diff --git a/packages/opencode/src/session/processor.ts b/packages/opencode/src/session/processor.ts
index d66e774900..497747a5df 100644
--- a/packages/opencode/src/session/processor.ts
+++ b/packages/opencode/src/session/processor.ts
@@ -352,7 +352,10 @@ export namespace SessionProcessor {
                 },
                 { text: ctx.currentText.text },
               )).text
-              ctx.currentText.time = { start: Date.now(), end: Date.now() }
+              {
+                const end = Date.now()
+                ctx.currentText.time = { start: ctx.currentText.time?.start ?? end, end }
+              }
               if (value.providerMetadata) ctx.currentText.metadata = value.providerMetadata
               yield* session.updatePart(ctx.currentText)
               ctx.currentText = undefined
diff --git a/packages/opencode/test/session/processor-effect.test.ts b/packages/opencode/test/session/processor-effect.test.ts
index f3a65b3ba5..a3b335b6da 100644
--- a/packages/opencode/test/session/processor-effect.test.ts
+++ b/packages/opencode/test/session/processor-effect.test.ts
@@ -21,7 +21,7 @@ import { Log } from "../../src/util/log"
 import * as CrossSpawnSpawner from "../../src/effect/cross-spawn-spawner"
 import { provideTmpdirServer } from "../fixture/fixture"
 import { testEffect } from "../lib/effect"
-import { reply, TestLLMServer } from "../lib/llm-server"
+import { raw, reply, TestLLMServer } from "../lib/llm-server"
 
 Log.init({ print: false })
 
@@ -218,6 +218,93 @@ it.live("session.processor effect tests capture llm input cleanly", () =>
   ),
 )
 
+it.live("session.processor effect tests preserve text start time", () =>
+  provideTmpdirServer(
+    ({ dir, llm }) =>
+      Effect.gen(function* () {
+        const gate = defer<void>()
+        const { processors, session, provider } = yield* boot()
+
+        yield* llm.push(
+          raw({
+            head: [
+              {
+                id: "chatcmpl-test",
+                object: "chat.completion.chunk",
+                choices: [{ delta: { role: "assistant" } }],
+              },
+              {
+                id: "chatcmpl-test",
+                object: "chat.completion.chunk",
+                choices: [{ delta: { content: "hello" } }],
+              },
+            ],
+            wait: gate.promise,
+            tail: [
+              {
+                id: "chatcmpl-test",
+                object: "chat.completion.chunk",
+                choices: [{ delta: {}, finish_reason: "stop" }],
+              },
+            ],
+          }),
+        )
+
+        const chat = yield* session.create({})
+        const parent = yield* user(chat.id, "hi")
+        const msg = yield* assistant(chat.id, parent.id, path.resolve(dir))
+        const mdl = yield* provider.getModel(ref.providerID, ref.modelID)
+        const handle = yield* processors.create({
+          assistantMessage: msg,
+          sessionID: chat.id,
+          model: mdl,
+        })
+
+        const run = yield* handle
+          .process({
+            user: {
+              id: parent.id,
+              sessionID: chat.id,
+              role: "user",
+              time: parent.time,
+              agent: parent.agent,
+              model: { providerID: ref.providerID, modelID: ref.modelID },
+            } satisfies MessageV2.User,
+            sessionID: chat.id,
+            model: mdl,
+            agent: agent(),
+            system: [],
+            messages: [{ role: "user", content: "hi" }],
+            tools: {},
+          })
+          .pipe(Effect.forkChild)
+
+        yield* Effect.promise(async () => {
+          const stop = Date.now() + 500
+          while (Date.now() < stop) {
+            const text = MessageV2.parts(msg.id).find((part): part is MessageV2.TextPart => part.type === "text")
+            if (text?.time?.start) return
+            await Bun.sleep(10)
+          }
+          throw new Error("timed out waiting for text part")
+        })
+        yield* Effect.sleep("20 millis")
+        gate.resolve()
+
+        const exit = yield* Fiber.await(run)
+        const text = MessageV2.parts(msg.id).find((part): part is MessageV2.TextPart => part.type === "text")
+
+        expect(Exit.isSuccess(exit)).toBe(true)
+        expect(text?.text).toBe("hello")
+        expect(text?.time?.start).toBeDefined()
+        expect(text?.time?.end).toBeDefined()
+        if (!text?.time?.start || !text.time.end) return
+        expect(text.time.start).toBeLessThan(text.time.end)
+      }),
+    { git: true, config: (url) => providerCfg(url) },
+  ),
+)
+
 it.live("session.processor effect tests stop after token overflow requests compaction", () =>
   provideTmpdirServer(
     ({ dir, llm }) =>