# 10 — Milestones, Testing, Risks

## Milestones

Each milestone ends with a verifiable outcome (✅).

### M0 — Scaffolding
Workspace + all crates compile empty; CI (fmt, clippy `-D warnings`, test). `harness-core`: id types, event bus, permission `evaluate` with table-driven tests, storage actor with roundtrip tests.
✅ `cargo test` green; a bin stub prints version.

### M1 — Headless core loop + Anthropic
Anthropic codec + provider (against fixtures), config loading, `Tool` trait + read/bash/glob/grep/edit/write (edit replacers ported **with opencode's test table**), engine loop end-to-end with a `MockProvider`, permission service with an auto-approve stub frontend. Debug command `harness run -p "<prompt>"`.
✅ Integration test: scripted MockProvider does text → tool call (read) → final text with correct parts persisted; `harness run` works against real Anthropic.

### M2 — TUI
Event loop, chat viewport + markdown renderer + cache, input, streaming render, permission modal wired to the real oneshot path, session picker/resume, abort.
✅ Manually drive a multi-turn session with permission-gated edits; TestBackend snapshot tests pass.

### M3 — All providers + auth
OpenAI (responses + chat codecs), Copilot (device-flow modal, token exchange with direct-Bearer fallback, `/models` routing to the three codecs), auth.json + token refresh, models.dev metadata + cost display, retry policy + doom-loop guard.
✅ The same session works on all three providers; device-flow login completes inside the TUI; costs shown.

### M4 — Multiagent
Agent registry (bundled markdown + overrides), task tool foreground/background, JobBoard + persistence + injection, aliases/reuse, depth limits, permission intersection, jobs pane + subtask drill-in.
✅ An orchestrator session spawns a background explorer; the board appears in next-turn context (verify via request logging); reuse by alias continues the same child session.

### M5 — MCP, LSP, commands/skills
rmcp integration + namespaced tools + permissions; LSP pool + diagnostics in edit/write output; markdown commands + skill tool.
✅ A config-declared MCP server's tool is callable with ask-permission; editing a broken `.rs` file surfaces rust-analyzer errors in the tool result; `/mycommand` works.

### M6 — Polish
Auto-compaction (Compactor impl + overflow trigger), session title generation (small_model), tool-output spill dir, theming, syntax-highlighted code blocks, crash-resume hardening, streaming-render perf pass.
✅ A session driven past the context limit compacts and continues correctly.

## Testing strategy

- **Provider decoders:** recorded SSE fixtures per codec (text-only, tool call, parallel tool calls, thinking, errors, mid-stream disconnect, `data:` split across chunks) → assert exact `Vec<LlmEvent>` via `insta` snapshots. Request builders snapshot outgoing JSON (cache_control placement, tool schemas, header sets) with `wiremock`.
- **Auth:** device-flow poll loop against wiremock (`authorization_pending → slow_down → success`); token-exchange expiry + refresh single-flight.
- **Tools:** tempdir-based unit tests; edit replacers get a direct port of opencode's `edit.test.ts` case table; bash timeout/kill-process-group; truncation boundaries.
- **Engine integration (MockProvider):** multi-step tool loop; permission ask/deny/reject via the real oneshot path; retry backoff (mock returns RateLimited twice); doom-loop trigger; cancellation mid-tool; task tool foreground + background with job-board assertions; depth-limit rejection; permission intersection.
- **Permission engine:** table-driven last-match-wins/wildcard tests mirroring opencode's semantics.
- **TUI:** ratatui `TestBackend` snapshots (empty session, streaming message, tool card, permission modal, jobs pane); input-handling unit tests on `AppState`.
- **Storage:** actor roundtrips; resume-after-simulated-crash (unfinished assistant → aborted).

## Top risks

1. **Copilot token exchange variance** — opencode ships direct-Bearer; classic Copilot API wants the `copilot_internal/v2/token` exchange. Mitigation: dual-path `token.rs`, verify live early in M3.
2. **SSE edge cases** — events split across TCP chunks, keepalive comments, provider-specific mid-stream error events. Mitigation: `eventsource-stream` + adversarial fixtures.
3. **Streaming markdown perf in ratatui** — no incremental layout. Mitigation: per-part render cache + tail-only re-render + plain-text-tail fallback.
4. **Edit replacer fidelity** — port the test suite, not just the code.
5. **Child-process lifecycle (MCP/LSP/bash)** — zombies. Mitigation: process-group kills + `Drop` guards + central `ChildRegistry`.

## Key reference files

| What | Where |
|---|---|
| Inner stream state machine to mirror | `~/repos/opencode/packages/opencode/src/session/processor.ts` |
| Outer loop semantics | `~/repos/opencode/packages/opencode/src/session/prompt.ts` |
| Permission evaluate/ask semantics | `~/repos/opencode/packages/opencode/src/permission/index.ts` |
| Edit replacer chain + tests (port verbatim) | `~/repos/opencode/packages/opencode/src/tool/edit.ts` |
| Copilot auth/headers/model routing | `~/repos/opencode/packages/opencode/src/plugin/github-copilot/{copilot,models}.ts` |
| Anthropic caching/beta headers | `~/repos/opencode/packages/opencode/src/provider/transform.ts` |
| Retry policy details | `~/repos/opencode/packages/opencode/src/session/retry.ts` |
| JobRecord, aliases, formatForPrompt | `~/repos/oh-my-opencode-slim/src/utils/background-job-board.ts` |
| Session-reuse mechanics | `~/repos/oh-my-opencode-slim/src/hooks/task-session-manager/index.ts` |
| Agent prompt content to port into markdown | `~/repos/oh-my-opencode-slim/src/agents/*.ts` |