diff --git a/mobile/src/session/use-mobile-pr-sidebar-controller-probe.test.ts b/mobile/src/session/use-mobile-pr-sidebar-controller-probe.test.ts
new file mode 100644
index 00000000000..0645b6659c4
--- /dev/null
+++ b/mobile/src/session/use-mobile-pr-sidebar-controller-probe.test.ts
@@ -0,0 +1,100 @@
+import { createElement } from 'react'
+import { act, create, type ReactTestRenderer } from 'react-test-renderer'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import type { RpcClient } from '../transport/rpc-client'
+
+const fetchGithubRepoSlugMock = vi.fn()
+
+// Only the repo probe matters here; the load path never runs without a branch.
+vi.mock('./github-pr-rpc', () => ({
+  fetchGithubRepoSlug: (...args: unknown[]) => fetchGithubRepoSlugMock(...args),
+  fetchHostedReviewForBranch: vi.fn(),
+  fetchPRChecks: vi.fn(),
+  fetchPRForBranch: vi.fn(),
+  fetchWorkItemDetails: vi.fn()
+}))
+vi.mock('../source-control/mobile-pr-link', () => ({
+  fetchWorktreeLinkedPR: vi.fn(async () => null)
+}))
+
+import {
+  useMobilePrSidebarController,
+  type MobilePrSidebarController
+} from './use-mobile-pr-sidebar-controller'
+
+let captured: MobilePrSidebarController | null = null
+
+function Harness(props: Parameters<typeof useMobilePrSidebarController>[0]) {
+  captured = useMobilePrSidebarController(props)
+  return null
+}
+
+async function flush(): Promise<void> {
+  // Two ticks: the probe's resolved promise (.then) plus its setState commit.
+  await act(async () => {
+    await Promise.resolve()
+    await Promise.resolve()
+  })
+}
+
+describe('useMobilePrSidebarController repo probe', () => {
+  const client = { sendRequest: vi.fn() } as unknown as RpcClient
+  let renderer: ReactTestRenderer | null = null
+
+  beforeEach(() => {
+    captured = null
+    fetchGithubRepoSlugMock.mockReset()
+  })
+
+  afterEach(() => {
+    act(() => {
+      renderer?.unmount()
+    })
+    renderer = null
+  })
+
+  // Regression: repo eligibility must not be gated on a branch. A detached HEAD /
+  // mid-rebase worktree (branch === null) still has to resolve the probe, or the
+  // Pull Request segment gets stranded on a forever spinner instead of the
+  // "Current branch unavailable" state.
+  it('resolves the probe when connected without a branch (detached HEAD)', async () => {
+    fetchGithubRepoSlugMock.mockResolvedValue({ ok: true, result: { owner: 'o', repo: 'r' } })
+    await act(async () => {
+      renderer = create(
+        createElement(Harness, {
+          client,
+          connState: 'connected',
+          worktreeId: 'w',
+          branch: null,
+          headSha: 'sha'
+        })
+      )
+    })
+    await flush()
+
+    expect(fetchGithubRepoSlugMock).toHaveBeenCalledWith(client, 'w')
+    expect(captured?.prSidebarRepoProbeLoaded).toBe(true)
+    expect(captured?.prSidebarIsGithubRepo).toBe(true)
+    // No branch means no PR load ran — state stays hidden, never a spinner.
+    expect(captured?.prSidebarState.kind).toBe('hidden')
+  })
+
+  it('does not probe until the client is connected', async () => {
+    fetchGithubRepoSlugMock.mockResolvedValue({ ok: true, result: { owner: 'o', repo: 'r' } })
+    await act(async () => {
+      renderer = create(
+        createElement(Harness, {
+          client,
+          connState: 'connecting',
+          worktreeId: 'w',
+          branch: null,
+          headSha: 'sha'
+        })
+      )
+    })
+    await flush()
+
+    expect(fetchGithubRepoSlugMock).not.toHaveBeenCalled()
+    expect(captured?.prSidebarRepoProbeLoaded).toBe(false)
+  })
+})
diff --git a/mobile/src/session/use-mobile-pr-sidebar-controller.ts b/mobile/src/session/use-mobile-pr-sidebar-controller.ts
index f59242a0583..415a7581b7d 100644
--- a/mobile/src/session/use-mobile-pr-sidebar-controller.ts
+++ b/mobile/src/session/use-mobile-pr-sidebar-controller.ts
@@ -70,7 +70,11 @@ export function useMobilePrSidebarController(input: PrSidebarControllerInput) {
   stateRef.current = state
   const headShaRef = useRef(headSha)
 
-  const ready = client !== null && connState === 'connected' && !!branch
+  // Repo eligibility (a GitHub remote) is independent of the branch, so the probe
+  // must not require one: a detached HEAD / mid-rebase worktree (branch === null)
+  // would otherwise never set repoProbeLoaded, stranding the PR segment on a
+  // forever spinner instead of the "Current branch unavailable" state.
+  const probeReady = client !== null && connState === 'connected'
   const identity = buildMobilePrSidebarIdentity({ worktreeId, branch })
 
   const buildDeps = useCallback((): PrSidebarLoadDeps | null => {
@@ -96,7 +100,7 @@ export function useMobilePrSidebarController(input: PrSidebarControllerInput) {
 
   useEffect(() => {
     let cancelled = false
-    if (!ready || !client) {
+    if (!probeReady || !client) {
       return
     }
     void fetchGithubRepoSlug(client, worktreeId).then((outcome) => {
@@ -108,7 +112,7 @@ export function useMobilePrSidebarController(input: PrSidebarControllerInput) {
     return () => {
       cancelled = true
     }
-  }, [ready, client, worktreeId])
+  }, [probeReady, client, worktreeId])
 
   useEffect(() => {
     if (!identity) {
diff --git a/mobile/src/source-control/MobileSourceControlPanel.tsx b/mobile/src/source-control/MobileSourceControlPanel.tsx
index 6936041a44a..332f62312f1 100644
--- a/mobile/src/source-control/MobileSourceControlPanel.tsx
+++ b/mobile/src/source-control/MobileSourceControlPanel.tsx
@@ -200,7 +200,10 @@ export function MobileSourceControlPanel({
   }, [activeTab, isHostedRepo, prBranch, prSidebarKind, prDetailsMissingFor])
 
   const prChip = useMemo(() => {
-    if (!isHostedRepo) {
+    // No branch (detached HEAD / mid-rebase) never runs a PR load, so the shared
+    // state stays 'hidden' — which the chip would render as a forever spinner.
+    // Hide the chip instead; the Pull Request segment shows "branch unavailable".
+    if (!isHostedRepo || !prBranch) {
       return null
     }
     const commentCount =
@@ -208,7 +211,7 @@ export function MobileSourceControlPanel({
         ? countUnresolvedReviewThreads(prController.prSidebarState.data.details?.comments)
         : null
     return buildMobilePrChipSummary(prController.prSidebarState, commentCount)
-  }, [isHostedRepo, prController.prSidebarState])
+  }, [isHostedRepo, prBranch, prController.prSidebarState])
 
   // Design: refresh the active segment's body work, plus git.status for the shared
   // branch card (counts/sync stay honest even while on History). Preserve ready