@nicknisi/pi-cloak

Redacts secrets and other sensitive content from read tool results before they enter model context. Rules are defined per-file-glob in a JSON config; when the agent reads a matching file, matched text is replaced with a masked string (e.g. S********) so credentials, tokens, and private values never reach the model while the agent can still see file structure and read around the masked regions.

What it adds

• Command: /cloak-status — reloads the config and notifies with current status: pi-cloak enabled=<bool> patterns=<n> config=<path>, or the load error if the config is missing/invalid.
• Event hooks:
  • session_start — reloads config; notifies a warning if the config file is missing or failed to parse (UI sessions only).
  • tool_result — intercepts results from the read tool only; rewrites text content parts in place when a rule matches the read path. Other tools and non-text content parts pass through untouched. Returns undefined (no modification) when disabled, when no rule matches, or when nothing changed.
• Config file: <agentDir>/cloak.json (see below).
• Exports (for other extensions/tests): loadState(configPath?) and cloakText(rawText, rawPath, cwd, state) are exported from index.ts.

No tools, keybindings, widgets, or custom entry types.

Install

pi install /Users/nicknisi/Developer/pi-extensions/packages/cloak

Configuration

Config is read from DEFAULT_CONFIG_PATH = join(getAgentDir(), "cloak.json") — i.e. ~/.pi/agent/cloak.json with a default pi setup. It is loaded at extension init and reloaded on session_start and /cloak-status. There is no live file watcher; edits take effect on the next session start or /cloak-status.

If the file is missing or invalid, the extension degrades to a disabled default config (no rules) and surfaces a warning notification on session start.

Top-level options

Key	Type	Default	Description
enabled	boolean	true	Master switch. When false, cloakText and the tool_result hook return input unchanged.
cloakCharacter	string	"*"	Fill character(s) used for the masked portion of a replacement. Repeated/sliced to length.
cloakLength	number | null	null	Fixed length for every masked replacement. When null, length is max(match.length, visiblePrefix.length) so masks preserve original length.
tryAllPatterns	boolean	true	When true, every pattern in a rule is applied to each line. When false, processing stops at the first pattern in the rule that produced a change.
patterns	CloakRuleConfig[]	[]	List of rules (see below).

Rule shape

{
  "filePattern": "**/.env*",
  "cloakPattern": "^([A-Z0-9_]+)=(.+)$",
  "replace": "$1="
}

Key	Type	Required	Description
filePattern	string | string[]	yes	Glob(s) matched against the read path. Supports * (within a segment), ** (across segments, **/ also matches zero directories), and ?. Matching is attempted against the raw path, the cwd-resolved absolute path, and each path's basename, so both **/.env* and .env work. A leading @ on the read path is stripped; ~ is expanded; backslashes are normalized to /.
cloakPattern	string | object | array	yes	Regex source string(s) applied line-by-line. Object form: { "pattern": string, "replace"?: string, "flags"?: string }. The g flag is always added.
replace	string	no	Rule-level default replacement template; a per-pattern replace overrides it.

Replacement semantics

Each match becomes visiblePrefix + mask:

• With a replace template, the visible prefix is the rendered template. Supported substitutions: $& (whole match), $1–$99 (capture groups), $$ (literal $). Unknown $x sequences are passed through literally.
• Without replace, the visible prefix is the first character of the match (e.g. hunter2 → h*******).
• The remainder is padded with cloakCharacter up to cloakLength, or to max(match.length, visible.length) when cloakLength is null. If the visible prefix is already longer than the target length, it is truncated and no mask is added.
• Line endings are preserved (\r\n stays \r\n). If no line changed, the original text object is returned unmodified.

Full example (~/.pi/agent/cloak.json)

{
  "enabled": true,
  "cloakCharacter": "*",
  "cloakLength": null,
  "tryAllPatterns": true,
  "patterns": [
    {
      "filePattern": ["**/.env", "**/.env.*"],
      "cloakPattern": {
        "pattern": "^([A-Z0-9_]+)=(.+)$",
        "replace": "$1="
      }
    },
    {
      "filePattern": "**/*.pem",
      "cloakPattern": ".+"
    },
    {
      "filePattern": "**/credentials.json",
      "cloakPattern": [
        { "pattern": "\"(private_key|client_secret)\":\\s*\"([^\"]+)\"", "replace": "\"$1\": \"" },
        { "pattern": "-----BEGIN [A-Z ]+-----.*-----END [A-Z ]+-----", "flags": "s" }
      ],
      "replace": ""
    }
  ]
}

Effect: in .env files API_KEY=sk-abc123 becomes API_KEY=*********; in .pem files every non-empty line becomes x********...; in credentials.json named fields keep their key and quote prefix with the value masked.

Usage

/cloak-status

Typical workflow: add rules to ~/.pi/agent/cloak.json, run /cloak-status in a session to reload and verify the pattern count, then any read of a matching file is masked before the model sees it.

Dependencies

• @earendil-works/pi-coding-agent (peer, *) — ExtensionAPI type and getAgentDir(); relies on the extension event API (pi.on, pi.registerCommand) and the tool_result event contract (event.toolName, event.input.path, mutable content parts).
• Node built-ins only otherwise: node:fs, node:os, node:path. No npm runtime dependencies, no workspace deps.

Caveats

• Only the read tool is cloaked. Content reaching the model via bash (cat, grep), edit diffs, or any other tool is not masked. Rules that depend on secrecy should assume shell access can bypass the cloak.
• Depends on the tool_result event returning { content } to mutate results, and on event.input.path being a string — both are pi internals that could change across versions.
• Regexes are compiled with new RegExp(spec) directly from config; an invalid regex throws during compileRule inside loadState's try/catch, which surfaces as a "failed to load" warning and disables all rules (falls back to empty defaults).
• Cloaking is line-oriented: patterns are applied per line, so multi-line secrets can only be matched if the regex itself spans within a single line (the s/m flags do not join lines).
• Glob matching is a hand-rolled globToRegExp, not a full glob library — no character classes ([...]) or brace expansion.
• The masked output length can leak the original secret length when cloakLength is null (default). Set cloakLength to a fixed number to avoid this.
• Config is not hot-reloaded on file change; reload requires a new session or /cloak-status.
• Package name is @nicknisi/pi-cloak, private, single-file extension. (Directory renamed cloak; package name kept.)