diff --git a/config/project-registry.json b/config/project-registry.json
index a93a473..d987eda 100644
--- a/config/project-registry.json
+++ b/config/project-registry.json
@@ -15,7 +15,7 @@
     {
       "id": "p04-gigabit",
       "aliases": ["p04", "gigabit", "gigaBIT"],
-      "description": "Curated staged docs for the P04 GigaBIT project.",
+      "description": "Curated staged docs for the P04 GigaBIT mirror architecture and OTA optics project.",
       "ingest_roots": [
         {
           "source": "vault",
diff --git a/docs/current-state.md b/docs/current-state.md
index f1a9d8c..3196942 100644
--- a/docs/current-state.md
+++ b/docs/current-state.md
@@ -43,6 +43,7 @@ now includes a first curated ingestion batch for the active projects.
   - template
   - proposal preview
   - approved registration
+  - safe update of existing project registrations
   - refresh
 - env-driven storage and deployment paths
 - Dalidou Docker deployment foundation
@@ -98,9 +99,9 @@ The Dalidou instance already contains:
 Current live stats after the latest documentation sync and active-project ingest
 passes:
 
-- `source_documents`: 35
-- `source_chunks`: 560
-- `vectors`: 560
+- `source_documents`: 36
+- `source_chunks`: 568
+- `vectors`: 568
 
 The broader long-term corpus is still not fully populated yet. Wider project and
 vault ingestion remains a deliberate next step rather than something already
@@ -162,10 +163,19 @@ The source refresh model now has a concrete foundation in code:
 - the API can return a registration template
 - the API can preview a registration without mutating state
 - the API can persist an approved registration
+- the API can update an existing registered project without changing its canonical id
 - the API can refresh one registered project at a time
 
 This lifecycle is now coherent end to end for normal use.
 
+The first live update pass on an existing registered project has also now been
+verified against `p04-gigabit`:
+
+- the registration description can be updated safely
+- the canonical project id remains unchanged
+- refresh still behaves cleanly after the update
+- `context/build` still returns useful project-specific context afterward
+
 ## Reliability Baseline
 
 The runtime has now been hardened in a few practical ways:
diff --git a/docs/next-steps.md b/docs/next-steps.md
index 5ef68ae..d0ef1b9 100644
--- a/docs/next-steps.md
+++ b/docs/next-steps.md
@@ -104,6 +104,8 @@ The next batch is successful if:
 
 - OpenClaw can use AtoCore naturally when context is needed
 - OpenClaw can also register a new project cleanly before refreshing it
+- existing project registrations can be refined safely before refresh when the
+  staged source set evolves
 - AtoCore answers correctly for the active project set
 - retrieval surfaces the seeded project docs instead of mostly AtoCore meta-docs
 - trusted project state remains concise and high confidence
diff --git a/docs/project-registration-policy.md b/docs/project-registration-policy.md
index f94e4ca..6ecabcb 100644
--- a/docs/project-registration-policy.md
+++ b/docs/project-registration-policy.md
@@ -2,7 +2,8 @@
 
 ## Purpose
 
-This document defines the normal path for adding a new project to AtoCore.
+This document defines the normal path for adding a new project to AtoCore and
+for safely updating an existing registration later.
 
 The goal is to make `register + refresh` the standard workflow instead of
 relying on long custom ingestion prompts every time.
@@ -18,6 +19,13 @@ Registration means:
 - the staged source roots for that project are defined
 - AtoCore and OpenClaw can later refresh that project consistently
 
+Updating a project means:
+
+- aliases can be corrected or expanded
+- the short registry description can be improved
+- ingest roots can be adjusted deliberately
+- the canonical project id remains stable
+
 ## Required Fields
 
 Each project registry entry must include:
@@ -82,6 +90,17 @@ For a new project:
 7. verify retrieval and context quality
 8. only later promote stable facts into Trusted Project State
 
+For an existing registered project:
+
+1. inspect the current entry with:
+   - `GET /projects`
+   - or `atocore.sh projects`
+2. update the registration if aliases, description, or roots need refinement:
+   - `PUT /projects/{id}`
+3. verify the updated entry
+4. refresh the project again
+5. verify retrieval and context quality did not regress
+
 ## What Not To Do
 
 Do not:
@@ -106,4 +125,5 @@ Other lifecycle endpoints:
 
 - `POST /projects/proposal`
 - `POST /projects/register`
+- `PUT /projects/{id}`
 - `POST /projects/{id}/refresh`
diff --git a/src/atocore/api/routes.py b/src/atocore/api/routes.py
index 11f86c2..d723eaf 100644
--- a/src/atocore/api/routes.py
+++ b/src/atocore/api/routes.py
@@ -39,6 +39,7 @@ from atocore.projects.registry import (
     list_registered_projects,
     register_project,
     refresh_registered_project,
+    update_project,
 )
 from atocore.retrieval.retriever import retrieve
 from atocore.retrieval.vector_store import get_vector_store
@@ -77,6 +78,12 @@ class ProjectRegistrationProposalRequest(BaseModel):
     ingest_roots: list[dict]
 
 
+class ProjectUpdateRequest(BaseModel):
+    aliases: list[str] | None = None
+    description: str | None = None
+    ingest_roots: list[dict] | None = None
+
+
 class QueryRequest(BaseModel):
     prompt: str
     top_k: int = 10
@@ -217,6 +224,23 @@ def api_project_registration(req: ProjectRegistrationProposalRequest) -> dict:
         raise HTTPException(status_code=400, detail=str(e))
 
 
+@router.put("/projects/{project_name}")
+def api_project_update(project_name: str, req: ProjectUpdateRequest) -> dict:
+    """Update an existing project registration."""
+    try:
+        return update_project(
+            project_name=project_name,
+            aliases=req.aliases,
+            description=req.description,
+            ingest_roots=req.ingest_roots,
+        )
+    except ValueError as e:
+        detail = str(e)
+        if detail.startswith("Unknown project"):
+            raise HTTPException(status_code=404, detail=detail)
+        raise HTTPException(status_code=400, detail=detail)
+
+
 @router.post("/projects/{project_name}/refresh", response_model=ProjectRefreshResponse)
 def api_refresh_project(project_name: str, purge_deleted: bool = False) -> ProjectRefreshResponse:
     """Refresh one registered project from its configured ingest roots."""
diff --git a/src/atocore/projects/registry.py b/src/atocore/projects/registry.py
index 613b8a1..021cd2f 100644
--- a/src/atocore/projects/registry.py
+++ b/src/atocore/projects/registry.py
@@ -122,6 +122,78 @@ def register_project(
     }
 
 
+def update_project(
+    project_name: str,
+    aliases: list[str] | tuple[str, ...] | None = None,
+    description: str | None = None,
+    ingest_roots: list[dict] | tuple[dict, ...] | None = None,
+) -> dict:
+    """Update an existing project registration in the registry file."""
+    existing = get_registered_project(project_name)
+    if existing is None:
+        raise ValueError(f"Unknown project: {project_name}")
+
+    final_aliases = _normalize_aliases(aliases) if aliases is not None else list(existing.aliases)
+    final_description = description.strip() if description is not None else existing.description
+    final_roots = (
+        _normalize_ingest_roots(ingest_roots)
+        if ingest_roots is not None
+        else [asdict(root) for root in existing.ingest_roots]
+    )
+    if not final_roots:
+        raise ValueError("At least one ingest root is required")
+
+    collisions = _find_name_collisions(
+        existing.project_id,
+        final_aliases,
+        exclude_project_id=existing.project_id,
+    )
+    if collisions:
+        collision_names = ", ".join(collision["name"] for collision in collisions)
+        raise ValueError(f"Project update has collisions: {collision_names}")
+
+    updated_entry = {
+        "id": existing.project_id,
+        "aliases": final_aliases,
+        "description": final_description,
+        "ingest_roots": final_roots,
+    }
+
+    resolved_roots = []
+    for root in final_roots:
+        source_ref = ProjectSourceRef(
+            source=root["source"],
+            subpath=root["subpath"],
+            label=root.get("label", ""),
+        )
+        resolved_path = _resolve_ingest_root(source_ref)
+        resolved_roots.append(
+            {
+                **root,
+                "path": str(resolved_path),
+                "exists": resolved_path.exists(),
+                "is_dir": resolved_path.is_dir(),
+            }
+        )
+
+    registry_path = _config.settings.resolved_project_registry_path
+    payload = _load_registry_payload(registry_path)
+    payload["projects"] = [
+        updated_entry if str(entry.get("id", "")).strip() == existing.project_id else entry
+        for entry in payload.get("projects", [])
+    ]
+    _write_registry_payload(registry_path, payload)
+
+    return {
+        "project": updated_entry,
+        "resolved_ingest_roots": resolved_roots,
+        "collisions": [],
+        "registry_path": str(registry_path),
+        "valid": True,
+        "status": "updated",
+    }
+
+
 def load_project_registry() -> list[RegisteredProject]:
     """Load project registry entries from JSON config."""
     registry_path = _config.settings.resolved_project_registry_path
@@ -294,13 +366,19 @@ def _validate_unique_project_names(projects: list[RegisteredProject]) -> None:
             seen[key] = project.project_id
 
 
-def _find_name_collisions(project_id: str, aliases: list[str]) -> list[dict]:
+def _find_name_collisions(
+    project_id: str,
+    aliases: list[str],
+    exclude_project_id: str | None = None,
+) -> list[dict]:
     collisions: list[dict] = []
     existing = load_project_registry()
     requested_names = [project_id, *aliases]
     for requested in requested_names:
         requested_key = requested.lower()
         for project in existing:
+            if exclude_project_id is not None and project.project_id == exclude_project_id:
+                continue
             project_names = [project.project_id, *project.aliases]
             if requested_key in {name.lower() for name in project_names}:
                 collisions.append(
diff --git a/tests/test_api_storage.py b/tests/test_api_storage.py
index 67cafe1..7492bf3 100644
--- a/tests/test_api_storage.py
+++ b/tests/test_api_storage.py
@@ -294,3 +294,102 @@ def test_project_register_endpoint_rejects_collisions(tmp_data_dir, monkeypatch)
 
     assert response.status_code == 400
     assert "collisions" in response.json()["detail"]
+
+
+def test_project_update_endpoint_persists_changes(tmp_data_dir, monkeypatch):
+    vault_dir = tmp_data_dir / "vault-source"
+    drive_dir = tmp_data_dir / "drive-source"
+    config_dir = tmp_data_dir / "config"
+    project_dir = vault_dir / "incoming" / "projects" / "p04-gigabit"
+    project_dir.mkdir(parents=True)
+    drive_dir.mkdir()
+    config_dir.mkdir()
+
+    registry_path = config_dir / "project-registry.json"
+    registry_path.write_text(
+        """
+{
+  "projects": [
+    {
+      "id": "p04-gigabit",
+      "aliases": ["p04", "gigabit"],
+      "description": "Old description",
+      "ingest_roots": [
+        {"source": "vault", "subpath": "incoming/projects/p04-gigabit"}
+      ]
+    }
+  ]
+}
+""".strip(),
+        encoding="utf-8",
+    )
+
+    monkeypatch.setenv("ATOCORE_VAULT_SOURCE_DIR", str(vault_dir))
+    monkeypatch.setenv("ATOCORE_DRIVE_SOURCE_DIR", str(drive_dir))
+    monkeypatch.setenv("ATOCORE_PROJECT_REGISTRY_PATH", str(registry_path))
+    config.settings = config.Settings()
+
+    client = TestClient(app)
+    response = client.put(
+        "/projects/p04",
+        json={
+            "aliases": ["p04", "gigabit", "gigabit-project"],
+            "description": "Updated P04 docs",
+        },
+    )
+
+    assert response.status_code == 200
+    body = response.json()
+    assert body["status"] == "updated"
+    assert body["project"]["aliases"] == ["p04", "gigabit", "gigabit-project"]
+    assert body["project"]["description"] == "Updated P04 docs"
+
+
+def test_project_update_endpoint_rejects_collisions(tmp_data_dir, monkeypatch):
+    vault_dir = tmp_data_dir / "vault-source"
+    drive_dir = tmp_data_dir / "drive-source"
+    config_dir = tmp_data_dir / "config"
+    vault_dir.mkdir()
+    drive_dir.mkdir()
+    config_dir.mkdir()
+
+    registry_path = config_dir / "project-registry.json"
+    registry_path.write_text(
+        """
+{
+  "projects": [
+    {
+      "id": "p04-gigabit",
+      "aliases": ["p04", "gigabit"],
+      "ingest_roots": [
+        {"source": "vault", "subpath": "incoming/projects/p04-gigabit"}
+      ]
+    },
+    {
+      "id": "p05-interferometer",
+      "aliases": ["p05", "interferometer"],
+      "ingest_roots": [
+        {"source": "vault", "subpath": "incoming/projects/p05-interferometer"}
+      ]
+    }
+  ]
+}
+""".strip(),
+        encoding="utf-8",
+    )
+
+    monkeypatch.setenv("ATOCORE_VAULT_SOURCE_DIR", str(vault_dir))
+    monkeypatch.setenv("ATOCORE_DRIVE_SOURCE_DIR", str(drive_dir))
+    monkeypatch.setenv("ATOCORE_PROJECT_REGISTRY_PATH", str(registry_path))
+    config.settings = config.Settings()
+
+    client = TestClient(app)
+    response = client.put(
+        "/projects/p04",
+        json={
+            "aliases": ["p04", "interferometer"],
+        },
+    )
+
+    assert response.status_code == 400
+    assert "collisions" in response.json()["detail"]
diff --git a/tests/test_project_registry.py b/tests/test_project_registry.py
index d03b2b1..a922ee6 100644
--- a/tests/test_project_registry.py
+++ b/tests/test_project_registry.py
@@ -10,6 +10,7 @@ from atocore.projects.registry import (
     list_registered_projects,
     register_project,
     refresh_registered_project,
+    update_project,
 )
 
 
@@ -381,3 +382,111 @@ def test_register_project_rejects_collisions(tmp_path, monkeypatch):
             raise AssertionError("Expected collision to prevent project registration")
     finally:
         config.settings = original_settings
+
+
+def test_update_project_persists_description_and_aliases(tmp_path, monkeypatch):
+    vault_dir = tmp_path / "vault"
+    drive_dir = tmp_path / "drive"
+    config_dir = tmp_path / "config"
+    staged = vault_dir / "incoming" / "projects" / "p04-gigabit"
+    staged.mkdir(parents=True)
+    drive_dir.mkdir()
+    config_dir.mkdir()
+    registry_path = config_dir / "project-registry.json"
+    registry_path.write_text(
+        json.dumps(
+            {
+                "projects": [
+                    {
+                        "id": "p04-gigabit",
+                        "aliases": ["p04", "gigabit"],
+                        "description": "Old description",
+                        "ingest_roots": [
+                            {
+                                "source": "vault",
+                                "subpath": "incoming/projects/p04-gigabit",
+                                "label": "Primary docs",
+                            }
+                        ],
+                    }
+                ]
+            }
+        ),
+        encoding="utf-8",
+    )
+
+    monkeypatch.setenv("ATOCORE_VAULT_SOURCE_DIR", str(vault_dir))
+    monkeypatch.setenv("ATOCORE_DRIVE_SOURCE_DIR", str(drive_dir))
+    monkeypatch.setenv("ATOCORE_PROJECT_REGISTRY_PATH", str(registry_path))
+
+    original_settings = config.settings
+    try:
+        config.settings = config.Settings()
+        result = update_project(
+            "p04",
+            aliases=["p04", "gigabit", "gigabit-project"],
+            description="Updated P04 project docs",
+        )
+    finally:
+        config.settings = original_settings
+
+    assert result["status"] == "updated"
+    assert result["project"]["id"] == "p04-gigabit"
+    assert result["project"]["aliases"] == ["p04", "gigabit", "gigabit-project"]
+    assert result["project"]["description"] == "Updated P04 project docs"
+
+    payload = json.loads(registry_path.read_text(encoding="utf-8"))
+    assert payload["projects"][0]["aliases"] == ["p04", "gigabit", "gigabit-project"]
+    assert payload["projects"][0]["description"] == "Updated P04 project docs"
+
+
+def test_update_project_rejects_colliding_aliases(tmp_path, monkeypatch):
+    vault_dir = tmp_path / "vault"
+    drive_dir = tmp_path / "drive"
+    config_dir = tmp_path / "config"
+    vault_dir.mkdir()
+    drive_dir.mkdir()
+    config_dir.mkdir()
+    registry_path = config_dir / "project-registry.json"
+    registry_path.write_text(
+        json.dumps(
+            {
+                "projects": [
+                    {
+                        "id": "p04-gigabit",
+                        "aliases": ["p04", "gigabit"],
+                        "ingest_roots": [
+                            {"source": "vault", "subpath": "incoming/projects/p04-gigabit"}
+                        ],
+                    },
+                    {
+                        "id": "p05-interferometer",
+                        "aliases": ["p05", "interferometer"],
+                        "ingest_roots": [
+                            {"source": "vault", "subpath": "incoming/projects/p05-interferometer"}
+                        ],
+                    },
+                ]
+            }
+        ),
+        encoding="utf-8",
+    )
+
+    monkeypatch.setenv("ATOCORE_VAULT_SOURCE_DIR", str(vault_dir))
+    monkeypatch.setenv("ATOCORE_DRIVE_SOURCE_DIR", str(drive_dir))
+    monkeypatch.setenv("ATOCORE_PROJECT_REGISTRY_PATH", str(registry_path))
+
+    original_settings = config.settings
+    try:
+        config.settings = config.Settings()
+        try:
+            update_project(
+                "p04-gigabit",
+                aliases=["p04", "interferometer"],
+            )
+        except ValueError as exc:
+            assert "collisions" in str(exc)
+        else:
+            raise AssertionError("Expected collision to prevent project update")
+    finally:
+        config.settings = original_settings