Implement Antithesis workloads by turning the property catalog into SDK assertions and test commands, then refine coverage after triage.

Antithesis Workload Skill version: 2026 09 08 2e4a837 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 launch 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 Read whatever provenance frontmatter is present in the catalog and include it when presenting status. Use whatever fields you find — the schema may evolve over time, so don't treat partial or older frontmatter as broken. Describe what's there in plain language. Examples: Full schema: "working from the catalog at commit abc12345abcd (2026 05 05), SUT path /foo , external refs: A, B." Partial: "working from the catalog at commit abc12345abcd (2026 05 05) — no SUT path or external refs recorded." Absent: "working from the catalog (no provenance recorded; predates the convention)." Workload runs every property cycle, so don't ask the user to re confirm provenance every run — display it as context and continue. The user will speak up if it no longer matches the system they're working on. The user facing commit display uses the short hash (first 12 characters) for readability; the frontmatter still stores the full SHA. Recommend one property at a time — don't dump the full catalog. A catalog can easily have dozens or hundreds of properties; an exhaustive status list is overwhelming and rarely what the user needs. This is the default: pick one, explain why, and wait for confirmation. The exception is when the user explicitly asks to discuss what to work on rather than receive a single recommendation. In that case, give a high level summary (counts by status, notable clusters, anything unusual) and have the conversation. Surface specific properties only as the conversation calls for them. Strategy for picking the recommendation: Getting started — when few or no properties are implemented yet — recommend a simple property: one whose test doesn't have a lot of moving parts. The highest priority properties tend to require the most setup and coordination, which is the wrong place to start. Simple properties build momentum, exercise the SDK and test harness end to end, and let you and the user develop a feel for the workflow. Tell the user this is the strategy you're using and why. Once you're cooking — multiple properties implemented and the harness validated end to end — switch to priority based ordering: 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. Tell the user when you're making this switch. Explain why you picked the property you picked, and wait for the user to confirm or choose differently before proceeding. For the chosen property, read both the catalog entry and its evidence file. Other scoping questions Ask the user only for blockers or scoping decisions you cannot infer safely, such as: The property catalog location, if it is not the standard antithesis/scratchbook/property catalog.md The project language or SDK choice, if the repo does not make it obvious Triage findings or known gaps, if iterating on an existing workload 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/product/test templates/test composer reference.md SDK reference: https://antithesis.com/docs/reference/sdk.md Properties and assertions: https://antithesis.com/docs/concepts/properties assertions/assertions.md Fault injection: https://antithesis.com/docs/product/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/interesting values.md Choosing the value menu for the property under test references/iteration.md Improving coverage and assertions after triage Recommended Workflows Implement next property 1. Detect implementation status, then recommend one property and explain why (see "Detect implementation status" and "Present and recommend" above) 2. Get user confirmation on which property to implement 3. Read references/component implementation.md 4. Read references/assertions.md 5. Read references/test commands.md 6. Read references/interesting values.md 7. Identify the property's value menu — boundary values plus configured limit families. See interesting values.md for the discovery process and worked examples 8. Implement the chosen property: assertions, test commands, and supporting code 9. Write Sometimes assertions as reach claims for the behaviors the workload is designed to drive (see references/assertions.md , "Sometimes Assertions as Workload Reach Claims"). Assert the precondition, not the violation. Use antithesis launch to run a test, then antithesis triage to check which assertions fired — unfired ones are evidence the workload isn't reaching its targets and the starting point for iteration Post triage iteration 1. Read references/iteration.md 2. Read references/assertions.md if assertions need to change 3. Read references/test commands.md if command coverage needs to change 4. 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. Design workloads to be fault tolerant. Unlike happy path tests where errors signal bugs, workloads run under fault injection and concurrent activity — transient errors are expected, not exceptional. Make progress toward a goal rather than bail on the first failure. 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 property names are inline con

antithesis-workload