From f2fd0b9923c38842490f47f0d699599ec41d380a Mon Sep 17 00:00:00 2001
From: Alexander Kireev <ak.chatman.media@gmail.com>
Date: Thu, 11 Jun 2026 04:44:43 +0700
Subject: [PATCH] fix: Duration.decode and Duration.times throwing on
 fractional values

---
 .changeset/duration-fractional-nanos-micros.md |  9 +++++++++
 packages/effect/src/Duration.ts                | 10 +++++++---
 packages/effect/test/Duration.test.ts          |  7 +++++++
 3 files changed, 23 insertions(+), 3 deletions(-)
 create mode 100644 .changeset/duration-fractional-nanos-micros.md

diff --git a/.changeset/duration-fractional-nanos-micros.md b/.changeset/duration-fractional-nanos-micros.md
new file mode 100644
index 00000000000..15be7a7fb2f
--- /dev/null
+++ b/.changeset/duration-fractional-nanos-micros.md
@@ -0,0 +1,9 @@
+---
+"effect": patch
+---
+
+Fix `Duration.decode` and `Duration.times` throwing on fractional values.
+
+`Duration.decode` accepts a decimal mantissa (e.g. `"1.5 micros"`), but the `nanos`/`micros` units passed the raw string to `BigInt`, which throws on non-integers. Fractional `nanos`/`micros` are now scaled to whole nanoseconds (rounded), e.g. `Duration.decode("1.5 micros")` is `1500` nanos and `Duration.decode("1.5 nanos")` is `2` nanos.
+
+`Duration.times` accepts any `number` multiplier, but multiplying a nanosecond-backed `Duration` by a non-integer threw because `BigInt` cannot convert a float. Non-integer multipliers are now supported, e.g. `Duration.times(Duration.nanos(2n), 2.5)` is `5` nanos.
diff --git a/packages/effect/src/Duration.ts b/packages/effect/src/Duration.ts
index 677138be127..9554b409f5a 100644
--- a/packages/effect/src/Duration.ts
+++ b/packages/effect/src/Duration.ts
@@ -113,13 +113,14 @@ export const decode = (input: DurationInput): Duration => {
     if (match) {
       const [_, valueStr, unit] = match
       const value = Number(valueStr)
+      const isFractional = valueStr.includes(".")
       switch (unit) {
         case "nano":
         case "nanos":
-          return nanos(BigInt(valueStr))
+          return isFractional ? make(BigInt(Math.round(value))) : nanos(BigInt(valueStr))
         case "micro":
         case "micros":
-          return micros(BigInt(valueStr))
+          return isFractional ? make(BigInt(Math.round(value * 1_000))) : micros(BigInt(valueStr))
         case "milli":
         case "millis":
           return millis(value)
@@ -651,7 +652,10 @@ export const times: {
   (self: DurationInput, times: number): Duration =>
     match(self, {
       onMillis: (millis) => make(millis * times),
-      onNanos: (nanos) => make(nanos * BigInt(times))
+      onNanos: (nanos) =>
+        Number.isInteger(times)
+          ? make(nanos * BigInt(times))
+          : make(BigInt(Math.round(Number(nanos) * times)))
     })
 )
 
diff --git a/packages/effect/test/Duration.test.ts b/packages/effect/test/Duration.test.ts
index 5250e6bd0e7..455dad9a926 100644
--- a/packages/effect/test/Duration.test.ts
+++ b/packages/effect/test/Duration.test.ts
@@ -39,6 +39,10 @@ describe("Duration", () => {
     deepStrictEqual(Duration.decode("1.5 seconds"), Duration.seconds(1.5))
     deepStrictEqual(Duration.decode("-1.5 seconds"), Duration.zero)
 
+    deepStrictEqual(Duration.decode("1.5 micros"), Duration.nanos(1500n))
+    deepStrictEqual(Duration.decode("1.5 nanos"), Duration.nanos(2n))
+    deepStrictEqual(Duration.decode("-1.5 nanos"), Duration.zero)
+
     deepStrictEqual(Duration.decode([500, 123456789]), Duration.nanos(500123456789n))
     deepStrictEqual(Duration.decode([-500, 123456789]), Duration.zero)
     deepStrictEqual(Duration.decode([Infinity, 0]), Duration.infinity)
@@ -224,6 +228,9 @@ describe("Duration", () => {
     deepStrictEqual(Duration.times(Duration.seconds(Infinity), 60), Duration.seconds(Infinity))
 
     deepStrictEqual(Duration.times("1 seconds", 60), Duration.minutes(1))
+
+    deepStrictEqual(Duration.times(Duration.nanos(2n), 2.5), Duration.nanos(5n))
+    deepStrictEqual(Duration.times(Duration.nanos(3n), 1.5), Duration.nanos(5n))
   })
 
   it("sum", () => {