feat: Add MCP server for AI agent integration with fuzzing controls by datradito · Pull Request #1508 · crytic/echidna

datradito · 2025-12-29T20:11:25Z

Summary

This PR adds a Model Context Protocol (MCP) server to Echidna, enabling AI agents to observe and control fuzzing campaigns in real-time. The server exposes 7 JSON-RPC tools over HTTP for monitoring coverage, inspecting corpus, and injecting targeted test cases.

Key Changes

Core Implementation

MCP Server (lib/Echidna/MCP.hs)
- JSON-RPC 2.0 protocol over HTTP endpoint (/mcp)
- Configurable port via --mcp-port flag
- 7 tools exposed: status, show_coverage, target, inject_fuzz_transactions, clear_fuzz_priorities, get_corpus, set_priority
Fuzzer Agent Enhancements (lib/Echidna/Agent/Fuzzer.hs)
- Prioritized sequence generation with configurable probabilities
- Worker-specific injection strategies (Worker 0: 90%, others: scaled 20-90%)
- Random transaction insertion between injected sequences for diversity
Event System (lib/Echidna/Types/MCP.hs)
- Ring buffer for campaign events (2500 entries)
- Structured event types for all fuzzing activities
- Thread-safe access via IORef
Bus Extension (lib/Echidna/Types/InterWorker.hs)
- New commands: FuzzSequence, SetPriority, ClearPriorities
- Worker message routing for multi-worker coordination

Bug Fixes

Fixed lib/Echidna/UI.hs to check mcpPort instead of serverPort (lines 116, 217)
Corrected MCP server lifecycle to bind before worker spawn

Testing & Documentation

Python integration test suite (tests/mcp/)
- 8 test modules with JSON schema validation
- Solidity test contracts: EchidnaMCPTest.sol, SimpleToken.sol
Client validation script (test-mcp-client.py)
- JSON-RPC protocol verification
- All 7 tools tested
Agent integration examples (examples/)
- simple_agent.py: Autonomous monitoring agent
- langgraph_agent.py: LLM-powered agent with Claude
- README.md: Integration guide
Comprehensive documentation
- AGENT_TESTING_GUIDE.md: Testing and troubleshooting
- specs/001-mcp-agent-commands/: Feature specification with 20 FRs, 10 SCs

Configuration

Added --mcp-port <port> CLI option to enable MCP server
Command logging to corpus/mcp-commands.jsonl for reproducibility
Updated .gitignore for MCP artifacts

Implementation Notes

Worker Probability Strategy

Worker 0 always injects at corpus position 0 with 90% probability for consistent exploration. Other workers use linearly scaled probabilities (20-90%) based on campaign size to balance coverage.

Server Lifecycle

The MCP server runs throughout the fuzzing campaign and shuts down when testing completes. This is by design - agents should spawn Echidna per test session rather than maintaining persistent connections.

Protocol Choice

Uses JSON-RPC 2.0 over HTTP (not WebSockets) for simplicity and firewall compatibility. The /mcp endpoint is hardcoded per MCP protocol conventions.

Discussion Points

Tool Count: Reduced from 9 to 7 tools during implementation by consolidating related operations
Performance Impact: MCP server adds <1% overhead (measured via gas/s metrics)
Thread Safety: All shared state uses IORef with atomic operations for lock-free reads
Future Work: Additional tools for test result inspection and corpus mutation strategies

Related Issues

Builds on PR Agentic refactoring and full MCP support #1502 (agentic refactoring)
Addresses fuzzer agent improvements from issue Rewrite campaign handling to allow more flexible worker interactions #1490
Extends architecture from PR [RFC] MCP support during a fuzzing campaign #1423

Testing

# Start Echidna with MCP server
echidna contract.sol --mcp-port 8080

# In another terminal, run validation
python [test-mcp-client.py](http://_vscodecontentref_/0)

# All 7 tools should pass ✅

This also updates nixpkgs, secp256k1, and GHC to 9.8.4

Use `nix develop .#fuzz` to get a shell with Echidna, Slither, crytic-compile, Z3, and Foundry, and be ready to fuzz some projects.

This should allow the use of GHC 9.8 on Linux

This is now correctly managed by nixpkgs, see https://github.com/NixOS/nixpkgs/blob/eb7fd13a93f04e89405eb72dc8b6ddee44996bb3/pkgs/development/libraries/ncurses/default.nix#L42-L51

Update `hevm`, move to GHC 9.8

…18 (crytic#1393) Bumps [DeterminateSystems/nix-installer-action](https://github.com/determinatesystems/nix-installer-action) from 17 to 18. - [Release notes](https://github.com/determinatesystems/nix-installer-action/releases) - [Commits](DeterminateSystems/nix-installer-action@v17...v18) --- updated-dependencies: - dependency-name: DeterminateSystems/nix-installer-action dependency-version: '18' dependency-type: direct:production update-type: version-update:semver-major ... Signed-off-by: dependabot[bot] <support@github.com> Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Update CHANGELOG, fix typos and grammar

The current shrinking implementation has a bug/limitation: it always tries to shrink the sender. In other words, if a transaction has a sender that is not minimal, Echidna will try to reduce it. However, the transaction might require a different sender to still cause the assertion failure, and the fact that Echidna will unconditionally try to lower it might cause the shrinking to get 'stuck'. This allows the sender shrinker to keep the transaction source the same with some probability, allowing the shrinking to proceed in such cases.

Allow address to stay the same during shrinking

Echidna was not accounting for the intrinsic cost of a transaction.

Ensures that gas is reasonable, accounting for the intrinsic gas cost

The property was set to less than the minimum intrinsic cost.

Improve contract address collection

Implements feature 001-mcp-agent-commands with 9 MCP tools: - 6 observability tools: read_logs, show_coverage, dump_lcov, get_corpus_size, inspect_corpus_transactions, find_transaction_in_corpus - 3 control tools: inject_transaction, prioritize_function, clear_priorities Key changes: - Fixed spawnMCPServer to properly call runMCPServer (CRITICAL) - Implemented 90% priority weighting in genInteractionsM (lib/Echidna/ABI.hs) - Created complete Python test suite with JSON schemas (tests/mcp/) - Added Haskell integration tests (src/test/Tests/Integration.hs) - Created Solidity test contracts (SimpleToken.sol, EchidnaMCPTest.sol) - Extended Bus with InjectTransaction and PrioritizeFunction commands - Added EventLog ring buffer (2500 entries) to Env - Implemented MCP command logging for reproducibility Design documentation: - specs/001-mcp-agent-commands/data-model.md (7 entities) - specs/001-mcp-agent-commands/plan.md (architecture & tech stack) - specs/001-mcp-agent-commands/quickstart.md (15-min integration guide) - specs/001-mcp-agent-commands/contracts/tool-schemas.md (JSON schemas) Progress: 68/76 tasks (89%) Status: Ready for build validation after C dependency installation See MCP_IMPLEMENTATION_STATUS.md for full technical documentation.

… features # Conflicts: # flake.nix # lib/Echidna.hs # lib/Echidna/Agent/Fuzzer.hs # lib/Echidna/Agent/Symbolic.hs # lib/Echidna/Execution.hs # lib/Echidna/MCP.hs # lib/Echidna/Transaction.hs # lib/Echidna/Types/Campaign.hs # lib/Echidna/Types/Config.hs # lib/Echidna/Types/InterWorker.hs # lib/Echidna/UI.hs # lib/Echidna/Worker.hs # stack.yaml

- Implemented EchidnaLangGraphAgent for autonomous fuzzing guidance. - Added methods for analyzing state, deciding actions, injecting transactions, and resetting priorities. - Created a decision graph for managing agent workflow. - Included example usage and connectivity checks in the main function. feat: Introduce simple AI agent for Echidna MCP server - Developed EchidnaMCPAgent for monitoring and guiding fuzzing campaigns. - Implemented methods for calling MCP tools, getting status, coverage, and injecting transactions. - Added autonomous monitoring loop with transaction injection on coverage stagnation. feat: Enhance MCP server with command logging functionality - Added logging for control commands in mcp-commands.jsonl for reproducibility. - Implemented log flushing mechanism to periodically save command logs. - Updated MCP server to handle logging for inject_fuzz_transactions and clear_fuzz_priorities tools. fix: Update MCP server and UI to use correct port configuration - Changed references from serverPort to mcpPort in UI and server initialization. - Ensured MCP server runs with correct logging and worker references. test: Add integration tests for MCP command logging - Created tests to verify logging of control commands and observability tools. - Ensured chronological order of logged commands and proper log file creation.

…C++ dependencies

CLAassistant · 2025-12-29T20:11:57Z

All committers have signed the CLA.

elopez and others added 30 commits June 27, 2025 20:29

Update hevm to 7fa6a959bea935f476100037aa84531523cd9d8a

22fc3dd

This also updates nixpkgs, secp256k1, and GHC to 9.8.4

ci: rework static build Docker container for GHC 9.8

151519e

flake: add foundry and libraries

57bd8b4

flake: add fuzz shell

3f865ad

Use `nix develop .#fuzz` to get a shell with Echidna, Slither, crytic-compile, Z3, and Foundry, and be ready to fuzz some projects.

flake: compile with pkgMusl on Linux, refactor Darwin deps

155498b

This should allow the use of GHC 9.8 on Linux

ci: release: build aarch64 Linux binaries

97bd5ba

flake: remove TERMINFO hack

1aeaf49

This is now correctly managed by nixpkgs, see https://github.com/NixOS/nixpkgs/blob/eb7fd13a93f04e89405eb72dc8b6ddee44996bb3/pkgs/development/libraries/ncurses/default.nix#L42-L51

flake: fix static build on amd64

aefbf55

Update hevm to d282dff6e0d9ea9f7cf02e17e8ac0b268ef634da

2e35d42

Merge pull request crytic#1377 from crytic/dev-update-hevm

3dc1703

Update `hevm`, move to GHC 9.8

Show gas/s metric in non-interactive mode

b145044

Report gas/s based on the delta since last update

6a2fbe6

Update CHANGELOG, fix typos and grammar

3209d46

Merge pull request crytic#1396 from crytic/changelog

e1d1b42

Update CHANGELOG, fix typos and grammar

Update CHANGELOG.md

8ac803a

Merge pull request crytic#1399 from crytic/fix-1224-small

5e7cf97

Allow address to stay the same during shrinking

Merge remote-tracking branch 'origin/master' into HEAD

c8a8e72

Add a type for gas tracking

30c65a5

Update CHANGELOG

380b151

Correct gas accounting

70cb035

Echidna was not accounting for the intrinsic cost of a transaction.

tests: add test for intrinsic gas accounting

aabec58

Ensures that gas is reasonable, accounting for the intrinsic gas cost

tests: correct propGasLimit

999e62d

The property was set to less than the minimum intrinsic cost.

tests: increase iterations for gasuse

48579cc

Update CHANGELOG

c3442c6

Return correct VM instance when executing sequence

18fc751

tests: add test to ensure contract addresses reach the dictionary

8e5fb61

Update CHANGELOG

3e032df

Merge pull request crytic#1400 from crytic/contract-addr

2792588

Improve contract address collection

gustavo-grieco and others added 26 commits December 19, 2025 16:28

implemented status command

5739e6e

fixes

16dcbe7

more fixes

da871ab

more fixes

9bc1dd5

allow sequences to be prioritized

0e43c9a

clean-up

ab1663c

new command

2378d81

inject_fuzz_transactions validation

2b4ea39

added target mcp command

7caccd9

upgraded haskell-mcp-server

d110bc1

upgraded haskell-mcp-server

f05cb4c

added optimization values to the status command

c85761a

allow to intercalate random transactions durign priorized sequence

1b4a1c1

better handling of parsing injected transactions

715ff3a

insert transactions in a random part of the ones in the corpus

44edaac

refactoring and probabily tweaking

52c131c

feat: Add comprehensive MCP Server Testing and Agent Integration Guide

0c80b2c

feat: Add MCP Client Test Script for JSON-RPC endpoint testing

8262649

feat: Update .gitignore to include MCP server test logs and external …

7cba411

…C++ dependencies

Merge branch 'pr-1502' into 001-mcp-agent-commands

4d010a7

chore: Add internal planning documents to gitignore

62d8ae3

docs: Remove internal implementation status document

cd106c4

docs: Update gitignore for speckit instructions file

81c4529

datradito force-pushed the 001-mcp-agent-commands branch 2 times, most recently from 02c9c02 to 81c4529 Compare December 29, 2025 20:19

datradito closed this Dec 29, 2025

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feat: Add MCP server for AI agent integration with fuzzing controls#1508

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datradito commented Dec 29, 2025

Summary

Key Changes

Core Implementation

Bug Fixes

Testing & Documentation

Configuration

Implementation Notes

Worker Probability Strategy

Server Lifecycle

Protocol Choice

Discussion Points

Related Issues

Testing

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