v21.4.0 — the hardening release

Install / update

Stop AgentQon first, then:

npm install -g agentqon@latest

agentqon setup --repair

agentqon

What changed

Backend — isolation and reliability

• Per-run isolation: concurrent runs can no longer cross model routing or
  share per-run state (the audit's top critical).
• Custom-agent instructions are tenant-scoped — no more leaking across
  accounts.
• Queue claiming is atomic, with real heartbeats and owner fencing; the
  inline runner claims the correct job.
• Vault configuration parsing fixed and now fails loudly instead of
  silently; the kill switch works in the default mode; approval state
  cannot be flipped after the fact; API errors no longer leak tracebacks.

CLI — the terminal hang is dead

• Fixed the Progress timer leak that hung the terminal after "ready"
  (16/16 new regression tests pass).
• Repair is staged-and-swapped, so it cannot brick an install, and it
  refuses to run while a server is live.
• Python detection now tries every interpreter on the machine.
• Server identity + version check on launch: a stale server left over
  from an older install is restarted, never silently reused. This was
  the root cause of the lingering ::1 loopback error in 21.2.x — the fix
  shipped in 21.2.1, but an old running server kept serving the bug.

Web UI

• Export downloads work again, including in Shield mode.
• Custom-agent registry capped at 100 rows with debounced filtering.
• An expired session now shows a clear "session expired — relaunch with
  agentqon" banner instead of failing silently.
• Run statuses are honest, and counts corrected to the verified 6,799
  agent roster.

Release pipeline

• The pack-gate now scans the compiled payload, asserts the package
  identity and the Python 3.12 build, and uses wider secret patterns.
• The package rename is a verified script (11 replacements, gate PASS
  with identity verified for this staging).

Test evidence

• Backend unit: 240 passed (the one sandbox queue-timing failure is
  environmental and proven as such).
• Integration: 149 passed.
• CLI (node): 16/16.
• UI: 25/25.

Note on dependencies

Three pins an early audit draft called "dead" (opentelemetry-api, PyYAML,
python-dotenv) are in fact required by FastAPI / uvicorn[standard] under
the hash-locked requirements — proven in a clean venv. They stay.