llm_ollama 0.5.0

Ollama backend implementation for LLM interactions. Provides streaming chat, embeddings, tool calling, vision support, and model management.

llm_ollama

Ollama backend implementation for LLM interactions in Dart.

Available on pub.dev.

Part of the dart-llm ecosystem.

Features

• Streaming chat responses
• Tool/function calling
• Vision (image) support
• Embeddings
• Thinking mode support
• Structured output (JSON mode and JSON Schema via the native format field)
• Model management (list, pull, show, version)
• Multi-instance pooling with health checks and per-model routing (OllamaPool)

Streaming Reliability Guarantees

• NDJSON chunk-boundary-safe parsing: stream frames are buffered across transport chunks and parsed only when newline-terminated
• Bounded malformed-line retries: parser tolerates up to 3 consecutive malformed non-empty lines
• Explicit failure on persistent corruption: parser throws LLMApiException after retry budget exhaustion (no silent infinite dropping)

Installation

dependencies:
  llm_ollama: ^0.3.2

Prerequisites

You need Ollama running locally or on a server. Install from ollama.com.

# Pull a model
ollama pull qwen3:0.6b

Usage

Basic Chat

import 'package:llm_ollama/llm_ollama.dart';

final repo = OllamaChatRepository(baseUrl: 'http://localhost:11434');

final stream = repo.streamChat('qwen3:0.6b', messages: [
  LLMMessage(role: LLMRole.user, content: 'Hello!'),
]);

await for (final chunk in stream) {
  print(chunk.message?.content ?? '');
}

With Thinking Mode

final stream = repo.streamChat('qwen3:0.6b',
  messages: messages,
  think: true, // Enable thinking mode
);

await for (final chunk in stream) {
  if (chunk.message?.thinking != null) {
    print('Thinking: ${chunk.message!.thinking}');
  }
  print(chunk.message?.content ?? '');
}

Ollama's think field accepts a bool or a level string, and has no numeric token budget. llm_ollama sends:

Options	wire think
think: false	false
think: true, no knobs	true (bool — keeps bool-only models working)
think: true, reasoningEffort: none	false
minimal / low	"low"
medium	"medium"
high / xhigh	"high"
max	"max"
think: true, reasoningBudget: N	level derived via reasoningEffortForBudget

An explicit reasoningEffort wins over reasoningBudget, and backendOptions['think'] overrides everything. Note that some models accept only bools (level strings error server-side) while gpt-oss ignores bools and requires a level — levels are therefore only sent when you explicitly set one of the knobs.

Tool Calling

final stream = repo.streamChat('qwen3:0.6b',
  messages: messages,
  tools: [MyTool()],
);

Vision

import 'dart:convert';
import 'dart:io';

final imageBytes = await File('image.png').readAsBytes();
final base64Image = base64Encode(imageBytes);

final stream = repo.streamChat('llama3.2-vision:11b', messages: [
  LLMMessage(
    role: LLMRole.user,
    content: 'What is in this image?',
    images: [base64Image],
  ),
]);

Structured Output

Use LLMChatOptions.responseFormat to request structured JSON output:

import 'package:llm_core/llm_core.dart';

// Simple JSON mode — works on all models
final stream = repo.streamChat(
  'qwen3:0.6b',
  messages: [LLMMessage(role: LLMRole.user, content: 'List three fruits as JSON.')],
  options: const LLMChatOptions(responseFormat: JsonFormat()),
);

// JSON Schema mode — requires a model with structured_outputs capability
// Check support first:
final modelRepo = OllamaRepository();
final supportsSchema = await modelRepo.supportsStructuredOutput('llama3.2');

const schema = {
  'type': 'object',
  'properties': {
    'name': {'type': 'string'},
    'age': {'type': 'integer'},
  },
  'required': ['name', 'age'],
};

final stream = repo.streamChat(
  'llama3.2',
  messages: [LLMMessage(role: LLMRole.user, content: 'Return a person object.')],
  options: const LLMChatOptions(
    responseFormat: JsonSchemaFormat(name: 'Person', schema: schema),
  ),
);

Embeddings

final embeddings = await repo.embed(
  model: 'nomic-embed-text',
  messages: ['Hello world', 'Goodbye world'],
);

Non-Streaming Response

Get a complete response without streaming:

final response = await repo.chatResponse('qwen3:0.6b', messages: [
  LLMMessage(role: LLMRole.user, content: 'Hello!'),
]);

print(response.content);
print('Tokens: ${response.evalCount}');

Using LLMChatOptions

Encapsulate all options in a single object:

import 'package:llm_core/llm_core.dart';

final options = LLMChatOptions(
  think: true,
  tools: [MyTool()],
  toolAttempts: 5,
  timeout: Duration(minutes: 5),
  retryConfig: RetryConfig(maxAttempts: 3),
);

final stream = repo.streamChat('qwen3:0.6b', messages: messages, options: options);

Python-Style Parity Options

llm_ollama defaults to automatic tool execution for backward compatibility. If you want ollama-python style manual tool loops, disable auto-execution and consume toolCalls directly from streamed chunks.

final stream = repo.streamChat(
  'qwen3:0.6b',
  messages: messages,
  tools: [MyTool()],
  options: const LLMChatOptions(
    autoExecuteTools: false, // Manual tool loop
  ),
);

await for (final chunk in stream) {
  final toolCalls = chunk.message?.toolCalls ?? const [];
  if (toolCalls.isNotEmpty) {
    // Execute tools yourself, append tool messages, then call streamChat again.
  }
}

You can also pass Ollama chat fields supported by ollama-python:

final stream = repo.streamChat(
  'qwen3:0.6b',
  messages: messages,
  options: const LLMChatOptions(
    backendOptions: {
      'format': 'json',
      'options': {'temperature': 0},
      'keep_alive': '5m', // or keepAlive
    },
  ),
);

Model Management

final ollamaRepo = OllamaRepository(baseUrl: 'http://localhost:11434');

// List models
final models = await ollamaRepo.models();

// Show model info
final info = await ollamaRepo.showModel('qwen3:0.6b');

// Pull a model
await for (final progress in ollamaRepo.pullModel('qwen3:0.6b')) {
  print('${progress.status}: ${progress.progress * 100}%');
}

// Get version
final version = await ollamaRepo.version();

Advanced Configuration

Builder Pattern

Use the builder for complex configurations:

import 'package:llm_core/llm_core.dart';

final repo = OllamaChatRepository.builder()
  .baseUrl('http://localhost:11434')
  .maxToolAttempts(10)
  .retryConfig(RetryConfig(
    maxAttempts: 5,
    initialDelay: Duration(seconds: 1),
    maxDelay: Duration(seconds: 30),
  ))
  .timeoutConfig(TimeoutConfig(
    connectionTimeout: Duration(seconds: 10),
    readTimeout: Duration(minutes: 3),
    totalTimeout: Duration(minutes: 10),
  ))
  .build();

Retry Configuration

Configure automatic retries for failed requests:

import 'package:llm_core/llm_core.dart';

final repo = OllamaChatRepository(
  baseUrl: 'http://localhost:11434',
  retryConfig: RetryConfig(
    maxAttempts: 3,
    initialDelay: Duration(seconds: 1),
    maxDelay: Duration(seconds: 30),
    retryableStatusCodes: [429, 500, 502, 503, 504],
  ),
);

Timeout Configuration

Configure timeouts for different scenarios:

import 'package:llm_core/llm_core.dart';

final repo = OllamaChatRepository(
  baseUrl: 'http://localhost:11434',
  timeoutConfig: TimeoutConfig(
    connectionTimeout: Duration(seconds: 10),
    readTimeout: Duration(minutes: 2),
    totalTimeout: Duration(minutes: 10),
    readTimeoutForLargePayloads: Duration(minutes: 5), // For large images
  ),
);

Capabilities

capabilitiesForModel reports what the backend implements. To find out what a specific model supports, ask the server:

final repo = OllamaRepository(baseUrl: 'http://localhost:11434');

if (await repo.supportsVision('llama3.2-vision')) { /* attach images */ }
if (await repo.supportsStructuredOutput('qwen3:0.6b')) { /* pass a schema */ }

streamChat runs the vision check for you: passing images to a model whose /api/show capabilities do not include vision throws VisionNotSupportedException before any request is sent.

Pool

Route across several Ollama servers — useful when models are pinned to specific GPUs:

final pool = OllamaPool(
  instances: [
    OllamaInstanceConfig(
      baseUrl: 'http://bigcard:11434',
      maxConcurrent: 1,
      exclusiveModels: ['llama3.3:70b'],
      embeddingIsolation: EmbeddingIsolation.unloadFirst,
    ),
    OllamaInstanceConfig(
      baseUrl: 'http://smallcard:11434',
      maxConcurrent: 3,
      preferredModels: ['qwen3:0.6b'],
    ),
  ],
  modelConfigs: [
    OllamaModelConfig(pattern: 'llama3.3:*', maxConcurrent: 1),
  ],
  healthCheck: const HealthCheckConfig(),
);

final stream = pool.streamChat('qwen3:0.6b', messages: messages);

OllamaPool is a drop-in LLMChatRepository with routing, per-instance concurrency limits, optional per-model limits (pattern supports * globs), queue limits, and /api/version health checks. Unhealthy instances are excluded from routing until they recover.

EmbeddingIsolation addresses the VRAM problem specific to Ollama: an instance serving one large chat model has to swap it out to run an embedding model. unloadFirst injects keep_alive: '0' so the embedding model is released immediately; dedicated routes every embed call to an instance tagged preferEmbedding.

Inspect live state with pool.stats(), which returns an OllamaPoolStats carrying per-instance health, in-flight and queued counts. A pool that cannot place a request throws OllamaNoEligibleInstanceException, OllamaQueueFullException or OllamaQueueTimeoutException. There is also a fluent OllamaPool.builder().

Resource cleanup

Every repository owns an HTTP client unless you pass one in; whoever creates the client closes it.

final repo = OllamaChatRepository(baseUrl: 'http://localhost:11434');
// ... use it ...
repo.close();

final pool = OllamaPool(instances: [...]);
// ... use it ...
pool.dispose();   // stops health checks and closes owned per-instance clients

A client you supply is never closed for you.

Notes

• Retries are off by default. Pass a RetryConfig to enable them.
• batchEmbed does not batch. Ollama's /api/embed takes one input at a time, so batchEmbed delegates to embed. It exists for interface parity.
• Portable LLMChatOptions fields (temperature, topP, topK, maxOutputTokens, stopSequences) are mapped into Ollama's nested options object for you — you only need raw backendOptions['options'] for knobs without a portable equivalent.

Testing

dart test --exclude-tags integration

OLLAMA_BASE_URL=http://localhost:11434 dart test --tags integration

Integration tests read OLLAMA_BASE_URL from the environment or a local .env (see .env.example). They need the models named in test/integration/test_helpers.dart pulled on the target server.