diff --git a/src/commands/rebase.ts b/src/commands/rebase.ts
index 3689a1a..ff7b220 100644
--- a/src/commands/rebase.ts
+++ b/src/commands/rebase.ts
@@ -16,23 +16,23 @@ export async function action(branch: string) {
   }
 
   const main = await git.mainBranch(root)
-  const spin = spinner("Fetching origin", branch)
+  const fetchSpin = spinner("Fetching origin", branch)
 
   await $`git -C ${root} fetch origin ${main}`.nothrow().quiet()
-  spin.text = `Rebasing onto origin/${main}`
+  fetchSpin.text = `Rebasing onto origin/${main}`
 
   let conflicts = await git.rebase(`origin/${main}`, worktree)
   if (conflicts.length === 0) {
-    spin.succeed(`Rebased ${branch} onto ${main}`)
+    fetchSpin.succeed(`Rebased ${branch} onto ${main}`)
     return
   }
 
-  spin.stop()
+  fetchSpin.stop()
   console.log(`◆ Rebase conflicts in ${conflicts.length} file(s). Resolving with Claude...`)
-  const spin2 = spinner("Starting container", branch)
+  const resolveSpin = spinner("Starting container", branch)
 
   try {
-    await vm.ensure((msg) => { spin2.text = msg })
+    await vm.ensure((msg) => { resolveSpin.text = msg })
 
     let round = 1
     while (conflicts.length > 0) {
@@ -41,16 +41,16 @@ export async function action(branch: string) {
       }
 
       await resolveConflicts(conflicts, worktree, (file) => {
-        spin2.text = `Resolving ${file} (round ${round})`
+        resolveSpin.text = `Resolving ${file} (round ${round})`
       })
 
       conflicts = await git.rebaseContinue(worktree)
       round++
     }
 
-    spin2.succeed(`Rebased ${branch} onto ${main} (resolved ${round - 1} conflict round(s))`)
+    resolveSpin.succeed(`Rebased ${branch} onto ${main} (resolved ${round - 1} conflict round(s))`)
   } catch (err) {
-    spin2.fail(String((err as Error).message ?? err))
+    resolveSpin.fail(String((err as Error).message ?? err))
     await git.rebaseAbort(worktree)
     process.exit(1)
   }
diff --git a/src/git.ts b/src/git.ts
index eb609b4..1f5c475 100644
--- a/src/git.ts
+++ b/src/git.ts
@@ -121,6 +121,12 @@ export async function abortMerge(cwd: string): Promise<void> {
 
 /** Rebase the current branch onto another. Returns conflicted file paths, or empty array if clean. */
 export async function rebase(onto: string, cwd: string): Promise<string[]> {
+  // Bail early if a rebase is already in progress
+  const inProgress = await $`git -C ${cwd} rev-parse --verify --quiet REBASE_HEAD`.nothrow().quiet()
+  if (inProgress.exitCode === 0) {
+    throw new Error(`A rebase is already in progress. Run "git -C ${cwd} rebase --abort" to cancel it first.`)
+  }
+
   const result = await $`git rebase ${onto}`.cwd(cwd).nothrow().quiet()
   if (result.exitCode === 0) return []
 
@@ -128,7 +134,9 @@ export async function rebase(onto: string, cwd: string): Promise<string[]> {
   const files = unmerged.trim().split("\n").filter(Boolean)
   if (files.length > 0) return files
 
-  throw new Error(`Failed to rebase onto "${onto}": ${result.stderr.toString().trim()}`)
+  // No conflicts but rebase still failed — include stderr for diagnostics
+  const stderr = result.stderr.toString().trim()
+  throw new Error(`Rebase onto "${onto}" failed: ${stderr || "(no output from git)"}`)
 }
 
 /** Continue a rebase after resolving conflicts. Returns conflicted files for the next commit, or empty if done. */