diff --git a/README.md b/README.md
index 64a17f3..de47959 100644
--- a/README.md
+++ b/README.md
@@ -54,7 +54,7 @@ By default the reference tool uses:
 
 ```text
 ~/.canned-prompts/catalog
-~/.canned-prompts/registry
+~/.canned-prompts/default    # the default registry
 ```
 
 Override them with:
diff --git a/reference/README.md b/reference/README.md
index 4632366..c7a2abe 100644
--- a/reference/README.md
+++ b/reference/README.md
@@ -29,7 +29,7 @@ Default locations:
 
 ```text
 ~/.canned-prompts/catalog
-~/.canned-prompts/registry
+~/.canned-prompts/default
 ```
 
 A **registry** stores packages flat, because an id is unambiguous within one
@@ -49,12 +49,16 @@ A **catalog** is namespaced by registry, because identity is registry-scoped
 For example:
 
 ```text
-~/.canned-prompts/catalog/house/practice/pqrst-estimate/0.1.0/
-~/.canned-prompts/catalog/local/practice/pqrst-estimate/0.1.0/
+~/.canned-prompts/catalog/default/practice/pqrst-estimate/1.0.0/
+~/.canned-prompts/catalog/local/practice/pqrst-estimate/1.0.0/
 ```
 
 A registry's name comes from its optional `registry.yaml`, and otherwise from
-its directory basename. `add` takes a package from a path rather than a
+its directory basename — which is why the default registry directory is called
+`default` and not `registry`: the basename reaches qualified references,
+catalog paths and index rows, and `registry:practice/thing` reads poorly. A
+store left at the old `~/.canned-prompts/registry` is reported with the command
+to move it, rather than a fresh empty one being created beside it. `add` takes a package from a path rather than a
 registry, so it files it under `local` (override with `--as`).
 
 Commands that take an ID accept a bare id or a qualified `<registry>:<id>`.
diff --git a/reference/canned_prompts.py b/reference/canned_prompts.py
index 953daf4..fd9ffc9 100755
--- a/reference/canned_prompts.py
+++ b/reference/canned_prompts.py
@@ -55,9 +55,30 @@ def default_catalog() -> Path:
 
 
 def default_registry() -> Path:
+    # Named "default" rather than "registry" because § 20.1 takes a registry's
+    # name from its directory basename, and that name reaches qualified
+    # references, catalog paths and index rows.
+    return home_dir() / "default"
+
+
+def legacy_registry() -> Path:
     return home_dir() / "registry"
 
 
+def check_legacy_registry(registry: Path) -> None:
+    """Refuse to silently start a fresh default store beside a populated one."""
+    if registry.resolve() != default_registry().resolve():
+        return
+    if registry.exists() or not legacy_registry().is_dir():
+        return
+    raise CannedPromptError(
+        f"the default registry moved from {legacy_registry()} to {registry}, so "
+        f"a registry's basename names it (§ 20.1) rather than reading as "
+        f"'registry:'. Move it:\n    mv {legacy_registry()} {registry}\n"
+        f"or keep using the old one explicitly with --registry {legacy_registry()}"
+    )
+
+
 def read_manifest(package_dir: Path) -> dict[str, Any]:
     manifest_path = package_dir / "prompt.yaml"
     if not manifest_path.is_file():
@@ -858,6 +879,7 @@ def cmd_publish(args: argparse.Namespace) -> None:
     src = Path(args.path)
     manifest = validate_package(src)
     registry = Path(args.registry).expanduser()
+    check_legacy_registry(registry)
     name = registry_name(registry) if registry.is_dir() else None
 
     policy, claim = namespace_policy(registry, manifest["id"]) if registry.is_dir() else ("open", None)
@@ -879,6 +901,7 @@ def cmd_publish(args: argparse.Namespace) -> None:
 
 def cmd_install(args: argparse.Namespace) -> None:
     registry = Path(args.registry).expanduser()
+    check_legacy_registry(registry)
     catalog = Path(args.catalog).expanduser()
     name = registry_name(registry)
 
diff --git a/reference/tests/test_canned_prompts.py b/reference/tests/test_canned_prompts.py
index f96d599..c2abe58 100644
--- a/reference/tests/test_canned_prompts.py
+++ b/reference/tests/test_canned_prompts.py
@@ -914,3 +914,31 @@ def test_empty_inclusion_is_not_flagged() -> None:
         origins={"a": "included from x/empty", "b": "included from x/b"},
     )
     assert cp.duplicate_inclusions(resolution) == []
+
+
+# --- default registry naming (CANP-WP-0003) ---
+
+def test_default_registry_is_named_default(tmp_path: Path, monkeypatch) -> None:
+    monkeypatch.setenv("CANNED_PROMPTS_HOME", str(tmp_path))
+    assert cp.default_registry().name == "default"
+
+
+def test_legacy_registry_is_reported_not_ignored(tmp_path: Path, monkeypatch) -> None:
+    """A fresh empty store beside a populated one would be worse than the wart."""
+    monkeypatch.setenv("CANNED_PROMPTS_HOME", str(tmp_path))
+    (tmp_path / "registry").mkdir()
+    with pytest.raises(cp.CannedPromptError, match="default registry moved"):
+        cp.check_legacy_registry(cp.default_registry())
+
+
+def test_no_complaint_once_migrated(tmp_path: Path, monkeypatch) -> None:
+    monkeypatch.setenv("CANNED_PROMPTS_HOME", str(tmp_path))
+    (tmp_path / "default").mkdir()
+    (tmp_path / "registry").mkdir()
+    cp.check_legacy_registry(cp.default_registry())
+
+
+def test_explicit_registry_path_is_never_second_guessed(tmp_path: Path, monkeypatch) -> None:
+    monkeypatch.setenv("CANNED_PROMPTS_HOME", str(tmp_path))
+    (tmp_path / "registry").mkdir()
+    cp.check_legacy_registry(tmp_path / "somewhere-else")
diff --git a/workplans/CANP-WP-0003-registry-naming-residual.md b/workplans/CANP-WP-0003-registry-naming-residual.md
index 8c5e2a4..96dbe47 100644
--- a/workplans/CANP-WP-0003-registry-naming-residual.md
+++ b/workplans/CANP-WP-0003-registry-naming-residual.md
@@ -4,7 +4,7 @@ type: workplan
 title: "Default registry name reads as 'registry:'"
 domain: agents
 repo: canned-prompts
-status: proposed
+status: finished
 owner: codex
 topic_slug: practice
 created: "2026-09-06"
@@ -20,7 +20,7 @@ Residual from `CANP-WP-0002` (`origin: residual`, `origin_ref: CANP-WP-0002`).
 
 ```task
 id: CANP-WP-0003-T01
-status: todo
+status: done
 priority: low
 state_hub_task_id: "ead2d409-2b80-5f50-9f0f-a397822ba2ae"
 ```
@@ -54,3 +54,28 @@ Options worth weighing:
    `registry.yaml` — already exists and is documented.
 
 Option 3 is the current state. Pick deliberately rather than by default.
+
+## Outcome
+
+**Decision (operator, 2026-09-06): option 2** — rename the default directory to
+`~/.canned-prompts/default`, so the § 20.1 basename rule produces a good name
+with no special case, no file written into the user's store, and no second
+naming mechanism.
+
+**The cost of deferring had been understated.** The workplan recorded this as
+reading poorly in one output line. It is not only display: the name reaches
+qualified references, the on-disk catalog layout (`catalog/registry/...`) and
+`index.yaml` rows (`registry: registry`). Once packages are installed and
+inclusions recorded, changing it is a migration rather than an edit — which is
+an argument for deciding early, not late.
+
+Delivered:
+
+- `default_registry()` returns `~/.canned-prompts/default`.
+- `check_legacy_registry` refuses to silently create a fresh empty store beside
+  a populated `~/.canned-prompts/registry`. It names the exact `mv`, and the
+  `--registry` flag for keeping the old one. Silently starting empty would have
+  been worse than the wart being fixed.
+- The check fires only for the default path; an explicitly passed `--registry`
+  is never second-guessed.
+- Docs updated in both READMEs. Tests 95 → 99.