feat: Add ReasoningBank for reusable reasoning strategies

[nebrass]

Summary

This PR implements the ReasoningBank feature based on the paper "Reasoning-Bank: Learning from the Traces of Thought" (arXiv:2509.25140).

What is ReasoningBank?

ReasoningBank enables agents to store and retrieve proven reasoning strategies, allowing them to learn from past successful task executions and apply those approaches to new, similar problems.

Components Added

Data Models (com.google.adk.reasoning):

• ReasoningStrategy - Immutable model representing a distilled reasoning approach with problem pattern, steps, and tags
• ReasoningTrace - Captures raw task execution data (task, output, reasoning steps)
• SearchReasoningResponse - Response model for strategy search

Service Layer:

• BaseReasoningBankService - Interface defining store and search operations
• InMemoryReasoningBankService - In-memory implementation using keyword matching with weighted scoring

Tool Integration (com.google.adk.tools):

• LoadReasoningStrategyTool - Function tool enabling agents to search and load relevant strategies
• LoadReasoningStrategyResponse - Tool response record

Context Integration:

• Added reasoningBankService field to InvocationContext
• Added searchReasoningStrategies() method to ToolContext

Usage Example

// Create and configure service
BaseReasoningBankService reasoningBank = new InMemoryReasoningBankService();

// Store a strategy
ReasoningStrategy strategy = ReasoningStrategy.builder()
    .id("math-strategy")
    .name("Math Problem Solving")
    .problemPattern("Mathematical word problems")
    .steps(ImmutableList.of("Identify unknowns", "Set up equations", "Solve"))
    .build();
reasoningBank.storeStrategy("myApp", strategy).blockingAwait();

// Configure agent with reasoning bank
InvocationContext context = InvocationContext.builder()
    .reasoningBankService(reasoningBank)
    // ... other config
    .build();

Test Plan

• Unit tests for ReasoningStrategy (5 tests)
• Unit tests for ReasoningTrace (5 tests)
• Unit tests for InMemoryReasoningBankService (10 tests)
• All existing tests pass (793 tests total)

Related

• Paper: Reasoning-Bank: Learning from the Traces of Thought
• This mirrors the Memory feature pattern in ADK (BaseMemoryService, InMemoryMemoryService, LoadMemoryTool)

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[gemini-code-assist]

Summary of Changes

Hello @nebrass, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces the foundational ReasoningBank feature, designed to enhance agent capabilities by allowing them to learn from and reuse successful problem-solving approaches. By providing mechanisms to store and retrieve distilled reasoning strategies and raw execution traces, agents can apply proven methods to new, similar tasks, thereby improving their efficiency and effectiveness. The implementation includes core data models, a service interface with an in-memory prototype, and seamless integration into the existing tool and invocation contexts.

Highlights

• New Feature: ReasoningBank: Introduces the ReasoningBank feature, enabling agents to store and retrieve proven reasoning strategies, based on the 'Reasoning-Bank: Learning from the Traces of Thought' paper.
• New Data Models: Added ReasoningStrategy (for distilled reasoning approaches), ReasoningTrace (for raw task execution data), and SearchReasoningResponse (for strategy search results).
• Service Layer Implementation: Defined BaseReasoningBankService interface and provided an InMemoryReasoningBankService implementation for prototyping, utilizing keyword matching for strategy retrieval.
• Tool Integration: Integrated LoadReasoningStrategyTool as a function tool, allowing agents to search for and load relevant strategies, along with its corresponding LoadReasoningStrategyResponse.
• Context Updates: Modified InvocationContext to include the reasoningBankService and ToolContext to expose a searchReasoningStrategies() method for agent access.

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[gemini-code-assist]

Code Review

This pull request introduces a ReasoningBank feature, which is a significant and well-implemented addition. The new components, including data models, services, and tool integrations, are clearly defined and follow the existing architectural patterns of the project. The code is well-documented and accompanied by a comprehensive set of unit tests, ensuring the new functionality is robust. I have a couple of minor suggestions for code refinement in the InMemoryReasoningBankService to improve conciseness and use more idiomatic Java constructs, but overall, this is excellent work.