[DOCS] [Environment] Missing `CLAUDE_CODE_DISABLE_ALTERNATE_SCREEN` env var documentation for opting out of fullscreen rendering

Documentation Type

Missing documentation (feature not documented)

Documentation Location

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

Section/Topic

"Enabling fullscreen rendering" section or a new "Disabling fullscreen rendering" section

Current Documentation

The fullscreen page documents two environment variables related to the alt-screen renderer:

You can also set the CLAUDE_CODE_NO_FLICKER environment variable before starting Claude Code: ``bash theme={null} CLAUDE_CODE_NO_FLICKER=1 claude ``

And disabling mouse capture while keeping fullscreen rendering:

If you rely on native selection all the time, set CLAUDE_CODE_DISABLE_MOUSE=1 to opt out of mouse capture while keeping the flicker-free rendering and flat memory: ``bash theme={null} CLAUDE_CODE_NO_FLICKER=1 CLAUDE_CODE_DISABLE_MOUSE=1 claude ``

There is no documentation for an env var to do the reverse: opt out of the fullscreen alternate-screen renderer entirely and keep the conversation in the terminal's native scrollback.

What's Wrong or Missing?

The changelog for v2.1.132 added CLAUDE_CODE_DISABLE_ALTERNATE_SCREEN=1 to let users opt out of the fullscreen alternate-screen renderer and keep the conversation in the terminal's native scrollback. This env var is not mentioned anywhere in the documentation.

Users who want to start Claude Code without fullscreen rendering have no documented environment-variable-based way to do so.

Suggested Improvement

Add documentation for CLAUDE_CODE_DISABLE_ALTERNATE_SCREEN=1 on both the fullscreen page and the env-vars reference.

For example, add a new "Disabling fullscreen rendering" subsection near the bottom of the fullscreen page where it already says:

To turn fullscreen rendering off, run /tui default, or unset the environment variable if you enabled it that way.

The documentation should note:

• CLAUDE_CODE_DISABLE_ALTERNATE_SCREEN=1 opts out of the alternate-screen renderer and keeps conversation output in the terminal's native scrollback
• This is useful for environments where users prefer native terminal scrollback
• The env-vars reference should list it alongside CLAUDE_CODE_NO_FLICKER

Example addition:

```bash theme={null}

Disable fullscreen rendering and keep conversation in native scrollback

CLAUDE_CODE_DISABLE_ALTERNATE_SCREEN=1 claude

### Impact

Medium - Makes feature difficult to understand

### Additional Context


**Affected Pages:**
| Page | Context |
|------|---------|
| https://code.claude.com/docs/en/fullscreen | Primary documentation - missing `CLAUDE_CODE_DISABLE_ALTERNATE_SCREEN` env var |
| https://code.claude.com/docs/en/env-vars | Environment variables reference does not list the new variable |

**Total scope:** 2 pages affected

The changelog entry for v2.1.132 reads:
> Added `CLAUDE_CODE_DISABLE_ALTERNATE_SCREEN=1` env var to opt out of the fullscreen alternate-screen renderer and keep the conversation in the terminal's native scrollback