The DeathByCaptcha C client is the official C11 library for DeathByCaptcha — the best captcha solving service for developers who need a reliable bypass captcha service in their automation pipelines. It provides a simple, well-documented interface for integrating CAPTCHA solving into any workflow — a particularly common need when used as a captcha solver for web scraping, where CAPTCHAs block access to the pages you need to extract data from. It supports both the HTTPS API (encrypted transport via libcurl — recommended when security is a priority) and the socket-based API (faster and lower latency, recommended for high-throughput production workloads).

Key features:

• 🧩 Send image, audio and modern token-based CAPTCHA types (reCAPTCHA v2/v3, Turnstile, GeeTest, etc.).
• 🔄 Unified client API across HTTPS and socket transports — switching is a single dbc_set_transport() call.
• 🔐 Built-in support for proxies, timeouts and advanced token parameters for modern CAPTCHA flows.
• 🏗️ Multiplatform CMake build system for Linux, macOS and Windows.

Quick start example (socket transport):

#include "deathbycaptcha.h"

dbc_client  client;
dbc_captcha captcha;

dbc_init(&client, "your_username", "your_password");

FILE *f = fopen("captcha.jpg", "rb");
if (dbc_decode_file(&client, &captcha, f, DBC_TIMEOUT) == 0)
    printf("Solved: %s\n", captcha.text);
fclose(f);

dbc_close(&client);

🚌 Transport options: Use DBC_TRANSPORT_HTTPS for encrypted communication via libcurl — credentials and data travel over TLS. Use DBC_TRANSPORT_SOCKET (the default) for lower latency and higher throughput — it is faster but communicates over a plain TCP connection to api.dbcapi.me on port 8123.

• Installation
• How to Use DBC API Clients
  • Common Clients' Interface
  • Available Methods
• Credentials & Configuration
  • Quick Setup
• CAPTCHA Types Quick Reference & Examples
  • Quick Start
  • Type Reference
  • Per-Type Code Snippets
• CAPTCHA Types Extended Reference
  • reCAPTCHA Image-Based API — Deprecated (Types 2 & 3)
  • reCAPTCHA Token API (v2 & v3)
  • reCAPTCHA v2 API FAQ
  • What is reCAPTCHA v3?
  • reCAPTCHA v3 API FAQ
  • Amazon WAF API (Type 16)
  • Cloudflare Turnstile API (Type 12)
• Tests and CI
• Project Layout
• Documentation
• Responsible Use
• Contributing
• Changelog / Releases
• License
• Badge Details

Build requirements and platform notes are in doc/BUILD.md.

# Clone the repository
git clone https://github.com/deathbycaptcha/deathbycaptcha-api-client-c11.git
cd deathbycaptcha-api-client-c11

# Development build (debug symbols, assertions enabled)
cmake --preset default
cmake --build --preset default

# Optimised release build
cmake --preset release
cmake --build --preset release

All clients must be initialised with your DeathByCaptcha credentials — either username and password, or an authtoken (available in the DBC user panel). Call dbc_set_transport() to switch between socket (default) and HTTPS transports.

#include "deathbycaptcha.h"

dbc_client client;

/* Username + password — socket transport (default, faster, lower latency) */
dbc_init(&client, username, password);

/* Username + password — HTTPS transport (encrypted TLS, recommended when security matters) */
dbc_init(&client, username, password);
dbc_set_transport(&client, DBC_TRANSPORT_HTTPS);

/* Authtoken only */
dbc_init_token(&client, authtoken);

/* Always release resources when done */
dbc_close(&client);

All clients share the same interface. Below is a summary of every available function.

All solve functions populate a dbc_captcha struct when successful:

/* Example usage after a successful solve */
dbc_captcha captcha;
if (dbc_decode_recaptcha_v2(&client, &captcha, sitekey, pageurl,
                             NULL, NULL, DBC_TOKEN_TIMEOUT) == 0) {
    printf("ID: %u  Token: %s\n", captcha.id, captcha.text);
    dbc_close_captcha(&captcha);
}

#include <stdio.h>
#include <stdlib.h>
#include "deathbycaptcha.h"

int main(void)
{
    dbc_client  client;
    dbc_captcha captcha;

    if (dbc_init(&client, "your_username", "your_password") != 0) {
        fprintf(stderr, "Failed to initialize client\n");
        return EXIT_FAILURE;
    }

    printf("Balance: %.2f US cents\n", dbc_get_balance(&client));

    FILE *f = fopen("captcha.jpg", "rb");
    if (f && dbc_decode_file(&client, &captcha, f, DBC_TIMEOUT) == 0) {
        printf("Solved CAPTCHA %u: %s\n", captcha.id, captcha.text);

        /* Report only if you are certain the solution is wrong: */
        /* dbc_report(&client, &captcha); */

        dbc_close_captcha(&captcha);
    } else {
        printf("Failed (timeout or error)\n");
    }
    if (f) fclose(f);

    dbc_close(&client);
    return EXIT_SUCCESS;
}

Credentials are compiled directly into example programs via #define constants, or passed to dbc_init() at runtime. For CI environments, set DBC_USERNAME and DBC_PASSWORD as repository secrets and pass them at build or test time.

# ① Build the library and CLI
cmake --preset default && cmake --build --preset default

# ② Edit an example with your credentials and compile it
#    (replace USERNAME / PASSWORD defines inside the .c file)
cd examples
gcc -o example.Normal_Captcha \
    example.Normal_Captcha.c \
    ../build/default/lib/libdeathbycaptcha.so \
    -I../src
./example.Normal_Captcha

# ③ Run the full test suite
cd ..
cmake --build --preset default --target test

# ④ Push to repo for GitHub Actions CI
git push

This section covers every supported CAPTCHA type, how to compile and run the corresponding example files, and ready-to-copy C code snippets. Start with the Quick Start below, then use the Type Reference to find the type you need.

1. 🔨 Build the library (see Installation)
2. 📂 Navigate to the examples/ directory and compile the example for the type you need:

cd examples

# Balance check
gcc -o get_balance get_balance.c ../build/default/lib/libdeathbycaptcha.so -I../src
./get_balance

# Standard image CAPTCHA (requires test.jpg in the examples/ directory)
gcc -o example.Normal_Captcha example.Normal_Captcha.c \
    ../build/default/lib/libdeathbycaptcha.so -I../src
./example.Normal_Captcha

⚠️ Always compile examples from the examples/ directory so relative paths (e.g. test.jpg) are resolved correctly.

Before compiling, add your DBC credentials inside the example file:

#define USERNAME  "your_username"
#define PASSWORD  "your_password"

The table below maps every supported type to its use case, a code snippet, and the corresponding example file in examples/.

Minimal usage snippet for each supported type. Use these as a starting point and refer to the full example files in examples/ for complete implementations.

Official description: Supported CAPTCHAs Full sample: example.Normal_Captcha.c

FILE *f = fopen("captcha.jpg", "rb");
dbc_decode_file(&client, &captcha, f, DBC_TIMEOUT);
fclose(f);

Official description: reCAPTCHA Token API (v2) Full sample: example.reCAPTCHA_v2.c

dbc_decode_recaptcha_v2(&client, &captcha,
    "sitekey",
    "https://target",
    "http://user:pass@127.0.0.1:1234", "HTTP",
    DBC_TOKEN_TIMEOUT);

Official description: reCAPTCHA v3 Full sample: example.reCAPTCHA_v3.c

dbc_decode_recaptcha_v3(&client, &captcha,
    "sitekey",
    "https://target",
    "verify", 0.3,
    "http://user:pass@127.0.0.1:1234", "HTTP",
    DBC_TOKEN_TIMEOUT);

Official description: reCAPTCHA v2 Enterprise Full sample: example.reCAPTCHA_v2_Enterprise.c

dbc_decode_recaptcha_enterprise(&client, &captcha,
    "sitekey",
    "https://target",
    "http://user:pass@127.0.0.1:1234", "HTTP",
    DBC_TOKEN_TIMEOUT);

Official description: GeeTest Full sample: example.Geetest_v3.c

const char *params =
    "{\"proxy\":\"http://user:pass@127.0.0.1:1234\","
    "\"proxytype\":\"HTTP\","
    "\"gt\":\"gt_value\","
    "\"challenge\":\"challenge_value\","
    "\"pageurl\":\"https://target\"}";
dbc_decode_token(&client, &captcha, 8, "geetest_params", params, DBC_TOKEN_TIMEOUT);

Official description: GeeTest Full sample: example.Geetest_v4.c

const char *params =
    "{\"proxy\":\"http://user:pass@127.0.0.1:1234\","
    "\"proxytype\":\"HTTP\","
    "\"captcha_id\":\"captcha_id\","
    "\"pageurl\":\"https://target\"}";
dbc_decode_token(&client, &captcha, 9, "geetest_params", params, DBC_TOKEN_TIMEOUT);

Official description: Text CAPTCHA Full sample: example.Textcaptcha.c

const char *params = "{\"textcaptcha\":\"What is two plus two?\"}";
dbc_decode_token(&client, &captcha, 11, "textcaptcha", params, DBC_TOKEN_TIMEOUT);

Official description: Cloudflare Turnstile Full sample: example.Turnstile.c

const char *params =
    "{\"proxy\":\"http://user:pass@127.0.0.1:1234\","
    "\"proxytype\":\"HTTP\","
    "\"sitekey\":\"sitekey\","
    "\"pageurl\":\"https://target\"}";
dbc_decode_token(&client, &captcha, 12, "turnstile_params", params, DBC_TOKEN_TIMEOUT);

Official description: Audio CAPTCHA Full sample: example.Audio.c

/* audio value must be prefixed with "base64:"; language is e.g. "en" */
const char *params =
    "{\"audio\":\"base64:<audio_base64>\","
    "\"language\":\"en\"}";
dbc_decode_token(&client, &captcha, 13, "audio", params, DBC_TOKEN_TIMEOUT);

Official description: Lemin Full sample: example.Lemin.c

const char *params =
    "{\"proxy\":\"http://user:pass@127.0.0.1:1234\","
    "\"proxytype\":\"HTTP\","
    "\"captchaid\":\"CROPPED_xxx\","
    "\"pageurl\":\"https://target\"}";
dbc_decode_token(&client, &captcha, 14, "lemin_params", params, DBC_TOKEN_TIMEOUT);

Official description: Capy Full sample: example.Capy.c

const char *params =
    "{\"proxy\":\"http://user:pass@127.0.0.1:1234\","
    "\"proxytype\":\"HTTP\","
    "\"captchakey\":\"PUZZLE_xxx\","
    "\"api_server\":\"https://api.capy.me/\","
    "\"pageurl\":\"https://target\"}";
dbc_decode_token(&client, &captcha, 15, "capy_params", params, DBC_TOKEN_TIMEOUT);

Official description: Amazon WAF Full sample: example.Amazon_Waf.c

const char *params =
    "{\"proxy\":\"http://user:pass@127.0.0.1:1234\","
    "\"proxytype\":\"HTTP\","
    "\"sitekey\":\"sitekey\","
    "\"pageurl\":\"https://target\","
    "\"iv\":\"iv_value\","
    "\"context\":\"context_value\"}";
dbc_decode_token(&client, &captcha, 16, "waf_params", params, DBC_TOKEN_TIMEOUT);

Official description: Siara Full sample: example.Siara.c

const char *params =
    "{\"proxy\":\"http://user:pass@127.0.0.1:1234\","
    "\"proxytype\":\"HTTP\","
    "\"slideurlid\":\"slide_master_url_id\","
    "\"pageurl\":\"https://target\","
    "\"useragent\":\"Mozilla/5.0\"}";
dbc_decode_token(&client, &captcha, 17, "siara_params", params, DBC_TOKEN_TIMEOUT);

Official description: MTCaptcha Full sample: example.Mtcaptcha.c

const char *params =
    "{\"proxy\":\"http://user:pass@127.0.0.1:1234\","
    "\"proxytype\":\"HTTP\","
    "\"sitekey\":\"MTPublic-xxx\","
    "\"pageurl\":\"https://target\"}";
dbc_decode_token(&client, &captcha, 18, "mtcaptcha_params", params, DBC_TOKEN_TIMEOUT);

Official description: Cutcaptcha Full sample: example.Cutcaptcha.c

const char *params =
    "{\"proxy\":\"http://user:pass@127.0.0.1:1234\","
    "\"proxytype\":\"HTTP\","
    "\"apikey\":\"api_key\","
    "\"miserykey\":\"misery_key\","
    "\"pageurl\":\"https://target\"}";
dbc_decode_token(&client, &captcha, 19, "cutcaptcha_params", params, DBC_TOKEN_TIMEOUT);

Official description: Friendly Captcha Full sample: example.Friendly.c

const char *params =
    "{\"proxy\":\"http://user:pass@127.0.0.1:1234\","
    "\"proxytype\":\"HTTP\","
    "\"sitekey\":\"FCMG...\","
    "\"pageurl\":\"https://target\"}";
dbc_decode_token(&client, &captcha, 20, "friendly_params", params, DBC_TOKEN_TIMEOUT);

Official description: DataDome Full sample: example.Datadome.c

const char *params =
    "{\"proxy\":\"http://user:pass@127.0.0.1:1234\","
    "\"proxytype\":\"HTTP\","
    "\"pageurl\":\"https://target\","
    "\"captcha_url\":\"https://target/captcha\"}";
dbc_decode_token(&client, &captcha, 21, "datadome_params", params, DBC_TOKEN_TIMEOUT);

Official description: Tencent Full sample: example.Tencent.c

const char *params =
    "{\"proxy\":\"http://user:pass@127.0.0.1:1234\","
    "\"proxytype\":\"HTTP\","
    "\"appid\":\"appid\","
    "\"pageurl\":\"https://target\"}";
dbc_decode_token(&client, &captcha, 23, "tencent_params", params, DBC_TOKEN_TIMEOUT);

Official description: ATB Full sample: example.Atb.c

const char *params =
    "{\"proxy\":\"http://user:pass@127.0.0.1:1234\","
    "\"proxytype\":\"HTTP\","
    "\"appid\":\"appid\","
    "\"apiserver\":\"https://cap.aisecurius.com\","
    "\"pageurl\":\"https://target\"}";
dbc_decode_token(&client, &captcha, 24, "atb_params", params, DBC_TOKEN_TIMEOUT);

Full API-level documentation for selected CAPTCHA types: parameter references, payload schemas, request/response formats, token lifespans, and integration notes.

⚠️ Deprecated. Types 2 (Coordinates) and 3 (Image Group) are legacy image-based reCAPTCHA challenge methods that are no longer used at captcha solving. Do not use them for new integrations — use the reCAPTCHA Token API (v2 & v3) instead.

The Token-based API solves reCAPTCHA challenges by returning a token you inject directly into the page form, rather than clicking images. Given a site URL and site key, DBC solves the challenge on its side and returns a token valid for one submission.

• Token Image API: Provided a site URL and site key, the API returns a token that you use to submit the form on the page with the reCAPTCHA challenge.

What's the Token Image API URL? To use the Token Image API you will have to send a HTTP POST Request to http://api.dbcapi.me/api/captcha What are the POST parameters for the Token image API?

• username: Your DBC account username
• password: Your DBC account password
• type=4: Type 4 specifies this is the reCAPTCHA v2 Token API
• token_params=json(payload): the data to access the recaptcha challenge json payload structure:

  • proxy: your proxy url and credentials (if any). Examples:

    • http://127.0.0.1:3128
    • http://user:password@127.0.0.1:3128

  • proxytype: your proxy connection protocol. For supported proxy types refer to Which proxy types are supported?. Example:

    • HTTP

  • googlekey: the google recaptcha site key of the website with the recaptcha. For more details about the site key refer to What is a recaptcha site key?. Example:

    • 6Le-wvkSAAAAAPBMRTvw0Q4Muexq9bi0DJwx_mJ-

  • pageurl: the url of the page with the recaptcha challenges. This url has to include the path in which the recaptcha is loaded. Example: if the recaptcha you want to solve is in http://test.com/path1, pageurl has to be http://test.com/path1 and not http://test.com.

  • data-s: This parameter is only required for solve the google search tokens, the ones visible, while google search trigger the robot protection. Use the data-s value inside the google search response html. For regulars tokens don't use this parameter.

The proxy parameter is optional, but we strongly recommend to use one to prevent token rejection by the provided page due to inconsistencies between the IP that solved the captcha (ours if no proxy is provided) and the IP that submitted the token for verification (yours). Note: If proxy is provided, proxytype is a required parameter. Full example of token_params:

{
  "proxy": "http://127.0.0.1:3128",
  "proxytype": "HTTP",
  "googlekey": "6Le-wvkSAAAAAPBMRTvw0Q4Muexq9bi0DJwx_mJ-",
  "pageurl": "http://test.com/path_with_recaptcha"
}

Example of token_params for google search captchas:

{
  "googlekey": "6Le-wvkSA...",
  "pageurl": "...",
  "data-s": "IUdfh4rh0sd..."
}

What's the response from the Token image API? The token image API response has the same structure as regular captchas' response. Refer to Polling for uploaded CAPTCHA status for details about the response. The token will come in the text field of dbc_captcha. It's valid for one use and has a 2 minute lifespan. It will be a string like the following:

"03AOPBWq_RPO2vLzyk0h8gH0cA2X4v3tpYCPZR6Y4yxKy1s3Eo7CHZRQntxrdsaD2H0e6S3547xi1FlqJB4rob46J0-wfZMj6YpyVa0WGCfpWzBWcLn7tO_EYsvEC_3kfLNINWa5LnKrnJTDXTOz-JuCKvEXx0EQqzb0OU4z2np4uyu79lc_NdvL0IRFc3Cslu6UFV04CIfqXJBWCE5MY0Ag918r14b43ZdpwHSaVVrUqzCQMCybcGq0yxLQf9eSexFiAWmcWLI5nVNA81meTXhQlyCn5bbbI2IMSEErDqceZjf1mX3M67BhIb4"

This API extends the reCAPTCHA v2 Token API with two additional parameters: action and minimal score (min_score). reCAPTCHA v3 returns a score from each user, that evaluate if user is a bot or human. Then the website uses the score value that could range from 0 to 1 to decide if will accept or not the requests. Lower scores near to 0 are identified as bot. The action parameter at reCAPTCHA v3 is an additional data used to separate different captcha validations like for example login, register, sales, etc.

What is action in reCAPTCHA v3? Is a new parameter that allows processing user actions on the website differently. To find this we need to inspect the javascript code of the website looking for call of grecaptcha.execute function. Example:

grecaptcha.execute('6Lc2fhwTAAAAAGatXTzFYfvlQMI2T7B6ji8UVV_f', {action: something})

Sometimes it's really hard to find it and we need to look through all javascript files. We may also try to find the value of action parameter inside ___grecaptcha_cfg configuration object. Also we can call grecaptcha.execute and inspect javascript code. The API will use "verify" default value it if we won't provide action in our request. What is min-score in reCAPTCHA v3 API? The minimal score needed for the captcha resolution. We recommend using the 0.3 min-score value, scores highers than 0.3 are hard to get. What are the POST parameters for the reCAPTCHA v3 API?

• username: Your DBC account username
• password: Your DBC account password
• type=5: Type 5 specifies this is reCAPTCHA v3 API
• token_params=json(payload): the data to access the recaptcha challenge json payload structure:

  • proxy: your proxy url and credentials (if any). Examples:

    • http://127.0.0.1:3128
    • http://user:password@127.0.0.1:3128

  • proxytype: your proxy connection protocol. For supported proxy types refer to Which proxy types are supported?. Example:

    • HTTP

  • googlekey: the google recaptcha site key of the website with the recaptcha. For more details about the site key refer to What is a recaptcha site key?. Example:

    • 6Le-wvkSAAAAAPBMRTvw0Q4Muexq9bi0DJwx_mJ-

  • pageurl: the url of the page with the recaptcha challenges. This url has to include the path in which the recaptcha is loaded. Example: if the recaptcha you want to solve is in http://test.com/path1, pageurl has to be http://test.com/path1 and not http://test.com.

  • action: The action name.

  • min_score: The minimal score, usually 0.3

The proxy parameter is optional, but we strongly recommend to use one to prevent rejection by the provided page due to inconsistencies between the IP that solved the captcha (ours if no proxy is provided) and the IP that submitted the solution for verification (yours). Note: If proxy is provided, proxytype is a required parameter. Full example of token_params:

{
  "proxy": "http://127.0.0.1:3128",
  "proxytype": "HTTP",
  "googlekey": "6Le-wvkSAAAAAPBMRTvw0Q4Muexq9bi0DJwx_mJ-",
  "pageurl": "http://test.com/path_with_recaptcha",
  "action": "example/action",
  "min_score": 0.3
}

What's the response from reCAPTCHA v3 API? The response has the same structure as regular captcha. Refer to Polling for uploaded CAPTCHA status for details about the response. The solution will come in the text field of dbc_captcha. It's valid for one use and has a 1 minute lifespan.

Amazon WAF Captcha (also referred to as AWS WAF Captcha) is part of the Intelligent Threat Mitigation system within Amazon AWS. It presents image-alignment challenges that DBC solves by returning a token you set as the aws-waf-token cookie on the target page.

• Official documentation: deathbycaptcha.com/api/amazonwaf
• C sample: examples/example.Amazon_Waf.c

API URL: Send a HTTP POST request to http://api.dbcapi.me/api/captcha

POST parameters:

• username: Your DBC account username
• password: Your DBC account password
• type=16: Type 16 specifies this is the Amazon WAF API
• waf_params=json(payload): The data needed to access the Amazon WAF challenge

waf_params payload fields:

The proxy parameter is optional but strongly recommended — using a proxy prevents token rejection caused by IP inconsistencies between the solving machine (DBC) and the submitting machine (yours). 📌 Note: If proxy is provided, proxytype is required.

Full example of waf_params:

{
  "proxy": "http://user:password@127.0.0.1:1234",
  "proxytype": "HTTP",
  "sitekey": "AQIDAHjcYu/GjX+QlghicBgQ/7bFaQZ+m5FKCMDnO+vTbNg96AHDh0IR5vgzHNceHYqZR+GO...",
  "pageurl": "https://efw47fpad9.execute-api.us-east-1.amazonaws.com/latest",
  "iv": "CgAFRjIw2vAAABSM",
  "context": "zPT0jOl1rQlUNaldX6LUpn4D6Tl9bJ8VUQ/NrWFxPii..."
}

Response: The API returns a token string valid for one use with a 1-minute lifespan. Once received, set it as the aws-waf-token cookie on the target page before submitting the form.

Cloudflare Turnstile is a CAPTCHA alternative that protects pages without requiring user interaction in most cases. DBC solves it by returning a token you inject into the target form or pass to the page's callback.

• Official documentation: deathbycaptcha.com/api/turnstile
• C sample: examples/example.Turnstile.c

API URL: Send a HTTP POST request to http://api.dbcapi.me/api/captcha

turnstile_params payload fields:

📌 Note: The proxy parameter is optional but strongly recommended to avoid rejection due to IP inconsistency between the solver and the submitter. If proxy is provided, proxytype becomes required.

Example turnstile_params (basic):

{
    "proxy": "http://user:password@127.0.0.1:1234",
    "proxytype": "HTTP",
    "sitekey": "0x4AAAAAAAGlwMzq_9z6S9Mh",
    "pageurl": "https://testsite.com/xxx-test"
}

Response: The API returns a token string valid for one use with a 2-minute lifespan. Submit it via the input[name="cf-turnstile-response"] field (or input[name="g-recaptcha-response"] when reCAPTCHA compatibility mode is enabled).

Workflow	Status
CI (unit + integration)
Tests Linux
Tests Windows
Tests macOS
CI 32-bit
Release CLI Binaries
Coverage

Coverage badge notes:

• Served via GitHub Pages as a shields.io endpoint JSON.
• No external service (Codecov, etc.) is used.
• No workflow commits back to master.

• src/: core library (deathbycaptcha.h, deathbycaptcha.c) and CLI (client.c).
• doc/: build guide, CLI guide, library guide, and dynamic loading examples.
• examples/: standalone .c programs — one per CAPTCHA type.
• tests/: unit and integration test harnesses.
• CMakeLists.txt, CMakePresets.json: multiplatform build system (Linux, macOS, Windows).

• Build guide
• CLI guide
• Library guide
• Examples guide
• Socket usage sample
• HTTPS usage sample
• Agent API metadata overview
• Socket API specification
• HTTP API specification

See Responsible Use Agreement.

Contributions should keep API behavior compatible with existing official clients and include tests for new functionality.

See CHANGELOG.md and the Releases page.

See LICENSE.

• CI indicates the main ci.yml workflow status on master. Runs build + unit + integration tests on Linux, macOS and Windows.
• Coverage reflects the latest coverage percentage published to GitHub Pages as a shields.io endpoint JSON. Updated on each push to master. No external service (Codecov, etc.) is used.
• Release CLI Binaries indicates packaging/release workflow status.
• OS-specific test badges in Tests and CI show per-platform validation coverage for Linux, Windows, and macOS.