Fix delimiter capture and namespace collision bugs (§3.1-3.2)

rlm/environments/local_repl.py

@@ -16,9 +16,22 @@
 from rlm.environments.base_env import NonIsolatedEnv
 
 # =============================================================================
-# Safe Builtins
+# Safe Builtins and Protected Names
 # =============================================================================
 
+# Protected scaffold names that cannot be overwritten by user code
+SCAFFOLD_NAMES = frozenset(
+    {
+        "context",
+        "llm_query",
+        "llm_query_batched",
+        "FINAL_VAR",
+        "SHOW_VARS",
+        "finish",
+        "finish_var",
+    }
+)
+
 # Safe builtins - blocks dangerous operations like eval/exec/input
 _SAFE_BUILTINS = {
     # Core types and functions
@@ -159,11 +172,26 @@ def setup(self):
         # Track LLM calls made during code execution
         self._pending_llm_calls: list[RLMChatCompletion] = []
 
+        # Track finish state for programmatic completion (§3.1 fix)
+        self._finish_answer: str | None = None
+
         # Add helper functions
         self.globals["FINAL_VAR"] = self._final_var
         self.globals["SHOW_VARS"] = self._show_vars
         self.globals["llm_query"] = self._llm_query
         self.globals["llm_query_batched"] = self._llm_query_batched
+        self.globals["finish"] = self._finish
+        self.globals["finish_var"] = self._finish_var
+
+        # Store original scaffold bindings for protection (§3.2 fix)
+        self._scaffold_bindings = {
+            "FINAL_VAR": self._final_var,
+            "SHOW_VARS": self._show_vars,
+            "llm_query": self._llm_query,
+            "llm_query_batched": self._llm_query_batched,
+            "finish": self._finish,
+            "finish_var": self._finish_var,
+        }
 
     def _final_var(self, variable_name: str) -> str:
         """Return the value of a variable as a final answer."""
@@ -192,6 +220,32 @@ def _show_vars(self) -> str:
             return "No variables created yet. Use ```repl``` blocks to create variables."
         return f"Available variables: {available}"
 
+    def _finish(self, value: Any) -> str:
+        """Signal completion with a final answer (programmatic FINAL)."""
+        self._finish_answer = str(value)
+        return f"Task completed with answer: {self._finish_answer}"
+
+    def _finish_var(self, variable_name: str) -> str:
+        """Signal completion with a variable's value (programmatic FINAL_VAR)."""
+        variable_name = variable_name.strip().strip("\"'")
+        if variable_name in self.locals:
+            self._finish_answer = str(self.locals[variable_name])
+            return f"Task completed with answer from variable '{variable_name}': {self._finish_answer}"
+
+        # Provide helpful error message with available variables
+        available = [k for k in self.locals.keys() if not k.startswith("_")]
+        if available:
+            return (
+                f"Error: Variable '{variable_name}' not found. "
+                f"Available variables: {available}. "
+                f"You must create and assign a variable BEFORE calling finish_var on it."
+            )
+        return (
+            f"Error: Variable '{variable_name}' not found. "
+            f"No variables have been created yet. "
+            f"You must create and assign a variable in a REPL block BEFORE calling finish_var on it."
+        )
+
     def _llm_query(self, prompt: str, model: str | None = None) -> str:
         """Query the LM via socket connection to the handler.
 
@@ -287,6 +341,9 @@ def add_context(
         # Alias context_0 as 'context' for backward compatibility
         if context_index == 0:
             self.execute_code(f"context = {var_name}")
+            # Protect 'context' in scaffold bindings
+            if hasattr(self, "_scaffold_bindings"):
+                self._scaffold_bindings["context"] = self.locals.get("context")
 
         self._context_count = max(self._context_count, context_index + 1)
         return context_index
@@ -370,6 +427,22 @@ def execute_code(self, code: str) -> REPLResult:
                     if key not in self.globals and not key.startswith("_"):
                         self.locals[key] = value
 
+                # Restore protected scaffold bindings if overwritten (§3.2 fix)
+                if hasattr(self, "_scaffold_bindings"):
+                    for name in SCAFFOLD_NAMES:
+                        if name in self._scaffold_bindings:
+                            # Check if binding was overwritten in globals
+                            if name in self.globals and self.globals[name] != self._scaffold_bindings[name]:
+                                self.globals[name] = self._scaffold_bindings[name]
+                            # Check if binding was overwritten in locals
+                            if name in self.locals and self.locals[name] != self._scaffold_bindings[name]:
+                                # For context, update the scaffold binding to track current value
+                                if name == "context":
+                                    self._scaffold_bindings[name] = self.locals[name]
+                                else:
+                                    # Restore other scaffold bindings
+                                    self.locals[name] = self._scaffold_bindings[name]
+
                 stdout = stdout_buf.getvalue()
                 stderr = stderr_buf.getvalue()
             except Exception as e:

rlm/utils/parsing.py

@@ -40,8 +40,20 @@ def find_final_answer(text: str, environment: "BaseEnv | None" = None) -> str |
     Returns:
         The final answer string, or None if no final answer pattern is found
     """
-    # Check for FINAL_VAR pattern first - must be at start of line
-    final_var_pattern = r"^\s*FINAL_VAR\((.*?)\)"
+    # Check if finish() or finish_var() were used programmatically (preferred)
+    if environment is not None:
+        try:
+            answer = getattr(environment, "_finish_answer", None)
+            if answer is not None and isinstance(answer, str):
+                return answer
+        except Exception:
+            pass  # Fall through to regex patterns
+
+    # Fallback to regex patterns for backward compatibility with models trained on FINAL() convention
+
+    # Check for FINAL_VAR pattern first - must be at start of line, non-greedy
+    # Use DOTALL to allow newlines within parentheses, but non-greedy to stop at first )
+    final_var_pattern = r"^\s*FINAL_VAR\((.*?)\)\s*$"
     match = re.search(final_var_pattern, text, re.MULTILINE | re.DOTALL)
     if match:
         variable_name = match.group(1).strip().strip('"').strip("'")
@@ -54,8 +66,9 @@ def find_final_answer(text: str, environment: "BaseEnv | None" = None) -> str |
         return None
 
     # Check for FINAL pattern - must be at start of line
-    # Use greedy matching to capture content with nested parentheses
-    final_pattern = r"^\s*FINAL\((.*)\)\s*$"
+    # Non-greedy (.*?) with DOTALL allows multiline but stops at first closing )
+    # This fixes the over-capture bug while still supporting multiline content
+    final_pattern = r"^\s*FINAL\((.*?)\)\s*$"
     match = re.search(final_pattern, text, re.MULTILINE | re.DOTALL)
     if match:
         return match.group(1).strip()