The playground's local manifest projection and builder now emit only
the resolved target path; workflow-name fallback, titles, and the
workflows-map key are unchanged.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
A tab left open across a deploy keeps running the previous build's
JavaScript indefinitely. index.html is fetched only on a full page load,
all later navigation is client-side, and hashed bundles are served
`immutable`, so nothing reveals that the code is stale. This produced a
false-positive bug report where two correctly-deployed fixes appeared to
be missing.
Publishes a build id and offers a reload when the running document falls
behind. The toast never reloads on its own; the only automatic reload is
recovery from a chunk that no longer exists.
Build id derivation
-------------------
The obvious approach — hash the emitted asset filenames, which already
embed content hashes — does not work: Bun's minified identifier naming is
not deterministic. Building an unchanged tree twice produces byte-different
output roughly one run in three (same length, ~100k differing bytes, all of
it mangled names). Output hashes therefore move with no source change,
which would fire the toast on redeploys of identical code and train people
to ignore it.
The id is instead derived from the bundle's source inputs, so it changes if
and only if something we control changed. Verified stable across eight
consecutive builds while the entry hash flipped between both variants.
This non-determinism also means two builds of the same commit embed
different bytes into the server binary, which is worth addressing
separately for reproducible builds.
Detection
---------
SWR with `refreshInterval` + `revalidateOnFocus`, per the repo's React
effects policy. SWR does not poll while the document is hidden, so
background tabs stay quiet without extra gating. Unknown state on either
side — missing meta tag, failed fetch, 503 during a dev rebuild — never
produces a prompt.
Stylesheet hashing
------------------
Tailwind's output was stable-named and therefore served `no-cache`, letting
a tab revalidate into new CSS while running old JS. Tailwind purges unused
classes per build, so classes the old bundle still emits could silently
lose their styles. It is now content-hashed and moves with the build.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
## Summary
Adds a new `/playground` route where users build a Fabro workflow by
chatting with Ask Fabro on the right while watching a live canvas
re-render on the left. The workflow can be downloaded as a `.fabro.zip`
or — eventually — launched as a real Fabro run; today the "Run for
real" button POSTs to `/api/v1/runs` and redirects to the resulting
`/runs/{id}` page, with a placeholder project/repo/folder picker.
The feature is built as a standalone component subtree under
`apps/fabro-web/app/components/playground/` with no `AppShell` or
`react-router` dependencies, so it can be re-embedded in other contexts
later by passing `chatEndpoint`, `authMode`, and an optional
`realRunRedirect` prop.
## What changed
**Frontend (`apps/fabro-web/`)**
- New `/playground` route + `<Playground>` component tree.
- Live SVG canvas via `@viz-js/viz` with click-to-inspect (read-only
node detail panel), pan, zoom, fit-to-window, and a simulated walk
through the graph driven by a Play button.
- Docked chat sidebar (assistant-ui) wired to the new
`/api/v1/playground/chat` endpoint, with auto-retry on parse failure
and a playground-specific tool-call summary that reads
`Wrote workflow.fabro (N nodes, M edges)`.
- File tabs (`workflow.fabro` / `workflow.toml` / `README.md`),
`.fabro.zip` download via `fflate`, and a "Run for real" toolbar
button that POSTs an inline `RunManifest` to `/api/v1/runs`.
- Draft persists across page refreshes via `localStorage`.
**Backend (`lib/crates/fabro-server/`)**
- New `POST /api/v1/playground/chat` SSE endpoint. Server is stateless
across turns: each request carries the full draft, the server runs
the LLM with a single `write_workflow_file` tool, streams
`StreamEvent` frames back, and lets the client own diffing/animating
the result into the canvas.
- Request-size caps before the LLM call (50 messages, 100 nodes, 200
edges) so a misbehaving or malicious client can't drag multi-MB
transcripts through token billing.
**Spec / wire contract**
- OpenAPI: new `playground/chat` operation + four new schemas
(`CreatePlaygroundChatRequest`, `PlaygroundWorkflowDraft`,
`PlaygroundWorkflowNode`, `PlaygroundWorkflowEdge`).
- `lib/packages/fabro-api-client` not regenerated yet (the playground
uses raw `fetch`); reviewers who want the TS client to pick up the
new types can run `bun run generate` in that package.
## Key design decisions
1. **Single `write_workflow_file` tool, not six per-op tools.** The
first cut exposed `add_node`/`update_node`/`connect`/etc. as
discrete tool calls. The model would routinely add nodes without
wiring them up, leaving the canvas in a broken half-state. Pivoted
to a single tool that takes the full new `workflow.fabro` content;
the browser parses the DOT, diffs it against the local draft, and
animates the resulting reducer ops in. The model only has to "get
the file right", and the canvas still paints node-by-node thanks
to the client-side animator.
2. **Stateless server.** Each chat turn POSTs the full current draft;
nothing is persisted server-side. Keeps the endpoint cheap, makes
refresh-resumption trivial (browser owns the truth), and means the
same endpoint can later sit behind a rate-limited anonymous variant
without growing per-session state.
3. **Standalone component subtree.** `<Playground>` has no
`AppShell`/router/store dependencies. All cross-cutting concerns
flow in as props (`chatEndpoint`, `authMode`, `realRunRedirect`).
This is the structural hook that makes future re-embedding possible
without a refactor.
4. **Chat is the only mutation path.** Click-to-inspect on the canvas
is read-only. Bi-directional canvas editing was explicitly cut from
scope to keep one source of truth for "how the workflow changed."
5. **Inline `RunManifest` instead of temp-dir-then-clone.** The
playground has no project to run against, so the `Run for real`
modal builds a `RunManifest` that carries the full DOT and
`workflow.toml` source inline (`workflows[key].{source, config}`).
`cwd` is pinned to a fixed `/tmp/fabro-playground` constant — no
LLM-controlled segment in a filesystem-looking field.
6. **React effects policy compliance.** All `useEffect` calls in
playground component code go through the existing primitives in
`app/hooks/effects.ts` (`useDocumentEvent`, `useInterval`) or a
purpose-named hook (`useCanvasRender`).
## Still outstanding (planned follow-ups)
- [ ] **Actually kicking off the ad-hoc run.** "Run for real" today
POSTs a manifest with a placeholder project/repo/folder
fieldset. The intent is to reuse the project-picker pattern
being introduced on the in-flight automations branch — once
that pattern lands, the disabled inputs in
`run-for-real-modal.tsx` become the live surface.
- [ ] **Header link to `/playground`.** No nav entry yet; users have
to type the URL directly.
- [ ] **Live SSE-driven canvas overlay** via
`GET /api/v1/runs/{id}/attach` — currently the modal redirects
to the standard run-view page; the "watch it build on the
playground canvas" experience comes when the `stage.*` events
are wired through.
- [ ] **Regenerate `lib/packages/fabro-api-client`** so the new types
ship to TS consumers.
- [ ] **Smoke test:** end-to-end download → unzip →
`fabro run <name>` round-trip.
- [ ] **`scripts/build.ts` dist-symlink bug:** `pruneOldBuilds` can
delete the directory `apps/fabro-web/dist` points at, which
pins the dev server in 503 "build in progress" forever.
Workaround documented; the real fix is a separate PR.
## Test plan
- [ ] `cd apps/fabro-web && bun run test app/components/playground/` —
111 tests pass
- [ ] `cd apps/fabro-web && bun run typecheck` — clean
- [ ] `cargo test -p fabro-server playground` — 6 tests pass
- [ ] Visit `/playground`; the canvas renders the welcome `start → ??? →
exit` ghost.
- [ ] Type "build me a release-notes workflow" in chat; nodes/edges
animate in; ack reads `Wrote workflow.fabro (N nodes, M edges)`.
- [ ] Click a node → inspector panel populates; click empty canvas →
deselects.
- [ ] Click `Simulate`; nodes light up `start → ... → exit` along the
resolved path.
- [ ] Click `Download .fabro`; unzip; `cd <unzipped> && fabro run
<name>` runs locally.
- [ ] Click `Run for real` → modal opens → confirm → POST succeeds →
redirected to `/runs/{id}` → run executes.
- [ ] Refresh the page; the draft persists from localStorage.
- [ ] Click `Start over` → `Yes`; canvas resets to welcome state.
---------
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
