HarmonyAI.SDK 0.4.0

HarmonyAI.SDK

AI RAG agent for chatting over the contents of a local (or multiple) documentation files (README.md, CHANGELOG.md, others). Uses Google Gemini to generate answers strictly constrained to the provided context.

Features

• Chat: IDocChatAgent.AskAsync returns ChatResponse (answer, used chunks, history, cache flag).
• No-answer contract: model returns [NO_ANSWER] when context lacks data; SDK sets ChatResponse.NoAnswer and you can render a docs link from DocumentationUrl.
• Conversation history with bounded turns (EnableConversationHistory, MaxHistoryTurns).
• Multi-file documentation (ReadmePaths).
• Vectors / RAG: chunking, embeddings, Top-K selection.
• Embeddings cache (hash + model based).
• Answer cache (LRU) keyed by context hash + question.
• Semantic answer reuse for similar questions (embeddings + Jaccard chunk overlap).
• Rate limiting (requests and prompt chars / minute).
• Token-based context budgeting (approximate tokens → characters).
• Telemetry hooks (cache hits, model calls, retries, rate limits).
• Retries with backoff and per-attempt timeouts.
• Adaptive chunking.
• Pseudo streaming + ready API for future native streaming.
• DI integration (AddHarmonyDocChat).
• Custom exceptions: GeminiApiException, RateLimitExceededException, DocumentationNotFoundException.

Installation

dotnet add package HarmonyAI.SDK

(Or build locally and install the package from artifacts.)

API key configuration

Set environment variable:

SETX GEMINI_API_KEY "your_key"  # Windows (requires new session)

Or pass the key via ReadmeDocAgentOptions.GeminiApiKey.

Usage example (simple answer)

using HarmonyAI.SDK.AI;

var agent = new ReadmeDocAgent(new ReadmeDocAgentOptions
{
    GeminiApiKey = Environment.GetEnvironmentVariable("GEMINI_API_KEY"),
    ReadmePath = "README.md", // documentation path
    MaxReadmeChars = 12000,
    Model = "gemini-1.5-flash"
});

string question = "How to run the sample agent?";
var answer = await agent.AnswerAsync(question);
Console.WriteLine(answer);

Chat example (IDocChatAgent)

using HarmonyAI.SDK.Chat;
using HarmonyAI.SDK.AI;

var agent = new ReadmeDocAgent(new ReadmeDocAgentOptions { GeminiApiKey = Environment.GetEnvironmentVariable("GEMINI_API_KEY") });
var r1 = await agent.AskAsync("What does this library do?");
Console.WriteLine(r1.Answer);
var r2 = await agent.AskAsync("Does it support multiple files?");
Console.WriteLine(r2.Answer);
// Access used chunks:
foreach (var c in r2.UsedChunks)
    Console.WriteLine($"Chunk #{c.Index} score={c.Score:F3} len={c.Text.Length}");

DI registration (Microsoft.Extensions.DependencyInjection)

using HarmonyAI.SDK.Extensions;
var services = new ServiceCollection();
services.AddHarmonyDocChat(o => {
    o.GeminiApiKey = Environment.GetEnvironmentVariable("GEMINI_API_KEY");
    o.ReadmePath = "README.md";
});
var provider = services.BuildServiceProvider();
var chat = provider.GetRequiredService<IDocChatAgent>();
var response = await chat.AskAsync("What is HarmonyAI.SDK?");

## Vectors (RAG / Vector Search)
Default `UseVectorSearch = true`. On first call:
1. README is split into chunks of `ChunkSize` with overlap `ChunkOverlap`.
2. Each chunk gets an embedding from `EmbeddingModel` (e.g. `text-embedding-004`).
3. Embeddings are cached in `.harmonyai.readme.embeddings.json` with file SHA256 and model name.
4. Subsequent queries load cache instead of recomputing embeddings.
5. The user question is also embedded; cosine similarity selects top `MaxChunksInPrompt` chunks.
6. Only those chunks go into the prompt (reduces hallucination and cost).

Changing README (content change -> new hash) triggers automatic cache rebuild.

Disable:
```csharp
var agent = new ReadmeDocAgent(new ReadmeDocAgentOptions { UseVectorSearch = false });

Multiple documentation files

You can provide several files instead of one ReadmePath via ReadmePaths:

var agent = new ReadmeDocAgent(new ReadmeDocAgentOptions {
    ReadmePaths = new[]{ "README.md", "CHANGELOG.md", "docs/intro.md" }
});

Files are merged with headers --- FILE:xyz --- aiding contextual references.

Answer cache

Enabled by default (EnableAnswerCache = true). Key = context hash + question. LRU limited by AnswerCacheCapacity (default 128). Repeated questions avoid API calls.

Disable:

new ReadmeDocAgentOptions { EnableAnswerCache = false };

Streaming (experimental)

AnswerStreamingAsync splits the final answer into fragments (pseudo-stream). Future: replace with native Gemini streaming.

await foreach (var chunk in agent.AnswerStreamingAsync("Question?"))
    Console.Write(chunk);

Rate limiting

Parameters:

RequestsPerMinuteLimit
PromptCharsPerMinuteLimit

Throws InvalidOperationException when exceeded. Example:

var agent = new ReadmeDocAgent(new ReadmeDocAgentOptions {
    RequestsPerMinuteLimit = 30,
    PromptCharsPerMinuteLimit = 200_000
});

Adaptive chunking

Enable with AdaptiveChunking = true. Approximate target number of chunks: AdaptiveTargetChunks. Options modify effective ChunkSize dynamically based on total document length.

var opts = new ReadmeDocAgentOptions {
    UseVectorSearch = true,
    AdaptiveChunking = true,
    AdaptiveTargetChunks = 50
};

Safety bounds: min effective size 200, max 4000 chars, overlap ⇐ 1/4 size.

Exceptions

• GeminiApiException – Gemini API response error (status, raw body if available).
• RateLimitExceededException – rate or prompt char limit exceeded.
• DocumentationNotFoundException – no documentation available.

Possible extensions / ideas

• Additional document types / chunking strategies
• Local embedding index options
• Persistent answer cache (disk / distributed)
• Cost governance (token accounting)

License

MIT

Tests

To run unit tests (xUnit):

dotnet test

Building and publishing the NuGet package

1. Pack

dotnet pack -c Release

Artifacts will be in bin/Release/.

2. (Optional) Local install to a sample app

dotnet nuget add source ./bin/Release --name LocalHarmony
dotnet add package HarmonyAI.SDK --prerelease

3. Publish to NuGet.org (requires API key)

dotnet nuget push bin/Release/*.nupkg --api-key $Env:NUGET_API_KEY --source https://api.nuget.org/v3/index.json

Changelog (summary)

• 0.4.0: Same-language answers; [NO_ANSWER] contract + NoAnswer flag; semantic reuse; token budget; telemetry; retry/timeouts; thread-safety.
• 0.3.0: First public release: chat interface, conversation, used chunks, DI, custom exceptions, docs.
• 0.2.0: Multi-file, LRU answer cache, streaming draft, markdown normalization, rate limiting, adaptive chunking, tests, SourceLink.
• 0.1.0: Basic agent + vector search + tests.