plan: trace charts iter 2 (serve) — render_chart_html, chart-viewer.js, aura chart verb

Iteration-2 (serve half) plan for spec 0056: a first-party chart-viewer.js (pure buildCharts + browser mount) with a node .mjs DOM guard; render_chart_html + ChartMode/ChartData/Series mirroring render_html; emit_chart + the spec-§6 union-spine join_on_ts alignment + the `aura chart <name> [--panels]` arms. uPlot already vendored (d534f10). RED-first; no existing-signature changes (no caller blast radius). refs #101
2026-06-19 00:25:06 +02:00
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+# Trace charts — iteration 2 (serve) — Implementation Plan
+
+> **Parent spec:** `docs/specs/0056-trace-charts-persist-and-serve.md`
+>
+> **For agentic workers:** REQUIRED SUB-SKILL: use the `implement` skill to run
+> this plan. Steps use `- [ ]` checkboxes for tracking.
+
+**Goal:** Read a persisted run's traces (`runs/traces/<name>/`) and serve them as a
+self-contained uPlot HTML chart via `aura chart <name> [--panels]` — feeds overlaid
+on a shared timestamp axis (default) or in timestamp-aligned stacked panels.
+
+**Architecture:** Three layers on top of iteration 1's on-disk artifact. A
+first-party `chart-viewer.js` exposes a pure `buildCharts(traces, mode)` (the
+`AURA_TRACES` → uPlot-config transform, no DOM) plus a browser-only `mount()`.
+`render_chart_html` (aura-cli/render.rs) assembles a self-contained page mirroring
+`render_html`: vendored uPlot (already checked in, commit d534f10) + `chart-viewer.js`
+inlined via `include_str!`, the data injected as `window.AURA_TRACES`. `emit_chart`
+(aura-cli/main.rs) reads the `TraceStore`, builds `ChartData` by the spec-§6 3-step
+union-spine `join_on_ts` alignment, and prints the page. The engine is untouched (C14).
+
+**Tech Stack:** Rust (`aura-cli`); the iteration-1 building blocks
+`aura_engine::{ColumnarTrace, join_on_ts, JoinedRow}` + `aura_registry::{TraceStore,
+RunTraces, TraceStoreError}`; vendored uPlot 1.6.32; `serde_json` (already an
+aura-cli dep); a `node` `.mjs` DOM guard mirroring `viewer_dot.rs`.
+
+---
+
+**Files this plan creates or modifies:**
+
+- Create: `crates/aura-cli/assets/chart-viewer.js` — first-party `AURA_TRACES` →
+  uPlot bootstrap (pure `buildCharts` + browser `mount`).
+- Create: `crates/aura-cli/tests/chart_viewer.rs` — `.rs` node-driver (shells `node`).
+- Create: `crates/aura-cli/tests/chart_viewer_build.mjs` — the DOM-less guard over
+  `buildCharts`.
+- Create: `crates/aura-cli/tests/fixtures/sample-traces.json` — an `AURA_TRACES`
+  fixture for the guard.
+- Modify: `crates/aura-cli/src/render.rs` — add `ChartMode`/`ChartData`/`Series` +
+  `render_chart_html` + a self-contained unit test (mirror `render.rs:92`).
+- Modify: `crates/aura-cli/src/main.rs` — imports (`:17–26`), `emit_chart` + the
+  `build_chart_data` alignment helper, the `["chart", …]` argv arms (`:885–914`,
+  before `["graph"]` at `:899`), `USAGE` (`:877–878`).
+- Test: `crates/aura-cli/tests/cli_run.rs` — a `chart` e2e sibling (HTML emitted;
+  missing run exits 2).
+
+uPlot is already vendored (commit d534f10: `assets/uPlot.iife.min.js` +
+`uPlot.min.css` + the `refresh-assets.sh` line) — no fetch in this plan.
+
+---
+
+### Task 1: `chart-viewer.js` + its DOM guard
+
+**Files:**
+- Create: `crates/aura-cli/assets/chart-viewer.js`
+- Create: `crates/aura-cli/tests/chart_viewer_build.mjs`
+- Create: `crates/aura-cli/tests/chart_viewer.rs`
+- Create: `crates/aura-cli/tests/fixtures/sample-traces.json`
+
+- [ ] **Step 1: Write the fixture**
+
+Create `crates/aura-cli/tests/fixtures/sample-traces.json` (an `AURA_TRACES` payload
+with two co-cadenced single-column series, matching what `render_chart_html` injects):
+
+```json
+{
+  "mode": "overlay",
+  "manifest": { "commit": "test", "params": [], "window": [1, 3], "seed": 0, "broker": "sim-optimal(pip_size=0.0001)" },
+  "taps": ["equity", "exposure"],
+  "xs": [1, 2, 3],
+  "series": [
+    { "name": "equity", "y_scale_id": "y_0", "points": [0.0, 0.001, 0.004] },
+    { "name": "exposure", "y_scale_id": "y_1", "points": [1.0, 1.0, -1.0] }
+  ]
+}
+```
+
+- [ ] **Step 2: Write the failing guard (.mjs + .rs driver)**
+
+Create `crates/aura-cli/tests/chart_viewer_build.mjs`:
+
+```js
+// Headless guard for the trace-chart viewer (chart-viewer.js). Property protected:
+// buildCharts maps an AURA_TRACES payload to uPlot configs WITHOUT a DOM — overlay
+// is one chart with every series on its own y-scale over the shared xs; panels is
+// one chart per series, each on the SAME shared xs (timestamp-aligned). It loads the
+// real viewer module (a fix/regression there is observed here) and drives the
+// exported pure `buildCharts`; uPlot itself (which needs `document`) is never
+// instantiated — mount() is browser-only and not called here.
+
+import { createRequire } from "node:module";
+import { readFileSync } from "node:fs";
+import { fileURLToPath } from "node:url";
+import { dirname, join } from "node:path";
+
+const require = createRequire(import.meta.url);
+const here = dirname(fileURLToPath(import.meta.url));
+const traces = JSON.parse(readFileSync(join(here, "fixtures", "sample-traces.json"), "utf8"));
+
+const fail = (msg) => { console.error("FAIL: " + msg); process.exit(1); };
+const eq = (a, b, msg) => { if (a !== b) fail(`${msg} (got ${a}, want ${b})`); };
+const sameArr = (a, b, msg) => {
+  if (!Array.isArray(a) || !Array.isArray(b) || a.length !== b.length || a.some((v, i) => v !== b[i])) fail(msg);
+};
+
+// No `document` global -> chart-viewer.js's browser mount is skipped; require gives
+// us only the pure export (mirrors viewer_dot_ids.mjs stubbing window before require).
+global.window = { AURA_TRACES: traces };
+const { buildCharts } = require(join(here, "..", "assets", "chart-viewer.js"));
+
+const n = traces.series.length;
+
+// overlay: ONE chart, all series superimposed on the shared xs, each on its own scale.
+const overlay = buildCharts(traces, "overlay");
+eq(overlay.length, 1, "overlay is one chart");
+eq(overlay[0].data.length, 1 + n, "overlay data = xs + N series");
+eq(overlay[0].opts.series.length, 1 + n, "overlay uPlot series = x + N");
+sameArr(overlay[0].data[0], traces.xs, "overlay x-axis is the shared xs");
+const scaleIds = overlay[0].opts.series.slice(1).map((s) => s.scale);
+eq(new Set(scaleIds).size, n, "each overlay series has a distinct y-scale");
+
+// panels: ONE chart per series, all timestamp-aligned on the SAME shared xs.
+const panels = buildCharts(traces, "panels");
+eq(panels.length, n, "panels = one chart per series");
+for (const p of panels) {
+  eq(p.data.length, 2, "each panel = xs + its one series");
+  sameArr(p.data[0], traces.xs, "panel shares the same xs (timestamp-aligned)");
+}
+
+console.log(`OK — overlay 1 chart / ${n} series, panels ${n} charts, shared xs.`);
+process.exit(0);
+```
+
+Create `crates/aura-cli/tests/chart_viewer.rs` (mirrors `viewer_dot.rs`):
+
+```rust
+//! Integration guard for the `aura chart` viewer's data transform.
+//!
+//! `chart-viewer.js` builds the uPlot configs in JavaScript, so the property
+//! "buildCharts maps AURA_TRACES to the right per-mode uPlot config shape" cannot
+//! be checked from Rust. This shells out to `node`, running
+//! `tests/chart_viewer_build.mjs`, which loads the real viewer module and asserts
+//! the overlay/panels config shape over a fixture — without instantiating uPlot
+//! (which needs a DOM). `node` is REQUIRED: if absent this test FAILS.
+
+use std::path::PathBuf;
+use std::process::Command;
+
+#[test]
+fn chart_viewer_builds_overlay_and_panels_configs() {
+    let script = PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+        .join("tests")
+        .join("chart_viewer_build.mjs");
+    assert!(script.exists(), "guard script missing at {}", script.display());
+
+    let out = match Command::new("node").arg(&script).output() {
+        Ok(out) => out,
+        Err(e) => panic!(
+            "node is required for the chart-viewer guard but could not be run \
+             ({e}); install Node.js or ensure `node` is on PATH"
+        ),
+    };
+
+    let stdout = String::from_utf8_lossy(&out.stdout);
+    let stderr = String::from_utf8_lossy(&out.stderr);
+    assert!(
+        out.status.success(),
+        "chart-viewer guard failed (exit {:?}).\n--- node stdout ---\n{stdout}\n--- node stderr ---\n{stderr}",
+        out.status.code()
+    );
+}
+```
+
+- [ ] **Step 3: Run the guard to verify it fails**
+
+Run: `cargo test -p aura-cli --test chart_viewer chart_viewer_builds_overlay_and_panels_configs`
+Expected: FAIL — node cannot `require` `assets/chart-viewer.js` (it does not exist yet), so the guard exits non-zero and the `.rs` assert reports the node stderr.
+
+- [ ] **Step 4: Write `chart-viewer.js`**
+
+Create `crates/aura-cli/assets/chart-viewer.js`:
+
+```js
+// The `aura chart` viewer: turns the injected window.AURA_TRACES (xs + per-series
+// Option<f64> points, already timestamp-union-aligned by the CLI) into uPlot charts.
+//
+// buildCharts is PURE (no DOM, no uPlot) and is the unit the headless guard drives.
+// mount() is browser-only — it instantiates the vendored global `uPlot` per config.
+(function () {
+  var PALETTE = ["#89b4fa", "#f38ba8", "#a6e3a1", "#f9e2af", "#cba6f7", "#94e2d5"];
+
+  // {xs, series:[{name, y_scale_id, points}]} + mode -> array of {opts, data} configs.
+  // overlay -> one chart, all series, each on its own auto-ranged y-scale (shared xs).
+  // panels  -> one chart per series, each on the SAME shared xs (timestamp-aligned).
+  function buildCharts(traces, mode) {
+    var xs = traces.xs;
+    var series = traces.series;
+    if (mode === "panels") {
+      return series.map(function (s, i) {
+        return {
+          opts: {
+            title: s.name,
+            scales: { x: { time: false }, [s.y_scale_id]: {} },
+            series: [{}, { label: s.name, scale: s.y_scale_id, stroke: PALETTE[i % PALETTE.length] }],
+            axes: [{}, { scale: s.y_scale_id }],
+          },
+          data: [xs, s.points],
+        };
+      });
+    }
+    // overlay (default)
+    var scales = { x: { time: false } };
+    var uSeries = [{}];
+    var axes = [{}];
+    series.forEach(function (s, i) {
+      scales[s.y_scale_id] = {};
+      uSeries.push({ label: s.name, scale: s.y_scale_id, stroke: PALETTE[i % PALETTE.length] });
+      // the first two series carry a drawn axis (left, then right); the rest keep
+      // their own auto-scale, read via the legend.
+      if (i < 2) axes.push({ scale: s.y_scale_id, side: i === 0 ? 3 : 1 });
+    });
+    return [{ opts: { scales: scales, series: uSeries, axes: axes }, data: [xs].concat(series.map(function (s) { return s.points; })) }];
+  }
+
+  // Browser-only: instantiate the vendored global uPlot per config into #stage.
+  function mount() {
+    var traces = window.AURA_TRACES;
+    var configs = buildCharts(traces, traces.mode);
+    var stage = document.getElementById("stage");
+    var w = stage.clientWidth || 900;
+    var h = configs.length > 1 ? Math.max(160, Math.floor(440 / configs.length)) : 460;
+    configs.forEach(function (cfg) {
+      var opts = Object.assign({ width: w, height: h }, cfg.opts);
+      // eslint-disable-next-line no-undef
+      new uPlot(opts, cfg.data, stage);
+    });
+  }
+
+  if (typeof window !== "undefined" && typeof document !== "undefined" && window.AURA_TRACES) {
+    if (document.readyState === "loading") document.addEventListener("DOMContentLoaded", mount);
+    else mount();
+  }
+  if (typeof module !== "undefined" && module.exports) module.exports = { buildCharts: buildCharts };
+})();
+```
+
+- [ ] **Step 5: Run the guard to verify it passes**
+
+Run: `cargo test -p aura-cli --test chart_viewer chart_viewer_builds_overlay_and_panels_configs`
+Expected: PASS — `OK — overlay 1 chart / 2 series, panels 2 charts, shared xs.` (1 passed).
+
+---
+
+### Task 2: `render_chart_html` + chart types (render.rs)
+
+**Files:**
+- Modify: `crates/aura-cli/src/render.rs` (types + fn after `render_html`; test in `mod tests`)
+
+- [ ] **Step 1: Write the failing self-contained test**
+
+Append inside the existing `#[cfg(test)] mod tests { … }` in `crates/aura-cli/src/render.rs`:
+
+```rust
+    fn sample_chart_data() -> ChartData {
+        ChartData {
+            manifest: aura_engine::RunManifest {
+                commit: "test".into(),
+                params: vec![],
+                window: (aura_engine::Timestamp(1), aura_engine::Timestamp(3)),
+                seed: 0,
+                broker: "sim-optimal(pip_size=0.0001)".into(),
+            },
+            taps: vec!["equity".into(), "exposure".into()],
+            xs: vec![1, 2, 3],
+            series: vec![
+                Series { name: "equity".into(), y_scale_id: "y_0".into(), points: vec![Some(0.0), Some(0.001), Some(0.004)] },
+                Series { name: "exposure".into(), y_scale_id: "y_1".into(), points: vec![Some(1.0), Some(1.0), Some(-1.0)] },
+            ],
+        }
+    }
+
+    #[test]
+    fn render_chart_html_is_self_contained_and_injects_traces() {
+        let html = render_chart_html(&sample_chart_data(), ChartMode::Overlay);
+        assert!(html.starts_with("<!doctype html>"), "not an HTML doc");
+        assert!(html.trim_end().ends_with("</html>"), "HTML doc not closed");
+        // self-contained: no remote asset
+        assert!(!html.contains("<script src"), "assets must be inlined");
+        // data injected as the viewer's source, with the mode reflected
+        assert!(html.contains("window.AURA_TRACES = {"), "AURA_TRACES not injected");
+        assert!(html.contains("\"mode\":\"overlay\""), "overlay mode not reflected");
+        assert!(html.contains("\"equity\""), "series name missing from injected data");
+        // the vendored uPlot bundle + first-party viewer are inlined
+        assert!(html.contains("uPlot=function"), "vendored uPlot bundle missing");
+        assert!(html.contains("buildCharts"), "chart-viewer.js not inlined");
+    }
+
+    #[test]
+    fn render_chart_html_reflects_panels_mode() {
+        let html = render_chart_html(&sample_chart_data(), ChartMode::Panels);
+        assert!(html.contains("\"mode\":\"panels\""), "panels mode not reflected");
+    }
+```
+
+- [ ] **Step 2: Run the test to verify it fails**
+
+Run: `cargo test -p aura-cli --lib render_chart_html`
+Expected: FAIL — compile error `cannot find type ChartData / Series / ChartMode / function render_chart_html` (not written yet).
+
+- [ ] **Step 3: Write the types + `render_chart_html`**
+
+In `crates/aura-cli/src/render.rs`, change the import line (`render.rs:9`) from
+`use aura_engine::Composite;` to:
+
+```rust
+use aura_engine::{Composite, RunManifest};
+```
+
+Add the three vendored/first-party asset consts beside the existing ones
+(`render.rs:55–57`):
+
+```rust
+const UPLOT_JS: &str = include_str!("../assets/uPlot.iife.min.js");
+const UPLOT_CSS: &str = include_str!("../assets/uPlot.min.css");
+const CHART_VIEWER_JS: &str = include_str!("../assets/chart-viewer.js");
+```
+
+Add this AFTER `render_html` ends (`render.rs:80`) and before `#[cfg(test)]`
+(`render.rs:82`):
+
+```rust
+/// Which way the chart draws the (timestamp-aligned) series.
+#[derive(Clone, Copy)]
+pub enum ChartMode {
+    /// One plot, all series superimposed, each on its own y-scale.
+    Overlay,
+    /// One stacked plot per series, all sharing the timestamp x-axis.
+    Panels,
+}
+
+/// One chart series: a name, its own y-scale id (so disparate magnitudes stay
+/// legible), and one `Option<f64>` per shared-x slot (`null` = a gap where the tap
+/// did not fire at that timestamp).
+#[derive(serde::Serialize)]
+pub struct Series {
+    pub name: String,
+    pub y_scale_id: String,
+    pub points: Vec<Option<f64>>,
+}
+
+/// The serve-ready chart payload: the shared timestamp axis, the per-(tap,column)
+/// series, and the run's manifest + tap list (for the page header). Injected verbatim
+/// as `window.AURA_TRACES` (plus the `mode`); `chart-viewer.js` renders it.
+pub struct ChartData {
+    pub manifest: RunManifest,
+    pub taps: Vec<String>,
+    pub xs: Vec<i64>,
+    pub series: Vec<Series>,
+}
+
+/// Assemble the self-contained uPlot chart page for one run's aligned traces.
+///
+/// Order is load-bearing (mirrors `render_html`): the uPlot global and CSS, then the
+/// injected `window.AURA_TRACES`, must be defined before `chart-viewer.js` runs.
+pub fn render_chart_html(data: &ChartData, mode: ChartMode) -> String {
+    let mode_str = match mode {
+        ChartMode::Overlay => "overlay",
+        ChartMode::Panels => "panels",
+    };
+    let traces = serde_json::json!({
+        "mode": mode_str,
+        "manifest": data.manifest,
+        "taps": data.taps,
+        "xs": data.xs,
+        "series": data.series,
+    })
+    .to_string();
+
+    let mut html = String::with_capacity(
+        SHELL_HEAD.len() + UPLOT_JS.len() + UPLOT_CSS.len() + CHART_VIEWER_JS.len() + traces.len() + 256,
+    );
+    html.push_str(SHELL_HEAD);
+    html.push_str("<style>");
+    html.push_str(UPLOT_CSS);
+    html.push_str("</style>\n<script>");
+    html.push_str(UPLOT_JS);
+    html.push_str("</script>\n<script>window.AURA_TRACES = ");
+    html.push_str(&traces);
+    html.push_str(";</script>\n<script>");
+    html.push_str(CHART_VIEWER_JS);
+    html.push_str("</script>\n</body>\n</html>\n");
+    html
+}
+```
+
+(`serde::Serialize` on `Series` lets `serde_json::json!` embed it; `RunManifest`
+already derives `Serialize`. `serde_json` is already an aura-cli dependency — used by
+`main.rs`'s `runs_family` JSON.)
+
+- [ ] **Step 4: Run the test to verify it passes**
+
+Run: `cargo test -p aura-cli --lib render_chart_html`
+Expected: PASS — `render_chart_html_is_self_contained_and_injects_traces` +
+`render_chart_html_reflects_panels_mode` green (2 passed).
+
+---
+
+### Task 3: `emit_chart` + serve-time alignment + the `chart` verb (main.rs)
+
+This task is one compile unit (new `emit_chart`/`build_chart_data` + two argv arms +
+imports + USAGE); it changes no existing signature, so there is no caller blast
+radius. The RED e2e (Step 1) compiles against the binary and fails before the arms
+exist.
+
+**Files:**
+- Test: `crates/aura-cli/tests/cli_run.rs` (chart e2e sibling)
+- Modify: `crates/aura-cli/src/main.rs` (imports `:17–26`, USAGE `:877–878`, argv
+  `:885–914`, new fns)
+
+- [ ] **Step 1: Write the failing e2e**
+
+Append to `crates/aura-cli/tests/cli_run.rs`:
+
+```rust
+#[test]
+fn chart_emits_self_contained_html_for_a_persisted_run() {
+    let cwd = temp_cwd("chart-serve");
+
+    // persist a run first (iteration 1), then chart it.
+    let traced = Command::new(BIN).args(["run", "--trace", "demo"]).current_dir(&cwd).output().expect("spawn run --trace");
+    assert!(traced.status.success(), "run --trace exit: {:?}", traced.status);
+
+    let chart = Command::new(BIN).args(["chart", "demo"]).current_dir(&cwd).output().expect("spawn chart");
+    assert!(chart.status.success(), "chart exit: {:?}", chart.status);
+    let html = String::from_utf8(chart.stdout).expect("utf-8 html");
+    assert!(html.starts_with("<!doctype html>"), "not an HTML doc: {:?}", &html[..html.len().min(40)]);
+    assert!(html.contains("window.AURA_TRACES = {"), "AURA_TRACES not injected");
+    assert!(html.contains("\"equity\""), "equity series missing from the chart");
+    assert!(html.contains("uPlot=function"), "vendored uPlot not inlined");
+
+    // a missing run is a usage error (stderr + exit 2), not a panic.
+    let missing = Command::new(BIN).args(["chart", "nope"]).current_dir(&cwd).output().expect("spawn chart nope");
+    assert_eq!(missing.status.code(), Some(2), "missing run must exit 2");
+    assert!(!missing.status.success());
+
+    let _ = std::fs::remove_dir_all(&cwd);
+}
+```
+
+- [ ] **Step 2: Run the e2e to verify it fails**
+
+Run: `cargo test -p aura-cli --test cli_run chart_emits_self_contained_html_for_a_persisted_run`
+Expected: FAIL — `["chart","demo"]` has no argv arm yet, so it hits the usage-error path (exit 2) and prints no HTML. (Tree compiles — only a new test added.)
+
+- [ ] **Step 3: Extend the imports**
+
+In `crates/aura-cli/src/main.rs`, add `join_on_ts, JoinedRow` to the
+`aura_engine::{…}` import (`main.rs:17–22`) and `RunTraces, TraceStoreError` to the
+`aura_registry::{…}` import (`main.rs:23–26`). Also bring in the new render types:
+the file already has `mod render;`, so reference them as `render::{ChartData, ChartMode, Series}`
+at the call sites (no `use` needed) — OR add `use render::{ChartData, ChartMode, Series};`
+after `mod render;` (`main.rs:14`). Use the explicit `use`:
+
+```rust
+mod render;
+use render::{ChartData, ChartMode, Series};
+```
+
+and the two engine/registry import lists become (only the added names shown in context):
+
+```rust
+use aura_engine::{
+    f64_field, join_on_ts, monte_carlo, param_stability, summarize, walk_forward, window_of,
+    ColumnarTrace, Composite, Edge, FlatGraph, GraphBuilder, Harness, JoinedRow, McAggregate,
+    McFamily, RollMode, RunManifest, RunReport, SourceSpec, SweepFamily, SyntheticSpec, Target,
+    VecSource, WalkForwardResult, WindowBounds, WindowRoller, WindowRun,
+};
+use aura_registry::{
+    group_families, mc_member_reports, optimize, rank_by, sweep_member_reports,
+    walkforward_member_reports, FamilyKind, Registry, RunTraces, TraceStore, TraceStoreError,
+};
+```
+
+- [ ] **Step 4: Add the alignment helper + `emit_chart`**
+
+Insert after `persist_traces` (it ends near `main.rs:174`):
+
+```rust
+/// Build the serve-ready `ChartData` from a run's read-back traces by the spec-§6
+/// 3-step union-spine alignment — no tap privileged, no point dropped:
+/// (1) xs = the sorted, deduped union of every tap's timestamps;
+/// (2) synthesize an empty-payload spine over xs and pass ALL taps (via
+///     `ColumnarTrace::to_rows`, which yields uniformly-f64 rows) as symmetric sides
+///     of `join_on_ts`, so no side row is dropped and none occupies the privileged
+///     `JoinedRow.spine`;
+/// (3) flatten each (tap, column) to a `Series` of `Option<f64>` over xs.
+fn build_chart_data(traces: RunTraces) -> ChartData {
+    let mut xs: Vec<i64> = traces.taps.iter().flat_map(|t| t.ts.iter().copied()).collect();
+    xs.sort_unstable();
+    xs.dedup();
+
+    let spine: Vec<(Timestamp, Vec<Scalar>)> = xs.iter().map(|&t| (Timestamp(t), Vec::new())).collect();
+    let tap_rows: Vec<Vec<(Timestamp, Vec<Scalar>)>> = traces.taps.iter().map(|t| t.to_rows()).collect();
+    let sides: Vec<&[(Timestamp, Vec<Scalar>)]> = tap_rows.iter().map(|r| r.as_slice()).collect();
+    let joined: Vec<JoinedRow> = join_on_ts(&spine, &sides);
+
+    let mut series: Vec<Series> = Vec::new();
+    for (i, tap) in traces.taps.iter().enumerate() {
+        for c in 0..tap.columns.len() {
+            let name = if tap.columns.len() == 1 { tap.tap.clone() } else { format!("{}[{c}]", tap.tap) };
+            let y_scale_id = format!("y_{}", series.len());
+            let points: Vec<Option<f64>> =
+                joined.iter().map(|r| r.sides[i].as_ref().map(|row| row[c].as_f64())).collect();
+            series.push(Series { name, y_scale_id, points });
+        }
+    }
+
+    ChartData {
+        manifest: traces.manifest,
+        taps: traces.taps.iter().map(|t| t.tap.clone()).collect(),
+        xs,
+        series,
+    }
+}
+
+/// `aura chart <name> [--panels]`: read the persisted run's traces, align them, and
+/// print the self-contained uPlot page. A missing run is a usage error (stderr +
+/// exit 2), per the CLI's convention — never a panic.
+fn emit_chart(name: &str, mode: ChartMode) {
+    let traces = match TraceStore::open("runs").read(name) {
+        Ok(t) => t,
+        Err(TraceStoreError::NotFound(n)) => {
+            eprintln!("aura: no recorded run '{n}' under runs/traces (run `aura run --trace {n}` first)");
+            std::process::exit(2);
+        }
+        Err(e) => {
+            eprintln!("aura: {e}");
+            std::process::exit(2);
+        }
+    };
+    print!("{}", render::render_chart_html(&build_chart_data(traces), mode));
+}
+```
+
+- [ ] **Step 5: Add the argv arms**
+
+In `main()`'s argv match, insert the two chart arms directly before the `["graph"]`
+arm (`main.rs:899`):
+
+```rust
+        ["chart", name] => emit_chart(name, ChartMode::Overlay),
+        ["chart", name, "--panels"] => emit_chart(name, ChartMode::Panels),
+```
+
+- [ ] **Step 6: Update `USAGE`**
+
+In the `USAGE` const (`main.rs:877–878`), add ` | aura chart <name> [--panels]` after
+the `aura graph` clause so every dispatched verb is advertised:
+
+```rust
+const USAGE: &str =
+    "usage: aura run [--macd] [--trace <name>] | aura run --real <SYMBOL> [--from <ms>] [--to <ms>] [--trace <name>] | aura chart <name> [--panels] | aura graph | aura sweep [--name <n>] | aura mc [--name <n>] | aura walkforward [--name <n>] | aura runs families | aura runs family <id> [rank <metric>]";
+```
+
+- [ ] **Step 7: Run the e2e to verify it passes**
+
+Run: `cargo test -p aura-cli --test cli_run chart_emits_self_contained_html_for_a_persisted_run`
+Expected: PASS — the persisted run charts to self-contained HTML carrying the equity
+series + inlined uPlot; `aura chart nope` exits 2 (1 passed).
+
+- [ ] **Step 8: Build + lint + workspace gate**
+
+Run: `cargo build --workspace`
+Expected: PASS — 0 errors.
+
+Run: `cargo test --workspace`
+Expected: PASS — Task 1 (`chart_viewer`), Task 2 (`render_chart_html_*`), Task 3
+(`chart_emits_*`) green, and no regression (the iteration-1 trace tests + the
+byte-for-byte default-run pins stay green).
+
+Run: `cargo clippy --workspace --all-targets -- -D warnings`
+Expected: PASS — no warnings. (Watch for: a `clippy::needless_range_loop` on the
+`for c in 0..tap.columns.len()` loop — if flagged, it reads `tap.columns[c]` only via
+the parallel `joined[..].sides[i]` index, so rewrite as `.iter().enumerate()` over
+`tap.columns` keeping `c`; an unused import if a name is mis-listed.)