diff --git a/packages/server/src/utils/checkout-git.test.ts b/packages/server/src/utils/checkout-git.test.ts
index 877e2ddde..2720b0d0a 100644
--- a/packages/server/src/utils/checkout-git.test.ts
+++ b/packages/server/src/utils/checkout-git.test.ts
@@ -3002,6 +3002,20 @@ const x = 1;
     expect(baseDiff.diff).not.toContain("file.txt");
   });
 
+  it("names both refs when a requested base ref does not match the stored one", async () => {
+    const worktree = await createLegacyWorktreeForTest({
+      branchName: "mismatch-feature",
+      cwd: repoDir,
+      baseBranch: "main",
+      worktreeSlug: "mismatch-feature",
+      paseoHome,
+    });
+
+    await expect(
+      getCheckoutDiff(worktree.worktreePath, { mode: "base", baseRef: "other" }, { paseoHome }),
+    ).rejects.toThrow("Base ref mismatch: stored main, requested other");
+  });
+
   it("excludes dirty working tree changes from Paseo worktree base diffs", async () => {
     const worktree = await createLegacyWorktreeForTest({
       branchName: "feature",
diff --git a/packages/server/src/utils/checkout-git.ts b/packages/server/src/utils/checkout-git.ts
index f518adfed..6d09eee0d 100644
--- a/packages/server/src/utils/checkout-git.ts
+++ b/packages/server/src/utils/checkout-git.ts
@@ -1134,6 +1134,12 @@ async function resolveBaseRefForCwd(
   };
 }
 
+// Names both refs rather than labelling either one correct: a caller's ref can be stale, but the
+// stored ref can equally be wrong, so the message states the two facts and leaves the diagnosis open.
+function baseRefMismatchError(refs: { stored: string; requested: string }): Error {
+  return new Error(`Base ref mismatch: stored ${refs.stored}, requested ${refs.requested}`);
+}
+
 async function isWorkingTreeDirty(cwd: string, context?: CheckoutContext): Promise<boolean> {
   const { stdout } = await runGitCommand(["status", "--porcelain"], {
     cwd,
@@ -2795,7 +2801,7 @@ async function resolveCheckoutDiffRefs(
     return null;
   }
   if (storedBaseRef && compare.baseRef && compare.baseRef !== storedBaseRef) {
-    throw new Error(`Base ref mismatch: expected ${baseRef}, got ${compare.baseRef}`);
+    throw baseRefMismatchError({ stored: storedBaseRef, requested: compare.baseRef });
   }
   const bestBaseRef = await resolveBestComparisonBaseRef(cwd, baseRef);
   return {
@@ -3009,7 +3015,7 @@ export async function mergeToBase(
     throw new Error("Unable to determine base branch for merge");
   }
   if (storedBaseRef && options.baseRef && options.baseRef !== storedBaseRef) {
-    throw new Error(`Base ref mismatch: expected ${baseRef}, got ${options.baseRef}`);
+    throw baseRefMismatchError({ stored: storedBaseRef, requested: options.baseRef });
   }
   if (!currentBranch) {
     throw new Error("Unable to determine current branch for merge");
@@ -3085,7 +3091,7 @@ export async function mergeFromBase(
     throw new Error("Unable to determine base branch for merge");
   }
   if (storedBaseRef && options.baseRef && options.baseRef !== storedBaseRef) {
-    throw new Error(`Base ref mismatch: expected ${baseRef}, got ${options.baseRef}`);
+    throw baseRefMismatchError({ stored: storedBaseRef, requested: options.baseRef });
   }
 
   const requireCleanTarget = options.requireCleanTarget ?? true;
@@ -3423,7 +3429,7 @@ export async function createPullRequest(
   }
   const normalizedBase = normalizeLocalBranchRefName(base);
   if (storedBaseRef && options.base && options.base !== storedBaseRef) {
-    throw new Error(`Base ref mismatch: expected ${base}, got ${options.base}`);
+    throw baseRefMismatchError({ stored: storedBaseRef, requested: options.base });
   }
 
   // The push deliberately happens before the adapter resolves the target