diff --git a/scripts/checkNoExternalHosts.js b/scripts/checkNoExternalHosts.js
index d45747e..92bd4d4 100644
--- a/scripts/checkNoExternalHosts.js
+++ b/scripts/checkNoExternalHosts.js
@@ -43,8 +43,15 @@ const CODE = new Set(['.js', '.jsx', '.mjs', '.cjs'])
 // A URL, or a bare dotted hostname with a real TLD. The TLD length floor is what
 // keeps `emailConfig.model` and `foo.js` out of it — a two-plus-letter final
 // label after at least one dot, with no path characters, is a host.
+// The `(?![-\w])` after the TLD is not redundant with `\b`: `\b` matches between
+// `l` and `-`, so `auth.email-verify` — an engagement TEMPLATE KEY, and one the
+// plan names (§4.6.1) — was read as the host `auth.email` with a stray suffix.
+// A real hostname's TLD is the last label, so a `-` or a word character following
+// it means the match is a truncation of a longer identifier rather than a
+// destination. Everything a host IS followed by (a quote, `/`, `:`, `?`) still
+// matches.
 const URL_LITERAL = /\b(?:https?|smtps?):\/\/[^\s'"`]+/
-const HOSTNAME_LITERAL = /\b(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+(?:com|net|org|io|dev|co|email|mail|cloud|app|us|eu)\b/i
+const HOSTNAME_LITERAL = /\b(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+(?:com|net|org|io|dev|co|email|mail|cloud|app|us|eu)(?![-\w])/i
 
 // Hosts that are not destinations: the loopback family, and the RFC 2606 names
 // reserved for documentation. A placeholder in an admin form's help text is the
diff --git a/server/db/schema.sql b/server/db/schema.sql
index 0b6763a..59ee52b 100644
--- a/server/db/schema.sql
+++ b/server/db/schema.sql
@@ -1847,3 +1847,47 @@ CREATE TABLE IF NOT EXISTS engagement_sends (
   -- an index range scan rather than a table scan: it runs once per rule per event.
   INDEX idx_engs_rule_window (rule_id, created_at)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
+
+-- §4.4. The mail (and, from Phase 7, in-app) bodies an operator can edit, stored
+-- as a validated block array rather than as raw HTML: `blocks` goes through the
+-- same validate-then-sanitize gate the CMS pages do, against the `email.*`
+-- registry (src/emailBlocks/). Storing operator HTML would hand the renderer an
+-- injection surface and give up the prop schemas.
+--
+-- Three columns carry the whole "ship a better default without stealing an
+-- operator's work" mechanism (§4.6.1 property 3). `seed_key` says which shipped
+-- template a row came from, `seed_version` which revision of it, and `customized`
+-- whether a person has since edited it. The seeder updates a row whose version is
+-- behind ONLY while `customized = 0`; a customized row is left exactly as it is
+-- and the newer default is surfaced in the admin list instead. Same posture
+-- `settingsJson` takes: never overwrite what someone chose.
+--
+-- `trigger_id` has no foreign key for the reason `engagement_rules.trigger_id`
+-- has none -- a trigger is declared in code, so the set of them is whatever
+-- registered on this boot. NULL means a reusable template not tied to one
+-- trigger, which is what every transactional seed is: `mailer` renders them by
+-- key, no rule involved.
+CREATE TABLE IF NOT EXISTS engagement_templates (
+  id              INT AUTO_INCREMENT PRIMARY KEY,
+  `key`           VARCHAR(96)  NOT NULL UNIQUE,
+  name            VARCHAR(160) NOT NULL,
+  trigger_id      VARCHAR(96)  NULL,
+  trigger_version INT          NULL,
+  channel         VARCHAR(32)  NOT NULL,
+  subject         VARCHAR(300) NULL,
+  blocks          MEDIUMTEXT   NOT NULL,
+  text_body       MEDIUMTEXT   NULL,
+  status          ENUM('draft','published') NOT NULL DEFAULT 'draft',
+  -- Editable, NOT deletable -- the pages.protected flag, for the same reason:
+  -- the system breaks without a password-reset body.
+  protected       TINYINT(1)   NOT NULL DEFAULT 0,
+  seed_key        VARCHAR(96)  NULL,
+  seed_version    INT          NULL,
+  customized      TINYINT(1)   NOT NULL DEFAULT 0,
+  updated_by      INT          NULL,
+  created_at      DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  updated_at      DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+  CONSTRAINT fk_engt_user FOREIGN KEY (updated_by) REFERENCES users(id) ON DELETE SET NULL,
+  INDEX idx_engt_trigger (trigger_id, channel, status),
+  INDEX idx_engt_seed (seed_key)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
diff --git a/server/db/seed.js b/server/db/seed.js
index 4f8201a..41c92ee 100644
--- a/server/db/seed.js
+++ b/server/db/seed.js
@@ -4,6 +4,7 @@ const settingsDb = require('../src/model/settings/settings.db')
 const wikiDb = require('../src/model/wiki/wiki.db')
 const users = require('../src/model/users/users.model')
 const { ensureSchema, close } = require('../src/utils/db')
+const { seedTemplates } = require('../src/engagement/templates')
 const brand = require('../src/config/brand')
 
 const log = require('../src/utils/logger')('seed')
@@ -74,6 +75,12 @@ async function seedDefaults() {
     // migration of pages seeded before the wiki upgrade).
     await wikiDb.assignCategoryBySlug(slug, categorySlug)
   }
+  // The shipped mail bodies (ENGAGEMENT.md §4.6.1). Idempotent, and it never
+  // overwrites a row an operator has edited — `customized = 1` is checked in the
+  // UPDATE's own WHERE, not in a read-then-write. Never throws: a template that
+  // failed to seed costs the shipped default, which `renderByKey` falls back to
+  // anyway, and must not stop a boot.
+  await seedTemplates()
   log.info('settings and wiki defaults ensured')
 }
 
diff --git a/server/src/blocks/sanitizeBlocks.js b/server/src/blocks/sanitizeBlocks.js
index c9d91d6..91d3ef6 100644
--- a/server/src/blocks/sanitizeBlocks.js
+++ b/server/src/blocks/sanitizeBlocks.js
@@ -4,44 +4,58 @@
 // normalizer (e.g. rich_text runs its html through the allowlist), stamping the
 // registry `version`, defaulting `visible` to true, and recursing one level into
 // container slots. Returns a new array; never mutates the input.
+//
+// Parameterized by a registry lookup for the same reason validateBlocks is
+// (engagement Phase 5a): the `email.*` family is a separate registry and must get
+// the same validate-then-sanitize order, not a second implementation of it.
 
 const { getBlock } = require('./registry')
 
-function sanitizeBlocks(blocks) {
-  if (!Array.isArray(blocks)) return []
-  return blocks.map(sanitizeOne)
-}
+/**
+ * Build a blocks sanitizer bound to one registry.
+ * @param {(type: string) => object|null} lookup registry `getBlock`
+ * @returns {(blocks: unknown) => object[]}
+ */
+function makeSanitizeBlocks(lookup) {
+  function sanitizeOne(block) {
+    const def = lookup(block.type)
+    if (!def) return block // unreachable after validation, but stay defensive
 
-function sanitizeOne(block) {
-  const def = getBlock(block.type)
-  if (!def) return block // unreachable after validation, but stay defensive
+    let props = block.props && typeof block.props === 'object' ? { ...block.props } : {}
 
-  let props = block.props && typeof block.props === 'object' ? { ...block.props } : {}
+    // Recurse into container slots first (leaf sub-blocks get sanitized too).
+    if (def.container) {
+      for (const slot of def.containerSlots) {
+        if (Array.isArray(props[slot])) props[slot] = props[slot].map(sanitizeOne)
+      }
+    }
 
-  // Recurse into container slots first (leaf sub-blocks get sanitized too).
-  if (def.container) {
-    for (const slot of def.containerSlots) {
-      if (Array.isArray(props[slot])) props[slot] = props[slot].map(sanitizeOne)
+    // Apply the block's own normalizer last (operates on its scalar props).
+    if (def.sanitize) {
+      try {
+        props = def.sanitize(props)
+      } catch {
+        // Leave props as-is; validation already passed, a sanitize throw shouldn't
+        // block the save.
+      }
+    }
+
+    return {
+      id: block.id,
+      type: block.type,
+      version: Number.isInteger(block.version) ? block.version : def.version,
+      visible: block.visible !== false,
+      props,
     }
   }
 
-  // Apply the block's own normalizer last (operates on its scalar props).
-  if (def.sanitize) {
-    try {
-      props = def.sanitize(props)
-    } catch {
-      // Leave props as-is; validation already passed, a sanitize throw shouldn't
-      // block the save.
-    }
-  }
-
-  return {
-    id: block.id,
-    type: block.type,
-    version: Number.isInteger(block.version) ? block.version : def.version,
-    visible: block.visible !== false,
-    props,
+  return function sanitizeBlocks(blocks) {
+    if (!Array.isArray(blocks)) return []
+    return blocks.map(sanitizeOne)
   }
 }
 
-module.exports = { sanitizeBlocks }
+// The page-registry binding — the export every existing caller already uses.
+const sanitizeBlocks = makeSanitizeBlocks(getBlock)
+
+module.exports = { sanitizeBlocks, makeSanitizeBlocks }
diff --git a/server/src/blocks/validateBlocks.js b/server/src/blocks/validateBlocks.js
index efd3acd..5675e9c 100644
--- a/server/src/blocks/validateBlocks.js
+++ b/server/src/blocks/validateBlocks.js
@@ -1,4 +1,4 @@
-// Server-side validation for a page's `blocks` array, run on every save before
+// Server-side validation for a stored `blocks` array, run on every save before
 // persisting. The admin UI validates client-side too, but that can be bypassed
 // by a direct API call, so this is the authoritative gate: it enforces the block
 // envelope (reserved keys only), that every `type` is a registered block, that
@@ -9,6 +9,14 @@
 // Returns { valid, errors } — a flat list of human-readable error strings, each
 // prefixed with the path to the offending block (e.g. `blocks[2].props.text`).
 // It never throws on bad input; callers turn a non-empty `errors` into a 400.
+//
+// **The walk is parameterized by a registry lookup, and the page registry is one
+// binding of it** (engagement Phase 5a). The `email.*` family is a SEPARATE
+// registry — its entries carry renderers instead of a cache policy, and a
+// CMS page must not validate with an email block inside it — but the envelope,
+// the id uniqueness, the schema dispatch and the nesting cap are the same rules
+// for both. Sharing the walk is what keeps them the same rules rather than two
+// copies that drift.
 
 const { getBlock, RESERVED_KEYS } = require('./registry')
 
@@ -18,114 +26,129 @@ const MAX_SUBBLOCKS = 50 // sub-blocks per container slot
 const ID_RE = /^[A-Za-z0-9_-]{1,40}$/
 
 /**
- * Validate a stored blocks array against the registry.
- * @param {unknown} blocks
- * @returns {{ valid: boolean, errors: string[] }}
+ * Build a blocks validator bound to one registry.
+ *
+ * @param {(type: string) => object|null} lookup registry `getBlock`
+ * @param {{ maxBlocks?: number, maxSubBlocks?: number }} [limits]
+ * @returns {(blocks: unknown) => { valid: boolean, errors: string[] }}
  */
-function validateBlocks(blocks) {
-  const errors = []
-  if (!Array.isArray(blocks)) {
-    return { valid: false, errors: ['blocks must be an array'] }
-  }
-  if (blocks.length > MAX_BLOCKS) {
-    errors.push(`blocks may not exceed ${MAX_BLOCKS} top-level entries`)
-  }
-  const seenIds = new Set()
-  blocks.forEach((block, i) => {
-    validateBlock(block, `blocks[${i}]`, seenIds, errors, { nested: false })
-  })
-  return { valid: errors.length === 0, errors }
-}
+function makeValidateBlocks(lookup, limits = {}) {
+  const maxBlocks = limits.maxBlocks || MAX_BLOCKS
+  const maxSubBlocks = limits.maxSubBlocks || MAX_SUBBLOCKS
 
-// Envelope: only the reserved keys, nothing smuggled at the top level.
-function checkEnvelope(block, path, errors) {
-  for (const key of Object.keys(block)) {
-    if (!RESERVED_KEYS.includes(key)) {
-      errors.push(`${path}.${key} is not an allowed top-level key`)
+  // Envelope: only the reserved keys, nothing smuggled at the top level.
+  function checkEnvelope(block, path, errors) {
+    for (const key of Object.keys(block)) {
+      if (!RESERVED_KEYS.includes(key)) {
+        errors.push(`${path}.${key} is not an allowed top-level key`)
+      }
     }
   }
-}
 
-// id — stable, unique across the whole page (top-level and nested share one
-// namespace since ids are the future join point for revision history).
-function checkId(block, path, seenIds, errors) {
-  if (typeof block.id !== 'string' || !ID_RE.test(block.id)) {
-    errors.push(`${path}.id must be a short id string`)
-  } else if (seenIds.has(block.id)) {
-    errors.push(`${path}.id duplicates another block id (${block.id})`)
-  } else {
-    seenIds.add(block.id)
-  }
-}
-
-// Per-block prop schema from the registry (skipped when props isn't an object —
-// that's already reported separately).
-function checkPropSchema(def, props, path, errors) {
-  if (!def.schema || !props || typeof props !== 'object') return
-  let schemaErrors = []
-  try {
-    schemaErrors = def.schema(props) || []
-  } catch (err) {
-    schemaErrors = [`schema threw: ${err.message}`]
-  }
-  for (const e of schemaErrors) errors.push(`${path}.props.${e}`)
-}
-
-// Nesting: only container blocks may hold sub-blocks, capped at one level.
-function checkNesting(def, props, path, seenIds, errors, nested) {
-  if (nested) {
-    errors.push(`${path} is a container and may not be nested inside another container`)
-    return
-  }
-  for (const slot of def.containerSlots) {
-    const sub = props ? props[slot] : undefined
-    if (sub === undefined) continue // an empty slot is allowed
-    if (!Array.isArray(sub)) {
-      errors.push(`${path}.props.${slot} must be an array of blocks`)
-      continue
+  // id — stable, unique across the whole document (top-level and nested share one
+  // namespace since ids are the future join point for revision history).
+  function checkId(block, path, seenIds, errors) {
+    if (typeof block.id !== 'string' || !ID_RE.test(block.id)) {
+      errors.push(`${path}.id must be a short id string`)
+    } else if (seenIds.has(block.id)) {
+      errors.push(`${path}.id duplicates another block id (${block.id})`)
+    } else {
+      seenIds.add(block.id)
     }
-    if (sub.length > MAX_SUBBLOCKS) {
-      errors.push(`${path}.props.${slot} may not exceed ${MAX_SUBBLOCKS} blocks`)
+  }
+
+  // Per-block prop schema from the registry (skipped when props isn't an object —
+  // that's already reported separately).
+  function checkPropSchema(def, props, path, errors) {
+    if (!def.schema || !props || typeof props !== 'object') return
+    let schemaErrors = []
+    try {
+      schemaErrors = def.schema(props) || []
+    } catch (err) {
+      schemaErrors = [`schema threw: ${err.message}`]
     }
-    sub.forEach((child, j) => {
-      validateBlock(child, `${path}.props.${slot}[${j}]`, seenIds, errors, { nested: true })
+    for (const e of schemaErrors) errors.push(`${path}.props.${e}`)
+  }
+
+  // Nesting: only container blocks may hold sub-blocks, capped at one level.
+  function checkNesting(def, props, path, seenIds, errors, nested) {
+    if (nested) {
+      errors.push(`${path} is a container and may not be nested inside another container`)
+      return
+    }
+    for (const slot of def.containerSlots) {
+      const sub = props ? props[slot] : undefined
+      if (sub === undefined) continue // an empty slot is allowed
+      if (!Array.isArray(sub)) {
+        errors.push(`${path}.props.${slot} must be an array of blocks`)
+        continue
+      }
+      if (sub.length > maxSubBlocks) {
+        errors.push(`${path}.props.${slot} may not exceed ${maxSubBlocks} blocks`)
+      }
+      sub.forEach((child, j) => {
+        validateBlock(child, `${path}.props.${slot}[${j}]`, seenIds, errors, { nested: true })
+      })
+    }
+  }
+
+  /**
+   * Validate one block envelope in place. `nested` = true when validating a
+   * sub-block inside a container slot, which forbids further nesting.
+   */
+  function validateBlock(block, path, seenIds, errors, { nested }) {
+    if (block === null || typeof block !== 'object' || Array.isArray(block)) {
+      errors.push(`${path} must be an object`)
+      return
+    }
+
+    checkEnvelope(block, path, errors)
+    checkId(block, path, seenIds, errors)
+
+    // visible — optional in input, but if present must be a boolean.
+    if (block.visible !== undefined && typeof block.visible !== 'boolean') {
+      errors.push(`${path}.visible must be a boolean`)
+    }
+
+    // props — always an object bag.
+    const props = block.props
+    if (props === null || typeof props !== 'object' || Array.isArray(props)) {
+      errors.push(`${path}.props must be an object`)
+    }
+
+    // type — must resolve to a registered block.
+    const def = typeof block.type === 'string' ? lookup(block.type) : null
+    if (!def) {
+      errors.push(`${path}.type is not a registered block type (${String(block.type)})`)
+      return // can't validate props or nesting without a definition
+    }
+
+    checkPropSchema(def, props, path, errors)
+    if (def.container) checkNesting(def, props, path, seenIds, errors, nested)
+  }
+
+  /**
+   * Validate a stored blocks array against the bound registry.
+   * @param {unknown} blocks
+   * @returns {{ valid: boolean, errors: string[] }}
+   */
+  return function validateBlocks(blocks) {
+    const errors = []
+    if (!Array.isArray(blocks)) {
+      return { valid: false, errors: ['blocks must be an array'] }
+    }
+    if (blocks.length > maxBlocks) {
+      errors.push(`blocks may not exceed ${maxBlocks} top-level entries`)
+    }
+    const seenIds = new Set()
+    blocks.forEach((block, i) => {
+      validateBlock(block, `blocks[${i}]`, seenIds, errors, { nested: false })
     })
+    return { valid: errors.length === 0, errors }
   }
 }
 
-/**
- * Validate one block envelope in place. `nested` = true when validating a
- * sub-block inside a container slot, which forbids further nesting.
- */
-function validateBlock(block, path, seenIds, errors, { nested }) {
-  if (block === null || typeof block !== 'object' || Array.isArray(block)) {
-    errors.push(`${path} must be an object`)
-    return
-  }
+// The page-registry binding — the export every existing caller already uses.
+const validateBlocks = makeValidateBlocks(getBlock)
 
-  checkEnvelope(block, path, errors)
-  checkId(block, path, seenIds, errors)
-
-  // visible — optional in input, but if present must be a boolean.
-  if (block.visible !== undefined && typeof block.visible !== 'boolean') {
-    errors.push(`${path}.visible must be a boolean`)
-  }
-
-  // props — always an object bag.
-  const props = block.props
-  if (props === null || typeof props !== 'object' || Array.isArray(props)) {
-    errors.push(`${path}.props must be an object`)
-  }
-
-  // type — must resolve to a registered block.
-  const def = typeof block.type === 'string' ? getBlock(block.type) : null
-  if (!def) {
-    errors.push(`${path}.type is not a registered block type (${String(block.type)})`)
-    return // can't validate props or nesting without a definition
-  }
-
-  checkPropSchema(def, props, path, errors)
-  if (def.container) checkNesting(def, props, path, seenIds, errors, nested)
-}
-
-module.exports = { validateBlocks, MAX_BLOCKS, MAX_SUBBLOCKS }
+module.exports = { validateBlocks, makeValidateBlocks, MAX_BLOCKS, MAX_SUBBLOCKS }
diff --git a/server/src/emailBlocks/index.js b/server/src/emailBlocks/index.js
new file mode 100644
index 0000000..fef1d06
--- /dev/null
+++ b/server/src/emailBlocks/index.js
@@ -0,0 +1,26 @@
+// Email block registry entrypoint. Requiring this module registers every
+// `email.*` block definition exactly once, then re-exports the registry API, the
+// renderer and the registry-bound validator/sanitizer. Anything that needs to
+// validate or render a mail template's blocks should require THIS module, not
+// ./registry or ./render directly, so the definitions are guaranteed loaded.
+//
+// Same shape as `blocks/index.js`, on purpose — the two families are siblings
+// (see ./registry.js for why they are not one registry).
+
+const registry = require('./registry')
+const render = require('./render')
+const interpolate = require('./interpolate')
+
+// ── Block definitions (self-register on require) ───────────────────────────
+require('./types/heading')
+require('./types/text')
+require('./types/button')
+require('./types/divider')
+require('./types/image')
+require('./types/itemList')
+
+module.exports = {
+  ...registry,
+  ...render,
+  ...interpolate,
+}
diff --git a/server/src/emailBlocks/interpolate.js b/server/src/emailBlocks/interpolate.js
new file mode 100644
index 0000000..f5afb46
--- /dev/null
+++ b/server/src/emailBlocks/interpolate.js
@@ -0,0 +1,79 @@
+// ── Template variable interpolation ────────────────────────────────────────
+//
+// ENGAGEMENT.md §4.6.2's security posture, as code: "variable interpolation is
+// HTML-escaped by default with no raw-HTML variable type in v1. A module supplies
+// data; it does not supply markup."
+//
+// The token grammar is deliberately the smallest thing that works: `{{ name }}`,
+// a bare declared variable name, and NOTHING else. No filters, no conditionals,
+// no loops, no dotted paths. Three reasons:
+//
+//  - A template is operator-authored data rendered by the server. Every construct
+//    added here is a construct an operator can get wrong and a construct someone
+//    has to sandbox.
+//  - §4.3 makes the trigger declaration the source of truth for what a template
+//    may reference, and a save-time check names the offending variable. That check
+//    can only be exact if a token is a name — `{{ user.profile.email }}` is not a
+//    declared variable, it is an expression over one.
+//  - Repetition is a BLOCK (`email.itemList`), not a template construct, so the
+//    one place a template needs "for each" already has a typed, validated home.
+//
+// A token whose variable has no value at render time becomes the empty string and
+// is reported in `missing`. It does not become "undefined", which is the failure
+// §4.3's versioning paragraph is about — a renamed variable rendering as the word
+// undefined in a person's inbox.
+
+// `{{ name }}` / `{{name}}`. Leading letter, then letters/digits/underscore —
+// the same shape §4.3's declarations use.
+const TOKEN_RE = /\{\{\s*([A-Za-z][A-Za-z0-9_]*)\s*\}\}/g
+
+/** Escape text for interpolation into HTML. Same table as utils/htmlShell.js. */
+function htmlEscape(s) {
+  return String(s).replace(
+    /[&<>"']/g,
+    (c) => ({ '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;', "'": '&#39;' }[c]),
+  )
+}
+
+/**
+ * Every distinct variable name a string references, in first-appearance order.
+ * This is what the save-time check (Phase 5b) walks to find undeclared variables.
+ * @param {unknown} str
+ * @returns {string[]}
+ */
+function scanTokens(str) {
+  if (typeof str !== 'string') return []
+  const found = []
+  for (const m of str.matchAll(TOKEN_RE)) {
+    if (!found.includes(m[1])) found.push(m[1])
+  }
+  return found
+}
+
+/**
+ * Substitute declared variables into a string.
+ *
+ * @param {unknown} str
+ * @param {Record<string, unknown>} values
+ * @param {{ escape?: boolean, missing?: Set<string> }} [opts]
+ *        `escape` (default true) HTML-escapes each value — pass false ONLY for the
+ *        plain-text part, where there is no markup to escape into and `&amp;` in a
+ *        person's inbox is a bug. `missing` collects names with no value.
+ * @returns {string}
+ */
+function interpolate(str, values, opts = {}) {
+  if (typeof str !== 'string' || str === '') return ''
+  const escape = opts.escape !== false
+  const missing = opts.missing || null
+  return str.replace(TOKEN_RE, (_match, name) => {
+    const value = values ? values[name] : undefined
+    if (value === undefined || value === null) {
+      if (missing) missing.add(name)
+      return ''
+    }
+    const asString = typeof value === 'string' ? value : String(value)
+    return escape ? htmlEscape(asString) : asString
+  })
+}
+
+module.exports = { TOKEN_RE, htmlEscape, scanTokens, interpolate }
diff --git a/server/src/emailBlocks/registry.js b/server/src/emailBlocks/registry.js
new file mode 100644
index 0000000..a58b9a8
--- /dev/null
+++ b/server/src/emailBlocks/registry.js
@@ -0,0 +1,120 @@
+// ── The `email.*` block registry ───────────────────────────────────────────
+//
+// ENGAGEMENT.md §4.4. A sibling of `blocks/registry.js`, not an extension of it,
+// settled with the org lead at the start of Phase 5a. Three reasons, in order of
+// how much they cost if ignored:
+//
+//  1. **These blocks render on the SERVER.** Page blocks do not: `blocks/` carries
+//     `schema` / `sanitize` / `cacheTTL` and the actual drawing happens in React
+//     (`client/src/blocks/BlockRenderer.jsx`). Mail has no React — a message body
+//     is a string this process produces — so an email definition carries `toHtml`
+//     and `toText`. `registerBlock` freezes a fixed field set and would silently
+//     DROP both.
+//  2. **One registry would be one namespace.** `blocks/validateBlocks.js`'s only
+//     server consumer is `pages.model.js`; registering `email.heading` into that
+//     Map makes a CMS page containing an email block validate and save, and the
+//     client renderer has nothing to draw for it.
+//  3. The two entry shapes genuinely differ: `cacheTTL` and `container` mean
+//     nothing to a mail body, and a renderer means nothing to a cached page block.
+//
+// What IS shared is everything that is the same rule for both, and it is shared by
+// binding rather than by copy: `propHelpers`, the envelope/id/nesting walk
+// (`makeValidateBlocks`) and the validate-then-sanitize order (`makeSanitizeBlocks`).
+// §4.4's "do not build a second editor" is honoured where it is about the editor —
+// Phase 5b drives these through the existing block/prop-panel machinery.
+//
+// A registered definition looks like:
+//   {
+//     type: 'email.heading',
+//     version: 1,
+//     schema: (props) => [],           // error strings ([] = valid)
+//     sanitize: (props) => props,      // optional, run on save AFTER validation
+//     toHtml: (props, ctx) => '<tr>…', // a table ROW; see render.js for the shell
+//     toText: (props, ctx) => 'text',  // '' means "contributes nothing"
+//   }
+//
+// `ctx` is the render context (render.js): resolved brand values, an `interp`
+// that substitutes declared variables HTML-escaped, and `interpText` that does
+// the same without escaping for the plain-text part.
+
+const registry = new Map()
+
+// Same envelope as a page block — deliberately the same constant list, because
+// the shared validator enforces it and the two must not diverge.
+const { RESERVED_KEYS } = require('../blocks/registry')
+
+/**
+ * Register an email block definition. Throws on a missing type, a duplicate, or a
+ * missing renderer — all three are programmer errors surfaced at boot.
+ * @param {object} def
+ * @returns {object} the normalized, frozen definition
+ */
+function registerEmailBlock(def) {
+  if (!def || typeof def.type !== 'string' || def.type.length === 0) {
+    throw new Error('registerEmailBlock: a block definition needs a string `type`')
+  }
+  if (!def.type.startsWith('email.')) {
+    // The prefix is not needed to disambiguate — this is its own Map — but a
+    // stored blocks array should say what it is when someone reads the row.
+    throw new Error(`registerEmailBlock: ${def.type} must be namespaced "email."`)
+  }
+  if (registry.has(def.type)) {
+    throw new Error(`registerEmailBlock: block type already registered: ${def.type}`)
+  }
+  if (typeof def.toHtml !== 'function' || typeof def.toText !== 'function') {
+    // §4.4: "Every block type gets a toText(props) alongside its renderer, so a
+    // text part always exists." A block that can only produce HTML would make a
+    // published template's text part depend on which blocks it happened to use.
+    throw new Error(`registerEmailBlock: ${def.type} needs both toHtml and toText`)
+  }
+  if (def.schema != null && typeof def.schema !== 'function') {
+    throw new Error(`registerEmailBlock: ${def.type}.schema must be a function`)
+  }
+  if (def.sanitize != null && typeof def.sanitize !== 'function') {
+    throw new Error(`registerEmailBlock: ${def.type}.sanitize must be a function`)
+  }
+  const entry = Object.freeze({
+    type: def.type,
+    label: def.label || def.type,
+    version: Number.isInteger(def.version) ? def.version : 1,
+    schema: def.schema || null,
+    sanitize: def.sanitize || null,
+    toHtml: def.toHtml,
+    toText: def.toText,
+    // The shared walk reads these; email has no containers, and saying so here is
+    // what lets `makeValidateBlocks` be the same function for both families.
+    container: false,
+    containerSlots: Object.freeze([]),
+  })
+  registry.set(entry.type, entry)
+  return entry
+}
+
+/** @returns {object|null} the definition for `type`, or null if unknown. */
+function getEmailBlock(type) {
+  return registry.get(type) || null
+}
+
+/** @returns {boolean} whether `type` is a registered email block. */
+function hasEmailBlock(type) {
+  return registry.has(type)
+}
+
+/** @returns {object[]} all registered definitions (registration order). */
+function listEmailBlocks() {
+  return [...registry.values()]
+}
+
+/** Drop every registered block. Test-only. */
+function _resetRegistry() {
+  registry.clear()
+}
+
+module.exports = {
+  RESERVED_KEYS,
+  registerEmailBlock,
+  getEmailBlock,
+  hasEmailBlock,
+  listEmailBlocks,
+  _resetRegistry,
+}
diff --git a/server/src/emailBlocks/render.js b/server/src/emailBlocks/render.js
new file mode 100644
index 0000000..53bdae3
--- /dev/null
+++ b/server/src/emailBlocks/render.js
@@ -0,0 +1,196 @@
+// ── Rendering a block array into a mail body ───────────────────────────────
+//
+// Pure and synchronous: everything that needs a database — the brand values, the
+// resolved theme, the site title — is resolved by `engagement/templates.js` and
+// arrives here as a plain object. That split is what lets the whole renderer be
+// tested without a MariaDB, and it is why the byte-comparison test for the five
+// transactional bodies (§5a acceptance) is a unit test rather than a live send.
+//
+// **The shell contributes structure and NO content.** No appended footer, no
+// injected logo, no "sent by" line. Two reasons, and the second is the load-bearing
+// one:
+//
+//  - A person's mail must say what the operator wrote and nothing else. An
+//    unsubscribe line is a variable inside the template (§4.6.1 lists
+//    `unsubscribeUrl` for exactly the two templates that need one), so an operator
+//    can move it, reword it, or see that a transactional mail correctly has none.
+//  - **The HTML and text parts must say the same things.** A shell that put a
+//    footer only in the HTML would make every message's two parts disagree, which
+//    is a deliverability signal and, worse, means the text reader is told less
+//    than the HTML reader. Every block produces both halves; nothing else does.
+//
+// The HTML is table-based and inline-styled throughout, which is not a stylistic
+// choice: `<div>` layout and a `<style>` block are the two things mail clients
+// most reliably break.
+
+const { htmlEscape, interpolate } = require('./interpolate')
+const { getEmailBlock } = require('./registry')
+const { makeValidateBlocks } = require('../blocks/validateBlocks')
+const { makeSanitizeBlocks } = require('../blocks/sanitizeBlocks')
+const { isSafeUrl } = require('../blocks/propHelpers')
+
+// Bound to the email registry — the same walk the page family gets, so the
+// envelope rules, id uniqueness and schema dispatch cannot drift between them.
+const validateEmailBlocks = makeValidateBlocks(getEmailBlock, { maxBlocks: 60 })
+const sanitizeEmailBlocks = makeSanitizeBlocks(getEmailBlock)
+
+// A stack every mail client resolves. No webfont: a @font-face in mail is either
+// stripped or silently ignored, and the fallback is what the reader sees anyway.
+const FONT_STACK = "-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,Helvetica,Arial,sans-serif"
+
+/**
+ * The mail palette — a light scaffold plus the deployment's accent.
+ *
+ * **Only the accent comes from the theme, and that is deliberate.** Every shipped
+ * preset (`config/themePresets.js`) is a DARK palette, and mail is not a page: a
+ * dark-background body is what §4.6.2 names as rendering "unreadable dark-on-dark
+ * in about a third of inboxes", because a good share of clients invert or force a
+ * background of their own. Deriving a light palette from a dark one would be a
+ * guess at six colours; taking the one colour that carries the brand — the accent,
+ * used for the button and for links — is exact. §4.6.1's property 2 holds either
+ * way: no seeded template contains a hex code, so one prebuilt image running as
+ * any shard mails in that shard's colour.
+ *
+ * @param {{ accent?: string }} [theme] resolved theme tokens
+ */
+function palette(theme = {}) {
+  const accent = isHex(theme.accent) ? theme.accent : '#7f99bd'
+  return Object.freeze({
+    accent,
+    onAccent: readableOn(accent),
+    heading: '#151a20',
+    text: '#33404d',
+    muted: '#6b7885',
+    rule: '#dfe4ea',
+    page: '#f4f6f8',
+    card: '#ffffff',
+    fontStack: FONT_STACK,
+  })
+}
+
+function isHex(v) {
+  return typeof v === 'string' && /^#[0-9a-fA-F]{3}([0-9a-fA-F]{3})?$/.test(v)
+}
+
+/** Black or white text over `hex`, whichever a reader can actually read. */
+function readableOn(hex) {
+  let h = hex.slice(1)
+  if (h.length === 3) h = h.split('').map((c) => c + c).join('')
+  const [r, g, b] = [0, 2, 4].map((i) => parseInt(h.slice(i, i + 2), 16) / 255)
+  // Relative luminance (WCAG). 0.45 rather than 0.5: the accents here are mid-tone
+  // and white-on-mid reads better than black-on-mid at button weight.
+  const lin = (c) => (c <= 0.03928 ? c / 12.92 : ((c + 0.055) / 1.055) ** 2.4)
+  const L = 0.2126 * lin(r) + 0.7152 * lin(g) + 0.0722 * lin(b)
+  return L > 0.45 ? '#151a20' : '#ffffff'
+}
+
+/**
+ * Build the render context every block's `toHtml` / `toText` receives.
+ *
+ * @param {object} opts
+ * @param {Record<string, unknown>} opts.values   variable values
+ * @param {object} [opts.theme]                   resolved theme tokens
+ * @param {string} [opts.baseUrl]                 absolute site base, for relative urls
+ * @param {Set<string>} [opts.missing]            collects unresolved variable names
+ */
+function buildContext({ values = {}, theme = {}, baseUrl = '', missing = new Set() }) {
+  const base = String(baseUrl || '').replace(/\/+$/, '')
+  const ctx = {
+    values,
+    missing,
+    palette: palette(theme),
+    escape: htmlEscape,
+    /** Interpolate + HTML-escape — for anything going into markup. */
+    h: (s) => interpolate(s, values, { escape: true, missing }),
+    /** Interpolate WITHOUT escaping — for the plain-text part only. */
+    t: (s) => interpolate(s, values, { escape: false, missing }),
+    /**
+     * Interpolate a URL and re-check it. Returns the URL or null.
+     *
+     * A stored `{{resetUrl}}` says nothing about where it points; the value
+     * arrives from a caller or a module at render time. Checking only the stored
+     * literal would mean a variable carrying `javascript:` becomes an href.
+     */
+    safeHref: (s) => {
+      const url = interpolate(s, values, { escape: false, missing })
+      return url && isSafeUrl(url) ? url : null
+    },
+    /** Same-origin path → absolute URL; http(s) unchanged; anything else null. */
+    absolute: (url) => {
+      if (!url) return null
+      if (/^https?:\/\//i.test(url)) return url
+      if (url.startsWith('/')) return base ? `${base}${url}` : null
+      return null
+    },
+  }
+  return ctx
+}
+
+/**
+ * Render a blocks array into the two body parts.
+ *
+ * Blocks are joined by a blank line in text and stacked as table rows in HTML.
+ * A block whose `toText` returns '' contributes nothing to the text part and does
+ * not leave a doubled blank line behind it (`email.divider` is the case).
+ *
+ * @returns {{ html: string, text: string }} html is the ROWS, not a document
+ */
+function renderBlocks(blocks, ctx) {
+  const rows = []
+  const paras = []
+  for (const block of Array.isArray(blocks) ? blocks : []) {
+    if (block && block.visible === false) continue
+    const def = block && typeof block.type === 'string' ? getEmailBlock(block.type) : null
+    if (!def) continue // unreachable after validation; never emit an unknown block
+    const props = block.props && typeof block.props === 'object' ? block.props : {}
+    try {
+      const html = def.toHtml(props, ctx)
+      if (html) rows.push(html)
+      const text = def.toText(props, ctx)
+      if (text) paras.push(text)
+    } catch {
+      // One misbehaving block must not cost the whole message. Skipped in both
+      // parts together, so the two never disagree about what the mail contains.
+    }
+  }
+  return { html: rows.join(''), text: paras.join('\n\n') }
+}
+
+/**
+ * Wrap rendered rows in the mail document.
+ * @param {string} rowsHtml
+ * @param {object} ctx
+ * @param {string} [title] the <title>, shown by a few webmail clients
+ */
+function renderDocument(rowsHtml, ctx, title = '') {
+  const p = ctx.palette
+  return (
+    '<!doctype html><html><head><meta charset="utf-8" />' +
+    '<meta name="viewport" content="width=device-width,initial-scale=1" />' +
+    // Tells a client that inverts colours that this body already handles both,
+    // so it leaves the palette alone instead of inverting the card to near-black.
+    '<meta name="color-scheme" content="light" />' +
+    '<meta name="supported-color-schemes" content="light" />' +
+    `<title>${htmlEscape(title)}</title></head>` +
+    `<body style="margin:0;padding:0;background:${p.page};">` +
+    `<table role="presentation" cellpadding="0" cellspacing="0" border="0" width="100%" style="background:${p.page};">` +
+    '<tr><td align="center" style="padding:24px 12px;">' +
+    `<table role="presentation" cellpadding="0" cellspacing="0" border="0" width="600" ` +
+    `style="width:100%;max-width:600px;background:${p.card};border:1px solid ${p.rule};border-radius:6px;">` +
+    '<tr><td style="padding:28px 28px 16px 28px;">' +
+    '<table role="presentation" cellpadding="0" cellspacing="0" border="0" width="100%">' +
+    rowsHtml +
+    '</table></td></tr></table></td></tr></table></body></html>'
+  )
+}
+
+module.exports = {
+  FONT_STACK,
+  palette,
+  readableOn,
+  buildContext,
+  renderBlocks,
+  renderDocument,
+  validateEmailBlocks,
+  sanitizeEmailBlocks,
+}
diff --git a/server/src/emailBlocks/types/button.js b/server/src/emailBlocks/types/button.js
new file mode 100644
index 0000000..513fa12
--- /dev/null
+++ b/server/src/emailBlocks/types/button.js
@@ -0,0 +1,86 @@
+// email.button — the call to action, and the one block whose two renderings are
+// deliberately NOT the same content.
+//
+// **`textLead` is why the plain-text part is authored rather than derived.** In
+// HTML this is a button reading "Choose a new password"; in plain text a button
+// is nothing, and what a reader needs is the sentence that introduces the URL
+// ("Choose a new password here:") followed by the URL on its own line. Deriving
+// the second from the first produces either a bare URL with no lead-in or the
+// button's label used as a sentence. §4.4 calls the text part generated-by-default
+// and overridable; this block is the reason the default has to be good enough that
+// an operator rarely reaches for the override.
+//
+// **The href is re-checked AFTER interpolation.** `url` is nearly always a token
+// (`{{resetUrl}}`), so nothing about the stored value tells you where it points —
+// the value arrives at render time from a module or a caller. A substituted URL
+// that is not http/https/same-origin loses its href and renders as inert text
+// rather than as a link the reader would have no reason to distrust.
+const { registerEmailBlock } = require('../registry')
+const { requiredText, optionalText, onlyKeys, isSafeUrl } = require('../../blocks/propHelpers')
+const { scanTokens } = require('../interpolate')
+
+const MAX_LABEL = 80
+const MAX_URL = 600
+const MAX_LEAD = 200
+
+registerEmailBlock({
+  type: 'email.button',
+  label: 'Button / link',
+  version: 1,
+  schema(props) {
+    const errors = onlyKeys(props, ['label', 'url', 'textLead'])
+    const label = requiredText('label', props.label, MAX_LABEL)
+    if (label) errors.push(label)
+    const lead = optionalText('textLead', props.textLead, MAX_LEAD)
+    if (lead) errors.push(lead)
+
+    const url = requiredText('url', props.url, MAX_URL)
+    if (url) {
+      errors.push(url)
+    } else if (scanTokens(props.url).length === 0 && !isSafeUrl(props.url)) {
+      // A literal url is checked here, at save. One built from variables cannot
+      // be — see the header note; render.js checks the substituted value instead.
+      errors.push('url must be a relative path, an http(s) URL, or a template variable')
+    }
+    return errors
+  },
+  toHtml(props, ctx) {
+    // An EMPTY url and an UNSAFE one are different failures and get different
+    // answers. Empty means the caller chose not to supply this link at all (an
+    // unsubscribe line on a transactional mail), so the block disappears from both
+    // parts. Unsafe means a value arrived that must not become an href — the label
+    // still renders, inert, because dropping it silently would hide from the
+    // reader that the mail was meant to offer them something.
+    if (ctx.t(props.url).trim() === '') return ''
+    const href = ctx.safeHref(props.url)
+    const label = ctx.h(props.label)
+    if (!href) {
+      return (
+        `<tr><td style="padding:4px 0 16px 0;font-family:${ctx.palette.fontStack};` +
+        `font-size:15px;color:${ctx.palette.muted};">${label}</td></tr>`
+      )
+    }
+    // Table-wrapped, inline-styled, with explicit padding on the anchor: the shape
+    // that survives Outlook, which ignores padding on a <td> containing an <a>.
+    return (
+      '<tr><td style="padding:4px 0 20px 0;">' +
+      '<table role="presentation" cellpadding="0" cellspacing="0" border="0"><tr>' +
+      `<td bgcolor="${ctx.palette.accent}" style="border-radius:4px;">` +
+      `<a href="${ctx.escape(href)}" style="display:inline-block;padding:11px 22px;` +
+      `font-family:${ctx.palette.fontStack};font-size:15px;font-weight:600;` +
+      `color:${ctx.palette.onAccent};text-decoration:none;border-radius:4px;">${label}</a>` +
+      '</td></tr></table>' +
+      // The bare URL under the button, for the clients that strip anchors and for
+      // the reader who wants to see where it goes before pressing it.
+      `<div style="padding-top:10px;font-family:${ctx.palette.fontStack};font-size:12px;` +
+      `line-height:1.5;color:${ctx.palette.muted};word-break:break-all;">${ctx.escape(href)}</div>` +
+      '</td></tr>'
+    )
+  },
+  toText(props, ctx) {
+    const url = ctx.t(props.url).trim()
+    if (url === '') return '' // see toHtml: no url, no block, in either part
+    const lead = props.textLead ? ctx.t(props.textLead).trim() : ''
+    return lead ? `${lead}\n${url}` : url
+  },
+})
diff --git a/server/src/emailBlocks/types/divider.js b/server/src/emailBlocks/types/divider.js
new file mode 100644
index 0000000..cc13fa3
--- /dev/null
+++ b/server/src/emailBlocks/types/divider.js
@@ -0,0 +1,29 @@
+// email.divider — a horizontal rule.
+//
+// **Its text form is the empty string, not a row of dashes.** A block whose only
+// job is visual separation has no plain-text equivalent, and render.js already
+// joins blocks with a blank line. Rendering `-----` would put a decoration in the
+// text part that the author never wrote and cannot remove without deleting the
+// rule from the HTML too. Returning '' is what the "'' means contributes nothing"
+// contract in registry.js exists for.
+const { registerEmailBlock } = require('../registry')
+const { onlyKeys } = require('../../blocks/propHelpers')
+
+registerEmailBlock({
+  type: 'email.divider',
+  label: 'Divider',
+  version: 1,
+  schema(props) {
+    return onlyKeys(props, [])
+  },
+  toHtml(_props, ctx) {
+    return (
+      '<tr><td style="padding:8px 0 20px 0;">' +
+      `<div style="height:1px;line-height:1px;font-size:0;background:${ctx.palette.rule};">&nbsp;</div>` +
+      '</td></tr>'
+    )
+  },
+  toText() {
+    return ''
+  },
+})
diff --git a/server/src/emailBlocks/types/heading.js b/server/src/emailBlocks/types/heading.js
new file mode 100644
index 0000000..9390626
--- /dev/null
+++ b/server/src/emailBlocks/types/heading.js
@@ -0,0 +1,41 @@
+// email.heading — a section heading inside a mail body.
+//
+// `level` is a SIZE, not a tag hierarchy: mail clients do not build an outline
+// from an email and several strip heading tags outright, so this renders a styled
+// <div> at one of three sizes rather than h1/h2/h3. Keeping the prop named `level`
+// means the prop panel Phase 5b reuses reads the same as the page block's.
+const { registerEmailBlock } = require('../registry')
+const { oneOf, requiredText, onlyKeys } = require('../../blocks/propHelpers')
+
+const LEVELS = ['h1', 'h2', 'h3']
+const MAX_TEXT = 200
+
+const SIZES = { h1: '24px', h2: '19px', h3: '16px' }
+
+registerEmailBlock({
+  type: 'email.heading',
+  label: 'Heading',
+  version: 1,
+  schema(props) {
+    const errors = onlyKeys(props, ['level', 'text'])
+    const level = oneOf('level', LEVELS)(props.level)
+    if (level) errors.push(level)
+    const text = requiredText('text', props.text, MAX_TEXT)
+    if (text) errors.push(text)
+    return errors
+  },
+  toHtml(props, ctx) {
+    // Same "nothing in, nothing out" rule as email.text: a heading that is one
+    // optional variable disappears rather than leaving its margin behind.
+    if (ctx.t(props.text).trim() === '') return ''
+    const size = SIZES[props.level] || SIZES.h2
+    return (
+      `<tr><td style="padding:0 0 12px 0;font-family:${ctx.palette.fontStack};` +
+      `font-size:${size};line-height:1.3;font-weight:700;color:${ctx.palette.heading};">` +
+      `${ctx.h(props.text)}</td></tr>`
+    )
+  },
+  toText(props, ctx) {
+    return ctx.t(props.text).trim()
+  },
+})
diff --git a/server/src/emailBlocks/types/image.js b/server/src/emailBlocks/types/image.js
new file mode 100644
index 0000000..7d20c61
--- /dev/null
+++ b/server/src/emailBlocks/types/image.js
@@ -0,0 +1,60 @@
+// email.image — an inline image.
+//
+// Two things differ from the page block of the same name, both because the reader
+// is in a mail client rather than on the site:
+//
+//  - **The src is absolutized.** `brand_assets` stores `/uploads/…` and every page
+//    renderer is same-origin, so a relative src has always been correct there. In
+//    an inbox there is no origin to be relative to; render.js's `absolute()` turns
+//    it into a URL against APP_BASE_URL / BRAND_URL, and an image that cannot be
+//    absolutized is DROPPED rather than emitted broken.
+//  - **`alt` is required.** Most mail clients block remote images by default, so
+//    for a large share of readers the alt text IS the image. On a web page it is
+//    an accessibility nicety; here it is the common case.
+const { registerEmailBlock } = require('../registry')
+const { requiredText, onlyKeys, isSafeUrl } = require('../../blocks/propHelpers')
+const { scanTokens } = require('../interpolate')
+
+const MAX_URL = 600
+const MAX_ALT = 200
+const MAX_WIDTH = 560
+
+registerEmailBlock({
+  type: 'email.image',
+  label: 'Image',
+  version: 1,
+  schema(props) {
+    const errors = onlyKeys(props, ['url', 'alt', 'width'])
+    const alt = requiredText('alt', props.alt, MAX_ALT)
+    if (alt) errors.push(alt)
+    const url = requiredText('url', props.url, MAX_URL)
+    if (url) {
+      errors.push(url)
+    } else if (scanTokens(props.url).length === 0 && !isSafeUrl(props.url)) {
+      errors.push('url must be a relative path, an http(s) URL, or a template variable')
+    }
+    if (props.width !== undefined) {
+      if (!Number.isInteger(props.width) || props.width < 16 || props.width > MAX_WIDTH) {
+        errors.push(`width must be a whole number between 16 and ${MAX_WIDTH}`)
+      }
+    }
+    return errors
+  },
+  toHtml(props, ctx) {
+    const src = ctx.absolute(ctx.safeHref(props.url))
+    if (!src) return '' // unresolvable: no broken image in someone's inbox
+    const width = props.width ? ` width="${props.width}"` : ''
+    const style = props.width
+      ? `max-width:100%;width:${props.width}px;height:auto;display:block;border:0;`
+      : 'max-width:100%;height:auto;display:block;border:0;'
+    return (
+      `<tr><td style="padding:0 0 16px 0;">` +
+      `<img src="${ctx.escape(src)}" alt="${ctx.h(props.alt)}"${width} style="${style}" /></td></tr>`
+    )
+  },
+  toText(props, ctx) {
+    // The alt text alone, with no [image] decoration: it was written to stand in
+    // for the picture, and in the text part standing in for it is all it does.
+    return ctx.t(props.alt)
+  },
+})
diff --git a/server/src/emailBlocks/types/itemList.js b/server/src/emailBlocks/types/itemList.js
new file mode 100644
index 0000000..a9284cd
--- /dev/null
+++ b/server/src/emailBlocks/types/itemList.js
@@ -0,0 +1,105 @@
+// email.itemList — the one repeating block, and the reason the token grammar in
+// interpolate.js needs no loop construct.
+//
+// It renders an ARRAY variable rather than an inline list: the prop is the NAME of
+// a declared variable (`items`), and the value arrives at render time. §4.6.1's
+// two generic templates — `notify.event` and `notify.digest` — are generic because
+// of this block: their variables are structural (`title`, `intro`, `items[]`), so
+// a trigger from any module renders through them with no authoring at all.
+//
+// **The item shape is `{ heading, excerpt?, url? }`, matching what
+// `teamNotify`/`teamDigestWorker` already build**, so Phase 6's migration onto the
+// engine is a rewiring rather than a reshaping of every producer.
+//
+// A non-array value, or an empty one, renders `emptyText` if there is one and
+// nothing at all otherwise. That is the same fail-soft posture `settingsJson`
+// takes: a stored value that is unusable is treated as absent, never as an error —
+// a digest whose item query returned nothing must still be a sendable mail.
+const { registerEmailBlock } = require('../registry')
+const { requiredText, optionalText, onlyKeys } = require('../../blocks/propHelpers')
+
+const MAX_NAME = 64
+const MAX_EMPTY = 200
+const MAX_ITEMS = 100
+const NAME_RE = /^[A-Za-z][A-Za-z0-9_]*$/
+
+/** Coerce whatever the caller passed into a bounded array of item objects. */
+function itemsOf(value) {
+  if (!Array.isArray(value)) return []
+  return value
+    .slice(0, MAX_ITEMS)
+    .map((item) => {
+      if (typeof item === 'string') return { heading: item }
+      if (!item || typeof item !== 'object') return null
+      return {
+        heading: item.heading == null ? '' : String(item.heading),
+        excerpt: item.excerpt == null ? '' : String(item.excerpt),
+        url: item.url == null ? '' : String(item.url),
+      }
+    })
+    .filter((item) => item && item.heading !== '')
+}
+
+registerEmailBlock({
+  type: 'email.itemList',
+  label: 'Item list',
+  version: 1,
+  schema(props) {
+    const errors = onlyKeys(props, ['variable', 'emptyText'])
+    const variable = requiredText('variable', props.variable, MAX_NAME)
+    if (variable) {
+      errors.push(variable)
+    } else if (!NAME_RE.test(props.variable)) {
+      errors.push('variable must be the name of a declared list variable')
+    }
+    const empty = optionalText('emptyText', props.emptyText, MAX_EMPTY)
+    if (empty) errors.push(empty)
+    return errors
+  },
+  toHtml(props, ctx) {
+    const items = itemsOf(ctx.values[props.variable])
+    if (items.length === 0) {
+      if (!props.emptyText) return ''
+      return (
+        `<tr><td style="padding:0 0 16px 0;font-family:${ctx.palette.fontStack};font-size:14px;` +
+        `line-height:1.55;color:${ctx.palette.muted};">${ctx.h(props.emptyText)}</td></tr>`
+      )
+    }
+    const rows = items
+      .map((item) => {
+        const href = ctx.absolute(ctx.safeHref(item.url))
+        const heading = ctx.escape(item.heading)
+        const title = href
+          ? `<a href="${ctx.escape(href)}" style="color:${ctx.palette.accent};text-decoration:none;font-weight:600;">${heading}</a>`
+          : `<span style="font-weight:600;color:${ctx.palette.heading};">${heading}</span>`
+        const excerpt = item.excerpt
+          ? `<div style="padding-top:4px;font-size:14px;color:${ctx.palette.muted};">${ctx.escape(item.excerpt)}</div>`
+          : ''
+        return (
+          `<tr><td style="padding:0 0 14px 0;border-left:3px solid ${ctx.palette.rule};padding-left:12px;` +
+          `font-family:${ctx.palette.fontStack};font-size:15px;line-height:1.5;color:${ctx.palette.text};">` +
+          `${title}${excerpt}</td></tr>`
+        )
+      })
+      .join('')
+    return (
+      '<tr><td style="padding:0 0 8px 0;">' +
+      `<table role="presentation" cellpadding="0" cellspacing="0" border="0" width="100%">${rows}</table>` +
+      '</td></tr>'
+    )
+  },
+  toText(props, ctx) {
+    const items = itemsOf(ctx.values[props.variable])
+    if (items.length === 0) return props.emptyText ? ctx.t(props.emptyText) : ''
+    // Heading flush left, excerpt and url indented two spaces, one blank line
+    // between items — the shape `mailer.sendTeamNotification` builds today.
+    return items
+      .map((item) => {
+        const lines = [item.heading]
+        if (item.excerpt) lines.push(`  ${item.excerpt}`)
+        if (item.url) lines.push(`  ${ctx.absolute(item.url) || item.url}`)
+        return lines.join('\n')
+      })
+      .join('\n\n')
+  },
+})
diff --git a/server/src/emailBlocks/types/text.js b/server/src/emailBlocks/types/text.js
new file mode 100644
index 0000000..879eb47
--- /dev/null
+++ b/server/src/emailBlocks/types/text.js
@@ -0,0 +1,69 @@
+// email.text — a run of plain-text paragraphs.
+//
+// **There is no rich-text email block, and that is the §4.6.2 posture rather than
+// an omission.** The page family has `rich_text` because a page author is trusted
+// staff writing into a surface the site's own CSS controls. A mail body is
+// different in both halves: the markup an operator writes here is re-rendered by
+// thirty mail clients with thirty different subsets of HTML, and the VALUES
+// interpolated into it come from modules and from game data. §4.6.2 settles the
+// second half — "a module supplies data; it does not supply markup" — and the
+// first is why even the operator's own markup earns nothing here: a <div> an
+// author typed is a layout bug in Outlook, while `email.heading` / `email.button`
+// are shapes this renderer knows how to make survive.
+//
+// So: blank line separates paragraphs, single newline is a line break, and every
+// character is escaped on the way into HTML.
+const { registerEmailBlock } = require('../registry')
+const { requiredText, onlyKeys } = require('../../blocks/propHelpers')
+
+const MAX_TEXT = 4000
+
+/** Split on blank lines; each paragraph keeps its internal single newlines. */
+function paragraphs(s) {
+  return String(s)
+    .split(/\n[ \t]*\n/)
+    .map((p) => p.replace(/^\n+|\n+$/g, ''))
+    .filter((p) => p !== '')
+}
+
+registerEmailBlock({
+  type: 'email.text',
+  label: 'Paragraph',
+  version: 1,
+  schema(props) {
+    const errors = onlyKeys(props, ['text', 'muted'])
+    const text = requiredText('text', props.text, MAX_TEXT)
+    if (text) errors.push(text)
+    if (props.muted !== undefined && typeof props.muted !== 'boolean') {
+      errors.push('muted must be a boolean')
+    }
+    return errors
+  },
+  toHtml(props, ctx) {
+    const color = props.muted ? ctx.palette.muted : ctx.palette.text
+    const size = props.muted ? '13px' : '15px'
+    // Interpolate FIRST, then split: a variable carrying a blank line becomes two
+    // paragraphs, which is what the contact-message mail needs (a player's typed
+    // message arrives as one variable and reads as they wrote it).
+    const body = ctx.h(props.text)
+    const parts = paragraphs(body)
+    // A block whose whole content is one optional variable renders NOTHING when
+    // that variable is absent, rather than an empty paragraph with its margin.
+    // This is what stands in for a conditional: `{{moreNote}}` on its own line is
+    // a line the caller can choose not to supply, and the template stays
+    // logic-free (interpolate.js).
+    if (parts.length === 0) return ''
+    const html = parts
+      .map((p) => `<p style="margin:0 0 12px 0;">${p.replace(/\n/g, '<br />')}</p>`)
+      .join('')
+    return (
+      `<tr><td style="padding:0;font-family:${ctx.palette.fontStack};font-size:${size};` +
+      `line-height:1.55;color:${color};">${html}</td></tr>`
+    )
+  },
+  toText(props, ctx) {
+    // Trimmed to match toHtml's "nothing in, nothing out": the two parts must
+    // agree about whether this block contributed anything at all.
+    return ctx.t(props.text).replace(/^\s+|\s+$/g, '')
+  },
+})
diff --git a/server/src/engagement/templateSeeds.js b/server/src/engagement/templateSeeds.js
new file mode 100644
index 0000000..9b6618e
--- /dev/null
+++ b/server/src/engagement/templateSeeds.js
@@ -0,0 +1,285 @@
+// ── The shipped template set (§4.6.1) ──────────────────────────────────────
+//
+// "A fresh deployment mails correctly before anyone opens the editor." Every body
+// that used to be a template literal inside `utils/mailer.js` is a row here, so
+// Phase 5 is a RELOCATION rather than a regression: nothing that sends mail today
+// starts depending on an operator authoring something first.
+//
+// **Nine seeds, six of them wired in this phase.** The five transactional bodies
+// plus `auth.email-verify` (which §4.6.1 lists as "new — Phase 9" and which Phase
+// 1b in fact already shipped) are rendered by `mailer` from this moment. The three
+// notification seeds are seeded but not yet rendered by anything: `notify.digest`
+// and `notify.team-post` belong to `teamNotify`/`teamDigestWorker`, which Phase 6
+// rewrites onto the engine, and `inapp.event` to the channel Phase 7 builds.
+// Settled with the org lead: seed all nine now so those phases open something
+// rather than shipping seeds of their own — a seeder bump is the mechanism of last
+// resort (property 3 below), not a per-phase routine.
+//
+// **`seedVersion` is the whole "improve a default without stealing an operator's
+// work" mechanism.** Bump it when a body changes; the seeder updates rows where
+// `customized = 0` and skips rows where it is 1. Do NOT bump it for a comment.
+//
+// ── Two conventions the bodies follow, both of which are visible to operators ──
+//
+// **1. Presentational fragments are variables, because templates have no logic.**
+// `mailer` used to build ` for the account “Darrow”` with a ternary. A template
+// cannot, by design (interpolate.js: no conditionals). So the ternary stays at the
+// call site and its RESULT arrives as a variable — `forWhom` — whose `example`
+// shows exactly what it produces, leading space and quotes included. That is the
+// price of a logic-free template language, and it is paid here rather than by
+// giving operator-authored data a conditional to get wrong.
+//
+// **2. Ambient brand variables are supplied by the renderer, not by the caller.**
+// `siteName`, `siteUrl`, `logoUrl` and `year` are available to every template and
+// cannot be overridden by whatever a caller passes (`engagement/templates.js`).
+// §4.6.1 property 2: "no template contains a literal hex code or a logo URL", so
+// one prebuilt image running as any shard mails in that shard's identity.
+
+// The ambient set, declared once so the editor's palette (Phase 5b) can offer them
+// on EVERY template rather than each seed having to list them.
+const AMBIENT_VARIABLES = Object.freeze([
+  { name: 'siteName', type: 'string', required: true, example: 'UOMysticmoon' },
+  { name: 'siteUrl', type: 'string', required: false, example: 'https://example.com' },
+  { name: 'logoUrl', type: 'string', required: false, example: 'https://example.com/brand/logo.png' },
+  { name: 'year', type: 'string', required: true, example: '2026' },
+])
+
+// A tiny helper so the block arrays below read as content rather than as JSON.
+const text = (id, body, opts = {}) => ({
+  id,
+  type: 'email.text',
+  props: opts.muted ? { text: body, muted: true } : { text: body },
+})
+const heading = (id, body, level = 'h1') => ({
+  id,
+  type: 'email.heading',
+  props: { level, text: body },
+})
+const button = (id, label, url, textLead) => ({
+  id,
+  type: 'email.button',
+  props: textLead ? { label, url, textLead } : { label, url },
+})
+const itemList = (id, variable, emptyText) => ({
+  id,
+  type: 'email.itemList',
+  props: emptyText ? { variable, emptyText } : { variable },
+})
+const divider = (id) => ({ id, type: 'email.divider', props: {} })
+
+const SEEDS = [
+  // ── Transactional: protected = 1, editable but not deletable ─────────────
+  {
+    key: 'auth.password-reset',
+    name: 'Password reset',
+    channel: 'email',
+    protected: true,
+    seedVersion: 1,
+    subject: 'Reset your {{siteName}} password',
+    variables: [
+      { name: 'username', type: 'string', required: false, example: 'Darrow' },
+      { name: 'forWhom', type: 'string', required: false, example: ' for the account “Darrow”' },
+      { name: 'resetUrl', type: 'string', required: true, example: 'https://example.com/reset/abc123' },
+    ],
+    blocks: [
+      text('p1', 'We received a request to reset the password{{forWhom}} at {{siteName}}.'),
+      button('cta', 'Choose a new password', '{{resetUrl}}', 'Choose a new password here:'),
+      text(
+        'p2',
+        'This link is single-use and expires in about an hour. If you didn\'t request this, ' +
+          'you can safely ignore this email — your password won\'t change.',
+      ),
+    ],
+  },
+  {
+    key: 'auth.invite',
+    name: 'Account invite',
+    channel: 'email',
+    protected: true,
+    seedVersion: 1,
+    subject: 'Your {{siteName}} invitation',
+    variables: [
+      { name: 'acceptUrl', type: 'string', required: true, example: 'https://example.com/invite/abc123' },
+      { name: 'roleLabel', type: 'string', required: false, example: ' as moderator' },
+      { name: 'invitedBy', type: 'string', required: false, example: ' by Aldric' },
+    ],
+    blocks: [
+      text('p1', 'You have been invited{{invitedBy}} to join {{siteName}}{{roleLabel}}.'),
+      button('cta', 'Accept your invitation', '{{acceptUrl}}', 'Accept your invitation and set up your account here:'),
+      text('p2', 'This link is single-use and will expire. If you weren\'t expecting this, you can ignore it.'),
+    ],
+  },
+  {
+    key: 'auth.email-verify',
+    name: 'Email address confirmation',
+    channel: 'email',
+    protected: true,
+    seedVersion: 1,
+    subject: 'Confirm your email address for {{siteName}}',
+    variables: [
+      { name: 'username', type: 'string', required: false, example: 'Darrow' },
+      { name: 'forWhom', type: 'string', required: false, example: ' “Darrow”' },
+      { name: 'verifyUrl', type: 'string', required: true, example: 'https://example.com/verify/abc123' },
+    ],
+    blocks: [
+      text('p1', 'The {{siteName}} account{{forWhom}} asked to use this address for contact and account recovery.'),
+      button('cta', 'Confirm this address', '{{verifyUrl}}', 'Confirm it here:'),
+      text(
+        'p2',
+        'This link is single-use and expires in about a day. Until it is used, nothing changes — ' +
+          'the account keeps whatever address it had.',
+      ),
+      text(
+        'p3',
+        'If you did not ask for this, you can ignore this email. Someone may have mistyped their ' +
+          'own address; no account of yours is affected and this link grants no access to anything.',
+      ),
+    ],
+  },
+  {
+    key: 'admin.contact-message',
+    name: 'Contact form message',
+    channel: 'email',
+    protected: true,
+    seedVersion: 1,
+    // `fromLabel` and `fromName` are the SAME missing name with two different
+    // fallbacks — 'a visitor' in the subject, 'unknown' in the body. That
+    // divergence is inherited from the literal this replaces, and the template is
+    // where it becomes visible and fixable: an operator who wants one word can now
+    // edit the subject line instead of a source file.
+    subject: '{{siteName}} contact from {{fromLabel}}',
+    variables: [
+      { name: 'fromLabel', type: 'string', required: true, example: 'a visitor' },
+      { name: 'fromName', type: 'string', required: true, example: 'unknown' },
+      { name: 'fromEmail', type: 'string', required: true, example: 'ann@example.com' },
+      { name: 'message', type: 'string', required: true, example: 'Is the shard open to new players?' },
+    ],
+    blocks: [
+      text('p1', 'From: {{fromName}} <{{fromEmail}}>'),
+      text('p2', '{{message}}'),
+    ],
+  },
+  {
+    key: 'admin.test',
+    name: 'Delivery test',
+    channel: 'email',
+    protected: true,
+    seedVersion: 1,
+    subject: '{{siteName}} email test',
+    variables: [
+      { name: 'transport', type: 'string', required: true, example: 'smtp' },
+      { name: 'sentAt', type: 'string', required: false, example: '2026-08-29 18:04 UTC' },
+    ],
+    blocks: [
+      text('p1', 'This is a test message confirming {{transport}} email delivery is working.'),
+    ],
+  },
+
+  // ── Notification: protected = 0, replaceable ─────────────────────────────
+  //
+  // **`notify.event` and `notify.digest` are generic on purpose** (§4.6.1 property
+  // 1): their variables are structural — `title`, `intro`, `items[]` — rather than
+  // domain-specific, so a trigger from core or from any module renders through
+  // them with NO authoring at all. This is what stops "add a trigger" from meaning
+  // "and now write a template".
+  {
+    key: 'notify.event',
+    name: 'Notification (single event)',
+    channel: 'email',
+    protected: false,
+    seedVersion: 1,
+    subject: '{{title}}',
+    variables: [
+      { name: 'title', type: 'string', required: true, example: 'Your house is close to collapsing' },
+      { name: 'intro', type: 'string', required: false, example: 'The Silver Anvil in Britain has entered its final decay stage.' },
+      { name: 'items', type: 'list', required: false, example: [{ heading: 'The Silver Anvil', excerpt: 'Britain, Trammel (1119, 1794)' }] },
+      { name: 'actionUrl', type: 'string', required: false, example: 'https://example.com/houses' },
+      { name: 'unsubscribeUrl', type: 'string', required: false, example: 'https://example.com/unsubscribe/abc123' },
+    ],
+    blocks: [
+      heading('h', '{{title}}'),
+      text('intro', '{{intro}}'),
+      itemList('items', 'items'),
+      button('cta', 'Open {{siteName}}', '{{actionUrl}}'),
+      divider('rule'),
+      button('unsub', 'Unsubscribe', '{{unsubscribeUrl}}', 'To stop these emails, use this link:'),
+    ],
+  },
+  {
+    key: 'notify.digest',
+    name: 'Notification digest',
+    channel: 'email',
+    protected: false,
+    seedVersion: 1,
+    subject: '{{siteName}}: {{periodLabel}}',
+    variables: [
+      { name: 'periodLabel', type: 'string', required: true, example: 'your daily summary' },
+      { name: 'intro', type: 'string', required: false, example: 'Here is what happened while you were away.' },
+      { name: 'items', type: 'list', required: false, example: [{ heading: 'New thread in Guild Hall', excerpt: 'Meeting moved to Friday', url: 'https://example.com/teams/1?thread=9' }] },
+      // Precomputed for the same reason `forWhom` is: "and 3 more" needs a
+      // conditional and a plural, and a template has neither.
+      { name: 'moreNote', type: 'string', required: false, example: 'and 3 more.' },
+      { name: 'scopeUrl', type: 'string', required: false, example: 'https://example.com/teams/1' },
+      { name: 'unsubscribeUrl', type: 'string', required: false, example: 'https://example.com/unsubscribe/abc123' },
+    ],
+    blocks: [
+      text('intro', '{{intro}}'),
+      itemList('items', 'items'),
+      text('more', '{{moreNote}}', { muted: true }),
+      button('cta', 'Open {{siteName}}', '{{scopeUrl}}'),
+      divider('rule'),
+      button('unsub', 'Unsubscribe', '{{unsubscribeUrl}}', 'To stop these emails, use this link:'),
+    ],
+  },
+  {
+    key: 'notify.team-post',
+    name: 'Team post notification',
+    channel: 'email',
+    protected: false,
+    seedVersion: 1,
+    subject: '{{teamName}}: {{threadTitle}}',
+    variables: [
+      { name: 'teamName', type: 'string', required: true, example: 'The Silver Anvil' },
+      { name: 'authorName', type: 'string', required: true, example: 'Aldric' },
+      { name: 'threadTitle', type: 'string', required: true, example: 'Meeting moved to Friday' },
+      { name: 'excerpt', type: 'string', required: false, example: 'We are pushing this week back a day so more people can make it.' },
+      { name: 'threadUrl', type: 'string', required: false, example: 'https://example.com/teams/1?thread=9' },
+      { name: 'unsubscribeUrl', type: 'string', required: false, example: 'https://example.com/unsubscribe/abc123' },
+    ],
+    blocks: [
+      text('p1', '{{authorName}} posted in {{teamName}}.'),
+      heading('h', '{{threadTitle}}', 'h2'),
+      text('excerpt', '{{excerpt}}', { muted: true }),
+      button('cta', 'Read the thread', '{{threadUrl}}'),
+      divider('rule'),
+      button('unsub', 'Unsubscribe', '{{unsubscribeUrl}}', 'To stop these emails for this team, use this link:'),
+    ],
+  },
+  {
+    key: 'inapp.event',
+    name: 'On-site notification',
+    channel: 'inapp',
+    protected: false,
+    seedVersion: 1,
+    // No subject: an inbox row has a title, and the title is a block. The column
+    // is email's, and leaving it NULL is how a non-email template says so.
+    subject: null,
+    variables: [
+      { name: 'title', type: 'string', required: true, example: 'Your house is close to collapsing' },
+      { name: 'body', type: 'string', required: false, example: 'The Silver Anvil in Britain has entered its final decay stage.' },
+      { name: 'url', type: 'string', required: false, example: 'https://example.com/houses' },
+    ],
+    blocks: [
+      heading('h', '{{title}}', 'h3'),
+      text('body', '{{body}}'),
+      button('cta', 'Open', '{{url}}'),
+    ],
+  },
+]
+
+/** @returns {object|null} the seed definition for `key`. */
+function seedByKey(key) {
+  return SEEDS.find((s) => s.key === key) || null
+}
+
+module.exports = { SEEDS, AMBIENT_VARIABLES, seedByKey }
diff --git a/server/src/engagement/templates.js b/server/src/engagement/templates.js
new file mode 100644
index 0000000..eb7abd3
--- /dev/null
+++ b/server/src/engagement/templates.js
@@ -0,0 +1,190 @@
+// ── Templates: resolve, render, seed ───────────────────────────────────────
+//
+// The seam between a stored `engagement_templates` row and the two body parts a
+// transport sends. Everything that needs a database happens here; `emailBlocks/`
+// stays pure and synchronous below it.
+//
+// **A missing row renders the shipped default rather than nothing.** `renderByKey`
+// falls back to `templateSeeds.js` whenever the row is absent or its blocks will
+// not parse. This is not defensive padding — it is what makes it safe for
+// `mailer` to depend on the database for a password-reset body at all. Before the
+// first seed runs, after a restore that dropped the table, on a deployment whose
+// operator deleted a row by hand: the mail still goes out, in the shipped wording,
+// and the `protected` flag stops the last of those from being reachable through
+// the API. The same posture `settingsJson` and `resolveThemeTokens` take — a
+// stored value that is unusable is treated as absent, never as an error.
+
+const templatesDb = require('../model/engagement/engagementTemplates.db')
+const settings = require('../model/settings/settings.model')
+const brand = require('../config/brand')
+const emailBlocks = require('../emailBlocks')
+const { SEEDS, AMBIENT_VARIABLES, seedByKey } = require('./templateSeeds')
+// The trigger registry lives with the module registries, not here — a trigger is
+// something a MODULE declares (see engagement/index.js's header).
+const { eventTrigger } = require('../modules/registries')
+const log = require('../utils/logger')('templates')
+
+const baseUrl = () => (process.env.APP_BASE_URL || brand.url || 'http://localhost:5173').replace(/\/+$/, '')
+
+/**
+ * The brand values every template may reference, resolved from the same places
+ * the site's own chrome resolves them (§4.6.1 property 2).
+ *
+ * **They are merged OVER the caller's values, not under.** A caller supplies the
+ * message; the deployment supplies its identity. Letting a caller pass its own
+ * `siteName` would mean a module — or a bug — could send mail that claims to be
+ * from somewhere else, which is precisely the thing a recipient cannot check.
+ *
+ * Never throws: a settings read that fails degrades to the BRAND_* env values, so
+ * mail is branded slightly less specifically rather than not sent.
+ */
+async function ambient() {
+  let name = brand.name
+  let logo = brand.logo
+  let theme = null
+  try {
+    name = await settings.getInstanceName()
+    const shell = await settings.getShellBrand()
+    logo = shell.logo || brand.logo
+    theme = shell.theme
+  } catch (err) {
+    log.warn('brand resolution failed; falling back to BRAND_* env', { message: err.message })
+  }
+  const base = baseUrl()
+  const absLogo = logo && logo.startsWith('/') ? `${base}${logo}` : logo || ''
+  return {
+    values: {
+      siteName: name,
+      siteUrl: base,
+      logoUrl: absLogo,
+      year: String(new Date().getUTCFullYear()),
+    },
+    // resolveThemeTokens speaks CSS custom properties; the renderer speaks colour
+    // names. One mapping, here, rather than the renderer knowing about CSS.
+    theme: { accent: theme ? theme['--accent'] : undefined },
+    baseUrl: base,
+  }
+}
+
+/**
+ * Which variables a template may reference — the input to Phase 5b's palette and
+ * to its save-time "undeclared variable" refusal.
+ *
+ * Two sources, because a template has two possible origins. One tied to a trigger
+ * reads §4.3's declaration, which is the authority for anything a module emits.
+ * One with no trigger — every transactional seed is one; `mailer` renders them by
+ * key with no rule involved — has no trigger to ask, so its shipped definition
+ * carries the list. Ambient brand variables are appended to both.
+ *
+ * @param {{ trigger_id?: string|null, seed_key?: string|null }} template
+ * @returns {Array<{name: string, type: string, required: boolean, example: unknown}>}
+ */
+function variablesFor(template) {
+  const own = []
+  if (template && template.trigger_id) {
+    const declared = eventTrigger(template.trigger_id)
+    if (declared && Array.isArray(declared.variables)) own.push(...declared.variables)
+  } else if (template && template.seed_key) {
+    const seed = seedByKey(template.seed_key)
+    if (seed) own.push(...seed.variables)
+  }
+  const names = new Set(own.map((v) => v.name))
+  return [...own, ...AMBIENT_VARIABLES.filter((v) => !names.has(v.name))]
+}
+
+/**
+ * Render one template into its two body parts.
+ *
+ * @param {object} template a row, or a seed definition
+ * @param {Record<string, unknown>} values
+ * @param {object} resolved the result of ambient()
+ * @returns {{ subject: string, html: string, text: string, missing: string[] }}
+ */
+function renderTemplate(template, values, resolved) {
+  const merged = { ...values, ...resolved.values }
+  const missing = new Set()
+  const ctx = emailBlocks.buildContext({
+    values: merged,
+    theme: resolved.theme,
+    baseUrl: resolved.baseUrl,
+    missing,
+  })
+  const rendered = emailBlocks.renderBlocks(template.blocks, ctx)
+  const subject = template.subject ? ctx.t(template.subject) : ''
+  // An authored `text_body` REPLACES the generated one (§4.4), and is interpolated
+  // like any other authored string. It is a per-template override, not an addition.
+  const text = template.text_body ? ctx.t(template.text_body) : rendered.text
+  return {
+    subject,
+    html: emailBlocks.renderDocument(rendered.html, ctx, subject),
+    text,
+    missing: [...missing],
+  }
+}
+
+/**
+ * Render the template stored under `key`, falling back to its shipped default.
+ * @returns {Promise<{subject: string, html: string, text: string, missing: string[]}|null>}
+ *          null only when `key` names neither a row nor a seed.
+ */
+async function renderByKey(key, values = {}) {
+  const resolved = await ambient()
+  let template = null
+  try {
+    template = await templatesDb.getByKey(key)
+  } catch (err) {
+    log.warn('template read failed; using the shipped default', { key, message: err.message })
+  }
+  if (!template || !Array.isArray(template.blocks) || template.blocks.length === 0) {
+    const seed = seedByKey(key)
+    if (!seed) return null
+    if (template) log.warn('stored template is unusable; using the shipped default', { key })
+    template = { subject: seed.subject, blocks: seed.blocks, text_body: null }
+  }
+  return renderTemplate(template, values, resolved)
+}
+
+/**
+ * Ensure every shipped template exists, and bring un-customized rows up to the
+ * current seed. Idempotent: a second run reports nine skips and writes nothing.
+ *
+ * Never throws — it is called from `seedDefaults()` on the boot path, and a
+ * template that failed to seed costs the shipped default (see the header note),
+ * not the deployment.
+ */
+async function seedTemplates() {
+  const counts = { inserted: 0, updated: 0, skipped: 0, invalid: 0 }
+  for (const seed of SEEDS) {
+    // Validated against the registry before it is stored, even though a seed is
+    // code rather than input. The alternative is a shipped block array that no
+    // renderer understands sitting in the table, which reads to an operator as
+    // their deployment being broken; refusing to write it leaves `renderByKey`'s
+    // fallback in charge and puts the reason in the boot log.
+    const { valid, errors } = emailBlocks.validateEmailBlocks(seed.blocks)
+    if (!valid) {
+      log.error('shipped template is invalid and was not seeded', { key: seed.key, errors })
+      counts.invalid += 1
+      continue
+    }
+    try {
+      counts[await templatesDb.seedOne(seed)] += 1
+    } catch (err) {
+      log.error('template seed failed', { key: seed.key, message: err.message })
+    }
+  }
+  // The third arm of §4.6.1 property 3: a customized row is never touched, and the
+  // fact that a better default now exists is surfaced instead of applied.
+  let stale = []
+  try {
+    stale = await templatesDb.staleCustomized(SEEDS.map((s) => ({ key: s.key, seedVersion: s.seedVersion })))
+  } catch {
+    stale = []
+  }
+  if (stale.length) {
+    log.info('customized templates have a newer shipped default', { keys: stale.map((t) => t.key) })
+  }
+  log.info('engagement templates ensured', counts)
+  return { ...counts, stale: stale.map((t) => t.key) }
+}
+
+module.exports = { ambient, variablesFor, renderTemplate, renderByKey, seedTemplates, baseUrl }
diff --git a/server/src/model/engagement/engagementTemplates.db.js b/server/src/model/engagement/engagementTemplates.db.js
new file mode 100644
index 0000000..0827fad
--- /dev/null
+++ b/server/src/model/engagement/engagementTemplates.db.js
@@ -0,0 +1,149 @@
+const { query } = require('../../utils/db')
+
+// Same JSON-column caveat as engagementRules.db.js — `blocks` is a MEDIUMTEXT
+// holding JSON rather than a JSON column (it can be large and is never queried
+// into), so it is always a string on the way out and always parsed here.
+function parseJson(value, fallback) {
+  if (value === null || value === undefined) return fallback
+  if (typeof value !== 'string') return value
+  try {
+    return JSON.parse(value)
+  } catch {
+    return fallback
+  }
+}
+
+// A stored `blocks` that will not parse degrades to an EMPTY array, not to an
+// error. Same posture `settingsJson` takes and the same one `resolveThemeTokens`
+// takes: a row hand-edited in the DB, or written by an older version of this code,
+// must not stop a password-reset mail from being attempted — the renderer produces
+// an empty body, the send log records it, and the operator is told in the admin
+// list rather than at 3am by a boot that will not come up.
+const hydrate = (row) =>
+  row && {
+    ...row,
+    blocks: parseJson(row.blocks, []),
+    protected: Boolean(row.protected),
+    customized: Boolean(row.customized),
+  }
+
+const list = async () =>
+  (await query('SELECT * FROM engagement_templates ORDER BY channel, `key`')).map(hydrate)
+
+const getById = async (id) => {
+  const [row] = await query('SELECT * FROM engagement_templates WHERE id = ?', [id])
+  return hydrate(row)
+}
+
+const getByKey = async (key) => {
+  const [row] = await query('SELECT * FROM engagement_templates WHERE `key` = ?', [key])
+  return hydrate(row)
+}
+
+/** Which of `keys` exist. Used to validate a rule's `template_keys` map. */
+const existingKeys = async (keys) => {
+  if (!Array.isArray(keys) || keys.length === 0) return []
+  const marks = keys.map(() => '?').join(',')
+  const rows = await query(`SELECT \`key\` FROM engagement_templates WHERE \`key\` IN (${marks})`, keys)
+  return rows.map((r) => r.key)
+}
+
+/**
+ * Insert a shipped template, or bring an un-customized one up to a newer seed.
+ *
+ * **The `customized = 0` guard is in the SQL, not in a read-then-write.** The
+ * seeder runs on every boot and a deployment can start two app processes at once;
+ * a check in JavaScript followed by an UPDATE is a window in which an operator's
+ * edit can be overwritten by a concurrent boot. `WHERE customized = 0` in the
+ * UPDATE closes it, and MariaDB's `ON DUPLICATE KEY UPDATE` cannot express a
+ * WHERE — so this is deliberately an INSERT IGNORE plus a guarded UPDATE rather
+ * than the upsert §4.6.1 sketches.
+ *
+ * @returns {'inserted'|'updated'|'skipped'} what happened, for the boot log
+ */
+const seedOne = async (t) => {
+  const inserted = await query(
+    'INSERT IGNORE INTO engagement_templates ' +
+      '(`key`, name, trigger_id, trigger_version, channel, subject, blocks, text_body, status, ' +
+      ' protected, seed_key, seed_version, customized) ' +
+      'VALUES (?, ?, ?, ?, ?, ?, ?, NULL, ?, ?, ?, ?, 0)',
+    [
+      t.key,
+      t.name,
+      t.triggerId ?? null,
+      t.triggerVersion ?? null,
+      t.channel,
+      t.subject ?? null,
+      JSON.stringify(t.blocks),
+      t.status || 'published',
+      t.protected ? 1 : 0,
+      t.key,
+      t.seedVersion,
+    ],
+  )
+  if (inserted.affectedRows === 1) return 'inserted'
+
+  const updated = await query(
+    'UPDATE engagement_templates SET name = ?, channel = ?, subject = ?, blocks = ?, ' +
+      'protected = ?, seed_version = ?, status = ? ' +
+      'WHERE seed_key = ? AND customized = 0 AND (seed_version IS NULL OR seed_version < ?)',
+    [
+      t.name,
+      t.channel,
+      t.subject ?? null,
+      JSON.stringify(t.blocks),
+      t.protected ? 1 : 0,
+      t.seedVersion,
+      t.status || 'published',
+      t.key,
+      t.seedVersion,
+    ],
+  )
+  return updated.affectedRows === 1 ? 'updated' : 'skipped'
+}
+
+/**
+ * Save an operator's edit. Always sets `customized = 1` — that flag is not a
+ * field the caller may choose, it is the record that a human touched this row, and
+ * it is the only thing standing between their work and the next seed bump.
+ *
+ * **`affectedRows === 1` here means "the row exists", not "something changed",**
+ * because the connector defaults to `foundRows: true` (the trap Phase 4a's
+ * cooldown check fell into). That is the semantics this caller wants — re-saving a
+ * template unchanged is a success, not a 404 — and it is stated rather than
+ * relied on, since the same expression means the other thing under `foundRows:
+ * false`. `seedOne`'s UPDATE above is safe under either reading: its WHERE only
+ * matches a row whose `seed_version` is behind, so a match always implies a write.
+ */
+const update = async (id, t, userId) => {
+  const res = await query(
+    'UPDATE engagement_templates SET name = ?, subject = ?, blocks = ?, text_body = ?, ' +
+      'status = ?, trigger_id = ?, trigger_version = ?, customized = 1, updated_by = ? WHERE id = ?',
+    [
+      t.name,
+      t.subject ?? null,
+      JSON.stringify(t.blocks),
+      t.textBody ?? null,
+      t.status,
+      t.triggerId ?? null,
+      t.triggerVersion ?? null,
+      userId ?? null,
+      id,
+    ],
+  )
+  return res.affectedRows === 1
+}
+
+/** Templates whose shipped default has moved on since the operator edited them. */
+const staleCustomized = async (pairs) => {
+  if (!Array.isArray(pairs) || pairs.length === 0) return []
+  const clauses = pairs.map(() => '(seed_key = ? AND seed_version < ?)').join(' OR ')
+  const params = pairs.flatMap((p) => [p.key, p.seedVersion])
+  const rows = await query(
+    `SELECT * FROM engagement_templates WHERE customized = 1 AND (${clauses})`,
+    params,
+  )
+  return rows.map(hydrate)
+}
+
+module.exports = { list, getById, getByKey, existingKeys, seedOne, update, staleCustomized }
diff --git a/server/src/utils/mailer.js b/server/src/utils/mailer.js
index 6f28973..f98737c 100644
--- a/server/src/utils/mailer.js
+++ b/server/src/utils/mailer.js
@@ -10,6 +10,11 @@
 // as an ordinary SMTP relay (`smtp.gmail.com:587` with an app password) — the
 // operator types those in like any other host; nothing in here knows about it.
 //
+// Engagement Phase 5a moved every subject and body out of this file. What each
+// sender still owns is its RECIPIENT, its headers and its failure contract; what
+// it says is an `engagement_templates` row rendered by `engagement/templates.js`
+// (§4.6.1), which an operator can edit and which falls back to the shipped seed.
+//
 // **The failure contracts are the point of this file.** Six call sites, five
 // senders, and each one degrades a specific way when mail is unconfigured. Those
 // contracts are unchanged by the transport rewrite and are asserted in
@@ -22,9 +27,39 @@
 const emailConfig = require('../model/emailConfig/emailConfig.model')
 const settings = require('../model/settings/settings.model')
 const { transports } = require('../engagement')
-const brand = require('../config/brand')
+const templates = require('../engagement/templates')
 const log = require('./logger')('mailer')
 
+/**
+ * The body for one message, from its template (engagement Phase 5a).
+ *
+ * Every subject and body in this file used to be a template literal; they are now
+ * `engagement_templates` rows an operator can edit, and this is the single seam
+ * where that happens. Three properties the senders below depend on:
+ *
+ *  - **It cannot fail.** `renderByKey` falls back to the shipped seed whenever the
+ *    row is missing or unusable, so no failure mode of the templates table can
+ *    stop a password-reset mail. It returns null only for a key that names neither
+ *    a row nor a seed, which is a programmer error and throws here rather than
+ *    sending a blank message.
+ *  - **The text part is byte-identical to what this file used to build**, which is
+ *    §5a's acceptance criterion and is pinned by `test/emailTemplates.test.js`.
+ *  - **The HTML part is new.** Nothing here had one before; mail is now
+ *    multipart/alternative, so a client that prefers HTML shows the branded body
+ *    and one that does not shows exactly the text it always showed.
+ */
+async function body(key, values) {
+  const rendered = await templates.renderByKey(key, values)
+  if (!rendered) throw new Error(`mailer: no template and no shipped seed for "${key}"`)
+  if (rendered.missing.length) {
+    // Not an error: an optional variable a caller chose not to supply renders as
+    // nothing by design. Logged because the other cause is a renamed variable in
+    // an operator's edited template, and that one reads as words gone missing.
+    log.debug('template variables had no value', { key, missing: rendered.missing })
+  }
+  return rendered
+}
+
 // Ready to send only when enabled, holding a complete credential for a
 // registered transport, and knowing which address to send as.
 async function isConfigured() {
@@ -100,13 +135,23 @@ async function sendContactMessage({ name, email, message }) {
   }
   const { transport, config } = built
   const to = await contactRecipient(config.senderEmail)
+  // `fromLabel` and `fromName` are the same missing name with the two different
+  // fallbacks this message has always used — 'a visitor' in the subject, 'unknown'
+  // in the body. Kept exactly, and now visible to an operator who wants one word.
+  const { subject, html, text } = await body('admin.contact-message', {
+    fromLabel: name || 'a visitor',
+    fromName: name || 'unknown',
+    fromEmail: email || 'no email',
+    message,
+  })
   try {
     await transport.sendMail({
       from: fromHeader(config),
       to,
       replyTo: replyToFor(config, email),
-      subject: `${brand.name} contact from ${name || 'a visitor'}`,
-      text: `From: ${name || 'unknown'} <${email || 'no email'}>\n\n${message}`,
+      subject,
+      text,
+      html,
     })
     await emailConfig.recordStatus({ status: 'connected', statusDetail: 'Last send OK', lastVerifiedAt: new Date() })
     return { sent: true }
@@ -165,13 +210,18 @@ async function sendTest(to) {
     err.code = 'NO_RECIPIENT'
     throw err
   }
+  const { subject, html, text } = await body('admin.test', {
+    transport: config.transport,
+    sentAt: new Date().toISOString(),
+  })
   try {
     await transport.sendMail({
       from: fromHeader(config),
       to: recipient,
       replyTo: replyToFor(config),
-      subject: `${brand.name} email test`,
-      text: `This is a test message confirming ${config.transport} email delivery is working.`,
+      subject,
+      text,
+      html,
     })
     await emailConfig.recordStatus({ status: 'connected', statusDetail: 'Test send OK', lastVerifiedAt: new Date() })
     return { sent: true, to: recipient }
@@ -196,18 +246,23 @@ async function sendInvite({ to, acceptUrl, role, invitedByName }) {
   const built = await buildTransport()
   if (!built) return { sent: false, reason: 'NOT_CONFIGURED' }
   const { transport, config } = built
+  // The two conditional fragments stay HERE, where a ternary belongs, and reach
+  // the template as values. §4.6.2's grammar has no conditional by design.
   const roleLabel = role && role !== 'player' ? ` as ${role}` : ''
   const by = invitedByName ? ` by ${invitedByName}` : ''
+  const { subject, html, text } = await body('auth.invite', {
+    acceptUrl,
+    roleLabel,
+    invitedBy: by,
+  })
   try {
     await transport.sendMail({
       from: fromHeader(config),
       to,
       replyTo: replyToFor(config),
-      subject: `Your ${brand.name} invitation`,
-      text:
-        `You have been invited${by} to join ${brand.name}${roleLabel}.\n\n` +
-        `Accept your invitation and set up your account here:\n${acceptUrl}\n\n` +
-        `This link is single-use and will expire. If you weren't expecting this, you can ignore it.`,
+      subject,
+      text,
+      html,
     })
     await emailConfig.recordStatus({ status: 'connected', statusDetail: 'Invite send OK', lastVerifiedAt: new Date() })
     return { sent: true }
@@ -229,17 +284,15 @@ async function sendPasswordReset({ to, resetUrl, username }) {
   if (!built) return { sent: false, reason: 'NOT_CONFIGURED' }
   const { transport, config } = built
   const forWhom = username ? ` for the account “${username}”` : ''
+  const { subject, html, text } = await body('auth.password-reset', { resetUrl, username, forWhom })
   try {
     await transport.sendMail({
       from: fromHeader(config),
       to,
       replyTo: replyToFor(config),
-      subject: `Reset your ${brand.name} password`,
-      text:
-        `We received a request to reset the password${forWhom} at ${brand.name}.\n\n` +
-        `Choose a new password here:\n${resetUrl}\n\n` +
-        `This link is single-use and expires in about an hour. If you didn't request ` +
-        `this, you can safely ignore this email — your password won't change.`,
+      subject,
+      text,
+      html,
     })
     await emailConfig.recordStatus({ status: 'connected', statusDetail: 'Password reset send OK', lastVerifiedAt: new Date() })
     return { sent: true }
@@ -266,19 +319,15 @@ async function sendEmailVerification({ to, verifyUrl, username }) {
   if (!built) return { sent: false, reason: 'NOT_CONFIGURED' }
   const { transport, config } = built
   const forWhom = username ? ` “${username}”` : ''
+  const { subject, html, text } = await body('auth.email-verify', { verifyUrl, username, forWhom })
   try {
     await transport.sendMail({
       from: fromHeader(config),
       to,
       replyTo: replyToFor(config),
-      subject: `Confirm your email address for ${brand.name}`,
-      text:
-        `The ${brand.name} account${forWhom} asked to use this address for contact and account recovery.\n\n` +
-        `Confirm it here:\n${verifyUrl}\n\n` +
-        `This link is single-use and expires in about a day. Until it is used, nothing changes — ` +
-        `the account keeps whatever address it had.\n\n` +
-        `If you did not ask for this, you can ignore this email. Someone may have mistyped their ` +
-        `own address; no account of yours is affected and this link grants no access to anything.`,
+      subject,
+      text,
+      html,
     })
     await emailConfig.recordStatus({ status: 'connected', statusDetail: 'Verification send OK', lastVerifiedAt: new Date() })
     return { sent: true }
diff --git a/server/test/checkNoExternalHosts.test.js b/server/test/checkNoExternalHosts.test.js
index 23f0aa4..095ecc5 100644
--- a/server/test/checkNoExternalHosts.test.js
+++ b/server/test/checkNoExternalHosts.test.js
@@ -73,6 +73,18 @@ test('an ordinary sentence with a full stop is not a hostname', () => {
   assert.deepEqual(hostsIn(`const msg = 'Send failed. Check the host and port.'`), [])
 })
 
+test('a dotted identifier is not a hostname just because a real TLD is a label', () => {
+  // `.email`, `.mail` and `.app` are real TLDs, so an engagement template key or a
+  // trigger id can look like a host to a regex. A real hostname's TLD is its LAST
+  // label; these carry on into another word.
+  assert.deepEqual(hostsIn(`const key = 'auth.email-verify'`), [])
+  assert.deepEqual(hostsIn(`await body('auth.email-verify', { verifyUrl })`), [])
+  assert.deepEqual(hostsIn(`const t = 'core.mail_bounced'`), [])
+  // …and the real thing still trips it, so the loosening did not blunt the check.
+  assert.deepEqual(hostsIn(`const h = 'smtp.somewhere.email'`), ['smtp.somewhere.email'])
+  assert.deepEqual(hostsIn(`const h = 'relay.somewhere.email:587'`), ['relay.somewhere.email'])
+})
+
 // ── the pieces, directly ────────────────────────────────────────────────────
 
 test('maskComments blanks comments but keeps string bodies and line count', () => {
diff --git a/server/test/emailTemplates.test.js b/server/test/emailTemplates.test.js
new file mode 100644
index 0000000..e7af13e
--- /dev/null
+++ b/server/test/emailTemplates.test.js
@@ -0,0 +1,468 @@
+// Engagement Phase 5a — the `email.*` block family, the renderer, and the shipped
+// template set (ENGAGEMENT.md §4.4 / §4.6.1).
+//
+// The centrepiece is the byte-comparison block: §5a's acceptance criterion is that
+// "every one of the five current message types renders byte-comparably from its
+// seeded template", so the strings below are the LITERALS this phase deleted from
+// `utils/mailer.js`, copied character for character. If a seed's wording changes,
+// these fail — which is the point. They are the only thing standing between an
+// edit to a block array and a silently reworded password-reset mail.
+
+process.env.DB_HOST = '127.0.0.1'
+process.env.DB_PORT = '59999'
+
+const { test } = require('node:test')
+const assert = require('node:assert/strict')
+
+const emailBlocks = require('../src/emailBlocks')
+const { SEEDS, AMBIENT_VARIABLES, seedByKey } = require('../src/engagement/templateSeeds')
+const templatesDb = require('../src/model/engagement/engagementTemplates.db')
+const settings = require('../src/model/settings/settings.model')
+const templates = require('../src/engagement/templates')
+
+const SITE = 'Runic Gateway'
+const BASE = 'https://shard.example.com'
+
+/** Render one seed the way mailer does, without any of the database. */
+function render(key, values = {}, opts = {}) {
+  const seed = seedByKey(key)
+  const ctx = emailBlocks.buildContext({
+    values: { siteName: SITE, siteUrl: BASE, year: '2026', logoUrl: '', ...values },
+    baseUrl: BASE,
+    theme: opts.theme || {},
+  })
+  const out = emailBlocks.renderBlocks(seed.blocks, ctx)
+  return {
+    subject: seed.subject ? ctx.t(seed.subject) : '',
+    text: out.text,
+    html: emailBlocks.renderDocument(out.html, ctx),
+    rows: out.html,
+    missing: [...ctx.missing],
+  }
+}
+
+// ── The acceptance criterion: byte-comparable bodies ────────────────────────
+
+test('password reset renders byte-identically to the literal it replaced', () => {
+  const r = render('auth.password-reset', {
+    resetUrl: 'https://shard.example.com/reset/tok',
+    username: 'Darrow',
+    forWhom: ' for the account “Darrow”',
+  })
+  assert.equal(r.subject, `Reset your ${SITE} password`)
+  assert.equal(
+    r.text,
+    `We received a request to reset the password for the account “Darrow” at ${SITE}.\n\n` +
+      'Choose a new password here:\nhttps://shard.example.com/reset/tok\n\n' +
+      "This link is single-use and expires in about an hour. If you didn't request " +
+      "this, you can safely ignore this email — your password won't change.",
+  )
+})
+
+test('password reset with no username keeps the other branch byte-identical too', () => {
+  // The ternary lives at the call site and reaches the template as a value, so
+  // BOTH of its branches have to survive the move — the empty one is the branch a
+  // template language with a conditional would most likely get wrong.
+  const r = render('auth.password-reset', { resetUrl: 'https://x.test/r', forWhom: '' })
+  assert.match(r.text, /^We received a request to reset the password at Runic Gateway\.\n\n/)
+})
+
+test('invite renders byte-identically', () => {
+  const r = render('auth.invite', {
+    acceptUrl: 'https://shard.example.com/invite/tok',
+    roleLabel: ' as moderator',
+    invitedBy: ' by Aldric',
+  })
+  assert.equal(r.subject, `Your ${SITE} invitation`)
+  assert.equal(
+    r.text,
+    `You have been invited by Aldric to join ${SITE} as moderator.\n\n` +
+      'Accept your invitation and set up your account here:\nhttps://shard.example.com/invite/tok\n\n' +
+      "This link is single-use and will expire. If you weren't expecting this, you can ignore it.",
+  )
+})
+
+test('email verification renders byte-identically', () => {
+  const r = render('auth.email-verify', {
+    verifyUrl: 'https://shard.example.com/verify/tok',
+    forWhom: ' “Darrow”',
+  })
+  assert.equal(r.subject, `Confirm your email address for ${SITE}`)
+  assert.equal(
+    r.text,
+    `The ${SITE} account “Darrow” asked to use this address for contact and account recovery.\n\n` +
+      'Confirm it here:\nhttps://shard.example.com/verify/tok\n\n' +
+      'This link is single-use and expires in about a day. Until it is used, nothing changes — ' +
+      'the account keeps whatever address it had.\n\n' +
+      'If you did not ask for this, you can ignore this email. Someone may have mistyped their ' +
+      'own address; no account of yours is affected and this link grants no access to anything.',
+  )
+})
+
+test('contact message renders byte-identically, both fallbacks included', () => {
+  const named = render('admin.contact-message', {
+    fromLabel: 'Ann',
+    fromName: 'Ann',
+    fromEmail: 'ann@player.com',
+    message: 'Is the shard open?',
+  })
+  assert.equal(named.subject, `${SITE} contact from Ann`)
+  assert.equal(named.text, 'From: Ann <ann@player.com>\n\nIs the shard open?')
+
+  // The two different fallbacks for one missing name are inherited from the
+  // literal and are asserted so a later tidy-up is a deliberate change.
+  const anon = render('admin.contact-message', {
+    fromLabel: 'a visitor',
+    fromName: 'unknown',
+    fromEmail: 'no email',
+    message: 'hi',
+  })
+  assert.equal(anon.subject, `${SITE} contact from a visitor`)
+  assert.equal(anon.text, 'From: unknown <no email>\n\nhi')
+})
+
+test('delivery test renders byte-identically', () => {
+  const r = render('admin.test', { transport: 'smtp' })
+  assert.equal(r.subject, `${SITE} email test`)
+  assert.equal(r.text, 'This is a test message confirming smtp email delivery is working.')
+})
+
+// ── The registries are siblings, not one namespace ──────────────────────────
+
+test('an email block is not a page block, and a page block is not an email block', () => {
+  const pageBlocks = require('../src/blocks')
+  const asPage = pageBlocks.validateBlocks([{ id: 'a', type: 'email.heading', props: { level: 'h1', text: 'x' } }])
+  assert.equal(asPage.valid, false)
+  assert.match(asPage.errors.join(' '), /not a registered block type \(email\.heading\)/)
+
+  const asEmail = emailBlocks.validateEmailBlocks([{ id: 'a', type: 'heading', props: { level: 'h1', text: 'x' } }])
+  assert.equal(asEmail.valid, false)
+  assert.match(asEmail.errors.join(' '), /not a registered block type \(heading\)/)
+})
+
+test('the shared walk enforces the same envelope for both families', () => {
+  const r = emailBlocks.validateEmailBlocks([
+    { id: 'a', type: 'email.text', props: { text: 'one' }, smuggled: 1 },
+    { id: 'a', type: 'email.text', props: { text: 'two' } },
+  ])
+  assert.equal(r.valid, false)
+  assert.match(r.errors.join(' '), /smuggled is not an allowed top-level key/)
+  assert.match(r.errors.join(' '), /duplicates another block id/)
+})
+
+test('a block registered without both renderers is refused at registration', () => {
+  const { registerEmailBlock } = require('../src/emailBlocks/registry')
+  assert.throws(
+    () => registerEmailBlock({ type: 'email.broken', toHtml: () => '' }),
+    /needs both toHtml and toText/,
+  )
+  assert.throws(
+    () => registerEmailBlock({ type: 'notEmail', toHtml: () => '', toText: () => '' }),
+    /must be namespaced "email\."/,
+  )
+})
+
+// ── Interpolation and the security posture (§4.6.2) ─────────────────────────
+
+test('an interpolated variable containing markup renders escaped in HTML and raw in text', () => {
+  const ctx = emailBlocks.buildContext({ values: { message: '<script>alert(1)</script>' }, baseUrl: BASE })
+  const block = { id: 'm', type: 'email.text', props: { text: '{{message}}' } }
+  const out = emailBlocks.renderBlocks([block], ctx)
+  assert.match(out.html, /&lt;script&gt;alert\(1\)&lt;\/script&gt;/)
+  assert.equal(out.html.includes('<script>'), false)
+  // The text part has no markup to escape into; `&lt;` in an inbox is the bug.
+  assert.equal(out.text, '<script>alert(1)</script>')
+})
+
+test('a variable carrying a javascript: url never becomes an href', () => {
+  const ctx = emailBlocks.buildContext({ values: { link: 'javascript:alert(1)' }, baseUrl: BASE })
+  const block = { id: 'b', type: 'email.button', props: { label: 'Press me', url: '{{link}}' } }
+  const out = emailBlocks.renderBlocks([block], ctx)
+  assert.equal(out.html.includes('href'), false)
+  assert.match(out.html, /Press me/) // inert, but not silently vanished
+})
+
+test('a literal unsafe url is refused at save, and a tokened one is allowed through', () => {
+  const bad = emailBlocks.validateEmailBlocks([
+    { id: 'b', type: 'email.button', props: { label: 'x', url: 'javascript:alert(1)' } },
+  ])
+  assert.equal(bad.valid, false)
+  const tokened = emailBlocks.validateEmailBlocks([
+    { id: 'b', type: 'email.button', props: { label: 'x', url: '{{resetUrl}}' } },
+  ])
+  assert.equal(tokened.valid, true)
+})
+
+test('the token grammar is names only — an expression is not a token', () => {
+  assert.deepEqual(emailBlocks.scanTokens('{{ user }} and {{other}}'), ['user', 'other'])
+  assert.deepEqual(emailBlocks.scanTokens('{{ user.email }}'), [])
+  const ctx = emailBlocks.buildContext({ values: { user: { email: 'a@b.c' } }, baseUrl: BASE })
+  assert.equal(ctx.t('{{ user.email }}'), '{{ user.email }}')
+})
+
+// ── "Nothing in, nothing out" — the stand-in for a conditional ──────────────
+
+test('a block whose only content is an absent variable disappears from BOTH parts', () => {
+  const r = render('notify.digest', {
+    periodLabel: 'your daily summary',
+    intro: 'Here is what happened.',
+    items: [{ heading: 'A thread', url: '/teams/1' }],
+    // moreNote, scopeUrl and unsubscribeUrl all absent
+  })
+  assert.equal(r.text.includes('undefined'), false)
+  assert.equal(r.text.includes('Unsubscribe'), false)
+  assert.equal(r.rows.includes('Unsubscribe'), false)
+  assert.equal(r.text, 'Here is what happened.\n\nA thread\n  https://shard.example.com/teams/1')
+})
+
+test('the divider contributes to the HTML and nothing to the text', () => {
+  const ctx = emailBlocks.buildContext({ values: {}, baseUrl: BASE })
+  const out = emailBlocks.renderBlocks(
+    [
+      { id: 'a', type: 'email.text', props: { text: 'one' } },
+      { id: 'r', type: 'email.divider', props: {} },
+      { id: 'b', type: 'email.text', props: { text: 'two' } },
+    ],
+    ctx,
+  )
+  assert.equal(out.text, 'one\n\ntwo') // no dashes, and no doubled blank line
+  assert.match(out.html, /background:#dfe4ea/)
+})
+
+test('an absent variable is reported rather than rendered as the word undefined', () => {
+  const r = render('auth.password-reset', { resetUrl: 'https://x.test/r' })
+  assert.equal(r.text.includes('undefined'), false)
+  assert.deepEqual(r.missing.sort(), ['forWhom'])
+})
+
+// ── The item list ───────────────────────────────────────────────────────────
+
+test('itemList renders the shape teamNotify already builds, and survives a bad one', () => {
+  const ctx = emailBlocks.buildContext({
+    values: {
+      items: [
+        { heading: 'First', excerpt: 'a line', url: '/teams/1?thread=9' },
+        'Second',
+        { excerpt: 'no heading' }, // dropped: an item with nothing to name
+        null,
+      ],
+    },
+    baseUrl: BASE,
+  })
+  const out = emailBlocks.renderBlocks([{ id: 'l', type: 'email.itemList', props: { variable: 'items' } }], ctx)
+  assert.equal(out.text, 'First\n  a line\n  https://shard.example.com/teams/1?thread=9\n\nSecond')
+  assert.match(out.html, /First/)
+})
+
+test('an empty list renders emptyText, or nothing at all when there is none', () => {
+  const ctx = emailBlocks.buildContext({ values: { items: [] }, baseUrl: BASE })
+  const withText = emailBlocks.renderBlocks(
+    [{ id: 'l', type: 'email.itemList', props: { variable: 'items', emptyText: 'Nothing new.' } }],
+    ctx,
+  )
+  assert.equal(withText.text, 'Nothing new.')
+  const without = emailBlocks.renderBlocks([{ id: 'l', type: 'email.itemList', props: { variable: 'items' } }], ctx)
+  assert.equal(without.text, '')
+  assert.equal(without.html, '')
+})
+
+// ── Branding is data (§4.6.1 property 2) ────────────────────────────────────
+
+test('every shipped template validates against the email registry', () => {
+  for (const seed of SEEDS) {
+    const { valid, errors } = emailBlocks.validateEmailBlocks(seed.blocks)
+    assert.equal(valid, true, `${seed.key}: ${errors.join('; ')}`)
+    assert.equal(typeof seed.seedVersion, 'number')
+    assert.equal(['email', 'inapp'].includes(seed.channel), true)
+  }
+  // The five transactional bodies the system itself depends on are protected.
+  const guarded = SEEDS.filter((s) => s.protected).map((s) => s.key)
+  assert.deepEqual(guarded, [
+    'auth.password-reset',
+    'auth.invite',
+    'auth.email-verify',
+    'admin.contact-message',
+    'admin.test',
+  ])
+})
+
+test('an invalid shipped template is refused rather than stored', async () => {
+  const seeded = []
+  templatesDb.seedOne = async (t) => {
+    seeded.push(t.key)
+    return 'inserted'
+  }
+  templatesDb.staleCustomized = async () => []
+  const original = SEEDS[0].blocks
+  try {
+    SEEDS[0].blocks = [{ id: 'x', type: 'email.nope', props: {} }]
+    const r = await templates.seedTemplates()
+    assert.equal(r.invalid, 1)
+    assert.equal(seeded.includes(SEEDS[0].key), false)
+  } finally {
+    SEEDS[0].blocks = original
+  }
+})
+
+test('no seeded template contains a hex colour or a hostname', () => {
+  for (const seed of SEEDS) {
+    const json = JSON.stringify(seed.blocks) + String(seed.subject || '')
+    assert.equal(/#[0-9a-fA-F]{6}\b/.test(json), false, `${seed.key} contains a hex colour`)
+    assert.equal(/https?:\/\//.test(json), false, `${seed.key} contains a literal URL`)
+  }
+})
+
+test('the accent comes from the resolved theme, and its text colour is readable over it', () => {
+  const light = emailBlocks.palette({ accent: '#f4d35e' })
+  assert.equal(light.accent, '#f4d35e')
+  assert.equal(light.onAccent, '#151a20')
+  const dark = emailBlocks.palette({ accent: '#2b3a55' })
+  assert.equal(dark.onAccent, '#ffffff')
+  // A stored value that is not a colour degrades to the shipped accent rather
+  // than reaching an inline style — the forgiving-on-read posture.
+  assert.equal(emailBlocks.palette({ accent: 'red; }' }).accent, '#7f99bd')
+})
+
+test('a relative image url is absolutized, and an unresolvable one is dropped', () => {
+  const withBase = emailBlocks.buildContext({ values: { logoUrl: '/uploads/logo.png' }, baseUrl: BASE })
+  const block = { id: 'i', type: 'email.image', props: { url: '{{logoUrl}}', alt: 'Logo' } }
+  assert.match(emailBlocks.renderBlocks([block], withBase).html, /src="https:\/\/shard\.example\.com\/uploads\/logo\.png"/)
+
+  const noBase = emailBlocks.buildContext({ values: { logoUrl: '/uploads/logo.png' }, baseUrl: '' })
+  const out = emailBlocks.renderBlocks([block], noBase)
+  assert.equal(out.html, '') // no broken image in someone's inbox
+  assert.equal(out.text, 'Logo') // the alt still stands in for it
+})
+
+// ── The document shell ──────────────────────────────────────────────────────
+
+test('the shell adds structure and no content', () => {
+  const r = render('admin.test', { transport: 'smtp' })
+  // Everything the text part says, the HTML says; nothing the HTML says is
+  // absent from the text. A footer in one and not the other is the failure.
+  assert.match(r.html, /This is a test message confirming smtp email delivery is working\./)
+  assert.equal(/unsubscribe/i.test(r.html), false)
+  assert.equal(/sent by/i.test(r.html), false)
+  assert.match(r.html, /^<!doctype html>/)
+  assert.match(r.html, /role="presentation"/)
+  assert.equal(r.html.includes('<style'), false) // a <style> block is what clients strip
+})
+
+// ── The variable contract ───────────────────────────────────────────────────
+
+test('every seeded variable carries an example, and every token is declared', () => {
+  for (const seed of SEEDS) {
+    const declared = new Set([...seed.variables.map((v) => v.name), ...AMBIENT_VARIABLES.map((v) => v.name)])
+    for (const v of seed.variables) {
+      assert.notEqual(v.example, undefined, `${seed.key}.${v.name} has no example`)
+    }
+    const used = new Set()
+    for (const b of seed.blocks) {
+      for (const value of Object.values(b.props)) {
+        if (typeof value === 'string') emailBlocks.scanTokens(value).forEach((t) => used.add(t))
+      }
+    }
+    if (seed.subject) emailBlocks.scanTokens(seed.subject).forEach((t) => used.add(t))
+    for (const name of used) {
+      assert.equal(declared.has(name), true, `${seed.key} references undeclared {{${name}}}`)
+    }
+  }
+})
+
+test('variablesFor answers from the seed for a template with no trigger, plus the ambient set', () => {
+  const names = templates.variablesFor({ seed_key: 'auth.invite' }).map((v) => v.name)
+  assert.deepEqual(names, ['acceptUrl', 'roleLabel', 'invitedBy', 'siteName', 'siteUrl', 'logoUrl', 'year'])
+  // A template that is neither seeded nor tied to a trigger still gets the brand
+  // values, because those come from the deployment rather than from the message.
+  assert.deepEqual(templates.variablesFor({}).map((v) => v.name), ['siteName', 'siteUrl', 'logoUrl', 'year'])
+})
+
+// ── The seeder and the render entrypoint ────────────────────────────────────
+
+test('the shipped default is used when the row is missing, and when it is unusable', async () => {
+  settings.getInstanceName = async () => SITE
+  settings.getShellBrand = async () => ({ logo: '', favicon: '', theme: null })
+
+  templatesDb.getByKey = async () => null
+  const missing = await templates.renderByKey('admin.test', { transport: 'smtp' })
+  assert.equal(missing.text, 'This is a test message confirming smtp email delivery is working.')
+
+  // A row whose blocks would not parse hydrates to [] (engagementTemplates.db.js)
+  // and must fall back too — this is the hand-edited-row case, and the one that
+  // would otherwise send an empty password reset.
+  templatesDb.getByKey = async () => ({ subject: 'wrong', blocks: [], text_body: null })
+  const broken = await templates.renderByKey('admin.test', { transport: 'smtp' })
+  assert.equal(broken.subject, `${SITE} email test`)
+
+  assert.equal(await templates.renderByKey('nope.not-a-key', {}), null)
+})
+
+test('an operator edit is rendered instead of the seed, and text_body overrides the generated text', async () => {
+  settings.getInstanceName = async () => SITE
+  settings.getShellBrand = async () => ({ logo: '', favicon: '', theme: null })
+  templatesDb.getByKey = async () => ({
+    subject: 'Edited: {{siteName}}',
+    blocks: [{ id: 'a', type: 'email.text', props: { text: 'Generated body.' } }],
+    text_body: 'A hand-written text part for {{siteName}}.',
+  })
+  const r = await templates.renderByKey('admin.test', {})
+  assert.equal(r.subject, `Edited: ${SITE}`)
+  assert.equal(r.text, `A hand-written text part for ${SITE}.`)
+  assert.match(r.html, /Generated body\./) // the override replaces the TEXT part only
+})
+
+test('a caller cannot override the deployment brand', async () => {
+  settings.getInstanceName = async () => SITE
+  settings.getShellBrand = async () => ({ logo: '', favicon: '', theme: null })
+  templatesDb.getByKey = async () => null
+  const r = await templates.renderByKey('admin.test', { transport: 'smtp', siteName: 'Somewhere Else' })
+  assert.equal(r.subject, `${SITE} email test`)
+})
+
+test('the seeder inserts, then skips, and never touches a customized row', async () => {
+  const calls = []
+  const state = new Map() // key → { seedVersion, customized }
+  templatesDb.seedOne = async (t) => {
+    calls.push(t.key)
+    const row = state.get(t.key)
+    if (!row) {
+      state.set(t.key, { seedVersion: t.seedVersion, customized: false })
+      return 'inserted'
+    }
+    if (row.customized) return 'skipped'
+    if (row.seedVersion < t.seedVersion) {
+      row.seedVersion = t.seedVersion
+      return 'updated'
+    }
+    return 'skipped'
+  }
+  templatesDb.staleCustomized = async () => []
+
+  const first = await templates.seedTemplates()
+  assert.equal(first.inserted, SEEDS.length)
+  assert.equal(calls.length, SEEDS.length)
+
+  const second = await templates.seedTemplates()
+  assert.equal(second.skipped, SEEDS.length)
+  assert.equal(second.inserted, 0) // re-running the seeder is a no-op
+
+  // A version bump reaches an untouched row and stops at a customized one.
+  state.get('auth.invite').seedVersion = 0
+  state.get('auth.password-reset').seedVersion = 0
+  state.get('auth.password-reset').customized = true
+  const third = await templates.seedTemplates()
+  assert.equal(third.updated, 1)
+  assert.equal(state.get('auth.password-reset').seedVersion, 0) // the operator's row, untouched
+})
+
+test('a seed that throws does not stop the boot or the other seeds', async () => {
+  let n = 0
+  templatesDb.seedOne = async () => {
+    n += 1
+    if (n === 2) throw new Error('deadlock')
+    return 'inserted'
+  }
+  templatesDb.staleCustomized = async () => []
+  const r = await templates.seedTemplates()
+  assert.equal(r.inserted, SEEDS.length - 1)
+})
diff --git a/server/test/mailer.test.js b/server/test/mailer.test.js
index a548d44..01d9119 100644
--- a/server/test/mailer.test.js
+++ b/server/test/mailer.test.js
@@ -16,6 +16,7 @@ const assert = require('node:assert/strict')
 const nodemailer = require('nodemailer')
 const emailConfig = require('../src/model/emailConfig/emailConfig.model')
 const settings = require('../src/model/settings/settings.model')
+const templatesDb = require('../src/model/engagement/engagementTemplates.db')
 const mailer = require('../src/utils/mailer')
 const db = require('../src/utils/db')
 
@@ -41,6 +42,14 @@ beforeEach(() => {
   transportCfg = null
   emailConfig.recordStatus = async () => {}
   settings.get = async () => 'contact@example.com'
+  // Engagement Phase 5a: every body now comes from `engagement_templates`, so a
+  // send reaches three more model functions than it used to. Stubbed here for the
+  // reason everything else in this file is — the suite must never touch a database
+  // — and `getByKey` answering null exercises the shipped-seed fallback, which is
+  // exactly the state a fresh deployment is in before its first seed runs.
+  settings.getInstanceName = async () => 'UOMysticmoon'
+  settings.getShellBrand = async () => ({ logo: '', favicon: '', theme: null })
+  templatesDb.getByKey = async () => null
   nodemailer.createTransport = (cfg) => {
     transportCfg = cfg
     return { sendMail: async (opts) => { sent = opts; return { messageId: '1' } } }