Claude Code Version Tracker: Environment Variables, Feature Gates & Models#

Published on March 7, 2026

We analyze every Claude Code release to document undocumented environment variables, feature gates, and model IDs. This page tracks all versions we've covered.

Looking for the full list? See The Complete List of Claude Code Environment Variables (500+) — every env var organized by category with practical tips.

Version History#

v2.1.143 — May 18, 2026#

CLAUDE_CODE_MAX_TURNS · CLAUDE_CODE_SUPERVISED · /goal · Agent View · Opus 4.7 Fast mode · 27 new env vars

Fifteen-release stretch (v2.1.129 → v2.1.143). /goal ships a real completion tracker for complex agentic work — declare a condition, Claude tracks progress and stops when it's met. Agent View (claude agents) becomes the user-facing surface for dispatched background sessions; CLAUDE_CODE_DISABLE_AGENTS_FLEET is removed and replaced by CLAUDE_CODE_DISABLE_AGENT_VIEW. Fast mode silently upgraded to Opus 4.7 at no extra cost (CLAUDE_CODE_OPUS_4_6_FAST_MODE_OVERRIDE pins back to 4.6). The agentic safety pair: CLAUDE_CODE_MAX_TURNS hard-caps conversation turns, CLAUDE_CODE_SUPERVISED tells Claude a human is watching. Hook args exec form lands — shell-less subprocess spawning for injection-safe hooks. MCP servers receive CLAUDE_PROJECT_DIR and survive /clear. Plugin marketplace shows context cost estimates before install. CLAUDE_CODE_STOP_HOOK_BLOCK_CAP ends the Ctrl+C hang. Three background session vars (CLAUDE_BG_AUTH_SNAPSHOT_PATH, CLAUDE_BG_STARTUP_WEDGE_MS, CLAUDE_BG_TCC_DISCLAIMED) document the BG failure modes. Rewind gains "Summarize up to here."

v2.1.128 — May 4, 2026#

CLAUDE_CODE_PROACTIVE · CLAUDE_CODE_SIMPLE_SYSTEM_PROMPT · Sonnet 4.6 default

v2.1.127 was an internal build. v2.1.128 ships two env vars: CLAUDE_CODE_PROACTIVE turns idle detection into action — Claude prompts you on return from an idle session ("Start a new task?") instead of waiting silently. The idle-watching infrastructure (CLAUDE_CODE_IDLE_THRESHOLD_MINUTES, CLAUDE_CODE_IDLE_TOKEN_THRESHOLD) was already in v2.1.126; this is the first user-visible behavior built on top of it. CLAUDE_CODE_SIMPLE_SYSTEM_PROMPT strips the system prompt down for background subagents — cuts the largest fixed per-turn token cost across parallel agent trees. Use it on leaf-node workers with a narrow job; leave it off on coordinators that need full tool and skill awareness. Sonnet 4.6 takes over as the embedded default for Claude Code Remote via undated alias, rolling forward automatically as Anthropic ships new checkpoints.

v2.1.126 — May 1, 2026#

CLAUDE_CODE_COLD_COMPACT · claude project purge · gateway model picker · 7 bug fixes

v2.1.124–v2.1.125 were internal builds. v2.1.126 ships claude project purge — surgical cleanup of transcripts, tasks, and config per project with --dry-run, --interactive, and --all flags. The /model picker now queries your gateway's /v1/models when ANTHROPIC_BASE_URL is set, showing what your environment actually serves instead of Anthropic's public catalog. --dangerously-skip-permissions now covers .claude/, .git/, .vscode/, and shell config writes — fully non-interactive CI at last. OAuth paste-in for WSL2, SSH, and containers. Security fix: managed sandbox allowManagedDomainsOnly restrictions were silently dropped when the org policy file had no sandbox block. Bug fixes: stream idle timeout after sleep, image paste breaking sessions (now auto-downscaled), Windows clipboard leaking to process args, CJK garbled in no-flicker mode, Ctrl+L erasing input, deferred tools missing in fork subagents on turn 1, Agent SDK hang on malformed tool names. Under the hood: CLAUDE_CODE_COLD_COMPACT enables the daemon to compact cold sessions on resume — solving the stale-context corruption that's affected sleep-resume and bridge-reattach scenarios since v2.1.62.

v2.1.123 — April 29, 2026#

290+ env vars (+30 net) · 17 models · 25 slash commands

Five-release stretch (v2.1.119 → v2.1.123). The background daemon — first flagged in v2.1.114 as a single CLAUDE_BG_BACKEND=daemon var — gets its complete IPC contract: rendezvous socket (CLAUDE_BG_RENDEZVOUS_SOCK), process isolation boundary (CLAUDE_BG_ISOLATION), job attribution (CLAUDE_BG_SOURCE), PTY recording (CLAUDE_PTY_RECORD), cold-start telemetry (CLAUDE_CODE_DAEMON_COLD_START), and a sequence-numbered bridge reconnection protocol (CLAUDE_BRIDGE_REATTACH_SEQ/SESSION). Sessions become first-class addressable objects via SESSION_ID/KIND/LOG/NAME — the plumbing behind v2.1.122's PR-URL→session /resume lookup. An agent fleet layer takes shape with selection (CLAUDE_AGENTS_SELECT), auto-relaunch tracking (CLAUDE_AGENTS_AUTO_RELAUNCHED_AT), and a kill switch (CLAUDE_CODE_DISABLE_AGENTS_FLEET). CoWork memory (CLAUDE_COWORK_MEMORY_GUIDELINES, CLAUDE_COWORK_MEMORY_INDEX_CONTENT) is the first inter-agent coordination primitive — a shared RAG layer with policy-governed writes. Daily wins: /config persists, alwaysLoad for MCP, PostToolUse hooks rewrite any tool output, claude ultrareview is a CLI subcommand, default effort raised to high for Pro/Max, three memory leaks fixed, Windows no longer requires Git Bash.

v2.1.118 — April 23, 2026#

260 env vars (+10 net) · 17 models · 25 slash commands (+1)

Four-release stretch (v2.1.115 → v2.1.118). The headline shift: forked subagents enabled on external builds via CLAUDE_CODE_FORK_SUBAGENT=1 — the Agent Teams multi-agent architecture leaves internal-only status. Subscription and rate-limit tier vars (CLAUDE_CODE_SUBSCRIPTION_TYPE, CLAUDE_CODE_RATE_LIMIT_TIER) describe a runtime moving toward per-plan capability differentiation. Named proxy vars (CLAUDE_CODE_HTTP_PROXY, CLAUDE_CODE_HTTPS_PROXY) simplify corporate proxy setup without the v2.1.114 auth helper protocol. Bridge reconnection handshake (CLAUDE_BRIDGE_REATTACH_SEQ, CLAUDE_BRIDGE_REATTACH_SESSION) and retry watchdog close the remaining "silent hang" surface alongside prior stall vars. CLAUDE_CODE_SIMPLE_SYSTEM_PROMPT for token-constrained deployments. DISABLE_UPDATES kill-switch for externally managed environments. This window also coincides with Anthropic's April 23 postmortem on the March–April quality regression (reasoning effort default, caching bug, verbosity system prompt) and usage limit reset for all subscribers. v2.1.116 delivered 67% /resume speed improvement; v2.1.118 added vim visual mode, /usage (merged /cost+/stats), /theme JSON editing, hooks invoking MCP tools, and WSL→Windows settings inheritance.

v2.1.114 — April 20, 2026#

250 env vars (+20 net) · 17 models (+1) · 24 slash commands

Seven-release stretch (v2.1.108 → v2.1.114). Two headline shifts: the CLI now spawns a native per-platform binary instead of bundled JS (v2.1.113) — packaging, supply-chain, and signing posture all tighten. And /fewer-permission-prompts (v2.1.111; originally announced as /less-permission-prompts) scans transcripts to build a prioritized settings allowlist — the first feature that actually reduces Claude Code's biggest daily friction point. Around those: fullscreen TUI (/tui fullscreen) with DECSTBM scrolling, /ultrareview cloud PR review, Opus 4.7 xhigh effort + /effort slider, 1-hour prompt caching on API key/Bedrock/Vertex/Foundry, proxy auth helper subprocess protocol (5 vars) for Kerberos/SSO, Agent Teams scaffolding (team name propagation, subagent prompt append, stall timeout, daemon backend), experimental Advisor Tool, session recap for telemetry-disabled users, readline-compatible Ctrl+A/E, wrapped-URL click targets, Windows Ctrl+Backspace. ~80 bug fixes across the range.

v2.1.108 — April 14, 2026#

234 env vars (+4 net) · 4 new, 0 removed

Limits reckoning release. Prompt cache TTL now user-configurable (ENABLE_PROMPT_CACHING_1H, FORCE_PROMPT_CACHING_5M). Rate limits vs. plan limits get separate error messages. Startup warning if caching accidentally disabled. DISABLE_TELEMETRY → 5-minute TTL bug fixed. REPL experimentation returns: CLAUDE_CODE_REPL and CLAUDE_REPL_VARIANT for A/B testing stateful execution. Skill discovery via Skill tool (CLAUDE_API_SKILL_DESCRIPTION). Internal team routing (CLAUDE_INTERNAL_ASSISTANT_TEAM_NAME). /undo alias for /rewind. /model warns before mid-conversation switch. /recap away summary. Lazy-loaded language grammars reduce memory footprint. 15+ bug fixes.

v2.1.107 — April 14, 2026#

230 env vars (+6 net) · 6 new, 0 removed

Multi-worktree orchestration plumbing: CLAUDE_CODE_BASE_REFS for diff base overrides, CLAUDE_CODE_REPO_CHECKOUTS for worktree storage paths, CLAUDE_CODE_RESUME_FROM_SESSION for session chaining. Away mode summaries (CLAUDE_CODE_ENABLE_AWAY_SUMMARY) for async agent supervision. Byte-level stream watchdog (CLAUDE_ENABLE_BYTE_WATCHDOG) catches stalled API connections below SSE layer. UltraReview preflight test fixture. PreCompact hooks, background plugin monitors, worktree reuse via path parameter. Stalled stream abort-and-retry, SSH color fix. v2.1.106 skipped.

v2.1.104 — April 12, 2026#

224 env vars (+2 net) · 2 new, 0 removed

Enterprise TLS certificate store control (CLAUDE_CODE_CERT_STORE) — OS CA store now trusted by default, bundled reverts to Node.js CAs. SDK OAuth refresh coordination (CLAUDE_CODE_SDK_HAS_OAUTH_REFRESH) prevents double-refresh races in IDE extensions. /team-onboarding command generates teammate ramp-up guides. /ultraplan auto-provisioning. Command injection fix in LSP binary detection. Virtual scroller memory leak fix. Hardcoded 5-minute timeout removed — respects API_TIMEOUT_MS. v2.1.101 changelog covers this range; v2.1.102–103 skipped.

v2.1.100 — April 10, 2026#

222 env vars (0 net) · 3 new, 3 removed

Context token ceiling (CLAUDE_CODE_MAX_CONTEXT_TOKENS) with DISABLE_COMPACT interop. Perforce VCS mode (CLAUDE_CODE_PERFORCE_MODE) — fail on read-only files with p4 edit hint. Script capability caps (CLAUDE_CODE_SCRIPT_CAPS) paired with PID namespace sandboxing. Google Vertex AI setup wizard. Focus view toggle (Ctrl+O). Monitor tool for streaming background script events. 30+ Bash permission security fixes closing bypass vectors and reducing false prompts. MCP memory leak fix (~50 MB/hr). REPL experiment variables removed. v2.1.99 skipped.

v2.1.96 — April 8, 2026#

222 env vars (0 net) · 0 new, 0 removed

Bedrock auth hotfix. Fixed 403 "Authorization header is missing" regression from v2.1.94 when using AWS_BEARER_TOKEN_BEDROCK or CLAUDE_CODE_SKIP_BEDROCK_AUTH. Binary extraction byte-identical to v2.1.94. v2.1.95 skipped.

v2.1.94 — April 7, 2026#

222 env vars (+5) · 5 new, 0 removed

Mantle auth proxy for Amazon Bedrock (CLAUDE_CODE_USE_MANTLE) with skip flag (CLAUDE_CODE_SKIP_MANTLE_AUTH). Sandbox state flag (CLAUDE_CODE_SANDBOXED). MCP server environment variable allowlist (CLAUDE_CODE_MCP_ALLOWLIST_ENV) — replaces all-or-nothing env inheritance. Team onboarding flows (CLAUDE_CODE_TEAM_ONBOARDING). --resume across worktrees. CJK text corruption fix. Write tool diff 60% faster. Default effort "high" for Team/Enterprise.

v2.1.92 — April 3, 2026#

217 env vars (+5) · 5 new, 0 removed

Proxy simulation without infrastructure (CLAUDE_CODE_SIMULATE_PROXY_USAGE). Fast mode org check bypass (CLAUDE_CODE_SKIP_FAST_MODE_ORG_CHECK). Remote Control session name prefix for CI/CD observability. CLAUDE_CODE_EXECPATH for symlinked/wrapped binary overrides. CLAUDE_BASE shorthand for base URL config. Interactive Bedrock setup wizard. Per-model cost breakdowns for subscribers. Policy-enforced remote settings refresh.

v2.1.91 — April 2, 2026#

212 env vars (−1 net) · 1 new, 2 removed

MCP 500K character tool result persistence override (_meta["anthropic/maxResultSizeChars"]). Plugin bin/ executable support — plugins can now ship and invoke native binaries. disableSkillShellExecution setting to lock down shell access in skills. Multi-line deep links via claude-cli://open?q=. Edit tool token optimization with shorter old_string anchors. CLAUDE_CODE_ENABLE_PROMPT_SUGGESTION replaces typo predecessor. Net −1 env var.

v2.1.90 — April 1, 2026#

213 env vars (+3 net) · 24 slash commands (+1)

New "Anthropic AWS" API provider (CLAUDE_CODE_USE_ANTHROPIC_AWS) — Anthropic's own AWS-hosted infrastructure, distinct from Bedrock. Companion CLAUDE_CODE_SKIP_ANTHROPIC_AWS_AUTH for IAM ambient credentials. Offline-resilient marketplace plugin caching (CLAUDE_CODE_PLUGIN_KEEP_MARKETPLACE_ON_FAILURE). /powerup interactive lessons. Prompt-cache regression fix (since v2.1.69). Quadratic SSE transport and transcript write fixes. PowerShell security hardening. Auto mode now respects explicit user constraints.

v2.1.89 — March 31, 2026#

210 env vars (+2 net) · 4 new, 2 removed

Agent cost steering for subagent delegation (CLAUDE_CODE_AGENT_COST_STEER). Session resume thresholds by time and token count. Claude API skill disable flag. Deferred tool execution for headless sessions. StructuredOutput schema cache ~50% failure rate fixed. Autocompact thrash loop detection. Edit tool no longer requires prior Read. MCP non-blocking connections. Named subagents in typeahead. CLAUDE_CODE_DISABLE_COMMAND_INJECTION_CHECK removed — safety check now mandatory.

v2.1.88 — March 30, 2026#

208 env vars (+4 net) · 41 feature gates · 16 models · 23 slash commands · 29 dynamic configs

7 new env vars, 3 removed. Terminal UX overhaul: CLAUDE_CODE_NO_FLICKER for flicker-free alt-screen rendering, CLAUDE_CODE_DISABLE_MOUSE / CLAUDE_CODE_DISABLE_MOUSE_CLICKS for granular mouse control, CLAUDE_CODE_SCROLL_SPEED for tunable scrolling. REPL mode emergence: CLAUDE_CODE_REPL and CLAUDE_REPL_MODE for lightweight stateless interactions. CLAUDE_CODE_DISABLE_POLICY_SKILLS for suppressing org-pushed skills. v2.1.87 hotfix for Cowork Dispatch. Prompt cache miss fix, structured output schema bug, memory leaks for 1 GiB+ files. Thinking summaries off by default.

v2.1.87 — March 30, 2026#

202 env vars (0 net, +2/-2) · 16 models · 22 slash commands · 29 dynamic configs

OAuth console override (CLAUDE_LOCAL_OAUTH_CONSOLE_BASE) completes the auth triptych. Trusted device token (CLAUDE_TRUSTED_DEVICE_TOKEN) for persistent sessions. MCP server env vars (CLAUDE_CODE_MCP_SERVER_NAME, CLAUDE_CODE_MCP_SERVER_URL) removed after 2 versions. Cowork Dispatch message delivery fix. Dispatch model selection. Boris Cherny's 15 hidden features thread: mobile app, /loop, /schedule, hooks, --bare default flip coming.

v2.1.86 — March 27, 2026#

204 env vars (+2) · 41 feature gates · 16 models · 22 slash commands · 29 dynamic configs

Trusted device token (CLAUDE_TRUSTED_DEVICE_TOKEN) for enterprise SSO and CI/CD environments. OAuth console base URL override (CLAUDE_LOCAL_OAUTH_CONSOLE_BASE) completes the full OAuth endpoint decomposition across three releases. 20+ bug fixes: --resume tool_use ID errors, /feedback OOM on long sessions, masked input token leaks on narrow terminals, MCP server startup stalls. X-Claude-Code-Session-Id header for proxy observability.

v2.1.85 — March 27, 2026#

202 env vars (+5 net) · 41 feature gates · 16 models · 22 slash commands · 29 dynamic configs

MCP server multiplexing env vars (CLAUDE_CODE_MCP_SERVER_NAME, CLAUDE_CODE_MCP_SERVER_URL). OAuth endpoint overrides (CLAUDE_LOCAL_OAUTH_API_BASE, CLAUDE_LOCAL_OAUTH_APPS_BASE). PowerShell parse timeout. Commit logging. Binary shrank 7.15 MB (194 → 187 MB) by replacing WASM yoga-layout with pure TypeScript. Conditional if fields for hooks. Scheduled task timestamps. /compact context-exceeded fix. Memory leak patches for remote sessions. CLAUDE_CODE_SUBAGENT_MODELU typo removed.

v2.1.84 — March 26, 2026#

197 env vars (+6) · 41 feature gates · 16 models · 22 slash commands · 29 dynamic configs

Idle session management with configurable thresholds, CLAUDE_STREAM_IDLE_TIMEOUT_MS stream watchdog (default 90s). Bedrock/Vertex/Foundry capability override env vars. TaskCreated and WorktreeCreate HTTP hooks. Deep links open in preferred terminal. PowerShell tool preview for Windows. MCP 2KB description cap and server deduplication. Stats screenshot via Ctrl+S in /stats (16x faster). Drive root deletion protection on Windows.

v2.1.83 — March 25, 2026#

191 env vars (+8) · 41 feature gates · 16 models · 22 slash commands · 29 dynamic configs

managed-settings.d/ drop-in directories for enterprise policy management. 8 new env vars including CLAUDE_CODE_SUBPROCESS_ENV_SCRUB, CLAUDE_CODE_DISABLE_NONSTREAMING_FALLBACK, CLAUDE_CODE_PROVIDER_MANAGED_BY_HOST. Transcript search, plugin keychain storage, CwdChanged/FileChanged hook events. Largest release by fix count — 40+ fixes spanning macOS exit hang, startup latency, MCP policy bypass, sandbox piped commands. v2.1.82 skipped in changelog.

v2.1.81 — March 21, 2026#

183 env vars (+1) · 41 feature gates · 16 models · 22 slash commands · 29 dynamic configs (-1)

--bare flag for stripped-down scripted -p calls (skips hooks, LSP, plugins, auto-memory). Concurrent OAuth fix for multi-session re-auth race condition (#24317). --channels permission relay to phone. /btw pasted text fix, ! bash mode discoverability. Plan mode hides "clear context" by default. 17 bug fixes across voice mode, enterprise proxies, worktrees, Remote Control, tmux.

v2.1.80 — March 20, 2026#

182 env vars (no change) · 41 feature gates · 16 models · 22 slash commands · 30 dynamic configs (+1)

--channels research preview for messaging platform integration (Telegram, Discord), simplified /plugin install flow, source: 'settings' plugin declarations, 80MB startup memory reduction on large repos. Fine-grained tool streaming fix for Bedrock/Vertex/proxy 400 errors, --resume parallel tool result restoration, voice mode WebSocket fix, managed settings startup bug. 7 bug fixes total.

v2.1.79 — March 18, 2026#

182 env vars (+3, -2) · 41 feature gates · 16 models · 22 slash commands

Subprocess env scrubbing (CLAUDE_CODE_SUBPROCESS_ENV_SCRUB), extra API metadata (CLAUDE_CODE_EXTRA_METADATA), refactored init path (CLAUDE_CODE_NEW_INIT). 18MB startup memory reduction, --console auth for API billing, non-streaming fallback timeout. 2 vars removed.

v2.1.78 — March 17, 2026#

181 env vars (+1) · 41 feature gates · 16 models · 22 slash commands

Plugin persistent state (CLAUDE_PLUGIN_DATA), custom model picker entries (ANTHROPIC_CUSTOM_MODEL_OPTION). StopFailure hook event, plugin agent frontmatter expansion, line-by-line streaming. Security hardening: sandbox bypass fixes, MCP deny rule enforcement.

v2.1.77 — March 17, 2026#

180 env vars (+1) · 41 feature gates · 16 models · 22 slash commands (+1 via changelog)

Cowork memory extra guidelines, /branch (renamed from /fork), /copy N index. Stabilization release with 25+ bug fixes: terminal rendering, tmux, teammate sessions, memory management.

v2.1.76 — March 14, 2026#

179 env vars (+3) · 41 feature gates · 16 models · 22 slash commands (+1 via changelog)

Account tagged ID, fast-mode network error bypass, workspace host paths. MCP elicitation support, /effort command. 14 bug fixes.

v2.1.75 — March 13, 2026#

176 env vars (+2) · 41 feature gates · 16 models · 22 slash commands (+1 via changelog)

Auto-compact window threshold, plugin option prefix, /color command. 1M context windows for Opus 4.6.

v2.1.74 — March 12, 2026#

174 env vars (+2, -1) · 41 feature gates · 16 models · 22 slash commands

Frame timing log, session-end hooks timeout. Two-stage classifier flag removed (graduated to default).

v2.1.73 — March 11, 2026#

158 env vars · 40 feature gates · 16 models · 22 slash commands (first baseline)

Maintenance release. First tracking of the full slash command inventory.

v2.1.72 — March 10, 2026#

173 env vars (+6) · 41 feature gates · 16 models

Brief mode, cron control, debug log levels, two-stage classifier.

v2.1.70 — March 6, 2026#

167 env vars (+3, -1) · 41 feature gates · 16 models

CCR v2 bridge, effort level toggle, delta MCP instructions.

v2.1.69 — March 5, 2026#

165 env vars (+82) · 41 feature gates (+41) · 16 models (+16)

Plugin system, mTLS, agent teams, context compaction.

v2.1.19 — January 27, 2025#

83 env vars · ~16 feature gates

First extraction. Agent swarms, Plan v2, debug flags.

What We Extract#

Each release goes through string extraction from the Claude Code npm package:

  • Environment variables — undocumented configuration knobs not in official docs
  • Statsig feature gates — A/B test flags that control unreleased features
  • Model IDs — all models supported in the binary
  • Architecture changes — new subsystems, removed features, renamed internals

Results are diffed against the previous version to surface what actually changed.

Official Documentation#

For officially supported environment variables, see the Anthropic Claude Code Environment Variables Reference. Our tracker covers the undocumented variables discovered through binary analysis that are not in the official docs.

FAQ#

How do you extract this data?

We analyze publicly observable behavior of the installed Claude Code software to document configuration options and feature flags.

Are these officially supported?

No. These are undocumented internals. They may change or disappear without notice.

How often do you update?

We cover every significant release shortly after it becomes available.

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.

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