fix(compression): harden provider context handoff

agent/context_engine.py

@@ -28,6 +28,30 @@ Lifecycle:
 from abc import ABC, abstractmethod
 from typing import Any, Dict, List, Optional
 
+from agent.redact import redact_sensitive_text
+
+
+MEMORY_CONTEXT_MAX_CHARS = 6_000
+_MEMORY_CONTEXT_HEAD_CHARS = 4_000
+_MEMORY_CONTEXT_TAIL_CHARS = 1_500
+_MEMORY_CONTEXT_TRUNCATION_MARKER = "\n...[memory provider context truncated]...\n"
+
+
+def sanitize_memory_context(memory_context: str) -> str:
+    """Prepare provider context for a context-engine/LLM egress boundary."""
+    sanitized = redact_sensitive_text(
+        memory_context.strip(),
+        force=True,
+        redact_url_credentials=True,
+    )
+    if len(sanitized) <= MEMORY_CONTEXT_MAX_CHARS:
+        return sanitized
+    return (
+        sanitized[:_MEMORY_CONTEXT_HEAD_CHARS]
+        + _MEMORY_CONTEXT_TRUNCATION_MARKER
+        + sanitized[-_MEMORY_CONTEXT_TAIL_CHARS:]
+    )
+
 
 class ContextEngine(ABC):
     """Base class all context engines must implement."""