I got sick of copypasting between ClaudeCode and Codex and was looking for a tool which parses the local sessions to create a new one. I found a few libraries out there but for some reason they carried over just the last ~10 messages.

handoff reads the full session history, uses tiktoken for token estimation, and gives you 3 tiers to choose from : full (conversation + tool calls + thinking + files modified), focused (no thinking blocks), or minimal (conversation only). It trims oldest messages first if the context is too large for the CLI arg limit.

it also checks if Claude's CLAUDE.md and MEMORY.md exist for that project directory and passes them along, so the receiving tool gets your project conventions.

zero-dependency TUI (just ANSI escape codes), single file, installs with uv tool install.