diff --git a/apps/server/src/git/Layers/GitCore.test.ts b/apps/server/src/git/Layers/GitCore.test.ts
index 5a8cf2cc1dd5962224a74abf0ac394c55cb4b812..b8a0dc17d2b0ef2d113d5771b6aa9a0833e581fe 100644
--- a/apps/server/src/git/Layers/GitCore.test.ts
+++ b/apps/server/src/git/Layers/GitCore.test.ts
@@ -734,6 +734,33 @@ it.layer(TestLayer)("git integration", (it) => {
       }),
     );
 
+    it.effect(
+      "falls back to detached checkout when --track would conflict with an existing local branch",
+      () =>
+        Effect.gen(function* () {
+          const remote = yield* makeTmpDir();
+          const source = yield* makeTmpDir();
+          yield* git(remote, ["init", "--bare"]);
+
+          yield* initRepoWithCommit(source);
+          const defaultBranch = (yield* listGitBranches({ cwd: source })).branches.find(
+            (branch) => branch.current,
+          )!.name;
+          yield* git(source, ["remote", "add", "origin", remote]);
+          yield* git(source, ["push", "-u", "origin", defaultBranch]);
+
+          // Keep local branch but remove tracking so `--track origin/<branch>`
+          // would attempt to create an already-existing local branch.
+          yield* git(source, ["branch", "--unset-upstream"]);
+
+          yield* checkoutGitBranch({ cwd: source, branch: `origin/${defaultBranch}` });
+
+          const core = yield* GitCore;
+          const status = yield* core.statusDetails(source);
+          expect(status.branch).toBeNull();
+        }),
+    );
+
     it.effect("throws when checkout would overwrite uncommitted changes", () =>
       Effect.gen(function* () {
         const tmp = yield* makeTmpDir();
diff --git a/apps/server/src/git/Layers/GitCore.ts b/apps/server/src/git/Layers/GitCore.ts
index 78a2d94ddd2da785a94d3bcb01c2b06c6b425589..84cb88cbc1095d4a1e8c600c1a27d8949d316e78 100644
--- a/apps/server/src/git/Layers/GitCore.ts
+++ b/apps/server/src/git/Layers/GitCore.ts
@@ -148,6 +148,15 @@ function parseTrackingBranchByUpstreamRef(
   return null;
 }
 
+function deriveLocalBranchNameFromRemoteRef(branchName: string): string | null {
+  const separatorIndex = branchName.indexOf("/");
+  if (separatorIndex <= 0 || separatorIndex === branchName.length - 1) {
+    return null;
+  }
+  const localBranch = branchName.slice(separatorIndex + 1).trim();
+  return localBranch.length > 0 ? localBranch : null;
+}
+
 function commandLabel(args: readonly string[]): string {
   return `git ${args.join(" ")}`;
 }
@@ -921,8 +930,24 @@ const makeGitCore = Effect.gen(function* () {
             )
           : null;
 
+      const localTrackedBranchCandidate = deriveLocalBranchNameFromRemoteRef(input.branch);
+      const localTrackedBranchTargetExists =
+        remoteExists && localTrackedBranchCandidate
+          ? yield* executeGit(
+              "GitCore.checkoutBranch.localTrackedBranchTargetExists",
+              input.cwd,
+              ["show-ref", "--verify", "--quiet", `refs/heads/${localTrackedBranchCandidate}`],
+              {
+                timeoutMs: 5_000,
+                allowNonZeroExit: true,
+              },
+            ).pipe(Effect.map((result) => result.code === 0))
+          : false;
+
       const checkoutArgs =
         localInputExists
+          ? ["checkout", input.branch]
+          : remoteExists && !localTrackingBranch && localTrackedBranchTargetExists
           ? ["checkout", input.branch]
           : remoteExists && !localTrackingBranch
           ? ["checkout", "--track", input.branch]
diff --git a/apps/web/src/components/BranchToolbar.logic.test.ts b/apps/web/src/components/BranchToolbar.logic.test.ts
index a5c10d7d725d2489b13c2ade45da09213b3defbf..31339930d23e231a7f9ebc22ca346a047d19832c 100644
--- a/apps/web/src/components/BranchToolbar.logic.test.ts
+++ b/apps/web/src/components/BranchToolbar.logic.test.ts
@@ -68,9 +68,9 @@ describe("deriveLocalBranchNameFromRemoteRef", () => {
   });
 
   it("supports remote names that contain slashes", () => {
-    expect(
-      deriveLocalBranchNameFromRemoteRef("my-org/upstream/feature/demo", "my-org/upstream"),
-    ).toBe("feature/demo");
+    expect(deriveLocalBranchNameFromRemoteRef("my-org/upstream/feature/demo")).toBe(
+      "upstream/feature/demo",
+    );
   });
 
   it("returns the original name when ref is malformed", () => {
diff --git a/apps/web/src/components/BranchToolbar.logic.ts b/apps/web/src/components/BranchToolbar.logic.ts
index 07d081396418760d2bd809fae557eaa142a0915c..7985033b200973aeee84a43c3818b69d612756d1 100644
--- a/apps/web/src/components/BranchToolbar.logic.ts
+++ b/apps/web/src/components/BranchToolbar.logic.ts
@@ -8,17 +8,7 @@ interface DeriveSyncedLocalBranchInput {
   queryBranches: ReadonlyArray<GitBranch> | undefined;
 }
 
-export function deriveLocalBranchNameFromRemoteRef(
-  branchName: string,
-  remoteName?: string,
-): string {
-  if (remoteName) {
-    const remotePrefix = `${remoteName}/`;
-    if (branchName.startsWith(remotePrefix) && branchName.length > remotePrefix.length) {
-      return branchName.slice(remotePrefix.length);
-    }
-  }
-
+export function deriveLocalBranchNameFromRemoteRef(branchName: string): string {
   const firstSeparatorIndex = branchName.indexOf("/");
   if (firstSeparatorIndex <= 0 || firstSeparatorIndex === branchName.length - 1) {
     return branchName;
diff --git a/apps/web/src/components/BranchToolbar.tsx b/apps/web/src/components/BranchToolbar.tsx
index be5f05bb9a41c8cb43843a455de4953803305476..94fcdba409fa623e38ccf45af71d69e6b592c7e7 100644
--- a/apps/web/src/components/BranchToolbar.tsx
+++ b/apps/web/src/components/BranchToolbar.tsx
@@ -179,7 +179,7 @@ export default function BranchToolbar({
     }
 
     const selectedBranchName = branch.isRemote
-      ? deriveLocalBranchNameFromRemoteRef(branch.name, branch.remoteName)
+      ? deriveLocalBranchNameFromRemoteRef(branch.name)
       : branch.name;
 
     checkoutMutation.mutate(branch.name, {