From 49f8a56244d210286eca314222b7971b3a74d842 Mon Sep 17 00:00:00 2001
From: Sebastian Lorenz <fubhy@fubhy.com>
Date: Mon, 3 Aug 2026 05:48:37 +0000
Subject: [PATCH 1/2] Add reproduction for Stream issue

---
 packages/effect/test/Stream.test.ts | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/packages/effect/test/Stream.test.ts b/packages/effect/test/Stream.test.ts
index 7e2912701c5..29aa2564e16 100644
--- a/packages/effect/test/Stream.test.ts
+++ b/packages/effect/test/Stream.test.ts
@@ -404,6 +404,16 @@ describe("Stream", () => {
         assert.deepStrictEqual(result, [1, 2, 3])
       }))
 
+    it.effect("range - zero chunk size does not change the emitted range", () =>
+      Effect.gen(function*() {
+        const result = yield* Stream.range(1, 3, 0).pipe(
+          Stream.take(4),
+          Stream.runCollect
+        )
+
+        assert.deepStrictEqual(result, [1, 2, 3])
+      }))
+
     it.effect("service", () =>
       Effect.gen(function*() {
         const result = yield* Stream.service(Greeter).pipe(

From 68fe429671fd35c7ef4e60ca37317da199d5733d Mon Sep 17 00:00:00 2001
From: Tim Smart <hello@timsmart.co>
Date: Tue, 4 Aug 2026 09:30:55 +1200
Subject: [PATCH 2/2] Fix Stream.range with zero chunk size

---
 .changeset/fix-stream-range-zero-chunk.md | 5 +++++
 packages/effect/src/Stream.ts             | 7 ++++---
 2 files changed, 9 insertions(+), 3 deletions(-)
 create mode 100644 .changeset/fix-stream-range-zero-chunk.md

diff --git a/.changeset/fix-stream-range-zero-chunk.md b/.changeset/fix-stream-range-zero-chunk.md
new file mode 100644
index 00000000000..cc28d66a7bf
--- /dev/null
+++ b/.changeset/fix-stream-range-zero-chunk.md
@@ -0,0 +1,5 @@
+---
+"effect": patch
+---
+
+Ensure `Stream.range` emits the full range when the chunk size is zero.
diff --git a/packages/effect/src/Stream.ts b/packages/effect/src/Stream.ts
index 263602b3627..a2655ef6f5c 100644
--- a/packages/effect/src/Stream.ts
+++ b/packages/effect/src/Stream.ts
@@ -1570,14 +1570,15 @@ export const range = (
   chunkSize = Channel.DefaultChunkSize
 ): Stream<number> =>
   min > max ? empty : fromPull(Effect.sync(() => {
+    const size = Math.max(1, chunkSize)
     let start = min
     let done = false
     return Effect.suspend(() => {
       if (done) return Cause.done()
       const remaining = max - start + 1
-      if (remaining > chunkSize) {
-        const chunk = Arr.range(start, start + chunkSize - 1)
-        start += chunkSize
+      if (remaining > size) {
+        const chunk = Arr.range(start, start + size - 1)
+        start += size
         return Effect.succeed(chunk)
       }
       const chunk = Arr.range(start, start + remaining - 1)