diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 87c2d79..b4d4d96 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -36,6 +36,9 @@ jobs:
           npm ci --ignore-scripts
           npm rebuild node-pty
 
+      - name: Check repository harness
+        run: npm run harness:check
+
       - name: Test with coverage
         run: npm run test:coverage
 
diff --git a/AGENTS.md b/AGENTS.md
new file mode 100644
index 0000000..3afb514
--- /dev/null
+++ b/AGENTS.md
@@ -0,0 +1,52 @@
+# Agent Map
+
+This file is a short map for coding agents. Keep detailed guidance in `docs/`
+and keep this file small enough to fit into every task context.
+
+## First Reads
+
+- `DEVELOPMENT.md` - project commands, coding rules, test rules, and PR shape.
+- `ARCHITECTURE.md` - package boundaries, data ownership, and runtime flow.
+- `docs/harness/README.md` - how this repository is prepared for agent work.
+- `docs/harness/validation.md` - which checks to run for each change type.
+- `docs/harness/worktree-runbook.md` - isolated local dev and test setup.
+- `docs/harness/pr-review.md` - self-review checklist before pushing.
+
+## Common Commands
+
+```bash
+npm ci --ignore-scripts
+npm run harness:check
+npm run test
+npm run test:e2e
+npm run build
+```
+
+Use the smallest relevant check while iterating. Before a broad PR, run
+`npm run harness:check`, `npm run test:coverage`, `npm run test:e2e`, and
+`npm run build`.
+
+## Code Ownership Map
+
+- `packages/client/src` - Vue 3 client, stores, routes, i18n, API helpers.
+- `packages/server/src` - Koa API, Socket.IO, persistence, Hermes integration.
+- `packages/desktop` - Electron wrapper, bundled Python/Hermes runtime, release artifacts.
+- `tests/client`, `tests/server`, `tests/shared` - Vitest coverage.
+- `tests/e2e` - Playwright browser coverage with mocked backend services.
+- `.github/workflows` - CI, release, Docker, and desktop packaging automation.
+
+## Hard Rules
+
+- Keep routes thin: put request handling in controllers and reusable behavior in services.
+- Keep Web UI state under `HERMES_WEB_UI_HOME` or `HERMES_WEBUI_STATE_DIR`.
+- Keep Hermes Agent state separate from Web UI state.
+- Register local API routes before proxy catch-all routes.
+- Use structured APIs and argument arrays instead of shell string construction.
+- Add user-facing strings to every locale file.
+- Do not mix unrelated refactors into a bug fix.
+
+## When The Agent Gets Stuck
+
+Improve the harness instead of repeating the same prompt. Add missing docs,
+tests, logs, scripts, or CI checks so the next agent can see and verify the
+constraint directly.
diff --git a/ARCHITECTURE.md b/ARCHITECTURE.md
new file mode 100644
index 0000000..8c0034f
--- /dev/null
+++ b/ARCHITECTURE.md
@@ -0,0 +1,89 @@
+# Architecture
+
+Hermes Web UI is a TypeScript monorepo that ships a browser dashboard, a Koa
+backend, and an Electron desktop distribution around Hermes Agent.
+
+## Package Boundaries
+
+| Area | Path | Responsibility |
+| --- | --- | --- |
+| Client | `packages/client/src` | Vue UI, routing, Pinia stores, API wrappers, i18n, browser-visible state. |
+| Server | `packages/server/src` | HTTP API, auth, Socket.IO, SQLite stores, file access, Hermes runtime integration. |
+| Desktop | `packages/desktop` | Electron shell, local Web UI server bootstrap, updater, bundled Python/Hermes runtime. |
+| Tests | `tests` | Vitest unit/integration tests and Playwright browser tests. |
+| CI | `.github/workflows` | Build, e2e, lockfile, Docker, and desktop release automation. |
+
+## Request Flow
+
+1. The browser loads the Vite-built client from the Koa server.
+2. Client modules call API helpers from `packages/client/src/api`.
+3. Server routes in `packages/server/src/routes` wire HTTP paths to controllers.
+4. Controllers validate request concerns and delegate reusable behavior to services.
+5. Services own side effects: files, SQLite, Hermes profiles, subprocesses, bridges, and credentials.
+6. Long-running chat and group-chat flows use Socket.IO namespaces managed by server services.
+
+Keep each layer narrow. Routes should not grow business logic, and client code
+should not duplicate server persistence rules.
+
+## State And Data Ownership
+
+- Web UI state defaults to `~/.hermes-web-ui` through `config.appHome`.
+- `HERMES_WEB_UI_HOME` and `HERMES_WEBUI_STATE_DIR` override Web UI state location.
+- Hermes Agent state lives under Hermes profile directories and must stay distinct from Web UI state.
+- Uploads default to `config.uploadDir`, which is derived from the Web UI home unless `UPLOAD_DIR` is set.
+- Profile-scoped Hermes data should use existing profile helpers instead of manually joining paths.
+
+## Server Structure
+
+- `routes/` registers HTTP and WebSocket entry points.
+- `controllers/` handles request-level behavior.
+- `services/` owns reusable IO, domain behavior, external process calls, and integration logic.
+- `db/` owns SQLite schemas and stores.
+- `middleware/` owns request middleware such as user auth.
+- `shared/` contains cross-server constants and helpers.
+
+Architecture rules:
+
+- Register local API routes before proxy catch-all routes.
+- Keep auth behavior centralized in `packages/server/src/services/auth.ts`.
+- Prefer `execFile` or `spawn` with argument arrays over shell command strings.
+- Use structured file and YAML/JSON parsers when editing structured data.
+
+## Client Structure
+
+- `views/` contains route-level screens.
+- `components/` contains reusable UI.
+- `stores/` contains Pinia state.
+- `api/` contains HTTP clients and should use `packages/client/src/api/client.ts`.
+- `i18n/` contains locale messages for user-facing strings.
+- `styles/` contains global styling and theme primitives.
+
+Frontend rules:
+
+- Use Vue 3 Composition API with `<script setup lang="ts">`.
+- Use existing Naive UI patterns before adding new UI conventions.
+- Add visible text to all locale files.
+- Keep component styles scoped unless the style is intentionally global.
+
+## Desktop Release Flow
+
+Desktop packaging is intentionally split:
+
+- Pull requests run a Linux desktop smoke test in `.github/workflows/build.yml`.
+- Published releases and manual dispatches run `.github/workflows/desktop-release.yml`.
+- Each release matrix target uploads only the artifact globs for its own platform.
+
+Do not make a Windows job require macOS `.dmg` files or a Linux job require
+Windows installers. Keep `fail_on_unmatched_files: true` where platform-specific
+artifact lists make the expectation explicit.
+
+## Validation Surface
+
+The minimum mechanical harness is:
+
+- `npm run harness:check` for repository docs, workflow, and package-script invariants.
+- `npm run test` or focused Vitest tests for local logic.
+- `npm run test:e2e` for browser-visible routing/auth/chat regressions.
+- `npm run build` for type checking and production bundles.
+
+See `docs/harness/validation.md` for change-specific commands.
diff --git a/docs/harness/README.md b/docs/harness/README.md
new file mode 100644
index 0000000..a271399
--- /dev/null
+++ b/docs/harness/README.md
@@ -0,0 +1,40 @@
+# Harness Overview
+
+This harness turns recurring project knowledge into files and checks that an
+agent can discover without chat history.
+
+## Goals
+
+- Make repository context legible through short maps and deeper docs.
+- Keep architecture constraints close to the code they protect.
+- Give agents a deterministic validation path before opening or updating a PR.
+- Prefer mechanical checks over reminder text when a rule can be verified.
+
+## Entry Points
+
+- `AGENTS.md` is the root map for coding agents.
+- `ARCHITECTURE.md` documents package boundaries and state ownership.
+- `DEVELOPMENT.md` remains the contributor rules and command reference.
+- `docs/harness/validation.md` maps change types to checks.
+- `docs/harness/worktree-runbook.md` explains isolated worktree development.
+- `docs/harness/pr-review.md` provides a PR self-review checklist.
+- `scripts/harness-check.mjs` enforces baseline repository invariants.
+
+## Operating Model
+
+1. Read the root map and the specific doc for the task.
+2. Make the smallest scoped change.
+3. Add or update focused tests when behavior changes.
+4. Run `npm run harness:check` and the relevant validation commands.
+5. If a failure pattern repeats, improve this harness with docs, tests, scripts,
+   or CI instead of relying on a longer prompt.
+
+## What Belongs In The Harness
+
+- Facts that future agents must know to work safely.
+- Checklists that prevent repeated PR review comments.
+- Scripts that fail fast on repository-wide invariants.
+- Runbooks for local, CI, release, and desktop packaging flows.
+
+Do not put long implementation notes in `AGENTS.md`. Add them under `docs/` and
+link to them from the map.
diff --git a/docs/harness/pr-review.md b/docs/harness/pr-review.md
new file mode 100644
index 0000000..ebf42ba
--- /dev/null
+++ b/docs/harness/pr-review.md
@@ -0,0 +1,41 @@
+# PR Self-Review
+
+Use this checklist before pushing or updating a pull request.
+
+## Scope
+
+- The PR title states the behavior being changed.
+- The diff is limited to the requested task and required harness updates.
+- Unrelated formatting or refactors are not bundled into the change.
+- User-facing text has locale coverage.
+
+## Architecture
+
+- Client code uses shared API helpers and existing UI patterns.
+- Server routes stay thin and delegate reusable behavior to controllers/services.
+- Web UI state uses `config.appHome` or documented helpers.
+- Hermes Agent state and Web UI state remain separate.
+- Subprocess calls use argument arrays instead of shell string construction.
+
+## Tests And Validation
+
+- A focused test was added or updated for behavior changes.
+- Browser-visible flows have e2e coverage when the risk justifies it.
+- `npm run harness:check` passes.
+- The PR body lists validation commands that actually ran.
+- Known limitations or follow-ups are called out.
+
+## Release And CI
+
+- Workflow changes were checked with `npm run harness:check`.
+- Desktop release artifacts remain platform-specific.
+- `fail_on_unmatched_files: true` is preserved when each matrix target has its
+  own expected artifact list.
+- Package manifest changes have matching lockfile changes when dependencies
+  change.
+
+## Before Merge
+
+- CI is green or failures are explained as unrelated.
+- The branch is mergeable.
+- The PR does not depend on hidden local state, credentials, or uncommitted files.
diff --git a/docs/harness/validation.md b/docs/harness/validation.md
new file mode 100644
index 0000000..3159287
--- /dev/null
+++ b/docs/harness/validation.md
@@ -0,0 +1,68 @@
+# Validation Guide
+
+Run the smallest relevant checks while iterating. Escalate to the broad checks
+when touching shared behavior, release automation, auth, persistence, or chat.
+
+## Always Run For PRs
+
+```bash
+npm run harness:check
+```
+
+For broad or shared changes, also run:
+
+```bash
+npm run test:coverage
+npm run test:e2e
+npm run build
+```
+
+## Change-Type Matrix
+
+| Change | Minimum local validation |
+| --- | --- |
+| Docs only | `npm run harness:check` |
+| Client component/store/API | focused `npm run test -- <pattern>`, then `npm run build` |
+| User-visible browser flow | focused Vitest plus `npm run test:e2e` |
+| Server controller/service/db | focused `npm run test -- tests/server/<file>` |
+| Auth, profile, or credential behavior | focused server tests plus relevant e2e auth tests |
+| Chat, Socket.IO, group chat | focused server tests plus relevant e2e chat tests |
+| Desktop packaging | `npm run harness:check`, `npm run build`, and a platform-specific desktop build when practical |
+| GitHub workflow | `npm run harness:check` and `actionlint` when available |
+| Package manifests | `npm ci --ignore-scripts` and lockfile workflow expectations |
+
+## CI Mapping
+
+- Build workflow: installs dependencies, runs coverage, builds production assets,
+  then runs a Linux desktop smoke test on pull requests.
+- Playwright workflow: runs browser e2e tests.
+- NPM lockfile workflow: verifies `package-lock.json` is synchronized.
+- Desktop release workflow: builds and uploads platform-specific desktop artifacts
+  for release tags.
+- Docker workflow: builds and publishes release images.
+
+## Release Workflow Guardrail
+
+Desktop release jobs must upload only the artifacts that their matrix target can
+produce. Keep artifact globs in matrix data and keep `fail_on_unmatched_files:
+true` so missing expected files still fail.
+
+Expected desktop release outputs:
+
+| Target | Required release globs |
+| --- | --- |
+| macOS | `*.dmg`, `*.dmg.blockmap`, `latest*.yml` |
+| Windows | `*.exe`, `*.exe.blockmap`, `latest*.yml` |
+| Linux x64 | `*.AppImage`, `*.deb`, `latest*.yml` |
+| Linux arm64 | `*.AppImage`, `latest*.yml` |
+
+## Failure Handling
+
+When a command fails:
+
+1. Read the first actionable error, not just the final stack trace.
+2. Check whether the failure indicates missing context, missing test coverage,
+   or a missing mechanical rule.
+3. Fix the product bug when there is one.
+4. Update docs or `scripts/harness-check.mjs` when the same class of mistake
+   should be prevented next time.
diff --git a/docs/harness/worktree-runbook.md b/docs/harness/worktree-runbook.md
new file mode 100644
index 0000000..c405bf8
--- /dev/null
+++ b/docs/harness/worktree-runbook.md
@@ -0,0 +1,64 @@
+# Worktree Runbook
+
+Use a separate git worktree for agent changes so local user work remains
+untouched.
+
+## Create A Worktree
+
+```bash
+git fetch origin --prune
+git worktree add -b codex/<short-topic> ../worktrees/hermes-web-ui-<short-topic> origin/main
+cd ../worktrees/hermes-web-ui-<short-topic>
+```
+
+If the repository uses a fork remote, push to the remote requested by the task.
+Do not rewrite or reset unrelated branches.
+
+## Install
+
+```bash
+npm ci --ignore-scripts
+npm rebuild node-pty
+```
+
+Desktop package dependencies are separate:
+
+```bash
+npm ci --prefix packages/desktop --no-audit --no-fund
+```
+
+## Isolated Runtime
+
+Use per-worktree state and ports to avoid colliding with a running local app:
+
+```bash
+export PORT=18648
+export HERMES_WEB_UI_HOME="$PWD/.tmp/hermes-web-ui"
+export HERMES_WEBUI_STATE_DIR="$HERMES_WEB_UI_HOME"
+export UPLOAD_DIR="$PWD/.tmp/uploads"
+npm run dev
+```
+
+Do not point `HERMES_WEB_UI_HOME` at a user's real `~/.hermes-web-ui` when a task
+only needs local verification.
+
+## Browser Checks
+
+For browser-visible changes:
+
+```bash
+npm run test:e2e
+```
+
+Prefer existing Playwright fixtures and mocked backend services. Add real-service
+requirements only when the behavior cannot be represented with mocks.
+
+## Cleanup
+
+After a PR is pushed and no more local work is needed:
+
+```bash
+git worktree remove ../worktrees/hermes-web-ui-<short-topic>
+```
+
+Only remove the worktree you created.
diff --git a/package.json b/package.json
index aba0bce..c307fcd 100644
--- a/package.json
+++ b/package.json
@@ -38,6 +38,7 @@
     "dev:client": "cross-env HERMES_WEB_UI_BACKEND_PORT=8647 vite --host --port 8649 --strictPort",
     "dev:server": "nodemon",
     "build": "vue-tsc -b && vite build && tsc --noEmit -p packages/server/tsconfig.json && node scripts/build-server.mjs",
+    "harness:check": "node scripts/harness-check.mjs",
     "prepare": "[ -d dist ] || npm run build",
     "preview": "NODE_ENV=production vite preview",
     "test": "vitest run",
diff --git a/scripts/harness-check.mjs b/scripts/harness-check.mjs
new file mode 100644
index 0000000..7e3633a
--- /dev/null
+++ b/scripts/harness-check.mjs
@@ -0,0 +1,132 @@
+#!/usr/bin/env node
+import { readFile } from 'node:fs/promises'
+import { existsSync } from 'node:fs'
+import path from 'node:path'
+
+const root = process.cwd()
+const failures = []
+
+function fail(message) {
+  failures.push(message)
+}
+
+async function readText(relativePath) {
+  return readFile(path.join(root, relativePath), 'utf8')
+}
+
+function requireFile(relativePath) {
+  if (!existsSync(path.join(root, relativePath))) {
+    fail(`Missing required harness file: ${relativePath}`)
+  }
+}
+
+function requireDir(relativePath) {
+  if (!existsSync(path.join(root, relativePath))) {
+    fail(`Missing required project directory: ${relativePath}`)
+  }
+}
+
+for (const file of [
+  'AGENTS.md',
+  'ARCHITECTURE.md',
+  'DEVELOPMENT.md',
+  'docs/harness/README.md',
+  'docs/harness/validation.md',
+  'docs/harness/worktree-runbook.md',
+  'docs/harness/pr-review.md',
+]) {
+  requireFile(file)
+}
+
+for (const dir of [
+  'packages/client/src',
+  'packages/server/src',
+  'packages/desktop',
+  'tests/client',
+  'tests/server',
+  'tests/e2e',
+  '.github/workflows',
+]) {
+  requireDir(dir)
+}
+
+const agents = await readText('AGENTS.md')
+const agentLines = agents.trimEnd().split(/\r?\n/)
+if (agentLines.length > 120) {
+  fail(`AGENTS.md should stay short; found ${agentLines.length} lines, expected <= 120`)
+}
+
+for (const requiredLink of [
+  'DEVELOPMENT.md',
+  'ARCHITECTURE.md',
+  'docs/harness/README.md',
+  'docs/harness/validation.md',
+  'docs/harness/worktree-runbook.md',
+  'docs/harness/pr-review.md',
+]) {
+  if (!agents.includes(requiredLink)) {
+    fail(`AGENTS.md must link to ${requiredLink}`)
+  }
+}
+
+const packageJson = JSON.parse(await readText('package.json'))
+for (const scriptName of [
+  'harness:check',
+  'test',
+  'test:coverage',
+  'test:e2e',
+  'build',
+]) {
+  if (!packageJson.scripts?.[scriptName]) {
+    fail(`package.json is missing script: ${scriptName}`)
+  }
+}
+
+const architecture = await readText('ARCHITECTURE.md')
+for (const phrase of [
+  'packages/client/src',
+  'packages/server/src',
+  'packages/desktop',
+  'HERMES_WEB_UI_HOME',
+  'fail_on_unmatched_files: true',
+]) {
+  if (!architecture.includes(phrase)) {
+    fail(`ARCHITECTURE.md should document: ${phrase}`)
+  }
+}
+
+const buildWorkflow = await readText('.github/workflows/build.yml')
+if (!buildWorkflow.includes('npm run harness:check')) {
+  fail('Build workflow must run npm run harness:check')
+}
+
+const desktopReleaseWorkflow = await readText('.github/workflows/desktop-release.yml')
+if (!desktopReleaseWorkflow.includes('files: ${{ matrix.artifact_files }}')) {
+  fail('desktop-release.yml must upload matrix-specific artifact_files')
+}
+
+for (const target of ['target_os: darwin', 'target_os: win32', 'target_os: linux']) {
+  if (!desktopReleaseWorkflow.includes(target)) {
+    fail(`desktop-release.yml is missing matrix target ${target}`)
+  }
+}
+
+for (const expectedGlob of ['*.dmg', '*.exe', '*.AppImage', 'latest*.yml']) {
+  if (!desktopReleaseWorkflow.includes(expectedGlob)) {
+    fail(`desktop-release.yml is missing expected artifact glob ${expectedGlob}`)
+  }
+}
+
+if (!desktopReleaseWorkflow.includes('fail_on_unmatched_files: true')) {
+  fail('desktop-release.yml must keep fail_on_unmatched_files: true')
+}
+
+if (failures.length > 0) {
+  console.error('Harness check failed:')
+  for (const failure of failures) {
+    console.error(`- ${failure}`)
+  }
+  process.exit(1)
+}
+
+console.log('Harness check passed')