The Context Is the Agent
The problem
The first question is conceptual: is agent memory a database feature, or is it the architecture that determines what the model can see and change? The answer matters because retrieval is only one operation. A memory system also decides how prompts are rewritten, which tools and files are visible, what survives compaction, how interaction history is represented, and whether the agent can modify its own persistent state.
Anthropic’s account starts from a finite “attention budget.” Its distinction between prompt engineering and context engineering reframes the task as continuous selection among system instructions, tool schemas, retrieved information, message history, and external artifacts. Letta approaches the same problem through an “LLM operating system” metaphor, separating kernel-managed context, user messages, memory blocks, files, and tools. Its more provocative argument is that memory cannot be bolted onto an otherwise stateless harness.
These readings belong together because they challenge the usual short- versus long-term-memory taxonomy. The important unit is not simply where information is stored, but how the harness turns external state into usable working context. That sets up the next question: once memory is treated as an active system, how should it write and revise itself?