Conciseness

No basic Java or stream concepts are explained; every rule is skill-specific and non-obvious ('Do not swap split("\\R") for String.lines(), which recognizes fewer line terminators', 'no CompletableFuture fan-out', 'Carry element + result, never null sentinels'). The telegraphic style keeps every token load-bearing, matching anchor 5 ('lean and efficient; assumes Claude's competence') rather than anchor 4, since no over-explained passage could be trimmed without losing a rule.

Actionability

Fully concrete and executable: a goal-to-API decision table ('Exactly one match, duplicates must fail' -> 'filter(...).limit(2).toList(), then a switch on the size'), complete Java snippets (the limit(2)+switch unique-match idiom, the Gatherers.mapConcurrent example, toMap with merge function SeatIndex::later), and a concrete verification scan. Specific examples cover the common cases, matching anchor 5; not anchor 4, since nothing is pseudocode or missing key details.

Workflow Clarity

Steps 0-7 are clearly sequenced (baseline check -> terminal choice -> implementation -> prompt constraints -> verification) with an explicit mid-flow 'Checkpoint: before writing the chain, confirm the chosen terminal returns the requested type' and a feedback loop at the end: 'Run the marker scan from hard-stops.md... fix hits, and re-scan', plus a verification checklist ('empty inputs, one element, duplicates, nulls, ordering, and baseline compatibility'). This matches anchor 5's validate -> fix -> retry pattern; not anchor 4, because validation checkpoints are explicit and looped rather than minor-gapped.

Progressive Disclosure

The body stays an overview of workflow rules while worked examples, antipattern detail, and version compatibility are split into three one-level-deep references (references/hard-stops.md, references/stream-examples.md, references/java-stream-api.md — all verified to exist on disk), each surfaced via a purpose table ('Replacement antipatterns and the marker scan to run') and contextual inline links ('Run the marker scan from hard-stops.md'). This matches anchor 5's clear overview with well-signaled one-level-deep references; no nesting or buried references exist.

Specificity

Concrete actions are named throughout — 'Review Java stream performance advice... clean up mutation and write or refactor Java Stream and Collector code' — plus an enumerated antipattern list ('materializing just to inspect, sorting before min/max, counting for existence, nested stream collections, unsafe null sorting, multi-line lambdas'). This is multiple specific concrete actions with comprehensive coverage, matching the anchor-5 example; it is not anchor 4 because no capability area of the domain is left uncovered, and not below because nothing is generic filler.

Completeness

The 'what' is explicit ('Review... clean up mutation and write or refactor Java Stream and Collector code. Avoid common stream antipatterns...') and the 'when' is an explicit trigger clause with concrete phrases: 'Use whenever a Java task writes, reviews, or refactors Stream API code (map, filter, flatMap, reduce, collect) or a collector'. Both questions are clearly and explicitly answered, exactly the anchor-5 pattern; not anchor 4 because the trigger guidance is fully explicit rather than merely present.

Trigger Term Quality

Natural terms a user would actually say appear comprehensively: 'parallelStream', 'findFirst or findAny', 'map, filter, flatMap, reduce, collect', 'grouping collectors', 'joining strings', 'sorted/limit/distinct stages', 'primitive stream totals', 'Optional values inside streams'. Coverage includes synonyms and variations ('Stream API code', 'parallel streams', 'stream first/any element lookup'), matching anchor 5 rather than anchor 4 where natural terms would be missing.

Distinctiveness Conflict Risk

The niche is the Java Stream API specifically, with distinct triggers unlikely to fire for a wrong skill: 'whether a lookup should use findFirst or findAny, lookups that must fail on duplicates, regex splitting inside a stream chain, result mutability, and stream chain layout'. A general Java or code-review skill would not claim these stream-specific API terms, so conflict risk is minimal per anchor 5; anchor 4 would require identifiable overlap with a closely related skill, which is absent.