What
The sandbox is the walled-off environment where Claude Code runs commands, with its own proxy controlling network access. When network.tlsTerminate is on, that proxy opens up HTTPS connections itself so it can inspect them. It now puts limits on these connections:
- Connections at once: 256 by default. Past that, new connections are refused with "too many TLS-terminated tunnels at once". The message points to
network.tlsTerminate.maxTunnels, the setting that changes the limit. - Setup timeout: a connection whose secure handshake (the opening exchange that sets up encryption) does not finish in time, 10 seconds by default, is closed.
- Byte budget: a cap on how much data is handled.
- Header size: limits on how large request headers can be.
- Deny header: an optional header used when a request is refused.
Why
If you use TLS termination in the sandbox and a task opens many HTTPS connections at once, some can now be refused or closed. Raise network.tlsTerminate.maxTunnels if you hit that limit.
Names in the bundlenetwork.tlsTerminate
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Confirmed since
Anthropic's documentation has since written up network.tlsTerminate, on Configure server-managed settings.
* **Sandbox network and isolation settings**: [sandbox](/docs/en/sandboxing) settings that let the sandbox proxy read, reroute, or authenticate traffic, or that weaken the sandbox's isolation: `sandbox.network.tlsTerminate`, `sandbox.netwo…server-managed-settings see the edit
One source agreesOne thing we can check says the same as this entry.
Anthropic's documentation agrees
Anthropic's documentation has since written up network.tlsTerminate, on Configure server-managed settings.