[vonovak]

Why

When a command fails, EasCommand.catch prints the (helpful) reason with Log.error, which writes to stdout. Then oclif prints <command> command failed. to stderr. A program that reads stderr for the error finds only the generic (not helpful) line.

Stacked on #4591. This is the second of four PRs: #4591 ← #4592 (this PR) ← #4593 ← #4594.

How

Add Log.errorToStderr and use it in EasCommand.catch only. Other Log.error and Log.warn calls stay on stdout:

• Some Log.error calls are not failures and exit 0, for example in env:get and env:delete.
• ora.ts keeps non-TTY output on stdout on purpose, because some CI systems treat stderr as a failure. A failing command already writes to stderr through oclif, so this PR adds no new stderr output to a run that succeeds.

With --json, nothing changes: stdout was already redirected to stderr.

Trade-off: a program that reads stderr for errors now finds the reason there, and a program that parses stdout no longer gets the reason mixed into it. A program that reads the reason from stdout must read stderr instead, so the changelog lists this under breaking changes. The callers in this repo that run eas-cli (build-tools and eas-build-cache-provider) read stdout only on success. On failure they log stderr or merge both streams.

Known limit: Log.errorToStderr uses chalk, which picks its color level from stdout. With eas ... 2>err.log in a terminal, the file gets color codes.

LLM Authorship

• Vojtech asked for errors on stderr. Claude Code wrote the change.

Test Plan

• Real run, not logged in, build:list --non-interactive: the reason (Either log in with eas login ...) is on stderr, next to Error: build:list command failed.. On 24.12.1 it was on stdout.
• tsc, oxlint and oxfmt are clean.

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.48%. Comparing base (7f317ab) to head (0f3bb8d).

Files with missing lines	Patch %	Lines
packages/eas-cli/src/log.ts	0.00%	3 Missing ⚠️

Additional details and impacted files

@@                        Coverage Diff                        @@
##           vonovak/dependency-notice-tty    #4592      +/-   ##
=================================================================
- Coverage                          74.48%   74.48%   -0.00%     
=================================================================
  Files                               1029     1029              
  Lines                              50390    50393       +3     
  Branches                           10891    10891              
=================================================================
  Hits                               37528    37528              
- Misses                             11872    11875       +3     
  Partials                             990      990              

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[github-actions]

Subscribed to pull request

File Patterns	Mentions
packages/eas-cli/**	@douglowder

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[douglowder]

eas-cli now uses changesets for changelogs (#4580). The required "Check for a changeset" check fails on PRs that edit CHANGELOG.md.

To update this PR:

1. Revert the changes to CHANGELOG.md.
2. Run yarn changeset, select the changed packages and the bump type, and write the summary.
3. Commit the new file in .changeset/.

The release adds the PR link and the author to the entry. If this PR needs no changelog entry, revert the CHANGELOG.md changes and add the "no changelog" label.

[github-actions]

✅ Thank you for adding a changeset!