What’s new in Undo 10.0 for C, C++, Go and Rust¶

See the sections below for the headline product improvements in Undo 10.0.

Undo AI: runtime context for AI agents¶

Release 10.0 introduces Undo AI, which gives your AI agent the runtime context it needs to investigate complex problems and answer questions about what your program actually did. The AI agent sees not just the source code, but the values the program produced, the paths it actually took, and the order in which things happened.

There are two ways to use it:

From your AI agent (such as Claude Code, Codex, Cursor, or GitHub Copilot in Visual Studio Code): configure the agent to use the new undo mcp MCP server shipped with the Undo Suite. The AI agent decides on its own when to investigate or capture a recording and which tools to call.
In UDB: load a recording or start a program in UDB as usual and use the new ai command to ask questions inline.

In both cases, all traffic flows between your machine and the LLM provider that your AI agent already uses; Undo-hosted servers are not in the loop. See How it works for the underlying mechanism, and Using AI effectively for guidance on getting the best results.

Note

AI features are not enabled in every license. If the ai command in UDB or the undo mcp server reports that AI is disabled, contact support@undo.io to upgrade your license.

Improvements in UDB¶

All Undo users are licensed to use UDB, Undo’s interactive time travel debugger. Release 10.0 benefits from the improvements listed below.

Smaller recordings with zstd compression¶

Undo recordings are now compressed using the zstd compression scheme instead of lz4. As a result, recordings are generally around 30% smaller, reducing the disk space and network bandwidth needed to store and share them.

More…¶

Further product changes relating to UDB are described in the CHANGELOG-udb.txt file included in your Undo release archive.

Improvements in Undo Team & OEM Editions¶

Undo Team & OEM Editions v10.0 benefit from the UDB improvements described above, including the smaller recordings produced by the new zstd compression scheme.

In addition, the placement of snapshots saved in recordings made by LiveRecorder has been improved. This results in faster time-travel and reverse commands when replaying those recordings.

Further product changes relating to Undo Team & OEM Editions are described in the following changelog files included in your Undo release archive:

undolr/CHANGELOG.txt for changes to LiveRecorder
keyserver/CHANGELOG.txt for changes to the Undo Keyserver

Removals¶

Release 10.0 removes some legacy product features and behaviors as described below.

The deprecated set hints enabled and show hints commands have been removed. Use set prompt-hints enabled and show prompt-hints instead.
Five environment variables and the --instr-heapsize command-line option have been renamed (for example, UNDO_instrheapsize is now UNDO_instr_cache_size). The original names are still available, but are deprecated. See CHANGELOG-udb.txt for the full list.

System requirements¶

There are no significant changes to the Undo system requirements in the 10.0 release.

For a list of the system requirements for a given release, see the documentation at docs/userguide/html/SystemRequirements.html in the release directory. The system requirements for the latest Undo release are always provided in full at System requirements.