From 5a3ee3c537b3226fed21ccc733314d775266b2d2 Mon Sep 17 00:00:00 2001
From: Teknium <127238744+teknium1@users.noreply.github.com>
Date: Wed, 22 Jul 2026 07:26:41 -0700
Subject: [PATCH] fix(compression): let handoff-strip supersede the head-copy
 skip

The summary_idx head-copy skip (from #69302) dropped the entire merged
handoff message, deleting the genuine prior-tail user content that
#47274's _strip_context_summary_handoff_message correctly unwraps.
Strip handles both shapes: standalone handoffs drop, merged handoffs
keep their real content. Caught by
test_recompression_of_current_merged_handoff_preserves_prior_tail_once
when both PRs landed together.
---
 agent/context_compressor.py | 22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/agent/context_compressor.py b/agent/context_compressor.py
index 8b5e983e6e3..feed9d3aab2 100644
--- a/agent/context_compressor.py
+++ b/agent/context_compressor.py
@@ -4040,19 +4040,15 @@ This compaction should PRIORITISE preserving all information related to the focu
         # Phase 4: Assemble compressed message list
         compressed = []
         for i in range(compress_start):
-            # If an earlier compaction handoff is in the protected head
-            # (common after resume / in-place compaction), do not carry it
-            # forward verbatim. It has already been rehydrated into
-            # _previous_summary above and _generate_summary() will emit the
-            # updated replacement below. Keeping both makes repeated
-            # compactions accumulate old summaries and prevents the live prompt
-            # from actually shrinking.
-            if (
-                summary_idx is not None
-                and i == summary_idx
-                and self._is_context_summary_content(messages[i].get("content"))
-            ):
-                continue
+            # An earlier compaction handoff in the protected head (common
+            # after resume / in-place compaction) must not be carried forward
+            # verbatim — it is already rehydrated into _previous_summary and
+            # _generate_summary() emits the updated replacement below.
+            # _strip_context_summary_handoff_message() handles both shapes:
+            # standalone handoffs strip to None (dropped), merged handoffs
+            # unwrap to their genuine prior-tail content (preserved). Do NOT
+            # short-circuit on summary_idx here: a merged handoff carries real
+            # user content that a blanket skip would silently delete.
             msg = _fresh_compaction_message_copy(messages[i])
             if i == 0 and msg.get("role") == "system":
                 existing = msg.get("content")