[DOCS] Fullscreen docs use an outdated tmux 3.4 synchronized-output threshold

Documentation Type

Incorrect/outdated documentation

Documentation Location

https://code.claude.com/docs/en/fullscreen

Section/Topic

The tmux synchronized-output behavior in the fullscreen rendering guide.

Current Documentation

The guide currently says:

“Claude Code turns on synchronized output automatically when it detects tmux 3.4 or later from the TERM_PROGRAM_VERSION variable, and falls back to querying the terminal directly for synchronized output support when the version can't be determined.”

What's Wrong or Missing?

The 2.1.212 release corrects the earlier 2.1.200 note: tmux through the 3.6 series lacks synchronized output, while newer tmux versions with support are detected automatically. The current “tmux 3.4 or later” wording tells users that versions known not to support the feature are eligible for automatic synchronized output.

Users on tmux 3.4–3.6 may follow the page and still see flicker, then incorrectly conclude that their terminal configuration or Claude Code installation is broken.

Suggested Improvement

Replace the fixed tmux 3.4 or later threshold with the corrected compatibility guidance. Explain that version detection is only an optimization and that actual synchronized-output support depends on the tmux version and terminal capability. Include the recommended fallback for affected versions: upgrade tmux, run Claude Code outside tmux, or use CLAUDE_CODE_FORCE_SYNC_OUTPUT only when the terminal and tmux path genuinely support it.

Update any matching wording in the terminal-configuration page and retain a version marker for the correction introduced in 2.1.212.

Impact

Medium - Makes feature difficult to understand

Additional Context

Affected Pages:

| Page | Context |
|------|---------|
| https://code.claude.com/docs/en/fullscreen | Current tmux 3.4 threshold and synchronized-output explanation |
| https://code.claude.com/docs/en/terminal-config | User troubleshooting and CLAUDE_CODE_FORCE_SYNC_OUTPUT guidance |
| https://code.claude.com/docs/en/env-vars | Force-sync environment variable reference |

Total scope: 3 pages should use the same corrected compatibility guidance.

The correction was published in Claude Code 2.1.212; the release notes are listed at https://code.claude.com/docs/en/changelog.