I am Gautier DI FOLCO working as Staff Software Engineer / Senior Haskell developer @ Wire. I am a professional Software Engineer, I have a solid track record of working with business owners to understand project requirements whist working to improve overall functionality of existing systems. With repeated success working from remote locations, I am a skilled collaborator and trusted leader.

• 🔭 I’m currently working as Staff Software Engineer / Senior Haskell developer @ Wire.
• 🌱 I’m currently learning nix, Observability, Product management, Rust
• 👯 I’m looking to collaborate on Haskell open source projects
• 💬 Ask me about Haskell, Backend development, Architecture
• 📫 How to reach me: gautier [dot] difolco [at] gmail [dot] com, ,
• 🔗 Other links: Personal website / Passeport
• ⚡ Fun fact: unbeatable pasta eater

• Haskell (Servant, Polysemy), Nix(OS)
• Github Actions
• Terraform
• Cassandra
• ElasticSearch
• PostGreSQL
• AWS
• Kubernetes

I have published some packages over Hackage (Haskell):

• antikythera (March 2025): Simple job/task/event scheduler/cronjob
• typed-range (September 2024): Strongly-typed ranges
• pure-sum (March 2024): provides a way to properly derive sum types instances (also -aeson)
• kill-bool (March 2023): Booleans strong-typing
• poolboy (March 2023): Simple work queue for bounded concurrency
• adhoc-fixtures (November 2022): Simplify tests fixtures (also -hspec)
• yarl (September 2022): simple extensible records library (with getField support)
• sized-wrapper (August 2022): provides a wrapper for sized values (also -aeson, -quickcheck, -text)
• librarian (July 2022): a rules-based files moving cli tool
• nonempty-wrapper (June 2022): provides a wrapper for non-empty values (also -aeson, -quickcheck, -text)
• pulsar-hs (September 2021): complete Apache Pulsar client and admin client
• aeson-modern-tojson (June 2021): aims to give a post 0.x way to derive aeson's ToJSON instances
• typed-time (May 2021): provides a type-level time format
• amqp-streamly (August 2020): Connect amqp (RabbitMQ) to streamly
• servant-streamly (July 2020) Streamly support for Servant
• dijkstra-simple (June 2020): a simple Dijkstra's shortest-path implementation

I have also published:

• grafana-dashboards.nix (nix) (September 2023): Nix tool used to fetch and transform Grafana Dashboards
• docker-soju (Docker) (August 2022): Dockerized version of soju (an IRC bouncer)
• coc-hls (npm) (December 2021): haskell-language-server coc.nvim extension
• danger-ormolu (RubyGems) (August 2021): ormulu integration in Danger (CI tool)

I also contributed to the following projects:

• gothic: Haskell client library for HashiCorp Vault KVv2
  • December 2025: upgrade dependencies to use crypton-connection
• ghc-proposals: GHC proposals
  • June 2026: Built-in HasField Solver Support for Polytype Fields under OverloadedRecordDot
• hsaml2: Haskell SAML2 library
  • July 2026: support crypton backend (crypton-asn1 + ram)
• tech-proposals: Haskell Foundation technical proposals
  • June 2026: Haskell security tooling integrations
  • June 2026: Decoupling the Haddock Declaration AST from GHC
• opencode: terminal-based AI coding tool
  • April 2026: make the mouse disablable in the TUI
• opencode-snip: snip integration for opencode
  • May 2026: fix snip prepend duplication
• blog.haskell.org: official Haskell blog
  • June 2026: write "Overview of Haskell security tooling" article
• telescope-live-grep-args.nvim: telescope.nvim extension for live grep with arguments
  • April 2026: replace tbl_flatten after Neovim 0.12 deprecation
• servant-openapi3: OpenAPI 3 support for Servant
  • January 2026: add required flag to request bodies, matching servant semantics
• machines: Networks of composable stream transducers
  • October 2025: fix duplicated Data.Machine.Process.process documentation
• hibet: Tibetan-English translator for CLI
  • October 2025: add Nix support
• haskell-language-server: Haskell IDE support via the language server protocol (LSP)
  • January 2026: fix sub-directory file path resolution
  • October 2025: rely on gitignore to exclude listed files in ghcide
  • October 2025: move most of ghcide README in hls documentation
• c2hs: pre-processor for Haskell FFI bindings to C libraries
  • October 2025: delete .travis.yml
• haskellfoundation.github.io: HaskellFundation website
  • June 2025: fix 404 error page
• Lyon-Tech-Hub-Calendar: Lyon Tech Hub calendar
  • November 2025: restore LTH calendar and filter deprecation event
• coderetreat.org: Global Day of Coderetreat website
  • October 2025: add Lyon Global Day of Code Retreat event
• haskell-companies: curated list of companies using Haskell
  • April 2025: add LivTours, drop Autogriff
• practical-web-dev-ghc: Practical Web Development with GHC
  • May 2025: fix JSON instances in RabbitMQ adapter
• rust-streamdeck: libusb based driver for Elgato StreamDeck devices
  • May 2025: add Cargo.lock
• servant-static-th: embed static directories in servant
  • October 2024: fix compilation
• servant: strongly-typed web server
  • October 2025: add OperationId
  • October 2025: set errBody of defaultErrorFormatters.notFoundErrorFormatter in servant-server
  • October 2024: recommend argon2 in JWT cookbook
• nix-tree: nix derivation dependency browser
  • October 2025: turn nix-tree into a library
  • October 2024: add --file flag
• crem: Haskell composable state-machine
  • October 2025: implement AutomatonM instance for StateMachineT
  • October 2024: add nothunks instances
  • October 2024: fix nix compilation
• eselsohr: self-hostable bookmark manager for storing web articles
  • October 2024: fix nix compilation
• git-cliff: ChangeLog generator
  • November 2024: add Nix CI
  • October 2024: add a basic Nix environment
• cabal-audit: cabal tool scanning dependencies for vulnerabilities
  • June 2026: support CycloneDX 1.7
  • May 2026: use purl
  • January 2026: fix security-advisory restore
  • August 2024: add sarif output (GitHub Code Scan)
• devenv: Nix-based developer environments
  • August 2024: add flag to disable containers tooling
• error-message-index: GHC error messages documentations
  • June 2024: document GHC-89347
• EventStoreDB-Client-Haskell: Haskell client to EventStore
  • June 2024: GHC 9.6 support
• one-time-password: Haskell implementation of one-time-password (HOTOP/TOTP)
  • April 2024: add nix (flake) support
  • December 2023: add nix (flake) support
  • December 2023: add a full CLI
• libsodium-bindings: Haskell bindings to libsodium (cryptographic library)
  • April 2024: add nix (flake) support
  • December 2023: fix flake (nix) derivation for reuse
• toml-parser: Haskell Toml parser
  • November 2023: Add GHC 9.8.1 support
• essence-of-live-coding: Universal Live Coding & Functional Reactive Programming Framework
  • October 2023: Add Selective instance to Cell
• hapistrano: Deploy tool for Haskell applications, like Capistrano for Rails
  • October 2024: add --dry-run flag
  • October 2023: Add interactive init command
• rhine: Haskell Functional Reactive Programming framework with type-level clocks
  • October 2023: Add support for dunai 0.11
• monocle: Changes-sets organization and monitoring tool
  • October 2025: upgrade to bloodhound 0.26.0.0
  • October 2023: Add Workspace name validation
• ergo: A modern IRC server (daemon/ircd) written in Go
  • October 2023: introduce Prometheus
• OpenSearch documentation: OpenSearch (ElasticSearch fork) documentation
  • October 2023: drop point in time in 1.3.x
• skip-duplicate-actions: Github Action to skip jobs on arbitrary conditions
  • September 2023: Upgrade to NodeJS 20
• lyontechhub.github.io: LyonTechHub (Community of tech communities of Lyon)
  • August 2024: rename Twitter to X
  • August 2023: Migrate from Angular to static site generation
• dhall-openssl: dhall types and utils to generate OpenSSL/LibreSSL configuration files
  • August 2023: Add CRL support
• microlens-aeson: microlens for aeson
  • August 2023: Add aeson 2.2.0.0 support
• nixpkgs: nix-based packages set
  • July 2026: snip: 0.15.0 -> 0.20.0
  • July 2026: nanobot: init at 0.2.2
  • June 2026: codegraph: init at 0.9.9
  • June 2026: codebase-memory-mcp: init at 0.8.1
  • June 2026: semble: init at 0.3.3
  • April 2026: snip: init at 0.8.1
  • June 2025: nixos/prometheus.alertmanagerIrcRelay: fix network-online.target ordering but not depending warning
  • April 2025: rust-streamdeck: init at 0.9.0
  • October 2024: nixos/minidlna: add package option
  • October 2024: nixos/vivid: init module
  • September 2024: fix vlc reference in nixos/services.mediatomb
  • September 2024: add meta.mainProgram to vlc
  • September 2024: upgrade gerbera to 2.3.0
  • April 2024: openpomodoro-cli: init at 0.3.0
  • December 2023: add desktop icon to appflowy
  • July 2023: add meta.mainProgram to eventstore
  • June 2023: upgrade curlie to 1.7.1
• curlie: curl Rust wrapper (like httpie)
  • May 2023: Fix curl long flags with value
• purebred-email: Haskell MIME e-mails parsing and manipulation library
  • March 2023: Fix documentation
• tmux-net-speed: tmux status bar net speed fragment
  • March 2023: Fix bash invocation
• cardano-documentation: Cardano blockchain documentation
  • March 2023: Fix a typo
• ploeh.github.com: Mark Seemann's blog
  • December 2023: Serialization with and without Reflection (article + follow-up)
• pg-entity: A pleasant PostgreSQL database layer for Haskell
  • October 2022: Fix resource-pool >= 0.3 compilation
• cachix-action: Build software only once and put it in a global cache
  • October 2022: Add flake support
• flora-server: A package index for the Haskell ecosystem
  • March 2023: Improve bulk performances
  • October 2022: Restore nix flake
  • October 2022: Add nix flake CI
  • October 2022: Improve bulk performances
• get-wasp: wasp installer
  • October 2022: Rework update usecase
• aeson: A fast JSON library
  • October 2022: Add @since in documentation
• hackage-server: Hackage-Server: A Haskell Package Repository
  • February 2024: Add vulnerability reporting link
  • December 2023: Replace lastVersion by referenceVersion (ignore deprecated versions)
  • February 2023: Fix lastVersion update in listings
  • October 2022: Add lastVersion in listings
• cabal: Official upstream development repository for Cabal and cabal-install
  • October 2022: Add generate PackageInfos
• hie-bios: Set up a GHC API session for various Haskell Projects
  • October 2022: Add logs over commands
• wasp: A programming language that understands what a web app is.
  • October 2022: Add cli update command
• password: datatypes and functions for easily working with passwords in Haskell
  • October 2025: be able to turn off instances in password-instances
  • October 2025: split password-instances into multiple packages
  • October 2025: add documentation about the password-cli
  • October 2025: upgrade password-cli dependencies bounds
  • October 2024: introduce golden tests
  • October 2023: Introduce CLI
  • October 2022: Add utilities functions
• nix-output-monitor: Pipe your nix-build output through the nix-output-monitor a.k.a nom to get additional information while building.
  • October 2025: fix Local store URL parsing
  • October 2023: replace Map with HashMap
  • October 2022: Drop flow-file operators
• conferer: Configuration management for Haskell
  • October 2022: Fix missing projects CI
• hemmet: Emmet-like text expansion tool capable to produce HTML, CSS, file trees, that stuff
  • October 2022: Add hlint & CI Github Action
• tomland: Bidirectional TOML serialization
  • October 2022: Add hlint Github Action
  • October 2022: Add Codec Selective instance
• iris: Haskell CLI Framework supporting Command Line Interface Guidelines
  • October 2022: Add hlint Github Action
• eclair-lang: A minimal, fast Datalog implementation in Haskell that compiles to LLVM
  • October 2022: Add hlint Github Action
• spaceship-vi-mode: vi-mode plugin for spaceship (a Zsh customisable prompt)
  • September 2022: Fix antigen deploy instructions
• zinza: Jinja style templating library for Haskell
  • September 2022: Add DerivingVia Generics newtypes
• event-streaming-patterns: Confluent/Kafka Messaging/Streaming patterns
  • August 2022: Fix code example
• hspec: hspec is a behavior-driven development testing library (à la RSpec)
  • August 2022: compute diffs (actual, expected) concurrently
  • August 2022: Add parallel result rendering
• cabal: Haskell main build tool
  • July 2022: Clarify cli flag documentation
• mercure: Server-Sent Event hub
  • July 2022: Add Caddy directive for Docker deployment
• hspec-discover: hspecs driver for tests discovery
  • June 2022: Add parallel runner
• optparse-generic: optparse-application Generics based library
  • April 2022: Add Parser/Record runner
• wai-extra: WAI utilities
  • March 2024: Add NoCache to MaxAge in wai-app-static
  • April 2022: Add Middlewares for health checks
  • April 2022: Add a dynamic Middleware builder
• easy-hls-nix: easy HLS installer (Nix)
  • March 2022: upgrade to HLS 1.6.1.0
• vim-slime: ViM plugin for interactions with terminal multiplexers
  • December 2021: Fix tmux support
• powerline-go: Powerline-like shell prompts customization
  • December 2021: Add vi-mode segment
• tmux-mem-cpu-load: tmux monitor (CPU, RAM, load) utils (for the status line)
  • December 2021: Change RAM units threshold and CPU usage color
• Apache Pulsar: distributed pub-sub messaging system
  • November 2021: Headers fixes and synchronous functions addition in the C client
• HaskellSchool: Haskell Foundation school
  • December 2021: start Parsers Combinators lesson
  • November 2021: fix nixpkgs version in shell.nix
• github: Haskell bindings for the GitHub API
  • October 2021: update RepoWebhookEvent
• generic-random: derive via GHC.Generics QuickCheck's Arbitrary instance
  • July 2021: Implement a type-level deriving via module
• openapi3: Haskell OpenAPI 3 types
  • May 2021: support for Specification Extensions
• bloodhound: ElasticSearch client
  • Since April 2022: Maintainer
  • February 2021: bug fixes
• pandoc: text format processing
  • January 2021: Support for Github wikilinks
• swcraftlyon.github.io: Software Craftsmanship Lyon website
  • May 2021: CR Coding dojo 2021-04-22
  • January 2021: Coding dojo du 2021-01-06
• nix-workshop: Nix workshop materials
  • May 2021: fix typo
• testcontainers-hs: manage Docker containers for tests
  • June 2022: Add naming strategies
  • May 2021: bug fixes
  • June-August 2020: Hspec support, bug fixes, aeson-optics usage
• aws-lambda-haskell-runtime-wai: AWS Lambda Haskell runtime WAI adapter
  • September 2020: update to aws-lambda-haskell-runtime 3.0.4
• cut-the-crap: Haskell spam filter CLI
  • May 2020: various improvements (drop optparse-generic, restore CLI long names)
• hatrace: strace-like
  • June 2020: Introduction of many syscalls