diff --git a/packages/app/src/pages/session/use-session-hash-scroll-core.ts b/packages/app/src/pages/session/use-session-hash-scroll-core.ts
new file mode 100644
index 000000000..0d0032f94
--- /dev/null
+++ b/packages/app/src/pages/session/use-session-hash-scroll-core.ts
@@ -0,0 +1,230 @@
+import type { UserMessage } from "@opencode-ai/sdk/v2"
+import { createEffect, createMemo, onCleanup, onMount } from "solid-js"
+import { messageIdFromHash } from "./message-id-from-hash"
+
+export type SessionHashScrollInput = {
+  sessionKey: () => string
+  sessionID: () => string | undefined
+  messagesReady: () => boolean
+  visibleUserMessages: () => UserMessage[]
+  historyMore: () => boolean
+  historyLoading: () => boolean
+  loadMore: (sessionID: string) => Promise<void>
+  turnStart: () => number
+  currentMessageId: () => string | undefined
+  pendingMessage: () => string | undefined
+  setPendingMessage: (value: string | undefined) => void
+  setActiveMessage: (message: UserMessage | undefined) => void
+  markHashTarget: (index: number) => void
+  autoScroll: { pause: () => void; forceScrollToBottom: () => void }
+  scroller: () => HTMLDivElement | undefined
+  anchor: (id: string) => string
+  scheduleScrollState: (el: HTMLDivElement) => void
+  consumePendingMessage: (key: string) => string | undefined
+  onMessageNavigation?: (messageID: string) => void
+  onMessageHashCleared?: () => void
+}
+
+type SessionHashScrollLocation = { hash: string; pathname: string; search: string }
+type SessionHashScrollNavigate = (to: string, options?: { replace?: boolean }) => void
+
+export const createSessionHashScroll = (
+  input: SessionHashScrollInput,
+  location: SessionHashScrollLocation,
+  navigate: SessionHashScrollNavigate,
+) => {
+  const visibleUserMessages = createMemo(() => input.visibleUserMessages())
+  const messageById = createMemo(() => new Map(visibleUserMessages().map((m) => [m.id, m])))
+  const messageIndex = createMemo(() => new Map(visibleUserMessages().map((m, i) => [m.id, i])))
+  let pendingKey = ""
+  let clearingHash: string | undefined
+
+  const frames = new Set<number>()
+  const queue = (fn: () => void) => {
+    const id = requestAnimationFrame(() => {
+      frames.delete(id)
+      fn()
+    })
+    frames.add(id)
+  }
+  const cancel = () => {
+    for (const id of frames) cancelAnimationFrame(id)
+    frames.clear()
+  }
+
+  const clearMessageHash = () => {
+    cancel()
+    input.consumePendingMessage(input.sessionKey())
+    if (input.pendingMessage()) input.setPendingMessage(undefined)
+    if (!location.hash) return
+    clearingHash = location.hash
+    navigate(location.pathname + location.search, { replace: true })
+    input.onMessageHashCleared?.()
+  }
+
+  const updateHash = (id: string) => {
+    const hash = `#${input.anchor(id)}`
+    if (location.hash === hash) return
+    clearingHash = undefined
+    navigate(location.pathname + location.search + hash, {
+      replace: true,
+    })
+  }
+
+  const scrollToElement = (el: HTMLElement, behavior: ScrollBehavior) => {
+    const root = input.scroller()
+    if (!root) return false
+
+    const a = el.getBoundingClientRect()
+    const b = root.getBoundingClientRect()
+    const sticky = root.querySelector("[data-session-title]")
+    const inset = sticky instanceof HTMLElement ? sticky.offsetHeight : 0
+    const top = Math.max(0, a.top - b.top + root.scrollTop - inset)
+    root.scrollTo({ top, behavior })
+    return true
+  }
+
+  const seek = (id: string, behavior: ScrollBehavior, left = 4): boolean => {
+    const el = document.getElementById(input.anchor(id))
+    if (el) return scrollToElement(el, behavior)
+    if (left <= 0) return false
+    queue(() => {
+      seek(id, behavior, left - 1)
+    })
+    return false
+  }
+
+  const scrollToMessage = (message: UserMessage, behavior: ScrollBehavior = "smooth") => {
+    cancel()
+    input.onMessageNavigation?.(message.id)
+    if (input.currentMessageId() !== message.id) input.setActiveMessage(message)
+
+    const index = messageIndex().get(message.id) ?? -1
+    if (index !== -1) input.markHashTarget(index)
+    if (index !== -1 && index < input.turnStart()) {
+      queue(() => {
+        seek(message.id, behavior)
+      })
+
+      updateHash(message.id)
+      return
+    }
+
+    if (seek(message.id, behavior)) {
+      updateHash(message.id)
+      return
+    }
+
+    updateHash(message.id)
+  }
+
+  const applyHash = (behavior: ScrollBehavior) => {
+    const hash = location.hash.slice(1)
+    if (!hash) {
+      input.autoScroll.forceScrollToBottom()
+      const el = input.scroller()
+      if (el) input.scheduleScrollState(el)
+      return
+    }
+
+    const messageId = messageIdFromHash(hash)
+    if (messageId) {
+      input.autoScroll.pause()
+      const msg = messageById().get(messageId)
+      if (msg) {
+        scrollToMessage(msg, behavior)
+        return
+      }
+      input.onMessageNavigation?.(messageId)
+      return
+    }
+
+    const target = document.getElementById(hash)
+    if (target) {
+      input.autoScroll.pause()
+      scrollToElement(target, behavior)
+      return
+    }
+
+    input.autoScroll.forceScrollToBottom()
+    const el = input.scroller()
+    if (el) input.scheduleScrollState(el)
+  }
+
+  createEffect(() => {
+    const hash = location.hash
+    if (!hash) {
+      clearingHash = undefined
+    } else if (hash === clearingHash) {
+      return
+    } else {
+      clearingHash = undefined
+    }
+    if (!input.sessionID() || !input.messagesReady()) return
+    cancel()
+    queue(() => applyHash("auto"))
+  })
+
+  createEffect(() => {
+    if (!input.sessionID() || !input.messagesReady()) return
+
+    visibleUserMessages()
+    input.turnStart()
+
+    let targetId = input.pendingMessage()
+    if (!targetId) {
+      const key = input.sessionKey()
+      if (pendingKey !== key) {
+        pendingKey = key
+        const next = input.consumePendingMessage(key)
+        if (next) {
+          input.setPendingMessage(next)
+          targetId = next
+        }
+      }
+    }
+
+    if (!targetId && !clearingHash) targetId = messageIdFromHash(location.hash)
+    if (!targetId) return
+
+    const pending = input.pendingMessage() === targetId
+    const msg = messageById().get(targetId)
+    if (!msg) return
+
+    if (pending) input.setPendingMessage(undefined)
+    if (input.currentMessageId() === targetId && !pending) return
+
+    input.autoScroll.pause()
+    cancel()
+    queue(() => scrollToMessage(msg, "auto"))
+  })
+
+  createEffect(() => {
+    const sessionID = input.sessionID()
+    if (!sessionID || !input.messagesReady()) return
+
+    visibleUserMessages()
+
+    let targetId = input.pendingMessage()
+    if (!targetId && !clearingHash) targetId = messageIdFromHash(location.hash)
+    if (!targetId) return
+    if (messageById().has(targetId)) return
+    if (!input.historyMore() || input.historyLoading()) return
+
+    void input.loadMore(sessionID)
+  })
+
+  onMount(() => {
+    if (typeof window !== "undefined" && "scrollRestoration" in window.history) {
+      window.history.scrollRestoration = "manual"
+    }
+  })
+
+  onCleanup(cancel)
+
+  return {
+    clearMessageHash,
+    scrollToMessage,
+    applyHash,
+  }
+}
diff --git a/packages/app/src/pages/session/use-session-hash-scroll.test.ts b/packages/app/src/pages/session/use-session-hash-scroll.test.ts
index 5bfa9b24c..8453d7566 100644
--- a/packages/app/src/pages/session/use-session-hash-scroll.test.ts
+++ b/packages/app/src/pages/session/use-session-hash-scroll.test.ts
@@ -1,4 +1,6 @@
 import { describe, expect, test } from "bun:test"
+import { createRoot, createSignal } from "solid-js"
+import { createSessionHashScroll } from "./use-session-hash-scroll-core"
 import { messageIdFromHash } from "./message-id-from-hash"
 
 describe("messageIdFromHash", () => {
@@ -17,7 +19,7 @@ describe("messageIdFromHash", () => {
 
 describe("useSessionHashScroll", () => {
   test("clearing a message hash notifies the timeline to leave hash history mode", async () => {
-    const source = await Bun.file(new URL("./use-session-hash-scroll.ts", import.meta.url)).text()
+    const source = await Bun.file(new URL("./use-session-hash-scroll-core.ts", import.meta.url)).text()
 
     expect(source).toContain("onMessageHashCleared")
     expect(source).toContain("input.onMessageHashCleared?.()")
@@ -31,26 +33,100 @@ describe("useSessionHashScroll", () => {
   })
 
   test("timeline cancels bottom follow before hash or active-message navigation", async () => {
-    const hashSource = await Bun.file(new URL("./use-session-hash-scroll.ts", import.meta.url)).text()
+    const hashSource = await Bun.file(new URL("./use-session-hash-scroll-core.ts", import.meta.url)).text()
     const timelineSource = await Bun.file(new URL("./use-session-timeline-interaction.ts", import.meta.url)).text()
     const sessionSource = await Bun.file(new URL("../session.tsx", import.meta.url)).text()
 
     expect(hashSource).toContain("onMessageNavigation")
     expect(hashSource).toContain("input.onMessageNavigation?.(message.id)")
-    expect(timelineSource).toContain("type: \"target_message\"")
+    expect(timelineSource).toContain('type: "target_message"')
     expect(timelineSource).toContain("const navigateMessageByOffset")
     expect(timelineSource).toContain("scrollDock.cancelBottomFollowLock()")
     expect(sessionSource).toContain("markScrollGesture: timelineInteraction.markScrollGesture")
     expect(sessionSource).toContain("navigateMessageByOffset: timelineInteraction.navigateMessageByOffset")
   })
 
-  test("hash navigation emits once for already rendered messages", async () => {
-    const source = await Bun.file(new URL("./use-session-hash-scroll.ts", import.meta.url)).text()
+  test("hash navigation scrolls an already rendered message without duplicate fallback navigation", async () => {
+    const root = document.createElement("div")
+    const target = document.createElement("div")
+    const scrollPositions: ScrollToOptions[] = []
+    const navigationCalls: string[] = []
+    const activeMessages: string[] = []
+    const markedTargets: number[] = []
 
-    expect(source).toContain(`if (msg) {
-        scrollToMessage(msg, behavior)
-        return
-      }
-      input.onMessageNavigation?.(messageId)`)
+    root.id = "session-root"
+    target.id = "message-msg_2"
+    root.append(target)
+    document.body.append(root)
+
+    root.getBoundingClientRect = () => ({
+      top: 0,
+      bottom: 400,
+      left: 0,
+      right: 400,
+      width: 400,
+      height: 400,
+      x: 0,
+      y: 0,
+      toJSON: () => ({}),
+    })
+    target.getBoundingClientRect = () => ({
+      top: 160,
+      bottom: 220,
+      left: 0,
+      right: 400,
+      width: 400,
+      height: 60,
+      x: 0,
+      y: 160,
+      toJSON: () => ({}),
+    })
+    root.scrollTo = (options?: ScrollToOptions | number) => {
+      if (typeof options === "object") scrollPositions.push(options)
+    }
+
+    const dispose = createRoot((dispose) => {
+      const [currentMessageId, setCurrentMessageId] = createSignal<string | undefined>()
+
+      const hashScroll = createSessionHashScroll(
+        {
+          sessionKey: () => "ses_1:/repo",
+          sessionID: () => "ses_1",
+          messagesReady: () => true,
+          visibleUserMessages: () => [{ id: "msg_1" }, { id: "msg_2" }] as any,
+          historyMore: () => false,
+          historyLoading: () => false,
+          loadMore: async () => undefined,
+          turnStart: () => 0,
+          currentMessageId,
+          pendingMessage: () => undefined,
+          setPendingMessage: () => undefined,
+          setActiveMessage: (message) => {
+            activeMessages.push(message?.id ?? "")
+            setCurrentMessageId(message?.id)
+          },
+          markHashTarget: (index) => markedTargets.push(index),
+          autoScroll: { pause: () => undefined, forceScrollToBottom: () => undefined },
+          scroller: () => root,
+          anchor: (id) => `message-${id}`,
+          scheduleScrollState: () => undefined,
+          consumePendingMessage: () => undefined,
+          onMessageNavigation: (messageID) => navigationCalls.push(messageID),
+        },
+        { hash: "#message-msg_2", pathname: "/session/ses_1", search: "" },
+        () => undefined,
+      )
+
+      hashScroll.applyHash("auto")
+      return dispose
+    })
+
+    expect(scrollPositions).toEqual([{ top: 160, behavior: "auto" }])
+    expect(activeMessages).toEqual(["msg_2"])
+    expect(markedTargets).toEqual([1])
+    expect(navigationCalls).toEqual(["msg_2"])
+
+    dispose()
+    root.remove()
   })
 })
diff --git a/packages/app/src/pages/session/use-session-hash-scroll.ts b/packages/app/src/pages/session/use-session-hash-scroll.ts
index 5260965e8..230256f1a 100644
--- a/packages/app/src/pages/session/use-session-hash-scroll.ts
+++ b/packages/app/src/pages/session/use-session-hash-scroll.ts
@@ -1,225 +1,9 @@
-import type { UserMessage } from "@opencode-ai/sdk/v2"
 import { useLocation, useNavigate } from "@solidjs/router"
-import { createEffect, createMemo, onCleanup, onMount } from "solid-js"
-import { messageIdFromHash } from "./message-id-from-hash"
-
-export const useSessionHashScroll = (input: {
-  sessionKey: () => string
-  sessionID: () => string | undefined
-  messagesReady: () => boolean
-  visibleUserMessages: () => UserMessage[]
-  historyMore: () => boolean
-  historyLoading: () => boolean
-  loadMore: (sessionID: string) => Promise<void>
-  turnStart: () => number
-  currentMessageId: () => string | undefined
-  pendingMessage: () => string | undefined
-  setPendingMessage: (value: string | undefined) => void
-  setActiveMessage: (message: UserMessage | undefined) => void
-  markHashTarget: (index: number) => void
-  autoScroll: { pause: () => void; forceScrollToBottom: () => void }
-  scroller: () => HTMLDivElement | undefined
-  anchor: (id: string) => string
-  scheduleScrollState: (el: HTMLDivElement) => void
-  consumePendingMessage: (key: string) => string | undefined
-  onMessageNavigation?: (messageID: string) => void
-  onMessageHashCleared?: () => void
-}) => {
-  const visibleUserMessages = createMemo(() => input.visibleUserMessages())
-  const messageById = createMemo(() => new Map(visibleUserMessages().map((m) => [m.id, m])))
-  const messageIndex = createMemo(() => new Map(visibleUserMessages().map((m, i) => [m.id, i])))
-  let pendingKey = ""
-  let clearingHash: string | undefined
+import { createSessionHashScroll, type SessionHashScrollInput } from "./use-session-hash-scroll-core"
 
+export const useSessionHashScroll = (input: SessionHashScrollInput) => {
   const location = useLocation()
   const navigate = useNavigate()
 
-  const frames = new Set<number>()
-  const queue = (fn: () => void) => {
-    const id = requestAnimationFrame(() => {
-      frames.delete(id)
-      fn()
-    })
-    frames.add(id)
-  }
-  const cancel = () => {
-    for (const id of frames) cancelAnimationFrame(id)
-    frames.clear()
-  }
-
-  const clearMessageHash = () => {
-    cancel()
-    input.consumePendingMessage(input.sessionKey())
-    if (input.pendingMessage()) input.setPendingMessage(undefined)
-    if (!location.hash) return
-    clearingHash = location.hash
-    navigate(location.pathname + location.search, { replace: true })
-    input.onMessageHashCleared?.()
-  }
-
-  const updateHash = (id: string) => {
-    const hash = `#${input.anchor(id)}`
-    if (location.hash === hash) return
-    clearingHash = undefined
-    navigate(location.pathname + location.search + hash, {
-      replace: true,
-    })
-  }
-
-  const scrollToElement = (el: HTMLElement, behavior: ScrollBehavior) => {
-    const root = input.scroller()
-    if (!root) return false
-
-    const a = el.getBoundingClientRect()
-    const b = root.getBoundingClientRect()
-    const sticky = root.querySelector("[data-session-title]")
-    const inset = sticky instanceof HTMLElement ? sticky.offsetHeight : 0
-    const top = Math.max(0, a.top - b.top + root.scrollTop - inset)
-    root.scrollTo({ top, behavior })
-    return true
-  }
-
-  const seek = (id: string, behavior: ScrollBehavior, left = 4): boolean => {
-    const el = document.getElementById(input.anchor(id))
-    if (el) return scrollToElement(el, behavior)
-    if (left <= 0) return false
-    queue(() => {
-      seek(id, behavior, left - 1)
-    })
-    return false
-  }
-
-  const scrollToMessage = (message: UserMessage, behavior: ScrollBehavior = "smooth") => {
-    cancel()
-    input.onMessageNavigation?.(message.id)
-    if (input.currentMessageId() !== message.id) input.setActiveMessage(message)
-
-    const index = messageIndex().get(message.id) ?? -1
-    if (index !== -1) input.markHashTarget(index)
-    if (index !== -1 && index < input.turnStart()) {
-      queue(() => {
-        seek(message.id, behavior)
-      })
-
-      updateHash(message.id)
-      return
-    }
-
-    if (seek(message.id, behavior)) {
-      updateHash(message.id)
-      return
-    }
-
-    updateHash(message.id)
-  }
-
-  const applyHash = (behavior: ScrollBehavior) => {
-    const hash = location.hash.slice(1)
-    if (!hash) {
-      input.autoScroll.forceScrollToBottom()
-      const el = input.scroller()
-      if (el) input.scheduleScrollState(el)
-      return
-    }
-
-    const messageId = messageIdFromHash(hash)
-    if (messageId) {
-      input.autoScroll.pause()
-      const msg = messageById().get(messageId)
-      if (msg) {
-        scrollToMessage(msg, behavior)
-        return
-      }
-      input.onMessageNavigation?.(messageId)
-      return
-    }
-
-    const target = document.getElementById(hash)
-    if (target) {
-      input.autoScroll.pause()
-      scrollToElement(target, behavior)
-      return
-    }
-
-    input.autoScroll.forceScrollToBottom()
-    const el = input.scroller()
-    if (el) input.scheduleScrollState(el)
-  }
-
-  createEffect(() => {
-    const hash = location.hash
-    if (!hash) {
-      clearingHash = undefined
-    } else if (hash === clearingHash) {
-      return
-    } else {
-      clearingHash = undefined
-    }
-    if (!input.sessionID() || !input.messagesReady()) return
-    cancel()
-    queue(() => applyHash("auto"))
-  })
-
-  createEffect(() => {
-    if (!input.sessionID() || !input.messagesReady()) return
-
-    visibleUserMessages()
-    input.turnStart()
-
-    let targetId = input.pendingMessage()
-    if (!targetId) {
-      const key = input.sessionKey()
-      if (pendingKey !== key) {
-        pendingKey = key
-        const next = input.consumePendingMessage(key)
-        if (next) {
-          input.setPendingMessage(next)
-          targetId = next
-        }
-      }
-    }
-
-    if (!targetId && !clearingHash) targetId = messageIdFromHash(location.hash)
-    if (!targetId) return
-
-    const pending = input.pendingMessage() === targetId
-    const msg = messageById().get(targetId)
-    if (!msg) return
-
-    if (pending) input.setPendingMessage(undefined)
-    if (input.currentMessageId() === targetId && !pending) return
-
-    input.autoScroll.pause()
-    cancel()
-    queue(() => scrollToMessage(msg, "auto"))
-  })
-
-  createEffect(() => {
-    const sessionID = input.sessionID()
-    if (!sessionID || !input.messagesReady()) return
-
-    visibleUserMessages()
-
-    let targetId = input.pendingMessage()
-    if (!targetId && !clearingHash) targetId = messageIdFromHash(location.hash)
-    if (!targetId) return
-    if (messageById().has(targetId)) return
-    if (!input.historyMore() || input.historyLoading()) return
-
-    void input.loadMore(sessionID)
-  })
-
-  onMount(() => {
-    if (typeof window !== "undefined" && "scrollRestoration" in window.history) {
-      window.history.scrollRestoration = "manual"
-    }
-  })
-
-  onCleanup(cancel)
-
-  return {
-    clearMessageHash,
-    scrollToMessage,
-    applyHash,
-  }
+  return createSessionHashScroll(input, location, navigate)
 }