diff --git a/src/data/sample.ts b/src/data/sample.ts
new file mode 100644
index 0000000..ffa635a
--- /dev/null
+++ b/src/data/sample.ts
@@ -0,0 +1,50 @@
+// Default Macroplan shown on first load — exercises every state:
+// on-time delivery, late delivery with slips, in-flight (green/orange/red),
+// an overdue Feature, and a Milestone with unmet required Features.
+export const SAMPLE_PLAN = `title = "Q3 — Checkout revamp"
+
+# A Feature: start week, Original Estimate (the immovable baseline), then any
+# Re-estimates (slips), an optional Delivery, and an optional Learning / Status.
+# Dates are TOML date literals; any day is snapped to that week's Monday.
+
+[[feature]]
+name = "Auth"
+start = 2026-06-01
+original = 2026-06-15
+delivered = 2026-06-15          # on time → ◉
+learning = "Spiking the OAuth flow first paid off — do discovery spikes earlier."
+
+[[feature]]
+name = "Payments"
+start = 2026-06-01
+original = 2026-06-15           # ◯ baseline
+reestimates = [2026-06-29, 2026-07-13]   # two slips → △ △
+delivered = 2026-07-20          # after the baseline → ▲ late
+learning = "Vendor lead time was the real constraint — derisk vendors up front."
+
+[[feature]]
+name = "Dashboard"
+start = 2026-06-01
+original = 2026-06-08           # already past 'now' and undelivered → overdue
+status = "red"
+note = "No recovery plan yet — needs an owner."
+
+[[feature]]
+name = "Search"
+start = 2026-06-08
+original = 2026-06-22
+reestimates = [2026-07-06]      # slipped once, still in flight → △
+status = "orange"
+note = "Third-party search API is flaky; spike a fallback."
+
+[[feature]]
+name = "Notifications"
+start = 2026-06-22
+original = 2026-07-06
+status = "green"
+
+[[milestone]]
+name = "MVP go-live"
+week = 2026-07-06
+requires = ["Auth", "Payments", "Dashboard"]
+`
diff --git a/src/model/parse.ts b/src/model/parse.ts
new file mode 100644
index 0000000..1dacdde
--- /dev/null
+++ b/src/model/parse.ts
@@ -0,0 +1,85 @@
+import { parse as parseToml } from 'smol-toml'
+import { toYmd } from './week'
+import type { RawPlan, RawFeature, RawMilestone, StatusLevel } from './types'
+
+/** Thrown for any malformed source — message is safe to show the author. */
+export class PlanParseError extends Error {
+  constructor(message: string) {
+    super(message)
+    this.name = 'PlanParseError'
+  }
+}
+
+const STATUSES: StatusLevel[] = ['green', 'orange', 'red']
+
+/** Parse + validate a Macroplan TOML source into the raw model. */
+export function parseMacroplan(source: string): RawPlan {
+  let data: Record<string, unknown>
+  try {
+    data = parseToml(source) as Record<string, unknown>
+  } catch (e) {
+    throw new PlanParseError(e instanceof Error ? e.message : String(e))
+  }
+
+  const features = asBlocks(data.feature, 'feature').map(parseFeature)
+  const milestones = asBlocks(data.milestone, 'milestone').map(parseMilestone)
+
+  return {
+    title: data.title != null ? String(data.title) : 'Untitled Macroplan',
+    features,
+    milestones,
+  }
+}
+
+function asBlocks(value: unknown, key: string): Record<string, unknown>[] {
+  if (value == null) return []
+  if (!Array.isArray(value)) {
+    throw new PlanParseError(`\`${key}\` must be written as [[${key}]] blocks`)
+  }
+  return value as Record<string, unknown>[]
+}
+
+function parseFeature(f: Record<string, unknown>, i: number): RawFeature {
+  const where = f.name ? `feature "${String(f.name)}"` : `feature #${i + 1}`
+  if (!f.name) throw new PlanParseError(`${where}: missing \`name\``)
+  if (f.start == null) throw new PlanParseError(`${where}: missing \`start\` date`)
+  if (f.original == null) throw new PlanParseError(`${where}: missing \`original\` estimate date`)
+  if (f.status != null && !STATUSES.includes(f.status as StatusLevel)) {
+    throw new PlanParseError(`${where}: \`status\` must be one of ${STATUSES.join(', ')}`)
+  }
+  if (f.reestimates != null && !Array.isArray(f.reestimates)) {
+    throw new PlanParseError(`${where}: \`reestimates\` must be a list of dates`)
+  }
+  return {
+    name: String(f.name),
+    start: toYmdOr(where, 'start', f.start),
+    original: toYmdOr(where, 'original', f.original),
+    reestimates: ((f.reestimates as unknown[]) ?? []).map((d) => toYmdOr(where, 'reestimates', d)),
+    delivered: f.delivered != null ? toYmdOr(where, 'delivered', f.delivered) : undefined,
+    learning: f.learning != null ? String(f.learning) : undefined,
+    status: f.status as StatusLevel | undefined,
+    note: f.note != null ? String(f.note) : undefined,
+  }
+}
+
+function parseMilestone(m: Record<string, unknown>, i: number): RawMilestone {
+  const where = m.name ? `milestone "${String(m.name)}"` : `milestone #${i + 1}`
+  if (!m.name) throw new PlanParseError(`${where}: missing \`name\``)
+  if (m.week == null) throw new PlanParseError(`${where}: missing \`week\` date`)
+  if (m.requires != null && !Array.isArray(m.requires)) {
+    throw new PlanParseError(`${where}: \`requires\` must be a list of feature names`)
+  }
+  return {
+    name: String(m.name),
+    week: toYmdOr(where, 'week', m.week),
+    requires: ((m.requires as unknown[]) ?? []).map(String),
+  }
+}
+
+function toYmdOr(where: string, field: string, value: unknown): string {
+  try {
+    return toYmd(value)
+  } catch {
+    throw new PlanParseError(`${where}: \`${field}\` must be a date (e.g. 2026-06-01)`)
+  }
+}
diff --git a/src/model/plan.ts b/src/model/plan.ts
new file mode 100644
index 0000000..d6796c4
--- /dev/null
+++ b/src/model/plan.ts
@@ -0,0 +1,79 @@
+import { mondayOf, weekRange, type WeekId } from './week'
+import type { RawPlan, RawFeature, Plan, FeatureRow, Marker, MilestoneLine } from './types'
+
+/**
+ * Derive the render-ready Plan from the raw model (component C2).
+ *
+ * On-time vs. late is judged ONLY against the Original Estimate, never a
+ * Re-estimate (ADR-0001). The full slip history (`◯` + every `△`) is preserved.
+ */
+export function buildPlan(raw: RawPlan, today: Date | string = new Date()): Plan {
+  const rows = raw.features.map(buildRow)
+  const nowWeek = mondayOf(today)
+
+  const milestones = raw.milestones.map((m): MilestoneLine => {
+    const week = mondayOf(m.week)
+    const unmet = m.requires.filter((name) => {
+      const row = rows.find((r) => r.name === name)
+      if (!row) return true // references an unknown Feature → can't be met
+      const delivery = row.markers.find(
+        (x) => x.kind === 'delivered-on-time' || x.kind === 'delivered-late',
+      )
+      return !delivery || delivery.week > week // undelivered, or delivered after the milestone
+    })
+    return { name: m.name, week, requires: m.requires, unmet }
+  })
+
+  // Range: earliest start to last marker/milestone (CONTEXT.md). Empty weeks drawn.
+  const allWeeks: WeekId[] = []
+  for (const r of rows) {
+    allWeeks.push(r.startWeek, r.barEndWeek)
+    for (const mk of r.markers) allWeeks.push(mk.week)
+  }
+  for (const m of milestones) allWeeks.push(m.week)
+
+  let weeks: WeekId[] = []
+  if (allWeeks.length) {
+    const start = allWeeks.reduce((a, b) => (a < b ? a : b))
+    const end = allWeeks.reduce((a, b) => (a > b ? a : b))
+    weeks = weekRange(start, end)
+  }
+  const nowInRange = weeks.length > 0 && nowWeek >= weeks[0] && nowWeek <= weeks[weeks.length - 1]
+
+  return { title: raw.title, weeks, rows, milestones, nowWeek, nowInRange }
+}
+
+function buildRow(f: RawFeature): FeatureRow {
+  const startWeek = mondayOf(f.start)
+  const originalWeek = mondayOf(f.original)
+  const deliveredWeek = f.delivered ? mondayOf(f.delivered) : undefined
+  const delivered = deliveredWeek != null
+  // ADR-0001: compare the Delivery week to the Original Estimate week only.
+  const onTime = delivered ? deliveredWeek! <= originalWeek : null
+
+  const markers: Marker[] = []
+  for (const re of f.reestimates) markers.push({ week: mondayOf(re), kind: 'reestimate' })
+  if (delivered) {
+    markers.push({ week: deliveredWeek!, kind: onTime ? 'delivered-on-time' : 'delivered-late' })
+  }
+  // The Original Estimate `◯` stands unless an on-time/early delivery already
+  // occupies (or precedes) it — then the delivery marker speaks for it.
+  if (!(delivered && onTime)) {
+    markers.push({ week: originalWeek, kind: 'original' })
+  }
+
+  const barEndWeek = [startWeek, ...markers.map((m) => m.week)].reduce((a, b) => (a > b ? a : b))
+
+  return {
+    name: f.name,
+    startWeek,
+    barEndWeek,
+    markers,
+    delivered,
+    onTime,
+    status: f.status,
+    note: f.note,
+    learning: f.learning,
+    slipCount: f.reestimates.length,
+  }
+}
diff --git a/src/model/types.ts b/src/model/types.ts
new file mode 100644
index 0000000..4e1f385
--- /dev/null
+++ b/src/model/types.ts
@@ -0,0 +1,70 @@
+import type { WeekId } from './week'
+
+export type StatusLevel = 'green' | 'orange' | 'red'
+
+// ── Raw model: as authored, after TOML parse + validation, before derivation ──
+
+export interface RawFeature {
+  name: string
+  start: string // yyyy-mm-dd
+  original: string // yyyy-mm-dd — the Original Estimate
+  reestimates: string[] // yyyy-mm-dd[]
+  delivered?: string // yyyy-mm-dd
+  learning?: string
+  status?: StatusLevel
+  note?: string
+}
+
+export interface RawMilestone {
+  name: string
+  week: string // yyyy-mm-dd
+  requires: string[] // Feature names
+}
+
+export interface RawPlan {
+  title: string
+  features: RawFeature[]
+  milestones: RawMilestone[]
+}
+
+// ── Derived model: render-ready (C2 output) ──
+
+export type MarkerKind =
+  | 'original' // ◯ Original Estimate, not yet delivered
+  | 'reestimate' // △ a slip to a later week
+  | 'delivered-on-time' // ◉ delivered on/before the Original Estimate
+  | 'delivered-late' // ▲ delivered after the Original Estimate
+
+export interface Marker {
+  week: WeekId
+  kind: MarkerKind
+}
+
+export interface FeatureRow {
+  name: string
+  startWeek: WeekId
+  barEndWeek: WeekId
+  markers: Marker[]
+  delivered: boolean
+  onTime: boolean | null // null while in-flight
+  status?: StatusLevel
+  note?: string
+  learning?: string
+  slipCount: number // number of Re-estimates
+}
+
+export interface MilestoneLine {
+  name: string
+  week: WeekId
+  requires: string[]
+  unmet: string[] // required Features not delivered on/before this week
+}
+
+export interface Plan {
+  title: string
+  weeks: WeekId[]
+  rows: FeatureRow[]
+  milestones: MilestoneLine[]
+  nowWeek: WeekId
+  nowInRange: boolean
+}
diff --git a/src/model/week.ts b/src/model/week.ts
new file mode 100644
index 0000000..add7257
--- /dev/null
+++ b/src/model/week.ts
@@ -0,0 +1,59 @@
+// Week math. A "Week" is identified by the ISO date (yyyy-mm-dd) of its Monday.
+// ISO yyyy-mm-dd strings sort lexicographically == chronologically, so plain
+// string comparison (`<`, `<=`) is valid week ordering — we lean on that.
+
+export type WeekId = string // 'yyyy-mm-dd', always a Monday
+
+/**
+ * Extract a yyyy-mm-dd string from a TOML date (smol-toml's `TomlDate.toISOString()`
+ * returns the authored local date, e.g. "2026-06-01") or a plain string.
+ */
+export function toYmd(value: unknown): string {
+  if (value instanceof Date) return value.toISOString().slice(0, 10)
+  if (typeof value === 'string') return value.slice(0, 10)
+  throw new Error(`expected a date, got ${JSON.stringify(value)}`)
+}
+
+// Anchor at UTC noon so day-of-week / day arithmetic never crosses a DST or
+// timezone boundary.
+function utcNoon(ymd: string): Date {
+  const [y, m, d] = ymd.split('-').map(Number)
+  return new Date(Date.UTC(y, m - 1, d, 12))
+}
+
+function fmt(dt: Date): string {
+  return dt.toISOString().slice(0, 10)
+}
+
+/** The Monday (yyyy-mm-dd) of the ISO week containing the given date. */
+export function mondayOf(value: unknown): WeekId {
+  const dt = utcNoon(toYmd(value))
+  const dow = dt.getUTCDay() // 0=Sun .. 6=Sat
+  const shift = dow === 0 ? -6 : 1 - dow
+  dt.setUTCDate(dt.getUTCDate() + shift)
+  return fmt(dt)
+}
+
+/** Add n weeks to a Monday WeekId (n may be negative). */
+export function addWeeks(week: WeekId, n: number): WeekId {
+  const dt = utcNoon(week)
+  dt.setUTCDate(dt.getUTCDate() + n * 7)
+  return fmt(dt)
+}
+
+/** Inclusive list of Monday WeekIds from start..end (both must already be Mondays). */
+export function weekRange(start: WeekId, end: WeekId): WeekId[] {
+  if (start > end) return [start]
+  const weeks: WeekId[] = []
+  for (let w = start; w <= end; w = addWeeks(w, 1)) weeks.push(w)
+  return weeks
+}
+
+/** Short column label for a week, e.g. "Jun 15". */
+export function weekLabel(week: WeekId): string {
+  return utcNoon(week).toLocaleDateString('en-US', {
+    month: 'short',
+    day: '2-digit',
+    timeZone: 'UTC',
+  })
+}