feat: give plugins their own settings and one settings screen

src/backend/database/db/index.ts

@@ -751,6 +751,21 @@ async function initializeCompleteDatabase(): Promise<void> {
         FOREIGN KEY (plugin_id) REFERENCES plugins (id) ON DELETE CASCADE
     );
 
+    CREATE TABLE IF NOT EXISTS plugin_settings (
+        id INTEGER PRIMARY KEY AUTOINCREMENT,
+        plugin_id TEXT NOT NULL,
+        scope TEXT NOT NULL,
+        scope_id TEXT,
+        key TEXT NOT NULL,
+        value TEXT,
+        encrypted INTEGER NOT NULL DEFAULT 0,
+        updated_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP,
+        UNIQUE (plugin_id, scope, scope_id, key),
+        FOREIGN KEY (plugin_id) REFERENCES plugins (id) ON DELETE CASCADE
+    );
+
+    CREATE INDEX IF NOT EXISTS idx_plugin_settings_plugin_scope ON plugin_settings (plugin_id, scope);
+
     CREATE TABLE IF NOT EXISTS rbac_known_permissions (
         id INTEGER PRIMARY KEY AUTOINCREMENT,
         permission TEXT NOT NULL,

src/backend/database/db/schema.mysql.ts

@@ -2252,6 +2252,49 @@ export const pluginStorage = mysqlTable(
   ],
 );
 
+/**
+ * Values for the settings fields a plugin declares in contributes.settings.
+ *
+ * scope_id is polymorphic: null for admin scope, a user id for user scope, a
+ * host id rendered as text for host scope. That is why it carries no foreign
+ * key - one column cannot point at two tables - so the user and host delete
+ * paths remove these rows explicitly. Cascading with the plugin is a real FK,
+ * because uninstalling should leave nothing behind.
+ *
+ * Secret fields are encrypted with the system key before they land here, and
+ * `encrypted` records which rows that applies to so a read knows to decrypt.
+ */
+export const pluginSettings = mysqlTable(
+  "plugin_settings",
+  {
+    id: int("id").autoincrement().primaryKey(),
+    pluginId: varchar("plugin_id", { length: 255 })
+      .notNull()
+      .references(() => plugins.id, { onDelete: "cascade" }),
+    /** admin | user | host */
+    scope: varchar("scope", { length: 255 }).notNull(),
+    scopeId: varchar("scope_id", { length: 255 }),
+    key: varchar("key", { length: 255 }).notNull(),
+    /** JSON-encoded, so a field keeps its declared type across a round trip. */
+    value: text("value"),
+    encrypted: boolean("encrypted")
+      .notNull()
+      .default(false),
+    updatedAt: varchar("updated_at", { length: 255 })
+      .notNull()
+      .default(sql`(CURRENT_TIMESTAMP)`),
+  },
+  (table) => [
+    uniqueIndex("idx_plugin_settings_scope_key").on(
+      table.pluginId,
+      table.scope,
+      table.scopeId,
+      table.key,
+    ),
+    index("idx_plugin_settings_plugin_scope").on(table.pluginId, table.scope),
+  ],
+);
+
 /**
  * Which of a plugin's migrations have been applied.
  *

src/backend/database/db/schema.pg.ts

@@ -2253,6 +2253,49 @@ export const pluginStorage = pgTable(
   ],
 );
 
+/**
+ * Values for the settings fields a plugin declares in contributes.settings.
+ *
+ * scope_id is polymorphic: null for admin scope, a user id for user scope, a
+ * host id rendered as text for host scope. That is why it carries no foreign
+ * key - one column cannot point at two tables - so the user and host delete
+ * paths remove these rows explicitly. Cascading with the plugin is a real FK,
+ * because uninstalling should leave nothing behind.
+ *
+ * Secret fields are encrypted with the system key before they land here, and
+ * `encrypted` records which rows that applies to so a read knows to decrypt.
+ */
+export const pluginSettings = pgTable(
+  "plugin_settings",
+  {
+    id: serial("id").primaryKey(),
+    pluginId: varchar("plugin_id", { length: 255 })
+      .notNull()
+      .references(() => plugins.id, { onDelete: "cascade" }),
+    /** admin | user | host */
+    scope: varchar("scope", { length: 255 }).notNull(),
+    scopeId: varchar("scope_id", { length: 255 }),
+    key: varchar("key", { length: 255 }).notNull(),
+    /** JSON-encoded, so a field keeps its declared type across a round trip. */
+    value: text("value"),
+    encrypted: boolean("encrypted")
+      .notNull()
+      .default(false),
+    updatedAt: varchar("updated_at", { length: 255 })
+      .notNull()
+      .default(sql`CURRENT_TIMESTAMP`),
+  },
+  (table) => [
+    uniqueIndex("idx_plugin_settings_scope_key").on(
+      table.pluginId,
+      table.scope,
+      table.scopeId,
+      table.key,
+    ),
+    index("idx_plugin_settings_plugin_scope").on(table.pluginId, table.scope),
+  ],
+);
+
 /**
  * Which of a plugin's migrations have been applied.
  *

src/backend/database/db/schema.ts

@@ -2251,6 +2251,49 @@ export const pluginStorage = sqliteTable(
   ],
 );
 
+/**
+ * Values for the settings fields a plugin declares in contributes.settings.
+ *
+ * scope_id is polymorphic: null for admin scope, a user id for user scope, a
+ * host id rendered as text for host scope. That is why it carries no foreign
+ * key - one column cannot point at two tables - so the user and host delete
+ * paths remove these rows explicitly. Cascading with the plugin is a real FK,
+ * because uninstalling should leave nothing behind.
+ *
+ * Secret fields are encrypted with the system key before they land here, and
+ * `encrypted` records which rows that applies to so a read knows to decrypt.
+ */
+export const pluginSettings = sqliteTable(
+  "plugin_settings",
+  {
+    id: integer("id").primaryKey({ autoIncrement: true }),
+    pluginId: text("plugin_id")
+      .notNull()
+      .references(() => plugins.id, { onDelete: "cascade" }),
+    /** admin | user | host */
+    scope: text("scope").notNull(),
+    scopeId: text("scope_id"),
+    key: text("key").notNull(),
+    /** JSON-encoded, so a field keeps its declared type across a round trip. */
+    value: text("value"),
+    encrypted: integer("encrypted", { mode: "boolean" })
+      .notNull()
+      .default(false),
+    updatedAt: text("updated_at")
+      .notNull()
+      .default(sql`CURRENT_TIMESTAMP`),
+  },
+  (table) => [
+    uniqueIndex("idx_plugin_settings_scope_key").on(
+      table.pluginId,
+      table.scope,
+      table.scopeId,
+      table.key,
+    ),
+    index("idx_plugin_settings_plugin_scope").on(table.pluginId, table.scope),
+  ],
+);
+
 /**
  * Which of a plugin's migrations have been applied.
  *

src/backend/database/repositories/factory.ts

@@ -34,6 +34,7 @@ import { OpenTabRepository } from "./open-tab-repository.js";
 import { OpksshTokenRepository } from "./opkssh-token-repository.js";
 import { PluginRepository } from "./plugin-repository.js";
 import { PluginStorageRepository } from "./plugin-storage-repository.js";
+import { PluginSettingsRepository } from "./plugin-settings-repository.js";
 import { PluginMigrationRepository } from "./plugin-migration-repository.js";
 import { PluginPermissionGrantRepository } from "./plugin-permission-grant-repository.js";
 import { PluginRegistryRepository } from "./plugin-registry-repository.js";
@@ -395,6 +396,13 @@ export function createCurrentPluginStorageRepository(): PluginStorageRepository
   );
 }
 
+export function createCurrentPluginSettingsRepository(): PluginSettingsRepository {
+  return new PluginSettingsRepository(
+    createCurrentRepositoryContext(),
+    createCurrentRepositoryWriteHook("plugin_settings_repository_write"),
+  );
+}
+
 export function createCurrentPluginMigrationRepository(): PluginMigrationRepository {
   return new PluginMigrationRepository(
     createCurrentRepositoryContext(),

src/backend/database/repositories/host-repository.ts

@@ -1,6 +1,6 @@
 import { and, eq, inArray, sql } from "drizzle-orm";
 import { randomUUID } from "crypto";
-import { hostAccess, hosts } from "../db/schema.js";
+import { hostAccess, hosts, pluginSettings } from "../db/schema.js";
 import type { DatabaseContext } from "./database-context.js";
 import { DataCrypto } from "../../utils/data-crypto.js";
 import { rowsAffected } from "./mutation-result.js";
@@ -338,6 +338,25 @@ export class HostRepository {
   }
 
   async deleteByUserId(userId: string): Promise<number> {
+    // Bulk path, so it never passes through deleteAccessForHost: clear the
+    // host-scope plugin settings for these hosts before the rows go.
+    const owned = await this.context.drizzle
+      .select({ id: hosts.id })
+      .from(hosts)
+      .where(eq(hosts.userId, userId));
+
+    if (owned.length > 0) {
+      await this.context.drizzle.delete(pluginSettings).where(
+        and(
+          eq(pluginSettings.scope, "host"),
+          inArray(
+            pluginSettings.scopeId,
+            owned.map((row) => String(row.id)),
+          ),
+        ),
+      );
+    }
+
     const result = await this.context.drizzle
       .delete(hosts)
       .where(eq(hosts.userId, userId));
@@ -350,6 +369,18 @@ export class HostRepository {
   }
 
   async deleteAccessForHost(hostId: number): Promise<number> {
+    // plugin_settings.scope_id is polymorphic, so it has no foreign key to
+    // ssh_data and the engine will not cascade it. Cleared alongside the
+    // access rows, which every host delete path already goes through.
+    await this.context.drizzle
+      .delete(pluginSettings)
+      .where(
+        and(
+          eq(pluginSettings.scope, "host"),
+          eq(pluginSettings.scopeId, String(hostId)),
+        ),
+      );
+
     const result = await this.context.drizzle
       .delete(hostAccess)
       .where(eq(hostAccess.hostId, hostId));

src/backend/database/repositories/plugin-settings-repository.ts

@@ -0,0 +1,191 @@
+import { and, eq, inArray, isNull } from "drizzle-orm";
+import { pluginSettings } from "../db/schema.js";
+import type { DatabaseContext } from "./database-context.js";
+import { rowsAffected } from "./mutation-result.js";
+import { insertReturning, updateReturning } from "./returning.js";
+
+export type PluginSettingsRecord = typeof pluginSettings.$inferSelect;
+
+export type PluginSettingsScope = "admin" | "user" | "host";
+
+/**
+ * Values behind ctx.settings and the /plugins/:id/settings routes.
+ *
+ * scope_id is null for admin scope, so every lookup has to use IS NULL rather
+ * than = NULL: SQL equality against null never matches, which would make an
+ * admin setting look unset no matter how often it was written.
+ */
+export class PluginSettingsRepository {
+  constructor(
+    private readonly context: DatabaseContext,
+    private readonly onWrite?: () => void | Promise<void>,
+  ) {}
+
+  private scopeMatch(
+    pluginId: string,
+    scope: PluginSettingsScope,
+    scopeId: string | null,
+  ) {
+    return and(
+      eq(pluginSettings.pluginId, pluginId),
+      eq(pluginSettings.scope, scope),
+      scopeId === null
+        ? isNull(pluginSettings.scopeId)
+        : eq(pluginSettings.scopeId, scopeId),
+    );
+  }
+
+  async get(
+    pluginId: string,
+    scope: PluginSettingsScope,
+    scopeId: string | null,
+    key: string,
+  ): Promise<PluginSettingsRecord | null> {
+    const rows = await this.context.drizzle
+      .select()
+      .from(pluginSettings)
+      .where(
+        and(
+          this.scopeMatch(pluginId, scope, scopeId),
+          eq(pluginSettings.key, key),
+        ),
+      )
+      .limit(1);
+
+    return rows[0] ?? null;
+  }
+
+  async getAll(
+    pluginId: string,
+    scope: PluginSettingsScope,
+    scopeId: string | null,
+  ): Promise<PluginSettingsRecord[]> {
+    return this.context.drizzle
+      .select()
+      .from(pluginSettings)
+      .where(this.scopeMatch(pluginId, scope, scopeId));
+  }
+
+  /**
+   * Every row for a set of scope ids, in one query.
+   *
+   * The host list would otherwise run one query per host, which is the shape
+   * that made other list endpoints slow at a few hundred hosts.
+   */
+  async getAllForScopeIds(
+    scope: PluginSettingsScope,
+    scopeIds: string[],
+  ): Promise<PluginSettingsRecord[]> {
+    if (scopeIds.length === 0) return [];
+
+    return this.context.drizzle
+      .select()
+      .from(pluginSettings)
+      .where(
+        and(
+          eq(pluginSettings.scope, scope),
+          inArray(pluginSettings.scopeId, scopeIds),
+        ),
+      );
+  }
+
+  async set(
+    pluginId: string,
+    scope: PluginSettingsScope,
+    scopeId: string | null,
+    key: string,
+    value: string | null,
+    encrypted = false,
+    now = new Date().toISOString(),
+  ): Promise<void> {
+    const where = and(
+      this.scopeMatch(pluginId, scope, scopeId),
+      eq(pluginSettings.key, key),
+    )!;
+
+    const existing = await this.context.drizzle
+      .select()
+      .from(pluginSettings)
+      .where(where)
+      .limit(1);
+
+    if (existing[0]) {
+      await updateReturning(
+        this.context,
+        pluginSettings,
+        { value, encrypted, updatedAt: now },
+        where,
+      );
+    } else {
+      await insertReturning(this.context, pluginSettings, {
+        pluginId,
+        scope,
+        scopeId,
+        key,
+        value,
+        encrypted,
+        updatedAt: now,
+      });
+    }
+
+    await this.afterWrite();
+  }
+
+  async delete(
+    pluginId: string,
+    scope: PluginSettingsScope,
+    scopeId: string | null,
+    key: string,
+  ): Promise<boolean> {
+    const result = await this.context.drizzle
+      .delete(pluginSettings)
+      .where(
+        and(
+          this.scopeMatch(pluginId, scope, scopeId),
+          eq(pluginSettings.key, key),
+        ),
+      );
+
+    const affected = rowsAffected(result) > 0;
+    if (affected) await this.afterWrite();
+    return affected;
+  }
+
+  async deleteByPlugin(pluginId: string): Promise<number> {
+    const result = await this.context.drizzle
+      .delete(pluginSettings)
+      .where(eq(pluginSettings.pluginId, pluginId));
+
+    const affected = rowsAffected(result);
+    if (affected > 0) await this.afterWrite();
+    return affected;
+  }
+
+  /**
+   * Removes every plugin's rows for one user or host.
+   *
+   * scope_id carries no foreign key, so the user and host delete paths call
+   * this instead of relying on the engine to cascade.
+   */
+  async deleteByScope(
+    scope: PluginSettingsScope,
+    scopeId: string,
+  ): Promise<number> {
+    const result = await this.context.drizzle
+      .delete(pluginSettings)
+      .where(
+        and(
+          eq(pluginSettings.scope, scope),
+          eq(pluginSettings.scopeId, scopeId),
+        ),
+      );
+
+    const affected = rowsAffected(result);
+    if (affected > 0) await this.afterWrite();
+    return affected;
+  }
+
+  private async afterWrite(): Promise<void> {
+    await this.onWrite?.();
+  }
+}

src/backend/database/repositories/user-repository.ts

@@ -1,5 +1,5 @@
-import { asc, eq, inArray, like, sql } from "drizzle-orm";
-import { users } from "../db/schema.js";
+import { and, asc, eq, inArray, like, sql } from "drizzle-orm";
+import { pluginSettings, users } from "../db/schema.js";
 import type { DatabaseContext } from "./database-context.js";
 import {
   countValue,
@@ -199,6 +199,15 @@ export class UserRepository {
   }
 
   async delete(id: string): Promise<boolean> {
+    // plugin_settings.scope_id is polymorphic, so it carries no foreign key to
+    // users and the engine will not cascade it. Removed here rather than in a
+    // route so every caller that deletes a user is covered.
+    await this.context.drizzle
+      .delete(pluginSettings)
+      .where(
+        and(eq(pluginSettings.scope, "user"), eq(pluginSettings.scopeId, id)),
+      );
+
     const result = await this.context.drizzle
       .delete(users)
       .where(eq(users.id, id));

src/backend/database/routes/host-plugin-settings.ts

@@ -0,0 +1,130 @@
+/**
+ * The pluginSettings map attached to a host on its way out.
+ *
+ * Without this the host editor would need one request per plugin per host,
+ * which is the shape that makes a list of a few hundred hosts slow. One query
+ * covers the whole list instead.
+ *
+ * Kept out of transformHostResponse because that function is synchronous and
+ * shared by every host read path. Secrets are always redacted here, so nothing
+ * on this path has to decrypt and the async work stays in one place.
+ */
+
+import type { PluginManifest } from "@termix/plugin-sdk/manifest";
+import { createCurrentPluginSettingsRepository } from "../repositories/factory.js";
+import type { PluginSettingsRecord } from "../repositories/plugin-settings-repository.js";
+import { declaredFields, resolveFieldValue } from "../../plugins/settings.js";
+import { getPluginRuntime } from "../../plugins/index.js";
+import { sshLogger } from "../../utils/logger.js";
+
+export type HostPluginSettings = Record<string, Record<string, unknown>>;
+
+/** Enabled plugins that declare host-scope settings, with their manifests. */
+function hostSettingsPlugins(): PluginManifest[] {
+  try {
+    const { loader } = getPluginRuntime();
+    return loader
+      .list()
+      .filter((plugin) => plugin.state === "active")
+      .map((plugin) => plugin.manifest)
+      .filter(
+        (manifest): manifest is PluginManifest =>
+          !!manifest && !!manifest.contributes?.settings?.host,
+      );
+  } catch {
+    // The runtime is not up in every context that renders a host.
+    return [];
+  }
+}
+
+/**
+ * Builds the map for a set of hosts in one query.
+ *
+ * Returns an empty map when no enabled plugin declares host settings, so the
+ * common case costs nothing.
+ */
+export async function loadHostPluginSettings(
+  hostIds: number[],
+): Promise<Map<number, HostPluginSettings>> {
+  const result = new Map<number, HostPluginSettings>();
+  const manifests = hostSettingsPlugins();
+  if (manifests.length === 0 || hostIds.length === 0) return result;
+
+  let rows: PluginSettingsRecord[] = [];
+  try {
+    rows = await createCurrentPluginSettingsRepository().getAllForScopeIds(
+      "host",
+      hostIds.map(String),
+    );
+  } catch (error) {
+    // A host list must not fail because a settings read did.
+    sshLogger.warn("Failed to load host plugin settings", {
+      operation: "host_plugin_settings",
+      error: error instanceof Error ? error.message : String(error),
+    });
+    return result;
+  }
+
+  const byHostAndPlugin = new Map<string, PluginSettingsRecord[]>();
+  for (const row of rows) {
+    const key = `${row.scopeId}:${row.pluginId}`;
+    const list = byHostAndPlugin.get(key);
+    if (list) list.push(row);
+    else byHostAndPlugin.set(key, [row]);
+  }
+
+  for (const hostId of hostIds) {
+    const perPlugin: HostPluginSettings = {};
+
+    for (const manifest of manifests) {
+      const fields = declaredFields(manifest, "host");
+      if (fields.length === 0) continue;
+
+      const stored = new Map(
+        (byHostAndPlugin.get(`${hostId}:${manifest.id}`) ?? []).map((row) => [
+          row.key,
+          row,
+        ]),
+      );
+
+      const values: Record<string, unknown> = {};
+      for (const field of fields) {
+        values[field.key] = await resolveFieldValue(
+          field,
+          stored.get(field.key),
+          { redactSecrets: true },
+        );
+      }
+      perPlugin[manifest.id] = values;
+    }
+
+    if (Object.keys(perPlugin).length > 0) result.set(hostId, perPlugin);
+  }
+
+  return result;
+}
+
+/** Attaches the map to already-transformed host objects, in place. */
+export function attachHostPluginSettings(
+  hosts: Record<string, unknown>[],
+  settings: Map<number, HostPluginSettings>,
+): void {
+  if (settings.size === 0) return;
+  for (const host of hosts) {
+    const hostId = Number(host.id);
+    const values = settings.get(hostId);
+    if (values) host.pluginSettings = values;
+  }
+}
+
+/** The single-host convenience wrapper. */
+export async function withHostPluginSettings(
+  host: Record<string, unknown>,
+): Promise<Record<string, unknown>> {
+  const hostId = Number(host.id);
+  if (!Number.isInteger(hostId)) return host;
+
+  const settings = await loadHostPluginSettings([hostId]);
+  const values = settings.get(hostId);
+  return values ? { ...host, pluginSettings: values } : host;
+}

src/backend/database/routes/host.ts

@@ -45,6 +45,11 @@ import {
   stripSensitiveFields,
   transformHostResponse,
 } from "./host-normalizers.js";
+import {
+  attachHostPluginSettings,
+  loadHostPluginSettings,
+  withHostPluginSettings,
+} from "./host-plugin-settings.js";
 import { validateParentHostId } from "./host-parent-validation.js";
 import { registerHostOpksshRoutes } from "./host-opkssh-routes.js";
 import { registerHostStepCaRoutes } from "./host-step-ca-routes.js";
@@ -1701,6 +1706,18 @@ router.get(
             )
           : stripSensitiveFields(host),
       );
+
+      // After sanitizing: the connect-level projection reduces a shared host
+      // to an allowlist, which would drop this again. One query for the list.
+      attachHostPluginSettings(
+        sanitized,
+        await loadHostPluginSettings(
+          sanitized
+            .map((host) => Number(host.id))
+            .filter((id) => Number.isInteger(id)),
+        ),
+      );
+
       res.json(sanitized);
     } catch (err) {
       sshLogger.error("Failed to fetch SSH hosts from database", err, {
@@ -1767,7 +1784,9 @@ router.get(
         const resolved =
           (await resolveHostCredentials(result, userId)) || result;
 
-        return res.json(stripSensitiveFields(resolved));
+        return res.json(
+          await withHostPluginSettings(stripSensitiveFields(resolved)),
+        );
       }
 
       // Not the owner: shared recipients get a sanitized view of the host.
@@ -1818,9 +1837,11 @@ router.get(
         (await resolveHostCredentials(sharedResult, userId)) || sharedResult;
 
       res.json(
-        sanitizeHostForRecipient(
-          resolvedSharedResult,
-          accessInfo.permissionLevel,
+        await withHostPluginSettings(
+          sanitizeHostForRecipient(
+            resolvedSharedResult,
+            accessInfo.permissionLevel,
+          ),
         ),
       );
     } catch (err) {

src/backend/database/routes/plugins.ts

@@ -14,9 +14,29 @@ import {
 } from "../repositories/factory.js";
 import { getPluginRuntime } from "../../plugins/index.js";
 import { invalidatePluginPermissionCache } from "../../plugins/permissions.js";
+import {
+  findField,
+  getAllSettings,
+  setSetting,
+  type PluginSettingsScope,
+} from "../../plugins/settings.js";
+import {
+  getAuditUsername,
+  getRequestMeta,
+  logAudit,
+} from "../../utils/audit-logger.js";
+import type {
+  PluginManifest,
+  PluginSettingsField,
+} from "@termix/plugin-sdk/manifest";
 
 const router = express.Router();
 
+/** A settings body is a flat object; an array or null is a client bug. */
+function isPlainBody(body: unknown): body is Record<string, unknown> {
+  return typeof body === "object" && body !== null && !Array.isArray(body);
+}
+
 const authManager = AuthManager.getInstance();
 const authenticateJWT = authManager.createAuthMiddleware();
 const permissionManager = PermissionManager.getInstance();
@@ -79,15 +99,18 @@ router.get("/", authenticateJWT, async (req: Request, res: Response) => {
 
       let contributes: unknown = null;
       let capabilities: string[] = [];
+      let icon: string | undefined;
       try {
         const manifest = JSON.parse(record.manifestJson) as {
           contributes?: unknown;
           capabilities?: unknown;
+          icon?: unknown;
         };
         contributes = manifest?.contributes ?? null;
         capabilities = Array.isArray(manifest?.capabilities)
           ? (manifest.capabilities as string[])
           : [];
+        icon = typeof manifest?.icon === "string" ? manifest.icon : undefined;
       } catch {
         contributes = null;
       }
@@ -99,6 +122,7 @@ router.get("/", authenticateJWT, async (req: Request, res: Response) => {
         enabled: record.state === "enabled",
         state: loaded?.state ?? record.state,
         contributes,
+        icon,
       };
 
       if (!canManage) return summary;
@@ -528,4 +552,535 @@ router.delete(
   },
 );
 
+/**
+ * Loads a plugin's manifest for the settings routes.
+ *
+ * Read from the loader rather than the database row so the fields a request is
+ * validated against are the ones the running build declares.
+ */
+async function loadManifestForSettings(
+  pluginId: string,
+): Promise<PluginManifest | null> {
+  const { loader } = getPluginRuntime();
+  const live = loader.get(pluginId);
+  if (live?.manifest) return live.manifest;
+
+  const record = await createCurrentPluginRepository().findById(pluginId);
+  if (!record) return null;
+  try {
+    return JSON.parse(record.manifestJson) as PluginManifest;
+  } catch {
+    return null;
+  }
+}
+
+/**
+ * Whether the caller may write a given field.
+ *
+ * Admin fields fall back to admin.plugins.manage, so a plugin that declares no
+ * permission of its own still cannot have its install-wide settings changed by
+ * an ordinary user. A field naming its own permission uses that instead.
+ */
+async function canWriteField(
+  userId: string,
+  manifest: PluginManifest,
+  scope: PluginSettingsScope,
+  field: PluginSettingsField,
+): Promise<boolean> {
+  // Admin scope always needs admin.plugins.manage. A field-level permission
+  // narrows who may write it; it never widens the scope's own gate, so a
+  // plugin cannot hand an ordinary user install-wide configuration by naming
+  // a permission that user happens to hold.
+  if (
+    scope === "admin" &&
+    !(await permissionManager.hasPermission(userId, "admin.plugins.manage"))
+  ) {
+    return false;
+  }
+
+  if (field.permission) {
+    const { resolvePermission } = await import("../../plugins/rbac.js");
+    return permissionManager.hasPermission(
+      userId,
+      resolvePermission(manifest, field.permission),
+    );
+  }
+
+  return true;
+}
+
+/** Applies a body of values to one scope, collecting per-field errors. */
+async function applySettings(
+  userId: string,
+  manifest: PluginManifest,
+  scope: PluginSettingsScope,
+  scopeId: string | null,
+  body: Record<string, unknown>,
+): Promise<Record<string, string>> {
+  const errors: Record<string, string> = {};
+
+  for (const [key, value] of Object.entries(body)) {
+    const field = findField(manifest, scope, key);
+    if (!field) {
+      errors[key] = "Not a settings field this plugin declares";
+      continue;
+    }
+    if (!(await canWriteField(userId, manifest, scope, field))) {
+      errors[key] = "You do not have permission to change this setting";
+      continue;
+    }
+
+    const error = await setSetting(manifest, scope, scopeId, key, value);
+    if (error) errors[key] = error;
+  }
+
+  return errors;
+}
+
+/**
+ * @openapi
+ * /plugins/{id}/settings/admin:
+ *   get:
+ *     summary: Read a plugin's install-wide settings
+ *     description: >
+ *       Returns every admin-scope field the plugin declares, with stored values
+ *       over declared defaults. Secret fields come back as { set: boolean } and
+ *       never carry their value, so a browser can render "configured" without
+ *       ever holding the secret.
+ *     tags:
+ *       - Plugins
+ *     parameters:
+ *       - in: path
+ *         name: id
+ *         required: true
+ *         schema:
+ *           type: string
+ *     responses:
+ *       200:
+ *         description: The plugin's admin settings.
+ *       403:
+ *         description: The caller lacks admin.plugins.manage.
+ *       404:
+ *         description: No such plugin.
+ */
+router.get(
+  "/:id/settings/admin",
+  authenticateJWT,
+  requireManagePlugins,
+  async (req: Request, res: Response) => {
+    const pluginId = String(req.params.id);
+    try {
+      const manifest = await loadManifestForSettings(pluginId);
+      if (!manifest) {
+        res.status(404).json({ error: "No such plugin" });
+        return;
+      }
+      const values = await getAllSettings(manifest, "admin", null, {
+        redactSecrets: true,
+      });
+      res.json({ id: pluginId, values });
+    } catch (error) {
+      databaseLogger.error(
+        `Failed to read admin settings for plugin ${pluginId}`,
+        error instanceof Error ? error : new Error(String(error)),
+        { operation: "plugin_settings_read" },
+      );
+      res.status(500).json({ error: "Failed to read the plugin's settings" });
+    }
+  },
+);
+
+/**
+ * @openapi
+ * /plugins/{id}/settings/admin:
+ *   put:
+ *     summary: Update a plugin's install-wide settings
+ *     description: >
+ *       Writes the given keys. Every value is validated against the field the
+ *       manifest declares, and a key the manifest never declared is rejected
+ *       rather than stored. Validation failures come back per field so a form
+ *       can show every problem at once. Sending a secret field back as
+ *       { set: true } leaves the stored value alone, so saving a form does not
+ *       clear a key it was never shown.
+ *     tags:
+ *       - Plugins
+ *     parameters:
+ *       - in: path
+ *         name: id
+ *         required: true
+ *         schema:
+ *           type: string
+ *     requestBody:
+ *       required: true
+ *       content:
+ *         application/json:
+ *           schema:
+ *             type: object
+ *     responses:
+ *       200:
+ *         description: The updated settings.
+ *       400:
+ *         description: One or more fields were rejected.
+ *       403:
+ *         description: The caller lacks admin.plugins.manage.
+ *       404:
+ *         description: No such plugin.
+ */
+router.put(
+  "/:id/settings/admin",
+  authenticateJWT,
+  requireManagePlugins,
+  async (req: Request, res: Response) => {
+    const pluginId = String(req.params.id);
+    const userId = (req as AuthenticatedRequest).userId as string;
+
+    if (!isPlainBody(req.body)) {
+      res.status(400).json({ error: "Body must be an object of settings" });
+      return;
+    }
+
+    try {
+      const manifest = await loadManifestForSettings(pluginId);
+      if (!manifest) {
+        res.status(404).json({ error: "No such plugin" });
+        return;
+      }
+
+      const errors = await applySettings(
+        userId,
+        manifest,
+        "admin",
+        null,
+        req.body,
+      );
+      if (Object.keys(errors).length > 0) {
+        res.status(400).json({ error: "Some settings were rejected", errors });
+        return;
+      }
+
+      const { ipAddress, userAgent } = getRequestMeta(req);
+      await logAudit({
+        userId,
+        username: await getAuditUsername(userId),
+        action: "update_plugin_settings",
+        resourceType: "setting",
+        resourceId: pluginId,
+        resourceName: manifest.name,
+        // Keys only: a value here could be the secret we just encrypted.
+        details: JSON.stringify({
+          scope: "admin",
+          keys: Object.keys(req.body),
+        }),
+        ipAddress,
+        userAgent,
+        success: true,
+      });
+
+      const values = await getAllSettings(manifest, "admin", null, {
+        redactSecrets: true,
+      });
+      res.json({ id: pluginId, values });
+    } catch (error) {
+      databaseLogger.error(
+        `Failed to update admin settings for plugin ${pluginId}`,
+        error instanceof Error ? error : new Error(String(error)),
+        { operation: "plugin_settings_write" },
+      );
+      res.status(500).json({ error: "Failed to update the plugin's settings" });
+    }
+  },
+);
+
+/**
+ * @openapi
+ * /plugins/{id}/settings/user:
+ *   get:
+ *     summary: Read the caller's own settings for a plugin
+ *     description: Returns every user-scope field the plugin declares for the authenticated user. The scope is always the caller, never a user id from the request.
+ *     tags:
+ *       - Plugins
+ *     parameters:
+ *       - in: path
+ *         name: id
+ *         required: true
+ *         schema:
+ *           type: string
+ *     responses:
+ *       200:
+ *         description: The caller's settings for this plugin.
+ *       404:
+ *         description: No such plugin.
+ */
+router.get(
+  "/:id/settings/user",
+  authenticateJWT,
+  async (req: Request, res: Response) => {
+    const pluginId = String(req.params.id);
+    const userId = (req as AuthenticatedRequest).userId as string;
+
+    try {
+      const manifest = await loadManifestForSettings(pluginId);
+      if (!manifest) {
+        res.status(404).json({ error: "No such plugin" });
+        return;
+      }
+      const values = await getAllSettings(manifest, "user", userId, {
+        redactSecrets: true,
+      });
+      res.json({ id: pluginId, values });
+    } catch (error) {
+      databaseLogger.error(
+        `Failed to read user settings for plugin ${pluginId}`,
+        error instanceof Error ? error : new Error(String(error)),
+        { operation: "plugin_settings_read" },
+      );
+      res.status(500).json({ error: "Failed to read the plugin's settings" });
+    }
+  },
+);
+
+/**
+ * @openapi
+ * /plugins/{id}/settings/user:
+ *   put:
+ *     summary: Update the caller's own settings for a plugin
+ *     description: Writes user-scope values for the authenticated user. The scope is always the caller, so one user can never write another's settings.
+ *     tags:
+ *       - Plugins
+ *     parameters:
+ *       - in: path
+ *         name: id
+ *         required: true
+ *         schema:
+ *           type: string
+ *     requestBody:
+ *       required: true
+ *       content:
+ *         application/json:
+ *           schema:
+ *             type: object
+ *     responses:
+ *       200:
+ *         description: The updated settings.
+ *       400:
+ *         description: One or more fields were rejected.
+ *       404:
+ *         description: No such plugin.
+ */
+router.put(
+  "/:id/settings/user",
+  authenticateJWT,
+  async (req: Request, res: Response) => {
+    const pluginId = String(req.params.id);
+    const userId = (req as AuthenticatedRequest).userId as string;
+
+    if (!isPlainBody(req.body)) {
+      res.status(400).json({ error: "Body must be an object of settings" });
+      return;
+    }
+
+    try {
+      const manifest = await loadManifestForSettings(pluginId);
+      if (!manifest) {
+        res.status(404).json({ error: "No such plugin" });
+        return;
+      }
+
+      const errors = await applySettings(
+        userId,
+        manifest,
+        "user",
+        userId,
+        req.body,
+      );
+      if (Object.keys(errors).length > 0) {
+        res.status(400).json({ error: "Some settings were rejected", errors });
+        return;
+      }
+
+      const values = await getAllSettings(manifest, "user", userId, {
+        redactSecrets: true,
+      });
+      res.json({ id: pluginId, values });
+    } catch (error) {
+      databaseLogger.error(
+        `Failed to update user settings for plugin ${pluginId}`,
+        error instanceof Error ? error : new Error(String(error)),
+        { operation: "plugin_settings_write" },
+      );
+      res.status(500).json({ error: "Failed to update the plugin's settings" });
+    }
+  },
+);
+
+/**
+ * @openapi
+ * /plugins/{id}/settings/host/{hostId}:
+ *   get:
+ *     summary: Read a plugin's settings for one host
+ *     description: Returns every host-scope field the plugin declares for that host. Requires edit access to the host, the same check the host editor itself uses.
+ *     tags:
+ *       - Plugins
+ *     parameters:
+ *       - in: path
+ *         name: id
+ *         required: true
+ *         schema:
+ *           type: string
+ *       - in: path
+ *         name: hostId
+ *         required: true
+ *         schema:
+ *           type: integer
+ *     responses:
+ *       200:
+ *         description: The plugin's settings for that host.
+ *       400:
+ *         description: Invalid host id.
+ *       403:
+ *         description: No edit access to that host.
+ *       404:
+ *         description: No such plugin.
+ */
+router.get(
+  "/:id/settings/host/:hostId",
+  authenticateJWT,
+  async (req: Request, res: Response) => {
+    const pluginId = String(req.params.id);
+    const userId = (req as AuthenticatedRequest).userId as string;
+    const hostId = Number(req.params.hostId);
+
+    if (!Number.isInteger(hostId) || hostId <= 0) {
+      res.status(400).json({ error: "Invalid host ID" });
+      return;
+    }
+
+    try {
+      const manifest = await loadManifestForSettings(pluginId);
+      if (!manifest) {
+        res.status(404).json({ error: "No such plugin" });
+        return;
+      }
+
+      const access = await permissionManager.canAccessHost(
+        userId,
+        hostId,
+        "edit",
+      );
+      if (!access.hasAccess) {
+        res.status(403).json({ error: "Access denied to host" });
+        return;
+      }
+
+      const values = await getAllSettings(manifest, "host", hostId, {
+        redactSecrets: true,
+      });
+      res.json({ id: pluginId, hostId, values });
+    } catch (error) {
+      databaseLogger.error(
+        `Failed to read host settings for plugin ${pluginId}`,
+        error instanceof Error ? error : new Error(String(error)),
+        { operation: "plugin_settings_read" },
+      );
+      res.status(500).json({ error: "Failed to read the plugin's settings" });
+    }
+  },
+);
+
+/**
+ * @openapi
+ * /plugins/{id}/settings/host/{hostId}:
+ *   put:
+ *     summary: Update a plugin's settings for one host
+ *     description: Writes host-scope values. Requires edit access to the host, so a user who may only connect to a shared host cannot change how a plugin treats it.
+ *     tags:
+ *       - Plugins
+ *     parameters:
+ *       - in: path
+ *         name: id
+ *         required: true
+ *         schema:
+ *           type: string
+ *       - in: path
+ *         name: hostId
+ *         required: true
+ *         schema:
+ *           type: integer
+ *     requestBody:
+ *       required: true
+ *       content:
+ *         application/json:
+ *           schema:
+ *             type: object
+ *     responses:
+ *       200:
+ *         description: The updated settings.
+ *       400:
+ *         description: Invalid host id, or one or more fields were rejected.
+ *       403:
+ *         description: No edit access to that host.
+ *       404:
+ *         description: No such plugin.
+ */
+router.put(
+  "/:id/settings/host/:hostId",
+  authenticateJWT,
+  async (req: Request, res: Response) => {
+    const pluginId = String(req.params.id);
+    const userId = (req as AuthenticatedRequest).userId as string;
+    const hostId = Number(req.params.hostId);
+
+    if (!Number.isInteger(hostId) || hostId <= 0) {
+      res.status(400).json({ error: "Invalid host ID" });
+      return;
+    }
+    if (!isPlainBody(req.body)) {
+      res.status(400).json({ error: "Body must be an object of settings" });
+      return;
+    }
+
+    try {
+      const manifest = await loadManifestForSettings(pluginId);
+      if (!manifest) {
+        res.status(404).json({ error: "No such plugin" });
+        return;
+      }
+
+      const access = await permissionManager.canAccessHost(
+        userId,
+        hostId,
+        "edit",
+      );
+      if (!access.hasAccess) {
+        res.status(403).json({ error: "Access denied to host" });
+        return;
+      }
+
+      const errors = await applySettings(
+        userId,
+        manifest,
+        "host",
+        String(hostId),
+        req.body,
+      );
+      if (Object.keys(errors).length > 0) {
+        res.status(400).json({ error: "Some settings were rejected", errors });
+        return;
+      }
+
+      const values = await getAllSettings(manifest, "host", hostId, {
+        redactSecrets: true,
+      });
+      res.json({ id: pluginId, hostId, values });
+    } catch (error) {
+      databaseLogger.error(
+        `Failed to update host settings for plugin ${pluginId}`,
+        error instanceof Error ? error : new Error(String(error)),
+        { operation: "plugin_settings_write" },
+      );
+      res.status(500).json({ error: "Failed to update the plugin's settings" });
+    }
+  },
+);
+
 export default router;

src/backend/database/routes/user-settings-routes.ts

@@ -338,120 +338,6 @@ export function registerUserSettingsRoutes(
     }
   });
 
-  /**
-   * @openapi
-   * /users/tailscale-settings:
-   *   get:
-   *     summary: Get Tailscale settings
-   *     description: Returns whether a Tailscale API key is configured (value is masked).
-   *     tags:
-   *       - Users
-   *     responses:
-   *       200:
-   *         description: Tailscale settings.
-   *         content:
-   *           application/json:
-   *             schema:
-   *               type: object
-   *               properties:
-   *                 apiKey:
-   *                   type: string
-   *                   description: Masked API key or empty string if not set.
-   *                 hasApiKey:
-   *                   type: boolean
-   *                 apiBaseUrl:
-   *                   type: string
-   *                   description: Custom control-plane API base URL (e.g. a Headscale instance), or empty string for the Tailscale default.
-   */
-  router.get("/tailscale-settings", authenticateJWT, async (_req, res) => {
-    try {
-      const settingsRepo = createCurrentSettingsRepository();
-      const apiKey = (await settingsRepo.get("tailscale_api_key")) ?? "";
-      const apiBaseUrl =
-        (await settingsRepo.get("tailscale_api_base_url")) ?? "";
-      res.json({
-        apiKey: apiKey
-          ? `${apiKey.slice(0, 6)}${"*".repeat(Math.max(0, apiKey.length - 6))}`
-          : "",
-        hasApiKey: !!apiKey,
-        apiBaseUrl,
-      });
-    } catch (err) {
-      authLogger.error("Failed to get Tailscale settings", err);
-      res.status(500).json({ error: "Failed to get Tailscale settings" });
-    }
-  });
-
-  /**
-   * @openapi
-   * /users/tailscale-settings:
-   *   patch:
-   *     summary: Update Tailscale settings (admin only)
-   *     description: Saves or clears the Tailscale API key used for device discovery.
-   *     tags:
-   *       - Users
-   *     requestBody:
-   *       required: true
-   *       content:
-   *         application/json:
-   *           schema:
-   *             type: object
-   *             properties:
-   *               apiKey:
-   *                 type: string
-   *               apiBaseUrl:
-   *                 type: string
-   *                 description: Optional custom control-plane API base URL (e.g. a Headscale instance). Leave empty to use the Tailscale default.
-   *     responses:
-   *       200:
-   *         description: Tailscale settings updated.
-   *       403:
-   *         description: Not authorized.
-   *       500:
-   *         description: Failed to update Tailscale settings.
-   */
-  router.patch("/tailscale-settings", authenticateJWT, async (req, res) => {
-    const userId = (req as AuthenticatedRequest).userId;
-    try {
-      const actor = await getAdminActor(userId);
-      if (!actor) {
-        return res.status(403).json({ error: "Not authorized" });
-      }
-      const { apiKey, apiBaseUrl } = req.body;
-      if (typeof apiKey !== "string") {
-        return res.status(400).json({ error: "apiKey must be a string" });
-      }
-      if (apiBaseUrl !== undefined && typeof apiBaseUrl !== "string") {
-        return res.status(400).json({ error: "apiBaseUrl must be a string" });
-      }
-      const settingsRepo = createCurrentSettingsRepository();
-      await settingsRepo.set("tailscale_api_key", apiKey);
-      if (apiBaseUrl !== undefined) {
-        await settingsRepo.set(
-          "tailscale_api_base_url",
-          apiBaseUrl.trim().replace(/\/+$/, ""),
-        );
-      }
-
-      const { ipAddress, userAgent } = getRequestMeta(req);
-      await logAudit({
-        userId,
-        username: actor.username ?? userId,
-        action: "update_tailscale_settings",
-        resourceType: "setting",
-        details: JSON.stringify({ hasApiKey: !!apiKey }),
-        ipAddress,
-        userAgent,
-        success: true,
-      });
-
-      res.json({ hasApiKey: !!apiKey });
-    } catch (err) {
-      authLogger.error("Failed to update Tailscale settings", err);
-      res.status(500).json({ error: "Failed to update Tailscale settings" });
-    }
-  });
-
   /**
    * @openapi
    * /users/command-history-enabled:

src/backend/plugins/ctx.ts

@@ -36,6 +36,7 @@ import {
 } from "./http.js";
 import { registerPluginWsRoute, registerPluginWsUpgrade } from "./ws.js";
 import { resolvePermission } from "./rbac.js";
+import * as pluginSettings from "./settings.js";
 import type { PluginManifest } from "@termix/plugin-sdk/manifest";
 import {
   PluginCapabilityError,
@@ -257,6 +258,18 @@ export function createPluginContext(
     { action: "db_client" },
   );
 
+  // The one settings call that leaves the plugin's own namespace, so the one
+  // that needs a capability and an audit line.
+  const settingsReadCore = guarded(
+    manifest,
+    "settings:read-core",
+    async (key: string) => pluginSettings.readCoreSetting(key),
+    {
+      action: "settings_read_core",
+      details: () => "read a core server setting",
+    },
+  );
+
   const dbRefs = guarded(
     manifest,
     "db:own",
@@ -474,6 +487,66 @@ export function createPluginContext(
       },
     },
 
+    settings: {
+      // Reading and writing a plugin's OWN settings is ungated. The manifest
+      // already declares every field, and a plugin that had to ask permission
+      // to read its own configuration would be useless. Only readCore, which
+      // reaches outside the plugin's namespace, is a capability.
+      get: (key) =>
+        pluginSettings.getSetting(manifest, "admin", null, key) as never,
+      set: async (key, value) => {
+        const error = await pluginSettings.setSetting(
+          manifest,
+          "admin",
+          null,
+          key,
+          value,
+        );
+        if (error) throw new Error(error);
+      },
+
+      getUser: (userId, key) =>
+        pluginSettings.getSetting(manifest, "user", userId, key) as never,
+      setUser: async (userId, key, value) => {
+        const error = await pluginSettings.setSetting(
+          manifest,
+          "user",
+          userId,
+          key,
+          value,
+        );
+        if (error) throw new Error(error);
+      },
+
+      getHost: (hostId, key) =>
+        pluginSettings.getSetting(manifest, "host", hostId, key) as never,
+      setHost: async (hostId, key, value) => {
+        const error = await pluginSettings.setSetting(
+          manifest,
+          "host",
+          hostId,
+          key,
+          value,
+        );
+        if (error) throw new Error(error);
+      },
+
+      getAll: (scope, scopeId) =>
+        pluginSettings.getAllSettings(manifest, scope, scopeId ?? null),
+
+      onChange: (key, listener) => {
+        const unsubscribe = pluginSettings.onSettingsChange(
+          pluginId,
+          key,
+          listener,
+        );
+        handle.bag.add(unsubscribe, `settings listener for "${key}"`);
+        return unsubscribe;
+      },
+
+      readCore: (key) => settingsReadCore(key),
+    },
+
     rbac: {
       // A short name takes this plugin's prefix; another plugin's id or a core
       // group is used as given, which is what makes a cross-plugin check
@@ -623,6 +696,7 @@ export async function disposePluginHandle(
   // Belt and braces: an offer made outside ctx, or one whose registration was
   // lost to a throw mid-activate, would otherwise outlive the plugin.
   secretRegistry.withdrawAllForPlugin(pluginId);
+  pluginSettings.clearSettingsListeners(pluginId);
 
   // Skipped when activate() never finished: a plugin's deactivate expects the
   // state activate builds, and calling it on a half-built plugin tends to

src/backend/plugins/settings.ts

@@ -0,0 +1,319 @@
+/**
+ * Plugin settings: validation, storage, encryption and change notification.
+ *
+ * One module behind both ctx.settings and the /plugins/:id/settings routes, so
+ * "what is a valid value", "which fields are secret" and "what a read hands
+ * back" are decided once. Two implementations would drift, and the one that
+ * drifted would be the one writing to the database.
+ *
+ * A field the manifest never declared is rejected rather than stored. That is
+ * what stops a PUT from filling a plugin's namespace with arbitrary keys, and
+ * it is why every entry point resolves the field first and the value second.
+ */
+
+import type {
+  PluginManifest,
+  PluginSettingsField,
+} from "@termix/plugin-sdk/manifest";
+import {
+  coerceSettingValue,
+  isRedactedSecret,
+  validateSettingValue,
+} from "@termix/plugin-sdk/settings";
+import { createCurrentPluginSettingsRepository } from "../database/repositories/factory.js";
+import type { PluginSettingsScope } from "../database/repositories/plugin-settings-repository.js";
+import {
+  decryptSystemSecret,
+  encryptSystemSecret,
+} from "../utils/system-secret-crypto.js";
+import { pluginLogger } from "../utils/logger.js";
+
+export type { PluginSettingsScope };
+
+/**
+ * Core settings a plugin may read through ctx.settings.readCore.
+ *
+ * Deliberately short. Everything here is either already visible in the UI to
+ * every user, or a switch a plugin has to honour to behave correctly. Adding
+ * to it means deciding that every plugin holding settings:read-core may see
+ * that value, so it is a review decision rather than a convenience.
+ */
+export const CORE_SETTINGS_ALLOWLIST: readonly string[] = [
+  "app_name",
+  "guac_enabled",
+  "global_metrics_interval",
+  "global_status_check_interval",
+];
+
+type ChangeListener = (value: unknown) => void;
+
+/** pluginId -> key -> listeners. In-process only; settings are not clustered. */
+const listeners = new Map<string, Map<string, Set<ChangeListener>>>();
+
+export function onSettingsChange(
+  pluginId: string,
+  key: string,
+  listener: ChangeListener,
+): () => void {
+  let byKey = listeners.get(pluginId);
+  if (!byKey) {
+    byKey = new Map();
+    listeners.set(pluginId, byKey);
+  }
+  let set = byKey.get(key);
+  if (!set) {
+    set = new Set();
+    byKey.set(key, set);
+  }
+  set.add(listener);
+
+  return () => {
+    set!.delete(listener);
+    if (set!.size === 0) byKey!.delete(key);
+    if (byKey!.size === 0) listeners.delete(pluginId);
+  };
+}
+
+function notify(pluginId: string, key: string, value: unknown): void {
+  for (const listener of listeners.get(pluginId)?.get(key) ?? []) {
+    try {
+      listener(value);
+    } catch (error) {
+      // A listener throwing must not fail the write that already happened.
+      pluginLogger.error(
+        `Plugin ${pluginId} settings listener for "${key}" failed`,
+        error instanceof Error ? error : new Error(String(error)),
+        { operation: "plugin_settings_change" },
+      );
+    }
+  }
+}
+
+/** Drops every listener a plugin registered. Called when it deactivates. */
+export function clearSettingsListeners(pluginId: string): void {
+  listeners.delete(pluginId);
+}
+
+/** The fields a manifest declares for one scope. */
+export function declaredFields(
+  manifest: PluginManifest,
+  scope: PluginSettingsScope,
+): PluginSettingsField[] {
+  const settings = manifest.contributes?.settings;
+  if (!settings) return [];
+
+  if (scope === "admin") return settings.admin ?? [];
+  if (scope === "user") return settings.user ?? [];
+
+  const host = settings.host;
+  if (!host) return [];
+
+  // The enable switch is a real stored key, so it has to behave like a field
+  // everywhere: validated on write, defaulted on read, rendered in the editor.
+  const enableField: PluginSettingsField[] = host.enableKey
+    ? [
+        {
+          key: host.enableKey,
+          type: "boolean",
+          labelKey: host.enableLabelKey,
+          default: false,
+        },
+      ]
+    : [];
+
+  return [...enableField, ...host.fields];
+}
+
+export function findField(
+  manifest: PluginManifest,
+  scope: PluginSettingsScope,
+  key: string,
+): PluginSettingsField | undefined {
+  return declaredFields(manifest, scope).find((field) => field.key === key);
+}
+
+function normalizeScopeId(
+  scope: PluginSettingsScope,
+  scopeId: string | number | undefined | null,
+): string | null {
+  if (scope === "admin") return null;
+  if (scopeId === undefined || scopeId === null) {
+    throw new Error(`Plugin settings scope "${scope}" requires a scope id`);
+  }
+  return String(scopeId);
+}
+
+/** Stored values are JSON so a field keeps its declared type on the way back. */
+function encode(value: unknown): string {
+  return JSON.stringify(value ?? null);
+}
+
+function decode(raw: string | null): unknown {
+  if (raw === null) return undefined;
+  try {
+    return JSON.parse(raw);
+  } catch {
+    return undefined;
+  }
+}
+
+export async function getSetting(
+  manifest: PluginManifest,
+  scope: PluginSettingsScope,
+  scopeId: string | number | null | undefined,
+  key: string,
+): Promise<unknown> {
+  const field = findField(manifest, scope, key);
+  if (!field) return undefined;
+
+  const row = await createCurrentPluginSettingsRepository().get(
+    manifest.id,
+    scope,
+    normalizeScopeId(scope, scopeId),
+    key,
+  );
+
+  if (!row || row.value === null) return field.default;
+
+  const decoded = decode(row.value);
+  if (decoded === undefined || decoded === null) return field.default;
+
+  if (row.encrypted && typeof decoded === "string") {
+    return decryptSystemSecret(decoded);
+  }
+  return decoded;
+}
+
+export interface SetSettingOptions {
+  /** Skips validation for a value core itself produced, such as a migration. */
+  trusted?: boolean;
+}
+
+/**
+ * Writes one value, after validating it against the declared field.
+ *
+ * Returns the error message when the value is rejected, or null on success,
+ * rather than throwing: a PUT reports every bad field at once and a throw per
+ * field would only ever surface the first.
+ */
+export async function setSetting(
+  manifest: PluginManifest,
+  scope: PluginSettingsScope,
+  scopeId: string | number | null | undefined,
+  key: string,
+  value: unknown,
+  options: SetSettingOptions = {},
+): Promise<string | null> {
+  const field = findField(manifest, scope, key);
+  if (!field) {
+    return `"${key}" is not a settings field this plugin declares`;
+  }
+
+  // Echoing a redacted secret back means "leave it alone", so a form can save
+  // without clearing a key it was never shown.
+  if (field.type === "secret" && isRedactedSecret(value)) return null;
+
+  const coerced = options.trusted ? value : coerceSettingValue(field, value);
+  if (!options.trusted) {
+    const error = validateSettingValue(field, coerced);
+    if (error) return error;
+  }
+
+  // Clearing a secret writes null rather than an encrypted empty string, so a
+  // read reports it as unset instead of "set to nothing".
+  const clearingSecret = field.type === "secret" && coerced === "";
+  const shouldEncrypt =
+    field.type === "secret" && typeof coerced === "string" && !clearingSecret;
+  const stored = clearingSecret
+    ? null
+    : shouldEncrypt
+      ? encode(await encryptSystemSecret(coerced as string))
+      : encode(coerced);
+
+  await createCurrentPluginSettingsRepository().set(
+    manifest.id,
+    scope,
+    normalizeScopeId(scope, scopeId),
+    key,
+    stored,
+    shouldEncrypt,
+  );
+
+  notify(manifest.id, key, coerced);
+  return null;
+}
+
+export interface GetAllOptions {
+  /** Replaces every secret with { set } so the value never leaves the server. */
+  redactSecrets?: boolean;
+}
+
+/**
+ * Every declared field for one scope, with stored values over defaults.
+ *
+ * Driven by the manifest rather than by the rows, so a field that was never
+ * written still comes back with its default and a stale row for a field the
+ * plugin has since dropped is ignored instead of being handed to the UI.
+ */
+export async function getAllSettings(
+  manifest: PluginManifest,
+  scope: PluginSettingsScope,
+  scopeId: string | number | null | undefined,
+  options: GetAllOptions = {},
+): Promise<Record<string, unknown>> {
+  const fields = declaredFields(manifest, scope);
+  if (fields.length === 0) return {};
+
+  const rows = await createCurrentPluginSettingsRepository().getAll(
+    manifest.id,
+    scope,
+    normalizeScopeId(scope, scopeId),
+  );
+  const byKey = new Map(rows.map((row) => [row.key, row]));
+
+  const values: Record<string, unknown> = {};
+  for (const field of fields) {
+    values[field.key] = await resolveFieldValue(
+      field,
+      byKey.get(field.key),
+      options,
+    );
+  }
+  return values;
+}
+
+/** Shared by getAllSettings and the host-list projection. */
+export async function resolveFieldValue(
+  field: PluginSettingsField,
+  row: { value: string | null; encrypted: boolean } | undefined,
+  options: GetAllOptions = {},
+): Promise<unknown> {
+  const decoded = row && row.value !== null ? decode(row.value) : undefined;
+  const hasValue = decoded !== undefined && decoded !== null && decoded !== "";
+
+  if (field.type === "secret") {
+    if (options.redactSecrets) return { set: hasValue };
+    if (!hasValue) return field.default;
+    return row!.encrypted && typeof decoded === "string"
+      ? decryptSystemSecret(decoded)
+      : decoded;
+  }
+
+  return hasValue ? decoded : field.default;
+}
+
+/**
+ * Reads a core server setting. The caller has already checked
+ * settings:read-core; this only enforces the allowlist.
+ */
+export async function readCoreSetting(key: string): Promise<string | null> {
+  if (!CORE_SETTINGS_ALLOWLIST.includes(key)) {
+    throw new Error(
+      `Core setting "${key}" is not readable by plugins. Readable keys: ${CORE_SETTINGS_ALLOWLIST.join(", ")}`,
+    );
+  }
+
+  const { createCurrentSettingsRepository } =
+    await import("../database/repositories/factory.js");
+  return createCurrentSettingsRepository().get(key);
+}

src/backend/starter.ts

@@ -344,6 +344,12 @@ async function provisionLocalDesktopUserIfNeeded(): Promise<void> {
           operation: "plugin_init",
         });
       }
+
+      // After seeding: plugin_settings has a foreign key to plugins, so there
+      // is nothing to migrate into until the plugin row exists.
+      const { runTailscaleSettingsMigration } =
+        await import("./utils/crypto-migration/tailscale-settings-migration.js");
+      await runTailscaleSettingsMigration();
     } catch (error) {
       systemLogger.warn("Plugin runtime failed to initialize", {
         operation: "plugin_init",

src/backend/tests/database/plugin-settings-cascade.test.ts

@@ -0,0 +1,147 @@
+/**
+ * plugin_settings cleanup when a user or host goes.
+ *
+ * scope_id is polymorphic, so it carries no foreign key and the engine will
+ * not cascade it. The repositories delete these rows explicitly, and these
+ * tests exist so a later refactor that drops those calls fails here rather
+ * than leaving orphaned settings behind forever.
+ */
+
+import { asc } from "drizzle-orm";
+import { afterEach, describe, expect, it } from "vitest";
+import { TestSqliteDatabase } from "./repositories/test-support.js";
+import { HostRepository } from "../../database/repositories/host-repository.js";
+import { UserRepository } from "../../database/repositories/user-repository.js";
+import type { DatabaseContext } from "../../database/repositories/database-context.js";
+import { pluginSettings } from "../../database/db/schema.js";
+
+let adapter: TestSqliteDatabase | null = null;
+let ctx: DatabaseContext | null = null;
+
+afterEach(async () => {
+  if (adapter) {
+    await adapter.close();
+    adapter = null;
+    ctx = null;
+  }
+});
+
+async function seed(): Promise<DatabaseContext> {
+  adapter = new TestSqliteDatabase();
+  const context = await adapter.connect();
+  ctx = context;
+
+  await adapter.exec(`
+    INSERT INTO users (id, username, password_hash)
+    VALUES ('user-1', 'alice', 'hash'), ('user-2', 'bob', 'hash');
+
+    INSERT INTO ssh_data (id, user_id, name, ip, port, username, auth_type)
+    VALUES
+      (7, 'user-1', 'seven', '10.0.0.7', 22, 'root', 'password'),
+      (8, 'user-1', 'eight', '10.0.0.8', 22, 'root', 'password'),
+      (9, 'user-2', 'nine', '10.0.0.9', 22, 'root', 'password');
+
+    INSERT INTO plugins (id, name, version, manifest_json)
+    VALUES ('sample', 'Sample', '1.0.0', '{}');
+  `);
+
+  return context;
+}
+
+async function addSetting(
+  scope: string,
+  scopeId: string | null,
+  key = "k",
+): Promise<void> {
+  await adapter!.exec(
+    `INSERT INTO plugin_settings (plugin_id, scope, scope_id, key, value)
+     VALUES ('sample', '${scope}', ${scopeId === null ? "NULL" : `'${scopeId}'`}, '${key}', '"v"')`,
+  );
+}
+
+async function remaining(): Promise<
+  { scope: string; scopeId: string | null }[]
+> {
+  const rows = await ctx!.drizzle
+    .select({
+      scope: pluginSettings.scope,
+      scopeId: pluginSettings.scopeId,
+    })
+    .from(pluginSettings)
+    .orderBy(asc(pluginSettings.scope), asc(pluginSettings.scopeId));
+  return rows;
+}
+
+describe("user deletion", () => {
+  it("removes that user's plugin settings", async () => {
+    const context = await seed();
+    await addSetting("user", "user-1");
+
+    await new UserRepository(context).delete("user-1");
+
+    expect(await remaining()).toEqual([]);
+  });
+
+  it("leaves another user's settings alone", async () => {
+    const context = await seed();
+    await addSetting("user", "user-1");
+    await addSetting("user", "user-2");
+
+    await new UserRepository(context).delete("user-1");
+
+    expect(await remaining()).toEqual([{ scope: "user", scopeId: "user-2" }]);
+  });
+
+  it("leaves admin-scope settings alone", async () => {
+    const context = await seed();
+    await addSetting("admin", null);
+    await addSetting("user", "user-1");
+
+    await new UserRepository(context).delete("user-1");
+
+    expect(await remaining()).toEqual([{ scope: "admin", scopeId: null }]);
+  });
+});
+
+describe("host deletion", () => {
+  it("removes that host's plugin settings", async () => {
+    const context = await seed();
+    await addSetting("host", "7");
+
+    await new HostRepository(context).deleteForUser("user-1", 7);
+
+    expect(await remaining()).toEqual([]);
+  });
+
+  it("leaves another host's settings alone", async () => {
+    const context = await seed();
+    await addSetting("host", "7");
+    await addSetting("host", "8");
+
+    await new HostRepository(context).deleteForUser("user-1", 7);
+
+    expect(await remaining()).toEqual([{ scope: "host", scopeId: "8" }]);
+  });
+
+  it("clears settings for every host in the bulk delete path", async () => {
+    const context = await seed();
+    await addSetting("host", "7");
+    await addSetting("host", "8");
+    await addSetting("host", "9");
+
+    await new HostRepository(context).deleteByUserId("user-1");
+
+    // Host 9 belongs to another user and keeps its settings.
+    expect(await remaining()).toEqual([{ scope: "host", scopeId: "9" }]);
+  });
+
+  it("does not confuse a host id with a user id", async () => {
+    const context = await seed();
+    await addSetting("host", "7");
+    await addSetting("user", "7");
+
+    await new HostRepository(context).deleteForUser("user-1", 7);
+
+    expect(await remaining()).toEqual([{ scope: "user", scopeId: "7" }]);
+  });
+});

src/backend/tests/database/routes/host-plugin-settings.test.ts

@@ -0,0 +1,244 @@
+/**
+ * The pluginSettings map attached to host responses.
+ *
+ * The host editor needs these with the host, not one request per plugin per
+ * host, so the shape and the query count both matter.
+ */
+
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import type { PluginManifest } from "@termix/plugin-sdk/manifest";
+
+interface Row {
+  pluginId: string;
+  scope: string;
+  scopeId: string | null;
+  key: string;
+  value: string | null;
+  encrypted: boolean;
+}
+
+const rows: Row[] = [];
+const loaded: { id: string; manifest: PluginManifest; state: string }[] = [];
+const getAllForScopeIds = vi.fn(async (scope: string, scopeIds: string[]) =>
+  rows.filter(
+    (row) => row.scope === scope && scopeIds.includes(row.scopeId ?? ""),
+  ),
+);
+
+vi.mock("../../../utils/logger.js", () => {
+  const logger = {
+    debug: vi.fn(),
+    info: vi.fn(),
+    warn: vi.fn(),
+    error: vi.fn(),
+    success: vi.fn(),
+  };
+  return { sshLogger: logger, pluginLogger: logger, databaseLogger: logger };
+});
+
+vi.mock("../../../database/repositories/factory.js", () => ({
+  createCurrentPluginSettingsRepository: () => ({ getAllForScopeIds }),
+}));
+
+vi.mock("../../../plugins/index.js", () => ({
+  getPluginRuntime: () => ({ loader: { list: () => loaded } }),
+}));
+
+vi.mock("../../../utils/system-secret-crypto.js", () => ({
+  isSystemEncrypted: (value: string) => value.startsWith("sysenc:v1:"),
+  encryptSystemSecret: async (plaintext: string) => plaintext,
+  decryptSystemSecret: async (stored: string) => stored,
+}));
+
+const {
+  attachHostPluginSettings,
+  loadHostPluginSettings,
+  withHostPluginSettings,
+} = await import("../../../database/routes/host-plugin-settings.js");
+
+function manifest(id: string, host: unknown): PluginManifest {
+  return {
+    id,
+    name: id,
+    version: "1.0.0",
+    description: "",
+    author: { name: "t" },
+    license: "MIT",
+    category: "Productivity",
+    engine: { termix: ">=2.9.0", api: "1" },
+    capabilities: [],
+    contributes: { settings: { host } },
+  } as PluginManifest;
+}
+
+const DOCKER = manifest("docker", {
+  enableKey: "enableDocker",
+  enableLabelKey: "k",
+  fields: [{ key: "socketPath", type: "string", labelKey: "k" }],
+});
+
+beforeEach(() => {
+  rows.length = 0;
+  loaded.length = 0;
+  getAllForScopeIds.mockClear();
+});
+
+describe("loadHostPluginSettings", () => {
+  it("returns nothing when no plugin declares host settings", async () => {
+    loaded.push({
+      id: "other",
+      manifest: manifest("other", undefined),
+      state: "active",
+    });
+
+    const result = await loadHostPluginSettings([1, 2]);
+
+    expect(result.size).toBe(0);
+    expect(getAllForScopeIds).not.toHaveBeenCalled();
+  });
+
+  it("ignores a plugin that is not running", async () => {
+    loaded.push({ id: "docker", manifest: DOCKER, state: "disabled" });
+
+    const result = await loadHostPluginSettings([1]);
+
+    expect(result.size).toBe(0);
+  });
+
+  it("uses one query for the whole list", async () => {
+    loaded.push({ id: "docker", manifest: DOCKER, state: "active" });
+
+    await loadHostPluginSettings([1, 2, 3, 4, 5]);
+
+    expect(getAllForScopeIds).toHaveBeenCalledTimes(1);
+    expect(getAllForScopeIds).toHaveBeenCalledWith("host", [
+      "1",
+      "2",
+      "3",
+      "4",
+      "5",
+    ]);
+  });
+
+  it("merges stored values over declared defaults", async () => {
+    loaded.push({ id: "docker", manifest: DOCKER, state: "active" });
+    rows.push({
+      pluginId: "docker",
+      scope: "host",
+      scopeId: "1",
+      key: "enableDocker",
+      value: JSON.stringify(true),
+      encrypted: false,
+    });
+
+    const result = await loadHostPluginSettings([1, 2]);
+
+    expect(result.get(1)).toEqual({
+      docker: { enableDocker: true, socketPath: undefined },
+    });
+    // Host 2 has nothing stored, so it falls back to the declared default.
+    expect(result.get(2)).toEqual({
+      docker: { enableDocker: false, socketPath: undefined },
+    });
+  });
+
+  it("keeps one host's values out of another's", async () => {
+    loaded.push({ id: "docker", manifest: DOCKER, state: "active" });
+    rows.push({
+      pluginId: "docker",
+      scope: "host",
+      scopeId: "1",
+      key: "socketPath",
+      value: JSON.stringify("/var/run/docker.sock"),
+      encrypted: false,
+    });
+
+    const result = await loadHostPluginSettings([1, 2]);
+
+    expect(result.get(1)!.docker.socketPath).toBe("/var/run/docker.sock");
+    expect(result.get(2)!.docker.socketPath).toBeUndefined();
+  });
+
+  it("redacts a host-scope secret", async () => {
+    loaded.push({
+      id: "vault",
+      manifest: manifest("vault", {
+        fields: [{ key: "token", type: "secret", labelKey: "k" }],
+      }),
+      state: "active",
+    });
+    rows.push({
+      pluginId: "vault",
+      scope: "host",
+      scopeId: "1",
+      key: "token",
+      value: JSON.stringify("s.verysecret"),
+      encrypted: true,
+    });
+
+    const result = await loadHostPluginSettings([1]);
+
+    expect(result.get(1)!.vault.token).toEqual({ set: true });
+    expect(JSON.stringify(result.get(1))).not.toContain("verysecret");
+  });
+
+  it("survives a failed settings read rather than failing the host list", async () => {
+    loaded.push({ id: "docker", manifest: DOCKER, state: "active" });
+    getAllForScopeIds.mockRejectedValueOnce(new Error("database is away"));
+
+    await expect(loadHostPluginSettings([1])).resolves.toEqual(new Map());
+  });
+
+  it("does nothing for an empty host list", async () => {
+    loaded.push({ id: "docker", manifest: DOCKER, state: "active" });
+
+    expect((await loadHostPluginSettings([])).size).toBe(0);
+    expect(getAllForScopeIds).not.toHaveBeenCalled();
+  });
+});
+
+describe("attachHostPluginSettings", () => {
+  it("attaches values to the matching host", () => {
+    const hosts = [{ id: 1 }, { id: 2 }] as Record<string, unknown>[];
+    const settings = new Map([[1, { docker: { enableDocker: true } }]]);
+
+    attachHostPluginSettings(hosts, settings);
+
+    expect(hosts[0].pluginSettings).toEqual({ docker: { enableDocker: true } });
+    expect(hosts[1].pluginSettings).toBeUndefined();
+  });
+
+  it("leaves hosts alone when there is nothing to attach", () => {
+    const hosts = [{ id: 1 }] as Record<string, unknown>[];
+
+    attachHostPluginSettings(hosts, new Map());
+
+    expect(hosts[0]).toEqual({ id: 1 });
+  });
+});
+
+describe("withHostPluginSettings", () => {
+  it("adds the map to a single host", async () => {
+    loaded.push({ id: "docker", manifest: DOCKER, state: "active" });
+
+    const result = await withHostPluginSettings({ id: 1, name: "web" });
+
+    expect(result.name).toBe("web");
+    expect(result.pluginSettings).toEqual({
+      docker: { enableDocker: false, socketPath: undefined },
+    });
+  });
+
+  it("returns the host unchanged when nothing contributes", async () => {
+    const host = { id: 1, name: "web" };
+
+    expect(await withHostPluginSettings(host)).toBe(host);
+  });
+
+  it("returns the host unchanged when its id is not a number", async () => {
+    loaded.push({ id: "docker", manifest: DOCKER, state: "active" });
+    const host = { name: "web" };
+
+    expect(await withHostPluginSettings(host)).toBe(host);
+  });
+});

src/backend/tests/plugins/settings-manifest.test.ts

@@ -0,0 +1,356 @@
+/**
+ * contributes.settings validation.
+ *
+ * A settings field is the one thing in a manifest that core writes to the
+ * database on a plugin's behalf, so the schema has to reject anything it would
+ * not know how to store or render.
+ */
+
+import { describe, expect, it } from "vitest";
+import {
+  parseManifest,
+  validateManifest,
+  SUPPORTED_PLUGIN_API_VERSION,
+} from "../../plugins/manifest.js";
+
+function base(overrides: Record<string, unknown> = {}) {
+  return {
+    id: "sample-plugin",
+    name: "Sample Plugin",
+    version: "1.0.0",
+    description: "A fixture.",
+    author: { name: "Termix Tests" },
+    license: "MIT",
+    category: "Productivity",
+    engine: { termix: ">=2.9.0", api: SUPPORTED_PLUGIN_API_VERSION },
+    capabilities: ["kv:own"],
+    ...overrides,
+  };
+}
+
+function withSettings(settings: unknown) {
+  return base({ contributes: { settings } });
+}
+
+describe("contributes.settings", () => {
+  it("accepts a manifest with every field type", () => {
+    const errors = validateManifest(
+      withSettings({
+        admin: [
+          { key: "apiKey", type: "secret", labelKey: "k" },
+          { key: "baseUrl", type: "string", labelKey: "k", default: "" },
+          { key: "retries", type: "number", labelKey: "k", min: 0, max: 5 },
+          { key: "enabled", type: "boolean", labelKey: "k" },
+          {
+            key: "mode",
+            type: "select",
+            labelKey: "k",
+            options: [{ value: "a", labelKey: "k" }],
+          },
+          {
+            key: "tags",
+            type: "multiselect",
+            labelKey: "k",
+            options: [{ value: "a", labelKey: "k" }],
+          },
+          { key: "notes", type: "textarea", labelKey: "k" },
+          { key: "raw", type: "json", labelKey: "k" },
+          { key: "browser", type: "custom", component: "devices" },
+        ],
+        user: [{ key: "theme", type: "string", labelKey: "k" }],
+        host: {
+          enableKey: "enableThing",
+          enableLabelKey: "k",
+          fields: [{ key: "port", type: "number", labelKey: "k" }],
+        },
+      }),
+    );
+
+    expect(errors).toEqual([]);
+  });
+
+  it("accepts a manifest with no settings at all", () => {
+    expect(validateManifest(base())).toEqual([]);
+  });
+
+  it("rejects an unknown field property", () => {
+    const errors = validateManifest(
+      withSettings({
+        admin: [{ key: "a", type: "string", labelKey: "k", wat: 1 }],
+      }),
+    );
+
+    expect(errors.join(" ")).toContain('Unknown field "wat"');
+  });
+
+  it("rejects an unknown scope", () => {
+    const errors = validateManifest(
+      withSettings({ global: [{ key: "a", type: "string", labelKey: "k" }] }),
+    );
+
+    expect(errors.join(" ")).toContain('Unknown field "global"');
+  });
+
+  it("rejects an unknown field type", () => {
+    const errors = validateManifest(
+      withSettings({ admin: [{ key: "a", type: "colour", labelKey: "k" }] }),
+    );
+
+    expect(errors.join(" ")).toContain("must be one of");
+  });
+
+  it("rejects a duplicate key within one scope", () => {
+    const errors = validateManifest(
+      withSettings({
+        admin: [
+          { key: "a", type: "string", labelKey: "k" },
+          { key: "a", type: "number", labelKey: "k" },
+        ],
+      }),
+    );
+
+    expect(errors.join(" ")).toContain('duplicates "a"');
+  });
+
+  it("allows the same key in two different scopes", () => {
+    const errors = validateManifest(
+      withSettings({
+        admin: [{ key: "shared", type: "string", labelKey: "k" }],
+        user: [{ key: "shared", type: "string", labelKey: "k" }],
+      }),
+    );
+
+    expect(errors).toEqual([]);
+  });
+
+  it("requires labelKey for everything but a custom field", () => {
+    expect(
+      validateManifest(
+        withSettings({ admin: [{ key: "a", type: "string" }] }),
+      ).join(" "),
+    ).toContain("labelKey");
+
+    expect(
+      validateManifest(
+        withSettings({ admin: [{ key: "a", type: "custom", component: "x" }] }),
+      ),
+    ).toEqual([]);
+  });
+
+  it("requires component on a custom field and forbids it elsewhere", () => {
+    expect(
+      validateManifest(
+        withSettings({ admin: [{ key: "a", type: "custom" }] }),
+      ).join(" "),
+    ).toContain("component");
+
+    expect(
+      validateManifest(
+        withSettings({
+          admin: [{ key: "a", type: "string", labelKey: "k", component: "x" }],
+        }),
+      ).join(" "),
+    ).toContain('only valid when type is "custom"');
+  });
+
+  it("requires non-empty options on select and multiselect", () => {
+    for (const type of ["select", "multiselect"]) {
+      expect(
+        validateManifest(
+          withSettings({ admin: [{ key: "a", type, labelKey: "k" }] }),
+        ).join(" "),
+      ).toContain("options must be a non-empty array");
+    }
+  });
+
+  it("rejects options on a field that has no options", () => {
+    const errors = validateManifest(
+      withSettings({
+        admin: [
+          {
+            key: "a",
+            type: "string",
+            labelKey: "k",
+            options: [{ value: "x", labelKey: "k" }],
+          },
+        ],
+      }),
+    );
+
+    expect(errors.join(" ")).toContain("only valid for select and multiselect");
+  });
+
+  it("rejects min greater than max", () => {
+    const errors = validateManifest(
+      withSettings({
+        admin: [{ key: "a", type: "number", labelKey: "k", min: 10, max: 1 }],
+      }),
+    );
+
+    expect(errors.join(" ")).toContain("must not be greater than");
+  });
+
+  it("rejects min or max on a non-number field", () => {
+    const errors = validateManifest(
+      withSettings({
+        admin: [{ key: "a", type: "string", labelKey: "k", min: 1 }],
+      }),
+    );
+
+    expect(errors.join(" ")).toContain("only valid for number fields");
+  });
+
+  it("rejects requires that names no boolean in the same scope", () => {
+    const errors = validateManifest(
+      withSettings({
+        admin: [
+          { key: "a", type: "string", labelKey: "k", requires: "missing" },
+        ],
+      }),
+    );
+
+    expect(errors.join(" ")).toContain("must name a boolean field");
+  });
+
+  it("rejects requires that names a non-boolean field", () => {
+    const errors = validateManifest(
+      withSettings({
+        admin: [
+          { key: "flag", type: "string", labelKey: "k" },
+          { key: "a", type: "string", labelKey: "k", requires: "flag" },
+        ],
+      }),
+    );
+
+    expect(errors.join(" ")).toContain("must name a boolean field");
+  });
+
+  it("accepts requires pointing at a boolean declared later", () => {
+    const errors = validateManifest(
+      withSettings({
+        admin: [
+          { key: "a", type: "string", labelKey: "k", requires: "flag" },
+          { key: "flag", type: "boolean", labelKey: "k" },
+        ],
+      }),
+    );
+
+    expect(errors).toEqual([]);
+  });
+
+  it("lets a host field require the section's enable key", () => {
+    const errors = validateManifest(
+      withSettings({
+        host: {
+          enableKey: "enableThing",
+          enableLabelKey: "k",
+          fields: [
+            {
+              key: "port",
+              type: "number",
+              labelKey: "k",
+              requires: "enableThing",
+            },
+          ],
+        },
+      }),
+    );
+
+    expect(errors).toEqual([]);
+  });
+
+  it("rejects a host field colliding with the enable key", () => {
+    const errors = validateManifest(
+      withSettings({
+        host: {
+          enableKey: "enableThing",
+          enableLabelKey: "k",
+          fields: [{ key: "enableThing", type: "boolean", labelKey: "k" }],
+        },
+      }),
+    );
+
+    expect(errors.join(" ")).toContain("already the section's enableKey");
+  });
+
+  it("requires enableLabelKey alongside enableKey", () => {
+    const errors = validateManifest(
+      withSettings({
+        host: { enableKey: "enableThing", fields: [] },
+      }),
+    );
+
+    expect(errors.join(" ")).toContain("enableLabelKey");
+  });
+
+  it("rejects a key that would not be index-safe", () => {
+    const errors = validateManifest(
+      withSettings({
+        admin: [{ key: "a".repeat(80), type: "string", labelKey: "k" }],
+      }),
+    );
+
+    expect(errors.join(" ")).toContain("short alphanumeric key");
+  });
+});
+
+describe("settings field permissions", () => {
+  it("rejects a short permission the plugin does not declare", () => {
+    const { errors } = parseManifest(
+      base({
+        contributes: {
+          settings: {
+            user: [
+              { key: "a", type: "string", labelKey: "k", permission: "use" },
+            ],
+          },
+        },
+      }),
+    );
+
+    expect(errors.join(" ")).toContain(
+      "not declared in contributes.permissions",
+    );
+  });
+
+  it("accepts a short permission the plugin declares", () => {
+    const { errors, manifest } = parseManifest(
+      base({
+        contributes: {
+          permissions: [{ name: "use", titleKey: "k", descriptionKey: "k" }],
+          settings: {
+            user: [
+              { key: "a", type: "string", labelKey: "k", permission: "use" },
+            ],
+          },
+        },
+      }),
+    );
+
+    expect(errors).toEqual([]);
+    expect(manifest?.contributes?.settings?.user?.[0].permission).toBe("use");
+  });
+
+  it("accepts a fully qualified permission from another namespace", () => {
+    // Cross-namespace ids cannot be checked here: the validator has no idea
+    // which other plugins exist. Taken as given, exactly like ctx.rbac does.
+    const { errors } = parseManifest(
+      base({
+        contributes: {
+          settings: {
+            user: [
+              {
+                key: "a",
+                type: "string",
+                labelKey: "k",
+                permission: "hosts.view",
+              },
+            ],
+          },
+        },
+      }),
+    );
+
+    expect(errors).toEqual([]);
+  });
+});

src/backend/tests/plugins/settings-routes.test.ts

@@ -0,0 +1,498 @@
+/**
+ * The /plugins/:id/settings routes.
+ *
+ * These decide who may change what, so the tests are mostly about refusal: a
+ * non-admin must not write install-wide configuration, a user must not write
+ * another user's settings or a host they cannot edit, and a secret must never
+ * come back over the wire.
+ */
+
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import express from "express";
+import type { AddressInfo } from "node:net";
+import type { Server } from "node:http";
+import type { PluginManifest } from "@termix/plugin-sdk/manifest";
+
+const state = vi.hoisted(() => ({
+  userId: "user-1",
+  permissions: new Set<string>(),
+  hostEditAccess: true,
+}));
+
+vi.mock("../../utils/logger.js", () => {
+  const logger = {
+    debug: vi.fn(),
+    info: vi.fn(),
+    warn: vi.fn(),
+    error: vi.fn(),
+    success: vi.fn(),
+  };
+  return { pluginLogger: logger, databaseLogger: logger, apiLogger: logger };
+});
+
+vi.mock("../../utils/auth-manager.js", () => ({
+  AuthManager: {
+    getInstance: () => ({
+      createAuthMiddleware:
+        () =>
+        (
+          req: express.Request,
+          res: express.Response,
+          next: express.NextFunction,
+        ) => {
+          (req as express.Request & { userId?: string }).userId = state.userId;
+          next();
+        },
+    }),
+  },
+}));
+
+vi.mock("../../utils/permission-manager.js", () => ({
+  PermissionManager: {
+    getInstance: () => ({
+      hasPermission: async (_userId: string, permission: string) =>
+        state.permissions.has(permission),
+      requirePermission:
+        (permission: string) =>
+        (
+          _req: express.Request,
+          res: express.Response,
+          next: express.NextFunction,
+        ) => {
+          if (!state.permissions.has(permission)) {
+            res.status(403).json({ error: "Insufficient permissions" });
+            return;
+          }
+          next();
+        },
+      canAccessHost: async () => ({
+        hasAccess: state.hostEditAccess,
+        isOwner: state.hostEditAccess,
+        isShared: false,
+      }),
+    }),
+  },
+}));
+
+vi.mock("../../utils/audit-logger.js", () => ({
+  logAudit: vi.fn(async () => {}),
+  getAuditUsername: vi.fn(async (id: string) => id),
+  getRequestMeta: () => ({ ipAddress: "127.0.0.1", userAgent: "test" }),
+}));
+
+const MANIFEST: PluginManifest = {
+  id: "sample",
+  name: "Sample",
+  version: "1.0.0",
+  description: "",
+  author: { name: "t" },
+  license: "MIT",
+  category: "Productivity",
+  engine: { termix: ">=2.9.0", api: "1" },
+  capabilities: [],
+  contributes: {
+    permissions: [{ name: "tweak", titleKey: "k", descriptionKey: "k" }],
+    settings: {
+      admin: [
+        { key: "apiKey", type: "secret", labelKey: "k" },
+        { key: "retries", type: "number", labelKey: "k", min: 0, max: 5 },
+        {
+          key: "narrowed",
+          type: "string",
+          labelKey: "k",
+          permission: "tweak",
+        },
+      ],
+      user: [
+        { key: "theme", type: "string", labelKey: "k", default: "dark" },
+        {
+          key: "advanced",
+          type: "string",
+          labelKey: "k",
+          permission: "tweak",
+        },
+      ],
+      host: {
+        enableKey: "enableThing",
+        enableLabelKey: "k",
+        fields: [{ key: "port", type: "number", labelKey: "k" }],
+      },
+    },
+  },
+} as PluginManifest;
+
+vi.mock("../../plugins/index.js", () => ({
+  getPluginRuntime: () => ({
+    loader: {
+      get: (id: string) =>
+        id === "sample"
+          ? { id, manifest: MANIFEST, state: "active" }
+          : undefined,
+      list: () => [{ id: "sample", manifest: MANIFEST, state: "active" }],
+    },
+  }),
+}));
+
+interface Row {
+  pluginId: string;
+  scope: string;
+  scopeId: string | null;
+  key: string;
+  value: string | null;
+  encrypted: boolean;
+}
+
+const rows: Row[] = [];
+
+function find(scope: string, scopeId: string | null, key: string) {
+  return rows.find(
+    (row) => row.scope === scope && row.scopeId === scopeId && row.key === key,
+  );
+}
+
+vi.mock("../../database/repositories/factory.js", () => ({
+  createCurrentPluginRepository: () => ({
+    findById: async (id: string) =>
+      id === "sample"
+        ? { id, manifestJson: JSON.stringify(MANIFEST), state: "enabled" }
+        : null,
+    listAll: async () => [],
+  }),
+  createCurrentPluginPermissionGrantRepository: () => ({
+    listByPlugin: async () => [],
+  }),
+  createCurrentPluginSettingsRepository: () => ({
+    get: async (
+      _pluginId: string,
+      scope: string,
+      scopeId: string | null,
+      key: string,
+    ) => find(scope, scopeId, key) ?? null,
+    getAll: async (_pluginId: string, scope: string, scopeId: string | null) =>
+      rows.filter((row) => row.scope === scope && row.scopeId === scopeId),
+    set: async (
+      pluginId: string,
+      scope: string,
+      scopeId: string | null,
+      key: string,
+      value: string | null,
+      encrypted = false,
+    ) => {
+      const existing = find(scope, scopeId, key);
+      if (existing) {
+        existing.value = value;
+        existing.encrypted = encrypted;
+        return;
+      }
+      rows.push({ pluginId, scope, scopeId, key, value, encrypted });
+    },
+  }),
+  createCurrentSettingsRepository: () => ({ get: async () => null }),
+}));
+
+vi.mock("../../utils/system-secret-crypto.js", () => ({
+  isSystemEncrypted: (value: string) => value.startsWith("sysenc:v1:"),
+  encryptSystemSecret: async (plaintext: string) =>
+    !plaintext || plaintext.startsWith("sysenc:v1:")
+      ? plaintext
+      : `sysenc:v1:${Buffer.from(plaintext, "utf8").toString("base64")}`,
+  decryptSystemSecret: async (stored: string) =>
+    stored.startsWith("sysenc:v1:")
+      ? Buffer.from(stored.slice("sysenc:v1:".length), "base64").toString(
+          "utf8",
+        )
+      : stored,
+}));
+
+const pluginRoutes = (await import("../../database/routes/plugins.js")).default;
+
+let server: Server;
+let baseUrl: string;
+
+beforeEach(async () => {
+  rows.length = 0;
+  state.userId = "user-1";
+  state.permissions = new Set<string>();
+  state.hostEditAccess = true;
+
+  const app = express();
+  app.use(express.json());
+  app.use("/plugins", pluginRoutes);
+
+  server = await new Promise<Server>((resolve) => {
+    const created = app.listen(0, "127.0.0.1", () => resolve(created));
+  });
+  baseUrl = `http://127.0.0.1:${(server.address() as AddressInfo).port}`;
+});
+
+afterEach(async () => {
+  await new Promise<void>((resolve) => server.close(() => resolve()));
+});
+
+function call(path: string, init?: RequestInit) {
+  return fetch(`${baseUrl}${path}`, {
+    ...init,
+    headers: { "content-type": "application/json", ...(init?.headers ?? {}) },
+  });
+}
+
+describe("admin scope", () => {
+  it("refuses a reader without admin.plugins.manage", async () => {
+    const response = await call("/plugins/sample/settings/admin");
+
+    expect(response.status).toBe(403);
+  });
+
+  it("refuses a writer without admin.plugins.manage", async () => {
+    const response = await call("/plugins/sample/settings/admin", {
+      method: "PUT",
+      body: JSON.stringify({ retries: 2 }),
+    });
+
+    expect(response.status).toBe(403);
+    expect(rows).toHaveLength(0);
+  });
+
+  it("lets an admin read and write", async () => {
+    state.permissions.add("admin.plugins.manage");
+
+    const write = await call("/plugins/sample/settings/admin", {
+      method: "PUT",
+      body: JSON.stringify({ retries: 3 }),
+    });
+    expect(write.status).toBe(200);
+
+    const read = await call("/plugins/sample/settings/admin");
+    expect((await read.json()).values.retries).toBe(3);
+  });
+
+  it("reports a rejected value per field", async () => {
+    state.permissions.add("admin.plugins.manage");
+
+    const response = await call("/plugins/sample/settings/admin", {
+      method: "PUT",
+      body: JSON.stringify({ retries: 99 }),
+    });
+
+    expect(response.status).toBe(400);
+    expect((await response.json()).errors.retries).toContain("at most 5");
+    expect(rows).toHaveLength(0);
+  });
+
+  it("refuses a key the manifest never declared", async () => {
+    state.permissions.add("admin.plugins.manage");
+
+    const response = await call("/plugins/sample/settings/admin", {
+      method: "PUT",
+      body: JSON.stringify({ somethingElse: "x" }),
+    });
+
+    expect(response.status).toBe(400);
+    expect((await response.json()).errors.somethingElse).toBeDefined();
+    expect(rows).toHaveLength(0);
+  });
+
+  it("never returns a secret's value", async () => {
+    state.permissions.add("admin.plugins.manage");
+
+    await call("/plugins/sample/settings/admin", {
+      method: "PUT",
+      body: JSON.stringify({ apiKey: "tskey-very-secret" }),
+    });
+
+    const response = await call("/plugins/sample/settings/admin");
+    const body = await response.text();
+
+    expect(body).not.toContain("tskey-very-secret");
+    expect(JSON.parse(body).values.apiKey).toEqual({ set: true });
+  });
+
+  it("treats a redacted echo as no change", async () => {
+    state.permissions.add("admin.plugins.manage");
+
+    await call("/plugins/sample/settings/admin", {
+      method: "PUT",
+      body: JSON.stringify({ apiKey: "tskey-original" }),
+    });
+    await call("/plugins/sample/settings/admin", {
+      method: "PUT",
+      body: JSON.stringify({ apiKey: { set: true }, retries: 1 }),
+    });
+
+    const row = rows.find((entry) => entry.key === "apiKey")!;
+    expect(
+      Buffer.from(
+        JSON.parse(row.value!).slice("sysenc:v1:".length),
+        "base64",
+      ).toString("utf8"),
+    ).toBe("tskey-original");
+  });
+
+  it("keeps the admin gate even for a field naming its own permission", async () => {
+    // Holding the field's permission is not enough: admin scope is admin
+    // scope, so a plugin cannot hand install-wide config to an ordinary user.
+    state.permissions.add("sample.tweak");
+
+    const response = await call("/plugins/sample/settings/admin", {
+      method: "PUT",
+      body: JSON.stringify({ narrowed: "x" }),
+    });
+
+    expect(response.status).toBe(403);
+    expect(rows).toHaveLength(0);
+  });
+
+  it("narrows an admin field to holders of its permission", async () => {
+    state.permissions.add("admin.plugins.manage");
+
+    const denied = await call("/plugins/sample/settings/admin", {
+      method: "PUT",
+      body: JSON.stringify({ narrowed: "x" }),
+    });
+    expect(denied.status).toBe(400);
+    expect((await denied.json()).errors.narrowed).toContain("permission");
+
+    state.permissions.add("sample.tweak");
+    const allowed = await call("/plugins/sample/settings/admin", {
+      method: "PUT",
+      body: JSON.stringify({ narrowed: "x" }),
+    });
+    expect(allowed.status).toBe(200);
+  });
+
+  it("404s for a plugin that does not exist", async () => {
+    state.permissions.add("admin.plugins.manage");
+
+    const response = await call("/plugins/nope/settings/admin");
+
+    expect(response.status).toBe(404);
+  });
+
+  it("rejects a body that is not an object", async () => {
+    state.permissions.add("admin.plugins.manage");
+
+    const response = await call("/plugins/sample/settings/admin", {
+      method: "PUT",
+      body: JSON.stringify([1, 2, 3]),
+    });
+
+    expect(response.status).toBe(400);
+  });
+});
+
+describe("user scope", () => {
+  it("lets any authenticated user read and write their own", async () => {
+    const write = await call("/plugins/sample/settings/user", {
+      method: "PUT",
+      body: JSON.stringify({ theme: "light" }),
+    });
+    expect(write.status).toBe(200);
+
+    const read = await call("/plugins/sample/settings/user");
+    expect((await read.json()).values.theme).toBe("light");
+  });
+
+  it("scopes writes to the caller, never to a user id in the body", async () => {
+    await call("/plugins/sample/settings/user", {
+      method: "PUT",
+      body: JSON.stringify({ theme: "light", userId: "someone-else" }),
+    });
+
+    // The bogus key is rejected and the row belongs to the caller.
+    expect(rows.every((row) => row.scopeId === "user-1")).toBe(true);
+
+    state.userId = "user-2";
+    const other = await call("/plugins/sample/settings/user");
+    expect((await other.json()).values.theme).toBe("dark");
+  });
+
+  it("refuses a user field gated on a permission the caller lacks", async () => {
+    const response = await call("/plugins/sample/settings/user", {
+      method: "PUT",
+      body: JSON.stringify({ advanced: "x" }),
+    });
+
+    expect(response.status).toBe(400);
+    expect((await response.json()).errors.advanced).toContain("permission");
+    expect(rows).toHaveLength(0);
+  });
+
+  it("allows it once the caller holds that permission", async () => {
+    state.permissions.add("sample.tweak");
+
+    const response = await call("/plugins/sample/settings/user", {
+      method: "PUT",
+      body: JSON.stringify({ advanced: "x" }),
+    });
+
+    expect(response.status).toBe(200);
+  });
+
+  it("refuses an admin field through the user route", async () => {
+    const response = await call("/plugins/sample/settings/user", {
+      method: "PUT",
+      body: JSON.stringify({ apiKey: "nope" }),
+    });
+
+    expect(response.status).toBe(400);
+    expect(rows).toHaveLength(0);
+  });
+});
+
+describe("host scope", () => {
+  it("lets a user with edit access read and write", async () => {
+    const write = await call("/plugins/sample/settings/host/7", {
+      method: "PUT",
+      body: JSON.stringify({ enableThing: true, port: 22 }),
+    });
+    expect(write.status).toBe(200);
+
+    const read = await call("/plugins/sample/settings/host/7");
+    const values = (await read.json()).values;
+    expect(values.enableThing).toBe(true);
+    expect(values.port).toBe(22);
+  });
+
+  it("refuses a host the caller cannot edit", async () => {
+    state.hostEditAccess = false;
+
+    const read = await call("/plugins/sample/settings/host/7");
+    expect(read.status).toBe(403);
+
+    const write = await call("/plugins/sample/settings/host/7", {
+      method: "PUT",
+      body: JSON.stringify({ port: 22 }),
+    });
+    expect(write.status).toBe(403);
+    expect(rows).toHaveLength(0);
+  });
+
+  it("rejects an invalid host id", async () => {
+    const response = await call("/plugins/sample/settings/host/not-a-number");
+
+    expect(response.status).toBe(400);
+  });
+
+  it("keeps each host's values apart", async () => {
+    await call("/plugins/sample/settings/host/7", {
+      method: "PUT",
+      body: JSON.stringify({ port: 22 }),
+    });
+    await call("/plugins/sample/settings/host/8", {
+      method: "PUT",
+      body: JSON.stringify({ port: 2222 }),
+    });
+
+    const seven = await (await call("/plugins/sample/settings/host/7")).json();
+    const eight = await (await call("/plugins/sample/settings/host/8")).json();
+
+    expect(seven.values.port).toBe(22);
+    expect(eight.values.port).toBe(2222);
+  });
+
+  it("returns the declared default for an untouched host", async () => {
+    const response = await call("/plugins/sample/settings/host/9");
+
+    expect((await response.json()).values.enableThing).toBe(false);
+  });
+});

src/backend/tests/plugins/settings.test.ts

@@ -0,0 +1,442 @@
+/**
+ * The plugin settings service.
+ *
+ * Storage is faked at the repository boundary; everything above it - schema
+ * lookup, validation, encryption, redaction and change notification - is the
+ * real implementation, because that is where the behaviour worth protecting
+ * lives.
+ */
+
+import { beforeEach, describe, expect, it, vi } from "vitest";
+import type { PluginManifest } from "@termix/plugin-sdk/manifest";
+
+interface Row {
+  pluginId: string;
+  scope: string;
+  scopeId: string | null;
+  key: string;
+  value: string | null;
+  encrypted: boolean;
+}
+
+const rows: Row[] = [];
+
+function find(
+  pluginId: string,
+  scope: string,
+  scopeId: string | null,
+  key: string,
+) {
+  return rows.find(
+    (row) =>
+      row.pluginId === pluginId &&
+      row.scope === scope &&
+      row.scopeId === scopeId &&
+      row.key === key,
+  );
+}
+
+const settingsRepository = {
+  get: vi.fn(
+    async (
+      pluginId: string,
+      scope: string,
+      scopeId: string | null,
+      key: string,
+    ) => find(pluginId, scope, scopeId, key) ?? null,
+  ),
+  getAll: vi.fn(
+    async (pluginId: string, scope: string, scopeId: string | null) =>
+      rows.filter(
+        (row) =>
+          row.pluginId === pluginId &&
+          row.scope === scope &&
+          row.scopeId === scopeId,
+      ),
+  ),
+  set: vi.fn(
+    async (
+      pluginId: string,
+      scope: string,
+      scopeId: string | null,
+      key: string,
+      value: string | null,
+      encrypted = false,
+    ) => {
+      const existing = find(pluginId, scope, scopeId, key);
+      if (existing) {
+        existing.value = value;
+        existing.encrypted = encrypted;
+        return;
+      }
+      rows.push({ pluginId, scope, scopeId, key, value, encrypted });
+    },
+  ),
+};
+
+const coreSettings = new Map<string, string>();
+
+vi.mock("../../database/repositories/factory.js", () => ({
+  createCurrentPluginSettingsRepository: () => settingsRepository,
+  createCurrentSettingsRepository: () => ({
+    get: async (key: string) => coreSettings.get(key) ?? null,
+  }),
+}));
+
+// Real AES would need the system key on disk. The prefix and the idempotence
+// are what the service depends on, so the double keeps both.
+vi.mock("../../utils/system-secret-crypto.js", () => ({
+  isSystemEncrypted: (value: string) => value.startsWith("sysenc:v1:"),
+  encryptSystemSecret: async (plaintext: string) =>
+    !plaintext || plaintext.startsWith("sysenc:v1:")
+      ? plaintext
+      : `sysenc:v1:${Buffer.from(plaintext, "utf8").toString("base64")}`,
+  decryptSystemSecret: async (stored: string) =>
+    stored.startsWith("sysenc:v1:")
+      ? Buffer.from(stored.slice("sysenc:v1:".length), "base64").toString(
+          "utf8",
+        )
+      : stored,
+}));
+
+const {
+  CORE_SETTINGS_ALLOWLIST,
+  clearSettingsListeners,
+  declaredFields,
+  findField,
+  getAllSettings,
+  getSetting,
+  onSettingsChange,
+  readCoreSetting,
+  setSetting,
+} = await import("../../plugins/settings.js");
+
+function manifest(settings: unknown): PluginManifest {
+  return {
+    id: "sample",
+    name: "Sample",
+    version: "1.0.0",
+    description: "",
+    author: { name: "t" },
+    license: "MIT",
+    category: "Productivity",
+    engine: { termix: ">=2.9.0", api: "1" },
+    capabilities: [],
+    contributes: { settings },
+  } as PluginManifest;
+}
+
+const ADMIN = manifest({
+  admin: [
+    { key: "apiKey", type: "secret", labelKey: "k" },
+    { key: "baseUrl", type: "string", labelKey: "k", default: "https://x" },
+    { key: "retries", type: "number", labelKey: "k", min: 0, max: 5 },
+    { key: "enabled", type: "boolean", labelKey: "k", default: false },
+    {
+      key: "mode",
+      type: "select",
+      labelKey: "k",
+      options: [
+        { value: "fast", labelKey: "k" },
+        { value: "slow", labelKey: "k" },
+      ],
+    },
+  ],
+});
+
+beforeEach(() => {
+  rows.length = 0;
+  coreSettings.clear();
+  clearSettingsListeners("sample");
+  vi.clearAllMocks();
+});
+
+describe("declaredFields", () => {
+  it("returns the fields for each scope", () => {
+    expect(declaredFields(ADMIN, "admin").map((f) => f.key)).toEqual([
+      "apiKey",
+      "baseUrl",
+      "retries",
+      "enabled",
+      "mode",
+    ]);
+    expect(declaredFields(ADMIN, "user")).toEqual([]);
+  });
+
+  it("treats the host enable key as a real boolean field", () => {
+    const withHost = manifest({
+      host: {
+        enableKey: "enableThing",
+        enableLabelKey: "k",
+        fields: [{ key: "port", type: "number", labelKey: "k" }],
+      },
+    });
+
+    const fields = declaredFields(withHost, "host");
+    expect(fields.map((f) => f.key)).toEqual(["enableThing", "port"]);
+    expect(fields[0]).toMatchObject({ type: "boolean", default: false });
+  });
+
+  it("finds a field by key", () => {
+    expect(findField(ADMIN, "admin", "baseUrl")?.type).toBe("string");
+    expect(findField(ADMIN, "admin", "nope")).toBeUndefined();
+  });
+});
+
+describe("setSetting", () => {
+  it("writes a valid value and reads it back", async () => {
+    expect(
+      await setSetting(ADMIN, "admin", null, "baseUrl", "https://y"),
+    ).toBeNull();
+    expect(await getSetting(ADMIN, "admin", null, "baseUrl")).toBe("https://y");
+  });
+
+  it("refuses a key the manifest never declared", async () => {
+    const error = await setSetting(ADMIN, "admin", null, "wat", "x");
+
+    expect(error).toContain("not a settings field this plugin declares");
+    expect(rows).toHaveLength(0);
+  });
+
+  it("refuses a value that fails the declared constraint", async () => {
+    expect(await setSetting(ADMIN, "admin", null, "retries", 99)).toContain(
+      "at most 5",
+    );
+    expect(
+      await setSetting(ADMIN, "admin", null, "mode", "sideways"),
+    ).toContain("must be one of");
+    expect(rows).toHaveLength(0);
+  });
+
+  it("coerces the strings a form actually sends", async () => {
+    expect(await setSetting(ADMIN, "admin", null, "retries", "3")).toBeNull();
+    expect(await getSetting(ADMIN, "admin", null, "retries")).toBe(3);
+
+    expect(
+      await setSetting(ADMIN, "admin", null, "enabled", "true"),
+    ).toBeNull();
+    expect(await getSetting(ADMIN, "admin", null, "enabled")).toBe(true);
+  });
+
+  it("keeps each scope separate", async () => {
+    const scoped = manifest({
+      admin: [{ key: "v", type: "string", labelKey: "k" }],
+      user: [{ key: "v", type: "string", labelKey: "k" }],
+      host: { fields: [{ key: "v", type: "string", labelKey: "k" }] },
+    });
+
+    await setSetting(scoped, "admin", null, "v", "a");
+    await setSetting(scoped, "user", "user-1", "v", "u");
+    await setSetting(scoped, "host", 7, "v", "h");
+
+    expect(await getSetting(scoped, "admin", null, "v")).toBe("a");
+    expect(await getSetting(scoped, "user", "user-1", "v")).toBe("u");
+    expect(await getSetting(scoped, "host", 7, "v")).toBe("h");
+    // A different user sees nothing of the first user's value.
+    expect(await getSetting(scoped, "user", "user-2", "v")).toBeUndefined();
+  });
+
+  it("stores a host id as text, matching the polymorphic scope column", async () => {
+    const scoped = manifest({
+      host: { fields: [{ key: "v", type: "string", labelKey: "k" }] },
+    });
+
+    await setSetting(scoped, "host", 12, "v", "x");
+
+    expect(rows[0].scopeId).toBe("12");
+    // Either spelling resolves to the same row.
+    expect(await getSetting(scoped, "host", "12", "v")).toBe("x");
+  });
+});
+
+describe("defaults", () => {
+  it("falls back to the declared default when nothing is stored", async () => {
+    expect(await getSetting(ADMIN, "admin", null, "baseUrl")).toBe("https://x");
+    expect(await getSetting(ADMIN, "admin", null, "enabled")).toBe(false);
+  });
+
+  it("returns undefined for a field with no default and no value", async () => {
+    expect(await getSetting(ADMIN, "admin", null, "retries")).toBeUndefined();
+  });
+
+  it("returns undefined for a key the manifest does not declare", async () => {
+    expect(await getSetting(ADMIN, "admin", null, "wat")).toBeUndefined();
+  });
+});
+
+describe("secrets", () => {
+  it("encrypts on the way in and decrypts on the way out", async () => {
+    await setSetting(ADMIN, "admin", null, "apiKey", "tskey-secret");
+
+    const row = rows.find((entry) => entry.key === "apiKey")!;
+    expect(row.encrypted).toBe(true);
+    expect(row.value).not.toContain("tskey-secret");
+    expect(JSON.parse(row.value!)).toMatch(/^sysenc:v1:/);
+
+    expect(await getSetting(ADMIN, "admin", null, "apiKey")).toBe(
+      "tskey-secret",
+    );
+  });
+
+  it("redacts a secret rather than returning it", async () => {
+    await setSetting(ADMIN, "admin", null, "apiKey", "tskey-secret");
+
+    const values = await getAllSettings(ADMIN, "admin", null, {
+      redactSecrets: true,
+    });
+
+    expect(values.apiKey).toEqual({ set: true });
+    expect(JSON.stringify(values)).not.toContain("tskey-secret");
+  });
+
+  it("reports an unset secret as set:false", async () => {
+    const values = await getAllSettings(ADMIN, "admin", null, {
+      redactSecrets: true,
+    });
+
+    expect(values.apiKey).toEqual({ set: false });
+  });
+
+  it("treats a redacted echo as leave-it-alone", async () => {
+    await setSetting(ADMIN, "admin", null, "apiKey", "original");
+
+    expect(
+      await setSetting(ADMIN, "admin", null, "apiKey", { set: true }),
+    ).toBeNull();
+
+    expect(await getSetting(ADMIN, "admin", null, "apiKey")).toBe("original");
+  });
+
+  it("lets a secret be replaced and cleared", async () => {
+    await setSetting(ADMIN, "admin", null, "apiKey", "first");
+    await setSetting(ADMIN, "admin", null, "apiKey", "second");
+    expect(await getSetting(ADMIN, "admin", null, "apiKey")).toBe("second");
+
+    await setSetting(ADMIN, "admin", null, "apiKey", "");
+    const values = await getAllSettings(ADMIN, "admin", null, {
+      redactSecrets: true,
+    });
+    expect(values.apiKey).toEqual({ set: false });
+  });
+
+  it("hands a plugin its own secret in the clear", async () => {
+    await setSetting(ADMIN, "admin", null, "apiKey", "tskey-secret");
+
+    const values = await getAllSettings(ADMIN, "admin", null);
+
+    expect(values.apiKey).toBe("tskey-secret");
+  });
+});
+
+describe("getAllSettings", () => {
+  it("is driven by the manifest, not by the stored rows", async () => {
+    await setSetting(ADMIN, "admin", null, "baseUrl", "https://y");
+    // A row for a field the plugin has since dropped.
+    rows.push({
+      pluginId: "sample",
+      scope: "admin",
+      scopeId: null,
+      key: "removedField",
+      value: JSON.stringify("stale"),
+      encrypted: false,
+    });
+
+    const values = await getAllSettings(ADMIN, "admin", null);
+
+    expect(values.baseUrl).toBe("https://y");
+    expect(values.enabled).toBe(false);
+    expect(values).not.toHaveProperty("removedField");
+  });
+
+  it("returns nothing for a scope the plugin declares no fields in", async () => {
+    expect(await getAllSettings(ADMIN, "user", "user-1")).toEqual({});
+  });
+});
+
+describe("onSettingsChange", () => {
+  it("fires on a successful write", async () => {
+    const listener = vi.fn();
+    onSettingsChange("sample", "baseUrl", listener);
+
+    await setSetting(ADMIN, "admin", null, "baseUrl", "https://z");
+
+    expect(listener).toHaveBeenCalledWith("https://z");
+  });
+
+  it("does not fire for a rejected write", async () => {
+    const listener = vi.fn();
+    onSettingsChange("sample", "retries", listener);
+
+    await setSetting(ADMIN, "admin", null, "retries", 99);
+
+    expect(listener).not.toHaveBeenCalled();
+  });
+
+  it("stops firing once unsubscribed", async () => {
+    const listener = vi.fn();
+    const unsubscribe = onSettingsChange("sample", "baseUrl", listener);
+
+    unsubscribe();
+    await setSetting(ADMIN, "admin", null, "baseUrl", "https://z");
+
+    expect(listener).not.toHaveBeenCalled();
+  });
+
+  it("only notifies listeners for that key and plugin", async () => {
+    const other = vi.fn();
+    const another = vi.fn();
+    onSettingsChange("sample", "enabled", other);
+    onSettingsChange("different-plugin", "baseUrl", another);
+
+    await setSetting(ADMIN, "admin", null, "baseUrl", "https://z");
+
+    expect(other).not.toHaveBeenCalled();
+    expect(another).not.toHaveBeenCalled();
+    clearSettingsListeners("different-plugin");
+  });
+
+  it("survives a listener that throws", async () => {
+    const good = vi.fn();
+    onSettingsChange("sample", "baseUrl", () => {
+      throw new Error("listener blew up");
+    });
+    onSettingsChange("sample", "baseUrl", good);
+
+    await expect(
+      setSetting(ADMIN, "admin", null, "baseUrl", "https://z"),
+    ).resolves.toBeNull();
+    expect(good).toHaveBeenCalled();
+  });
+
+  it("drops every listener when the plugin deactivates", async () => {
+    const listener = vi.fn();
+    onSettingsChange("sample", "baseUrl", listener);
+
+    clearSettingsListeners("sample");
+    await setSetting(ADMIN, "admin", null, "baseUrl", "https://z");
+
+    expect(listener).not.toHaveBeenCalled();
+  });
+});
+
+describe("readCoreSetting", () => {
+  it("returns an allowlisted key", async () => {
+    coreSettings.set("app_name", "Termix");
+
+    expect(await readCoreSetting("app_name")).toBe("Termix");
+  });
+
+  it("refuses a key that is not on the allowlist", async () => {
+    coreSettings.set("jwt_secret", "nope");
+
+    await expect(readCoreSetting("jwt_secret")).rejects.toThrow(
+      /not readable by plugins/,
+    );
+  });
+
+  it("does not expose anything sensitive through the allowlist", () => {
+    for (const key of CORE_SETTINGS_ALLOWLIST) {
+      expect(key).not.toMatch(/secret|password|token|key$/i);
+    }
+  });
+});

src/backend/tests/utils/tailscale-settings-migration.test.ts

@@ -0,0 +1,228 @@
+/**
+ * The Tailscale settings migration.
+ *
+ * An upgrade must be lossless: an install that had a working API key must keep
+ * working without anyone re-entering it. That is the whole point of the test,
+ * and running it twice proves a restart cannot corrupt what it moved.
+ */
+
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+interface Row {
+  pluginId: string;
+  scope: string;
+  scopeId: string | null;
+  key: string;
+  value: string | null;
+  encrypted: boolean;
+}
+
+const coreSettings = new Map<string, string>();
+const pluginRows: Row[] = [];
+let pluginInstalled = true;
+
+const pluginSettingsRepository = {
+  get: async (
+    pluginId: string,
+    scope: string,
+    scopeId: string | null,
+    key: string,
+  ) =>
+    pluginRows.find(
+      (row) =>
+        row.pluginId === pluginId &&
+        row.scope === scope &&
+        row.scopeId === scopeId &&
+        row.key === key,
+    ) ?? null,
+  set: async (
+    pluginId: string,
+    scope: string,
+    scopeId: string | null,
+    key: string,
+    value: string | null,
+    encrypted = false,
+  ) => {
+    const existing = pluginRows.find(
+      (row) =>
+        row.pluginId === pluginId &&
+        row.scope === scope &&
+        row.scopeId === scopeId &&
+        row.key === key,
+    );
+    if (existing) {
+      existing.value = value;
+      existing.encrypted = encrypted;
+      return;
+    }
+    pluginRows.push({ pluginId, scope, scopeId, key, value, encrypted });
+  },
+};
+
+vi.mock("../../database/repositories/factory.js", () => ({
+  createCurrentPluginRepository: () => ({
+    findById: async (id: string) =>
+      pluginInstalled && id === "tailscale" ? { id } : null,
+  }),
+  createCurrentPluginSettingsRepository: () => pluginSettingsRepository,
+  createCurrentSettingsRepository: () => ({
+    get: async (key: string) => coreSettings.get(key) ?? null,
+    delete: async (key: string) => coreSettings.delete(key),
+  }),
+}));
+
+vi.mock("../../utils/system-secret-crypto.js", () => ({
+  isSystemEncrypted: (value: string) => value.startsWith("sysenc:v1:"),
+  encryptSystemSecret: async (plaintext: string) =>
+    !plaintext || plaintext.startsWith("sysenc:v1:")
+      ? plaintext
+      : `sysenc:v1:${Buffer.from(plaintext, "utf8").toString("base64")}`,
+  decryptSystemSecret: async (stored: string) =>
+    stored.startsWith("sysenc:v1:")
+      ? Buffer.from(stored.slice("sysenc:v1:".length), "base64").toString(
+          "utf8",
+        )
+      : stored,
+}));
+
+const { runTailscaleSettingsMigration } =
+  await import("../../utils/crypto-migration/tailscale-settings-migration.js");
+
+function storedValue(key: string): unknown {
+  const row = pluginRows.find((entry) => entry.key === key);
+  return row?.value === null || row?.value === undefined
+    ? undefined
+    : JSON.parse(row.value);
+}
+
+beforeEach(() => {
+  coreSettings.clear();
+  pluginRows.length = 0;
+  pluginInstalled = true;
+});
+
+describe("runTailscaleSettingsMigration", () => {
+  it("moves an existing key and base URL into plugin settings", async () => {
+    coreSettings.set("tailscale_api_key", "tskey-api-legacy");
+    coreSettings.set("tailscale_api_base_url", "https://headscale.example");
+
+    const result = await runTailscaleSettingsMigration();
+
+    expect(result.moved).toEqual([
+      "tailscale_api_key",
+      "tailscale_api_base_url",
+    ]);
+    expect(storedValue("apiKey")).toMatch(/^sysenc:v1:/);
+    expect(storedValue("apiBaseUrl")).toBe("https://headscale.example");
+  });
+
+  it("encrypts the key, which was stored in plaintext before", async () => {
+    coreSettings.set("tailscale_api_key", "tskey-api-legacy");
+
+    await runTailscaleSettingsMigration();
+
+    const row = pluginRows.find((entry) => entry.key === "apiKey")!;
+    expect(row.encrypted).toBe(true);
+    expect(row.value).not.toContain("tskey-api-legacy");
+  });
+
+  it("leaves the base URL readable, since it is not a secret", async () => {
+    coreSettings.set("tailscale_api_base_url", "https://headscale.example");
+
+    await runTailscaleSettingsMigration();
+
+    const row = pluginRows.find((entry) => entry.key === "apiBaseUrl")!;
+    expect(row.encrypted).toBe(false);
+  });
+
+  it("removes the legacy rows so no plaintext key is left behind", async () => {
+    coreSettings.set("tailscale_api_key", "tskey-api-legacy");
+    coreSettings.set("tailscale_api_base_url", "https://headscale.example");
+
+    await runTailscaleSettingsMigration();
+
+    expect(coreSettings.has("tailscale_api_key")).toBe(false);
+    expect(coreSettings.has("tailscale_api_base_url")).toBe(false);
+  });
+
+  it("is idempotent: a second run changes nothing", async () => {
+    coreSettings.set("tailscale_api_key", "tskey-api-legacy");
+    coreSettings.set("tailscale_api_base_url", "https://headscale.example");
+
+    await runTailscaleSettingsMigration();
+    const afterFirst = JSON.parse(JSON.stringify(pluginRows));
+
+    const second = await runTailscaleSettingsMigration();
+
+    expect(second.moved).toEqual([]);
+    expect(pluginRows).toEqual(afterFirst);
+  });
+
+  it("cannot double-encrypt the key across runs", async () => {
+    coreSettings.set("tailscale_api_key", "tskey-api-legacy");
+
+    await runTailscaleSettingsMigration();
+    const first = storedValue("apiKey");
+
+    await runTailscaleSettingsMigration();
+
+    expect(storedValue("apiKey")).toBe(first);
+    expect(String(storedValue("apiKey")).match(/sysenc:v1:/g)).toHaveLength(1);
+  });
+
+  it("drops a stale legacy row when the value was already moved", async () => {
+    // An interrupted run, or a downgrade that rewrote the old key.
+    await pluginSettingsRepository.set(
+      "tailscale",
+      "admin",
+      null,
+      "apiKey",
+      JSON.stringify("sysenc:v1:already"),
+      true,
+    );
+    coreSettings.set("tailscale_api_key", "tskey-plaintext-leftover");
+
+    const result = await runTailscaleSettingsMigration();
+
+    expect(result.skipped).toContain("tailscale_api_key");
+    expect(storedValue("apiKey")).toBe("sysenc:v1:already");
+    expect(coreSettings.has("tailscale_api_key")).toBe(false);
+  });
+
+  it("does nothing on a fresh install with no legacy rows", async () => {
+    const result = await runTailscaleSettingsMigration();
+
+    expect(result.moved).toEqual([]);
+    expect(pluginRows).toEqual([]);
+  });
+
+  it("skips an empty legacy value rather than storing one", async () => {
+    coreSettings.set("tailscale_api_key", "");
+
+    const result = await runTailscaleSettingsMigration();
+
+    expect(result.moved).toEqual([]);
+    expect(pluginRows).toEqual([]);
+  });
+
+  it("waits for the plugin row, because of the foreign key", async () => {
+    pluginInstalled = false;
+    coreSettings.set("tailscale_api_key", "tskey-api-legacy");
+
+    const result = await runTailscaleSettingsMigration();
+
+    expect(result.moved).toEqual([]);
+    expect(pluginRows).toEqual([]);
+    // Still there for the next boot, once the plugin is seeded.
+    expect(coreSettings.get("tailscale_api_key")).toBe("tskey-api-legacy");
+  });
+
+  it("moves each key independently", async () => {
+    coreSettings.set("tailscale_api_key", "tskey-api-legacy");
+
+    const result = await runTailscaleSettingsMigration();
+
+    expect(result.moved).toEqual(["tailscale_api_key"]);
+    expect(storedValue("apiBaseUrl")).toBeUndefined();
+  });
+});

src/backend/utils/crypto-migration/tailscale-settings-migration.ts

@@ -0,0 +1,105 @@
+/**
+ * Moves the Tailscale API key and base URL out of core settings.
+ *
+ * Both lived in the core `settings` table, written by a core route that existed
+ * only to serve one plugin. A6 gives plugins their own settings, so they belong
+ * in plugin_settings under the tailscale plugin.
+ *
+ * The key was stored in plaintext, and the route that read it back masked only
+ * its tail while being open to any authenticated user. Landing it as a secret
+ * field encrypts it at rest, so this migration is a fix as much as a move.
+ *
+ * Idempotent in two ways: it stops when a value is already present in the new
+ * home, and encryptSystemSecret returns an already-encrypted value unchanged,
+ * so a second pass can neither duplicate nor double-encrypt.
+ */
+
+import { databaseLogger } from "../logger.js";
+import {
+  createCurrentPluginRepository,
+  createCurrentPluginSettingsRepository,
+  createCurrentSettingsRepository,
+} from "../../database/repositories/factory.js";
+import { encryptSystemSecret } from "../system-secret-crypto.js";
+
+const PLUGIN_ID = "tailscale";
+
+/** Legacy core key -> the field the plugin now declares. */
+const MOVES: { legacyKey: string; field: string; secret: boolean }[] = [
+  { legacyKey: "tailscale_api_key", field: "apiKey", secret: true },
+  { legacyKey: "tailscale_api_base_url", field: "apiBaseUrl", secret: false },
+];
+
+export interface TailscaleSettingsMigrationResult {
+  moved: string[];
+  skipped: string[];
+}
+
+export async function runTailscaleSettingsMigration(): Promise<TailscaleSettingsMigrationResult> {
+  const moved: string[] = [];
+  const skipped: string[] = [];
+
+  try {
+    // The FK to plugins means there is nothing to migrate into until the
+    // plugin has been seeded. Not an error: a build without it just has no
+    // tailscale rows.
+    const plugin = await createCurrentPluginRepository().findById(PLUGIN_ID);
+    if (!plugin) return { moved, skipped };
+
+    const settingsRepository = createCurrentSettingsRepository();
+    const pluginSettingsRepository = createCurrentPluginSettingsRepository();
+
+    for (const move of MOVES) {
+      const legacyValue = await settingsRepository.get(move.legacyKey);
+      if (legacyValue === null || legacyValue === "") {
+        continue;
+      }
+
+      const existing = await pluginSettingsRepository.get(
+        PLUGIN_ID,
+        "admin",
+        null,
+        move.field,
+      );
+      if (existing && existing.value !== null) {
+        // Already moved. Drop the stale copy rather than leaving a plaintext
+        // key behind for a reader that predates this change.
+        await settingsRepository.delete(move.legacyKey);
+        skipped.push(move.legacyKey);
+        continue;
+      }
+
+      const stored = move.secret
+        ? await encryptSystemSecret(legacyValue)
+        : legacyValue;
+
+      await pluginSettingsRepository.set(
+        PLUGIN_ID,
+        "admin",
+        null,
+        move.field,
+        JSON.stringify(stored),
+        move.secret,
+      );
+
+      await settingsRepository.delete(move.legacyKey);
+      moved.push(move.legacyKey);
+    }
+
+    if (moved.length > 0) {
+      databaseLogger.info(
+        `Moved ${moved.length} Tailscale setting(s) into plugin settings`,
+        { operation: "tailscale_settings_migration", moved: moved.join(", ") },
+      );
+    }
+  } catch (error) {
+    // A failed migration must not stop the backend. The plugin falls back to
+    // "no key configured", which is a visible, recoverable state.
+    databaseLogger.warn("Tailscale settings migration failed", {
+      operation: "tailscale_settings_migration",
+      error: error instanceof Error ? error.message : String(error),
+    });
+  }
+
+  return { moved, skipped };
+}