CLI variables are global to the invocation, not scoped to a task: `args.Parse` turns every word holding `=` into a global and every other word into a call, so `task build ENV=dev deploy` and `task build deploy ENV=dev` are the same command. The engine assumed the opposite and, as soon as a word matched a task, served only that task's variables — nothing at all when it had none. `task build <TAB>` and even `task build de<TAB>` went silent, where all five legacy wrappers offered task names at every position.
The engine now unions the still-unset requirements of every task named on the line, and falls through to task names once they are all set. The line resolves itself: fill in what blocks execution, then add another task. Keeping the two families exclusive means each keeps a coherent directive, so nothing loses its trailing space.
Task words are matched with FindMatchingTasks instead of a hand-built list of names truncated at their first `*`, which is why `task wildcard-foo <TAB>` used to offer task names rather than the variables of `wildcard-*`. Completion also disables fuzzy matching: a suggestion list has no "did you mean".
Three fixes ride along. `--sort default` left the sorter nil and cleared the one NewExecutor had set, so completion listed tasks in Taskfile order while `--list` sorted them — and a single templated description silently restored the sort through GetTaskList. The bash wrapper never defined KeepOrder, losing the declaration order of `requires`; it now passes `compopt -o nosort`, which bash 3.2 ignores as it already ignores nospace. And the shell suite unsets TASK_EXE and GO_TASK_PROGNAME: fish, Nushell and PowerShell resolve the binary through them, so an ambient value silently tested something other than the binary just built.
Bash, Fish, Zsh, Nushell and PowerShell now share a single backend: `task __complete` returns the suggestions plus a directive, and every wrapper is a thin shim around it. All five shells offer the same suggestions — task names, aliases, flags, flag values and per-task CLI variables. The Zsh `show-aliases` and `verbose` zstyles keep working, now backed by the `--no-aliases` and `--no-descriptions` completion flags.
The engine is opt-in via `task --new-completion <shell>`, leaving `--completion` and the legacy scripts untouched; it will become the default in a future release. The new wrappers live under `completion/next/`.
Completing a keystroke never reaches the network, never blocks on a stdin entrypoint, and honors every flag that decides how the Taskfile is loaded. Ref resolution shared by `requires` and enum completion moved to `internal/refs`.
A cross-shell test suite exercises the protocol in Go with thin shell smoke tests, and runs in CI.
