diff --git a/apps/server/src/provider/Layers/ClaudeAdapter.test.ts b/apps/server/src/provider/Layers/ClaudeAdapter.test.ts
index 3e883fa1cf5..2735b69a187 100644
--- a/apps/server/src/provider/Layers/ClaudeAdapter.test.ts
+++ b/apps/server/src/provider/Layers/ClaudeAdapter.test.ts
@@ -1711,6 +1711,133 @@ describe("ClaudeAdapterLive", () => {
     );
   });
 
+  it.effect("consumes undeclared and UX-internal system subtypes without warning rows", () => {
+    const harness = makeHarness();
+    return Effect.gen(function* () {
+      const adapter = yield* ClaudeAdapter;
+      const runtimeEvents: Array<ProviderRuntimeEvent> = [];
+      const runtimeEventsFiber = yield* Stream.runForEach(adapter.streamEvents, (event) =>
+        Effect.sync(() => runtimeEvents.push(event)),
+      ).pipe(Effect.forkChild);
+
+      yield* adapter.startSession({
+        threadId: THREAD_ID,
+        provider: ProviderDriverKind.make("claudeAgent"),
+        runtimeMode: "full-access",
+      });
+
+      // Undeclared wire-only roster snapshot + every typed UX-internal
+      // subtype and top-level type consumed silently: none may surface as
+      // unknown-subtype warnings.
+      for (const message of [
+        {
+          type: "system",
+          subtype: "background_tasks_changed",
+          tasks: [{ task_id: "t1", task_type: "local_agent", description: "Say hi" }],
+          session_id: "session",
+          uuid: "roster",
+        },
+        {
+          type: "system",
+          subtype: "task_updated",
+          task_id: "t1",
+          patch: { status: "running" },
+          session_id: "session",
+          uuid: "tu",
+        },
+        { type: "system", subtype: "commands_changed", session_id: "session", uuid: "cc" },
+        { type: "system", subtype: "model_refusal_fallback", session_id: "session", uuid: "mrf" },
+        { type: "system", subtype: "local_command_output", session_id: "session", uuid: "lco" },
+        { type: "system", subtype: "plugin_install", session_id: "session", uuid: "pi" },
+        { type: "system", subtype: "memory_recall", session_id: "session", uuid: "mr" },
+        { type: "system", subtype: "elicitation_complete", session_id: "session", uuid: "ec" },
+        { type: "prompt_suggestion", suggestion: "try this", session_id: "session", uuid: "ps" },
+        {
+          type: "system",
+          subtype: "notification",
+          key: "context",
+          text: "low priority note",
+          priority: "low",
+          session_id: "session",
+          uuid: "notif",
+        },
+      ]) {
+        harness.query.emit(message as unknown as SDKMessage);
+      }
+      // High-priority notifications DO surface as a warning row.
+      harness.query.emit({
+        type: "system",
+        subtype: "notification",
+        key: "limit",
+        text: "context window nearly full",
+        priority: "high",
+        session_id: "session",
+        uuid: "notif-high",
+      } as unknown as SDKMessage);
+      // session_state_changed maps to the matching session states.
+      for (const [state, uuid] of [
+        ["running", "ssc-run"],
+        ["requires_action", "ssc-req"],
+        ["idle", "ssc-idle"],
+      ]) {
+        harness.query.emit({
+          type: "system",
+          subtype: "session_state_changed",
+          state,
+          session_id: "session",
+          uuid,
+        } as unknown as SDKMessage);
+      }
+      // api_retry maps to a session heartbeat, not a warning row.
+      harness.query.emit({
+        type: "system",
+        subtype: "api_retry",
+        attempt: 3,
+        max_retries: 10,
+        retry_delay_ms: 1000,
+        error_status: 502,
+        error: { type: "api_error" },
+        session_id: "session",
+        uuid: "retry",
+      } as unknown as SDKMessage);
+      yield* Effect.yieldNow;
+      yield* Effect.yieldNow;
+
+      const warnings = runtimeEvents.filter((event) => event.type === "runtime.warning");
+      // Exactly one warning: the high-priority notification. Nothing else.
+      assert.deepEqual(
+        warnings.map((event) => event.payload.message),
+        ["context window nearly full"],
+      );
+      const sessionStates = runtimeEvents
+        .filter((event) => event.type === "session.state.changed")
+        .map((event) =>
+          event.type === "session.state.changed"
+            ? `${event.payload.state}:${event.payload.reason ?? ""}`
+            : "",
+        )
+        .filter(
+          (entry) => entry.startsWith("running:session_state") || entry.includes("session_state"),
+        );
+      assert.deepEqual(sessionStates, [
+        "running:session_state:running",
+        "waiting:session_state:requires_action",
+        "ready:session_state:idle",
+      ]);
+      const heartbeat = runtimeEvents.find(
+        (event) =>
+          event.type === "session.state.changed" &&
+          typeof event.payload.reason === "string" &&
+          event.payload.reason.startsWith("api_retry:"),
+      );
+      assert.equal(heartbeat?.type, "session.state.changed");
+      runtimeEventsFiber.interruptUnsafe();
+    }).pipe(
+      Effect.provideService(Random.Random, makeDeterministicRandomService()),
+      Effect.provide(harness.layer),
+    );
+  });
+
   it.effect("emits thread token usage updates from Claude task progress", () => {
     const harness = makeHarness();
     return Effect.gen(function* () {
diff --git a/apps/server/src/provider/Layers/ClaudeAdapter.ts b/apps/server/src/provider/Layers/ClaudeAdapter.ts
index 5ccd011ef09..757d7a00eb2 100644
--- a/apps/server/src/provider/Layers/ClaudeAdapter.ts
+++ b/apps/server/src/provider/Layers/ClaudeAdapter.ts
@@ -2585,6 +2585,17 @@ export const makeClaudeAdapter = Effect.fn("makeClaudeAdapter")(function* (
       },
     };
 
+    // Undeclared-but-real subtypes (absent from the SDK's union, so they can't
+    // be switch cases): consumed intentionally without emitting, otherwise
+    // they fall through to the unknown-subtype warning and surface as spurious
+    // error rows in client work logs. `background_tasks_changed` is a roster
+    // snapshot ({tasks: [...]}) — the task_* lifecycle events carry the
+    // authoritative per-agent data and the typed background_tasks control
+    // request is the reconciliation source.
+    if ((message.subtype as string) === "background_tasks_changed") {
+      return;
+    }
+
     switch (message.subtype) {
       case "init":
         yield* offerRuntimeEvent({
@@ -2697,6 +2708,11 @@ export const makeClaudeAdapter = Effect.fn("makeClaudeAdapter")(function* (
           },
         });
         return;
+      // Task state patch (status/backgrounded/end_time). No runtime mapping
+      // yet — the terminal task_notification reports the outcome — but it
+      // must not surface as an unknown-subtype warning row.
+      case "task_updated":
+        return;
       case "task_notification":
         yield* emitThreadTokenUsage(
           context,
@@ -2741,6 +2757,52 @@ export const makeClaudeAdapter = Effect.fn("makeClaudeAdapter")(function* (
         return;
       case "thinking_tokens":
         return;
+      case "api_retry":
+        // Transport-level retry heartbeat. Surfacing each attempt as a
+        // warning row spammed the work log (10 rows during a 502 storm);
+        // the terminal result/error path reports the actual failure. Keep
+        // the session visibly alive instead.
+        yield* offerRuntimeEvent({
+          ...base,
+          type: "session.state.changed",
+          payload: {
+            state: "running",
+            reason: `api_retry:${message.attempt}/${message.max_retries}`,
+          },
+        });
+        return;
+      case "session_state_changed":
+        // Authoritative turn-over signal from the CLI.
+        yield* offerRuntimeEvent({
+          ...base,
+          type: "session.state.changed",
+          payload: {
+            state:
+              message.state === "running"
+                ? "running"
+                : message.state === "requires_action"
+                  ? "waiting"
+                  : "ready",
+            reason: `session_state:${message.state}`,
+          },
+        });
+        return;
+      case "notification":
+        // User-facing CLI notification (e.g. context-limit warnings). Only
+        // high-priority ones warrant a work-log row.
+        if (message.priority === "high" || message.priority === "immediate") {
+          yield* emitRuntimeWarning(context, message.text, message);
+        }
+        return;
+      // Inner protocol/UX details with no T3 surface today — consumed
+      // deliberately so they don't masquerade as unknown-subtype warnings.
+      case "model_refusal_fallback":
+      case "local_command_output":
+      case "plugin_install":
+      case "commands_changed":
+      case "memory_recall":
+      case "elicitation_complete":
+        return;
       case "permission_denied":
         yield* offerRuntimeEvent({
           ...base,
@@ -2760,13 +2822,21 @@ export const makeClaudeAdapter = Effect.fn("makeClaudeAdapter")(function* (
           message,
         );
         return;
-      default:
+      default: {
+        // Exhaustiveness guard: every subtype in the SDK's typed union is
+        // handled above, so `message` narrows to never here — a new SDK
+        // release adding a subtype fails this typecheck instead of silently
+        // warning at runtime. The runtime fallback still catches undeclared
+        // wire-only subtypes (like background_tasks_changed used to be).
+        message satisfies never;
+        const unknownMessage = message as never as { subtype: string };
         yield* emitRuntimeWarning(
           context,
-          describeUnknownSdkMessage(`Claude system message '${message.subtype}'`, message),
+          describeUnknownSdkMessage(`Claude system message '${unknownMessage.subtype}'`, message),
           message,
         );
         return;
+      }
     }
   });
 
@@ -2874,13 +2944,21 @@ export const makeClaudeAdapter = Effect.fn("makeClaudeAdapter")(function* (
       case "rate_limit_event":
         yield* handleSdkTelemetryMessage(context, message);
         return;
-      default:
+      // Composer prompt suggestions have no T3 surface; consumed deliberately.
+      case "prompt_suggestion":
+        return;
+      default: {
+        // Exhaustiveness guard (see handleSystemMessage): new SDK top-level
+        // message types fail typecheck here instead of warning at runtime.
+        message satisfies never;
+        const unknownMessage = message as never as { type: string };
         yield* emitRuntimeWarning(
           context,
-          describeUnknownSdkMessage(`Claude SDK message '${message.type}'`, message),
+          describeUnknownSdkMessage(`Claude SDK message '${unknownMessage.type}'`, message),
           message,
         );
         return;
+      }
     }
   });