feat: Support structured output with LMStudio

README.md

@@ -39,7 +39,7 @@ auto_session = true
 
 [openai]
 key = sk-...
-model = gpt-4.1-nano-2025-04-14
+`model = gpt-5-nano
 
 [gemini]
 key = ...
@@ -69,8 +69,8 @@ seance chat "What is the speed of light?"
 # Specify a provider for your query
 seance chat "Explain the theory of relativity" --provider gemini
 
-# Use piped content as input
-cat src/seance.nim | seance chat "Explain what this Nim code does."
+# Use piping to write your PR descriptions
+git diff main... | seance chat "Write a conventional commit PR"
 ```
 
 ### 3. Session Management
@@ -104,7 +104,7 @@ This will delete all sessions older than 10 days, or whatever you specify with -
   seance chat "This chat should not be saved." --no_session
   ```
 
-- **Using a JSON Schema**: To force the output to be in a specific JSON format, you can use the `--json` flag. For the Gemini, Anthropic, and OpenAI providers, you can also use the `--schema` flag to provide a JSON schema to which the output must conform.
+- **Using a JSON Schema**: To force the output to be in a specific JSON format, you can use the `--json` flag. For the Gemini, Anthropic, OpenAI, and LMStudio providers, you can also use the `--schema` flag to provide a JSON schema to which the output must conform.
 
   ```bash
   # Create a schema file

seance.nimble

@@ -1,6 +1,6 @@
 # Package
 
-version       = "0.4.0"
+version       = "0.5.0"
 author        = "Emre Şafak"
 description   = "A CLI tool and library for interacting with various LLMs"
 license       = "MIT"

src/seance/providers/lmstudio.nim

@@ -96,15 +96,21 @@ method chat*(provider: LMStudioProvider, messages: seq[ChatMessage], model: Opti
     processedMessages.add(ChatMessage(role: system, content: "Return the response in JSON format."))
 
   var requestBody: string
+  let request = LMStudioChatRequest(model: usedModel, messages: processedMessages)
+  var requestJson = %*request
   if jsonMode:
-    let schemaNode = schema.get(%*{"type": "object"})
-    let request = LMStudioChatRequest(model: usedModel, messages: processedMessages)
-    var requestJson = %*request
-    requestJson["response_format"] = %*{"type": "json_object"}
-    requestBody = $requestJson
-  else:
-    let request = LMStudioChatRequest(model: usedModel, messages: processedMessages)
-    requestBody = $(%*request)
+    if schema.isSome:
+      requestJson["response_format"] = %*{
+        "type": "json_schema",
+        "json_schema": {
+          "name": "json_schema",
+          "strict": true,
+          "schema": schema.get()
+        }
+      }
+    else:
+      requestJson["response_format"] = %*{"type": "json_object"}
+  requestBody = $requestJson
 
   info "LMStudio Request Body: " & requestBody
   debug "curl -X POST " & endpoint & " -H \"Content-Type: application/json\" -d '" & requestBody & "'"

tests/t_providers_lmstudio.nim

@@ -167,3 +167,25 @@ suite "LMStudio Provider":
     let requestJson = parseJson(capturedRequestBody)
     check requestJson["model"].getStr() == "model-2"
     check result.model == "model-2"
+
+  test "chat method sends correct request with json schema":
+    mockHttpResponse = Response(
+      status: "200 OK",
+      bodyStream: newStringStream("""{"choices": [{"message": {"role": "assistant", "content": "{\"tool_code\":\"ls()\"}"}}]}""")
+    )
+
+    let conf = ProviderConfig(key: "", model: none(string), endpoint: none(string))
+    let provider = newProvider(some(LMStudio), some(conf))
+    provider.postRequestHandler = mockPostRequestHandler
+
+    let schema = %*{"type": "object", "properties": {"tool_code": {"type": "string"}}}
+    let result = provider.chat(testMessages, model = none(string), jsonMode = true, schema = some(schema))
+
+    check capturedUrl == DefaultLMStudioEndpoint
+    let requestJson = parseJson(capturedRequestBody)
+    check requestJson.hasKey("response_format")
+    let responseFormat = requestJson["response_format"]
+    check responseFormat["type"].getStr() == "json_schema"
+    check responseFormat["json_schema"]["name"].getStr() == "json_schema"
+    check responseFormat["json_schema"]["strict"].getBool() == true
+    check responseFormat["json_schema"]["schema"] == schema