mosh: Model-driven Open Security Harness

Find security vulnerabilities in your applications and resolve them, using AI to simulate the tasks a security researcher runs - test live applications, source code or provide both to create more effective hypothesis and tests.

Why do I need a harness?

Using LLMs to test the security of an application is a lot more than just pointing a model at it and letting it go. The application needs to be scoped, the tests need to be adapted to the application, the model needs tools to interact with the application under test and execution needs to be controlled, evidenced, and repeatable. mosh implements the harness that wraps around models to conduct deep security testing.

mosh simulates the core tasks a security researcher performs when testing an application:

• Discovery: map the application surface, routes, links, forms, JavaScript assets, third-party services, source code and observable technologies.
• Security planning: turn discovery evidence into scoped, testable security hypotheses that may combine live testing and source code review.
• Test execution: run ready tests through controlled Docker-backed tooling using explicit engagement settings.
• Reporting: write Markdown reports, structured event logs, and shared memory so findings are reviewable and reproducible.

When more advanced LLM models are released, you do not need to modify the harness, just configure mosh to use the new models instead so you can immediate benefit from new frontier model capabilities.

Installation

0. Install these prerequisites first:

• Python 3.11 -- 3.13
• uv (Python package manager)
• Docker

1. Clone the repository:

git clone https://github.com/llmora/mosh.git
cd mosh

2. Run setup:

./scripts/setup.sh

The setup script runs uv sync to install dependencies in a .venv virtual environment, then builds the Docker tool images.

3. Use uv run to execute the CLI without activating the environment:

uv run mosh engagement create --title "Example App"
uv run mosh engagement attach eng_a1b2c3d4 https://app.example.com
uv run mosh discover eng_a1b2c3d4

All command examples in this README use uv run mosh so they work without activating the virtual environment. If you prefer to activate the environment manually, run:

source .venv/bin/activate

After activation, you can omit uv run and use mosh ....

Configuration

Set an LLM API key before running the CLI. mosh reads configuration from exported environment variables and from an optional .env file in the directory where you run the CLI. Exported environment variables take precedence over values in .env, and .env is intended for local settings only.

For the default direct DeepSeek setup, open an account at deepseek.com and generate an API key:

export DEEPSEEK_API_KEY="your-deepseek-api-key"

Or route through OpenRouter, open an account at openrouter.ai and generate an API key:

export OPENROUTER_API_KEY="your-openrouter-api-key"

Instead of exporting values every time, you can create a local .env file:

DEEPSEEK_API_KEY=your-deepseek-api-key
OPENROUTER_API_KEY=your-openrouter-api-key
MOSH_MAX_DEPTH=5
MOSH_SECURITY_COMMAND_TIMEOUT=300
MOSH_REFINE_ENGAGEMENT_TEMPLATE_WITH_LLM=true

Do not commit .env; it is ignored by git.

Model Selection

By default, mosh uses DeepSeek models to balance quality and cost. To choose different models, create mosh.yaml in the directory where you run the CLI and configure the models you want to run:

models:
  discovery_live:
    crawler: deepseek/deepseek-v4-flash
    technology_mapper: deepseek/deepseek-v4-flash
    reporter: deepseek/deepseek-v4-flash

  discovery_source:
    intake: deepseek/deepseek-v4-flash
    mapper: deepseek/deepseek-v4-flash
    route_resolver: deepseek/deepseek-v4-flash
    dependency_config: deepseek/deepseek-v4-flash
    component_mapper: deepseek/deepseek-v4-flash
    gap_analyst: deepseek/deepseek-v4-flash
    reporter: deepseek/deepseek-v4-flash

  planning:
    planner: deepseek/deepseek-v4-flash
    evidence_linker: deepseek/deepseek-v4-flash
    reviewer: deepseek/deepseek-v4-pro
    reporter: deepseek/deepseek-v4-flash
    engagement_refiner: deepseek/deepseek-v4-flash

  testing:
    executor: deepseek/deepseek-v4-flash
    reviewer: deepseek/deepseek-v4-pro
    reporter: deepseek/deepseek-v4-flash

  reporting:
    writer: deepseek/deepseek-v4-flash
    reviewer: deepseek/deepseek-v4-pro

Only include the agents you want to override; omitted agents keep their defaults. For example:

models:
  discovery_live:
    crawler: openai/gpt-5.2-mini

  discovery_source:
    mapper: openai/gpt-5.2-mini

  planning:
    evidence_linker: openai/gpt-5.2-mini
    reviewer: openai/gpt-5.2

  testing:
    reviewer: openai/gpt-5.2

  reporting:
    reviewer: openai/gpt-5.2

Use OpenRouter model IDs such as openai/gpt-5.2 or anthropic/claude-sonnet-4.5. DeepSeek IDs such as deepseek/deepseek-v4-flash use DEEPSEEK_API_KEY directly when it is set; otherwise they route through OpenRouter and require OPENROUTER_API_KEY.

Running a security scan

1. Create an engagement and attach assets

An engagement is the top-level assessment container. Assets are the components that make up an assessment, such as live URLs, source trees, repository URLs, etc.

You do not need to provide all of these, e.g. mosh works with just a single asset - but providing more assets allows better security hypotheses to be created and tested, leading to more effective vulnerability identification.

$ uv run mosh engagement create --title "Example App"
Engagement created: eng_a1b2c3d4

$ uv run mosh engagement attach eng_a1b2c3d4 https://app.example.com
Attached: asset_live_1 (live_url)

$ uv run mosh engagement attach eng_a1b2c3d4 /path/to/repo
Attached: asset_source_1 (source_tree)

mosh infers the asset type from the locator. Use --type when a URL is ambiguous, for example when a GitHub URL should be treated as a live web target instead of a source repository.

2. Run discovery

Run discovery for every attached asset that does not already have discovery output:

uv run mosh discover eng_a1b2c3d4

You can optionally specify an asset to discover, instead of running discovery on all assets:

uv run mosh discover eng_a1b2c3d4 --asset asset_live_1

Discovery writes the result of the discovery of each asset in a markdown report:

report/<engagement-id>/assets/<asset-id>/discovery/report.md

3. Create a security test plan

After all the assets have been discovered, the planning phase performs the key task of understanding the application, its key business risks and then produces a list of testable hypothesis that, if confirmed, would confirm a major flaw in the application:

uv run mosh plan eng_a1b2c3d4

This writes the engagement security plan under:

report/<engagement-id>/plan/plan.md

5. Review The Engagement File

Planning also identifies any pre-requisites to test the hypothesis, such as credentials, test records, etc. Before running security testing, review and edit the engagement template:

report/<engagement-id>/engagement_template.yaml

This file is deliberately small. It is where you confirm:

• Authorization and active testing permissions
• Alternative staging or pre-production target mappings (useful if you do not want to run tests against production)
• Execution limits
• Credentials by role
• Safe test data
• ... and anything else you believe is interesting for the tests execution

You can also add other information that you may think will be useful to the testing, the model inspects and automatically uses anything you have provided to improve its testing (for instance if your preprod instance requires SASE credentials or headers, just drop them in the file).

The testing crew treats this file as execution configuration.

6. Run Security Testing

When the plan and engagement file are ready, run:

uv run mosh test eng_a1b2c3d4

Temporary targeted execution for testing the tester is available with a hypothesis ID from plan/plan.md:

uv run mosh test eng_a1b2c3d4 --hypothesis AUTH-001

Repeat --hypothesis or pass comma-separated IDs to run a small subset.

If an engagement later gains another input, attach the new asset, then re-run discovery, planning, and testing with the engagement ID. Existing evidence is reused, new mappings enrich the plan, and only ready hypotheses execute.

Security testing writes the output of the hypothesis verification to:

report/<engagement-id>/security-testing/executed_tests/<hypothesis>.md

Preflight and execution history are stored in the same engagement-scoped result tree:

report/<engagement-id>/security-testing/preflight.md
report/<engagement-id>/security-testing/executed_tests/
report/<engagement-id>/security-testing/executed_tests/history/

Security testing uses one executor per hypothesis. The executor can use live target tools, source inspection tools, source-local harnesses, or both, depending on the planned test steps and attached artifacts. For source-backed tests, it can read bounded source slices, search nonignored text files, write generated harnesses or fuzz scripts under /work, run local commands with explicit environment overrides, start a local process in the security tools container, issue localhost HTTP requests to it, and stop it after collecting evidence. The repository is mounted read-only at /source and /work is the only writable workspace.

Every security-testing run starts with a preflight. The preflight reads the security test plan and engagement file, then separates planned tests into:

• Executable tests: hypotheses with the required attached artifacts and engagement inputs available.
• Blocked tests: required information is missing or the engagement file does not allow the test yet.

Open preflight.md after the first run. It tells you which tests were ready, which were blocked, and what information is missing. After a successful test run, the CLI also prints any blocked tests that still prevent completion, with clear engagement template fields to update. Common blockers include missing authorization confirmation, active testing permission, role credentials, safe test data, or target mappings.

You can run security testing repeatedly to incrementally complete the test:

uv run mosh test eng_a1b2c3d4

If you fill in missing information in engagement_template.yaml and run the command again, previously blocked tests will become ready and be executed.

If executed tests discover new application surface area, mosh updates the discovery report and refreshes the security test plan. It does not immediately auto-run newly planned tests; run test again when you are ready to execute any newly ready tests.

This self-learning feedback loop ensures that all the information discovered during testing is used during the engagement to produce better results.

7. Create The Final Report

When security testing is complete, create the customer-facing engagement report:

uv run mosh report eng_a1b2c3d4

Final reporting writes:

report/<engagement-id>/final-report/report.md

The final report is different from the working documents used during testing. It incorporates the main discovery context, the executed test outcomes, the confirmed findings, severity, remediation guidance, and an appendix for tests that produced no finding, were inconclusive, failed, or were not confirmed by review.

The report is structured as a customer deliverable:

• Executive summary: security-executive prose covering application context, what was tested, overall security posture, headline risks, and finding counts by severity
• At a glance: short prose summary of the business/application context, confirmed findings, highest qualitative severity, no-finding tests, inconclusive tests, and a human-readable engagement timeline
• Remediation priorities: findings ordered by qualitative severity so fixes can be prioritized quickly
• Engagement overview: prose explanation of target, lifecycle dates from discovery through final reporting, scope, limitations, and testing approach
• Summary of findings: findings table sorted by severity and remediation priority, severity counts, and confirmed/inconclusive/failed/no-finding breakdown
• Key discovery areas: important routes, auth areas, APIs, forms, technologies, exposed surfaces, and limitations
• Detailed findings: confirmed findings only, with evidence, impact, technical remediation guidance, source-specific fix details or pseudo-code when available, retest guidance, and references when available
• Tests with no findings or inconclusive: concise appendix for hypotheses that were not confirmed
• Appendix: methodology, tools used, evidence index, and raw report references

Qualitative severity is taken from hypotheses results and put in the context of the business impact.

End-To-End Example

uv run mosh engagement create --title "Example App"
uv run mosh engagement attach eng_a1b2c3d4 https://app.example.com
uv run mosh engagement attach eng_a1b2c3d4 /path/to/repo
uv run mosh discover eng_a1b2c3d4
uv run mosh plan eng_a1b2c3d4

# Review and edit report/eng_a1b2c3d4/engagement_template.yaml.

uv run mosh test eng_a1b2c3d4

# If the CLI reports blocked tests, add the missing engagement details and run it again.
uv run mosh test eng_a1b2c3d4

uv run mosh report eng_a1b2c3d4

What you get

After a full run, you have:

• A discovery report describing observed application surface area
• A security test plan grounded in discovery evidence and business risks
• An editable engagement template for permissions, targets, credentials, limits, and safe test data
• Executed test reports, including resolution
• A final customer-facing report

Resolving vulnerabilities

Security testing reports are written to:

report/<engagement-id>/security-testing/executed_tests/

Each executed test report is designed to support remediation, not just detection. Use it to understand:

• what was tested
• which target and role were used
• what evidence was collected
• whether the issue was accepted, rejected, or needs more review
• what fix or mitigation is recommended
• what should be rerun after the application has been changed

A practical remediation loop looks like this:

1. Review the executed test report and confirm the finding against the recorded evidence.
2. Fix the vulnerable behavior in the application.
3. Redeploy the application to the target environment covered by the engagement file.
4. Run security testing again:

uv run mosh test eng_a1b2c3d4

mosh compares the current plan and execution metadata with previous reports. Tests that are already current and accepted are skipped, while tests that need fresh evidence can run again. This makes repeat testing useful after a fix: you keep the historical reports, but the current run shows whether the issue still reproduces.

If a fix changes the application surface, run discovery and planning again before retesting:

uv run mosh discover eng_a1b2c3d4 --refresh
uv run mosh plan eng_a1b2c3d4
uv run mosh test eng_a1b2c3d4

Keep the engagement file up to date as the application changes. New roles, test accounts, safe test data, or staging mappings can unblock additional tests and give mosh enough context to validate more of the application.

Implementation

Model-driven Open Security Harness keeps the runtime architecture simple by using crews of agents for each key engagement phase organised around this pattern:

orchestrator -> agent -> tools

The orchestrator coordinates the run. Agents own specialist work. Tools are invoked by agents. Tools run inside Docker containers rather than being installed on the host.

Current crews:

• Live discovery crew: crawls and summarizes live application surfaces, identifies business context and correlated assets for more effective planning.
• Planning crew: turns discovery evidence and business context into testable security hypotheses.
• Testing crew: checks ready hypotheses using the engagement file and security testing tools.

Contributing

mosh is easy to explain, practical, and intentionally focused. Good contributions make it more useful without making it harder to understand.

The SPEC.md file goes into the details of the implementation and includes the future roadmap of the project - if you are up for it we would love it if you contribute to the development of mosh.

Please follow these guidelines:

• Work in small, reviewable changes.
• Add or update tests for every behavior change.
• Keep SPEC.md in sync when product behavior, architecture, output format, or roadmap changes.
• Keep this README.md in sync when installation, configuration, commands, examples, or user-facing behavior changes. But keep it light, detailed descriptions belong in the spec file.
• Preserve the crew -> orchestrator -> agent -> tools architecture.
• Keep external security tools in Docker containers rather than requiring host installs.
• Avoid broad refactors unless they directly support the change being made.
• If you are using supporting code development agents please make sure they pay attention to the AGENTS.md file.

Before opening a pull request create tests that validate your change and ensure all tests pass:

uv run python -m unittest discover -v

Also run the relevant CLI flow against an application you are authorized to test when your change affects runtime behavior.

If you are working on docker tool image improvements, make sure you regularly rebuild the images:

./scripts/setup.sh --force-docker

License

mosh is licensed under the Apache License, Version 2.0. See LICENSE.

If you are working on docker tool image improvements, make sure you regularly rebuild the images:

./scripts/setup.sh --force-docker