diff --git a/.m/config.yaml b/.m/config.yaml
index b5ea9ae..67b5311 100644
--- a/.m/config.yaml
+++ b/.m/config.yaml
@@ -1,6 +1,3 @@
-# Project-specific mai configuration
-# Auto-generated by 'mai init' — run 'mai setup' to customize
-
 provider: claude
 providers:
     claude:
@@ -47,21 +44,13 @@ worker:
     name_scheme: role
     default_level: standard
     auto_discard: false
-    max_workers: 5
+    max_workers: 7
     persistent: true
 head:
-    name: "paliadin"
-    max_loops: 50
-    infinity_mode: false
-    max_idle_duration: 2h0m0s
-    backoff_intervals:
-        - 5
-        - 10
-        - 15
-        - 30
+    name: paliadin
 capacity:
     global:
-        max_workers: 5
+        max_workers: 7
         max_heads: 3
     per_worker:
         max_tasks_lifetime: 0
diff --git a/frontend/src/client/i18n.ts b/frontend/src/client/i18n.ts
index 6d41911..f968a0d 100644
--- a/frontend/src/client/i18n.ts
+++ b/frontend/src/client/i18n.ts
@@ -1415,10 +1415,15 @@ const translations: Record<Lang, Record<string, string>> = {
     "projects.team.role.local_counsel": "Local Counsel",
     "projects.team.role.expert": "Experte",
     "projects.team.role.observer": "Beobachter",
+    "projects.team.responsibility.admin": "Admin",
+    "projects.team.responsibility.admin.hint": "Kann Team und Rollen auf diesem Projekt und Unterprojekten verwalten",
     "projects.team.responsibility.lead": "Leitung",
     "projects.team.responsibility.member": "Mitglied",
     "projects.team.responsibility.observer": "Beobachter",
     "projects.team.responsibility.external": "Extern",
+    "projects.team.error.last_admin": "Mindestens ein Admin muss auf diesem Projekt oder einem übergeordneten verbleiben.",
+    "projects.team.error.forbidden": "Diese Aktion ist nicht erlaubt.",
+    "projects.team.error.generic": "Aktion fehlgeschlagen.",
     "projects.team.profession.partner": "Partner",
     "projects.team.profession.of_counsel": "Of Counsel",
     "projects.team.profession.associate": "Associate",
@@ -4094,10 +4099,15 @@ const translations: Record<Lang, Record<string, string>> = {
     "projects.team.role.local_counsel": "Local Counsel",
     "projects.team.role.expert": "Expert",
     "projects.team.role.observer": "Observer",
+    "projects.team.responsibility.admin": "Admin",
+    "projects.team.responsibility.admin.hint": "Can manage team and roles on this project and its sub-projects",
     "projects.team.responsibility.lead": "Lead",
     "projects.team.responsibility.member": "Member",
     "projects.team.responsibility.observer": "Observer",
     "projects.team.responsibility.external": "External",
+    "projects.team.error.last_admin": "At least one admin must remain on this project or an ancestor.",
+    "projects.team.error.forbidden": "This action is not permitted.",
+    "projects.team.error.generic": "Action failed.",
     "projects.team.profession.partner": "Partner",
     "projects.team.profession.of_counsel": "Of Counsel",
     "projects.team.profession.associate": "Associate",
diff --git a/frontend/src/client/projects-detail.ts b/frontend/src/client/projects-detail.ts
index 611a6f5..8f63df3 100644
--- a/frontend/src/client/projects-detail.ts
+++ b/frontend/src/client/projects-detail.ts
@@ -34,6 +34,12 @@ interface Project {
   grant_date?: string | null;
   court?: string | null;
   case_number?: string | null;
+  // t-paliad-223: piggybacked onto the GET /api/projects/{id} payload so
+  // the team panel can render an inline <select> for callers who can
+  // change responsibilities (global_admin or effective_project_admin on
+  // this project / ancestor). Optional for back-compat with cached
+  // payloads.
+  effective_admin?: boolean;
   updated_at: string;
   created_at: string;
 }
@@ -2494,6 +2500,11 @@ function renderTeam() {
   }
   empty.style.display = "none";
 
+  // t-paliad-223: callers with effective_project_admin authority see an
+  // inline <select> on the Rolle cell. Everyone else sees the read-only
+  // <span>. The bool comes from the GET /api/projects/{id} payload.
+  const canEditResponsibility = !!project?.effective_admin;
+
   body.innerHTML = teamMembers
     .map((m) => {
       // t-paliad-148: profession is firm-wide (read-only badge) and
@@ -2519,11 +2530,20 @@ function renderTeam() {
           : "";
       const officeLabel = m.user_office ? tDyn("office." + m.user_office) || m.user_office : "";
       const profCls = m.user_profession ? "projekt-team-profession" : "projekt-team-profession projekt-team-profession--none";
+
+      // Inline-select only on direct rows where the caller can edit.
+      // Inherited rows stay read-only — the edit must happen at the
+      // ancestor where the row is direct.
+      const responsibilityCell =
+        canEditResponsibility && !m.inherited
+          ? renderResponsibilitySelect(m.user_id, responsibility)
+          : `<span class="projekt-team-responsibility">${esc(responsibilityLabel)}</span>`;
+
       return `<tr>
         <td><strong>${esc(m.user_display_name || m.user_email)}</strong>
             <span class="form-hint">&middot; ${esc(m.user_email)}${officeLabel ? " &middot; " + esc(officeLabel) : ""}</span></td>
         <td><span class="${profCls}" title="${escAttr(professionTitle)}">${esc(professionLabel)}</span></td>
-        <td><span class="projekt-team-responsibility">${esc(responsibilityLabel)}</span></td>
+        <td>${responsibilityCell}</td>
         <td>${source}</td>
         <td>${removeBtn}</td>
       </tr>`;
@@ -2542,6 +2562,47 @@ function renderTeam() {
       if (resp.ok) {
         await loadTeam(project.id);
         renderTeam();
+      } else {
+        await showTeamErrorToast(resp);
+      }
+    });
+  });
+
+  body.querySelectorAll<HTMLSelectElement>(".team-responsibility-select").forEach((sel) => {
+    // Capture the pre-change value on focus so we can roll back the
+    // <select> if the PATCH fails (e.g. last-admin guard).
+    sel.dataset.previous = sel.value;
+    sel.addEventListener("focus", () => {
+      sel.dataset.previous = sel.value;
+    });
+    sel.addEventListener("change", async () => {
+      if (!project) return;
+      const userID = sel.dataset.userId!;
+      const previous = sel.dataset.previous || "member";
+      const next = sel.value;
+      if (next === previous) return;
+      sel.disabled = true;
+      try {
+        const resp = await fetch(
+          `/api/projects/${project.id}/team/${encodeURIComponent(userID)}`,
+          {
+            method: "PATCH",
+            headers: { "Content-Type": "application/json" },
+            body: JSON.stringify({ responsibility: next }),
+          },
+        );
+        if (!resp.ok) {
+          sel.value = previous;
+          await showTeamErrorToast(resp);
+          return;
+        }
+        sel.dataset.previous = next;
+        // Refresh the team list so derived/descendant sections re-render
+        // with the new authority shape.
+        await loadTeam(project.id);
+        renderTeam();
+      } finally {
+        sel.disabled = false;
       }
     });
   });
@@ -2725,7 +2786,54 @@ function wireExportButton(projectID: string): void {
 function canRemoveTeamMember(m: ProjectTeamMember): boolean {
   if (!me) return false;
   if (m.user_id === me.id) return true;
-  return me.global_role === "global_admin";
+  if (me.global_role === "global_admin") return true;
+  // t-paliad-223: effective_project_admin (from the project payload)
+  // also covers remove. RLS makes the request fail anyway if the bit is
+  // stale; this just hides the affordance.
+  return !!project?.effective_admin;
+}
+
+// t-paliad-223: build the inline <select> for the responsibility cell.
+// Options mirror the IsValidResponsibility set in approval_levels.go.
+function renderResponsibilitySelect(userID: string, current: string): string {
+  const options = ["admin", "lead", "member", "observer", "external"]
+    .map((v) => {
+      const label = tDyn(`projects.team.responsibility.${v}`) || v;
+      const sel = v === current ? " selected" : "";
+      return `<option value="${esc(v)}"${sel}>${esc(label)}</option>`;
+    })
+    .join("");
+  return `<select class="team-responsibility-select projekt-team-responsibility" data-user-id="${esc(userID)}">${options}</select>`;
+}
+
+// t-paliad-223: surface backend error responses (last-admin guard / 403
+// from RLS / etc.) as a transient toast. We have no global toast service
+// yet on this page, so write into #team-msg.
+async function showTeamErrorToast(resp: Response): Promise<void> {
+  const msg = document.getElementById("team-msg") as HTMLParagraphElement | null;
+  if (!msg) return;
+  let text = "";
+  try {
+    const data = (await resp.json()) as { error?: string };
+    text = data?.error || "";
+  } catch {
+    text = "";
+  }
+  if (!text) {
+    if (resp.status === 409) text = t("projects.team.error.last_admin") || "Mindestens ein Admin muss auf diesem Projekt oder einem übergeordneten verbleiben.";
+    else if (resp.status === 403 || resp.status === 404) text = t("projects.team.error.forbidden") || "Diese Aktion ist nicht erlaubt.";
+    else text = t("projects.team.error.generic") || "Aktion fehlgeschlagen.";
+  }
+  msg.textContent = text;
+  msg.classList.add("form-msg--error");
+  // Auto-clear after 5s so a stale error doesn't linger past the next
+  // successful action.
+  window.setTimeout(() => {
+    if (msg.textContent === text) {
+      msg.textContent = "";
+      msg.classList.remove("form-msg--error");
+    }
+  }, 5000);
 }
 
 function initTeamForm(id: string) {
diff --git a/frontend/src/i18n-keys.ts b/frontend/src/i18n-keys.ts
index db38878..e3fbbc1 100644
--- a/frontend/src/i18n-keys.ts
+++ b/frontend/src/i18n-keys.ts
@@ -2233,6 +2233,9 @@ export type I18nKey =
   | "projects.team.derived.from"
   | "projects.team.derived.visibility"
   | "projects.team.direct"
+  | "projects.team.error.forbidden"
+  | "projects.team.error.generic"
+  | "projects.team.error.last_admin"
   | "projects.team.inherited.hint"
   | "projects.team.profession.associate"
   | "projects.team.profession.hint"
@@ -2243,6 +2246,8 @@ export type I18nKey =
   | "projects.team.profession.paralegal"
   | "projects.team.profession.partner"
   | "projects.team.profession.senior_pa"
+  | "projects.team.responsibility.admin"
+  | "projects.team.responsibility.admin.hint"
   | "projects.team.responsibility.external"
   | "projects.team.responsibility.lead"
   | "projects.team.responsibility.member"
diff --git a/frontend/src/projects-detail.tsx b/frontend/src/projects-detail.tsx
index 25ac68b..2282da6 100644
--- a/frontend/src/projects-detail.tsx
+++ b/frontend/src/projects-detail.tsx
@@ -262,6 +262,7 @@ export function renderProjectsDetail(): string {
                       <div className="form-field">
                         <label htmlFor="team-responsibility" data-i18n="projects.detail.team.form.responsibility">Rolle im Projekt</label>
                         <select id="team-responsibility">
+                          <option value="admin" data-i18n="projects.team.responsibility.admin">Admin</option>
                           <option value="lead" data-i18n="projects.team.responsibility.lead">Lead</option>
                           <option value="member" selected data-i18n="projects.team.responsibility.member">Mitglied</option>
                           <option value="observer" data-i18n="projects.team.responsibility.observer">Beobachter</option>
diff --git a/internal/db/migrations/111_project_admin_and_select.down.sql b/internal/db/migrations/111_project_admin_and_select.down.sql
new file mode 100644
index 0000000..b00291c
--- /dev/null
+++ b/internal/db/migrations/111_project_admin_and_select.down.sql
@@ -0,0 +1,65 @@
+-- Reverse of 111_project_admin_and_select.up.sql.
+--
+-- Drops effective_project_admin, restores the original RLS policies,
+-- and shrinks the responsibility CHECK back to four values. Any rows
+-- still carrying responsibility='admin' would violate the restored
+-- CHECK; the down-migration backfills them to 'lead' (the closest
+-- existing role) before re-adding the constraint.
+
+-- ============================================================================
+-- 1. Backfill any responsibility='admin' rows to 'lead'.
+-- ============================================================================
+
+UPDATE paliad.project_teams
+   SET responsibility = 'lead'
+ WHERE responsibility = 'admin';
+
+-- ============================================================================
+-- 2. Restore the original CHECK (lead/member/observer/external).
+-- ============================================================================
+
+ALTER TABLE paliad.project_teams
+    DROP CONSTRAINT IF EXISTS project_teams_responsibility_check;
+
+ALTER TABLE paliad.project_teams
+    ADD CONSTRAINT project_teams_responsibility_check
+    CHECK (responsibility IN ('lead', 'member', 'observer', 'external'));
+
+-- ============================================================================
+-- 3. Restore the pre-110 RLS policies.
+-- ============================================================================
+
+DROP POLICY IF EXISTS project_teams_update ON paliad.project_teams;
+CREATE POLICY project_teams_update
+    ON paliad.project_teams FOR UPDATE
+    USING (paliad.can_see_project(project_id))
+    WITH CHECK (paliad.can_see_project(project_id));
+
+DROP POLICY IF EXISTS project_teams_insert ON paliad.project_teams;
+CREATE POLICY project_teams_insert
+    ON paliad.project_teams FOR INSERT
+    WITH CHECK (
+        user_id = auth.uid()
+        OR paliad.can_see_project(project_id)
+    );
+
+DROP POLICY IF EXISTS project_teams_delete ON paliad.project_teams;
+CREATE POLICY project_teams_delete
+    ON paliad.project_teams FOR DELETE
+    USING (
+        paliad.can_see_project(project_id)
+        AND (
+            user_id = auth.uid()
+            OR EXISTS (
+                SELECT 1 FROM paliad.users u
+                 WHERE u.id = auth.uid()
+                   AND u.global_role = 'global_admin'
+            )
+        )
+    );
+
+-- ============================================================================
+-- 4. Drop the predicate function.
+-- ============================================================================
+
+DROP FUNCTION IF EXISTS paliad.effective_project_admin(uuid, uuid);
diff --git a/internal/db/migrations/111_project_admin_and_select.up.sql b/internal/db/migrations/111_project_admin_and_select.up.sql
new file mode 100644
index 0000000..7abd3e9
--- /dev/null
+++ b/internal/db/migrations/111_project_admin_and_select.up.sql
@@ -0,0 +1,152 @@
+-- t-paliad-223 Slice A: Project Admin role on project_teams.responsibility +
+-- inheritable role-edit gate.
+--
+-- Design: docs/design-team-admin-rework-2026-05-20.md (gauss, m-locked
+-- 2026-05-20 via head's "all R approved").
+--
+-- Adds a fifth 'admin' value to the project_teams.responsibility enum
+-- (orthogonal to the profession-driven approval ladder — admin does NOT
+-- open the 4-Augen gate by itself). Introduces paliad.effective_project_admin
+-- which mirrors paliad.can_see_project's shape and walks the ltree path
+-- to compute inheritance. Replaces the three write-side RLS policies on
+-- paliad.project_teams so role edits are gated on the new predicate
+-- instead of "anyone with visibility".
+--
+-- Day-1 deploy = no behaviour change for callers who never use the admin
+-- value: existing lead/member/observer/external rows keep their meaning,
+-- and the global_admin shortcut + self-join INSERT / self-DELETE remain
+-- intact.
+--
+-- Sections:
+--   1. ALTER project_teams.responsibility CHECK to include 'admin'.
+--   2. CREATE paliad.effective_project_admin(uuid, uuid).
+--   3. Replace project_teams_update policy: gated on effective_project_admin.
+--   4. Replace project_teams_insert policy: self-join OR effective_project_admin.
+--   5. Replace project_teams_delete policy: self / global_admin / effective_project_admin.
+
+-- ============================================================================
+-- 1. Extend responsibility CHECK to include 'admin'.
+--
+-- 'admin' inherits down the project tree (see effective_project_admin in §2).
+-- A user marked admin on a Mandant-level project is implicitly admin on
+-- every Litigation / Patent / Case descendant — same shape as how 'lead'
+-- already inherits.
+-- ============================================================================
+
+ALTER TABLE paliad.project_teams
+    DROP CONSTRAINT IF EXISTS project_teams_responsibility_check;
+
+ALTER TABLE paliad.project_teams
+    ADD CONSTRAINT project_teams_responsibility_check
+    CHECK (responsibility IN ('admin', 'lead', 'member', 'observer', 'external'));
+
+COMMENT ON COLUMN paliad.project_teams.responsibility IS
+    'Per-project responsibility. admin = can manage team + roles on this '
+    'project and descendants (inherited via paliad.effective_project_admin). '
+    'lead/member open the 4-Augen approval gate; observer/external close it. '
+    'admin is orthogonal to the approval gate — it does NOT open it by itself.';
+
+-- ============================================================================
+-- 2. paliad.effective_project_admin(_user_id, _project_id)
+--
+-- Mirrors paliad.can_see_project: STABLE SECURITY DEFINER, ltree path-walk
+-- against projects.path. Two branches:
+--   (a) global_admin short-circuit — firm-wide admins are always admin.
+--   (b) ancestor-or-self project_teams row with responsibility='admin'.
+--
+-- Used by the project_teams_update / _insert / _delete policies below
+-- and by ProjectService for the effective_admin payload field.
+--
+-- The ltree-array cast is the same pattern can_see_project uses; the
+-- existing GiST index on projects.path is the load-bearing index. No new
+-- index needed.
+-- ============================================================================
+
+CREATE OR REPLACE FUNCTION paliad.effective_project_admin(_user_id uuid, _project_id uuid)
+RETURNS boolean
+LANGUAGE sql STABLE SECURITY DEFINER
+SET search_path TO 'paliad', 'public'
+AS $$
+    SELECT EXISTS (
+        SELECT 1 FROM paliad.users u
+         WHERE u.id = _user_id
+           AND u.global_role = 'global_admin'
+    )
+    OR EXISTS (
+        SELECT 1
+          FROM paliad.projects      target
+          JOIN paliad.project_teams pt
+            ON pt.user_id = _user_id
+           AND pt.responsibility = 'admin'
+           AND pt.project_id = ANY(string_to_array(target.path, '.')::uuid[])
+         WHERE target.id = _project_id
+    );
+$$;
+
+COMMENT ON FUNCTION paliad.effective_project_admin(uuid, uuid) IS
+    'True iff the user is global_admin OR has responsibility=admin on the '
+    'project itself or any ancestor in the materialised ltree path. '
+    'Drives the role-edit gate on project_teams (UPDATE/INSERT/DELETE RLS).';
+
+-- ============================================================================
+-- 3. project_teams_update policy: gated on effective_project_admin.
+--
+-- Before: USING + CHECK = can_see_project (anyone with visibility could
+-- edit anyone's responsibility — the load-bearing gap that t-paliad-223
+-- closes).
+-- After: USING + CHECK = effective_project_admin (only project-admins
+-- and global_admins can change roles).
+-- ============================================================================
+
+DROP POLICY IF EXISTS project_teams_update ON paliad.project_teams;
+
+CREATE POLICY project_teams_update
+    ON paliad.project_teams FOR UPDATE
+    USING (paliad.effective_project_admin(auth.uid(), project_id))
+    WITH CHECK (paliad.effective_project_admin(auth.uid(), project_id));
+
+-- ============================================================================
+-- 4. project_teams_insert policy: self-join OR effective_project_admin.
+--
+-- The self-join branch (user_id = auth.uid()) preserves the legacy
+-- creator-as-lead INSERT in ProjectService.Create: the project creator
+-- auto-joins their own project with responsibility='lead' before any
+-- admin exists. Without this branch, the first-ever team row on a new
+-- project would fail because no admin has been granted yet.
+--
+-- For all other inserts (adding other users), the caller must be an
+-- effective_project_admin on the target project.
+-- ============================================================================
+
+DROP POLICY IF EXISTS project_teams_insert ON paliad.project_teams;
+
+CREATE POLICY project_teams_insert
+    ON paliad.project_teams FOR INSERT
+    WITH CHECK (
+        user_id = auth.uid()
+        OR paliad.effective_project_admin(auth.uid(), project_id)
+    );
+
+-- ============================================================================
+-- 5. project_teams_delete policy: self / global_admin / effective_project_admin.
+--
+-- Additive: self-remove + global_admin still work; project-admin can now
+-- also remove members.
+-- ============================================================================
+
+DROP POLICY IF EXISTS project_teams_delete ON paliad.project_teams;
+
+CREATE POLICY project_teams_delete
+    ON paliad.project_teams FOR DELETE
+    USING (
+        paliad.can_see_project(project_id)
+        AND (
+            user_id = auth.uid()
+            OR EXISTS (
+                SELECT 1 FROM paliad.users u
+                 WHERE u.id = auth.uid()
+                   AND u.global_role = 'global_admin'
+            )
+            OR paliad.effective_project_admin(auth.uid(), project_id)
+        )
+    );
diff --git a/internal/handlers/handlers.go b/internal/handlers/handlers.go
index 32e6b2c..a60fdaf 100644
--- a/internal/handlers/handlers.go
+++ b/internal/handlers/handlers.go
@@ -325,6 +325,7 @@ func Register(mux *http.ServeMux, client *auth.Client, giteaAPIToken string, svc
 	// Team membership endpoints for Project detail "Team" tab.
 	protected.HandleFunc("GET /api/projects/{id}/team", handleListProjectTeam)
 	protected.HandleFunc("POST /api/projects/{id}/team", handleAddProjectTeamMember)
+	protected.HandleFunc("PATCH /api/projects/{id}/team/{user_id}", handleChangeProjectTeamMemberResponsibility)
 	protected.HandleFunc("DELETE /api/projects/{id}/team/{user_id}", handleRemoveProjectTeamMember)
 	// t-paliad-139 — sub-team aggregation surfaces for the Team tab.
 	protected.HandleFunc("GET /api/projects/{id}/team/derived", handleListDerivedTeam)
diff --git a/internal/handlers/projects.go b/internal/handlers/projects.go
index 638d6c1..ed4ebdf 100644
--- a/internal/handlers/projects.go
+++ b/internal/handlers/projects.go
@@ -11,6 +11,7 @@ import (
 	"github.com/google/uuid"
 
 	"mgit.msbls.de/m/paliad/internal/auth"
+	"mgit.msbls.de/m/paliad/internal/models"
 	"mgit.msbls.de/m/paliad/internal/services"
 )
 
@@ -104,6 +105,8 @@ func writeServiceError(w http.ResponseWriter, err error) {
 		})
 	case errors.Is(err, services.ErrEventTypeSlugTaken):
 		writeJSON(w, http.StatusConflict, map[string]string{"error": err.Error()})
+	case errors.Is(err, services.ErrLastProjectAdmin):
+		writeJSON(w, http.StatusConflict, map[string]string{"error": err.Error()})
 	default:
 		log.Printf("ERROR service: %v", err)
 		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "internal error"})
@@ -319,7 +322,24 @@ func handleGetProject(w http.ResponseWriter, r *http.Request) {
 		writeServiceError(w, err)
 		return
 	}
-	writeJSON(w, http.StatusOK, p)
+	// t-paliad-223: piggyback effective_project_admin onto the project
+	// payload so the frontend can drive the inline role-edit affordance
+	// without a second round-trip. JSON-merge via a small wrapper that
+	// embeds the existing Project shape — every existing caller keeps
+	// reading the same fields and gains effective_admin as additive.
+	effAdmin, err := dbSvc.team.IsEffectiveProjectAdmin(r.Context(), uid, id)
+	if err != nil {
+		writeServiceError(w, err)
+		return
+	}
+	type projectWithPermissions struct {
+		*models.Project
+		EffectiveAdmin bool `json:"effective_admin"`
+	}
+	writeJSON(w, http.StatusOK, projectWithPermissions{
+		Project:        p,
+		EffectiveAdmin: effAdmin,
+	})
 }
 
 // GET /api/projects/{id}/children — direct children.
diff --git a/internal/handlers/teams.go b/internal/handlers/teams.go
index e520f57..d1e4d70 100644
--- a/internal/handlers/teams.go
+++ b/internal/handlers/teams.go
@@ -93,6 +93,53 @@ func handleListMembershipsIndex(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, rows)
 }
 
+// PATCH /api/projects/{id}/team/{user_id} — change a direct member's
+// responsibility. Body: {"responsibility": "<admin|lead|member|observer|external>"}.
+//
+// Authorisation is RLS-enforced (project_teams_update gated on
+// effective_project_admin in mig 111). Non-admins get a pq permission
+// error from the UPDATE; we surface that as 404 to avoid leaking that
+// the row exists. The last-admin guard runs inside the service tx and
+// returns ErrLastProjectAdmin (mapped to 409 by writeServiceError).
+func handleChangeProjectTeamMemberResponsibility(w http.ResponseWriter, r *http.Request) {
+	if !requireDB(w) {
+		return
+	}
+	uid, ok := requireUser(w, r)
+	if !ok {
+		return
+	}
+	projectID, err := uuid.Parse(r.PathValue("id"))
+	if err != nil {
+		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid project id"})
+		return
+	}
+	userID, err := uuid.Parse(r.PathValue("user_id"))
+	if err != nil {
+		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid user id"})
+		return
+	}
+	var body struct {
+		Responsibility string `json:"responsibility"`
+	}
+	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid JSON"})
+		return
+	}
+	m, err := dbSvc.team.ChangeResponsibility(r.Context(), uid, projectID, userID, body.Responsibility)
+	if err != nil {
+		if errors.Is(err, sql.ErrNoRows) {
+			writeJSON(w, http.StatusNotFound, map[string]string{
+				"error": "no direct membership found",
+			})
+			return
+		}
+		writeServiceError(w, err)
+		return
+	}
+	writeJSON(w, http.StatusOK, m)
+}
+
 // DELETE /api/projects/{id}/team/{user_id} — remove a direct member.
 // Inherited memberships can't be removed at the child level.
 func handleRemoveProjectTeamMember(w http.ResponseWriter, r *http.Request) {
diff --git a/internal/services/approval_levels.go b/internal/services/approval_levels.go
index 57a6df6..c4c04bc 100644
--- a/internal/services/approval_levels.go
+++ b/internal/services/approval_levels.go
@@ -25,7 +25,14 @@ const (
 
 // Project-level responsibility values on paliad.project_teams.responsibility.
 // Open the ladder gate (lead/member) or close it (observer/external).
+//
+// ResponsibilityAdmin (t-paliad-223) is orthogonal to the approval gate —
+// it grants role-edit authority on the project + descendants via the
+// paliad.effective_project_admin predicate, but does NOT by itself open
+// the 4-Augen approval gate. An Admin who has no profession set is still
+// not an approver. Use responsibilityOpensGate to test the approval axis.
 const (
+	ResponsibilityAdmin    = "admin"
 	ResponsibilityLead     = "lead"
 	ResponsibilityMember   = "member"
 	ResponsibilityObserver = "observer"
@@ -143,7 +150,7 @@ func IsValidProfession(p string) bool {
 // recognised project-responsibility enum values. Used by TeamService.
 func IsValidResponsibility(r string) bool {
 	switch r {
-	case ResponsibilityLead, ResponsibilityMember,
+	case ResponsibilityAdmin, ResponsibilityLead, ResponsibilityMember,
 		ResponsibilityObserver, ResponsibilityExternal:
 		return true
 	}
diff --git a/internal/services/approval_service_test.go b/internal/services/approval_service_test.go
index d8dbf96..e9ea71f 100644
--- a/internal/services/approval_service_test.go
+++ b/internal/services/approval_service_test.go
@@ -190,7 +190,8 @@ func TestIsValidProfession(t *testing.T) {
 }
 
 func TestIsValidResponsibility(t *testing.T) {
-	for _, r := range []string{"lead", "member", "observer", "external"} {
+	// t-paliad-223 added 'admin'; the four legacy values stay valid.
+	for _, r := range []string{"admin", "lead", "member", "observer", "external"} {
 		t.Run(r, func(t *testing.T) {
 			if !IsValidResponsibility(r) {
 				t.Errorf("IsValidResponsibility(%q) must be true", r)
@@ -206,6 +207,30 @@ func TestIsValidResponsibility(t *testing.T) {
 	}
 }
 
+// t-paliad-223: admin maps to legacy 'lead' for the deprecated shadow
+// column. The other mappings are unchanged from t-paliad-148. Pin them
+// so a future refactor doesn't silently flip them.
+func TestLegacyRoleFromResponsibility(t *testing.T) {
+	cases := []struct {
+		in, want string
+	}{
+		{ResponsibilityAdmin, "lead"},
+		{ResponsibilityLead, "lead"},
+		{ResponsibilityObserver, "observer"},
+		{ResponsibilityExternal, "local_counsel"},
+		{ResponsibilityMember, "associate"},
+		{"", "associate"}, // unknown / empty falls through to associate
+	}
+	for _, c := range cases {
+		t.Run(c.in, func(t *testing.T) {
+			got := legacyRoleFromResponsibility(c.in)
+			if got != c.want {
+				t.Errorf("legacyRoleFromResponsibility(%q) = %q, want %q", c.in, got, c.want)
+			}
+		})
+	}
+}
+
 func TestApprovalEventType(t *testing.T) {
 	cases := []struct {
 		entity, step, want string
diff --git a/internal/services/project_service.go b/internal/services/project_service.go
index 5fec303..6041093 100644
--- a/internal/services/project_service.go
+++ b/internal/services/project_service.go
@@ -44,6 +44,12 @@ var (
 	ErrForbidden = errors.New("forbidden")
 	// ErrInvalidInput signals a bad request (empty required field etc.).
 	ErrInvalidInput = errors.New("invalid input")
+	// ErrLastProjectAdmin guards demoting / removing the last remaining
+	// effective_project_admin from a project + its ancestor chain. t-paliad-223
+	// invariant: every project should keep at least one admin somewhere in
+	// its ancestor chain so a non-global-admin can still manage the team.
+	// Handlers map to 409 Conflict.
+	ErrLastProjectAdmin = errors.New("cannot remove last project admin from project + ancestors")
 	// ErrInvalidProceedingTypeCategory signals that the caller supplied
 	// a proceeding_type_id pointing at a non-fristenrechner-category row.
 	// Phase 3 Slice 5 soft-merge (t-paliad-186, design §3.F): only
diff --git a/internal/services/team_service.go b/internal/services/team_service.go
index a989826..8a23041 100644
--- a/internal/services/team_service.go
+++ b/internal/services/team_service.go
@@ -13,6 +13,7 @@ package services
 import (
 	"context"
 	"database/sql"
+	"errors"
 	"fmt"
 	"strings"
 
@@ -80,9 +81,13 @@ func (s *TeamService) AddMember(ctx context.Context, callerID, projectID, userID
 // column. external → 'local_counsel' is intentionally narrower than the
 // new enum (loses the expert distinction); we accept that for the short
 // transition window.
+//
+// ResponsibilityAdmin (t-paliad-223) maps to legacy 'lead' — the closest
+// legacy match. The legacy column is dead either way; the mapping is
+// purely cosmetic until the column is dropped.
 func legacyRoleFromResponsibility(r string) string {
 	switch r {
-	case ResponsibilityLead:
+	case ResponsibilityAdmin, ResponsibilityLead:
 		return "lead"
 	case ResponsibilityObserver:
 		return "observer"
@@ -99,11 +104,43 @@ func legacyRoleFromResponsibility(r string) string {
 // RemoveMember deletes a direct team membership. Inherited memberships (from
 // ancestors) can't be removed at the child level — the caller must remove
 // the ancestor row to break the inheritance.
+//
+// t-paliad-223 last-admin guard: if the row being removed carries
+// responsibility='admin', refuse when it would leave the project + its
+// ancestor chain with zero admins. Wrapped in a tx so the count + delete
+// are atomic; ErrLastProjectAdmin bubbles up unchanged for the handler
+// to map to 409.
 func (s *TeamService) RemoveMember(ctx context.Context, callerID, projectID, userID uuid.UUID) error {
 	if _, err := s.projects.GetByID(ctx, callerID, projectID); err != nil {
 		return err
 	}
-	res, err := s.db.ExecContext(ctx,
+
+	tx, err := s.db.BeginTxx(ctx, nil)
+	if err != nil {
+		return fmt.Errorf("begin tx: %w", err)
+	}
+	defer tx.Rollback()
+
+	// Look up the row first so we know whether to run the guard.
+	var existing models.ProjectTeamMember
+	if err := tx.GetContext(ctx, &existing,
+		`SELECT id, project_id, user_id, role, responsibility, inherited, added_by, created_at
+		   FROM paliad.project_teams
+		  WHERE project_id = $1 AND user_id = $2 AND inherited = false`,
+		projectID, userID); err != nil {
+		if errors.Is(err, sql.ErrNoRows) {
+			return sql.ErrNoRows
+		}
+		return fmt.Errorf("lookup team member: %w", err)
+	}
+
+	if existing.Responsibility == ResponsibilityAdmin {
+		if err := assertProjectKeepsAdmin(ctx, tx, projectID, userID); err != nil {
+			return err
+		}
+	}
+
+	res, err := tx.ExecContext(ctx,
 		`DELETE FROM paliad.project_teams
 		  WHERE project_id = $1 AND user_id = $2 AND inherited = false`,
 		projectID, userID)
@@ -113,6 +150,104 @@ func (s *TeamService) RemoveMember(ctx context.Context, callerID, projectID, use
 	if rows, _ := res.RowsAffected(); rows == 0 {
 		return sql.ErrNoRows
 	}
+	if err := tx.Commit(); err != nil {
+		return fmt.Errorf("commit remove team member: %w", err)
+	}
+	return nil
+}
+
+// ChangeResponsibility updates a direct team member's responsibility.
+// RLS enforces the authorisation (only effective_project_admin can pass
+// the project_teams_update WITH CHECK); this method handles validation
+// + the last-admin guard when the change is AWAY from admin.
+//
+// Inherited rows can't be edited here — the caller must change the
+// ancestor row. Trying to update an inherited row returns sql.ErrNoRows.
+func (s *TeamService) ChangeResponsibility(ctx context.Context, callerID, projectID, userID uuid.UUID, newResponsibility string) (*models.ProjectTeamMember, error) {
+	if !IsValidResponsibility(newResponsibility) {
+		return nil, fmt.Errorf("%w: invalid responsibility %q", ErrInvalidInput, newResponsibility)
+	}
+	if _, err := s.projects.GetByID(ctx, callerID, projectID); err != nil {
+		return nil, err
+	}
+
+	tx, err := s.db.BeginTxx(ctx, nil)
+	if err != nil {
+		return nil, fmt.Errorf("begin tx: %w", err)
+	}
+	defer tx.Rollback()
+
+	// Read current row so we know whether the guard needs to fire and so
+	// we can short-circuit no-op writes.
+	var current models.ProjectTeamMember
+	if err := tx.GetContext(ctx, &current,
+		`SELECT id, project_id, user_id, role, responsibility, inherited, added_by, created_at
+		   FROM paliad.project_teams
+		  WHERE project_id = $1 AND user_id = $2 AND inherited = false`,
+		projectID, userID); err != nil {
+		if errors.Is(err, sql.ErrNoRows) {
+			return nil, sql.ErrNoRows
+		}
+		return nil, fmt.Errorf("lookup team member: %w", err)
+	}
+	if current.Responsibility == newResponsibility {
+		// No-op; commit the empty tx so caller still gets a typed result.
+		_ = tx.Commit()
+		return &current, nil
+	}
+
+	if current.Responsibility == ResponsibilityAdmin && newResponsibility != ResponsibilityAdmin {
+		if err := assertProjectKeepsAdmin(ctx, tx, projectID, userID); err != nil {
+			return nil, err
+		}
+	}
+
+	legacyRole := legacyRoleFromResponsibility(newResponsibility)
+
+	var updated models.ProjectTeamMember
+	if err := tx.GetContext(ctx, &updated,
+		`UPDATE paliad.project_teams
+		    SET responsibility = $3, role = $4
+		  WHERE project_id = $1 AND user_id = $2 AND inherited = false
+		RETURNING id, project_id, user_id, role, responsibility, inherited, added_by, created_at`,
+		projectID, userID, newResponsibility, legacyRole); err != nil {
+		if errors.Is(err, sql.ErrNoRows) {
+			return nil, sql.ErrNoRows
+		}
+		return nil, fmt.Errorf("change responsibility: %w", err)
+	}
+	if err := tx.Commit(); err != nil {
+		return nil, fmt.Errorf("commit change responsibility: %w", err)
+	}
+	return &updated, nil
+}
+
+// assertProjectKeepsAdmin returns ErrLastProjectAdmin iff removing the
+// (projectID, excludeUserID) admin row would leave the project's ancestor
+// chain (project + every ancestor up to the root) with zero admins.
+//
+// Counts admin rows on every row in the ancestor chain, excluding the row
+// being changed. Uses the same ltree path-walk as paliad.can_see_project.
+//
+// This is a service-layer guard; we don't put it in an RLS WITH CHECK
+// because the count happens post-mutation in a typical WITH CHECK, and
+// the natural place to express it is here where we already hold the tx.
+func assertProjectKeepsAdmin(ctx context.Context, tx *sqlx.Tx, projectID, excludeUserID uuid.UUID) error {
+	var remaining int
+	if err := tx.GetContext(ctx, &remaining, `
+		SELECT count(*)
+		  FROM paliad.projects p
+		  JOIN paliad.project_teams pt
+		    ON pt.project_id = ANY(string_to_array(p.path, '.')::uuid[])
+		   AND pt.responsibility = 'admin'
+		 WHERE p.id = $1
+		   AND NOT (pt.project_id = $1 AND pt.user_id = $2)
+	`, projectID, excludeUserID); err != nil {
+		return fmt.Errorf("count remaining admins: %w", err)
+	}
+	if remaining == 0 {
+		return ErrLastProjectAdmin
+	}
 	return nil
 }
 
@@ -259,6 +394,27 @@ func (s *TeamService) ListMembershipsIndex(ctx context.Context, callerID uuid.UU
 	return out, nil
 }
 
+// IsEffectiveProjectAdmin reports whether the user is global_admin OR has
+// responsibility='admin' on the project itself or any ancestor in the
+// materialised ltree path.
+//
+// Delegates to paliad.effective_project_admin SQL (t-paliad-223 mig 111).
+// The function is STABLE SECURITY DEFINER so it sees rows regardless of
+// the caller's RLS context — the boolean answer doesn't leak data.
+//
+// Used by the project-detail handler to drive the inline-select affordance
+// in the team panel: only effective_project_admins see the editable
+// <select>; everyone else sees a read-only <span>.
+func (s *TeamService) IsEffectiveProjectAdmin(ctx context.Context, userID, projectID uuid.UUID) (bool, error) {
+	var b bool
+	if err := s.db.GetContext(ctx, &b,
+		`SELECT paliad.effective_project_admin($1, $2)`,
+		userID, projectID); err != nil {
+		return false, fmt.Errorf("effective_project_admin: %w", err)
+	}
+	return b, nil
+}
+
 // ---------------------------------------------------------------------------
 
 // pathToIDStrings splits a materialised path into its UUID labels as strings,