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cass source build fails with `rustc 1.94.0 is not supported` or `E0554`

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Source: Troubleshooting reference

On a host with glibc < 2.38 (e.g. Ubuntu 22.04) cass has no usable prebuilt, so memory.sh builds it from source — and you see one of:

rustc 1.94.0 is not supported by the following packages: sysinfo@0.39.5 requires rustc 1.95 …
# or, on a newer stable:
error[E0554]: `#![feature]` may not be used on the stable release channel

Two root causes stacked:

  1. cass requires nightly. A dependency gates #![feature(try_trait_v2)] and the repo pins channel = "nightly". Stable can’t build it — an old stable fails the MSRV check, a new stable fails E0554.
  2. A stray Homebrew rust shadows rustup. A rust formula (a lingering build dependency — not in the Brewfile, nothing depends on it) puts cargo/rustc in brew/bin at an old version. In bootstrap’s PATH that shadows rustup, so cargo resolved to brew’s 1.94.0 even after rust.sh updated rustup’s stable to 1.97.1.

Confirm:

Terminal window
which -a cargo          # a brew/bin/cargo at an old version is the smoking gun
rustup toolchain list   # is `nightly` installed?

Fix (already baked into current memory.sh — this is for older checkouts or manual recovery):

Terminal window
brew uninstall rust     # remove the orphan shadow (safe: nothing depends on it)
rustup toolchain install nightly --profile minimal
$CARGO_HOME/bin/cargo +nightly install --git \
  https://github.com/Dicklesworthstone/coding_agent_session_search \
  coding-agent-search --bin cass --locked --root "$LOCAL_PLAT"

_cass_build_from_source now installs nightly on demand and calls $CARGO_HOME/bin/cargo +nightly explicitly, so it no longer depends on PATH resolution or the default toolchain.