diff --git a/docs/Tuning-Guide.md b/docs/Tuning-Guide.md
index 38c4532..37165d8 100644
--- a/docs/Tuning-Guide.md
+++ b/docs/Tuning-Guide.md
@@ -645,7 +645,7 @@ How long a new head's review waits while its checks are pending. A review
 judges the CI result (R1), and waiting keeps it off a GPU that CI is using
 (the `nisse` project's end-to-end tests). Finished checks, passed or failed,
 end the wait; after this long it reviews anyway and the CI result reads as
-pending.
+pending. 0 never waits.
 
 - **Too low:** reviews run beside CI, slower on a shared GPU, without its result.
 - **Too high:** a stuck runner delays reviews that long.
@@ -656,7 +656,8 @@ pending.
 
 How long a new head with no checks at all waits for some to appear: Gitea
 Actions reports a push's checks a moment after it. Past this, a repository
-without CI is reviewed at once.
+without CI is reviewed at once. 0 reviews such a head at once (the live
+review test, whose fresh repository has no CI).
 
 - **Too low:** a review starts before CI has reported, and runs beside it.
 - **Too high:** repositories without CI wait that long for every review.
diff --git a/nisse-core/src/nisse_core/config.py b/nisse-core/src/nisse_core/config.py
index aaa59eb..d17d93f 100644
--- a/nisse-core/src/nisse_core/config.py
+++ b/nisse-core/src/nisse_core/config.py
@@ -81,13 +81,14 @@ def read_file(path: Path, errors: list[str]) -> dict[str, Any]:
     return loaded
 
 
-def positive(value: Any, kind: type) -> int | float | None:
+def positive(value: Any, kind: type, *, zero: bool = False) -> int | float | None:
+    """``value`` as ``kind`` if above 0 (or 0 itself, given ``zero``)."""
     # bool is an int in Python; `true` for a turn limit is a mistake.
     if isinstance(value, bool) or not isinstance(value, int | float):
         return None
     if kind is int and not float(value).is_integer():
         return None
-    if value <= 0:
+    if value < 0 or (value == 0 and not zero):
         return None
     return kind(value)
 
@@ -132,9 +133,13 @@ def parse_tuning(
             if spec is None:
                 errors.append(f"tuning.{name}.{key}: unknown setting")
                 continue
-            number = positive(value, float if spec.type in (float, "float") else int)
+            # A field with metadata {"zero": True} may also be 0 ("don't wait").
+            zero = bool(spec.metadata.get("zero"))
+            kind = float if spec.type in (float, "float") else int
+            number = positive(value, kind, zero=zero)
             if number is None:
-                errors.append(f"tuning.{name}.{key}: must be a positive number")
+                need = "zero or more" if zero else "a positive number"
+                errors.append(f"tuning.{name}.{key}: must be {need}")
                 continue
             values[key] = number
         sections[name] = cls(**values)
diff --git a/nisse-core/tests/test_shared_config.py b/nisse-core/tests/test_shared_config.py
index 4ad585e..234904d 100644
--- a/nisse-core/tests/test_shared_config.py
+++ b/nisse-core/tests/test_shared_config.py
@@ -19,6 +19,7 @@ from nisse_core.config import (
 class Review:
     max_rounds: int = 3
     wait_s: float = 60.0
+    grace_s: float = field(default=5.0, metadata={"zero": True})
 
 
 @dataclass(frozen=True)
@@ -45,6 +46,17 @@ def test_an_agents_own_tuning_sections() -> None:
     ]
 
 
+def test_a_field_may_opt_in_to_zero() -> None:
+    errors: list[str] = []
+    tuning = parse_tuning({"review": {"grace_s": 0}}, Tuning, errors)
+    assert tuning.review.grace_s == 0 and errors == []
+    parse_tuning({"review": {"grace_s": -1, "wait_s": 0}}, Tuning, errors)
+    assert errors == [
+        "tuning.review.grace_s: must be zero or more",
+        "tuning.review.wait_s: must be a positive number",
+    ]
+
+
 def test_references_and_people() -> None:
     errors: list[str] = []
     env = {"TOKEN": "s3cret"}
diff --git a/nisse-review/src/nisse_review/config.py b/nisse-review/src/nisse_review/config.py
index e69bd5f..0bb0f46 100644
--- a/nisse-review/src/nisse_review/config.py
+++ b/nisse-review/src/nisse_review/config.py
@@ -56,9 +56,9 @@ class ReviewTuning:
     diff_chars: int = 60000  # the diff in the review's context; files on demand
     attempts: int = 2  # failed runs on one PR before saying so on it
     # A new head waits for its CI to finish: at most ci_wait_s while checks
-    # are pending, and ci_grace_s for checks to appear at all.
-    ci_wait_s: float = 3600.0
-    ci_grace_s: float = 120.0
+    # are pending, and ci_grace_s for checks to appear at all. 0: don't wait.
+    ci_wait_s: float = field(default=3600.0, metadata={"zero": True})
+    ci_grace_s: float = field(default=120.0, metadata={"zero": True})
 
 
 @dataclass(frozen=True)
diff --git a/nisse-review/tests/test_review.py b/nisse-review/tests/test_review.py
index 8785ff4..ed6f91a 100644
--- a/nisse-review/tests/test_review.py
+++ b/nisse-review/tests/test_review.py
@@ -431,6 +431,21 @@ def test_a_repository_pattern_must_be_owner_slash_name(tmp_path: Path) -> None:
             ReviewConfig.from_tree({**tree, "repositories": [bad]}, {})
 
 
+def test_the_ci_waits_may_be_zero(tmp_path: Path) -> None:
+    # The live test's repository has no CI: it reviews with no grace at all.
+    from nisse_review.config import ReviewConfig
+
+    tree = {
+        "state_db": str(tmp_path / "s.db"),
+        "llm": {"base_url": "http://llm", "token": "k"},
+        "roles": {"reviewer": "local", "expert": "frontier"},
+        "gitea": {"url": "https://g", "token": "t", "operators": ["don"]},
+        "tuning": {"review": {"ci_wait_s": 0, "ci_grace_s": 0}},
+    }
+    review = ReviewConfig.from_tree(tree, {}).tuning.review
+    assert (review.ci_wait_s, review.ci_grace_s) == (0, 0)
+
+
 def test_diff_lines_are_the_heads_lines_a_diff_shows() -> None:
     diff = (
         "--- a/x.py\n+++ b/x.py\n@@ -1,3 +1,4 @@\n a\n-b\n+c\n+d\n e\n"