Compound Learning Writer

/ce-compound

Outcome: one qualifying solved problem is written as a durable learning under <root>/solutions/, grounded against the current tree, discoverable by the next agent.

Done: a qualifying doc is written or updated, its frontmatter and claims validated, vocabulary capture recorded, and the mode's completion report emitted; when no learning qualifies, nothing is written and the report says why.

One learning per run. A session that produced several gets several sequential runs, never one batched run. Read references/research.md; it explains what batching breaks.

Preconditions

Document only a problem that is solved and verified.

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A learning earns its place only when it holds durable project reasoning that is not readily recoverable from the final code, tests, types, comments, or existing documentation, and losing it would plausibly cause recurrence, material risk, or substantial rediscovery. Apply this counterfactual: if the learning document disappeared, would a future engineer reading the final implementation still be likely to repeat the mistake or redo substantial investigation? Completion, effort, and diff size do not establish eligibility.

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If the counterfactual fails, write nothing and report why. Judge this from the session rather than asking. An explicit invocation requests the judgment now but does not lower the bar.

An existing learning that became materially inaccurate or incomplete qualifies because leaving it would mislead. Update that learning instead of creating a duplicate.

ce-compound does not bootstrap CONCEPTS.md. It seeds the learning's own area as a side effect, never the whole repo. Send a standalone request to create or bootstrap that file to ce-compound-refresh, then exit.

Mode Detection

/ce-compound [brief context]
/ce-compound mode:non-interactive depth:lightweight [context]
/ce-compound mode:non-interactive depth:full [context]

Enter non-interactive mode when either holds: the arguments you were invoked with contain the mode:non-interactive token or its deprecated alias mode:headless, or the invocation makes non-interactive intent unmistakable, such as a caller or standing instruction asking to run ce-compound "headless", "non-interactively", "unattended", or "without prompts/questions". Both tokens together is not a conflict. Bare "automatically" or "auto-run" is not on its own a non-interactive signal: it speaks to invoking the skill, not to suppressing its prompts. An ambiguous or absent signal defaults to interactive. Tokens starting with mode: or depth: are flags, not context: strip them before treating the remainder as the brief context hint. Once detected, non-interactive mode applies for the entire run.

Depth is chosen only by an explicit token, only in non-interactive mode, and at most one depth token is accepted. depth:lightweight routes directly to Lightweight Mode. depth:full or no depth token enters Full Mode, including its automatic session-history probe. A non-interactive call carrying no depth token therefore behaves as it always has. Non-interactive lightweight asks no blocking questions and launches no subagents. If the invocation carries an unknown depth: token, multiple depth: tokens, or a depth: token without non-interactive intent, do not guess: emit the non-interactive failure report with the reason and end with Documentation skipped.

Non-interactive mode asks nothing. It asks no blocking question of any kind, in any phase, because a caller reaching this path has no human to answer one. Every non-interactive exit, including one taken before any phase runs, ends on a terminal signal a caller parses: Documentation complete, or Documentation skipped with the reason when no doc was written. Interactive mode asks only where the step's own reference says to, which is the Discoverability Check consent and, when several stale docs are in play, which refresh to run.

Artifact Root

Resolve <root> when you first compose a <root>/solutions/ path, and pass a subagent the resolved path rather than the config.

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Resolve the CE artifact root <root> before composing any artifact path.

• Read docs_root from <repo-root>/.compound-engineering/config.yaml only (<repo-root> = git rev-parse --show-toplevel). Do not read it from config.local.yaml. Unset -> <root> is docs, exactly as before.
• Validate a set value: a repo-relative directory whose real, symlink-resolved path stays inside the repo and is neither the repo root nor under .git/. Otherwise stop with an error naming docs_root and the value -- never fall back to docs.
• Use <root> as the sole artifact location: create it if absent, compose each path as <root>/<subdir> with this skill's own subdirectory, and never also read docs.

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