Claude Code 2.1.280

September 22, 2026

A major update introduces Opus 5.5 as the default model for Opus plans, featuring a substantial 1M context window. This release delivers significant stability and user experience improvements, with critical fixes for auto-mode infinite retries, persistent conversation failures due to API errors, and various interface issues like dialog handling and input loss. Users will also find expanded mouse support, clearer permissions management, and enhanced reliability for background agents and integrations in VS Code and Slack.

Added

Added Claude Opus 5.5 (`claude-opus-5-5`), now the default Opus model — 1M context, $4/$20 per Mtok with $0.20/Mtok cache reads
Added mouse support to more lists in fullscreen mode: the wheel scrolls the `/skills` list, and a skill's state options in `/plugin` can be clicked
Added `CLAUDE_CODE_MAX_MCP_DESCRIPTION_LENGTH` to change the 2,048-character cap on MCP tool descriptions and server instructions for every MCP server in the session
Added hook output sizes and the number of oversized outputs saved to a file to the `hook_execution_complete` OpenTelemetry event
Added a Status dialog, with a typed `/status`, showing the session's version, account, model and server details
Added a Sandbox dialog for the sandbox mode, the unsandboxed fallback and excluded commands, opened from the panel menu or by typing `/sandbox`
Added a Claude in Chrome dialog (extension status, the install, reconnect and permissions pages, the enabled-by-default setting), opened from the panel menu or by typing `/chrome`
Added Export conversation, with a typed `/export`, to copy or save the conversation as plain text
Added each skill's source, token estimate and on/off state to the Slash commands dialog, with a click to change the state, and a typed `/skills` that opens it
Added a typed `/plan` that switches to plan mode, sends a first planning prompt, or shows the session's plan

Improved

Improved `/permissions`: focus returns to the rule list after viewing, adding or deleting a rule, and the delete-rule and remove-directory confirmations now default to No
Improved `/permissions` tab navigation: ←/→ and Tab pressed in a rule list now switch tabs without moving focus to the tab bar
Improved `/cost` cache-miss causes to name thinking mode and thinking display changes
Improved the Artifact tool so that when Claude cannot read an artifact link it was given, it tells the user before continuing
Improved `/install-github-app`: the GitHub CLI check and repository selection steps now show "Esc to cancel"
Improved the `/artifacts` and `/workflows` lists: a scrollbar at the right edge shows how much of a long list is hidden and where you are in it
Improved the workflow progress tree: running agents and phases now show a dim dot instead of ⟳
Improved `/plugin`'s Add Marketplace form in fullscreen: it no longer draws a box inside the pane, and its text and key hints line up with the rest of `/plugin`
Improved the `/workflows` detail view in fullscreen: it no longer draws a second horizontal rule under the pane's divider
Improved code blocks that don't name a language: they are now colored like inline code, so commands stand out from the surrounding text
Improved `/btw` asked while a tool is still running: the side question now knows that call is in progress instead of reading it as a failed one
Improved the UserPromptSubmit hook timeout notice and the debug log to name which hook command timed out
Improved `@` file suggestions: a file whose name contains the query now ranks above one that only matches across its folder names
Improved artifact pages: no Print buttons, confirm dialogs or device features the viewer blocks, email and phone details shown as text, and dark mode that reaches form controls and scrollbars
Improved `/ultrareview` uploads: renamed copies of key files, such as `id_rsa copy` or `kubeconfig (1).yaml`, now also stay on your machine
Improved the cross-session messaging startup warning to explain that `--debug-file` writes a debug log to a path you choose
Improved pasted-text handling in the chat box: a paste over 800 characters or over 2 line breaks is now marked so Claude can tell it from what you typed
Improved prompt handling in the chat box: invisible Unicode formatting and tag characters are removed from pasted text with a notice, and from anything else before it is sent

Changed

Reverted `ctrl+l` / `cmd+k` in fullscreen mode clearing the transcript view (added in 2.1.260); they redraw the screen again
Changed the default model on Pro and Team Standard plans from Sonnet to Opus, matching Max, Team Premium, and Enterprise
Changed an effort level saved before `/effort` became per-model to no longer apply to newly released models such as Opus 5.5; they start at their default until you pick a level
Changed Opus 4.7, Opus 4.8 and Fable 5 to stop holding their launch-default effort over `/effort` in `-p` or the Agent SDK, a project, managed or `--settings` `effortLevel`, or a per-model level
Changed `/autocompact`'s footer hint to name ←/→, the keys that adjust other ordered values
Changed `/fast`'s footer to name Space as the toggle key
Self-hosted runner: Changed git in lifecycle hooks to ignore hook folders and programs named in the runner's shared git files; local-path and `git://` remotes there now need `GIT_ALLOW_PROTOCOL`
Changed plugin marketplaces whose name imitates a reserved marketplace name to be refused when added, and to stop loading if one was already added
Changed `PermissionRequest` hooks: an agent-type hook no longer runs there, since its answer could never allow or deny the request; it now shows an error pointing to command or http hooks
Changed "Open in New Tab" to open Claude beside the editor group you are working in rather than after the last group
[Claude Code on the web] Changed the admin Routines on/off setting to live under Admin settings → Capabilities → Remote sessions; the Claude Code admin page now links to it
[Claude Code on the web] Improved cloud sessions viewed in the Claude app: Claude now saves files meant for you where the app can open them
[Claude Code on the web] Removed the empty repository picker shown when starting a session on a self-hosted environment in an organization where an admin has turned GitHub off
[Claude Tag] Added Slack's native Working indicator, Stop button and thread title to Claude's threads in channels; the indicator stays up until Claude finishes, and Stop interrupts the task
[Claude Tag] Added a short notice in the Slack channel when a guest joining, or the last guest leaving, changes how Claude responds there under a Restrict or Channel only guest setting
[Claude Tag] Improved the GitHub banner in Claude Tag admin settings to say why GitHub isn't connected: not signed in, app not linked or not installed, sign-in expired, or SSO not authorized
[Code Review] Improved the Code Review check run to say when REVIEW.md instructions were cut or left out of a review for exceeding a size limit, naming the file and the limit

Fixed

Fixed writes through a symlinked path being judged by their in-tree spelling: the prompt names where the write lands, and `acceptEdits`, allow rules and auto mode no longer approve one landing outside
Fixed auto mode retrying an action over and over when a safety check declined to review it; the action is now denied once, noting that retrying won't help
Fixed auto mode denying actions over and over without pause when a safety check gave no answer; retries now back off, and the turn stops with a message after ten in a row
Fixed Write calls failing validation when a model sends `path`, `file_text`, `file_content` or a stray `description` instead of `file_path` and `content`
Fixed Ctrl+C or Ctrl+D pressed twice in most dialogs (`/model`, `/effort`, `/config`, `/status`, `/usage`, `/plugin`, `/sandbox`, `/permissions`, `/artifacts`, `/mobile`, `/login`, `/upgrade`, `/usage-credits`, `/install-github-app`, `/setup-bedrock`, `/setup-vertex`) quitting Claude Code instead of closing the dialog
Fixed a click that only brought the terminal window to the front also triggering the item under the pointer — in search pickers, tab bars, agent/workflow rows, slash-command links and suggestion dropdowns
Fixed a stray `n` closing dialogs and a stray `y` confirming them; Enter and Esc accept and cancel (bind `y`/`n` to `confirm:yes`/`confirm:no` in `keybindings.json` to restore)
Fixed text fields in dialogs losing a typed letter, digit or Space to a keybinding on that key
Fixed the prompt line staying scrambled on Windows terminals after invisible characters were removed on Enter; the screen is now repainted so you review the exact text that will be sent
Fixed the invisible-character cleanup removing the zero-width non-joiner that Persian and Arabic text uses to attach a suffix to a Latin word or number, such as the plural of "PDF"
Fixed voice dictation not stopping on Ctrl+C (the prompt cleared but the microphone kept recording), Esc not cancelling while a transcript was processing, and held Space starting dictation from the transcript view and vim NORMAL mode
Fixed a model switch made from a host app (Claude Desktop, VS Code, SDK) while Claude is working causing a prompt-cache miss on the next prompt
Fixed resumed fork subagents rebuilding their tool list instead of re-sending the one they first used, which broke prompt caching for that agent
Fixed subagent hand-back messages showing an internal provenance preamble when expanded outside verbose mode
Fixed `installed_plugins.json` keeping the install-time commit after updating a plugin from a GitHub repository or git URL that tracks a branch or tag
Fixed skills in `~/.claude/skills/` being moved to `~/.claude/skills/.trash/` when a `manifest.json` in that folder listed their names
Fixed the session feedback survey showing no hover highlight on light and ANSI themes
Fixed `/workflows` briefly showing a one-row list before opening the only run
Fixed the mouse wheel not scrolling selection lists with hidden options (such as `/model` and `/permissions`) in fullscreen mode
Fixed a skill you switched off showing the same red ✘ as a plugin that failed to load in `/plugin` and `/skills`; off now shows a dim ◯
Fixed multi-select option descriptions being indented under the option number instead of under the label
Fixed the search box in `/plugin`, `/skills` and `/mcp` losing its right border in fullscreen mode
Fixed `/mcp` showing △ in the server list but ⚠ in the detail view for the same server; the list, detail views and `/plugin` now all show ⚠
Fixed Home and End doing nothing in the `/config` settings list and in selection lists such as `/model`, `/memory` and permission prompts
Fixed PgUp/PgDn in the `/skills` menu wrapping past the first or last skill instead of stopping there
Fixed Tab silently changing the selected setting's value in the `/config` list; it now does nothing there
Fixed conversations failing on every turn with a "role 'system' must precede an 'assistant' message" API error
Fixed conversations with the advisor on failing every turn with API Error 400 "Input tag 'advisor_20260301'" behind a proxy or gateway that doesn't support it; the request now retries without it
Fixed a session failing on every turn and `/compact` when its saved history held a malformed notice about MCP tools that could not be loaded
Fixed a crash when resuming a session whose saved transcript holds a malformed system message or a memory-saved notice without its file list
Fixed one cause of long-running fullscreen sessions exiting with "Claude Code exited after an unrecoverable interface error": a damaged cached message list is now rebuilt
Fixed Claude Code hanging when a settings file, or a file it re-reads after an edit, is replaced by a named pipe mid-read
Fixed `/config` crashing and some on/off preferences being misread when a preference that has moved to `settings.json` still holds a value like `null` or `"false"` in `~/.claude.json`
Fixed resuming a session with unfinished background agents, shells or workflows starting a model turn on its own before you typed anything
Fixed messages sent to a background subagent being silently lost in headless and SDK sessions when the subagent was finishing its turn
Fixed a finished subagent's report being lost when the conversation that launched it was compacted before the report was read
Fixed background subagents being unable to use the LSP tool when an LSP plugin is active
Fixed background shell tasks reporting benign non-zero exits (e.g. grep with no matches) as failures
Fixed background sessions (`claude --bg`) being unable to run git, hooks, plugins and other helper programs when an environment variable handed to the session contained a NUL character
Fixed Ctrl+C needing three or four presses to exit while background subagents are running; two presses now exit
Fixed IDE selection being dropped when a sent prompt comes back into the input, such as pressing Esc to edit it, rewinding to it, or pressing Esc while startup hooks run
Fixed a `!` shell-mode prompt stashed with Ctrl+S coming back as a plain prompt when restored, and `/` listing file paths right after stashing one
Fixed `claude agents` showing a blank, unresponsive screen instead of an error when the temp directory is full, not writable or owned by another user
Fixed an MCP server re-added under the same name after `claude mcp remove` still showing as needing authentication instead of reconnecting
Fixed background plugin marketplace auto-update ignoring git credential helpers, so private-repo marketplaces were re-cloned every run or never updated
Fixed `claude plugin update` clearing a plugin's recorded commit and moving it to version "unknown" when the official marketplace's snapshot file is a link or too large
Fixed the Artifact tool silently disappearing when your organization's policy can't be loaded (for example behind a web proxy); Claude now says what's blocking it
Fixed artifact republishes silently resetting stored database access rules or dropping the viewer profile scope when that capability was re-sent without them; they are now refused
Fixed `/ultrareview` reporting a stopped cloud review as completed or as an error to retry, and waiting out the full timeout when its session was deleted or the signed-in account changed
Fixed the Claude app showing a missing or stale context usage figure for Remote Control and cloud sessions right after /compact or /clear
Fixed the Claude app's diff view for Remote Control and cloud sessions dropping a branch's committed files whenever there are also uncommitted changes
Fixed cloud and self-hosted runner sessions failing with "Authentication failed" after waiting out a long overload during which the session's access token was rotated
Fixed memory write conflicts in Cowork sessions showing Claude only the start and end of a memory file over about 10,800 characters, so the retried write dropped the middle
Self-hosted runner: Fixed lifecycle-hook commits failing to sign under `--configure-git`
Windows: Fixed background cleanup deleting a directory symlink or junction used to relocate `~/.claude/session-env`, `image-cache` or another cleaned-up folder
Self-hosted runner: Fixed a turn that ended right at a `--retire-at` release losing its finished signal; the runner now briefly waits for the turn to be reported before stopping the session
Fixed the effort chip showing a stale saved effort level instead of the level the session runs at
Fixed Claude Code never starting when the Python extension hangs while activating; it now starts after 60 seconds without the Python environment
Fixed the plan approval card never offering auto mode: when auto mode is available, its first option is now "Yes, and use auto mode", as in the terminal
Fixed arrow-key navigation in the session list stopping after archiving or unarchiving a session from the keyboard
Fixed paste marker lines showing in your own messages after reopening a session
[Claude Code on the web] Fixed `gh` and GitHub API calls inside a cloud session on a GitHub Enterprise Server repository failing after about eight hours; the token now renews automatically
[Claude Code on the web] Fixed a routine that resumes an existing session running with its old prompt and name when it was edited moments before the scheduled run started
[Claude Code on the web] Fixed file links in a cloud session transcript that point outside the session's working directory opening a file card that never loads; they're now disabled and say why
[Claude Code on the web] Fixed auto mode refusing to retry a tool call because an approval prompt that expired unanswered, or was superseded by a newer message, had been recorded as your rejection
[Claude Tag] Fixed scheduled routines silently failing to run in Slack workspaces that were connected to Claude before the workspace joined its Enterprise Grid
[Claude Tag] Fixed Claude asking you to re-upload a Slack file when a brief file-scanning outage, not the file, was the problem; it now retries the scan and is told when the scanner is down
[Claude Tag] Fixed a bullet in Claude's Slack reply whose text starts with +, - or * rendering as an empty bullet with a stray nested item; it now shows as one bullet with the character kept
[Claude Tag] Fixed the Slack notice for a failed cloud environment setup script sometimes being a generic "mention me to retry"; it now names the setup script and says to fix it first