Every new AI session starts cold. Switch tools, hit a token limit, or come back tomorrow and the agent has no idea what you were doing. context0 saves a structured checkpoint per git branch: what’s done, what’s next, blockers, tests, and key files. On the next session, the agent can load that checkpoint and pick up where it left off. Free, open source, local-only. Works with Claude Code, Cursor, and Codex.