diff --git a/.changeset/tv2-1-zone-resolver.md b/.changeset/tv2-1-zone-resolver.md
new file mode 100644
index 0000000..6094532
--- /dev/null
+++ b/.changeset/tv2-1-zone-resolver.md
@@ -0,0 +1,9 @@
+---
+"@sentiness/core": patch
+---
+
+Add the internal `resolveZones` zone resolver (`packages/core/src/zones`), the
+foundation for Phase V2 per-zone execution. It maps a v2 config's `zones` into
+rooted, option-merged placements (`absRoot = join(repoRoot, path)`; catalog
+options deep-merged with per-zone overrides). No public API change — the module is
+internal to `core` and not re-exported from `index.ts`.
diff --git a/.changeset/tv2-3-checkcontext-reporoot.md b/.changeset/tv2-3-checkcontext-reporoot.md
new file mode 100644
index 0000000..46835d1
--- /dev/null
+++ b/.changeset/tv2-3-checkcontext-reporoot.md
@@ -0,0 +1,9 @@
+---
+"@sentiness/check-sdk": minor
+---
+
+Add `CheckContext.repoRoot` so checks can reach the repository root independently
+of `cwd`. In a polyglot monorepo `cwd` is the zone root (e.g. `crates/engine`)
+while `repoRoot` is the repository root, for the rare check that needs repo-level
+context. Additive and backward-compatible for the documented consumer pattern
+(checks read the context); single-zone runs set `repoRoot === cwd`.
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f69ebbf..3e28741 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -6,6 +6,43 @@ on:
   pull_request:
 
 jobs:
+  changeset:
+    # Standard guardrail: every PR must consciously decide the release question.
+    # `changeset status` fails when a publishable package changed without a
+    # changeset; if the change needs no release, add an empty one
+    # (`pnpm changeset add --empty`). Runs only on PRs — pushes to main consume
+    # changesets via the release workflow's "Version Packages" PR.
+    name: Changeset
+    if: github.event_name == 'pull_request'
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v5
+        with:
+          fetch-depth: 0
+
+      - name: Fetch base branch
+        run: git fetch origin main:refs/remotes/origin/main
+
+      - name: Enable Corepack
+        run: corepack enable
+
+      - name: Setup Node
+        uses: actions/setup-node@v5
+        with:
+          node-version: 22
+          cache: pnpm
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile --ignore-scripts
+
+      # Skipped on the Changesets "Version Packages" PR, which consumes the
+      # changeset files (so the gate would otherwise fail and block releases).
+      # The job still runs and reports success, satisfying the required check.
+      - name: Require a changeset (or an explicit empty one)
+        if: github.head_ref != 'changeset-release/main'
+        run: pnpm changeset status --since=origin/main
+
   verify:
     runs-on: ubuntu-latest
     steps:
diff --git a/docs/progress.md b/docs/progress.md
index 3be9925..c5d6ea6 100644
--- a/docs/progress.md
+++ b/docs/progress.md
@@ -105,6 +105,34 @@ the repo root. All existing check `makeContext` test helpers gained
 `pnpm -r typecheck`, `pnpm -r test` (core 209, SDK 13 incl. the new `repoRoot`
 type test, all checks + cli green), and `pnpm lint` (219 files) are clean.
 
+### TV2.1 zone resolver — done (2026-06-17)
+
+New pure module `packages/core/src/zones/zones.ts` exporting `resolveZones(config,
+repoRoot)`, the resolver Phase V2 per-zone execution (TV2.2) builds on. It maps the
+v2 `ResolvedConfig.zones` into `ResolvedZone[]`, each carrying `path`, `absRoot`
+(`join(repoRoot, path)`), and `ResolvedCheckPlacement[]`:
+
+- `tier` = zone override → catalog entry → fallback. **Deviation flagged:** the
+  spec types `placement.tier` as a required `Tier`, but `resolveZones` is pure over
+  config and cannot see a check's `defaultTier`; the config tier is optional. Since
+  `init` always writes a `tier` per catalog entry, the resolver uses
+  `zoneOverride.tier ?? catalogEntry.tier ?? 'standard'`. The `'standard'` fallback
+  only bites hand-written configs that omit tier; TV2.2 can refine the effective
+  tier against `check.defaultTier` where the `Check` instance is in scope.
+- `options` = catalog options deep-merged with the zone override (zone wins;
+  `thresholds` and nested plain objects merge recursively, arrays/primitives
+  replace). Resolution metadata (`version`, `path`, `tier`) never leaks into
+  `options`; `id`/`tier` are stripped from the override.
+- Single-root configs need no special case — `resolveConfig` already normalizes an
+  absent `zones` to one zone at `'.'` with every catalog id, so the root zone's
+  `absRoot === repoRoot`.
+
+Internal to `core` (the runner imports it directly; not re-exported from
+`index.ts`). `pnpm --filter @sentiness/core typecheck`, the 6-case `zones.test.ts`
+(root normalization, absRoot join, multi-zone, override/threshold deep-merge,
+bare-id catalog tier, repeated check across zones), the full core suite (215
+tests), and `pnpm lint` (221 files) are green.
+
 ## Implementation approach
 
 The implementation should progress in usable slices, not by completing the whole specification before the CLI can run.
diff --git a/packages/core/src/zones/zones.test.ts b/packages/core/src/zones/zones.test.ts
new file mode 100644
index 0000000..98da9c2
--- /dev/null
+++ b/packages/core/src/zones/zones.test.ts
@@ -0,0 +1,131 @@
+import { asCheckId } from '@sentiness/check-sdk';
+import { describe, expect, it } from 'vitest';
+import { resolveConfig, type SentinessConfigV2, validateConfig } from '../config/config.js';
+import { resolveZones } from './zones.js';
+
+function makeConfig(overrides: Partial<SentinessConfigV2>): ReturnType<typeof resolveConfig> {
+  return resolveConfig(
+    validateConfig({
+      schemaVersion: '2.0',
+      engine: '2.0.0',
+      checks: {},
+      ...overrides,
+    }),
+  );
+}
+
+describe('resolveZones', () => {
+  it('normalizes a single-root config to one zone at "." with every catalog check', () => {
+    const config = makeConfig({
+      checks: {
+        biome: { version: '*', tier: 'fast' },
+        knip: { version: '*', tier: 'standard' },
+      },
+    });
+
+    const zones = resolveZones(config, '/repo');
+
+    expect(zones).toHaveLength(1);
+    const [root] = zones;
+    expect(root?.path).toBe('.');
+    expect(root?.absRoot).toBe('/repo');
+    expect(root?.checks.map((c) => c.id)).toEqual([asCheckId('biome'), asCheckId('knip')]);
+    expect(root?.checks.map((c) => c.tier)).toEqual(['fast', 'standard']);
+  });
+
+  it('roots each zone at repoRoot joined with the zone path', () => {
+    const config = makeConfig({
+      checks: { biome: { version: '*', tier: 'fast' } },
+      zones: [{ path: 'apps/web', checks: ['biome'] }],
+    });
+
+    const zones = resolveZones(config, '/repo');
+
+    expect(zones).toHaveLength(1);
+    expect(zones[0]?.path).toBe('apps/web');
+    expect(zones[0]?.absRoot).toBe('/repo/apps/web');
+  });
+
+  it('resolves multiple zones, each owning its own checks', () => {
+    const config = makeConfig({
+      checks: {
+        biome: { version: '*', tier: 'fast' },
+        knip: { version: '*', tier: 'standard' },
+        clippy: { version: '*', tier: 'fast' },
+      },
+      zones: [
+        { path: 'apps/web', checks: ['biome', 'knip'] },
+        { path: 'crates/engine', checks: ['clippy'] },
+      ],
+    });
+
+    const zones = resolveZones(config, '/repo');
+
+    expect(zones).toHaveLength(2);
+    expect(zones[0]?.checks.map((c) => c.id)).toEqual([asCheckId('biome'), asCheckId('knip')]);
+    expect(zones[1]?.absRoot).toBe('/repo/crates/engine');
+    expect(zones[1]?.checks.map((c) => c.id)).toEqual([asCheckId('clippy')]);
+  });
+
+  it('merges per-zone overrides over the catalog entry (zone wins; thresholds deep-merge)', () => {
+    const config = makeConfig({
+      checks: {
+        biome: {
+          version: '*',
+          tier: 'fast',
+          thresholds: { a: 1, b: 2 },
+          extraArgs: ['--from-catalog'],
+        },
+      },
+      zones: [
+        {
+          path: 'apps/web',
+          checks: [{ id: 'biome', tier: 'standard', thresholds: { b: 9 } }],
+        },
+      ],
+    });
+
+    const [placement] = resolveZones(config, '/repo')[0]?.checks ?? [];
+
+    expect(placement?.tier).toBe('standard');
+    // thresholds deep-merge: catalog `a` survives, zone `b` overrides.
+    expect(placement?.options.thresholds).toEqual({ a: 1, b: 9 });
+    // catalog-only option survives.
+    expect(placement?.options.extraArgs).toEqual(['--from-catalog']);
+    // resolution metadata never leaks into check options.
+    expect(placement?.options).not.toHaveProperty('version');
+    expect(placement?.options).not.toHaveProperty('path');
+    expect(placement?.options).not.toHaveProperty('tier');
+  });
+
+  it('takes the catalog tier when a zone references a check by bare id', () => {
+    const config = makeConfig({
+      checks: { biome: { version: '*', tier: 'slow' } },
+      zones: [{ path: 'apps/web', checks: ['biome'] }],
+    });
+
+    const [placement] = resolveZones(config, '/repo')[0]?.checks ?? [];
+
+    expect(placement?.tier).toBe('slow');
+  });
+
+  it('yields one placement per zone for a check shared across zones, with catalog options', () => {
+    const config = makeConfig({
+      checks: { biome: { version: '*', tier: 'fast', thresholds: { a: 1 } } },
+      zones: [
+        { path: 'apps/web', checks: ['biome'] },
+        { path: 'apps/admin', checks: ['biome'] },
+      ],
+    });
+
+    const zones = resolveZones(config, '/repo');
+
+    expect(zones).toHaveLength(2);
+    const web = zones[0]?.checks[0];
+    const admin = zones[1]?.checks[0];
+    expect(web?.id).toBe(asCheckId('biome'));
+    expect(admin?.id).toBe(asCheckId('biome'));
+    expect(web?.options).toEqual({ thresholds: { a: 1 } });
+    expect(admin?.options).toEqual({ thresholds: { a: 1 } });
+  });
+});
diff --git a/packages/core/src/zones/zones.ts b/packages/core/src/zones/zones.ts
new file mode 100644
index 0000000..be80b67
--- /dev/null
+++ b/packages/core/src/zones/zones.ts
@@ -0,0 +1,96 @@
+import { join } from 'node:path';
+import { asCheckId, type CheckId, type Tier } from '@sentiness/check-sdk';
+import type { CatalogCheckEntry, ResolvedConfig, ZoneCheckOverride } from '../config/config.js';
+
+/**
+ * One check placed inside one zone, with its tier and options already resolved
+ * from the catalog entry plus any per-zone override.
+ */
+export type ResolvedCheckPlacement = {
+  readonly id: CheckId;
+  /** Catalog tier, overridden by the zone entry; `'standard'` if neither sets one. */
+  readonly tier: Tier;
+  /** Check-specific options (catalog merged with the zone override, zone winning). */
+  readonly options: Readonly<Record<string, unknown>>;
+};
+
+/** A resolved zone: a repo subdirectory and the checks rooted at it. */
+export type ResolvedZone = {
+  readonly path: string; // repo-relative ('.' for the root zone)
+  readonly absRoot: string; // repoRoot joined with path
+  readonly checks: readonly ResolvedCheckPlacement[];
+};
+
+// Keys on a catalog entry that drive package/tier resolution rather than the
+// check's runtime behavior; they must never leak into a placement's `options`.
+const RESOLUTION_KEYS: ReadonlySet<string> = new Set(['version', 'path', 'tier']);
+
+function isPlainObject(value: unknown): value is Record<string, unknown> {
+  return typeof value === 'object' && value !== null && !Array.isArray(value);
+}
+
+/** Recursively merges plain objects; arrays and primitives are replaced wholesale. */
+function deepMerge(
+  base: Readonly<Record<string, unknown>>,
+  override: Readonly<Record<string, unknown>>,
+): Record<string, unknown> {
+  const result: Record<string, unknown> = { ...base };
+  for (const [key, value] of Object.entries(override)) {
+    const existing = result[key];
+    result[key] =
+      isPlainObject(existing) && isPlainObject(value) ? deepMerge(existing, value) : value;
+  }
+  return result;
+}
+
+function catalogOptions(entry: CatalogCheckEntry): Record<string, unknown> {
+  const out: Record<string, unknown> = {};
+  for (const [key, value] of Object.entries(entry)) {
+    if (!RESOLUTION_KEYS.has(key)) {
+      out[key] = value;
+    }
+  }
+  return out;
+}
+
+function overrideOptions(override: ZoneCheckOverride): Record<string, unknown> {
+  const out: Record<string, unknown> = {};
+  for (const [key, value] of Object.entries(override)) {
+    if (key !== 'id' && key !== 'tier') {
+      out[key] = value;
+    }
+  }
+  return out;
+}
+
+/**
+ * Pure resolution of a v2 config's zones into rooted, option-merged placements.
+ *
+ * A single-root config (no `zones`) is already normalized by `resolveConfig` to
+ * one zone at `'.'` carrying every catalog check, so this function does not need
+ * a special case for it. A check id may appear in several zones — each yields its
+ * own placement; the same catalog version applies (one version per repo by
+ * design). The function never touches the filesystem.
+ */
+export function resolveZones(config: ResolvedConfig, repoRoot: string): readonly ResolvedZone[] {
+  return config.zones.map((zone) => {
+    const checks = zone.checks.map((entry): ResolvedCheckPlacement => {
+      const isBareId = typeof entry === 'string';
+      const id = isBareId ? entry : entry.id;
+      const catalogEntry = config.checks[id];
+      const base = catalogEntry ? catalogOptions(catalogEntry) : {};
+      const override = isBareId ? {} : overrideOptions(entry);
+      const tier: Tier = (isBareId ? undefined : entry.tier) ?? catalogEntry?.tier ?? 'standard';
+      return {
+        id: asCheckId(id),
+        tier,
+        options: deepMerge(base, override),
+      };
+    });
+    return {
+      path: zone.path,
+      absRoot: join(repoRoot, zone.path),
+      checks,
+    };
+  });
+}