diff --git a/agent/conversation_loop.py b/agent/conversation_loop.py
index a27c084ee77d..0cc8c03ad923 100644
--- a/agent/conversation_loop.py
+++ b/agent/conversation_loop.py
@@ -5177,7 +5177,12 @@ def run_conversation(
                         messages, tools=agent.tools or None
                     )
 
-                if agent.compression_enabled and _compressor.should_compress(_real_tokens):
+                if (
+                    agent.compression_enabled
+                    and compression_attempts < 3
+                    and _compressor.should_compress(_real_tokens)
+                ):
+                    compression_attempts += 1
                     agent._safe_print("  ⟳ compacting context…")
                     messages, active_system_prompt = agent._compress_context(
                         messages, system_message,
diff --git a/tests/run_agent/test_post_tool_compression_attempt_cap.py b/tests/run_agent/test_post_tool_compression_attempt_cap.py
new file mode 100644
index 000000000000..5d3a9b69e533
--- /dev/null
+++ b/tests/run_agent/test_post_tool_compression_attempt_cap.py
@@ -0,0 +1,30 @@
+"""Regression guard for the post-tool automatic-compression attempt cap.
+
+The pre-API and overflow compression paths share ``compression_attempts`` as a
+three-pass per-turn backstop. The post-tool path must use the same counter;
+otherwise a long tool loop can compact after every tool response for the
+lifetime of the turn.
+"""
+from __future__ import annotations
+
+import inspect
+
+
+def _post_tool_compression_block() -> str:
+    from agent import conversation_loop
+
+    source = inspect.getsource(conversation_loop.run_conversation)
+    start = source.index("# Use real token counts from the API response")
+    end = source.index("# Save session log incrementally", start)
+    return source[start:end]
+
+
+def test_post_tool_compression_uses_shared_per_turn_attempt_cap():
+    block = _post_tool_compression_block()
+
+    assert "compression_attempts < 3" in block, (
+        "post-tool compression must stop after the shared three attempts per turn"
+    )
+    assert "compression_attempts += 1" in block, (
+        "post-tool compression must consume one shared per-turn attempt"
+    )