proto: add model and base_url to OpenAI provider, deprecate top-level model

Add model and base_url fields to the OpenAI provider configuration.
Keep the existing top-level model field but mark it as deprecated for
backward compatibility. The new provider.openai.model field takes
precedence when both are set.

This allows for a gradual migration path while making the schema cleaner
and more extensible for future providers with different model requirements.

Changes:
- Added optional model field to Provider.OpenAI message
- Added optional base_url field to Provider.OpenAI message
- Marked top-level model field as deprecated in AIAgent, AIAgentCreate, and AIAgentUpdate
- Updated comments to indicate migration path
- Regenerated all protobuf code and OpenAPI specs

Co-Authored-By: Claude <[email protected]>

Author: birdayz

backend/pkg/protogen/redpanda/api/dataplane/v1alpha3/ai_agent.pb.go

@@ -4375,7 +4375,7 @@ paths:
         content:
           multipart/form-data:
             schema:
-              example: '{"name":"redact-orders", "input_topic_name":"orders", "output_topic_names":["orders-redacted"], "environment_variables":[{"key":"LOGGER_LEVEL", "value":"DEBUG"}]}'
+              example: '{"name":"redact-orders","input_topic_name":"orders","output_topic_names":["orders-redacted"],"environment_variables":[{"key":"LOGGER_LEVEL","value":"DEBUG"}]}'
               properties:
                 metadata:
                   $ref: '#/components/schemas/DeployTransformRequest'

frontend/src/protogen/redpanda/api/dataplane/v1alpha3/ai_agent_pb.ts

@@ -22,6 +22,9 @@ components:
           description: Map of MCP servers that this AI agent can use.
           type: object
         model:
+          description: |-
+            Deprecated: Use provider.openai.model instead. This field is kept for backward compatibility.
+            If both are set, provider.openai.model takes precedence.
           type: string
         provider:
           $ref: '#/components/schemas/AIAgent.Provider'
@@ -49,7 +52,6 @@ components:
         - display_name
         - system_prompt
         - provider
-        - model
         - service_account
       type: object
     AIAgent.MCPServer:
@@ -68,6 +70,13 @@ components:
       properties:
         api_key:
           type: string
+        base_url:
+          type: string
+        model:
+          description: |-
+            Model to use for this AI agent. If not set, falls back to the deprecated top-level model field.
+            Preferred over the top-level model field when both are set.
+          type: string
       required:
         - api_key
       type: object
@@ -115,6 +124,9 @@ components:
           description: Map of MCP servers that this AI agent can use.
           type: object
         model:
+          description: |-
+            Deprecated: Use provider.openai.model instead. This field is kept for backward compatibility.
+            If both are set, provider.openai.model takes precedence.
           type: string
         provider:
           $ref: '#/components/schemas/AIAgent.Provider'
@@ -134,7 +146,6 @@ components:
         - display_name
         - system_prompt
         - provider
-        - model
         - service_account
       type: object
     AIAgentUpdate:
@@ -154,6 +165,9 @@ components:
           description: Map of MCP servers that this AI agent can use.
           type: object
         model:
+          description: |-
+            Deprecated: Use provider.openai.model instead. This field is kept for backward compatibility.
+            If both are set, provider.openai.model takes precedence.
           type: string
         provider:
           $ref: '#/components/schemas/AIAgent.Provider'

proto/gen/openapi/openapi.json

@@ -5608,7 +5608,7 @@ paths:
         content:
           multipart/form-data:
             schema:
-              example: '{"name":"redact-orders","input_topic_name":"orders","output_topic_names":["orders-redacted"],"environment_variables":[{"key":"LOGGER_LEVEL","value":"DEBUG"}]}'
+              example: '{"name":"redact-orders", "input_topic_name":"orders", "output_topic_names":["orders-redacted"], "environment_variables":[{"key":"LOGGER_LEVEL", "value":"DEBUG"}]}'
               properties:
                 metadata:
                   $ref: '#/components/schemas/DeployTransformRequest'

proto/gen/openapi/openapi.v1alpha2.json

@@ -50,11 +50,12 @@ message AIAgent {
     (google.api.field_behavior) = REQUIRED,
     (buf.validate.field).required = true
   ];
+  // Deprecated: Use provider.openai.model instead. This field is kept for backward compatibility.
+  // If both are set, provider.openai.model takes precedence.
   string model = 7 [
-    (google.api.field_behavior) = REQUIRED,
     (google.api.field_behavior) = IMMUTABLE,
-    (buf.validate.field).required = true,
-    (buf.validate.field).string.max_len = 128
+    (buf.validate.field).string.max_len = 128,
+    deprecated = true
   ];
 
   // Map of MCP servers that this AI agent can use.
@@ -95,6 +96,13 @@ message AIAgent {
         (buf.validate.field).required = true,
         (buf.validate.field).string.pattern = "^\\$\\{secrets\\.[A-Za-z_][A-Za-z0-9_]*(\\.[A-Za-z_][A-Za-z0-9_]*)?\\}$"
       ];
+      // Model to use for this AI agent. If not set, falls back to the deprecated top-level model field.
+      // Preferred over the top-level model field when both are set.
+      string model = 2 [
+        (google.api.field_behavior) = IMMUTABLE,
+        (buf.validate.field).string.max_len = 128
+      ];
+      string base_url = 3;
     }
 
     oneof provider {
@@ -374,11 +382,12 @@ message AIAgentCreate {
     (google.api.field_behavior) = REQUIRED,
     (buf.validate.field).required = true
   ];
+  // Deprecated: Use provider.openai.model instead. This field is kept for backward compatibility.
+  // If both are set, provider.openai.model takes precedence.
   string model = 6 [
-    (google.api.field_behavior) = REQUIRED,
     (google.api.field_behavior) = IMMUTABLE,
-    (buf.validate.field).required = true,
-    (buf.validate.field).string.max_len = 128
+    (buf.validate.field).string.max_len = 128,
+    deprecated = true
   ];
 
   // Map of MCP servers that this AI agent can use.
@@ -502,7 +511,12 @@ message AIAgentUpdate {
   // LLM configuration settings for the AI agent.
   AIAgent.Provider provider = 4;
 
-  string model = 6 [(buf.validate.field).string.max_len = 128];
+  // Deprecated: Use provider.openai.model instead. This field is kept for backward compatibility.
+  // If both are set, provider.openai.model takes precedence.
+  string model = 6 [
+    (buf.validate.field).string.max_len = 128,
+    deprecated = true
+  ];
 
   // Map of MCP servers that this AI agent can use.
   map<string, AIAgent.MCPServer> mcp_servers = 7;