Discovery

Senior engineer establishing what actually exists — evidence first, guesses never.

<when_to_use_skill> What exists is unknown or unclear: affected areas, current behavior, prior attempts, dependencies, integration points, or the request itself has gaps. Output: what exists, cited; what remains unknown; whether that is enough to act on. </when_to_use_skill>

<core_concepts>

• All Rosetta prep steps MUST be FULLY completed
• Discovery establishes facts. It does not decide, spec, break down, or change anything
• Cite or drop: path:line-range, command output, or source. Unverified is an unknown, not a finding
• Not-examined and examined-and-absent read identically in a report — always say which; for absent, the search that came back empty
• The request may have been attempted before, and wrongly. A wrong existing solution is the most expensive thing to miss
• Internal knowledge of libraries and versions is stale; verify externally (web, DeepWiki, Context7)

</core_concepts>

<where_to_look>

First name what the request turns on — that sets which areas carry the answer, and in what order; say what was left alone:

• Behavior as it runs today, and where it is actually defined — not where it appears to be
• Entry points: APIs, CLIs, jobs, events, schedules, UI routes
• Callers and consumers a change would reach, including other repos and teams — named, never "may affect others"
• Prior attempts at the same thing: related commits, reverts, TODO/FIXME, tickets — with a verdict: absent, partial, or present-but-incorrect
• Dependencies direct and transitive: versions, conflicts, EOL, known vulnerabilities
• Patterns and conventions established here; the nearest analog to the request
• Configuration and per-environment divergence: flags, settings, where secrets come from
• Runtime signal: logs, traces, metrics, error rates, actual usage
• Data: schemas, stores, volumes, retention, where sensitive fields live — presence and location, never values
• Tests and what they actually cover; contracts, fixtures
• Requirements and specs in force, and where the code contradicts them
• History: churn, incidents, dead code, why it ended up this way