debug-task

moon task debugger

A workflow-oriented diagnostic skill for troubleshooting moon tasks. This is not a reference manual — it guides you through a structured debugging flow so you can isolate the problem quickly.

For conceptual background, see the moon documentation.

Before you start: Ask the user for the <project>:<task> target to debug. If they haven't provided a specific target, prompt them for it — the diagnostic flow requires a concrete target to inspect.

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Quick-start: 5-step diagnostic flow

Work through these steps in order. Most issues resolve by step 3.

Step 1: Inspect the resolved task configuration

The first thing to check is whether the task is configured the way the user expects. moon merges configuration from multiple sources (global tasks, project config, inheritance), so the resolved result can surprise people.

# Show the fully resolved task config (with inheritance applied)
moon task <project>:<task>

# Machine-readable version for programmatic inspection
moon task <project>:<task> --json

What to verify:

• command vs script — if the command contains pipes (|), redirects (>), chained commands (&&), or complex syntax, it must use script, not command.
• inputs — are they too broad (**/* captures everything) or too narrow (missing source files)? Check state.defaultInputs (true = using default **/*) and state.emptyInputs (true = explicitly set to []). Both keys are omitted from the JSON entirely when false, as is state.setRunInCi.
• outputs — are they declared for build tasks? Missing outputs means the cache can never hydrate artifacts. In v2.3+, outputs also affect the default cacheStrategy of any task that depends on this one (see Step 4).
• toolchains — is the correct toolchain(s) assigned? An incorrect toolchain means wrong tool versions.
• deps — are task dependencies correct and complete? In v2.3+, each dep entry can carry a cacheStrategy (hash / ignored / outputs) that controls whether the dep contributes to this task's cache hash. If omitted, the default depends on whether the dep declares outputs.
• options — check persistent, runInCI, cache, affectedFiles, mutex, timeout, retryCount, allowFailure, and os.
• env — in v2.5+, environment variables can also be inherited from a workspace-level env in .moon/tasks/**/* (merged into the project's env, project wins), and the project can change the merge behavior via workspace.mergeStrategies.env. A variable with a surprising value may come from a layer outside the task.
• checks v2.4+ — shell scripts that run before the task. Their type determines the outcome: a requirement failing makes the task fail, all condition checks passing makes the task skip, and a fingerprint folds script output into the task hash. A surprising fail, skip, or cache invalidation often traces back to a check.
• tags v2.3+ — labels for grouping tasks. Affects targets like :#quality and MQL taskTag queries. If a task isn't matched by a #tag target you expected, check this list.
• type — build (has outputs), test (default), or run (persistent)
• preset — server or utility apply multiple option defaults at once.