1 # AGENTS.md
2
3 This file provides guidance to AI coding agents when working with code in this repository.
4
5 ## What this is
6
7 `sigit` ("siGit Code") is a single Rust binary: a local-first AI coding agent that runs LLM
8 inference on-device (via the `onde` crate / GGUF models) or against a hosted/OpenAI-compatible
9 endpoint. It exposes itself two ways from the *same* binary, chosen at startup by whether stdin
10 is a TTY:
11
12 - **ACP mode** (stdin not a TTY): speaks the Agent Client Protocol over stdio for editor
13 integration (Zed, VS Code ACP Client). Cross-platform.
14 - **Interactive terminal mode** (stdin is a TTY): a full-screen ratatui chat UI. **Unix-only**
15 it relies on fd redirection to keep logs out of the TUI, so Windows gets ACP mode only.
16
17 Before the TTY/ACP split, `main` also dispatches the account subcommands `sigit login`,
18 `sigit logout`, `sigit whoami` (see `src/main.rs` `main()`).
19
20 ## Working in this repo
21
22 **IMPORTANT — branch naming:** Prefix every working branch with `feature/` (new functionality)
23 or `fix/` (bug fixes) — never a tool- or agent-name prefix like `claude/`. Name the branch after
24 the *changes it contains*, as a short, descriptive, kebab-case slug that is self-explanatory
25 from the name alone (e.g. `feature/tool-permission-system`, `fix/glob-mtime-sort`), never after
26 a task, ticket, or session id (not `feature/task-q003hm`).
27
28 **IMPORTANT — pull request target:** Always open pull requests against the `development` branch,
29 never `main`. `main` is release-only; `development` is where day-to-day work integrates.
30
31 **IMPORTANT — branch off `development`:** Start every working branch from the latest
32 `origin/development`. Exception: when new work *depends on* a feature branch that has not merged
33 yet (e.g. it builds on tools or APIs that branch introduces), it may be stacked on top of that
34 branch instead. When stacking: merge the base PR into `development` first, then rebase the
35 stacked branch onto `development` before opening its pull request, so each PR shows only its own
36 commits.
37
38 **IMPORTANT — run CI before pushing:** Run the full CI gate locally and confirm it is green
39 *before* pushing a branch or opening a pull request — never push work that fails these:
40
41 ```sh
42 cargo fmt -- --check # formatting
43 cargo clippy --tests -- -D warnings # lint (warnings are errors)
44 cargo test --locked # tests
45 ```
46
47 ## Agent assets layout
48
49 `.agents/` is the canonical home for agent assets; every other agent path in
50 the repo is a symlink into it, never a copy:
51
52 - `.agents/AGENTS.md` — this file, the project instructions. The root
53 `AGENTS.md` and `CLAUDE.md` are symlinks to it, so agents.md-standard tools,
54 Claude Code, and sigit itself (via `src/instructions.rs`, which prefers
55 `AGENTS.md` over `CLAUDE.md` in the same directory and therefore reads it
56 once) all load the same content. Edit this file; never replace the root
57 symlinks with real files.
58 - `.agents/skills/` — all project skills. `.claude/skills` is a symlink to it,
59 which is how both Claude Code and sigit itself (via `src/skills.rs`) discover
60 them. Add new skills under `.agents/skills/<name>/SKILL.md`, never as real
61 files under `.claude/`.
62
63 ## Build / test / lint
64
65 ```sh
66 cargo build # debug build
67 cargo build --release # release binary at target/release/sigit
68 cargo run # launches interactive TUI (stdin is a TTY)
69 cargo test # CI runs: cargo test --locked --target <target>
70 cargo clippy --tests -- -D warnings # CI gate: clippy is -D warnings on all 4 targets
71 cargo fmt -- --check # CI gate (edition 2024)
72 ```
73
74 CI (`.github/workflows/ci.yml`) runs fmt + clippy + test across four targets:
75 `aarch64-apple-darwin`, `x86_64-apple-darwin`, `x86_64-unknown-linux-gnu`,
76 `x86_64-pc-windows-msvc`. Clippy is `-D warnings`, so warnings fail the build.
77
78 Run a single test: `cargo test <test_name>`.
79
80 ## Critical platform constraint: `#[cfg(unix)]` dead code
81
82 The interactive client is `#[cfg(unix)]`-only. The `InferenceBackend` seam (`backend.rs`) and
83 provider resolution (`provider.rs`) are consumed by both the interactive client and the ACP
84 server, but several of their items are reached only through the Unix-only interactive paths, so
85 the dead-code lint is suppressed *on non-Unix targets only*.
86
87 Consequence: code can pass clippy on macOS/Linux but fail on the Windows target (or vice versa).
88 When touching `backend.rs`, `provider.rs`, or the interactive path, keep the `cfg` gates intact —
89 don't "fix" an unused-warning by deleting code that's live on Unix.
90
91 ## Architecture
92
93 The agent loop is backend-agnostic. The flow: a turn (messages + tool specs) goes to an
94 `InferenceBackend`, which returns assistant text and/or tool calls; the loop executes tools and
95 feeds results back. Neither the loop nor ACP/TUI surfaces depend on a concrete backend.
96
97 - **`src/main.rs`** — entry point, mode dispatch, the full ACP `Agent` impl (session lifecycle:
98 new/load/fork/prompt/cancel, config options, slash-command advertisement), and the `SYSTEM_PROMPT`
99 (note: it bakes in smbCloud-specific context the agent should use when the repo is clearly
100 smbCloud, and stay general otherwise).
101 - **`src/backend.rs`** — the `InferenceBackend` trait and neutral types (`ToolSpec`, `ToolCall`,
102 `ToolResult`, `TurnResult`). Two impls: `LocalBackend` (on-device via `onde::ChatEngine`) and
103 `OpenAiBackend` (any OpenAI-compatible HTTP endpoint).
104 - **`src/provider.rs`** — decides *which* backend serves inference. Resolution order, first match
105 wins: (1) override via `OPENAI_BASE_URL`+`OPENAI_API_KEY` or active profile in
106 `~/.config/sigit/providers.toml`; (2) siGit Code Cloud when logged in; (3) on-device.
107 - **`src/tools.rs`** — agent tool schemas + execution: `read_file`, `create_directory`,
108 `list_directory`, `search_files`, `glob`, `read_website`, `create_file`, `edit_file`,
109 `multi_edit`, `delete_file`, `run_command`, `write_todos`, `remember`. Add a tool in both the
110 spec list (`all_tools`) and the execute `match` (`execute_tool`). `run_command` also enforces
111 commit attribution: when a command creates a new commit that lacks the
112 `Co-Authored-By: siGit Code` trailer (`COMMIT_CO_AUTHOR_TRAILER`), it amends the trailer in —
113 unless the commit already exists on a remote, which is never rewritten.
114 - **`src/skills.rs`**[Agent Skills](https://agentskills.io) support. Discovers skill
115 folders (each with a `SKILL.md`: YAML frontmatter `name` + `description`, then Markdown
116 instructions) from `.sigit/skills/` and `.claude/skills/` in the cwd, `$SIGIT_CONFIG_DIR/skills/`,
117 and `~/.claude/skills/`. Progressive disclosure: the discovery list (name + description) is
118 baked into the dynamically-built `skill` tool's description, and activating a skill (the model
119 calls `skill` with a name) loads the full `SKILL.md` body. The `skill` tool is appended in the
120 `*_as_specs`/`build_tool_specs` layer (not in `all_tools()`) so its description can be dynamic,
121 and only when at least one skill exists.
122 - **`src/mcp.rs`**[Model Context Protocol](https://modelcontextprotocol.io) *client*. Two
123 transports: **Streamable HTTP** (one JSON-RPC POST endpoint, `url` in `mcp.toml`; replies are
124 `application/json` or SSE) and **stdio** (`command` + optional `args`/`[server.env]` in
125 `mcp.toml`; sigit spawns the server and speaks newline-delimited JSON-RPC over its
126 stdin/stdout, stderr inherited into sigit's log). `url` and `command` are mutually exclusive —
127 both or neither is a config error, logged and skipped. Both transports run the same
128 `initialize`/`tools/list` handshake and forward `tools/call`. Discovery is best-effort at
129 startup (`mcp::init`, called from both branches of `main()`) and cached in a process-global so
130 the synchronous spec builders (`mcp::tool_specs`) and the async dispatch (`mcp::call_tool`) can
131 both read it; `/reload` does *not* re-run it, so config changes need a restart. stdio children
132 live for the process; a dead child fails calls with an in-band error string (no auto-restart).
133 Tools are namespaced `mcp__<server>__<tool>`, appended in the `*_as_specs`/`build_tool_specs`
134 layer and routed in `tools::execute_tool` via `mcp::is_mcp_tool`. The official server
135 (`<cloud>/mcp`, default `https://sigit.si/api/v1/mcp`) is baked in (always HTTP) and authed
136 with the cloud session token; extra servers live in `mcp.toml` (global
137 `$SIGIT_CONFIG_DIR/mcp.toml` and project-local `.sigit/mcp.toml`). The stdio path is covered by
138 `tests/mcp_stdio.rs`, driven by the test-only `src/bin/mcp_stdio_stub.rs` helper binary
139 (excluded from the published crate via `exclude` in `Cargo.toml`).
140 - **`src/permissions.rs`** — tool permission policy. Every tool call passes through
141 `decision_for` before executing: read-only tools always run; mutating tools (and all
142 `mcp__*`/unknown tools) are governed by, in order: per-session plan mode (`/plan` — deny all
143 mutating tools with a present-a-plan message), session "always allow" grants, per-tool
144 overrides and the default mode from `[permissions]` in `settings.toml` (`allow`/`ask`/`deny`,
145 default `ask`; `SIGIT_PERMISSIONS` env overrides the default). On `ask`, the ACP path sends
146 `session/request_permission` (allow once / allow for session / deny) and the TUI pauses the
147 inference task on a y/a/n prompt. Note: ACP turn-affecting handlers run in `cx.spawn`ed tasks
148 serialized by `SiGitAgent::turn_lock` so the dispatch loop can route the client's permission
149 answer mid-turn — don't move them back inline, and don't await client requests from inline
150 handlers (deadlock).
151 - **`src/instructions.rs`** — project instruction files, the always-on counterpart to skills.
152 Reads `AGENTS.md` (the cross-tool [agents.md](https://agents.md) standard) and `CLAUDE.md`,
153 walking from the session cwd up to the repo root (nearest ancestor with `.git`, never above it),
154 plus a global file under `$SIGIT_CONFIG_DIR`. Files are ordered outermost-first so the deepest
155 (most specific) wins. The combined block is injected via `session_context_message` in `main.rs`
156 — pushed as a system message at every ACP session entry point (new/load/fork + model switch)
157 and appended to the system prompt on the cloud and TUI-startup paths.
158 - **`src/chat.rs`** — the Unix-only ratatui TUI. Loading-spinner phase then chat; uses
159 `tokio::select!` to multiplex terminal events with streaming tokens.
160 - **`src/setup.rs`** — model cache location, local model discovery, selected-model persistence.
161 Must run (`setup_shared_model_cache`) *before* anything touches `ChatEngine`/`hf-hub`, since
162 those read env vars once at init.
163 - **`src/account.rs`** — siGit Code Cloud auth (`/login`, `/logout`, `/whoami`); authenticates
164 against the account API and stores a session token. Performs no console I/O.
165 - **`src/credentials.rs`** — local session-token store (TOML, `0600` on Unix).
166 - **`src/models.rs`** — model-picker types shared across platforms.
167
168 Slash commands (`/help`, `/models`, `/skills`, `/mcp`, `/login`, `/logout`, `/whoami`, `/reload`,
169 `/plan`, `/permissions`, `/clear`, `/status`) are advertised via `advertise_commands` in `main.rs`
170 and handled in both the TUI and ACP sessions.
171
172 ## Model cache (macOS)
173
174 On macOS the HF model cache lives in an App Group container shared with the siGit desktop app:
175 `~/Library/Group Containers/group.com.ondeinference.apps/models/`. Other platforms fall back to
176 `~/.cache/huggingface/`. The CLI reuses a model the desktop app already downloaded. First run
177 downloads a GGUF model (~1–2 GB) from Hugging Face.
178
179 ## Logging
180
181 In TTY (interactive) mode, *all* output — `log`, `tracing`, stray `println!` — is redirected to
182 `$TMPDIR/sigit.log` so the ratatui surface stays clean; the TUI holds a separate fd to the real
183 terminal. In ACP mode, stdout is reserved for protocol JSON and logs go to stderr. Control
184 verbosity with `RUST_LOG`.
185
186 ## Relevant env vars
187
188 `OPENAI_BASE_URL` / `OPENAI_API_KEY` (provider override), `SIGIT_API_URL` (account API base,
189 default `https://sigit.si`), `SIGIT_CLOUD_URL`, `SIGIT_CONFIG_DIR` (default `~/.config/sigit`),
190 `SIGIT_MODEL`, `SIGIT_MCP` (`off` disables MCP), `SIGIT_MCP_OFFICIAL` (`off` drops the baked-in
191 server), `SIGIT_PERMISSIONS` (`allow`/`ask`/`deny` — overrides the default permission mode for
192 mutating tools; the escape hatch for clients without permission-request support),
193 `HF_HOME` / `HF_HUB_CACHE`, `RUST_LOG`.
194
195 ## Releasing
196
197 Version lives in `Cargo.toml`. The binary is published to five registries via separate workflows
198 (`release-crates`, `release-github`, `release-homebrew`, `release-npm`, `release-pypi`); the
199 `npm/` and `pypi/` dirs hold the wrapper-package templates. Update `CHANGELOG.md` for releases.