registry / cowork-harness / 0.24.0

cowork-harness@0.24.0

Scriptable, CI-friendly harness for Claude Cowork's runtime contract for testing skills across scenarios — same agent, mounts, egress allowlist, permission protocol, and sandbox limitations.

AI Security Review

scanned 7d ago · by lpm-firewall-ai

No confirmed malicious attack surface is established. The package is an agent test harness with user-invoked sandbox, decider, sync, and staging features; the risky primitives are aligned with that purpose and are not lifecycle-triggered.

Static reason

One or more suspicious static signals were detected.; previous stored version diff introduced dangerous source

Trigger

User runs cowork-harness CLI commands such as run/chat/skill/sync with chosen options.

Impact

Runs local agent/sandbox workflows and may stage configured files under harness session directories; no unconsented install-time persistence or exfiltration found.

Mechanism

user-invoked agent harness orchestration

Rationale

Static inspection found a legitimate Claude Cowork skill-testing harness with shell/spawn/network-related capabilities gated behind explicit CLI use and no npm install-time mutation of foreign AI-agent control surfaces. Scanner hits map to package-aligned runtime features, vendored support files, or publish-time scripts rather than concrete malicious behavior.

Evidence

package.jsondist/runtime/hostloop.jsdist/decide/external-channel.jsdist/sync/cowork-sync.jsdist/runtime/stage.jsdist/secrets.jsdist/runtime/host-env.js.claude/skills/cowork-harness/SKILL.md

Decision evidence

public snapshot

AI called this Clean at 88.0% confidence as Benign with low false-positive risk.

Evidence for block

dist/runtime/hostloop.js spawns a native Claude agent and Docker sidecar for the hostloop fidelity tier.
dist/decide/external-channel.js intentionally supports operator-supplied --decider-cmd with shell:true.
dist/sync/cowork-sync.js has a user-invoked sync path that reads Claude Desktop files and runs npx @electron/asar.

Evidence against

package.json has no install/postinstall/preinstall hook; prepublishOnly and prepack are publish-time only.
Shipped .claude/skills/cowork-harness files are package content, not lifecycle-installed into a user/home agent surface.
dist/runtime/stage.js stages config and mcp.json into harness-owned session workspace paths, with containment checks.
dist/secrets.js scrubs known auth tokens and encoded variants from emitted artifacts/decider context.
dist/runtime/host-env.js passes only expected Claude/Anthropic auth env to the spawned agent.
Dangerous primitives are documented CLI/runtime harness features activated by user commands, not import-time behavior.

Behavioral surface

Source

ChildProcessCryptoEnvironmentVarsEvalFilesystemNetworkShell

Supply chain

HighEntropyStringsUrlStrings

ManifestNo manifest risk signals triggered.

scanned 78 file(s), 1.25 MB of source, external domains: api.anthropic.com, cloud-images.ubuntu.com, deb.nodesource.com, downloads.claude.ai, example.com, nodejs.org, raw.githubusercontent.com

Source & flagged code

7 flagged

dist/decide/external-channel.jsView file

Lines 1-24javascript

1import { warn, envPositiveNumber } from "../io.js";

2import { mkdirSync, readdirSync, existsSync, readFileSync, writeFileSync, renameSync, rmSync } from "node:fs";

3import { join } from "node:path";

4import readline from "node:readline";

5import { spawn } from "node:child_process";

6/** A sequential line reader over a stream that buffers across chunk boundaries (readline does this). */

High

Child Process

Package source references child process execution.

dist/decide/external-channel.jsView on unpkg · L4

7function lineReader(input) {

8 const rl = readline.createInterface({ input, crlfDelay: Infinity });

9 const queue = [];

10 const waiters = [];

11 let done = false;

12 rl.on("line", (l) => (waiters.length ? waiters.shift()(l) : queue.push(l)));

13 rl.on("close", () => {

14 done = true;

15 while (waiters.length)

16 waiters.shift()(null);

17 });

18 return {

19 next: () => new Promise((resolve) => {

20 if (queue.length)

21 return resolve(queue.shift());

22 if (done)

23 return resolve(null);

24 waiters.push(resolve);

Lines 194-234javascript

194 // remove the exit listener registered for this channel so repeated fileChannel() calls

195 // in one process don't accumulate listeners past the MaxListenersExceededWarning threshold.

196 process.removeListener("exit", exitHandler);

197 // That exit listener was the only writer of done.json — a long-lived embedder that close()s but

198 // keeps running must still release a `gates --follow` watcher. Write the marker here too (idempotent,

199 // and not matched by the cleanup globs below, so it survives).

200 writeDoneMarker(dir);

201 // Best-effort remove processed files on close (req/resp + .done markers + tmp).

dist/decide/decider.jsView file

Lines 967-1007javascript

967}

968function evalPredicate(expr, input) {

969 // (additive): expose the whole input object as `input` so predicates can reach keys that are not

970 // valid JS identifiers — `input["file-path"]`, `input["foo.bar"]`. We ALSO keep binding each input key as

971 // a bare parameter (`command.includes(...)`), the form used by shipped example scenarios and the docs —

972 // dropping it would silently false-deny those on first run. Only identifier-shaped keys can be bound as a

973 // bare parameter (a key like `file-path` is not a legal parameter name and would fail `new Function`

dist/sync/cowork-sync.jsView file

Lines 145-185javascript

145 return {

146 appVersion,

147 agentVersion,

148 allowDomains,

149 networkMode,

150 requireFullVmSandbox,

151 asarFingerprint: fingerprint,

152 gates,

153 spawnEnv,

154 unknownDeltas: unknown,

155 notes,

156 };

python/conftest.pyView file

•path = python/conftest.py kind = build_helper sizeBytes = 544 magicHex = [redacted]

Medium

Ships Build Helper

Package ships non-JavaScript build or shell helper files.

python/conftest.pyView on unpkg

.claude/skills/cowork-harness/scripts/_vendor/yaml/scanner.pyView file

•path = .claude/skills/cowork-harness/scripts/_vendor/yaml/scanner.py kind = payload_in_excluded_dir sizeBytes = 51279 magicHex = [redacted]

High

Payload In Excluded Dir

Package hides binary, compressed, or executable-looking payloads in test/fixture/hidden paths.

.claude/skills/cowork-harness/scripts/_vendor/yaml/scanner.pyView on unpkg

dist/runtime/hostloop.jsView file

•matchType = previous_version_dangerous_delta matchedPackage = cowork-harness@0.23.0 matchedIdentity = npm:Y293b3JrLWhhcm5lc3M:0.23.0 similarity = 0.867 summary = stored previous version shares package body but lacks this dangerous source file

Critical

Previous Version Dangerous Delta

This package version adds a dangerous source file absent from the previous stored version; route for source-aware review.

dist/runtime/hostloop.jsView on unpkg

Source & flagged code

7 flagged · loading source

dist/decide/external-channel.jsView file

4import readline from "node:readline"; L5: import { spawn } from "node:child_process"; L6: /** A sequential line reader over a stream that buffers across chunk boundaries (readline does this). */

High

Child Process

Package source references child process execution.

dist/decide/external-channel.jsView on unpkg · L4

214export function spawnChannel(cmd) { L215: // `shell: true` is INTENTIONAL, not an injection surface. `--decider-cmd` is OPERATOR-supplied — L216: // the same trust class as the harness process itself (whoever runs the harness wrote this string). Shell

High

Shell

Package source references shell execution.

dist/decide/external-channel.jsView on unpkg · L214

dist/decide/decider.jsView file

987try { L988: fn = new Function(...params, `"use strict"; return (${expr});`); L989: }

Low

Eval

Package source references a known benign dynamic code generation pattern.

dist/decide/decider.jsView on unpkg · L987

dist/sync/cowork-sync.jsView file

165try { L166: execFileSync("npx", ["--yes", "@electron/asar", "extract", ASAR, tmp], { stdio: "ignore" }); L167: const bundle = readIf(join(tmp, ".vite/build/index.js")) ?? "";

High

Runtime Package Install

Package source invokes a package manager install command at runtime.

dist/sync/cowork-sync.jsView on unpkg · L165

python/conftest.pyView file

•path = python/conftest.py kind = build_helper sizeBytes = 544 magicHex = [redacted]

Medium

Ships Build Helper

Package ships non-JavaScript build or shell helper files.

python/conftest.pyView on unpkg

.claude/skills/cowork-harness/scripts/_vendor/yaml/scanner.pyView file

•path = .claude/skills/cowork-harness/scripts/_vendor/yaml/scanner.py kind = payload_in_excluded_dir sizeBytes = 51279 magicHex = [redacted]

High

Payload In Excluded Dir

Package hides binary, compressed, or executable-looking payloads in test/fixture/hidden paths.

.claude/skills/cowork-harness/scripts/_vendor/yaml/scanner.pyView on unpkg

dist/runtime/hostloop.jsView file

Critical

Previous Version Dangerous Delta

This package version adds a dangerous source file absent from the previous stored version; route for source-aware review.

dist/runtime/hostloop.jsView on unpkg

Findings

1 Critical4 High4 Medium6 Low

CriticalPrevious Version Dangerous Deltadist/runtime/hostloop.js

HighChild Processdist/decide/external-channel.js

HighShelldist/decide/external-channel.js

HighRuntime Package Installdist/sync/cowork-sync.js

HighPayload In Excluded Dir.claude/skills/cowork-harness/scripts/_vendor/yaml/scanner.py

MediumNetwork

MediumEnvironment Vars

MediumShips Build Helperpython/conftest.py

MediumStructural Risk Force Deep Review

LowNon Install Lifecycle Scripts

LowScripts Present

LowEvaldist/decide/decider.js

LowFilesystem

LowHigh Entropy Strings

LowUrl Strings

Source & flagged code

7 flagged

dist/decide/external-channel.jsView file

Lines 1-24javascript

1import { warn, envPositiveNumber } from "../io.js";

2import { mkdirSync, readdirSync, existsSync, readFileSync, writeFileSync, renameSync, rmSync } from "node:fs";

3import { join } from "node:path";

4import readline from "node:readline";

5import { spawn } from "node:child_process";

6/** A sequential line reader over a stream that buffers across chunk boundaries (readline does this). */

High

Child Process

Package source references child process execution.

dist/decide/external-channel.jsView on unpkg · L4

7function lineReader(input) {

8 const rl = readline.createInterface({ input, crlfDelay: Infinity });

9 const queue = [];

10 const waiters = [];

11 let done = false;

12 rl.on("line", (l) => (waiters.length ? waiters.shift()(l) : queue.push(l)));

13 rl.on("close", () => {

14 done = true;

15 while (waiters.length)

16 waiters.shift()(null);

17 });

18 return {

19 next: () => new Promise((resolve) => {

20 if (queue.length)

21 return resolve(queue.shift());

22 if (done)

23 return resolve(null);

24 waiters.push(resolve);

Lines 194-234javascript

194 // remove the exit listener registered for this channel so repeated fileChannel() calls

195 // in one process don't accumulate listeners past the MaxListenersExceededWarning threshold.

196 process.removeListener("exit", exitHandler);

197 // That exit listener was the only writer of done.json — a long-lived embedder that close()s but

198 // keeps running must still release a `gates --follow` watcher. Write the marker here too (idempotent,

199 // and not matched by the cleanup globs below, so it survives).

200 writeDoneMarker(dir);

201 // Best-effort remove processed files on close (req/resp + .done markers + tmp).

dist/decide/decider.jsView file

Lines 967-1007javascript

967}

968function evalPredicate(expr, input) {

969 // (additive): expose the whole input object as `input` so predicates can reach keys that are not

970 // valid JS identifiers — `input["file-path"]`, `input["foo.bar"]`. We ALSO keep binding each input key as

971 // a bare parameter (`command.includes(...)`), the form used by shipped example scenarios and the docs —

972 // dropping it would silently false-deny those on first run. Only identifier-shaped keys can be bound as a

973 // bare parameter (a key like `file-path` is not a legal parameter name and would fail `new Function`

dist/sync/cowork-sync.jsView file

Lines 145-185javascript

145 return {

146 appVersion,

147 agentVersion,

148 allowDomains,

149 networkMode,

150 requireFullVmSandbox,

151 asarFingerprint: fingerprint,

152 gates,

153 spawnEnv,

154 unknownDeltas: unknown,

155 notes,

156 };

python/conftest.pyView file

•path = python/conftest.py kind = build_helper sizeBytes = 544 magicHex = [redacted]

Medium

Ships Build Helper

Package ships non-JavaScript build or shell helper files.

python/conftest.pyView on unpkg

.claude/skills/cowork-harness/scripts/_vendor/yaml/scanner.pyView file

•path = .claude/skills/cowork-harness/scripts/_vendor/yaml/scanner.py kind = payload_in_excluded_dir sizeBytes = 51279 magicHex = [redacted]

High

Payload In Excluded Dir

Package hides binary, compressed, or executable-looking payloads in test/fixture/hidden paths.

.claude/skills/cowork-harness/scripts/_vendor/yaml/scanner.pyView on unpkg

dist/runtime/hostloop.jsView file

Critical

Previous Version Dangerous Delta

This package version adds a dangerous source file absent from the previous stored version; route for source-aware review.

dist/runtime/hostloop.jsView on unpkg