fix(context): clamp shell output cap and count byte-trimmed dropped lines

Treat tool_output_max_tokens as a ceiling so an explicit model-supplied
cap can't exceed it, and derive the truncation notice's dropped-line
count from the lines actually kept after the byte-trim pass. Also cast
the pygments fallback lexer so it satisfies the resolve_lexer return
type under the pre-commit mypy hook.

strix/agents/factory.py

@@ -246,12 +246,18 @@ def _format_validation_error(tool_name: str, exc: ValidationError) -> str:
 
 
 def _apply_shell_output_cap(parsed: dict[str, Any]) -> None:
-    """Default the SDK shell tools' own token cap so a single command can't
-    dump unbounded output into history. The SDK truncates head+tail when the
-    model omits the field; respect an explicit model-supplied value.
+    """Bound the SDK shell tools' own token cap so a single command can't dump
+    unbounded output into history. The SDK truncates head+tail from this value.
+
+    The configured cap is a ceiling: a missing value defaults to it, and a
+    larger model-supplied value is clamped down to it. A smaller explicit value
+    is respected, so the model can still ask for less.
     """
-    if parsed.get("max_output_tokens") is None:
-        parsed["max_output_tokens"] = load_settings().context.tool_output_max_tokens
+    ceiling = load_settings().context.tool_output_max_tokens
+    requested = parsed.get("max_output_tokens")
+    parsed["max_output_tokens"] = (
+        ceiling if not isinstance(requested, int) or requested > ceiling else requested
+    )
 
 
 def _wrap_exec_command(tool: FunctionTool) -> FunctionTool:

strix/report/writer.py

@@ -10,7 +10,7 @@ import re
 import tempfile
 from datetime import UTC, datetime
 from pathlib import Path
-from typing import TYPE_CHECKING, Any
+from typing import TYPE_CHECKING, Any, cast
 
 from pygments.lexers import PythonLexer, get_lexer_by_name, guess_lexer
 from pygments.lexers.special import TextLexer
@@ -74,10 +74,10 @@ def resolve_lexer(language: str | None, code: str) -> Lexer:
     try:
         lexer = guess_lexer(code)
     except ClassNotFound:
-        return PythonLexer()
+        return cast("Lexer", PythonLexer())
     # ``guess_lexer`` returns the plain-text lexer when it can't detect anything.
     if isinstance(lexer, TextLexer):
-        return PythonLexer()
+        return cast("Lexer", PythonLexer())
     return lexer
 
 

strix/tools/output_store.py

@@ -66,7 +66,11 @@ def bound_text(text: str, *, max_lines: int, max_bytes: int) -> str:
     if tail and _byte_len(tail) > half_bytes:
         tail = _take_suffix(tail, half_bytes)
 
-    dropped_lines = max(0, len(lines) - head_lines - tail_lines)
+    # Count kept lines from the final slices: the byte pass above may have
+    # dropped whole lines from head/tail, so deriving this from the original
+    # head_lines/tail_lines would undercount what was actually removed.
+    kept_lines = len(head.split("\n")) + (len(tail.split("\n")) if tail else 0)
+    dropped_lines = max(0, len(lines) - kept_lines)
     dropped_bytes = max(0, total_bytes - _byte_len(head) - _byte_len(tail))
     notice = _TRUNCATION_NOTICE.format(lines=dropped_lines, bytes=dropped_bytes)
     return f"{head}\n\n{notice}\n\n{tail}" if tail else f"{head}\n\n{notice}"

tests/test_agent_factory_shell.py

@@ -41,7 +41,7 @@ async def test_wrap_exec_command_defaults_shell_to_bash() -> None:
 
 
 @pytest.mark.asyncio
-async def test_wrap_exec_command_preserves_explicit_output_cap() -> None:
+async def test_wrap_exec_command_preserves_smaller_explicit_output_cap() -> None:
     captured: dict[str, str] = {}
     wrapped = factory._wrap_exec_command(_capturing_exec_tool(captured))
 
@@ -52,6 +52,20 @@ async def test_wrap_exec_command_preserves_explicit_output_cap() -> None:
     assert json.loads(captured["raw_input"])["max_output_tokens"] == 42
 
 
+@pytest.mark.asyncio
+async def test_wrap_exec_command_clamps_oversized_explicit_output_cap() -> None:
+    captured: dict[str, str] = {}
+    wrapped = factory._wrap_exec_command(_capturing_exec_tool(captured))
+    ceiling = load_settings().context.tool_output_max_tokens
+
+    await wrapped.on_invoke_tool(
+        cast("Any", None),
+        json.dumps({"cmd": "echo hi", "max_output_tokens": ceiling * 100}),
+    )
+
+    assert json.loads(captured["raw_input"])["max_output_tokens"] == ceiling
+
+
 @pytest.mark.asyncio
 @pytest.mark.parametrize("shell", ["/bin/zsh", ""])
 async def test_wrap_exec_command_preserves_explicit_shell(shell: str) -> None:

tests/test_output_store.py

@@ -2,6 +2,8 @@
 
 from __future__ import annotations
 
+import re
+
 from strix.tools.output_store import bound_text
 
 
@@ -44,3 +46,18 @@ def test_notice_reports_dropped_counts() -> None:
 
     assert "lines" in bounded
     assert "bytes" in bounded
+
+
+def test_dropped_line_count_accounts_for_byte_trimming() -> None:
+    # A tight byte budget forces the byte pass to drop whole lines from the
+    # head/tail slices; the notice must count those, not just the middle.
+    text = "\n".join(f"line-{i}" for i in range(200))
+    bounded = bound_text(text, max_lines=20, max_bytes=40)
+
+    match = re.search(r"\[\.\.\. (\d+) lines", bounded)
+    assert match is not None, bounded
+    dropped = int(match.group(1))
+    kept = [ln for ln in bounded.splitlines() if ln and "truncated" not in ln]
+    assert dropped == 200 - len(kept)
+    # The naive middle-only count (max_lines split evenly) would under-report.
+    assert dropped > 200 - 20