Impertio-Studio

@impertio-studio source repo

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Postgres Core Security Model · impertio-studio bundle
Use when designing PostgreSQL permission models, picking which role attributes to grant, or auditing existing privileges before a security review. Prevents over-granting SUPERUSER, leaving public schema writable, forgetting ALTER DEFAULT PRIVILEGES for future tables, and confusion between role attributes and predefined roles. Covers role attributes (LOGIN, SUPERUSER, REPLICATION, BYPASSRLS, CREATEDB, CREATEROLE, INHERIT), GRANT/REVOKE matrix, ALTER DEFAULT PRIVILEGES, predefined roles (pg_read_all_data, pg_write_all_data, pg_monitor, pg_use_reserved_connections v16+, pg_maintain v17+), role membership, SET ROLE. Keywords: GRANT, REVOKE, role, predefined role, BYPASSRLS, SUPERUSER, ALTER DEFAULT PRIVILEGES, pg_read_all_data, pg_maintain, permission denied, who can see this table, how to set up read-only user, where do default privileges come from

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Postgres Core Version Matrix · impertio-studio bundle
Use when targeting PostgreSQL 15, 16, or 17 and needing to know which feature is available where, or migrating across versions. Prevents writing queries that fail on older supported versions, missing v17 features that solve real problems, and confusion about which MERGE / RETURNING / JSON_TABLE behavior applies. Covers per-version feature delta (v15 MERGE/security_invoker/row filters/public lockdown, v16 logical-from-standby/COPY DEFAULT/role membership rewrite, v17 incremental backup/MERGE-RETURNING/JSON_TABLE/transaction_timeout/pg_createsubscriber). Keywords: PostgreSQL 15, PostgreSQL 16, PostgreSQL 17, MERGE, RETURNING, JSON_TABLE, incremental backup, pg_createsubscriber, transaction_timeout, COPY DEFAULT, security_invoker, logical replication from standby, which feature is in which version, can I use this on v15, how to detect version, what's new in postgres 17, syntax error on old version, feature unavailable, ERROR function does not exist, missing GUC

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Postgres Impl Advisory Locks · impertio-studio bundle
Use when coordinating across application instances, ensuring a scheduled job runs at most once, or building a distributed mutex with PostgreSQL. Prevents session-level lock leaks (held until disconnect), key collisions between unrelated subsystems, and advisory locks misbehaving through a transaction-mode connection pooler. Covers session-level vs transaction-level advisory locks, pg_advisory_lock / pg_advisory_xact_lock / pg_try_advisory_lock, shared variants, single-key vs two-key namespacing, pg_locks inspection, cron-at-most-once and distributed-mutex patterns. Keywords: advisory lock, pg_advisory_lock, pg_advisory_xact_lock, pg_try_advisory_lock, distributed lock, mutex, cron at most once, job coordination, SKIP LOCKED, advisory lock leak, run job once across instances, application lock, pg_locks advisory

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Postgres Impl Backup Restore · impertio-studio bundle
Use when setting up backups, choosing logical vs physical, doing point-in-time recovery, or configuring v17 incremental backup. Prevents slow restore from plain-format dumps (no parallel), missing roles after restore (forgot pg_dumpall globals), and being unable to recover to a precise time without WAL archiving. Covers logical vs physical decision, pg_dump formats (plain / custom / directory / tar) and --jobs parallelism, pg_restore, pg_dumpall globals, pg_basebackup, PITR with WAL archiving, v17 incremental backup (summarize_wal + pg_combinebackup). Keywords: pg_dump, pg_restore, pg_basebackup, pg_dumpall, backup, restore, PITR, point in time recovery, WAL archiving, incremental backup, pg_combinebackup, custom format, parallel restore, how to back up postgres, restore is slow, recover to a specific time, lost my roles after restore

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Postgres Syntax Upsert Merge · impertio-studio bundle
Use when writing idempotent inserts, multi-action data sync, or migrating from MySQL INSERT ... ON DUPLICATE KEY UPDATE. Prevents 23505 unique_violation when ON CONFLICT misconfigured, non-deterministic MERGE source race, and using MERGE when simpler UPSERT suffices. Covers INSERT ... ON CONFLICT (v9.5+) conflict_target rules, DO NOTHING vs DO UPDATE, EXCLUDED pseudo-table, MERGE statement (v15+), MERGE-RETURNING (v17+), merge_action(), UPSERT vs MERGE decision tree. Keywords: ON CONFLICT, UPSERT, MERGE, EXCLUDED, DO UPDATE, DO NOTHING, merge_action, RETURNING, idempotent insert, INSERT ON DUPLICATE KEY UPDATE, unique violation 23505, how to do upsert in postgres, when to use merge instead of upsert, MERGE cardinality violation, ERROR there is no unique or exclusion constraint matching the ON CONFLICT specification, ERROR MERGE command cannot affect row a second time

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Postgres Errors Serialization · impertio-studio bundle
Use when choosing a transaction isolation level, handling serialization_failure errors, or preventing write-skew anomalies. Prevents treating 40001 as a hard error instead of retrying, retrying only the last statement instead of the whole transaction, and assuming REPEATABLE READ prevents write skew (only SERIALIZABLE does). Covers READ COMMITTED vs REPEATABLE READ vs SERIALIZABLE, SSI predicate locks, SQLSTATE 40001 serialization_failure, the whole-transaction retry pattern with backoff, SET TRANSACTION ISOLATION LEVEL, read-only deferrable transactions, isolation-level decision tree. Keywords: serialization failure, 40001, isolation level, READ COMMITTED, REPEATABLE READ, SERIALIZABLE, SSI, predicate lock, write skew, retry transaction, could not serialize access, transaction keeps failing, which isolation level, phantom read

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Postgres Impl Indexing Strategy · impertio-studio bundle
Use when a query is slow, picking which index type to create, or auditing a table for missing and redundant indexes. Prevents missing FK-column indexes (slow joins and cascade deletes), expression-index mismatch (index never used), redundant indexes bloating writes, and reaching for B-tree where GIN/GiST/BRIN fits. Covers B-tree / GIN / GiST / SP-GiST / BRIN / Hash decision tree, partial index, expression index, multicolumn column-ordering, INCLUDE covering columns (v11+), index-only scans, CREATE INDEX CONCURRENTLY. Keywords: index, B-tree, GIN, GiST, SP-GiST, BRIN, Hash, partial index, expression index, covering index, INCLUDE, multicolumn index, CREATE INDEX CONCURRENTLY, query is slow, which index should I use, missing index on foreign key, index not being used, too many indexes

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Postgres Impl Postgis 3d Raster · impertio-studio bundle
Use when working with 3D geometry, volumetric calculations, or raster (gridded) data in PostGIS. Prevents calling 3D functions without postgis_sfcgal installed (function not found), bloating tables with in-db rasters that should be out-db, and choosing raster where vector fits. Covers postgis_sfcgal 3D predicates (ST_3DIntersects, ST_3DDistance, ST_Volume), ST_Extrude, Z-coordinate handling, postgis_raster type (ST_Value, ST_Band, ST_Clip), in-db vs out-db storage, raster vs vector decision, postgis_topology overview. Keywords: PostGIS 3D, postgis_sfcgal, ST_3DDistance, ST_3DIntersects, ST_Extrude, ST_Volume, raster, postgis_raster, ST_Value, ST_Clip, postgis_topology, function does not exist sfcgal, 3D query, raster vs vector, gridded data, volumetric

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Postgres Syntax Arrays Ranges · impertio-studio bundle
Use when storing list-valued columns, modelling time/number intervals, or preventing overlapping bookings with exclusion constraints. Prevents seqscan on range-overlap queries from missing GiST index, CSV-in-text instead of native array, and off-by-one errors from inclusive vs exclusive range bounds. Covers array literals + operators (= ANY, @>, &&, ||), unnest WITH ORDINALITY, array_agg, range types (int4range, tstzrange, daterange), range operators (@>, &&, -|-), multirange (v14+), GiST exclusion constraints for non-overlap. Keywords: array, ARRAY, ANY, unnest, array_agg, range type, int4range, tstzrange, daterange, multirange, range overlap, exclusion constraint, GiST, EXCLUDE USING gist, overlapping bookings, how to store a list, prevent double booking, range query is slow

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Postgres Syntax Cte Recursive · impertio-studio bundle
Use when writing readable multi-stage queries, traversing parent/child trees, or constructing data-modifying CTEs that return both before and after states. Prevents pre-v12 fence-reliance breaking under v12+ inlining (NOT MATERIALIZED default), infinite-loop recursive CTEs without termination, and reaching for stored procedures when a recursive CTE suffices. Covers non-recursive CTE, RECURSIVE CTE (UNION ALL vs UNION, termination, SEARCH/CYCLE v14+), MATERIALIZED vs NOT MATERIALIZED (v12+), data-modifying CTE (INSERT/UPDATE/DELETE in WITH), tree-walk + graph patterns. Keywords: CTE, WITH, WITH RECURSIVE, MATERIALIZED, NOT MATERIALIZED, SEARCH, CYCLE, data-modifying CTE, tree walk, graph traversal, recursive query, my recursive CTE never returns, query inlined unexpectedly, how to traverse parent_id, fence broken v12, ERROR aggregate functions are not allowed in WITH RECURSIVE, infinite loop CTE, out of memory recursive

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Postgres Syntax Lateral Joins · impertio-studio bundle
Use when computing per-row dynamic subqueries, top-N-per-group results, or expanding JSON arrays per row in a JOIN clause. Prevents losing outer rows when LATERAL subquery returns empty (use LEFT JOIN LATERAL ON true), and reaching for LATERAL when a simple JOIN suffices (less optimizer-friendly). Covers LATERAL semantics, INNER vs LEFT JOIN LATERAL, correlated subquery equivalence, top-N-per-group pattern, LATERAL with set-returning functions, LATERAL vs scalar subquery decision tree. Keywords: LATERAL, CROSS JOIN LATERAL, LEFT JOIN LATERAL, top N per group, per row subquery, correlated subquery, generate_series LATERAL, unnest in JOIN, missing rows when joining, why do I lose rows in lateral, jsonb_array_elements per row, polygons vertices LATERAL, lateral subquery empty

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Postgres Agents Query Reviewer · impertio-studio bundle
Use when reviewing SQL queries for correctness and performance before they ship, or auditing existing queries in a codebase. Prevents rubber-stamping queries without checking index usage, missing a WHERE-less UPDATE/DELETE, and overlooking implicit casts or un-indexed JSONB and LIKE patterns that force seqscans. Covers a deterministic SQL review checklist (SELECT *, missing WHERE, implicit casts, JSONB GIN gaps, leading-wildcard LIKE, N+1, OFFSET pagination, NOT IN with NULLs, fan-out), severity grading, and which sibling skill to cite per finding. Keywords: SQL review, query review, code review, query reviewer, SELECT star, missing WHERE, N+1 query, implicit cast, seqscan, slow query review, review my SQL, is this query good, audit queries, query checklist

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Postgres Impl Schema Archaeology · impertio-studio bundle
Use when exploring an unfamiliar database, finding what references a table, locating unused or redundant indexes, or auditing a mature schema. Prevents slow introspection from using information_schema where pg_catalog is faster, DROP cascade surprises from skipping pg_depend, and missing orphan rows or wraparound risk in a legacy database. Covers information_schema vs pg_catalog, FK-graph navigation via pg_constraint, table + index size queries, unused index detection (pg_stat_user_indexes), redundant index detection, orphan row queries, sequence vs IDENTITY audit, pg_depend dependency graph, psql introspection shortcuts. Keywords: pg_catalog, information_schema, pg_class, pg_attribute, pg_constraint, pg_depend, pg_stat_user_indexes, pg_relation_size, foreign key graph, unused index, redundant index, orphan rows, schema introspection, how to explore a database, what references this table, find unused indexes, inherited a legacy database

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Postgres Agents Schema Reviewer · impertio-studio bundle
Use when reviewing a PostgreSQL schema or DDL design before it ships, or auditing an existing schema for structural problems. Prevents shipping tables with no primary key, un-indexed foreign keys, multi-tenant tables with no RLS strategy, SERIAL where IDENTITY belongs, and timestamp instead of timestamptz for event times. Covers a deterministic schema review checklist (snake_case naming, IDENTITY vs SERIAL, missing PK, FK indexing, redundant indexes, RLS coverage, jsonb vs CSV-in-text, timestamptz, normalization), severity grading, cite-sibling-skill per finding, GOOD / NEEDS-WORK / POOR verdict. Keywords: schema review, DDL review, database design review, table design, naming convention, missing primary key, foreign key index, RLS coverage, normalization, IDENTITY vs serial, review my schema, is this schema good, audit database design, schema checklist

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Postgres Errors Connection Auth · impertio-studio bundle
Use when connections fail with authentication errors, no pg_hba.conf entry, SSL handshake problems, or too-many-connections. Prevents trust auth on production hosts, sslmode=require giving a false sense of security (no server verification), editing pg_hba.conf without reloading, and raising max_connections instead of using a pooler. Covers pg_hba.conf rule format and ordering, auth methods (trust / peer / md5 / scram-sha-256 / cert), "no pg_hba.conf entry" and "password authentication failed" diagnosis, password_encryption, SSL sslmode levels, SQLSTATE 28000 / 28P01 / 53300, connection pooling guidance. Keywords: pg_hba.conf, authentication failed, no pg_hba.conf entry for host, scram-sha-256, md5, peer, trust, sslmode, SSL connection, password authentication failed, too many connections, 28P01, 53300, cannot connect to postgres, connection refused, max_connections

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Postgres Errors Replication Lag · impertio-studio bundle
Use when a replica is behind, a replication slot is bloating WAL, or a logical subscription is stuck. Prevents primary disk filling from an inactive slot, discovering lag only at failover time, and ignoring a stuck subscription that never self-heals after a hard conflict. Covers streaming lag monitoring (pg_stat_replication write/flush/replay lag, LSN diff), replication slot bloat (pg_replication_slots), max_slot_wal_keep_size safety cap, logical subscription lag + stuck-subscription recovery (conflict resolution, SKIP), lag root causes. Keywords: replication lag, pg_stat_replication, replay_lag, replication slot, pg_replication_slots, max_slot_wal_keep_size, could not start WAL streaming, subscription stuck, pg_stat_subscription, replica is behind, WAL not being removed, slot bloat, standby lag, logical replication stuck

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Postgres Impl Logical Replication · impertio-studio bundle
Use when replicating selected tables between databases, setting up zero-downtime upgrades, or debugging a stuck subscription. Prevents UPDATE/DELETE silently not replicating (REPLICA IDENTITY missing on PK-less table), unbounded WAL growth from abandoned slots, and broken replication after an un-synced DDL change. Covers CREATE PUBLICATION / SUBSCRIPTION, REPLICA IDENTITY (DEFAULT / FULL / INDEX), row filters + column lists (v15+), logical-from-standby (v16+), bidirectional (v16+), pg_createsubscriber (v17+), slot management, initial sync, DDL-not-replicated caveat. Keywords: logical replication, CREATE PUBLICATION, CREATE SUBSCRIPTION, REPLICA IDENTITY, replication slot, row filter, column list, pg_createsubscriber, bidirectional replication, subscription stuck, WAL growing, updates not replicating, how to replicate one table, zero downtime upgrade

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Postgres Impl Pgvector Similarity · impertio-studio bundle
Use when storing embeddings for semantic search, picking hnsw vs ivfflat, or debugging why a vector query does a seqscan. Prevents index opclass not matching the query distance operator (index unused), building ivfflat on an empty table (poor recall), and exceeding the indexable dimension limit. Covers CREATE EXTENSION vector, vector / halfvec / sparsevec / bit types, distance operators (<->, <=>, <#>, <+>), ivfflat vs hnsw decision, operator classes, dimension limits, ORDER BY ... LIMIT k query pattern, ef_search tuning, hybrid search with tsvector. Keywords: pgvector, vector, embedding, hnsw, ivfflat, cosine distance, <=>, <->, similarity search, semantic search, vector_cosine_ops, dimension limit, hybrid search, vector query is slow, embedding seqscan, which vector index, RAG retrieval

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Postgres Impl Postgis Geometry 2d · impertio-studio bundle
Use when querying spatial data, picking geometry vs geography, or speeding up "find points near X" queries with PostGIS. Prevents losing the GiST index by using ST_Distance in WHERE (use ST_DWithin), seqscan from missing spatial index, and wrong results from mixing SRIDs without ST_Transform. Covers CREATE EXTENSION postgis, geometry vs geography, SRID (4326 / 3857 / projected), GiST spatial index, spatial predicates (ST_Intersects / ST_Within / ST_DWithin / ST_Distance), ST_Transform, ST_Buffer, constructors, measurement functions. Keywords: PostGIS, geometry, geography, SRID, 4326, 3857, GiST, ST_Intersects, ST_DWithin, ST_Distance, ST_Transform, ST_Contains, spatial index, spatial query is slow, find points near, distance in meters, my postgis query does seqscan, wrong distance results

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Postgres Syntax Full Text Search · impertio-studio bundle
Use when building search over text columns, ranking results by relevance, or choosing between full-text search and trigram fuzzy matching. Prevents to_tsquery syntax errors on raw user input (use websearch_to_tsquery), seqscan from missing GIN index, and config mismatch between index expression and query. Covers tsvector / tsquery, to_tsvector, plainto_tsquery / phraseto_tsquery / websearch_to_tsquery, @@ match, ts_rank / ts_rank_cd, ts_headline, GIN vs GiST index choice, generated tsvector column (v12+), setweight, FTS vs pg_trgm decision. Keywords: full text search, tsvector, tsquery, to_tsvector, websearch_to_tsquery, ts_rank, GIN, ts_headline, setweight, text search, search is slow, how to do search in postgres, fuzzy search, relevance ranking, search returns nothing

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Postgres Syntax Window Functions · impertio-studio bundle
Use when computing running totals, rank within partition, top-N-per-group via window, or comparing rows to neighbours. Prevents LAST_VALUE returning current row (wrong default frame), filtering on window result in WHERE (illegal, must wrap), and reaching for GROUP BY when window suffices. Covers OVER clause, PARTITION BY, frame clauses (ROWS/RANGE/GROUPS v11+), EXCLUDE (v11+), named windows, ranking (RANK/DENSE_RANK/ROW_NUMBER/NTILE), offset (LAG/LEAD/FIRST_VALUE/LAST_VALUE/NTH_VALUE), window vs aggregate decision tree. Keywords: window function, OVER, PARTITION BY, frame clause, ROWS BETWEEN, RANGE BETWEEN, GROUPS, LAG, LEAD, RANK, DENSE_RANK, ROW_NUMBER, NTILE, named window, running total, top N per group, why is LAST_VALUE returning current row, can I use window in WHERE

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Postgres Impl Streaming Replication · impertio-studio bundle
Use when setting up a hot-standby replica, choosing synchronous_commit durability, or debugging replica lag and query cancellation. Prevents disk filling from a physical slot without max_slot_wal_keep_size, primary stalls when a synchronous standby goes down, and standby query cancellation from conflicting vacuum. Covers pg_basebackup clone, primary_conninfo + standby.signal, hot_standby, physical replication slots, WAL archiving, synchronous_commit modes, synchronous_standby_names quorum, pg_promote, cascading replication, pg_stat_replication monitoring, hot_standby_feedback. Keywords: streaming replication, hot standby, pg_basebackup, replication slot, synchronous_commit, synchronous_standby_names, pg_promote, standby.signal, pg_stat_replication, replica lag, max_slot_wal_keep_size, query canceled on standby, disk full replication, how to set up a replica, failover

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Postgres Agents Migration Reviewer · impertio-studio bundle
Use when reviewing a database migration for production safety before it runs, or auditing a migration file in a pull request. Prevents shipping a plain CREATE INDEX that locks writes, a full-rewrite ALTER COLUMN TYPE, a breaking DROP/RENAME without expand-contract, and migrations that stall all traffic without lock_timeout. Covers a deterministic migration safety checklist (CONCURRENTLY, rewrite-triggering ALTERs, NOT VALID + VALIDATE, breaking changes, lock_timeout, chunked backfill, CONCURRENTLY-in-transaction), severity grading, safe-rewrite suggestions, SAFE / NEEDS-CHANGES / UNSAFE verdict. Keywords: migration review, migration safety, zero downtime, review migration, CREATE INDEX CONCURRENTLY, ALTER TABLE lock, breaking change, expand contract, is this migration safe, will this migration lock the table, migration checklist, schema change review

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Postgres Errors Statement Timeouts · impertio-studio bundle
Use when queries are canceled by timeout, sessions hold locks while idle, or you need to bound query and transaction duration safely. Prevents a forgotten open transaction blocking vacuum forever (set idle_in_transaction_session_timeout), blindly retrying a statement_timeout caused by a missing index, and migrations stalling all traffic without lock_timeout. Covers statement_timeout (57014), lock_timeout (55P03), idle_in_transaction_session_timeout (25P03), idle_session_timeout (v14+), transaction_timeout (v17+), per-role/per-database scoping, fail-fast vs retry decision. Keywords: statement_timeout, lock_timeout, idle_in_transaction_session_timeout, idle_session_timeout, transaction_timeout, 57014, query_canceled, 55P03, 25P03, query canceled due to statement timeout, idle in transaction, query takes too long, how to limit query time, canceling statement

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Postgres Impl Zero Downtime Migrations · impertio-studio bundle
Use when altering a table on a live production database, adding indexes or constraints without downtime, or backfilling a new column. Prevents plain CREATE INDEX locking writes (use CONCURRENTLY), ALTER COLUMN TYPE full-rewrite locks, migrations stalling all traffic behind a long query (set lock_timeout), and single huge backfill UPDATEs. Covers ALTER TABLE rewrite rules (metadata-only vs full rewrite), CREATE INDEX / REINDEX CONCURRENTLY, ADD COLUMN with default (v11+), safe NOT NULL + FK via NOT VALID + VALIDATE, lock_timeout, chunked backfill, expand-contract pattern. Keywords: zero downtime migration, ALTER TABLE, CREATE INDEX CONCURRENTLY, REINDEX CONCURRENTLY, NOT VALID, VALIDATE CONSTRAINT, lock_timeout, backfill, expand contract, table rewrite, migration locked the table, ALTER blocks writes, how to add column safely, add not null without downtime

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Postgres Errors Constraint Violations · impertio-studio bundle
Use when inserts or updates fail with unique, foreign-key, not-null, check, or exclusion constraint errors. Prevents the catch-23505-then-UPDATE race (use ON CONFLICT atomically), slow cascading deletes from un-indexed FK columns, and impossible inserts from circular FKs without DEFERRABLE. Covers SQLSTATE 23505 unique_violation, 23503 foreign_key_violation, 23502 not_null_violation, 23514 check_violation, 23P01 exclusion_violation, deferrable constraints, FK indexing, NOT VALID constraints, ON CONFLICT handling. Keywords: constraint violation, 23505, unique violation, 23503, foreign key violation, 23502, not null violation, 23514, check violation, exclusion violation, deferrable constraint, duplicate key error, foreign key error, insert fails, cannot delete row referenced, ON CONFLICT

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Postgres Impl Query Performance Toolkit · impertio-studio bundle
Use when a query is slow, reading an EXPLAIN plan, finding the worst queries on a server, or diagnosing lock waits. Prevents trusting EXPLAIN cost as real time, running EXPLAIN ANALYZE on a destructive query in production (it executes), and chasing the plan when stale statistics are the real cause. Covers EXPLAIN / EXPLAIN ANALYZE / BUFFERS, reading plan nodes (Seq/Index/Bitmap/Nested-Loop/Hash/Merge/Sort/Aggregate/Memoize v14+), cost model, estimate-vs-actual rows, pg_stat_statements forensics, pg_stat_activity, pg_locks + pg_blocking_pids, extended statistics (CREATE STATISTICS). Keywords: EXPLAIN, EXPLAIN ANALYZE, BUFFERS, query plan, Seq Scan, Index Scan, Bitmap, Nested Loop, Hash Join, Memoize, pg_stat_statements, pg_stat_activity, pg_locks, pg_blocking_pids, CREATE STATISTICS, query is slow, how to read explain, find slow queries, why is this query slow, lock wait

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Shadcn Core CLI · impertio-studio bundle
Use when running any shadcn CLI command (init, add, view, search, apply, preset, build, docs, info, migrate), when writing or editing components.json, when choosing between tsconfig path aliases and package.json#imports aliases (new in shadcn@4.7.0), when wiring a custom or private registry, or when a shadcn invocation overwrote local component edits unexpectedly. Prevents the silent-overwrite trap from running `add` without `--diff` after local modifications, the "Cannot find baseColor" failure from a malformed components.json, the registry-resolution miss from forgetting the `{name}` placeholder, and the immutable-field surprise from trying to change `style`, `baseColor`, or `cssVariables` after init. Covers every CLI command and flag, the complete components.json schema, registry resolution semantics, and the package.json#imports alternative to tsconfig paths. Keywords: shadcn cli, npx shadcn add, pnpm dlx shadcn, shadcn init, shadcn diff, shadcn update, shadcn migrate, shadcn migrate icons, shadcn migrate

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Shadcn Core Stack · impertio-studio bundle
Use when reading or writing any shadcn ui component, especially when figuring out which library owns which concern (a11y, variants, class composition, icons), when a prop or class string is not behaving as expected, when picking between raw Radix and the shadcn-wrapped component, when adding tailwind-merge or cva to an existing project, when an LLM is asked to "rebuild a shadcn-style component" and needs to know the exact runtime layers, and when migrating from Tailwind v3 to v4 inside a shadcn project. Prevents the common mistakes of (a) concatenating className strings without `cn()`, causing duplicate utility classes to leak through, (b) bypassing the shadcn-copied component to import Radix primitives directly, losing the project's styling, (c) defining `cva` variants in the wrong order so that `compoundVariants` never trigger, (d) installing wrong package versions (radix-ui unified vs @radix-ui/react-* legacy, cva 1.0 beta vs 0.7 stable, tailwind-merge v2 for Tailwind v3 vs v3 for Tailwind v4), and (e) tre

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Shadcn Core Blocks · impertio-studio bundle
Use when scaffolding a full page (dashboard, login, signup, sidebar layout, calendar app), bootstrapping a starter template from shadcn's gallery, evaluating block vs hand-composed components, choosing between the default / new-york / sera / luma styles, or recovering after a `shadcn add <block>` rerun overwrote local customisations. Prevents six common block-system failures : treating blocks as immutable starter templates (they are owned code, edit freely), running `shadcn add <block>` over a customised copy without `--diff` and losing work, mixing multiple style enum values inside one project, importing block sub-components from package paths instead of the local copied location, expecting blocks to auto-update when shadcn ships new revisions, and conflating blocks with components in CLI invocation when they accept different mental models for ownership and customisation. Covers the blocks distribution surface (a separate gallery at /blocks distinct from /components), block category landscape (dashboard, sid

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Shadcn Core Theming · impertio-studio bundle
Use when wiring shadcn ui colors, dark mode, the design-token palette, or migrating a project between Tailwind v3 and Tailwind v4, or when pasting theme output from https://ui.shadcn.com/themes into a project. Prevents the single largest source of AI-generated style bugs in shadcn projects : the HSL-space-separated (Tailwind v3) versus oklch (Tailwind v4) format split, the hsl(var(--background)) wrapper convention versus the bare var(--background) convention, the bg-background utility semantics difference, and dark-mode flash-of-unstyled-content from a missing suppressHydrationWarning on the html element. Covers the exhaustive CSS-custom-property token catalog (core, sidebar, chart, radius scale), the @theme inline directive (v4) versus the tailwind.config.js theme.extend.colors block (v3), the next-themes ThemeProvider wiring on Next.js, the custom localStorage ThemeProvider on Vite, the useTheme hook, the mode-toggle component, and the copy-from-themes-page workflow. Keywords: shadcn theming, design tokens,

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Shadcn Core Registry · impertio-studio bundle
Use when authoring or consuming a shadcn registry, when configuring the `registries` field in components.json, when wiring a private or paid component library behind a namespace prefix like `@myorg/datepicker`, when securing a custom registry with bearer tokens or API keys, when hosting a `registry.json` plus per-item JSON files, or when explaining why the `style`, `baseColor`, or `cssVariables` fields cannot be changed after `init`. Prevents the missing-`{name}`-placeholder trap that breaks every namespace install, the committed-secret leak from inlining an API key instead of using `${ENV_VAR}` expansion, the alias-mismatch silent failure from setting `aliases.components` to one path while imports reference another, the immutable-field surprise from editing `style`/`baseColor`/`cssVariables` post-init, and the Tailwind v3-vs-v4 config-shape confusion. Covers every components.json field in depth (purpose, constraints, defaults, immutability), the URL-template syntax with `{name}` and `{style}` placeholders, e

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Shadcn Syntax Form · impertio-studio bundle
Use when building forms with shadcn ui and react-hook-form plus zod, when composing the seven Form primitives (Form, FormField, FormItem, FormLabel, FormControl, FormDescription, FormMessage), when wiring zodResolver to useForm, when deciding between Controller and register for a given input type, when validation errors fail to render under a field, when an input value never reaches the submit handler, or when an input throws a "switched from uncontrolled to controlled" warning. Prevents the common form failures : using register on a non-native control (Select, Checkbox, RadioGroup, Switch) so its value never enters form-state, forgetting FormMessage so zod errors silently never render, defining the zod schema inside the component body so it re-creates every render and kills memoised resolver references, calling handleSubmit without wiring it to the form's onSubmit prop so validation never runs, omitting the outer Form spread so FormField cannot reach the form context, and setting defaultValues to undefined s

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Shadcn Syntax Chart · impertio-studio bundle
Use when building data visualizations with the shadcn Chart primitive that wraps Recharts (Bar, Line, Area, Pie, Radar, Scatter, RadialBar, Composed). Prevents the common mistake of using Recharts directly (loses shadcn theming), inlining hex colors (breaks dark mode), forgetting `'use client'` (RSC crash), or omitting `ChartConfig` (no CSS-var color generation). Covers the five wrappers (ChartContainer, ChartTooltip, ChartTooltipContent, ChartLegend, ChartLegendContent), the `ChartConfig` type, the `--chart-1..5` and `var(--color-<dataKey>)` color convention, theme-aware light/dark color resolution, and per-chart-type Recharts composition. Keywords: shadcn chart, shadcn ui chart, recharts wrapper, ChartContainer, ChartTooltip, ChartTooltipContent, ChartLegend, ChartLegendContent, ChartConfig, bar chart, line chart, area chart, pie chart, radar chart, scatter chart, stacked area chart, chart colors, theme-aware chart, --chart-1 css var, --color-dataKey, dark mode chart, how do I make a chart in shadcn, my cha

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Shadcn Syntax Field · impertio-studio bundle
Use when building forms in shadcn ui evergreen-2026 and the new Field primitive family is the recommended path, when composing Field, FieldLabel, FieldDescription, FieldError, FieldGroup, FieldSet, FieldLegend, FieldContent, FieldSeparator, or FieldTitle, when wiring accessibility attributes (htmlFor, id, aria-invalid, aria-describedby) by hand around a controlled input, when integrating shadcn inputs with react-hook-form Controller WITHOUT the higher-level Form / FormField wrappers, when integrating with TanStack Form, when choosing between the older Form composition path and the newer Field path, or when an error message fails to render under a Field-wrapped input. Prevents the common Field failures : omitting FieldLabel htmlFor so the label does not focus the control, rendering FieldError outside its parent Field so data-invalid styling never applies, mixing Field with FormField in the same field tree, forgetting aria-invalid on the inner input so screen readers do not announce the error, and using Field a

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Shadcn Syntax Sheet · impertio-studio bundle
Use when building a side panel, slide-in drawer, off-canvas navigation, filter panel, settings tray, or any container that enters from the top, right, bottom, or left edge of the viewport in shadcn ui. Prevents the common mistakes of omitting SheetTitle (Radix a11y violation), choosing Sheet on mobile where Drawer would feel native, using side="bottom" Sheet where Drawer is the documented mobile-first pattern, and overriding SheetContent styles in a way that breaks the slide-in animation. Covers the side prop (top, right, bottom, left), the eight exported primitives (Sheet, SheetTrigger, SheetClose, SheetContent, SheetHeader, SheetFooter, SheetTitle, SheetDescription), controlled vs uncontrolled state (open + onOpenChange forwarded to the Radix Dialog primitive), showCloseButton prop on SheetContent, Sheet-vs-Dialog decision, and Sheet-vs-Drawer decision. Keywords: shadcn sheet, side panel, drawer-style dialog, SheetContent, SheetTitle, SheetTrigger, SheetClose, SheetDescription, navigation menu sheet, settin

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Shadcn Syntax Table · impertio-studio bundle
Use when adding, customising, or debugging the shadcn ui Table primitive (the eight subcomponents Table, TableHeader, TableBody, TableFooter, TableRow, TableHead, TableCell, TableCaption), rendering a static, read-only table for product lists, invoice line-items, settings rows, metric summaries, or any tabular data that does NOT need sorting, filtering, pagination, or row selection, deciding between the styling primitive (this skill) and the TanStack-Table-driven DataTable recipe (shadcn-impl-data-table), composing a TableFooter sum row, adding a TableCaption for screen-reader access, dropping a shadcn Table inside a Card / Dialog / Drawer / Sheet surface, or diagnosing why a Table renders unstyled, breaks alignment, or refuses to scroll horizontally on mobile. Prevents the canonical Table-primitive failures : reaching for the Table primitive when the design actually needs sortable / filterable / paginated columns (those require the TanStack recipe in shadcn-impl-data-table, NOT this skill), shipping a Table

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Shadcn Impl Data Table · impertio-studio bundle
Use when building any sortable, filterable, paginated, selectable, or column-toggleable table in shadcn ui : the official shadcn DataTable is NOT a primitive component but a documented recipe that composes TanStack Table v8 (@tanstack/react-table) with the shadcn Table primitive. Use this skill any time the task involves columns of data, row selection with bulk actions, pagination of a list, server-side data loading with sorting or filtering, column-visibility toggles, or resizable columns. Prevents the recurring bugs : forgetting getCoreRowModel and getting zero rows, mixing client-side and server-side state so sorting fires twice, missing getRowId so row-selection keys collide, setting manualPagination without pageCount so pagination breaks, forgetting 'use client' on the DataTable component, defining a ColumnDef without accessorKey or accessorFn so cells render undefined, and importing TanStack helpers from the wrong package. Covers the ColumnDef typing pattern, the useReactTable hook composition, the six

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Shadcn Syntax Button · impertio-studio bundle
Use when adding, customising, or debugging a shadcn ui Button, choosing between the six built-in variants (default / destructive / outline / secondary / ghost / link), choosing between the size variants (default / sm / lg / icon plus the v4-only xs / icon-xs / icon-sm / icon-lg), using the `asChild` Slot pattern to wrap a Next.js Link, a react-router Link, or any other custom anchor as the rendered button element, typing a Button-derived component with `VariantProps<typeof buttonVariants>`, building an icon-only button, building a loading button with a spinner, understanding the focus-ring difference between Tailwind v3 and v4 output, or diagnosing why a Button renders unstyled, ignores `className`, or crashes the page after `asChild` is added. Prevents the canonical Button-level failures : passing multiple children inside `<Button asChild>` (Slot.Root only accepts one), using `asChild` with a child that is not a forwardRef-compatible component, dropping an icon into `size="default"` instead of `size="icon"`

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Shadcn Syntax Dialog · impertio-studio bundle
Use when adding, debugging, or refactoring a shadcn ui Dialog (a focus- trapped modal that overlays the page), composing its ten primitives (Dialog / DialogTrigger / DialogPortal / DialogOverlay / DialogContent / DialogHeader / DialogFooter / DialogTitle / DialogDescription / DialogClose), deciding between controlled (`open` + `onOpenChange`) and uncontrolled (`defaultOpen` or no state at all) operation, visually hiding the title with an sr-only span while keeping screen- reader compliance, closing the dialog after a form submit, swapping the default close button via `showCloseButton={false}` on DialogContent, retargeting the portal container, or wrapping a custom button via `<DialogClose asChild>`. Prevents the canonical Dialog failures : passing `open` without `onOpenChange` (the dialog becomes read-only and uncloseable), omitting DialogTitle (Radix dev-mode throws an a11y warning + axe flags it as critical), rendering DialogContent outside DialogPortal (z-index conflicts and stacking-context bugs in transf

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Shadcn Syntax Drawer · impertio-studio bundle
Use when building a mobile-first bottom-sheet, swipe-to-dismiss panel, multi-stop drawer (snap points), or any sliding surface that enters from the bottom (default), top, left, or right edge of the viewport in shadcn ui. The Drawer is Vaul-backed (emilkowalski/vaul) and is a separate primitive family from Dialog and Sheet : it owns its own `Drawer / DrawerTrigger / DrawerPortal / DrawerOverlay / DrawerContent / DrawerHeader / DrawerFooter / DrawerTitle / DrawerDescription / DrawerClose` composition, exposes Vaul-only props (`snapPoints`, `shouldScaleBackground`, `setBackgroundColorOnScale`, `direction`, `dismissible`, `nested`, `handleOnly`, `closeThreshold`, `activeSnapPoint`, `onDrag`, `onRelease`), and is the documented half of the responsive Dialog-on-desktop / Drawer-on-mobile recipe. Prevents the canonical Drawer failures : omitting DrawerTitle (Radix Dialog a11y rule applies via Vaul ; axe-core flags the dialog as missing accessible name), reaching for Drawer on a desktop side-panel (Sheet is the corre

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Shadcn Syntax Command · impertio-studio bundle
Use when adding, debugging, or refactoring a shadcn ui Command primitive (the cmdk-backed command-palette / fuzzy-filter list), composing its nine parts (Command / CommandDialog / CommandInput / CommandList / CommandEmpty / CommandGroup / CommandItem / CommandSeparator / CommandShortcut), deciding between an inline Command surface and the modal CommandDialog wrapping, wiring the Cmd+K / Ctrl+K global hotkey via useEffect + keydown listener, switching from cmdk's built-in fuzzy filter to server-side / async filtering via `shouldFilter={false}` with externally-managed `items` state plus CommandLoading, providing a stable `value` prop on every CommandItem so cmdk can identify it for filtering and keyboard navigation, handling `onSelect: (value: string) => void` to route the user's choice, building a Combobox by rendering Command inside a Popover (the canonical shadcn recipe), or building nested / multi-page command palettes with sub-routes via a React-state `pages` stack. Prevents the canonical Command failures

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Shadcn Syntax Sidebar · impertio-studio bundle
Use when building an application shell, dashboard navigation, admin sidebar, collapsible side navigation, or any persistent vertical navigation rail in shadcn ui. Prevents the common mistakes of rendering Sidebar outside a SidebarProvider (throws "useSidebar must be used within a SidebarProvider"), omitting the 'use client' directive on the layout that hosts the Provider, choosing the wrong collapsible variant for desktop versus mobile, placing SidebarInset without a sibling Sidebar (layout collapse), and skipping the cookie-based persistence handshake in server-rendered frameworks. Covers all 23 exported primitives (SidebarProvider, Sidebar, SidebarTrigger, SidebarRail, SidebarInset, SidebarInput, SidebarHeader, SidebarFooter, SidebarSeparator, SidebarContent, SidebarGroup, SidebarGroupLabel, SidebarGroupAction, SidebarGroupContent, SidebarMenu, SidebarMenuItem, SidebarMenuButton, SidebarMenuAction, SidebarMenuBadge, SidebarMenuSkeleton, SidebarMenuSub, SidebarMenuSubItem, SidebarMenuSubButton) plus the useS

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Shadcn Core Architecture · impertio-studio bundle
Use when starting a new project that needs UI components, evaluating shadcn ui versus a traditional component library (MUI, Chakra, Mantine, Ant Design), explaining why shadcn lacks an `npm install shadcn-ui` command, or onboarding a developer who searches npm for a `shadcn-ui` package. Prevents the four most common shadcn mental-model failures : treating shadcn as an npm runtime dependency, importing from a non-existent `shadcn-ui` package, expecting library-style auto-upgrades via `npm update`, and overwriting local component customisations by re-running `shadcn add` without first inspecting the diff. Covers the copy-not-install paradigm, the five officially documented pillars (Open Code, Composition, Distribution, Beautiful Defaults, AI-Ready), the evergreen-2026 versioning model, registry resolution, and the deliberate tradeoffs versus traditional component libraries. Foundational reading. Every other skill in this package assumes the reader has internalised the ownership doctrine documented here. Keyword

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Shadcn Syntax Input Otp · impertio-studio bundle
Use when building a one-time-password, verification-code, MFA, two-factor, SMS-code, or PIN-entry input in shadcn ui evergreen-2026, when composing InputOTP, InputOTPGroup, InputOTPSlot, and InputOTPSeparator, when wiring a 6-digit numeric code, a 4-digit PIN, or an alphanumeric token, when enabling iOS and Android SMS autofill via autoComplete one-time-code, when handling paste of a full code in one operation, when constraining allowed characters via the pattern prop, when reacting to a fully entered code via onComplete, when integrating an OTP input with react-hook-form Controller, or when an OTP renders as a single empty input with no slots visible. Prevents the common Input OTP failures : omitting maxLength so the underlying OTPInput renders zero slots and the user sees an empty box, forgetting the index prop on InputOTPSlot so every slot reads from the same context entry, passing a JavaScript RegExp object to the pattern prop instead of a regex source string or one of the exported constants, trying to re

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Shadcn Syntax Selectors · impertio-studio bundle
Use when picking the right "selector" primitive in a shadcn ui app and you are unsure whether to reach for a Native HTML `<select>`, a shadcn Select (Radix Select wrapped, 10 primitives), a Combobox recipe (Popover + Command composed by hand or the new 2026 Combobox primitive), or a Command palette (CommandDialog as a Cmd+K action launcher) ; covers the four-way decision criteria (list size, searchability, async loading, palette UX, mobile-native-picker need), the form-binding contract per selector (Native works with `register`, Radix Select and Combobox require `Controller`), the Combobox-as-recipe composition (Popover + Command + CommandInput + CommandList + CommandEmpty + CommandGroup + CommandItem), the Command-palette hotkey wiring (Cmd+K via `useEffect` + `keydown` listener), the async options pattern (server-fetched, loading state, empty state, error state), and the a11y wiring per selector (`aria-expanded` / `aria-controls` / `aria-activedescendant`). Prevents the canonical selector failures : binding

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Shadcn Errors Form State · impertio-studio bundle
Use when a shadcn Form built on react-hook-form silently submits with missing values, when a Radix Select or Checkbox or RadioGroup or Switch never updates form state, when FormMessage refuses to render the zod error, when the console logs "A component is changing an uncontrolled input to be controlled" on first keystroke, when the entire form re-renders on every character typed, when an async zod refine never blocks submission, when handleSubmit fires with no validation, when formState.isDirty or formState.isValid stays stuck at false, when reset() does not clear errors, when a file input loses its FileList after the first render, when a server validation response should light up specific field errors, when defaultValues is partially specified and some fields jump from uncontrolled to controlled, or when a typo in the zod schema field path causes a field to never validate without warning. Prevents the six recurring react-hook-form failures inside shadcn Form composition : using register on a non-native contr

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Shadcn Impl Theming Custom · impertio-studio bundle
Use when building or customizing a theme in a shadcn ui project, wiring the dark mode toggle, replacing the default primary color with a brand color, copying the output of the ui.shadcn.com themes builder into globals.css, or overriding the styling of one specific component instance without touching the global tokens. This is the end-to-end workflow recipe : the token catalog, oklch versus HSL format split, and v3 versus v4 wiring rules live in shadcn-core-theming. Prevents the flash-of-unstyled-content on first paint that comes from a missing suppressHydrationWarning, the silent "bg-primary did not change" symptom that comes from editing tokens without re-running the dev server, the two-ThemeProvider double-mount that breaks the toggle, the next-themes attribute mismatch that disables Tailwind's dark variants, and the brand-color contrast trap that ships an inaccessible palette. Covers the three-step theme-builder workflow (pick base style and radius, pick primary, copy CSS), the Tailwind v3 globals.css plus

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Shadcn Impl Form Validation · impertio-studio bundle
Use when building an end-to-end form workflow in shadcn ui that combines the Form composition primitives with react-hook-form and zod, when wiring the full pipeline from zod schema to typed submit handler to server-error display, when adding async validation (email availability, username taken, coupon check), when surfacing API errors back to a specific field via setError, when toggling a submit button between idle, submitting, success, and disabled states, when resetting a form after successful submit to clear stale state, when building a multi-step wizard that preserves form state across pages, or when wiring a file upload control into the react-hook-form value tree. Prevents the common end-to-end form failures: defining the zod schema inside the component so the resolver re-creates every render, mixing schema validation with manual setError on the same field so the two systems race and the user sees flickering error text, omitting form.handleSubmit on the form element so the browser submits natively and re

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Shadcn Syntax Variant Cva · impertio-studio bundle
Use when defining or modifying variants on a shadcn ui component, writing a new component that needs `variant` / `size` props, extending the Button with a custom variant, debugging why a `className` override is not winning, or inferring TypeScript props from a `cva()` call. Prevents the common mistakes : concatenating Tailwind class strings with `+ " "` instead of `cn()`, forgetting `tailwind-merge` so duplicate utilities leak through, mis-ordering `compoundVariants` so the override loses to the default, omitting `VariantProps` so consumers cannot extend the component type, and re-implementing variant logic with hand-written `if`-branches that destroy type inference. Covers the full `cva(base, config)` signature (base as string or string array, `variants`, `compoundVariants`, `defaultVariants`), the `VariantProps<typeof X>` inference pattern, the canonical `cn(...inputs)` helper composition of `clsx` plus `twMerge`, the evaluation order (default then variant then compound), and the Radix `Slot` (`asChild`) po

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Shadcn Syntax Toast Sonner · impertio-studio bundle
Use when adding, debugging, or migrating notification toasts in a shadcn ui project, mounting the top-level `<Toaster />` in your app root, calling `toast()` / `toast.success` / `toast.error` / `toast.warning` / `toast.info` / `toast.loading` / `toast.promise`, configuring the Toaster's `position`, `duration`, `expand`, `richColors`, or `closeButton` props, dismissing a toast programmatically via `toast.dismiss(id)`, wrapping a fetch / mutation with `toast.promise` for the loading -> success / error state machine, or removing dead `useToast()` hook calls left over from a pre-2026 shadcn project. Prevents the canonical toast failures : trying to import `useToast` from `@/components/ui/use-toast` (the file no longer exists ; the hook + the Radix-based Toast component were REMOVED per the shadcn 2026 changelog), calling `toast()` before any `<Toaster />` is mounted (the call is silently dropped), mounting two `<Toaster />` instances and getting duplicated stacks, calling `toast()` from inside a React Server Comp

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Shadcn Agents Cva Validator · impertio-studio bundle
Use when reviewing, validating, or auditing a shadcn ui component that uses class-variance-authority (cva), when an LLM has just produced a Button-like, Badge-like, Alert-like, or any other cva-driven component and you must verify the variant API before accepting the diff, when a consumer className does not visually win and you suspect cva merge order or a missing cn() call, when extending an existing shadcn component with a new variant or compoundVariant and you want a deterministic checklist before commit, when porting a hand-written variants-via-if-branches component to cva, when writing a custom primitive that should follow the shadcn convention, when verifying that VariantProps inference is exported so consumers can extend the component type, or when running a code-review pass on AI-generated cva code to catch the canonical mistakes (nested cn inside cva, compoundVariants placed before variants, missing defaultVariants, raw className concatenation, asChild without Slot, variant key typos that silently di

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Shadcn Impl Component Install · impertio-studio bundle
Use when adding a new component to a project that already uses shadcn, when bootstrapping shadcn for the first time in a fresh app, when deciding between `shadcn add`, a hand-built primitive, or a pre-built block, when wiring path aliases (tsconfig paths or the new package.json#imports resolver from shadcn@4.7.0), when re-running `add` against a file you have already customised, or when an `add` invocation has surfaced broken imports or missing radix dependencies. Prevents the silent-overwrite destruction from running `add --overwrite` without `--diff` first, the broken-imports trap from running `add` before `init`, the alias-mismatch bug where `tsconfig` paths and `components.json` aliases disagree, the bypass-the-CLI mistake of pip-installing `@radix-ui/react-*` packages by hand instead of letting `add` resolve them, and the long-tail stale-code problem from never re-running the CLI after upstream bug fixes ship. Covers the full add-or-customise-or-block decision tree, the init-then-add-then-customise workf

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Shadcn Agents Form Validator · impertio-studio bundle
Use when validating a react-hook-form + zod + shadcn Form integration in a code review, a draft AI-generated form, or a bug report ("my validation does not trigger", "the error message never shows", "the Select does not bind", "submit fires but values are undefined", "the field reads as uncontrolled then controlled"), when auditing whether a zod schema and a shadcn Form composition agree on every field name, when verifying Controller-vs-register correctness for custom controls (Select, Checkbox, RadioGroup, Switch, DatePicker, Combobox), when confirming every FormField has a FormMessage so zod errors are visible to the user, when checking that defaultValues covers every schema key (no undefined-to-string controlled / uncontrolled warning), when verifying the submit handler is wrapped in form.handleSubmit, when checking that zodResolver is actually passed to useForm, when ensuring no nested FormProvider / shadcn Form context is duplicated, and when emitting a structured pass / fail verdict over a form code blo

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Shadcn Syntax Menu Primitives · impertio-studio bundle
Use when adding, debugging, or refactoring any shadcn ui menu surface : DropdownMenu (button-triggered popup), ContextMenu (right-click on an area), Menubar (horizontal File / Edit / View desktop-app bar), or NavigationMenu (site-wide nav with viewport + mega-menu content). Picks the correct primitive family from the interaction model rather than from the visual shape, composes the shared Radix Menu surface (Root / Trigger / Content / Item / Group / Label / Separator / CheckboxItem / RadioGroup / RadioItem / Sub / SubTrigger / SubContent / Portal / Shortcut), and wires CheckboxItem / RadioGroup state, sub- menus, item shortcuts, and the special NavigationMenu surface (List / Item / Trigger / Content / Link / Indicator / Viewport). Prevents the canonical menu failures : stripping `"use client"` from the menu file so DropdownMenu / ContextMenu / Menubar break with a hydration error, reaching for DropdownMenu when the UX is a right- click context menu (or vice versa), nesting MenubarSeparator outside MenubarCont

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Shadcn Errors Radix Controlled · impertio-studio bundle
Use when a shadcn Dialog / Sheet / Drawer / DropdownMenu / Popover / HoverCard / Select / AlertDialog / ContextMenu / Collapsible / Accordion / Tabs is stuck open, refuses to close, never opens, fires `onOpenChange` at unexpected times, drops focus after a form submit, crashes with "React.Children.only expected to receive a single child" when wrapped in `asChild`, renders behind another element with higher z-index, anchors its popper to the wrong position inside a `transform`ed parent, traps focus inside the wrong container, or swallows the Escape key. Prevents the half-controlled state trap (passing `open` without `onOpenChange` makes the primitive read-only and uncloseable), the `asChild` Slot crash (Slot accepts exactly one child and that child MUST forward refs), the `asChild` silent-prop- swallow (a `<div>` child ignores `onClick` and `aria-*` that Slot forwards), the Portal stacking-context trap (a `transform` / `filter` / `perspective` / `will-change` ancestor reroots the popper coordinate system), the

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Shadcn Errors CLI Sync Mismatch · impertio-studio bundle
Use when re-running `shadcn add <component>` would overwrite a file in `components/ui/` that you have edited locally, when a teammate reports that "the CLI wiped my changes", when deciding whether to update a shadcn component to pick up upstream fixes (Calendar v9, cmdk break, security patch) without losing custom variants, or when you need a deterministic strategy to keep custom code alive across `--overwrite` runs. Prevents the silent-destruction trap where `pnpm dlx shadcn@latest add button --overwrite` blasts local edits with zero confirmation, the miss-the-upstream-fix trap where teams freeze a component and stop receiving critical patches, and the inline-custom-variants trap where edits embedded directly in `components/ui/<name>.tsx` are unrecoverable after a re-add. Covers the diff-first workflow with `add --diff`, the three resolution strategies (vendor / diff-merge / fork), the custom-variants-in-a-separate-file pattern that survives any re-add, pre-update git hygiene, the `migrate icons` and `migrat

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Shadcn Errors Styling Conflicts · impertio-studio bundle
Use when a className override on a shadcn component does not visually take effect, when two Tailwind utility classes appear in the rendered DOM but only one applies, when a cva variant looks correct in code but the consumer className does not win, when porting code from Tailwind v3 to v4 and class semantics shift, when adding arbitrary values (bg-[#fff], size-[28px]) next to preset utilities, when the important modifier (! prefix in v3, suffix in v4) behaves unexpectedly, when a component built with cva looks unstyled or doubled-up, or when reviewing PRs that build className strings with template literals or string concatenation. Prevents the canonical class-merging bugs: skipping cn() so duplicates leak through the DOM, calling cn() inside cva (no-op since cva already runs clsx), assuming the important modifier always overrides plain utilities, mixing arbitrary properties with their preset equivalents, and applying v3-only class names in a v4 project. Covers the cn() helper rule (clsx + tailwind-merge wrappe

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Shadcn Impl Framework Integration · impertio-studio bundle
Use when initializing shadcn ui inside a Vite, Next.js (App or Pages Router), React Router v7 (former Remix), Astro, or TanStack Start project, or when diagnosing per-framework init issues like wrong rsc flag, broken `@/*` alias resolution, or missing ThemeProvider wiring. Prevents the recurring failure mode where the CLI is run with the wrong `-t` template and produces a `components.json` whose `rsc` value mismatches the framework's RSC capability, silently dropping `"use client"` directives in Vite or duplicating them in Next.js. Covers per-framework init commands, the four alias-resolution systems (tsconfig paths for Next/Vite/React-Router, package.json#imports for TanStack Start, astro.config + tsconfig for Astro), components.json defaults per framework, Tailwind v3 vs v4 wiring per framework, and the three distinct ThemeProvider patterns (next-themes for Next.js, custom React Context for Vite/React-Router/TanStack Start, inline script for Astro). Keywords: shadcn vite, shadcn nextjs, shadcn nextjs app ro

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Shadcn Syntax Layout Primitives · impertio-studio bundle
Use when adding, debugging, or refactoring any of the four shadcn ui layout-helper primitives : Resizable (drag-to-resize split panes), ScrollArea (custom-styled scrollable region with a Radix scrollbar), Separator (horizontal or vertical divider), or AspectRatio (lock a container to a width:height ratio like 16/9, 1/1, 9/16). Composes the right subcomponents per primitive (ResizablePanelGroup / ResizablePanel / ResizableHandle ; ScrollArea / ScrollBar ; Separator with orientation + decorative ; AspectRatio with ratio), wires their prop surfaces against the underlying libraries (react-resizable-panels v4 for Resizable, Radix UI for ScrollArea / Separator / AspectRatio), and explains the `"use client"` story per primitive (all four ship with `"use client"` in the v4 registry source, contrary to the "pure-styling = server-safe" rumor). Prevents the canonical layout-helper failures : rendering a ResizablePanel outside a ResizablePanelGroup so react-resizable- panels crashes ("Panel components must be rendered wi

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Shadcn Agents Component Selector · impertio-studio bundle
Use when a user describes a UI requirement in plain English ("a modal to edit a record", "a searchable dropdown of countries", "show a non-blocking success message", "a right-click menu on a table row", "a sortable table of users") and the correct shadcn primitive is not yet obvious, when an existing implementation picks the wrong shadcn component for the interaction model ("Dialog used as a mobile bottom-sheet", "Select used for a 200-item searchable list", "Tooltip used for content with a link inside", "Toast (Sonner) used for a destructive confirmation"), when validating a code-review or AI-generated draft against the shadcn component catalogue, when choosing between Dialog vs Sheet vs Drawer, Select vs Combobox vs Command, DropdownMenu vs ContextMenu vs Menubar vs NavigationMenu, Tooltip vs HoverCard vs Popover, Button vs Link vs asChild composition, Toast (Sonner) vs Alert vs AlertDialog, Card vs Skeleton vs Spinner for loading states, Form (react-hook-form) vs Field (new 2026 primitive) for form composi

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Shadcn Errors Cmdk Version Drift · impertio-studio bundle
Use when a shadcn ui Command primitive (command palette, Combobox, search list, fuzzy filter, multi-select dropdown) stops filtering, renders the full list regardless of typing, fails to highlight or click items, throws "TypeError : undefined is not iterable (cannot read property Symbol(Symbol.iterator))" on a CommandItem rendered outside CommandList, silently ignores a third `keywords` argument passed to the `filter` prop, no longer matches values typed in uppercase, loses keyboard focus inside a Vaul Drawer, returns zero results despite `shouldFilter={false}`, or fails to import `CommandLoading` from the shadcn wrapper. Prevents the six recurring drift traps : (1) writing a 2-arg `(value, search) => number` filter against cmdk >= 1.0.0 where the signature is `(value, search, keywords) => number` so the third argument is silently dropped and per-item `keywords` boosting never fires, (2) writing a custom `filter` that does a case-sensitive `===` or `includes` check against raw `value` and raw `search` so that

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Shadcn Errors React Day Picker V9 · impertio-studio bundle
Use when a shadcn `Calendar` (or any direct `react-day-picker` DayPicker) silently renders nothing, throws a TypeScript error on the `selected` prop, loses every CSS rule after a `react-day-picker` upgrade, shows an unstyled grid of buttons, fails to compile a custom `Caption` / `Day` / `IconLeft` / `IconRight` component, fires a Matcher warning for `disabledDays`, ignores `selectedDays` entirely, throws "DayPickerProps is not a function" or "Cannot read properties of undefined (reading 'mode')", crashes after `npm install react-day-picker@9` on a code base that pre-dates the v9 release, or no longer responds to the `fromMonth` / `toMonth` boundary props. Prevents the v8 syntax in v9 trap (the file compiles but the calendar is read-only, invisible, or unstyled because every prop name moved), the missing `mode` prop trap (v9 makes `mode` mandatory on every `selected` usage and TypeScript fails the type narrowing), the classNames-with-old-keys trap (v9 keys every entry by a `UI` enum string like `day_button` /

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Shadcn Syntax Calendar Datepicker · impertio-studio bundle
Use when adding, customising, or debugging a shadcn ui Calendar or Date Picker, choosing between the three react-day-picker v9 selection modes (single / multiple / range), typing the `selected` state and the `onSelect` callback for each mode (Date vs Date[] vs DateRange), wiring a DatePicker by composing Calendar inside a Popover with a Button trigger that formats the date via date-fns, localising the calendar to Dutch / German / French via the `dateLib` adapter, disabling specific dates with a `disabled` matcher or a date-fns predicate, styling the calendar via `classNames` + `modifiers` + `modifiersClassNames`, swapping the day renderer through the `components` prop, or migrating an existing Calendar file from react-day-picker v8 to v9 after running `shadcn add calendar --overwrite`. Prevents the canonical Calendar failures : omitting the required `mode` prop so TypeScript narrows `selected` to `undefined` and the calendar never marks any day as selected, importing v8-only props (`selectedDays`, `disabledDa

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Shadcn Impl Responsive Dialog Drawer · impertio-studio bundle
Use when building a modal surface that must look correct on both desktop and mobile in shadcn ui, when the design calls for a centered Dialog on large screens but a bottom-sheet Drawer on phones, when the user reports that the current Dialog feels cramped on a phone or that the on-screen keyboard covers the form fields, when wiring a delete-confirmation, edit-profile, filter-panel, share-sheet, or settings modal that must respect platform conventions (native swipe-down dismiss on iOS / Android), when building a responsive Combobox where the dropdown must become a full-height Drawer on mobile, when porting an existing Dialog to also work well on touch devices, or when the user asks "how do I make a responsive modal". Prevents the recurring failure modes of an ad-hoc responsive modal: rendering BOTH the Dialog and the Drawer simultaneously so two open surfaces appear at once and the ARIA tree has duplicate role=dialog nodes, calling useMediaQuery without an SSR guard so Next.js logs a hydration mismatch on ever

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Shadcn Impl Rsc Vs Client Boundaries · impertio-studio bundle
Use when wiring shadcn components into a Next.js App Router project, when deciding whether a given shadcn primitive needs a `"use client"` directive, when seeing the "Error: useState is not a function" or "Cannot read properties of null (reading useContext)" hydration errors from a Radix primitive in a server component, when designing the server-shell-plus-client-island layout for a page, when wrapping a context-providing library (next-themes, TanStack Query, jotai, zustand) for the App Router, or when the `rsc` field in `components.json` is set but the generated component file is still missing the directive. Prevents the over-clientification anti-pattern of marking the whole layout `"use client"` (defeats the streaming + RSC bundle savings of App Router), the missing-directive crash where a Radix-state component (Dialog, Select, Sidebar) renders on the server and throws `useState is not a function`, the forgotten Provider wrapper where next-themes ThemeProvider is imported directly into a server layout and c

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Shadcn Agents Rsc Boundary Validator · impertio-studio bundle
Use when auditing a Next.js App Router codebase that consumes shadcn ui for misplaced or missing `"use client"` directives, when reviewing a pull request that adds shadcn primitives and you must confirm the boundary is correct before merging, when a build fails with the `useState is not a function` / `Cannot read properties of null (reading useContext)` Radix hydration crash, when `components.json` has been edited (toggled `rsc:true` <-> `rsc:false`, or added to a Vite / Astro / Pages-Router project where the flag must be `false`), when an AI-generated patch has slapped `"use client"` on `app/layout.tsx` or on every component file, when a Server Component tries to pass `onClick` / `onChange` / a class instance into a client child, when a Provider (next-themes ThemeProvider, TanStack Query QueryClientProvider, jotai Provider, zustand Provider, Sonner Toaster) has been imported directly into a server layout instead of through a thin client wrapper, or when a code-review checklist must enforce the RSC boundary r

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Shadcn Errors Tailwind V3 V4 Migration · impertio-studio bundle
Use when a shadcn ui project must move from Tailwind CSS v3 to v4, when colors break or look washed out after a Tailwind upgrade, when the dark mode toggle stops applying after switching the stylesheet, when `bg-background` renders transparent instead of the theme color, when `tailwindcss-animate` is missing in `package.json` but components still try to animate, when the Tailwind build emits "unknown at-rule @theme" or "unknown at-rule @custom-variant", when `tailwind.config.js` is still present in a project that imports the v4 stylesheet, when ring outlines on Button or Input changed thickness after the upgrade, when PostCSS fails with "tailwindcss is not a PostCSS plugin", or when AI-generated code mixes v3 syntax (`@tailwind base`, `hsl(var(--background))`, `darkMode: ['class']`) with v4 syntax (`@import "tailwindcss"`, `oklch()`, `@custom-variant dark`) in the same file. Prevents the canonical migration bugs: keeping `tailwind.config.js` alongside `@theme inline` so two config sources fight, leaving HSL s

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Shadcn Syntax Popover Tooltip Hovercard · impertio-studio bundle
Use when picking between Popover, Tooltip, and HoverCard for any floating panel above the page : a click-to-open form panel, a short hover hint on an icon button, a rich preview card that appears when the cursor lingers on a user mention, a date picker container, a filter popover, or any other "small panel anchored to an element" UX. Use when debugging why a Tooltip never appears (missing `TooltipProvider` at the app root), why a HoverCard flickers as the cursor passes over an avatar list (zero `openDelay`), why a Tooltip works on desktop but is invisible on iPad (Radix hides Tooltip on touch by design), why focus jumps to the body after a Popover closes (`modal={true}` focus-trap on a non-modal panel), or why a Popover refuses to close when controlled (passing `open` without `onOpenChange`). Use when choosing which primitive to install for an emoji-picker, a colour-picker, a notification preview, a profile-card preview on hover, a help-text hint on a form label, or a confirm-action popover. Prevents the cano

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Rust Syntax Macros Procedural · impertio-studio bundle
Use when the user writes a derive macro / attribute macro / function-like proc-macro, parses TokenStream with `syn`, generates code with `quote!`, reports errors with `syn::Error`, or sets up a proc-macro crate. Prevents mixing proc-macro and library code in same crate, missing `proc-macro = true`, using compiler-side `proc_macro` directly outside the entry point, or producing unhygienic identifiers. Covers: three macro kinds (derive / attribute / function-like), `proc_macro` (compiler), `proc_macro2` (testable wrapper), `syn` (parsing), `quote!` (generation), span-aware errors via `syn::Error::new_spanned`, hygiene differences vs macro_rules, re-exporting macros from parent crate. Keywords: proc-macro, "procedural macro", "#[derive]", "derive macro", "attribute macro", "function-like macro", "proc_macro = true", proc_macro, proc_macro2, syn, "syn::Parse", quote, "quote!", TokenStream, "syn::Error", "compile_error!", span, hygiene, "diagnostic", "do_not_recommend", "do I need syn", "what is quote".

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Rust Syntax Iterators Closures · impertio-studio bundle
Use when the user writes iterator chains (map / filter / fold / collect), implements `Iterator` manually, picks between `Fn` / `FnMut` / `FnOnce`, uses `move` closures, encounters closure capture-rules (edition 2021 disjoint captures), or writes async closures (1.85). Prevents using imperative loops where adapters fit, picking `FnOnce` when `Fn` would do, forgetting `move` for spawn-style closures, and confusing `collect` type inference. Covers: Iterator trait + Item type, adapters (map / filter / take / skip / fold / reduce / collect / sum / count / enumerate / zip / chain / flat_map), lazy evaluation, `collect::<Vec<_>>()` turbofish, custom Iterator impl, IntoIterator vs Iterator, `Fn` / `FnMut` / `FnOnce`, `move` closures, edition-2021 disjoint captures, async closures (1.85), returning closures (`Box<dyn Fn>` vs `impl Fn`). Keywords: Iterator, iter, "for loop", map, filter, fold, collect, "into_iter", "iter_mut", closure, "|x|", Fn, FnMut, FnOnce, "move closure", "async closure", "async ||", "disjoint cap

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Rust Syntax Macros Declarative · impertio-studio bundle
Use when the user writes a `macro_rules!`, debugs a macro hygiene issue, counts tokens via TT-munching, picks fragment specifiers, handles repetitions, or uses `$crate` for cross-crate macro references. Prevents fragment-specifier mismatches, identifier hygiene mistakes, missing `$crate` in exported macros, and naive recursion limits. Covers: `macro_rules!` declaration, all fragment specifiers (ident, expr, ty, pat, path, block, stmt, item, tt, meta, vis, literal, lifetime), repetition `$(...)+` `$(...)*` with separators, hygiene rules, `$crate`, TT-munching recursion, edition-2024 `expr` fragment widening, `macro_rules!` import scoping. Keywords: macro_rules, "declarative macro", "macro by example", fragment specifier, "ident expr ty pat path block stmt item tt meta vis literal lifetime", repetition, "$()*", "$()+", hygiene, "$crate", "TT munching", "recursion limit", "expr fragment 2024", "macro export", "macro_export", "macro_use", "what is $tt".

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Rust Impl Serde · impertio-studio bundle
Use when the user derives Serialize / Deserialize, writes custom impls, picks enum representation (externally / internally / adjacently / untagged), uses `flatten` / `with` / `rename_all`, or chooses between JSON / TOML / YAML / bincode. Prevents enum-rep ambiguity, forgetting `serde(borrow)` for zero-copy `&'a str`, picking untagged with overlapping fields, and deriving without enabling the `derive` feature. Covers: Serialize / Deserialize derives, container attributes (rename_all, deny_unknown_fields, transparent, default, tag, content), field attributes (rename, skip, skip_serializing_if, default, with, serialize_with, deserialize_with, flatten, alias, borrow), enum representations, custom impl when derive insufficient, serde_json common patterns, format-crate selection (TOML / YAML / bincode / MessagePack). Keywords: serde, Serialize, Deserialize, "#[derive(Serialize, Deserialize)]", rename, rename_all, "#[serde(...)]", flatten, with, "serialize_with", "deserialize_with", skip, "skip_serializing_if", defa

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Rust Impl No Std · impertio-studio bundle
Use when the user adds `#![no_std]`, supports embedded targets, needs the alloc crate, writes a `#[panic_handler]`, registers a `#[global_allocator]`, or designs a hybrid std + no_std library via feature flag. Prevents using std-only APIs in no_std, missing `#[panic_handler]`, picking alloc-free patterns when alloc is acceptable, and forgetting the `default = ["std"]` feature pattern. Covers: `#![no_std]` crate attribute, core crate (no allocation, no OS), alloc crate (Vec/Box/Rc/Arc/String when allocator available), `extern crate alloc;`, `#[panic_handler]` requirement when not std, `#[global_allocator]` hook, lang items (when needed in embedded), default = ["std"] feature pattern for hybrid library, testing no_std crates. Keywords: no_std, "#![no_std]", "no-std", embedded, core, alloc, "extern crate alloc", "panic_handler", "global_allocator", "lang items", "default = [std]", hybrid std, "no_std library", "no allocator", "embassy", "embedded Rust", "thumb target", "Cortex-M", "panic = abort", "core::fmt".

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Rust Impl Testing · impertio-studio bundle
Use when the user writes unit tests (`#[test]`), integration tests in `tests/`, doc tests, async tests, criterion benches, uses `cargo nextest`, or controls panicking tests via `#[should_panic]`. Prevents mixing integration tests in same crate, doc tests that compile only against stale signatures, async tests without runtime, and unguarded panicking tests. Covers: `#[test]` unit tests, `#[cfg(test)]` module convention, integration tests in `tests/` (each file is a separate crate), doc tests in /// comments, `cargo test --doc`, `#[should_panic]` / `#[should_panic(expected = "...")]`, `#[ignore]` for slow tests, `cargo nextest run`, property testing crates (proptest, quickcheck), snapshot testing (insta), criterion benches, common test helpers via `tests/common/mod.rs`. Keywords: test, "#[test]", "cargo test", "#[cfg(test)]", "tests directory", integration test, doc test, "cargo test --doc", "should_panic", ignore, "cargo test --ignored", "cargo nextest", nextest, criterion, benchmark, proptest, quickcheck, ins

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Rust Impl Channels · impertio-studio bundle
Use when the user picks a channel: std::sync::mpsc (sync), tokio::sync::mpsc (async), tokio::sync::oneshot (single value), tokio::sync::broadcast (fan-out), tokio::sync::watch (latest-value), crossbeam-channel (lock-free + sync), or flume (alternative with select!). Prevents blocking the async executor by using std::sync::mpsc, picking unbounded when bounded is needed for backpressure, and using oneshot where mpsc fits. Covers: std::sync::mpsc (Sender / Receiver / sync_channel), tokio::sync::mpsc (bounded + unbounded), tokio::sync::oneshot (send + recv), tokio::sync::broadcast (fan-out, lagging consumer recovery), tokio::sync::watch (overwritable latest value), crossbeam-channel (lock-free, select! macro), flume (alternative). Backpressure patterns (bounded mpsc, try_send vs send().await). Keywords: channel, mpsc, oneshot, broadcast, watch, "std::sync::mpsc", "tokio::sync::mpsc", "tokio::sync::oneshot", "tokio::sync::broadcast", "tokio::sync::watch", crossbeam, flume, "bounded channel", "unbounded channel", b

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Rust Impl Clap CLI · impertio-studio bundle
Use when the user builds a CLI with clap 4.x, uses derive Parser API or builder API, defines subcommands, custom value parsers, env-var fallback, or shell completions. Prevents picking builder when derive suffices, missing `--features = ["derive"]`, omitting `value_parser` for non-string types, and confusing `Args` group with `Subcommand`. Covers: derive Parser API (`#[derive(Parser, Args, Subcommand, ValueEnum)]`), builder API (when derive is insufficient), nested Subcommand enums, `value_parser` (custom + range), env var fallback `env = "VAR"`, defaults `default_value` / `default_value_t`, required vs optional args, multiple values, shell completions via `clap_complete`, `Args` for shared argument groups. Keywords: clap, "#[derive(Parser)]", Parser, Subcommand, Args, ValueEnum, "clap derive", "clap builder", "value_parser", env, "default_value", "default_value_t", "shell completion", "clap_complete", "command line", CLI, argparse, "parse_from", "Parser::parse", subcommand, "nested command", required, "long

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Rust Syntax Gats · impertio-studio bundle
Use when the user needs Generic Associated Types: `type Item<'a>` in a trait, the `LendingIterator` pattern, callback registries parameterised by lifetime, or families of types whose lifetime/type varies per call. Prevents reaching for higher-kinded-type work-arounds that have been obsolete since 1.65, missing required `where` clauses on GAT bounds, or confusing GATs with regular associated types. Covers: GAT syntax (`type Item<'a>` in trait + impl), lifetime GATs, the `LendingIterator` family, callback registries, type-parameter-by-lifetime patterns, GAT bound requirements (`where Self: 'a`). Keywords: GAT, "generic associated type", "type Item<'a>", "LendingIterator", "where Self: 'a", "associated type with lifetime", "associated type with generic", "lifetime in associated type", "stream of borrows", "self-borrow", "higher-kinded type Rust", "1.65 stabilization", lifetime GAT, type GAT.

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Rust Core Toolchain · impertio-studio bundle
Use when the user asks about the Rust toolchain: rustup (channels, components, targets), cargo subcommands, rustc flags, clippy lint categories, rustfmt configuration, MSRV management, or how to set up a Rust workspace. Prevents using the wrong channel, missing required components, ignoring clippy categories, or making code unbuildable on the project's MSRV. Covers: rustup (channels stable/beta/nightly, components rustfmt/clippy/rust-src/rust-analyzer, `rustup target add`, `rust-toolchain.toml` override), cargo (most-used subcommands), rustc (edition flag, target triple, optimization levels), clippy (7 lint categories), rustfmt (edition-aware), MSRV management via `rust-version`. Keywords: rustup, cargo, rustc, clippy, rustfmt, toolchain, "install Rust", channel, stable, beta, nightly, "what command", component, target triple, "rust-toolchain.toml", optimization level, lint categories, correctness, pedantic, "how do I lint", "format Rust", MSRV, rust-version, "cargo build", "cargo check", "cargo test".

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Rust Errors Async · impertio-studio bundle
Use when the user hits "future cannot be sent between threads safely", "future is not Send", Pin/Unpin errors, lifetime errors inside an `async fn`, "cannot move out of pinned", or AFIT dyn-dispatch problems. Prevents holding a MutexGuard or Rc across `.await`, storing a non-Unpin future on the stack wrongly, and reflexively reaching for `async_trait` when AFIT now works. Covers: Future not Send (holding non-Send across .await: MutexGuard, Rc, RefCell::Ref), cannot-move-out-of-pinned, !Unpin future on stack, lifetime errors in async fn signatures, async fn in trait dyn-dispatch limits (when async_trait crate is still needed), tokio blocking-in-async runtime panics, block_on inside a running runtime; fix patterns. Keywords: "future is not Send", "future cannot be sent between threads", "cannot be sent between threads safely", "held across an await point", "MutexGuard across await", Pin, Unpin, "cannot move out of", "not Unpin", "async lifetime", "async fn in trait", AFIT, async_trait, "block_on", "blocking the

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Rust Impl Workspaces · impertio-studio bundle
Use when the user organises multiple crates into a Cargo workspace, sets up `[workspace.dependencies]` inheritance, manages member crates, chooses resolver 2 vs 3, or hits dependency drift across workspace members. Prevents dependency drift, repeated edition / rust-version specs across members, target-directory clutter, and accidental member-exclude. Covers: virtual workspace (top-level Cargo.toml with `[workspace]` only), workspace inheritance (`workspace = true`, `[workspace.dependencies]`, `[workspace.package]`, `[workspace.lints]`), member discovery (`members = []`, `default-members`, `exclude`), shared target directory, resolver versions 2 and 3 (when each matters), member-specific dependencies dev vs prod. Keywords: workspace, "Cargo workspace", "[workspace]", "virtual manifest", "workspace.dependencies", "workspace.package", "workspace.lints", "workspace = true", inheritance, "default-members", "exclude member", "shared target", "resolver = 2", "resolver = 3", "MSRV resolver", "multi-crate", monorepo,

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Rust Syntax Traits · impertio-studio bundle
Use when the user defines or implements a trait, asks about default methods / supertraits / marker traits / blanket impls / sealed traits, encounters orphan-rule errors, or needs to choose between inherent impl and trait impl. Prevents orphan-rule violations, accidentally exposing an extensible trait users can implement, and confusing inherent vs trait methods. Covers: trait definition syntax (required + default methods), supertraits, marker traits (Send / Sync / Sized / Copy / Unpin), blanket impls, sealed trait pattern, inherent vs trait impl, orphan rule + coherence, derive macros (Copy / Clone / Debug / PartialEq / Eq / Hash / Default). Keywords: trait, "trait definition", "default method", supertrait, "marker trait", "blanket impl", "sealed trait", "orphan rule", coherence, "inherent impl", "impl Trait for Type", "newtype wrapper", "cannot impl foreign trait", derive, "#[derive]", "method not found", E0117, E0119, E0120, E0210, "what does trait do", "how to add method".

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Rust Syntax Unsafe · impertio-studio bundle
Use when the user writes `unsafe fn` or `unsafe { }` blocks, dereferences raw pointers, calls FFI, uses `transmute`, deals with `MaybeUninit`, asks about undefined behavior, runs `miri`, or works with strict-provenance APIs (1.84). Prevents UB via aliasing violations, deref of a dangling pointer, breaking auto-trait invariants, missing `unsafe_op_in_unsafe_fn` warnings in edition 2024, and skipping `// SAFETY:` comments. Covers: the 8 superpowers post-2024 (deref raw ptr, call unsafe fn, access mut static, impl unsafe trait, union field, unsafe extern blocks, target_feature, unsafe attributes), undefined-behavior enumeration verbatim from the Reference, strict-provenance APIs (1.84: `expose_provenance`, `with_addr`, `map_addr`, `addr_of!`, `addr_of_mut!`), `unsafe_op_in_unsafe_fn` warn-by-default in 2024, soundness contracts, raw pointers vs references, `transmute`, `MaybeUninit`, `UnsafeCell`, miri verification. Keywords: unsafe, "unsafe fn", "unsafe block", "raw pointer", "*const", "*mut", "deref pointer",

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Rust Core Type System · impertio-studio bundle
Use when the user needs to understand Rust's type system fundamentals: nominal typing, zero-sized types, repr attributes, niche optimization, primitive types, the never type, type-state pattern, or const generics. Prevents misusing repr(C) when default repr suffices, packing types unsafely, assuming structural typing, or surprises with edition-2024 never-type fallback. Covers: nominal vs structural, ZST + PhantomData, repr (Rust/C/transparent/packed/align), niche optimization (NonZero, Option<NonNull>), primitives (integers/floats/bool/char/unit), never type `!` and edition-2024 fallback change, type-state pattern, const generics overview. Keywords: type system, nominal typing, zero-sized type, ZST, PhantomData, repr C, repr transparent, repr packed, niche optimization, NonZero, never type, "!", bottom type, divergence, type state, const generics, primitive types, "what is unit", "how big is", layout, alignment, "Option<NonZeroU32> size", "what is a tag", edition 2024 fallback.

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Rust Errors Runtime · impertio-studio bundle
Use when a Rust program panics at runtime: index out of bounds, unwrap on None / Err, integer overflow, division by zero, or the user must choose panic = "unwind" vs "abort", read a backtrace, or guard an FFI boundary with catch_unwind. Prevents shipping `.unwrap()` on fallible paths, relying on unwind across an FFI boundary, and being surprised that release builds wrap integer overflow. Covers: panic mechanics (panic! macro, unwind vs abort, drop during unwind), RUST_BACKTRACE=1 / full, debug-assertions (on in dev, off in release), integer overflow (panics in dev, wraps in release, overflow-checks override), division by zero, slice index out of bounds vs `.get()`, panic = "abort" profile tradeoffs, catch_unwind for FFI, process::abort vs process::exit. Keywords: panic, "thread panicked", "index out of bounds", "called unwrap on", "unwrap on None", "unwrap on Err", "attempt to add with overflow", "integer overflow", "divide by zero", "attempt to divide by zero", RUST_BACKTRACE, backtrace, "unwind", "abort", "

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Rust Impl Async Tokio · impertio-studio bundle
Use when the user sets up a tokio runtime, spawns tasks, uses `select!`, applies timeouts, manages cancellation, uses `JoinSet` for structured concurrency, or chooses between current_thread and multi_thread runtime. Prevents blocking the executor with sync code, missing #[tokio::main], misusing block_on, and ignoring task-cancellation semantics. Covers: runtime setup via `#[tokio::main]` or `tokio::runtime::Runtime::new`, `tokio::spawn` vs `spawn_blocking` vs `task::block_in_place`, JoinHandle (abort, abort_handle, .await), `select!` macro (branches, biased mode, fallback), timeouts (`tokio::time::timeout`), cancellation via drop, `JoinSet` for structured concurrency (ordered + unordered joining), `tokio::task_local!`, blocking-in-async detection. Keywords: tokio, "#[tokio::main]", "tokio::spawn", spawn_blocking, "block_in_place", JoinHandle, "tokio::select!", select macro, timeout, "tokio::time::timeout", cancellation, "drop cancel", JoinSet, "structured concurrency", "task_local", current_thread, multi_thre

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Rust Impl Concurrency · impertio-studio bundle
Use when the user picks between Mutex / RwLock / atomics, designs Arc<Mutex<T>> patterns, deals with Mutex poisoning, uses scoped threads (1.63+), or needs Ordering enum for atomics. Prevents lock-ordering deadlocks, choosing Mutex when atomic suffices, ignoring poisoning, and Send/Sync mismatches. Covers: Arc<Mutex<T>> (thread-safe shared mutable state), Arc<RwLock<T>> (many readers OR one writer), atomics (AtomicBool / AtomicUsize / AtomicPtr / Ordering enum Relaxed/Acquire/Release/AcqRel/SeqCst), Mutex poisoning (.lock() returns Result), parking_lot (no poisoning, faster contention), lock ordering, scoped threads (std::thread::scope, 1.63+), thread_local!, compare-and-swap. Keywords: concurrency, "Arc<Mutex>", "Arc<RwLock>", Mutex, RwLock, atomic, AtomicBool, AtomicUsize, AtomicPtr, Ordering, Relaxed, Acquire, Release, AcqRel, SeqCst, "lock poisoning", "PoisonError", parking_lot, "lock ordering", "deadlock prevention", "scoped threads", "thread::scope", thread_local, "compare-and-swap", CAS, fetch_add, loc

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Rust Impl Ffi Bindgen · impertio-studio bundle
Use when the user binds a Rust library to C (cbindgen) or imports a C library into Rust (bindgen), declares `extern "C"` functions, uses `#[repr(C)]` types, manages opaque pointers, or works with file descriptors via `BorrowedFd` / `OwnedFd`. Prevents `unsafe extern` requirement misses in 2024, `Box<dyn Fn>` callback ABI issues, raw `c_char` ownership confusion, and fd-leak via raw `RawFd`. Covers: C FFI patterns (`extern "C"`, `#[repr(C)]`, `#[unsafe(no_mangle)]` in 2024, `unsafe extern` block in 2024), bindgen workflow (build.rs config, header inclusion, allowlist / blocklist), cbindgen workflow (cbindgen.toml, generate C header from Rust API), opaque types (pointer-to-incomplete pattern), string passing (CString / CStr / *const c_char), error handling across FFI, function-pointer callbacks, `BorrowedFd` / `OwnedFd` / `AsFd` / `AsRawFd` for unix fd safety, Drop guards for foreign resources. Keywords: FFI, "extern C", "#[repr(C)]", "#[no_mangle]", "#[unsafe(no_mangle)]", "unsafe extern", bindgen, cbindgen, "

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Rust Core Memory Model · impertio-studio bundle
Use when the user needs the conceptual overview of Rust memory: ownership, move vs copy vs clone, drop semantics, RAII, stack vs heap, smart pointer choice (Box / Rc / Arc), interior mutability (Cell / RefCell / Mutex), or Send/Sync auto-traits. Prevents misusing clone() to silence the borrow checker, picking Arc<Mutex> when atomic suffices, treating Rc as thread-safe, or forgetting that Drop runs even on panic. Covers: ownership rules, move semantics, Copy/Clone/Drop traits, RAII, stack vs heap, niche optimization mention, Box/Rc/Arc semantic differences, Cell/RefCell/UnsafeCell, Send/Sync overview. Keywords: ownership, move, copy, clone, drop, RAII, stack vs heap, Box, Rc, Arc, RefCell, Cell, Mutex, Send, Sync, interior mutability, "why do I need to clone", "moved value error", "cannot borrow", memory layout, "double free", "what is Drop", smart pointer, reference counting, ownership transfer, "what does &str cost", auto trait.

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Rust Syntax Generics · impertio-studio bundle
Use when the user writes generic functions / types / impl blocks, needs trait bounds, where clauses, const generics, or wonders about monomorphization vs dyn dispatch trade-offs. Prevents over-constraining with `'static`, mixing up trait-bound syntax, or assuming generic Rust code emits runtime polymorphism (it doesn't, it's monomorphized). Covers: type parameters `<T>`, trait bounds `T: Trait`, multiple bounds with `+`, `where` clauses, monomorphization implications (code-size, compile-time), const generics (`N: usize`, where they can/cannot appear), generic lifetime parameters mixed with type parameters, default generic types (`<T = Default>`). Keywords: generic, "type parameter", "<T>", "trait bound", "where clause", "T: Trait", monomorphization, "code bloat", "const generic", "N: usize", "generic function", "generic struct", "generic impl", "default generic type", PhantomData generic, "compile time generics", "expanded at compile time", "generic over".

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Rust Core Async Runtime · impertio-studio bundle
Use when the user needs the conceptual overview of Rust async: the Future trait, how executors work, Send across .await, Pin/Unpin overview, the choice between tokio/async-std/smol/embassy runtimes, and structured concurrency basics. Prevents picking the wrong runtime, blocking the executor with sync code, holding non-Send across .await, ignoring the waker contract, or confusing async fn with parallel execution. Covers: Future trait + Poll, waker contract, executor model, Send across .await rules, Pin/Unpin overview, runtime choice matrix (tokio multi-thread default, async-std mostly-deprecated, smol minimalist, embassy embedded), structured concurrency overview (JoinSet, parent-child task lifetime). Keywords: async runtime, Future trait, Poll, executor, tokio, async-std, smol, embassy, "what is .await", "how does async work", waker, Pin, Unpin, Send across await, structured concurrency, JoinSet, "async fn doesn't run", "future never completes", multi-thread vs current-thread, "which runtime", "block on", tas

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Rust Errors Lifetimes · impertio-studio bundle
Use when the user hits lifetime-related error codes E0106 / E0623 / E0495 / E0700 / E0759 / E0515, or wonders why elision didn't infer their lifetime, or how the 2024 RPIT capture default broke a 2021 signature. Prevents reflexively adding `'static`, missing the `+ use<'a, T>` 2024 opt-out, or restructuring an API when adding a lifetime annotation would suffice. Covers: E0106 missing lifetime specifier, E0623 lifetime mismatch (input vs output), E0495 cannot infer appropriate lifetime, E0700 hidden type captures lifetime not in scope (RPIT 2021 vs 2024), E0759 lifetime of reference outlives lifetime of borrowed content, E0515 returns reference to local variable; fix patterns: explicit annotation, HRTB, 'static bound (when sound), restructure to remove borrow, `+ use<...>` opt-out for RPIT 2024. Keywords: E0106, E0623, E0495, E0700, E0759, E0515, "missing lifetime", "missing lifetime specifier", "lifetime mismatch", "cannot infer appropriate lifetime", "hidden type captures lifetime", "outlives", "doesn't live

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Rust Impl Build Scripts · impertio-studio bundle
Use when the user writes a `build.rs`, generates code into `OUT_DIR`, links native libraries, triggers rebuilds via `cargo:rerun-if-changed`, sets `cargo:rustc-cfg`, or detects platform capabilities at build time. Prevents stale builds from missing `rerun-if-changed`, code generation in `src/`, native library link order mistakes, and missing `cargo:warning=` for non-fatal hints. Covers: build.rs basics (runs before package compile), `OUT_DIR` env var, directives (`cargo:rerun-if-changed=PATH`, `cargo:rerun-if-env-changed=VAR`, `cargo:rustc-cfg=KEY[=VALUE]`, `cargo:rustc-env=KEY=VALUE`, `cargo:rustc-link-lib`, `cargo:rustc-link-search`, `cargo:warning=`), generating code into `OUT_DIR` + `include!`, linking native libraries, bindgen workflow inside build.rs. Keywords: build.rs, "build script", "OUT_DIR", "cargo:rerun-if-changed", "cargo:rerun-if-env-changed", "cargo:rustc-cfg", "cargo:rustc-env", "cargo:rustc-link-lib", "cargo:rustc-link-search", "cargo:warning", "include!", "code generation", "build dependenc

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Rust Impl Cargo Project · impertio-studio bundle
Use when the user sets up a new Cargo crate, edits Cargo.toml, adds dependencies, configures features (additive principle), tunes profiles, uses `[patch]` / `[replace]`, declares lints in `[lints]`, or wants the MSRV-aware resolver behavior (1.84). Prevents non-additive feature design, mixing dev with build dependencies, accidental release-profile overrides, and missing `rust-version` declarations. Covers: `cargo new` vs `cargo init` (lib / bin), Cargo.toml structure ([package], [dependencies], [dev-dependencies], [build-dependencies], target-specific deps), version requirements (caret / tilde / exact / wildcards), features (additive principle, `dep:` prefix, weak `?` deps, default features), profiles (dev / release / test / bench / custom), `[patch]` and `[replace]`, `[lints]` table (recent stabilization), MSRV-aware resolver (1.84), `package` metadata fields. Keywords: cargo, "Cargo.toml", "cargo new", "cargo init", "cargo add", dependencies, features, "default features", "no-default-features", "dep:" prefi

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Rust Impl Cross Compile · impertio-studio bundle
Use when the user cross-compiles to another target triple, uses `rustup target add`, uses the `cross` crate, configures per-target linker via `.cargo/config.toml`, or guards code with `cfg(target_os = "...")`. Prevents missing target triple installation, picking wrong target for the use case (musl vs gnu, msvc vs gnu on Windows), and using `cfg` without `cfg_attr` for selective attributes. Covers: target triple format (arch-vendor-os-env), common triples (x86_64-unknown-linux-gnu, x86_64-unknown-linux-musl, aarch64-apple-darwin, x86_64-pc-windows-msvc, x86_64-pc-windows-gnu, wasm32-unknown-unknown, wasm32-wasi), `rustup target add`, `cargo build --target <triple>`, `cross` crate (container-based), conditional compilation `cfg(target_os = "...", target_arch = "...", target_pointer_width = "...", target_feature = "...")`, `cfg_attr`, `.cargo/config.toml` for per-target linker / runner. Keywords: "cross-compile", "cross compile", "target triple", "rustup target add", "cargo build --target", "cross crate", "musl

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Rust Syntax Borrowing · impertio-studio bundle
Use when the user writes code that triggers borrow-checker errors, asks "can I have & and &mut at the same time", encounters E0502 / E0499 / E0596, needs interior mutability (Cell / RefCell), splits a borrow across struct fields, or asks about reborrowing. Prevents borrow-checker fights via clone(), introduces interior mutability prematurely, or assumes NLL handles every case. Covers: `&T` (shared) vs `&mut T` (exclusive) rules, Non-Lexical Lifetimes (NLL), two-phase borrows, reborrowing, splitting borrows across struct fields and slices (`split_at_mut`), interior mutability (Cell for Copy, RefCell runtime-checked, Mutex thread-safe). Keywords: borrow, borrowing, "&", "&mut", "shared reference", "mutable reference", NLL, "non-lexical lifetimes", reborrow, "two-phase borrow", "split borrow", "split_at_mut", "interior mutability", Cell, RefCell, Mutex, E0502, E0499, E0596, "cannot borrow as mutable", "already borrowed", "multiple mutable borrows".

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Rust Syntax Lifetimes · impertio-studio bundle
Use when the user must write a lifetime annotation, encounters E0106 / E0623 / E0495 / E0700 / E0759, needs to understand the three elision rules, the 'static bound vs &'static T, HRTB `for<'a>`, lifetime subtyping, variance (covariant / contravariant / invariant), or edition-2024 RPIT precise-capturing. Prevents over-annotating, confusing `T: 'static` (no internal short borrow) with `&'static T` (reference lives for program), or missing variance-related compile failures. Covers: explicit annotations, three elision rules, `'static` two senses, HRTB, lifetime subtyping (`'a: 'b`), variance, NLL behaviour reminder, edition-2024 RPIT capture (`+ use<'a, T>`). Keywords: lifetime, "'a", "lifetime annotation", "missing lifetime", "lifetime elision", "elision rule", "for<'a>", HRTB, "higher-rank trait bound", "'static", "static bound", variance, covariance, contravariance, invariance, PhantomData lifetime, E0106, E0623, E0495, E0700, E0759, "hidden lifetime", "precise capturing", "use<>", "doesn't live long enough",

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Rust Syntax Ownership · impertio-studio bundle
Use when the user writes Rust code that triggers ownership-transfer compile errors, asks "why moved value", asks to choose between Copy / Clone / Drop, encounters E0382 / E0507 / E0509 / E0382, or needs to design APIs around ownership transfer. Prevents excessive cloning, accidental moves, Copy+Drop mistakes, partial-move confusion, and ownership patterns that defeat the borrow checker. Covers: the three ownership rules, move semantics (by-value transfer on assignment / fn arg / return), Copy trait (which types qualify, why String / Vec / Box do not), Clone trait, scope-based drop and explicit `drop()`, ownership transfer patterns (builder, into-impl, by-value method receivers), partial moves out of fields. Keywords: ownership, move, moved value, "use of moved value", E0382, E0507, E0509, "cannot move out of", Copy, Clone, Drop, "drop function", scope, "ownership transfer", "by value", partial move, "move out of borrowed content", builder pattern, into method, "do I need to clone", "why can't I use this".

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Rust Errors Build Link · impertio-studio bundle
Use when the user hits linker errors ("linker `cc` not found", "undefined reference to", "could not find native static library"), duplicate-symbol errors from multiple major versions in the dependency tree, MSRV mismatches, or surprising feature-unification behavior. Prevents blind `cargo clean`, ignoring `cargo tree -d` duplicate analysis, and treating a feature-unification surprise as a compiler bug. Covers: missing linker / build-essentials per OS, "undefined reference" (missing native lib, library order, build.rs link directives), "could not find native static library" (rustc-link-search path), duplicate symbols from multiple major versions (cargo tree -d, [patch], version unification), MSRV mismatch (dependency needs newer rustc), feature unification surprises, `cargo update -p` targeted upgrades, when `cargo clean` is and is not the answer. Keywords: "linker cc not found", "linker not found", "undefined reference", "could not find native static library", "note: ld returned", "duplicate symbol", "multipl

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Rust Impl Error Handling · impertio-studio bundle
Use when the user designs Result-returning APIs, picks between Result and panic, uses the `?` operator with From conversion, defines custom error types, or considers core::error::Error (1.81) vs std::error::Error. Prevents `.unwrap()` in library code, hidden panics in `?` chains via wrong From impl, mixing thiserror and anyhow in library context, and forgetting source chain for error context. Covers: Result<T, E> vs Option<T>, `?` operator + From conversion chain, custom enum / struct error types, From impls for error conversion, the Error trait (std::error::Error, core::error::Error since 1.81 for no_std), source-chain pattern, panic vs Result decision, Result combinators (map / map_err / and_then / or_else / ok_or). Keywords: Result, Option, "? operator", From, "error conversion", "Error trait", "std::error::Error", "core::error::Error", "1.81 core error", "custom error", "error type", "thiserror vs anyhow", "library error", "panic vs Result", "map_err", "and_then", "or_else", "ok_or", "source chain", ".unw

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797 published skills · page 6 of 8