gadfly/README.md

# 🪰 Gadfly

**An AI gadfly for your pull requests.** Gadfly is an *adversarial* code reviewer that
runs in Gitea Actions: on every PR it reads your actual repository, hunts for real
problems, verifies them against the code, and posts its findings as a comment. It does not
praise your code. A gadfly does not let things slide.

> ### 🤖 Heads up: this is a vibe-coded project
> Gadfly was built almost entirely by an AI agent (Claude Code), prompts and all — the
> reviewer's "brain" is a language model, and so was most of the author. It works and it's
> tested, but treat it accordingly: **it is advisory only, it never blocks a merge, and you
> should still review its reviews.** Issues and PRs welcome; expect the occasional
> AI-flavored rough edge.

## What makes it different

Most LLM "review my diff" bots read the diff in isolation and hallucinate problems they
can't actually see — a "missing import" that's three lines above the hunk, a "broken
caller" in a file they never opened. Gadfly is **agentic**: the model has read-only tools
over the checked-out repo and is *required* to use them before reporting anything.

- **Tools:** `read_file`, `list_dir`, `grep`, `find_files`, `get_diff`.
- **Verify-before-claiming discipline:** baked into the system prompt — open the file,
  grep the symbol, or drop the finding.
- **Two passes:** a *review* pass drafts findings, then an adversarial *recheck* pass
  independently re-verifies each one against the code and drops the ones it can't confirm,
  recomputing the verdict. This is what kills "confident but wrong."
- **Semantic-bug hunting:** it's told not to trust a plausible-looking constant, conversion
  factor, or formula — re-derive the expected value, because that's where real bugs hide.

Every review leads with a one-line verdict: **No material issues found**, **Minor issues**,
or **Blocking issues found**.

## Turn it on for a repo

Gadfly ships as a container image, so consuming repos don't build anything — they just run
it. Drop one file in your repo and set a couple of secrets/vars:

1. Copy [`examples/adversarial-review.yml`](examples/adversarial-review.yml) to
   `.gitea/workflows/adversarial-review.yml` in your repo.
2. Add repo config:
   - **secret** `OLLAMA_CLOUD_API_KEY` — your [Ollama Cloud](https://ollama.com) key (empty
     ⇒ Gadfly posts a harmless "not configured" notice instead of reviewing). *Not needed if
     you point Gadfly at a different provider — see [Models & providers](#models--providers).*
   - **var** `OLLAMA_REVIEW_MODELS` *(optional)* — comma-separated model ids
     (default `qwen3-coder:480b-cloud,gpt-oss:120b-cloud`). One comment per model.
   - **var** `GADFLY_ALLOWED_USERS` *(optional)* — who may re-trigger via comment; empty ⇒
     any repo collaborator.

`GITEA_TOKEN` is provided automatically by Actions; comments post as the `gitea-actions`
user, scoped to that repo — no bot account needed.

## Models & providers

Gadfly is built on [majordomo](https://gitea.stevedudenhoeffer.com/steve/majordomo), so the
reviewer model is not hard-wired — it can target anything majordomo supports. Pick a provider
by setting `GADFLY_PROVIDER` (used to prefix bare model ids); point at a custom endpoint with
`GADFLY_BASE_URL`; supply a key with `GADFLY_API_KEY` or the provider's standard env var. A
`GADFLY_MODEL`/`GADFLY_MODELS` value that already contains a `provider/` prefix (or is a
majordomo failover chain / alias) is used verbatim.

| Provider | `GADFLY_PROVIDER` | Key env | Status |
|----------|-------------------|---------|--------|
| **Ollama Cloud** (default) | `ollama-cloud` | `OLLAMA_API_KEY` / `OLLAMA_CLOUD_API_KEY` | ✅ in active use |
| **Local Ollama** | `ollama` | none (`OLLAMA_HOST` or `GADFLY_BASE_URL` for a remote daemon) | ✅ tested |
| **OpenAI-compatible** (incl. local Ollama's `/v1`) | `openai` + `GADFLY_BASE_URL` | `OPENAI_API_KEY` (any non-empty for Ollama) | ✅ tested against Ollama |
| **OpenAI** | `openai` | `OPENAI_API_KEY` | ⚠️ wired, **untested** |
| **Anthropic** | `anthropic` | `ANTHROPIC_API_KEY` | ⚠️ wired, **untested** |
| **Google (Gemini)** | `google` | `GOOGLE_API_KEY` / `GEMINI_API_KEY` | ⚠️ wired, **untested** |

> ### 🧪 Honest status
> Only the **Ollama** paths above are actually exercised. The OpenAI / Anthropic / Google
> providers come "for free" from majordomo's abstraction and *should* work, but I haven't
> spent money verifying them — treat them as untested. The OpenAI-**compatible** path **is**
> tested, because you can point it at a local Ollama (`GADFLY_BASE_URL=http://localhost:11434/v1`)
> and exercise the exact same code an OpenAI/OpenRouter endpoint would hit, for free. If you
> try a cloud provider and it works (or doesn't), please open an issue.

For arbitrary endpoints you can also skip `GADFLY_PROVIDER`/`GADFLY_BASE_URL` and define a
majordomo `LLM_*` env DSN, then reference it by name in `GADFLY_MODEL` (advanced; HTTPS only).

### Triggers

1. A **new/reopened/ready** non-draft PR — automatic.
2. Commenting **`@gadfly review`** on a PR — re-review on demand (gated to allowed users).
3. **workflow_dispatch** — manual, with a `pr_number` input.

(Pushing new commits does *not* auto-re-review — comment `@gadfly review` after pushing
fixes. This keeps usage down.)

## How it's packaged

```
cmd/gadfly/            the agentic reviewer binary (majordomo + Ollama Cloud); zero deps beyond stdlib + majordomo
scripts/run.sh         fetches the PR diff, runs the reviewer, upserts one labeled comment
scripts/system-prompt.txt  the reviewer persona + verification discipline
entrypoint.sh          the container brains: trigger gating, clone, model loop (logic lives here, not in YAML)
Dockerfile             multi-stage; build-time module creds (BuildKit secrets) never reach the final image
.gitea/workflows/build-image.yml   push to main → :latest; tag v* → :<tag> + :latest
examples/              the ~15-line stub a consuming repo drops in
```

The image is published to `gitea.stevedudenhoeffer.com/steve/gadfly`. Every push to `main`
rebuilds and republishes `:latest` (plus `:sha-<short>`); pushing a `v*` tag publishes that
pinned version (plus `:latest`). Pin consumers to a `:vN` tag for stability, or track
`:latest` to ride main.

## Configuration (advanced)

The reviewer binary reads these (the stub/entrypoint set sane defaults):

| Env | Default | Meaning |
|-----|---------|---------|
| `GADFLY_MODEL` | — | model id, or `provider/model` spec, or majordomo alias/chain |
| `GADFLY_PROVIDER` | `ollama-cloud` | provider prefix for a bare model id |
| `GADFLY_BASE_URL` | — | override endpoint (OpenAI/Ollama-compatible servers) |
| `GADFLY_API_KEY` | — | provider key; falls back to the provider's standard env |
| `GADFLY_MAX_STEPS` | 24 | review-pass tool-step cap |
| `GADFLY_RECHECK` | on | set `0`/`false` to skip the recheck pass |
| `GADFLY_RECHECK_MAX_STEPS` | 16 | recheck-pass step cap |
| `GADFLY_TIMEOUT_SECS` | 300 | overall deadline (both passes) |
| `GADFLY_MAX_DIFF_CHARS` | 60000 | diff chars embedded in the prompt (full diff via `get_diff`) |
| `GADFLY_TRIGGER_PHRASE` | `@gadfly review` | comment phrase that re-triggers |
| `GADFLY_ALLOWED_USERS` | *(collaborators)* | comma-separated allow-list for comment triggers |

## Building locally

```sh
go build ./cmd/gadfly      # needs read access to the private majordomo module
go test ./...
```

## License

MIT — see [LICENSE](LICENSE).