From 1d55f96e01a476accbf078feed716516e6705bfc Mon Sep 17 00:00:00 2001
From: Hernan Javier Ardila Sanchez <hjasgr@gmail.com>
Date: Fri, 29 May 2026 06:44:22 +0200
Subject: [PATCH] fix(combo): preserve system messages during context handoff
 summary generation (#2865)

Integrated into release/v3.8.6.
---
 open-sse/services/contextHandoff.ts           | 28 ++++++++--
 tests/unit/context-handoff.test.ts            | 52 +++++++++++++++++++
 tests/unit/dockerignore-docs-coverage.test.ts |  2 +-
 3 files changed, 77 insertions(+), 5 deletions(-)

diff --git a/open-sse/services/contextHandoff.ts b/open-sse/services/contextHandoff.ts
index e592764561..d65a550cdb 100644
--- a/open-sse/services/contextHandoff.ts
+++ b/open-sse/services/contextHandoff.ts
@@ -230,16 +230,36 @@ function formatMessagesForPrompt(messages: MessageLike[]): string {
     .join("\n\n");
 }
 
-function selectMessagesForSummary(messages: MessageLike[], maxMessages: number): MessageLike[] {
-  const recentMessages = messages.slice(-maxMessages);
+export function selectMessagesForSummary(messages: MessageLike[], maxMessages: number): MessageLike[] {
+  const validMessages = messages.filter((m) => m && typeof m === "object");
+  const system = validMessages.filter(
+    (m) => typeof m.role === "string" && (m.role === "system" || m.role === "developer")
+  );
+  const nonSystem = validMessages.filter(
+    (m) => typeof m.role !== "string" || (m.role !== "system" && m.role !== "developer")
+  );
+
+  const recentMessages = [...system, ...nonSystem.slice(-maxMessages)];
   let working = [...recentMessages];
 
-  while (working.length > 1) {
+  while (working.length > system.length + 1) {
     const history = formatMessagesForPrompt(working);
     if (estimateTokens(history) <= MAX_HISTORY_TOKENS_FOR_SUMMARY) {
       return working;
     }
-    working = working.slice(1);
+    working = [...system, ...working.slice(system.length + 1)];
+  }
+
+  const fallbackHistory = formatMessagesForPrompt(working);
+  if (estimateTokens(fallbackHistory) > MAX_HISTORY_TOKENS_FOR_SUMMARY) {
+    // If there are system messages, return them so the caller can still produce context.
+    // If there are no system messages (system=[]), fall back to the single most-recent
+    // non-system message rather than returning [] which would silently drop the handoff.
+    if (system.length > 0) {
+      return system;
+    }
+    const lastNonSystem = nonSystem[nonSystem.length - 1];
+    return lastNonSystem ? [lastNonSystem] : [];
   }
 
   return working;
diff --git a/tests/unit/context-handoff.test.ts b/tests/unit/context-handoff.test.ts
index 99e79a88a4..86eeb23024 100644
--- a/tests/unit/context-handoff.test.ts
+++ b/tests/unit/context-handoff.test.ts
@@ -368,3 +368,55 @@ test("context handoff DB module upserts and deletes active handoffs", () => {
   handoffDb.deleteHandoff("sess-db", "relay-combo");
   assert.equal(handoffDb.getHandoff("sess-db", "relay-combo"), null);
 });
+
+test("selectMessagesForSummary filters falsy values and preserves system/developer messages", () => {
+  const messages: (contextHandoff.MessageLike | null | undefined | false)[] = [
+    null,
+    undefined,
+    { role: "system", content: "System 1" },
+    false,
+    { role: "user", content: "User 1" },
+    { role: "developer", content: "Dev 1" },
+    { role: "assistant", content: "Assistant 1" },
+    { role: "user", content: "User 2" },
+  ];
+
+  const selected = contextHandoff.selectMessagesForSummary(
+    messages as contextHandoff.MessageLike[],
+    2
+  );
+  
+  assert.equal(selected.length, 4);
+  assert.equal(selected[0].role, "system");
+  assert.equal(selected[1].role, "developer");
+  assert.equal(selected[2].role, "assistant");
+  assert.equal(selected[3].role, "user");
+  assert.equal(selected[3].content, "User 2");
+});
+
+test("selectMessagesForSummary with no system messages and oversized single remaining message still produces non-empty selection", () => {
+  // Build a single very large non-system message that exceeds MAX_HISTORY_TOKENS_FOR_SUMMARY
+  // (token estimator is ~4 chars/token, so 8000 tokens ≈ 32000 chars).
+  const hugeContent = "x".repeat(40000);
+  const messages: contextHandoff.MessageLike[] = [
+    { role: "user", content: "first message" },
+    { role: "assistant", content: hugeContent },
+  ];
+
+  const selected = contextHandoff.selectMessagesForSummary(messages, 10);
+
+  // The function must return at least one message rather than [] so the handoff is not silently dropped.
+  assert.ok(selected.length > 0, "expected at least one message to be selected");
+
+  // formatMessagesForPrompt on the result must produce a non-empty string
+  // (guards the regression: previously returned [] → empty historyText → handoff skipped).
+  const historyText = selected
+    .map((m, i) => {
+      const role = typeof m.role === "string" ? m.role : "unknown";
+      const content = typeof m.content === "string" ? m.content.trim() : "";
+      return content ? `[${i + 1}] ${role.toUpperCase()}:\n${content}` : "";
+    })
+    .filter(Boolean)
+    .join("\n\n");
+  assert.ok(historyText.length > 0, "historyText must be non-empty so the handoff is generated");
+});
diff --git a/tests/unit/dockerignore-docs-coverage.test.ts b/tests/unit/dockerignore-docs-coverage.test.ts
index 7934d27f1a..c3fb6176ea 100644
--- a/tests/unit/dockerignore-docs-coverage.test.ts
+++ b/tests/unit/dockerignore-docs-coverage.test.ts
@@ -154,7 +154,7 @@ test("#2348 .dockerignore keeps every doc the in-product viewer needs", () => {
 
 test("#2348 .dockerignore still excludes the heavy i18n tree", () => {
   const parsed = parseDockerignore(fs.readFileSync(DOCKERIGNORE, "utf8"));
-  const heavy = "docs/i18n/pt-BR/docs/AUTO-COMBO.md";
+  const heavy = "docs/i18n/pt-BR/docs/routing/AUTO-COMBO.md";
   assert.ok(
     isIgnored(heavy, parsed),
     `${heavy} should be excluded from Docker context but is not — image size will balloon`