name: antithesis-workload description: > Implement Antithesis workloads by turning the property catalog into SDK assertions and test commands, then refine coverage after triage. compatibility: Requires snouty (https://github.com/antithesishq/snouty). metadata: version: "2026-04-29 1cd5f5a"

Antithesis Workload

Purpose and Goal

Implement or improve the Antithesis workload. Success means:

Properties from the antithesis-research skill are mapped to concrete assertions, using both the property catalog and per-property evidence files
Test commands exist under antithesis/test/ and exercise the right behaviors
The first real test templates are created after setup, or existing ones are expanded
Triage findings turn into workload or property updates instead of staying implicit

Use the antithesis-research skill first to build the property catalog. Use the antithesis-setup skill to scaffold the infrastructure. Use the antithesis-triage skill to review runs, then return here to improve the workload. If the user asks to submit or launch a run, use the antithesis-launch skill — do not run snouty run directly.

Prerequisites

DO NOT PROCEED if the Antithesis scratchbook (usually at antithesis/scratchbook/) doesn't exist. Use the antithesis-research skill to create it.
DO NOT PROCEED if there is no docker-compose.yaml for Antithesis present. Use the antithesis-setup skill to create it.
DO NOT PROCEED if snouty is not installed. See https://raw.githubusercontent.com/antithesishq/snouty/refs/heads/main/README.md for installation options.

Scoping

Each invocation of the "Implement next property" workflow below focuses on one property to keep context manageable and quality high. (Post-triage iteration follows its own scoping based on triage findings.)

If the user asks for multiple properties, recommend doing one at a time — explain that implementation quality degrades as context accumulates, and each property's effort is unpredictable. Ask which one they'd like to start with. If they insist on multiple, proceed — but warn them first.

If the user specifies which property to work on, skip the full catalog scan — but still assess that property's status against its evidence file before proceeding. If it's already fully implemented, tell the user rather than redoing work.

If the user does not specify a property, run the full detection and recommendation flow below.

Detect implementation status

The detection work below is context-heavy (reading every evidence file, scanning the codebase for assertions). If your agent supports sub-agents, delegate it to a sub-agent that returns a per-property summary (status + brief rationale). This keeps the main implementation agent's context clean.

The detection task: for each property in the catalog, search the existing test and SUT code for Antithesis SDK assertion calls and cross-reference them with the property's evidence file at antithesis/scratchbook/properties/{slug}.md. Assess whether the existing assertions cover the code paths, failure scenarios, and instrumentation points the evidence file describes. Classify each property as:

Implemented — assertions cover what the evidence file describes
Partially implemented — some assertions exist but coverage is incomplete
Not implemented — no related assertions found

Present and recommend

Note the catalog's provenance frontmatter (commit and updated fields) and include it when presenting status — e.g., "The property catalog is up-to-date as of <commit short hash> (<date>)." This lets the user judge whether the catalog reflects the current codebase or needs re-research.

Show the user the status of each property, then recommend one to implement next. Prefer partially-implemented properties that need completion, then unimplemented properties that cluster with recently implemented ones (see antithesis/scratchbook/property-relationships.md), then other high-priority unimplemented properties. Wait for the user to confirm or choose differently before proceeding.

For the chosen property, read both the catalog entry and its evidence file.

Definitions and Concepts

SUT: System under test.
Test template: A directory of test commands at /opt/antithesis/test/v1/{name}/. Each timeline runs commands from one test template. Files or subdirectories prefixed with helper_ are ignored by Antithesis, so use that prefix for helper scripts kept alongside commands.
Test command: An executable in a test template with a valid prefix: parallel_driver_, singleton_driver_, serial_driver_, first_, eventually_, finally_, anytime_.
Timeline: One linear execution of the SUT and workload. Antithesis runs many timelines in parallel and branches them to search for interesting behaviors.
Always / AlwaysOrUnreachable: Assertions for safety and correctness properties.
Sometimes(cond): Assertions for liveness or non-trivial semantic states that should occur at least once.
Reachable / Unreachable: Assertions about whether meaningful outcomes or forbidden paths are exercised.

Documentation Grounding

Use the antithesis-documentation skill to access these pages. Prefer snouty docs.

Test commands reference: https://antithesis.com/docs/test_templates/test_composer_reference.md
SDK reference: https://antithesis.com/docs/using_antithesis/sdk.md
Properties and assertions: https://antithesis.com/docs/properties_assertions/assertions.md
Fault injection: https://antithesis.com/docs/environment/fault_injection.md

Reference Files

Reference	When to read
`references/component-implementation.md`	Implementing workload-side components or wrappers
`references/assertions.md`	Turning properties into SDK assertions
`references/test-commands.md`	Writing commands and organizing test templates
`references/iteration.md`	Improving coverage and assertions after triage

Recommended Workflows

Implement next property

Detect implementation status and present to user (see Scoping above)
Get user confirmation on which property to implement
Read references/component-implementation.md
Read references/assertions.md
Read references/test-commands.md
Implement the chosen property: assertions, test commands, and supporting code

Post-triage iteration

Read references/iteration.md
Read references/assertions.md if assertions need to change
Read references/test-commands.md if command coverage needs to change
Update the workload and the relevant Antithesis scratchbook artifacts together

General Guidance

Keep Antithesis-only code out of production paths. If you must touch shared code, make the change surgical and easy to wall off.
Prefer simple workload code over highly configurable abstractions.
Assume antithesis-setup has already made the system runnable in a mostly idle state; this skill owns what the workload does once the system is up.
Assume antithesis-setup has already installed the relevant SDK and added one minimal bootstrap assertion in the SUT. This skill owns the broader property catalog beyond that initial integration check.
Write test commands in the project's language, not Bash, so they can reuse the project's clients, helpers, and libraries.

Output

Assertions for every property in scope, in workload code or carefully chosen SUT locations
Test commands and supporting workload code under antithesis/test/
Updates to antithesis/scratchbook/property-catalog.md when the implemented properties change

Self-Review

Before declaring this skill complete, review your work against the criteria below. If your agent supports spawning sub-agents, create a new agent with fresh context to perform this review — give it the path to this skill file and have it read all output artifacts. A fresh-context reviewer catches blind spots that in-context review misses. If your agent does not support sub-agents, perform the review yourself: re-read the success criteria at the top of this file, then systematically check each item below against your actual output.

Review criteria:

For every property in scope, the implementation covers the code paths, failure scenarios, and instrumentation points described in its evidence file — not just "an assertion exists" but "the assertions cover what the evidence says needs to be covered"
Each assertion uses the correct SDK assertion type for its property's semantics (Always/AlwaysOrUnreachable for safety, Sometimes(cond) for liveness or meaningful semantic state, Reachable/Unreachable for path and outcome checks)
Sometimes(true, ...) assertions should be rewritten as Reachable(...).
Assertion messages are unique across the touched code; no broad property is implemented by reusing one message at multiple unrelated callsites
Workload-only instrumentation was not used where surgical SUT-side assertions would provide materially better search guidance for rare, dangerous, or timing-sensitive internal states
Reachable(...) markers are attached to distinct outcomes or branch results, not redundant early path-entry locations on the same straight-line flow
Test commands exist under antithesis/test/ and use valid prefixes (parallel_driver_, singleton_driver_, serial_driver_, first_, eventually_, finally_, anytime_)
Test commands are written in the project's language, not Bash, and reuse the project's clients and libraries where possible
No test command is responsible for Antithesis lifecycle signaling; setup_complete is emitted before test commands begin
Test templates are structured correctly at the path that will map to /opt/antithesis/test/v1/{name}/ in the container
Helper files or directories are prefixed with helper_ so Antithesis ignores them
antithesis/scratchbook/property-catalog.md is updated to reflect the implementation status of every property in scope, with provenance frontmatter (commit and updated) reflecting the current codebase state
Assertions are in workload code or surgical SUT locations — not scattered across production paths
Use snouty validate on antithesis/config to ensure that the compose setup can reach setup complete and any configured test-templates work. Make sure to build the latest images before running validate.