diff --git a/server/src/model/teams/teamAccess.db.js b/server/src/model/teams/teamAccess.db.js
new file mode 100644
index 0000000..e21fe9a
--- /dev/null
+++ b/server/src/model/teams/teamAccess.db.js
@@ -0,0 +1,94 @@
+// SQL for the two tables the access resolver reads: forum grants (path 3) and
+// staff leadership overrides (§2.5.1).
+//
+// Kept separate from teams.db.js on purpose. The four authority paths are four
+// tables answering four questions, and the single most important structural rule
+// in TEAMS.md is that no resolver reads another path's table — a file boundary is
+// a cheap way to make crossing one visible in a diff.
+
+const { query } = require('../../utils/db')
+
+// ── team_forum_grants (path 3) ─────────────────────────────────────────────
+
+const GRANT_COLUMNS = `
+  id, team_id, user_id, username, granted_by, granted_username, granted_at, reason,
+  revoked_by, revoked_username, revoked_at, revoke_reason`
+
+/** The caller's ACTIVE grant on a team, or undefined. At most one, by the unique key. */
+async function activeGrant(teamId, userId) {
+  const rows = await query(
+    `SELECT ${GRANT_COLUMNS} FROM team_forum_grants
+     WHERE team_id = ? AND user_id = ? AND revoked_at IS NULL`,
+    [teamId, userId],
+  )
+  return rows[0]
+}
+
+/** The whole ledger for a team, revoked rows included — the admin grant view. */
+async function grantLedger(teamId) {
+  return query(
+    `SELECT ${GRANT_COLUMNS} FROM team_forum_grants WHERE team_id = ? ORDER BY granted_at DESC, id DESC`,
+    [teamId],
+  )
+}
+
+/** Active grants only, for the "Forum guests" list and the per-team cap. */
+async function activeGrants(teamId) {
+  return query(
+    `SELECT ${GRANT_COLUMNS} FROM team_forum_grants WHERE team_id = ? AND revoked_at IS NULL
+     ORDER BY granted_at`,
+    [teamId],
+  )
+}
+
+// ── team_leader_overrides (§2.5.1) ─────────────────────────────────────────
+
+const OVERRIDE_COLUMNS = 'team_id, member_key, effect, actor_user_id, actor_username, reason, created_at'
+
+async function overridesForTeam(teamId) {
+  return query(`SELECT ${OVERRIDE_COLUMNS} FROM team_leader_overrides WHERE team_id = ? ORDER BY member_key`,
+    [teamId])
+}
+
+async function overrideFor(teamId, memberKey) {
+  const rows = await query(
+    `SELECT ${OVERRIDE_COLUMNS} FROM team_leader_overrides WHERE team_id = ? AND member_key = ?`,
+    [teamId, memberKey],
+  )
+  return rows[0]
+}
+
+/**
+ * Set or replace one override.
+ *
+ * The projection is never touched by this — `team_members.is_leader` keeps saying
+ * what the game says and this keeps saying what staff decided, which is the entire
+ * point (§2.5.1). An override applied INTO the projection would be clobbered by
+ * the next sync, fifteen minutes later.
+ */
+async function setOverride({ teamId, memberKey, effect, actorUserId, actorUsername, reason }) {
+  await query(
+    `INSERT INTO team_leader_overrides (team_id, member_key, effect, actor_user_id, actor_username, reason)
+     VALUES (?, ?, ?, ?, ?, ?)
+     ON DUPLICATE KEY UPDATE
+       effect = VALUES(effect), actor_user_id = VALUES(actor_user_id),
+       actor_username = VALUES(actor_username), reason = VALUES(reason), created_at = NOW()`,
+    [teamId, memberKey, effect, actorUserId, actorUsername, reason],
+  )
+}
+
+async function clearOverride(teamId, memberKey) {
+  const res = await query('DELETE FROM team_leader_overrides WHERE team_id = ? AND member_key = ?',
+    [teamId, memberKey])
+  return res.affectedRows > 0
+}
+
+module.exports = {
+  activeGrant,
+  grantLedger,
+  activeGrants,
+  overridesForTeam,
+  overrideFor,
+  setOverride,
+  clearOverride,
+}
diff --git a/server/src/model/teams/teamAccess.model.js b/server/src/model/teams/teamAccess.model.js
new file mode 100644
index 0000000..83cecfe
--- /dev/null
+++ b/server/src/model/teams/teamAccess.model.js
@@ -0,0 +1,131 @@
+// ── The four authority paths ───────────────────────────────────────────────
+//
+// The single most important structural rule in TEAMS.md (§2.5): these are four
+// tables answering four questions, and **no resolver reads another path's table.**
+//
+//   1. Is this account a member?          module      team_members
+//   2. Does this account lead the Team?   module      team_members.is_leader,
+//                                                     plus a staff override
+//   3. May it use the Team forum?         CORE        team_forum_grants OR path 1
+//   4. May it get external-platform       CORE,       nothing of its own
+//      access?                            derived
+//
+// The temptation this file exists to resist is collapsing 1 and 3 into one
+// boolean. They answer different questions about different populations: a forum
+// grant may name any Runic Gateway account, including one with no game identity
+// at all — that is the point of it, since letting an unlinked guildmate into the
+// forum must not require a staff ticket. Treating "has forum access" as "is a
+// member" would put that person on the roster, in the member count, and into the
+// external-platform grant, which is where it stops being a modelling preference
+// and becomes an impersonation risk (path 4 below).
+//
+// Non-contamination is the invariant: a manual grant never writes the membership
+// projection, in either direction, ever. Both facts coexist and neither migrates
+// into the other.
+
+const accessDb = require('./teamAccess.db')
+const teamsDb = require('./teams.db')
+const identities = require('../userIdentities/userIdentities.model')
+
+/**
+ * Path 3 — forum access. Two reads, OR'd, and nothing else.
+ *
+ * `viaGrant` is reported even when membership also holds, deliberately: both
+ * facts are true, the UI presents membership as the current reason, and the grant
+ * survives as audit history. Collapsing them into one boolean is what loses the
+ * record of who let this person in and why.
+ */
+async function forumAccess(teamId, userId) {
+  if (!userId) return { allowed: false, viaMembership: false, viaGrant: false, isLeader: false }
+
+  const [grant, member] = await Promise.all([
+    accessDb.activeGrant(teamId, userId),   // path 3's own table
+    teamsDb.activeByUser(teamId, userId),   // path 1
+  ])
+
+  return {
+    allowed: Boolean(grant) || Boolean(member),
+    viaMembership: Boolean(member),
+    viaGrant: Boolean(grant),
+    isLeader: member ? await isLeader(teamId, member) : false,
+  }
+}
+
+/**
+ * Path 2 — leadership, with the staff override applied ON TOP of the synced value
+ * at read time (§2.5.1).
+ *
+ * Applied at read rather than written into the projection because the sync owns
+ * that column and rewrites it every interval. An override that lived in
+ * `team_members` would be undone fifteen minutes after staff set it, which is the
+ * whole reason this is a separate table read here.
+ */
+async function isLeader(teamId, member) {
+  if (!member) return false
+  const override = await accessDb.overrideFor(teamId, member.member_key)
+  if (override) return override.effect === 'grant'
+  return Boolean(member.is_leader)
+}
+
+/** Leadership for a caller identified by user id rather than by a member row. */
+async function isLeaderByUser(teamId, userId) {
+  if (!userId) return false
+  const member = await teamsDb.activeByUser(teamId, userId)
+  return isLeader(teamId, member)
+}
+
+/**
+ * Path 4 — external-platform eligibility. Computed, no table of its own, and
+ * deliberately blind to path 3.
+ *
+ * The reason, stated so nobody "fixes" it later: an integration cannot verify
+ * that an unlinked, forum-granted account corresponds to a real game member, so
+ * it must not hand that account a privilege on a platform where impersonation has
+ * consequences. A forum is a room on the operator's own site with a known
+ * moderator; a Discord role is an identity claim in someone else's space.
+ */
+async function externalEligible(teamId, userId, platform) {
+  if (!userId || !platform) return false
+  const member = await teamsDb.activeByUser(teamId, userId)  // path 1 ONLY
+  if (!member || member.user_id == null) return false        // must be a LINKED game member
+  const linked = await identities.listForUser(userId)
+  return linked.some((i) => i.provider === platform)
+}
+
+/**
+ * A team's roster with overrides folded in, for the admin view and the Team page.
+ *
+ * The rows returned carry `is_leader` as RESOLVED — synced value plus override —
+ * and `is_leader_synced` as what the game actually said, so the admin surface can
+ * show that a decision was made rather than silently presenting it as fact.
+ */
+async function rosterWithOverrides(teamId, { includeDeparted = false } = {}) {
+  const [members, overrides] = await Promise.all([
+    teamsDb.membersByTeam(teamId, { includeDeparted }),
+    accessDb.overridesForTeam(teamId),
+  ])
+  const byKey = new Map(overrides.map((o) => [o.member_key, o]))
+  return members.map((m) => {
+    const override = byKey.get(m.member_key)
+    return {
+      ...m,
+      is_leader_synced: Boolean(m.is_leader),
+      is_leader: override ? override.effect === 'grant' : Boolean(m.is_leader),
+      leader_override: override
+        ? { effect: override.effect, reason: override.reason, by: override.actor_username, at: override.created_at }
+        : null,
+    }
+  })
+}
+
+module.exports = {
+  forumAccess,
+  isLeader,
+  isLeaderByUser,
+  externalEligible,
+  rosterWithOverrides,
+  setLeaderOverride: accessDb.setOverride,
+  clearLeaderOverride: accessDb.clearOverride,
+  grantLedger: accessDb.grantLedger,
+  activeGrants: accessDb.activeGrants,
+}
diff --git a/server/test/teamAccess.test.js b/server/test/teamAccess.test.js
new file mode 100644
index 0000000..3d70ce2
--- /dev/null
+++ b/server/test/teamAccess.test.js
@@ -0,0 +1,209 @@
+// The four authority paths, and the rule that they stay four
+// (docs/website/TEAMS.md §2.5).
+//
+// Two of these tests are named for invariants rather than for behaviour, because
+// what they protect is a structural property that a perfectly reasonable-looking
+// refactor destroys: "has forum access" is never read as "is a member", and a
+// grant never writes the membership projection. Both are one `||` away from being
+// wrong, and neither failure is visible on any screen — the first shows up as a
+// stranger on a public roster, the second as a Discord role handed to an account
+// nobody can tie to a real player.
+const { test, beforeEach, afterEach } = require('node:test')
+const assert = require('node:assert/strict')
+
+const accessDb = require('../src/model/teams/teamAccess.db')
+const teamsDb = require('../src/model/teams/teams.db')
+const identities = require('../src/model/userIdentities/userIdentities.model')
+const access = require('../src/model/teams/teamAccess.model')
+
+const saved = []
+function patch(mod, name, fn) {
+  saved.push([mod, name, mod[name]])
+  mod[name] = fn
+}
+
+// Every read the four paths can make, stubbed to "nothing there". Each test then
+// states only the fact it is about, which is what makes a crossed path obvious:
+// a resolver reading a table it should not would come back empty and the
+// assertion would say so.
+function stubAll() {
+  patch(accessDb, 'activeGrant', async () => undefined)
+  patch(accessDb, 'overrideFor', async () => undefined)
+  patch(accessDb, 'overridesForTeam', async () => [])
+  patch(teamsDb, 'activeByUser', async () => undefined)
+  patch(teamsDb, 'membersByTeam', async () => [])
+  patch(identities, 'listForUser', async () => [])
+}
+
+const memberRow = (extra = {}) => ({
+  team_id: 1, member_key: '0x1', user_id: 7, is_leader: 0, status: 'active', display_name: 'Aldric', ...extra,
+})
+const grantRow = (extra = {}) => ({ id: 1, team_id: 1, user_id: 7, granted_by: 2, revoked_at: null, ...extra })
+
+beforeEach(stubAll)
+afterEach(() => {
+  while (saved.length) {
+    const [mod, name, fn] = saved.pop()
+    mod[name] = fn
+  }
+})
+
+// ── Path 3: forum access is membership OR a grant ──────────────────────────
+
+test('a member has forum access via membership', async () => {
+  patch(teamsDb, 'activeByUser', async () => memberRow())
+  const result = await access.forumAccess(1, 7)
+  assert.deepEqual(result, { allowed: true, viaMembership: true, viaGrant: false, isLeader: false })
+})
+
+test('a granted non-member has forum access via the grant', async () => {
+  patch(accessDb, 'activeGrant', async () => grantRow())
+  const result = await access.forumAccess(1, 7)
+  assert.deepEqual(result, { allowed: true, viaMembership: false, viaGrant: true, isLeader: false })
+})
+
+test('both reasons are reported when both hold', async () => {
+  // Not collapsed into one boolean: both facts are true, membership is what the
+  // UI shows as the current reason, and the grant stays as the record of who let
+  // this person in before they were a member.
+  patch(accessDb, 'activeGrant', async () => grantRow())
+  patch(teamsDb, 'activeByUser', async () => memberRow())
+  const result = await access.forumAccess(1, 7)
+  assert.equal(result.viaMembership, true)
+  assert.equal(result.viaGrant, true)
+})
+
+test('a revoked grant and no membership is no access', async () => {
+  // activeGrant returns nothing for a revoked row — the resolver never sees one.
+  const result = await access.forumAccess(1, 7)
+  assert.equal(result.allowed, false)
+})
+
+test('an anonymous caller is refused without touching a table', async () => {
+  let reads = 0
+  patch(accessDb, 'activeGrant', async () => { reads += 1 })
+  patch(teamsDb, 'activeByUser', async () => { reads += 1 })
+  const result = await access.forumAccess(1, null)
+  assert.equal(result.allowed, false)
+  assert.equal(reads, 0)
+})
+
+// ── Invariant 3: non-contamination ─────────────────────────────────────────
+
+test('INVARIANT — a grant never writes the membership projection', async () => {
+  // The grant path reads its own table and nothing else. Asserted by making every
+  // membership WRITE explode: if resolving a grant ever wrote a member row, this
+  // is where it would surface.
+  for (const name of ['upsertMember', 'markDeparted', 'setLeaders', 'setMemberLeader']) {
+    patch(teamsDb, name, async () => { throw new Error(`forumAccess wrote team_members via ${name}`) })
+  }
+  patch(accessDb, 'activeGrant', async () => grantRow())
+  const result = await access.forumAccess(1, 7)
+  assert.equal(result.allowed, true)
+  assert.equal(result.viaMembership, false, 'a grant is not a membership, in either direction')
+})
+
+test('INVARIANT — a granted, unlinked user is not on the roster', async () => {
+  // The roster is path 1's table alone. A granted user with no membership row
+  // appears nowhere in it, which is what keeps them out of every membership count.
+  patch(accessDb, 'activeGrant', async () => grantRow({ user_id: 99 }))
+  patch(teamsDb, 'membersByTeam', async () => [memberRow()])
+
+  const roster = await access.rosterWithOverrides(1)
+  assert.equal(roster.length, 1)
+  assert.equal(roster.every((m) => m.user_id !== 99), true, 'a forum guest is not a member')
+})
+
+// ── Path 4: external access is blind to path 3 ─────────────────────────────
+
+test('INVARIANT — a forum grant does not make an account externally eligible', async () => {
+  // The named test from §2.5. An integration cannot verify that an unlinked,
+  // forum-granted account corresponds to a real game member, so it must not hand
+  // that account a privilege on a platform where impersonation has consequences.
+  patch(accessDb, 'activeGrant', async () => grantRow())
+  patch(identities, 'listForUser', async () => [{ provider: 'discord', subject: 'd1' }])
+
+  assert.equal(await access.externalEligible(1, 7, 'discord'), false)
+})
+
+test('a linked member with a linked Discord identity is eligible', async () => {
+  patch(teamsDb, 'activeByUser', async () => memberRow({ user_id: 7 }))
+  patch(identities, 'listForUser', async () => [{ provider: 'discord', subject: 'd1' }])
+  assert.equal(await access.externalEligible(1, 7, 'discord'), true)
+})
+
+test('a member with no Discord identity is not eligible — hop 3 of the chain', async () => {
+  patch(teamsDb, 'activeByUser', async () => memberRow())
+  patch(identities, 'listForUser', async () => [{ provider: 'google', subject: 'g1' }])
+  assert.equal(await access.externalEligible(1, 7, 'discord'), false)
+})
+
+test('eligibility is per platform, not "linked to anything"', async () => {
+  patch(teamsDb, 'activeByUser', async () => memberRow())
+  patch(identities, 'listForUser', async () => [{ provider: 'discord', subject: 'd1' }])
+  assert.equal(await access.externalEligible(1, 7, 'matrix'), false)
+})
+
+test('a non-member is never eligible', async () => {
+  patch(identities, 'listForUser', async () => [{ provider: 'discord', subject: 'd1' }])
+  assert.equal(await access.externalEligible(1, 7, 'discord'), false)
+})
+
+// ── Path 2: leadership, and the staff override on top ──────────────────────
+
+test('leadership follows the synced value when no override exists', async () => {
+  patch(teamsDb, 'activeByUser', async () => memberRow({ is_leader: 1 }))
+  assert.equal(await access.isLeaderByUser(1, 7), true)
+})
+
+test('a deny override outranks a synced leader', async () => {
+  patch(teamsDb, 'activeByUser', async () => memberRow({ is_leader: 1 }))
+  patch(accessDb, 'overrideFor', async () => ({ member_key: '0x1', effect: 'deny' }))
+  assert.equal(await access.isLeaderByUser(1, 7), false)
+})
+
+test('a grant override promotes someone the game does not call a leader', async () => {
+  patch(teamsDb, 'activeByUser', async () => memberRow({ is_leader: 0 }))
+  patch(accessDb, 'overrideFor', async () => ({ member_key: '0x1', effect: 'grant' }))
+  assert.equal(await access.isLeaderByUser(1, 7), true)
+})
+
+test('an override survives a resync, because it is never written into the projection', async () => {
+  // The projection keeps saying what the game says; the override keeps saying what
+  // staff decided. Applied at READ time, so a sync fifteen minutes later cannot
+  // undo it — which is the entire point of §2.5.1.
+  patch(accessDb, 'overridesForTeam', async () => [
+    { member_key: '0x1', effect: 'deny', reason: 'harassment', actor_username: 'mod1', created_at: 'then' },
+  ])
+  patch(teamsDb, 'membersByTeam', async () => [memberRow({ is_leader: 1 })])
+
+  const roster = await access.rosterWithOverrides(1)
+  assert.equal(roster[0].is_leader, false, 'the resolved answer is the override')
+  assert.equal(roster[0].is_leader_synced, true, 'what the game says is still visible')
+  assert.equal(roster[0].leader_override.reason, 'harassment')
+  assert.equal(roster[0].leader_override.by, 'mod1')
+})
+
+test('a member with no override carries no override field', async () => {
+  patch(teamsDb, 'membersByTeam', async () => [memberRow({ is_leader: 1 })])
+  const roster = await access.rosterWithOverrides(1)
+  assert.equal(roster[0].leader_override, null)
+  assert.equal(roster[0].is_leader, true)
+})
+
+test('leadership resolves through forumAccess too, override included', async () => {
+  patch(teamsDb, 'activeByUser', async () => memberRow({ is_leader: 0 }))
+  patch(accessDb, 'overrideFor', async () => ({ member_key: '0x1', effect: 'grant' }))
+  const result = await access.forumAccess(1, 7)
+  assert.equal(result.isLeader, true)
+})
+
+test('a granted non-member is never a leader', async () => {
+  // isLeader is path 2, which is a property of a MEMBER row. Someone with only a
+  // forum grant has no member row, so there is nothing to promote.
+  patch(accessDb, 'activeGrant', async () => grantRow())
+  patch(accessDb, 'overrideFor', async () => ({ member_key: '0x1', effect: 'grant' }))
+  const result = await access.forumAccess(1, 7)
+  assert.equal(result.allowed, true)
+  assert.equal(result.isLeader, false)
+})