diff --git a/docs/api/openapi.yaml b/docs/api/openapi.yaml
index fcadfa331..d52c8ad1c 100644
--- a/docs/api/openapi.yaml
+++ b/docs/api/openapi.yaml
@@ -20721,9 +20721,11 @@ components:
                 minLength: 1
                 maxLength: 80
               severity:
-                type: integer
-                minimum: 1
-                maximum: 4
+                anyOf:
+                  - type: integer
+                    minimum: 1
+                    maximum: 4
+                  - type: "null"
             required:
               - key
         note:
@@ -20859,9 +20861,11 @@ components:
                 minLength: 1
                 maxLength: 80
               severity:
-                type: integer
-                minimum: 1
-                maximum: 4
+                anyOf:
+                  - type: integer
+                    minimum: 1
+                    maximum: 4
+                  - type: "null"
             required:
               - key
         note:
@@ -20975,9 +20979,11 @@ components:
                       minLength: 1
                       maxLength: 80
                     severity:
-                      type: integer
-                      minimum: 1
-                      maximum: 4
+                      anyOf:
+                        - type: integer
+                          minimum: 1
+                          maximum: 4
+                        - type: "null"
                   required:
                     - key
               note:
diff --git a/src/lib/validations/__tests__/cycle-day-log-symptoms.test.ts b/src/lib/validations/__tests__/cycle-day-log-symptoms.test.ts
new file mode 100644
index 000000000..021c808db
--- /dev/null
+++ b/src/lib/validations/__tests__/cycle-day-log-symptoms.test.ts
@@ -0,0 +1,65 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  cycleDayLogInputSchema,
+  cycleDayLogPatchSchema,
+} from "@/lib/validations/cycle";
+
+/**
+ * A symptom picked without an intensity is the ordinary way to log one.
+ *
+ * The sheet holds the picker as key to intensity and sends `severity: null`
+ * for every symptom the user did not rate, which is most of them. The schema
+ * took a number or nothing at all, so those entries came back 422 and the
+ * sheet showed "Could not save. Try again." with no way to tell why. The link
+ * row has always stored an unrated symptom as a plain presence; only the
+ * gate at the door disagreed, and nothing tested it.
+ */
+const BASE_INPUT = {
+  date: "2026-09-17",
+  loggedAt: new Date().toISOString(),
+} as const;
+
+describe("cycle day-log symptoms accept an unrated selection", () => {
+  for (const [name, schema] of [
+    ["create", cycleDayLogInputSchema],
+    ["patch", cycleDayLogPatchSchema],
+  ] as const) {
+    it(`${name}: takes a symptom with no intensity at all`, () => {
+      const parsed = schema.safeParse({
+        ...BASE_INPUT,
+        symptoms: [{ key: "cramps" }],
+      });
+      expect(parsed.success, JSON.stringify(parsed.error?.issues)).toBe(true);
+    });
+
+    it(`${name}: takes an explicit null intensity, which is what the sheet sends`, () => {
+      const parsed = schema.safeParse({
+        ...BASE_INPUT,
+        symptoms: [
+          { key: "cramps", severity: null },
+          { key: "back_pain", severity: null },
+        ],
+      });
+      expect(parsed.success, JSON.stringify(parsed.error?.issues)).toBe(true);
+    });
+
+    it(`${name}: still takes a rated symptom`, () => {
+      const parsed = schema.safeParse({
+        ...BASE_INPUT,
+        symptoms: [{ key: "cramps", severity: 3 }],
+      });
+      expect(parsed.success).toBe(true);
+    });
+
+    it(`${name}: still refuses an intensity outside 1 to 4`, () => {
+      for (const severity of [0, 5, 2.5]) {
+        const parsed = schema.safeParse({
+          ...BASE_INPUT,
+          symptoms: [{ key: "cramps", severity }],
+        });
+        expect(parsed.success, `severity ${severity}`).toBe(false);
+      }
+    });
+  }
+});
diff --git a/src/lib/validations/cycle.ts b/src/lib/validations/cycle.ts
index dad5f0ce3..86fbd8cab 100644
--- a/src/lib/validations/cycle.ts
+++ b/src/lib/validations/cycle.ts
@@ -131,7 +131,12 @@ export const cycleDayLogInputSchema = z.object({
     .array(
       z.object({
         key: z.string().min(1).max(80),
-        severity: z.number().int().min(1).max(4).optional(),
+        // NULL is the ordinary case, not an edge: picking a symptom without
+        // tapping an intensity is how most entries are logged, and the link
+        // row stores that as a plain presence. Rejecting it refused every
+        // unrated symptom with a 422 the sheet could only show as
+        // "Could not save".
+        severity: z.number().int().min(1).max(4).nullable().optional(),
       }),
     )
     .max(40)
@@ -181,7 +186,12 @@ export const cycleDayLogPatchSchema = z.object({
     .array(
       z.object({
         key: z.string().min(1).max(80),
-        severity: z.number().int().min(1).max(4).optional(),
+        // NULL is the ordinary case, not an edge: picking a symptom without
+        // tapping an intensity is how most entries are logged, and the link
+        // row stores that as a plain presence. Rejecting it refused every
+        // unrated symptom with a 422 the sheet could only show as
+        // "Could not save".
+        severity: z.number().int().min(1).max(4).nullable().optional(),
       }),
     )
     .max(40)