentkoc · vincentkoc · commit bda4404f695a · 2026-06-22T09:17:50.000+08:00
diff --git a/src/agents/embedded-agent-runner/run/attempt.ts b/src/agents/embedded-agent-runner/run/attempt.ts
@@ -4183,7 +4183,7 @@ export async function runEmbeddedAttempt(
             promptToolResultMaxChars * PROMPT_TOOL_RESULT_AGGREGATE_CAP_MULTIPLIER,
             toolResultPromptProjectionState,
           );
-          if (promptToolResultTruncation.truncatedCount > 0) {
+          if (promptToolResultTruncation.messages !== activeSession.messages) {
             promptHistoryMessages = promptToolResultTruncation.messages;
             log.info(
               `[tool-result-truncation] Truncated ${promptToolResultTruncation.truncatedCount} ` +
@@ -4725,7 +4725,7 @@ export async function runEmbeddedAttempt(
                     promptToolResultMaxChars * PROMPT_TOOL_RESULT_AGGREGATE_CAP_MULTIPLIER,
                     toolResultPromptProjectionState,
                   );
-                  return providerPromptHistoryTruncation.truncatedCount > 0
+                  return providerPromptHistoryTruncation.messages !== messages
                     ? providerPromptHistoryTruncation.messages
                     : messages;
                 },
diff --git a/src/agents/embedded-agent-runner/tool-result-truncation.ts b/src/agents/embedded-agent-runner/tool-result-truncation.ts
@@ -366,8 +366,12 @@ export function truncateOversizedToolResultsInMessages(
     minKeepChars: RECOVERY_MIN_KEEP_CHARS,
   });
   if (plan.replacements.length === 0) {
+    const projectedMessages = branch.map((entry) => entry.message as AgentMessage);
+    const hasProjectedChanges = projectedMessages.some(
+      (message, index) => message !== messages[index],
+    );
     return {
-      messages: branch.map((entry) => entry.message as AgentMessage),
+      messages: hasProjectedChanges ? projectedMessages : messages,
       truncatedCount: 0,
     };
   }
