ENG-736 - Delete model_prefixes: route models off the harness's own fetched-or-shipped list

backend/druks/harnesses/base.py

@@ -68,14 +68,9 @@ class Harness(ABC):
     name: str
     # Harness identity + shipped config, the seed source for the per-harness
     # ``HarnessSettings`` row the operator then tunes. Subclasses set provider,
-    # model_prefixes, models and default_model; effort/timeout default to the
-    # shipped values.
+    # models and default_model; effort/timeout default to the shipped values.
     provider: ClassVar[str]
-    # The model-name namespaces this harness runs — a model routes to the harness
-    # that owns its namespace, so a new model in a known one runs with no release.
-    model_prefixes: ClassVar[tuple[str, ...]]
-    # Suggested models for the settings picker and the ``default_model`` seed —
-    # advisory: any string in a matching namespace runs.
+    # Suggested models for the settings picker and the ``default_model`` seed.
     models: ClassVar[tuple[str, ...]]
     default_model: ClassVar[str]
     # The provider's model-list endpoint the picker refresh fetches.
@@ -87,12 +82,6 @@ class Harness(ABC):
     _TOKEN_URL: str
     _CLIENT_ID: str
 
-    @classmethod
-    def has_model(cls, model: str) -> bool:
-        """Whether ``model`` runs on this harness — matched by name namespace, so
-        a new model in a known namespace routes with no release."""
-        return model == cls.name or model.startswith(cls.model_prefixes)
-
     def __init__(
         self,
         *,

backend/druks/harnesses/claude.py

@@ -36,7 +36,6 @@ class ClaudeHarness(Harness):
     # (``--output-format stream-json``), so the transcript is the stdout.
     name = "claude"
     provider = "anthropic"
-    model_prefixes = ("claude-",)
     models = ("claude-opus-4-7", "claude-sonnet-4-6", "claude-haiku-4-5")
     default_model = "claude-opus-4-7"
     model_discovery_url = "https://api.anthropic.com/v1/models?limit=100"

backend/druks/harnesses/codex.py

@@ -271,7 +271,6 @@ class CodexHarness(Harness):
     # symmetric with claude. session.jsonl is still snapshotted for cost.
     name = "codex"
     provider = "openai"
-    model_prefixes = ("gpt-", "o1", "o3", "o4")
     models = ("gpt-5.5",)
     default_model = "gpt-5.5"
     # ``client_version`` is required and lower-bounds the list (the server

backend/druks/harnesses/registry.py

@@ -1,3 +1,5 @@
+from druks.user_settings.models import HarnessSettings
+
 from .base import Harness
 from .exceptions import HarnessError
 
@@ -17,10 +19,12 @@ def get_harness(name: str) -> type[Harness] | None:
 
 
 def get_harness_for_model(model: str) -> type[Harness]:
-    """The harness that runs ``model``, matched by name namespace — a model in a
-    known namespace routes even if it postdates this release. A miss means no
-    installed harness owns its namespace."""
-    for harness in get_harnesses():
-        if harness.has_model(model):
-            return harness
+    """The harness that runs ``model`` from its fetched-or-shipped model list.
+
+    A miss raises loudly; namespace-shaped models do not route until a fetch
+    stores them on the harness settings row.
+    """
+    for row in HarnessSettings.all():
+        if model == row.name or any(m["id"] == model for m in row.allowed_models):
+            return row.harness
     raise HarnessError(f"no harness runs model {model!r}")

backend/druks/harnesses/subprocess.py

@@ -16,9 +16,9 @@ def read_result_json(output_path: Path, *, name: str) -> dict[str, Any]:
     except FileNotFoundError as error:
         raise HarnessError(f"{name} did not write result JSON.") from error
 
-    if text.startswith("```"):
+    if text[:3] == "```":
         lines = text.splitlines()
-        if lines and lines[0].startswith("```"):
+        if lines and lines[0][:3] == "```":
             lines = lines[1:]
         if lines and lines[-1].strip() == "```":
             lines = lines[:-1]

backend/druks/user_settings/routes.py

@@ -7,8 +7,9 @@
 from druks.durable.engine import apply_schedules
 from druks.extensions.loader import get_extension, iter_extensions
 from druks.extensions.registry import workflows
+from druks.harnesses.exceptions import HarnessError
 from druks.harnesses.models import HarnessConnection
-from druks.harnesses.registry import get_harnesses
+from druks.harnesses.registry import get_harness_for_model, get_harnesses
 from druks.notifications.models import Destination
 
 from . import reads
@@ -67,11 +68,19 @@ async def update_harness_settings(
 ) -> HarnessResponse:
     harness, row = _resolve_harness(name)
     updates = body.model_dump(exclude_unset=True, by_alias=False)
-    if "model" in updates and not harness.has_model(updates["model"]):
-        raise HTTPException(
-            status_code=422,
-            detail=f"{updates['model']!r} is not a {harness.name} model.",
-        )
+    if "model" in updates:
+        try:
+            resolved = get_harness_for_model(updates["model"])
+        except HarnessError as exc:
+            raise HTTPException(
+                status_code=422,
+                detail=f"{updates['model']!r} is not a {harness.name} model.",
+            ) from exc
+        if resolved.name != harness.name:
+            raise HTTPException(
+                status_code=422,
+                detail=f"{updates['model']!r} is not a {harness.name} model.",
+            )
     _validate_effort(updates.get("effort"))
     _validate_timeout(updates.get("timeout"))
     if updates:
@@ -114,14 +123,17 @@ async def get_extension_settings() -> ExtensionsSettingsResponse:
 
 
 # An agent's model override is client data — reject a model no installed harness
-# can run (nothing owns its namespace). A model new to a known namespace passes,
-# so new models need no release.
+# lists.
 def _validate_model(value: str | None) -> None:
-    if value is not None and not any(harness.has_model(value) for harness in get_harnesses()):
+    if value is None:
+        return
+    try:
+        get_harness_for_model(value)
+    except HarnessError as exc:
         raise HTTPException(
             status_code=422,
             detail=f"No installed harness runs model {value!r}.",
-        )
+        ) from exc
 
 
 def _validate_effort(value: str | None) -> None:

backend/tests/test_harness_model_routing.py

@@ -3,21 +3,40 @@
 from druks.harnesses.codex import CodexHarness
 from druks.harnesses.exceptions import HarnessError
 from druks.harnesses.registry import get_harness_for_model
+from druks.user_settings.models import HarnessSettings
+from druks.user_settings.routes import _validate_model
+from fastapi import HTTPException
 
 
-def test_new_model_in_known_namespace_routes_without_a_release():
-    # Models absent from the shipped ``models`` tuples still route by namespace,
-    # so a provider's new model runs the day it ships.
-    assert get_harness_for_model("claude-opus-5") is ClaudeHarness
-    assert get_harness_for_model("gpt-6") is CodexHarness
-    assert get_harness_for_model("o4-mini") is CodexHarness
+def test_shipped_tuple_fallback_routes_shipped_models(db_session):
+    assert get_harness_for_model("claude-opus-4-7") is ClaudeHarness
+    assert get_harness_for_model("gpt-5.5") is CodexHarness
 
 
-def test_family_token_routes_to_its_harness():
+def test_fetched_list_routes_provider_models(db_session):
+    HarnessSettings.require("claude").models_fetched = [
+        {"id": "claude-fable-5", "label": "Claude Fable 5"}
+    ]
+    db_session.flush()
+
+    assert get_harness_for_model("claude-fable-5") is ClaudeHarness
+
+
+def test_bare_harness_name_routes(db_session):
     assert get_harness_for_model("claude") is ClaudeHarness
     assert get_harness_for_model("codex") is CodexHarness
 
 
-def test_unroutable_model_raises():
+def test_unknown_model_raises_harness_error(db_session):
     with pytest.raises(HarnessError):
         get_harness_for_model("llama-3-70b")
+    with pytest.raises(HarnessError):
+        get_harness_for_model("claude-opus-99")
+
+
+def test_settings_reject_model_missing_from_lists_returns_422(db_session):
+    with pytest.raises(HTTPException) as error:
+        _validate_model("llama-3-70b")
+
+    assert error.value.status_code == 422
+    assert error.value.detail == "No installed harness runs model 'llama-3-70b'."