diff --git a/backend/onyx/background/celery/tasks/scheduled_tasks/tasks.py b/backend/onyx/background/celery/tasks/scheduled_tasks/tasks.py
index 5fe802759b..581a3a4834 100644
--- a/backend/onyx/background/celery/tasks/scheduled_tasks/tasks.py
+++ b/backend/onyx/background/celery/tasks/scheduled_tasks/tasks.py
@@ -51,9 +51,13 @@ from onyx.db.scheduled_task import (
     mark_run_status,
 )
 from onyx.server.features.build.scheduled_tasks.executor import (
-    DEFAULT_EXECUTOR_BUDGET_SECONDS,
     run_scheduled_task_logic,
 )
+from onyx.server.features.build.timeouts import (
+    QUEUE_RESIDENCY_SECONDS,
+    TURN_BUDGET_SECONDS,
+    TURN_RECLAIM_SLACK_SECONDS,
+)
 from onyx.server.features.build.utils import is_craft_enabled_for_user
 from onyx.server.settings.store import load_settings
 
@@ -65,19 +69,15 @@ from onyx.server.settings.store import load_settings
 # concurrent ticks just see "no rows" and exit.
 DISPATCH_BATCH_SIZE = 50
 
-# How long the executor message can sit on the `scheduled_tasks` queue
-# before Celery drops it. After 15 min we'd rather let the next beat tick
-# re-dispatch a new run row than execute a stale one.
-RUN_EXPIRES_SECONDS = 15 * 60
-
-# Stuck-run sweeper thresholds. The QUEUED threshold needs to comfortably
-# exceed the longest plausible queue wait + executor startup. The RUNNING
-# threshold should exceed the executor budget by enough margin that a
-# well-behaved run that hits its own budget gets there first and marks
-# itself FAILED (rather than the sweeper). Budget is 30 min by default;
-# 45 min gives 50% slack.
-STUCK_QUEUED_OLDER_THAN = timedelta(minutes=15)
-STUCK_RUNNING_OLDER_THAN = timedelta(seconds=DEFAULT_EXECUTOR_BUDGET_SECONDS + 15 * 60)
+# Celery expiry and the stuck-QUEUED sweep are one policy: a run that sat
+# queued past the residency limit is dropped unexecuted and its row reclaimed
+# by the same threshold. A RUNNING row is stuck only past budget + slack, so a
+# well-behaved run that hits its own budget always marks itself FAILED first.
+RUN_EXPIRES_SECONDS = QUEUE_RESIDENCY_SECONDS
+STUCK_QUEUED_OLDER_THAN = timedelta(seconds=QUEUE_RESIDENCY_SECONDS)
+STUCK_RUNNING_OLDER_THAN = timedelta(
+    seconds=TURN_BUDGET_SECONDS + TURN_RECLAIM_SLACK_SECONDS
+)
 
 
 # --- Dispatch ----------------------------------------------------------------
diff --git a/backend/onyx/server/features/build/configs.py b/backend/onyx/server/features/build/configs.py
index 744ff8a0b6..a01ec50080 100644
--- a/backend/onyx/server/features/build/configs.py
+++ b/backend/onyx/server/features/build/configs.py
@@ -37,6 +37,10 @@ SANDBOX_MAX_CONCURRENT_PER_ORG = int(
 SANDBOX_APPROVAL_WAIT_TIMEOUT_SECONDS = int(
     os.environ.get("SANDBOX_APPROVAL_WAIT_TIMEOUT_SECONDS", "180")
 )
+# Margin a client-side wait must add over the approval window so a decision
+# landing at the wire never races the client's own timeout. Shared by the
+# AGENTS.md guidance and the inactivity-backstop default below.
+SANDBOX_APPROVAL_WAIT_MARGIN_SECONDS = 20
 SANDBOX_IDLE_CLEANUP_INTERVAL_SECONDS = int(
     os.environ.get("SANDBOX_IDLE_CLEANUP_INTERVAL_SECONDS", "60")
 )
@@ -168,18 +172,21 @@ SANDBOX_DOCKER_CPU_LIMIT = float(os.environ.get("SANDBOX_DOCKER_CPU_LIMIT", "1.0
 SSE_KEEPALIVE_INTERVAL = float(os.environ.get("SSE_KEEPALIVE_INTERVAL", "15.0"))
 
 # Maximum time opencode-serve may go without emitting a turn event. Coarse
-# liveness backstop only: it must stay above opencode's own per-tool timeouts
-# (bash defaults to 180s here, webfetch 120s) so it never pre-empts a healthy
-# long-running tool — it exists to catch stalls opencode does not bound itself
-# (LLM-stream hangs, non-bash/MCP tool hangs). The turn budget is the hard ceiling.
+# liveness backstop only: it must stay above every in-tool wait so it never
+# pre-empts a healthy long-running tool — opencode's bash tool defaults to
+# 180s, and a proxy-parked approval inside a tool call holds the stream
+# silent for the full approval window, hence the derivation. It exists to
+# catch stalls opencode does not bound itself (LLM-stream hangs, non-bash/MCP
+# tool hangs). The turn budget is the hard ceiling.
 OPENCODE_PROMPT_INACTIVITY_TIMEOUT_SECONDS = float(
-    os.environ.get("OPENCODE_PROMPT_INACTIVITY_TIMEOUT_SECONDS", "200.0")
+    os.environ.get(
+        "OPENCODE_PROMPT_INACTIVITY_TIMEOUT_SECONDS",
+        str(
+            SANDBOX_APPROVAL_WAIT_TIMEOUT_SECONDS + SANDBOX_APPROVAL_WAIT_MARGIN_SECONDS
+        ),
+    )
 )
 
-# Hard ceiling for background prompt-slot renewal, so a leaked holder cannot
-# retain mutual exclusion indefinitely.
-PROMPT_SLOT_KEEP_ALIVE_MAX_SECONDS = 30 * 60.0
-
 # Prompt-slot lock lease; renewed on every sandbox event/keepalive, so a dead
 # holder strands the slot for at most this long.
 PROMPT_SLOT_LEASE_SECONDS = float(os.environ.get("PROMPT_SLOT_LEASE_SECONDS", "120.0"))
@@ -203,8 +210,11 @@ OPENCODE_SERVE_CONNECT_TIMEOUT = float(
 OPENCODE_SERVE_REQUEST_TIMEOUT = float(
     os.environ.get("OPENCODE_SERVE_REQUEST_TIMEOUT", "30.0")
 )
-# Idle timeout for /event SSE. The reader reconnects (with backoff) if the
-# stream is silent for this long.
+# Idle timeout for the raw /event SSE connection to opencode-serve. The
+# reader reconnects (with backoff) if no bytes arrive for this long. Its
+# floor is opencode-serve's own emission cadence on /event — NOT our
+# downstream UI keepalive, which is synthesized after the bus and never
+# reaches this connection.
 OPENCODE_SERVE_EVENT_READ_TIMEOUT = float(
     os.environ.get("OPENCODE_SERVE_EVENT_READ_TIMEOUT", "60.0")
 )
diff --git a/backend/onyx/server/features/build/interactive_turns/api.py b/backend/onyx/server/features/build/interactive_turns/api.py
index 8d40c04d3e..2c796af761 100644
--- a/backend/onyx/server/features/build/interactive_turns/api.py
+++ b/backend/onyx/server/features/build/interactive_turns/api.py
@@ -21,6 +21,7 @@ from onyx.db.enums import Permission
 from onyx.db.models import User
 from onyx.error_handling.error_codes import OnyxErrorCode
 from onyx.error_handling.exceptions import OnyxError
+from onyx.server.features.build.configs import SSE_KEEPALIVE_INTERVAL
 from onyx.server.features.build.db.build_session import get_build_session
 from onyx.server.features.build.interactive_turns.executor import (
     start_interactive_turn_runner,
@@ -33,16 +34,18 @@ from onyx.server.features.build.interactive_turns.state import (
 )
 from onyx.server.features.build.session.manager import SessionManager
 from onyx.server.features.build.session.streaming import SSE_KEEPALIVE
+from onyx.server.features.build.timeouts import POLL_INTERVAL_SECONDS
 from onyx.utils.logger import setup_logger
 
 router = APIRouter()
 logger = setup_logger()
 
-LIVE_STREAM_READY_POLL_SECONDS = 0.25
-LIVE_STREAM_KEEPALIVE_SECONDS = 15.0
-LIVE_STREAM_RUNNER_RETRY_SECONDS = 5.0
 TERMINAL_STREAM_EVENT_TYPES = frozenset(("prompt_response", "error"))
 
+# Throttle on runner-claim retries from the attach stream; must be well under
+# RUNNER_STALE_AFTER_SECONDS so a stolen turn restarts promptly.
+LIVE_STREAM_RUNNER_RETRY_SECONDS = 5.0
+
 
 def _format_stream_error(detail: str) -> str:
     payload = {
@@ -194,7 +197,7 @@ def get_interactive_turn_events(
 
             yield SSE_KEEPALIVE
             maybe_start_runner()
-            time.sleep(LIVE_STREAM_READY_POLL_SECONDS)
+            time.sleep(POLL_INTERVAL_SECONDS)
 
         try:
             with get_session_with_current_tenant() as stream_db_session:
@@ -203,7 +206,7 @@ def get_interactive_turn_events(
                 for chunk in session_manager.subscribe_to_existing_session_events(
                     session_id,
                     user_id,
-                    keepalive_seconds=LIVE_STREAM_KEEPALIVE_SECONDS,
+                    keepalive_seconds=SSE_KEEPALIVE_INTERVAL,
                 ):
                     yield chunk
                     chunk_type = _stream_chunk_type(chunk)
@@ -229,8 +232,9 @@ def get_interactive_turn_events(
                         continue
                     terminal_error_detail = None
                     # Not redundant with the attach-time force start: a dead
-                    # runner's turn only becomes reclaimable 90s after its last
-                    # heartbeat; claim no-ops while the turn is healthy.
+                    # runner's turn only becomes reclaimable
+                    # RUNNER_STALE_AFTER_SECONDS after its last heartbeat;
+                    # claim no-ops while the turn is healthy.
                     maybe_start_runner()
                 if terminal_error_detail:
                     yield _format_stream_error(terminal_error_detail)
diff --git a/backend/onyx/server/features/build/interactive_turns/executor.py b/backend/onyx/server/features/build/interactive_turns/executor.py
index beee517f10..1c5055e6a6 100644
--- a/backend/onyx/server/features/build/interactive_turns/executor.py
+++ b/backend/onyx/server/features/build/interactive_turns/executor.py
@@ -31,10 +31,6 @@ from onyx.server.features.build.sandbox.event_schema import (
 )
 from onyx.server.features.build.sandbox.event_schema import Error as SandboxError
 from onyx.server.features.build.sandbox.models import PromptAttachment
-from onyx.server.features.build.sandbox.serve_transport import (
-    PROMPT_SLOT_FAST_FAIL_ACQUIRE_SECONDS,
-    PROMPT_SLOT_WAIT_OUT_ORPHAN_SECONDS,
-)
 from onyx.server.features.build.sandbox.sse import SSEKeepalive
 from onyx.server.features.build.session.interrupt_signal import (
     clear_interrupt,
@@ -42,6 +38,11 @@ from onyx.server.features.build.session.interrupt_signal import (
 )
 from onyx.server.features.build.session.manager import SessionManager
 from onyx.server.features.build.session.streaming import BuildStreamingState
+from onyx.server.features.build.timeouts import (
+    PROMPT_SLOT_FAST_FAIL_ACQUIRE_SECONDS,
+    PROMPT_SLOT_WAIT_OUT_ORPHAN_SECONDS,
+    TURN_BUDGET_SECONDS,
+)
 from onyx.utils.logger import setup_logger
 from shared_configs.contextvars import (
     CURRENT_TENANT_ID_CONTEXTVAR,
@@ -50,8 +51,6 @@ from shared_configs.contextvars import (
 
 logger = setup_logger()
 
-DEFAULT_INTERACTIVE_TURN_BUDGET_SECONDS = 30 * 60
-
 MAX_TIMEOUT_CONTINUATIONS = 2
 _TOOL_TIMEOUT_CONTINUATION_PROMPT = (
     "Your last step was cancelled — it exceeded the "
@@ -131,7 +130,7 @@ def start_interactive_turn_runner(turn_id: UUID) -> None:
 def run_claimed_interactive_build_turn(
     turn: InteractiveTurn,
     *,
-    budget_seconds: int = DEFAULT_INTERACTIVE_TURN_BUDGET_SECONDS,
+    budget_seconds: int = TURN_BUDGET_SECONDS,
 ) -> None:
     """Execute a turn that this runner has already claimed in CacheBackend."""
     cache = get_cache_backend()
@@ -225,7 +224,7 @@ def _drive_interactive_turn(
             return
 
         try:
-            # Re-fence after the (possibly long) slot wait: a reclaim acquire
+            # Re-check ownership after the (possibly long) slot wait: a reclaim acquire
             # can block past RUNNER_STALE_AFTER_SECONDS, letting another
             # runner steal the turn — it must not reach the prompt POST.
             if not touch_turn(cache=cache, turn_id=turn_id, runner_id=runner_id):
diff --git a/backend/onyx/server/features/build/interactive_turns/state.py b/backend/onyx/server/features/build/interactive_turns/state.py
index 9413004f4e..be816780aa 100644
--- a/backend/onyx/server/features/build/interactive_turns/state.py
+++ b/backend/onyx/server/features/build/interactive_turns/state.py
@@ -10,8 +10,19 @@ from uuid import UUID, uuid4
 
 from onyx.cache.interface import CacheBackend, CacheLock
 from onyx.server.features.build.sandbox.models import PromptAttachment
+from onyx.server.features.build.timeouts import (
+    ACTIVE_TURN_TTL_SECONDS,
+    REQUEST_ID_TTL_SECONDS,
+    RUNNER_STALE_AFTER_SECONDS,
+)
 from onyx.utils.datetime import datetime_to_utc
 
+# Turn-state mutex: guards a handful of Redis round-trips per mutation; the
+# lease only needs to exceed the longest critical section. Ownership is
+# decided by the runner_id compare, never by this lease.
+TURN_LOCK_LEASE_SECONDS = 60.0
+TURN_LOCK_WAIT_SECONDS = 10.0
+
 
 class InteractiveTurnStatus(StrEnum):
     QUEUED = "QUEUED"
@@ -28,11 +39,6 @@ TURN_STATUS_FAILED = InteractiveTurnStatus.FAILED
 TURN_STATUS_CANCELLED = InteractiveTurnStatus.CANCELLED
 
 ACTIVE_TURN_STATUSES = frozenset((TURN_STATUS_QUEUED, TURN_STATUS_RUNNING))
-ACTIVE_TURN_TTL_SECONDS = 45 * 60
-REQUEST_ID_TTL_SECONDS = 60 * 60
-TURN_LOCK_LEASE_SECONDS = 60.0
-TURN_LOCK_WAIT_SECONDS = 10.0
-RUNNER_STALE_AFTER_SECONDS = 90.0
 
 
 class InteractiveTurnLockError(Exception):
diff --git a/backend/onyx/server/features/build/sandbox/kubernetes/sidecar_client.py b/backend/onyx/server/features/build/sandbox/kubernetes/sidecar_client.py
index 34eaab27a8..67bc36e5a0 100644
--- a/backend/onyx/server/features/build/sandbox/kubernetes/sidecar_client.py
+++ b/backend/onyx/server/features/build/sandbox/kubernetes/sidecar_client.py
@@ -25,6 +25,11 @@ from onyx.server.features.build.sandbox.image.sandbox_daemon.contract import (
     FilesystemListResponse,
 )
 from onyx.server.features.build.sandbox.models import FilesystemEntry
+from onyx.server.features.build.timeouts import (
+    BULK_TRANSFER_TIMEOUT_SECONDS,
+    CONNECT_TIMEOUT_SECONDS,
+    RPC_TIMEOUT_SECONDS,
+)
 
 _SIDECAR_CHUNK_SIZE = 8 * 1024 * 1024
 
@@ -130,7 +135,7 @@ class SidecarClient:
         sandbox_id: UUID,
         session_id: UUID,
         path: str,
-        timeout_seconds: float = 30.0,
+        timeout_seconds: float = RPC_TIMEOUT_SECONDS,
     ) -> list[FilesystemEntry]:
         payload = FilesystemListRequest(session_id=session_id, path=path)
         body = payload.model_dump_json().encode()
@@ -222,7 +227,7 @@ class SidecarClient:
         archive_file: IO[bytes],
         sha256_hex: str,
         operation_label: str,
-        timeout_seconds: float = 300.0,
+        timeout_seconds: float = BULK_TRANSFER_TIMEOUT_SECONDS,
     ) -> None:
         def body() -> Iterator[bytes]:
             archive_file.seek(0)
@@ -248,7 +253,7 @@ class SidecarClient:
         sandbox_id: UUID,
         endpoint_path: str,
         operation_label: str,
-        timeout_seconds: float = 300.0,
+        timeout_seconds: float = BULK_TRANSFER_TIMEOUT_SECONDS,
     ) -> None:
         body = b""
         self._post(
@@ -350,7 +355,7 @@ class SidecarClient:
     def _timeout_for_post(remaining_seconds: float) -> httpx.Timeout:
         return httpx.Timeout(
             remaining_seconds,
-            connect=min(5.0, remaining_seconds),
+            connect=min(CONNECT_TIMEOUT_SECONDS, remaining_seconds),
             read=remaining_seconds,
             write=remaining_seconds,
         )
diff --git a/backend/onyx/server/features/build/sandbox/opencode/event_bus.py b/backend/onyx/server/features/build/sandbox/opencode/event_bus.py
index 696775d470..78a07b8943 100644
--- a/backend/onyx/server/features/build/sandbox/opencode/event_bus.py
+++ b/backend/onyx/server/features/build/sandbox/opencode/event_bus.py
@@ -17,6 +17,7 @@ from typing import Any
 
 import httpx
 
+from onyx.server.features.build.timeouts import CONNECT_TIMEOUT_SECONDS
 from onyx.utils.logger import setup_logger
 
 logger = setup_logger()
@@ -52,7 +53,7 @@ class PodEventBus:
         auth: httpx.Auth | None,
         *,
         directory: str | None = None,
-        connect_timeout: float = 10.0,
+        connect_timeout: float = CONNECT_TIMEOUT_SECONDS,
         event_read_timeout: float | None = None,
         reload_auth: Callable[[], httpx.Auth | None] | None = None,
     ) -> None:
diff --git a/backend/onyx/server/features/build/sandbox/serve_transport.py b/backend/onyx/server/features/build/sandbox/serve_transport.py
index fbfb14f7e2..b028459932 100644
--- a/backend/onyx/server/features/build/sandbox/serve_transport.py
+++ b/backend/onyx/server/features/build/sandbox/serve_transport.py
@@ -28,8 +28,8 @@ from onyx.server.features.build.configs import (
     OPENCODE_PROMPT_INACTIVITY_TIMEOUT_SECONDS,
     OPENCODE_SERVE_EVENT_READ_TIMEOUT,
     OPENCODE_SERVER_USERNAME,
-    PROMPT_SLOT_KEEP_ALIVE_MAX_SECONDS,
     PROMPT_SLOT_LEASE_SECONDS,
+    SSE_KEEPALIVE_INTERVAL,
 )
 from onyx.server.features.build.db.sandbox import get_sandbox_by_id
 from onyx.server.features.build.sandbox.event_schema import (
@@ -48,6 +48,11 @@ from onyx.server.features.build.sandbox.opencode.serve_client import (
     translate_opencode_event,
 )
 from onyx.server.features.build.sandbox.sse import SSEKeepalive
+from onyx.server.features.build.timeouts import (
+    POLL_INTERVAL_SECONDS,
+    PROMPT_SLOT_FAST_FAIL_ACQUIRE_SECONDS,
+    PROMPT_SLOT_KEEP_ALIVE_MAX_SECONDS,
+)
 from onyx.server.metrics.craft_sandbox import (
     SandboxProvisionPhase,
     time_provision_phase,
@@ -63,13 +68,6 @@ _API_SERVER_HOSTNAME = os.environ.get("HOSTNAME", "unknown")
 
 # opencode-serve boot lags backend Ready by ~1–3s warm, up to ~15s cold.
 OPENCODE_SERVE_READY_TIMEOUT_SECONDS = 30
-OPENCODE_SERVE_READY_POLL_INTERVAL_SECONDS = 0.25
-
-# How long a new turn waits for the previous turn's slot before giving up.
-PROMPT_SLOT_FAST_FAIL_ACQUIRE_SECONDS = 10.0
-
-# Must exceed the lease so a reclaimed turn can wait out a dead holder's slot.
-PROMPT_SLOT_WAIT_OUT_ORPHAN_SECONDS = PROMPT_SLOT_LEASE_SECONDS + 10.0
 
 # Live attach streams are UI-facing. Coalesce adjacent text deltas just long
 # enough to avoid one React update per tiny opencode token burst, while keeping
@@ -412,7 +410,7 @@ class _ServeMixin:
                         last_err = f"health_check returned status={status} for {url}"
                     except Exception as e:
                         last_err = f"{url}: {type(e).__name__}: {e}"
-                time.sleep(OPENCODE_SERVE_READY_POLL_INTERVAL_SECONDS)
+                time.sleep(POLL_INTERVAL_SECONDS)
         finally:
             for _, client in clients:
                 client.close()
@@ -808,7 +806,7 @@ class _ServeMixin:
         opencode_session_id: str,
         *,
         directory: str,
-        keepalive_seconds: float = 15.0,
+        keepalive_seconds: float = SSE_KEEPALIVE_INTERVAL,
     ) -> Generator[SandboxEvent, None, None]:
         """Stream translated sandbox events for an opencode session. Caller closes
         via ``GeneratorExit``. ``directory`` is required: opencode-serve scopes
diff --git a/backend/onyx/server/features/build/sandbox/util/agent_instructions.py b/backend/onyx/server/features/build/sandbox/util/agent_instructions.py
index 3d88ac9a37..c59adb4b61 100644
--- a/backend/onyx/server/features/build/sandbox/util/agent_instructions.py
+++ b/backend/onyx/server/features/build/sandbox/util/agent_instructions.py
@@ -4,7 +4,10 @@ from collections.abc import Iterable
 from pathlib import Path
 
 from onyx.db.models import ExternalApp
-from onyx.server.features.build.configs import SANDBOX_APPROVAL_WAIT_TIMEOUT_SECONDS
+from onyx.server.features.build.configs import (
+    SANDBOX_APPROVAL_WAIT_MARGIN_SECONDS,
+    SANDBOX_APPROVAL_WAIT_TIMEOUT_SECONDS,
+)
 from onyx.utils.logger import setup_logger
 
 logger = setup_logger()
@@ -156,7 +159,9 @@ def generate_agent_instructions(
     )
     content = content.replace(
         "{{APPROVAL_CLIENT_TIMEOUT_SECONDS}}",
-        str(SANDBOX_APPROVAL_WAIT_TIMEOUT_SECONDS + 20),
+        str(
+            SANDBOX_APPROVAL_WAIT_TIMEOUT_SECONDS + SANDBOX_APPROVAL_WAIT_MARGIN_SECONDS
+        ),
     )
     content = content.replace("{{DISABLED_TOOLS_SECTION}}", disabled_tools_section)
     content = content.replace("{{CONNECTABLE_APPS_LIST}}", connectable_apps_section)
diff --git a/backend/onyx/server/features/build/sandbox/util/api_url_check.py b/backend/onyx/server/features/build/sandbox/util/api_url_check.py
index 0e5e88bb48..380566b5f8 100644
--- a/backend/onyx/server/features/build/sandbox/util/api_url_check.py
+++ b/backend/onyx/server/features/build/sandbox/util/api_url_check.py
@@ -13,12 +13,11 @@ import httpx
 
 from onyx.error_handling.error_codes import OnyxErrorCode
 from onyx.error_handling.exceptions import OnyxError
+from onyx.server.features.build.timeouts import CONNECT_TIMEOUT_SECONDS
 from onyx.utils.logger import setup_logger
 
 logger = setup_logger()
 
-_PROBE_TIMEOUT_SECONDS = 5.0
-
 _validated = False
 _validated_lock = threading.Lock()
 
@@ -28,7 +27,7 @@ def _probe_health(base_url: str) -> httpx.Response | None:
     try:
         return httpx.get(
             f"{base_url}/health",
-            timeout=_PROBE_TIMEOUT_SECONDS,
+            timeout=CONNECT_TIMEOUT_SECONDS,
             follow_redirects=True,
         )
     except httpx.HTTPError:
diff --git a/backend/onyx/server/features/build/scheduled_tasks/api.py b/backend/onyx/server/features/build/scheduled_tasks/api.py
index 5c65044ec2..72e0dc7d0c 100644
--- a/backend/onyx/server/features/build/scheduled_tasks/api.py
+++ b/backend/onyx/server/features/build/scheduled_tasks/api.py
@@ -52,6 +52,7 @@ from onyx.server.features.build.scheduled_tasks.schedule import (
     human_readable,
     next_n_fires,
 )
+from onyx.server.features.build.timeouts import QUEUE_RESIDENCY_SECONDS
 from onyx.utils.datetime import datetime_to_utc
 from onyx.utils.logger import setup_logger
 from shared_configs.contextvars import get_current_tenant_id
@@ -63,11 +64,6 @@ logger = setup_logger()
 # Constants
 # ---------------------------------------------------------------------------
 
-# Number of seconds before a queued executor task is dropped. Mirrors
-# ``check-for-pruning`` and ``check-for-indexing`` — 15 minutes is plenty for
-# the worker to pick up the task; anything still queued past that is dead.
-EXECUTOR_TASK_EXPIRES_SECONDS = 900
-
 # Number of future fires returned by the detail endpoint for UI preview.
 NEXT_RUNS_PREVIEW_COUNT = 3
 
@@ -343,7 +339,7 @@ def _enqueue_executor(run_id: UUID) -> None:
         kwargs={"run_id": str(run_id), "tenant_id": tenant_id},
         queue=OnyxCeleryQueues.SCHEDULED_TASKS,
         priority=OnyxCeleryPriority.MEDIUM,
-        expires=EXECUTOR_TASK_EXPIRES_SECONDS,
+        expires=QUEUE_RESIDENCY_SECONDS,
     )
 
 
diff --git a/backend/onyx/server/features/build/scheduled_tasks/executor.py b/backend/onyx/server/features/build/scheduled_tasks/executor.py
index 0134cdf445..70cebdb62a 100644
--- a/backend/onyx/server/features/build/scheduled_tasks/executor.py
+++ b/backend/onyx/server/features/build/scheduled_tasks/executor.py
@@ -60,17 +60,12 @@ from onyx.server.features.build.sandbox.event_schema import (
 from onyx.server.features.build.session.locks import session_creation_lock
 from onyx.server.features.build.session.manager import SessionManager
 from onyx.server.features.build.session.streaming import BuildStreamingState
+from onyx.server.features.build.timeouts import TURN_BUDGET_SECONDS
 from onyx.utils.logger import setup_logger
 
 logger = setup_logger()
 
 
-# Per-run wall-clock budget (monotonic). Tasks that blow past this are
-# marked ``failed (error_class=timeout)``. The stuck-run sweeper uses a
-# slightly larger threshold (45 min) so a hung run that fails to honor the
-# budget still gets cleaned up out-of-band.
-DEFAULT_EXECUTOR_BUDGET_SECONDS = 30 * 60
-
 # Summary length on the run row (per spec: ~120 chars of final agent
 # message).
 SUMMARY_MAX_CHARS = 120
@@ -167,7 +162,7 @@ def _notify(
 def run_scheduled_task_logic(
     run_id: UUID,
     *,
-    budget_seconds: int = DEFAULT_EXECUTOR_BUDGET_SECONDS,
+    budget_seconds: int = TURN_BUDGET_SECONDS,
 ) -> None:
     """Execute a single scheduled-task run end-to-end.
 
@@ -632,10 +627,3 @@ def _drive_agent(
             # approval gate, budget exceeded, exception). Matches the
             # interactive path's finally in _stream_cli_agent_response.
             prompt_slot_cm.__exit__(None, None, None)
-
-
-# Re-export for the Celery task wrapper.
-__all__ = [
-    "DEFAULT_EXECUTOR_BUDGET_SECONDS",
-    "run_scheduled_task_logic",
-]
diff --git a/backend/onyx/server/features/build/session/api.py b/backend/onyx/server/features/build/session/api.py
index 4e9e3fe486..3f2d24f306 100644
--- a/backend/onyx/server/features/build/session/api.py
+++ b/backend/onyx/server/features/build/session/api.py
@@ -25,6 +25,7 @@ from onyx.db.scheduled_task import get_scheduled_run_context
 from onyx.error_handling.error_codes import OnyxErrorCode
 from onyx.error_handling.exceptions import OnyxError
 from onyx.redis.redis_pool import get_redis_client
+from onyx.server.features.build.configs import SSE_KEEPALIVE_INTERVAL
 from onyx.server.features.build.db.build_session import (
     allocate_nextjs_port,
     get_build_session,
@@ -75,6 +76,7 @@ from onyx.server.features.build.session.sandbox_lifecycle import (
     rollback_failed_provisioning,
 )
 from onyx.server.features.build.session.streaming import SSE_KEEPALIVE
+from onyx.server.features.build.timeouts import POLL_INTERVAL_SECONDS
 from onyx.server.features.build.utils import sanitize_filename, validate_file
 from onyx.skills.push import build_user_skills_payload
 from onyx.utils.logger import setup_logger
@@ -1026,10 +1028,6 @@ def get_session_scheduled_run_context(
     )
 
 
-LIVE_STREAM_READY_POLL_SECONDS = 1.0
-LIVE_STREAM_KEEPALIVE_SECONDS = 15.0
-
-
 def _scheduled_run_is_running(
     *,
     db_session: Session,
@@ -1094,7 +1092,7 @@ def get_session_scheduled_run_events(
                     break
 
             yield SSE_KEEPALIVE
-            time.sleep(LIVE_STREAM_READY_POLL_SECONDS)
+            time.sleep(POLL_INTERVAL_SECONDS)
 
         try:
             with get_session_with_current_tenant() as stream_db_session:
@@ -1102,7 +1100,7 @@ def get_session_scheduled_run_events(
                 for chunk in session_manager.subscribe_to_existing_session_events(
                     session_id,
                     user_id,
-                    keepalive_seconds=LIVE_STREAM_KEEPALIVE_SECONDS,
+                    keepalive_seconds=SSE_KEEPALIVE_INTERVAL,
                 ):
                     yield chunk
                     stream_db_session.expire_all()
diff --git a/backend/onyx/server/features/build/session/manager.py b/backend/onyx/server/features/build/session/manager.py
index 0fabcd9bc2..d710345ea2 100644
--- a/backend/onyx/server/features/build/session/manager.py
+++ b/backend/onyx/server/features/build/session/manager.py
@@ -36,7 +36,6 @@ from onyx.server.features.build.configs import (
     MAX_TOTAL_UPLOAD_SIZE_BYTES,
     MAX_UPLOAD_FILES_PER_SESSION,
     OPENCODE_DISABLED_TOOLS,
-    PROMPT_SLOT_KEEP_ALIVE_MAX_SECONDS,
 )
 from onyx.server.features.build.db.build_session import (
     allocate_nextjs_port,
@@ -62,10 +61,7 @@ from onyx.server.features.build.sandbox.models import (
     FilesystemEntry,
     PromptAttachment,
 )
-from onyx.server.features.build.sandbox.serve_transport import (
-    PROMPT_SLOT_FAST_FAIL_ACQUIRE_SECONDS,
-    PromptSlot,
-)
+from onyx.server.features.build.sandbox.serve_transport import PromptSlot
 from onyx.server.features.build.sandbox.snapshot_manager import SnapshotManager
 from onyx.server.features.build.sandbox.util.agent_instructions import (
     build_connectable_apps_list,
@@ -95,6 +91,10 @@ from onyx.server.features.build.session.sandbox_lifecycle import (
     hydrate_managed_content,
 )
 from onyx.server.features.build.session.streaming import BuildStreamingState
+from onyx.server.features.build.timeouts import (
+    PROMPT_SLOT_FAST_FAIL_ACQUIRE_SECONDS,
+    PROMPT_SLOT_KEEP_ALIVE_MAX_SECONDS,
+)
 from onyx.skills.push import build_user_skills_payload
 from onyx.utils.logger import setup_logger
 from onyx.utils.threadpool_concurrency import start_thread_with_context
@@ -103,6 +103,9 @@ from shared_configs.contextvars import get_current_tenant_id
 
 logger = setup_logger()
 
+# Webapp-ready probe on the UI-poll hot path; any response (even 404) counts.
+_WEBAPP_PROBE_TIMEOUT_SECONDS = 2.0
+
 _DISPOSE_PENDING_TTL_SECONDS = 24 * 3600
 
 
@@ -1431,7 +1434,7 @@ class SessionManager:
                 f"{internal_url}/api/build/sessions/{session_id}/webapp"
                 "/_next/static/onyx-ready-probe.js"
             )
-            with httpx.Client(timeout=2.0) as client:
+            with httpx.Client(timeout=_WEBAPP_PROBE_TIMEOUT_SECONDS) as client:
                 client.get(probe_url)
             return True
         except Exception:
diff --git a/backend/onyx/server/features/build/session/streaming.py b/backend/onyx/server/features/build/session/streaming.py
index ce952945da..0fee6fddcd 100644
--- a/backend/onyx/server/features/build/session/streaming.py
+++ b/backend/onyx/server/features/build/session/streaming.py
@@ -32,7 +32,6 @@ from onyx.db.models import BuildSession
 from onyx.sandbox_proxy import approval_cache
 from onyx.server.features.build import connect_app
 from onyx.server.features.build.configs import (
-    PROMPT_SLOT_KEEP_ALIVE_MAX_SECONDS,
     SANDBOX_HEARTBEAT_REFRESH_INTERVAL_SECONDS,
 )
 from onyx.server.features.build.db.build_session import (
@@ -69,6 +68,7 @@ from onyx.server.features.build.sandbox.models import PromptAttachment
 from onyx.server.features.build.sandbox.opencode.serve_client import _merge_field_meta
 from onyx.server.features.build.sandbox.serve_transport import PromptSlot
 from onyx.server.features.build.sandbox.sse import SSEKeepalive
+from onyx.server.features.build.timeouts import PROMPT_SLOT_KEEP_ALIVE_MAX_SECONDS
 from onyx.utils.logger import setup_logger
 from onyx.utils.threadpool_concurrency import start_thread_with_context
 from shared_configs.contextvars import CURRENT_TENANT_ID_CONTEXTVAR
diff --git a/backend/onyx/server/features/build/timeouts.py b/backend/onyx/server/features/build/timeouts.py
new file mode 100644
index 0000000000..da61579634
--- /dev/null
+++ b/backend/onyx/server/features/build/timeouts.py
@@ -0,0 +1,121 @@
+"""Craft timeout registry.
+
+Every Craft time constant is one of four things:
+
+1. a **root** — a policy number a human chooses,
+2. a **derivation** — arithmetic over a root, encoded here so tuning the root
+   moves every dependent value with it,
+3. the **fixed kit** — genuinely independent short timeouts in a small
+   taxonomy (connect / RPC / bulk transfer / mutex lease), or
+4. a **cadence** — poll and retry intervals.
+
+Residence rule: a constant lives here only if it is used by multiple files,
+is a derivation (or feeds one), or belongs to the shared client-I/O taxonomy.
+A single-file, free-standing constant is defined at its point of use.
+Env-tunable values (anything with its own ``os.environ`` read) live in
+``configs.py`` even when their default is derived (e.g.
+``OPENCODE_PROMPT_INACTIVITY_TIMEOUT_SECONDS``); pure non-tunable derivations
+over those roots live here (e.g. ``RUNNER_STALE_AFTER_SECONDS``).
+
+Ordering invariants (asserted by
+``tests/unit/onyx/server/features/craft/test_timeout_registry.py``):
+
+    cadences < probes/connect < mutex leases
+      < QUEUE_RESIDENCY < TURN_BUDGET < ACTIVE_TURN_TTL < REQUEST_ID_TTL
+    RUNNER_STALE_AFTER == 6 x SSE_KEEPALIVE_INTERVAL
+    OPENCODE_PROMPT_INACTIVITY > SANDBOX_APPROVAL_WAIT (configs.py)
+    SANDBOX_HEARTBEAT_REFRESH << SANDBOX_IDLE_TIMEOUT (configs.py)
+
+The client-I/O taxonomy (connect / RPC / bulk) is orthogonal to the ordering
+chain — a bulk transfer legitimately outlasts most other bounds.
+"""
+
+from onyx.server.features.build.configs import (
+    PROMPT_SLOT_LEASE_SECONDS,
+    SSE_KEEPALIVE_INTERVAL,
+)
+
+# =============================================================================
+# Turn family (root: TURN_BUDGET_SECONDS)
+# =============================================================================
+
+# Wall-clock budget of one agent turn, interactive or scheduled.
+TURN_BUDGET_SECONDS = 30 * 60
+
+# Margin past the budget before out-of-band cleanup (stuck-run sweeper, turn
+# TTL expiry) treats a run/turn as abandoned: a well-behaved turn that hits
+# its own budget must always finalize itself first.
+TURN_RECLAIM_SLACK_SECONDS = 15 * 60
+
+# Redis TTL of the turn record + active-turn pointer. Refreshed on every
+# heartbeat; the absolute floor is the budget plus slack so a live
+# budget-compliant turn's admission block never evaporates under it.
+ACTIVE_TURN_TTL_SECONDS = TURN_BUDGET_SECONDS + TURN_RECLAIM_SLACK_SECONDS
+
+# Post-terminal retention of the turn record and the client_request_id →
+# turn_id dedupe key: an idempotent send-message retry (or the attach stream
+# reading a FAILED turn's error) must still resolve after the turn finishes.
+TURN_RETENTION_SECONDS = 15 * 60
+REQUEST_ID_TTL_SECONDS = ACTIVE_TURN_TTL_SECONDS + TURN_RETENTION_SECONDS
+
+# Ceiling for background prompt-slot renewal by holders whose progress is
+# client-paced or opaque (session delete, subagent turns). It IS the turn
+# budget: a slot held longer than any turn may run is leaked.
+PROMPT_SLOT_KEEP_ALIVE_MAX_SECONDS = TURN_BUDGET_SECONDS
+
+# =============================================================================
+# Liveness cadence family (root: SSE_KEEPALIVE_INTERVAL, configs.py)
+# =============================================================================
+
+# A turn runner heartbeats on every consumed event, and the transport emits a
+# keepalive at least every SSE_KEEPALIVE_INTERVAL even while the agent is
+# silent — so the runner is dead after k missed keepalives, not after any
+# turn-length-derived time. Derived so env-tuning the keepalive moves this
+# with it; a fixed value would silently break turn recovery.
+RUNNER_STALE_AFTER_SECONDS = 6 * SSE_KEEPALIVE_INTERVAL
+
+# =============================================================================
+# Queue residency family (root: QUEUE_RESIDENCY_SECONDS)
+# =============================================================================
+
+# One policy, three enforcement points: how long a queued scheduled run may
+# sit before (a) Celery expires the message unexecuted and (b) the stuck-run
+# sweeper reclaims its QUEUED row. They must move together or
+# expired-but-unswept / swept-but-unexpired windows appear.
+QUEUE_RESIDENCY_SECONDS = 15 * 60
+
+# =============================================================================
+# Fixed kit — client I/O taxonomy
+# =============================================================================
+
+# Establishing a connection to an in-cluster peer; also full-request probes
+# on hot paths, where any response counts.
+CONNECT_TIMEOUT_SECONDS = 5.0
+
+# Unary request/response calls with small payloads (sidecar directory
+# listings, managed-content pushes — the latter retried on failure).
+RPC_TIMEOUT_SECONDS = 30.0
+
+# Archive upload/download (session snapshots, opencode history). Sized to
+# "snapshotting can take minutes"; the reaper is fail-closed on snapshot
+# failure, so shrinking this converts slow-but-working snapshots into
+# never-sleeping sandboxes.
+BULK_TRANSFER_TIMEOUT_SECONDS = 300.0
+
+# =============================================================================
+# Fixed kit — mutexes (critical-section leases, never budget-derived)
+# =============================================================================
+
+# Prompt-slot acquire policy: a second turn racing a live one bounces fast
+# ("concurrent turn in flight") instead of queueing; a reclaimed turn must
+# instead wait out a dead holder's full lease before taking the slot.
+PROMPT_SLOT_FAST_FAIL_ACQUIRE_SECONDS = 10.0
+PROMPT_SLOT_WAIT_OUT_ORPHAN_SECONDS = PROMPT_SLOT_LEASE_SECONDS + 10.0
+
+# =============================================================================
+# Cadences
+# =============================================================================
+
+# Shared interval for poll-a-fast-local-resource loops (live-stream readiness;
+# provisioning wait loops adopt it as they move onto the registry).
+POLL_INTERVAL_SECONDS = 0.5
diff --git a/backend/tests/unit/onyx/server/features/craft/interactive_turns/test_executor.py b/backend/tests/unit/onyx/server/features/craft/interactive_turns/test_executor.py
index f03e3d82d5..9028650ea4 100644
--- a/backend/tests/unit/onyx/server/features/craft/interactive_turns/test_executor.py
+++ b/backend/tests/unit/onyx/server/features/craft/interactive_turns/test_executor.py
@@ -26,7 +26,7 @@ from onyx.server.features.build.sandbox.event_schema import (
     PromptResponse,
 )
 from onyx.server.features.build.sandbox.event_schema import Error as SandboxError
-from onyx.server.features.build.sandbox.serve_transport import (
+from onyx.server.features.build.timeouts import (
     PROMPT_SLOT_FAST_FAIL_ACQUIRE_SECONDS,
     PROMPT_SLOT_WAIT_OUT_ORPHAN_SECONDS,
 )
diff --git a/backend/tests/unit/onyx/server/features/craft/interactive_turns/test_state.py b/backend/tests/unit/onyx/server/features/craft/interactive_turns/test_state.py
index 4bf26e7285..9d9f5299f0 100644
--- a/backend/tests/unit/onyx/server/features/craft/interactive_turns/test_state.py
+++ b/backend/tests/unit/onyx/server/features/craft/interactive_turns/test_state.py
@@ -4,7 +4,6 @@ from collections.abc import Callable
 from uuid import UUID, uuid4
 
 from onyx.server.features.build.interactive_turns.state import (
-    REQUEST_ID_TTL_SECONDS,
     TURN_STATUS_FAILED,
     TURN_STATUS_QUEUED,
     TURN_STATUS_RUNNING,
@@ -19,6 +18,7 @@ from onyx.server.features.build.interactive_turns.state import (
     touch_turn,
 )
 from onyx.server.features.build.sandbox.models import PromptAttachment
+from onyx.server.features.build.timeouts import REQUEST_ID_TTL_SECONDS
 from tests.unit.fakes import FakeCache
 
 
diff --git a/backend/tests/unit/onyx/server/features/craft/interactive_turns/test_turns_api.py b/backend/tests/unit/onyx/server/features/craft/interactive_turns/test_turns_api.py
index fbb2b98988..545a90e88b 100644
--- a/backend/tests/unit/onyx/server/features/craft/interactive_turns/test_turns_api.py
+++ b/backend/tests/unit/onyx/server/features/craft/interactive_turns/test_turns_api.py
@@ -122,7 +122,7 @@ def test_get_interactive_turn_events_waits_then_forwards_live_stream(
         ) -> Iterator[str]:
             assert session_id_arg == session_id
             assert user_id_arg == user_id
-            assert keepalive_seconds == turns_api.LIVE_STREAM_KEEPALIVE_SECONDS
+            assert keepalive_seconds == turns_api.SSE_KEEPALIVE_INTERVAL
             finish_turn(
                 cache=cache,
                 turn_id=turn_id,
@@ -286,7 +286,7 @@ def test_get_interactive_turn_events_yields_failed_turn_error_after_stream_chunk
         ) -> Iterator[str]:
             assert session_id_arg == session_id
             assert user_id_arg == user_id
-            assert keepalive_seconds == turns_api.LIVE_STREAM_KEEPALIVE_SECONDS
+            assert keepalive_seconds == turns_api.SSE_KEEPALIVE_INTERVAL
             finish_turn(
                 cache=cache,
                 turn_id=turn_id,
@@ -354,7 +354,7 @@ def test_get_interactive_turn_events_retries_runner_start_mid_stream(
         ) -> Iterator[str]:
             assert session_id_arg == session_id
             assert user_id_arg == user_id
-            assert keepalive_seconds == turns_api.LIVE_STREAM_KEEPALIVE_SECONDS
+            assert keepalive_seconds == turns_api.SSE_KEEPALIVE_INTERVAL
             for i in range(3):
                 yield (
                     "event: message\n"
@@ -429,7 +429,7 @@ def test_get_interactive_turn_events_rate_limits_runner_retry_within_window(
         ) -> Iterator[str]:
             assert session_id_arg == session_id
             assert user_id_arg == user_id
-            assert keepalive_seconds == turns_api.LIVE_STREAM_KEEPALIVE_SECONDS
+            assert keepalive_seconds == turns_api.SSE_KEEPALIVE_INTERVAL
             for i in range(3):
                 yield (
                     "event: message\n"
diff --git a/backend/tests/unit/onyx/server/features/craft/sandbox/test_send_message_timeout_plumbing.py b/backend/tests/unit/onyx/server/features/craft/sandbox/test_send_message_timeout_plumbing.py
index 26e3c645f9..0a0e5be2e4 100644
--- a/backend/tests/unit/onyx/server/features/craft/sandbox/test_send_message_timeout_plumbing.py
+++ b/backend/tests/unit/onyx/server/features/craft/sandbox/test_send_message_timeout_plumbing.py
@@ -8,13 +8,13 @@ from uuid import uuid4
 
 from onyx.server.features.build.configs import (
     OPENCODE_PROMPT_INACTIVITY_TIMEOUT_SECONDS,
-    PROMPT_SLOT_KEEP_ALIVE_MAX_SECONDS,
 )
 from onyx.server.features.build.sandbox.event_schema import PromptResponse
 from onyx.server.features.build.sandbox.kubernetes.kubernetes_sandbox_manager import (
     KubernetesSandboxManager,
 )
 from onyx.server.features.build.sandbox.models import PromptAttachment
+from onyx.server.features.build.timeouts import PROMPT_SLOT_KEEP_ALIVE_MAX_SECONDS
 
 
 class _FakeServeClient:
diff --git a/backend/tests/unit/onyx/server/features/craft/test_timeout_registry.py b/backend/tests/unit/onyx/server/features/craft/test_timeout_registry.py
new file mode 100644
index 0000000000..9472511630
--- /dev/null
+++ b/backend/tests/unit/onyx/server/features/craft/test_timeout_registry.py
@@ -0,0 +1,95 @@
+"""Pins the Craft timeout registry: root values, derivations, and the
+ordering invariants documented in ``onyx/server/features/build/timeouts.py``.
+
+Value pins are the spec (hardcoded, not re-derived); relationship asserts are
+the invariants that must survive any retuning of a root. Constants defined at
+their point of use (single-file, free-standing) are imported from there.
+"""
+
+from onyx.server.features.build.configs import (
+    OPENCODE_PROMPT_INACTIVITY_TIMEOUT_SECONDS,
+    PROMPT_SLOT_LEASE_SECONDS,
+    SANDBOX_APPROVAL_WAIT_TIMEOUT_SECONDS,
+    SANDBOX_HEARTBEAT_REFRESH_INTERVAL_SECONDS,
+    SANDBOX_IDLE_TIMEOUT_SECONDS,
+    SSE_KEEPALIVE_INTERVAL,
+)
+from onyx.server.features.build.interactive_turns.api import (
+    LIVE_STREAM_RUNNER_RETRY_SECONDS,
+)
+from onyx.server.features.build.interactive_turns.state import (
+    TURN_LOCK_LEASE_SECONDS,
+    TURN_LOCK_WAIT_SECONDS,
+)
+from onyx.server.features.build.timeouts import (
+    ACTIVE_TURN_TTL_SECONDS,
+    BULK_TRANSFER_TIMEOUT_SECONDS,
+    CONNECT_TIMEOUT_SECONDS,
+    POLL_INTERVAL_SECONDS,
+    PROMPT_SLOT_FAST_FAIL_ACQUIRE_SECONDS,
+    PROMPT_SLOT_KEEP_ALIVE_MAX_SECONDS,
+    PROMPT_SLOT_WAIT_OUT_ORPHAN_SECONDS,
+    QUEUE_RESIDENCY_SECONDS,
+    REQUEST_ID_TTL_SECONDS,
+    RPC_TIMEOUT_SECONDS,
+    RUNNER_STALE_AFTER_SECONDS,
+    TURN_BUDGET_SECONDS,
+)
+
+
+def test_root_values_pin_the_spec() -> None:
+    assert TURN_BUDGET_SECONDS == 30 * 60
+    assert QUEUE_RESIDENCY_SECONDS == 15 * 60
+
+
+def test_turn_derivations() -> None:
+    assert ACTIVE_TURN_TTL_SECONDS == 45 * 60
+    assert REQUEST_ID_TTL_SECONDS == 60 * 60
+    assert REQUEST_ID_TTL_SECONDS > ACTIVE_TURN_TTL_SECONDS
+    # The identity is the spec: a slot held past any possible turn is leaked.
+    assert PROMPT_SLOT_KEEP_ALIVE_MAX_SECONDS == TURN_BUDGET_SECONDS
+
+
+def test_keepalive_derivations() -> None:
+    # The coupling IS the spec: env-tuning the keepalive must move runner
+    # staleness with it — a fixed stale threshold under a raised keepalive
+    # steals turns from healthy silent tool calls. The literal pins the
+    # multiplier and the default keepalive together.
+    assert RUNNER_STALE_AFTER_SECONDS == 6 * SSE_KEEPALIVE_INTERVAL
+    assert RUNNER_STALE_AFTER_SECONDS == 90.0
+    assert LIVE_STREAM_RUNNER_RETRY_SECONDS < RUNNER_STALE_AFTER_SECONDS
+
+
+def test_approval_inactivity_coupling() -> None:
+    # A tool call parked at the approval proxy holds the event stream silent
+    # for the full approval window; the inactivity backstop must outlast it.
+    assert (
+        OPENCODE_PROMPT_INACTIVITY_TIMEOUT_SECONDS
+        > SANDBOX_APPROVAL_WAIT_TIMEOUT_SECONDS
+    )
+
+
+def test_lock_invariants() -> None:
+    assert PROMPT_SLOT_WAIT_OUT_ORPHAN_SECONDS > PROMPT_SLOT_LEASE_SECONDS
+    assert PROMPT_SLOT_FAST_FAIL_ACQUIRE_SECONDS < PROMPT_SLOT_LEASE_SECONDS
+    assert TURN_LOCK_WAIT_SECONDS < TURN_LOCK_LEASE_SECONDS
+
+
+def test_ordering_chain() -> None:
+    mutex_leases = (TURN_LOCK_LEASE_SECONDS, PROMPT_SLOT_LEASE_SECONDS)
+
+    assert POLL_INTERVAL_SECONDS < CONNECT_TIMEOUT_SECONDS
+    assert CONNECT_TIMEOUT_SECONDS < min(mutex_leases)
+    assert max(mutex_leases) < QUEUE_RESIDENCY_SECONDS
+    assert QUEUE_RESIDENCY_SECONDS < TURN_BUDGET_SECONDS
+    assert TURN_BUDGET_SECONDS < ACTIVE_TURN_TTL_SECONDS
+    assert ACTIVE_TURN_TTL_SECONDS < REQUEST_ID_TTL_SECONDS
+    assert RPC_TIMEOUT_SECONDS < BULK_TRANSFER_TIMEOUT_SECONDS
+
+
+def test_idle_family_invariants() -> None:
+    # Heartbeat refresh must be far under the idle timeout or live sandboxes
+    # read as idle between refreshes.
+    assert (
+        SANDBOX_HEARTBEAT_REFRESH_INTERVAL_SECONDS * 10 <= SANDBOX_IDLE_TIMEOUT_SECONDS
+    )