# ollie Architecture

## Philosophy

ollie is a small, extensible core library for building agentic systems. It has no binary of its own — frontends and consumers live in separate repos and import ollie as a dependency. The internal surface area is kept minimal; everything a consumer needs is exported under `pkg/`.

## Overview

<img src="architecture.svg?v=6" width="60%">

## Package Layout

```
pkg/
  agent/         — Core interface, agent loop, session and context management
  backend/       — Backend interface + implementations
  config/        — Agent config struct and loader
  env/           — Environment variable loading (env file + shell)
  log/           — Structured logging
  paths/         — Config and data directory resolution
  skills/        — Skill file discovery and loading
  store/         — Store interfaces and implementations (FlatDir, Session, Batch, Skill)
  tools/         — Server and Dispatcher interfaces
  tools/execute/ — execute.Server: execute_code

internal/
  sandbox/       — landrun sandbox config and command wrapper
```

### Why internal/sandbox?

The sandbox package is an implementation detail of `pkg/tools/execute`. It has no stable public API and no reason to be imported by consumers directly. Keeping it internal prevents accidental coupling.

## Extension Points

Consumers extend ollie by implementing or composing its interfaces:

- **`backend.Backend`** — swap or add LLM backends
- **`tools.Server`** — add a new tool server; all servers are equal
- **`tools.Dispatcher`** — replace the tool router entirely (e.g. remote dispatcher, mock)
- **`agent.Core`** — the agent's public API; frontends drive it without knowing internals. Includes `Close()` to release session resources (tmpdir under `/tmp/ollie/`).

All tool servers implement the same `tools.Server` interface. There is no special "builtin" concept — `execute.Server` is registered by name, and is torn down and recreated on `/agent` switches.

Each built-in server package exports a `Decl` function (`func Decl(...) func() tools.Server`) — a parameterized factory that produces a fresh server instance. `tools.NewDispatcherFunc` takes a map of name→Decl result and returns a `func() tools.Dispatcher` suitable for `agent.AgentCoreConfig.NewDispatcher`.

`execute.Decl(cwd string)` accepts a working directory used as `cmd.Dir` for sandboxed commands. Pass `""` to fall back to `os.Getwd()`.

**Adding a new tool server:**
1. Implement `tools.Server` in a new package under `pkg/tools/`
2. Export `func Decl(...) func() tools.Server`
3. Register the Decl result by name in `tools.NewDispatcherFunc` — no frontend changes needed

## Data Flow

```
Frontend
  └── agent.Core.Submit(prompt)
        └── loop.run()
              ├── backend.ChatStream()              — LLM call
              └── tools.Dispatcher.Dispatch(...)   — tool dispatch
                    ├── "execute"   → tools.Server
                    │       execute_code
                    └── "<servername>"  → tools.Server
```

All tool calls go through one `tools.Dispatcher.Dispatch` path. Every registered server is a `tools.Server`; the dispatcher routes by name and is agnostic to how any server is implemented.

## execute_code

`execute_code` is the only built-in tool. It is a unified primitive that handles simple execution, sequential composition, and parallel fan-out through a single `steps` array of pipeline stages.

Each stage is one of:
- `{code, language}` — inline code (default: bash)
- `{tool, args}` — named script from `OLLIE_TOOLS_PATH`; language detected from shebang
- `{parallel: [...]}` — concurrent fan-out; each element is a `{code}` or `{tool}` step; outputs concatenated in submission order

Stages run sequentially, each stage's stdout fed to the next stage's stdin. A single simple stage is the degenerate case and returns raw output directly.

```
steps=[{code: "ls"}]                          — simple execution
steps=[{code: "grep error log"}, {code:"wc"}] — sequential pipeline
steps=[{parallel:[{code:"wc a"},{code:"wc b"}]}] — parallel fan-out
steps=[{parallel:[...]}, {code:"sort"}]        — fan-out then transform
```

`OLLIE_TOOLS_PATH` defaults to `~/.config/ollie/tools`. `{tool}` steps resolve scripts from this path.

## Script Namespaces

User-facing scripts are organized by the 9P namespace they are hosted under and installed to `~/.config/ollie/scripts/{ns}/`:

| Namespace | Purpose | Scripts |
|---|---|---|
| `s/` | Session management and one-shot queries | `sh`, `ls`, `kill`, `cleanup`, `b`, `bfg`, `bbg` |
| `u/` | Utility scripts; compositions of `s/` primitives | `optimize` |

`s/b` is the core one-shot runner. `s/bfg` and `s/bbg` are thin wrappers: `s/bfg` blocks until the agent finishes and writes the result to stdout; `s/bbg` returns immediately and prints the session path. `u/` scripts have no special server backing — they are executable scripts that compose other namespaces via the filesystem.

## Tool Scripts

All capabilities beyond `execute_code` itself are implemented as tool scripts in `OLLIE_TOOLS_PATH`, invoked via `{tool}` steps. The agent discovers available scripts via `t/idx`.

Examples from the default install: `file_read`, `file_write`, `file_edit`, `file_glob`, `file_grep`, `memory_remember`, `memory_recall`, `reasoning_think`, `task_plan`, `task_complete`, `subagent_spawn`.

## Sub-agents

Sub-agents are implemented as a tool script (`subagent_spawn`) on top of the `s/` namespace. The script writes a session spec to `s/new`, blocks on `s/{id}/statewait` per job in background subshells, joins on all, and concatenates results. The `s/` namespace handles agent lifecycle, cancellation, and result storage.

For heterogeneous parallel delegation (N agents, N different prompts), a `{parallel:[...]}` stage composes with `subagent_spawn` — each parallel step is one shell invocation with a distinct prompt:

```
execute_code {parallel} stage
  ├── subagent_spawn "prompt A"  →  s/{id-0}/chat
  ├── subagent_spawn "prompt B"  →  s/{id-1}/chat
  └── subagent_spawn "prompt C"  →  s/{id-2}/chat
                                        ↓
                               concatenated in submission order
```

The architecture boundary is clean: `execute_code` is the only built-in tool in `core`; everything else is a tool script; `s/` is a 9P namespace. No layer knows about the others.

## Typical Consumer Setup

```go
newDispatcher := tools.NewDispatcherFunc(map[string]func() tools.Server{
    "execute": execute.Decl(cwd),  // "" falls back to os.Getwd()
})

env := agent.BuildAgentEnv(cfg, newDispatcher(), cwd)

core := agent.NewAgentCore(agent.AgentCoreConfig{
    Backend:       be,
    CWD:           cwd,
    Env:           env,
    NewDispatcher: newDispatcher,
    // ...
})
```

`BuildAgentEnv` wires together the pre-registered servers with the config. On `/agent` switches, `NewDispatcher` is called to produce a fresh dispatcher — all servers are torn down and recreated for the new agent config. `CWD` is preserved across switches.

## Session Lifecycle

`NewAgentCore` creates `/tmp/ollie/{sessionID}` when a session starts. `Core.Close()` removes it recursively. olliesrv calls `Close()` from `killSession` (individual session removal) and `Shutdown` (server stop — iterates all sessions). `SetSessionID` renames the tmpdir atomically alongside the persisted session files.

`!<cmd>` shell commands run in the session's current working directory (`Core.CWD()`), not the process working directory.

## Session and Context

`agent.Session` owns the message history. A `contextBuilder` enforces a rolling window to prevent unbounded prompt growth. When the window fills, older messages are either evicted (with a compaction notice injected) or proactively summarized via `/compact`.

## Sandboxing

`internal/sandbox` wraps commands with [landrun](https://github.com/landlock-lsm/landrun) (Landlock LSM). Configuration is layered:

1. Named sandbox config (`~/.config/ollie/sandbox/<name>.yaml`; `default` is used when unspecified)

If `superpowerd` is running, commands are additionally wrapped with `superpowers run-session` for privilege scoping (optional, detected at runtime).

## HTTP Gateway

`ollie-httpgw` is a thin translation layer between HTTP and 9P. It connects to
`olliesrv` as a 9P client and exposes the same namespace over REST-style HTTP,
so any HTTP client can interact with ollie without a 9P library.

Each HTTP method maps to a 9P primitive: `GET` → read/stat, `POST` → write,
`DELETE` → remove, `PATCH` → wstat (rename). The gateway serializes file content
to JSON where the format is well-defined (key-value files, tab-separated records,
session index); raw text falls through as-is.

Sensitive internal paths (`tr/`, `help`, `statewait`, `systemprompt`, etc.) are
blocked at the gateway layer and never exposed over HTTP.

```
HTTP client (browser, curl, script)
        │  HTTP/JSON  :8080
        ▼
  ollie-httpgw
        │  9P protocol
        ▼
  olliesrv  ($NAMESPACE/ollie  or  tcp:9564)
```

The gateway can connect to a local server via the Plan 9 namespace (default) or
to a remote server via TCP (`-net tcp -addr host:9564`), making it equally useful
for local setups and container/remote deployments.

## Frontends

All frontends interact with the same 9P namespace, either directly or via httpgw:

| Frontend | Interface | Talks to |
|---|---|---|
| `s/sh` | terminal (readline) | 9P filesystem directly |
| ollie-tui | terminal (TUI) | `agent.Core` library |
| ellie | Emacs buffer | 9P filesystem directly |
| Web UI | browser (Preact SPA) | `ollie-httpgw` over HTTP |

The web UI (`webui/`) is a Preact single-page application. It polls
`/s/{id}/chat` every two seconds for new output and proxies all API paths to
`ollie-httpgw`. It has no knowledge of 9P; the gateway is the only boundary.

Frontends that use `agent.Core` directly (ollie-tui) embed the core library and
manage sessions in-process. Frontends that use the filesystem (s/sh, ellie, web
UI) are decoupled from the implementation entirely — they work equally well
against a local or remote `olliesrv`.