fix(gateway): always inject reply-to pointer, not just when quoted text is absent

gateway/run.py

@@ -3887,14 +3887,14 @@ async def _prepare_inbound_message_text(
                 message_text = f"{context_note}\n\n{message_text}"
 
         if getattr(event, "reply_to_text", None) and event.reply_to_message_id:
+            # Always inject the reply-to pointer — even when the quoted text
+            # already appears in history. The prefix isn't deduplication, it's
+            # disambiguation: it tells the agent *which* prior message the user
+            # is referencing. History can contain the same or similar text
+            # multiple times, and without an explicit pointer the agent has to
+            # guess (or answer for both subjects). Token overhead is minimal.
             reply_snippet = event.reply_to_text[:500]
-            found_in_history = any(
-                reply_snippet[:200] in (msg.get("content") or "")
-                for msg in history
-                if msg.get("role") in ("assistant", "user", "tool")
-            )
-            if not found_in_history:
-                message_text = f'[Replying to: "{reply_snippet}"]\n\n{message_text}'
+            message_text = f'[Replying to: "{reply_snippet}"]\n\n{message_text}'
 
         if "@" in message_text:
             try:

tests/gateway/test_reply_to_injection.py

@@ -0,0 +1,159 @@
+"""Tests for reply-to pointer injection in _prepare_inbound_message_text.
+
+The `[Replying to: "..."]` prefix is a *disambiguation pointer*, not
+deduplication. It must always be injected when the user explicitly replies
+to a prior message — even when the quoted text already exists somewhere
+in the conversation history. History can contain the same or similar text
+multiple times, and without an explicit pointer the agent has to guess
+which prior message the user is referencing.
+"""
+import pytest
+
+from gateway.config import GatewayConfig, Platform, PlatformConfig
+from gateway.platforms.base import MessageEvent
+from gateway.run import GatewayRunner
+from gateway.session import SessionSource
+
+
+def _make_runner() -> GatewayRunner:
+    runner = object.__new__(GatewayRunner)
+    runner.config = GatewayConfig(
+        platforms={Platform.TELEGRAM: PlatformConfig(enabled=True, token="fake")},
+    )
+    runner.adapters = {}
+    runner._model = "openai/gpt-4.1-mini"
+    runner._base_url = None
+    return runner
+
+
+def _source() -> SessionSource:
+    return SessionSource(
+        platform=Platform.TELEGRAM,
+        chat_id="123",
+        chat_name="DM",
+        chat_type="private",
+        user_name="Alice",
+    )
+
+
+@pytest.mark.asyncio
+async def test_reply_prefix_injected_when_text_absent_from_history():
+    runner = _make_runner()
+    source = _source()
+    event = MessageEvent(
+        text="What's the best time to go?",
+        source=source,
+        reply_to_message_id="42",
+        reply_to_text="Japan is great for culture, food, and efficiency.",
+    )
+
+    result = await runner._prepare_inbound_message_text(
+        event=event,
+        source=source,
+        history=[{"role": "user", "content": "unrelated"}],
+    )
+
+    assert result is not None
+    assert result.startswith(
+        '[Replying to: "Japan is great for culture, food, and efficiency."]'
+    )
+    assert result.endswith("What's the best time to go?")
+
+
+@pytest.mark.asyncio
+async def test_reply_prefix_still_injected_when_text_in_history():
+    """Regression test: the pointer must survive even when the quoted text
+    already appears in history. Previously a `found_in_history` guard
+    silently dropped the prefix, leaving the agent to guess which prior
+    message the user was referencing."""
+    runner = _make_runner()
+    source = _source()
+    quoted = "Japan is great for culture, food, and efficiency."
+    event = MessageEvent(
+        text="What's the best time to go?",
+        source=source,
+        reply_to_message_id="42",
+        reply_to_text=quoted,
+    )
+
+    history = [
+        {"role": "user", "content": "I'm thinking of going to Japan or Italy."},
+        {
+            "role": "assistant",
+            "content": (
+                f"{quoted} Italy is better if you prefer a relaxed pace."
+            ),
+        },
+        {"role": "user", "content": "How long should I stay?"},
+        {"role": "assistant", "content": "For Japan, 10-14 days is ideal."},
+    ]
+
+    result = await runner._prepare_inbound_message_text(
+        event=event,
+        source=source,
+        history=history,
+    )
+
+    assert result is not None
+    assert result.startswith(f'[Replying to: "{quoted}"]')
+    assert result.endswith("What's the best time to go?")
+
+
+@pytest.mark.asyncio
+async def test_no_prefix_without_reply_context():
+    runner = _make_runner()
+    source = _source()
+    event = MessageEvent(text="hello", source=source)
+
+    result = await runner._prepare_inbound_message_text(
+        event=event,
+        source=source,
+        history=[],
+    )
+
+    assert result == "hello"
+
+
+@pytest.mark.asyncio
+async def test_no_prefix_when_reply_to_text_is_empty():
+    """reply_to_message_id alone without text (e.g. a reply to a media-only
+    message) should not produce an empty `[Replying to: ""]` prefix."""
+    runner = _make_runner()
+    source = _source()
+    event = MessageEvent(
+        text="hi",
+        source=source,
+        reply_to_message_id="42",
+        reply_to_text=None,
+    )
+
+    result = await runner._prepare_inbound_message_text(
+        event=event,
+        source=source,
+        history=[],
+    )
+
+    assert result == "hi"
+
+
+@pytest.mark.asyncio
+async def test_reply_snippet_truncated_to_500_chars():
+    runner = _make_runner()
+    source = _source()
+    long_text = "x" * 800
+    event = MessageEvent(
+        text="follow-up",
+        source=source,
+        reply_to_message_id="42",
+        reply_to_text=long_text,
+    )
+
+    result = await runner._prepare_inbound_message_text(
+        event=event,
+        source=source,
+        history=[],
+    )
+
+    assert result is not None
+    assert result.startswith('[Replying to: "' + "x" * 500 + '"]')
+    assert "x" * 501 not in result