From 8e9a6bf9032a3710f935eb0a3c10967b774f320d Mon Sep 17 00:00:00 2001
From: Ahmed Allam <ahmed39652003@gmail.com>
Date: Sat, 25 Jul 2026 23:46:11 +0000
Subject: [PATCH] fix(context): reject tool-output byte ceilings below the
 notice size

A configured tool_output_max_bytes smaller than the truncation notice
itself can't fit a bounded preview, so a persisted result could exceed the
ceiling. Enforce a config floor (ge=1024) so nonsensical values are
rejected at load time instead of being worked around at runtime.
---
 strix/config/settings.py    |  6 +++++-
 strix/tools/output_store.py |  3 ++-
 tests/test_config_loader.py | 19 ++++++++++++++++++-
 3 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/strix/config/settings.py b/strix/config/settings.py
index edb0ab09..d7c795b6 100644
--- a/strix/config/settings.py
+++ b/strix/config/settings.py
@@ -69,7 +69,11 @@ class ContextSettings(BaseSettings):
     summary_max_tokens: int = Field(default=4_096, gt=0, alias="STRIX_CONTEXT_SUMMARY_TOKENS")
     tool_output_max_tokens: int = Field(default=8_000, gt=0, alias="STRIX_TOOL_OUTPUT_MAX_TOKENS")
     tool_output_max_lines: int = Field(default=2_000, gt=0, alias="STRIX_TOOL_OUTPUT_MAX_LINES")
-    tool_output_max_bytes: int = Field(default=50 * 1024, gt=0, alias="STRIX_TOOL_OUTPUT_MAX_BYTES")
+    # Floor comfortably above the truncation-notice size so a preview
+    # (head+tail+notice) always fits within the configured ceiling.
+    tool_output_max_bytes: int = Field(
+        default=50 * 1024, ge=1024, alias="STRIX_TOOL_OUTPUT_MAX_BYTES"
+    )
 
 
 class RuntimeSettings(BaseSettings):
diff --git a/strix/tools/output_store.py b/strix/tools/output_store.py
index 3e622c08..6e6e6202 100644
--- a/strix/tools/output_store.py
+++ b/strix/tools/output_store.py
@@ -49,7 +49,8 @@ def bound_text(text: str, *, max_lines: int, max_bytes: int) -> str:
     byte size). The removed middle is replaced with a notice recording how
     many lines and bytes were dropped so the agent knows output was elided.
     ``max_bytes`` bounds the *entire* joined result, notice and separators
-    included.
+    included, and must be large enough to hold the notice itself (guaranteed by
+    the ``tool_output_max_bytes`` config floor).
     """
     lines = text.split("\n")
     total_bytes = _byte_len(text)
diff --git a/tests/test_config_loader.py b/tests/test_config_loader.py
index be0bfb8f..0d37e1e8 100644
--- a/tests/test_config_loader.py
+++ b/tests/test_config_loader.py
@@ -6,10 +6,11 @@ import json
 from typing import TYPE_CHECKING
 
 import pytest
-from pydantic import AliasChoices, Field
+from pydantic import AliasChoices, Field, ValidationError
 from pydantic.fields import FieldInfo
 
 from strix.config import loader
+from strix.config.settings import ContextSettings
 
 
 if TYPE_CHECKING:
@@ -120,6 +121,22 @@ def test_read_json_overrides_uses_json_when_no_alias_in_environ(tmp_path: Path)
     assert loader._read_json_overrides(path) == {"llm": {"api_key": "sk-file"}}
 
 
+# --------------------------------------------------------------------------- #
+# ContextSettings validation
+# --------------------------------------------------------------------------- #
+
+
+def test_tool_output_max_bytes_rejects_sub_notice_values() -> None:
+    # A ceiling below the truncation notice can't fit a bounded preview, so it
+    # is rejected at load time rather than producing over-cap persisted output.
+    with pytest.raises(ValidationError):
+        ContextSettings(STRIX_TOOL_OUTPUT_MAX_BYTES=64)
+
+
+def test_tool_output_max_bytes_accepts_floor() -> None:
+    assert ContextSettings(STRIX_TOOL_OUTPUT_MAX_BYTES=1024).tool_output_max_bytes == 1024
+
+
 # --------------------------------------------------------------------------- #
 # _aliases_for
 # --------------------------------------------------------------------------- #