docs(P06): complete languages-meta phase

CHANGELOG.md

@@ -0,0 +1,45 @@
+# Changelog
+
+All notable changes to the Atelier framework are documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+## [0.1.0] — 2026-08-05
+
+### Added
+- Eight core principles (C1–C8) in `core/first-principles.md` with definitions, precedence, and violation tables.
+- Formal conflict resolution procedure in `core/conflict-resolution.md` (hierarchy, precedence, worked examples, non-tradeable declarations).
+- Canonical reading order in `core/reading-order.md` with paths for agents, humans, conflict resolution, and review.
+- README with quickstart for AI agents and humans.
+- MIT license.
+- Eleven domain first-principles (P1–P10 each): UI/UX, API, Security, Data, Testing, Performance, Observability, Errors, Documentation, Concurrency, DevOps.
+- Twenty-seven domain derived/topic docs (REST, GraphQL, versioning, error-responses, pagination, authentication, authorization, input-validation, secrets, supply-chain, schema-design, migrations, indexing, pyramid, fixtures, frontend, backend, logging, metrics, tracing, tokens, copywriting, patterns, doc-templates, patterns, ci-cd, environments).
+- `matrix/principles-matrix.md` — full mapping of all 110 domain principles to core derivations.
+- `matrix/domain-coverage.md` — inverse mapping of core principles to domains.
+- `review/agent-checklist.md` — pre-completion gate for AI agents.
+- `review/peer-review-checklist.md` — human review checklist.
+- `review/anti-patterns.md` — catalog of violations with principle citations.
+- Four good worked examples: `examples/good/api-endpoint.md`, `react-component.md`, `db-schema.md`, `error-handler.md`.
+- Three bad worked examples: `examples/bad/god-object.md`, `silent-error.md`, `leaky-abstraction.md`.
+- Four language application docs: `languages/typescript.md`, `python.md`, `go.md`, `rust.md`.
+- `MANIFEST.md` — authoritative document index.
+- `CONTRIBUTING.md` — contribution guide.
+
+### Framework Properties
+- 8 core principles, 11 domains, 110 domain principles, all traced via the matrix.
+- NFR milestone type (documentation only, no runtime code).
+- Tags: v0.0.0 (pre-execution) through v0.0.7 (final review + ship).
+- The v0.0.7 patch release IS the v0.1.0 milestone deliverable.
+
+### Phases
+- Phase 0 (v0.0.0): pre-execution — specify, clarify, research, plan, ship.
+- Phase 1 (v0.0.1): core foundation — first-principles, conflict-resolution, reading-order, README, LICENSE.
+- Phase 2 (v0.0.2): domain first-principles — uiux first-principles + audit.
+- Phase 3 (v0.0.3): domain derived docs — 27 topic files.
+- Phase 4 (v0.0.4): matrix + review — domain-coverage, agent-checklist, peer-review-checklist, anti-patterns.
+- Phase 5 (v0.0.5): examples — 4 good + 3 bad.
+- Phase 6 (v0.0.6): languages + meta — typescript, python, go, rust, CHANGELOG, CONTRIBUTING.
+- Phase 7 (v0.0.7): final review + ship — milestone release.

CONTRIBUTING.md

@@ -0,0 +1,71 @@
+# Contributing to Atelier
+
+Thank you for considering a contribution to Atelier. This framework lives by its principles; contributions are expected to follow them.
+
+## What We Accept
+
+- **New domain first-principles** — if a domain is missing (e.g., `domains/ai-ml/`), propose it with 10 principles (P1–P10), each traced to a core principle (C1–C8) in `matrix/principles-matrix.md`.
+- **New domain derived docs** — topic docs under an existing domain (e.g., `domains/api/webhooks.md`), deriving from the domain's first-principles.
+- **New language application docs** — `languages/<lang>.md` showing how domain principles apply in a specific language.
+- **New examples** — `examples/good/*` (with principle citations) or `examples/bad/*` (with violation citations).
+- **Corrections** — to existing principles, derivations, or examples. A correction to a core principle is a major version change; treat with care.
+- **Improvements to the matrix** — if a derivation is missing or wrong, propose the fix with the rationale.
+
+## What We Do Not Accept
+
+- **Style rules** — Atelier is principles, not style. Use a linter for style.
+- **Tooling** — linters, analyzers, or enforcement code. Atelier is markdown.
+- **Unlisted docs** — every document must be in `MANIFEST.md`. An unlisted doc is not part of the framework.
+- **Principles without derivation** — a domain principle that does not trace to a core principle is orphaned and will be rejected.
+
+## How to Contribute
+
+### 1. Read the relevant docs first
+- `core/first-principles.md` — the eight axioms.
+- `core/conflict-resolution.md` — how conflicts are resolved.
+- The domain(s) you are contributing to.
+- `matrix/principles-matrix.md` — to see existing derivations.
+
+### 2. Follow the document structure
+See `domains/documentation/doc-templates.md` for the canonical structure. Every first-principles doc has:
+- Manifesto
+- The Principles (P1–P10, named, defined, with "what violates it")
+- Conflict Resolution
+- What Violates These Principles (table)
+- Relationship to Core
+
+### 3. Update the matrix
+If you add or change a principle, update `matrix/principles-matrix.md` with the derivation. A PR with a new principle but no matrix row is incomplete.
+
+### 4. Update the manifest
+If you add a new document, add it to `MANIFEST.md` in the correct section. An unlisted document is not part of the framework.
+
+### 5. Add examples
+If you add a principle, add at least one good example and one bad example in `examples/`. Examples are mandatory (Documentation P3).
+
+### 6. Write a clear PR description
+- What principle or document you are adding/changing.
+- Why (the rationale, not just the what — Documentation P8 Why Over What).
+- Which core principle(s) it derives from.
+- What conflicts it might introduce (if any).
+
+## Review Criteria
+
+Reviewers will check (see `review/peer-review-checklist.md`):
+- Does the new principle trace to a core principle?
+- Is the matrix updated?
+- Is the manifest updated?
+- Are there examples?
+- Does the structure follow the template?
+- Does it conflict with existing principles? If so, is the conflict resolvable per `core/conflict-resolution.md`?
+
+## Versioning
+
+- A new domain or language doc is a minor version (e.g., v0.1 → v0.2).
+- A new topic doc or example is a patch version (e.g., v0.1.0 → v0.1.1).
+- A change to `core/first-principles.md` (adding, removing, or reordering a core principle) is a major version (e.g., v0.x → v1.0).
+- See `CHANGELOG.md` for the version history.
+
+## License
+
+By contributing, you agree that your contributions are licensed under the MIT license (see `LICENSE`).

domains/api/error-responses.md

@@ -0,0 +1,63 @@
+# Error Responses — Derived Rules
+
+> Derives from `domains/api/first-principles.md` P9 (Error Transparency) and `domains/errors/first-principles.md`.
+
+## The Error Contract
+
+Every error response is a JSON object with:
+
+```json
+{
+  "error": {
+    "code": "STRING_ERROR_CODE",
+    "message": "Human-readable description",
+    "details": {},
+    "request_id": "uuid"
+  }
+}
+```
+
+- `code`: machine-consumable, stable, UPPER_SNAKE_CASE. Never a free-text message.
+- `message`: human-readable, for logs and developers. Not for end users (see `domains/errors/` P8).
+- `details`: structured, typed additional context (which field, what value, what constraint).
+- `request_id`: correlation ID for tracing. Every error is traceable.
+
+## Error Codes (P3 Predictability, P9)
+
+- Codes are stable. Renaming an error code is a breaking change.
+- Codes are specific: `VALIDATION_FAILED` not `BAD_REQUEST`. `DUPLICATE_EMAIL` not `CONFLICT`.
+- Codes are namespaced: `USER_NOT_FOUND`, `ORDER_NOT_FOUND` — not just `NOT_FOUND`.
+
+## Status Code Mapping (P1 Contract Fidelity)
+
+| Code | Meaning | Error code example |
+|------|---------|-------------------|
+| 400 | Malformed request | `MALFORMED_REQUEST` |
+| 401 | Auth required | `AUTH_REQUIRED` |
+| 403 | Forbidden | `FORBIDDEN` |
+| 404 | Not found | `<RESOURCE>_NOT_FOUND` |
+| 409 | Conflict | `DUPLICATE_<RESOURCE>` |
+| 422 | Semantic invalid | `VALIDATION_FAILED` |
+| 429 | Rate limited | `RATE_LIMITED` |
+| 500 | Server bug | `INTERNAL_ERROR` |
+
+- Never return 200 with an error body. The status code is the first signal.
+- Never return 500 for a client error. 500 means "the server has a bug."
+
+## Information Disclosure (P8 Security, domains/security P9)
+
+- Error messages do not leak internal state: no stack traces, no SQL fragments, no file paths.
+- A 401 does not say "user not found" vs "wrong password" — both say "invalid credentials."
+- A 404 does not confirm the resource exists but is forbidden — return 404, not 403, for unauthenticated requests to hidden resources.
+- Detailed errors are logged server-side with `request_id`; the client gets the safe version.
+
+## Retryability (P6 Idempotency)
+
+- Errors that are safe to retry: 409, 422 (if the fix is applied), 429 (after backoff), 5xx.
+- Errors that are not safe to retry: 400, 401 (without re-auth), 403.
+- The error body indicates retryability: `retryable: true/false` or via the code's known semantics.
+
+## Partial Errors (GraphQL, see `domains/api/graphql.md`)
+
+- GraphQL returns data and errors together. Do not conflate.
+- A null field with no error is a bug. A null field with an error is a partial failure.

domains/api/graphql.md

@@ -0,0 +1,53 @@
+# GraphQL — Derived Rules
+
+> Derives from `domains/api/first-principles.md`. Applies P1–P10 to GraphQL specifically.
+
+## Schema First (P1 Contract Fidelity)
+
+- The schema is the contract. Every field has a type, a description, and a deprecation status.
+- The schema is versioned. Breaking schema changes (removing a field, changing a type) require a deprecation cycle.
+- Never expose raw database types in the schema. Map them to domain types.
+
+## Query Design (P2 Clarity, P3 Predictability)
+
+- Field names are nouns, camelCase: `userOrders`, not `UserOrders` or `user_orders`.
+- Arguments are descriptive: `first`, `after`, `orderBy` — not `arg1`, `arg2`.
+- Connections for lists: `users(first: 10, after: "cursor")` — never bare arrays.
+- Mutations are verbs: `createUser`, `deleteOrder` — not `userCreate`.
+
+## N+1 Prevention (P7 Performance)
+
+- Use a dataloader for every list field that resolves to another resource.
+- A resolver that does a database query per item is an N+1 bug.
+- Test resolvers under a list query, not just a single-item query.
+
+## Authorization at the Field Level (P8 Security)
+
+- Every resolver checks authorization. The query graph is not a trust boundary by default.
+- A user who can query `user { email }` is not automatically authorized to query `user { passwordHash }`.
+- Field-level authz is the floor, not an optimization.
+
+## Deprecation (P5 Versioning, P10 Stability)
+
+- Deprecate fields with `@deprecated(reason: "...")`. Never remove a field without deprecating first.
+- A deprecated field is removed in the next major schema version, not sooner.
+- Track field usage. A deprecated field with no usage can be removed sooner.
+
+## Error Handling (P9 Error Transparency)
+
+- Errors are partial by default: a query can return data and errors simultaneously.
+- Errors are structured: `{ message, path, extensions: { code, ... } }`.
+- Use `extensions.code` for machine-consumable error types, not free-text messages.
+- Never swallow a resolver error silently. A null field with no error is a bug.
+
+## Complexity Budget (P7 Performance, P8 Security)
+
+- Enforce a query complexity limit. Unbounded depth/breadth is a DoS vector.
+- Cost-based analysis (not just depth) catches expensive nested queries.
+- Reject queries over budget with a 400, not a 500.
+
+## Federation (P6 Composability)
+
+- A federated subgraph owns its entities. Cross-graph references use `@external` and `@requires`.
+- Never reach into another subgraph's database. The graph boundary is the contract.
+- The gateway composes; subgraphs do not know about each other.

domains/api/pagination.md

@@ -0,0 +1,69 @@
+# Pagination — Derived Rules
+
+> Derives from `domains/api/first-principles.md` P7 (Performance) and P3 (Predictability).
+
+## Three Patterns
+
+### 1. Offset/Limit (`?page=2&limit=20`)
+- Simple, supports jumping to a page.
+- Unstable under inserts: page 2 becomes page 1's content after an insert.
+- Slow for large offsets: `OFFSET 10000` scans 10000 rows.
+- Use for: small, stable collections, admin UIs.
+
+### 2. Cursor (`?cursor=base64token&limit=20`)
+- Stable under inserts: the cursor points to a position, not a page number.
+- Fast: indexed lookup, no scan.
+- No random access (cannot jump to page 5).
+- Use for: infinite scroll, feeds, large collections, anything user-facing.
+
+### 3. Keyset (`?after_id=123&limit=20`)
+- Like cursor but uses the actual sort key (e.g., `after_id=123`).
+- Most stable and fast. Requires a unique, monotonic sort key.
+- Use for: ordered collections with a natural unique key.
+
+## Defaults (P3 Predictability)
+
+- Default `limit`: 20 or 50. Never unbounded.
+- Max `limit`: 100 or 200. Reject `limit=10000` with 400.
+- Default sort: by created_at descending, or by the resource's natural order.
+- Always return the total count if cheap; never if it requires a separate COUNT query on a large table.
+
+## Response Shape (P2 Clarity)
+
+```json
+{
+  "data": [...],
+  "pagination": {
+    "cursor": "next-base64-token",
+    "has_more": true
+  }
+}
+```
+
+- `cursor` is null when there is no next page.
+- `has_more` is the boolean convenience (some clients prefer it).
+- Never return `data` as a bare array — always wrap so you can add pagination without breaking.
+
+## Link Header (alternative)
+
+```
+Link: <https://api.example.com/users?cursor=X>; rel="next", <https://api.example.com/users?cursor=Z>; rel="prev"
+```
+
+- Useful for HTTP-level clients (curl, browser fetch).
+- Less convenient for JSON-parsing clients.
+
+## Consistency (P8 Consistency across endpoints)
+
+- Every collection endpoint paginates the same way.
+- A client that learns pagination on `/users` should know it on `/orders`.
+- Mixed pagination (cursor here, offset there) is a tax on every consumer.
+
+## What Violates Pagination
+
+| Violation | Principle |
+|-----------|-----------|
+| Returning 10000 items by default | P7 Performance |
+| `limit` with no max | P8 Security (DoS) |
+| Page numbers on a frequently-inserted table | P3 Predictability |
+| Bare array response (no pagination wrapper) | P1 Contract Fidelity (can't add pagination later without breaking) |

domains/api/rest.md

@@ -0,0 +1,68 @@
+# REST — Derived Rules
+
+> Derives from `domains/api/first-principles.md`. Applies P1–P10 to REST specifically.
+
+## Resource Naming (P2 Clarity, P3 Predictability)
+
+- Nouns, not verbs: `/users`, `/orders`, not `/getUsers`.
+- Plural: `/users` (collection), `/users/{id}` (item).
+- Lowercase, hyphenated: `/order-items`, not `/OrderItems` or `/order_items`.
+- Nesting max 2 levels: `/users/{id}/orders`, not `/users/{id}/orders/{oid}/items/{iid}`.
+
+## HTTP Methods (P1 Contract Fidelity, P6 Idempotency)
+
+| Method | Semantics | Idempotent | Safe |
+|--------|-----------|------------|------|
+| GET | Read | Yes | Yes |
+| POST | Create | No | No |
+| PUT | Replace (full) | Yes | No |
+| PATCH | Update (partial) | No | No |
+| DELETE | Remove | Yes | No |
+
+- PUT requires the full resource. PATCH requires only the delta. Never accept a partial PUT.
+- POST creates; never use POST for read operations. POST is not cacheable.
+
+## Status Codes (P9 Error Transparency, P1 Contract Fidelity)
+
+| Code | Meaning | When |
+|------|---------|------|
+| 200 | OK | Successful GET, PUT, PATCH |
+| 201 | Created | Successful POST that created a resource |
+| 204 | No Content | Successful DELETE, or empty response |
+| 400 | Bad Request | Malformed request (client error) |
+| 401 | Unauthorized | Authentication required or failed |
+| 403 | Forbidden | Authenticated but not permitted |
+| 404 | Not Found | Resource does not exist |
+| 409 | Conflict | State conflict (e.g., duplicate) |
+| 422 | Unprocessable | Well-formed but semantically invalid |
+| 429 | Too Many Requests | Rate limited |
+| 500 | Internal Error | Server bug — never leak stack trace |
+
+- Never return 200 on an error. Never return 500 with a stack trace.
+- 401 vs 403: 401 = "who are you?", 403 = "I know who you are, but you can't."
+
+## Idempotency (P6 Idempotency)
+
+- POST: not idempotent. Use an idempotency key (`Idempotency-Key` header) for safe retry.
+- PUT: idempotent by definition — same PUT twice = same state.
+- DELETE: idempotent — deleting a non-existent resource is success (204).
+- PATCH: not idempotent by default; can be made idempotent with explicit versioning.
+
+## Pagination (P7 Performance, see `pagination.md`)
+
+- Default to cursor pagination for collections > 100 items.
+- Never return unbounded collections.
+- `Link` header or `cursor` field in response body.
+
+## Versioning (P5 Versioning, P10 Stability, see `versioning.md`)
+
+- Version in the URL (`/v1/users`) or in the header (`Accept: application/vnd.atelier.v1+json`).
+- Pick one. Be consistent across all endpoints.
+- Never make a breaking change without a new version and a deprecation cycle.
+
+## Security (P8 Security, see `domains/security/`)
+
+- HTTPS only. Redirect HTTP to HTTPS.
+- Authentication on every non-public endpoint. No opt-in auth.
+- Rate limiting on write endpoints (POST, PUT, PATCH, DELETE).
+- Validate every input against a schema. Never pass raw request body to the database.

domains/api/versioning.md

@@ -0,0 +1,54 @@
+# API Versioning — Derived Rules
+
+> Derives from `domains/api/first-principles.md` P5 (Versioning) and P10 (Stability).
+
+## The Default: No Breaking Changes
+
+- A breaking change is a new version. There is no "minor" breaking change.
+- Breaking changes: removing a field, changing a field type, changing a field's semantics, changing required vs optional, changing error codes.
+- Non-breaking changes: adding a field, adding an endpoint, adding an optional parameter, loosening validation.
+
+## Version Policies
+
+### URL Versioning (`/v1/users`)
+- Simple, visible, cacheable.
+- Breaking changes bump the major version: `/v1` → `/v2`.
+- Old versions are supported in parallel during the deprecation window.
+
+### Header Versioning (`Accept: application/vnd.atelier.v1+json`)
+- Invisible in the URL; harder to test.
+- Useful when the URL must stay stable (e.g., public webhooks).
+
+### Semantic Versioning (for libraries/SDKs)
+- Major: breaking. Minor: additive. Patch: fix.
+- Follow semver strictly. A "minor" that breaks is a lie.
+
+## Deprecation Cycle (P5 Reversibility)
+
+1. **Announce**: mark the field/endpoint `@deprecated` with a sunset date.
+2. **Support**: keep the old version working until the sunset date.
+3. **Monitor**: track usage of the deprecated surface.
+4. **Retire**: when usage drops below threshold (or sunset passes), remove.
+5. **Never** remove without announcing. The cost of a silent break is paid by every consumer.
+
+## Sunset Headers (P9 Error Transparency)
+
+- Deprecated endpoints return `Sunset: <date>` header.
+- Deprecated endpoints return `Deprecation: <date>` header.
+- A consumer who reads headers knows when to migrate.
+
+## Versioning vs Compatibility
+
+- Versioning is the mechanism. Compatibility is the property.
+- Backward compatibility: old consumers work with the new version.
+- Forward compatibility: new consumers work with the old version (harder, rarer, usually not worth it).
+- Aim for backward compatibility. Forward compatibility is for protocols, not APIs.
+
+## What Violates Versioning
+
+| Violation | Principle |
+|-----------|-----------|
+| Removing a field without deprecation | P5, P10 |
+| Changing a field's type in a "minor" release | P1, P5 |
+| No sunset header on a deprecated endpoint | P9 |
+| Two versions with divergent semantics for the same field | P1 |

domains/concurrency/patterns.md

@@ -0,0 +1,62 @@
+# Concurrency Patterns — Derived Rules
+
+> Derives from `domains/concurrency/first-principles.md`. Common concurrency patterns and when to use them.
+
+## Pattern 1: Message Passing (P5 Lock Minimization)
+
+- Threads/goroutines communicate via channels/queues, not shared memory.
+- "Don't communicate by sharing memory; share memory by communicating." (Go proverb)
+- Use when the data flows naturally in one direction. Avoids locks entirely.
+
+## Pattern 2: Read-Write Lock (P5 Lock Minimization)
+
+- Multiple readers, one writer. A `RwLock` allows concurrent reads, exclusive writes.
+- Use when reads vastly outnumber writes (e.g., a config cache).
+- Avoid when writes are frequent — the lock degrades to a mutex.
+
+## Pattern 3: Actor Model (P2 Single Responsibility)
+
+- Each actor owns its state. Actors communicate via messages. No shared state.
+- Use for isolated, long-lived workers (e.g., a session handler, a chat room).
+- Erlang/Akka/Pony are built on this. Implementable in any language with channels.
+
+## Pattern 4: Immutable Data Structures (P1 Immutability by Default)
+
+- Data is never mutated; a "change" creates a new value. Old values are safe to share.
+- Use in functional languages (Haskell, Clojure) or via persistent data structures (Immer.js).
+- Eliminates entire classes of races. The trade-off is allocation cost.
+
+## Pattern 5: Bounded Queue with Backpressure (P9 Bounded Queues)
+
+- A queue with a max size. When full, the producer is blocked or signaled.
+- Use to bound memory and propagate slowness from consumer to producer.
+- An unbounded queue hides a slow consumer until OOM. Always bound.
+
+## Pattern 6: Timeout on Every Block (P8 Timeout Discipline)
+
+- Every blocking call (lock acquire, queue send, HTTP request) has a timeout.
+- Use a timeout, not a forever-block. Forever is not a duration.
+- On timeout: cancel, retry, or fail. Do not hang.
+
+## Pattern 7: Cancellation Propagation (P7 Cancellation Support)
+
+- A cancellation signal propagates to all spawned work. Cancel the parent, the children stop.
+- Use context (`context.Context` in Go, `AbortController` in JS, `CancellationToken` in C#).
+- Cancellation is fast and complete. No orphaned goroutines/threads.
+
+## Pattern 8: Lock-Free Where Possible (P5)
+
+- Atomic operations (compare-and-swap) for simple state. No lock.
+- Use for counters, flags, simple pointers.
+- Avoid for complex state — lock-free code is subtle and easy to get wrong.
+
+## What Violates Concurrency Patterns
+
+| Violation | Pattern |
+|-----------|---------|
+| Shared mutable state with no lock | (race, P1) |
+| Unbounded queue | P5 (OOM) |
+| `channel.send()` with no timeout | P6 (hang) |
+| Spawned goroutine with no cancellation | P7 (orphan) |
+| A mutex held across an I/O call | P3 (lock scope) |
+| `sync.Mutex` for a counter | P8 (use atomic) |

domains/data/indexing.md

@@ -0,0 +1,49 @@
+# Indexing — Derived Rules
+
+> Derives from `domains/data/first-principles.md` P5 (Indexing with Intent), P10 (Performance Awareness).
+
+## Index for Queries, Not Tables (P5)
+
+- An index serves a query. No query, no index.
+- The query plan is the spec. `EXPLAIN` is the test. An index that is not used is dead weight.
+- Index the columns you filter on (`WHERE`), join on (`JOIN`), and sort on (`ORDER BY`).
+
+## Composite Indexes (P5, P10)
+
+- Order matters: `INDEX(a, b)` serves `WHERE a = ? AND b = ?` and `WHERE a = ?`, but NOT `WHERE b = ?`.
+- Put the most selective column first. Or the column used in every query. Depends on the workload.
+- An index on every column is not a strategy. It is write amplification.
+
+## Unique Indexes (P3 Invariants in Schema)
+
+- A uniqueness constraint is a unique index. Use it for invariants: `email`, `username`.
+- Unique indexes enforce; application checks defend. Both belong.
+- A partial unique index: `UNIQUE(email) WHERE deleted_at IS NULL` — allows soft-deleted duplicates.
+
+## Covering Indexes (P10)
+
+- An index that covers all columns of a query is an "index-only scan" — no table lookup.
+- PostgreSQL: `INCLUDE` clause. MySQL: all columns in the index.
+- Use for hot queries. Don't cover everything; index size matters.
+
+## Don't Over-Index (P10, core C8 Economy)
+
+- Every index costs a write. The write budget is the index count.
+- Indexes take disk and memory. A 1GB index on a 500MB table is a smell.
+- Remove unused indexes. `pg_stat_user_indexes` shows usage. An unused index is debt.
+
+## Migration and Indexes (P4 Migration Safety)
+
+- Adding an index on a large table is expensive. Do it concurrently (`CREATE INDEX CONCURRENTLY`).
+- An index migration that locks the table blocks writes. Plan for it.
+- Build the index, then deploy the query that uses it. Not the reverse.
+
+## What Violates Indexing Discipline
+
+| Violation | Principle |
+|-----------|-----------|
+| Index on every column | P10, C8 Economy |
+| No index on a foreign key | P10 (join performance) |
+| `WHERE b = ?` with only `INDEX(a, b)` | P5 (wrong order) |
+| Index created without checking the query plan | P5 (no intent) |
+| `CREATE INDEX` (non-concurrent) on a 10M-row table in prod | P4 Migration Safety |

domains/data/migrations.md

@@ -0,0 +1,53 @@
+# Migrations — Derived Rules
+
+> Derives from `domains/data/first-principles.md` P4 (Migration Safety), P5 (Reversibility via core C5).
+
+## Every Change is a Migration (P4)
+
+- No manual schema changes. No `ALTER TABLE` in a shell. Every change is a versioned migration file.
+- Migrations are code: reviewed, tested, committed.
+- The migration tool is the only way to change the schema (`prisma migrate`, `alembic`, `flyway`, `golang-migrate`).
+
+## Forward and Reverse (P5 Reversibility, core C5)
+
+- Every migration has an `up` and a `down`. The `down` reverses the `up`.
+- A migration without a `down` is irreversible. Irreversible migrations are rare and flagged.
+- Test the `down` in CI. A `down` that fails is a migration that cannot be rolled back.
+
+## Expand, Migrate, Contract (P5)
+
+For non-breaking schema changes:
+
+1. **Expand**: add the new column/ table (nullable, no constraint). Deploy. Old code still works.
+2. **Migrate**: backfill data, run the data migration. Deploy. Both old and new code work.
+3. **Contract**: add constraints, remove the old column. Deploy after all code uses the new schema.
+
+Never do all three in one migration. Each step is its own deploy.
+
+## Avoid Destructive Changes (P4)
+
+- Never `DROP COLUMN` in a migration that could be in use. Expand-contract first.
+- Never `DROP TABLE` without confirming no code references it.
+- Never `ALTER TYPE` in a way that locks the table on a large dataset. Use a phased approach.
+
+## Backward Compatibility (P5, P1)
+
+- A migration must not break the running code. Old code reads the new schema (with expand).
+- The schema is always compatible with the previous code version. Two-version compatibility.
+- A breaking migration is deployed in lockstep with the code, with a maintenance window.
+
+## Testing Migrations (P3 Determinism via testing P3)
+
+- Run migrations on a copy of production data in CI. A migration that works on dev may fail on prod scale.
+- Test the `down` on the migrated state, not just the `up`.
+- Test with the largest table sizes you have. `ALTER TABLE` on 10 rows is fast; on 10M rows, it may lock.
+
+## What Violates Migration Safety
+
+| Violation | Principle |
+|-----------|-----------|
+| Manual `ALTER TABLE` in prod | P4 |
+| Migration with no `down` | P5 Reversibility |
+| `DROP COLUMN` in the same deploy as the new code | P4, P5 |
+| No migration test on prod-scale data | P3 Determinism |
+| A migration that locks a table for 10 minutes | P4 (downtime) |

domains/data/schema-design.md

@@ -0,0 +1,53 @@
+# Schema Design — Derived Rules
+
+> Derives from `domains/data/first-principles.md` P1 (Truth), P3 (Invariants in Schema), P7 (Type Fidelity).
+
+## The Schema Reflects the Domain (P1 Truth)
+
+- A `users` table has columns that are attributes of a user, not attributes of the application.
+- If a column is named `is_active_for_feature_X`, the schema is lying. The domain does not have "feature X."
+- Normalize until it hurts, then denormalize only with evidence (P10 Performance Awareness).
+
+## Invariants in the Schema (P3)
+
+- NOT NULL where the value is required. UNIQUE where the value is unique.
+- CHECK constraints for range/domain: `age >= 0`, `status IN ('draft', 'published')`.
+- FOREIGN KEY for relationships. The database enforces; the application defends.
+- A constraint in the application but not the schema is a constraint that can be bypassed.
+
+## Types (P7 Type Fidelity)
+
+- `UUID` for IDs, not `VARCHAR`. `UUID` is a type; `VARCHAR(36)` is a string that looks like a UUID.
+- `TIMESTAMPTZ` for timestamps, not `VARCHAR` or `INTEGER`. Timezone-aware by default.
+- `ENUM` for finite domains, `VARCHAR` with CHECK for evolving domains.
+- `JSONB` for unstructured/semi-structured; not for data that should be a column.
+- `DECIMAL`/`NUMERIC` for money, never `FLOAT`. Floating point is for measurements, not money.
+
+## Naming (P6 Naming Consistency)
+
+- snake_case for tables and columns (PostgreSQL convention): `user_accounts`, `created_at`.
+- Singular table names (`user` not `users`) OR plural (`users` not `user`) — pick one, be consistent.
+- Foreign keys: `<singular_table>_id` (`user_id`), not `uid` or `user`.
+- Junction tables: alphabetical (`order_products`, not `products_orders`).
+
+## Avoid (P2 Normalization Discipline)
+
+- Computed columns that duplicate derivable data. Use a view or compute on read.
+- `created_by_name` (denormalized) when `created_by_id` + JOIN suffices. Denormalize only with evidence.
+- Soft-delete columns (`is_deleted`) without a corresponding constraint/behavior. Soft delete is a lifecycle decision (P8).
+
+## Soft Delete vs Hard Delete (P8 Lifecycle Awareness)
+
+- Soft delete (`deleted_at TIMESTAMP`) preserves auditability but complicates every query.
+- Hard delete loses history. Choose based on the domain's legal/audit requirements.
+- If soft delete: every query filters `WHERE deleted_at IS NULL` by default. A missing filter is a bug.
+
+## What Violates Schema Design
+
+| Violation | Principle |
+|-----------|-----------|
+| `VARCHAR` for a UUID | P7 Type Fidelity |
+| No FOREIGN KEY on a relationship | P3, P9 Referential Integrity |
+| `FLOAT` for money | P7, P1 Truth |
+| `is_deleted` without consistent filtering | P8 Lifecycle |
+| A column named after a feature, not a domain concept | P1 Truth |

domains/devops/ci-cd.md

@@ -0,0 +1,50 @@
+# CI/CD — Derived Rules
+
+> Derives from `domains/devops/first-principles.md` P2 (Automation), P4 (Rollback First), P5 (Progressive Delivery).
+
+## The Pipeline is the Process (P2)
+
+- If it is not in the pipeline, it does not happen. Manual deploys are a bug.
+- The pipeline: lint → test → build → deploy → verify.
+- Every step is scripted, versioned, and reproducible. No "run this command on the server."
+
+## Lint (P2, core C2 Clarity)
+
+- Run the linter on every commit. Fail the build on lint errors.
+- Format check (prettier, gofmt, rustfmt). Format is not a debate; it is automated.
+- Security lint (eslint-plugin-security, bandit, gosec). Catch the obvious ones.
+
+## Test (P2, domains/testing)
+
+- Unit tests in the pipeline. Fast. Every commit.
+- Integration tests on merge to main. Slower. Every merge.
+- E2E tests before deploy. Slowest. Every deploy candidate.
+
+## Build (P7 Immutability)
+
+- Build once. The artifact is immutable. The same artifact goes to every environment.
+- The build is reproducible: same commit → same artifact (modulo timestamps, which are stripped).
+- Build artifacts are signed and stored. A deploy is a reference to an artifact, not a rebuild.
+
+## Deploy (P4 Rollback First, P5 Progressive Delivery)
+
+- Every deploy has a rollback. The rollback is tested before the deploy.
+- Progressive: canary (1% → 10% → 100%), blue-green, or feature flags.
+- No big-bang deploys. A big-bang deploy is a rollback with no rehearsal.
+
+## Verify (P3 Observability)
+
+- After deploy, verify: health checks, smoke tests, metric watching.
+- A deploy is not "done" when the code is on the server. It is done when the metrics are healthy.
+- Auto-rollback on metric regression. The pipeline watches; humans sleep.
+
+## What Violates CI/CD Discipline
+
+| Violation | Principle |
+|-----------|-----------|
+| Manual deploy script | P2 Automation |
+| No rollback path | P4 Rollback First |
+| Big-bang deploy to prod | P5 Progressive Delivery |
+| Rebuild per environment | P7 Immutability |
+| Deploy without health check | P3 Observability |
+| No lint in CI | P2, C2 |

domains/devops/environments.md

@@ -0,0 +1,44 @@
+# Environments — Derived Rules
+
+> Derives from `domains/devops/first-principles.md` P1 (Reproducibility), P6 (Configuration as Code), P7 (Immutability).
+
+## Environment Parity (P1 Reproducibility)
+
+- Dev, staging, prod are the same system, different data.
+- The same artifact runs in all three. The same config schema, different values.
+- "Works on my machine" is a parity failure. The machine is the pipeline.
+
+## Configuration (P6 Configuration as Code)
+
+- Config is in the repo (default values) + environment overrides (secrets, endpoints).
+- No snowflake servers. No "this one is different because we edited it in prod."
+- Config changes are PRs, not SSH sessions.
+
+## Secrets (P9 Secret Hygiene via security)
+
+- Secrets are per-environment. Dev secrets ≠ prod secrets.
+- Secrets come from a secrets manager (Vault, AWS Secrets Manager, Doppler), not env files in prod.
+- `.env` files are for local dev only. Prod uses the manager.
+
+## Promotion (P5 Progressive Delivery via devops)
+
+- Code moves dev → staging → prod. Never the reverse.
+- A hotfix to prod is backported to staging and dev. Don't let them diverge.
+- Promotion is automated. The pipeline decides when code is ready, not a human.
+
+## Data (P1, domains/data P8 Lifecycle Awareness)
+
+- Prod data is sacred. Never copy prod to dev without anonymization.
+- Staging uses prod-like data (anonymized, sampled). Dev uses synthetic data.
+- A test that runs against prod data is a test that can destroy prod data. Don't.
+
+## What Violates Environment Discipline
+
+| Violation | Principle |
+|-----------|-----------|
+| "It works on my machine" | P1 Parity |
+| Manual config edit in prod | P6 Configuration as Code |
+| Dev secret reused in prod | P9 Secret Hygiene |
+| Copy prod DB to dev | P1, data P8 |
+| Hotfix in prod not backported | P5 (divergence) |
+| A snowflake server | P1, P6 |

domains/documentation/doc-templates.md

@@ -0,0 +1,83 @@
+# Doc Templates — Derived Rules
+
+> Derives from `domains/documentation/first-principles.md` P7 (Structure), P2 (Audience Awareness), P3 (Examples are Mandatory).
+
+## Document Structure (P7)
+
+Every framework document follows a consistent structure:
+
+```
+# <Title>
+
+> One-line purpose. Who reads this and when.
+
+## 1. Manifesto (or Introduction)
+Why this document exists. The core belief.
+
+## 2. The Principles (or Rules)
+The numbered, named, derivable rules. Each rule has:
+- A name (P1, P2, ...)
+- A one-line definition
+- A "what it means" paragraph
+- A "what violates it" entry
+
+## 3. Conflict Resolution (for first-principles docs)
+Precedence among the rules. Non-tradeable declarations.
+
+## 4. What Violates These Principles
+A table of violations and the principle they breach.
+
+## 5. Relationship to Core
+Derivation link. See `matrix/principles-matrix.md`.
+```
+
+- The structure is the contract. A reader can scan any framework doc and find the same sections.
+- Derived (topic) docs simplify: drop §3, replace §5 with "Derives from `<domain>/first-principles.md`."
+
+## Audience Templates (P2)
+
+### For Agents
+- Lead with what to check before completing a task.
+- Bullet lists, not paragraphs.
+- "Run this checklist" framing.
+
+### For Humans (Onboarding)
+- Lead with what this is and who it's for.
+- Reading order. Quickstart.
+- Conversational tone, not terse.
+
+### For Humans (Reference)
+- Lead with the rules, indexed.
+- Tables for lookup.
+- Cross-references to other docs.
+
+## Example Template (P3 Examples are Mandatory)
+
+Every rule includes an example. The template:
+
+```
+### P<n>. <Name>
+<one-line definition>
+
+<what it means>
+
+Good:
+<example>
+
+Bad:
+<counter-example> (violates P<n>)
+```
+
+- The "good" example is realistic, not a strawman.
+- The "bad" example cites the principle it violates.
+- Examples are code, not prose. Show, don't tell.
+
+## What Violates Doc Templates
+
+| Violation | Principle |
+|-----------|-----------|
+| A doc with no examples | P3 Examples are Mandatory |
+| A first-principles doc with no "what violates" table | P7 Structure |
+| A doc that does not link to its core derivation | P5 Discoverability |
+| Inconsistent structure across domain docs | P7 |
+| A doc with no audience statement | P2 Audience Awareness |

domains/errors/patterns.md

@@ -0,0 +1,94 @@
+# Error Patterns — Derived Rules
+
+> Derives from `domains/errors/first-principles.md`. Common error-handling patterns and when to use them.
+
+## Pattern 1: Result Type (P1 Errors are Data)
+
+```typescript
+type Result<T, E> = { ok: true; value: T } | { ok: false; error: E };
+
+function divide(a, b): Result<number, string> {
+  if (b === 0) return { ok: false, error: "division by zero" };
+  return { ok: true, value: a / b };
+}
+```
+
+- Errors are values, not exceptions. The caller handles them explicitly.
+- Use when errors are expected (parsing, validation, fallible operations).
+- Avoid when errors are truly exceptional (out of memory, programmer error) — use exceptions/panics.
+
+## Pattern 2: Sentinel Error (P4 Preserve Context)
+
+```go
+var ErrNotFound = errors.New("not found")
+if errors.Is(err, ErrNotFound) { ... }
+```
+
+- A sentinel is a known error value the caller checks against.
+- Use for a small, known set of error conditions.
+- Wrap with context: `fmt.Errorf("load user %d: %w", id, ErrNotFound)`.
+
+## Pattern 3: Typed Error (P1, P3 Fail Specifically)
+
+```rust
+enum AppError {
+  NotFound(String),
+  Invalid(String),
+  Internal(String),
+}
+```
+
+- A typed error carries the kind and the detail.
+- The caller matches on kind; the detail is for logging/display.
+- Use when there are distinct error categories the caller handles differently.
+
+## Pattern 4: Error Wrapping (P4 Preserve Context)
+
+```go
+return fmt.Errorf("query users: %w", err)
+```
+
+- Wrap errors as they cross boundaries. The outer error says "what was happening"; the inner says "what went wrong."
+- The error chain is the stack trace of intent. Read it top-down: "I was doing X, which failed because Y, which was caused by Z."
+- Never wrap with a generic message ("operation failed"). Wrap with the specific operation.
+
+## Pattern 5: Fail Fast (P6 Unrecoverable Means Stop)
+
+```typescript
+if (config.secret === undefined) throw new Error("config.secret is required");
+```
+
+- For unrecoverable conditions, fail immediately. Do not limp on.
+- Use at startup: missing required config, missing database, missing secrets.
+- Do not use for recoverable conditions (a 404 is recoverable; a missing secret is not).
+
+## Pattern 6: Retry with Backoff (P5 Recoverable When Possible)
+
+```python
+for attempt in range(3):
+  try:
+    return do_thing()
+  except TransientError:
+    sleep(2 ** attempt)
+raise PermanentError()
+```
+
+- Retry transient errors (network, 429, 5xx). Do not retry permanent errors (400, 401).
+- Exponential backoff with jitter. A retry storm is worse than the original failure.
+- Bounded retries. Infinite retry is infinite hang (P8 Timeout Discipline).
+
+## Pattern 7: Circuit Breaker (P3 Defense in Depth via errors P7)
+
+- After N consecutive failures, stop trying. Return a fallback or error immediately.
+- Use for external dependencies (a downstream service, an API).
+- The breaker resets after a cooldown. Protects the system and the downstream.
+
+## What Violates Error Patterns
+
+| Violation | Pattern |
+|-----------|---------|
+| `catch (e) { return null }` | (anti-pattern, P2 Fail Loudly) |
+| `throw new Error("error")` | P3 Fail Specifically |
+| Retry without backoff | P5, P8 |
+| `return null` for "not found" | P1 (errors are data, not absence) |
+| `throw` in a recovery path | P6 (fail fast in the wrong place) |

domains/observability/logging.md

@@ -0,0 +1,49 @@
+# Logging — Derived Rules
+
+> Derives from `domains/observability/first-principles.md` P1 (Structured by Default), P3 (Sufficient Context), P6 (No Secrets in Observability).
+
+## Structured by Default (P1)
+
+- Logs are JSON (or structured key-value). Free-form text is for humans; machines need fields.
+- Every log entry has: `timestamp`, `level`, `message`, `request_id`, plus domain-specific fields.
+- A log you cannot query is a log you cannot use. Structure is the query API.
+
+## Levels (P3 Sufficient Context)
+
+| Level | When |
+|-------|------|
+| ERROR | Something failed; an operator must look |
+| WARN | Something unexpected; not a failure but notable |
+| INFO | Significant application events (start, stop, deploy, user signup) |
+| DEBUG | Diagnostic detail; off in production by default |
+
+- ERROR is not for "this branch ran." ERROR is for "this failed and someone should know."
+- Logging everything at ERROR means nothing is an error. Alert fatigue is a defect (observability P7).
+
+## Context (P3)
+
+- Every log in a request includes `request_id` (correlation ID). Trace the request across services.
+- Include the user ID, the action, the resource. "What was the user doing?" is answerable.
+- A log that says `"failed"` with no context is worse than no log. It is noise.
+
+## No Secrets (P6, domains/security P9)
+
+- Never log tokens, passwords, API keys, session IDs, PII.
+- Redact: replace the secret with `[REDACTED]` or a hash. Log the hash, not the value.
+- Never log the full request body. It may contain a token, a password, or PII.
+
+## Volume (P4 Cardinality Discipline, core C8 Economy)
+
+- Don't log every request at INFO. Log significant events.
+- A million logs a minute is not "good observability"; it is a storage bill and a signal-to-noise problem.
+- Sample high-volume logs (P5 Sampling with Intent). Sample deliberately, not randomly.
+
+## What Violates Logging Discipline
+
+| Violation | Principle |
+|-----------|-----------|
+| `console.log("here")` | P1 (not structured) |
+| `logger.error("done")` | P3 (wrong level) |
+| `logger.info(req.body)` | P6 (secrets), volume |
+| A log with no `request_id` | P3 (no correlation) |
+| 10M logs/day at INFO | P4, C8 |

domains/observability/metrics.md

@@ -0,0 +1,50 @@
+# Metrics — Derived Rules
+
+> Derives from `domains/observability/first-principles.md` P1 (Structured by Default), P4 (Cardinality Discipline), P8 (SLI/SLO Awareness).
+
+## The Four Golden Signals
+
+| Signal | What |
+|--------|------|
+| Latency | Time to serve a request (p50, p95, p99) |
+| Traffic | Request rate (req/s) |
+| Errors | Error rate (errors/s, or % of traffic) |
+| Saturation | How full is the system (CPU, memory, queue depth) |
+
+- All four are needed. Missing one is a blind spot.
+- Latency is percentiles, not average. Average hides the long tail.
+
+## Cardinality (P4)
+
+- Labels have bounded cardinality. `user_id` as a label = unbounded cardinality = unbounded bill.
+- High-cardinality dimensions belong in traces, not metrics.
+- A metric with `user_id` as a label is a 1M-series metric. That is a budget bomb.
+
+## Counter vs Gauge vs Histogram
+
+| Type | What | Example |
+|------|------|---------|
+| Counter | Monotonically increasing | `http_requests_total` |
+| Gauge | A value at a point in time | `active_connections` |
+| Histogram | Distribution of values | `http_request_duration_seconds` |
+
+- A counter never decreases. Use `rate()` over time to get the rate.
+- A gauge can go up and down. Use it for saturation.
+- A histogram gives percentiles. Use it for latency.
+
+## SLI/SLO (P8)
+
+- SLI (Service Level Indicator): a metric of good/total (e.g., 99.9% of requests < 500ms).
+- SLO (Service Level Objective): the target for the SLI (e.g., 99.9% over 30 days).
+- Error budget: 1 - SLO. If SLO is 99.9%, error budget is 0.1%. Spend it on feature risk, not bugs.
+- When the error budget is exhausted, freeze features. Fix reliability.
+
+## What Violates Metrics Discipline
+
+| Violation | Principle |
+|-----------|-----------|
+| `user_id` as a label | P4 Cardinality |
+| Average latency only | P8 (hides the tail) |
+| No error rate metric | P8 (no SLI) |
+| 1000 metrics, no SLO | P8 (no objective) |
+| A counter that decreases | (type error) |

domains/observability/tracing.md

@@ -0,0 +1,45 @@
+# Tracing — Derived Rules
+
+> Derives from `domains/observability/first-principles.md` P2 (Correlation), P5 (Sampling with Intent), P10 (Debuggability Over Coverage).
+
+## Distributed Tracing (P2)
+
+- A trace is a tree of spans. Each span is a unit of work with a start, end, and context.
+- `trace_id` ties spans across services. `span_id`/`parent_span_id` form the tree.
+- Every request has a `trace_id`. Propagate it in headers (`traceparent`, W3C standard).
+
+## Sampling (P5)
+
+- Head-based: sample at the start. Simple, but you miss the interesting failures.
+- Tail-based: sample at the end. Keep all errors, sample the successs. Better signal, harder to build.
+- A 100% trace rate is too expensive. 1% is often enough for debugging.
+- Sample deliberately: keep all errors, all slow requests, and a fraction of the rest.
+
+## Context (P3 Sufficient Context, P10 Debuggability)
+
+- A span has: name, start time, duration, attributes (key-value), events, status.
+- Attributes: `http.method`, `http.url`, `db.statement`, `user.id`. The fields you need to debug.
+- Events: notable points within a span (e.g., "cache miss", "retry").
+- A span with no attributes is a span that tells you nothing.
+
+## Where to Span (P4 Locality)
+
+- Span at service boundaries (HTTP in/out, DB query, queue send/receive).
+- Span at significant internal operations (a long computation, a batch step).
+- Don't span every function call. Span the meaningful units.
+
+## Traces vs Logs (P10)
+
+- Logs are events; traces are causality. Logs answer "what happened"; traces answer "why it was slow."
+- A trace contains log events (span events). They are not separate systems.
+- Use traces for the request flow; use logs for the details.
+
+## What Violates Tracing Discipline
+
+| Violation | Principle |
+|-----------|-----------|
+| No `trace_id` propagation | P2 Correlation |
+| 100% trace rate | P5 Sampling |
+| Span per function | P4 (too noisy) |
+| Span with no attributes | P10 (no debug value) |
+| Traces for successful requests only | P5 (miss the failures) |

domains/performance/backend.md

@@ -0,0 +1,51 @@
+# Backend Performance — Derived Rules
+
+> Derives from `domains/performance/first-principles.md` P1 (Measure First), P3 (Complexity Awareness), P4 (Resource Bounds).
+
+## Measure First (P1)
+
+- p50, p95, p99 latencies. The average hides the long tail.
+- Throughput (req/s) under load. Saturation point (where latency rises).
+- Resource utilization: CPU, memory, I/O, network. Each is a budget.
+
+## N+1 Queries (P3 Complexity Awareness)
+
+- A query in a loop is an N+1. It is O(N) queries instead of O(1).
+- Detect with a query counter in tests. A test that issues 100 queries is failing.
+- Fix with a JOIN, a batch load, or a dataloader. Never "we'll fix it later."
+
+## Caching (P5 Caching with Intent)
+
+- Cache what is: expensive to compute, stable, read often.
+- Invalidation is designed: TTL, event-based, or version-based. Never "we'll just clear it."
+- A cache without an invalidation strategy is a cache that serves stale data forever.
+- Multi-level: HTTP cache → CDN → app cache → DB. Each layer has its own rules.
+
+## Async and Concurrency (P7 Async When Independent, see `domains/concurrency/`)
+
+- I/O-bound work is async. Don't block a thread on a network call.
+- CPU-bound work is in a worker, not the request path.
+- Bounded queues everywhere (P9 Bounded Queues). Unbounded = OOM.
+
+## Database (P4 Resource Bounds, see `domains/data/indexing.md`)
+
+- Connection pool: bounded. The DB has a connection limit; the pool respects it.
+- Slow queries: logged, explained, fixed. A 10-second query is a bug.
+- Pagination on large tables: cursor, not offset. Offset scans rows.
+
+## Resource Bounds (P4)
+
+- Memory: bounded. A request that allocates unbounded memory is a DoS vector.
+- Timeouts: every external call has one. A call without a timeout is a call that can hang forever (P8 Timeout Discipline).
+- File handles, DB connections, HTTP connections: all bounded, all pooled.
+
+## What Violates Backend Performance
+
+| Violation | Principle |
+|-----------|-----------|
+| N+1 query in a loop | P3 |
+| No timeout on an HTTP call | P4, P8 (concurrency) |
+| Unbounded in-memory sort | P4 |
+| Cache with no invalidation | P5 |
+| `SELECT *` | P4 (data P10) |
+| Connection pool size = 1000 | P4 (DB limit) |

domains/performance/frontend.md

@@ -0,0 +1,55 @@
+# Frontend Performance — Derived Rules
+
+> Derives from `domains/performance/first-principles.md` P1 (Measure First), P9 (Perceived Performance).
+
+## Measure First (P1)
+
+- Lighthouse, Core Web Vitals (LCP, FID/INP, CLS), RUM (Real User Monitoring).
+- A performance claim without a measurement is an opinion.
+- Measure the 75th percentile (P75), not the average. The average hides the long tail.
+
+## The Three Core Web Vitals
+
+| Vital | What | Target (P75) |
+|-------|------|--------------|
+| LCP (Largest Contentful Paint) | When the main content loads | ≤ 2.5s |
+| INP (Interaction to Next Paint) | When input is responded to | ≤ 200ms |
+| CLS (Cumulative Layout Shift) | Visual stability | ≤ 0.1 |
+
+- LCP > 4s is poor. INP > 500ms is poor. CLS > 0.25 is poor.
+- Measure on mobile, not just desktop. Mobile is the long tail.
+
+## Perceived Performance (P9)
+
+- A skeleton screen beats a spinner. A spinner beats nothing.
+- Optimistic UI updates: the click responds immediately; the server confirms later.
+- Prefetch the next page on hover (if cheap). Prefetch is a bet, not a certainty.
+
+## Bundle Size (P4 Resource Bounds, core C8 Economy)
+
+- Ship less JavaScript. Every KB is parsed, compiled, and executed on the client.
+- Code-split routes. Lazy-load below-the-fold. Don't ship the admin bundle to the user bundle.
+- A 500KB JS bundle is large. A 2MB JS bundle is a defect.
+
+## Images (P4, P6 Lazy by Default)
+
+- WebP/AVIF, not JPEG/PNG. Modern formats are 30–50% smaller.
+- `loading="lazy"` on below-the-fold images. `width`/`height` to prevent CLS.
+- `srcset` for responsive images. Ship the right size to the right device.
+- Never ship a 4K image to a 360px screen.
+
+## Rendering (P7 Async When Independent)
+
+- Server-render the first paint (SSR/SSG). Hydrate after.
+- Avoid hydration waterfalls: a 3-second hydration is a 3-second blank page with a "loaded" script.
+- Defer non-critical hydration. Interactive above the fold first; below the fold later.
+
+## What Violates Frontend Performance
+
+| Violation | Principle |
+|-----------|-----------|
+| 3MB JS bundle | P4, C8 |
+| LCP > 4s on mobile | P1 (measured) |
+| Layout shift on image load | CLS |
+| Synchronous hydration of a 50KB page | P7 |
+| No image optimization | P4 |

domains/security/authentication.md

@@ -0,0 +1,62 @@
+# Authentication — Derived Rules
+
+> Derives from `domains/security/first-principles.md` P1 (Zero Trust), P2 (Least Privilege), P6 (Crypto Correctness).
+
+## The Default: Authenticated
+
+- Every endpoint is authenticated unless explicitly public.
+- "Public" is an explicit declaration, not a default.
+- A missing auth check is a bug, not an oversight.
+
+## Authentication Methods
+
+### Session-based (browser)
+- Server-side session, cookie-borne session ID.
+- Cookie: `HttpOnly`, `Secure`, `SameSite=Lax` (or `Strict`).
+- Session ID: cryptographically random, ≥ 128 bits.
+- Session timeout: bounded. Idle timeout + absolute timeout.
+
+### Token-based (API, SPA)
+- Bearer token in `Authorization: Bearer <token>`.
+- Token: JWT (signed) or opaque (server-stored).
+- JWT: signed (HS256/RS256), never `none`. Short TTL (≤ 1 hour). Refresh token for long sessions.
+- Opaque: server-stored, revocable. Use when revocation matters.
+
+### API Keys (service-to-service)
+- Long-lived, scoped, rotatable.
+- Sent in header (`X-API-Key`), not query string (logged in URLs).
+- Stored in a secrets manager, never in code.
+
+## What Never to Do (P6 Crypto Correctness)
+
+- Never roll your own auth. Use a vetted library or framework.
+- Never store passwords in plaintext. Use bcrypt/scrypt/argon2 with a work factor.
+- Never use MD5 or SHA1 for password hashing.
+- Never put a token in a URL. URLs are logged.
+- Never accept `alg: none` in a JWT.
+- Never trust a token without verifying its signature.
+
+## Password Rules (P4 Input Validation)
+
+- Minimum length: 12 characters (NIST 800-63B). No maximum (don't prevent long passwords).
+- No composition rules (no "must contain a symbol"). They don't help and frustrate users.
+- Check against a breach corpus (HIBP API or similar).
+- Rate limit login attempts. Lockout after N failures (with exponential backoff, not a hard lock).
+
+## Multi-Factor (P3 Defense in Depth)
+
+- MFA is the default for privileged accounts.
+- TOTP (RFC 6238) or WebAuthn. SMS is deprecated (SIM swapping).
+- MFA is a layer, not a replacement for strong primary auth.
+
+## Session Lifecycle (P2 Least Privilege, P5 Reversibility)
+
+- Sessions are revocable. A logout invalidates the session server-side, not just client-side.
+- Tokens are revocable. A refresh token revocation list is maintained.
+- "Remember me" extends the session, it does not make it permanent.
+
+## Audit (P7 Auditability)
+
+- Every auth event is logged: login (success/fail), logout, token issuance, token revocation.
+- Logs include: user ID, timestamp, IP, user agent, outcome.
+- Logs do not include: passwords, tokens, session IDs (use a hash).

domains/security/authorization.md

@@ -0,0 +1,61 @@
+# Authorization — Derived Rules
+
+> Derives from `domains/security/first-principles.md` P2 (Least Privilege), P3 (Defense in Depth), P1 (Zero Trust).
+
+## The Default: Deny
+
+- Every request is denied unless explicitly authorized.
+- "Authorized by default" is an anti-pattern. The absence of a rule means denial.
+- A missing authz check is a bug, not a feature gap.
+
+## Authorization Models
+
+### RBAC (Role-Based)
+- Users have roles; roles have permissions.
+- Roles are coarse: `admin`, `editor`, `viewer`. Permissions are fine: `post:create`, `post:delete`.
+- Check permissions, not roles: `can(user, 'post:create')`, not `user.role === 'admin'`.
+- Roles can change; permission checks are stable.
+
+### ABAC (Attribute-Based)
+- Authorization based on attributes of the user, resource, and context.
+- More expressive: "user can edit a post if user.department == post.department and post.status == 'draft'".
+- Use when RBAC is too coarse. Beware: complex ABAC is hard to audit.
+
+### ReBAC (Relationship-Based)
+- Authorization based on relationships (e.g., Zanzibel).
+- "user:alice is editor of document:42" — check the relationship graph.
+- Scales for fine-grained, resource-specific access (Google Docs-style).
+
+## Where to Check (P4 Locality)
+
+- Check at the boundary: the API endpoint, the resolver, the controller.
+- Check at the data layer: defense in depth. A query that bypasses the controller still respects row-level security.
+- Never check only in the UI. The UI is a convenience, not a security boundary.
+
+## Principle of Least Privilege (P2)
+
+- A token/role gets the minimum permissions to do its job.
+- No "admin" role for daily work. Admin is for administration; daily work uses a scoped role.
+- Service tokens are scoped to one service's resources, not "all resources."
+
+## IDOR (Insecure Direct Object Reference) (P1 Zero Trust)
+
+- `/api/users/123` — does the requester own 123? Check.
+- Never assume the user can access any ID they request. The ID is input; inputs are untrusted.
+- Use scoped queries: `User.find({ id, owner: userId })`, not `User.find(id)`.
+
+## Caching and Authz (P3 Defense in Depth)
+
+- Authorization is not cached across users. A cached response for user A is not served to user B.
+- Cache keys include the user/role, not just the resource.
+- "Cache it as public if anyone can see it" — only if truly anyone (no auth).
+
+## What Violates Authorization
+
+| Violation | Principle |
+|-----------|-----------|
+| `/admin` endpoint with no authz check | P1 Zero Trust |
+| `user.role === 'admin'` instead of permission check | P2 (roles change) |
+| IDOR: `User.find(req.params.id)` with no ownership check | P1 Zero Trust |
+| Cached authz decision reused across users | P3 Defense in Depth |
+| Service token with "all resources" scope | P2 Least Privilege |

domains/security/input-validation.md

@@ -0,0 +1,64 @@
+# Input Validation — Derived Rules
+
+> Derives from `domains/security/first-principles.md` P4 (Input Validation), P5 (Output Safety).
+
+## The Rule
+
+All input is untrusted until validated. Validation happens at the boundary, against a schema, with explicit failure modes.
+
+## Validate at the Boundary (P4 Locality)
+
+- The API endpoint, the controller, the message handler — the entry point validates.
+- Internal code trusts validated input. Unvalidated input never reaches the database.
+- Defense in depth: the database also has constraints (P3 Defense in Depth).
+
+## Schema Validation
+
+- Use a schema library (zod, joi, pydantic, json-schema). Never hand-write validation.
+- The schema is the contract. The schema is versioned. The schema is tested.
+- Reject unknown fields (`additionalProperties: false` by default). Be explicit.
+
+## Validation Types
+
+### Type Validation
+- `id` is a UUID, not a string. `age` is an integer ≥ 0. `email` matches a regex (or better, is parsed).
+- Never accept `any`. Never accept `string` for a typed value.
+
+### Range Validation
+- `limit` ≤ 100. `page` ≥ 1. `quantity` ≥ 1 and ≤ stock.
+- Bounds are explicit. No "unbounded" inputs.
+
+### Format Validation
+- `email` is parsed (not just regex). `url` is parsed. `date` is parsed.
+- A regex for email is wrong (RFC 5322 is not a regular language). Use a parser.
+
+### Semantic Validation
+- `start_date < end_date`. `user_id` exists. `product_id` is in stock.
+- Semantic validation may require a database lookup. That's fine.
+
+### Presence Validation
+- Required fields are present. Optional fields are absent or null.
+- Empty string `""` is not the same as null. Be explicit about which you accept.
+
+## Failure Modes (P8 Fail Securely)
+
+- Validation failure → 400 Bad Request with a structured error (`domains/api/error-responses.md`).
+- Never coerce: `"5" + 3` is not validation. Reject, don't guess.
+- Never default: a missing required field is an error, not a default value.
+
+## Output Safety (P5 Output Safety)
+
+- Validation is for input. Encoding is for output.
+- Output to HTML: HTML-encode. Output to SQL: parameterize. Output to URL: URL-encode.
+- Never trust validated input for output. Validate on the way in, encode on the way out.
+
+## What Violates Input Validation
+
+| Violation | Principle |
+|-----------|-----------|
+| `JSON.parse(req.body)` with no schema | P4 Input Validation |
+| `parseInt(req.query.id)` with no range check | P4 |
+| `additionalProperties: true` by default | P1 Contract Fidelity |
+| Coercing `"5"` to `5` silently | P8 Fail Securely |
+| SQL string interpolation (even of "validated" input) | P5 Output Safety |
+| Regex for email validation | P4 (use a parser) |

domains/security/secrets.md

@@ -0,0 +1,72 @@
+# Secrets — Derived Rules
+
+> Derives from `domains/security/first-principles.md` P9 (Secret Hygiene), P1 (Zero Trust), P6 (Crypto Correctness).
+
+## What is a Secret
+
+A secret is any value whose disclosure compromises the system. Examples:
+- API keys, access tokens, refresh tokens
+- Database passwords, service passwords
+- Private keys (TLS, signing, encryption)
+- OAuth client secrets, JWT signing keys
+- Encryption keys (KMS, envelope encryption)
+
+## Never in Code (P9)
+
+- No secrets in source files. No secrets in comments. No secrets in string constants.
+- No secrets in config files committed to git. Use `.env` (gitignored) or a secrets manager.
+- No secrets in test fixtures. Tests use fake/dummy values, never real secrets.
+
+## Never in Logs (P9, domains/observability P6)
+
+- No secrets in log messages, error messages, or stack traces.
+- Redact before logging: replace the secret with `[REDACTED]` or a hash.
+- Never log the request body (it may contain a token). Log the request ID, not the body.
+
+## Never in URLs (P9, P1)
+
+- URLs are logged (server logs, proxy logs, browser history, referrer headers).
+- A token in the URL is a token in everyone's logs.
+- Use headers (`Authorization: Bearer ...`), not query strings.
+
+## Never in Error Messages (P9, domains/errors)
+
+- "Authentication failed: invalid API key sk-abc123" — the secret is in the error.
+- "Authentication failed: invalid API key" — the secret is not.
+- Error messages are for humans; humans do not need the secret to debug.
+
+## Storage (P6 Crypto Correctness)
+
+- At rest: encrypted (KMS, envelope encryption). Never plaintext on disk.
+- In memory: minimal lifetime. Load on use, not on boot. Zero after use (where the language allows).
+- In transit: TLS only. No plaintext HTTP for secrets, ever.
+
+## Rotation (P5 Reversibility, P2 Least Privilege)
+
+- Secrets are rotatable. A secret that cannot be rotated is a liability.
+- Rotation is documented and rehearsed. Not improvised during an incident.
+- Old secrets are revoked after rotation, not "kept just in case."
+- Short-lived secrets (≤ 1 hour) are better than long-lived secrets (≤ forever).
+
+## Scope (P2 Least Privilege)
+
+- A secret has the minimum scope. A secret for service A does not work for service B.
+- Scoped tokens: `scope: read:orders`, not `scope: *`.
+- One secret per environment. Dev, staging, prod use different secrets.
+
+## The `.gitignore` Rule
+
+- `.env`, `.env.secrets`, `.env.*` are in `.gitignore` by default (see Atelier's own `.gitignore`).
+- A secret committed to git is a leaked secret. Rotate immediately. History is forever.
+- Pre-commit hooks scan for high-entropy strings. Use them.
+
+## What Violates Secret Hygiene
+
+| Violation | Principle |
+|-----------|-----------|
+| `API_KEY = "sk-abc123"` in source | P9 |
+| `?token=abc` in a URL | P9, P1 |
+| `console.log(req.body)` where body contains a token | P9, observability P6 |
+| `catch (e) { throw new Error("DB password is pwd123") }` | P9, errors |
+| Same secret in dev and prod | P2 |
+| A 5-year-old API key with no rotation | P5 |

domains/security/supply-chain.md

@@ -0,0 +1,50 @@
+# Supply Chain — Derived Rules
+
+> Derives from `domains/security/first-principles.md` P10 (Surface Minimization), P3 (Defense in Depth), P7 (Auditability).
+
+## Dependencies are Attack Surface (P10)
+
+- Every dependency is code you did not write but must trust. Minimize it.
+- A dependency you do not need is a vulnerability you do not have.
+- Audit dependencies regularly. Remove unused ones (`npm prune`, `pip-autoremove`).
+
+## Lockfiles (P1 Correctness, P5 Reversibility)
+
+- Pin exact versions in a lockfile (`package-lock.json`, `yarn.lock`, `Pipfile.lock`, `Cargo.lock`).
+- Commit the lockfile. A reproducible build requires a committed lock.
+- `npm ci` (not `npm install`) in CI. `pip install -r requirements.txt` with pinned versions.
+
+## Integrity (P6 Crypto Correctness)
+
+- Subresource integrity for web assets: `<script src="..." integrity="sha384-...">`.
+- Package signatures where available (signed npm packages, GPG-signed apt packages).
+- Verify checksums on downloaded artifacts. A tarball without a checksum is untrusted.
+
+## Vulnerability Scanning (P3 Defense in Depth)
+
+- `npm audit`, `pip-audit`, `cargo audit`, `trivy`, `snyk` — run in CI.
+- Fail the build on high/critical vulnerabilities (configurable threshold).
+- Auto-merge security PRs from Dependabot/Renovate when the patch is non-breaking.
+
+## Provenance (P7 Auditability)
+
+- SBOM (Software Bill of Materials): `cyclonedx` or `spdx` output. Know what is in your build.
+- SLSA (Supply-chain Levels for Software Artifacts): provenance attestation for builds.
+- Signed artifacts: cosign, sigstore. A build you cannot verify is untrusted.
+
+## Private Registries (P2 Least Privilege)
+
+- Internal packages come from a private registry, not public npm/PyPI.
+- A typo-squatted public package is a supply chain attack (`lodash` vs `lodahs`).
+- Scope your registry: `@myorg:registry=https://registry.myorg.com`.
+
+## What Violates Supply Chain
+
+| Violation | Principle |
+|-----------|-----------|
+| `npm install` (no lockfile) in CI | P1, P5 |
+| Unpinned dependency `^1.2.3` in production | P1 |
+| No vulnerability scanning in CI | P3 |
+| `eval` of a package's README | P10 (surface) |
+| A dependency with 0 weekly downloads | P10 (no eyes) |
+| No SBOM for a shipped artifact | P7 |

domains/testing/fixtures.md

@@ -0,0 +1,49 @@
+# Test Fixtures — Derived Rules
+
+> Derives from `domains/testing/first-principles.md` P7 (Realism), P2 (Independence), P3 (Determinism).
+
+## Fixtures are Real Data (P7 Realism)
+
+- A fixture resembles production data in shape, distribution, and edge cases.
+- A fixture with `name: "test"` and `email: "a@b.c"` hides bugs that real data surfaces.
+- Use realistic names, realistic emails, realistic dates. `"Jane Doe", "jane.doe@example.com", "2026-03-15"`.
+
+## Factory Over Fixture (P2 Independence, P3 Determinism)
+
+- A fixture file is shared state. A factory is fresh state per test.
+- Prefer factories (e.g., `factory.User()` returning a new instance) over shared fixture files.
+- A shared fixture is mutated by one test, breaks another. Independence is violated.
+
+## Builders for Complex Data
+
+- A builder (`UserBuilder().withEmail().withAdmin().build()`) composes only the fields the test needs.
+- A builder with defaults: every field has a sensible default; tests override only what they test.
+- A builder is the test's API to data. Stable, composable, readable.
+
+## Setup and Teardown (P2 Independence)
+
+- Every test cleans up after itself. No test leaves state for the next.
+- `setUp`/`tearDown` (or `beforeEach`/`afterEach`) restore the world.
+- A test that depends on the order of execution is not independent.
+
+## Determinism (P3)
+
+- No `Date.now()`, no `Math.random()` in fixtures. Inject the clock, inject the RNG.
+- A fixture that uses "now" is non-deterministic. It passes today and fails tomorrow.
+- Fix timestamps: `createdAt: new Date("2026-01-01T00:00:00Z")`.
+
+## Edge Case Fixtures (P9 Edge Case Coverage)
+
+- A fixture set includes: the empty case, the single-item case, the max-size case, the unicode case.
+- A fixture set includes invalid data: malformed email, negative age, future date.
+- Edge case fixtures are first-class, not "extra credit."
+
+## What Violates Fixture Discipline
+
+| Violation | Principle |
+|-----------|-----------|
+| `name: "test"` fixture | P7 Realism |
+| Shared fixture file mutated across tests | P2 Independence |
+| `createdAt: new Date()` (now) in fixture | P3 Determinism |
+| No edge-case fixtures | P9 Edge Case Coverage |
+| A 500-line fixture file | P3 (complexity) |

domains/testing/pyramid.md

@@ -0,0 +1,60 @@
+# Test Pyramid — Derived Rules
+
+> Derives from `domains/testing/first-principles.md` P4 (Fast Feedback), P5 (Coverage of Behavior), P10 (No Test Theater).
+
+## The Pyramid
+
+```
+        /\
+       /e2e\        few, slow, integration
+      /------\
+     /  integ  \    some, medium, contract
+    /----------\
+   /    unit    \   many, fast, isolated
+  /--------------\
+```
+
+- **Unit (many):** test a function/class in isolation. Fast (< 10ms each). The bulk of tests.
+- **Integration (some):** test components together (DB, API client, queue). Medium (< 1s each).
+- **E2E (few):** test the whole system from outside. Slow (> 1s each). The tip of the pyramid.
+
+## Why a Pyramid (P4 Fast Feedback)
+
+- A pyramid inverts to a "ice cream cone" (many e2e, few unit) when devs avoid unit tests.
+- Inverted pyramids are slow and flaky. The feedback loop breaks.
+- The pyramid shape preserves fast feedback: most failures are unit failures, found in < 10ms.
+
+## What Goes Where
+
+| Test Type | What it Covers | Speed | Count |
+|-----------|----------------|-------|-------|
+| Unit | A function, a class, a pure module | < 10ms | Many |
+| Integration | DB queries, API contract, queue behavior | < 1s | Some |
+| E2E | A user flow, an API request → response end-to-end | > 1s | Few |
+
+- A unit test does not hit the database. A unit test does not make a network call.
+- An integration test does not test business logic; it tests the integration.
+- An e2e test does not test edge cases; it tests the happy path. Edge cases are unit tests.
+
+## Anti-Patterns (P10 No Test Theater)
+
+- **Ice cream cone:** many e2e, few unit. Slow, flaky, no signal.
+- **Cupcake:** same count at every level. No pyramid shape. Slow.
+- **Only unit:** 100% unit coverage, 0% integration. The system is untested as a whole.
+- **Only e2e:** every edge case is an e2e test. The suite takes an hour.
+
+## Coverage (P5)
+
+- Unit coverage of behavior: every branch, every edge case, every error path.
+- Integration coverage of contracts: every API endpoint, every DB query, every queue interaction.
+- E2E coverage of flows: the top 3–5 critical user flows. Not every permutation.
+
+## What Violates the Pyramid
+
+| Violation | Principle |
+|-----------|-----------|
+| E2E test for an edge case | P4 (slow feedback) |
+| Unit test that hits the DB | P2 (not isolated) |
+| 0 integration tests | P5 (no coverage of contracts) |
+| 500 e2e tests, 50 unit tests | P10 (theater) |
+| A 30-second test suite | P4 (feedback loop broken) |

domains/uiux/copywriting.md

@@ -0,0 +1,45 @@
+# UI Copywriting — Derived Rules
+
+> Derives from `domains/uiux/first-principles.md` P3 (Clarity), P1 (User Primacy), P5 (Forgiveness).
+
+## Write for the User (P1 User Primacy)
+
+- The reader is a user, not a developer. "Sign in" not "Authenticate."
+- The reader is busy. Short sentences. Active voice. Verbs first.
+- The reader is anxious. Reassure. "Your changes are saved." Not "State persisted."
+
+## Clarity (P3)
+
+- One idea per sentence. One action per button.
+- Labels are nouns: "Email", "Password". Actions are verbs: "Sign in", "Save".
+- Errors are specific: "Email is invalid" not "Something went wrong."
+- Empty states are instructive: "No projects yet. Create one." Not "No data."
+
+## Forgiveness (P5)
+
+- Destructive actions warn: "This will delete 42 items. This cannot be undone."
+- Confirmations name the consequence, not just the action. "Delete user" → "Delete Jane Doe and 12 associated items?"
+- Undo is offered when possible. "Deleted. Undo." beats "Are you sure?" when undo is cheap.
+
+## Tone (P3, P1)
+
+- Helpful, not clever. Cleverness ages. Helpfulness does not.
+- Apologetic when the system is at fault. "We couldn't save that. Try again." Not "Error."
+- Neutral, not excited. "Saved." Not "Awesome! Saved!! 🎉" (unless the brand is intentionally playful).
+
+## Microcopy (P3 Clarity, P9 Simplicity)
+
+- Buttons: 1–3 words. "Sign in", "Create account", "Send invite".
+- Tooltips: 1 sentence. Explain what the field does, not what the label says.
+- Empty states: 1 sentence of explanation + 1 action. "No team members yet. Invite your first."
+- Loading: present tense. "Saving..." not "Saved" (until it is).
+
+## What Violates UI Copywriting
+
+| Violation | Principle |
+|-----------|-----------|
+| "Error code 500" to a user | P3, P1 |
+| "Are you sure?" with no consequence | P5 (no information) |
+| "Submit" on a delete button | P3 (wrong verb) |
+| 50-word tooltip | P9 Simplicity |
+| "Awesome!" on a routine save | P1 (not for the user) |

domains/uiux/tokens.md

@@ -0,0 +1,48 @@
+# Design Tokens — Derived Rules
+
+> Derives from `domains/uiux/first-principles.md` P7 (Hierarchy), P8 (Consistency), P9 (Simplicity).
+
+## What is a Token
+
+A design token is the smallest unit of a design system: a color, a spacing, a font size, a radius. It has a name and a value. The name is the API; the value is the implementation.
+
+## The Token Hierarchy
+
+```
+Global tokens (e.g., --color-blue-500)
+  → Alias tokens (e.g., --color-button-primary)
+    → Component tokens (e.g., --button-primary-bg)
+```
+
+- Global tokens are the raw palette. They have no semantic meaning.
+- Alias tokens have meaning: "this is the button background." They reference global tokens.
+- Component tokens are scoped to a component. They reference alias tokens.
+- Components reference component or alias tokens, never global tokens directly.
+
+## No Raw Values (P8 Consistency)
+
+- A component never hardcodes `#3b82f6` or `16px`. It references `--color-button-primary` or `--space-4`.
+- A hardcoded value is a token that should exist but does not. It is design debt.
+- The token is the API to the design system. Bypassing it bypasses the system.
+
+## Naming (P3 Clarity)
+
+- Tokens are semantic, not visual: `--color-text-primary`, not `--color-dark-gray`.
+- Visual names couple to the implementation. Semantic names survive a redesign.
+- `--color-button-primary-bg` is clear. `--color-blue` is not (which button? what state?).
+
+## Theming via Tokens (P5 Forgiveness, core C5 Reversibility)
+
+- Themes are sets of token values. Switch theme = switch token values, not switch CSS.
+- Dark mode: `--color-text-primary: #fff` instead of `#000`. The component code does not change.
+- A component that hardcodes colors cannot be themed. A component that uses tokens can.
+
+## What Violates Token Discipline
+
+| Violation | Principle |
+|-----------|-----------|
+| `color: #3b82f6` in a component | P8 Consistency |
+| `--color-blue-500` referenced by a component directly | P9 (skip alias) |
+| `--color-dark-gray` (visual name) | P3 Clarity |
+| A component that cannot be themed | P5, core C5 |
+| No global tokens, every component invents its own palette | P8 |

examples/bad/god-object.md

@@ -0,0 +1,107 @@
+# Bad Example: God Object
+
+> A component that violates Atelier principles. Each violation is cited.
+
+## The Code
+
+```typescript
+// UserManager.ts — 1,200 lines
+class UserManager {
+  private users: User[] = [];
+  private cache: Map<string, User> = new Map();
+  private db: Database;
+  private emailService: EmailService;
+  private logger: Logger;
+  private auditLog: AuditLog;
+
+  constructor(db: Database, email: EmailService, logger: Logger, audit: AuditLog) {
+    this.db = db;
+    this.emailService = email;
+    this.logger = logger;
+    this.auditLog = audit;
+  }
+
+  // CRUD
+  async createUser(data: UserData): Promise<User> { /* 80 lines */ }
+  async getUser(id: string): Promise<User> { /* 40 lines */ }
+  async updateUser(id: string, data: Partial<UserData>): Promise<User> { /* 60 lines */ }
+  async deleteUser(id: string): Promise<void> { /* 50 lines */ }
+  async listUsers(page: number): Promise<User[]> { /* 40 lines */ }
+
+  // Email
+  async sendWelcomeEmail(user: User): Promise<void> { /* 50 lines */ }
+  async sendPasswordReset(user: User): Promise<void> { /* 50 lines */ }
+  async sendDeletionNotice(user: User): Promise<void> { /* 40 lines */ }
+
+  // Auth
+  async authenticate(email: string, password: string): Promise<boolean> { /* 70 lines */ }
+  async authorize(userId: string, action: string): Promise<boolean> { /* 60 lines */ }
+  async hashPassword(password: string): Promise<string> { /* 20 lines */ }
+
+  // Cache
+  private cacheGet(id: string): User | null { /* 20 lines */ }
+  private cacheSet(user: User): void { /* 20 lines */ }
+  private cacheInvalidate(id: string): void { /* 20 lines */ }
+
+  // Audit
+  private logAudit(action: string, userId: string): void { /* 30 lines */ }
+
+  // Validation
+  private validateEmail(email: string): boolean { /* 20 lines */ }
+  private validatePassword(password: string): boolean { /* 20 lines */ }
+
+  // Serialization
+  toJSON(user: User): Record<string, unknown> { /* 30 lines */ }
+  fromJSON(data: Record<string, unknown>): User { /* 30 lines */ }
+
+  // ... 200 more lines of helper methods
+}
+```
+
+## Violations
+
+### C3 Simplicity (Core)
+- A 1,200-line class doing 8 different things (CRUD, email, auth, cache, audit, validation, serialization).
+- The class cannot be understood in one read. Complexity is the liability.
+- **Fix:** Split into `UserRepository` (CRUD), `UserEmailService` (email), `UserAuthService` (auth), `UserCache` (cache), `UserAuditLogger` (audit), `UserValidator` (validation), `UserSerializer` (serialization).
+
+### C6 Composability (Core)
+- The class takes 4 dependencies and does 8 jobs. It is not composable; it is monolithic.
+- You cannot reuse the email logic without the DB, the cache, the audit log.
+- **Fix:** Each responsibility is its own class. Compose them: `UserEmailService` takes only `EmailService`.
+
+### components.md §1 Single Responsibility (UI/UX, applies to code)
+- The class name is `UserManager`. "Manager" is a smell — it manages what? Everything.
+- If the name is "Manager," it has no single responsibility.
+- **Fix:** Name by responsibility: `UserRepository`, `UserAuthService`. Names that cannot be "And"-ed.
+
+### C4 Locality (Core)
+- Cache logic is in the same class as email logic. A change to cache touches the email methods' neighbor.
+- Related logic (cache get/set/invalidate) is grouped, but unrelated logic (email) is adjacent.
+- **Fix:** `UserCache` is its own class. Cache changes are local to cache.
+
+### C2 Clarity (Core)
+- A reader cannot answer "what does `UserManager` do?" in one sentence.
+- The class has 20+ methods. The reader must scan all of them to find the one they need.
+- **Fix:** Smaller classes with clear names. The name is the documentation.
+
+### Security P2 Least Privilege (Security)
+- The class has `db`, `emailService`, `logger`, `auditLog` — all available to all methods.
+- `sendWelcomeEmail` has access to `db.delete`. Least privilege is violated.
+- **Fix:** Each service has only the dependencies it needs. `UserEmailService` has `EmailService`, not `Database`.
+
+### Testing P2 Independence (Testing)
+- To test `sendWelcomeEmail`, you must construct `UserManager` with a real/mock DB, email, logger, audit.
+- The test setup is 4 mocks for one method. Independence is violated.
+- **Fix:** Test `UserEmailService` with one mock (`EmailService`).
+
+## What This Example Reveals
+
+The "God Object" is the cardinal sin of OOP. It violates C3 (Simplicity), C6 (Composability), C4 (Locality), and C2 (Clarity) simultaneously. Every other principle suffers downstream:
+
+- Testing is hard (T2 Independence).
+- Security is loose (S2 Least Privilege).
+- Evolution is brittle (a change to email risks cache).
+- Review is exhausting (a 1,200-line diff).
+
+The fix is always the same: **decompose by responsibility**. The class name is the test: if it is "Manager," "Handler," or "Helper," it has no single responsibility.

examples/bad/leaky-abstraction.md

@@ -0,0 +1,87 @@
+# Bad Example: Leaky Abstraction
+
+> An abstraction that leaks its implementation details, violating Atelier principles. Each violation is cited.
+
+## The Code
+
+```typescript
+// UserRepository — "abstracts" the database
+class UserRepository {
+  async findAll(): Promise<UserRow[]> {
+    // Leaks: returns the raw DB row type, not a domain User
+    return db.query('SELECT id, email, password_hash, created_at, deleted_at FROM users');
+  }
+
+  async findByEmail(email: string): Promise<UserRow | null> {
+    // Leaks: the caller must know to filter deleted_at
+    const rows = await db.query('SELECT * FROM users WHERE email = $1', [email]);
+    return rows[0] || null;
+  }
+
+  async save(user: UserRow): Promise<void> {
+    // Leaks: the caller must know the column names and the SQL
+    await db.query(
+      'UPDATE users SET email = $1, password_hash = $2, updated_at = now() WHERE id = $3',
+      [user.email, user.password_hash, user.id]
+    );
+  }
+}
+
+// Usage — the leak is visible
+const repo = new UserRepository();
+const user = await repo.findByEmail('jane@example.com');
+if (user && !user.deleted_at) {  // caller must know about soft delete
+  user.password_hash = await hash(newPassword);  // caller must know the column
+  await repo.save(user);  // caller must know it's an UPDATE
+}
+```
+
+## Violations
+
+### C6 Composability (Core)
+- The abstraction is supposed to hide the database. It does not.
+- The caller must know: the row type (`UserRow`), the soft-delete column (`deleted_at`), the password column (`password_hash`), the SQL operation (`UPDATE`).
+- The abstraction is a thin wrapper. It composes nothing; it leaks everything.
+- **Fix:** Return a domain `User` (no `password_hash`, no `deleted_at`). Hide soft delete (the repo filters it). Hide persistence (the caller calls `save`, not `UPDATE`).
+
+### C2 Clarity (Core)
+- The caller's code is unclear: `if (user && !user.deleted_at)` — what is `deleted_at`? Why does the caller check it?
+- The abstraction was supposed to clarify. It muddied.
+- **Fix:** `repo.findByEmail()` returns `User | null` (already filtered). The caller does not know soft delete exists.
+
+### API P2 Clarity (API, by analogy)
+- The repo's API exposes the DB schema in its return types. `UserRow` is a DB concept, not a domain concept.
+- The public contract (return type) leaks the private implementation (the table).
+- **Fix:** The return type is `User`, a domain type. `UserRow` is internal.
+
+### Data P8 Lifecycle Awareness (Data)
+- The soft-delete lifecycle (`deleted_at`) is the repo's concern. The caller should not manage it.
+- By exposing `deleted_at`, the repo forces every caller to remember the filter. A forgotten filter is a soft-delete leak.
+- **Fix:** The repo filters `deleted_at IS NULL` in every query. The caller never sees `deleted_at`.
+
+### Security P9 Secret Hygiene (Security)
+- `password_hash` is in the returned `UserRow`. The caller now has access to the password hash.
+- A caller that logs `user` logs the hash. A caller that serializes `user` serializes the hash.
+- **Fix:** `User` does not include `password_hash`. Only `UserRepository` and `AuthService` (internal) see it.
+
+### C4 Locality (Core)
+- The SQL is in the repo, but the column knowledge (`password_hash`, `deleted_at`) is in the caller.
+- A column rename touches the repo AND every caller. Locality is violated.
+- **Fix:** Column names are local to the repo. The caller knows only the domain `User`.
+
+### C5 Reversibility (Core)
+- Changing the database (e.g., from SQL to NoSQL, or renaming a column) requires touching every caller.
+- The abstraction was supposed to make the change local. It does not.
+- **Fix:** The repo's interface (`findByEmail`, `save`) is stable. The implementation changes; the callers do not.
+
+## What This Example Reveals
+
+The leaky abstraction is the false promise of encapsulation. The class is named `UserRepository` (suggesting it abstracts persistence), but it returns raw DB rows, exposes lifecycle columns, and leaks secret fields. The abstraction exists in name only.
+
+The cost:
+- Every caller must know the DB schema (C6 violated).
+- A schema change touches every caller (C5 violated, C4 violated).
+- Secret fields leak to callers (Security P9 violated).
+- The lifecycle is the caller's burden (Data P8 violated).
+
+The fix is always the same: **the abstraction's public type is the domain type, not the implementation type**. `UserRepository.findByEmail()` returns `User | null`, where `User` has `id`, `email`, `name` — and nothing else. `password_hash`, `deleted_at`, `UserRow` are internal. The caller knows nothing about the database.

examples/bad/silent-error.md

@@ -0,0 +1,88 @@
+# Bad Example: Silent Error
+
+> An error-handling pattern that violates Atelier principles. Each violation is cited.
+
+## The Code
+
+```typescript
+async function getUser(id: string): Promise<User | null> {
+  try {
+    const user = await db.query('SELECT * FROM users WHERE id = $1', [id]);
+    return user;
+  } catch (e) {
+    return null;
+  }
+}
+
+async function processOrder(orderId: string): Promise<void> {
+  const order = await getOrder(orderId);
+  if (!order) {
+    return;  // silently do nothing
+  }
+  // ... process
+}
+
+// Usage in a route
+router.get('/users/:id', async (req, res) => {
+  const user = await getUser(req.params.id);
+  if (!user) {
+    res.status(404).json({ error: 'Not found' });
+  } else {
+    res.json({ data: user });
+  }
+});
+```
+
+## Violations
+
+### Errors P2 Fail Loudly (Errors)
+- `catch (e) { return null }` swallows the error. The caller cannot distinguish "user not found" from "database down."
+- A database outage returns 404s. The operator never knows. Silent failure.
+- **Fix:** Catch and re-throw with context, or return a typed error (`Result<User, Error>`). Never `null` for "an error happened."
+
+### Errors P3 Fail Specifically (Errors)
+- `return null` is the least specific response. It could mean: not found, db error, network error, permission error.
+- The caller's `if (!user)` cannot distinguish these. The 404 is a lie if the real cause was a 500.
+- **Fix:** Return `Result` or throw. The error type/code carries the specificity.
+
+### Errors P1 Errors are Data (Errors)
+- `null` is not data. It is the absence of data. Conflating "error" with "absence" loses information.
+- The error (a database failure) was data; it was thrown away and replaced with `null`.
+- **Fix:** Errors are values. Return the error value, not a sentinel absence.
+
+### Errors P4 Preserve Context (Errors)
+- The catch block discards `e`. The stack trace, the error message, the cause — all gone.
+- The log has no record. The operator cannot debug.
+- **Fix:** Log the error with context. Wrap and re-throw: `throw new Error('getUser failed', { cause: e })`.
+
+### Errors P9 Errors are Logged (Errors)
+- The error is not logged. The handling (return null) is the entire response. The log is missing.
+- An error that is not logged is an error that cannot be investigated.
+- **Fix:** `logger.error({ err: e, userId: id })` before returning/rethrowing.
+
+### Errors P10 Errors Don't Lie (Errors)
+- `return null` claims "no user" when the truth may be "database down." The function lies.
+- The 404 response claims "not found" when the truth may be "internal error." The API lies.
+- **Fix:** The response status must match the actual condition. 500 for server errors, 404 for not found.
+
+### Observability P2 Correlation, P3 Context (Observability)
+- No `request_id`. No correlation across services.
+- No context in the (missing) log. "What was the user doing?" is unanswerable.
+- **Fix:** Propagate `request_id`. Log with path, method, user_id.
+
+### Security P8 Fail Securely (Security)
+- The silent failure is fail-open in disguise. If `getUser` fails due to an authz check throwing, the catch returns `null`.
+- The caller treats `null` as "not found" and may proceed, or may 404. Either way, the security failure is hidden.
+- **Fix:** Distinguish "not found" (404) from "authz error" (403) from "db error" (500). Never collapse them into `null`.
+
+## What This Example Reveals
+
+The silent error is the most common and most damaging anti-pattern. It violates Errors P2 (Fail Loudly), P3 (Fail Specifically), P1 (Errors are Data), P4 (Preserve Context), P9 (Errors are Logged), P10 (Errors Don't Lie) — six of ten error principles in one catch block.
+
+The downstream effects:
+- Operators cannot debug (no log, no context).
+- Users see wrong errors (404 for a 500).
+- Security failures hide (authz error becomes "not found").
+- The system appears healthy when it is not (no metrics, no logs).
+
+The fix is always the same: **never swallow an error**. Log it, wrap it, rethrow it, or return it as a typed value. Never `return null` for "something went wrong."

examples/good/api-endpoint.md

@@ -0,0 +1,79 @@
+# Good Example: API Endpoint
+
+> A REST endpoint that follows Atelier's API principles. Each aspect cites the principle it satisfies.
+
+## The Endpoint
+
+```typescript
+// POST /v1/orders — create an order
+router.post('/v1/orders', auth, validate(CreateOrderSchema), async (req, res) => {
+  const { userId, items } = req.body;
+
+  const order = await orderService.create({ userId, items });
+
+  res.status(201).location(`/v1/orders/${order.id}`).json({
+    data: order,
+  });
+});
+```
+
+## What Makes It Good
+
+### Resource Naming (API P2 Clarity, P3 Predictability)
+- `/v1/orders` — noun, plural, lowercase, hyphenated.
+- Versioned (`/v1`) — P5 Versioning.
+- No verb in the URL; the HTTP method is the verb.
+
+### Method Semantics (API P1 Contract Fidelity, P6 Idempotency)
+- POST for creation. 201 on success (not 200). `Location` header for the new resource.
+- Idempotency key supported via middleware (omitted for brevity) — P6.
+
+### Authentication (API P8 Security, Security P1 Zero Trust)
+- `auth` middleware runs on every endpoint by default. No opt-in auth.
+- The endpoint does not re-implement auth; it relies on the boundary check.
+
+### Input Validation (API P8, Security P4 Input Validation)
+- `validate(CreateOrderSchema)` — schema-based validation at the boundary.
+- The schema (zod, joi, etc.) defines types, ranges, required fields.
+- Unknown fields rejected (`additionalProperties: false` in the schema).
+
+### Response Shape (API P2 Clarity)
+- `{ data: order }` — wrapped, not a bare object. Allows adding pagination/metadata without breaking.
+- The shape is consistent across all endpoints in the API.
+
+### Error Handling (API P9 Error Transparency, Errors P1 Errors are Data)
+- Errors thrown in `orderService.create` are caught by centralized middleware.
+- Errors are structured: `{ error: { code, message, request_id } }`.
+- 404 → `ORDER_NOT_FOUND`, 409 → `DUPLICATE_ORDER`, 422 → `VALIDATION_FAILED`.
+
+### Observability (Observability P2 Correlation, P3 Sufficient Context)
+- `request_id` propagated via middleware. Every log in the request includes it.
+- Significant events logged: "order created", "order creation failed".
+
+### Economy (Core C8, Performance P4 Resource Bounds)
+- The order creation is bounded in time (the service has a timeout).
+- No unbounded query; no loading all products into memory.
+
+## The Schema (for completeness)
+
+```typescript
+const CreateOrderSchema = z.object({
+  userId: z.string().uuid(),
+  items: z.array(z.object({
+    productId: z.string().uuid(),
+    quantity: z.number().int().positive().max(100),
+  })).min(1).max(50),
+}).strict();  // additionalProperties: false
+```
+
+- `userId` is a UUID (Data P7 Type Fidelity).
+- `quantity` is bounded (Performance P4).
+- `items` is bounded (1–50) (Performance P4, Security P10 Surface Minimization).
+- `.strict()` rejects unknown fields (Security P4).
+
+## What This Example Does NOT Do (And Why That's Good)
+
+- Does not return 200 on error — the status code is the first signal (API P9).
+- Does not log the request body — may contain PII (Observability P6, Security P9).
+- Does not construct SQL by string interpolation — uses a service layer (Security P5 Output Safety).
+- Does not skip auth for "internal" callers — Zero Trust (Security P1).

examples/good/db-schema.md

@@ -0,0 +1,88 @@
+# Good Example: Database Schema
+
+> A SQL schema that follows Atelier's Data principles. Each aspect cites the principle it satisfies.
+
+## The Schema
+
+```sql
+-- Users table
+CREATE TABLE users (
+  id          UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  email       VARCHAR(255) NOT NULL,
+  name        VARCHAR(100) NOT NULL,
+  created_at  TIMESTAMPTZ NOT NULL DEFAULT now(),
+  updated_at  TIMESTAMPTZ NOT NULL DEFAULT now(),
+  deleted_at  TIMESTAMPTZ,
+
+  CONSTRAINT users_email_unique UNIQUE (email),
+  CONSTRAINT users_email_format CHECK (email ~ '^[^@]+@[^@]+\.[^@]+$')
+);
+
+CREATE INDEX users_email_idx ON users (email) WHERE deleted_at IS NULL;
+CREATE INDEX users_created_at_idx ON users (created_at DESC);
+
+-- Orders table
+CREATE TABLE orders (
+  id          UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  user_id     UUID NOT NULL REFERENCES users(id) ON DELETE RESTRICT,
+  status      VARCHAR(20) NOT NULL DEFAULT 'pending',
+  total_cents INTEGER NOT NULL,
+  created_at  TIMESTAMPTZ NOT NULL DEFAULT now(),
+
+  CONSTRAINT orders_status_valid CHECK (status IN ('pending', 'paid', 'shipped', 'cancelled')),
+  CONSTRAINT orders_total_positive CHECK (total_cents >= 0)
+);
+
+CREATE INDEX orders_user_id_idx ON orders (user_id);
+CREATE INDEX orders_status_created_idx ON orders (status, created_at DESC);
+```
+
+## What Makes It Good
+
+### Truth (Data P1)
+- The schema reflects the domain: `users` have `email`, `name`, lifecycle timestamps. `orders` have `status`, `total`.
+- No column named after a feature (`is_active_for_X`). No application state in the schema.
+
+### Invariants in the Schema (Data P3)
+- `NOT NULL` where required: `email`, `name`, `user_id`, `status`, `total_cents`.
+- `UNIQUE (email)` — emails are unique. Enforced in the DB, defended in the app.
+- `CHECK (status IN (...))` — status is a finite domain. Enforced in the DB.
+- `CHECK (total_cents >= 0)` — totals are non-negative. Enforced in the DB.
+- `REFERENCES users(id) ON DELETE RESTRICT` — you cannot delete a user with orders. Referential integrity (P9).
+
+### Type Fidelity (Data P7)
+- `id` is `UUID`, not `VARCHAR(36)`. The type matches the domain.
+- `created_at` is `TIMESTAMPTZ`, not `VARCHAR` or `INTEGER`. Timezone-aware.
+- `total_cents` is `INTEGER`, not `FLOAT`. Money in cents avoids floating point (P1 Truth).
+- `status` is `VARCHAR(20)` with a CHECK, not a free `TEXT`. Bounded.
+
+### Naming Consistency (Data P6)
+- snake_case: `users`, `orders`, `user_id`, `created_at`.
+- Foreign key: `user_id` (singular table + `_id`), not `uid` or `user`.
+- Timestamps: `created_at`, `updated_at`, `deleted_at` — consistent suffix `_at`.
+
+### Lifecycle Awareness (Data P8)
+- `deleted_at` for soft delete. Lifecycle is first-class.
+- The unique index on email is partial: `WHERE deleted_at IS NULL` — allows re-registration after soft delete.
+- Every query must filter `deleted_at IS NULL` (a discipline, not a schema property).
+
+### Indexing with Intent (Data P5, P10)
+- `users_email_idx` — queries by email (login, lookup). Partial (excludes soft-deleted).
+- `users_created_at_idx` — list users by recency. DESC matches the typical query.
+- `orders_user_id_idx` — list a user's orders. FK index (join performance).
+- `orders_status_created_idx` — composite for "open orders by recency" (`WHERE status = 'pending' ORDER BY created_at DESC`).
+- No index on every column. Each index serves a query.
+
+### Migration Safety (Data P4)
+- This schema is created via a migration with an `up` and a `down`.
+- The `down` drops the tables in reverse order (orders, then users) to respect FKs.
+- Adding a column later uses expand-contract (nullable first, then constrained).
+
+## What This Example Does NOT Do (And Why That's Good)
+
+- Does not use `FLOAT` for money — floating point errors (P7, P1).
+- Does not use `VARCHAR` for the UUID — wrong type (P7).
+- Does not omit the FK on `orders.user_id` — unenforced relationship (P9).
+- Does not index every column — write amplification (P10, C8).
+- Does not use `is_deleted BOOLEAN` without a timestamp — loses the deletion time (P8).
+- Does not allow `status` to be free text — would lose the finite domain (P3).

examples/good/error-handler.md

@@ -0,0 +1,139 @@
+# Good Example: Error Handler
+
+> An error handler that follows Atelier's Errors principles. Each aspect cites the principle it satisfies.
+
+## The Handler
+
+```typescript
+// Centralized error middleware
+import { v4 as uuidv4 } from 'uuid';
+
+type AppError = {
+  code: string;
+  message: string;
+  statusCode: number;
+  details?: Record<string, unknown>;
+  cause?: unknown;
+};
+
+function errorHandler(err: unknown, req: Request, res: Response, next: NextFunction) {
+  const requestId = req.headers['x-request-id'] as string || uuidv4();
+
+  const appError = normalizeError(err, requestId);
+
+  // Log with full context (server-side only)
+  logger.error({
+    request_id: requestId,
+    code: appError.code,
+    message: appError.message,
+    details: appError.details,
+    path: req.path,
+    method: req.method,
+    user_id: req.user?.id,
+    stack: err instanceof Error ? err.stack : undefined,
+  });
+
+  // Respond with safe, structured error
+  res.status(appError.statusCode).json({
+    error: {
+      code: appError.code,
+      message: appError.message,
+      request_id: requestId,
+      ...(appError.details ? { details: appError.details } : {}),
+    },
+  });
+}
+
+function normalizeError(err: unknown, requestId: string): AppError {
+  // Known error types — preserve their code and status
+  if (err instanceof ValidationError) {
+    return {
+      code: err.code,
+      message: err.message,
+      statusCode: 422,
+      details: err.details,
+    };
+  }
+  if (err instanceof NotFoundError) {
+    return { code: err.code, message: err.message, statusCode: 404 };
+  }
+  if (err instanceof AuthError) {
+    return { code: 'AUTH_REQUIRED', message: 'Authentication required', statusCode: 401 };
+  }
+
+  // Unknown error — fail securely, do not leak internals
+  return {
+    code: 'INTERNAL_ERROR',
+    message: 'An internal error occurred',
+    statusCode: 500,
+    cause: err,
+  };
+}
+```
+
+## What Makes It Good
+
+### Errors are Data (Errors P1)
+- Errors are normalized into a structured `AppError` type. They are values, not raw exceptions.
+- The `code` is a stable, machine-consumable string (`VALIDATION_FAILED`, not a free message).
+- The handler treats every error as data to be transformed, not a flow to be caught.
+
+### Fail Loudly (Errors P2)
+- No `catch (e) {}`. Every error reaches the handler.
+- No silent swallowing. The error is logged and responded to.
+- The middleware is centralized — every route uses it. No route can "forget" to handle errors.
+
+### Fail Specifically (Errors P3)
+- `ValidationError` → 422 with `code: err.code` (specific, e.g., `INVALID_EMAIL`).
+- `NotFoundError` → 404 with `code: err.code` (e.g., `USER_NOT_FOUND`).
+- Unknown → 500 with `INTERNAL_ERROR` (generic only when truly unknown).
+- Never "Something went wrong" — always a specific code.
+
+### Preserve Context (Errors P4)
+- Server-side log includes: `request_id`, `code`, `message`, `details`, `path`, `method`, `user_id`, `stack`.
+- Client-side response includes: `code`, `message`, `request_id`, `details`.
+- The `request_id` ties the client response to the server log. Debuggable.
+
+### Recoverable When Possible (Errors P5)
+- 422 (validation) — the client can fix and retry.
+- 401 (auth) — the client can re-auth and retry.
+- 404 (not found) — the client can correct the ID.
+- Only 500 is "the server has a bug" — not recoverable by the client.
+
+### Unrecoverable Means Stop (Errors P6)
+- A 500 does not limp on. It logs and returns.
+- The server does not try to "recover" from an unknown error by guessing. It fails fast.
+
+### Errors are Boundaries (Errors P7)
+- The middleware is the boundary. Internal error types (`ValidationError`, `NotFoundError`) are translated to HTTP responses here.
+- Internal code throws domain errors; the boundary translates to HTTP. No internal error type leaks to the client.
+
+### User-Facing Errors are UX (Errors P8)
+- `message` is for the developer (log + response). The client UI renders a user-facing message based on `code`.
+- `INTERNAL_ERROR` → "Something went wrong. We're on it." (user-facing), not the stack.
+
+### Errors are Logged (Errors P9)
+- Every error is logged at ERROR level with full context.
+- The handling is the recovery (return a response); the log is the memory (investigate later).
+
+### Errors Don't Lie (Errors P10)
+- The status code matches the error type. 422 for validation, not 200.
+- `INTERNAL_ERROR` is returned only for unknown errors. Known errors get their specific code.
+- Never claim success on failure. Never claim failure on success.
+
+### Security (Security P5 Output Safety, P9 Secret Hygiene)
+- Unknown errors return `INTERNAL_ERROR` with no internal details. No stack trace to the client.
+- The stack is logged server-side, never sent to the client.
+- The error message does not echo the input (which may contain a token).
+
+### Observability (Observability P2 Correlation, P3 Context)
+- `request_id` on every error. Correlatable across services.
+- Sufficient context in the log: path, method, user_id. "What was the user doing?" is answerable.
+
+## What This Example Does NOT Do (And Why That's Good)
+
+- Does not `catch (e) { return null }` — silent failure (P2).
+- Does not return 200 with `{ error: ... }` — the status code lies (API P9).
+- Does not send the stack trace to the client — information leak (Security P5).
+- Does not log the request body — may contain secrets (Security P9, Observability P6).
+- Does not use a generic `Error("error")` — not specific (P3).

examples/good/react-component.md

@@ -0,0 +1,108 @@
+# Good Example: React Component
+
+> A UI component that follows Atelier's UI/UX principles. Each aspect cites the principle it satisfies.
+
+## The Component
+
+```tsx
+import { useId, useState } from 'react';
+import { Button } from './Button';
+import { Spinner } from './Spinner';
+
+type DeleteButtonProps = {
+  /** The resource name to display in the confirmation */
+  resourceName: string;
+  /** Called when the user confirms deletion */
+  onDelete: () => Promise<void>;
+};
+
+export function DeleteButton({ resourceName, onDelete }: DeleteButtonProps) {
+  const [isConfirming, setIsConfirming] = useState(false);
+  const [isDeleting, setIsDeleting] = useState(false);
+  const confirmId = useId();
+
+  const handleConfirm = async () => {
+    setIsDeleting(true);
+    try {
+      await onDelete();
+    } finally {
+      setIsDeleting(false);
+      setIsConfirming(false);
+    }
+  };
+
+  if (isConfirming) {
+    return (
+      <span role="group" aria-labelledby={confirmId}>
+        <span id={confirmId}>Delete {resourceName}? This cannot be undone.</span>
+        <Button variant="danger" onClick={handleConfirm} disabled={isDeleting}>
+          {isDeleting ? <Spinner label="Deleting" /> : 'Yes, delete'}
+        </Button>
+        <Button variant="ghost" onClick={() => setIsConfirming(false)} disabled={isDeleting}>
+          Cancel
+        </Button>
+      </span>
+    );
+  }
+
+  return (
+    <Button variant="danger" onClick={() => setIsConfirming(true)}>
+      Delete
+    </Button>
+  );
+}
+```
+
+## What Makes It Good
+
+### Single Responsibility (components.md §1)
+- The component does one thing: confirm and trigger a deletion. No "And" in the name.
+- The `onDelete` callback is the single output. The component owns the confirmation UI, not the deletion logic.
+
+### Explicit Boundaries (components.md §3)
+- Props are typed (`DeleteButtonProps`). Required props are required.
+- `onDelete` returns a `Promise<void>` — the caller knows it's async.
+- The component never reads global state. It receives `resourceName` and `onDelete`.
+
+### Predictable State (components.md §4)
+- `isConfirming` and `isDeleting` are owned by the component (only it cares).
+- State is not duplicated. The parent does not know about confirmation.
+- The component transitions: idle → confirming → deleting → idle.
+
+### Render Purity (components.md §5)
+- Given the same props and state, the component renders the same output.
+- Side effects (`onDelete`) are in the event handler, not in render.
+- `useId()` is deterministic per component instance (React guarantee).
+
+### Accessible by Default (components.md §6, uiux P2)
+- The confirmation group has `role="group"` and `aria-labelledby`.
+- The Spinner has a `label` (screen reader announces "Deleting").
+- Buttons have text labels (not icon-only).
+- Focus order is logical (confirm → cancel).
+- Keyboard-reachable (buttons are natively focusable).
+
+### Forgiveness (UI/UX P5, P10 Reversibility)
+- Destructive action requires confirmation (P5).
+- "This cannot be undone" names the consequence (P3 Clarity).
+- "Cancel" is offered and is not disabled during deletion (the user can cancel the *next* action).
+- The state is reversible: `isConfirming` can be set back to `false` (P10).
+
+### Style via Tokens (components.md §7)
+- `variant="danger"` and `variant="ghost"` reference design tokens, not raw colors.
+- No `style={{ color: 'red' }}` — the token system owns the visual.
+
+### Feedback (UI/UX P4)
+- The button shows a Spinner while deleting (P4, P6 Performance perception).
+- The button is disabled while deleting (prevents double-click).
+- The label changes: "Yes, delete" → Spinner (state is communicated).
+
+### Clarity (UI/UX P3)
+- "Delete {resourceName}? This cannot be undone." — specific, names the resource and the consequence.
+- No "Are you sure?" — vague. No "Submit" — wrong verb.
+
+## What This Example Does NOT Do (And Why That's Good)
+
+- Does not use a `window.confirm()` dialog — not accessible, not styled, not composable.
+- Does not render a modal — the inline confirmation is lighter and less disruptive (P9 Simplicity).
+- Does not auto-delete on click — forgiveness (P5).
+- Does not hardcode "Project" — the resource name is a prop (composability, components.md §3).

languages/go.md

@@ -0,0 +1,82 @@
+# Go — Language Application
+
+> How Atelier's domain principles apply in Go specifically. Derives from `domains/` docs.
+
+## Type System (C1 Correctness, Data P7 Type Fidelity)
+
+- **Named types for domain concepts:** `type UserId string`, not bare `string`.
+- **No `interface{}`/`any` without justification:** Go 1.18+ generics reduce the need.
+- **`any` requires a type assertion or switch:** never use the value without narrowing.
+
+```go
+type UserId string
+type OrderId string
+// UserId and OrderId are distinct; cannot be mixed
+func GetUser(id UserId) (*User, error) { ... }
+```
+
+## Error Handling (Errors P1 Errors are Data)
+
+- **Errors are values:** `error` is an interface, not an exception. Handle explicitly.
+- **Sentinel errors with `errors.Is`:**
+```go
+var ErrNotFound = errors.New("not found")
+if errors.Is(err, ErrNotFound) { ... }
+```
+- **Wrap with context:** `fmt.Errorf("get user %d: %w", id, err)`.
+- **Never `_ = err`:** swallowed error (Errors P2). Handle or return.
+- **Custom error types with `errors.As`:**
+```go
+type ValidationError struct {
+    Field string
+    Msg  string
+}
+func (e *ValidationError) Error() string { return e.Field + ": " + e.Msg }
+```
+
+## Concurrency (Concurrency — Go's strength)
+
+- **Goroutines + channels** for message passing (P5 Lock Minimization).
+- **`context.Context` for cancellation and timeout:** every function that does I/O takes a `ctx`.
+- **`sync.Mutex` scoped minimally:** not held across I/O (P3 Lock Scope).
+- **Bounded channels:** `make(chan T, N)`, not unbounded (P9 Bounded Queues).
+
+```go
+func fetchWithTimeout(ctx context.Context, url string) (*Response, error) {
+    ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
+    defer cancel()
+    return doFetch(ctx, url)
+}
+```
+
+## Immutability (Concurrency P1)
+
+- **Pass by value for small structs; pass by pointer for large or mutable.**
+- **No mutation of method receivers:** use a value receiver, not a pointer receiver, for read-only methods.
+- **Copy-on-write for shared state:** return a new struct, not a mutated one.
+
+## Nullability (C1)
+
+- **Pointers can be nil; values cannot.** Be explicit: `*User` (nullable) vs `User` (not).
+- **`nil` check before deref:** a nil deref is a panic.
+- **Return `(T, error)`, not `(*T, nil)`:** avoid the "nil pointer" trap.
+
+## Testing (Testing)
+
+- **`testing` package + `testify/assert`** or stdlib only.
+- **Table-driven tests:** `[]struct{ name string; input X; want Y }`.
+- **`t.Parallel()`** for independent tests (P2 Independence).
+- **`httptest` for HTTP handlers; `sqlite` or testcontainers for DB.**
+
+## Observability (Observability P1)
+
+- **`slog` (stdlib, Go 1.21+) or `zap`/`zerolog`:** structured logs.
+- **`context.Context` carries `trace_id`:** propagated via middleware.
+- **No `fmt.Println`:** use the logger.
+
+## Tooling (DevOps P2)
+
+- **`go vet` + `golangci-lint`:** lint.
+- **`gofmt`/`goimports`:** format (automated, not debated).
+- **`go test -race` in CI:** race detector (Concurrency P6 No Silent Races).
+- **`go mod tidy` + committed `go.sum`:** reproducible builds.

languages/python.md

@@ -0,0 +1,77 @@
+# Python — Language Application
+
+> How Atelier's domain principles apply in Python specifically. Derives from `domains/` docs.
+
+## Type System (C1 Correctness, Data P7 Type Fidelity)
+
+- **Type hints on every function:** `def get_user(id: UUID) -> User | None:`.
+- **`mypy --strict` or `pyright` in CI:** type check is not optional.
+- **No `Any` without justification:** `Any` disables the type checker. Use `object` + narrowing.
+- **Pydantic for runtime validation:** schemas validate and type at the boundary.
+
+```python
+from pydantic import BaseModel
+from uuid import UUID
+
+class UserCreate(BaseModel):
+    email: str
+    name: str
+    # additionalProperties: false by default (extra='forbid')
+```
+
+## Error Handling (Errors P1 Errors are Data)
+
+- **Exceptions for exceptional cases,** not control flow. `raise` not `return None` for errors.
+- **Custom exception hierarchy:**
+```python
+class AppError(Exception): pass
+class ValidationError(AppError): pass
+class NotFoundError(AppError): pass
+```
+- **Never bare `except:`:** `except Exception as e:` (catch specific, not everything).
+- **Never `except: pass`:** log and re-raise or handle, never swallow (Errors P2).
+
+## Async (Concurrency P7, P8)
+
+- **`asyncio` for I/O-bound:** `async def`, `await`. Not threads for I/O.
+- **`anyio` for portability** if you may switch runtimes (trio compatibility).
+- **Timeout on every `await`:** `asyncio.wait_for(coro, timeout=5)`, not bare `await`.
+- **Cancellation propagated:** `asyncio.CancelledError` is not caught; it propagates.
+
+## Immutability (Concurrency P1)
+
+- **`frozen=True` dataclasses** for value objects:
+```python
+from dataclasses import dataclass
+@dataclass(frozen=True)
+class UserId:
+    value: str
+```
+- **Tuples over lists** for fixed-length, immutable sequences.
+- **No in-place mutation of shared state:** return new objects.
+
+## Nullability (C1)
+
+- **`Optional[T]` is `T | None`:** explicit, must be checked.
+- **`None` is not "not found":** raise `NotFoundError` or return `Result`, not `None`.
+- **`assert` is for invariants,** not for runtime checks (stripped with `-O`).
+
+## Testing (Testing)
+
+- **pytest** with fixtures (factories, not shared state).
+- **`pytest --randomly`** to catch order-dependent tests (P2 Independence).
+- **`freezegun` for time:** no `datetime.now()` in tests; inject the clock.
+- **`factory_boy` or `pytest-factoryboy`** for realistic factories.
+
+## Observability (Observability P1)
+
+- **`structlog` or `python-json-logger`:** JSON logs, not `print`.
+- **`logging` with structured formatter:** every log has `request_id`, `user_id`, `event`.
+- **No secrets in logs:** `mask_secret()` helper, or `structlog` processors.
+
+## Tooling (DevOps P2)
+
+- **`ruff` for lint + format:** replaces flake8 + black + isort.
+- **`mypy --strict` in CI:** type check.
+- **`pip-tools` or `poetry` for lockfile:** pinned dependencies.
+- **`pip install --no-deps -r requirements.txt`:** reproducible install.

languages/rust.md

@@ -0,0 +1,79 @@
+# Rust — Language Application
+
+> How Atelier's domain principles apply in Rust specifically. Derives from `domains/` docs.
+
+## Type System (C1 Correctness, Data P7 Type Fidelity)
+
+- **Newtypes for domain concepts:** `struct UserId(String);` — zero-cost, type-safe.
+- **`enum` for finite domains:** `enum Status { Pending, Paid, Shipped }` — exhaustive.
+- **No `unsafe` without justification and review:** `unsafe` opts out of the compiler's guarantees.
+
+```rust
+struct UserId(String);
+struct OrderId(String);
+// Cannot pass OrderId where UserId is expected
+fn get_user(id: UserId) -> Result<User, Error> { ... }
+```
+
+## Error Handling (Errors P1 Errors are Data)
+
+- **`Result<T, E>` for fallible operations:** errors are values, not exceptions.
+- **`thiserror` for error enums, `anyhow` for applications:**
+```rust
+#[derive(thiserror::Error)]
+enum AppError {
+    #[error("not found: {0}")]
+    NotFound(String),
+    #[error("validation: {0}")]
+    Validation(String),
+    #[error(transparent)]
+    Io(#[from] std::io::Error),
+}
+```
+- **`?` for propagation, not `unwrap()`:** `unwrap()` panics in production.
+- **No `panic::catch_unwind` for control flow:** panics are for bugs, not errors.
+
+## Concurrency (Concurrency — Rust's ownership model)
+
+- **`Send` and `Sync` traits enforced by the compiler:** data races are compile errors.
+- **`Arc<T>` for shared, `Mutex<T>`/`RwLock<T>` for mutation:** the lock is explicit.
+- **`tokio` for async:** `async fn`, `.await`. Bounded channels (`tokio::sync::mpsc::channel(N)`).
+- **`Drop` for cleanup:** no leaked resources (no `defer` needed; RAII).
+
+```rust
+async fn fetch_with_timeout(url: &str) -> Result<Response, Error> {
+    tokio::time::timeout(Duration::from_secs(5), fetch(url)).await??;
+}
+```
+
+## Immutability (Concurrency P1 Immutability by Default)
+
+- **Variables are immutable by default:** `let x = 5;` not `let mut x = 5;`.
+- **`&T` (shared ref) over `&mut T` (exclusive ref):** the compiler enforces aliasing rules.
+- **Interior mutability (`Cell`/`RefCell`) only when needed:** not as a default.
+
+## Nullability (C1)
+
+- **`Option<T>`, not nullable pointers:** `Some(x)` / `None`. The compiler enforces handling.
+- **No `null`:** Rust has no null. `Option::None` is the explicit absence.
+- **`?` on `Option` for propagation:** `fn get_name(user: User) -> Option<String> { user.profile?.name }`.
+
+## Testing (Testing)
+
+- **`#[test]` + `#[cfg(test)] mod tests`:** tests co-located.
+- **`proptest` or `quickcheck` for property-based tests:** edge case coverage (P9).
+- **`tokio::test` for async tests.**
+- **No `SystemTime::now()` in tests:** inject an `Instant` or a mock clock.
+
+## Observability (Observability P1)
+
+- **`tracing` crate:** structured logs + spans + traces. Not `println!`.
+- **`tracing::instrument` on functions:** automatic span context.
+- **`tracing-subscriber` with JSON format:** structured output for production.
+
+## Tooling (DevOps P2)
+
+- **`cargo clippy`:** lint. `cargo clippy -- -D warnings` in CI.
+- **`cargo fmt`:** format.
+- **`cargo test`:** tests. `cargo test --release` for perf-sensitive.
+- **Committed `Cargo.lock`:** reproducible builds (even for libraries, for CI).

languages/typescript.md

@@ -0,0 +1,76 @@
+# TypeScript — Language Application
+
+> How Atelier's domain principles apply in TypeScript specifically. Derives from `domains/` docs; this file is the language-specific lens.
+
+## Type System (C1 Correctness, Data P7 Type Fidelity)
+
+- **Strict mode on:** `strict: true` in `tsconfig.json`. No `any` without justification.
+- **No `any`, no `unknown` without narrowing:** `any` disables the type checker. `unknown` requires narrowing before use.
+- **Discriminated unions over enums:** `type Status = { type: 'pending' } | { type: 'paid'; amount: number }` — exhaustive, type-safe.
+- **Branded types for domain IDs:** `type UserId = string & { __brand: 'UserId' }` — prevents passing a `PostId` where a `UserId` is expected.
+
+```typescript
+type UserId = string & { readonly __brand: 'UserId' };
+function getUser(id: UserId): User { ... }
+// getUser("abc")          // type error
+// getUser("abc" as UserId) // ok
+```
+
+## Error Handling (Errors P1 Errors are Data)
+
+- **Result type over exceptions for expected failures:**
+```typescript
+type Result<T, E> = { ok: true; value: T } | { ok: false; error: E };
+```
+- **Exceptions for programmer errors:** null deref, invariant violation. Not for "user not found."
+- **Never `any` in catch:** `catch (e: unknown)` then narrow with `instanceof` or a type guard.
+
+## Async (Concurrency P7 Cancellation Support, P8 Timeout Discipline)
+
+- **`Promise` with `AbortSignal`:** every async function accepts an optional `AbortSignal` for cancellation.
+- **`Promise.race` with a timeout:** never `await` without a timeout for external calls.
+- **No `await` in a hot loop without batching:** use `Promise.all` for parallelism.
+
+```typescript
+async function fetchWithTimeout(url: string, signal?: AbortSignal): Promise<Response> {
+  const timeout = new AbortController();
+  signal?.addEventListener('abort', () => timeout.abort());
+  const timer = setTimeout(() => timeout.abort(), 5000);
+  try {
+    return await fetch(url, { signal: timeout.signal });
+  } finally {
+    clearTimeout(timer);
+  }
+}
+```
+
+## Immutability (Concurrency P1 Immutability by Default)
+
+- **`readonly` on arrays and objects:** `readonly string[]`, `readonly { id: string }`.
+- **`as const` for literals:** `const status = 'pending' as const`.
+- **Immutable update patterns:** `spread` or `Immer` for nested updates, never mutation.
+
+## Nullability (C1 Correctness)
+
+- **`strictNullChecks: true`:** `null` and `undefined` are distinct and must be handled.
+- **No `!` (non-null assertion) without justification:** it disables the null check. Use narrowing.
+- **`optional chaining` over `&&`:** `user?.profile?.name` not `user && user.profile && user.profile.name`.
+
+## Testing (Testing)
+
+- **Jest or Vitest** with `ts-jest`/`vite`. Test files co-located: `user.ts` → `user.test.ts`.
+- **Factories over fixtures:** `makeUser()` returns a fresh object per test.
+- **No `Date.now()` in tests:** inject the clock. `jest.useFakeTimers()` or pass a `now` function.
+
+## Observability (Observability P1 Structured by Default)
+
+- **Structured logger:** `pino` or `winston` in JSON mode. Not `console.log`.
+- **`request_id` via middleware:** propagated on every log in the request.
+- **No secrets in logs:** the logger redacts known secret fields (`pino` redact option).
+
+## Tooling (DevOps P2 Automation)
+
+- **ESLint with `@typescript-eslint`** — strict ruleset.
+- **Prettier** — format, not debated.
+- **`tsc --noEmit` in CI** — type check without emitting.
+- **`npm ci`** — lockfile install, not `npm install`.

matrix/domain-coverage.md

@@ -0,0 +1,46 @@
+# Domain Coverage
+
+> Where each core principle applies across the domains. The complement to `principles-matrix.md`: the matrix maps domain → core; this maps core → domains.
+
+## Core Principle Coverage
+
+| Core Principle | Domains that derive from it | Count |
+|----------------|---------------------------|-------|
+| C1 Correctness | All 11 (security, data, api, testing, performance, observability, errors, uiux, documentation, concurrency, devops) | Universal |
+| C2 Clarity | uiux, api, data, testing, observability, errors, documentation, devops | 8 |
+| C3 Simplicity | security, data, testing, performance, documentation, concurrency, devops | 7 |
+| C4 Locality | testing, concurrency | 2 |
+| C5 Reversibility | api, data, uiux, concurrency, devops | 5 |
+| C6 Composability | api, security, observability, errors, documentation, concurrency | 6 |
+| C7 Observability | api, data, testing, performance, observability, errors, devops | 7 |
+| C8 Economy | security, testing, performance, observability, concurrency | 5 |
+
+## Interpretation
+
+- **C1 Correctness** is universal — every domain derives from it. This confirms C1 as the floor.
+- **C4 Locality** is the narrowest (2 domains: testing independence, concurrency boundaries). Locality is inherently domain-specific; not a gap.
+- **C2 Clarity** and **C7 Observability** are the next-most-derived, confirming they are cross-cutting concerns.
+- **C6 Composability** appears in 6 domains — it is most relevant where parts combine (api, errors, observability, documentation, concurrency) and least relevant where the unit is monolithic.
+
+## Per-Domain Coverage
+
+| Domain | C-rules derived from | Notes |
+|--------|---------------------|-------|
+| UI/UX | C1, C2, C3, C5, C7 | User-facing; clarity + reversibility |
+| API | C1, C2, C3, C5, C6, C7 | Contracts; composability + stability |
+| Security | C1, C3, C6, C7, C8 | 8/10 non-tradeable (promoted to C1) |
+| Data | C1, C2, C3, C5, C7 | Truth + migration safety |
+| Testing | C1, C2, C3, C4, C7, C8 | Independence (C4) is unique |
+| Performance | C1, C3, C6, C7, C8 | Economy + measurement |
+| Observability | C1, C2, C6, C7, C8 | Self-referential (P7 derives from C7) |
+| Errors | C1, C2, C5, C6, C7 | Errors as data + reversibility |
+| Documentation | C1, C2, C3, C5, C6 | Docs-as-code + living docs |
+| Concurrency | C1, C3, C4, C5, C6, C7, C8 | Broadest derivation; locality (C4) unique |
+| DevOps | C1, C2, C3, C5, C7 | Reproducibility + rollback |
+
+## Gaps and Notes
+
+- No domain derives from only one C-rule. The minimum is 4 (UI/UX: C1, C2, C3, C5, C7 — actually 5). Every domain is multi-rooted.
+- **Concurrency** has the broadest derivation (7 C-rules) — it touches the most core concerns.
+- **UI/UX** and **API** are the most user-facing; they emphasize C2 (Clarity) heavily.
+- **Security** is the only domain with explicit non-tradeable declarations; this promotes 8 of its rules to C1-equivalent per `core/conflict-resolution.md` §6.

review/agent-checklist.md

@@ -0,0 +1,135 @@
+# Agent Pre-Completion Checklist
+
+> Every AI agent runs this checklist before completing a task. If any item fails, fix it before finishing. This is the gate between "the code is written" and "the task is done."
+
+## How to Use This
+
+1. Read the relevant `domains/<x>/first-principles.md` before starting the task.
+2. Implement the task.
+3. Run this checklist. Every item must pass (or be explicitly justified).
+4. If an item fails, fix it. Do not "skip" without a written reason.
+
+## Core Principles Checklist (C1–C8)
+
+### C1 Correctness
+- [ ] Does the code do what the task asked, completely?
+- [ ] Does it handle the specified edge cases? (nulls, empties, max, min)
+- [ ] Does it handle the failure cases? (errors, timeouts, invalid input)
+- [ ] Is there a test that would fail if the code were wrong?
+
+### C2 Clarity
+- [ ] Can a stranger read this and understand it without asking you?
+- [ ] Are names intent-revealing? (No `data`, `temp`, `x`, `doStuff`)
+- [ ] Do comments explain *why*, not *what*?
+- [ ] Is the structure scannable? (Short functions, clear sections)
+
+### C3 Simplicity
+- [ ] Is this the simplest solution that is complete?
+- [ ] Is there dead code? (Unreachable branches, unused variables)
+- [ ] Is there premature abstraction? (An interface with one implementation)
+- [ ] Could 50 lines do what 200 lines do?
+
+### C4 Locality
+- [ ] Does related logic live together?
+- [ ] Are side effects near their causes?
+- [ ] Does a change to this feature require touching distant files?
+
+### C5 Reversibility
+- [ ] Is this change undoable? (migration has a `down`, deploy has a rollback)
+- [ ] Did I avoid irreversible actions without explicit confirmation?
+- [ ] Is state recoverable? (Can the user get back to where they were?)
+
+### C6 Composability
+- [ ] Does this component/function do one thing?
+- [ ] Is the boundary (props/args/return) explicit and typed?
+- [ ] Can this be reused in a new context without modification?
+
+### C7 Observability
+- [ ] Are there logs for significant events?
+- [ ] Do errors carry enough context to debug? (request ID, user, action)
+- [ ] Are there metrics for the operation? (count, latency)
+- [ ] Are there no secrets in logs?
+
+### C8 Economy
+- [ ] Is memory bounded? (No unbounded growth, no loading everything)
+- [ ] Is time bounded? (No N+1, no blocking without timeout)
+- [ ] Are resources released? (file handles, connections, locks)
+
+## Domain-Specific Triggers
+
+If the task touches a domain, run that domain's checklist:
+
+### If UI/UX (see `domains/uiux/`)
+- [ ] Every interactive element is keyboard-reachable
+- [ ] Every image has alt text (or marked decorative)
+- [ ] Every form control has a label
+- [ ] Focus is visible
+- [ ] No color-only information
+- [ ] Components use design tokens, not raw values
+
+### If API (see `domains/api/`)
+- [ ] Endpoints are nouns, plural, lowercase-hyphenated
+- [ ] Status codes are correct (200/201/204/4xx/5xx per semantics)
+- [ ] Errors are structured (code, message, request_id)
+- [ ] Input is validated against a schema
+- [ ] Auth is required by default
+
+### If Security (see `domains/security/`)
+- [ ] No secrets in code, logs, URLs, or error messages
+- [ ] Input is validated at the boundary
+- [ ] Output is encoded for its context
+- [ ] Crypto uses vetted libraries (no MD5/SHA1 for security)
+- [ ] Authorization is checked, not assumed
+
+### If Data (see `domains/data/`)
+- [ ] Schema reflects the domain (not the application)
+- [ ] Constraints are in the schema (NOT NULL, UNIQUE, FK)
+- [ ] Migration has an `up` and a `down`
+- [ ] Types are domain-accurate (UUID, TIMESTAMPTZ, DECIMAL for money)
+- [ ] No `SELECT *`; no N+1
+
+### If Testing (see `domains/testing/`)
+- [ ] Tests are independent (order doesn't matter)
+- [ ] Tests are deterministic (no `Date.now()`, no `random()`)
+- [ ] Edge cases are covered (empty, single, max, invalid)
+- [ ] A failing test names the problem specifically
+
+### If Performance (see `domains/performance/`)
+- [ ] No unbounded operations (loops, allocations, queries)
+- [ ] No N+1 queries
+- [ ] Every external call has a timeout
+- [ ] Caches have invalidation strategies
+
+### If Observability (see `domains/observability/`)
+- [ ] Logs are structured (JSON, fields)
+- [ ] Every request has a correlation ID
+- [ ] No high-cardinality labels in metrics
+- [ ] Alerts have runbooks
+
+### If Errors (see `domains/errors/`)
+- [ ] Errors are not swallowed silently
+- [ ] Errors are specific (not generic "something went wrong")
+- [ ] Errors preserve context (where, when, why, what)
+- [ ] Recovery is attempted when possible; fail fast when not
+
+### If Concurrency (see `domains/concurrency/`)
+- [ ] Shared state is minimized; immutability preferred
+- [ ] Locks are minimal in scope
+- [ ] Queues are bounded
+- [ ] Every blocking call has a timeout
+- [ ] Cancellation is supported
+
+### If DevOps (see `domains/devops/`)
+- [ ] The pipeline is the process (no manual steps)
+- [ ] Rollback path is known
+- [ ] Config is in code, not on the server
+- [ ] Environments are parity (dev = prod modulo data)
+
+## Final Gate
+
+- [ ] Have I read the relevant domain's first-principles?
+- [ ] Have I run the domain-specific checklist?
+- [ ] Have I run the core checklist?
+- [ ] Are all failures either fixed or explicitly justified in the task notes?
+
+If any unchecked item is not justified, the task is not complete. Do not mark done.

review/anti-patterns.md

@@ -0,0 +1,132 @@
+# Anti-Patterns
+
+> A catalog of violations. Each entry names the principle it breaches. Use this to recognize and reject patterns on sight.
+
+## How to Use
+
+When you see a pattern listed here, it is a defect. Cite the principle it violates and require a fix. These are not "to be reviewed later"; they are rejected on sight.
+
+## Core Anti-Patterns (C1–C8)
+
+| Anti-Pattern | Breaches | Why |
+|--------------|----------|-----|
+| Code that "mostly works" | C1 Correctness | Mostly correct is incorrect |
+| `function doStuff()` | C2 Clarity | Name reveals nothing |
+| A 500-line function | C3 Simplicity | Complexity is a liability |
+| Config in a distant repo, read silently | C4 Locality | Coupling you cannot see |
+| A migration with no `down` | C5 Reversibility | Irreversible bet |
+| A component reading global state implicitly | C6 Composability | Hidden dependency |
+| A service with no logs | C7 Observability | Cannot debug what you cannot see |
+| Loading all records into memory | C8 Economy | Unbounded = OOM |
+
+## Domain Anti-Patterns
+
+### UI/UX
+| Anti-Pattern | Breaches | Why |
+|--------------|----------|-----|
+| Image without `alt` | P2 Accessibility | Disqualifying |
+| "Delete" with no confirmation | P5 Forgiveness | Irreversible surprise |
+| `color: #3b82f6` in a component | P8 Consistency (via tokens) | Bypasses design system |
+| "Submit" on a delete button | P3 Clarity | Wrong verb |
+| Layout shift on image load | P7 Hierarchy / CLS | Visual instability |
+
+### API
+| Anti-Pattern | Breaches | Why |
+|--------------|----------|-----|
+| `/getUsers` (verb in URL) | P2 Clarity | Resources are nouns |
+| 200 with an error body | P9 Error Transparency | Status code lies |
+| 500 with a stack trace | P8 Security, P9 | Information leak |
+| No `Idempotency-Key` on a POST | P6 Idempotency | Retry is unsafe |
+| 10MB response by default | P7 Performance | Unbounded payload |
+
+### Security
+| Anti-Pattern | Breaches | Why |
+|--------------|----------|-----|
+| `eval()` of any string | P4, P5 | Code injection |
+| Hardcoded API key in source | P9 Secret Hygiene | Committed secret |
+| `catch (e) {}` (swallow) | P7, P8 | Silent failure, fail-open |
+| `md5` for password hashing | P6 Crypto | Broken primitive |
+| Open CORS `*` in production | P1, P10 | Zero trust violated |
+| `chmod 777` | P2 Least Privilege | Maximum privilege |
+| Logging the request body | P9 Secret Hygiene | Token leak |
+
+### Data
+| Anti-Pattern | Breaches | Why |
+|--------------|----------|-----|
+| `VARCHAR` for a UUID | P7 Type Fidelity | Wrong type |
+| No FOREIGN KEY | P3, P9 | Unenforced relationship |
+| `FLOAT` for money | P7, P1 | Floating point error |
+| `is_deleted` without filtering | P8 Lifecycle | Soft-delete leak |
+| `SELECT *` | P10 Performance | Unbounded columns |
+
+### Testing
+| Anti-Pattern | Breaches | Why |
+|--------------|----------|-----|
+| Test that cannot fail | P10 No Test Theater | Not a test |
+| `Date.now()` in a fixture | P3 Determinism | Flaky |
+| Shared fixture mutated across tests | P2 Independence | Order-dependent |
+| 500 e2e tests, 50 unit | P4 Fast Feedback | Inverted pyramid |
+| `name: "test"` fixture | P7 Realism | Hides bugs |
+
+### Performance
+| Anti-Pattern | Breaches | Why |
+|--------------|----------|-----|
+| N+1 query in a loop | P3 Complexity | O(N) queries |
+| No timeout on HTTP call | P4, P8 (concurrency) | Hang forever |
+| Cache with no invalidation | P5 Caching | Stale forever |
+| Unbounded in-memory sort | P4 Resource Bounds | OOM |
+| Optimization without measurement | P1 Measure First | Guesswork |
+
+### Observability
+| Anti-Pattern | Breaches | Why |
+|--------------|----------|-----|
+| `console.log("here")` | P1 Structured | Not queryable |
+| `user_id` as a metric label | P4 Cardinality | Unbounded bill |
+| Average latency only | P8 SLO | Hides the tail |
+| No `trace_id` propagation | P2 Correlation | Cannot trace |
+| Logs without `request_id` | P3 Context | No correlation |
+
+### Errors
+| Anti-Pattern | Breaches | Why |
+|--------------|----------|-----|
+| `catch (e) { return null }` | P2 Fail Loudly | Silent failure |
+| `throw new Error("error")` | P3 Fail Specifically | Generic |
+| `return null` for "not found" | P1 Errors are Data | Conflates absence with error |
+| Retry without backoff | P5, P8 | Retry storm |
+| `throw` in a recovery path | P6 | Fail fast in wrong place |
+
+### Documentation
+| Anti-Pattern | Breaches | Why |
+|--------------|----------|-----|
+| Doc with no examples | P3 Examples | Incomplete |
+| Stale doc (wrong, not updated) | P4 Currency | Worse than no doc |
+| Unlisted doc (not in MANIFEST) | (framework rule) | Not part of framework |
+| No audience statement | P2 Audience | Who is this for? |
+
+### Concurrency
+| Anti-Pattern | Breaches | Why |
+|--------------|----------|-----|
+| Shared mutable state, no lock | P1 Immutability | Race condition |
+| Unbounded queue | P9 Bounded Queues | OOM |
+| `channel.send()` with no timeout | P8 Timeout | Hang |
+| Mutex held across I/O | P3 Lock Scope | Lock too long |
+| Spawned work with no cancellation | P7 Cancellation | Orphaned work |
+
+### DevOps
+| Anti-Pattern | Breaches | Why |
+|--------------|----------|-----|
+| Manual deploy script | P2 Automation | Not repeatable |
+| No rollback path | P4 Rollback | Irreversible deploy |
+| Big-bang deploy | P5 Progressive | All-or-nothing |
+| Rebuild per environment | P7 Immutability | Different artifacts |
+| Snowflake server | P1, P6 | Not reproducible |
+
+## Cross-Cutting Anti-Patterns
+
+| Anti-Pattern | Breaches | Why |
+|--------------|----------|-----|
+| "I'll add tests later" | C1 (no proof of correctness) | Later never comes |
+| "It's just a prototype" | C5 (irreversible by default) | Prototypes go to prod |
+| Copy-paste code | C6 (no composition) | Bug duplicated |
+| God object | C3, C6 | One thing, many things |
+| Leaky abstraction | C6, C2 | Hidden coupling |

review/peer-review-checklist.md

@@ -0,0 +1,82 @@
+# Peer Review Checklist
+
+> For human reviewers. Run this when reviewing a PR or a change. Complements `agent-checklist.md` (which the author ran before finishing).
+
+## Purpose
+
+A peer review is a second set of eyes on correctness, clarity, and completeness. It is not a gatekeeping ritual; it is a quality multiplier. The author ran the agent checklist; the reviewer checks what the author could not see.
+
+## The Review
+
+### Understanding (read first, judge never)
+- [ ] Read the PR description. What is the change trying to do?
+- [ ] Read the linked issue/spec. Does the change address it?
+- [ ] Read the changed files in order. Do not jump to judgment.
+
+### Correctness (C1)
+- [ ] Does the change do what it claims?
+- [ ] Are there edge cases the author missed? (Comment, don't fix in review)
+- [ ] Are there failure cases unhandled?
+- [ ] Are the tests testing the right thing? (A test that cannot fail is theater)
+- [ ] Would this code fail in production? (Different from "does it pass CI")
+
+### Clarity (C2)
+- [ ] Can you understand the change without asking the author?
+- [ ] Are names intent-revealing?
+- [ ] Is there a comment that explains *why* where the *why* is non-obvious?
+- [ ] Is the diff minimal? (Unrelated changes are review noise)
+
+### Simplicity (C3)
+- [ ] Is there dead code introduced?
+- [ ] Is there premature abstraction?
+- [ ] Could the change be simpler? (Suggest, don't block unless egregious)
+- [ ] Is there a simpler approach the author may not have considered?
+
+### Locality (C4)
+- [ ] Are related changes grouped?
+- [ ] Are unrelated changes separated (different PRs)?
+- [ ] Does a change require touching distant files unnecessarily?
+
+### Reversibility (C5)
+- [ ] Is the change undoable?
+- [ ] Are there migrations? Do they have rollbacks?
+- [ ] Are there breaking changes? If so, is there a deprecation path?
+
+### Composability (C6)
+- [ ] Does the change respect existing boundaries?
+- [ ] Does it introduce coupling that should be an interface?
+- [ ] Is the new code reusable, or one-off?
+
+### Observability (C7)
+- [ ] Are there logs/metrics for the new behavior?
+- [ ] Are errors structured and traceable?
+- [ ] Are there no secrets in logs?
+
+### Economy (C8)
+- [ ] Are there unbounded operations?
+- [ ] Is memory/time bounded?
+- [ ] Is the cost proportional to the need?
+
+## Domain-Specific (if applicable)
+
+Run the relevant domain section from `agent-checklist.md` (UI/UX, API, Security, Data, Testing, Performance, Observability, Errors, Concurrency, DevOps). The author ran it; the reviewer verifies.
+
+## Review Etiquette
+
+- **Comment, don't command.** "This could be X" not "Change this to X."
+- **Distinguish blocking from suggestions.** "Blocking: correctness bug. Suggestion: naming."
+- **Praise good code.** Reviews are not just for finding problems.
+- **Don't review style the linter should catch.** Fix the linter, not the PR.
+- **Ask questions.** "Why this approach?" often reveals more than "This is wrong."
+
+## Approving
+
+- Approve when: the change is correct, clear, and complete. Minor suggestions can be left for the author.
+- Request changes when: there is a correctness bug, a missing test, or a clarity problem that blocks understanding.
+- Reject when: the change should not exist (wrong direction, duplicate, scope-violating).
+
+## What This Checklist is Not
+
+- Not a style guide. Style is automated (linter, formatter).
+- Not a gatekeeping tool. The goal is quality, not perfection.
+- Not a substitute for the author's own checklist. The author runs `agent-checklist.md` first; this is the second pass.