Claude Code v2.1.75 — 2 New Environment Variables: Auto-Compact Window & Plugin Options#
Published on March 13, 2026
Part of the Claude Code Version Tracker series. | Official Changelog
Claude Code v2.1.75 adds 2 new environment variables and a new /color slash command compared to v2.1.74. This release also enables 1M context windows for Opus 4.6 by default on Max, Team, and Enterprise plans.
What Changed#
| v2.1.74 | v2.1.75 | |
|---|---|---|
| Environment variables | 174 | 176 (+2) |
| Model IDs | 16 | 16 (no change) |
| Feature gates | 41 | 41 (no change) |
| Dynamic configs | 29 | 29 (no change) |
| Slash commands | 22 | 22 (+1 via changelog)[1] |
New Environment Variables (2)#
| Variable | Likely Purpose |
|---|---|
CLAUDE_CODE_AUTO_COMPACT_WINDOW | Controls the token window threshold at which automatic context compaction kicks in. Works alongside the existing CLAUDE_AUTOCOMPACT_PCT_OVERRIDE variable but likely provides a fixed token count rather than a percentage — giving more precise control over when the conversation is summarized and trimmed. Particularly relevant now that 1M context windows are available on higher-tier plans. |
CLAUDE_PLUGIN_OPTION_ | A prefix-style variable (note the trailing underscore) for passing configuration options to installed plugins. This follows the pattern of CLAUDE_PLUGIN_OPTION_<PLUGIN_NAME>=<value>, allowing users to configure plugin behavior through environment variables without modifying settings files. This is a standard pattern for exposing per-plugin knobs in a flat env-var namespace. |
New Slash Command (1)#
| Command | What It Does |
|---|---|
/color | Sets a custom prompt-bar color for your current session.[1] Useful for visually distinguishing between multiple Claude Code sessions running in different terminal tabs or projects. The color persists for the session duration and resets on exit. Available to all users. |
What These Tell Us#
Context management is getting more granular. The addition of CLAUDE_CODE_AUTO_COMPACT_WINDOW alongside the simultaneous rollout of 1M context windows for Opus 4.6 is not coincidental. Larger context windows create a new tuning problem: compact too early and you waste expensive capacity; compact too late and you hit token limits mid-thought. A fixed-window threshold gives power users — especially those running agentic pipelines via the SDK — precise control over that tradeoff. This is the third compaction-related variable (after CLAUDE_AUTOCOMPACT_PCT_OVERRIDE and CLAUDE_CODE_DISABLE_PRECOMPACT_SKIP), signaling that context lifecycle management is becoming a first-class concern.
The plugin system is maturing. CLAUDE_PLUGIN_OPTION_ is a prefix-based env var pattern, meaning it's not one variable but an entire namespace. This is a significant architectural signal: plugins can now accept user configuration through the environment, which is the standard mechanism for CI/CD and containerized deployments. Combined with existing variables for plugin caching (CLAUDE_CODE_PLUGIN_CACHE_DIR), git timeouts (CLAUDE_CODE_PLUGIN_GIT_TIMEOUT_MS), and seed directories (CLAUDE_CODE_PLUGIN_SEED_DIR), the plugin infrastructure is steadily moving from "install and use" toward "install, configure, and deploy at scale."
Sources#
[1] Claude Code CHANGELOG.md — The /color command appears in the official changelog for v2.1.75 but was not captured by our binary string extraction. This can happen when command names are constructed dynamically or registered through the plugin system rather than appearing as static strings.
This analysis is conducted for independent security research and interoperability purposes under fair use principles. All trademarks belong to their respective owners. The information presented here documents publicly observable behavior of installed software and is not intended to circumvent any technological protection measures, infringe on intellectual property rights, or encourage unauthorized use. Use these findings at your own discretion.
Related Versions#
- Claude Code v2.1.74 — 2 New Environment Variables — frame timing diagnostics, session-end hook timeouts
- Claude Code v2.1.73 — Slash Commands Inventory — first baseline of built-in slash commands
- Claude Code v2.1.72 — 6 New Environment Variables — brief mode, cron control, two-stage classifier
- Claude Code v2.1.70 — 3 New Environment Variables — CCR v2 bridge, effort level, delta MCP
Related: Context Window Management Guide | Claude Code Productivity Tips | The Agentic Engineering Playbook