diff --git a/package.json b/package.json
new file mode 100644
index 0000000..eed2fae
--- /dev/null
+++ b/package.json
@@ -0,0 +1,21 @@
+{
+  "name": "@verstak/plugin-sdk",
+  "version": "0.1.0",
+  "description": "Verstak Plugin SDK — TypeScript types and runtime API for plugin development",
+  "main": "dist/index.js",
+  "types": "dist/index.d.ts",
+  "files": [
+    "dist/",
+    "schemas/"
+  ],
+  "scripts": {
+    "build": "tsc",
+    "test": "vitest run",
+    "lint": "tsc --noEmit",
+    "prepack": "npm run build"
+  },
+  "devDependencies": {
+    "typescript": "^5.4.0",
+    "vitest": "^1.6.0"
+  }
+}
diff --git a/schemas/capabilities.json b/schemas/capabilities.json
new file mode 100644
index 0000000..12c4585
--- /dev/null
+++ b/schemas/capabilities.json
@@ -0,0 +1,66 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.mirv.top/verstak/verstak-sdk/schemas/capabilities.json",
+  "title": "Verstak Capability Registry",
+  "description": "Known capability names and their descriptions for the Verstak platform",
+  "type": "object",
+  "properties": {
+    "capabilities": {
+      "type": "array",
+      "items": {
+        "$ref": "#/$defs/CapabilityEntry"
+      }
+    }
+  },
+  "$defs": {
+    "CapabilityEntry": {
+      "type": "object",
+      "properties": {
+        "name": { "type": "string" },
+        "description": { "type": "string" },
+        "status": {
+          "type": "string",
+          "enum": ["stable", "draft", "deprecated"]
+        }
+      },
+      "required": ["name", "description", "status"]
+    }
+  },
+  "capabilities": [
+    { "name": "editor.text", "description": "Text editing capability (any format)", "status": "draft" },
+    { "name": "editor.text.markdown", "description": "Markdown text editing", "status": "draft" },
+    { "name": "editor.note.markdown", "description": "Markdown note editing (extends editor.text.markdown with note metadata)", "status": "draft" },
+    { "name": "viewer.file", "description": "File viewer (any type)", "status": "draft" },
+    { "name": "viewer.image", "description": "Image viewer", "status": "draft" },
+    { "name": "viewer.text", "description": "Text file viewer", "status": "draft" },
+    { "name": "viewer.markdown", "description": "Markdown rendered viewer", "status": "draft" },
+    { "name": "preview.markdown", "description": "Markdown preview panel", "status": "draft" },
+    { "name": "preview.file", "description": "File preview panel", "status": "draft" },
+    { "name": "workspace.files", "description": "File workspace management", "status": "draft" },
+    { "name": "workspace.notes", "description": "Note workspace management", "status": "draft" },
+    { "name": "vault.files", "description": "Low-level vault file read/write access", "status": "draft" },
+    { "name": "entity.file", "description": "File entity type support", "status": "draft" },
+    { "name": "entity.note", "description": "Note entity type support", "status": "draft" },
+    { "name": "note.registry", "description": "Note metadata registry", "status": "draft" },
+    { "name": "file.browser", "description": "File browser tree/list UI", "status": "draft" },
+    { "name": "activity.log", "description": "Activity event logging", "status": "draft" },
+    { "name": "activity.provider", "description": "Activity event provider", "status": "draft" },
+    { "name": "activity.reconstruction", "description": "Activity reconstruction from events", "status": "draft" },
+    { "name": "worklog", "description": "Worklog/journal entry capability", "status": "draft" },
+    { "name": "journal", "description": "Journal UI capability", "status": "draft" },
+    { "name": "report.worklog", "description": "Worklog report generation", "status": "draft" },
+    { "name": "capture.browser", "description": "Browser capture receiver", "status": "draft" },
+    { "name": "browser.inbox", "description": "Browser inbox UI capability", "status": "draft" },
+    { "name": "domain.binding", "description": "Domain-to-case binding", "status": "draft" },
+    { "name": "search", "description": "Full-text search capability", "status": "draft" },
+    { "name": "search.provider", "description": "Search result provider", "status": "draft" },
+    { "name": "search.indexer", "description": "Search indexer service", "status": "draft" },
+    { "name": "secret-store", "description": "Encrypted secret storage", "status": "draft" },
+    { "name": "secrets.read-ui", "description": "Secret read user interface", "status": "draft" },
+    { "name": "secrets.write-ui", "description": "Secret write user interface", "status": "draft" },
+    { "name": "case.templates", "description": "Case template provider", "status": "draft" },
+    { "name": "link.resolver", "description": "Internal link resolver (verstak://)", "status": "draft" },
+    { "name": "importer", "description": "Data import capability", "status": "draft" },
+    { "name": "exporter", "description": "Data export capability", "status": "draft" }
+  ]
+}
diff --git a/schemas/contributions.json b/schemas/contributions.json
new file mode 100644
index 0000000..3da65cf
--- /dev/null
+++ b/schemas/contributions.json
@@ -0,0 +1,49 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.mirv.top/verstak/verstak-sdk/schemas/contributions.json",
+  "title": "Verstak Contribution Points Registry",
+  "description": "Known contribution points that plugins can register",
+  "type": "object",
+  "properties": {
+    "contributionPoints": {
+      "type": "array",
+      "items": {
+        "$ref": "#/$defs/ContributionPoint"
+      }
+    }
+  },
+  "$defs": {
+    "ContributionPoint": {
+      "type": "object",
+      "properties": {
+        "id": { "type": "string" },
+        "description": { "type": "string" },
+        "type": {
+          "type": "string",
+          "enum": ["view", "command", "item", "provider", "panel", "action", "entry"]
+        },
+        "status": {
+          "type": "string",
+          "enum": ["stable", "draft", "deprecated"]
+        }
+      },
+      "required": ["id", "description", "type", "status"]
+    }
+  },
+  "contributionPoints": [
+    { "id": "sidebar.items", "description": "Sidebar navigation items", "type": "item", "status": "draft" },
+    { "id": "main.views", "description": "Main content views", "type": "view", "status": "draft" },
+    { "id": "case.tabs", "description": "Case detail tabs", "type": "view", "status": "draft" },
+    { "id": "file.actions", "description": "File context actions", "type": "action", "status": "draft" },
+    { "id": "note.actions", "description": "Note context actions", "type": "action", "status": "draft" },
+    { "id": "context.menu", "description": "Context menu entries", "type": "entry", "status": "draft" },
+    { "id": "commands", "description": "Command palette commands", "type": "command", "status": "draft" },
+    { "id": "settings.panels", "description": "Plugin settings panels", "type": "panel", "status": "draft" },
+    { "id": "search.providers", "description": "Search result providers", "type": "provider", "status": "draft" },
+    { "id": "activity.providers", "description": "Activity event providers", "type": "provider", "status": "draft" },
+    { "id": "status.bar.items", "description": "Status bar items", "type": "item", "status": "draft" },
+    { "id": "importers", "description": "Data import providers", "type": "provider", "status": "draft" },
+    { "id": "exporters", "description": "Data export providers", "type": "provider", "status": "draft" },
+    { "id": "protocol.receivers", "description": "Custom protocol message receivers", "type": "provider", "status": "draft" }
+  ]
+}
diff --git a/schemas/events/browser.json b/schemas/events/browser.json
new file mode 100644
index 0000000..17c9392
--- /dev/null
+++ b/schemas/events/browser.json
@@ -0,0 +1,131 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.mirv.top/verstak/verstak-sdk/schemas/events/browser.json",
+  "title": "Verstak Browser Events",
+  "description": "Event schemas for browser extension and browser-inbox plugin communication",
+  "type": "object",
+  "properties": {
+    "events": {
+      "type": "array",
+      "items": {
+        "$ref": "#/$defs/BrowserEvent"
+      }
+    }
+  },
+  "$defs": {
+    "BrowserEvent": {
+      "type": "object",
+      "properties": {
+        "name": { "type": "string" },
+        "description": { "type": "string" },
+        "schema": {
+          "type": "object",
+          "properties": {
+            "type": { "type": "string", "const": "object" },
+            "properties": {
+              "type": "object",
+              "additionalProperties": {
+                "oneOf": [
+                  { "type": "string" },
+                  { "type": "integer" },
+                  { "type": "boolean" },
+                  { "type": "array" },
+                  { "type": "object" }
+                ]
+              }
+            },
+            "required": {
+              "type": "array",
+              "items": { "type": "string" }
+            }
+          },
+          "required": ["type", "properties", "required"]
+        }
+      },
+      "required": ["name", "description", "schema"]
+    }
+  },
+  "events": [
+    {
+      "name": "browser.capture.page",
+      "description": "Full page capture sent from browser extension",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "url": { "type": "string", "description": "Page URL" },
+          "title": { "type": "string", "description": "Page title" },
+          "html": { "type": "string", "description": "Page HTML content" },
+          "text": { "type": "string", "description": "Page text content" },
+          "capturedAt": { "type": "string", "description": "ISO 8601 timestamp" },
+          "domain": { "type": "string", "description": "Extracted domain" }
+        },
+        "required": ["url", "title", "capturedAt"]
+      }
+    },
+    {
+      "name": "browser.capture.selection",
+      "description": "Selected text sent from browser extension",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "url": { "type": "string", "description": "Source page URL" },
+          "title": { "type": "string", "description": "Source page title" },
+          "text": { "type": "string", "description": "Selected text content" },
+          "capturedAt": { "type": "string", "description": "ISO 8601 timestamp" },
+          "domain": { "type": "string", "description": "Extracted domain" }
+        },
+        "required": ["url", "title", "text", "capturedAt"]
+      }
+    },
+    {
+      "name": "browser.capture.link",
+      "description": "Link sent from browser extension",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "url": { "type": "string", "description": "Link URL" },
+          "title": { "type": "string", "description": "Link text/title" },
+          "capturedAt": { "type": "string", "description": "ISO 8601 timestamp" },
+          "domain": { "type": "string", "description": "Extracted domain" }
+        },
+        "required": ["url", "capturedAt"]
+      }
+    },
+    {
+      "name": "browser.desktop.status",
+      "description": "Desktop status response to browser extension ping",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "online": { "type": "boolean", "description": "Whether desktop is reachable" },
+          "version": { "type": "string", "description": "Desktop version" },
+          "checkedAt": { "type": "string", "description": "ISO 8601 timestamp" }
+        },
+        "required": ["online", "checkedAt"]
+      }
+    },
+    {
+      "name": "browser.pending.flush",
+      "description": "Flush pending captures from browser queue to desktop",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "items": {
+            "type": "array",
+            "items": {
+              "type": "object",
+              "properties": {
+                "type": { "type": "string", "enum": ["page", "selection", "link"] },
+                "payload": { "type": "object" },
+                "queuedAt": { "type": "string" }
+              },
+              "required": ["type", "payload"]
+            }
+          },
+          "flushedAt": { "type": "string", "description": "ISO 8601 timestamp" }
+        },
+        "required": ["items", "flushedAt"]
+      }
+    }
+  ]
+}
diff --git a/schemas/events/lifecycle.json b/schemas/events/lifecycle.json
new file mode 100644
index 0000000..22856a8
--- /dev/null
+++ b/schemas/events/lifecycle.json
@@ -0,0 +1,145 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.mirv.top/verstak/verstak-sdk/schemas/events/lifecycle.json",
+  "title": "Verstak Lifecycle Events",
+  "description": "Event schemas for plugin and application lifecycle events",
+  "type": "object",
+  "properties": {
+    "events": {
+      "type": "array",
+      "items": {
+        "$ref": "#/$defs/LifecycleEvent"
+      }
+    }
+  },
+  "$defs": {
+    "LifecycleEvent": {
+      "type": "object",
+      "properties": {
+        "name": { "type": "string" },
+        "description": { "type": "string" },
+        "schema": {
+          "type": "object",
+          "properties": {
+            "type": { "type": "string", "const": "object" },
+            "properties": { "type": "object" },
+            "required": { "type": "array", "items": { "type": "string" } }
+          },
+          "required": ["type", "properties", "required"]
+        }
+      },
+      "required": ["name", "description", "schema"]
+    }
+  },
+  "events": [
+    {
+      "name": "plugin.enabled",
+      "description": "A plugin has been enabled",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "pluginId": { "type": "string", "description": "Plugin identifier" },
+          "version": { "type": "string", "description": "Plugin version" },
+          "enabledAt": { "type": "string", "description": "ISO 8601 timestamp" }
+        },
+        "required": ["pluginId", "enabledAt"]
+      }
+    },
+    {
+      "name": "plugin.disabled",
+      "description": "A plugin has been disabled",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "pluginId": { "type": "string", "description": "Plugin identifier" },
+          "disabledAt": { "type": "string", "description": "ISO 8601 timestamp" }
+        },
+        "required": ["pluginId", "disabledAt"]
+      }
+    },
+    {
+      "name": "plugin.failed",
+      "description": "A plugin has failed to load or run",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "pluginId": { "type": "string", "description": "Plugin identifier" },
+          "error": { "type": "string", "description": "Error message" },
+          "phase": {
+            "type": "string",
+            "description": "Lifecycle phase where failure occurred",
+            "enum": ["discovery", "validation", "dependency", "permissions", "sidecar", "frontend", "registration", "runtime"]
+          },
+          "failedAt": { "type": "string", "description": "ISO 8601 timestamp" }
+        },
+        "required": ["pluginId", "error", "phase", "failedAt"]
+      }
+    },
+    {
+      "name": "plugin.installed",
+      "description": "A new plugin has been installed",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "pluginId": { "type": "string" },
+          "version": { "type": "string" },
+          "source": { "type": "string", "enum": ["official", "local", "third-party"] },
+          "installedAt": { "type": "string" }
+        },
+        "required": ["pluginId", "version", "source", "installedAt"]
+      }
+    },
+    {
+      "name": "plugin.uninstalled",
+      "description": "A plugin has been uninstalled",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "pluginId": { "type": "string" },
+          "preserveData": { "type": "boolean", "description": "Whether user chose to keep data" },
+          "uninstalledAt": { "type": "string" }
+        },
+        "required": ["pluginId", "uninstalledAt"]
+      }
+    },
+    {
+      "name": "app.started",
+      "description": "Application has started",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "version": { "type": "string", "description": "Application version" },
+          "startedAt": { "type": "string", "description": "ISO 8601 timestamp" },
+          "pluginsLoaded": { "type": "integer", "description": "Number of plugins loaded" },
+          "pluginsFailed": { "type": "integer", "description": "Number of plugins failed" }
+        },
+        "required": ["version", "startedAt"]
+      }
+    },
+    {
+      "name": "app.shuttingdown",
+      "description": "Application is shutting down",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "shutdownAt": { "type": "string", "description": "ISO 8601 timestamp" },
+          "reason": { "type": "string", "description": "Shutdown reason" }
+        },
+        "required": ["shutdownAt"]
+      }
+    },
+    {
+      "name": "capability.changed",
+      "description": "Available capabilities have changed (plugin enabled/disabled)",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "added": { "type": "array", "items": { "type": "string" }, "description": "Capabilities that became available" },
+          "removed": { "type": "array", "items": { "type": "string" }, "description": "Capabilities that were removed" },
+          "changedAt": { "type": "string", "description": "ISO 8601 timestamp" }
+        },
+        "required": ["changedAt"]
+      }
+    }
+  ]
+}
diff --git a/schemas/events/vault.json b/schemas/events/vault.json
new file mode 100644
index 0000000..d199971
--- /dev/null
+++ b/schemas/events/vault.json
@@ -0,0 +1,159 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.mirv.top/verstak/verstak-sdk/schemas/events/vault.json",
+  "title": "Verstak Vault Events",
+  "description": "Event schemas for vault and case lifecycle events",
+  "type": "object",
+  "properties": {
+    "events": {
+      "type": "array",
+      "items": {
+        "$ref": "#/$defs/VaultEvent"
+      }
+    }
+  },
+  "$defs": {
+    "VaultEvent": {
+      "type": "object",
+      "properties": {
+        "name": { "type": "string" },
+        "description": { "type": "string" },
+        "schema": {
+          "type": "object",
+          "properties": {
+            "type": { "type": "string", "const": "object" },
+            "properties": { "type": "object" },
+            "required": { "type": "array", "items": { "type": "string" } }
+          },
+          "required": ["type", "properties", "required"]
+        }
+      },
+      "required": ["name", "description", "schema"]
+    }
+  },
+  "events": [
+    {
+      "name": "vault.opened",
+      "description": "Vault has been opened and is ready",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "path": { "type": "string", "description": "Absolute path to vault root" },
+          "version": { "type": "string", "description": "Vault schema version" },
+          "openedAt": { "type": "string", "description": "ISO 8601 timestamp" }
+        },
+        "required": ["path", "openedAt"]
+      }
+    },
+    {
+      "name": "vault.closed",
+      "description": "Vault is about to close",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "closedAt": { "type": "string", "description": "ISO 8601 timestamp" },
+          "clean": { "type": "boolean", "description": "Whether vault closed cleanly" }
+        },
+        "required": ["closedAt"]
+      }
+    },
+    {
+      "name": "case.selected",
+      "description": "A case has been selected in the navigation",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "caseId": { "type": "string", "description": "Case identifier" },
+          "casePath": { "type": "string", "description": "Case filesystem path" },
+          "caseType": { "type": "string", "description": "Case type (client, project, etc.)" },
+          "selectedAt": { "type": "string", "description": "ISO 8601 timestamp" }
+        },
+        "required": ["caseId", "casePath"]
+      }
+    },
+    {
+      "name": "file.added",
+      "description": "A file has been added to the vault",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "path": { "type": "string", "description": "File path relative to vault" },
+          "size": { "type": "integer", "description": "File size in bytes" },
+          "mimeType": { "type": "string", "description": "File MIME type" },
+          "caseId": { "type": "string", "description": "Associated case identifier" },
+          "addedAt": { "type": "string", "description": "ISO 8601 timestamp" }
+        },
+        "required": ["path", "addedAt"]
+      }
+    },
+    {
+      "name": "file.changed",
+      "description": "A file in the vault has been modified",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "path": { "type": "string", "description": "File path relative to vault" },
+          "size": { "type": "integer", "description": "New file size" },
+          "changedAt": { "type": "string", "description": "ISO 8601 timestamp" }
+        },
+        "required": ["path", "changedAt"]
+      }
+    },
+    {
+      "name": "file.deleted",
+      "description": "A file has been deleted from the vault",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "path": { "type": "string", "description": "File path relative to vault" },
+          "deletedAt": { "type": "string", "description": "ISO 8601 timestamp" }
+        },
+        "required": ["path", "deletedAt"]
+      }
+    },
+    {
+      "name": "note.saved",
+      "description": "A note has been saved",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "noteId": { "type": "string", "description": "Note identifier" },
+          "title": { "type": "string", "description": "Note title" },
+          "path": { "type": "string", "description": "Note file path relative to vault" },
+          "caseId": { "type": "string", "description": "Associated case identifier" },
+          "savedAt": { "type": "string", "description": "ISO 8601 timestamp" }
+        },
+        "required": ["noteId", "path", "savedAt"]
+      }
+    },
+    {
+      "name": "activity.recorded",
+      "description": "An activity event has been recorded",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "type": { "type": "string", "description": "Activity type (file.opened, note.saved, etc.)" },
+          "caseId": { "type": "string", "description": "Associated case" },
+          "details": { "type": "object", "description": "Activity-specific details" },
+          "recordedAt": { "type": "string", "description": "ISO 8601 timestamp" }
+        },
+        "required": ["type", "recordedAt"]
+      }
+    },
+    {
+      "name": "case.created",
+      "description": "A new case has been created",
+      "schema": {
+        "type": "object",
+        "properties": {
+          "caseId": { "type": "string" },
+          "casePath": { "type": "string" },
+          "caseType": { "type": "string" },
+          "template": { "type": "string", "description": "Template used, if any" },
+          "createdAt": { "type": "string" }
+        },
+        "required": ["caseId", "casePath", "createdAt"]
+      }
+    }
+  ]
+}
diff --git a/schemas/manifest.json b/schemas/manifest.json
new file mode 100644
index 0000000..b3cd309
--- /dev/null
+++ b/schemas/manifest.json
@@ -0,0 +1,362 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.mirv.top/verstak/verstak-sdk/schemas/manifest.json",
+  "title": "Verstak Plugin Manifest",
+  "description": "Schema for Verstak plugin.json manifest files",
+  "type": "object",
+  "required": [
+    "schemaVersion",
+    "id",
+    "name",
+    "version",
+    "apiVersion",
+    "provides",
+    "permissions"
+  ],
+  "properties": {
+    "schemaVersion": {
+      "type": "integer",
+      "description": "Schema version for the manifest format",
+      "enum": [1]
+    },
+    "id": {
+      "type": "string",
+      "description": "Unique plugin identifier (e.g. 'official.notes')",
+      "pattern": "^[a-zA-Z][a-zA-Z0-9.-]*$"
+    },
+    "name": {
+      "type": "string",
+      "description": "Human-readable plugin name"
+    },
+    "version": {
+      "type": "string",
+      "description": "Plugin semantic version",
+      "pattern": "^\\d+\\.\\d+\\.\\d+(-[a-zA-Z0-9.]+)?$"
+    },
+    "apiVersion": {
+      "type": "string",
+      "description": "Verstak Platform API version this plugin targets",
+      "pattern": "^\\d+$"
+    },
+    "description": {
+      "type": "string",
+      "description": "Brief description of the plugin's purpose"
+    },
+    "source": {
+      "type": "string",
+      "description": "Plugin source classification",
+      "enum": ["official", "local", "third-party"]
+    },
+    "icon": {
+      "type": "string",
+      "description": "Path to plugin icon (relative to plugin root)"
+    },
+    "provides": {
+      "type": "array",
+      "description": "Capabilities this plugin provides",
+      "items": {
+        "type": "string"
+      },
+      "minItems": 1
+    },
+    "requires": {
+      "type": "array",
+      "description": "Required capabilities — plugin cannot load without these",
+      "items": {
+        "type": "string"
+      },
+      "default": []
+    },
+    "optionalRequires": {
+      "type": "array",
+      "description": "Optional capabilities — plugin degrades gracefully without these",
+      "items": {
+        "type": "string"
+      },
+      "default": []
+    },
+    "permissions": {
+      "type": "array",
+      "description": "Runtime permissions requested by the plugin",
+      "items": {
+        "type": "string",
+        "enum": [
+          "vault.read",
+          "vault.write",
+          "vault.watch",
+          "storage.namespace",
+          "storage.migrations",
+          "events.publish",
+          "events.subscribe",
+          "ui.register",
+          "commands.register",
+          "network.local",
+          "network.remote",
+          "process.spawn",
+          "secrets.read",
+          "secrets.write",
+          "sync.participate"
+        ]
+      },
+      "minItems": 1
+    },
+    "frontend": {
+      "type": "object",
+      "description": "Frontend bundle configuration",
+      "properties": {
+        "entry": {
+          "type": "string",
+          "description": "Path to the frontend entry JavaScript file"
+        },
+        "style": {
+          "type": "string",
+          "description": "Path to the frontend stylesheet"
+        }
+      },
+      "required": ["entry"]
+    },
+    "backend": {
+      "type": "object",
+      "description": "Backend sidecar configuration",
+      "properties": {
+        "type": {
+          "type": "string",
+          "enum": ["sidecar"],
+          "description": "Backend type (only 'sidecar' supported)"
+        },
+        "entry": {
+          "type": "object",
+          "description": "Platform-specific binaries",
+          "patternProperties": {
+            "^(linux|windows|darwin)-(amd64|arm64)$": {
+              "type": "string",
+              "description": "Path to the binary for this platform"
+            }
+          },
+          "minProperties": 1
+        },
+        "healthCheck": {
+          "type": "object",
+          "description": "Sidecar health check configuration",
+          "properties": {
+            "type": {
+              "type": "string",
+              "enum": ["rpc", "stdio", "tcp"],
+              "default": "rpc"
+            },
+            "timeout": {
+              "type": "integer",
+              "description": "Health check timeout in milliseconds",
+              "default": 5000
+            }
+          }
+        }
+      },
+      "required": ["type", "entry"]
+    },
+    "migrations": {
+      "type": "object",
+      "description": "Database migration configuration",
+      "properties": {
+        "path": {
+          "type": "string",
+          "description": "Path to migrations directory"
+        }
+      }
+    },
+    "contributes": {
+      "type": "object",
+      "description": "UI and action contributions",
+      "properties": {
+        "views": {
+          "type": "array",
+          "items": {
+            "$ref": "#/$defs/ContributionView"
+          }
+        },
+        "commands": {
+          "type": "array",
+          "items": {
+            "$ref": "#/$defs/ContributionCommand"
+          }
+        },
+        "settingsPanels": {
+          "type": "array",
+          "items": {
+            "$ref": "#/$defs/ContributionSettingsPanel"
+          }
+        },
+        "sidebarItems": {
+          "type": "array",
+          "items": {
+            "$ref": "#/$defs/ContributionSidebarItem"
+          }
+        },
+        "fileActions": {
+          "type": "array",
+          "items": {
+            "$ref": "#/$defs/ContributionAction"
+          }
+        },
+        "noteActions": {
+          "type": "array",
+          "items": {
+            "$ref": "#/$defs/ContributionAction"
+          }
+        },
+        "contextMenuEntries": {
+          "type": "array",
+          "items": {
+            "$ref": "#/$defs/ContributionContextMenuEntry"
+          }
+        },
+        "searchProviders": {
+          "type": "array",
+          "items": {
+            "$ref": "#/$defs/ContributionSearchProvider"
+          }
+        },
+        "activityProviders": {
+          "type": "array",
+          "items": {
+            "$ref": "#/$defs/ContributionActivityProvider"
+          }
+        },
+        "statusBarItems": {
+          "type": "array",
+          "items": {
+            "$ref": "#/$defs/ContributionStatusBarItem"
+          }
+        }
+      }
+    },
+    "sync": {
+      "type": "object",
+      "description": "Sync configuration — what data this plugin allows syncing",
+      "properties": {
+        "namespaces": {
+          "type": "array",
+          "description": "Storage namespaces allowed for sync",
+          "items": {
+            "type": "string"
+          }
+        },
+        "participate": {
+          "type": "boolean",
+          "description": "Whether this plugin participates in sync at all",
+          "default": false
+        }
+      }
+    }
+  },
+  "$defs": {
+    "ContributionView": {
+      "type": "object",
+      "properties": {
+        "id": { "type": "string" },
+        "title": { "type": "string" },
+        "icon": { "type": "string" },
+        "component": { "type": "string" }
+      },
+      "required": ["id", "component"]
+    },
+    "ContributionCommand": {
+      "type": "object",
+      "properties": {
+        "id": { "type": "string" },
+        "title": { "type": "string" },
+        "keybinding": { "type": "string" },
+        "icon": { "type": "string" },
+        "handler": { "type": "string" }
+      },
+      "required": ["id", "title"]
+    },
+    "ContributionSettingsPanel": {
+      "type": "object",
+      "properties": {
+        "id": { "type": "string" },
+        "title": { "type": "string" },
+        "component": { "type": "string" },
+        "icon": { "type": "string" }
+      },
+      "required": ["id", "title", "component"]
+    },
+    "ContributionSidebarItem": {
+      "type": "object",
+      "properties": {
+        "id": { "type": "string" },
+        "title": { "type": "string" },
+        "icon": { "type": "string" },
+        "view": { "type": "string" },
+        "position": {
+          "type": "integer",
+          "description": "Sort order (lower = higher)"
+        }
+      },
+      "required": ["id", "title", "view"]
+    },
+    "ContributionAction": {
+      "type": "object",
+      "properties": {
+        "id": { "type": "string" },
+        "label": { "type": "string" },
+        "icon": { "type": "string" },
+        "capability": {
+          "type": "string",
+          "description": "Required capability for this action to appear"
+        },
+        "handler": { "type": "string" }
+      },
+      "required": ["id", "label"]
+    },
+    "ContributionContextMenuEntry": {
+      "type": "object",
+      "properties": {
+        "id": { "type": "string" },
+        "label": { "type": "string" },
+        "context": {
+          "type": "string",
+          "enum": ["file", "note", "case", "folder"]
+        },
+        "group": { "type": "string" },
+        "capability": { "type": "string" },
+        "handler": { "type": "string" }
+      },
+      "required": ["id", "label", "context"]
+    },
+    "ContributionSearchProvider": {
+      "type": "object",
+      "properties": {
+        "id": { "type": "string" },
+        "label": { "type": "string" },
+        "handler": { "type": "string" }
+      },
+      "required": ["id", "label", "handler"]
+    },
+    "ContributionActivityProvider": {
+      "type": "object",
+      "properties": {
+        "id": { "type": "string" },
+        "events": {
+          "type": "array",
+          "items": { "type": "string" }
+        },
+        "handler": { "type": "string" }
+      },
+      "required": ["id", "handler"]
+    },
+    "ContributionStatusBarItem": {
+      "type": "object",
+      "properties": {
+        "id": { "type": "string" },
+        "label": { "type": "string" },
+        "position": {
+          "type": "string",
+          "enum": ["left", "right"]
+        },
+        "handler": { "type": "string" }
+      },
+      "required": ["id", "label"]
+    }
+  }
+}
diff --git a/schemas/permissions.json b/schemas/permissions.json
new file mode 100644
index 0000000..f60a032
--- /dev/null
+++ b/schemas/permissions.json
@@ -0,0 +1,46 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.mirv.top/verstak/verstak-sdk/schemas/permissions.json",
+  "title": "Verstak Permissions Registry",
+  "description": "Known runtime permissions and their safety levels",
+  "type": "object",
+  "properties": {
+    "permissions": {
+      "type": "array",
+      "items": {
+        "$ref": "#/$defs/PermissionEntry"
+      }
+    }
+  },
+  "$defs": {
+    "PermissionEntry": {
+      "type": "object",
+      "properties": {
+        "name": { "type": "string" },
+        "description": { "type": "string" },
+        "dangerous": {
+          "type": "boolean",
+          "description": "If true, user must explicitly approve before enabling plugin"
+        }
+      },
+      "required": ["name", "description", "dangerous"]
+    }
+  },
+  "permissions": [
+    { "name": "vault.read", "description": "Read vault files and metadata", "dangerous": false },
+    { "name": "vault.write", "description": "Write vault files and metadata", "dangerous": true },
+    { "name": "vault.watch", "description": "Watch vault file changes", "dangerous": false },
+    { "name": "storage.namespace", "description": "Read/write plugin's own storage namespace", "dangerous": false },
+    { "name": "storage.migrations", "description": "Run database migrations in plugin namespace", "dangerous": false },
+    { "name": "events.publish", "description": "Publish events to the event bus", "dangerous": false },
+    { "name": "events.subscribe", "description": "Subscribe to events on the event bus", "dangerous": false },
+    { "name": "ui.register", "description": "Register UI components and contributions", "dangerous": false },
+    { "name": "commands.register", "description": "Register command palette commands", "dangerous": false },
+    { "name": "network.local", "description": "Connect to localhost network services", "dangerous": false },
+    { "name": "network.remote", "description": "Connect to remote network services", "dangerous": true },
+    { "name": "process.spawn", "description": "Spawn external processes", "dangerous": true },
+    { "name": "secrets.read", "description": "Read secrets from the secret store", "dangerous": true },
+    { "name": "secrets.write", "description": "Write secrets to the secret store", "dangerous": true },
+    { "name": "sync.participate", "description": "Participate in vault sync", "dangerous": true }
+  ]
+}
diff --git a/schemas/sync.json b/schemas/sync.json
new file mode 100644
index 0000000..b792e55
--- /dev/null
+++ b/schemas/sync.json
@@ -0,0 +1,177 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.mirv.top/verstak/verstak-sdk/schemas/sync.json",
+  "title": "Verstak Sync Operations",
+  "description": "Sync operation schemas for vault synchronization between devices",
+  "type": "object",
+  "properties": {
+    "SyncOperation": {
+      "$ref": "#/$defs/SyncOperation"
+    },
+    "SyncBatch": {
+      "$ref": "#/$defs/SyncBatch"
+    },
+    "SyncManifest": {
+      "$ref": "#/$defs/SyncManifest"
+    }
+  },
+  "$defs": {
+    "SyncOperation": {
+      "type": "object",
+      "description": "A single sync operation entry",
+      "required": ["op", "id", "timestamp"],
+      "properties": {
+        "op": {
+          "type": "string",
+          "description": "Operation type",
+          "enum": ["add", "modify", "delete", "rename"]
+        },
+        "id": {
+          "type": "string",
+          "description": "Unique operation identifier (UUID)"
+        },
+        "timestamp": {
+          "type": "string",
+          "description": "ISO 8601 timestamp of the operation"
+        },
+        "deviceId": {
+          "type": "string",
+          "description": "Originating device identifier"
+        },
+        "entityType": {
+          "type": "string",
+          "description": "Entity type being synced",
+          "enum": ["file", "note", "plugin_state", "vault_meta"]
+        },
+        "entityPath": {
+          "type": "string",
+          "description": "Entity path relative to vault root"
+        },
+        "hash": {
+          "type": "string",
+          "description": "Content hash (SHA-256) for content verification"
+        },
+        "size": {
+          "type": "integer",
+          "description": "File size in bytes"
+        },
+        "mimeType": {
+          "type": "string",
+          "description": "MIME type of the entity"
+        },
+        "pluginNamespace": {
+          "type": "string",
+          "description": "Plugin namespace, if syncing plugin state"
+        },
+        "oldPath": {
+          "type": "string",
+          "description": "Previous path for rename operations"
+        },
+        "metadata": {
+          "type": "object",
+          "description": "Arbitrary metadata key-value pairs",
+          "additionalProperties": { "type": "string" }
+        }
+      }
+    },
+    "SyncBatch": {
+      "type": "object",
+      "description": "A batch of sync operations sent between devices",
+      "required": ["batchId", "deviceId", "operations", "timestamp"],
+      "properties": {
+        "batchId": {
+          "type": "string",
+          "description": "Unique batch identifier (UUID)"
+        },
+        "deviceId": {
+          "type": "string",
+          "description": "Originating device identifier"
+        },
+        "operations": {
+          "type": "array",
+          "description": "List of sync operations in this batch",
+          "items": {
+            "$ref": "#/$defs/SyncOperation"
+          }
+        },
+        "timestamp": {
+          "type": "string",
+          "description": "ISO 8601 timestamp of batch creation"
+        },
+        "lastSyncTimestamp": {
+          "type": "string",
+          "description": "Timestamp of the last successful sync from this device"
+        },
+        "sequence": {
+          "type": "integer",
+          "description": "Sequence number for ordering batches"
+        }
+      }
+    },
+    "SyncManifest": {
+      "type": "object",
+      "description": "Vault sync manifest for initial reconciliation",
+      "required": ["deviceId", "entries"],
+      "properties": {
+        "deviceId": { "type": "string" },
+        "entries": {
+          "type": "array",
+          "items": {
+            "type": "object",
+            "required": ["path", "hash", "updatedAt"],
+            "properties": {
+              "path": { "type": "string" },
+              "hash": { "type": "string" },
+              "size": { "type": "integer" },
+              "updatedAt": { "type": "string" },
+              "deleted": { "type": "boolean", "default": false }
+            }
+          }
+        }
+      }
+    },
+    "Conflict": {
+      "type": "object",
+      "description": "Conflict record when two devices modify the same entity",
+      "required": ["entityPath", "localHash", "remoteHash", "localTimestamp", "remoteTimestamp"],
+      "properties": {
+        "entityPath": { "type": "string" },
+        "localHash": { "type": "string" },
+        "remoteHash": { "type": "string" },
+        "localTimestamp": { "type": "string" },
+        "remoteTimestamp": { "type": "string" },
+        "resolution": {
+          "type": "string",
+          "enum": ["local_wins", "remote_wins", "manual"],
+          "description": "How the conflict was resolved"
+        },
+        "resolvedAt": { "type": "string" }
+      }
+    },
+    "PairingRequest": {
+      "type": "object",
+      "description": "Device pairing request payload",
+      "required": ["deviceName", "deviceType", "publicKey"],
+      "properties": {
+        "deviceName": { "type": "string" },
+        "deviceType": {
+          "type": "string",
+          "enum": ["desktop", "mobile"]
+        },
+        "publicKey": { "type": "string", "description": "Device public key for auth" },
+        "clientVersion": { "type": "string" }
+      }
+    },
+    "PairingResponse": {
+      "type": "object",
+      "description": "Device pairing response",
+      "required": ["deviceId", "token", "pairedAt"],
+      "properties": {
+        "deviceId": { "type": "string" },
+        "token": { "type": "string", "description": "Auth token for this device" },
+        "pairedAt": { "type": "string" },
+        "serverVersion": { "type": "string" }
+      }
+    }
+  }
+}
diff --git a/src/index.ts b/src/index.ts
new file mode 100644
index 0000000..5dea4f3
--- /dev/null
+++ b/src/index.ts
@@ -0,0 +1,11 @@
+// Verstak Plugin SDK — Public API
+
+export * from './types';
+export { VerstakPluginAPI, createPluginAPI } from './plugin-api';
+export { RPCServer, RPCClient } from './rpc';
+export {
+  createTestManifest,
+  createTestPluginState,
+  createMockPluginAPI,
+  validateManifest,
+} from './test-utils';
diff --git a/src/plugin-api.ts b/src/plugin-api.ts
new file mode 100644
index 0000000..4af96ea
--- /dev/null
+++ b/src/plugin-api.ts
@@ -0,0 +1,166 @@
+// Verstak Plugin SDK — VerstakPluginAPI
+// The official runtime API available to all plugins in the frontend context.
+
+import type { PluginSettings } from './types';
+
+/**
+ * VerstakPluginAPI — единственный способ для frontend плагина
+ * общаться с core платформы.
+ *
+ * Экземпляр API передаётся плагину при активации через глобальную
+ * переменную `window.__VERSTAK_PLUGIN_API__`.
+ */
+export class VerstakPluginAPI {
+  private pluginId: string;
+  private capabilities = new Set<string>();
+
+  constructor(pluginId: string) {
+    this.pluginId = pluginId;
+  }
+
+  /**
+   * Инициализация API — вызывается core после загрузки frontend bundle.
+   * @internal
+   */
+  _init(capabilities: string[]): void {
+    this.capabilities = new Set(capabilities);
+  }
+
+  // ─── View Registration ─────────────────────────────────────
+
+  /**
+   * Зарегистрировать view для отображения в UI Shell.
+   */
+  registerView(id: string, component: unknown): void {
+    this._postMessage('register.view', { id, component });
+  }
+
+  /**
+   * Зарегистрировать панель настроек плагина.
+   */
+  registerSettingsPanel(id: string, title: string, component: unknown): void {
+    this._postMessage('register.settingsPanel', { id, title, component });
+  }
+
+  /**
+   * Зарегистрировать команду для command palette.
+   */
+  registerCommand(id: string, title: string, handler: () => void, keybinding?: string): void {
+    this._postMessage('register.command', { id, title, keybinding, handler: handler.toString() });
+  }
+
+  /**
+   * Зарегистрировать действия для файлов.
+   */
+  registerFileAction(id: string, label: string, handler: (filePath: string) => void, capability?: string): void {
+    this._postMessage('register.fileAction', { id, label, handler: handler.toString(), capability });
+  }
+
+  /**
+   * Зарегистрировать действия для заметок.
+   */
+  registerNoteAction(id: string, label: string, handler: (noteId: string) => void, capability?: string): void {
+    this._postMessage('register.noteAction', { id, label, handler: handler.toString(), capability });
+  }
+
+  /**
+   * Зарегистрировать provider поиска.
+   */
+  registerSearchProvider(id: string, label: string, handler: (query: string) => unknown[]): void {
+    this._postMessage('register.searchProvider', { id, label, handler: handler.toString() });
+  }
+
+  // ─── Capabilities ──────────────────────────────────────────
+
+  /**
+   * Проверить, доступна ли capability.
+   */
+  hasCapability(name: string): boolean {
+    return this.capabilities.has(name);
+  }
+
+  /**
+   * Получить список всех доступных capabilities.
+   */
+  getAvailableCapabilities(): string[] {
+    return Array.from(this.capabilities);
+  }
+
+  // ─── Backend Communication ─────────────────────────────────
+
+  /**
+   * Вызвать backend метод плагина через RPC.
+   */
+  async callBackend(method: string, args: unknown[] = []): Promise<unknown> {
+    return this._rpcCall(method, args);
+  }
+
+  // ─── Settings ──────────────────────────────────────────────
+
+  /**
+   * Прочитать настройки плагина.
+   */
+  async readSettings(): Promise<PluginSettings> {
+    const result = await this._rpcCall('readSettings', []);
+    return result as PluginSettings;
+  }
+
+  /**
+   * Записать настройки плагина.
+   */
+  async writeSettings(settings: PluginSettings): Promise<void> {
+    await this._rpcCall('writeSettings', [settings]);
+  }
+
+  // ─── Event Bus ─────────────────────────────────────────────
+
+  /**
+   * Подписаться на событие event bus.
+   */
+  subscribe(event: string, handler: (payload: unknown) => void): void {
+    this._postMessage('subscribe', { event, handler: handler.toString() });
+  }
+
+  /**
+   * Опубликовать событие в event bus.
+   */
+  publish(event: string, payload: unknown): void {
+    this._postMessage('publish', { event, payload });
+  }
+
+  // ─── Internal ──────────────────────────────────────────────
+
+  private _postMessage(type: string, data: Record<string, unknown>): void {
+    window.dispatchEvent(new CustomEvent('verstak:plugin', {
+      detail: { pluginId: this.pluginId, type, data }
+    }));
+  }
+
+  private async _rpcCall(method: string, args: unknown[]): Promise<unknown> {
+    return new Promise((resolve, reject) => {
+      const callId = `${this.pluginId}:${Date.now()}:${Math.random()}`;
+      const handler = (event: CustomEvent) => {
+        if (event.detail.callId === callId) {
+          window.removeEventListener('verstak:rpc:response', handler as EventListener);
+          if (event.detail.error) {
+            reject(new Error(event.detail.error));
+          } else {
+            resolve(event.detail.result);
+          }
+        }
+      };
+      window.addEventListener('verstak:rpc:response', handler as EventListener);
+      this._postMessage('rpc', { callId, method, args });
+    });
+  }
+}
+
+/**
+ * Создать экземпляр VerstakPluginAPI.
+ * Core вызывает эту функцию после загрузки frontend bundle,
+ * передавая pluginId и список доступных capabilities.
+ */
+export function createPluginAPI(pluginId: string): VerstakPluginAPI {
+  const api = new VerstakPluginAPI(pluginId);
+  return api;
+}
diff --git a/src/rpc.ts b/src/rpc.ts
new file mode 100644
index 0000000..9a8a6c5
--- /dev/null
+++ b/src/rpc.ts
@@ -0,0 +1,112 @@
+// Verstak Plugin SDK — RPC Client for Sidecar Communication
+
+export type RPCTransport = 'stdio' | 'tcp';
+
+export interface RPCRequest {
+  jsonrpc: '2.0';
+  id: string;
+  method: string;
+  params: unknown[];
+}
+
+export interface RPCResponse {
+  jsonrpc: '2.0';
+  id: string;
+  result?: unknown;
+  error?: RPCError;
+}
+
+export interface RPCError {
+  code: number;
+  message: string;
+  data?: unknown;
+}
+
+/**
+ * RPC клиент для общения backend sidecar с core платформы.
+ * Использует JSON-RPC 2.0 протокол.
+ */
+export class RPCServer {
+  private handlers = new Map<string, (params: unknown[]) => Promise<unknown>>();
+
+  constructor() {
+  }
+
+  /**
+   * Зарегистрировать обработчик RPC метода.
+   */
+  registerMethod(method: string, handler: (params: unknown[]) => Promise<unknown>): void {
+    this.handlers.set(method, handler);
+  }
+
+  /**
+   * Обработать входящий RPC запрос.
+   */
+  async handleRequest(request: RPCRequest): Promise<RPCResponse> {
+    const handler = this.handlers.get(request.method);
+    if (!handler) {
+      return {
+        jsonrpc: '2.0',
+        id: request.id,
+        error: { code: -32601, message: `Method not found: ${request.method}` }
+      };
+    }
+
+    try {
+      const result = await handler(request.params);
+      return { jsonrpc: '2.0', id: request.id, result };
+    } catch (err) {
+      return {
+        jsonrpc: '2.0',
+        id: request.id,
+        error: { code: -32000, message: err instanceof Error ? err.message : String(err) }
+      };
+    }
+  }
+
+  /**
+   * Создать RPC запрос.
+   */
+  createRequest(method: string, params: unknown[] = []): RPCRequest {
+    return {
+      jsonrpc: '2.0',
+      id: `${Date.now()}:${Math.random()}`,
+      method,
+      params
+    };
+  }
+
+  /**
+   * Разобрать RPC ответ.
+   */
+  parseResponse(data: string): RPCResponse {
+    return JSON.parse(data) as RPCResponse;
+  }
+}
+
+/**
+ * RPC клиент (для core, вызывает методы sidecar).
+ */
+export class RPCClient {
+  private requestId = 0;
+
+  /**
+   * Создать JSON-RPC запрос.
+   */
+  call(method: string, params: unknown[] = []): string {
+    const request: RPCRequest = {
+      jsonrpc: '2.0',
+      id: `${++this.requestId}`,
+      method,
+      params
+    };
+    return JSON.stringify(request) + '\n';
+  }
+
+  /**
+   * Разобрать ответ.
+   */
+  parseResponse(data: string): RPCResponse {
+    return JSON.parse(data.trim()) as RPCResponse;
+  }
+}
diff --git a/src/test-utils.ts b/src/test-utils.ts
new file mode 100644
index 0000000..b91a475
--- /dev/null
+++ b/src/test-utils.ts
@@ -0,0 +1,101 @@
+// Verstak Plugin SDK — Test Utilities
+
+import type { PluginManifest, PluginState } from './types';
+
+/**
+ * Создать тестовый manifest для unit-тестов.
+ */
+export function createTestManifest(overrides?: Partial<PluginManifest>): PluginManifest {
+  return {
+    schemaVersion: 1,
+    id: 'test.plugin',
+    name: 'Test Plugin',
+    version: '0.1.0',
+    apiVersion: '1',
+    description: 'A test plugin for platform verification',
+    source: 'local',
+    provides: ['test.capability'],
+    requires: [],
+    optionalRequires: [],
+    permissions: ['events.publish', 'events.subscribe'],
+    ...overrides
+  };
+}
+
+/**
+ * Создать тестовое состояние плагина.
+ */
+export function createTestPluginState(overrides?: Partial<PluginState>): PluginState {
+  return {
+    id: 'test.plugin',
+    manifest: createTestManifest(),
+    status: 'loaded',
+    enabled: true,
+    loadedAt: new Date().toISOString(),
+    ...overrides
+  };
+}
+
+/**
+ * Создать заглушку VerstakPluginAPI для тестов.
+ */
+export function createMockPluginAPI(): {
+  registerView: ReturnType<typeof vi.fn>;
+  registerCommand: ReturnType<typeof vi.fn>;
+  registerSettingsPanel: ReturnType<typeof vi.fn>;
+  hasCapability: ReturnType<typeof vi.fn>;
+  callBackend: ReturnType<typeof vi.fn>;
+  subscribe: ReturnType<typeof vi.fn>;
+  publish: ReturnType<typeof vi.fn>;
+} {
+  return {
+    registerView: vi.fn(),
+    registerCommand: vi.fn(),
+    registerSettingsPanel: vi.fn(),
+    hasCapability: vi.fn().mockReturnValue(false),
+    callBackend: vi.fn().mockResolvedValue(undefined),
+    subscribe: vi.fn(),
+    publish: vi.fn(),
+  };
+}
+
+/**
+ * Валидатор plugin manifest.
+ */
+export function validateManifest(manifest: unknown): { valid: boolean; errors: string[] } {
+  const errors: string[] = [];
+
+  if (!manifest || typeof manifest !== 'object') {
+    return { valid: false, errors: ['Manifest must be an object'] };
+  }
+
+  const m = manifest as Record<string, unknown>;
+
+  if (m.schemaVersion !== 1) {
+    errors.push(`schemaVersion must be 1, got ${m.schemaVersion}`);
+  }
+  if (typeof m.id !== 'string' || !m.id) {
+    errors.push('id must be a non-empty string');
+  }
+  if (typeof m.name !== 'string' || !m.name) {
+    errors.push('name must be a non-empty string');
+  }
+  if (typeof m.version !== 'string' || !/^\d+\.\d+\.\d+/.test(m.version as string)) {
+    errors.push('version must be a valid semver (e.g. 0.1.0)');
+  }
+  if (typeof m.apiVersion !== 'string' || !m.apiVersion) {
+    errors.push('apiVersion must be a non-empty string');
+  }
+  if (!Array.isArray(m.provides) || m.provides.length === 0) {
+    errors.push('provides must be a non-empty array');
+  }
+  if (!Array.isArray(m.permissions) || m.permissions.length === 0) {
+    errors.push('permissions must be a non-empty array');
+  }
+
+  return { valid: errors.length === 0, errors };
+}
+
+// Re-export vi for test files
+import { vi } from 'vitest';
+export { vi };
diff --git a/src/types.ts b/src/types.ts
new file mode 100644
index 0000000..2e62b45
--- /dev/null
+++ b/src/types.ts
@@ -0,0 +1,345 @@
+// Verstak Plugin SDK — Core TypeScript Types
+
+// ─── Manifest ────────────────────────────────────────────────
+
+export type PluginSource = 'official' | 'local' | 'third-party';
+
+export interface PluginManifest {
+  schemaVersion: 1;
+  id: string;
+  name: string;
+  version: string;
+  apiVersion: string;
+  description?: string;
+  source?: PluginSource;
+  icon?: string;
+  provides: string[];
+  requires?: string[];
+  optionalRequires?: string[];
+  permissions: Permission[];
+  frontend?: FrontendConfig;
+  backend?: BackendConfig;
+  migrations?: MigrationConfig;
+  contributes?: ContributionPoints;
+  sync?: SyncConfig;
+}
+
+export interface FrontendConfig {
+  entry: string;
+  style?: string;
+}
+
+export interface BackendConfig {
+  type: 'sidecar';
+  entry: Record<string, string>;
+  healthCheck?: HealthCheckConfig;
+}
+
+export interface HealthCheckConfig {
+  type?: 'rpc' | 'stdio' | 'tcp';
+  timeout?: number;
+}
+
+export interface MigrationConfig {
+  path: string;
+}
+
+export interface SyncConfig {
+  namespaces?: string[];
+  participate?: boolean;
+}
+
+// ─── Capabilities ────────────────────────────────────────────
+
+export type CapabilityName = string;
+
+export interface CapabilityEntry {
+  name: CapabilityName;
+  description: string;
+  status: 'stable' | 'draft' | 'deprecated';
+}
+
+// ─── Permissions ─────────────────────────────────────────────
+
+export type Permission =
+  | 'vault.read'
+  | 'vault.write'
+  | 'vault.watch'
+  | 'storage.namespace'
+  | 'storage.migrations'
+  | 'events.publish'
+  | 'events.subscribe'
+  | 'ui.register'
+  | 'commands.register'
+  | 'network.local'
+  | 'network.remote'
+  | 'process.spawn'
+  | 'secrets.read'
+  | 'secrets.write'
+  | 'sync.participate';
+
+export interface PermissionEntry {
+  name: Permission;
+  description: string;
+  dangerous: boolean;
+}
+
+// ─── Contribution Points ─────────────────────────────────────
+
+export interface ContributionPoints {
+  views?: ContributionView[];
+  commands?: ContributionCommand[];
+  settingsPanels?: ContributionSettingsPanel[];
+  sidebarItems?: ContributionSidebarItem[];
+  fileActions?: ContributionAction[];
+  noteActions?: ContributionAction[];
+  contextMenuEntries?: ContributionContextMenuEntry[];
+  searchProviders?: ContributionSearchProvider[];
+  activityProviders?: ContributionActivityProvider[];
+  statusBarItems?: ContributionStatusBarItem[];
+}
+
+export interface ContributionView {
+  id: string;
+  title: string;
+  icon?: string;
+  component: string;
+}
+
+export interface ContributionCommand {
+  id: string;
+  title: string;
+  keybinding?: string;
+  icon?: string;
+  handler?: string;
+}
+
+export interface ContributionSettingsPanel {
+  id: string;
+  title: string;
+  component: string;
+  icon?: string;
+}
+
+export interface ContributionSidebarItem {
+  id: string;
+  title: string;
+  icon?: string;
+  view: string;
+  position?: number;
+}
+
+export interface ContributionAction {
+  id: string;
+  label: string;
+  icon?: string;
+  capability?: CapabilityName;
+  handler?: string;
+}
+
+export interface ContributionContextMenuEntry {
+  id: string;
+  label: string;
+  context: 'file' | 'note' | 'case' | 'folder';
+  group?: string;
+  capability?: CapabilityName;
+  handler?: string;
+}
+
+export interface ContributionSearchProvider {
+  id: string;
+  label: string;
+  handler: string;
+}
+
+export interface ContributionActivityProvider {
+  id: string;
+  events?: string[];
+  handler: string;
+}
+
+export interface ContributionStatusBarItem {
+  id: string;
+  label: string;
+  position?: 'left' | 'right';
+  handler?: string;
+}
+
+// ─── Plugin State ────────────────────────────────────────────
+
+export type PluginStatus =
+  | 'discovered'
+  | 'disabled'
+  | 'loading'
+  | 'loaded'
+  | 'degraded'
+  | 'failed'
+  | 'incompatible'
+  | 'missing-required-capability';
+
+export interface PluginState {
+  id: string;
+  manifest: PluginManifest;
+  status: PluginStatus;
+  error?: string;
+  enabled: boolean;
+  loadedAt?: string;
+}
+
+// ─── Events ──────────────────────────────────────────────────
+
+export interface VerstakEvent {
+  name: string;
+  timestamp: string;
+  payload: Record<string, unknown>;
+}
+
+// Browser events
+export interface BrowserCapturePageEvent extends VerstakEvent {
+  name: 'browser.capture.page';
+  payload: {
+    url: string;
+    title: string;
+    html?: string;
+    text?: string;
+    capturedAt: string;
+    domain?: string;
+  };
+}
+
+export interface BrowserCaptureSelectionEvent extends VerstakEvent {
+  name: 'browser.capture.selection';
+  payload: {
+    url: string;
+    title: string;
+    text: string;
+    capturedAt: string;
+    domain?: string;
+  };
+}
+
+export interface BrowserCaptureLinkEvent extends VerstakEvent {
+  name: 'browser.capture.link';
+  payload: {
+    url: string;
+    title?: string;
+    capturedAt: string;
+    domain?: string;
+  };
+}
+
+// Vault events
+export interface VaultOpenedEvent extends VerstakEvent {
+  name: 'vault.opened';
+  payload: {
+    path: string;
+    version?: string;
+    openedAt: string;
+  };
+}
+
+export interface CaseSelectedEvent extends VerstakEvent {
+  name: 'case.selected';
+  payload: {
+    caseId: string;
+    casePath: string;
+    caseType?: string;
+    selectedAt: string;
+  };
+}
+
+export interface FileChangedEvent extends VerstakEvent {
+  name: 'file.changed';
+  payload: {
+    path: string;
+    size?: number;
+    changedAt: string;
+  };
+}
+
+export interface NoteSavedEvent extends VerstakEvent {
+  name: 'note.saved';
+  payload: {
+    noteId: string;
+    title?: string;
+    path: string;
+    caseId?: string;
+    savedAt: string;
+  };
+}
+
+// Lifecycle events
+export interface PluginEnabledEvent extends VerstakEvent {
+  name: 'plugin.enabled';
+  payload: {
+    pluginId: string;
+    version?: string;
+    enabledAt: string;
+  };
+}
+
+export interface PluginDisabledEvent extends VerstakEvent {
+  name: 'plugin.disabled';
+  payload: {
+    pluginId: string;
+    disabledAt: string;
+  };
+}
+
+// ─── Sync Types ──────────────────────────────────────────────
+
+export type SyncOpType = 'add' | 'modify' | 'delete' | 'rename';
+export type SyncEntityType = 'file' | 'note' | 'plugin_state' | 'vault_meta';
+
+export interface SyncOperation {
+  op: SyncOpType;
+  id: string;
+  timestamp: string;
+  deviceId?: string;
+  entityType?: SyncEntityType;
+  entityPath?: string;
+  hash?: string;
+  size?: number;
+  mimeType?: string;
+  pluginNamespace?: string;
+  oldPath?: string;
+  metadata?: Record<string, string>;
+}
+
+export interface SyncBatch {
+  batchId: string;
+  deviceId: string;
+  operations: SyncOperation[];
+  timestamp: string;
+  lastSyncTimestamp?: string;
+  sequence?: number;
+}
+
+export interface SyncManifestEntry {
+  path: string;
+  hash: string;
+  size?: number;
+  updatedAt: string;
+  deleted?: boolean;
+}
+
+export interface SyncManifest {
+  deviceId: string;
+  entries: SyncManifestEntry[];
+}
+
+export interface Conflict {
+  entityPath: string;
+  localHash: string;
+  remoteHash: string;
+  localTimestamp: string;
+  remoteTimestamp: string;
+  resolution?: 'local_wins' | 'remote_wins' | 'manual';
+  resolvedAt?: string;
+}
+
+// ─── Settings ────────────────────────────────────────────────
+
+export interface PluginSettings {
+  [key: string]: unknown;
+}
diff --git a/tsconfig.json b/tsconfig.json
new file mode 100644
index 0000000..95dd596
--- /dev/null
+++ b/tsconfig.json
@@ -0,0 +1,22 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "declaration": true,
+    "declarationMap": true,
+    "sourceMap": true,
+    "outDir": "dist",
+    "rootDir": "src",
+    "strict": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "exactOptionalPropertyTypes": false,
+    "skipLibCheck": true,
+    "esModuleInterop": true,
+    "forceConsistentCasingInFileNames": true,
+    "resolveJsonModule": true
+  },
+  "include": ["src/**/*"],
+  "exclude": ["node_modules", "dist", "**/*.test.ts"]
+}