fix(nix-web-monitor): bust stale UI cache, harden WebSocket send and lag resync#806
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…lag resync Three fixes after the WebSocket switch: - index.html is now served with Cache-Control: no-store. It names the content-hashed asset files, so a browser that cached it across a rebuild requests assets the new server no longer has. nix store mtimes are a constant epoch, so no-cache would 304 the stale copy; no-store forces a fresh fetch each load. This is the durable fix for the "Expected a JavaScript module but got text/html" load failure. - A missing asset now 404s instead of falling back to index.html. Serving HTML for a missing /assets/*.js is what surfaces as the wrong-MIME error; the SPA fallback was unnecessary (the dashboard has no client-side routing). - Each WebSocket frame send is bounded by a 30s timeout, so a client that completes the handshake then stops reading drops instead of pinning its task. - On broadcast Lagged, the server now re-subscribes under the read lock alongside the reset snapshot, dropping the buffered backlog instead of replaying it on top of the reset (replay double-applied non-idempotent appends like log lines).
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2 added, 0 removed pie showData title Rebuilt checks by category
"image" : 13
"rust" : 10
"blast" : 1
"lint" : 1
flowchart LR
c0["ix-mcp"]
c1["nix-web-monitor-0.1.0"]
c2["blast-radius-test"]
c3["lint"]
c4["rust-nix-web-monitor.clippy"]
c0 --> k1["image-kernel-dev"]
c0 --> k2["image-minecraft"]
c0 --> k3["image-minecraft-bedrock"]
c0 --> k4["image-minecraft-status"]
c0 --> k5["image-minecraft_1.21.11-fabric"]
c1 --> k8["rust-nix-web-monitor.nix-web-monitor-all"]
c1 --> k9["rust-nix-web-monitor.nix-web-monitor-tests-delta_encode_round_trips_through_msgpack"]
c1 --> k10["rust-nix-web-monitor.nix-web-monitor-tests-state_endpoint_serves_snapshot_json"]
c1 --> k11["rust-nix-web-monitor.nix-web-monitor-tests-ws_route_requires_websocket_upgrade"]
c1 --> k12["rust-nix-web-monitor.package"]
changed checks (23)
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Andrew Gazelka (andrewgazelka)
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Jun 7, 2026
…dropped reset seed (#811) Redesign of the build view after the WebSocket switch (#804) and cache fix (#806), addressing the reported issues: derivations floated as many orphan roots instead of one goal, rows were noisy (`.drv` + store hash + version all competing), there was no keyboard navigation, and the log drawer named the pinned build by an opaque activity id. Also fixes a latent bug that left the build tree empty on a page loaded mid-build. ## Single goal-rooted tree Every derivation now hangs under one synthetic root labeled with the Nix command (`nix build .#ix`), so the view is always a single tree from the goal instead of a forest. Before, any derivation whose parent closure had not yet been queried floated as its own top-level root; mid-build that meant a wall of orphans (the reported screenshot). Now those nest under the command root, and the real goal settles as its single child once edges resolve. The root row carries a live rollup: `succeeded/total` plus `running`/`failed` counts and an elapsed clock that freezes when the build finishes. `command` is threaded server → snapshot → client (and through the client working-model so it survives projection). ## Readable rows `splitDerivation` now yields `{ name, version }` with the `.drv` suffix and store hash dropped: the package **name** leads, the **version** trails dimmed, the full path stays in the row title. Applies to the tree and the flat list. ## Vim navigation The build panel owns `j`/`k` (move), `h` (collapse / step to parent), `l` (expand / step to first child), `gg`/`G` (first/last), `o`/Enter (pin the cursor's logs). Arrows mirror them. The cursor is a distinct highlight from the click selection and scrolls into view as it moves. The log drawer keeps only `/` and Esc so the two key handlers never contend. ## Logs name the build The log drawer's selection chip shows the pinned build's package name instead of `build #<id>`. ## Bug fix: WebSocket reset seed was discarded `runSession` did `applyDelta(working, delta)` and ignored the return. `applyDelta` mutates in place for incremental deltas but returns a fresh object for `reset` (the seed), so the seed — which carries the builds/activities for a page loaded mid-build — was silently dropped (logs survived only because their delta mutates in place). A page loaded onto an in-progress build showed an empty tree. Fixed by capturing the return (`working = applyDelta(...)`). This is the bug that made every browser-rendered tree come up empty until now. ## Cleanup (existing code improved) Shared row helpers (`whereLabel`, `isRemote`, `elapsedMs`, `durationLabel`) moved to `lib/build-row.ts`, removing the copy in both views. Pure tree helpers (`flattenVisible`, `hasChildren`, `parentByDrv`) live in `build-tree.ts`, reused by the keyboard layer. ## Validation - `nix build .#nix-web-monitor` (Rust + Svelte: svelte-check 0 errors, eslint clean, vite build) - **Live Playwright run against a real `nix build`**: confirmed the single command root, `name`+dimmed-version rows with no `.drv`, vim `j` moving the cursor, the logs chip showing `hello`, and builds/activities rendering (regression fix). Server `/api/state` was diffed against the browser DOM to catch the reset-seed drop. AI-generated with Claude Opus 4.8. <!-- Macroscope's pull request summary starts here --> <!-- Macroscope will only edit the content between these invisible markers, and the markers themselves will not be visible in the GitHub rendered markdown. --> <!-- If you delete either of the start / end markers from your PR's description, Macroscope will append its summary at the bottom of the description. --> > [!NOTE] > ### Add goal-rooted build tree, vim navigation, and readable row labels to nix-web-monitor > - Adds a sticky root row to the build tree labeled with the invoked Nix command (e.g. `nix build .#foo`), showing aggregated build stats and elapsed time; the command is seeded from the server's [`MonitorState::new`](https://github.com/indexable-inc/index/pull/811/files#diff-b199662dc1ba66ad897244a9b7d9bf18327c06101b3425c83e9ff61f8ec6d627) and propagated through snapshots to the UI. > - Implements vim-style keyboard navigation (j/k/h/l, gg/G, Enter/o to expand/collapse) in [`BuildTable.svelte`](https://github.com/indexable-inc/index/pull/811/files#diff-c6118e9e853915cf57a07cc4b8b260cf6439944c6ef4e07cf86989dc1c6a64a9) with cursor highlight and auto-scroll. > - Updates derivation row labels to show `name` and `version` instead of store hash prefixes, using a refactored [`splitDerivation`](https://github.com/indexable-inc/index/pull/811/files#diff-d9f5256217da8c7536b8dc20f19d3ad1f66d8f8bad822ed6e2790cacddf18553) that strips `.drv` and splits out version. > - Extracts shared duration and host helpers into [`build-row.ts`](https://github.com/indexable-inc/index/pull/811/files#diff-40e6796962fb82eb6d7abecbfce89d974555a898a4541b731e29fd65f351687a) and unifies their use across `BuildTable`, `BuildTree`, and `LogPanel`. > - Fix: [`monitor-transport.ts`](https://github.com/indexable-inc/index/pull/811/files#diff-3600e88edc89da306e3911677f724371bfc3126f68f93276d8bc303912c1c52a) now reassigns `working` on `applyDelta`, so a `reset` delta (initial seed on page load) correctly replaces client state instead of being silently discarded. > > <!-- Macroscope's review summary starts here --> > > <sup><a href="https://app.macroscope.com">Macroscope</a> summarized 672c507.</sup> > <!-- Macroscope's review summary ends here --> > <!-- macroscope-ui-refresh --> <!-- Macroscope's pull request summary ends here -->
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Follow-ups after the WebSocket switch (#804), including the user-reported "Expected a JavaScript module but got text/html" UI load failure.
index.html stale-cache → wrong-MIME load failure (the visible bug)
index.htmlnames the content-hashed asset files. It was served with no cache headers, and nix store mtimes are a constant epoch, so a browser kept a staleindex.htmlacross a rebuild and asked for/assets/index-<oldhash>.js, which the new server no longer has. The SPA fallback then answered that missing asset withindex.html(text/html), and strict MIME checking rejected it.Two fixes:
index.htmlis served withCache-Control: no-storeso the browser always re-fetches it and its asset references stay in sync with the server. (no-cachewouldn't be enough: the constant epoch mtime would 304 the stale copy.)index.html. The dashboard has no client-side routing, so the HTML fallback was unnecessary; serving HTML for a missing.jsis exactly what produced the MIME error.WebSocket hardening (from the #804 review)
Lagged, the server now re-subscribes under the read lock alongside the reset snapshot, dropping the buffered backlog instead of replaying it on top of the reset (replay double-counted non-idempotent appends like log lines).Validation
nix build .#nix-web-monitorGET /→cache-control: no-store; real asset →200 text/javascript; missing asset →404; WS still seeds theDelta::Resetindex_is_served_no_store,missing_asset_404s_instead_of_html_fallbackAI-generated with Claude Opus 4.8.
Note
Fix stale UI cache and harden WebSocket send/lag resync in nix-web-monitor
index.htmlwithCache-Control: no-storevia a dedicatedserve_indexhandler, busting stale browser caches. Missing static assets now return 404 instead of falling back toindex.html.send_frame()helper that wraps each WebSocket send with a 30sSEND_TIMEOUT, dropping unresponsive clients that stop reading.RecvError::Lagged), the server now re-subscribes to drop the stale backlog and sends a freshResetsnapshot instead of replaying non-idempotent deltas.index.htmlis read from disk at startup; the server will fail to start if the file is missing.index.htmlis absent will now error immediately rather than at request time.Macroscope summarized 7a291d1.