lm-lib/README.md

lm-lib

lm-lib is a modular Java library for building LLM-powered applications on top of OpenAI-compatible APIs. It has two main responsibilities:

• A client layer for model profiles, chat and text completions, streaming, reasoning capture, token and cost accounting, caching, retries, and interceptors
• An agent runtime for prompt templating, conversation orchestration, branching, merging, grading, and execution tracing

The library exists to keep model integration and multi-step orchestration out of application code. Instead of manually wiring REST requests, prompt formatting, cache checks, token counting, and agent flow control in every project, you configure profiles and compose agents while lm-lib handles the repetitive infrastructure.

Overview

lm-lib is designed for applications that need more than single prompt-response calls. It supports direct completion use cases, but it is especially useful when you need structured multi-step flows such as classification, planning, fan-out analysis, synthesis, grading, and feedback loops.

Current provider support is centered on OpenAI-compatible endpoints, including local servers that expose the same API shape. The library supports both chat completions and legacy text completions, with model-specific prompt strategies for text completion models.

Key Capabilities

• OpenAI-compatible chat and text completions
• Streaming and non-streaming APIs
• Separate reasoning capture for models that expose reasoning output
• Model profile loading from properties or direct programmatic profile creation
• Category-based model selection and runtime custom categories
• Token counting with pluggable tokenizer strategies
• Request statistics including cached tokens, reasoning tokens, duration, throughput, and cost
• Optional completion caching with per-request cache bypass controls
• Completion interceptors for logging, accounting, rate limiting, and guardrails
• Agentic execution with conversation management, branching, merging, retries, and graph tracing
• Built-in response handlers for text, accumulation, JSON, CSV, and CSV-to-object unmarshalling
• Conventional graders and agent graders with optional feedback loops
• Spring Boot auto-configuration with selective module enablement

Requirements

• Java 25 or higher
• Spring Boot 4.0 or higher

Setup

The library intentionally keeps most dependencies in provided scope so consuming applications can control their own dependency tree.

Mandatory Dependency

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-restclient</artifactId>
</dependency>

Configuration

The library is split into auto-configured modules that can be enabled or disabled independently.

Module Enable/Disable Properties

Property	Type	Default	Description
lmlib.profile.enabled	Boolean	true	Enables model profile loading and resolution.
lmlib.tokenizer.enabled	Boolean	true	Enables tokenizer beans for token counting and fallback token estimation.
lmlib.restclient.enabled	Boolean	true	Enables REST client configuration for HTTP communication.
lmlib.prompt.enabled	Boolean	true	Enables built-in prompt strategies for text completion models.
lmlib.client.enabled	Boolean	true	Enables completion clients. Depends on profile, tokenizer, and restclient modules.
lmlib.agent.enabled	Boolean	true	Enables the agent executor. Depends on the client module.

If you disable a module that another module depends on, you must provide the missing beans yourself.

REST Client Configuration

Property	Type	Default	Description
lmlib.client.proxy.enabled	Boolean	false	Enables an HTTP proxy for LLM requests.
lmlib.client.proxy.host	String		Proxy host.
lmlib.client.proxy.port	Integer	0	Proxy port.
lmlib.client.proxy.user	String		Proxy username.
lmlib.client.proxy.password	String		Proxy password.
lmlib.client.tls.verification.disabled	Boolean	false	Disables TLS certificate verification. Not recommended in production.
lmlib.client.retry.max-attempts	Integer	5	Maximum retry attempts for failed HTTP calls.
lmlib.client.retry.backoff-interval-min	Long	125	Minimum retry backoff in milliseconds.
lmlib.client.retry.backoff-interval-max	Long	2500	Maximum retry backoff in milliseconds.

Tokenizer Configuration

Property	Type	Default	Description
tokenizer.strategy	String	jTokkit	Token counting strategy. Supported values are jTokkit and llamaServer.

Optional Dependencies

Caching Support

If you want Spring cache support for services such as model profile loading or client retrieval, add:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-cache</artifactId>
</dependency>
<dependency>
    <groupId>com.github.ben-manes.caffeine</groupId>
    <artifactId>caffeine</artifactId>
</dependency>

Then provide a CacheManager:

@Bean
public CacheManager cacheManager() {
    return new CaffeineCacheManager();
}

Tokenizer Dependencies

For the recommended jTokkit tokenizer:

<dependency>
    <groupId>com.knuddels</groupId>
    <artifactId>jtokkit</artifactId>
</dependency>

For llamaServer, no extra dependency is required because tokenization is delegated to the remote server.

Model Profiles

Model profiles describe how a request should be sent to a model and how its usage should be accounted for. They can be loaded from .properties files, selected dynamically at runtime, or created programmatically.

1. Predefined Categories

Use properties to map model categories to profile files:

profile.model.s=local-small-model
profile.model.m=llama3.3-70b-local
profile.model.l=gpt-4
profile.model.xl=gpt-4-turbo
profile.model.hot=high-temperature-model
profile.model.cold=deterministic-model

Each value refers to a profile file on the classpath without the .properties suffix.

final var client = clientService.getClient(ModelCategory.MEDIUM);
final var completion = client.conversation(ModelCategory.LARGE, conversation, false);

2. Custom Categories

Create categories dynamically when predefined ones are too restrictive:

final var customCategory = new ModelCategory("profile-name", "CUSTOM");

final var client = clientService.getClient(customCategory);
final var completion = client.conversation(customCategory, conversation, false);

This is useful for runtime routing, model experiments, or per-tenant profile selection.

3. Programmatic ModelProfile Creation

Create a ModelProfile directly when you want full runtime control and do not want to depend on properties files:

final var modelProfile = new ModelProfile(
    "",                                    // prompts
    "cl100k_base",                        // tokenEncoding
    2000,                                  // maxTokens
    32768,                                 // maxContextLength
    0.7,                                   // temperature
    1.0,                                   // topP
    ModelProfile.ModelProvider.OAI_CHAT_COMPLETION,
    "gpt-5.1",                            // modelName
    "https://api.openai.com/v1",          // url
    System.getenv("OPENAI_API_KEY"),      // apiKey
    new BigDecimal("1.25").divide(new BigDecimal(1000000)),
    new BigDecimal("0.125").divide(new BigDecimal(1000000)),
    new BigDecimal("10.0").divide(new BigDecimal(1000000)),
    BigDecimal.ZERO,
    null,
    null,
    "DYNAMIC"
);

final var client = clientService.getClient(modelProfile);
final var completion = client.conversation(modelProfile, conversation, false);

Agents can also use a specific profile directly:

final var agent = new Agent(
    "MyAgent",
    AgentType.START_CONVERSATION,
    null,
    modelProfile,
    "You are a helpful assistant.",
    "{{userInput}}",
    new TextAgentResponseHandler("response"),
    null, null, null,
    AgentNext::end
);

Model Profile Properties

Each profile file is a .properties resource on the classpath.

Property	Type	Required	Description	Example
category	String	No	Short profile label used in logging and graph traces. If omitted in the file, it is inferred from the ModelCategory used to load it.	M, L, CUSTOM
prompts	String	Yes	Prompt strategy name for text completions. Use an empty value for chat completions.	llama4, gpt-oss, no, ``
tokenEncoding	String	Yes	Token encoding scheme used for token counting.	cl100k_base, none
maxTokens	Integer	Yes	Maximum response tokens.	1500, 2500
maxContextLength	Integer	Yes	Maximum total context length.	16000, 32768, 128000
temperature	Double	Yes	Sampling temperature. Must be greater than zero.	0.2, 0.4, 0.7
topP	Double	Yes	Nucleus sampling parameter. Must be greater than zero.	1.0, 0.9
modelProvider	Enum	Yes	Completion client type.	OAI_CHAT_COMPLETION, OAI_TEXT_COMPLETION
modelName	String	No	Model name or deployment. Can be empty for endpoints where the model should be auto-detected.	gpt-4, Llama-3.3-70B-Instruct, ``
url	String	Yes	Base API URL.	https://api.openai.com/v1, http://localhost:5001
apiKey	String	No	Bearer token or Spring placeholder. Can be empty for local servers.	sk-..., ${apikey}, ``
cost1MInTokens	Double	Yes	Cost per 1 million input tokens.	0.71, 5.00, 0
cost1MCachedInTokens	Double	No	Cost per 1 million cached input tokens. Defaults to cost1MInTokens.	0.35, 0
cost1MOutTokens	Double	Yes	Cost per 1 million output tokens.	0.71, 15.00, 0
cost1MReasoningOutTokens	Double	No	Cost per 1 million reasoning output tokens. Defaults to 0.	0, 60.00
reasoningEffort	String	No	Reasoning effort for reasoning-capable models.	low, medium, high
reasoningSummaryDetails	String	No	How reasoning content should be summarized.	auto, concise, detailed

Notes:

• Missing required properties cause runtime errors.
• If modelName is empty, the library can resolve a model name from the remote endpoint when supported.
• Cost properties are only used for statistics and accounting.
• cost1MCachedInTokens defaults to the normal input token cost when not provided.
• cost1MReasoningOutTokens defaults to 0 when not provided.
• Reasoning properties only apply to models that expose separate reasoning output.

Example Profile Files

Local chat completion:

category=M
prompts=
tokenEncoding=cl100k_base
maxTokens=2500
maxContextLength=16000
temperature=0.4
topP=1.0
modelProvider=OAI_CHAT_COMPLETION
modelName=
url=http://localhost:5001
apiKey=
cost1MInTokens=0
cost1MOutTokens=0
reasoningEffort=medium
reasoningSummaryDetails=auto

Local text completion:

category=S
prompts=gpt-oss
tokenEncoding=cl100k_base
maxTokens=2500
maxContextLength=16000
temperature=0.4
topP=1.0
modelProvider=OAI_TEXT_COMPLETION
modelName=
url=http://localhost:5001
apiKey=
cost1MInTokens=0
cost1MOutTokens=0

OpenAI-Compatible Clients

The library currently supports these provider types:

modelProvider=OAI_CHAT_COMPLETION
modelProvider=OAI_TEXT_COMPLETION

Chat completions are the preferred default. They are simpler to use because the library only needs to send the conversation. Text completions are still useful when you need explicit prompt formatting or must work with instruct models that depend on raw prompt structure.

For text completions, select a prompt strategy with the prompts property. lm-lib ships built-in strategies for common model families including Llama, GPT-OSS, Gemma, Mistral, Phi, Qwen, Vicuna, ChatML, Alpaca, and a no-formatting strategy.

Example:

prompts=llama3

Use jTokkit or llamaServer for tokenization depending on your deployment model.

Usage

Typical integration flow:

1. Add the required dependencies.
2. Configure one or more model profiles.
3. Optionally provide a CachedClientRepository if requests should be cached.
4. Use ClientService for direct completion calls.
5. Use AgentExecutorService for multi-step agentic flows.

Client Usage

final var client = clientService.getClient(ModelCategory.MEDIUM);
final var completion = client.conversation(ModelCategory.MEDIUM, conversation, false);

Completions and Streaming

Both streaming and non-streaming execution paths are supported.

• Non-streaming calls return a final Completion object when the request finishes.
• Streaming calls accept a Consumer<Chunk> and still return the final Completion after the stream completes.
• Each Chunk exposes both content() and reasoningContent().
• Final Completion objects expose response(), reasoning(), finishReason(), and statistics().

This lets you stream visible output while still capturing final structured accounting data.

Completions Cache

If a CachedClientRepository bean is available, lm-lib will wrap clients with a caching layer.

Direct client calls support a skipCache flag:

final var cached = client.conversation(ModelCategory.MEDIUM, conversation, false);
final var fresh = client.conversation(ModelCategory.MEDIUM, conversation, true);

final var streamed = client.streamConversation(ModelCategory.MEDIUM, conversation, chunk -> {
    System.out.print(chunk.content());
}, true);

skipCache=true bypasses reading a cached response for that request but still stores the fresh result afterwards.

For cached streaming responses, the cache layer replays the cached final result back through the chunk consumer as a single chunk.

Completion Interceptors

Implement CompletionInterceptor to observe or modify requests and responses centrally.

Common use cases:

• Cost and usage accounting
• Rate limiting
• Logging and tracing
• Circuit breaking
• Request validation or policy enforcement

Interceptors receive the resolved ModelProfile, so they can react to model category, model cost, token limits, provider, or any other profile setting.

@Component
public class MyInterceptor implements CompletionInterceptor {

    @Override
    public Conversation before(ModelProfile modelProfile, Conversation conversation) {
        LOGGER.info("Using model: {} at {}", modelProfile.modelName(), modelProfile.url());
        return conversation;
    }

    @Override
    public Completion after(ModelProfile modelProfile, Conversation conversation, Completion completion) {
        trackCosts(modelProfile, completion.statistics());
        return completion;
    }
}

Graders

lm-lib includes both conventional graders and agent-based graders.

Conventional Graders

Grader2

Recommended for standalone binary evaluation outside agent flows.

• Approach: multiple independent assessments with majority voting
• Trade-off: slower than a single pass, but more robust against individual grading errors
• Feedback loop: not supported

final var result = Grader2.assessScoreBinary(
    "Does the text mention feature X?",
    textToGrade,
    clientService
);

Grader

Deprecated. Use Grader2.

Agent Graders

AnswerGrader2

Recommended when you need a detailed score and explanation inside an agent flow.

• Returns a 0-100 rating plus an explanation
• Supports optional feedback loop retries when the rating is <= 60
• Uses qaQuestion, qaAnswer, qaOutputDescription, and optionally qaFeedbackLoopDestination

context.setStringValue("qaQuestion", "Is this a good solution?");
context.setStringValue("qaAnswer", answerText);
context.setValue("qaOutputDescription", Boolean.FALSE);
context.setStringValue("qaFeedbackLoopDestination", "AnswerRefiner");
final var result = agentExecutorService.walk("AnswerGrader2", context);

AnswerGraderBinary

Recommended when speed matters more than detailed scoring.

• Returns a pass/fail evaluation
• Supports the same optional feedback loop mechanism
• Can run with or without short explanations

context.setStringValue("qaQuestion", "Does this answer the question?");
context.setStringValue("qaAnswer", answerText);
context.setValue("qaOutputDescription", Boolean.FALSE);
context.setStringValue("qaFeedbackLoopDestination", "AnswerRefiner");
final var result = agentExecutorService.walk("AnswerGraderBinary", context);

AnswerGrader

Deprecated. Use AnswerGrader2.

Feedback Loop Mechanism

AnswerGrader2 and AnswerGraderBinary can send feedback back to another agent when evaluation fails.

Behavior:

1. The grader evaluates the answer.
2. If evaluation fails and fewer than two attempts have been made, the grader writes feedback to qaFeedback and routes back to qaFeedbackLoopDestination.
3. The source agent can revise the answer and resubmit it.
4. After the retry limit or a successful evaluation, the flow continues with the final result.

For useful feedback loops, keep qaOutputDescription enabled so the grader produces explanatory feedback.

Agentic Flows

The agent runtime executes graph-based workflows over an AgentContext. It supports prompt templating, branching, merging, streaming, retries, grading, and execution tracing.

Quick Start

final var context = new AgentContext(List.of(new Agent1(), new Agent2()));
context.setStringValue("key", "Payload here");
context.setStringValues("key2", List.of("All context keys", "support collections", "for aggregation"));
context.setValue("key3", new RandomDatatype());
context.setSkipCache(true);
context.setAlwaysSkipCache(true);

final var resultContexts = agentExecutorService.walk("Agent1", context);
final var resultContext = resultContexts.getFirst();

LOGGER.info(
    resultContext.getStringValue("blogPost") + "\n\n" +
    resultContext.getGraph().toString() + "\n" +
    resultContext.getRequestStatistic().toString()
);

If you do not pass agents explicitly, the framework can autowire all agent beans from the Spring context.

Two Ways to Implement Agents

Use either:

• BaseAgent for more explicit lifecycle overrides and larger agents
• Agent record for concise composition-based definitions

BaseAgent Example

public class BlogPostAgent implements BaseAgent {

    @Override
    public String name() {
        return "BlogPostAgent";
    }

    @Override
    public AgentType agentType(final AgentContext ctx) {
        return AgentType.START_CONVERSATION_WITH_SYSTEM_PROMPT;
    }

    @Override
    public ModelCategory modelCategory(final AgentContext ctx) {
        return ModelCategory.MEDIUM;
    }

    @Override
    public ModelProfile modelProfile(final AgentContext ctx) {
        return null;
    }

    @Override
    public String systemPrompt() {
        return "You are a concise technical blog writer.";
    }

    @Override
    public String textTemplate() {
        return "Write a blog post about {{topic}} using these bullets:\n\n{{points}}";
    }

    @Override
    public AgentResponseHandler responseHandler(final AgentContext ctx) {
        return new TextAgentResponseHandler("blogPost");
    }

    @Override
    public void preProcess(final AgentContext ctx) {
    }

    @Override
    public void postProcess(final AgentContext ctx) {
    }

    @Override
    public List<AgentContext> merge(final List<AgentContext> contexts) {
        return null;
    }

    @Override
    public AgentNext chooseNextAgent(final AgentContext ctx) {
        return AgentNext.END;
    }
}

Agent Record Example

final var blogPostAgent = new Agent(
    "BlogPostAgent",
    AgentType.START_CONVERSATION_WITH_SYSTEM_PROMPT,
    ModelCategory.MEDIUM,
    null,
    "You are a concise technical blog writer.",
    "Write a blog post about {{topic}} using these bullets:\n\n{{points}}",
    new TextAgentResponseHandler("blogPost"),
    null,
    null,
    null,
    ctx -> AgentNext.END
);

BaseAgent Reference

Method	Purpose	Default
name()	Unique agent identifier. Required.	none
agentType(context)	Defines conversation behavior and execution mode. Required.	none
modelCategory(context)	Chooses a model category when modelProfile() returns null.	ModelCategory.MEDIUM
modelProfile(context)	Supplies a specific model profile and overrides modelCategory().	null
systemPrompt()	Optional system instruction.	null
textTemplate()	Optional user prompt template.	null
responseHandler(context)	Parses the model response.	new TextAgentResponseHandler("response")
preProcess(context)	Runs before completion.	no-op
postProcess(context)	Runs after completion.	no-op
merge(contexts)	Merges split contexts after branching.	null
chooseNextAgent(context)	Selects the next agent or ends the flow. Required.	none

Agent Types

Type	Behavior	Typical Use
START_CONVERSATION	Starts a fresh conversation without forcing a system prompt.	New thread
START_CONVERSATION_WITH_SYSTEM_PROMPT	Starts a fresh conversation with systemPrompt().	Controlled resets
CONVERSATION	Continues an existing conversation.	Iterative refinement
CONVERSATION_WITH_SYSTEM_PROMPT	Continues with a dedicated system turn at index 0.	Persistent system role
COMPLETION	Stateless single-shot completion.	Transformations and one-off generation
PROCESSING_ONLY	Skips LLM calls entirely.	Pure context manipulation

Lifecycle

For each split, execution proceeds in this order:

1. preProcess()
2. Template expansion and optional branching
3. Optional LLM request unless skipped
4. Response parsing with up to two attempts
5. postProcess()
6. Optional merge
7. Next-agent selection

Template Placeholders

Placeholder	Expects	Behavior
{{{key}}}	Any JSON-serializable value	Inserts JSON verbatim
{{key}}	List	Joins values with double newlines
[[key]]	List	Branches and inserts the current element
`[[key	hidden]]`	List

Hidden placeholders are useful when you need branching keyed by internal identifiers that should not be shown to the model.

Branching and Merging

Use [[key]] placeholders to branch. Each key must resolve to a list. The number of splits equals the smallest list size across the branched keys. Each split receives only its own element values for the branched keys.

Merge behavior:

• Return null from merge() to keep split contexts separate
• Return one context for many-to-one aggregation
• Return multiple contexts for custom fan-in or transformation strategies

Utility helper:

BaseAgent.mergeContexts(List.of("blogPost", "ideas"), contexts)

Execution Graph

Each context accumulates a graph trace that documents the path through the flow.

Symbol	Meaning
M, S, L, HOT, COLD	Model category short name
agent name	Executed agent
○	Completion skipped
⇉ x/n	Branch split x of n
size↣merged	Merge size summary
→	Next agent is a COMPLETION agent
🗨	Next agent starts a new conversation
↴	Continue existing conversation
✓, ✗	Grading result
⚠	Parse attempt failed and will retry
☢	Fatal error
‖	Continuation of an already-started graph

Example:

M, CodeSummarizer, ↴, M, FeatureIdentifier, →, ⇉ 1/5, M, FeatureAnalyzer, 5↣1, →, M, AnswerGenerator

Response Handlers

Handler	Purpose	Notes
TextAgentResponseHandler	Stores the full response under one key	Supports streaming and reasoning aggregation into <key>_reasoning
AccumulateTextAgentResponseHandler	Appends each response to a list	Useful for collecting multiple variants
JsonAgentResponseHandler	Parses loose JSON and flattens values into context lists	Retries after parse failures
CsvAgentResponseHandler	Parses CSV into column-based context keys	Useful for structured tabular extraction
CsvUnmarshallingAgentResponseHandler	Parses CSV rows into typed objects	Useful when the target output maps cleanly to record-like structures

TextAgentResponseHandler

Streaming behavior:

1. Initializes the target key to an empty string.
2. Appends each chunk's content() to the main key.
3. Appends each chunk's reasoningContent() to <key>_reasoning.
4. Runs final handle() after streaming ends.

JsonAgentResponseHandler

Behavior summary:

1. Extracts the first plausible JSON object from the response.
2. Parses it with permissive Jackson settings.
3. Flattens nested data into list-valued context keys.
4. Retries once if parsing fails.

CSV Handlers

The CSV handlers are useful when you want models to emit lightweight structured tabular output instead of JSON.

• CsvAgentResponseHandler stores parsed columns under separate context keys.
• CsvUnmarshallingAgentResponseHandler converts rows into typed objects and stores them under one context key.

Streaming Agent Execution

If context.setStreaming(true) is enabled and the handler implements StreamedAgentResponseHandler, chunk updates are processed during generation. You can also pass a callback to AgentExecutorService.walk(...) to receive AgentContext updates during streaming.

Skipping LLM Calls

Set context.setSkipNextCompletion(true) to turn the next step into a processing-only pass. The flag resets automatically after that step.

Cache Bypass Controls

Agent execution supports two cache flags:

• setSkipCache(true) bypasses cache reads for the next prompt only and then resets
• setAlwaysSkipCache(true) bypasses cache reads for every later prompt until disabled

Both still allow fresh responses to be written back into the cache.

Retry and Parse Handling

Each completion is parsed with a fresh response handler instance per attempt.

• If handle() returns false or throws, the framework retries once.
• If parsing still fails, the context is marked with AgentErrorType.PARSING, receives ☢, and does not continue into merge or next-agent chaining.
• If parsing failed because of an exception, the cause is stored on the context via getErrorException().

Error Handling

Errors are isolated to the affected split.

• Runtime failures become AgentErrorType.GENERAL
• Final parse failures become AgentErrorType.PARSING
• Successful branches continue even when some branches fail
• Returned results include errored contexts after successful ones so callers can inspect failures

AgentContext Flags and State

Field or Flag	Purpose
conversation	Holds the current conversation history
requestStatistic	Aggregates token, cost, and duration statistics
graph	Stores the execution trace
lastCompletion	Holds the most recent completion
skipNextCompletion	Skips the next LLM call
skipCache	Bypasses cache reads once
alwaysSkipCache	Bypasses cache reads until disabled
streaming	Enables streaming-aware execution
errorType and errorException	Capture execution failures
custom context keys	Store arbitrary values shared between agents

Best Practices

• Use chat completions by default and fall back to text completions only when raw prompt control matters.
• Prefer small or medium model categories for cheap filtering or classification steps.
• Escalate to larger or more expensive profiles only for synthesis or high-value reasoning steps.
• Keep response handlers deterministic and side-effect free.
• Use processing-only agents for context shaping instead of spending an LLM call.
• Use grading to gate expensive downstream work and to assert llm responses in unit tests
• Use hidden placeholders when a branch key is operationally useful but should not be shown to the model.

Example Execution Trace

Sample output from AgentTest#agenticFlow:

gemma3-12b-it-q5_k_m
M, CodeSummarizer, ↴, M, FeatureIdentifier, →, ⇉ 1/5, M, FeatureAnalyzer, 5↣1, →, M, AnswerGenerator
AgentRequestStatistic [requests=8, cachedPrompts=0, inTokens=27393, outTokens=4861, requestDuration=PT3M30.415881394S, getEffectiveDuration()=PT2M22.102597491S, getTps()=226.98, getOutTps()=34.21, getCost()=0]

This trace shows a typical pattern: summarize, identify multiple features, fan out into parallel analysis, merge results, and generate a final answer while preserving usage statistics.