fix(task): avoid duplicated stderr on task failure in replacing mode by jdx · Pull Request #8275 · jdx/mise

jdx · 2026-02-21T14:48:32Z

Summary

When a task fails in --output replacing mode, on_error() re-printed all accumulated output (stdout + stderr) via pr.println(), but stderr was already printed during execution, causing duplication
Fix by tagging each output line with its source (stdout vs stderr) and only replaying stdout lines in on_error(), since stdout was hidden behind the progress indicator (pr.set_message()) while stderr was already permanently visible

Test plan

Verified --output replacing no longer duplicates stderr on task failure
Verified stdout is still shown on failure (it was hidden behind progress indicator)
Verified all other output modes (default, prefix, interleave, raw, quiet, silent, timed, keep-order) are unaffected
Verified successful tasks are unaffected
All 481 unit tests pass

🤖 Generated with Claude Code

Note

Low Risk
Small, localized change to command output handling on failures; main risk is inadvertently suppressing or mis-ordering error output in edge cases.

Overview
Fixes a failure-mode logging bug where --output replacing could duplicate stderr by replaying all captured output on error.

CmdLineRunner now tags captured lines with an OutputSource and updates on_error to replay only stdout (and only when stdout was hidden behind the progress indicator), leaving stderr to be shown just once during execution. Also updates the raw-exec error path to pass an empty output vector and tweaks contributor guidance in CLAUDE.md to prefer the task scope for task-related changes.

^{Written by Cursor Bugbot for commit 5b1339e. This will update automatically on new commits. Configure here.}

gemini-code-assist · 2026-02-21T14:48:43Z

Summary of Changes

Hello @jdx, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses an issue where error messages from stderr were duplicated when tasks failed in the 'replacing' output mode. The core change involves distinguishing between stdout and stderr lines when accumulating output, ensuring that only stdout, which was previously hidden by progress indicators, is replayed upon task failure, thereby providing a cleaner and more accurate error presentation.

Highlights

Eliminated duplicate stderr output: When a task failed in --output replacing mode, stderr was printed twice: once during execution and again by the on_error() function. This has been resolved.
Output source tagging: The combined_output now stores each line along with a boolean indicating if it originated from stdout or stderr, allowing for selective replaying.
Refined error output handling: The on_error() function was updated to only replay stdout lines, as stderr lines were already visible during execution, preventing redundancy.

Changelog

src/cmd.rs
- Modified the combined_output vector to store tuples of (String, bool) to differentiate between stdout and stderr lines.
- Updated calls to on_error to pass the new Vec<(String, bool)> type instead of a single String.
- Refactored the on_error function to filter and only print stdout lines when replaying output on task failure, preventing stderr duplication.

Activity

Verified that --output replacing no longer duplicates stderr on task failure.
Confirmed that stdout is still displayed on failure, as it was previously hidden by the progress indicator.
Ensured that all other output modes (default, prefix, interleave, raw, quiet, silent, timed, keep-order) remain unaffected.
Confirmed that successful tasks are unaffected by these changes.
All 481 unit tests passed, indicating no regressions.

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Code Review

The pull request addresses a bug where stderr output was duplicated when a task failed in --output replacing mode. The fix involves tagging output lines as either stdout or stderr and replaying only stdout lines on error, as stderr was already printed during execution. This is a good fix that improves the user experience by preventing redundant output. The changes are well-tested and consider various output modes and success/failure scenarios.

Copilot

Pull request overview

This PR fixes a bug where stderr output was duplicated when a task failed in --output replacing mode. The fix distinguishes between stdout and stderr in the accumulated output buffer and only replays stdout on error, since stderr was already displayed during execution.

Changes:

Modified output accumulation to track whether each line came from stdout or stderr using a tuple (String, bool)
Updated on_error() to filter and replay only stdout lines, preventing stderr duplication
Updated all on_error() call sites to pass the new Vec<(String, bool)> type instead of String

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Copilot · 2026-02-21T14:52:53Z

src/cmd.rs

                    let line = self.redactor.redact(&line);
                    self.on_stdout(line.clone());
-                    combined_output.push(line);
+                    combined_output.push((line, true));


Consider using a more descriptive tuple field name or a struct to improve code readability. The boolean flag 'true' for stdout and 'false' for stderr is not immediately clear from the code. A struct like struct OutputLine { content: String, is_stdout: bool } or using a named tuple pattern would make the intent clearer and reduce the risk of confusion.

When a task fails in replacing output mode, on_error() re-printed all accumulated output (stdout + stderr) via pr.println(). But stderr lines were already printed during execution via pr.println() in on_stderr(), causing them to appear twice. Fix by tagging each output line with its source (stdout vs stderr) and only replaying stdout lines in on_error(). Stdout needs replay because it was only shown transiently via pr.set_message() (progress indicator), while stderr was already permanently printed. Also update CLAUDE.md to clarify that task-related changes should use the `task` scope, not `run`. Fixes #8267 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

github-actions · 2026-02-21T15:11:17Z

Hyperfine Performance

`mise x -- echo`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`mise-2026.2.17 x -- echo`	22.9 ± 1.1	21.8	35.0	1.00
`mise x -- echo`	23.0 ± 1.6	21.6	38.8	1.01 ± 0.08

`mise env`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`mise-2026.2.17 env`	22.0 ± 1.2	21.1	35.6	1.00
`mise env`	22.5 ± 1.2	21.1	26.4	1.02 ± 0.08

`mise hook-env`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`mise-2026.2.17 hook-env`	22.7 ± 1.1	21.6	39.5	1.00
`mise hook-env`	22.8 ± 0.5	22.0	25.1	1.01 ± 0.05

`mise ls`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`mise-2026.2.17 ls`	19.8 ± 0.3	19.2	22.0	1.00
`mise ls`	19.9 ± 0.2	19.4	21.1	1.00 ± 0.02

`xtasks/test/perf`

Command	mise-2026.2.17	mise	Variance
install (cached)	123ms	124ms	+0%
ls (cached)	75ms	75ms	+0%
bin-paths (cached)	79ms	79ms	+0%
task-ls (cached)	813ms	800ms	+1%

@jdx

### 🚀 Features - **(install)** auto-lock all platforms after tool installation by @jdx in [#8277](#8277) ### 🐛 Bug Fixes - **(config)** respect --yes flag for config trust prompts by @jdx in [#8288](#8288) - **(exec)** strip shims from PATH on Unix to prevent infinite recursion by @jdx in [#8276](#8276) - **(install)** validate --locked before --dry-run short-circuit by @altendky in [#8290](#8290) - **(release)** refresh PATH after mise up in release-plz by @jdx in [#8292](#8292) - **(schema)** replace unevaluatedProperties with additionalProperties by @jdx in [#8285](#8285) - **(task)** avoid duplicated stderr on task failure in replacing mode by @jdx in [#8275](#8275) - **(task)** use process groups to kill child process trees on Unix by @jdx in [#8279](#8279) - **(task)** run depends_post tasks even when parent task fails by @jdx in [#8274](#8274) - **(task)** suggest similar commands when mistyping a CLI subcommand by @jdx in [#8286](#8286) - **(task)** execute monorepo subdirectory prepare steps from root by @jdx in [#8291](#8291) - **(upgrade)** don't force-reinstall already installed versions by @jdx in [#8282](#8282) - **(watch)** restore terminal state after watchexec exits by @jdx in [#8273](#8273) ### 📚 Documentation - clarify that MISE_CEILING_PATHS excludes the ceiling directory itself by @jdx in [#8283](#8283) ### Chore - replace gen-release-notes script with communique by @jdx in [#8289](#8289) ### New Contributors - @altendky made their first contribution in [#8290](#8290) ## 📦 Aqua Registry Updates #### New Packages (4) - [`Skarlso/crd-to-sample-yaml`](https://github.com/Skarlso/crd-to-sample-yaml) - [`kunobi-ninja/kunobi-releases`](https://github.com/kunobi-ninja/kunobi-releases) - [`swanysimon/markdownlint-rs`](https://github.com/swanysimon/markdownlint-rs) - [`tmux/tmux-builds`](https://github.com/tmux/tmux-builds) #### Updated Packages (2) - [`firecow/gitlab-ci-local`](https://github.com/firecow/gitlab-ci-local) - [`k1LoW/runn`](https://github.com/k1LoW/runn)

@jdx

## [2026.2.18](https://github.com/jdx/mise/compare/v2026.2.17..v2026.2.18) - 2026-02-21 ### 🚀 Features - **(install)** auto-lock all platforms after tool installation by @jdx in [#8277](jdx/mise#8277) ### 🐛 Bug Fixes - **(config)** respect --yes flag for config trust prompts by @jdx in [#8288](jdx/mise#8288) - **(exec)** strip shims from PATH on Unix to prevent infinite recursion by @jdx in [#8276](jdx/mise#8276) - **(install)** validate --locked before --dry-run short-circuit by @altendky in [#8290](jdx/mise#8290) - **(release)** refresh PATH after mise up in release-plz by @jdx in [#8292](jdx/mise#8292) - **(schema)** replace unevaluatedProperties with additionalProperties by @jdx in [#8285](jdx/mise#8285) - **(task)** avoid duplicated stderr on task failure in replacing mode by @jdx in [#8275](jdx/mise#8275) - **(task)** use process groups to kill child process trees on Unix by @jdx in [#8279](jdx/mise#8279) - **(task)** run depends_post tasks even when parent task fails by @jdx in [#8274](jdx/mise#8274) - **(task)** suggest similar commands when mistyping a CLI subcommand by @jdx in [#8286](jdx/mise#8286) - **(task)** execute monorepo subdirectory prepare steps from root by @jdx in [#8291](jdx/mise#8291) - **(upgrade)** don't force-reinstall already installed versions by @jdx in [#8282](jdx/mise#8282) - **(watch)** restore terminal state after watchexec exits by @jdx in [#8273](jdx/mise#8273) ### 📚 Documentation - clarify that MISE_CEILING_PATHS excludes the ceiling directory itself by @jdx in [#8283](jdx/mise#8283) ### Chore - replace gen-release-notes script with communique by @jdx in [#8289](jdx/mise#8289) ### New Contributors - @altendky made their first contribution in [#8290](jdx/mise#8290) ### 📦 Aqua Registry Updates #### New Packages (4) - [`Skarlso/crd-to-sample-yaml`](https://github.com/Skarlso/crd-to-sample-yaml) - [`kunobi-ninja/kunobi-releases`](https://github.com/kunobi-ninja/kunobi-releases) - [`swanysimon/markdownlint-rs`](https://github.com/swanysimon/markdownlint-rs) - [`tmux/tmux-builds`](https://github.com/tmux/tmux-builds) #### Updated Packages (2) - [`firecow/gitlab-ci-local`](https://github.com/firecow/gitlab-ci-local) - [`k1LoW/runn`](https://github.com/k1LoW/runn) ## [2026.2.17](https://github.com/jdx/mise/compare/v2026.2.16..v2026.2.17) - 2026-02-19 ### 🚀 Features - **(prepare)** update mtime of outputs after command is run by @halms in [#8243](jdx/mise#8243) ### 🐛 Bug Fixes - **(install)** use backend bin paths for per-tool postinstall hooks by @jdx in [#8234](jdx/mise#8234) - **(use)** write to config.toml instead of config.local.toml by @jdx in [#8240](jdx/mise#8240) - default legacy .mise.backend installs to non-explicit by @jean-humann in [#8245](jdx/mise#8245) ### 🚜 Refactor - **(config)** consolidate flat task_* settings into nested task.* by @jdx in [#8239](jdx/mise#8239) ### Chore - **(prepare)** refactor common code into ProviderBase by @halms in [#8246](jdx/mise#8246) ### 📦 Aqua Registry Updates #### Updated Packages (1) - [`namespacelabs/foundation/nsc`](https://github.com/namespacelabs/foundation/nsc)

…dx#8275) ## Summary - When a task fails in `--output replacing` mode, `on_error()` re-printed all accumulated output (stdout + stderr) via `pr.println()`, but stderr was already printed during execution, causing duplication - Fix by tagging each output line with its source (stdout vs stderr) and only replaying stdout lines in `on_error()`, since stdout was hidden behind the progress indicator (`pr.set_message()`) while stderr was already permanently visible Fixes jdx#8267 ## Test plan - [x] Verified `--output replacing` no longer duplicates stderr on task failure - [x] Verified stdout is still shown on failure (it was hidden behind progress indicator) - [x] Verified all other output modes (default, prefix, interleave, raw, quiet, silent, timed, keep-order) are unaffected - [x] Verified successful tasks are unaffected - [x] All 481 unit tests pass 🤖 Generated with [Claude Code](https://claude.com/claude-code)  --- > [!NOTE] > **Low Risk** > Small, localized change to command output handling on failures; main risk is inadvertently suppressing or mis-ordering error output in edge cases. > > **Overview** > Fixes a failure-mode logging bug where `--output replacing` could duplicate stderr by replaying all captured output on error. > > `CmdLineRunner` now tags captured lines with an `OutputSource` and updates `on_error` to replay **only stdout** (and only when stdout was hidden behind the progress indicator), leaving stderr to be shown just once during execution. Also updates the raw-exec error path to pass an empty output vector and tweaks contributor guidance in `CLAUDE.md` to prefer the `task` scope for task-related changes. > > <sup>Written by [Cursor Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit 5b1339e. This will update automatically on new commits. Configure [here](https://cursor.com/dashboard?tab=bugbot).</sup>  Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

@jdx

### 🚀 Features - **(install)** auto-lock all platforms after tool installation by @jdx in [jdx#8277](jdx#8277) ### 🐛 Bug Fixes - **(config)** respect --yes flag for config trust prompts by @jdx in [jdx#8288](jdx#8288) - **(exec)** strip shims from PATH on Unix to prevent infinite recursion by @jdx in [jdx#8276](jdx#8276) - **(install)** validate --locked before --dry-run short-circuit by @altendky in [jdx#8290](jdx#8290) - **(release)** refresh PATH after mise up in release-plz by @jdx in [jdx#8292](jdx#8292) - **(schema)** replace unevaluatedProperties with additionalProperties by @jdx in [jdx#8285](jdx#8285) - **(task)** avoid duplicated stderr on task failure in replacing mode by @jdx in [jdx#8275](jdx#8275) - **(task)** use process groups to kill child process trees on Unix by @jdx in [jdx#8279](jdx#8279) - **(task)** run depends_post tasks even when parent task fails by @jdx in [jdx#8274](jdx#8274) - **(task)** suggest similar commands when mistyping a CLI subcommand by @jdx in [jdx#8286](jdx#8286) - **(task)** execute monorepo subdirectory prepare steps from root by @jdx in [jdx#8291](jdx#8291) - **(upgrade)** don't force-reinstall already installed versions by @jdx in [jdx#8282](jdx#8282) - **(watch)** restore terminal state after watchexec exits by @jdx in [jdx#8273](jdx#8273) ### 📚 Documentation - clarify that MISE_CEILING_PATHS excludes the ceiling directory itself by @jdx in [jdx#8283](jdx#8283) ### Chore - replace gen-release-notes script with communique by @jdx in [jdx#8289](jdx#8289) ### New Contributors - @altendky made their first contribution in [jdx#8290](jdx#8290) ## 📦 Aqua Registry Updates #### New Packages (4) - [`Skarlso/crd-to-sample-yaml`](https://github.com/Skarlso/crd-to-sample-yaml) - [`kunobi-ninja/kunobi-releases`](https://github.com/kunobi-ninja/kunobi-releases) - [`swanysimon/markdownlint-rs`](https://github.com/swanysimon/markdownlint-rs) - [`tmux/tmux-builds`](https://github.com/tmux/tmux-builds) #### Updated Packages (2) - [`firecow/gitlab-ci-local`](https://github.com/firecow/gitlab-ci-local) - [`k1LoW/runn`](https://github.com/k1LoW/runn)

Copilot AI review requested due to automatic review settings February 21, 2026 14:48

jdx changed the title ~~fix(run): avoid duplicated stderr on task failure in replacing mode~~ fix(task): avoid duplicated stderr on task failure in replacing mode Feb 21, 2026

Copilot started reviewing on behalf of jdx February 21, 2026 14:48 View session

jdx force-pushed the fix/task-failure-output-duplication branch from 8ed0258 to 10cdab4 Compare February 21, 2026 14:50

gemini-code-assist bot reviewed Feb 21, 2026

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jdx force-pushed the fix/task-failure-output-duplication branch from 10cdab4 to 5b1339e Compare February 21, 2026 14:53

jdx enabled auto-merge (squash) February 21, 2026 14:59

jdx merged commit b78abf5 into main Feb 21, 2026
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jdx deleted the fix/task-failure-output-duplication branch February 21, 2026 15:10

mise-en-dev mentioned this pull request Feb 21, 2026

chore: release 2026.2.18 #8259

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BrewTestBot mentioned this pull request Feb 21, 2026

mise 2026.2.18 Homebrew/homebrew-core#268760

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fix(task): avoid duplicated stderr on task failure in replacing mode#8275

fix(task): avoid duplicated stderr on task failure in replacing mode#8275
jdx merged 1 commit intomainfrom
fix/task-failure-output-duplication

jdx commented Feb 21, 2026 •

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jdx commented Feb 21, 2026 • edited by cursor bot Loading Uh oh! There was an error while loading. Please reload this page.

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jdx commented Feb 21, 2026 •

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