“Agent memory” sounds like one feature, but in practice it is at least four different problems: session state, durable memory, project context, and recall strategy. The current generation of agent systems does not solve these in the same way. OpenClaw treats memory as file-backed knowledge plus retrieval tools; Hermes Agent separates bounded persistent memory from a searchable session archive; Codex CLI leans on local transcripts, layered project instructions, and skills; Claude Code combines persistent CLAUDE.md rules with auto memory and resumable sessions.