diff --git a/README.md b/README.md
index 4d1ed7c..44c42cd 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # SourceOS/SociOS Typed Contracts
 
-**SourceOS/SociOS Typed Contracts** is the canonical, machine-readable specification for the SourceOS metadata governance platform and the SociOS agent plane. It defines the full set of JSON Schemas, an OpenAPI REST surface, an AsyncAPI event spine, and a JSON-LD / Hydra semantic overlay that together make up the "contract layer" every implementation component must satisfy.
+**SourceOS/SociOS Typed Contracts** is the canonical, machine-readable specification for the SourceOS metadata governance platform and the SociOS agent plane. It defines the full set of JSON Schemas, additive OpenAPI / AsyncAPI patch fragments, and a JSON-LD / Hydra semantic overlay that together make up the "contract layer" every implementation component must satisfy.
 
 > **Spec version:** `2.0.0`  |  **License:** see [LICENSE](LICENSE)
 
@@ -8,19 +8,19 @@
 
 ## Why this repository exists
 
-A metadata governance platform can only unify data meaning, policy, provenance, and agent execution if every component agrees on the *shape* of the objects it exchanges.  This repository is that shared agreement.  Downstream consumers include:
+A metadata governance platform can only unify data meaning, policy, provenance, and agent execution if every component agrees on the *shape* of the objects it exchanges. This repository is that shared agreement. Downstream consumers include:
 
-- **API services** — scaffolded from `openapi.yaml` (metadata plane) and `openapi.agent-plane.patch.yaml` (agent plane).
-- **Event consumers** — Kafka topics declared in `asyncapi.yaml` + `asyncapi.agent-plane.patch.yaml`.
+- **API services** — scaffolded from `openapi.yaml` plus additive patch fragments such as `openapi.agent-plane.patch.yaml` and `openapi.fog.patch.yaml`.
+- **Event consumers** — Kafka topics declared in `asyncapi.yaml` plus additive channel fragments such as `asyncapi.agent-plane.patch.yaml` and `asyncapi.fog.patch.yaml`.
 - **Validators** — AJV (Node.js) or `jsonschema` (Python) loaded from `schemas/`.
 - **Code generators** — TypeScript types via [quicktype](https://quicktype.io); Python models via [datamodel-code-generator](https://github.com/koxudaxi/datamodel-code-generator).
-- **Semantic tooling** — JSON-LD context + Hydra API documentation in `semantic/`.
+- **Semantic tooling** — JSON-LD context + Hydra API documentation in `semantic/`, including additive vocabulary seeds such as `semantic/fog-vocabulary.jsonld`.
 
 ---
 
 ## Repository layout
 
-```
+```text
 sourceos-spec/
 ├── README.md                         # This file
 ├── ARCHITECTURE.md                   # Two-plane architecture, schema families, lifecycle
@@ -30,27 +30,31 @@ sourceos-spec/
 │
 ├── openapi.yaml                      # Metadata-plane REST API (v2)
 ├── openapi.agent-plane.patch.yaml    # Additive agent-plane REST endpoints
+├── openapi.fog.patch.yaml            # Additive fog-layer REST endpoints
 ├── asyncapi.yaml                     # Metadata-plane event channels
 ├── asyncapi.agent-plane.patch.yaml   # Agent-plane event channels
+├── asyncapi.fog.patch.yaml           # Fog-layer event channels
 │
-├── schemas/                          # 54 JSON Schema (draft 2020-12) files
+├── schemas/                          # Top-level JSON Schema files (draft 2020-12)
 │   └── README.md                     # Schema catalog and URN patterns
 │
 ├── examples/                         # Conforming example payloads (one per type)
 │   └── README.md
 │
 ├── semantic/                         # JSON-LD context + Hydra API documentation
-│   └── README.md
+│   ├── README.md
+│   └── fog-vocabulary.jsonld         # Additive fog vocabulary seed
 │
 └── docs/
-    └── adr/                          # Architecture Decision Records
+    ├── adr/                          # Architecture Decision Records
+    └── contract-additions/           # Discoverability notes for additive families
 ```
 
 ---
 
 ## Schema families
 
-The 54 schemas are organised into six families that map directly to the Open Metadata Types taxonomy areas:
+The schemas are organised into domain-oriented families that map to the SourceOS / SociOS contract surface:
 
 | # | Family | Key schemas |
 |---|--------|-------------|
@@ -63,6 +67,7 @@ The 54 schemas are organised into six families that map directly to the Open Met
 | + | **Execution / Provenance** | `Dataset`, `RunRecord`, `WorkflowSpec`, `WorkflowNode`, `WorkflowEdge`, `WorkloadSpec`, `DataSphere`, `ProvenanceRecord`, `EventEnvelope`, `MappingSpec` |
 | + | **Agent Plane** | `AgentSession`, `ExecutionDecision`, `ExecutionSurface`, `SkillManifest`, `MemoryEntry`, `SessionReceipt`, `SessionReview`, `TelemetryEvent`, `FrustrationSignal` |
 | + | **Release / Experiments** | `ExperimentFlag`, `RolloutPolicy`, `ReleaseReceipt` |
+| + | **Fog Layer** | `Topic`, `TopicEnvelope`, `ReplicationPolicy`, `ContentRef`, `Offer`, `WorkOrder`, `UsageReceipt`, `SettlementEvent` |
 
 ---
 
@@ -128,4 +133,3 @@ fastapi-codegen --input openapi.yaml --output app/
 ## Contributing
 
 See [CONTRIBUTING.md](CONTRIBUTING.md) for schema authoring conventions, the URN naming guide, and the pull-request checklist.
-
diff --git a/examples/README.md b/examples/README.md
index 90ef4ef..404934c 100644
--- a/examples/README.md
+++ b/examples/README.md
@@ -6,9 +6,9 @@ This directory contains one conforming JSON example payload for each top-level s
 
 ## What the examples show
 
-The examples are designed to tell a coherent end-to-end story: a personal health dataset is catalogued, governed, transformed by an obfuscation workload, and released — all within an agent session.  They share cross-reference URNs so you can trace the full lifecycle:
+The examples are designed to tell a coherent end-to-end story: a personal health dataset is catalogued, governed, transformed by an obfuscation workload, and released — all within an agent session. They share cross-reference URNs so you can trace the full lifecycle:
 
-```
+```text
 connector.json       ──► asset.json
                               │
                               ▼
@@ -41,6 +41,23 @@ agent_session.json  ──►  execution_decision.json  ──►  session_recei
 
 ---
 
+## Recent additions — Fog Layer examples
+
+The fog example set illustrates the new FogVault / FogCompute contract family:
+
+| File | Schema type | Description |
+|------|------------|-------------|
+| `content_ref.json` | ContentRef | Content-addressed reference for fog blobs / manifests |
+| `topic.json` | Topic | FogVault topic definition with replication and encryption metadata |
+| `topic_envelope.json` | TopicEnvelope | Append-only topic entry envelope with integrity and encryption metadata |
+| `replication_policy.json` | ReplicationPolicy | Replica / ack / retention / compaction policy example |
+| `offer.json` | Offer | FogCompute provider offer advertising local resources |
+| `workorder.json` | WorkOrder | FogCompute request with image, inputs, outputs, and verification mode |
+| `usage_receipt.json` | UsageReceipt | Worker-emitted execution receipt with metered resource usage |
+| `settlement_event.json` | SettlementEvent | Optional mapping from receipt to settlement backend / credits |
+
+---
+
 ## File index
 
 | File | Schema type | Description |
@@ -52,30 +69,37 @@ agent_session.json  ──►  execution_decision.json  ──►  session_recei
 | `comment.json` | Comment | A review note on a field mapping |
 | `community.json` | Community | The data-governance team community |
 | `connector.json` | Connector | A local S3 connector |
+| `content_ref.json` | ContentRef | Content-addressed reference for fog blobs / manifests |
 | `dataset.json` | Dataset | Personal health observations dataset |
 | `data_sphere.json` | DataSphere | The personal-curated execution environment |
-| `policy_decision.json` | PolicyDecision | An `export` permit decision with an obfuscation obligation |
 | `execution_decision.json` | ExecutionDecision | Agent allow-decision for a tool invocation |
-| `experiment_flag.json` | ExperimentFlag | A feature flag for the new obfuscation algorithm |
 | `event_envelope.json` | EventEnvelope | Event published when the run completes |
+| `experiment_flag.json` | ExperimentFlag | A feature flag for the new obfuscation algorithm |
 | `field.json` | Field | The `patient.dateOfBirth` field with PII tags and quality metrics |
 | `frustration_signal.json` | FrustrationSignal | A frustration signal from a repeated-failure condition |
 | `glossary.json` | GlossaryTerm | Glossary term for "Date of Birth" |
 | `mapping.json` | MappingSpec | A field mapping between two dataset fields |
 | `memory_entry.json` | MemoryEntry | A learned memory entry from an agent session |
+| `offer.json` | Offer | FogCompute provider offer |
 | `policy.json` | Policy | Health export must be obfuscated |
+| `policy_decision.json` | PolicyDecision | An `export` permit decision with an obfuscation obligation |
 | `provenance.json` | ProvenanceRecord | Provenance record for the obfuscation run |
 | `rating.json` | Rating | A 5-star rating on the health observations dataset |
 | `release_receipt.json` | ReleaseReceipt | Release receipt for spec version 2.0.0 |
+| `replication_policy.json` | ReplicationPolicy | Fog topic replication/retention policy example |
 | `rollout_policy.json` | RolloutPolicy | Rollout rules for the obfuscation experiment flag |
 | `run.json` | RunRecord | The obfuscation workload run record |
 | `schema.json` | SchemaDefinition | The schema for health observations |
 | `session_receipt.json` | SessionReceipt | Receipt for the completed agent session |
 | `session_review.json` | SessionReview | Post-session learning review |
+| `settlement_event.json` | SettlementEvent | Optional receipt-to-settlement mapping |
 | `skill_manifest.json` | SkillManifest | The obfuscation skill manifest |
 | `telemetry_event.json` | TelemetryEvent | An informational telemetry event from the agent session |
-| `capability_token.json` | CapabilityToken | Capability token for the export operation |
+| `topic.json` | Topic | FogVault topic definition |
+| `topic_envelope.json` | TopicEnvelope | FogVault append-only entry envelope |
 | `workflow_spec.json` | WorkflowSpec | The health-data obfuscation workflow |
+| `workorder.json` | WorkOrder | FogCompute work order |
+| `usage_receipt.json` | UsageReceipt | FogCompute execution receipt |
 
 ---
 
@@ -92,14 +116,12 @@ ajv validate -s ../schemas/Dataset.json -d dataset.json
 cd ..
 for example in examples/*.json; do
   name=$(basename "$example" .json)
-  # Find matching schema (PascalCase title)
   python3 - <<EOF
-import json, sys, glob
+import json
 ex = json.load(open("$example"))
 t = ex.get("type") or ex.get("title")
 if t:
-    f = f"schemas/{t}.json"
-    print(f)
+    print(f"schemas/{t}.json")
 EOF
 done
 ```
@@ -108,8 +130,8 @@ done
 
 ## Adding a new example
 
-See [CONTRIBUTING.md](../CONTRIBUTING.md#writing-examples) for the full guide.  Key rules:
-1. The filename must be the schema `title` lowercased, e.g. `AgentSession` → `agent_session.json`.
+See [CONTRIBUTING.md](../CONTRIBUTING.md#writing-examples) for the full guide. Key rules:
+1. The filename should match the schema title in the repository’s naming convention.
 2. All required fields must be present and valid.
-3. Use existing cross-reference URNs from this directory so the example set stays coherent.
+3. Use coherent cross-reference URNs where possible so the example set stays navigable.
 4. Run `ajv validate` before committing.
diff --git a/schemas/README.md b/schemas/README.md
index 5a98037..1b4efd8 100644
--- a/schemas/README.md
+++ b/schemas/README.md
@@ -1,6 +1,29 @@
 # Schema Catalog
 
-This directory contains all 54 JSON Schema (draft 2020-12) files that make up the SourceOS/SociOS Typed Contracts specification.
+This directory contains the JSON Schema (draft 2020-12) files that make up the SourceOS/SociOS Typed Contracts specification.
+
+---
+
+## Recent additions — Fog Layer
+
+The FogVault / FogCompute contract family adds the following top-level schemas:
+
+| File | Type | URN prefix |
+|------|------|-----------|
+| `ContentRef.json` | ContentRef | _(digest-based content reference)_ |
+| `Offer.json` | Offer | `urn:srcos:offer:` |
+| `ReplicationPolicy.json` | ReplicationPolicy | _(top-level policy object)_ |
+| `SettlementEvent.json` | SettlementEvent | `urn:srcos:settlement:` |
+| `Topic.json` | Topic | `urn:srcos:topic:` |
+| `TopicEnvelope.json` | TopicEnvelope | `urn:srcos:topic-entry:` |
+| `UsageReceipt.json` | UsageReceipt | `urn:srcos:receipt:usage:` |
+| `WorkOrder.json` | WorkOrder | `urn:srcos:workorder:` |
+
+These types support:
+- append-only Merkle-log topics
+- explicit replication/retention policy
+- content-addressed storage references
+- compute offers, work orders, receipts, and optional settlement mappings
 
 ---
 
@@ -15,6 +38,7 @@ This directory contains all 54 JSON Schema (draft 2020-12) files that make up th
 | `Comment.json` | Comment | `urn:srcos:comment:` |
 | `Community.json` | Community | `urn:srcos:community:` |
 | `Connector.json` | Connector | `urn:srcos:connector:` |
+| `ContentRef.json` | ContentRef | _(digest-based content reference)_ |
 | `DataRef.json` | DataRef | _(sub-object, no top-level id)_ |
 | `DataSphere.json` | DataSphere | `urn:srcos:sphere:` |
 | `Dataset.json` | Dataset | `urn:srcos:dataset:` |
@@ -34,6 +58,7 @@ This directory contains all 54 JSON Schema (draft 2020-12) files that make up th
 | `ObjectContext.json` | ObjectContext | _(sub-object, no id)_ |
 | `ObjectSelector.json` | ObjectSelector | _(sub-object inside Policy scope)_ |
 | `Obligation.json` | Obligation | _(sub-object, no id)_ |
+| `Offer.json` | Offer | `urn:srcos:offer:` |
 | `Party.json` | Party | `urn:srcos:party:` |
 | `PhysicalAsset.json` | PhysicalAsset | `urn:srcos:asset:` |
 | `Policy.json` | Policy | `urn:srcos:policy:` |
@@ -45,23 +70,29 @@ This directory contains all 54 JSON Schema (draft 2020-12) files that make up th
 | `QualityMetric.json` | QualityMetric | _(sub-object inside Field.quality)_ |
 | `Rating.json` | Rating | `urn:srcos:rating:` |
 | `ReleaseReceipt.json` | ReleaseReceipt | `urn:srcos:release-receipt:` |
+| `ReplicationPolicy.json` | ReplicationPolicy | _(top-level policy object)_ |
 | `RolloutPolicy.json` | RolloutPolicy | `urn:srcos:rollout:` |
 | `Rule.json` | Rule | _(sub-object inside Policy)_ |
 | `RunRecord.json` | RunRecord | `urn:srcos:run:` |
 | `SchemaDefinition.json` | SchemaDefinition | `urn:srcos:schema:` |
 | `SessionReceipt.json` | SessionReceipt | `urn:srcos:receipt:session:` |
 | `SessionReview.json` | SessionReview | `urn:srcos:session-review:` |
+| `SettlementEvent.json` | SettlementEvent | `urn:srcos:settlement:` |
 | `SkillManifest.json` | SkillManifest | `urn:srcos:skill:` |
 | `SubjectContext.json` | SubjectContext | _(sub-object, no id)_ |
 | `SubjectSelector.json` | SubjectSelector | _(sub-object inside Policy scope)_ |
 | `TagAssignment.json` | TagAssignment | _(sub-object inside Field/GlossaryTerm)_ |
 | `TelemetryEvent.json` | TelemetryEvent | `urn:srcos:telemetry:` |
+| `Topic.json` | Topic | `urn:srcos:topic:` |
+| `TopicEnvelope.json` | TopicEnvelope | `urn:srcos:topic-entry:` |
 | `Trigger.json` | Trigger | _(sub-object inside WorkflowSpec)_ |
+| `UsageReceipt.json` | UsageReceipt | `urn:srcos:receipt:usage:` |
 | `ValidValues.json` | ValidValues | _(sub-object inside EntityField)_ |
 | `WorkflowEdge.json` | WorkflowEdge | _(sub-object inside WorkflowSpec)_ |
 | `WorkflowNode.json` | WorkflowNode | _(sub-object inside WorkflowSpec)_ |
 | `WorkflowSpec.json` | WorkflowSpec | `urn:srcos:workflow:` |
 | `WorkloadSpec.json` | WorkloadSpec | `urn:srcos:workload:` |
+| `WorkOrder.json` | WorkOrder | `urn:srcos:workorder:` |
 
 ---
 
@@ -163,6 +194,19 @@ This directory contains all 54 JSON Schema (draft 2020-12) files that make up th
 | `RolloutPolicy` | Audience-based percentage rollout rules for an `ExperimentFlag` |
 | `ReleaseReceipt` | A verified release record with artifact hashes and gate check results |
 
+### Fog Layer
+
+| Schema | Description |
+|--------|-------------|
+| `Topic` | An append-only topic contract for FogVault channels |
+| `TopicEnvelope` | A typed append-only entry envelope for topic events and payloads |
+| `ReplicationPolicy` | Replication, retention, and compaction policy for a fog topic |
+| `ContentRef` | A content-addressed reference to blobs, chunks, or manifests |
+| `Offer` | A FogCompute provider offer advertising resources and constraints |
+| `WorkOrder` | A FogCompute request describing workload, inputs, outputs, and verification mode |
+| `UsageReceipt` | A worker-emitted usage and output receipt for a completed work order |
+| `SettlementEvent` | An optional settlement mapping from receipt to credits/tokens/backend |
+
 ---
 
 ## Validation
@@ -183,4 +227,4 @@ done
 
 ## Versioning
 
-Schema evolution follows [Semantic Versioning](https://semver.org/).  See [CONTRIBUTING.md](../CONTRIBUTING.md#breaking-vs-additive-changes) for the full policy and [CHANGELOG.md](../CHANGELOG.md) for the history.
+Schema evolution follows [Semantic Versioning](https://semver.org/). See [CONTRIBUTING.md](../CONTRIBUTING.md#breaking-vs-additive-changes) for the full policy and [CHANGELOG.md](../CHANGELOG.md) for the history.
diff --git a/semantic/README.md b/semantic/README.md
index 37642c9..8f4946e 100644
--- a/semantic/README.md
+++ b/semantic/README.md
@@ -1,6 +1,6 @@
 # Semantic Overlay
 
-This directory provides the JSON-LD and Hydra semantic overlay for the SourceOS/SociOS specification.  These files make the schema types and REST API self-describing to Linked Data tooling.
+This directory provides the JSON-LD and Hydra semantic overlay for the SourceOS/SociOS specification. These files make the schema types and REST API self-describing to Linked Data tooling.
 
 ---
 
@@ -8,8 +8,25 @@ This directory provides the JSON-LD and Hydra semantic overlay for the SourceOS/
 
 | File | Purpose |
 |------|---------|
-| `context.jsonld` | JSON-LD `@context` mapping all 54 schema type names to stable IRIs under `https://schemas.srcos.ai/v2/` |
+| `context.jsonld` | JSON-LD `@context` mapping schema type names to stable IRIs under `https://schemas.srcos.ai/v2/` |
 | `hydra.jsonld` | A `hydra:ApiDocumentation` document describing the REST API's supported classes and operations |
+| `fog-vocabulary.jsonld` | Additive fog vocabulary seed for FogVault / FogCompute types and key predicates |
+
+---
+
+## Recent additions — Fog vocabulary
+
+The fog layer currently contributes a seed semantic vocabulary in `fog-vocabulary.jsonld` covering:
+- `Topic`
+- `TopicEnvelope`
+- `ReplicationPolicy`
+- `ContentRef`
+- `Offer`
+- `WorkOrder`
+- `UsageReceipt`
+- `SettlementEvent`
+
+This vocabulary is intentionally lightweight and is expected to be folded into the broader semantic overlay as the fog contract family stabilizes.
 
 ---
 
@@ -21,8 +38,7 @@ Include the context in any JSON document to make it a JSON-LD document:
 {
   "@context": "https://schemas.srcos.ai/v2/context.jsonld",
   "@type": "Dataset",
-  "id": "urn:srcos:dataset:health_obs",
-  ...
+  "id": "urn:srcos:dataset:health_obs"
 }
 ```
 
@@ -40,14 +56,14 @@ Or embed the context inline:
 The context maps:
 - `id` → `@id` (every `id` field becomes the node's IRI)
 - `type` → `@type` (every `type` field becomes the node's RDF type)
-- All 54 schema type names to `srcos:<TypeName>` IRIs
-- Selected cross-vocabulary terms: `prov:wasGeneratedBy`, `prov:used`, `prov:wasAssociatedWith`
+- schema type names to `srcos:<TypeName>` IRIs
+- selected cross-vocabulary terms such as `prov:wasGeneratedBy`, `prov:used`, `prov:wasAssociatedWith`
 
 ---
 
 ## `hydra.jsonld` — Hydra API documentation
 
-The Hydra document is a machine-readable API description that extends the JSON-LD context.  It can be served at `/.well-known/hydra` to make the API self-describing.
+The Hydra document is a machine-readable API description that extends the JSON-LD context. It can be served at `/.well-known/hydra` to make the API self-describing.
 
 The document lists every resource class supported by the API with its supported operations (HTTP methods), expected inputs, and returned types.
 
@@ -82,7 +98,7 @@ When adding a new first-class schema type:
 
 1. Add a mapping to `context.jsonld`: `"NewType": "srcos:NewType"`
 2. Add a `hydra:supportedClass` entry to `hydra.jsonld` with at minimum `hydra:title`, `hydra:description`, and the applicable `hydra:supportedOperation` entries.
-3. Update this README's file table.
+3. Update this README's file table and any additive vocabulary seeds if the new type is being staged incrementally.
 
 See [CONTRIBUTING.md](../CONTRIBUTING.md#6-update-the-semantic-context-if-needed) for the full guide.