Download a model via REST API

Usage

lms_download(
  model,
  quantization = NULL,
  host = "http://localhost:1234",
  ...,
  token = NULL
)

Arguments

model: Character. The model to download. Accepts model catalog identifiers (e.g., "openai/gpt-oss-20b") and exact Hugging Face links. Must be one name, given as a single string.
quantization: Character. Optional. Quantization level of the model to download (e.g., "Q4_K_M"). Only supported for Hugging Face links.
host: Character. The host address of the local server. Defaults to "http://localhost:1234".
...: Additional arguments passed to the request.
token: Character or NULL. An API token for a server that requires authentication. NULL reads the rlmstudio.token option and then the RLMSTUDIO_API_TOKEN environment variable. See rlmstudio_token.

Value

A character string containing the download job_id, or "already_downloaded", invisibly, if the model is already downloaded. The call aborts with rlmstudio_bad_response when the reply holds neither a job_id string nor the status "already_downloaded". It also aborts when the reply is not a JSON object whose status is a string.

Server not running

Functions that call the LM Studio REST API open a TCP connection to the hostname and port named in host before they send the request. A function that checks its own arguments does that first, so a bad model, job_id, input, inputs, or schema aborts with an argument message and no condition class even when the server is down. A condition of class rlmstudio_no_server is raised when that connection cannot be opened. A refused connection raises it. So do an address the package cannot parse and a hostname that does not resolve. An address that neither accepts nor refuses the connection also raises it. That case waits for the operating system to give up, which can take a minute. Start the server with lms_server_start(), or give host the address that your server listens on.

The check reads the port and nothing else. Any process holding that port accepts the connection, so the condition is not raised even though no LM Studio server is there. The call then does not raise rlmstudio_no_server, and what it does depends on what answers. On a status-200 body that does not parse as JSON, the chat functions, lms_embed(), list_models(), lms_load(), lms_download(), lms_download_status(), and lms_unload_all() raise rlmstudio_bad_response. lms_unload() does not read the body, so it can report success. A body that parses as JSON but has another shape can come back unchanged with simplify = FALSE. With simplify = TRUE, the chat functions and lms_embed() raise rlmstudio_bad_response for it. list_models() raises it for a model list with another shape, and so do lms_unload_all() and lms_load() without force = TRUE, which read that list. lms_load(), lms_download(), and lms_download_status() raise it for a reply of their own with another shape, such as {}. A process that does not answer in HTTP gives an httr2_failure error. Use lms_server_ready() for the stronger test: it asks the host for a model list and reports TRUE only for a model list that list_models() can read.

lms_chat_batch() checks the server once before its first input, and lms_chat() checks it again for each input. If that check finds the server gone during the batch, the batch aborts with rlmstudio_no_server, and no request goes out after that. The condition then carries a results field, a list as long as inputs. Its elements before the lost input hold the values that format = "list" returns for those inputs. The element of the lost input and every element after it are NULL. The check before the first input adds no results field. A connection that fails after the check passes, such as a server that stops during a request, raises an httr2_failure error instead. That error aborts the batch and carries no results field.

API failure

A condition of class rlmstudio_api_error is raised when a REST call returns a response that the wrapper treats as a failure. The condition carries a status field, which holds the HTTP response status as an integer.

lms_chat_batch() does not abort on it. The element of the failed input holds the condition, or NA where the result is text, and the batch warns once and goes on. See the details of lms_chat_batch().

Malformed response

A condition of class rlmstudio_bad_response is raised when the server answers with a status the wrapper accepts and a body the wrapper cannot read. It is raised where a wrapper checks the body before it reshapes it, rather than indexing straight into whatever arrived. Ten functions raise it: lms_embed(), lms_chat(), lms_chat_native(), lms_chat_openresponses(), lms_chat_openai(), list_models(), lms_load(), lms_download(), lms_download_status(), and lms_unload_all(). lms_chat() raises it through the chat function it calls. lms_unload_all() raises it through list_models(), and so does lms_load() unless force = TRUE.

All ten raise it for a status-200 body that does not parse as JSON, such as an HTML page from a proxy, JSON text that stops part way, or an empty body. In the functions that take simplify, the body is parsed before simplify is read, so the condition is raised whatever simplify is. The body is parsed by its content and not by its Content-Type header, so valid JSON under text/plain is read as JSON. The body is read as JSON text and nothing else. A body whose text is a URL or the path of a file does not parse, and the package does not fetch the URL or read the file. The message says that the body did not parse as JSON and that something other than LM Studio may be answering on the host. It does not hold the body text.

list_models() also raises it for a status-200 model list with the wrong shape. lms_unload_all() and lms_load() without force = TRUE raise it through list_models(). A model list must follow four rules. Each field is read by its exact name, so a field named keyX does not stand in for key.

The body is a JSON object whose models field is an array. The array can be empty.
Each entry of models is a JSON object. Its type and key are strings, and its loaded_instances is an array.
The size_bytes of an entry is a number, or absent, or null.
Each entry of loaded_instances is a JSON object whose id is a string with a character that is not whitespace.

The rules are checked before the type and loaded filters, so an entry that the filters drop can still raise the condition. The message names the field or entry that broke a rule. lms_server_ready() applies the same rules and returns FALSE for a body that breaks one.

lms_load(), lms_download(), and lms_download_status() also raise it for a status-200 reply of their own with the wrong shape. Each reply must follow the rule of its function. Each field is read by its exact name. The rules check the type of a field and not its value, with two exceptions. The status of a load reply must be "loaded", and a download reply whose status is "already_downloaded" needs no job_id.

A reply of lms_load() is a JSON object whose status is the string "loaded". With echo_load_config = TRUE, its load_config is also a JSON object.
A reply of lms_download() is a JSON object whose status is a string. If the status is not "already_downloaded", its job_id is a string.
A reply of lms_download_status() is a JSON object whose job_id and status are strings. Its total_size_bytes, downloaded_bytes, and bytes_per_second are each a number, or absent, or null.

The message names the field that broke the rule, or it says that the body is not a JSON object. It also says that something other than LM Studio may be answering on the host.

lms_embed() raises it on an embeddings block it cannot trust. The vectors it returns are placed by the index that the response reports, so a block with a missing, repeated, or out-of-range index would otherwise pair a vector with the wrong text and give back a matrix that is silently wrong.

lms_chat_native() and lms_chat_openresponses() raise it with simplify = TRUE when the reply holds no readable answer text. Both read the answer from the items of type "message" in the output array. They raise it when output is missing, empty, or not an array, or when an item in it is not a JSON object. They also raise it when no item has the type "message", as in a reply that holds only reasoning or a tool call. The text of a message must be one string. For lms_chat_native() that is the content of the item. For lms_chat_openresponses() it is the text of each part of type "output_text". For lms_chat_openresponses() only, the content of each message must be an array of JSON objects, and the messages together must hold at least one "output_text" part.

With simplify = TRUE and logprobs = TRUE, lms_chat_openresponses() also raises it for a logprobs value that breaks one of these rules. The logprobs value of each "output_text" part is checked. A logprobs value, token, logprob, or top_logprobs that is null or absent passes its rule. A null step or candidate breaks rule 2 or rule 5.

The value is an array.
Each step in the array is a JSON object.
The token of a step is a string.
The logprob of a step is a number.
The top_logprobs of a step is an array of JSON objects.
The token and logprob of each of those objects follow rules 3 and 4.

The parts are checked in order, then the steps of a part, then the candidates of a step, one at a time. Within a step, rules 3 and 4 and the array test of rule 5 come before the candidates. The message names the first broken rule that this order reaches. These checks run only after the text of every "output_text" part is read, so a reply that also has a bad text in any part gets the text message. Parts of other types, such as a refusal, are not checked, and with logprobs = FALSE no part is checked. Fields are read by their exact names, so a field whose name only starts with the one asked for, such as tokenX, reads as absent and gives NA in the data frame.

Apart from a body that does not parse as JSON, lms_chat_openai() raises it in three cases, all only with simplify = TRUE. The first case is a response whose choices field is missing, empty, or not an array, or whose first element is not a JSON object with a message object in it, so there is no reply to read. This case is raised with or without a schema, and with logprobs = TRUE as well. The second case is a reply that does not parse. A schema was given, logprobs = FALSE, and the reply content is not one string of valid JSON. The third case is reply content that is not one string, such as null, a missing content field, a number, or an array. A reply that holds only a tool call has null content. This case is raised without a schema, and with logprobs = TRUE with or without one. In the second and third cases, if the server reports the finish reason "length", the token limit cut the reply off. The message then says so and names max_tokens.

With simplify = TRUE, lms_chat_native(), lms_chat_openresponses(), and lms_chat_openai() also raise it for a body that is a bare JSON value, such as 5, "s", or true. The message says that the response body is not a JSON object. A body of null gets the message about its missing output or choices field instead. lms_chat() can raise the condition through all three chat functions.

The condition carries a status field, which holds the HTTP response status as an integer. Today the status is always 200: each of these functions reads the body only after a 200, and reports every other status as an rlmstudio_api_error instead. A condition from lms_chat_openai() also carries two more fields. The content field holds the reply content, and the finish_reason field holds the finish reason of the first choice. Both are NULL for a response with no choices. In the third case, content holds the value that was read, which is NULL for null or missing content. For the second and third cases, the message names the content field, so you can read what the model wrote without a second request. The other messages of the chat functions and lms_embed() name simplify = FALSE, which returns the body unchanged, with one exception. A body that did not parse as JSON is checked before that argument is read, so its message points at the host instead. For such a body, the content and finish_reason fields of a condition from lms_chat_openai() are NULL.

Examples

if (FALSE) { # \dontrun{
lms_server_start()

# Download a model by its HuggingFace identifier
job_id <- lms_download("google/gemma-3-1b")

# Download with a specific quantization level
lms_download("google/gemma-3-1b", quantization = "4bit")
} # }