--debug
A Claude Code CLI flag, read out of the shipped bundle. It has been in the build since v2.1.138, including the newest one read.
Enable debug mode with optional category filtering, such as --debug='mcp,startup' or --debug='!1p'. The filter binds only in the = form; a space-separated filter enables debug mode without filtering
Anthropic's own wording. Read off CLI reference, captured 2026-09-26.
In the changelogs
24Releases whose published page names --debug.
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v2.1.305
Some failed logins now suggest running with
--debugOne kind of login failure now tells you to run with
--debugto see the underlying error, and sign-in links can ask for one extra scopefound in this entry's text, named in this entry
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v2.1.305
Sign-in can fall back to pasting a code from the browser
If Claude Code cannot receive the browser sign-in automatically, it now asks you to paste the code shown after signing in
found in this entry's text
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v2.1.304
/usage now says when you can try again after a rate limit
When /usage is rate limited, its message now shows when it can be tried again instead of saying "try again in a moment"
found in this entry's text
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v2.1.299
Claude Code now warns when skill or command names are refused
A new high-priority notice reports how many skill or command names were refused and tells you to rerun with
--debugto see whichfound in this entry's text
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v2.1.295
claude mcp servegains an HTTP mode, limited to remote cloud sessionsIn remote cloud sessions only,
claude mcp servecan now listen over HTTP with--transport,--portand--session-tunnelfound in this entry's text
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v2.1.290
Unusual or very long cloud error messages are hidden unless you use --debug
Error text from the cloud service is now hidden when it is too long or has unusual characters, and --debug shows it
found in this entry's text, named in this entry
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v2.1.290
Clearer errors when moving a session to the cloud fails
A failed move of a session to the cloud now shows the server's message, falling back to a hint about --debug if it is too generic
found in this entry's text, named in this entry
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v2.1.286
Error message for when Claude Test cannot connect its browser helper
Claude Code contains an error saying Claude Test did not start because its browser helper did not connect, with steps to try
found in this entry's text
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v2.1.282
claude remote-controlaccepts--debugand-dinstead of failingclaude remote-controlno longer stops with an unknown-argument error when given--debug,-dor--debug=…found in this entry's text, named in this entry
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v2.1.281
Recap failure reports an outcome
A failed recap now records its outcome as failed, alongside the "Couldn't generate a recap" message
found in this entry's text
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v2.1.280
Peer address debug string simplified
The Peer address line in the debug info panel no longer tells you to check the --debug log
found in this entry's text
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v2.1.257
New profile-related availability/error reasons
Two new reasons explain a profile whose base URL is not the Anthropic API host or whose credential fails to authenticate.
found in this entry's text, named in this entry
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v2.1.247
Renaming a session warns when other sessions may keep the old name
Renaming a session now warns you when the new name didn't reach other running sessions, pointing at --debug.
named in this entry, found in this entry's text
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v2.1.234
claude mcp servegains transport plumbing, still stdio onlyThe MCP serve command reads transport and port options internally, but stdio is the only choice offered.
found in this entry's text
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v2.1.232
Gateway settings failures now say what actually went wrong
Gateway settings failures now name the exact cause, from TLS mismatch to a rejected credential.
named in this entry, found in this entry's text
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v2.1.227
Debug logging rebuilt around a single logger instance
Debug logging now runs through one logger that keeps queued lines when it restarts.
found in this entry's text
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v2.1.208
Engine log prefix renamed from [shoji-engine] to [engine]
found in this entry's text
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v2.1.206
Plan Publishing as Artifact
found in this entry's text
- v2.1.193
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v2.1.118
Improved Recap Messages
found in this entry's text
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v2.0.52
Buffered Debug Logging
found in this entry's text
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v2.0.12
What This Release Does NOT Include
found in this entry's text
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v1.0.89
Debug Output Filtering
found in this entry's text
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v0.2.114
Debug Mode
found in this entry's text
First cited
9The earliest release whose published evidence quoted --debug was v2.1.247, 26 Aug 2026. That is the oldest release this project wrote about it, so it is a floor on the name's age and not the release that introduced it. It is not a presence reading: which builds carried the name is the table below.
3 further spans in the ledger name it. The list above is the earliest first and stops at 6.
Presence across releases
1Build by build
149One row per release since the first build this name was read out of. Absent means the build was read and the name was not in it, never mined means no bundle for that release was ever archived, and a declared type or a default is only ever what that release's own bundle stated.
Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the CLI flag does. All CLI flags.