diff --git a/tools/v1/individual/follow-up-reminder/docs/DATA_OWNERSHIP_CONTRACT.md b/tools/v1/individual/follow-up-reminder/docs/DATA_OWNERSHIP_CONTRACT.md
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+# Follow-up Reminder Data Ownership Contract
+
+## Owned Data
+
+The isolated tool owns only local, caller-supplied or synthetic data shapes:
+
+- normalized email snapshots passed into the engine.
+- reminder review models returned to a future UI.
+- signals and warnings derived from bounded local text scans.
+- synthetic fixtures used for local tests and review.
+- local UI state for loading, empty, error, and review views.
+
+The tool does not own mailbox records, message labels, calendar events,
+notification jobs, user accounts, wallet accounts, Stellar transactions,
+database rows, provider credentials, or app route state.
+
+## Input Boundary
+
+All caller-provided email data is untrusted. Guards should validate the shape,
+sanitize text, cap sizes, and bound existing reminder lists before the engine
+runs. The engine scans only bounded text and returns a review model. It does not
+store or transmit input data.
+
+Required safe input properties:
+
+- `messageId` is a non-empty synthetic or caller-provided message key.
+- `subject` and `body` are bounded strings.
+- `senderAddress` is caller-supplied display data, not an identity guarantee.
+- `receivedAt` is an ISO timestamp used only for local relative-date resolution.
+- `existingReminders` is a bounded list of local duplicate keys.
+
+## Output Boundary
+
+Reminder outputs are advisory:
+
+- `draft` means a user may review and edit a suggestion.
+- `no_action` means no reminder should be presented by default.
+- `dueAt` can be null when the due date is missing or ambiguous.
+- `warnings` explain uncertainty and must be visible in a future UI.
+
+The engine cannot confirm a reminder, create a calendar event, send a
+notification, mutate an inbox, change labels, mark messages read, archive,
+delete, or reply to email.
+
+## Integration Handoff
+
+A future integration issue must document:
+
+1. which product component supplies normalized email snapshots.
+2. where user confirmation is captured.
+3. how reminders are persisted after explicit confirmation.
+4. which system owns notifications or calendar writes.
+5. how duplicate keys are derived across sessions.
+6. how user data is protected in logs, analytics, and tests.
+
+Until that handoff exists, this folder remains a self-contained mini-product
+with no production side effects.
diff --git a/tools/v1/individual/follow-up-reminder/docs/MODULE_BOUNDARIES.md b/tools/v1/individual/follow-up-reminder/docs/MODULE_BOUNDARIES.md
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+# Follow-up Reminder Module Boundaries
+
+## Folder Scope
+
+All Follow-up Reminder work for this issue stays inside:
+
+```text
+tools/v1/individual/follow-up-reminder/
+```
+
+This V1 individual tool is isolated from the main app until a future integration
+issue explicitly connects it. This architecture contract does not modify app
+shells, routes, inbox internals, mail rendering, auth, wallet, Stellar,
+database, notification, calendar, provider, analytics, or shared design-system
+code.
+
+## Module Ownership
+
+| Layer      | Current or planned path                | Responsibility                                                               |
+| ---------- | -------------------------------------- | ---------------------------------------------------------------------------- |
+| Public API | `index.ts`                             | Re-export stable engine, guard, fixture, and type contracts.                 |
+| Engine     | `services/followUpReminder.ts`         | Convert normalized email input into an advisory reminder review model.       |
+| Guards     | `services/guards.ts`                   | Validate, sanitize, and bound untrusted caller input before engine use.      |
+| Fixtures   | `services/fixtures.ts` and `fixtures/` | Provide deterministic synthetic email and review cases.                      |
+| Components | `components/`                          | Render isolated loading, empty, error, card, and review states.              |
+| Tests      | `tests/`                               | Verify engine, guard, component, fixture, and architecture behavior locally. |
+| Docs       | `docs/` and `REVIEW_NOTES.md`          | Document usage, threats, fixtures, review flow, and contribution boundaries. |
+
+## Dependency Direction
+
+Allowed dependency direction:
+
+```text
+index.ts
+  -> services/followUpReminder.ts
+  -> services/guards.ts
+  -> services/fixtures.ts
+components/
+  -> index.ts or services/*
+tests/
+  -> services/*, components/*, docs/*, fixtures/*
+docs/
+  -> describes behavior only
+```
+
+Rules:
+
+- services stay pure and never import React, routing, app stores, browser-only
+  APIs, network clients, calendar clients, notification senders, wallet code, or
+  database clients.
+- components may import local services and fixtures, but must not mount
+  themselves into the app shell or routes.
+- tests may inspect local docs and fixtures, but must not depend on app-wide
+  integration state.
+- docs and fixtures must use synthetic `.test` or `example.*` data only.
+
+## State Contract
+
+The engine returns advisory review models only:
+
+- `draft` when a reminder suggestion should be shown for explicit user review.
+- `no_action` when the email is low confidence or has no actionable signal.
+
+A future UI owns loading and error presentation while gathering email input. The
+engine remains synchronous and read-only. It never schedules, confirms, sends,
+snoozes, completes, dismisses, saves, or mutates product state.
+
+## Future Contributor Rules
+
+Contributors may:
+
+- add folder-local docs, fixtures, tests, guards, engine helpers, hooks, and
+  components.
+- extend signal detection when tests and fixture notes document the behavior.
+- refine isolated components without changing shared design-system primitives.
+
+Contributors may not:
+
+- write outside `tools/v1/individual/follow-up-reminder/` for this tool issue.
+- add live network calls, secrets, paid services, production data, mailbox
+  mutation, calendar writes, notification sends, wallet calls, Stellar calls, or
+  database persistence.
+- import from app routes, inbox internals, auth, wallet, Stellar, database,
+  notification, analytics, or provider modules.
+
+## Review Checklist
+
+- Changed files are limited to this tool folder.
+- Engine and guards remain folder-local and deterministic.
+- Public exports continue to represent advisory reminder models only.
+- Docs explain what future contributors may and may not change.
+- No integration code, production data, or external services are introduced.
diff --git a/tools/v1/individual/follow-up-reminder/fixtures/architecture-boundary-map.json b/tools/v1/individual/follow-up-reminder/fixtures/architecture-boundary-map.json
new file mode 100644
index 000000000..9b7e72556
--- /dev/null
+++ b/tools/v1/individual/follow-up-reminder/fixtures/architecture-boundary-map.json
@@ -0,0 +1,74 @@
+{
+  "tool": "Follow-up Reminder",
+  "root": "tools/v1/individual/follow-up-reminder/",
+  "releaseTier": "V1",
+  "audience": "individual",
+  "modules": [
+    {
+      "name": "public-api",
+      "path": "index.ts",
+      "owns": "stable exports",
+      "mayImport": ["services/followUpReminder", "services/guards", "services/fixtures"],
+      "mustNotImport": ["src/routes", "src/features", "wallet", "stellar", "database"]
+    },
+    {
+      "name": "engine",
+      "path": "services/followUpReminder.ts",
+      "owns": "reminder review model derivation",
+      "mayImport": [],
+      "mustNotImport": ["react", "network", "calendar", "notifications", "database"]
+    },
+    {
+      "name": "guards",
+      "path": "services/guards.ts",
+      "owns": "input validation and sanitization",
+      "mayImport": ["services/followUpReminder"],
+      "mustNotImport": ["src/", "network", "secrets", "provider clients"]
+    },
+    {
+      "name": "fixtures",
+      "path": "services/fixtures.ts",
+      "owns": "synthetic review data",
+      "mayImport": [],
+      "mustNotImport": ["production data", "network", "secrets"]
+    },
+    {
+      "name": "components",
+      "path": "components/",
+      "owns": "isolated visual states",
+      "mayImport": ["index.ts", "services/followUpReminder", "services/fixtures"],
+      "mustNotImport": ["src/routes", "inbox internals", "wallet", "database"]
+    },
+    {
+      "name": "tests",
+      "path": "tests/",
+      "owns": "contract verification",
+      "mayImport": ["services", "components", "docs", "fixtures"],
+      "mustNotImport": ["app shell", "production data", "provider clients"]
+    },
+    {
+      "name": "docs",
+      "path": "docs/",
+      "owns": "architecture, threat, fixture, and review notes",
+      "mayImport": [],
+      "mustNotImport": ["credentials", "external setup secrets"]
+    }
+  ],
+  "forbiddenIntegrationAreas": [
+    "main app shell",
+    "dashboard layout",
+    "navigation",
+    "routing",
+    "inbox architecture",
+    "mail rendering",
+    "authentication",
+    "wallet core",
+    "Stellar core",
+    "database schema",
+    "notifications",
+    "calendar writes",
+    "shared design system"
+  ],
+  "allowedStates": ["draft", "no_action"],
+  "uiOwnedStates": ["loading", "empty", "error", "review"]
+}
diff --git a/tools/v1/individual/follow-up-reminder/tests/architecture-boundaries.test.mjs b/tools/v1/individual/follow-up-reminder/tests/architecture-boundaries.test.mjs
new file mode 100644
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--- /dev/null
+++ b/tools/v1/individual/follow-up-reminder/tests/architecture-boundaries.test.mjs
@@ -0,0 +1,134 @@
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { dirname, join } from "node:path";
+import { describe, it } from "node:test";
+import { fileURLToPath } from "node:url";
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const root = join(__dirname, "..");
+const docs = join(root, "docs");
+const moduleMap = JSON.parse(
+  readFileSync(join(root, "fixtures", "architecture-boundary-map.json"), "utf8"),
+);
+const moduleBoundaries = readFileSync(join(docs, "MODULE_BOUNDARIES.md"), "utf8");
+const dataOwnership = readFileSync(join(docs, "DATA_OWNERSHIP_CONTRACT.md"), "utf8");
+
+describe("module boundary documentation", () => {
+  it("states the folder-local scope and forbidden integration areas", () => {
+    assert.match(moduleBoundaries, /tools\/v1\/individual\/follow-up-reminder\//);
+
+    for (const forbidden of [
+      "app shell",
+      "routes",
+      "inbox internals",
+      "wallet",
+      "Stellar",
+      "database",
+      "notification",
+      "calendar",
+      "shared design-system",
+    ]) {
+      assert.ok(moduleBoundaries.includes(forbidden), `missing forbidden area: ${forbidden}`);
+    }
+  });
+
+  it("documents required layers for the self-contained mini-product", () => {
+    for (const layer of [
+      "Public API",
+      "Engine",
+      "Guards",
+      "Fixtures",
+      "Components",
+      "Tests",
+      "Docs",
+    ]) {
+      assert.ok(moduleBoundaries.includes(layer), `missing layer: ${layer}`);
+    }
+  });
+
+  it("keeps engine state advisory and read-only", () => {
+    assert.match(moduleBoundaries, /draft/);
+    assert.match(moduleBoundaries, /no_action/);
+    assert.match(moduleBoundaries, /never schedules/);
+    assert.match(moduleBoundaries, /read-only/);
+  });
+});
+
+describe("data ownership contract", () => {
+  it("defines owned local data and product data that remains out of scope", () => {
+    for (const owned of [
+      "normalized email snapshots",
+      "reminder review models",
+      "signals and warnings",
+    ]) {
+      assert.ok(dataOwnership.includes(owned), `missing owned data: ${owned}`);
+    }
+
+    for (const external of [
+      "mailbox records",
+      "calendar events",
+      "notification jobs",
+      "wallet accounts",
+    ]) {
+      assert.ok(dataOwnership.includes(external), `missing external data: ${external}`);
+    }
+  });
+
+  it("requires future integration handoff before product side effects", () => {
+    assert.match(dataOwnership, /Integration Handoff/);
+    assert.match(dataOwnership, /explicit confirmation/);
+    assert.match(dataOwnership, /no production side effects/);
+  });
+});
+
+describe("architecture boundary map fixture", () => {
+  it("is scoped to the Follow-up Reminder tool", () => {
+    assert.equal(moduleMap.tool, "Follow-up Reminder");
+    assert.equal(moduleMap.root, "tools/v1/individual/follow-up-reminder/");
+    assert.equal(moduleMap.releaseTier, "V1");
+    assert.equal(moduleMap.audience, "individual");
+  });
+
+  it("covers the expected module owners", () => {
+    const moduleNames = new Set(moduleMap.modules.map((entry) => entry.name));
+    for (const expected of [
+      "public-api",
+      "engine",
+      "guards",
+      "fixtures",
+      "components",
+      "tests",
+      "docs",
+    ]) {
+      assert.ok(moduleNames.has(expected), `missing module: ${expected}`);
+    }
+  });
+
+  it("gives every module import constraints", () => {
+    for (const entry of moduleMap.modules) {
+      assert.equal(typeof entry.path, "string");
+      assert.equal(typeof entry.owns, "string");
+      assert.ok(Array.isArray(entry.mayImport));
+      assert.ok(Array.isArray(entry.mustNotImport));
+      assert.ok(entry.mustNotImport.length > 0);
+    }
+  });
+
+  it("keeps integration areas and state ownership explicit", () => {
+    for (const area of [
+      "routing",
+      "inbox architecture",
+      "wallet core",
+      "database schema",
+      "calendar writes",
+    ]) {
+      assert.ok(
+        moduleMap.forbiddenIntegrationAreas.includes(area),
+        `missing forbidden area: ${area}`,
+      );
+    }
+
+    assert.deepEqual(moduleMap.allowedStates, ["draft", "no_action"]);
+    assert.deepEqual(moduleMap.uiOwnedStates, ["loading", "empty", "error", "review"]);
+  });
+});