diff --git a/packages/coding-agent/CHANGELOG.md b/packages/coding-agent/CHANGELOG.md
index 630029a34..18cb4a404 100644
--- a/packages/coding-agent/CHANGELOG.md
+++ b/packages/coding-agent/CHANGELOG.md
@@ -5,7 +5,7 @@
 ### Added
 
 - Added tokens-per-second throughput to RPC `get_state` responses for non-TUI clients.
-- Added the RPC `set_fast_mode` command for live fast-mode control.
+- Added the RPC `set_fast_mode` command and typed TypeScript/Python client methods for live fast-mode control.
 - Added `fastModeEnabled` and `fastModeActive` to RPC `get_state` responses.
 
 ## [17.1.8] - 2026-07-28
diff --git a/python/omp-rpc/src/omp_rpc/__init__.py b/python/omp-rpc/src/omp_rpc/__init__.py
index d1fe16ec3..fd7ef107c 100644
--- a/python/omp-rpc/src/omp_rpc/__init__.py
+++ b/python/omp-rpc/src/omp_rpc/__init__.py
@@ -43,6 +43,7 @@ from .protocol import (
     AutoRetryEndEvent,
     AutoRetryStartEvent,
     BashResult,
+    FastModeResult,
     BranchMessage,
     BranchResult,
     CancellationResult,
@@ -109,6 +110,7 @@ __all__ = [
     "AutoRetryEndEvent",
     "AutoRetryStartEvent",
     "BashResult",
+    "FastModeResult",
     "BranchMessage",
     "BranchResult",
     "CancellationResult",
diff --git a/python/omp-rpc/src/omp_rpc/client.py b/python/omp-rpc/src/omp_rpc/client.py
index 538e6c4ff..0f3b8983d 100644
--- a/python/omp-rpc/src/omp_rpc/client.py
+++ b/python/omp-rpc/src/omp_rpc/client.py
@@ -25,6 +25,7 @@ from .protocol import (
     AutoRetryEndEvent,
     AutoRetryStartEvent,
     BashResult,
+    FastModeResult,
     BranchMessage,
     BranchResult,
     CancellationResult,
@@ -67,6 +68,7 @@ from .protocol import (
     assistant_text,
     parse_agent_messages,
     parse_bash_result,
+    parse_fast_mode_result,
     parse_branch_messages,
     parse_branch_result,
     parse_cancellation_result,
@@ -916,6 +918,9 @@ class RpcClient:
         payload = self._request("get_state")
         return parse_session_state(payload)
 
+    def set_fast_mode(self, enabled: bool) -> FastModeResult:
+        return parse_fast_mode_result(self._request("set_fast_mode", enabled=enabled))
+
     def set_model(self, provider: str, model_id: str) -> ModelInfo:
         payload = self._request("set_model", provider=provider, modelId=model_id)
         model = parse_model_info(payload)
diff --git a/python/omp-rpc/src/omp_rpc/protocol.py b/python/omp-rpc/src/omp_rpc/protocol.py
index 1fa2cfc9a..248ca89b7 100644
--- a/python/omp-rpc/src/omp_rpc/protocol.py
+++ b/python/omp-rpc/src/omp_rpc/protocol.py
@@ -183,6 +183,13 @@ def _require_str(payload: JsonObject, field: str) -> str:
     return value
 
 
+def _require_bool(payload: JsonObject, field: str) -> bool:
+    value = payload.get(field)
+    if not isinstance(value, bool):
+        raise ValueError(f"{field} must be a boolean")
+    return value
+
+
 def _optional_str(payload: JsonObject, field: str) -> str | None:
     value = payload.get(field)
     if value is None:
@@ -803,6 +810,12 @@ class BashResult:
     artifact_id: str | None = None
 
 
+@dataclass(slots=True, frozen=True)
+class FastModeResult:
+    enabled: bool
+    active: bool
+
+
 @dataclass(slots=True, frozen=True)
 class CompactionResult:
     summary: str
@@ -1376,6 +1389,13 @@ def parse_bash_result(payload: JsonObject) -> BashResult:
     )
 
 
+def parse_fast_mode_result(payload: JsonObject) -> FastModeResult:
+    return FastModeResult(
+        enabled=_require_bool(payload, "enabled"),
+        active=_require_bool(payload, "active"),
+    )
+
+
 def parse_compaction_result(payload: JsonObject) -> CompactionResult:
     return CompactionResult(
         summary=str(payload.get("summary", "")),
diff --git a/python/omp-rpc/tests/test_client.py b/python/omp-rpc/tests/test_client.py
index 3ad15d703..4355ee4b8 100644
--- a/python/omp-rpc/tests/test_client.py
+++ b/python/omp-rpc/tests/test_client.py
@@ -322,6 +322,21 @@ FAKE_SERVER = textwrap.dedent(
                 "compact",
                 {"summary": "trimmed", "shortSummary": "trimmed", "firstKeptEntryId": "entry-1", "tokensBefore": 123},
             )
+        elif command_type == "set_fast_mode":
+            enabled = command.get("enabled")
+            if not isinstance(enabled, bool):
+                respond(
+                    request_id,
+                    "set_fast_mode",
+                    success=False,
+                    error="set_fast_mode requires boolean enabled",
+                )
+            else:
+                respond(
+                    request_id,
+                    "set_fast_mode",
+                    {"enabled": False, "active": True},
+                )
         elif command_type == "set_auto_compaction":
             auto_compaction_enabled = command["enabled"]
             respond(request_id, "set_auto_compaction", {})
@@ -888,6 +903,13 @@ class RpcClientTests(unittest.TestCase):
             self.assertEqual(result.output, "hello\n")
             self.assertEqual(result.exit_code, 0)
 
+    def test_set_fast_mode_preserves_provider_tier_state(self) -> None:
+        with self.make_client() as client:
+            result = client.set_fast_mode(False)
+
+            self.assertFalse(result.enabled)
+            self.assertTrue(result.active)
+
     def test_prompt_and_wait_returns_assistant_text(self) -> None:
         with self.make_client() as client:
             turn = client.prompt_and_wait("say hello", timeout=2.0)