Add D&D NPC interaction artifact codec

docs/roadmap/dnd-npc-interactions.md

@@ -0,0 +1,197 @@
+# D&D NPC Interactions
+
+Status: Accepted
+
+## Purpose
+
+The normalized NPC registry intentionally answers only who was identified in a
+session. It does not answer whether an NPC was merely mentioned, participated
+in dialogue, or fought alongside or against the party. Add a separate,
+ordered NPC-interaction artifact for that occurrence-level information rather
+than expanding the identity registry.
+
+This feature preserves the minimal-extractor policy: the model identifies one
+bounded kind of interaction and its supporting transcript evidence. It does
+not summarize the interaction, infer relationships, or maintain NPC state.
+
+## Desired End State
+
+A D&D pipeline can run NPC extraction first and supply its accepted normalized
+registry to a later `dnd/npc-interactions` lane. The later lane emits an ordered
+list of evidenced interaction occurrences involving registry NPCs.
+
+The production identities should be:
+
+- extractor and normalizer key: `dnd/npc-interactions`;
+- artifact kind: `dnd/npc-interaction-list`;
+- durable schema ID: `notarius.dnd.npc_interactions`;
+- durable schema name: `notarius_dnd_npc_interactions_v1`;
+- durable schema version: `v1`; and
+- media type: `application/json`.
+
+The lane must use the existing D&D module organization, shared prompt assets,
+typed artifact pipeline, codec boundary, registration pattern, and default
+validator composition.
+
+## Artifact Contract
+
+The durable payload is an object containing an `interactions` array. The array
+may be empty. Each interaction contains exactly:
+
+- `name`: the canonical NPC name from the supplied registry;
+- `kind`: one value from the bounded interaction vocabulary; and
+- `source_refs`: one or more current-transcript ranges supporting both the NPC
+  identity and the classified interaction.
+
+Every object rejects unknown fields. The model-facing response should contain
+only the corresponding name, kind, and source-unit range candidates. Notarius
+attaches the current source identity deterministically; the model must not
+reproduce it.
+
+Do not add a separate interaction ID in the durable contract. Stable ordering,
+the canonical NPC name, the bounded kind, and exact evidence ranges are enough
+to identify and audit an occurrence for the present use cases. Revisit durable
+cross-artifact identity only with a concrete consumer requirement.
+
+## Interaction Vocabulary
+
+Use this closed vocabulary:
+
+| Kind | Meaning |
+| --- | --- |
+| `mentioned` | The NPC is referred to, but is not established as present or communicating in the evidenced passage. |
+| `noncombat_presence` | The NPC is present and relevant to the passage but does not meaningfully participate in dialogue or combat. |
+| `dialogue` | The NPC speaks, responds, or is directly engaged in a meaningful non-combat exchange. |
+| `combat_ally` | The NPC actively participates in combat on the party's side. |
+| `combat_opponent` | The NPC actively participates in combat against the party. |
+| `other` | The transcript clearly establishes a direct NPC occurrence that fits none of the preceding kinds. |
+
+`other` is a residual category for positively evidenced activity, not an
+escape hatch for uncertain classification. Omit a candidate when the
+transcript does not support one category.
+
+When activities overlap within one occurrence, apply this precedence:
+
+1. active combat participation outranks dialogue, presence, and mention;
+2. dialogue outranks non-combat presence and mention;
+3. non-combat presence outranks mention; and
+4. `other` applies only when none of the defined categories describes the
+   evidenced activity.
+
+Combat alignment is not resolved by precedence. An NPC cannot be both a combat
+ally and combat opponent in one occurrence; split the record when its alignment
+meaningfully changes.
+
+## Occurrence Boundaries And Ordering
+
+An occurrence represents one NPC, one interaction kind, and one locally
+coherent transcript passage. Combine repeated evidence only while it supports
+the same uninterrupted activity. Create separate occurrences when:
+
+- the interaction kind changes;
+- combat alignment changes;
+- a scene or meaningful absence separates repeated activity; or
+- the NPC is first mentioned and later becomes present.
+
+Extraction remains chunk-scoped, so an occurrence must not span accepted chunk
+boundaries. Merge and normalization must not semantically combine occurrences
+from different chunks.
+
+Order the durable list by the earliest valid source position. Use canonical
+name, interaction kind, and canonical source ranges as deterministic
+tie-breakers. Remove only exact duplicate records; do not use model judgment to
+collapse nearby occurrences.
+
+## NPC Grounding And Evidence
+
+The extractor declares the existing `npcs` reference slot and requires a bound,
+accepted NPC registry. The normal same-run configuration binds the normalized
+output of an earlier NPC lane through an ordered generated reference. Existing
+framework support for a compatible external registry may remain available, but
+must not weaken the artifact contract.
+
+Present the registry's names-only projection to the model. An emitted name must
+match one canonical registry name exactly after the registry's established
+lookup rules are applied, and the durable artifact retains that canonical
+display name. Do not copy NPC IDs or registry source references into an
+interaction.
+
+The registry establishes available identity, not occurrence. Every interaction
+must cite current transcript ranges that independently support both the NPC and
+the selected kind. Campaign references and generated artifacts may disambiguate
+a name, but they never become interaction evidence.
+
+If no registry NPC has an evidenced interaction, the correct artifact is an
+empty list. A missing, rejected, or incompatible required registry handoff is a
+pipeline dependency failure rather than a request to extract ungrounded names.
+
+## Prompt And Model Boundary
+
+Follow the established D&D prompt ordering and cache-boundary policy. Stable
+shared instructions, lane instructions, campaign references, and the NPC
+names-only projection precede the variable transcript. Factor wording shared
+with the spell and combat lanes into the existing shared asset pattern rather
+than creating nearly identical package-local messages.
+
+The prompt must:
+
+- define the closed vocabulary and precedence rules;
+- ask for occurrences involving only supplied registry NPCs;
+- distinguish mention from presence and dialogue;
+- require current-transcript evidence for identity and kind;
+- forbid summaries, relationship inference, sentiment, aliases, and invented
+  names; and
+- permit an empty result.
+
+Keep the private JSON Schema structural. Deterministic code owns canonical-name
+resolution, enum enforcement at the durable boundary, source-range validation,
+ordering, exact deduplication, and evidence invariants.
+
+## Validation And Quality
+
+Provide production validators and default chains at extraction and
+normalization boundaries consistent with the existing D&D artifacts. The
+append-only merge does not require a separate default validator chain.
+Deterministic validation must reject:
+
+- missing or extra fields;
+- empty or unrecognized NPC names;
+- names absent from the supplied registry;
+- unknown interaction kinds;
+- empty, malformed, out-of-source, or reversed evidence ranges; and
+- records whose evidence comes from a reference rather than the current
+  transcript.
+
+Any relatedness validator should remain warning-only unless evaluation
+demonstrates a reliable deterministic rejection rule. Diagnostics must be
+bounded and must not leak reference contents.
+
+Evaluate the lane on a small human-reviewed transcript set that includes every
+category, transitions between categories, multiple occurrences for one NPC,
+mentions followed by appearances, alignment changes, repeated evidence across
+chunks, and empty output. Review category agreement, evidence sufficiency,
+ordering, duplicate behavior, and reliability on the smaller models the
+application is intended to support. Treat model-output evaluation as a human
+development aid, not a brittle deterministic test oracle.
+
+## Documentation Outcomes
+
+When implemented, document the durable artifact in `docs/integrations/`, add
+the selectable module and validator contracts to configuration documentation,
+update the current module and pipeline internals, and provide a maintained
+ordered-pipeline example showing NPC extraction followed by interaction
+extraction. Future behavior must remain in this roadmap until it exists.
+
+## Non-Goals
+
+This scope does not:
+
+- add occurrence fields to the normalized NPC registry;
+- summarize dialogue, combat, or NPC behavior;
+- infer disposition, relationships, factions, motives, or persistent state;
+- identify player characters or anonymous groups as NPCs;
+- add scene participants or duplicate scene-description responsibilities;
+- reconcile NPC aliases or perform LLM-assisted semantic deduplication;
+- derive interaction records from registry evidence; or
+- introduce a DAG, concurrent cross-lane reconciliation, or a new reference
+  mechanism.

docs/roadmap/future.md

@@ -18,28 +18,10 @@ not as committed release dates.
 
 ### Extract NPC Interactions
 
-- Add an ordered NPC-interaction artifact that records how an identifiable NPC
+Add a minimal, ordered `dnd/npc-interactions` artifact after NPC identity
-  participates in the session without adding occurrence-level state to the
+extraction. The proposed contract, occurrence semantics, category policy,
-  normalized NPC registry. Use `npc-interactions` as the working lane and
+grounding rules, evidence requirements, and non-goals are defined in
-  product name; the exact artifact kind may be finalized with its contract.
+[D&D NPC Interactions](dnd-npc-interactions.md).
-- Keep each record minimal: canonical NPC `name`, one bounded interaction
-  `kind`, and transcript `source_refs` supporting both the identity and
-  classification.
-- Start with the mutually exclusive vocabulary `mentioned`,
-  `noncombat_presence`, `dialogue`, `combat_ally`, `combat_opponent`, and
-  `other`. Define narrow inclusion rules and category precedence before
-  implementation so overlapping activity does not produce arbitrary labels.
-- Model interactions as ordered occurrences rather than one scalar NPC
-  category. The same NPC may therefore have separate records when the
-  transcript establishes distinct interactions, such as dialogue followed by
-  hostile combat.
-- Run NPC identity extraction first and provide its accepted names-only
-  projection to the interaction extractor for grounding. Registry names may
-  disambiguate identity but never establish that an interaction occurred, and
-  registry source references must not be copied into interaction evidence.
-- Evaluate category agreement, evidence sufficiency, duplicate behavior, and
-  smaller-model reliability on human-reviewed transcripts before expanding the
-  enum or adding additional fields.
 
 ### Export Accepted Chunk Maps
 

docs/roadmap/implementation.md

@@ -0,0 +1,570 @@
+# D&D NPC Interactions Implementation Plan
+
+Status: Ready for implementation
+
+## Objective
+
+Implement the accepted [D&D NPC Interactions](dnd-npc-interactions.md)
+roadmap as a production D&D artifact lane. The finished lane must extract an
+ordered list of minimal, evidence-grounded NPC interaction occurrences from
+each accepted transcript chunk, ground every NPC against a required accepted
+NPC registry, and preserve the existing fixed pipeline and generated-reference
+architecture.
+
+This plan is the implementation authority for sequencing and file-level work.
+The feature roadmap remains authoritative for product intent, category
+semantics, occurrence boundaries, evidence policy, and non-goals. Follow
+[ADR-0009](../adr/0009-minimal-evidence-grounded-extraction-artifacts.md)
+throughout: do not add descriptive, analytical, relationship, or state fields.
+
+## Fixed Decisions
+
+The implementation must use these identities:
+
+| Concern | Identity |
+| --- | --- |
+| Extractor key | `dnd/npc-interactions` |
+| Normalizer key | `dnd/npc-interactions` |
+| Artifact kind | `dnd/npc-interaction-list` |
+| Durable schema ID | `notarius.dnd.npc_interactions` |
+| Durable schema name | `notarius_dnd_npc_interactions_v1` |
+| Durable schema version | `v1` |
+| Durable media type | `application/json` |
+| Private prompt ID | `dnd.npc_interactions` |
+| Private response schema ID | `notarius.dnd.npc_interactions.llm` |
+| Reference slot | `npcs` |
+
+Use a top-level `interactions` array. Each durable record has exactly `name`,
+`kind`, and `source_refs`. Do not add an interaction ID. The closed kind
+vocabulary is `mentioned`, `noncombat_presence`, `dialogue`, `combat_ally`,
+`combat_opponent`, and `other`.
+
+The `npcs` slot is required for both extraction and normalization. It accepts
+only the existing `dnd/npc-list` JSON artifact within the existing NPC registry
+size limit. A bound registry with an empty `npcs` array is valid and requires an
+empty interaction artifact. An absent binding, malformed registry, failed
+generated handoff, or unknown interaction name is not permission to perform
+ungrounded extraction.
+
+Use the existing `internal/modules/dnd/npcs/registry.Resolver` for construction-
+time external references and operation-time generated references. The
+extractor presents only `Registry.PromptInput()` to the model. Name lookup uses
+the registry's established comparison-key policy before normalization; the
+normalizer replaces a recognized variant with the exact canonical registry
+display name. Registry source references and campaign references never become
+interaction evidence.
+
+An occurrence is one NPC, one kind, and one coherent passage within one
+accepted chunk. The model must split a category or combat-alignment transition.
+No occurrence spans chunks. Merge preserves chunk order. Normalization:
+
+1. replaces recognized names with canonical registry display names;
+2. sorts and exact-deduplicates each record's source references;
+3. orders records by earliest valid source position, then canonical name,
+   interaction kind, and the canonical source-reference sequence;
+4. removes records only when canonical name, kind, and the complete canonical
+   source-reference sequence are all identical; and
+5. never semantically combines nearby, overlapping, or cross-chunk records.
+
+The private model response remains structural and contains name, kind, and
+integer start/end unit candidates. Mapping attaches the current source ID.
+Invalid strings, kinds, and ranges must survive mapping far enough for the
+deterministic validator that owns the rule to reject them.
+
+For the final record comparator, use source-document unit position for the
+earliest valid reference. Compare canonical names first by the existing NPC
+identity comparison key and then by exact display string; compare kinds by
+their string values; and compare canonical reference sequences
+lexicographically by `source_id`, start-unit document position, and end-unit
+document position. Records with valid evidence precede records without it;
+normalized output validation rejects the latter before durable encoding.
+
+No framework change, new identity subsystem, DAG behavior, LLM-assisted
+deduplication, or scene dependency is part of this plan.
+
+## Testing And Documentation Rules
+
+Apply [Testing Policy](../policy/testing.md) at every stage:
+
+- Protect artifact round trips, required fields, enum values, source
+  provenance, registry grounding, deterministic ordering, exact
+  deduplication, reference immutability, and generated handoff behavior.
+- Use the real codec, registry, resolver, normalizer, and pipeline machinery
+  when they are fast and deterministic. Stub only the structured LLM boundary.
+- Keep provider calls offline and deterministic.
+- Test each policy at its narrowest stable owner. Do not repeat every codec,
+  validator, and normalizer case in an end-to-end test.
+- Do not add a prompt-cache “change detector” based on exact message count,
+  shared-prefix length, token count, or prompt hash. Reuse the shared prompt
+  assets, test rendered behavior and manifest composition, and document the
+  ordering policy instead.
+- Do not use broad golden snapshots for prompts or diagnostics. A maintained
+  durable JSON fixture is appropriate because the complete serialized artifact
+  is an intentional integration contract.
+
+Until the final stage, keep unimplemented behavior only in roadmap
+documentation. Update current-behavior documentation and examples in the same
+stage that makes the production lane selectable.
+
+## Stage 1 — Add The Typed Artifact And Durable Codec
+
+### Goal
+
+Establish the domain type and strict serialized boundary without changing the
+production module catalog.
+
+### Changes
+
+1. Extend `internal/modules/dnd/types.go` with:
+   - `NPCInteractionListKind`;
+   - a string-backed `NPCInteractionKind`;
+   - exported constants for all six accepted values;
+   - `NPCInteractionList` with `Interactions []NPCInteraction`; and
+   - `NPCInteraction` with `Name string`, `Kind NPCInteractionKind`, and
+     `SourceRefs []source.SourceRef`.
+2. Add `internal/modules/dnd/codec/npcinteractions` following the existing NPC
+   and combat-turn codec boundary:
+   - expose the fixed schema constants and `MediaType`;
+   - implement the typed artifact codec for `dnd.NPCInteractionList`;
+   - keep `EncodeCandidate` and `DecodeCandidate` strict about one JSON value
+     and unknown fields while preserving typed semantic candidates;
+   - make approved `Encode` and `Decode` enforce non-empty names, the closed
+     kind enum, at least one structurally valid source reference, and the
+     durable schema shape; and
+   - report only `interaction_count` in codec metadata.
+3. Add
+   `internal/modules/dnd/codec/npcinteractions/assets/schemas/dnd_npc_interactions.v1.json`.
+   It must require the top-level array and all three record fields, reject
+   unknown fields at every object level, encode the six-value enum, require at
+   least one source reference, and use the established durable source-reference
+   shape.
+4. Add a small maintained fixture under
+   `internal/modules/dnd/codec/npcinteractions/testdata/` containing at least
+   two ordered records with distinct kinds and source ranges.
+
+### Tests
+
+At the codec package boundary, cover:
+
+- fixture decode/encode round trip and canonical compact JSON;
+- exact kind, schema identity, version, media type, and Go type registration;
+- empty-list support and nil-versus-present-empty behavior where the existing
+  codecs distinguish it;
+- strict rejection of malformed JSON, trailing values, and unknown fields;
+- approved-boundary rejection of each meaningful required-field, enum, and
+  source-reference violation;
+- candidate-boundary preservation of semantic values for later validators; and
+- defensive copies for schema bytes and metadata.
+
+Do not duplicate source-document existence checks in the codec; those belong to
+the source-reference validator.
+
+### Completion Criteria
+
+- The new types and codec compile and pass focused tests.
+- The codec can be registered into an isolated artifact codec registry with
+  exact type `dnd.NPCInteractionList`.
+- No production registrar or configuration catalog exposes the new kind yet.
+
+## Stage 2 — Implement The Chunk-Scoped Extractor And Prompt
+
+### Goal
+
+Add an independently testable LLM-backed extractor that requires NPC grounding,
+maps only minimal private output, and follows the established D&D prompt-cache
+layout.
+
+### Changes
+
+1. Add `internal/modules/dnd/extract/npcinteractions` using the current D&D
+   extractor organization:
+   - `assets.go`;
+   - `canonicalize.go`;
+   - `extractor.go`;
+   - `model.go`;
+   - `schema.go`;
+   - `scriptorium_assets.go`;
+   - corresponding focused tests; and
+   - package-local embedded prompt and schema assets.
+2. Give the extractor strict empty options, required capabilities `chunks` and
+   `source.transcript`, provided capability `dnd.npc_interactions`, and artifact
+   kind `dnd.NPCInteractionListKind`.
+3. Build its reference slots from `shared.ReferenceSlots(...)`, then append the
+   `npcs` slot with:
+   - `Required: true`;
+   - accepted media type `application/json`;
+   - accepted artifact kind `dnd.NPCListKind`;
+   - the existing registry maximum byte count; and
+   - a description stating that the accepted registry is required identity
+     grounding, not evidence.
+   Return defensive, consistently sorted slot declarations from both
+   `ModuleSpec()` and the constructed extractor.
+4. Construct an `npcregistry.Resolver` from the preparation-time reference set.
+   Resolve operation references inside `Extract`, require `Registry.Bound()`,
+   and fail before the LLM call if the required registry is absent or invalid.
+   Preserve the resolver's content-safe error behavior.
+5. Use `shared.ChunkPromptMaterial` and `shared.PromptInputs`. Replace the
+   ordinary `npcs` input with the resolved names-only `Registry.PromptInput()`.
+   Do not place full registry bytes, NPC IDs, registry evidence, or provenance
+   in prompt inputs.
+6. Add these assets:
+   - `assets/prompts/dnd.npc_interactions.yaml`;
+   - `assets/prompts/task.md`;
+   - `assets/prompts/instructions.md`; and
+   - `assets/schemas/dnd_npc_interactions_llm.v1.json`.
+7. Use the existing shared prompt assets in this exact semantic order:
+   common system; common extraction evidence; common identity; common campaign
+   references; common NPC grounding; lane task; lane instructions; variable
+   transcript. Preserve the established cache-control placement used by the
+   spell and combat-turn manifests.
+8. Revise the shared `common-dnd-npcs.md` wording once so it truthfully applies
+   to all three consumers: a normalized registry is always presented to the
+   prompt and may be empty. Keep its identity, context-only rule, and
+   prohibition on treating registry provenance as event evidence. Do not fork a
+   nearly identical interaction-specific grounding asset.
+9. The lane prompt must state the category definitions, precedence, occurrence
+   splitting rules, registry-only name restriction, empty-output behavior, and
+   exclusions from the feature roadmap. Keep the response schema structural:
+   it requires the envelope and fields but leaves enum membership, non-empty
+   values, and source semantics to deterministic validators.
+10. Map private records to `dnd.NPCInteractionList`, attach the current source
+    ID, sort and exact-deduplicate ranges within each candidate, and stable-sort
+    candidates with valid evidence by earliest source-document position.
+    Preserve invalid candidate fields rather than repairing or dropping them.
+11. Expose prompt, response-schema, and mapping-policy identities through
+    manifest metadata and checkpoint fingerprints, following the current D&D
+    extractors. Include the NPC names-only projection digest in local checkpoint
+    identity. For a preparation-time external registry, expose only bounded
+    digest/count metadata; do not place names or source content in metadata.
+    Generated-reference provenance remains framework-owned.
+
+### Tests
+
+At stable package boundaries, cover:
+
+- nil/cancelled/invalid extraction requests and provider failures;
+- required-slot declaration and rejection of an unbound or malformed registry
+  before any LLM call;
+- operation-time generated registry resolution by an extractor prepared
+  without generated bytes;
+- exact names-only registry prompt input and separation from transcript
+  evidence;
+- empty registry plus empty response;
+- mapping of every category, current-source attachment, evidence
+  canonicalization, and source-position ordering;
+- preservation of invalid names, kinds, and ranges for validators;
+- strict private JSON shape and unknown-field rejection;
+- prompt rendering with required inputs, category policy, shared assets, and
+  transcript-last ordering;
+- prompt/schema registration and content-safe metadata/fingerprints; and
+- defensive module specifications and strict rejection of unknown options.
+
+Run the existing spell and combat-turn prompt/asset tests after changing the
+shared NPC prompt fragment. Do not assert an exact shared-prefix length.
+
+### Completion Criteria
+
+- The extractor is constructible and testable through the typed extractor
+  contract.
+- A valid request makes one scheduled structured-completion call and returns a
+  typed candidate with current-source provenance.
+- Missing required NPC grounding cannot reach the model.
+- The extractor remains unregistered in the production D&D family until later
+  stages provide the rest of the lane.
+
+## Stage 3 — Add Deterministic Artifact Validators
+
+### Goal
+
+Give each semantic invariant one clear validation owner and make invalid model
+output a rejection rather than a normalization repair or framework error.
+
+### Changes
+
+Add these typed validator packages, each with strict empty options, bounded
+diagnostics, typed registration, and the fixed artifact kind:
+
+1. `internal/modules/dnd/validate/npcinteractions/shape`
+   (`extract/dnd/npc-interactions/shape`):
+   - require a non-empty trimmed name without mutating it;
+   - require one of the six kinds; and
+   - require at least one source-reference candidate with structurally required
+     values.
+2. `internal/modules/dnd/validate/npcinteractions/registry`
+   (`extract/dnd/npc-interactions/registry`):
+   - use `npcregistry.Resolver` at construction and operation time;
+   - require a bound registry;
+   - approve a name when `Registry.Lookup` recognizes it under the established
+     comparison policy;
+   - reject unknown names in stable record order; and
+   - never use registry evidence as transcript evidence.
+3. `internal/modules/dnd/validate/npcinteractions/source_refs`
+   (`extract/dnd/npc-interactions/source_refs`):
+   - require the current source identity;
+   - require referenced units to exist; and
+   - require valid inclusive start/end order through the current document.
+   Follow the established D&D citation helpers and rejection aggregation
+   limits rather than introducing a generic framework dependency on the
+   interaction type.
+4. `internal/modules/dnd/validate/npcinteractions/source_relatedness`
+   (`extract/dnd/npc-interactions/source_relatedness`):
+   - inspect only current transcript text covered by the cited ranges;
+   - emit at most one bounded warning per record when the NPC name cannot be
+     related to that evidence;
+   - do not claim to validate category agreement; and
+   - ignore campaign and registry content for relatedness.
+5. `internal/modules/dnd/validate/npcinteractions/invariants`
+   (`normalize/dnd/npc-interactions/invariants`):
+   - require the exact canonical display name returned by registry lookup;
+   - require canonical source-reference order with no duplicate ranges;
+   - require the complete list order defined in Fixed Decisions; and
+   - reject exact duplicate normalized records.
+
+The registry and invariants validators must support operation-time generated
+references. Construction-time metadata and fingerprints follow the resolver
+pattern used by registry-aware modules and must not include NPC names or
+content.
+
+### Tests
+
+Give each policy one primary test owner:
+
+- shape tests own empty names, enum membership, and missing evidence;
+- registry tests own required binding, comparison-key recognition, unknown
+  names, operation-time generated overrides, empty registries, and content-safe
+  failures;
+- source-reference tests own wrong source IDs, missing units, reversed ranges,
+  and valid multi-range records;
+- relatedness tests own current-transcript-only warnings and bounded
+  diagnostics; and
+- invariant tests own exact canonical names, final ordering, canonical evidence
+  sequences, and duplicate rejection.
+
+Also verify that validators do not mutate artifacts, source documents, or
+registries and that their specs register only for
+`dnd.NPCInteractionListKind`.
+
+### Completion Criteria
+
+- Valid typed candidates are approved and malformed or ungrounded candidates
+  are rejected at the intended boundary.
+- No validator silently canonicalizes, drops, or merges records.
+- References can explain identity but cannot satisfy source evidence checks.
+
+## Stage 4 — Add Deterministic Merge And Normalization
+
+### Goal
+
+Preserve chunk-scoped occurrences through merge, then produce the canonical
+ordered artifact without semantic inference.
+
+### Changes
+
+1. Add `internal/modules/dnd/normalize/npcinteractions` with strict empty
+   options and the fixed module key and artifact kind.
+2. Declare the same required `npcs` reference slot as the extractor. Construct
+   and resolve `npcregistry.Resolver` at the same preparation/operation
+   boundaries, and require a bound registry.
+3. Implement the normalization algorithm in Fixed Decisions:
+   - clone all nested values;
+   - normalize display whitespace only as needed for lookup;
+   - replace every recognized name with the registry's exact canonical display
+     name;
+   - canonicalize each reference list without merging overlapping ranges;
+   - compute order from source-document positions rather than assuming numeric
+     unit IDs are contiguous;
+   - apply every specified tie-breaker; and
+   - collapse only exact records after canonicalization.
+4. Preserve nil versus present-empty list behavior consistently with the other
+   D&D normalizers.
+5. Emit bounded warnings for visible canonical-name changes, reference
+   canonicalization, record reordering, and exact duplicate removal. Use stable
+   reason codes and the shared D&D diagnostics helpers. Never include reference
+   content in a warning.
+6. Add an append-only merger function for `dnd.NPCInteractionList` beside the
+   other D&D typed append functions in
+   `internal/modules/dnd/register/merge.go`. It must preserve accepted
+   chunk/lane order, preserve present-empty semantics, and deep-clone source
+   reference slices so outputs do not alias inputs. Do not register it until
+   Stage 5.
+7. Add normalization-policy and NPC projection identities to checkpoint
+   fingerprints. Manifest metadata may include the policy identity and bounded
+   external-registry digest/count, but not names or source content.
+
+### Tests
+
+Cover:
+
+- canonical registry name replacement, including Unicode/case/spacing lookup;
+- required and operation-time generated registry behavior;
+- source-reference ordering and exact range deduplication;
+- ordering by real document position with all deterministic tie-breakers;
+- separation of category transitions, alignment transitions, nearby records,
+  overlapping-but-nonidentical evidence, and nonidentical records from
+  different chunks;
+- collapse of exact duplicates only;
+- stable, bounded warnings;
+- nil/present-empty behavior;
+- input ownership and nested-slice cloning; and
+- append-order merger behavior independently of normalization.
+
+Use table-driven pure normalization cases for the dense ordering and duplicate
+rules, and package-level normalizer tests for resolver and warning behavior.
+
+### Completion Criteria
+
+- Normalization is deterministic and idempotent.
+- Running normalization twice does not change the value or emit new
+  transformation warnings on the second pass.
+- Semantically distinct occurrences remain distinct.
+- The module and merger compile but are not yet selectable through production
+  composition.
+
+## Stage 5 — Compose The Complete Production Lane
+
+### Goal
+
+Register the complete typed lane atomically so configuration cannot select a
+partial implementation.
+
+### Changes
+
+Update the D&D registrar:
+
+1. In `internal/modules/dnd/register/modules.go`, register:
+   - the NPC-interaction codec;
+   - extractor and prompt assets;
+   - the append-order merger variant for
+     `dnd.NPCInteractionListKind`;
+   - the `dnd/npc-interactions` normalizer; and
+   - the generic no-op normalizer variant for the new exact Go type.
+2. In `internal/modules/dnd/register/validators.go`, register all five domain
+   validators plus generic always-accept and always-reject typed variants for
+   the new artifact type.
+3. In `internal/modules/dnd/register/chains.go`, register:
+   - extraction chain:
+     `generic/valid_json`,
+     `extract/dnd/npc-interactions/shape`,
+     `extract/dnd/npc-interactions/registry`,
+     `extract/dnd/npc-interactions/source_refs`,
+     `generic/valid_json_schema`,
+     `extract/dnd/npc-interactions/source_relatedness`;
+   - normalization chain:
+     `generic/valid_json`,
+     `extract/dnd/npc-interactions/shape`,
+     `extract/dnd/npc-interactions/registry`,
+     `normalize/dnd/npc-interactions/invariants`,
+     `extract/dnd/npc-interactions/source_refs`,
+     `generic/valid_json_schema`,
+     `extract/dnd/npc-interactions/source_relatedness`.
+4. Do not add a default merge validator chain. The append merger performs no
+   semantic mutation, and extraction plus normalized boundaries own the
+   consequential policies.
+5. Extend registrar contract tests to verify exact typed coverage, keys,
+   artifact kinds, prompt/schema assets, reference-slot agreement, and default
+   validator order.
+
+### Tests
+
+- Extend the existing D&D family registration test rather than creating
+  parallel catalog snapshots.
+- Verify that the extractor and normalizer both expose required compatible
+  `npcs` slots and that generated `dnd/npc-list` bindings resolve only from an
+  earlier step.
+- Verify production resolution rejects a missing required binding, a later or
+  same-step producer, a wrong artifact kind, and incompatible media/schema
+  metadata through existing resolver behavior.
+- Avoid retesting the framework's general ordered-step failure matrix; add only
+  interaction-specific composition cases not already covered generically.
+
+### Completion Criteria
+
+- Production registration exposes one complete type-consistent lane.
+- A valid two-step NPC-to-interactions pipeline resolves and prepares.
+- Invalid or missing NPC dependencies fail before source parsing or LLM work
+  whenever statically discoverable.
+
+## Stage 6 — Prove The Workflow And Publish Current Contracts
+
+### Goal
+
+Exercise the assembled generated-reference workflow and move all implemented
+behavior into its canonical current documentation.
+
+### Changes
+
+1. Add one representative integration test under
+   `internal/modules/integration` with focused testdata:
+   - step 1 extracts and normalizes NPCs;
+   - step 2 consumes the generated NPC artifact in an interaction lane;
+   - the fake structured LLM returns multiple interaction kinds and at least
+     one name variant;
+   - the assertion proves the names-only handoff, current-transcript evidence,
+     canonical name, stable chronology, and final durable artifact.
+2. Include one failure assertion showing that a rejected or absent normalized
+   NPC producer prevents interaction extraction. Reuse the existing runner
+   dependency behavior; do not duplicate every framework failure case.
+3. Add `examples/dnd-npc-interactions.config.yml` as a complete copyable
+   two-step profile. The first step produces `npcs`; the second step binds that
+   exact step/lane artifact to its `npcs` reference and selects
+   `dnd/npc-interactions` for extract and normalize.
+4. Add the example to the existing CLI production configuration contract test
+   so it is parsed and resolved offline.
+5. Add the durable external contract at
+   `docs/integrations/dnd-npc-interaction-artifacts.md`. It owns schema
+   identity, JSON shape, categories, evidence semantics, ordering,
+   normalization, validator chains, generated-reference behavior, and manifest
+   metadata.
+6. Update current canonical documentation:
+   - `docs/config.md` for module/validator catalogs, default chains, required
+     reference slot, and the maintained example;
+   - `docs/internal/modules.md` for implementation ownership, prompt inputs,
+     registry resolution, validation, merge, and normalization;
+   - `docs/internal/overview.md` for the implemented component inventory;
+   - `docs/internal/llm.md` only as needed to include the new lane in the
+     existing D&D prompt-order/cache policy without duplicating the manifest;
+   - `docs/integrations/dnd-npc-artifacts.md` to identify NPC interactions as a
+     consumer while retaining the rule that registry evidence is not event
+     evidence; and
+   - any directly affected configuration or integration links.
+7. Remove the NPC-interactions entry from `docs/roadmap/future.md` once the
+   production behavior and current documentation are complete. Change
+   `docs/roadmap/dnd-npc-interactions.md` to `Status: Implemented` pending its
+   later retirement; do not leave it as the canonical current contract.
+8. Create a small human-review worksheet or fixture set only if the repository
+   already has an appropriate non-test evaluation home. Otherwise record the
+   manual evaluation results in the implementation handoff rather than
+   inventing a new framework. Exercise all six categories, transitions,
+   repeated occurrences, mentions followed by presence, combat alignment
+   changes, cross-chunk repetition, and empty output on at least one intended
+   smaller model. Do not make model agreement a deterministic CI gate.
+
+### Validation
+
+Run focused tests while implementing, then run:
+
+```sh
+go test ./...
+go vet ./...
+go build ./cmd/notarius
+```
+
+Also run `git diff --check`, inspect the complete documentation diff for
+current-versus-future claims, and verify every new relative documentation link.
+
+### Completion Criteria
+
+- All repository checks pass offline.
+- The maintained example resolves with an explicit earlier NPC producer.
+- The integration test proves the accepted generated artifact, not registry
+  source references, grounds the later model request.
+- Durable output contains only `name`, `kind`, and current-transcript
+  `source_refs` per occurrence.
+- Current documentation owns implemented contracts, while the feature roadmap
+  is marked implemented and `future.md` no longer advertises the work as
+  pending.
+
+## Open Questions
+
+None. The feature roadmap and fixed decisions above define the product and
+architectural choices required for implementation.

internal/modules/dnd/codec/npcinteractions/assets/schemas/dnd_npc_interactions.v1.json

@@ -0,0 +1,50 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "notarius.dnd.npc_interactions",
+  "type": "object",
+  "additionalProperties": false,
+  "required": ["interactions"],
+  "properties": {
+    "interactions": {
+      "type": "array",
+      "items": {
+        "type": "object",
+        "additionalProperties": false,
+        "required": ["name", "kind", "source_refs"],
+        "properties": {
+          "name": {
+            "type": "string",
+            "minLength": 1
+          },
+          "kind": {
+            "type": "string",
+            "enum": ["mentioned", "noncombat_presence", "dialogue", "combat_ally", "combat_opponent", "other"]
+          },
+          "source_refs": {
+            "type": "array",
+            "minItems": 1,
+            "items": {
+              "type": "object",
+              "additionalProperties": false,
+              "required": ["source_id", "start_unit_id", "end_unit_id"],
+              "properties": {
+                "source_id": {
+                  "type": "string",
+                  "minLength": 1
+                },
+                "start_unit_id": {
+                  "type": "integer",
+                  "minimum": 1
+                },
+                "end_unit_id": {
+                  "type": "integer",
+                  "minimum": 1
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+}

internal/modules/dnd/codec/npcinteractions/codec.go

@@ -0,0 +1,140 @@
+// Package npcinteractions encodes durable D&D NPC interaction artifacts.
+package npcinteractions
+
+import (
+	"bytes"
+	"embed"
+	"encoding/json"
+	"fmt"
+	"io"
+	"strings"
+
+	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
+	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd"
+)
+
+const (
+	SchemaID      = "notarius.dnd.npc_interactions"
+	SchemaName    = "notarius_dnd_npc_interactions_v1"
+	SchemaVersion = "v1"
+	MediaType     = "application/json"
+)
+
+//go:embed assets/schemas/dnd_npc_interactions.v1.json
+var schemaAssets embed.FS
+
+var _ contracts.ArtifactCodec[dnd.NPCInteractionList] = (*Codec)(nil)
+
+type Codec struct{}
+
+func New() *Codec { return &Codec{} }
+
+func (c *Codec) Kind() contracts.ArtifactKind { return dnd.NPCInteractionListKind }
+
+func (c *Codec) Schema() contracts.ArtifactSchema {
+	raw, err := schemaAssets.ReadFile("assets/schemas/dnd_npc_interactions.v1.json")
+	if err != nil {
+		return contracts.ArtifactSchema{}
+	}
+	return contracts.ArtifactSchema{
+		ID:         SchemaID,
+		Name:       SchemaName,
+		Version:    SchemaVersion,
+		JSONSchema: append([]byte(nil), raw...),
+	}
+}
+
+func (c *Codec) MediaType() string { return MediaType }
+
+func (c *Codec) Metadata(value dnd.NPCInteractionList) map[string]any {
+	return map[string]any{"interaction_count": len(value.Interactions)}
+}
+
+func (c *Codec) Encode(value dnd.NPCInteractionList) ([]byte, error) {
+	if err := validate(value); err != nil {
+		return nil, fmt.Errorf("encode dnd npc interaction list: %w", err)
+	}
+	return c.EncodeCandidate(value)
+}
+
+// EncodeCandidate provides the durable representation before semantic
+// validators have approved a value.
+func (c *Codec) EncodeCandidate(value dnd.NPCInteractionList) ([]byte, error) {
+	content, err := json.Marshal(value)
+	if err != nil {
+		return nil, fmt.Errorf("encode dnd npc interaction list: %w", err)
+	}
+	return content, nil
+}
+
+func (c *Codec) Decode(content []byte) (dnd.NPCInteractionList, error) {
+	value, err := c.DecodeCandidate(content)
+	if err != nil {
+		return dnd.NPCInteractionList{}, err
+	}
+	if err := validate(value); err != nil {
+		return dnd.NPCInteractionList{}, fmt.Errorf("decode dnd npc interaction list: %w", err)
+	}
+	return value, nil
+}
+
+// DecodeCandidate reads one strict durable JSON value before semantic
+// validators have approved it.
+func (c *Codec) DecodeCandidate(content []byte) (dnd.NPCInteractionList, error) {
+	decoder := json.NewDecoder(bytes.NewReader(content))
+	decoder.DisallowUnknownFields()
+	var value dnd.NPCInteractionList
+	if err := decoder.Decode(&value); err != nil {
+		return dnd.NPCInteractionList{}, fmt.Errorf("decode dnd npc interaction list: %w", err)
+	}
+	var trailing any
+	if err := decoder.Decode(&trailing); err != io.EOF {
+		return dnd.NPCInteractionList{}, fmt.Errorf("decode dnd npc interaction list: multiple JSON values")
+	}
+	return value, nil
+}
+
+func validate(value dnd.NPCInteractionList) error {
+	if value.Interactions == nil {
+		return fmt.Errorf("interactions must be present")
+	}
+	for index, interaction := range value.Interactions {
+		prefix := fmt.Sprintf("interactions[%d]", index)
+		if strings.TrimSpace(interaction.Name) == "" {
+			return fmt.Errorf("%s.name must not be empty", prefix)
+		}
+		if !validInteractionKind(interaction.Kind) {
+			return fmt.Errorf("%s.kind must be supported", prefix)
+		}
+		if len(interaction.SourceRefs) == 0 {
+			return fmt.Errorf("%s.source_refs must contain at least one reference", prefix)
+		}
+		for refIndex, ref := range interaction.SourceRefs {
+			refPrefix := fmt.Sprintf("%s.source_refs[%d]", prefix, refIndex)
+			if strings.TrimSpace(ref.SourceID) == "" {
+				return fmt.Errorf("%s.source_id must not be empty", refPrefix)
+			}
+			if ref.StartUnitID <= 0 {
+				return fmt.Errorf("%s.start_unit_id must be positive", refPrefix)
+			}
+			if ref.EndUnitID <= 0 {
+				return fmt.Errorf("%s.end_unit_id must be positive", refPrefix)
+			}
+		}
+	}
+	return nil
+}
+
+func validInteractionKind(value dnd.NPCInteractionKind) bool {
+	switch value {
+	case dnd.NPCInteractionKindMentioned,
+		dnd.NPCInteractionKindNoncombatPresence,
+		dnd.NPCInteractionKindDialogue,
+		dnd.NPCInteractionKindCombatAlly,
+		dnd.NPCInteractionKindCombatOpponent,
+		dnd.NPCInteractionKindOther:
+		return true
+	default:
+		return false
+	}
+}

internal/modules/dnd/codec/npcinteractions/codec_test.go

@@ -0,0 +1,183 @@
+package npcinteractions
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"os"
+	"reflect"
+	"strings"
+	"testing"
+
+	"gitea.maximumdirect.net/eric/notarius/internal/core/source"
+	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
+	"gitea.maximumdirect.net/eric/notarius/internal/framework/pipeline"
+	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd"
+)
+
+func validList() dnd.NPCInteractionList {
+	return dnd.NPCInteractionList{Interactions: []dnd.NPCInteraction{
+		{
+			Name: "Mira Thorn", Kind: dnd.NPCInteractionKindDialogue,
+			SourceRefs: []source.SourceRef{{SourceID: "session-alpha", StartUnitID: 1, EndUnitID: 2}},
+		},
+		{
+			Name: "Hooded Guard", Kind: dnd.NPCInteractionKindCombatOpponent,
+			SourceRefs: []source.SourceRef{{SourceID: "session-alpha", StartUnitID: 3, EndUnitID: 3}},
+		},
+	}}
+}
+
+func TestCodecMatchesMaintainedDurableFixture(t *testing.T) {
+	raw, err := os.ReadFile("testdata/dnd_npc_interactions.v1.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	codec := New()
+	value, err := codec.Decode(raw)
+	if err != nil {
+		t.Fatalf("Decode() error = %v", err)
+	}
+	if want := validList(); !reflect.DeepEqual(value, want) {
+		t.Fatalf("Decode() = %#v, want %#v", value, want)
+	}
+	encoded, err := codec.Encode(value)
+	if err != nil {
+		t.Fatalf("Encode() error = %v", err)
+	}
+	var compact bytes.Buffer
+	if err := json.Compact(&compact, raw); err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(encoded, compact.Bytes()) {
+		t.Fatalf("Encode() = %s, want %s", encoded, compact.Bytes())
+	}
+}
+
+func TestCodecOwnsDurableSchemaAndRegistersExactType(t *testing.T) {
+	codec := New()
+	schema := codec.Schema()
+	if codec.Kind() != dnd.NPCInteractionListKind || codec.MediaType() != MediaType {
+		t.Fatalf("codec identity = %q/%q", codec.Kind(), codec.MediaType())
+	}
+	if schema.ID != SchemaID || schema.Name != SchemaName || schema.Version != SchemaVersion || !json.Valid(schema.JSONSchema) {
+		t.Fatalf("schema = %#v", schema)
+	}
+	registry := pipeline.NewArtifactCodecRegistry()
+	if err := pipeline.RegisterArtifactCodec(registry, codec); err != nil {
+		t.Fatal(err)
+	}
+	spec, ok := registry.Spec(dnd.NPCInteractionListKind)
+	if !ok || spec.SchemaDigest != contracts.DigestArtifactSchema(schema) {
+		t.Fatalf("registered spec = %#v, %t", spec, ok)
+	}
+	if _, err := registry.Encode(dnd.NPCInteractionListKind, dnd.NPCList{}); err == nil {
+		t.Fatal("Encode() error = nil, want exact type rejection")
+	} else {
+		var typeErr *pipeline.ArtifactCodecTypeError
+		if !errors.As(err, &typeErr) {
+			t.Fatalf("Encode() error = %T, want ArtifactCodecTypeError", err)
+		}
+	}
+}
+
+func TestCodecSupportsEmptyListAndPreservesCollectionPresenceInCandidates(t *testing.T) {
+	codec := New()
+	empty := dnd.NPCInteractionList{Interactions: []dnd.NPCInteraction{}}
+	content, err := codec.Encode(empty)
+	if err != nil || string(content) != `{"interactions":[]}` {
+		t.Fatalf("Encode() = %s, %v", content, err)
+	}
+	for _, candidate := range []dnd.NPCInteractionList{
+		{},
+		empty,
+		{Interactions: []dnd.NPCInteraction{{Name: " ", Kind: "unsupported", SourceRefs: nil}}},
+		{Interactions: []dnd.NPCInteraction{{Name: " ", Kind: "unsupported", SourceRefs: []source.SourceRef{}}}},
+		{Interactions: []dnd.NPCInteraction{{Name: " ", Kind: "unsupported", SourceRefs: []source.SourceRef{{StartUnitID: 0, EndUnitID: -1}}}}},
+	} {
+		content, err := codec.EncodeCandidate(candidate)
+		if err != nil || !json.Valid(content) {
+			t.Fatalf("EncodeCandidate() = %s, %v", content, err)
+		}
+		decoded, err := codec.DecodeCandidate(content)
+		if err != nil || !reflect.DeepEqual(decoded, candidate) {
+			t.Fatalf("DecodeCandidate() = %#v, %v; want %#v", decoded, err, candidate)
+		}
+	}
+}
+
+func TestCodecStrictlyRejectsMalformedUnknownAndTrailingJSON(t *testing.T) {
+	validJSON := `{"interactions":[{"name":"Mira Thorn","kind":"dialogue","source_refs":[{"source_id":"session","start_unit_id":1,"end_unit_id":1}]}]}`
+	for _, test := range []struct{ name, raw, want string }{
+		{"malformed", `{`, "decode dnd npc interaction list"},
+		{"unknown top-level", `{"interactions":[],"unexpected":true}`, "unknown field"},
+		{"unknown interaction field", strings.Replace(validJSON, `"kind":"dialogue"`, `"kind":"dialogue","unexpected":true`, 1), "unknown field"},
+		{"unknown source reference field", strings.Replace(validJSON, `"end_unit_id":1`, `"end_unit_id":1,"unexpected":true`, 1), "unknown field"},
+		{"trailing", `{"interactions":[]} {}`, "multiple JSON values"},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			if _, err := New().Decode([]byte(test.raw)); err == nil || !strings.Contains(err.Error(), test.want) {
+				t.Fatalf("Decode() error = %v, want %q", err, test.want)
+			}
+		})
+	}
+}
+
+func TestCodecRejectsRequiredShapeEnumAndReferenceBoundaries(t *testing.T) {
+	tests := []struct {
+		name  string
+		value dnd.NPCInteractionList
+		want  string
+	}{
+		{"nil interactions", dnd.NPCInteractionList{}, "interactions must be present"},
+		{"blank name", mutate(validList(), func(v *dnd.NPCInteractionList) { v.Interactions[0].Name = " " }), "name must not be empty"},
+		{"unsupported kind", mutate(validList(), func(v *dnd.NPCInteractionList) { v.Interactions[0].Kind = "unsupported" }), "kind must be supported"},
+		{"nil source refs", mutate(validList(), func(v *dnd.NPCInteractionList) { v.Interactions[0].SourceRefs = nil }), "source_refs must contain"},
+		{"empty source ID", mutate(validList(), func(v *dnd.NPCInteractionList) { v.Interactions[0].SourceRefs[0].SourceID = " " }), "source_id must not be empty"},
+		{"non-positive start", mutate(validList(), func(v *dnd.NPCInteractionList) { v.Interactions[0].SourceRefs[0].StartUnitID = 0 }), "start_unit_id must be positive"},
+		{"non-positive end", mutate(validList(), func(v *dnd.NPCInteractionList) { v.Interactions[0].SourceRefs[0].EndUnitID = 0 }), "end_unit_id must be positive"},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			if _, err := New().Encode(test.value); err == nil || !strings.Contains(err.Error(), test.want) {
+				t.Fatalf("Encode() error = %v, want %q", err, test.want)
+			}
+		})
+	}
+}
+
+func TestCodecAcceptsEveryInteractionKind(t *testing.T) {
+	for _, kind := range []dnd.NPCInteractionKind{
+		dnd.NPCInteractionKindMentioned,
+		dnd.NPCInteractionKindNoncombatPresence,
+		dnd.NPCInteractionKindDialogue,
+		dnd.NPCInteractionKindCombatAlly,
+		dnd.NPCInteractionKindCombatOpponent,
+		dnd.NPCInteractionKindOther,
+	} {
+		value := validList()
+		value.Interactions[0].Kind = kind
+		if _, err := New().Encode(value); err != nil {
+			t.Fatalf("Encode(%q) error = %v", kind, err)
+		}
+	}
+}
+
+func TestCodecSchemaAndMetadataAreDefensive(t *testing.T) {
+	codec := New()
+	first := codec.Schema()
+	first.JSONSchema[0] = '['
+	if second := codec.Schema(); !json.Valid(second.JSONSchema) || second.JSONSchema[0] == '[' {
+		t.Fatal("Schema() returned shared bytes")
+	}
+	metadata := codec.Metadata(validList())
+	metadata["other"] = true
+	if next := codec.Metadata(validList()); len(next) != 1 || next["interaction_count"] != 2 {
+		t.Fatalf("Metadata() = %#v", next)
+	}
+}
+
+func mutate(value dnd.NPCInteractionList, change func(*dnd.NPCInteractionList)) dnd.NPCInteractionList {
+	change(&value)
+	return value
+}

internal/modules/dnd/codec/npcinteractions/testdata/dnd_npc_interactions.v1.json

@@ -0,0 +1,18 @@
+{
+  "interactions": [
+    {
+      "name": "Mira Thorn",
+      "kind": "dialogue",
+      "source_refs": [
+        {"source_id": "session-alpha", "start_unit_id": 1, "end_unit_id": 2}
+      ]
+    },
+    {
+      "name": "Hooded Guard",
+      "kind": "combat_opponent",
+      "source_refs": [
+        {"source_id": "session-alpha", "start_unit_id": 3, "end_unit_id": 3}
+      ]
+    }
+  ]
+}

internal/modules/dnd/types.go

@@ -12,6 +12,8 @@ const NPCListKind contracts.ArtifactKind = "dnd/npc-list"
 
 const CombatTurnListKind contracts.ArtifactKind = "dnd/combat-turn-list"
 
+const NPCInteractionListKind contracts.ArtifactKind = "dnd/npc-interaction-list"
+
 type SpellList struct {
 	SpellCasts []SpellCast `json:"spell_casts"`
 }
@@ -51,3 +53,24 @@ type CombatTurn struct {
 	TurnKind   CombatTurnKind     `json:"turn_kind"`
 	SourceRefs []source.SourceRef `json:"source_refs"`
 }
+
+type NPCInteractionKind string
+
+const (
+	NPCInteractionKindMentioned         NPCInteractionKind = "mentioned"
+	NPCInteractionKindNoncombatPresence NPCInteractionKind = "noncombat_presence"
+	NPCInteractionKindDialogue          NPCInteractionKind = "dialogue"
+	NPCInteractionKindCombatAlly        NPCInteractionKind = "combat_ally"
+	NPCInteractionKindCombatOpponent    NPCInteractionKind = "combat_opponent"
+	NPCInteractionKindOther             NPCInteractionKind = "other"
+)
+
+type NPCInteractionList struct {
+	Interactions []NPCInteraction `json:"interactions"`
+}
+
+type NPCInteraction struct {
+	Name       string             `json:"name"`
+	Kind       NPCInteractionKind `json:"kind"`
+	SourceRefs []source.SourceRef `json:"source_refs"`
+}