Function data_dir_hash16 

pub fn data_dir_hash16(data_dir: &Path, version: &str) -> String

First 16 hex chars of FNV-1a-64 over the canonical-lowercase data_dir path combined with the build version string.

Including the version ensures that two different release binaries (e.g. 0.40.2 and 0.41.0) that share the same channel data dir (~/.agentmux/channels/stable/) produce DISTINCT pipe names and therefore satisfy the CLAUDE.md multi-version concurrency guarantee: each version is an independent single-instance domain.

Without the version, both binaries hash to the same pipe name and the second one silently forwards its “open window” request to the first, activating the wrong version. version should be the semver string from CARGO_PKG_VERSION (e.g. "0.41.0"). The \x00 separator never appears in a filesystem path, so path + version are always unambiguously distinguishable.