feat(skills): ship ue-design-skills bundle, licensing and delivery gate
Phase 0 of the handoff plan, as a marketplace rather than a flat skills/ directory. Content moved out of the LyraResearch archive and depersonalised: addresses stay in the archive, recipes ship. - plugins/ue-design-skills: 17 skills, 232 failure-mode entries, each with the six required fields; catalog.json as the harness-neutral source of truth and .claude-plugin/ as one adapter over it. - _gate: 16 rules, one poisoned fixture per rule, plus surface coverage so a declared file cannot silently miss the line rules. - ADR-0002 (harness-neutral bundle behind a marketplace) and ADR-0003 (split licensing: CC BY-ND 4.0 prose, Apache-2.0 code and metadata). - LICENSE files at both levels, CONTRIBUTING.md, docs/licensing-options.md as the material the licence decision grew from. Verified: gate.py 0 violations; test_gate.py 16/16 rules redden on their fixtures with a clean baseline and 2 root files reaching the line rules. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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# Failure modes: cross-system architecture
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Ten failures that belong to **no single subsystem**, which is why each one
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survived review of every subsystem it passes through.
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The shared property here is different from the other documents in this bundle.
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Elsewhere the mechanism is "a check exists and cannot fire". Here it is: **every
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individual component is correct, and the defect lives in the seam.** Nobody owns
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a seam. A reviewer of the messaging layer sees a correct bus; a reviewer of the
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UI sees a correct widget; the failure is that the UI reconstructs state from the
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bus, and that fact is written down nowhere.
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That has a practical consequence for how these are detected. Most recipes below
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are not a single search — they are a **join between two searches**, and the
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finding is in the difference between the two result sets.
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Where a mechanism is fully described by another skill, the entry says so and does
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not restate it. Identifiers (`AG-01` and up) are stable and resolve back to the
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audited material in the research archive.
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---
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## Abstraction
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### AG-01 - A layer adopted for completeness rather than pressure
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**Mechanism.** A modular architecture is copied whole from a reference project
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because it is the reference's architecture, without asking which variability each
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layer absorbs. Every layer is correctly implemented and paid for in full.
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**Why it is silent.** Nothing fails. The cost is not a defect but a permanent tax:
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every new mechanic now needs a class, a definition asset, a tag, an action, a
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plugin, a validation rule and a UI extension. The team experiences this as "the
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engine is like this".
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**Why the obvious check misses it.** Review asks "is this implemented correctly?"
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and the answer is yes at every layer. The question that finds it — "what are the
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two concrete variants this layer separates?" — is not part of any code review,
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because it is not about code.
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**Symptom.** Feature velocity that falls as the project matures, with no single
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slow component. Estimates that are consistently wrong in the same direction.
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**Detect.** Count the axes against the variants they serve:
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```bash
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rg -c "class \w+ : public UGameFeatureAction" --glob "*.h" . # action types
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fd -e uasset -p "Experiences|GameFeature" | wc -l # variants shipped
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```
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The finding is arithmetic, not textual: **planned variants fewer than
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architectural axes.** In the audited reference, five feature plugins out of
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eighty-one total carried the modular machinery — which pays for that project and
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would not pay for a single-mode title.
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**Guardrail.** For each layer, name two real variabilities it separates before
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adopting it. If you cannot, defer the layer. See `ue-reference-project-adoption`
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for the full classification and the adoption budget.
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---
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### AG-02 - Distributed control flow with no trace
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**Mechanism.** A request travels definition → feature → action → extension event →
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component → tag → message → widget. Each hop is decoupled by design.
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**Why it is silent.** Decoupling is working exactly as intended. The absence of a
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call stack is the feature, not a defect.
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**Why the obvious check misses it.** A debugger shows one hop. Each hop's owner
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can explain their hop. Nobody can explain the path, because reconstructing it
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requires reading assets, config and code in three modules — and it has to be
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reconstructed again next time.
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**Symptom.** "Who triggered this?" costs an afternoon. Bugs reproduce reliably
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while no class looks responsible. New engineers take months rather than weeks.
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**Detect.** Test the property directly rather than searching for it: take a
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recent bug and ask an engineer who did not write the feature to reconstruct the
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path **from logs and dumps alone**, without opening assets. Then measure what
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they needed and did not have.
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Structurally, the precondition is visible:
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```bash
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rg -c "GetSubsystem<|BroadcastMessage|SendGameFrameworkComponentExtensionEvent" --glob "*.cpp" .
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rg -c "UE_LOG.*Verbose.*(World|LocalPlayer|Experience|Feature)" --glob "*.cpp" .
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```
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A large first number with a small second is the finding: heavy indirection, no
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correlated logging.
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**Guardrail.** Structured lifecycle logs carrying world, player, experience,
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plugin, action and owner identifiers; a generated composition graph; one index of
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semantic tags and their consumers. Indirection without observability is not
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architecture, it is a maze.
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---
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## Ownership and lifecycle
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### AG-03 - Activation reviewed, deactivation assumed
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**Mechanism.** Adding a component, a binding, a widget or a grant is easy and
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visible. The inverse operation is written from memory, or not at all.
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**Why it is silent.** Development restarts the editor instead of deactivating.
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The happy path is exercised hundreds of times a day; the reverse path is
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exercised by nobody until a player switches modes.
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**Why the obvious check misses it.** Both functions usually exist and look
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symmetric. The asymmetry is in what each enumerates — see `ue-modular-gameplay`
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recipes MG-01 through MG-06 for the six distinct shapes this takes, each with its
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own recipe.
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**Symptom.** The second activation produces duplicates. Reported long after the
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first, and usually attributed to the feature that was activated second.
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**Detect.** The behavioural test is stronger than any search, and it is the one
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gate this whole skill exists to insist on:
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```text
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baseline → activate → verify additions → deactivate → verify baseline
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→ reactivate → verify exactly one copy
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```
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Run it with the actor existing before activation, spawned after activation, and
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destroyed before deactivation.
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**Guardrail.** An ownership ledger — resource, receipt, inverse — filled in
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**before** implementation. A blank middle column is a rejected design, not a
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follow-up task.
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---
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### AG-04 - A subsystem's lifetime mistaken for resource ownership
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**Mechanism.** A long-lived subsystem holds registrations for resources owned by
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short-lived objects. Weak references prevent crashes, so nothing appears wrong.
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**Why it is silent.** Weak pointers do their job: the dead object is not called.
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The **record** remains, and records are not visible in any profiler view that
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answers "is this leaking?".
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**Why the obvious check misses it.** The code is defensively written and looks
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careful. Weak references read as evidence that ownership was considered — when
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they are precisely the mechanism that lets the bookkeeping rot silently.
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**Symptom.** Registration lists that grow across a session; cleanup that resorts
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to clearing everything because per-owner removal was never possible; the same
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resource removed twice by two owners.
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**Detect.** For every registry, compare adds against removes and check the key:
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```bash
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rg -n "\.Add\(|\.Emplace\(|\.FindOrAdd\(" --glob "*.cpp" . | rg -i "listener|extension|handle|request"
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rg -n "\.Remove\(|\.RemoveSwap\(|Unregister" --glob "*.cpp" . | rg -i "listener|extension|handle|request"
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```
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A registry with adds and no owner-keyed removal is the finding. A registry whose
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only removal is a full clear is the same finding, one step later.
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**Guardrail.** Every dynamic resource has exactly one named owner and one receipt.
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Shared resources use reference counts or leases. "The subsystem owns it" is not an
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answer; subsystems outlive the things they track.
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---
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## Context
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### AG-05 - Global state where the scope is world or player
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**Mechanism.** A registration, cache or setting is keyed globally, while the
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things it describes belong to a world, a local player or an activation context.
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**Why it is silent.** With one world and one player — the configuration in which
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almost all testing happens — global and scoped are indistinguishable. The code is
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correct in the case you run.
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**Why the obvious check misses it.** The accessor reads naturally: a player asking
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for its own settings, a subsystem holding its own registry. The scope error is one
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line inside an accessor, or a missing key in a map declaration.
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**Symptom.** Multi-world editor sessions cross-contaminate; split-screen players
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share what should be per-player; a listen server processes an event twice. Each
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appears as an unrelated bug in a different subsystem.
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**Detect.** For every mutable registry, ask what the minimum sufficient key is,
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then check what it actually is:
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```bash
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rg -n "TMap<.*>\s+\w+;" --glob "*.h" . | rg -v "FObjectKey|FGameFeatureStateChangeContext|ULocalPlayer"
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rg -n -A4 "::Get\w*Settings\(\)" --glob "*.cpp" . | rg "::Get\(\)|GEngine->"
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```
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The second search is the specific case documented in
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`ue-game-settings-architecture` GS-03: a per-player accessor returning a global
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singleton, whose tell is a proliferation of "primary player only" conditions
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elsewhere.
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**Guardrail.** Key every mutable record by the minimum context that makes it
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correct — activation context, world handle, local player where applicable. Then
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run the required matrix: multi-world editor, dedicated server plus client, listen
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server, two local players, map travel.
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---
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### AG-06 - Editor behaviour that differs from the shipped configuration
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**Mechanism.** A branch keyed on running in the editor loads more, validates less,
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or guesses identifiers that the packaged build resolves strictly.
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**Why it is silent.** Both branches are correct for their environment. The editor
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branch is usually more permissive, so everything works better where you are
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looking.
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**Why the obvious check misses it.** The branch is a single condition in a
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subsystem nobody reads while working on a feature. Its consequences appear in
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memory profiles, cook results and packaged-only failures — three places that are
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each somebody else's job.
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**Symptom.** Memory numbers that describe no shipping configuration. Features that
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work in the editor and silently do nothing when packaged. Asset identifiers that
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resolve in one and not the other.
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**Detect.** Enumerate every editor divergence and judge each one deliberately:
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```bash
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rg -n "GIsEditor|WITH_EDITOR|IsRunningCommandlet|GIsPlayInEditorWorld" --glob "*.cpp" . -A3
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rg -n "bShouldGuessTypeAndNameInEditor|PreloadInEditor|bOnlyCookProduction" Config/
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```
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In the audited reference this finds an editor branch that loads **both** role
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bundles — which alone invalidates in-editor residency measurement — and a
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configuration that guesses asset identifiers in the editor and not in the build.
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**Guardrail.** Keep a written list of editor divergences and their justification.
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Any measurement taken in the editor states which divergences apply to it.
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See `ue-asset-loading-and-memory` AL-10.
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---
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## Data and validation
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### AG-07 - A data graph with no compiler
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**Mechanism.** Null references, wrong identifiers, cross-plugin cycles, prototype
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content and semantic mismatches are all valid data. They load, they cook, they run.
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**Why it is silent.** Data does not compile. There is no stage that can reject it
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except one somebody chose to write — and that validation is typically
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editor-only, so it does not run where it would matter.
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**Why the obvious check misses it.** The validation *exists*, which satisfies the
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question "is the data validated?". What it does not do is run in the build. In the
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audited reference, eleven of twelve validation implementations were compiled out
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of non-editor builds.
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**Symptom.** A production playlist pointing at a test mode; a health pickup
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granting a weapon definition; a missing bundle discovered only in a packaged
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build.
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**Detect.** Count validation, then count how much of it survives the build:
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```bash
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rg -c "IsDataValid" --glob "*.cpp" .
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rg -n -B6 "IsDataValid" --glob "*.cpp" . | rg -c "WITH_EDITOR"
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rg -n "class \w*ValidationCommandlet|UEditorValidatorBase" --glob "*.h" .
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```
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A ratio close to one, with no commandlet or automation path, means the data graph
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is unvalidated where it ships. See `ue-data-driven-architecture` DD-09 and DD-10.
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**Guardrail.** Run the same validation in automation that you run in the editor.
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Add a production-root allow list so prototype paths cannot reach a shipped
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playlist.
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---
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### AG-08 - A generic hook with no consumer
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**Mechanism.** A public field or extension point is stored, copied and threaded
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through an API — and never read by anything that changes behaviour.
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**Why it is silent.** Every "is this used?" check answers yes, because the value
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*is* used: passed, assigned, copied. What is missing is the comparison, the
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branch, or the sort.
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**Why the obvious check misses it.** This is the single most repeated shape in
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this whole bundle, and it earns its own cross-system entry because it recurs in
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every subsystem independently: an ordering field that never sorts, a viewer
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identity that is ignored, a benchmark decision with no caller, a profile suffix
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that is never populated, a removal function with an empty body, a flag written in
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a constructor and never read.
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**Symptom.** A designer configures a documented setting and observes no effect,
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concludes their data is wrong, and works around it.
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**Detect.** The general form — mentions minus comparisons:
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```bash
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F='Priority'
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rg -c "\b$F\b" --glob "*.cpp" --glob "*.h" . # mentions
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rg -n "\b$F\b\s*(<|>|<=|>=|==)|Sort.*\b$F\b|\b$F\b.*Sort" --glob "*.cpp" .
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```
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Mentions without comparisons is the finding. Per-subsystem instances have their
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own recipes: `ue-ui-architecture` UI-01, `ue-cosmetics-and-teams` CT-10,
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`ue-game-settings-architecture` GS-06 and GS-07, `ue-gas-architecture` GA-06,
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`ue-modular-gameplay` MG-01.
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**Guardrail.** Every public setting gets a consumer test: mutate it in a fixture,
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assert an observable delta. Anything without one is implemented, removed, or
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marked unsupported — never left as configurable decoration.
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---
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## Verification
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### AG-09 - Single-process testing of a distributed property
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**Mechanism.** A listen-server host shares memory with its client, so the
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client/server split that produces a whole class of defects does not exist during
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the test that would have caught it.
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**Why it is silent.** The tests pass. They are real tests exercising real code;
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they simply cannot express the failure.
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**Why the obvious check misses it.** Coverage looks good and the feature demonstrably
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works. The missing dimension is a **configuration**, not a code path, so no
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coverage tool reports it.
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**Symptom.** Features that ship having never run in the configuration they will
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run in. Bugs that appear at first playtest and are attributed to the network layer.
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**Detect.** This one is answered by an inventory rather than a search: list the
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failure modes that require a separate process, and confirm each has a test in a
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configuration that has one. From this bundle, the ones that cannot occur in a
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single process include replicated-versus-validated confusion, call-site authority
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guards, multicast used where state belongs, incomplete replicated-array callbacks,
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readiness gates that assume a controller, and prediction with no correction path
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(`ue-multiplayer-authority` NA-01, NA-04, NA-11, NA-13, NA-17, NA-19).
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**Guardrail.** A dedicated server with two remote clients, one under latency and
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packet loss, as the **minimum** configuration for accepting a networked feature.
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Plus a mid-match joiner.
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---
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### AG-10 - A version set that drifts silently
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**Mechanism.** Engine, reference sample and plugins evolve independently. Code
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copied from a sample at one version keeps running against another.
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**Why it is silent.** Compilation succeeds. Serialized fields still load. A stub
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that changed behaviour between versions still returns something plausible.
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**Why the obvious check misses it.** Documentation for the current version is
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easy to find and describes the current version — not the vendored copy in the
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project. Reading the docs actively produces false confidence.
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**Symptom.** A method that "works differently now"; a structure size assertion
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that fails after an upgrade; content that disagrees with the plugin that reads it.
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**Detect.** Pin and verify rather than search. Where code manually enumerates the
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members of an engine structure, a size assertion is the correct tripwire:
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```bash
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rg -n "static_assert\(sizeof\(" --glob "*.cpp" --glob "*.h" .
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```
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In the audited reference this appears five times against one engine structure. A
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failing assertion after an upgrade is a **feature**: it means a new field would
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otherwise have been silently ignored by five hand-written functions.
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**Guardrail.** Pin the engine, sample and plugin versions. Keep compile-time
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guards where you enumerate engine structures by hand. Re-run structural and
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behavioural probes after every upgrade, and never treat a documentation page as
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evidence about the code in your tree.
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Reference in New Issue
Block a user