diff --git a/alembic/versions/0003_fc2b_ml_pipeline.py b/alembic/versions/0003_fc2b_ml_pipeline.py
new file mode 100644
index 0000000..584bffe
--- /dev/null
+++ b/alembic/versions/0003_fc2b_ml_pipeline.py
@@ -0,0 +1,172 @@
+"""fc2b: ML pipeline — allowlist, aliases, centroids, ml_settings
+
+Revision ID: 0003
+Revises: 0002
+Create Date: 2026-05-15
+
+"""
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+from pgvector.sqlalchemy import Vector
+
+revision: str = "0003"
+down_revision: Union[str, None] = "0002"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # 3.1 rename wd14_* -> tagger_*
+    op.alter_column("image_record", "wd14_predictions", new_column_name="tagger_predictions")
+    op.alter_column(
+        "image_record", "wd14_model_version", new_column_name="tagger_model_version"
+    )
+
+    # 3.2 tag_allowlist
+    op.create_table(
+        "tag_allowlist",
+        sa.Column("tag_id", sa.Integer(), nullable=False),
+        sa.Column(
+            "min_confidence", sa.Float(), nullable=False, server_default="0.95"
+        ),
+        sa.Column(
+            "added_at", sa.DateTime(timezone=True), nullable=False,
+            server_default=sa.func.now(),
+        ),
+        sa.ForeignKeyConstraint(
+            ["tag_id"], ["tag.id"], name="fk_tag_allowlist_tag_id_tag",
+            ondelete="CASCADE",
+        ),
+        sa.PrimaryKeyConstraint("tag_id", name="pk_tag_allowlist"),
+        sa.CheckConstraint(
+            "min_confidence > 0 AND min_confidence <= 1",
+            name="ck_tag_allowlist_confidence_range",
+        ),
+    )
+
+    # 3.3 tag_suggestion_rejection
+    op.create_table(
+        "tag_suggestion_rejection",
+        sa.Column("image_record_id", sa.Integer(), nullable=False),
+        sa.Column("tag_id", sa.Integer(), nullable=False),
+        sa.Column(
+            "rejected_at", sa.DateTime(timezone=True), nullable=False,
+            server_default=sa.func.now(),
+        ),
+        sa.ForeignKeyConstraint(
+            ["image_record_id"], ["image_record.id"],
+            name="fk_tsr_image_record_id_image_record", ondelete="CASCADE",
+        ),
+        sa.ForeignKeyConstraint(
+            ["tag_id"], ["tag.id"], name="fk_tsr_tag_id_tag", ondelete="CASCADE",
+        ),
+        sa.PrimaryKeyConstraint(
+            "image_record_id", "tag_id", name="pk_tag_suggestion_rejection"
+        ),
+    )
+    op.create_index(
+        "ix_tag_suggestion_rejection_tag", "tag_suggestion_rejection", ["tag_id"]
+    )
+
+    # 3.4 tag_alias
+    op.create_table(
+        "tag_alias",
+        sa.Column("alias_string", sa.String(length=255), nullable=False),
+        sa.Column("alias_category", sa.String(length=32), nullable=False),
+        sa.Column("canonical_tag_id", sa.Integer(), nullable=False),
+        sa.Column(
+            "created_at", sa.DateTime(timezone=True), nullable=False,
+            server_default=sa.func.now(),
+        ),
+        sa.ForeignKeyConstraint(
+            ["canonical_tag_id"], ["tag.id"],
+            name="fk_tag_alias_canonical_tag_id_tag", ondelete="CASCADE",
+        ),
+        sa.PrimaryKeyConstraint(
+            "alias_string", "alias_category", name="pk_tag_alias"
+        ),
+    )
+    op.create_index("ix_tag_alias_canonical", "tag_alias", ["canonical_tag_id"])
+
+    # 3.5 tag_reference_embedding (centroids)
+    op.create_table(
+        "tag_reference_embedding",
+        sa.Column("tag_id", sa.Integer(), nullable=False),
+        sa.Column("embedding", Vector(1152), nullable=False),
+        sa.Column("reference_count", sa.Integer(), nullable=False),
+        sa.Column("model_version", sa.String(length=128), nullable=False),
+        sa.Column(
+            "updated_at", sa.DateTime(timezone=True), nullable=False,
+            server_default=sa.func.now(),
+        ),
+        sa.ForeignKeyConstraint(
+            ["tag_id"], ["tag.id"],
+            name="fk_tag_reference_embedding_tag_id_tag", ondelete="CASCADE",
+        ),
+        sa.PrimaryKeyConstraint("tag_id", name="pk_tag_reference_embedding"),
+    )
+
+    # 3.6 ml_settings singleton
+    op.create_table(
+        "ml_settings",
+        sa.Column("id", sa.Integer(), nullable=False),
+        sa.Column(
+            "suggestion_threshold_artist", sa.Float(), nullable=False,
+            server_default="0.30",
+        ),
+        sa.Column(
+            "suggestion_threshold_character", sa.Float(), nullable=False,
+            server_default="0.50",
+        ),
+        sa.Column(
+            "suggestion_threshold_copyright", sa.Float(), nullable=False,
+            server_default="0.50",
+        ),
+        sa.Column(
+            "suggestion_threshold_general", sa.Float(), nullable=False,
+            server_default="0.95",
+        ),
+        sa.Column(
+            "centroid_similarity_threshold", sa.Float(), nullable=False,
+            server_default="0.55",
+        ),
+        sa.Column(
+            "min_reference_images", sa.Integer(), nullable=False,
+            server_default="5",
+        ),
+        sa.Column(
+            "tagger_model_version", sa.String(length=128), nullable=False,
+            server_default="camie-tagger-v2",
+        ),
+        sa.Column(
+            "embedder_model_version", sa.String(length=128), nullable=False,
+            server_default="siglip-so400m-patch14-384",
+        ),
+        sa.Column(
+            "updated_at", sa.DateTime(timezone=True), nullable=False,
+            server_default=sa.func.now(),
+        ),
+        sa.PrimaryKeyConstraint("id", name="pk_ml_settings"),
+        sa.CheckConstraint("id = 1", name="ck_ml_settings_singleton"),
+    )
+    op.execute("INSERT INTO ml_settings (id) VALUES (1)")
+
+
+def downgrade() -> None:
+    op.drop_table("ml_settings")
+    op.drop_table("tag_reference_embedding")
+    op.drop_index("ix_tag_alias_canonical", table_name="tag_alias")
+    op.drop_table("tag_alias")
+    op.drop_index(
+        "ix_tag_suggestion_rejection_tag", table_name="tag_suggestion_rejection"
+    )
+    op.drop_table("tag_suggestion_rejection")
+    op.drop_table("tag_allowlist")
+    op.alter_column(
+        "image_record", "tagger_model_version", new_column_name="wd14_model_version"
+    )
+    op.alter_column(
+        "image_record", "tagger_predictions", new_column_name="wd14_predictions"
+    )
diff --git a/backend/app/models/__init__.py b/backend/app/models/__init__.py
index 8052e9b..69e4e73 100644
--- a/backend/app/models/__init__.py
+++ b/backend/app/models/__init__.py
@@ -9,9 +9,14 @@ from .image_record import ImageRecord
 from .import_batch import ImportBatch
 from .import_settings import ImportSettings
 from .import_task import ImportTask
+from .ml_settings import MLSettings
 from .post import Post
 from .source import Source
 from .tag import Tag, TagKind, image_tag
+from .tag_alias import TagAlias
+from .tag_allowlist import TagAllowlist
+from .tag_reference_embedding import TagReferenceEmbedding
+from .tag_suggestion_rejection import TagSuggestionRejection
 
 __all__ = [
     "Base",
@@ -28,4 +33,9 @@ __all__ = [
     "ImportBatch",
     "ImportTask",
     "ImportSettings",
+    "MLSettings",
+    "TagAlias",
+    "TagAllowlist",
+    "TagReferenceEmbedding",
+    "TagSuggestionRejection",
 ]
diff --git a/backend/app/models/image_record.py b/backend/app/models/image_record.py
index 9df4845..b303e7c 100644
--- a/backend/app/models/image_record.py
+++ b/backend/app/models/image_record.py
@@ -56,8 +56,8 @@ class ImageRecord(Base):
     )
 
     # ML fields (populated by FC-2's ml-worker)
-    wd14_predictions: Mapped[dict | None] = mapped_column(JSON, nullable=True)
-    wd14_model_version: Mapped[str | None] = mapped_column(String(128), nullable=True)
+    tagger_predictions: Mapped[dict | None] = mapped_column(JSON, nullable=True)
+    tagger_model_version: Mapped[str | None] = mapped_column(String(128), nullable=True)
     # 1152 = SigLIP-so400m embedding dim. Swapping models in FC-2 may require
     # a column-width migration.
     siglip_embedding: Mapped[list[float] | None] = mapped_column(Vector(1152), nullable=True)
diff --git a/backend/app/models/ml_settings.py b/backend/app/models/ml_settings.py
new file mode 100644
index 0000000..9586b8c
--- /dev/null
+++ b/backend/app/models/ml_settings.py
@@ -0,0 +1,42 @@
+"""MLSettings — single-row table holding ML pipeline tunables."""
+
+from datetime import datetime
+
+from sqlalchemy import CheckConstraint, DateTime, Float, Integer, String, func
+from sqlalchemy.orm import Mapped, mapped_column
+
+from .base import Base
+
+
+class MLSettings(Base):
+    __tablename__ = "ml_settings"
+    __table_args__ = (CheckConstraint("id = 1", name="ck_ml_settings_singleton"),)
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True)
+    suggestion_threshold_artist: Mapped[float] = mapped_column(
+        Float, nullable=False, default=0.30
+    )
+    suggestion_threshold_character: Mapped[float] = mapped_column(
+        Float, nullable=False, default=0.50
+    )
+    suggestion_threshold_copyright: Mapped[float] = mapped_column(
+        Float, nullable=False, default=0.50
+    )
+    suggestion_threshold_general: Mapped[float] = mapped_column(
+        Float, nullable=False, default=0.95
+    )
+    centroid_similarity_threshold: Mapped[float] = mapped_column(
+        Float, nullable=False, default=0.55
+    )
+    min_reference_images: Mapped[int] = mapped_column(
+        Integer, nullable=False, default=5
+    )
+    tagger_model_version: Mapped[str] = mapped_column(
+        String(128), nullable=False, default="camie-tagger-v2"
+    )
+    embedder_model_version: Mapped[str] = mapped_column(
+        String(128), nullable=False, default="siglip-so400m-patch14-384"
+    )
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), nullable=False, server_default=func.now()
+    )
diff --git a/backend/app/models/tag_alias.py b/backend/app/models/tag_alias.py
new file mode 100644
index 0000000..3a21375
--- /dev/null
+++ b/backend/app/models/tag_alias.py
@@ -0,0 +1,24 @@
+"""TagAlias — maps a model's (name, category) prediction to the operator's
+canonical tag. Resolved at suggestion-read time so raw predictions stay
+unmolested in image_record.tagger_predictions.
+"""
+
+from datetime import datetime
+
+from sqlalchemy import DateTime, ForeignKey, String, func
+from sqlalchemy.orm import Mapped, mapped_column
+
+from .base import Base
+
+
+class TagAlias(Base):
+    __tablename__ = "tag_alias"
+
+    alias_string: Mapped[str] = mapped_column(String(255), primary_key=True)
+    alias_category: Mapped[str] = mapped_column(String(32), primary_key=True)
+    canonical_tag_id: Mapped[int] = mapped_column(
+        ForeignKey("tag.id", ondelete="CASCADE"), nullable=False, index=True
+    )
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), nullable=False, server_default=func.now()
+    )
diff --git a/backend/app/models/tag_allowlist.py b/backend/app/models/tag_allowlist.py
new file mode 100644
index 0000000..6508178
--- /dev/null
+++ b/backend/app/models/tag_allowlist.py
@@ -0,0 +1,26 @@
+"""TagAllowlist — tags the operator opted-in to auto-apply via maintenance."""
+
+from datetime import datetime
+
+from sqlalchemy import CheckConstraint, DateTime, Float, ForeignKey, func
+from sqlalchemy.orm import Mapped, mapped_column
+
+from .base import Base
+
+
+class TagAllowlist(Base):
+    __tablename__ = "tag_allowlist"
+    __table_args__ = (
+        CheckConstraint(
+            "min_confidence > 0 AND min_confidence <= 1",
+            name="ck_tag_allowlist_confidence_range",
+        ),
+    )
+
+    tag_id: Mapped[int] = mapped_column(
+        ForeignKey("tag.id", ondelete="CASCADE"), primary_key=True
+    )
+    min_confidence: Mapped[float] = mapped_column(Float, nullable=False, default=0.95)
+    added_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), nullable=False, server_default=func.now()
+    )
diff --git a/backend/app/models/tag_reference_embedding.py b/backend/app/models/tag_reference_embedding.py
new file mode 100644
index 0000000..2dc841b
--- /dev/null
+++ b/backend/app/models/tag_reference_embedding.py
@@ -0,0 +1,23 @@
+"""TagReferenceEmbedding — per-tag centroid (mean SigLIP embedding of members)."""
+
+from datetime import datetime
+
+from pgvector.sqlalchemy import Vector
+from sqlalchemy import DateTime, ForeignKey, Integer, String, func
+from sqlalchemy.orm import Mapped, mapped_column
+
+from .base import Base
+
+
+class TagReferenceEmbedding(Base):
+    __tablename__ = "tag_reference_embedding"
+
+    tag_id: Mapped[int] = mapped_column(
+        ForeignKey("tag.id", ondelete="CASCADE"), primary_key=True
+    )
+    embedding: Mapped[list[float]] = mapped_column(Vector(1152), nullable=False)
+    reference_count: Mapped[int] = mapped_column(Integer, nullable=False)
+    model_version: Mapped[str] = mapped_column(String(128), nullable=False)
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), nullable=False, server_default=func.now()
+    )
diff --git a/backend/app/models/tag_suggestion_rejection.py b/backend/app/models/tag_suggestion_rejection.py
new file mode 100644
index 0000000..8a834fe
--- /dev/null
+++ b/backend/app/models/tag_suggestion_rejection.py
@@ -0,0 +1,25 @@
+"""TagSuggestionRejection — per-image dismissed suggestions.
+
+Prevents re-suggestion AND prevents allowlist auto-apply on that image.
+"""
+
+from datetime import datetime
+
+from sqlalchemy import DateTime, ForeignKey, func
+from sqlalchemy.orm import Mapped, mapped_column
+
+from .base import Base
+
+
+class TagSuggestionRejection(Base):
+    __tablename__ = "tag_suggestion_rejection"
+
+    image_record_id: Mapped[int] = mapped_column(
+        ForeignKey("image_record.id", ondelete="CASCADE"), primary_key=True
+    )
+    tag_id: Mapped[int] = mapped_column(
+        ForeignKey("tag.id", ondelete="CASCADE"), primary_key=True, index=True
+    )
+    rejected_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), nullable=False, server_default=func.now()
+    )
diff --git a/tests/test_migration_0003.py b/tests/test_migration_0003.py
new file mode 100644
index 0000000..a46f76c
--- /dev/null
+++ b/tests/test_migration_0003.py
@@ -0,0 +1,56 @@
+"""Smoke test for migration 0003: model classes import, schema shape correct."""
+
+from backend.app.models import (
+    Base,
+    ImageRecord,
+    MLSettings,
+    TagAlias,
+    TagAllowlist,
+    TagReferenceEmbedding,
+    TagSuggestionRejection,
+)
+
+
+def test_new_tables_registered():
+    expected = {
+        "tag_allowlist",
+        "tag_suggestion_rejection",
+        "tag_alias",
+        "tag_reference_embedding",
+        "ml_settings",
+    }
+    assert expected.issubset(Base.metadata.tables.keys())
+
+
+def test_image_record_columns_renamed():
+    cols = {c.name for c in ImageRecord.__table__.columns}
+    assert "tagger_predictions" in cols
+    assert "tagger_model_version" in cols
+    assert "wd14_predictions" not in cols
+    assert "wd14_model_version" not in cols
+
+
+def test_tag_alias_composite_pk():
+    pk_cols = {c.name for c in TagAlias.__table__.primary_key.columns}
+    assert pk_cols == {"alias_string", "alias_category"}
+
+
+def test_ml_settings_singleton_constraint():
+    names = {c.name for c in MLSettings.__table__.constraints}
+    assert "ck_ml_settings_singleton" in names
+
+
+def test_tag_reference_embedding_has_vector():
+    cols = {c.name for c in TagReferenceEmbedding.__table__.columns}
+    assert "embedding" in cols
+    assert "reference_count" in cols
+
+
+def test_tag_allowlist_confidence_check():
+    names = {c.name for c in TagAllowlist.__table__.constraints}
+    assert "ck_tag_allowlist_confidence_range" in names
+
+
+def test_tag_suggestion_rejection_pk():
+    pk_cols = {c.name for c in TagSuggestionRejection.__table__.primary_key.columns}
+    assert pk_cols == {"image_record_id", "tag_id"}