diff --git a/.env.example b/.env.example
index 718679b..b8e833e 100644
--- a/.env.example
+++ b/.env.example
@@ -5,12 +5,18 @@ OPENAI_API_KEY=sk-...
 QDRANT_URL=http://localhost:6333
 QDRANT_API_KEY=
 
-# Fixed models (not configurable per strategy)
-EMBEDDING_MODEL=text-embedding-3-small
+# Default cloud Embedding Model (registry id / OpenAI model name)
+EMBEDDING_MODEL=text-embedding-3-large
 LLM_MODEL=gpt-4o-mini
 
+# Local Ollama embeddings (Active model switched in Admin)
+OLLAMA_BASE_URL=http://192.168.10.10:11435
+
 # Retrieval defaults
 TOP_K=5
+# Neighbor Expansion for fixed_size only (ADR-0023); 0 = off
+NEIGHBOR_PREV=0
+NEIGHBOR_NEXT=0
 
 # LLM generation parameters
 TEMPERATURE=0.0
diff --git a/src/chunking/embedding_models.py b/src/chunking/embedding_models.py
new file mode 100644
index 0000000..4e2915a
--- /dev/null
+++ b/src/chunking/embedding_models.py
@@ -0,0 +1,153 @@
+"""Embedding Model Registry — static catalog of Cloud and Local models."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+from enum import Enum
+
+
+class Provider(str, Enum):
+    CLOUD = "cloud"
+    LOCAL = "local"
+
+
+@dataclass(frozen=True)
+class EmbeddingModelSpec:
+    """One entry in the Embedding Model Registry."""
+
+    id: str
+    provider: Provider
+    model_name: str
+    dimension: int
+    display_name: str
+    task_prefixes: bool = False
+    # Default Semantic Boundary Detection threshold (Admin may override in SQLite)
+    default_semantic_threshold: float = 0.3
+
+
+# Stable id for legacy unscoped OpenAI corpora / historical Experiment backfill (1536-d).
+LEGACY_CLOUD_MODEL_ID = "text-embedding-3-small"
+# Default Corpus/Boundary when Admin settings are unset (new installs & fallbacks).
+DEFAULT_CLOUD_MODEL_ID = "text-embedding-3-large"
+
+_SEMANTIC_THRESHOLD_SETTING_PREFIX = "semantic_threshold:"
+
+
+def semantic_threshold_setting_key(model_id: str) -> str:
+    return f"{_SEMANTIC_THRESHOLD_SETTING_PREFIX}{model_id}"
+
+
+def _build_registry() -> dict[str, EmbeddingModelSpec]:
+    # Prefer explicit registry entries over EMBEDDING_MODEL aliasing a different
+    # OpenAI model under a single id (wrong dimension / provenance).
+    cloud_small = EmbeddingModelSpec(
+        id=LEGACY_CLOUD_MODEL_ID,
+        provider=Provider.CLOUD,
+        model_name="text-embedding-3-small",
+        dimension=1536,
+        display_name="OpenAI text-embedding-3-small",
+        task_prefixes=False,
+        default_semantic_threshold=0.3,
+    )
+    cloud_large = EmbeddingModelSpec(
+        id=DEFAULT_CLOUD_MODEL_ID,
+        provider=Provider.CLOUD,
+        model_name="text-embedding-3-large",
+        dimension=3072,
+        display_name="OpenAI text-embedding-3-large",
+        task_prefixes=False,
+        default_semantic_threshold=0.3,
+    )
+    local = EmbeddingModelSpec(
+        id="nomic-embed-text-v2-moe",
+        provider=Provider.LOCAL,
+        model_name="nomic-embed-text-v2-moe:latest",
+        dimension=768,
+        display_name="Ollama nomic-embed-text-v2-moe",
+        task_prefixes=True,
+        default_semantic_threshold=0.6,
+    )
+    return {
+        cloud_small.id: cloud_small,
+        cloud_large.id: cloud_large,
+        local.id: local,
+    }
+
+
+def get_registry() -> dict[str, EmbeddingModelSpec]:
+    """Return the Embedding Model Registry (built from config)."""
+    return _build_registry()
+
+
+def get_model(model_id: str) -> EmbeddingModelSpec:
+    """Look up a registry entry by stable id.
+
+    Raises:
+        KeyError: If model_id is not registered.
+    """
+    registry = get_registry()
+    if model_id not in registry:
+        known = ", ".join(sorted(registry))
+        raise KeyError(f"Unknown Embedding Model '{model_id}'. Registered: {known}")
+    return registry[model_id]
+
+
+def list_models() -> list[EmbeddingModelSpec]:
+    """All registered Embedding Models in stable order (default cloud first)."""
+    registry = get_registry()
+    preferred = [
+        DEFAULT_CLOUD_MODEL_ID,
+        LEGACY_CLOUD_MODEL_ID,
+        "nomic-embed-text-v2-moe",
+    ]
+    order = preferred + [mid for mid in registry if mid not in preferred]
+    return [registry[mid] for mid in order if mid in registry]
+
+
+def default_model_id() -> str:
+    """Default Corpus/Boundary Embedding Model id when Admin settings are unset."""
+    return DEFAULT_CLOUD_MODEL_ID
+
+
+def get_semantic_threshold(model_id: str) -> float:
+    """Resolve Semantic Boundary Detection threshold for a model.
+
+    Order: Admin SQLite override → registry default → global SEMANTIC_THRESHOLD.
+    """
+    from src.storage import sqlite as db
+
+    model = get_model(model_id)
+    stored = db.get_app_setting(semantic_threshold_setting_key(model_id))
+    if stored is not None and stored != "":
+        return float(stored)
+    return model.default_semantic_threshold
+
+
+def set_semantic_threshold(model_id: str, threshold: float) -> float:
+    """Persist Admin override for a model's semantic_threshold (0 < t <= 1)."""
+    from src.storage import sqlite as db
+
+    get_model(model_id)  # validate registry id
+    if not (0.0 < threshold <= 1.0):
+        raise ValueError("semantic_threshold must be in (0, 1]")
+    db.set_app_setting(semantic_threshold_setting_key(model_id), str(threshold))
+    return threshold
+
+
+def apply_task_prefixes(
+    texts: list[str],
+    *,
+    model: EmbeddingModelSpec,
+    purpose: str,
+) -> list[str]:
+    """Apply Nomic-style task prefixes when the model requires them.
+
+    purpose: \"document\" → search_document; \"query\" → search_query.
+    """
+    if not model.task_prefixes:
+        return texts
+    if purpose == "query":
+        prefix = "search_query: "
+    else:
+        prefix = "search_document: "
+    return [prefix + t if not t.startswith(prefix) else t for t in texts]
diff --git a/src/core/config.py b/src/core/config.py
index 3e2d10b..0ac6314 100644
--- a/src/core/config.py
+++ b/src/core/config.py
@@ -10,15 +10,21 @@ class Settings(BaseSettings):
 
     # OpenAI
     openai_api_key: str
-    embedding_model: str = "text-embedding-3-small"
+    embedding_model: str = "text-embedding-3-large"
     llm_model: str = "gpt-4o-mini"
 
+    # Local embeddings (Ollama) — Admin switches models; host stays in config
+    ollama_base_url: str = "http://192.168.10.10:11435"
+
     # Qdrant
     qdrant_url: str = "http://localhost:6333"
     qdrant_api_key: str | None = None
 
     # Retrieval
     top_k: int = 5
+    # Neighbor Expansion for fixed_size (ADR-0023); 0/0 = off
+    neighbor_prev: int = 0
+    neighbor_next: int = 0
 
     # LLM generation
     temperature: float = 0.0
diff --git a/src/core/dependencies.py b/src/core/dependencies.py
index 427eb6d..4a5ecc2 100644
--- a/src/core/dependencies.py
+++ b/src/core/dependencies.py
@@ -14,6 +14,13 @@ def get_openai_client() -> OpenAI:
     return OpenAI(api_key=settings.openai_api_key)
 
 
+@lru_cache()
+def get_ollama_client() -> OpenAI:
+    """Return a cached OpenAI-compatible client pointed at Ollama."""
+    base = settings.ollama_base_url.rstrip("/")
+    return OpenAI(base_url=f"{base}/v1", api_key="ollama")
+
+
 @lru_cache()
 def get_qdrant_client() -> QdrantClient:
     """Return a cached Qdrant client singleton."""