# Regex Lab (oci · ghcr.io/basitalisandhu/mcp-regex-lab)

Test regular expressions in a timeout-guarded worker, explain them, find catastrophic backtracking.

- Trust score: 48/100 (low)
- Change this week: +28
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-10-16

## Components

- oci · `ghcr.io/basitalisandhu/mcp-regex-lab`: 48/100 (this document), [markdown](https://verifymcp.io/servers/basitalisandhu-mcp-regex-lab/ghcr-io-basitalisandhu-mcp-regex-lab.md), [page](https://verifymcp.io/servers/basitalisandhu-mcp-regex-lab/ghcr-io-basitalisandhu-mcp-regex-lab)

## Channel facts

- Registry: `oci`
- Package: `ghcr.io/basitalisandhu/mcp-regex-lab`
- Version: `0.2.1`
- Transport: `stdio`

## Trust breakdown

How this component scores in each security and reliability category. Every signal is checked automatically from public evidence about the published package, including repeated runs of it in an isolated sandbox, and we only credit what we can confirm. Scores are 0–100 per category. Scoring method: https://verifymcp.io/docs/scoring (what has changed: https://verifymcp.io/docs/scoring/changelog)

Scored 2026-10-16.

- **Supply Chain Security**: 0/100
  - No malware scan is available for this kind of package: the supply-chain vendors we use do not cover it. This is a permanent gap in our coverage, not a finding about the package.
  - Known CVEs could not be checked: this artifact ships no SBOM or dependency manifest, so there is no dependency list to read.
  - Install-script risk not yet assessed.
  - Dependency health could not be checked: this artifact ships no SBOM or dependency manifest, so there is no dependency list to read.
- **Provenance & Transparency**: 100/100
  - Source repository is publicly reachable at the declared URL.
  - Cryptographically verified build provenance (signed, bound to basitalisandhu/dev-mcp-servers).
  - Clear OSI-approved license (MIT).
  - Actively maintained (last published 2 days ago).
  - Publishes a security disclosure policy (SECURITY.md).
- **Schema Quality & AI Usability**: 60/100
  - AI-judged instruction clarity (good).
  - Context-footprint check failed: tool/resource definitions use about 672 tokens (~224/item across 3 items; 3 tools + 0 resources), over budget; trim descriptions and params.
  - Usage-examples check failed: none of the tools include examples.
- **Stability & Change Management**: 0/100
  - Stability not yet verified: not enough scan history yet (needs a 30-day window).
- **Tool Coverage**: 91/100
  - 100% of tools have a non-trivial description (not blank, and not just the tool's name).
  - 73% of tool parameters carry a description.
- **Tool Safety**: 100/100
  - No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.
  - We read all 3 captured tool definition(s), and no name or description among them implies an irreversible operation.
  - An AI judge read all 4 captured unit(s) of tool text and found none that tries to manipulate the model reading it.
- **Capabilities**: 100/100
  - Implements a supported MCP spec version (2025-11-25); the latest is 2026-07-28.

**Unverified: 2 categories.** Categories scored 0 because we could not verify them: a data source with nothing on this package, evidence we could not reach, or a check we could not run. We only credit what we can confirm.

## Install

### How do I install the Regex Lab MCP server?

Regex Lab runs locally as a container image, launched with docker run --rm -i ghcr.io/basitalisandhu/mcp-regex-lab:0.2.1. Ready-made configuration for Claude, Cursor, VS Code, Codex and 3 more is on this page, copied from each client's own documentation.

### Claude

```bash
claude mcp add basitalisandhu-mcp-regex-lab -- docker run --rm -i ghcr.io/basitalisandhu/mcp-regex-lab:0.2.1
```

### Cursor

```json
{
  "mcpServers": {
    "basitalisandhu-mcp-regex-lab": {
      "command": "docker",
      "args": [
        "run",
        "--rm",
        "-i",
        "ghcr.io/basitalisandhu/mcp-regex-lab:0.2.1"
      ]
    }
  }
}
```

### VS Code

```json
{
  "servers": {
    "basitalisandhu-mcp-regex-lab": {
      "command": "docker",
      "args": [
        "run",
        "--rm",
        "-i",
        "ghcr.io/basitalisandhu/mcp-regex-lab:0.2.1"
      ]
    }
  }
}
```

### Codex

```bash
codex mcp add basitalisandhu-mcp-regex-lab -- docker run --rm -i ghcr.io/basitalisandhu/mcp-regex-lab:0.2.1
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "basitalisandhu-mcp-regex-lab": {
      "type": "local",
      "command": [
        "docker",
        "run",
        "--rm",
        "-i",
        "ghcr.io/basitalisandhu/mcp-regex-lab:0.2.1"
      ],
      "enabled": true
    }
  }
}
```

### Hermes

```yaml
mcp_servers:
  basitalisandhu-mcp-regex-lab:
    command: "docker"
    args: ["run", "--rm", "-i", "ghcr.io/basitalisandhu/mcp-regex-lab:0.2.1"]
```

### Netclaw

```json
{
  "McpServers": {
    "basitalisandhu-mcp-regex-lab": {
      "Transport": "stdio",
      "Command": "docker",
      "Arguments": [
        "run",
        "--rm",
        "-i",
        "ghcr.io/basitalisandhu/mcp-regex-lab:0.2.1"
      ]
    }
  }
}
```

### Other

```json
{
  "mcpServers": {
    "basitalisandhu-mcp-regex-lab": {
      "command": "docker",
      "args": [
        "run",
        "--rm",
        "-i",
        "ghcr.io/basitalisandhu/mcp-regex-lab:0.2.1"
      ]
    }
  }
}
```

## Changelog

Every change recorded for this component, newest first. Days that predate change tracking, or that we cannot explain, say so: "we were watching and nothing happened" and "we were not watching" are different claims.

### 2026-10-14 (score 48, +28)

- [security improvement] Injection markers: unverified → pass
- [security] First check of Judged manipulation: pass
- [security] Stability: Stability not yet verified: not enough scan history yet (needs a 30-day window).
- [functional improvement] Tool coverage: unverified → 100
- [functional improvement] MCP protocol: unverified → pass
- [functional] First check of Schema quality: fail
- [functional] First check of Destructive annotations: pass
- [functional] First check of Schema quality: fail
- [functional] First check of Schema quality: good
- [functional] First check of Tool coverage: 73

### 2026-10-13 (score 20, 0)

- [functional] Package version: 0.2.0 → 0.2.1

### 2026-10-12 (score 20, 0)

- [functional] Package version: 0.1.1 → 0.2.0

### 2026-10-07 (score 20)

First indexed and scored.

## MCP tools (3)

### `test_regex` (~201 tokens)

Test a regex against samples

Run a pattern against up to 50 sample strings (each up to 20000 characters) and return every match with its start and end offsets, matched text, numbered and named capture groups with their offsets, and optionally the result of String.prototype.replace with the given replacement. Execution runs in a worker thread and is stopped after timeout_ms (default 2000, max 10000); results for samples finished before the timeout are still returned. At most 200 matches per sample are listed.

Input parameters:

- `flags` (string): RegExp flags such as i, m, s, u. g and d are added automatically when matching.
- `pattern` (string, required): JavaScript regular expression source, without the surrounding slashes.
- `replacement` (string): If given, each sample is also shown after replace(pattern, replacement); $1 and $<name> work as in JavaScript.
- `samples` (array, required)
- `timeout_ms` (integer)

### `explain_regex` (~125 tokens)

Explain a regex

Parse a pattern and describe it construct by construct: literals, character classes, escapes, anchors, groups (capturing, named, non-capturing, lookaround), quantifiers (greedy and lazy) and alternation, as indented lines plus the number of capturing groups. Reports a syntax error with its position when the pattern does not parse.

Input parameters:

- `flags` (string): RegExp flags such as i, m, s, u. g and d are added automatically when matching.
- `pattern` (string, required): JavaScript regular expression source, without the surrounding slashes.

### `check_redos` (~247 tokens)

Check a regex for catastrophic backtracking

Statically look for the constructs that cause exponential or polynomial backtracking: an unbounded repeat nested inside another (such as (a+)+ or (\d+\s?)*), alternatives that can match the same text inside a repeated group (such as (a|ab)*), and consecutive repeats that accept the same characters (such as \d+\d+). Each finding names the construct, a severity (high: likely exponential; medium: polynomial or needs review) and a character that exercises it. With probe (default true), the pattern is then timed in a worker against crafted non-matching inputs of growing length (from the probe character) and the timings are returned; the worker is terminated after timeout_ms (default 2000). No findings and flat timings is good evidence, not a proof, that the pattern is safe.

Input parameters:

- `flags` (string): RegExp flags such as i, m, s, u. g and d are added automatically when matching.
- `pattern` (string, required): JavaScript regular expression source, without the surrounding slashes.
- `probe` (boolean): Time the pattern against crafted inputs. Default true.
- `timeout_ms` (integer)

## Diagnostics

Captured diagnostic sections: Provenance. The full working is on the page: https://verifymcp.io/servers/basitalisandhu-mcp-regex-lab/ghcr-io-basitalisandhu-mcp-regex-lab#diagnostics

## Score history

- 2026-10-16: 48
- 2026-10-15: 48
- 2026-10-14: 48
- 2026-10-13: 20
- 2026-10-12: 20
- 2026-10-07: 20

## Common questions

### What is the Regex Lab MCP server?

Regex Lab is an MCP server listed in the public MCP registry as io.github.basitalisandhu/mcp-regex-lab. Test regular expressions in a timeout-guarded worker, explain them, find catastrophic backtracking. This page covers its container image (ghcr.io/basitalisandhu/mcp-regex-lab).

### Is the Regex Lab MCP server safe to use?

Regex Lab scores 48 out of 100 on VerifyMCP. Its build provenance is signed and verified. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.

### What tools does the Regex Lab MCP server expose?

Regex Lab exposes 3 tools: test_regex, explain_regex, check_redos. Their descriptions and schemas cost roughly 573 tokens of context every time the server is loaded.

### Is the Regex Lab MCP server still maintained?

Regex Lab is still listed as active in the MCP registry. We last reached this channel on 16 October 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.

### What licence is the Regex Lab MCP server under?

Regex Lab declares the MIT licence, which is OSI-approved. That covers the source only, and says nothing about the cost of any service it calls.

## Links

- GitHub Container Registry: https://ghcr.io/basitalisandhu/mcp-regex-lab
- Repository: https://github.com/basitalisandhu/dev-mcp-servers
- Website: https://basitalisandhu.github.io/dev-mcp-servers/
- Changelog RSS feed: https://verifymcp.io/servers/basitalisandhu-mcp-regex-lab/ghcr-io-basitalisandhu-mcp-regex-lab.xml
- Changelog JSON feed: https://verifymcp.io/servers/basitalisandhu-mcp-regex-lab/ghcr-io-basitalisandhu-mcp-regex-lab.json
- HTML version of this page: https://verifymcp.io/servers/basitalisandhu-mcp-regex-lab/ghcr-io-basitalisandhu-mcp-regex-lab