diff --git a/contract.lock.json b/contract.lock.json
index a042e62..6861d1e 100644
--- a/contract.lock.json
+++ b/contract.lock.json
@@ -3,12 +3,12 @@
   "source": {
     "repository": "https://github.com/1lck/Lithe-IDEA",
     "directory": "shared/contracts/plugins/v1",
-    "revision": "ced042289b5fbf9b6562eacd8da1f15428b5849d"
+    "revision": "7a24126eca3a26775daeb84db38ae04bec938d1a"
   },
   "files": [
     {
       "path": "README.md",
-      "sha256": "b30695e1c297812ad009937b78daf12f23b74d4c111c602614e393c25d5b5693"
+      "sha256": "ceb7d20d4c47fa48154813727c5c8e06563cf0fbdcd7d62ed45f36cb7c6913c3"
     },
     {
       "path": "fixtures/backend-workspace.plugin.json",
@@ -194,6 +194,10 @@
       "path": "fixtures/node-runtime.plugin.json",
       "sha256": "3cbc80303dca796302653982d3f55fdc2072aea69a2517286a06e73fbc3c4499"
     },
+    {
+      "path": "fixtures/plugin-logging.json",
+      "sha256": "ada9fe4b6a030466fc3ed8819683e645007720cf2310b709ff0c1873c80025a5"
+    },
     {
       "path": "fixtures/project-generator-templates/.gitattributes",
       "sha256": "5ab88980b2cd4db0455bb2d5c3703db6668d28f254c41a92a6feff64604af9f7"
diff --git a/contract/v1/README.md b/contract/v1/README.md
index e60e180..ab35b71 100644
--- a/contract/v1/README.md
+++ b/contract/v1/README.md
@@ -394,6 +394,63 @@ backend are `plugin.launch.unavailable`. Core never creates or
 reads any of these paths. The command also serves API 1
 manifests, whose arguments are returned unchanged.
 
+#### Structured plugin diagnostics (logging protocol 1)
+
+Every plugin-owned process may negotiate `capabilities.experimental.litheLogging`:
+the host offers `{ "versions": [1] }` in `initialize`, and the SDK answers
+`{ "version": 1 }`. The current official SDKs require that offer. This protocol
+is independent of function, build, VCS, and toolchain protocol versions.
+
+After successful initialization, the backend sends a JSON-RPC notification
+`lithe/log`. Its params contain only these fields; unknown fields are rejected:
+
+| Field | Meaning |
+| --- | --- |
+| `kind` | `operationFinished`, `operationFailed`, `degraded`, or `recovered`. These select INFO, ERROR, WARN, and WARN catalog events respectively. |
+| `operation` | A registered function ID (up to 64 bytes), `function-call` for a longer registered ID, a supported `lithe/build/*` or `lithe/vcs/*` request method, `lithe/keymap/import`, or the SDK-owned stages `initialize`, `shutdown`, `notification`, `result-encoding`. Arbitrary display labels and user input are refused. |
+| `durationMs` | Required for finished/failed, absent for degraded/recovered. Monotonic elapsed integer milliseconds, 0 through 9007199254740991. |
+| `code` | Required except for finished. Stable category, 1–64 ASCII bytes from letters, digits, `._:/-$`; never an exception message, command line, query, or response body. |
+| `count` | Optional affected item count, a nonnegative JSON safe integer. |
+| `operationId` | Optional originating wire operation ID, 1–128 ASCII token bytes. The SDK obtains it from the call context. Core resolves a still-active wire request to its host operation; unknown or retired IDs provide no correlation. |
+
+The notification must precede the corresponding RPC response so its wire ID
+still belongs to the active host operation. Cancellation is an expected result
+and does not produce an operation failure. The SDK owns automatic function and
+domain request terminal facts; plugin handlers must not duplicate them. A
+handler records a warning only when it actually recovers or returns a degraded
+result. Frequently repeated read/preview/poll functions suppress successful
+terminal facts; their failures remain observable.
+
+Core supplies the installed plugin ID and routes these facts to
+`plugins/<id>/host`. Plugins cannot provide an event ID, channel, severity,
+message, arbitrary fields, error body, or writer path. The fixed catalog events
+are `plugins.operation.finished`, `plugins.operation.failed`,
+`plugins.operation.fallback_selected`, and `plugins.operation.recovery_finished`.
+Malformed or unnegotiated input produces one category-only
+`plugins.diagnostics.rejected` warning per process session, without retaining
+the rejected payload. Ingress admits at most 600 facts per minute per session,
+then uses the existing bounded Core handoff to the host's single writer;
+overload increments its dropped counter. No polling timer or extra writer is
+created. Fixture: `fixtures/plugin-logging.json`.
+
+Severity follows the actual result. An operation that failed for the user is
+ERROR, a recovery or fallback is WARN, and a useful successful user operation
+is INFO. The source stream is not a severity: unclassified stderr is DEBUG
+evidence, while standard `window/logMessage`/`window/showMessage` types retain
+their explicit error/warning/info/detail semantics through separate catalog
+events. Raw stdout is reserved for protocol frames. Source code, credentials,
+SQL, HTTP headers/bodies, terminal history, protocol payloads, and command
+output must never be included in diagnostic fields.
+
+Native upstream files may use `${logDir}` only when the host supplies the
+current local writable session directory. They remain separate files, not
+structured catalog events. Keep metadata and caches in `${stateDir}` or
+`${workspaceStateDir}`, and never infer a writable log path from `${pluginDir}`.
+These runtime files do not modify installed resources or participate in build
+resource reuse. Hosts without a local `logDirectory` reject launches requiring
+`${logDir}`. The current macOS writer persists v2; Windows's writer migration
+remains a separate platform task.
+
 #### Plugin settings (API 2)
 
 A plugin may declare options the user can change, one set per plugin and
diff --git a/contract/v1/fixtures/plugin-logging.json b/contract/v1/fixtures/plugin-logging.json
new file mode 100644
index 0000000..e606b4c
--- /dev/null
+++ b/contract/v1/fixtures/plugin-logging.json
@@ -0,0 +1,28 @@
+{
+  "version": 1,
+  "offer": { "litheLogging": { "versions": [1] } },
+  "answer": { "litheLogging": { "version": 1 } },
+  "notifications": [
+    { "kind": "operationFinished", "operation": "database.call", "durationMs": 18, "operationId": "7" },
+    { "kind": "operationFailed", "operation": "database.call", "durationMs": 20, "code": "database.unavailable", "operationId": "8" },
+    { "kind": "degraded", "operation": "database.call", "code": "result_size_limited", "count": 1000, "operationId": "9" },
+    { "kind": "recovered", "operation": "database.call", "code": "connection_restored" }
+  ],
+  "rejected": [
+    { "kind": "operationFinished", "operation": "database.call", "durationMs": -1 },
+    { "kind": "operationFailed", "operation": "database.call", "durationMs": 1, "code": "database.failed", "message": "private request contents" },
+    { "kind": "operationFinished", "operation": "unregistered.query", "durationMs": 1 },
+    { "kind": "degraded", "operation": "database.call", "code": "query failed with private data" },
+    { "kind": "degraded", "operation": "database.call", "code": "limit", "count": 9007199254740992 }
+  ],
+  "registeredFunctions": ["database.call"],
+  "plugin": "io.example.database",
+  "events": [
+    "plugins.operation.finished",
+    "plugins.operation.failed",
+    "plugins.operation.fallback_selected",
+    "plugins.operation.recovery_finished"
+  ],
+  "levels": ["INFO", "ERROR", "WARN", "WARN"],
+  "channel": "plugins/io.example.database/host"
+}