Hop

Hop is prompt-native version control for coding agents.

Every instruction becomes an immutable state before project effects. Agent work produces checkpoint and proposal states beneath it. Landing a proposal creates a new accepted state and safely materializes it in the visible project folder without moving the user’s Git branch or real index. Controller integrations may capture the stronger pre-delivery boundary as well.

A0 accepted
├─ P1 prompt
│  └─ C1 checkpoint
│     └─ R1 proposal
└─ P2 prompt
   └─ R2 proposal

A0 + R1 → A1 accepted

Git provides source-tree storage, diffs, worktrees, and interoperability. Hop’s prompt-state graph, evidence, and acceptance history live separately in .hop/hop.db.

Current status

This repository contains the first local alpha kernel. It supports:

• Existing and unborn Git repositories
• Codex Desktop first-action prompt capture and session-aware follow-ups
• Controller-grade pre-delivery prompt capture
• Isolated detached worktrees per attempt
• Immutable checkpoints and proposals
• Checks bound to exact source trees
• Real three-way content merging, including compatible same-file edits
• Agent-ready reconciliation workspaces for genuine merge conflicts
• Optional validation on the final integrated tree
• Compare-and-swap acceptance
• Safe visible-root materialization on Desktop landing
• Controller-only internal acceptance plus explicit root synchronization
• Forward-only undo of the latest accepted transition
• Git-compatible accepted commits under refs/hop/accepted
• SQLite WAL state graph and machine-readable JSON output
• Pre-persistence credential redaction across prompts, summaries, and check evidence
• Embedded, installable vendor-neutral agent skill with implicit invocation enabled

It does not yet include a trusted raw-prompt hook, project knowledge, claims, remote synchronization, a GUI, or semantic merging.

Start with Installation and Getting started, or browse the documentation wiki. See the product blueprint for the complete model, design principles, and phased roadmap.

How the pieces fit

Prompt in Codex Desktop
  │
  ▼
Hop skill's first action ──> hop begin ──> prompt state + workspace
                                                │
                                                ▼
                                      edit → check → propose
                                                │
                                                ▼
Agent                           validate → auto-land → accepted state
                                                   → visible project root

The user continues typing into Codex Desktop normally. The skill invokes hop begin before inspecting or changing the project. hop begin initializes Hop when needed, uses CODEX_THREAD_ID to recognize follow-ups, checkpoints prior effects, and returns the isolated workspace. The skill confines work to that workspace, validates it, and automatically lands a successful proposal. hop land advances accepted state and then projects that exact tree into the selected folder. It proceeds only when the visible source still matches an accepted Hop state, so user edits are never overwritten. The original task prompt is the authorization; no extra landing prompt is required. Say review first or proposal only to opt into manual approval. This is a pre-project-effect boundary: the prompt is stored after Codex receives it but before the agent performs project work. A controller or future trusted prompt hook can provide strict pre-delivery capture.

Installation

Packaged releases require Git 2.40 or newer. Go is not required unless you use the developer installation path.

macOS and Linux — recommended

The installer detects your operating system and CPU, downloads the matching release archive, verifies its SHA-256 checksum, installs hop to ~/.local/bin, adds that directory to your shell PATH when necessary, and installs the Codex skill:

curl -fsSL https://githop.xyz/hop/hop/raw/branch/main/scripts/install.sh | sh

To inspect the installer before running it:

curl -fsSLO https://githop.xyz/hop/hop/raw/branch/main/scripts/install.sh
less install.sh
sh install.sh

Pin a version or choose another destination with environment variables:

HOP_VERSION=v0.1.0 HOP_INSTALL_DIR="$HOME/bin" sh install.sh

Windows PowerShell

Run PowerShell as your normal user. The installer verifies the release, installs hop.exe under %LOCALAPPDATA%\Programs\Hop, adds it to your user PATH, and installs the Codex skill:

irm https://githop.xyz/hop/hop/raw/branch/main/scripts/install.ps1 | iex

Go install — developer path

If Go 1.26 or newer is already installed:

go install githop.xyz/hop/hop/cmd/hop@latest
hop skill install --force

Ensure $(go env GOPATH)/bin is on PATH. Tagged module builds report the tag through hop version.

Build from source

Cloning is supported, but it is the contributor/fallback path rather than the normal product installation:

git clone https://githop.xyz/hop/hop.git
cd hop
go test ./...
go build -trimpath -o hop ./cmd/hop
mkdir -p "$HOME/.local/bin"
install -m 755 hop "$HOME/.local/bin/hop"
"$HOME/.local/bin/hop" skill install --force

Verify the installation

hop version
hop help

The packaged installers install two things:

• the hop CLI; and
• the embedded Hop agent skill at ${CODEX_HOME:-~/.codex}/skills/hop.

No project is modified during installation. A project receives its local .hop/ state only when Hop first runs inside that project.

Release installer URLs become available after the corresponding Gitea Release is published. Until the first public release exists, use the source build.

Getting started

1. Install Hop using one of the methods above.
2. Restart Codex Desktop if it was open during installation.
3. Open any existing Git project in Codex Desktop.
4. Ask Codex to change the project normally. You do not need to run hop init, create a branch, or route prompts through another application.
5. After the first task, run hop status in the project to inspect its accepted state and confirm the visible root is synchronized.

The skill is configured for implicit use on every local repository turn. If an agent ever fails to activate it automatically, mention $hop in that task as a deterministic fallback.

The agent's first project action is equivalent to:

hop begin --agent codex --heredoc <<'HOP_PROMPT_EOF'
<the current user message>
HOP_PROMPT_EOF

The agent—not the user—runs this command. It initializes Hop without changing the current Git branch, working tree, or index, stores the prompt, and returns the state IDs and isolated workspace. Follow-up messages in the same Codex task automatically continue the same Hop attempt.

For another agent runtime, export the embedded skill to that runtime's skills directory:

hop skill install --path /path/to/agent/skills --force

After editing the printed workspace, the agent runs this lifecycle automatically:

hop check P_... -- go test ./...
hop propose --summary "Added password reset emails" P_...
hop land R_... -- go test ./...

The command supplied to land runs in a temporary worktree containing the exact final tree that would become accepted. If it fails, refs/hop/accepted and the SQLite accepted head do not move. After acceptance, Hop updates only the visible working files through a disposable Git index; HEAD, the active branch, and the real index do not move. Compatible edits to the same file are merged automatically. A genuine merge conflict becomes a fresh agent reconciliation workspace, which the skill resolves, checks, and lands without asking the user to manage source-control mechanics. The agent pauses only for an explicit review-first request, failed validation, visible-root divergence, unresolved product intent, or newly required destructive/external scope.

land and accept are intentionally different:

hop land R_... -- go test ./...   # Desktop: accept and synchronize the selected folder
hop accept R_... -- go test ./... # Controller: accept internally, leave the folder untouched
hop sync                          # Catch a stale visible folder up to accepted state

hop sync is also the upgrade path for projects accepted by an older Hop build. It synchronizes only when the folder still matches an accepted ancestor.

Inspect the project:

hop status
hop graph
hop state P_...
hop diff R_...
hop history
hop sync
hop doctor

Inspect or hand the skill to a harness without installing it:

hop skill print

For a harness or controller that can capture prompts before delivery, initialize and start explicitly:

hop init
hop start --agent codex --heredoc <<'HOP_PROMPT_EOF'
Add password reset emails
HOP_PROMPT_EOF
eval "$(hop env P_...)"

In this mode, deliver the same message only after hop start succeeds. Use hop prompt --from P_... --heredoc for controller-managed follow-ups.

Undo the latest accepted transition without rewriting history:

hop undo

Parallel work

Two prompts started from the same accepted state receive independent worktrees:

hop start --agent codex "Add a health endpoint"
hop start --agent claude "Add an account empty state"

If their changed paths are disjoint, both proposals can land in either order. The second proposal is composed onto the latest accepted tree and validated there.

If both proposals changed the same file, Hop performs a real three-way merge. Independent hunks and identical changes land automatically. Only genuine merge conflicts pause acceptance; hop land prepares a fresh reconciliation workspace and the agent resolves, retests, reproposes, and lands it automatically. Text conflicts use diff3 markers; structural and binary conflicts may not. The visible project root remains at the last accepted state until that resolution passes.

State model

Kind	Prefix	Meaning
Accepted	A_	Canonical project revision
Prompt	P_	Exact instruction and pre-effect context
Checkpoint	C_	Immutable workspace progress
Proposal	R_	Frozen candidate result
Failed	F_	Terminal failed execution state
Cancelled	X_	Terminal cancelled execution state

Each Hop state references an immutable Git tree and synthetic commit. Multiple prompt states can reference the same tree while remaining distinct occurrences.

Source objects are pinned beneath refs/hop/states/*, preventing Git garbage collection from deleting states referenced by SQLite. Accepted source history is mirrored at refs/hop/accepted and can be exported as ordinary Git commits later.

Storage

.hop/
├── hop.db                 SQLite state graph and audit log
├── workspaces/            isolated attempt worktrees
├── integration/           temporary final-state validation worktrees
└── accept.lock            short-lived acceptance serialization lock

The repository’s .git/info/exclude receives .hop/; the public .gitignore, current branch, and real Git index are left alone. hop land, hop sync, and hop undo update visible source files only after confirming that the folder matches accepted Hop history.

Initialization refuses to proceed if .hop is already tracked as user-owned project source.

JSON protocol

Add --json anywhere:

hop --json status
hop begin --agent codex --heredoc --json

Successful output follows:

{
  "ok": true,
  "data": {}
}

The JSON shape is an alpha contract and may evolve before the first tagged release.

Safety boundary

Hop uses Git's three-way content merge rather than treating shared paths as conflicts. Textual cleanliness still cannot prove behavioral compatibility, so automatic acceptance reruns the strongest relevant validation on the exact final tree. Manual acceptance remains available as an explicit review-first mode.

Desktop landing fails closed when nonignored visible source does not exactly match an accepted Hop state or when an ignored/untracked path would be overwritten. It never uses reset --hard, moves HEAD, or rewrites the user's real index. The lower-level hop accept command deliberately retains controller-only behavior and does not update the visible root.

Agent-reported scope and test claims are never used as the source of truth. Hop computes source trees and changed paths itself.

Non-secret prompt text and check output are stored locally in SQLite without encryption. Before persistence, Hop redacts high-confidence provider tokens and contextual credentials, private keys, authorization headers, and credential-bearing URLs. The same boundary sanitizes proposal summaries plus recorded validation commands and output.

Detection cannot recognize every private or future token format. Prefer environment variables or a secret manager, and rotate any real credential pasted into any agent prompt even when Hop reports that it redacted the value.

Skill-driven Desktop capture stores the agent's verbatim transcription of the visible message and attachment references. It cannot prove byte-for-byte fidelity with Codex's raw submission. A trusted UserPromptSubmit hook is the future deterministic capture boundary; the skill remains the no-UI-change alpha workflow.