diff --git a/src/lib/onboard/sandbox-provider-cleanup.ts b/src/lib/onboard/sandbox-provider-cleanup.ts
index d23b4482516..74373890756 100644
--- a/src/lib/onboard/sandbox-provider-cleanup.ts
+++ b/src/lib/onboard/sandbox-provider-cleanup.ts
@@ -70,7 +70,7 @@ const TOLERATED_DETACH_OUTPUT_RE =
 
 const MISSING_SANDBOX_OUTPUT_RE = /sandbox[^\n]{0,200}?(?:\bNotFound\b|\bnot\s+found\b)/i;
 
-const ATTACHED_TO_SANDBOX_RE = /attached\s+to\s+sandbox\(\s*es?\s*\)?\s*:\s*([^"\n]+)/i;
+const ATTACHED_TO_SANDBOX_RE = /attached\s+to(?:\s|│)+sandbox\(\s*es?\s*\)?\s*:\s*([^"\n]+)/i;
 
 const MAX_WARNING_OUTPUT_CHARS = 500;
 
diff --git a/test/sandbox-provider-cleanup.test.ts b/test/sandbox-provider-cleanup.test.ts
index 761bc8c734f..e6dac9e2340 100644
--- a/test/sandbox-provider-cleanup.test.ts
+++ b/test/sandbox-provider-cleanup.test.ts
@@ -304,6 +304,14 @@ describe("parseAttachedSandboxes", () => {
     expect(parseAttachedSandboxes(output)).toEqual(["spark-nemo"]);
   });
 
+  it("parses an OpenShell diagnostic wrapped with continuation markers", () => {
+    const output =
+      "Error: × code: 'The system is not in a state required for the operation's\n" +
+      "│ execution', message: \"provider 'compatible-endpoint' is attached to\n" +
+      '│ sandbox(es): e2e-diag"';
+    expect(parseAttachedSandboxes(output)).toEqual(["e2e-diag"]);
+  });
+
   it("parses multiple sandbox names from the same diagnostic", () => {
     const output = "provider 'x' is attached to sandbox(es): alpha, beta, gamma";
     expect(parseAttachedSandboxes(output)).toEqual(["alpha", "beta", "gamma"]);
@@ -382,7 +390,7 @@ describe("deleteProviderWithRecovery", () => {
     expect(result.recoveryFailures).toEqual([]);
   });
 
-  it("parses attached sandbox(es) and retries delete after force-detach", () => {
+  it("retries delete after force-detaching a sandbox from a wrapped diagnostic", () => {
     let attempt = 0;
     const calls: string[][] = [];
     const runOpenshell = vi.fn((args: string[]) => {
@@ -394,7 +402,9 @@ describe("deleteProviderWithRecovery", () => {
             status: 1,
             stdout: "",
             stderr:
-              "Error: status: FailedPrecondition, message: \"provider 'p' is attached to sandbox(es): orphan-one\"",
+              "Error: × code: 'The system is not in a state required for the operation's\n" +
+              "│ execution', message: \"provider 'p' is attached to\n" +
+              '│ sandbox(es): orphan-one"',
           };
         }
         return { status: 0, stdout: "", stderr: "" };