# D&D Module Internals

This guide records the conventions shared by the production D&D module family.
It complements [Module Internals](modules.md), which owns generic registration
and extension mechanics, and [Configuration](../config.md), which owns the
selectable keys, bindings, reference syntax, and default validator chains.

## Durable Artifact Contracts

The nine lanes have separate durable wire contracts. This guide deliberately
does not repeat their JSON shapes or schemas.

| Lane | Durable contract |
| --- | --- |
| Spells | [spell artifacts](../integrations/dnd-spell-artifacts.md) |
| NPC registry | [NPC registry artifacts](../integrations/dnd-npc-registry-artifacts.md) |
| Combat turns | [combat-turn artifacts](../integrations/dnd-combat-turn-artifacts.md) |
| Item events | [item-event artifacts](../integrations/dnd-item-event-artifacts.md) |
| NPC occurrences | [NPC-occurrence artifacts](../integrations/dnd-npc-occurrence-artifacts.md) |
| Scene descriptions | [scene-description artifacts](../integrations/dnd-scene-description-artifacts.md) |
| Enemy events | [enemy-event artifacts](../integrations/dnd-enemy-event-artifacts.md) |
| Location registry | [location-registry artifacts](../integrations/dnd-location-registry-artifacts.md) |
| Location occurrences | [location-occurrence artifacts](../integrations/dnd-location-occurrence-artifacts.md) |

## Family Composition

The D&D registrar registers the family’s artifact codecs, extractors, typed
append-order mergers, normalizers, validators, prompt assets, fallback LLM
profile asset, and default validator chains. Each extractor and normalizer has
a stable module spec, explicit execution class, strict option decoding, and a
typed builder. Scene chunking, every extractor, NPC normalization, and location
normalization are registered as `llm_backed`; the remaining current D&D mergers
and normalizers are `deterministic`. The metadata is available to catalog inspection and
resolved-pipeline debug data and determines which selected bindings inherit the
pipeline profile. Configuration remains the canonical owner of the exact keys,
profile precedence, and validator order.

Private structured-LLM response schemas are deliberately minimal. They reject
invalid JSON structure, missing required fields, incompatible types, and
unknown fields, while preserving semantic candidates for deterministic
validation. Do not promote a private response envelope into a durable schema;
the contracts above define durable data.

## Prompt Construction

D&D LLM-facing content lives beneath `assets/dnd/`. Each module contributes a
local `prompt.yaml` declaration and `instructions.md`; input-specific files
such as a catalog, registry, grounding projection, or candidate collection are
local only when that module needs them. New extractor content uses its feature
subtree, while families with both extraction and normalization content use their
`extract` and `normalize` subtrees. Shared visual-provenance fragments use
the `common-dnd-` prefix.

The owning module’s manifest is the source of truth for which local and shared
assets are selected, their mount paths, their message order, cache controls,
and the files included in its prompt fingerprint. Shared fragments belong to
the D&D shared implementation and are selected by name rather than copied into
module directories. The root `assets` package is a content-only boundary; its
physical ownership and rationale are defined by
[ADR-0011](../adr/0011-centralize-llm-assets.md).

Put each rule at its narrowest owner:

- universal behavior belongs in the shared system asset;
- D&D-family behavior belongs in a selected `common-dnd-` asset;
- rules for an input projection belong with that input asset;
- lane-specific policy belongs in the module’s `instructions.md`; and
- transport-envelope shape belongs in the private response schema.

A rule is eligible for the system prompt only when every D&D LLM prompt needs
it regardless of lane, inputs, or response shape. Module instructions must not
repeat rules selected from shared assets or schemas. Reintroduce such repetition
only after observational evaluation with representative transcripts shows that
it improves results at the intended target models and cost; structural prompt
tests alone are not that evidence.

Every maintained D&D LLM prompt selects `dnd-extraction` as its default
profile. The D&D registrar registers the fallback, while an operator can
replace it with a complete profile of the same ID from the configured PromptKit
source. Deployment profile selection is documented in
[Configuration](../config.md#promptkit-profiles).

The transcript assets have distinct consumers. Scene chunking consumes the
complete-session `common-dnd-transcript-full.md`; extraction prompts consume
the current-chunk `common-dnd-transcript-chunk.md`; and NPC and location
normalization consume `common-dnd-transcript-windows.md` alongside their
candidate collections. Player, party, glossary, and compatible campaign
references provide disambiguating context, not evidence. Reference material is
canonically ordered before rendering so equivalent inputs remain stable.

Extraction prompts render the common system and identity messages first, then
cached campaign references and the cached chunk transcript. Evidence policy and
any lane-specific registry, catalog, or grounding projection follow that
prefix. The final module instructions message is ephemeral. This keeps the
reusable extraction prefix identical while preserving the lane-specific suffix.

Scene chunking intentionally uses a different order: system, cached campaign
references, uncached module instructions, then the final ephemeral full
transcript. Entity normalization also has its own order: system, uncached
module instructions, ephemeral reconciliation policy, uncached candidates, and
final ephemeral transcript windows. These orders and cache controls are prompt
behavior; change them only through the owning manifest and prompt declaration.

## Evidence, Candidates, And Normalization

The current transcript is the only durable evidence source. Extractors assign
the current source identity, preserve candidate evidence ranges for validators,
and canonically order or remove exact duplicate ranges without asking the
model to repair semantic errors. Campaign context and generated artifacts may
ground names or control routing, but they never establish evidence for a D&D
result.

Default chains keep responsibilities separate: structural validators assess the
candidate, source-reference validators resolve cited ranges against the current
source, durable-schema validation checks an approved representation, and
relatedness validators report advisory evidence concerns. The configured order
is documented in
[Configuration](../config.md#production-validator-keys-and-default-chains).

Enemy-event extraction additionally rejects a second `engaged` observation for
the same comparison identity within one scene-scoped result. Normalization may
combine results from distinct scenes, so it intentionally does not apply that
rule. Configuration owns the exact validator key and chain position.

Normalizers are deterministic for spells, combat turns, item events, NPC
occurrences, scene descriptions, enemy events, and location occurrences. They canonicalize display
values and evidence, use source-document order for stable output, and issue
bounded warnings for changes or collapsed duplicates. The NPC and location
normalizers are intentional exceptions: each first produces a deterministic
candidate set, then may use a bounded structured-LLM proposal to reconcile
identity groups. Invalid or unusable proposals retain the deterministic result
and surface retry or fallback diagnostics; the model does not directly replace
durable records.

## Generated References And Grounding

Normalized D&D artifacts can be handed to a later step through a generated
reference binding. The framework verifies artifact compatibility and retains
producer provenance; consumers resolve the handed-off artifact into an
immutable, validated projection for each operation. External files are checked
during preparation, while generated artifacts are resolved at the handoff.

NPC registries are names-only grounding projections: they may canonicalize
actors for spells and combat turns and are required for NPC occurrences, but
they do not supply evidence. Scene-description registries are eligibility-only
projections: they retain the current chunk’s classification data, not scene
prose or evidence, and exist to route combat extraction. Enemy-event extraction
also projects combat turns to `actor` and `turn_kind` and filters NPC
occurrences to `combat_opponent` names and kinds. Location registries project
ordered `{id, name}` pairs to location-occurrence extraction and normalization;
exact ID/name matching keeps same-name locations distinguishable. These compact
projections, like NPC grounding, are source-free guidance and never event
evidence.

## Lane-Specific Rules

The following differences are intentional and should remain explicit when a
shared helper changes.

| Lane | Intentional behavior |
| --- | --- |
| Spells | May use a spell-catalog overlay and optional NPC grounding; the catalog validator supplies domain-specific semantic checks. |
| NPCs | Does not consume an NPC registry. Its normalizer is the LLM-assisted reconciliation exception described above. |
| Combat turns | Requires a scene-description artifact. It calls the LLM only for an exact `combat` classification; exact non-combat classifications return an accepted empty result, while missing or mismatched classifications return an empty result with a bounded warning. Optional NPC grounding never becomes evidence. |
| Item events | Uses campaign context for disambiguation but has no NPC-registry or scene-description dependency. |
| NPC occurrences | Requires the normalized NPC registry at extraction and normalization, using it for canonical actor grounding only. |
| Scene descriptions | Produces the classifications consumed by combat routing; it does not consume an NPC registry or provide evidence for combat artifacts. |
| Enemy events | Requires NPC, scene-description, combat-turn, and NPC-occurrence artifacts. It calls the LLM only for an exact `combat` classification, records ordered observations rather than terminal state, and normalizes recognized names through the NPC registry while preserving grounded collective labels. |
| Location registry | Produces a source-anchored, session-scoped registry from stable proper names or unique in-world designations. Its LLM-assisted reconciliation is proposal-only and never collapses same-name places without validated identity and evidence rules. |
| Location occurrences | Requires the normalized location registry for both extraction and normalization. Its [durable occurrence categories](../integrations/dnd-location-occurrence-artifacts.md#occurrence-categories) distinguish explicit speculation from unsupported inference; the deterministic normalizer enforces exact registry grounding and never turns registry provenance into occurrence evidence. |

The combat and scene-description contracts describe their exact handoff and
empty-result behavior in more detail:
[combat turns](../integrations/dnd-combat-turn-artifacts.md) and
[scene descriptions](../integrations/dnd-scene-description-artifacts.md).
The [enemy-event contract](../integrations/dnd-enemy-event-artifacts.md)
defines its durable semantics; [Configuration](../config.md) owns its
selectable bindings and validation chains.

## Focused Verification

When changing D&D behavior, test the affected codec, extractor, normalizer,
validator, prompt-asset manifest, and registry projection. Also test generated
handoffs at the integration boundary and run the full D&D module suite:

~~~sh
go test ./internal/modules/dnd/...
go test ./internal/modules/integration/...
~~~