diff --git a/alembic/versions/0088_reconcile_models_with_schema.py b/alembic/versions/0088_reconcile_models_with_schema.py
new file mode 100644
index 0000000..6117dd3
--- /dev/null
+++ b/alembic/versions/0088_reconcile_models_with_schema.py
@@ -0,0 +1,48 @@
+"""Reconcile the database with what the models have always claimed (#3275).
+
+Milestone 328 discovered ~130 places where the ORM models and the deployed
+schema disagreed. Almost all of them were the MODEL being wrong — missing
+`server_default`s, indexes and CHECK constraints that only ever existed in a
+migration — and those are fixed in the model files with no DDL at all, because
+the database already had them.
+
+This migration carries the remainder: the one case where the MODEL was right
+and the database was missing something.
+
+`tag.fandom_id` is declared `index=True` on the model, but no migration ever
+created that index. Every autogenerate run since would have proposed adding
+it; nobody ran one, so the model and the database simply drifted apart and
+stayed that way.
+
+Deliberately NOT in this migration: making `image_record.sha256` unique. The
+model says `unique=True` and `0001` created a plain, non-unique index, so
+duplicates are possible today and the ORM believes they are not. Adding the
+constraint is a real change that FAILS if duplicates already exist, and if
+they do exist the right response is a dedupe decision rather than a constraint
+— so it needs an answer about live data before it is written, not after.
+Tracked in #3275.
+
+Revision ID: 0088
+Revises: 0087
+Create Date: 2026-08-30
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+
+revision: str = "0088"
+down_revision: Union[str, None] = "0087"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # IF NOT EXISTS because the index is what the model already asks for: any
+    # database built from metadata rather than from this chain will have it,
+    # and this migration must be a no-op there rather than an error.
+    op.execute("CREATE INDEX IF NOT EXISTS ix_tag_fandom_id ON tag (fandom_id)")
+
+
+def downgrade() -> None:
+    op.execute("DROP INDEX IF EXISTS ix_tag_fandom_id")
diff --git a/backend/app/models/artist.py b/backend/app/models/artist.py
index e7ca894..fb3401c 100644
--- a/backend/app/models/artist.py
+++ b/backend/app/models/artist.py
@@ -27,10 +27,10 @@ class Artist(Base):
     notes: Mapped[str | None] = mapped_column(Text, nullable=True)
 
     # True once a Source is attached; flips false if all sources removed.
-    is_subscription: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
+    is_subscription: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False, server_default="false")
 
     # Per-artist scheduling overrides; null means "use global default".
-    auto_check: Mapped[bool] = mapped_column(Boolean, nullable=False, default=True)
+    auto_check: Mapped[bool] = mapped_column(Boolean, nullable=False, default=True, server_default="true")
     check_interval_seconds: Mapped[int | None] = mapped_column(Integer, nullable=True)
 
     created_at: Mapped[datetime] = mapped_column(
diff --git a/backend/app/models/backup_run.py b/backend/app/models/backup_run.py
index 1717aea..ad7b4f0 100644
--- a/backend/app/models/backup_run.py
+++ b/backend/app/models/backup_run.py
@@ -20,7 +20,7 @@ feedback_check_existing_enums):
 
 from datetime import datetime
 
-from sqlalchemy import JSON, BigInteger, DateTime, ForeignKey, Integer, String, Text
+from sqlalchemy import BigInteger, DateTime, ForeignKey, Index, Integer, JSON, String, Text, text
 from sqlalchemy.orm import Mapped, mapped_column
 
 from .base import Base
@@ -29,10 +29,18 @@ from .base import Base
 class BackupRun(Base):
     __tablename__ = "backup_run"
 
+
+    __table_args__ = (
+        # alembic 0017: reporting indexes, never declared on the model (#3275).
+        Index("ix_backup_run_kind_started", "kind", text("started_at DESC")),
+        Index("ix_backup_run_status_finished", "status", text("finished_at DESC")),
+        Index("ix_backup_run_tag_partial", "tag", postgresql_where=text("tag IS NOT NULL")),
+    )
     id: Mapped[int] = mapped_column(Integer, primary_key=True)
     kind: Mapped[str] = mapped_column(String(16), nullable=False, index=True)
     status: Mapped[str] = mapped_column(
         String(16), nullable=False, default="pending", index=True,
+        server_default="pending",
     )
     tag: Mapped[str | None] = mapped_column(String(64), nullable=True, index=True)
     triggered_by: Mapped[str] = mapped_column(String(32), nullable=False)
diff --git a/backend/app/models/download_event.py b/backend/app/models/download_event.py
index 7fe5b37..3ec00ae 100644
--- a/backend/app/models/download_event.py
+++ b/backend/app/models/download_event.py
@@ -25,8 +25,8 @@ class DownloadEvent(Base):
         DateTime(timezone=True), nullable=False, server_default=func.now()
     )
     finished_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
-    bytes_downloaded: Mapped[int] = mapped_column(BigInteger, nullable=False, default=0)
-    files_count: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
+    bytes_downloaded: Mapped[int] = mapped_column(BigInteger, nullable=False, default=0, server_default="0")
+    files_count: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
     error: Mapped[str | None] = mapped_column(Text, nullable=True)
     metadata_: Mapped[dict] = mapped_column(
         "metadata", JSONB, nullable=False, default=dict,
diff --git a/backend/app/models/external_link.py b/backend/app/models/external_link.py
index 0902e28..dcf8ee8 100644
--- a/backend/app/models/external_link.py
+++ b/backend/app/models/external_link.py
@@ -16,6 +16,7 @@ doesn't delete the link record).
 from datetime import datetime
 
 from sqlalchemy import (
+    CheckConstraint,
     DateTime,
     Float,
     ForeignKey,
@@ -38,6 +39,16 @@ STATUSES = ("pending", "downloading", "downloaded", "failed", "skipped", "dead")
 class ExternalLink(Base):
     __tablename__ = "external_link"
     __table_args__ = (
+        # alembic 0028 enum CHECKs. Rule 36 territory: a new host or status value
+        # needs its constraint swapped in the same migration (#3275).
+        CheckConstraint(
+            "host IN ('mega', 'gdrive', 'mediafire', 'dropbox', 'pixeldrain')",
+            name="ck_external_link_host",
+        ),
+        CheckConstraint(
+            "status IN ('pending', 'downloading', 'downloaded', 'failed', 'skipped', 'dead')",
+            name="ck_external_link_status",
+        ),
         # One row per (post, url). The full url (incl. #fragment) is the identity
         # — the same file linked twice in a post collapses to one row.
         Index("uq_external_link_post_url", "post_id", "url", unique=True),
diff --git a/backend/app/models/gpu_job.py b/backend/app/models/gpu_job.py
index dba5997..931b455 100644
--- a/backend/app/models/gpu_job.py
+++ b/backend/app/models/gpu_job.py
@@ -50,7 +50,8 @@ class GpuJob(Base):
     # What to compute, e.g. 'ccip' (detect figures + CCIP-embed) or 'siglip_region'.
     task: Mapped[str] = mapped_column(String(32), nullable=False)
     status: Mapped[str] = mapped_column(
-        String(16), nullable=False, default="pending", index=True
+        String(16), nullable=False, default="pending", index=True,
+        server_default="pending",
     )
     # pending | leased | done | error
     lease_token: Mapped[str | None] = mapped_column(String(64), nullable=True)
@@ -60,7 +61,7 @@ class GpuJob(Base):
     lease_expires_at: Mapped[datetime | None] = mapped_column(
         DateTime(timezone=True), nullable=True
     )
-    attempts: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
+    attempts: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
     error: Mapped[str | None] = mapped_column(Text, nullable=True)
     # Triage verdict for an ERRORED job (#125): NULL = not yet probed;
     # 'defect' = the integrity probe says the FILE itself is bad (surfaced for
diff --git a/backend/app/models/head_auto_apply_run.py b/backend/app/models/head_auto_apply_run.py
index 08c359a..031109b 100644
--- a/backend/app/models/head_auto_apply_run.py
+++ b/backend/app/models/head_auto_apply_run.py
@@ -24,10 +24,11 @@ class HeadAutoApplyRun(Base):
     id: Mapped[int] = mapped_column(Integer, primary_key=True)
     # dry_run=True is a PREVIEW: scores + counts what WOULD apply, writes nothing
     # (preview/apply parity, rule 93).
-    dry_run: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
+    dry_run: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False, server_default="false")
     params: Mapped[dict[str, Any]] = mapped_column(JSONB, nullable=False)
     status: Mapped[str] = mapped_column(
-        String(16), nullable=False, default="running", index=True
+        String(16), nullable=False, default="running", index=True,
+        server_default="running",
     )
     # running | ready | error
     started_at: Mapped[datetime] = mapped_column(
diff --git a/backend/app/models/head_metric.py b/backend/app/models/head_metric.py
index a034e51..7afc104 100644
--- a/backend/app/models/head_metric.py
+++ b/backend/app/models/head_metric.py
@@ -24,9 +24,9 @@ class HeadMetric(Base):
         ForeignKey("tag.id", ondelete="CASCADE"), primary_key=True
     )
     # An auto-applied (source='head_auto') tag the operator later REMOVED.
-    n_misfires: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
+    n_misfires: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
     # A tag with a head that the operator added by HAND (the head missed it).
-    n_underfires: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
+    n_underfires: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
     updated_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), nullable=False, server_default=func.now()
     )
diff --git a/backend/app/models/head_metrics_snapshot.py b/backend/app/models/head_metrics_snapshot.py
index a9ec7ac..651344e 100644
--- a/backend/app/models/head_metrics_snapshot.py
+++ b/backend/app/models/head_metrics_snapshot.py
@@ -28,9 +28,9 @@ class HeadMetricsSnapshot(Base):
         DateTime(timezone=True), nullable=False, server_default=func.now(), index=True
     )
     # Current count of source='head_auto' applications still standing.
-    n_auto_applied: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
-    n_misfires: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
-    n_underfires: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
+    n_auto_applied: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
+    n_misfires: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
+    n_underfires: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
     # The head's measured quality at snapshot time (null if no head exists).
     ap: Mapped[float | None] = mapped_column(Float, nullable=True)
     precision_cv: Mapped[float | None] = mapped_column(Float, nullable=True)
diff --git a/backend/app/models/head_training_run.py b/backend/app/models/head_training_run.py
index fd5858e..21c4ac7 100644
--- a/backend/app/models/head_training_run.py
+++ b/backend/app/models/head_training_run.py
@@ -24,7 +24,8 @@ class HeadTrainingRun(Base):
     # Training parameters: {min_positives, neg_ratio, precision_target, ...}.
     params: Mapped[dict[str, Any]] = mapped_column(JSONB, nullable=False)
     status: Mapped[str] = mapped_column(
-        String(16), nullable=False, default="running", index=True
+        String(16), nullable=False, default="running", index=True,
+        server_default="running",
     )
     # running | ready | error
     started_at: Mapped[datetime] = mapped_column(
diff --git a/backend/app/models/image_record.py b/backend/app/models/image_record.py
index 32d6eaa..be273ce 100644
--- a/backend/app/models/image_record.py
+++ b/backend/app/models/image_record.py
@@ -14,10 +14,12 @@ from sqlalchemy import (
     Enum,
     Float,
     ForeignKey,
+    Index,
     Integer,
     String,
     Text,
     func,
+    text,
 )
 from sqlalchemy.orm import Mapped, mapped_column
 
@@ -29,6 +31,12 @@ ORIGIN_CHOICES = ("downloaded", "imported_filesystem", "uploaded")
 class ImageRecord(Base):
     __tablename__ = "image_record"
 
+
+    __table_args__ = (
+        # alembic 0035/0071: the date-ordered browse indexes (#3275).
+        Index("ix_image_record_effective_date", text("effective_date DESC"), text("id DESC")),
+        Index("ix_image_record_earliest_post_date", text("earliest_post_date DESC"), text("id DESC")),
+    )
     id: Mapped[int] = mapped_column(Integer, primary_key=True)
 
     # On-disk identity
@@ -47,7 +55,8 @@ class ImageRecord(Base):
     # Integrity verification status. FC-2e populates this; FC-2a leaves rows at 'unknown'.
     # Values: 'unknown' (default), 'ok', 'corrupt', 'failed_verification'.
     integrity_status: Mapped[str] = mapped_column(
-        String(24), nullable=False, default="unknown", index=True
+        String(24), nullable=False, default="unknown", index=True,
+        server_default="unknown",
     )
 
     # Thumbnail (populated by FC-2)
diff --git a/backend/app/models/import_batch.py b/backend/app/models/import_batch.py
index 474f111..8d8fa61 100644
--- a/backend/app/models/import_batch.py
+++ b/backend/app/models/import_batch.py
@@ -21,17 +21,17 @@ class ImportBatch(Base):
     )
     finished_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
 
-    total_files: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
-    imported: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
-    skipped: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
-    failed: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
-    attachments: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
+    total_files: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
+    imported: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
+    skipped: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
+    failed: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
+    attachments: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
     # Deep-scan only: count of already-imported files whose sidecar metadata
     # got re-applied this run (post/source/provenance upsert). Stays 0 on
     # quick-scan batches. See `Importer.import_one(deep_scan=True)`.
-    refreshed: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
+    refreshed: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
 
-    status: Mapped[str] = mapped_column(String(16), nullable=False, default="running", index=True)
+    status: Mapped[str] = mapped_column(String(16), nullable=False, default="running", index=True, server_default="running")
     # running | complete | cancelled
 
     tasks = relationship("ImportTask", back_populates="batch", cascade="all, delete-orphan")
diff --git a/backend/app/models/import_settings.py b/backend/app/models/import_settings.py
index f4b8937..74ac13f 100644
--- a/backend/app/models/import_settings.py
+++ b/backend/app/models/import_settings.py
@@ -17,60 +17,71 @@ class ImportSettings(Base):
     __table_args__ = (CheckConstraint("id = 1", name="singleton"),)
 
     id: Mapped[int] = mapped_column(Integer, primary_key=True)
-    import_scan_path: Mapped[str] = mapped_column(Text, nullable=False, default="/import")
+    import_scan_path: Mapped[str] = mapped_column(Text, nullable=False, default="/import", server_default="/import")
 
-    min_width: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
-    min_height: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
+    min_width: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
+    min_height: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
 
-    skip_transparent: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
-    transparency_threshold: Mapped[float] = mapped_column(Float, nullable=False, default=0.9)
+    skip_transparent: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False, server_default="false")
+    transparency_threshold: Mapped[float] = mapped_column(Float, nullable=False, default=0.9, server_default="0.9")
 
-    skip_single_color: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
-    single_color_threshold: Mapped[float] = mapped_column(Float, nullable=False, default=0.95)
-    single_color_tolerance: Mapped[int] = mapped_column(Integer, nullable=False, default=30)
+    skip_single_color: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False, server_default="false")
+    single_color_threshold: Mapped[float] = mapped_column(Float, nullable=False, default=0.95, server_default="0.95")
+    single_color_tolerance: Mapped[int] = mapped_column(Integer, nullable=False, default=30, server_default="30")
 
-    phash_threshold: Mapped[int] = mapped_column(Integer, nullable=False, default=10)
+    phash_threshold: Mapped[int] = mapped_column(Integer, nullable=False, default=10, server_default="10")
 
     # FC-3c downloader knobs
     download_rate_limit_seconds: Mapped[float] = mapped_column(
-        Float, nullable=False, default=3.0
+        Float, nullable=False, default=3.0,
+        server_default="3",
     )
     download_validate_files: Mapped[bool] = mapped_column(
-        Boolean, nullable=False, default=True
+        Boolean, nullable=False, default=True,
+        server_default="true",
     )
 
     # FC-3d scheduling knobs
     download_schedule_default_seconds: Mapped[int] = mapped_column(
-        Integer, nullable=False, default=28800
+        Integer, nullable=False, default=28800,
+        server_default="28800",
     )
     download_event_retention_days: Mapped[int] = mapped_column(
-        Integer, nullable=False, default=90
+        Integer, nullable=False, default=90,
+        server_default="90",
     )
     download_failure_warning_threshold: Mapped[int] = mapped_column(
-        Integer, nullable=False, default=5
+        Integer, nullable=False, default=5,
+        server_default="5",
     )
 
     # FC-3h backup knobs.
     backup_db_nightly_enabled: Mapped[bool] = mapped_column(
         Boolean, nullable=False, default=False,
+        server_default="false",
     )
     backup_db_nightly_hour_utc: Mapped[int] = mapped_column(
         Integer, nullable=False, default=3,
+        server_default="3",
     )
     backup_db_keep_last_n: Mapped[int] = mapped_column(
         Integer, nullable=False, default=14,
+        server_default="14",
     )
     backup_images_keep_last_n: Mapped[int] = mapped_column(
         Integer, nullable=False, default=3,
+        server_default="3",
     )
 
     # FC-6.3 series continuation matcher. enabled gates the rescan; threshold is
     # the weighted-score cut-off (0..1) above which a pending suggestion is made.
     series_suggest_enabled: Mapped[bool] = mapped_column(
         Boolean, nullable=False, default=True,
+        server_default="true",
     )
     series_suggest_threshold: Mapped[float] = mapped_column(
         Float, nullable=False, default=0.5,
+        server_default="0.5",
     )
 
     # #830 off-platform file-host downloads — per-host enable lever (default on,
diff --git a/backend/app/models/import_task.py b/backend/app/models/import_task.py
index 3c947c1..c3d9f11 100644
--- a/backend/app/models/import_task.py
+++ b/backend/app/models/import_task.py
@@ -13,10 +13,12 @@ from sqlalchemy import (
     Boolean,
     DateTime,
     ForeignKey,
+    Index,
     Integer,
     String,
     Text,
     func,
+    text,
 )
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
@@ -26,6 +28,10 @@ from .base import Base
 class ImportTask(Base):
     __tablename__ = "import_task"
 
+
+    __table_args__ = (
+        Index("ix_import_task_created_at_desc", text("created_at DESC")),
+    )
     id: Mapped[int] = mapped_column(Integer, primary_key=True)
     batch_id: Mapped[int] = mapped_column(
         ForeignKey("import_batch.id", ondelete="CASCADE"), nullable=False, index=True
@@ -33,14 +39,14 @@ class ImportTask(Base):
 
     source_path: Mapped[str] = mapped_column(Text, nullable=False)
     task_type: Mapped[str] = mapped_column(String(16), nullable=False)  # media|archive
-    status: Mapped[str] = mapped_column(String(16), nullable=False, default="pending", index=True)
+    status: Mapped[str] = mapped_column(String(16), nullable=False, default="pending", index=True, server_default="pending")
 
     # Poison-pill circuit breaker (alembic 0026). recovery_count tracks
     # how many times the stuck-task sweep has re-queued this row; after
     # the cap it's failed with a diagnostic instead of looping. refetched
     # bounds the one-shot re-download remediation to a single attempt.
-    recovery_count: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
-    refetched: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
+    recovery_count: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
+    refetched: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False, server_default="false")
 
     result_image_id: Mapped[int | None] = mapped_column(
         ForeignKey("image_record.id", ondelete="SET NULL"), nullable=True
diff --git a/backend/app/models/library_audit_run.py b/backend/app/models/library_audit_run.py
index a2d4bc2..6ac9bb2 100644
--- a/backend/app/models/library_audit_run.py
+++ b/backend/app/models/library_audit_run.py
@@ -8,7 +8,7 @@ reads it and routes through cleanup_service.delete_images.
 from datetime import datetime
 from typing import Any
 
-from sqlalchemy import DateTime, Integer, String, Text, func
+from sqlalchemy import DateTime, Integer, String, Text, func, text
 from sqlalchemy.dialects.postgresql import JSONB
 from sqlalchemy.orm import Mapped, mapped_column
 
@@ -23,6 +23,7 @@ class LibraryAuditRun(Base):
     params: Mapped[dict[str, Any]] = mapped_column(JSONB, nullable=False)
     status: Mapped[str] = mapped_column(
         String(16), nullable=False, default="running", index=True,
+        server_default="running",
     )
     # running | ready | applied | cancelled | error
     started_at: Mapped[datetime] = mapped_column(
@@ -31,14 +32,16 @@ class LibraryAuditRun(Base):
     finished_at: Mapped[datetime | None] = mapped_column(
         DateTime(timezone=True), nullable=True,
     )
-    scanned_count: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
-    matched_count: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
-    matched_ids: Mapped[list[int]] = mapped_column(JSONB, nullable=False, default=list)
+    scanned_count: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
+    matched_count: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
+    matched_ids: Mapped[list[int]] = mapped_column(
+        JSONB, nullable=False, default=list, server_default=text("'[]'::jsonb")
+    )
     error: Mapped[str | None] = mapped_column(Text, nullable=True)
     # Chunked-scan state (alembic 0039): keyset cursor the next chunk resumes
     # from, and the last time a chunk made progress (so the recovery sweep can
     # tell a progressing multi-chunk audit from a stuck one).
-    resume_after_id: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
+    resume_after_id: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
     last_progress_at: Mapped[datetime | None] = mapped_column(
         DateTime(timezone=True), nullable=True,
     )
diff --git a/backend/app/models/ml_settings.py b/backend/app/models/ml_settings.py
index 72da17b..3e1570a 100644
--- a/backend/app/models/ml_settings.py
+++ b/backend/app/models/ml_settings.py
@@ -31,17 +31,20 @@ class MLSettings(Base):
     # queueing embed work nothing will consume (the daily GPU 'embed' backfill
     # covers those images instead).
     cpu_embed_enabled: Mapped[bool] = mapped_column(
-        Boolean, nullable=False, default=True
+        Boolean, nullable=False, default=True,
+        server_default="true",
     )
     # Video embedding (#747). Sample one frame every N seconds (fixed CADENCE, not
     # a fixed count) so coverage reflects real screen time regardless of length;
     # cap the total so a long video can't explode into hundreds of embeds. The
     # per-frame SigLIP embeddings are mean-pooled. Operator-tunable.
     video_frame_interval_seconds: Mapped[float] = mapped_column(
-        Float, nullable=False, default=4.0
+        Float, nullable=False, default=4.0,
+        server_default="4",
     )
     video_max_frames: Mapped[int] = mapped_column(
-        Integer, nullable=False, default=64
+        Integer, nullable=False, default=64,
+        server_default="64",
     )
     # Tagging-v2 head training (#114). The head is the suggestion source that
     # LEARNS from the operator's tags (replacing Camie + centroid). A concept
@@ -49,10 +52,12 @@ class MLSettings(Base):
     # head_auto_apply_precision is the precision bar a head must clear (at some
     # operating point) to "graduate" into earned auto-apply. Operator-tunable.
     head_min_positives: Mapped[int] = mapped_column(
-        Integer, nullable=False, default=8
+        Integer, nullable=False, default=8,
+        server_default="8",
     )
     head_auto_apply_precision: Mapped[float] = mapped_column(
-        Float, nullable=False, default=0.97
+        Float, nullable=False, default=0.97,
+        server_default="0.97",
     )
     # Earned auto-apply (#114). A graduated head fires (tags images without a
     # human) when this master switch is on AND the head has at least
@@ -61,29 +66,34 @@ class MLSettings(Base):
     # default (operator-asked 2026-06-29: opt-OUT, not opt-in); the support +
     # measured-precision gates keep it safe, and every auto-tag is reversible.
     head_auto_apply_enabled: Mapped[bool] = mapped_column(
-        Boolean, nullable=False, default=True
+        Boolean, nullable=False, default=True,
+        server_default="true",
     )
     head_auto_apply_min_positives: Mapped[int] = mapped_column(
         # Support floor raised 30→50 (operator-asked 2026-07-06): a head needs
         # more human labels before it may fire without a human.
-        Integer, nullable=False, default=50
+        Integer, nullable=False, default=50,
+        server_default="30",
     )
     # CCIP character-match cosine cut (#114). 0.85 default — the v1 flat 0.75
     # over-fired (high-reference characters matched a scatter of images); 0.85
     # keeps the confident single-character matches. Tunable from the agent card.
     ccip_match_threshold: Mapped[float] = mapped_column(
-        Float, nullable=False, default=0.85
+        Float, nullable=False, default=0.85,
+        server_default="0.85",
     )
     # CCIP auto-apply (#114). Confident matches (>= ccip_auto_apply_threshold,
     # above the suggest cut) auto-tag on a daily sweep. ON by default (opt-out);
     # single-character references + the high bar keep it safe, every tag reversible.
     ccip_auto_apply_enabled: Mapped[bool] = mapped_column(
-        Boolean, nullable=False, default=True
+        Boolean, nullable=False, default=True,
+        server_default="true",
     )
     ccip_auto_apply_threshold: Mapped[float] = mapped_column(
         # Raised 0.92→0.95 (operator-asked 2026-07-06) so only very confident
         # character matches auto-tag.
-        Float, nullable=False, default=0.95
+        Float, nullable=False, default=0.95,
+        server_default="0.92",
     )
     # -- Presentation chrome auto-hide (#141) -------------------------------
     # `banner` (chrome — clusters on UI, not content) auto-applies on the sweep
@@ -95,13 +105,16 @@ class MLSettings(Base):
     # (opt-out); every auto-tag is reversible. NOTE (#1464): `wip` + `editor
     # screenshot` are no longer chrome — they went to the PROCESS path below.
     presentation_auto_apply_enabled: Mapped[bool] = mapped_column(
-        Boolean, nullable=False, default=True
+        Boolean, nullable=False, default=True,
+        server_default="true",
     )
     presentation_auto_apply_threshold: Mapped[float] = mapped_column(
-        Float, nullable=False, default=0.90
+        Float, nullable=False, default=0.90,
+        server_default="0.90",
     )
     presentation_conflict_threshold: Mapped[float] = mapped_column(
-        Float, nullable=False, default=0.50
+        Float, nullable=False, default=0.50,
+        server_default="0.50",
     )
     # -- Process auto-apply (#1464) ----------------------------------------
     # `wip` / `editor screenshot` are PROCESS art — unfinished pieces + program
@@ -115,24 +128,29 @@ class MLSettings(Base):
     # (PresentationReview, mode='process') rather than silently marked. OFF by
     # default — a new whole-library auto-tagger is opt-in; every auto-tag reversible.
     process_auto_apply_enabled: Mapped[bool] = mapped_column(
-        Boolean, nullable=False, default=False
+        Boolean, nullable=False, default=False,
+        server_default="false",
     )
     process_auto_apply_threshold: Mapped[float] = mapped_column(
-        Float, nullable=False, default=0.90
+        Float, nullable=False, default=0.90,
+        server_default="0.9",
     )
     process_conflict_threshold: Mapped[float] = mapped_column(
-        Float, nullable=False, default=0.50
+        Float, nullable=False, default=0.50,
+        server_default="0.5",
     )
     # Default = SigLIP 2 (so400m, 512px) for new installs (migration 0069);
     # existing libraries keep their stored value until the operator re-embeds.
     embedder_model_version: Mapped[str] = mapped_column(
-        String(128), nullable=False, default="siglip2-so400m-patch16-512"
+        String(128), nullable=False, default="siglip2-so400m-patch16-512",
+        server_default="siglip2-so400m-patch16-512",
     )
     # The HF model NAME the embedder loads (server CPU embed + announced to the
     # GPU agent in the lease). Operator-settable so the embedder is a choice, not
     # a hardcode (#1190): set name + version together, then re-embed + retrain.
     embedder_model_name: Mapped[str] = mapped_column(
-        String(128), nullable=False, default="google/siglip2-so400m-patch16-512"
+        String(128), nullable=False, default="google/siglip2-so400m-patch16-512",
+        server_default="google/siglip2-so400m-patch16-512",
     )
     # -- Crop proposers / detectors (#1202, #134) --------------------------
     # WHERE-to-crop YOLO detectors feeding the crop→SigLIP bag + CCIP. Config
@@ -145,20 +163,24 @@ class MLSettings(Base):
     # person: general COCO figure detector for Western/realistic art the anime
     # person-detector misses → NMS-merged with imgutils → CCIP + concept.
     detector_person_enabled: Mapped[bool] = mapped_column(
-        Boolean, nullable=False, default=True
+        Boolean, nullable=False, default=True,
+        server_default="true",
     )
     detector_person_weights: Mapped[str] = mapped_column(
-        String(512), nullable=False, default="yolo11n.pt"
+        String(512), nullable=False, default="yolo11n.pt",
+        server_default="yolo11n.pt",
     )
     detector_person_conf: Mapped[float] = mapped_column(
-        Float, nullable=False, default=0.35
+        Float, nullable=False, default=0.35,
+        server_default="0.35",
     )
     # anatomy: booru_yolo anime/furry/NSFW torso components → concept crops.
     # Default = yolov11m_aa22 (26 classes, best mAP50-95 0.96), committed in the
     # upstream repo so the URL resolves. License UNSTATED — fine for a private
     # homelab (operator accepted #1202).
     detector_anatomy_enabled: Mapped[bool] = mapped_column(
-        Boolean, nullable=False, default=True
+        Boolean, nullable=False, default=True,
+        server_default="true",
     )
     detector_anatomy_weights: Mapped[str] = mapped_column(
         String(512), nullable=False,
@@ -166,37 +188,47 @@ class MLSettings(Base):
             "https://github.com/aperveyev/booru_yolo/raw/main/models/"
             "yolov11m_aa22.pt"
         ),
+        server_default="https://github.com/aperveyev/booru_yolo/raw/main/models/yolov11m_aa22.pt",
     )
     detector_anatomy_conf: Mapped[float] = mapped_column(
-        Float, nullable=False, default=0.30
+        Float, nullable=False, default=0.30,
+        server_default="0.30",
     )
     # panel: comic page → panel regions → concept crops (Apache-2.0, YOLOv12x).
     detector_panel_enabled: Mapped[bool] = mapped_column(
-        Boolean, nullable=False, default=True
+        Boolean, nullable=False, default=True,
+        server_default="true",
     )
     detector_panel_weights: Mapped[str] = mapped_column(
         String(512), nullable=False,
         default="mosesb/best-comic-panel-detection::best.pt",
+        server_default="mosesb/best-comic-panel-detection::best.pt",
     )
     detector_panel_conf: Mapped[float] = mapped_column(
-        Float, nullable=False, default=0.30
+        Float, nullable=False, default=0.30,
+        server_default="0.30",
     )
     # Per-frame caps bound the crop→embed explosion; max_regions is the hard
     # per-job backstop; dedupe_iou drops near-duplicate crops before the embed.
     detector_max_figures: Mapped[int] = mapped_column(
-        Integer, nullable=False, default=8
+        Integer, nullable=False, default=8,
+        server_default="8",
     )
     detector_max_components: Mapped[int] = mapped_column(
-        Integer, nullable=False, default=8
+        Integer, nullable=False, default=8,
+        server_default="8",
     )
     detector_max_panels: Mapped[int] = mapped_column(
-        Integer, nullable=False, default=8
+        Integer, nullable=False, default=8,
+        server_default="8",
     )
     detector_max_regions: Mapped[int] = mapped_column(
-        Integer, nullable=False, default=128
+        Integer, nullable=False, default=128,
+        server_default="128",
     )
     detector_dedupe_iou: Mapped[float] = mapped_column(
-        Float, nullable=False, default=0.85
+        Float, nullable=False, default=0.85,
+        server_default="0.85",
     )
     # -- CCIP character prototypes (#1317) ---------------------------------
     # The per-character reference set is precomputed + refreshed INCREMENTALLY
@@ -208,7 +240,8 @@ class MLSettings(Base):
         String(128), nullable=True
     )
     ccip_prototype_cap: Mapped[int] = mapped_column(
-        Integer, nullable=False, default=64
+        Integer, nullable=False, default=64,
+        server_default="64",
     )
     updated_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), nullable=False, server_default=func.now()
diff --git a/backend/app/models/patreon_failed_media.py b/backend/app/models/patreon_failed_media.py
index 79976ef..26557fe 100644
--- a/backend/app/models/patreon_failed_media.py
+++ b/backend/app/models/patreon_failed_media.py
@@ -35,7 +35,7 @@ class PatreonFailedMedia(Base):
         ForeignKey("source.id", ondelete="CASCADE"), nullable=False, index=True
     )
     filehash: Mapped[str] = mapped_column(String(128), nullable=False)
-    attempts: Mapped[int] = mapped_column(Integer, nullable=False, default=1)
+    attempts: Mapped[int] = mapped_column(Integer, nullable=False, default=1, server_default="1")
     last_error: Mapped[str | None] = mapped_column(Text, nullable=True)
     first_failed_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), nullable=False, server_default=func.now()
diff --git a/backend/app/models/pixiv_failed_media.py b/backend/app/models/pixiv_failed_media.py
index a33d15e..7737594 100644
--- a/backend/app/models/pixiv_failed_media.py
+++ b/backend/app/models/pixiv_failed_media.py
@@ -35,7 +35,7 @@ class PixivFailedMedia(Base):
         ForeignKey("source.id", ondelete="CASCADE"), nullable=False, index=True
     )
     filehash: Mapped[str] = mapped_column(String(128), nullable=False)
-    attempts: Mapped[int] = mapped_column(Integer, nullable=False, default=1)
+    attempts: Mapped[int] = mapped_column(Integer, nullable=False, default=1, server_default="1")
     last_error: Mapped[str | None] = mapped_column(Text, nullable=True)
     first_failed_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), nullable=False, server_default=func.now()
diff --git a/backend/app/models/post.py b/backend/app/models/post.py
index 4183330..1cc15a4 100644
--- a/backend/app/models/post.py
+++ b/backend/app/models/post.py
@@ -9,15 +9,17 @@ artist-filter queries don't depend on the Source detour).
 from datetime import datetime
 
 from sqlalchemy import (
-    JSON,
     CheckConstraint,
     DateTime,
     ForeignKey,
+    Index,
     Integer,
+    JSON,
     String,
     Text,
     UniqueConstraint,
     func,
+    text,
 )
 from sqlalchemy.orm import Mapped, mapped_column
 
@@ -27,6 +29,10 @@ from .base import Base
 class Post(Base):
     __tablename__ = "post"
     __table_args__ = (
+        # alembic 0030. The comment above described this index; nothing declared
+        # it, so autogenerate proposed dropping it (#3275).
+        Index("uq_post_artist_external_id_null_source", "artist_id", "external_post_id",
+              unique=True, postgresql_where=text("source_id IS NULL")),
         # Source-bound dedup. Postgres treats NULL != NULL so rows
         # with source_id IS NULL aren't deduped by this constraint;
         # the partial unique index `uq_post_artist_external_id_null_source`
diff --git a/backend/app/models/presentation_review.py b/backend/app/models/presentation_review.py
index 73da13f..e18e298 100644
--- a/backend/app/models/presentation_review.py
+++ b/backend/app/models/presentation_review.py
@@ -11,7 +11,7 @@ are pruned by retention.
 
 from datetime import datetime
 
-from sqlalchemy import DateTime, Float, ForeignKey, String, func
+from sqlalchemy import DateTime, Float, ForeignKey, Index, String, func
 from sqlalchemy.orm import Mapped, mapped_column
 
 from .base import Base
@@ -20,6 +20,10 @@ from .base import Base
 class PresentationReview(Base):
     __tablename__ = "presentation_review"
 
+
+    __table_args__ = (
+        Index("ix_presentation_review_resolved_at", "resolved_at"),
+    )
     image_record_id: Mapped[int] = mapped_column(
         ForeignKey("image_record.id", ondelete="CASCADE"), primary_key=True
     )
diff --git a/backend/app/models/source.py b/backend/app/models/source.py
index 1bf6c67..1c29e6f 100644
--- a/backend/app/models/source.py
+++ b/backend/app/models/source.py
@@ -5,7 +5,7 @@ Multiple sources per artist support creators with cross-platform presence.
 
 from datetime import datetime
 
-from sqlalchemy import JSON, Boolean, DateTime, ForeignKey, Integer, String, Text
+from sqlalchemy import Boolean, DateTime, ForeignKey, Integer, JSON, String, Text
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
 from .base import Base
@@ -20,7 +20,7 @@ class Source(Base):
     )
     platform: Mapped[str] = mapped_column(String(64), nullable=False)
     url: Mapped[str] = mapped_column(Text, nullable=False)
-    enabled: Mapped[bool] = mapped_column(Boolean, nullable=False, default=True)
+    enabled: Mapped[bool] = mapped_column(Boolean, nullable=False, default=True, server_default="true")
 
     config_overrides: Mapped[dict | None] = mapped_column(JSON, nullable=True)
 
@@ -32,7 +32,7 @@ class Source(Base):
     # by _update_source_health alongside last_error; cleared on 'ok'.
     error_type: Mapped[str | None] = mapped_column(String(32), nullable=True, index=True)
     check_interval_override: Mapped[int | None] = mapped_column(Integer, nullable=True)
-    consecutive_failures: Mapped[int] = mapped_column(Integer, nullable=False, default=0)
+    consecutive_failures: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
 
     # alembic 0031: sticky deep-scan budget. When > 0, the next N download
     # runs use gallery-dl's full-walk config (skip: True + 1800s timeout);
diff --git a/backend/app/models/subscribestar_failed_media.py b/backend/app/models/subscribestar_failed_media.py
index 9201aa7..d12ff73 100644
--- a/backend/app/models/subscribestar_failed_media.py
+++ b/backend/app/models/subscribestar_failed_media.py
@@ -34,7 +34,7 @@ class SubscribeStarFailedMedia(Base):
         ForeignKey("source.id", ondelete="CASCADE"), nullable=False, index=True
     )
     filehash: Mapped[str] = mapped_column(String(128), nullable=False)
-    attempts: Mapped[int] = mapped_column(Integer, nullable=False, default=1)
+    attempts: Mapped[int] = mapped_column(Integer, nullable=False, default=1, server_default="1")
     last_error: Mapped[str | None] = mapped_column(Text, nullable=True)
     first_failed_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), nullable=False, server_default=func.now()
diff --git a/backend/app/models/tag.py b/backend/app/models/tag.py
index 8d5a256..d3107d0 100644
--- a/backend/app/models/tag.py
+++ b/backend/app/models/tag.py
@@ -15,11 +15,13 @@ from sqlalchemy import (
     Column,
     DateTime,
     ForeignKey,
+    Index,
     Integer,
     String,
     Table,
     false,
     func,
+    text,
 )
 from sqlalchemy import (
     Enum as SQLEnum,
@@ -67,7 +69,7 @@ image_tag = Table(
         primary_key=True,
     ),
     Column("tag_id", ForeignKey("tag.id", ondelete="CASCADE"), primary_key=True),
-    Column("source", String(32), nullable=False, default="manual"),
+    Column("source", String(32), nullable=False, default="manual", server_default="manual"),
     Column("created_at", DateTime(timezone=True), nullable=False, server_default=func.now()),
 )
 
@@ -75,6 +77,10 @@ image_tag = Table(
 class Tag(Base):
     __tablename__ = "tag"
     __table_args__ = (
+        # alembic 0002. An EXPRESSION index — COALESCE cannot be expressed as a
+        # UniqueConstraint, which is why it only ever existed in a migration (#3275).
+        Index("uq_tag_name_kind_fandom", "name", "kind", text("COALESCE(fandom_id, 0)"),
+              unique=True),
         CheckConstraint(
             "(fandom_id IS NULL) OR (kind = 'character')",
             name="ck_tag_fandom_requires_character",
@@ -87,6 +93,7 @@ class Tag(Base):
         SQLEnum(TagKind, name="tag_kind", values_callable=lambda e: [m.value for m in e]),
         nullable=False,
         default=TagKind.general,
+        server_default="general",
     )
     fandom_id: Mapped[int | None] = mapped_column(
         ForeignKey("tag.id", ondelete="SET NULL"), nullable=True, index=True
diff --git a/backend/app/models/tag_alias.py b/backend/app/models/tag_alias.py
index 93f4755..533cec3 100644
--- a/backend/app/models/tag_alias.py
+++ b/backend/app/models/tag_alias.py
@@ -5,7 +5,7 @@ in image_prediction stay unmolested.
 
 from datetime import datetime
 
-from sqlalchemy import DateTime, ForeignKey, String, func
+from sqlalchemy import DateTime, ForeignKey, Index, String, func
 from sqlalchemy.orm import Mapped, mapped_column
 
 from .base import Base
@@ -14,10 +14,17 @@ from .base import Base
 class TagAlias(Base):
     __tablename__ = "tag_alias"
 
+
+    __table_args__ = (
+        # Named explicitly: the database calls this ix_tag_alias_canonical, while
+        # a bare index=True on the column would generate ix_tag_alias_canonical_tag_id
+        # and silently propose a drop+create on the next autogenerate (#3275).
+        Index("ix_tag_alias_canonical", "canonical_tag_id"),
+    )
     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
+        ForeignKey("tag.id", ondelete="CASCADE"), nullable=False
     )
     created_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
index 8a834fe..02756de 100644
--- a/backend/app/models/tag_suggestion_rejection.py
+++ b/backend/app/models/tag_suggestion_rejection.py
@@ -5,7 +5,7 @@ Prevents re-suggestion AND prevents allowlist auto-apply on that image.
 
 from datetime import datetime
 
-from sqlalchemy import DateTime, ForeignKey, func
+from sqlalchemy import DateTime, ForeignKey, Index, func
 from sqlalchemy.orm import Mapped, mapped_column
 
 from .base import Base
@@ -14,11 +14,16 @@ from .base import Base
 class TagSuggestionRejection(Base):
     __tablename__ = "tag_suggestion_rejection"
 
+
+    __table_args__ = (
+        # Named explicitly; see tag_alias for why (#3275).
+        Index("ix_tag_suggestion_rejection_tag", "tag_id"),
+    )
     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
+        ForeignKey("tag.id", ondelete="CASCADE"), primary_key=True
     )
     rejected_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), nullable=False, server_default=func.now()
diff --git a/backend/app/models/task_run.py b/backend/app/models/task_run.py
index e8eac05..c24ed46 100644
--- a/backend/app/models/task_run.py
+++ b/backend/app/models/task_run.py
@@ -15,7 +15,7 @@ backend.app.tasks.maintenance.recover_stalled_task_runs (Beat 5 min).
 
 from datetime import datetime
 
-from sqlalchemy import DateTime, Integer, String, Text
+from sqlalchemy import DateTime, Index, Integer, String, Text, text
 from sqlalchemy.orm import Mapped, mapped_column
 
 from .base import Base
@@ -24,6 +24,13 @@ from .base import Base
 class TaskRun(Base):
     __tablename__ = "task_run"
 
+
+    __table_args__ = (
+        # alembic 0016: the three task-history indexes (#3275).
+        Index("ix_task_run_name_started", "task_name", text("started_at DESC")),
+        Index("ix_task_run_queue_started", "queue", text("started_at DESC")),
+        Index("ix_task_run_status_started", "status", text("started_at DESC")),
+    )
     id: Mapped[int] = mapped_column(Integer, primary_key=True)
     celery_task_id: Mapped[str] = mapped_column(
         String(64), nullable=False, index=True,
@@ -40,6 +47,7 @@ class TaskRun(Base):
     duration_ms: Mapped[int | None] = mapped_column(Integer, nullable=True)
     status: Mapped[str] = mapped_column(
         String(16), nullable=False, default="running", index=True,
+        server_default="running",
     )
     error_type: Mapped[str | None] = mapped_column(String(128), nullable=True)
     error_message: Mapped[str | None] = mapped_column(Text, nullable=True)