diff --git a/src/atocore/api/routes.py b/src/atocore/api/routes.py
index b0f23d8..b3e2416 100644
--- a/src/atocore/api/routes.py
+++ b/src/atocore/api/routes.py
@@ -30,6 +30,7 @@ from atocore.interactions.service import (
     list_interactions,
     record_interaction,
 )
+from atocore.engineering.mirror import generate_project_overview
 from atocore.engineering.service import (
     ENTITY_TYPES,
     RELATIONSHIP_TYPES,
@@ -1074,6 +1075,25 @@ def api_create_relationship(req: RelationshipCreateRequest) -> dict:
     }
 
 
+@router.get("/projects/{project_name}/mirror")
+def api_project_mirror(project_name: str) -> dict:
+    """Generate a human-readable project overview from structured data.
+
+    Layer 3 of the AtoCore architecture. The mirror is DERIVED from
+    entities, project state, and memories — it is not canonical truth.
+    Returns markdown that can be rendered, saved to a file, or served
+    as a dashboard page.
+    """
+    from atocore.projects.registry import resolve_project_name as _resolve
+
+    canonical = _resolve(project_name)
+    try:
+        markdown = generate_project_overview(canonical)
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=f"Mirror generation failed: {e}")
+    return {"project": canonical, "format": "markdown", "content": markdown}
+
+
 @router.get("/admin/backup/{stamp}/validate")
 def api_validate_backup(stamp: str) -> dict:
     """Validate that a previously created backup is structurally usable."""
diff --git a/src/atocore/engineering/mirror.py b/src/atocore/engineering/mirror.py
new file mode 100644
index 0000000..55a59fc
--- /dev/null
+++ b/src/atocore/engineering/mirror.py
@@ -0,0 +1,220 @@
+"""Human Mirror — derived readable project views from structured data.
+
+Layer 3 of the AtoCore architecture. Generates human-readable markdown
+pages from the engineering entity graph, Trusted Project State, and
+active memories. These pages are DERIVED — they are not canonical
+machine truth. They are support surfaces for human inspection and
+audit comfort.
+
+The mirror never invents content. Every line traces back to an entity,
+a state entry, or a memory. If the structured data is wrong, the
+mirror is wrong — fix the source, not the page.
+"""
+
+from __future__ import annotations
+
+from atocore.context.project_state import get_state
+from atocore.engineering.service import (
+    get_entities,
+    get_relationships,
+)
+from atocore.memory.service import get_memories
+from atocore.observability.logger import get_logger
+
+log = get_logger("mirror")
+
+
+def generate_project_overview(project: str) -> str:
+    """Generate a full project overview page in markdown."""
+    sections = [
+        _header(project),
+        _state_section(project),
+        _system_architecture(project),
+        _decisions_section(project),
+        _requirements_section(project),
+        _materials_section(project),
+        _vendors_section(project),
+        _active_memories_section(project),
+        _footer(project),
+    ]
+    return "\n\n".join(s for s in sections if s)
+
+
+def _header(project: str) -> str:
+    return (
+        f"# {project} — Project Overview\n\n"
+        f"> This page is auto-generated from AtoCore structured data.\n"
+        f"> It is a **derived view**, not canonical truth. "
+        f"If something is wrong here, fix the source data."
+    )
+
+
+def _state_section(project: str) -> str:
+    entries = get_state(project)
+    if not entries:
+        return ""
+
+    lines = ["## Trusted Project State"]
+    by_category: dict[str, list] = {}
+    for e in entries:
+        by_category.setdefault(e.category.upper(), []).append(e)
+
+    for cat in ["DECISION", "REQUIREMENT", "STATUS", "FACT", "MILESTONE", "CONFIG", "CONTACT"]:
+        items = by_category.get(cat, [])
+        if not items:
+            continue
+        lines.append(f"\n### {cat.title()}")
+        for item in items:
+            value = item.value[:300]
+            lines.append(f"- **{item.key}**: {value}")
+            if item.source:
+                lines.append(f"  *(source: {item.source})*")
+
+    return "\n".join(lines)
+
+
+def _system_architecture(project: str) -> str:
+    systems = get_entities(entity_type="system", project=project)
+    subsystems = get_entities(entity_type="subsystem", project=project)
+    components = get_entities(entity_type="component", project=project)
+    interfaces = get_entities(entity_type="interface", project=project)
+
+    if not systems and not subsystems and not components:
+        return ""
+
+    lines = ["## System Architecture"]
+
+    for system in systems:
+        lines.append(f"\n### {system.name}")
+        if system.description:
+            lines.append(f"{system.description}")
+
+        rels = get_relationships(system.id, direction="outgoing")
+        children = []
+        for rel in rels:
+            if rel.relationship_type == "contains":
+                child = next(
+                    (s for s in subsystems + components if s.id == rel.target_entity_id),
+                    None,
+                )
+                if child:
+                    children.append(child)
+
+        if children:
+            lines.append("\n**Contains:**")
+            for child in children:
+                desc = f" — {child.description}" if child.description else ""
+                lines.append(f"- [{child.entity_type}] **{child.name}**{desc}")
+
+                child_rels = get_relationships(child.id, direction="both")
+                for cr in child_rels:
+                    if cr.relationship_type in ("uses_material", "interfaces_with", "constrained_by"):
+                        other_id = (
+                            cr.target_entity_id
+                            if cr.source_entity_id == child.id
+                            else cr.source_entity_id
+                        )
+                        other = next(
+                            (e for e in get_entities(project=project, limit=200)
+                             if e.id == other_id),
+                            None,
+                        )
+                        if other:
+                            lines.append(
+                                f"  - *{cr.relationship_type}* → "
+                                f"[{other.entity_type}] {other.name}"
+                            )
+
+    return "\n".join(lines)
+
+
+def _decisions_section(project: str) -> str:
+    decisions = get_entities(entity_type="decision", project=project)
+    if not decisions:
+        return ""
+
+    lines = ["## Decisions"]
+    for d in decisions:
+        lines.append(f"\n### {d.name}")
+        if d.description:
+            lines.append(d.description)
+        rels = get_relationships(d.id, direction="outgoing")
+        for rel in rels:
+            if rel.relationship_type == "affected_by_decision":
+                affected = next(
+                    (e for e in get_entities(project=project, limit=200)
+                     if e.id == rel.target_entity_id),
+                    None,
+                )
+                if affected:
+                    lines.append(
+                        f"- Affects: [{affected.entity_type}] {affected.name}"
+                    )
+
+    return "\n".join(lines)
+
+
+def _requirements_section(project: str) -> str:
+    reqs = get_entities(entity_type="requirement", project=project)
+    constraints = get_entities(entity_type="constraint", project=project)
+    if not reqs and not constraints:
+        return ""
+
+    lines = ["## Requirements & Constraints"]
+    for r in reqs:
+        lines.append(f"- **{r.name}**: {r.description}" if r.description else f"- **{r.name}**")
+    for c in constraints:
+        lines.append(f"- [constraint] **{c.name}**: {c.description}" if c.description else f"- [constraint] **{c.name}**")
+
+    return "\n".join(lines)
+
+
+def _materials_section(project: str) -> str:
+    materials = get_entities(entity_type="material", project=project)
+    if not materials:
+        return ""
+
+    lines = ["## Materials"]
+    for m in materials:
+        desc = f" — {m.description}" if m.description else ""
+        lines.append(f"- **{m.name}**{desc}")
+
+    return "\n".join(lines)
+
+
+def _vendors_section(project: str) -> str:
+    vendors = get_entities(entity_type="vendor", project=project)
+    if not vendors:
+        return ""
+
+    lines = ["## Vendors"]
+    for v in vendors:
+        desc = f" — {v.description}" if v.description else ""
+        lines.append(f"- **{v.name}**{desc}")
+
+    return "\n".join(lines)
+
+
+def _active_memories_section(project: str) -> str:
+    memories = get_memories(project=project, active_only=True, limit=20)
+    if not memories:
+        return ""
+
+    lines = ["## Active Memories"]
+    for m in memories:
+        conf = f" (conf: {m.confidence:.2f})" if m.confidence < 1.0 else ""
+        refs = f" | refs: {m.reference_count}" if m.reference_count > 0 else ""
+        lines.append(f"- [{m.memory_type}]{conf}{refs} {m.content[:200]}")
+
+    return "\n".join(lines)
+
+
+def _footer(project: str) -> str:
+    from datetime import datetime, timezone
+
+    now = datetime.now(timezone.utc).strftime("%Y-%m-%d %H:%M UTC")
+    return (
+        f"---\n\n"
+        f"*Generated by AtoCore Human Mirror at {now}. "
+        f"This is a derived view — not canonical truth.*"
+    )