V2 fabric

.gitignore

@@ -53,3 +53,4 @@ logs/
 csv/*.csv
 screenshots/
 *.png
+.mcp.json

backend/agent_builder/routes.py

@@ -7,21 +7,21 @@
 Action layer: marshals HTTP ↔ service, no business logic.
 """
 
-from pydantic import ValidationError
-from quart import Blueprint, jsonify, request
-
 import asyncio
 import json
 
+from pydantic import ValidationError
+from quart import Blueprint, jsonify, request
+
+from .engine.event_bus import agent_event_bus
+from .engine.prompt_builder import DEFAULT_OUTPUT_SCHEMA
 from .models import (
     AgentDefinitionCreate,
     AgentDefinitionUpdate,
     AgentRunCreate,
     CriteriaType,
     RunStatus,
 )
-from .engine.prompt_builder import DEFAULT_OUTPUT_SCHEMA
-from .engine.event_bus import agent_event_bus
 
 agent_builder_bp = Blueprint("agent_builder", __name__)
 
@@ -119,6 +119,21 @@ async def workbench_ui_config():
                 "input_schema": op.get_mcp_input_schema(),
             })
 
+    llm_catalog = {
+        "backend": "unknown",
+        "provider": None,
+        "default_model": "",
+        "fallback_models": [],
+        "available_models": [],
+        "source": "unavailable",
+    }
+    try:
+        from llm_service import get_llm_service
+
+        llm_catalog = get_llm_service().get_model_catalog()
+    except Exception:
+        pass
+
     return jsonify({
         "module": "agent_fabric",
         "version": "2",
@@ -132,6 +147,7 @@ async def workbench_ui_config():
             "max_tokens": 4096,
         },
         "llm_config_fields": ["model", "temperature", "recursion_limit", "max_tokens", "output_instructions", "output_schema"],
+        "llm": llm_catalog,
         "default_output_schema": DEFAULT_OUTPUT_SCHEMA,
         "endpoints": endpoints,
     })

backend/agent_builder/tests/test_e2e.py

@@ -15,9 +15,10 @@
 sys.path.insert(0, str(Path(__file__).resolve().parent.parent.parent))
 
 import app as backend_app_module
+from workbench_integration import _tool_registry
+
 from agent_builder import WorkbenchService
 from agent_builder.routes import configure_blueprint
-from workbench_integration import _tool_registry
 
 
 class _ToolCallMessage:
@@ -105,6 +106,8 @@ async def test_create_run_and_evaluate_agent(self) -> None:
                 data = await resp.get_json()
                 self.assertIn("tool_called", data["criteria_types"])
                 self.assertIn("completed", data["run_statuses"])
+                self.assertIn("llm", data)
+                self.assertIn("available_models", data["llm"])
 
                 # List tools
                 resp = await client.get("/api/workbench/tools")

backend/llm_service.py

@@ -152,6 +152,49 @@ async def health_check(self) -> bool:
         except Exception as e:
             logger.warning(f"LLM health check failed ({self._backend}): {e}")
             return False
+
+    def get_model_catalog(self) -> dict[str, Any]:
+        """Return backend/model metadata for UI model selection."""
+        fallback_models = list(getattr(self, '_fallback_models', []))
+        configured_models = [self.model, *fallback_models]
+        available_models: list[str] = []
+        source = "configured"
+        provider = None
+
+        if self._backend == "litellm":
+            provider = self.model.split("/", 1)[0] if "/" in self.model else None
+            try:
+                import litellm
+
+                discovered = litellm.get_valid_models(
+                    custom_llm_provider=provider,
+                    check_provider_endpoint=False,
+                )
+                if discovered:
+                    available_models = [m for m in discovered if isinstance(m, str) and m.strip()]
+                    source = "litellm"
+            except Exception as exc:
+                logger.warning("Failed to discover LiteLLM models: %s", exc)
+
+        merged_models: list[str] = []
+        seen: set[str] = set()
+        for model_name in [*configured_models, *available_models]:
+            if not isinstance(model_name, str):
+                continue
+            normalized = model_name.strip()
+            if not normalized or normalized in seen:
+                continue
+            merged_models.append(normalized)
+            seen.add(normalized)
+
+        return {
+            "backend": self._backend,
+            "provider": provider,
+            "default_model": self.model,
+            "fallback_models": fallback_models,
+            "available_models": merged_models,
+            "source": source,
+        }
 
     async def structured_chat(
         self,

backend/tests/test_llm_service.py

@@ -6,18 +6,18 @@
 """
 
 import os
-import pytest
 from unittest.mock import AsyncMock, MagicMock, patch
-from pydantic import BaseModel, Field
 
-from llm_service import LLMService, get_llm_service
+import pytest
 from kba_exceptions import (
-    LLMUnavailableError,
-    LLMTimeoutError,
-    LLMRateLimitError,
     LLMAuthenticationError,
+    LLMRateLimitError,
+    LLMTimeoutError,
+    LLMUnavailableError,
 )
 from kba_output_models import KBAOutputSchema
+from llm_service import LLMService, get_llm_service
+from pydantic import BaseModel, Field
 
 
 # Test Pydantic Schema
@@ -137,6 +137,43 @@ async def test_health_check_litellm(self):
             assert result is True
 
 
+class TestLLMServiceModelCatalog:
+    """Test model catalog exposure for UI selection."""
+
+    def test_model_catalog_uses_litellm_discovery(self):
+        service = LLMService(model='github_copilot/gpt-4o', backend='litellm')
+        service._fallback_models = ['github_copilot/gpt-4o-mini']
+
+        with patch('litellm.get_valid_models') as mock_get_valid_models:
+            mock_get_valid_models.return_value = ['github_copilot/gpt-4o', 'github_copilot/claude-sonnet-4']
+
+            catalog = service.get_model_catalog()
+
+        assert catalog['backend'] == 'litellm'
+        assert catalog['provider'] == 'github_copilot'
+        assert catalog['default_model'] == 'github_copilot/gpt-4o'
+        assert catalog['fallback_models'] == ['github_copilot/gpt-4o-mini']
+        assert catalog['available_models'] == [
+            'github_copilot/gpt-4o',
+            'github_copilot/gpt-4o-mini',
+            'github_copilot/claude-sonnet-4',
+        ]
+        assert catalog['source'] == 'litellm'
+
+    def test_model_catalog_falls_back_to_configured_models(self):
+        service = LLMService(model='github_copilot/gpt-4o', backend='litellm')
+        service._fallback_models = ['github_copilot/gpt-4o-mini']
+
+        with patch('litellm.get_valid_models', side_effect=Exception('boom')):
+            catalog = service.get_model_catalog()
+
+        assert catalog['available_models'] == [
+            'github_copilot/gpt-4o',
+            'github_copilot/gpt-4o-mini',
+        ]
+        assert catalog['source'] == 'configured'
+
+
 class TestLLMServiceStructuredOutputOpenAI:
     """Test structured output generation with OpenAI backend"""
 
@@ -505,8 +542,9 @@ async def mock_acompletion(**kwargs):
     def test_fallback_chain_deduplication(self):
         """Test that fallback chain deduplicates the primary model"""
         with patch.dict(os.environ, {"LITELLM_FALLBACK_MODELS": "github_copilot/gpt-4o,github_copilot/claude-sonnet-4,github_copilot/gpt-4o"}):
-            import llm_service
             from importlib import reload
+
+            import llm_service
             reload(llm_service)
 
             service = llm_service.LLMService(model='github_copilot/gpt-4o', backend='litellm')

backend/tests/test_workbench_integration_e2e.py

@@ -104,6 +104,8 @@ async def test_create_run_and_evaluate_agent_with_csv_tool(self) -> None:
                 self.assertIn("/api/workbench/runs/{run_id}/evaluate", endpoint_paths)
                 self.assertIn("tool_called", ui_config_data["criteria_types"])
                 self.assertIn("completed", ui_config_data["run_statuses"])
+                self.assertIn("llm", ui_config_data)
+                self.assertIn("available_models", ui_config_data["llm"])
 
                 tools_resp = await client.get("/api/workbench/tools")
                 self.assertEqual(tools_resp.status_code, 200)

frontend/src/features/workbench/AgentCreateForm.jsx

@@ -1,23 +1,25 @@
 import {
-  Button,
-  Card,
-  Checkbox,
-  Combobox,
-  Field,
-  Input,
-  Option,
-  Text,
-  Textarea,
-  makeStyles,
-  tokens,
+    Button,
+    Card,
+    Checkbox,
+    Combobox,
+    Dropdown,
+    Field,
+    Input,
+    Option,
+    Text,
+    Textarea,
+    makeStyles,
+    tokens,
 } from '@fluentui/react-components'
 import { useEffect, useState } from 'react'
 import {
-  createWorkbenchAgent,
-  improvePrompt,
-  suggestOutputSchema,
-  updateWorkbenchAgent,
+    createWorkbenchAgent,
+    improvePrompt,
+    suggestOutputSchema,
+    updateWorkbenchAgent,
 } from '../../services/api'
+import { buildModelOptions } from './modelOptions'
 import SchemaEditor from './SchemaEditor'
 
 const useStyles = makeStyles({
@@ -120,6 +122,7 @@ const EMPTY_FORM = {
   name: '',
   description: '',
   systemPrompt: '',
+  model: '',
   requiresInput: false,
   requiredInputDescription: '',
   showInMenu: false,
@@ -137,13 +140,14 @@ function formDataFromAgent(agent) {
     name: agent.name || '',
     description: agent.description || '',
     systemPrompt: agent.system_prompt || '',
+    model: agent.model || '',
     requiresInput: Boolean(agent.requires_input),
     requiredInputDescription: agent.required_input_description || '',
     showInMenu: Boolean(agent.show_in_menu),
   }
 }
 
-export default function AgentCreateForm({ tools, onAgentCreated, initialData }) {
+export default function AgentCreateForm({ tools, onAgentCreated, initialData, modelOptions = [], serviceDefaultModel = '' }) {
   const styles = useStyles()
   const isEditing = Boolean(initialData?.id)
 
@@ -175,6 +179,7 @@ export default function AgentCreateForm({ tools, onAgentCreated, initialData })
       name: tpl.name,
       description: tpl.description,
       systemPrompt: tpl.system_prompt,
+      model: '',
       requiresInput: Boolean(tpl.requires_input),
       requiredInputDescription: tpl.required_input_description || '',
       showInMenu: Boolean(tpl.show_in_menu),
@@ -286,6 +291,7 @@ export default function AgentCreateForm({ tools, onAgentCreated, initialData })
       name: formData.name.trim(),
       description: formData.description.trim(),
       system_prompt: formData.systemPrompt.trim(),
+      model: formData.model.trim(),
       requires_input: formData.requiresInput,
       required_input_description: formData.requiresInput
         ? formData.requiredInputDescription.trim()
@@ -325,6 +331,9 @@ export default function AgentCreateForm({ tools, onAgentCreated, initialData })
   const submitLabel = isEditing
     ? (submitting ? 'Saving...' : 'Save Agent')
     : (submitting ? 'Creating...' : 'Create Agent')
+  const resolvedModelOptions = buildModelOptions(modelOptions, formData.model)
+  const selectedModelOption = formData.model || '__service_default__'
+  const modelDisplayValue = formData.model || (serviceDefaultModel ? `Service default (${serviceDefaultModel})` : 'Service default')
 
   return (
     <div className={styles.grid}>
@@ -427,6 +436,26 @@ export default function AgentCreateForm({ tools, onAgentCreated, initialData })
             />
           </Field>
           {fieldErrors.systemPrompt && <Text>{fieldErrors.systemPrompt}</Text>}
+          <Field label="Model">
+            <Dropdown
+              data-testid="workbench-agent-model-select"
+              value={modelDisplayValue}
+              selectedOptions={[selectedModelOption]}
+              onOptionSelect={(_, data) => {
+                const nextModel = data.optionValue === '__service_default__' ? '' : (data.optionValue || '')
+                setFormData((prev) => ({ ...prev, model: nextModel }))
+              }}
+            >
+              <Option value="__service_default__">
+                {serviceDefaultModel ? `Service default (${serviceDefaultModel})` : 'Service default'}
+              </Option>
+              {resolvedModelOptions.map((modelName) => (
+                <Option key={modelName} value={modelName}>
+                  {modelName}
+                </Option>
+              ))}
+            </Dropdown>
+          </Field>
           <Button
             data-testid="workbench-improve-prompt-button"
             disabled={improvingPrompt || !formData.systemPrompt.trim()}