Update Log

September 12, 2026 release refresh

Updated for Claude Code v2.1.263–v2.1.269 (September 6–11). npm checked on September 12, 2026 KST: latest/next=2.1.269, stable=2.1.236. Keep latest-feature evaluation separate from a team's stable-channel rollout.

• Plugins: claude plugin eval produces JSON and HTML evaluation reports; install, uninstall, update, enable, and disable accept --json. --plugin-dir can point to a parent directory containing multiple plugins.
• Commands and settings: /output-style [name] works over Remote Control and in cloud/headless sessions. maxEffortLevel caps effort globally or per model under modelSettings. bashEditDiffEnabled adds file-edit diffs to Bash results.
• Recovery and compatibility: 2.1.266 fixes forced gateway sign-in; 2.1.268 fixes HTTP 400s on Anthropic-compatible endpoints introduced in 2.1.265. /goal retries with backoff or pauses with a reason after API, network, or usage-limit failures.
• Permissions and operations: fixes cover symlink deny/ask rules, Bash tee write boundaries, and secrets in MCP/plugin errors. WebFetch has a default 300-second deadline. /ultrareview --post posts the PR comment directly when findings arrive.

Sources: official changelog, npm dist-tags.

Updated: both locales of the index, setup, verification, and relevant command/operations chapters. Entries below retain their historical verification dates.

2026-09-05

• Raised the baseline to Claude Code v2.1.261 and npm latest/next=2.1.261, stable=2.1.236 after reviewing v2.1.252~261 and the Claude Fable 5.1 docs.
• Documented Claude Fable 5.1 (claude-fable-5-1, released 2026-09-01) as the default Fable model from v2.1.257 with a v2.1.255 minimum: alias resolution, /model claude-fable-5 for the legacy model, gateway sessions staying on Fable 5, pricing with $0.25/MTok cache reads, retention, and the Mythos 5.1 distinction.
• Added the category-based classifier fallback table, switchModelsOnFlag, and the third-party ANTHROPIC_DEFAULT_OPUS_MODEL requirement.
• Added Fable 5.1 Messages API breaking changes (forced tool_choice, model-bound thinking blocks, history-editing invalidation from 2026-08-31 accounts) and additive features (per-message effort, turn-scoped system messages, display: "updates", provenance).
• Updated effort guidance (no default-effort hold on Opus 5 and Fable 5.1, session-only s, cache-preserving effort changes on Fable 5.1), 1M auto-compact timing, CLAUDE_CODE_SUBAGENT_MODEL_FORCE, and the [1m] subagent fix across index, setup, context, subagents, headless, and verification.

2026-08-28

• Raised the baseline to Claude Code v2.1.247 and npm latest/next=2.1.247, stable=2.1.231 after reviewing v2.1.239~247.
• Added loop usage breakdowns, managed model picker/pricing and prompt-cache TTL settings, and the Auto-mode rules tab.
• Added partial subagent continuation, fallback-model handling, resilient headless auto-continuation, /claude-api upgrade/cost optimization, and feedback drafts.
• Added the Sonnet 5 1M compaction threshold change plus wildcard, marketplace, and third-party gateway credential hardening.

2026-08-20

• Raised the baseline to Claude Code v2.1.237 and npm latest/next=2.1.237, stable=2.1.228 after reviewing v2.1.221~237.
• Added interactive fork mode, background subagent spawning, cross-session messaging and session mentions, and removal of the old 200-per-session total.
• Added self-hosted runners, remote-control --continue, GitLab merge-request workflows, plugin command/archive sources, and server-supplied runner hooks.
• Added ANTHROPIC_DEFAULT_MODEL, the newer-model Task/Todo default and compatibility flag, the Concise output style, prompt-caching fix, and the release window's trust, sandbox, OAuth, worktree, and Remote Control hardening.

2026-08-03

• Re-checked the official changelog, local CLI, and npm: v2.1.220 remains latest and next, while v2.1.212 remains stable.
• Found no stable release or command addition, removal, or rename after the August 1 update.
• Updated the cover and verification dates while retaining the v2.1.206–220 operating guidance.

2026-08-01

• Raised the baseline to Claude Code v2.1.220 and checked npm dist-tags (latest=2.1.220, stable=2.1.212, next=2.1.220).
• Updated model guidance for Opus 5 as the default Opus path, its 1M context and fast-mode support, current provider alias resolution, and full-name pinning.
• Documented the /fork background-session and /subtask inherited-context split, 200-per-session and 20-concurrent subagent defaults, configurable three-layer nesting, and budget enforcement for background subagents.
• Added sandbox.network.strictAllowlist, sandbox.filesystem.disabled, DirectoryAdded, mcp_server_errors, nested --forward-subagent-text, medium workflow sizing, background /code-review, and manual-only /verify and /code-review behavior.

2026-07-10

• Updated the English handbook baseline to Claude Code v2.1.205 after checking the official changelog and npm dist-tags (latest=2.1.205, stable=2.1.197; excluded next=2.1.206 because it has no public changelog entry yet).
• Added v2.1.202 workflow sizing and OTel attributes, and clarified that /review is the fast single-pass path while /code-review <level> <PR> is the multi-agent path.
• Added v2.1.203 Agent View, background session, worktree, Remote Control, login-expiry, and MCP roots operating notes.
• Added the v2.1.204 headless SessionStart hook-streaming fix and v2.1.205 Auto-mode transcript protection, unresolved rm -rf prompting, --json-schema validation fixes, full /doctor setup checkup with /checkup alias, and updater/Agent View improvements.

2026-07-04

• Updated the English handbook baseline to Claude Code v2.1.201 after checking the official changelog and npm dist-tags (latest=2.1.201, stable=2.1.185).
• Documented the Fable 5 redeployment: Fable 5 and Mythos 5 were suspended for all users on 2026-06-12 under US export controls (~19 days) and Fable 5 was restored globally on 2026-07-01 with an improved safety classifier targeting the reported vulnerability-finding behavior; the automatic Fable-to-Opus fallback follows it.
• Added the Fable 5 plan-usage note (Pro/Max/Team/select Enterprise include Fable 5 up to 50% of weekly usage limits through 2026-07-07, then usage credits) and the Fable 5 vs Mythos 5 distinction (Mythos 5 has no classifiers and is Project Glasswing invitation-only, not selectable via /model).
• Added v2.1.198–v2.1.201 operating notes: subagents run in the background by default (v2.1.198), Claude in Chrome GA, /dataviz skill, SSL/streaming/subagent fixes (v2.1.199), default permission mode "Manual" (v2.1.200), and Sonnet 5 mid-conversation system-role removal (v2.1.201).

2026-07-01

• Updated the English handbook baseline to Claude Code v2.1.197 after checking the official changelog and npm dist-tags (latest=2.1.197, stable=2.1.185).
• Reflected Sonnet 5 as the current Sonnet path in Claude Code: Anthropic API sonnet maps to Sonnet 5, Pro/Team Standard/Enterprise subscription seat defaults use Sonnet 5, and Sonnet 5 supports native 1M context plus low through max effort.
• Added v2.1.191~v2.1.196 operating notes for organization default model labels, clickable file attachments, .mcp.json self-approval hardening, background job transcript preservation, PowerShell git command exit-code handling, Remote mid-turn crash recovery, and background agent/plugin validation fixes.

2026-06-25

• Updated the English handbook baseline to Claude Code v2.1.190 after checking the official changelog and npm dist-tags (latest=2.1.190, stable=2.1.179).
• Added v2.1.181~v2.1.190 operating notes for sandbox.credentials, destructive-command sandbox auto-approval, Windows PowerShell sandbox fixes, MCP login/logout, MCP idle timeout, misleading MCP status fixes, non-interactive fallback reliability, output-schema determinism, Korean paste handling, and app/schema bug fixes.
• Refreshed model guidance for model restriction and deprecation-warning behavior: main model restrictions center on Opus/Sonnet/Haiku/Fable families, Haiku remains subagent-only for this path, and deprecated models should trigger warnings.
• Refreshed subagent/background guidance for the three-level nesting cap, nested-agent stability, Agent deny rules, and background permission-prompt handling.

2026-06-13

• Fixed English locale internal links so they no longer leak to the Korean edition: the cross-references to the subagents chapter (in the context page) and the plan-mode chapter (in the multi-session page) now point to /en/books/... instead of bare /books/....
• Editorial review pass with no content, model, or policy changes for this handbook.

2026-06-10

• Updated the English handbook baseline to Claude Code v2.1.170 and Claude Fable 5.
• Added fable and best alias guidance, including the fact that Fable 5 is not the default and requires v2.1.170 or later.
• Documented Fable-specific automatic fallback to Opus, --safe-mode troubleshooting, Fable data-retention/thinking constraints, and ANTHROPIC_DEFAULT_FABLE_MODEL.
• Added fallbackModel chain guidance for overload or availability failures before long autonomous sessions.
• Added detailed v2.1.169 operating notes for /cd, self-hosted runner post-session hooks, and bundled skill/workflow disabling.
• Added the v2.1.170 transcript persistence fix for sessions launched from VS Code integrated terminals or shells inheriting Claude Code environment variables.
• Kept Opus 4.8 as the default high-capability Opus path and clarified when to use Fable, Opus, Sonnet, and Haiku.

2026-05-29

• Updated the English handbook baseline to Claude Code v2.1.154 and Claude Opus 4.8.
• Added current model alias guidance: Anthropic API, Claude Platform on AWS, and Bedrock/Vertex/Foundry resolve opus and sonnet differently.
• Documented /model default-saving behavior, resumed-session model preservation, and full model name pinning for reproducible work.
• Added Agent View, background sessions, claude --bg --exec, dynamic workflows, /goal, and /workflows to the operating model.
• Added current command guidance for /usage-credits, /reload-skills, /run, /verify, /run-skill-generator, /code-review, and the updated /simplify role.
• Added headless notes for --session-id, background-session automation, app-level verification, and nonessential-traffic controls.

2026-05-05

• Added the first English locale handbook: Claude Code Complete Guide.
• Registered claude-code-advanced under the English content tree.
• Documented the expected behavior for unsupported English handbook routes.
• Added English titles, descriptions, chapter labels, and internal links.

Editorial Policy

The English edition is localized by book, not by global fallback. A book becomes available in English only when its English content tree is present and registered.

This prevents Korean content from appearing under English URLs and keeps search, sitemap, home, and preview behavior aligned with actual content availability.