diff --git a/backend/app/routers/reports.py b/backend/app/routers/reports.py
index 9a552e5..d065116 100644
--- a/backend/app/routers/reports.py
+++ b/backend/app/routers/reports.py
@@ -1,5 +1,7 @@
 """Reports endpoints — export coverage summaries and test results.
 
+Thin HTTP adapter: delegates all data logic to coverage_report_service.
+
 Endpoints
 ---------
 GET /reports/coverage-summary    — full coverage JSON report
@@ -15,24 +17,21 @@ from typing import Optional
 
 from fastapi import APIRouter, Depends, Query
 from fastapi.responses import StreamingResponse
-from sqlalchemy import func
 from sqlalchemy.orm import Session
 
 from app.database import get_db
 from app.dependencies.auth import get_current_user
-from app.models.enums import TestState
-from app.models.technique import Technique
-from app.models.test import Test
 from app.models.user import User
+from app.services.coverage_report_service import (
+    build_coverage_csv_rows,
+    build_coverage_summary,
+    build_remediation_status_report,
+    build_test_results_report,
+)
 
 router = APIRouter(prefix="/reports", tags=["reports"])
 
 
-# ---------------------------------------------------------------------------
-# GET /reports/coverage-summary
-# ---------------------------------------------------------------------------
-
-
 @router.get("/coverage-summary")
 def coverage_summary(
     tactic: Optional[str] = Query(None, description="Filter by tactic"),
@@ -41,63 +40,7 @@ def coverage_summary(
     current_user: User = Depends(get_current_user),
 ):
     """Full coverage report as JSON — technique-by-technique with test counts."""
-    query = db.query(Technique)
-    if tactic:
-        from app.utils import escape_like
-        query = query.filter(Technique.tactic.ilike(f"%{escape_like(tactic)}%"))
-
-    techniques = query.order_by(Technique.mitre_id).all()
-
-    rows = []
-    for t in techniques:
-        # Count tests per state for this technique
-        test_counts = (
-            db.query(Test.state, func.count(Test.id))
-            .filter(Test.technique_id == t.id)
-            .group_by(Test.state)
-            .all()
-        )
-        counts = {str(state): count for state, count in test_counts}
-
-        # Filter by platform if requested (check if technique platforms contain it)
-        if platform and platform.lower() not in [p.lower() for p in (t.platforms or [])]:
-            continue
-
-        rows.append({
-            "mitre_id": t.mitre_id,
-            "name": t.name,
-            "tactic": t.tactic,
-            "platforms": t.platforms,
-            "status_global": t.status_global,
-            "total_tests": sum(counts.values()),
-            "tests_by_state": counts,
-        })
-
-    total = len(rows)
-    validated = sum(1 for r in rows if r["status_global"] == "validated")
-    partial = sum(1 for r in rows if r["status_global"] == "partial")
-    not_covered = sum(1 for r in rows if r["status_global"] == "not_covered")
-    in_progress = sum(1 for r in rows if r["status_global"] == "in_progress")
-    not_evaluated = sum(1 for r in rows if r["status_global"] == "not_evaluated")
-
-    return {
-        "generated_at": datetime.utcnow().isoformat(),
-        "summary": {
-            "total_techniques": total,
-            "validated": validated,
-            "partial": partial,
-            "not_covered": not_covered,
-            "in_progress": in_progress,
-            "not_evaluated": not_evaluated,
-            "coverage_percentage": round((validated / total * 100) if total > 0 else 0, 1),
-        },
-        "techniques": rows,
-    }
-
-
-# ---------------------------------------------------------------------------
-# GET /reports/coverage-csv
-# ---------------------------------------------------------------------------
+    return build_coverage_summary(db, tactic=tactic, platform=platform)
 
 
 @router.get("/coverage-csv")
@@ -108,57 +51,22 @@ def coverage_csv(
     current_user: User = Depends(get_current_user),
 ):
     """Export coverage as a downloadable CSV."""
-    query = db.query(Technique)
-    if tactic:
-        from app.utils import escape_like
-        query = query.filter(Technique.tactic.ilike(f"%{escape_like(tactic)}%"))
-
-    techniques = query.order_by(Technique.mitre_id).all()
+    rows = build_coverage_csv_rows(db, tactic=tactic, platform=platform)
 
     output = io.StringIO()
     writer = csv.writer(output)
-    writer.writerow([
-        "MITRE ID", "Name", "Tactic", "Platforms", "Status",
-        "Total Tests", "Validated", "In Progress", "Not Covered",
-    ])
-
-    for t in techniques:
-        if platform and platform.lower() not in [p.lower() for p in (t.platforms or [])]:
-            continue
-
-        test_counts = (
-            db.query(Test.state, func.count(Test.id))
-            .filter(Test.technique_id == t.id)
-            .group_by(Test.state)
-            .all()
-        )
-        counts = {str(state): count for state, count in test_counts}
-
-        writer.writerow([
-            t.mitre_id,
-            t.name,
-            t.tactic,
-            ", ".join(t.platforms or []),
-            t.status_global,
-            sum(counts.values()),
-            counts.get("validated", 0),
-            sum(counts.get(s, 0) for s in ["draft", "red_executing", "blue_evaluating", "in_review"]),
-            counts.get("rejected", 0),
-        ])
+    for row in rows:
+        writer.writerow(row)
 
     output.seek(0)
+    filename = f"aegis_coverage_{datetime.utcnow().strftime('%Y%m%d')}.csv"
     return StreamingResponse(
         iter([output.getvalue()]),
         media_type="text/csv",
-        headers={"Content-Disposition": f"attachment; filename=aegis_coverage_{datetime.utcnow().strftime('%Y%m%d')}.csv"},
+        headers={"Content-Disposition": f"attachment; filename={filename}"},
     )
 
 
-# ---------------------------------------------------------------------------
-# GET /reports/test-results
-# ---------------------------------------------------------------------------
-
-
 @router.get("/test-results")
 def test_results(
     state: Optional[str] = Query(None),
@@ -168,68 +76,7 @@ def test_results(
     current_user: User = Depends(get_current_user),
 ):
     """Report of test results with optional filters."""
-    query = db.query(Test)
-
-    if state:
-        query = query.filter(Test.state == state)
-    if date_from:
-        try:
-            dt = datetime.fromisoformat(date_from)
-            query = query.filter(Test.created_at >= dt)
-        except ValueError:
-            pass
-    if date_to:
-        try:
-            dt = datetime.fromisoformat(date_to)
-            query = query.filter(Test.created_at <= dt)
-        except ValueError:
-            pass
-
-    tests = query.order_by(Test.created_at.desc()).all()
-
-    # Summary
-    total = len(tests)
-    by_state = {}
-    by_result = {}
-    for t in tests:
-        s = t.state.value if hasattr(t.state, "value") else str(t.state)
-        by_state[s] = by_state.get(s, 0) + 1
-        if t.detection_result:
-            r = t.detection_result.value if hasattr(t.detection_result, "value") else str(t.detection_result)
-            by_result[r] = by_result.get(r, 0) + 1
-
-    return {
-        "generated_at": datetime.utcnow().isoformat(),
-        "filters": {"state": state, "date_from": date_from, "date_to": date_to},
-        "summary": {
-            "total_tests": total,
-            "by_state": by_state,
-            "by_detection_result": by_result,
-        },
-        "tests": [
-            {
-                "id": str(t.id),
-                "name": t.name,
-                "technique_id": str(t.technique_id),
-                "state": t.state.value if hasattr(t.state, "value") else str(t.state),
-                "platform": t.platform,
-                "attack_success": t.attack_success,
-                "detection_result": (
-                    t.detection_result.value if t.detection_result and hasattr(t.detection_result, "value")
-                    else str(t.detection_result) if t.detection_result else None
-                ),
-                "red_validation_status": t.red_validation_status,
-                "blue_validation_status": t.blue_validation_status,
-                "created_at": t.created_at.isoformat() if t.created_at else None,
-            }
-            for t in tests
-        ],
-    }
-
-
-# ---------------------------------------------------------------------------
-# GET /reports/remediation-status
-# ---------------------------------------------------------------------------
+    return build_test_results_report(db, state=state, date_from=date_from, date_to=date_to)
 
 
 @router.get("/remediation-status")
@@ -239,34 +86,4 @@ def remediation_status(
     current_user: User = Depends(get_current_user),
 ):
     """Report of remediation status across all tests."""
-    query = db.query(Test).filter(Test.remediation_steps.isnot(None))
-
-    if status:
-        query = query.filter(Test.remediation_status == status)
-
-    tests = query.order_by(Test.created_at.desc()).all()
-
-    by_status = {}
-    for t in tests:
-        s = t.remediation_status or "unset"
-        by_status[s] = by_status.get(s, 0) + 1
-
-    return {
-        "generated_at": datetime.utcnow().isoformat(),
-        "summary": {
-            "total_with_remediation": len(tests),
-            "by_status": by_status,
-        },
-        "tests": [
-            {
-                "id": str(t.id),
-                "name": t.name,
-                "technique_id": str(t.technique_id),
-                "state": t.state.value if hasattr(t.state, "value") else str(t.state),
-                "remediation_status": t.remediation_status,
-                "remediation_steps": t.remediation_steps,
-                "remediation_assignee": str(t.remediation_assignee) if t.remediation_assignee else None,
-            }
-            for t in tests
-        ],
-    }
+    return build_remediation_status_report(db, status=status)
diff --git a/backend/app/services/coverage_report_service.py b/backend/app/services/coverage_report_service.py
new file mode 100644
index 0000000..c33f1df
--- /dev/null
+++ b/backend/app/services/coverage_report_service.py
@@ -0,0 +1,234 @@
+"""Coverage report data service.
+
+Extracts query and aggregation logic from the reports router so
+that the router remains a thin HTTP adapter.  Fixes the N+1
+technique/test-count pattern by using a single grouped query.
+
+This module is framework-agnostic: no FastAPI imports.
+"""
+
+from __future__ import annotations
+
+from datetime import datetime
+
+from sqlalchemy import func
+from sqlalchemy.orm import Session
+
+from app.models.technique import Technique
+from app.models.test import Test
+from app.utils import escape_like
+
+
+def _technique_test_counts(
+    db: Session,
+    technique_ids: list,
+) -> dict:
+    """Return ``{technique_id: {state_str: count}}`` in a single query."""
+    if not technique_ids:
+        return {}
+    rows = (
+        db.query(Test.technique_id, Test.state, func.count(Test.id))
+        .filter(Test.technique_id.in_(technique_ids))
+        .group_by(Test.technique_id, Test.state)
+        .all()
+    )
+    result: dict = {}
+    for tid, state, count in rows:
+        result.setdefault(tid, {})[str(state)] = count
+    return result
+
+
+def build_coverage_summary(
+    db: Session,
+    *,
+    tactic: str | None = None,
+    platform: str | None = None,
+) -> dict:
+    """Build the full coverage summary report as a dict."""
+    query = db.query(Technique)
+    if tactic:
+        query = query.filter(Technique.tactic.ilike(f"%{escape_like(tactic)}%"))
+
+    techniques = query.order_by(Technique.mitre_id).all()
+    counts_map = _technique_test_counts(db, [t.id for t in techniques])
+
+    rows = []
+    for t in techniques:
+        if platform and platform.lower() not in [p.lower() for p in (t.platforms or [])]:
+            continue
+
+        counts = counts_map.get(t.id, {})
+        rows.append({
+            "mitre_id": t.mitre_id,
+            "name": t.name,
+            "tactic": t.tactic,
+            "platforms": t.platforms,
+            "status_global": t.status_global,
+            "total_tests": sum(counts.values()),
+            "tests_by_state": counts,
+        })
+
+    total = len(rows)
+    validated = sum(1 for r in rows if r["status_global"] == "validated")
+    partial = sum(1 for r in rows if r["status_global"] == "partial")
+    not_covered = sum(1 for r in rows if r["status_global"] == "not_covered")
+    in_progress = sum(1 for r in rows if r["status_global"] == "in_progress")
+    not_evaluated = sum(1 for r in rows if r["status_global"] == "not_evaluated")
+
+    return {
+        "generated_at": datetime.utcnow().isoformat(),
+        "summary": {
+            "total_techniques": total,
+            "validated": validated,
+            "partial": partial,
+            "not_covered": not_covered,
+            "in_progress": in_progress,
+            "not_evaluated": not_evaluated,
+            "coverage_percentage": round((validated / total * 100) if total > 0 else 0, 1),
+        },
+        "techniques": rows,
+    }
+
+
+def build_coverage_csv_rows(
+    db: Session,
+    *,
+    tactic: str | None = None,
+    platform: str | None = None,
+) -> list[list]:
+    """Build rows for a CSV coverage export (header + data)."""
+    query = db.query(Technique)
+    if tactic:
+        query = query.filter(Technique.tactic.ilike(f"%{escape_like(tactic)}%"))
+
+    techniques = query.order_by(Technique.mitre_id).all()
+    counts_map = _technique_test_counts(db, [t.id for t in techniques])
+
+    header = [
+        "MITRE ID", "Name", "Tactic", "Platforms", "Status",
+        "Total Tests", "Validated", "In Progress", "Not Covered",
+    ]
+    rows = [header]
+
+    in_progress_states = {"draft", "red_executing", "blue_evaluating", "in_review"}
+
+    for t in techniques:
+        if platform and platform.lower() not in [p.lower() for p in (t.platforms or [])]:
+            continue
+
+        counts = counts_map.get(t.id, {})
+        rows.append([
+            t.mitre_id,
+            t.name,
+            t.tactic,
+            ", ".join(t.platforms or []),
+            t.status_global,
+            sum(counts.values()),
+            counts.get("validated", 0),
+            sum(counts.get(s, 0) for s in in_progress_states),
+            counts.get("rejected", 0),
+        ])
+
+    return rows
+
+
+def build_test_results_report(
+    db: Session,
+    *,
+    state: str | None = None,
+    date_from: str | None = None,
+    date_to: str | None = None,
+) -> dict:
+    """Build a test results report with optional filters."""
+    query = db.query(Test)
+
+    if state:
+        query = query.filter(Test.state == state)
+    if date_from:
+        try:
+            query = query.filter(Test.created_at >= datetime.fromisoformat(date_from))
+        except ValueError:
+            pass
+    if date_to:
+        try:
+            query = query.filter(Test.created_at <= datetime.fromisoformat(date_to))
+        except ValueError:
+            pass
+
+    tests = query.order_by(Test.created_at.desc()).all()
+
+    by_state: dict[str, int] = {}
+    by_result: dict[str, int] = {}
+    for t in tests:
+        s = t.state.value if hasattr(t.state, "value") else str(t.state)
+        by_state[s] = by_state.get(s, 0) + 1
+        if t.detection_result:
+            r = t.detection_result.value if hasattr(t.detection_result, "value") else str(t.detection_result)
+            by_result[r] = by_result.get(r, 0) + 1
+
+    return {
+        "generated_at": datetime.utcnow().isoformat(),
+        "filters": {"state": state, "date_from": date_from, "date_to": date_to},
+        "summary": {
+            "total_tests": len(tests),
+            "by_state": by_state,
+            "by_detection_result": by_result,
+        },
+        "tests": [
+            {
+                "id": str(t.id),
+                "name": t.name,
+                "technique_id": str(t.technique_id),
+                "state": t.state.value if hasattr(t.state, "value") else str(t.state),
+                "platform": t.platform,
+                "attack_success": t.attack_success,
+                "detection_result": (
+                    t.detection_result.value if t.detection_result and hasattr(t.detection_result, "value")
+                    else str(t.detection_result) if t.detection_result else None
+                ),
+                "red_validation_status": t.red_validation_status,
+                "blue_validation_status": t.blue_validation_status,
+                "created_at": t.created_at.isoformat() if t.created_at else None,
+            }
+            for t in tests
+        ],
+    }
+
+
+def build_remediation_status_report(
+    db: Session,
+    *,
+    status: str | None = None,
+) -> dict:
+    """Build a remediation status report."""
+    query = db.query(Test).filter(Test.remediation_steps.isnot(None))
+
+    if status:
+        query = query.filter(Test.remediation_status == status)
+
+    tests = query.order_by(Test.created_at.desc()).all()
+
+    by_status: dict[str, int] = {}
+    for t in tests:
+        s = t.remediation_status or "unset"
+        by_status[s] = by_status.get(s, 0) + 1
+
+    return {
+        "generated_at": datetime.utcnow().isoformat(),
+        "summary": {
+            "total_with_remediation": len(tests),
+            "by_status": by_status,
+        },
+        "tests": [
+            {
+                "id": str(t.id),
+                "name": t.name,
+                "technique_id": str(t.technique_id),
+                "state": t.state.value if hasattr(t.state, "value") else str(t.state),
+                "remediation_status": t.remediation_status,
+                "remediation_steps": t.remediation_steps,
+                "remediation_assignee": str(t.remediation_assignee) if t.remediation_assignee else None,
+            }
+            for t in tests
+        ],
+    }