Cloakroom

Cloakroom is free and open source. It masks API keys, passwords and personal data (names, emails, addresses and the like) on your machine before your AI coding agent sees them. Works with Claude Code, Codex CLI and Gemini CLI.

Cloakroom swaps your secrets and personal data for placeholders before Claude sees them, and puts the real values back in the files Claude writes.

On test data it hadn't seen before, Cloakroom let through 0 of 1,005 personal details (the other tools we tested let through 119 to 992) and 0 of 77 keys and passwords in the formats vendors really issue. Its weak spot is false alarms: it masks more harmless text than secret-only tools do. Results

Install (inside Claude Code, one line at a time):

/plugin marketplace add shanjeevrajendran/cloakroom
/plugin install cloakroom@cloakroom

Or, from a terminal:

claude plugin marketplace add shanjeevrajendran/cloakroom
claude plugin install cloakroom@cloakroom

Then restart Claude Code. Details and other tools: Get started.

A placeholder is a label such as PII_PERSON_1 or PII_SECRET_1. The AI sees the label and works with it. The real value stays on your machine.

Cloakroom catches personal data as well as keys. It masks the data and lets the AI carry on, instead of stopping the whole step. And it learns from your corrections.

It runs on your machine, sets itself up on first start, and works on Mac, Windows and Linux. Free and open source. It's new, so expect rough edges.

New in 0.7, it also protects two other AI coding agents that run in a terminal (Mac and Linux):

• OpenAI's Codex CLI: run cloakroom install codex (Codex).
• Google's Gemini CLI: run cloakroom install gemini (Gemini CLI).

New in 0.8:

• See which keys your agents saw: cloakroom exposure lists the keys and passwords Claude Code, Codex CLI and Gemini CLI saw, each as a hint (ghp_…LmPq), never the key, and ends with a "Rotate these" list. It lists only what Cloakroom detected (details).
• A warning when a pull changes what your agent runs: cloakroom scan lists every command a repo's agent and editor config would run and flags the npm worm's shape. After cloakroom install git-hook, each pull, checkout or merge that adds or changes such a command prints it. It warns, never blocks (details).

What works where

✓ Masked: the AI sees a placeholder, never the real value · ⛔ Stopped: Cloakroom blocks it and tells you how to send it safely · ✗ Not covered: Cloakroom can't see it

Why typed messages are stopped instead of masked: these agents let an add-on stop what you type, but not reliably change it. So Cloakroom stops a message holding a key or personal data before it's sent, and nothing reaches the AI.

MCP tools are add-ons that give the AI extra abilities, such as a browser or a database. "Block message" is explained under the table.

Protection	Claude Code	Codex CLI	Gemini CLI
Prompts you type	⛔ Stopped before sending (the AI never sees it); Cloakroom tells you how to resend it safely	⛔ Stopped before sending (the AI never sees it); Cloakroom tells you how to resend it safely	⛔ Stopped before sending (the AI never sees it); Cloakroom tells you how to resend it safely; ✗ pictures in a prompt aren't checked
File reads	✓	✓ Masked when read through the shell (sent as a block message)	✓ Masked (sent as a block message)
Command output	✓	✓ Masked (sent as a block message); ✗ long-running commands	✓ Masked (sent as a block message)
MCP tool output	✓	✓ Masked (sent as a block message)	✓ Masked (sent as a block message)
Images and PDFs	✓	✗ Not covered: pictures opened with view_image	✓ Masked: the text in pictures is read on your machine; ⛔ PDFs held back
Real values put back in commands and edits	✓	✓; ⛔ unknown commands are refused, not asked about	✓
Real values kept out of web and MCP calls	✓	✓; ✗ Codex's own web search (runs on OpenAI's servers)	✓
Keys written into files git would commit	✓	✓	✓
The agent's git commit / git push check	✓	✓	✓
Commands that send secrets or placeholders over the internet	✓	⛔ Stopped: refused, not asked about	✓
Calls that move money	✓	✓	✓
Check on commits you make yourself	✓	✓	✓
Systems	Mac, Linux, Windows	Mac, Linux	Mac, Linux

Cloakroom works through hooks: small checks the agent runs before and after each action, such as reading a file or running a command.

• Block message: Codex and Gemini CLI can't swap a tool's output for a masked copy. So Cloakroom blocks the original, and the AI reads the masked text in the block message instead.
• Codex ignores Cloakroom's hooks until you approve them once (type /hooks inside Codex).
• Gemini CLI lets an action through unchecked when a check runs past its time limit.

Both were tested live (Codex 0.164, Gemini CLI 0.65). Everything else: Known limits.

Recent releases

• 0.8.0 (2026-10-27): cloakroom exposure shows which keys your agents saw, with a rotate list; cloakroom scan and a git-hook warning when a pull changes the commands a repo's agent config would run; three fixes found by a live agent test (Results).
• 0.7.2 (2026-10-25): the check on commits you make yourself works on Windows too; clearer README and docs.
• 0.7.1 (2026-10-25): when a check is skipped and an action goes through unchecked, it's logged and counted in cloakroom report; cloakroom install git-hook checks the commits you make yourself; Codex can hold long-running commands.
• 0.7.0 (2026-10-24): Cloakroom also protects Codex CLI and Gemini CLI, on Mac and Linux.
• 0.6.6 (2026-10-24): a secret Cloakroom has already seen is still caught when a command scrambles it (hashed, hex-encoded or written backwards).

Claude Code plugin updates arrive a few days after each PyPI release (PyPI is the Python package site), once the release has settled. All changes: CHANGELOG.md.

Hand Claude the files you'd never paste into a chat:

• Bank statements (PDF, scan or CSV): "sort a year of spending by category." Claude sees amounts and merchants, not your name, address or account number.
• Support tickets: "draft replies to this week's tickets." Claude writes to a placeholder name (PII_PERSON_1); the drafts saved on your disk have the real names.
• Medical or HR records: names, birth dates, addresses and ID numbers are masked, so Claude can summarise or tidy a record without knowing whose it is.
• .env files and logs: Claude fixes the config without ever seeing the password or API key.
• Disguised copies: a key or email that a command hashed, hex-encoded or reversed is still masked (what's covered).
• Finance work: bank and card numbers are masked, calls that move money wait for your OK, and cloakroom report with a log that shows any later edit is your audit trail (for finance teams).
• Scans and photos of documents: read on your machine (no upload) and masked like any other file.
• Learns from you: when it masks something harmless (a false alarm), mark it once in the dashboard and a rule stops it next time.

Get started

You need Claude Code, installed and signed in. Then:

1. Open a terminal. Mac: press Cmd+Space, type "Terminal", press Enter. Windows: open Start, type "PowerShell", press Enter. Linux: press Ctrl+Alt+T. Type claude and press Enter.

2. Add Cloakroom. Inside Claude Code, type these two lines, one at a time. If it asks where to install, pick the option for all your projects (user scope).

   /plugin marketplace add shanjeevrajendran/cloakroom
   /plugin install cloakroom@cloakroom
   

3. Restart Claude Code. Type /exit, then claude again. Cloakroom now installs itself. Keys and card numbers are covered within seconds if uv or pipx (tools that install Python programs) is already installed, or in about a minute when Cloakroom has to download them first; names and addresses a few minutes later, once the detection model has downloaded (about 1 GB on a Mac, up to about 4 GB elsewhere). Until then, Claude's actions (reading files, running commands, using add-ons) wait. It also updates itself when the plugin updates (an install you made by hand is left alone). On a Mac, if it asks to use the "cloakroom" item in your Keychain, click Always Allow (it only lets Cloakroom read its own key).

4. Check it. Open a new terminal window and run:

   cloakroom doctor       # every line should say ok
   cloakroom dashboard    # opens your alerts in the browser
   

What you need first:

• Windows, Mac and Linux: nothing. When neither uv nor pipx (tools that install Python programs) is there, Cloakroom fetches uv (a fixed version, checked against its known SHA-256 fingerprint before it runs), and uv brings its own Python. That needs curl or wget, which macOS and most Linux systems have. If a Linux machine has neither, Cloakroom tells you the steps: sudo apt install curl (Ubuntu/Debian) or sudo dnf install curl (Fedora/RHEL), then restart Claude Code.
• Intel Mac: only the pattern rules run, so keys, cards and ID numbers are caught but most names and addresses are not. The detection model for names and addresses needs PyTorch or ONNX Runtime, and neither is built for Intel Macs.

If something looks wrong:

• cloakroom not found: open a new terminal. The program lives in ~/.local/bin (on Windows, %USERPROFILE%\.local\bin); the installer adds that folder to your shell profile (~/.zshenv for zsh, ~/.bashrc and ~/.profile or ~/.bash_profile for bash) or, on Windows, to your user PATH.
• Still setting up, or it failed: progress, and numbered steps when something needs you, are written to ~/.cloakroom/bootstrap.log. More in Setup.

Tested from clean installs on macOS, Windows and Ubuntu.

Prefer to install by hand: uv tool install "cloakroom[model,torch,ocr]" (Python 3.10+; the part in brackets adds the detection model and OCR, which reads text out of pictures), then add the plugin as above.

How it works

When Claude reads a file or runs a command, Cloakroom checks the result on your machine first. Each real value it finds is swapped for a placeholder. The pair is kept in the vault, an encrypted file on your machine. When Claude writes a file or runs a command that holds a placeholder, Cloakroom puts the real value back just before it runs.

  Claude Code reads a file or runs a tool
        │   "Nadia Petrov called about…"    sk_live_51Hx9Q…
        ▼
  ┌────────────────────────────────────────────┐
  │ Cloakroom  (on your machine)               │
  │   rules + local model  ->  find the values │
  │   encrypted vault      ->  remember them   │
  └────────────────────────────────────────────┘
        │   "PII_PERSON_1 called about…"    PII_SECRET_1
        ▼
  the model works with placeholders only
        │   Write reply.md: "Hi PII_PERSON_1,"
        ▼
  Cloakroom puts the real value back, locally
        │
        ▼
  reply.md on your disk: "Hi Nadia Petrov,"

Details: docs-HOW-IT-WORKS.md.

Extra protections

Masking is the core. These come with it, on by default, and need nothing from you.

Real values don't leave your machine

• Commands that send data are held: a command that would send a secret Cloakroom has seen off your machine (curl, wget, ssh, scp, rsync, nc, git push with credentials, a key typed straight into an Authorization header) is held: it doesn't run until you say so. The message names what it found by placeholder only. If you meant it, type cr: allow, then ask Claude to run the same command again: it passes once.
• One-line scripts count too: python -c, node -e, ruby -e, perl -e, php -r, deno eval and bash -c commands that can connect to the internet are treated like curl.
• Encoded copies count: a secret Cloakroom has seen is also caught when a program rewrites it in a common way (base64-encoded, URL-encoded or JSON-escaped).
• Disguised copies count: that secret is also caught hashed, as hex or reversed (details).
• Web, MCP and subagent calls carry placeholders only: a web fetch, an MCP tool call or a prompt to a subagent (a helper AI that Claude starts) that holds a real value is stopped before it runs.
• Pictures and PDFs become masked text: PDFs, scans, photos and images returned by MCP tools are read on your machine and Claude gets masked text, never the file or the picture. Without OCR an image is held back, with a one-line reason.

Disguised copies

Once Cloakroom has seen a key, password, card or account number, or an email, it also looks for copies a command changed on the way. Each copy gets its own placeholder, and the exact copy is put back in files Claude writes.

• Covered: MD5, SHA-1 and SHA-256 hashes of a key or an email; hex (6b39..., 0x..., 6b 39 ..., \x6b...); a key or password of 12+ characters written backwards; pairs like user:password or DB_PASSWORD=... in hex or URL encoding; a card or account number's last 4 digits right after "ending in", "last 4" or ****; an email's username on its own when it can't be an ordinary word (r.okafor77, not admin).
• Not covered: salted or keyed hashes (bcrypt, HMAC), other hashes, a name in different capitals, initials, a last 4 with no word pointing at it, and anything Cloakroom hasn't seen in plain form first.

Keys stay out of git

Git saves versions of your code, and those versions are often shared online.

• Files git would commit: when Claude writes a file, a key or password that would end up in a tracked file is refused, and Claude is told to use .env instead. Ignored files and .env work as before.
• Commits and pushes: before Claude runs git commit or git push, Cloakroom reads what would be committed or pushed. A key or password there holds the command, naming the file and placeholder; cr: allow lets it run once.
• Commits you make yourself: cloakroom install git-hook (in a repo) also checks commits you make yourself, with the same rules and your own known secrets (your always-mask values), no agent needed. It adds pre-commit and pre-push hooks (where core.hooksPath points, if set) and never changes a hook another tool put there: it skips it and prints the one line to add to it. Skip the check once with git's own --no-verify; remove it with cloakroom uninstall git-hook. One repo at a time (no --global: git's template folder would only reach new clones). Mac, Linux and Windows (Git Bash, PowerShell or cmd: git runs the check, whichever window you commit from).
• A trusted repo that changes under you: Claude Code, Codex, Gemini CLI and VS Code ask before trusting a new folder, but not again when a folder you already trusted changes. A pull can add a hook that runs the next time you open the agent there (the Tensorlake npm worm did this in October 2026). The same cloakroom install git-hook adds post-checkout and post-merge hooks: after a pull, checkout or merge, Cloakroom compares the commands in .claude/settings.json, .mcp.json, .codex/, .gemini/settings.json and .vscode/tasks.json before and after, and prints each new or changed one with its file and line. It only warns: nothing is blocked or edited. cloakroom scan [folder] lists every such command at any time and flags the worm's shape (an agent hook running a file in .vscode/ and a folder-open task running a file in .claude/).
• Agent config files: a real key written into .mcp.json, .claude/settings.json, .cursor/mcp.json or a copy of claude_desktop_config.json in a repo is refused. Claude is told to point to a setting kept outside the file instead, such as ${GITHUB_TOKEN}.

You stay in control, and can show it

• Claude can't turn Cloakroom off: its settings change only from the dashboard or when you type cr: pause or cr: resume.
• A log you can check and export: each line of the activity log carries a fingerprint (hash) of the line before it, so an edited or removed line shows up. cloakroom report (or Export on the dashboard) gives counts per day and session, without values.
• Placeholders can't be guessed: each one ends in a short tag only your machine can make (PII_SECRET_1_k7q2ab), and only placeholders issued in this session get their real value back. A file that names PII_SECRET_1 to fish for a key gets nothing; after three such tries in a session you see one line.
• Files Claude wrote stay masked: when a real value is put back into a file, Cloakroom remembers where (never the value), so reading that file again later, even in a new session, shows the placeholder.
• Old transcripts can be cleaned: cloakroom clean-history finds keys and passwords already sitting in old Claude Code transcripts (saved records of past chats) and your prompt history, and replaces them on your yes, with a backup you delete.
• See which keys your agent saw: cloakroom exposure lists the keys and passwords your coding agents saw, so you know what to rotate. It reads Cloakroom's own log (per session and agent: where the key was seen and what Cloakroom did) and scans old Claude Code, Codex CLI and Gemini CLI transcripts for keys from before Cloakroom. It ends with a "Rotate these" checklist. It shows a hint (ghp_…LmPq), never the key, and only reads the transcripts. It lists only what Cloakroom detected: a key it missed has no line, so no line is not proof a key is safe.

For finance teams

• Bank numbers are masked: US routing numbers (a valid ABA check digit plus a word or field like "routing" or "ABA") and bank account numbers (next to "account number", "acct", "checking account", "DDA", in a CSV column of that name, a line of an ACH payment file, or beside a routing number in the same record) become PII_BANK_1_k7q2ab. Digits with no such word stay as they are, so order numbers, phone numbers and ZIP+4 codes are left alone.
• Calls that move money are held: a write to a payment, payout or transfer API (Stripe, Plaid, Dwolla, Wise, Adyen, PayPal, Square, Increase, Modern Treasury, Column) from curl, PowerShell or a payment CLI, or an MCP tool named for it (send_money, create_payout, initiate_transfer), waits until you type cr: allow; then it runs once. Reads such as a balance check pass. Add your own hosts and tools in ~/.cloakroom/config.json with "money_hosts": ["payments.example.com/api/wires"] and "money_tools": ["disburse"]; turn the hold off with "money_hold": false.
• The audit trail: every hold and every cr: allow lands in the same activity log that shows later edits (above), so cloakroom report shows them per day and session.

• cloakroom report [--since 2026-10-01] [--format csv|json]: counts per day and session by data kind and action (masked, withheld: output not passed on, held, allowed once, denied), with paths reduced to their extension and top folder. It starts with what it covers and what it can't: a miss leaves no line, and other agents, machines without Cloakroom and prompts sent with cr! are not in it. A "Checks skipped" section counts the calls let through without a full check (too large, too slow, a git error, the model not ready), by check and reason; you're also told about each reason once per session when it happens.
• cloakroom report --verify: checks that no line of the log was changed (the hash chain) and prints the last line's fingerprint (the head hash). Keep that somewhere else: anyone who rewrites every later line can rebuild the chain. The log keeps "log_months" months (default 12).
• cloakroom clean-history [--dry-run]: the first run only counts, per project. Files changed in the last ten minutes (an open session) are skipped.
• cloakroom exposure [--since 2026-10-01] [--format text|json]: keys and passwords seen with Cloakroom and found in old agent transcripts, with a hint (a known prefix such as sk- or ghp_ and, for values of 16 characters or more, the last 4) and a rotate checklist. It lists only what Cloakroom detected: a key it missed has no line.
• cloakroom scan [folder]: lists every command the agent and editor config in a folder would run (.claude/settings.json, .mcp.json, .codex/, .gemini/settings.json, .vscode/tasks.json), with its file and line, and flags the npm worm's shape. Read-only.
• Pull, checkout and merge warning: cloakroom install git-hook adds post-checkout and post-merge hooks that print each new or changed command in those files. It warns, never blocks. Run it again in a repo that already has the hook to get the new ones.
• Commit and push check: it reads the changes you staged for the commit (for git push, the commits no remote has yet) within two seconds; a larger or slower one runs unchecked. Repos that commit sample keys need "allow_secret_paths".

Dashboard

Where you correct Cloakroom. Each false alarm you mark can become a rule, so it stops happening. The detection model itself never changes.

cloakroom dashboard opens a page that Cloakroom serves from your own machine only (127.0.0.1). You're signed in with a one-time link.

• Alerts: every masked, withheld or blocked call, with the kinds found and how long the check took. Open one to see its placeholders; the real values show only when you click Reveal.
• Your labels: mark an alert correct, a false alarm, or type what it missed.
• Rules from your labels: a false alarm suggests "never mask this", a miss suggests "always mask this". You approve each one, or later let rules apply by themselves once Cloakroom has tested them against your past labels; rules that would unmask a key, password, card or ID number always wait for you. Undo puts everything back. The detection model never changes. Details: the handbook.
• Private by design: the activity log holds no values or text; labels and rules are encrypted like the vault.

When Cloakroom blocks your prompt

Claude Code lets Cloakroom stop a prompt but not rewrite it. So a prompt holding a key, an email, a phone, a card or an ID number is stopped before it's sent, and the AI never sees it. Names alone and plain dates go through. The block message says what it found, and how to get past it:

Type	What happens
cr! at the start of your prompt	that one prompt is sent as it is
cr: pause 10m	prompts aren't blocked for 10 minutes (any number, up to 240); each shows the time left
cr: resume	checks are back on

Files and command output stay masked the whole time. Only you can do this: Claude never sees these commands and can't change Cloakroom's settings. Usually better still: put the detail in a file and ask Claude to read it. It gets masked on the way in and the real values come back when Claude writes.

Why Cloakroom

Claude Code reads whatever your task touches: .env files, logs, customer exports, support tickets. All of it goes to the model. Secret scanners catch keys with a known shape, but a customer's name in a ticket or an address in a log looks like ordinary text to them.

• Catches personal data, not just keys. A small detection model on your machine, plus rules, finds names, emails, phone numbers and addresses that have no fixed shape. On fresh test sets it let through 0 of 1,005 of them; the other tools we tested let through 119 to 992 (Results).
• Claude keeps working. Placeholders stay the same for the whole session, and the real values are put back when Claude writes a file or runs a command locally.
• Runs on your machine. Detection, OCR, the encrypted vault (where the real values wait) and the put-back are all local. The only network call is the one-time model download (the OCR models ship inside the package).
• Mac, Windows and Linux. One install on all three, with the vault key in each system's own secure store: Keychain on macOS; Credential Manager on Windows (runs in PowerShell or Git Bash, tested on Windows Server); Secret Service on Linux (tested on Ubuntu 24.04, plus automatic tests on every change).
• No graphics card needed. Each file or command is checked in a fraction of a second on an ordinary laptop (cloakroom doctor prints your numbers).
• Catches encoded output. If a command prints data in a scrambled but reversible form (base64, hex dumps from xxd or od), Cloakroom turns it back into text and checks it too.
• If it can't check, it doesn't let things through. When Cloakroom isn't ready, Claude's file reads and commands wait instead of passing unchecked. Your prompts still get a quick rules check, with a warning, so you're never locked out.

Results

In short: in our tests Cloakroom let through fewer secrets and personal details than the other tools we tried, and masked more harmless text by mistake. The tables below are the detail.

• Good at: personal data (names, emails, phone numbers, addresses) and secrets in odd places. On fresh test sets it let through 0 of 1,005 personal details; the other Claude Code tools we tested let through 119 to 992. It masks, so Claude keeps working; one other tool blocks the whole step instead.
• Weaker at: False alarms. Cloakroom is tuned to mask rather than risk a leak, so it masks more harmless text than secret-only scanners; Claude still gets the job done with a placeholder. Label a false alarm in the dashboard and a rule stops it next time.
• What a false alarm costs: Claude sees a placeholder where it needed the real text. Nothing leaks.

A live agent run (bench/black-october/): the same Claude Code task on a repo of 11 dummy keys and passwords, once without Cloakroom and once with it, then two secret scanners on what each run left behind. Without Cloakroom the model saw all 11 (11 of 11); with it, none (0 of 11), and none reached the saved transcript or the commit. One machine, one model, one prompt: it shows the pieces work together, not a rate you should expect everywhere.

Unless it says otherwise, every number comes from a test set run once, before Cloakroom was adjusted for it. All tools at default settings, offline, tested 12 to 14 October 2026 (Cloakroom's rows rerun 24 October for 0.6.2). maisecrets' maintainers reproduced our numbers and pointed out where the older sets were unfair to them (keys in formats vendors don't issue, and the regions setting); the key-format set and the setting below are the fix. The maintainers of the compared tools were contacted before publishing. Method, versions and every run: bench/RESULTS.md.

Made-up agent traffic (five sets written by a different model: chats, logs, config files, spreadsheets, support tickets): 1,339 key and personal values (the rest are in RESULTS.md) and 200 safe look-alikes. Fewer is better. These sets have been seen by now, so Cloakroom's second row is not an honest score; the first row is its run before any tuning on them.

Tool	Personal data leaked (of 1,005)	Keys, passwords, cards, IDs leaked (of 334)	False alarms (of 200 safe samples)
Cloakroom, first run	0	4	60
Cloakroom today (has seen these sets, so not a fair score)	1	2	20
sensitive-canary (blocks the call instead of masking)	119	40	16
maisecrets ("regions": ["us", "uk", "in"])	547	54	6
claude-code-redact, PII on	607	101	31
redact-hook	817-822	143-157	35-40
claude-code-redact, secrets only	992	179	2

Some of these tools only aim at secrets, so their personal-data column shows scope as much as quality. Cloakroom's one leak today: a date of birth in a dating-profile export.

Keys in the formats vendors really issue (a new set written after the first comparison: 15 key types, passwords with no fixed shape, encoded emails; 77 values, 15 look-alikes):

Tool	Leaked (of 77)	False alarms (of 15)
Cloakroom	0	2
maisecrets	3	1
sensitive-canary	14	3
redact-hook (default / aggressive)	15	5
claude-code-redact (PII on / secrets only)	17	2 / 1

Real passwords and keys from public code (Samsung CredData): 14,471 real secrets and 15,422 harmless look-alikes, each line checked alone, the way a tool output reaches Claude. One repository is almost all cipher test vectors (sample keys for testing encryption code), which maisecrets' keyword rule is built to catch: first number without it, in brackets the whole set.

Tool	Real secrets caught (of every 100), higher is better	False alarms (of every 100 harmless look-alikes), lower is better
Cloakroom	73 (65)	19 (22)
maisecrets	58 (68)	7 (6)
claude-code-redact	36 (31)	8 (7)
sensitive-canary (blocks the call instead of masking)	30 (27)	21 (18)
redact-hook, default	27 (19)	5 (4)
redact-hook, aggressive	36 (26)	12 (20)

Without the test-vector repository, Cloakroom catches the most; with it, maisecrets does, and maisecrets is the most precise either way (of what it masks, 86 to 91 in 100 are real secrets, against Cloakroom's 73 to 74). Cloakroom masks far more harmless look-alikes (3,457 against maisecrets' 997 on the whole set, down from 3,903 before 0.6.2): false alarms are Cloakroom's main open problem (precision, recall and F1 for every tool).

On public datasets we didn't write (run once; details in bench/public/RESULTS.md):

Dataset	Personal details found (of every 100)	Masks that were not labelled personal data (of every 100)
TAB, real court rulings from the European Court of Human Rights	95	19
Gretel, made-up finance documents	85	48

On Gretel, over half of those extra masks are number strings Cloakroom treats as account or reference numbers; the rest are mostly names and addresses Gretel leaves unlabelled.

Codex

Cloakroom also works with OpenAI's Codex CLI, on Mac and Linux (tested with Codex 0.164).

1. Install the program by hand: uv tool install "cloakroom[model,torch,ocr]".
2. Run cloakroom install codex. It adds four hooks to ~/.codex/hooks.json and leaves your own hooks alone.
3. Start Codex (codex), type /hooks, open each of the four Cloakroom hooks and trust it. Until you do, Codex skips them, and codex exec (Codex run without the chat screen) gives no warning, so nothing is masked. cloakroom doctor shows whether they're installed.

What works as in Claude Code: shell output and MCP results are masked before the model sees them, placeholders in shell commands and patches (Codex's file edits) get their real values back on your machine, real values are kept out of MCP calls, and a prompt holding a secret is stopped with what to do next. What's different:

• Codex can't swap a tool's output for a masked copy, so Cloakroom blocks the original and the AI reads the masked text in the block message.
• Codex hooks can't ask you. A command that would send placeholders off the machine, or one Cloakroom doesn't know, is stopped instead of asked about.
• Open gap: a command that runs longer than Codex waits (10 seconds by default), such as a dev server, a watch or a slow build, hands its first output to the model while it is still running, and Codex runs no hook on that output, so it is not masked. To close most of it, set "codex_hold_long_running": true in ~/.cloakroom/config.json (off by default for now): commands that obviously keep running (tail -f, watch, npm run dev and other dev servers, docker logs -f, docker compose up, kubectl logs -f, journalctl -f, ping without -c, --watch...) are then held, with one line saying their output won't be masked; cr: allow lets one run once. A slow build or a command that only sometimes runs long isn't caught.

To remove it: cloakroom uninstall codex. More in Known limits.

Gemini CLI

Cloakroom also works with Google's Gemini CLI, on Mac and Linux (built against Gemini CLI 0.65).

1. Install the program by hand: uv tool install "cloakroom[model,torch,ocr]".
2. Run cloakroom install gemini. It writes one thing: a Gemini extension named cloakroom in ~/.gemini/extensions/cloakroom/ (gemini-extension.json and hooks/hooks.json, four hooks that call the cloakroom program). Your settings.json and your own hooks and extensions aren't touched. Gemini runs the hooks from its next start, in every folder; gemini extensions list shows it, cloakroom doctor too, and warns when the extension is disabled or Gemini's hooks are switched off.

What works as in Claude Code: the output of every tool (shell, file reads, MCP) is masked before the model sees it, pictures are read by local OCR or held back, placeholders in shell commands, write_file and replace get their real values back on your machine, real values are kept out of MCP calls and web tools, and a prompt holding a secret is stopped with what to do next. What's different:

• Gemini can't swap a tool's output for a masked copy, so Cloakroom blocks the original and the AI reads the masked text in the block message.
• Prompts can only be stopped, not masked: a stopped prompt isn't sent, so the AI never sees it. Gemini could rewrite a prompt on its way to the AI, but it keeps the original in the conversation and sends that to Google on other calls no hook sees.
• Gemini lets an action through unchecked when a hook runs past its time limit. So Cloakroom never waits for its detection model to load: until it's ready, checks use the pattern rules only (keys, cards, ID numbers), and names and addresses may be missed.

To remove it: cloakroom uninstall gemini (deletes that folder, nothing else). More in Known limits.

In an editor

• Claude Code in VS Code or JetBrains: Cloakroom works as in the terminal. The VS Code extension runs Claude Code with your plugins, and the JetBrains plugin runs claude in the editor's built-in terminal.
• Codex in VS Code (OpenAI's Codex extension): the extension's own Codex reads the same ~/.codex/hooks.json, so it loads Cloakroom's hooks. Trust them first in the codex CLI (/hooks, step 3 above); the Codex limits above apply.
• Gemini Code Assist in VS Code: Cloakroom does not protect you there. Its agent mode doesn't run the hooks that Gemini extensions bring. Use the Gemini CLI in a terminal instead (VS Code's own terminal is fine).
• Antigravity, and editors not listed here: not supported. Cloakroom installs nothing there.

More in Known limits.

Ways to run

• Full mode (default): rules plus the local model. Catches keys and personal data written as plain text.
• Rules mode (CLOAKROOM_MODE=rules): pattern rules only, no detection model. Instant, and installs with plain uv tool install cloakroom. Catches keys, card numbers and IDs, but misses most names and addresses.
• Outside Claude Code: cloakroom check FILE shows what would be masked, cloakroom explain FILE shows why, cloakroom mask FILE prints what Claude would see.
• Dry run (CLOAKROOM_DRY_RUN=1): a test mode that lets everything through and only logs what it would have done.
• Settings in ~/.cloakroom/config.json: "allow" for your own exceptions, "mask_all_dates": true to mask every date (by default only birth dates and dates in someone's record), "mask_own_username": true to mask your own login name in paths too, "allow_images": true to let pictures through unchecked (with a warning), "allow_secret_paths": ["tests/fixtures/*"] (file patterns, relative to the project folder) for files where sample keys may be written (or committed) even though git would commit them, "log_months" for how many months of the activity log to keep (default 12).
• Report and log check: cloakroom report, see Extra protections.

Exceptions, how the model runs (backends), automated builds (CI) and troubleshooting: the handbook.

FAQ

Does it send my data anywhere? No. It downloads the detection model once from Hugging Face (a fixed version); the OCR models come inside the package. Everything else runs on your own machine (127.0.0.1).

How much slower is Claude? Each action is checked by a small program running in the background on your machine: about 20 to 70 ms (thousandths of a second) on Apple Silicon, where the model runs on the built-in graphics chip (an M5 Max to an 8 GB M1 Air), 60 ms on an Apple M-series processor alone, about 300 ms on a small 2-core cloud server. Without an Apple Silicon or NVIDIA graphics chip, a fast processor-only version of the model is built on first start. The first run downloads the model once (about 1 GB). cloakroom doctor prints your numbers.

Will it mask things it shouldn't? Sometimes, see above. Documented examples (Stripe test cards, example.com, fictional 555 numbers), plain dates and job titles are left alone. Mark a false alarm on the dashboard and it suggests a rule, or add exceptions to allow in ~/.cloakroom/config.json. cloakroom check FILE previews masks.

What doesn't it protect? It stops accidental leaks, like a key in a file Claude happened to open. It isn't a sandbox (a sealed-off space the AI can't get out of). Out of scope: a prompt injection (hidden text in a file that steers Claude) set on smuggling data out piece by piece, what you type into a prompt (a prompt with a key or personal data is stopped before it's sent but can't be rewritten, and names alone go through), and Claude Code's own local logs. Keys are kept out of files git would commit when Claude writes them with Write or Edit, but a file a shell command writes some other way (a script, cp, sed -i) is not checked yet, so a commit made from it can still carry a key. Details: docs-LIMITS.md.

What about PDFs, scans and photos? Cloakroom pulls the text out on your machine and masks it like any file; Claude gets the text, never the PDF or the picture. Scanned pages and photos (png, jpg) are read by OCR (reading text from an image), running on your processor with its models inside the package: no download, no cloud, no account. Screenshots and images returned by MCP tools (a browser or desktop tool, say) get the same treatment: the picture is read by local OCR and Claude gets the masked text in its place. The trade-off: Claude reads the text, it doesn't see the picture (layout, colours, charts and anything that isn't text are lost), and OCR can miss or misread small or faint text. Without OCR (no cloakroom[ocr], or an Intel Mac) such an image is held back, and Claude is told why. A scan it can't read in time, encrypted PDFs, figures in a notebook and other pictures are held back, and Claude is told so; to show Claude a picture anyway, attach it to your own prompt. Page and time limits: known limits.

How do I remove it? See Uninstall.

More

• Write-up: why I built it and how masking, reading pictures, putting values back and the dashboard fit together
• How it works: how values are found, what's left alone on purpose, where real values are kept and how they're put back
• Changelog · Setup details · Known limits · Benchmark
• Found a way around it? Please report it privately: SECURITY.md

Author

Made by Shanjeev Rajendran · GitHub · LinkedIn

Credits

Detection model: PII-Tracer. The one-string hook command that runs in both bash and PowerShell comes from maisecrets (Apache-2.0). Licensed Apache-2.0.