Claude Code v2.1.70 — 3 New Environment Variables and 1 Removed#
Published on March 6, 2026
Part of the Claude Code Version Tracker series. | Official Env Vars
Claude Code v2.1.70 is a minor release with 3 new environment variables and 1 removal. No changes to feature gates, dynamic configs, model IDs, or spinner words.
If you missed it, the v2.1.69 deep dive covered the jump from 83 to 165 env vars across 50 versions. This post covers what changed in the single version since.
What Changed#
| v2.1.69 | v2.1.70 | |
|---|---|---|
| Environment variables | 165 | 167 (+3, -1) |
| Model IDs | 16 | 16 (no change) |
| Feature gates | 41 | 41 (no change) |
| Dynamic configs | 30+ | 30+ (no change) |
New Environment Variables (3)#
| Variable | Likely Purpose |
|---|---|
CLAUDE_BRIDGE_USE_CCR_V2 | Toggle for CCR v2 bridge protocol — companion to the existing CLAUDE_CODE_USE_CCR_V2 introduced in v2.1.69. Suggests the bridge layer (IDE extensions, remote sessions) is being migrated to the same v2 router used by cowork/multi-agent. |
CLAUDE_CODE_ALWAYS_ENABLE_EFFORT | Force-enable reasoning effort level regardless of other settings. Useful for ensuring CLAUDE_CODE_EFFORT_LEVEL always takes effect, even in contexts where it might be overridden (e.g., sub-agents, SDK mode). |
CLAUDE_CODE_MCP_INSTR_DELTA | Delta/incremental MCP instruction updates. Instead of sending full MCP server instructions every turn, this likely enables sending only changes — reducing overhead for sessions with many MCP servers. |
What These Tell Us#
The CCR v2 migration continues. In v2.1.69 we saw CLAUDE_CODE_USE_CCR_V2 for cowork sessions; now the bridge layer gets the same treatment. This is Anthropic unifying the routing infrastructure across standalone CLI, IDE extensions, and multi-agent workflows.
CLAUDE_CODE_MCP_INSTR_DELTA is particularly interesting for heavy MCP users. If you run multiple MCP servers (LSP, database, file system, etc.), the cumulative instruction payload can eat into your context window. Delta updates would only send what changed, potentially freeing up tokens for actual work.
Removed (1)#
| Variable | Notes |
|---|---|
CLAUDE_CODE_SPAWNED_BY_SERVER | Was used to indicate a server-spawned process. Added in v2.1.69's remote/server mode batch. Removed after just one version — likely internalized or replaced by a different detection mechanism. |
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 v2.1.72 — 6 New Environment Variables — brief mode, cron control, two-stage classifier
- 165 Environment Variables in Claude Code 2.1.69 — the big v2.1.19 → v2.1.69 comparison
- 83 Undocumented Claude Code Environment Variables (v2.1.19) — the original extraction
Related: Context Window Management Guide | Claude Code Productivity Tips