diff --git a/.changeset/fix-streamsse-data-identifier.md b/.changeset/fix-streamsse-data-identifier.md
new file mode 100644
index 0000000000..ff1b7e0e8f
--- /dev/null
+++ b/.changeset/fix-streamsse-data-identifier.md
@@ -0,0 +1,7 @@
+---
+"effect": patch
+---
+
+Fix `HttpApiSchema.StreamSse({ data })` so the decoded data schema keeps its identifier in the generated OpenAPI spec.
+
+The SSE `data` field is encoded as a JSON string, and that string wrapper was claiming the data schema's `identifier`, pushing the real schema to a suffixed name (e.g. `MyEvent` became the `string` wrapper while the decoded object became `MyEvent1`). This inverted the names for OpenAPI codegen consumers. The wrapper now gets its own `${identifier}Stream` name, leaving the data schema's identifier intact.
diff --git a/packages/effect/src/unstable/httpapi/HttpApiSchema.ts b/packages/effect/src/unstable/httpapi/HttpApiSchema.ts
index 622f08e01e..c52bc22a37 100644
--- a/packages/effect/src/unstable/httpapi/HttpApiSchema.ts
+++ b/packages/effect/src/unstable/httpapi/HttpApiSchema.ts
@@ -406,7 +406,7 @@ export const StreamSse: {
   const events = options.events ?? (options.data === undefined ? undefined : Schema.Struct({
     id: Schema.UndefinedOr(Schema.String),
     event: Schema.String,
-    data: Schema.fromJsonString(options.data)
+    data: sseDataJsonSchema(options.data)
   }))
   if (events === undefined) {
     throw new Error("StreamSse requires either an events schema or a data schema")
@@ -422,6 +422,14 @@ export const StreamSse: {
   })
 }
 
+const sseDataJsonSchema = (data: Schema.Constraint) => {
+  const json = Schema.fromJsonString(data)
+  const identifier = SchemaAST.resolveIdentifier(data.ast)
+  // The SSE transport field is a JSON string. Give that wrapper its own
+  // OpenAPI identifier so it does not claim the decoded data schema's name.
+  return identifier === undefined ? json : json.annotate({ identifier: `${identifier}Stream` })
+}
+
 /**
  * Creates a streaming `Uint8Array` success response schema.
  *
diff --git a/packages/effect/test/unstable/httpapi/OpenApi.test.ts b/packages/effect/test/unstable/httpapi/OpenApi.test.ts
index 5b6dd0620a..61b4261de6 100644
--- a/packages/effect/test/unstable/httpapi/OpenApi.test.ts
+++ b/packages/effect/test/unstable/httpapi/OpenApi.test.ts
@@ -36,4 +36,40 @@ describe("OpenApi", () => {
     assert.property(streamExtension, "causeSchema")
     assert.property(streamExtension, "errorSchema")
   })
+
+  it("preserves the data schema identifier for SSE streams", () => {
+    const Event = Schema.Struct({
+      kind: Schema.String,
+      payload: Schema.String
+    }).annotate({ identifier: "MyEvent" })
+
+    const Api = HttpApi.make("Api").add(
+      HttpApiGroup.make("test").add(
+        HttpApiEndpoint.get("stream", "/stream", {
+          success: [HttpApiSchema.StreamSse({ data: Event })]
+        })
+      )
+    )
+
+    const spec = OpenApi.fromApi(Api)
+    const schemas = spec.components?.schemas
+
+    // The decoded data schema keeps its identifier instead of being suffixed.
+    assert.deepStrictEqual(schemas?.MyEvent, {
+      type: "object",
+      properties: {
+        kind: { type: "string" },
+        payload: { type: "string" }
+      },
+      required: ["kind", "payload"],
+      additionalProperties: false
+    })
+
+    // The JSON-string transport wrapper gets its own `${identifier}Stream` name.
+    assert.deepStrictEqual(schemas?.MyEventStream, {
+      type: "string",
+      contentSchema: { $ref: "#/components/schemas/MyEvent" },
+      contentMediaType: "application/json"
+    })
+  })
 })