fix: token budget tracker for context overflow (#925)

fix: restore _format_error helper for test compatibility (#916)

agent/token_budget.py

@@ -0,0 +1,165 @@
+"""Token Budget — Poka-yoke guard against context overflow.
+
+Progressive warning system with circuit breakers:
+- 60%: Log warning, suggest summarization
+- 80%: Auto-compress, drop raw tool outputs
+- 90%: Block verbose tools, force wrap-up
+- 95%: Graceful termination with summary
+
+Usage:
+    from agent.token_budget import TokenBudget
+    budget = TokenBudget(max_tokens=128000)
+    budget.record_usage(prompt_tokens=500, completion_tokens=200)
+    status = budget.check()
+    # status.level: ok, warning, compress, block, terminate
+"""
+
+from __future__ import annotations
+
+import logging
+import time
+from dataclasses import dataclass, field
+from enum import Enum
+from typing import Any, Dict, List, Optional
+
+logger = logging.getLogger(__name__)
+
+
+class BudgetLevel(Enum):
+    """Token budget alert levels."""
+    OK = "ok"                 # < 60%
+    WARNING = "warning"       # 60-80%
+    COMPRESS = "compress"     # 80-90%
+    BLOCK = "block"           # 90-95%
+    TERMINATE = "terminate"   # > 95%
+
+
+@dataclass
+class BudgetStatus:
+    """Current budget status."""
+    level: BudgetLevel
+    used_tokens: int
+    max_tokens: int
+    percentage: float
+    remaining: int
+    message: str
+    actions: List[str] = field(default_factory=list)
+
+
+# Default thresholds
+THRESHOLDS = {
+    BudgetLevel.WARNING: 0.60,
+    BudgetLevel.COMPRESS: 0.80,
+    BudgetLevel.BLOCK: 0.90,
+    BudgetLevel.TERMINATE: 0.95,
+}
+
+
+class TokenBudget:
+    """Track token usage and enforce context limits."""
+
+    def __init__(self, max_tokens: int = 128000,
+                 thresholds: Optional[Dict[BudgetLevel, float]] = None):
+        self._max_tokens = max_tokens
+        self._thresholds = thresholds or THRESHOLDS
+        self._prompt_tokens = 0
+        self._completion_tokens = 0
+        self._tool_output_tokens = 0
+        self._history: List[Dict[str, Any]] = []
+
+    @property
+    def used_tokens(self) -> int:
+        return self._prompt_tokens + self._completion_tokens
+
+    @property
+    def remaining(self) -> int:
+        return max(0, self._max_tokens - self.used_tokens)
+
+    @property
+    def percentage(self) -> float:
+        if self._max_tokens == 0:
+            return 0
+        return self.used_tokens / self._max_tokens
+
+    def record_usage(self, prompt_tokens: int = 0, completion_tokens: int = 0,
+                     tool_output_tokens: int = 0):
+        """Record token usage from an API call."""
+        self._prompt_tokens += prompt_tokens
+        self._completion_tokens += completion_tokens
+        self._tool_output_tokens += tool_output_tokens
+        self._history.append({
+            "time": time.time(),
+            "prompt": prompt_tokens,
+            "completion": completion_tokens,
+            "tool_output": tool_output_tokens,
+            "total_used": self.used_tokens,
+        })
+
+    def check(self) -> BudgetStatus:
+        """Check current budget status and return appropriate actions."""
+        pct = self.percentage
+
+        if pct >= self._thresholds.get(BudgetLevel.TERMINATE, 0.95):
+            level = BudgetLevel.TERMINATE
+            msg = f"Context {pct:.0%} full. Session must terminate with summary."
+            actions = ["generate_summary", "terminate_session"]
+        elif pct >= self._thresholds.get(BudgetLevel.BLOCK, 0.90):
+            level = BudgetLevel.BLOCK
+            msg = f"Context {pct:.0%} full. Blocking verbose tool calls."
+            actions = ["block_verbose_tools", "force_wrap_up", "suggest_summary"]
+        elif pct >= self._thresholds.get(BudgetLevel.COMPRESS, 0.80):
+            level = BudgetLevel.COMPRESS
+            msg = f"Context {pct:.0%} full. Auto-compressing conversation."
+            actions = ["auto_compress", "drop_raw_tool_outputs", "suggest_summary"]
+        elif pct >= self._thresholds.get(BudgetLevel.WARNING, 0.60):
+            level = BudgetLevel.WARNING
+            msg = f"Context {pct:.0%} used. Consider summarizing."
+            actions = ["suggest_summary", "log_warning"]
+        else:
+            level = BudgetLevel.OK
+            msg = f"Context OK: {self.used_tokens}/{self._max_tokens} tokens ({pct:.0%})"
+            actions = []
+
+        return BudgetStatus(
+            level=level,
+            used_tokens=self.used_tokens,
+            max_tokens=self._max_tokens,
+            percentage=round(pct, 3),
+            remaining=self.remaining,
+            message=msg,
+            actions=actions,
+        )
+
+    def should_truncate_tool_output(self, estimated_tokens: int) -> bool:
+        """Check if a tool output should be truncated."""
+        if self.used_tokens + estimated_tokens > self._max_tokens * 0.95:
+            return True
+        return False
+
+    def get_truncation_budget(self) -> int:
+        """Get max tokens available for next tool output."""
+        budget = self.remaining - int(self._max_tokens * 0.05)  # Reserve 5%
+        return max(0, budget)
+
+    def reset(self):
+        """Reset budget for new session."""
+        self._prompt_tokens = 0
+        self._completion_tokens = 0
+        self._tool_output_tokens = 0
+        self._history.clear()
+
+    def get_report(self) -> Dict[str, Any]:
+        """Generate usage report."""
+        status = self.check()
+        return {
+            "status": status.level.value,
+            "used_tokens": self.used_tokens,
+            "max_tokens": self._max_tokens,
+            "remaining": self.remaining,
+            "percentage": status.percentage,
+            "prompt_tokens": self._prompt_tokens,
+            "completion_tokens": self._completion_tokens,
+            "tool_output_tokens": self._tool_output_tokens,
+            "message": status.message,
+            "actions": status.actions,
+        }

tools/code_execution_tool.py

@@ -883,43 +883,6 @@ def _execute_remote(
     return json.dumps(result, ensure_ascii=False)
 
 
-# ---------------------------------------------------------------------------
-# Main entry point
-# ---------------------------------------------------------------------------
-
-def _validate_python_syntax(code: str) -> Optional[str]:
-    """Validate Python syntax before execution.
-
-    Returns a JSON error string if syntax is invalid, None if valid.
-    This is a poka-yoke (mistake-proofing) guard that catches ~83% of
-    execute_code errors before subprocess spawn.
-    """
-    import ast as _ast
-
-    try:
-        _ast.parse(code)
-        return None  # Syntax is valid
-    except SyntaxError as e:
-        # Build a helpful error message
-        line_no = e.lineno or "?"
-        msg = e.msg or "syntax error"
-        # Show the offending line if available
-        lines = code.split("\n")
-        context = ""
-        if e.lineno and e.lineno <= len(lines):
-            context = f"\n  Line {line_no}: {lines[e.lineno - 1].rstrip()}"
-            if e.offset:
-                context += f"\n  {' ' * (e.offset + 7)}^"
-
-        return json.dumps({
-            "error": f"Python syntax error on line {line_no}: {msg}{context}",
-            "syntax_error": True,
-            "line": e.lineno,
-            "offset": e.offset,
-            "message": msg,
-        })
-
-
 # ---------------------------------------------------------------------------
 # Main entry point
 # ---------------------------------------------------------------------------
@@ -953,13 +916,6 @@ def execute_code(
     if not code or not code.strip():
         return tool_error("No code provided.")
 
-    # Poka-yoke: validate Python syntax before execution
-    # Catches ~83% of execute_code errors (syntax, NameError from bad code)
-    # before wasting time on subprocess spawn.
-    _syntax_result = _validate_python_syntax(code)
-    if _syntax_result is not None:
-        return _syntax_result
-
     # Dispatch: remote backends use file-based RPC, local uses UDS
     from tools.terminal_tool import _get_env_config
     env_type = _get_env_config()["env_type"]

tools/skill_manager_tool.py

@@ -44,6 +44,34 @@ from typing import Dict, Any, Optional, Tuple
 
 logger = logging.getLogger(__name__)
 
+
+def _format_error(
+    message: str,
+    skill_name: str = None,
+    file_path: str = None,
+    suggestion: str = None,
+    context: dict = None,
+) -> Dict[str, Any]:
+    """Format an error with rich context for better debugging."""
+    parts = [message]
+    if skill_name:
+        parts.append(f"Skill: {skill_name}")
+    if file_path:
+        parts.append(f"File: {file_path}")
+    if suggestion:
+        parts.append(f"Suggestion: {suggestion}")
+    if context:
+        for key, value in context.items():
+            parts.append(f"{key}: {value}")
+    return {
+        "success": False,
+        "error": " | ".join(parts),
+        "skill_name": skill_name,
+        "file_path": file_path,
+        "suggestion": suggestion,
+    }
+
+
 # Import security scanner — agent-created skills get the same scrutiny as
 # community hub installs.
 try: