docs: add extending-codeman.md, the third-party integration guide

Codeman has no plugin runtime by design: running third-party code inside the process that spawns agents, on a server people expose over a tunnel, would trade away the security posture that is a reason to use it. But it already has four extension seams that work from any language with nothing installed, and they were undocumented. Documents web tabs (render your own UI as a tab), the SSE event channel (react when an agent needs you), the HTTP API plus the codeman CLI (drive it from a script), and hook events. Every endpoint, schema field, event name and header in the page was read from source and then verified against a running instance, including the localhost-only CORS behavior and the SSE framing the example depends on. Also corrects a stale line in CLAUDE.md: it claimed the HTTP/SSE API was internal/unstable, which contradicts docs/versioning-policy.md, where the API under /api/v1 was finalized as part of the stable surface for the 1.0 cut. No new stability commitment is made here; the page makes an existing one discoverable. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-09-30 12:39:42 +02:00 · 2026-08-06 02:03:39 +02:00
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+# Extending Codeman
+
+Codeman has no plugin runtime, and that is a deliberate choice rather than a
+missing feature. A plugin runtime means running third-party code inside a process
+that spawns agents with your credentials, on a server people routinely expose
+over a tunnel or Tailscale. Codeman's security model is one of its reasons to
+exist, so it does not hand that away for an extension mechanism.
+
+Instead there are four seams that already work, from any language, with nothing
+installed:
+
+| You want to | Use | Runs where |
+| --- | --- | --- |
+| Show your own UI inside Codeman | [Web tabs](#seam-1-web-tabs) | Your own process, rendered as a tab |
+| React when an agent needs you | [SSE events](#seam-2-sse-events) | Anywhere that can hold an HTTP connection |
+| Drive Codeman from a script | [HTTP API](#seam-3-http-api-and-cli) or the `codeman` CLI | Anywhere |
+| React inside a Claude session | [Hooks](#seam-4-hooks) | The agent's own machine |
+
+Everything below is covered by the stability promise in
+[`versioning-policy.md`](versioning-policy.md): endpoint paths, the response
+envelope, `errorCode` values, and SSE event names are stable. Additive changes
+(new endpoints, new optional fields, new events) are non-breaking. Breaking
+changes ship under a new prefix (`/api/v2`).
+
+## Before you start
+
+**Base URL.** `http://127.0.0.1:3000` by default. Prefer the versioned prefix
+`/api/v1/...` for anything you publish; the unversioned `/api/...` is an alias.
+
+**Auth.** If `CODEMAN_PASSWORD` is set, send HTTP Basic on every request, or
+authenticate once and keep the `codeman_session` cookie. With no password set,
+Codeman is loopback-only and unauthenticated.
+
+```bash
+curl -u admin:$CODEMAN_PASSWORD http://127.0.0.1:3000/api/v1/sessions
+```
+
+**Envelope.** Every response is `{"success": true, "data": ...}` or
+`{"success": false, "error": "...", "errorCode": "..."}`. Check the HTTP status
+or `body.success`, then read `body.data`. The full `errorCode` to status mapping
+is in [`api-reference.md`](api-reference.md).
+
+## Seam 1: Web tabs
+
+The highest-leverage seam. Any web app you can serve locally becomes a tab beside
+your agent sessions. You write a normal web page; Codeman handles embedding it.
+
+```bash
+curl -u admin:$PASS -X POST http://127.0.0.1:3000/api/v1/webviews \
+  -H 'Content-Type: application/json' \
+  -d '{"name":"My Dashboard","url":"http://127.0.0.1:8787","icon":"📊"}'
+```
+
+Fields: `name` (1 to 60 chars), `url`, and optionally `icon` (a single glyph, max
+8 code units), `embedMode` (`proxy` by default, or `direct`), and `trusted`.
+
+Related endpoints: `GET /api/v1/webviews`, `PATCH /api/v1/webviews/:id`,
+`DELETE /api/v1/webviews/:id`, `POST /api/v1/webviews/probe` (reachability and
+framing check), `POST /api/v1/webviews/:id/open`.
+
+### Why it is proxied
+
+By default your page is served through Codeman's own origin at `/webview/:cap/*`
+rather than framed directly. A direct iframe fails three ways at once: production
+is HTTPS so `http://` targets are blocked as mixed content, many dashboards send
+`X-Frame-Options: DENY`, and Codeman's own `default-src 'self'` CSP blocks
+cross-origin frames. Proxying solves all three without weakening the CSP.
+
+### The two things that will confuse you
+
+A proxied frame is sandboxed and therefore **opaque-origin** unless you set
+`trusted: true`. Two consequences look like bugs in your own app:
+
+1. **Root-absolute URLs built at runtime** (`/assets/x.png` assembled in JS)
+   escape the injected `<base>` tag. Codeman injects a `runtimeUrlShim()` that
+   patches the common DOM sinks, but if you construct URLs in an unusual way,
+   prefer relative paths.
+2. **Same-host `fetch` and `XHR` are CORS-checked with `Origin: null`.** Codeman
+   handles this with `buildProxyCorsHeaders()`, and the proxy is exempt from the
+   global `OPTIONS` short-circuit. If you see "Failed to fetch" while the page
+   itself renders fine, this is the area to look at.
+
+⚠️ `trusted: true` opts out of the sandbox. A proxied page is served from
+Codeman's origin, so `allow-same-origin` lets it read the Codeman page and call
+the API that spawns agents. Only mark your own trusted code.
+
+## Seam 2: SSE events
+
+`GET /api/v1/events` is a Server-Sent Events stream. Each message is
+`event: <name>` plus `data: <json>`. There are 149 event names following a
+`domain:action` convention, registered in `src/web/sse-events.ts`.
+
+The ones most integrations want:
+
+| Event | Meaning |
+| --- | --- |
+| `session:created`, `session:deleted` | A session appeared or went away |
+| `session:idle` | The agent stopped working |
+| `session:completion` | A completion message was detected |
+| `session:exit`, `session:error` | The session ended or failed |
+| `hook:permission_prompt` | The agent is asking for permission |
+| `hook:idle_prompt`, `hook:stop` | The agent is waiting on you, or stopped |
+| `hook:task_completed`, `task:completed` | Work finished |
+| `subagent:discovered`, `subagent:completed` | Background agent lifecycle |
+| `mux:died` | A multiplexer session died unexpectedly |
+| `cron:runCreated`, `cron:runUpdated` | Scheduled job activity |
+
+### Filtering
+
+`?sessions=id1,id2` suppresses only the high-volume `session:terminal` stream for
+sessions you did not list. Lifecycle and metadata events are always delivered, so
+you cannot accidentally filter away the thing you are listening for.
+
+Pass `?clientId=<uuid>` to enable live filter updates through
+`POST /api/v1/events/subscribe` without reconnecting the stream.
+
+### Example: notify when any agent needs you
+
+```js
+const res = await fetch('http://127.0.0.1:3000/api/v1/events', {
+  headers: { Authorization: 'Basic ' + btoa(`admin:${process.env.CODEMAN_PASSWORD}`) },
+});
+const reader = res.body.getReader();
+const decoder = new TextDecoder();
+let buf = '';
+const WANTED = new Set(['hook:permission_prompt', 'hook:idle_prompt', 'session:idle']);
+
+for (;;) {
+  const { value, done } = await reader.read();
+  if (done) break;
+  buf += decoder.decode(value, { stream: true });
+  const frames = buf.split('\n\n');
+  buf = frames.pop() ?? '';
+  for (const frame of frames) {
+    const name = frame.match(/^event: (.+)$/m)?.[1];
+    const data = frame.match(/^data: (.+)$/m)?.[1];
+    if (name && WANTED.has(name)) notify(name, JSON.parse(data ?? '{}'));
+  }
+}
+```
+
+## Seam 3: HTTP API and CLI
+
+Around 199 handlers across 21 route files cover sessions, cases, files, cron,
+respawn, Ralph, the orchestrator, search, and admin. Each route module carries an
+`@fileoverview` describing its endpoints.
+
+The common ones:
+
+```bash
+# List sessions (live + persisted + transcript history, deduped)
+curl -u admin:$PASS http://127.0.0.1:3000/api/v1/sessions/unified
+
+# Create a session
+curl -u admin:$PASS -X POST http://127.0.0.1:3000/api/v1/sessions \
+  -H 'Content-Type: application/json' \
+  -d '{"workingDir":"/home/me/project","mode":"claude"}'
+
+# Send a prompt (single-line only, "\r" submits)
+curl -u admin:$PASS -X POST http://127.0.0.1:3000/api/v1/sessions/$ID/input \
+  -H 'Content-Type: application/json' \
+  -d '{"input":"run the tests","useScreen":true}'
+```
+
+For shell scripting, the `codeman` CLI is the same surface without the HTTP
+plumbing:
+
+```
+codeman session start|stop|list|logs     codeman task add|list|status|remove|clear
+codeman ralph start|stop|status|reset    codeman users add|passwd|list
+codeman status | list | attach <path>    codeman doctor
+```
+
+## Seam 4: Hooks
+
+Claude Code hooks post to `POST /api/v1/hook-event` from inside an agent session.
+Codeman installs its own hooks automatically, but the endpoint is open to yours.
+
+```json
+{ "event": "task_completed", "sessionId": "abc123", "data": { "any": "json" } }
+```
+
+`event` must be one of `permission_prompt`, `elicitation_dialog`, `idle_prompt`,
+`stop`, `teammate_idle`, `task_completed`. Each becomes the matching `hook:*` SSE
+event.
+
+⚠️ This endpoint skips Basic auth so hooks keep working, but when auth is active
+the loopback bypass requires the `X-Codeman-Hook-Secret` header
+(`~/.codeman/hook-secret`) unconditionally.
+
+## Gotchas
+
+Every one of these has cost somebody real time.
+
+- **CORS is localhost-only.** `Access-Control-Allow-Origin` is echoed only for
+  `localhost`, `127.0.0.1`, and `::1`. A browser app on any other origin cannot
+  call the API. Integrate server-side.
+- **A missing `Origin` header is allowed**, which is why curl, CLIs, and hooks
+  work. Cross-site origins are blocked by the CSRF guard.
+- **Reverse-proxy domains are rejected** by the anti-DNS-rebinding Host allowlist
+  unless added via `CODEMAN_ALLOWED_HOSTS=host,.suffix`.
+- **`null` is not `undefined`.** Request schemas use Zod `.optional()`, which
+  accepts `undefined` only. `JSON.stringify({ field: null })` keeps the null on
+  the wire and fails with `INVALID_INPUT`. Omit the key instead. This has caused
+  shipped bugs more than once.
+- **`text/plain` bodies stay raw.** Auto-parsing them as JSON enabled
+  simple-request CSRF, so it is deliberate. Send `application/json`.
+- **Prompts are single-line.** Input is delivered as text plus a separate Enter;
+  a multi-line string breaks the agent's input handling. Send `\r` to submit.
+- **Unwrap the envelope** before reading fields. `data` is not the response body.
+
+## Publishing your integration
+
+There is no registry and no review queue. Add the GitHub topic
+**`codeman-integration`** to your public repository so others can find it, and
+link back to Codeman in your README.
+
+If a real ecosystem of these appears, a manifest format and an install command
+become worth building. Until then, these four seams are the contract, and they
+require nothing of you but HTTP.
+
+## What Codeman deliberately does not have
+
+- **No in-process plugin runtime.** See the reasoning at the top of this page.
+- **No build or startup hooks** for third-party code. Run your own process.
+- **No per-plugin config or state directories.** Manage your own files.
+- **No sandbox**, because there is nothing to sandbox. Your integration is your
+  process, with your permissions, talking HTTP.