Panic when attempting to run parallel tasks with "replacing" output option #8985

chrisschaaf · 2026-04-09T21:25:41Z

chrisschaaf
Apr 9, 2026

Hello, I found some interesting behavior that I think may be a bug. When executing tasks in parallel and setting output to replacing, mise panics and hangs.

Steps To Reproduce

Minimal mise.toml config:

[settings.task]
output = "replacing"

[tasks.parallel]
description = "Run tasks in parallel via direct tasks array"
run = [{ tasks = ["task:1", "task:2", "task:3"] }]

[tasks.parallel_wildcard]
description = "Run tasks in parallel with wildcard notation"
run = [{ task = "task:*" }]

[tasks."task:1"]
run = "sleep 1 && echo 'task 1 done'"

[tasks."task:2"]
run = "sleep 1 && echo 'task 2 done'"

[tasks."task:3"]
run = "sleep 1 && echo 'task 3 done'"

Run the task group with the replacing output style:

mise run parallel
mise run parallel_wildcard
mise run "task:*"

Expected Behavior

Ideally, mise manages the concurrent output smoothly and results in something like this for all 3 run commands:

❯ mise run parallel
[task:2] task 2 done
[task:3] task 3 done
[task:1] task 1 done

Alternatively, mise either:

automatically falls back to another output style when parallel execution is detected.
throws a graceful error stating that replacing output is not supported for parallel tasks.

Actual Behavior

For mise run parallel and mise run parallel_wildcard:

The application panics and crashes multiple times (seemingly once per parallel task):

❯ RUST_BACKTRACE=full mise run parallel
[parallel]                                                                                             ◜
=== Async Backtrace (panic occurred in tokio runtime) ===
[no accessible async backtrace]
------- TASK DUMP TREE -------

=== End Async Backtrace ===

The application panicked (crashed).
Message:  called `Option::unwrap()` on a `None` value
Location: src/task/task_output_handler.rs:303

  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ BACKTRACE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
   1: backtrace::capture::Backtrace::new::h94ba56b491689c29
      at <unknown source file>:<unknown line>
   2: color_eyre::config::PanicHook::panic_report::h464e97cf2df2c227
      at <unknown source file>:<unknown line>
   3: color_eyre::config::PanicHook::into_panic_hook::{{closure}}::hd6ceebc49589dd3a
      at <unknown source file>:<unknown line>
   4: mise::install_panic_hook::{{closure}}::hea364f6117e8c40e
      at <unknown source file>:<unknown line>
   5: std::panicking::panic_with_hook::h657ee82e431041f8
      at <unknown source file>:<unknown line>
   6: std::panicking::panic_handler::{{closure}}::hd0ef6f87b4fd1427
      at <unknown source file>:<unknown line>
   7: std::sys::backtrace::__rust_end_short_backtrace::hbd8bf96e4ee54567
      at <unknown source file>:<unknown line>
   8: __rustc[16f1505adc47261a]::rust_begin_unwind<unknown>
      at <unknown source file>:<unknown line>
   9: core::panicking::panic_fmt::ha09fb24313daf262
      at <unknown source file>:<unknown line>
  10: core::panicking::panic::hb152b149bd05e810
      at <unknown source file>:<unknown line>
  11: core::option::unwrap_failed::h639b4bdf1cab8c92
      at <unknown source file>:<unknown line>
  12: mise::task::task_output_handler::OutputHandler::eprint::hbf43101a929b9654
      at <unknown source file>:<unknown line>
  13: mise::task::task_executor::TaskExecutor::run_task_sched::{{closure}}::ha17b96e4917b022c
      at <unknown source file>:<unknown line>
  14: tokio::runtime::task::core::Core<T,S>::poll::h8fafcd37ee47f584
      at <unknown source file>:<unknown line>
  15: tokio::runtime::task::raw::poll::hd4b60063787c6eaa
      at <unknown source file>:<unknown line>
  16: tokio::runtime::scheduler::multi_thread::worker::Context::run_task::hd8f7499b97418c62
      at <unknown source file>:<unknown line>
  17: tokio::runtime::scheduler::multi_thread::worker::run::he998a0b6d3232472
      at <unknown source file>:<unknown line>
  18: tokio::runtime::task::raw::poll::h47bd1f9677e193da
      at <unknown source file>:<unknown line>
  19: std::sys::backtrace::__rust_begin_short_backtrace::ha34eb6879aecc698
      at <unknown source file>:<unknown line>
  20: core::ops::function::FnOnce::call_once{{vtable.shim}}::h29c11b8eef796158
      at <unknown source file>:<unknown line>
  21: std::sys::thread::unix::Thread::new::thread_start::h7cf39b7a7f135f48
      at <unknown source file>:<unknown line>
  22: __pthread_cond_wait<unknown>
      at <unknown source file>:<unknown line>

Run with COLORBT_SHOW_HIDDEN=1 environment variable to disable frame filtering.
The application panicked (crashed).
Message:  called `Option::unwrap()` on a `None` value
Location: src/task/task_output_handler.rs:303

  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ BACKTRACE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
   1: backtrace::capture::Backtrace::new::h94ba56b491689c29
      at <unknown source file>:<unknown line>
   2: color_eyre::config::PanicHook::panic_report::h464e97cf2df2c227
      at <unknown source file>:<unknown line>
   3: color_eyre::config::PanicHook::into_panic_hook::{{closure}}::hd6ceebc49589dd3a
      at <unknown source file>:<unknown line>
   4: mise::install_panic_hook::{{closure}}::hea364f6117e8c40e
      at <unknown source file>:<unknown line>
   5: std::panicking::panic_with_hook::h657ee82e431041f8
      at <unknown source file>:<unknown line>
   6: std::panicking::panic_handler::{{closure}}::hd0ef6f87b4fd1427
      at <unknown source file>:<unknown line>
   7: std::sys::backtrace::__rust_end_short_backtrace::hbd8bf96e4ee54567
      at <unknown source file>:<unknown line>
   8: __rustc[16f1505adc47261a]::rust_begin_unwind<unknown>
      at <unknown source file>:<unknown line>
   9: core::panicking::panic_fmt::ha09fb24313daf262
      at <unknown source file>:<unknown line>
  10: core::panicking::panic::hb152b149bd05e810
      at <unknown source file>:<unknown line>
  11: core::option::unwrap_failed::h639b4bdf1cab8c92
      at <unknown source file>:<unknown line>
  12: mise::task::task_output_handler::OutputHandler::eprint::hbf43101a929b9654
      at <unknown source file>:<unknown line>
  13: mise::task::task_executor::TaskExecutor::run_task_sched::{{closure}}::ha17b96e4917b022c
      at <unknown source file>:<unknown line>
  14: tokio::runtime::task::core::Core<T,S>::poll::h8fafcd37ee47f584
      at <unknown source file>:<unknown line>
  15: tokio::runtime::task::raw::poll::hd4b60063787c6eaa
      at <unknown source file>:<unknown line>
  16: tokio::runtime::scheduler::multi_thread::worker::Context::run_task::hd8f7499b97418c62
      at <unknown source file>:<unknown line>
  17: tokio::runtime::scheduler::multi_thread::worker::run::he998a0b6d3232472
      at <unknown source file>:<unknown line>
  18: tokio::runtime::task::raw::poll::h47bd1f9677e193da
      at <unknown source file>:<unknown line>
  19: std::sys::backtrace::__rust_begin_short_backtrace::ha34eb6879aecc698
      at <unknown source file>:<unknown line>
  20: core::ops::function::FnOnce::call_once{{vtable.shim}}::h29c11b8eef796158
      at <unknown source file>:<unknown line>
  21: std::sys::thread::unix::Thread::new::thread_start::h7cf39b7a7f135f48
      at <unknown source file>:<unknown line>
  22: __pthread_cond_wait<unknown>
      at <unknown source file>:<unknown line>

Run with COLORBT_SHOW_HIDDEN=1 environment variable to disable frame filtering.
The application panicked (crashed).
Message:  called `Option::unwrap()` on a `None` value
Location: src/task/task_output_handler.rs:303

  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ BACKTRACE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
   1: backtrace::capture::Backtrace::new::h94ba56b491689c29
      at <unknown source file>:<unknown line>
   2: color_eyre::config::PanicHook::panic_report::h464e97cf2df2c227
      at <unknown source file>:<unknown line>
   3: color_eyre::config::PanicHook::into_panic_hook::{{closure}}::hd6ceebc49589dd3a
      at <unknown source file>:<unknown line>
   4: mise::install_panic_hook::{{closure}}::hea364f6117e8c40e
      at <unknown source file>:<unknown line>
   5: std::panicking::panic_with_hook::h657ee82e431041f8
      at <unknown source file>:<unknown line>
   6: std::panicking::panic_handler::{{closure}}::hd0ef6f87b4fd1427
      at <unknown source file>:<unknown line>
   7: std::sys::backtrace::__rust_end_short_backtrace::hbd8bf96e4ee54567
      at <unknown source file>:<unknown line>
   8: __rustc[16f1505adc47261a]::rust_begin_unwind<unknown>
      at <unknown source file>:<unknown line>
   9: core::panicking::panic_fmt::ha09fb24313daf262
      at <unknown source file>:<unknown line>
  10: core::panicking::panic::hb152b149bd05e810
      at <unknown source file>:<unknown line>
  11: core::option::unwrap_failed::h639b4bdf1cab8c92
      at <unknown source file>:<unknown line>
  12: mise::task::task_output_handler::OutputHandler::eprint::hbf43101a929b9654
      at <unknown source file>:<unknown line>
  13: mise::task::task_executor::TaskExecutor::run_task_sched::{{closure}}::ha17b96e4917b022c
      at <unknown source file>:<unknown line>
  14: tokio::runtime::task::core::Core<T,S>::poll::h8fafcd37ee47f584
      at <unknown source file>:<unknown line>
  15: tokio::runtime::task::raw::poll::hd4b60063787c6eaa
      at <unknown source file>:<unknown line>
  16: tokio::runtime::scheduler::multi_thread::worker::Context::run_task::hd8f7499b97418c62
      at <unknown source file>:<unknown line>
  17: tokio::runtime::scheduler::multi_thread::worker::run::he998a0b6d3232472
      at <unknown source file>:<unknown line>
  18: tokio::runtime::task::raw::poll::h47bd1f9677e193da
      at <unknown source file>:<unknown line>
  19: std::sys::backtrace::__rust_begin_short_backtrace::ha34eb6879aecc698
      at <unknown source file>:<unknown line>
  20: core::ops::function::FnOnce::call_once{{vtable.shim}}::h29c11b8eef796158
      at <unknown source file>:<unknown line>
  21: std::sys::thread::unix::Thread::new::thread_start::h7cf39b7a7f135f48
      at <unknown source file>:<unknown line>
  22: __pthread_cond_wait<unknown>
      at <unknown source file>:<unknown line>

[parallel]

For mise run "task:*", it does work, though it only outputs a single line after completing:

❯ mise run "task:*"
[task:1]                  task 1 done

Environment

❯ mise version
              _                                        __
   ____ ___  (_)_______        ___  ____        ____  / /___ _________
  / __ `__ \/ / ___/ _ \______/ _ \/ __ \______/ __ \/ / __ `/ ___/ _ \
 / / / / / / (__  )  __/_____/  __/ / / /_____/ /_/ / / /_/ / /__/  __/
/_/ /_/ /_/_/____/\___/      \___/_/ /_/     / .___/_/\__,_/\___/\___/
                                            /_/                 by @jdx
2026.4.7 macos-arm64 (2026-04-09)

❯ uname -a
Darwin US-<serial-number-redacted> 25.3.0 Darwin Kernel Version 25.3.0: Wed Jan 28 20:54:55 PST 2026; root:xnu-12377.91.3~2/RELEASE_ARM64_T6031 arm64 arm Darwin

Answered by chrisschaaf

Apr 10, 2026

Validated that #8986 / 2026.4.8 fixed this for me.

View full answer

chrisschaaf · 2026-04-10T19:03:36Z

chrisschaaf
Apr 10, 2026
Author

Validated that #8986 / 2026.4.8 fixed this for me.

0 replies

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Panic when attempting to run parallel tasks with "replacing" output option #8985

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Panic when attempting to run parallel tasks with "replacing" output option #8985

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chrisschaaf Apr 9, 2026

Steps To Reproduce

Expected Behavior

Actual Behavior

Environment

Replies: 1 comment

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chrisschaaf Apr 10, 2026 Author

chrisschaaf
Apr 9, 2026

chrisschaaf
Apr 10, 2026
Author