[DOCS] Fast mode docs still instruct users to set removed `CLAUDE_CODE_OPUS_4_6_FAST_MODE_OVERRIDE`

Documentation Type

Incorrect/outdated documentation

Documentation Location

https://code.claude.com/docs/en/env-vars

Section/Topic

CLAUDE_CODE_OPUS_4_6_FAST_MODE_OVERRIDE in the environment variables reference, plus the Opus 4.6 override note in the fast mode guide

Current Documentation

The docs currently say:

CLAUDE_CODE_OPUS_4_6_FAST_MODE_OVERRIDE — Set to 1 to pin fast mode to Claude Opus 4.6 instead of the current fast mode default, which depends on your Claude Code version. With the variable set, /fast runs on Opus 4.6. Fast mode for Opus 4.6 is deprecated, and this variable will be removed when it is retired

And the fast mode page still says:

Opus 4.8 is the fast mode default in Claude Code v2.1.154 and later. On v2.1.142 through v2.1.153, fast mode defaults to Opus 4.7. To pin fast mode to Opus 4.6 instead, set CLAUDE_CODE_OPUS_4_6_FAST_MODE_OVERRIDE=1; this override will be removed when fast mode for Opus 4.6 is retired.

What's Wrong or Missing?

Claude Code's v2.1.160 changelog says:

Removed CLAUDE_CODE_OPUS_4_6_FAST_MODE_OVERRIDE; the environment variable is now a no-op

The documentation still presents that variable as a supported way to change /fast behavior. After v2.1.160, readers who follow either page are told to set a variable that no longer does anything.

This is one root cause across two pages:

A. env-vars still documents the variable as active

It says setting the variable pins fast mode to Opus 4.6 and changes /fast behavior.

B. fast-mode still recommends the removed variable

It points users to CLAUDE_CODE_OPUS_4_6_FAST_MODE_OVERRIDE=1 as the way to keep using Opus 4.6 fast mode.

Suggested Improvement

Update both pages to match v2.1.160:

• Mark CLAUDE_CODE_OPUS_4_6_FAST_MODE_OVERRIDE as removed and now a no-op in env-vars, or remove the entry entirely if removed variables are not kept in the reference.
• Replace the fast-mode guidance that recommends this variable with the supported fallback from the changelog: switch explicitly with /model claude-opus-4-6[1m] and then /fast on.
• State the version boundary clearly so readers know the variable stopped working in v2.1.160.

Impact

Medium - Makes feature difficult to understand

Additional Context

Affected Pages:

| Page | Line(s) | Context |
|------|---------|---------|
| https://code.claude.com/docs/en/env-vars | 212 | Environment variable reference still says the variable pins /fast to Opus 4.6 |
| https://code.claude.com/docs/en/fast-mode | 54 | Fast mode guide still tells readers to set the removed variable |

Total scope: 2 pages affected

Version cross-reference: In v2.1.160, https://code.claude.com/docs/en/changelog says "Removed CLAUDE_CODE_OPUS_4_6_FAST_MODE_OVERRIDE; the environment variable is now a no-op".