diff --git a/script/LspProbe.lean b/script/LspProbe.lean
new file mode 100644
index 000000000000..b6e15cad575a
--- /dev/null
+++ b/script/LspProbe.lean
@@ -0,0 +1,78 @@
+import Lean.Data.Lsp
+
+/-!
+
+Usage: `lsp-probe FILE.lean`
+
+A small CLI for driving `lean --server` via `Lean.Lsp.Ipc` and dumping every
+published diagnostic for a target file. Useful for debugging language-server
+behavior end-to-end without a real editor in the loop.
+
+Mirrors the test pattern in `tests/server/diags.lean` — initialize, didOpen,
+`Ipc.collectDiagnostics`, shutdown — but as an installed binary instead of a
+CTest-only script.
+
+The spawned server defaults to `lean` on `PATH`; override with
+`LEAN_PROBE_BIN=/path/to/lean lsp-probe FILE.lean`.
+
+-/
+
+open IO Lean Lsp JsonRpc
+
+def severityName : Option DiagnosticSeverity → String
+  | some .error => "Error"
+  | some .warning => "Warning"
+  | some .information => "Info"
+  | some .hint => "Hint"
+  | none => "?"
+
+def main (args : List String) : IO UInt32 := do
+  let some path := args[0]? | do
+    eprintln "usage: lsp-probe FILE.lean"
+    return 1
+  let abs ← IO.FS.realPath (System.FilePath.mk path)
+  let uri := System.Uri.pathToUri abs.toString
+  let text ← FS.readFile abs
+
+  let leanBin := (← IO.getEnv "LEAN_PROBE_BIN").getD "lean"
+  Ipc.runWith leanBin #["--server"] do
+    Ipc.writeRequest ⟨0, "initialize",
+      (toJson <| ({ processId? := none, capabilities := {}, rootUri? := some uri }
+        : InitializeParams))⟩
+    discard <| Ipc.readResponseAs 0 InitializeResult
+    Ipc.writeNotification ⟨"initialized", InitializedParams.mk⟩
+
+    Ipc.writeNotification ⟨"textDocument/didOpen",
+      ({ textDocument := { uri, languageId := "lean", version := 1, text }
+         : DidOpenTextDocumentParams })⟩
+
+    let some notif ← Ipc.collectDiagnostics 1 uri 1
+      | do
+        println "no diagnostics received"
+        Ipc.shutdown 99
+        discard <| Ipc.waitForExit
+    let diags := notif.param.diagnostics
+    println s!"=== {diags.size} diagnostics ==="
+    for d in diags do
+      let line := d.range.start.line
+      let col := d.range.start.character
+      let code := match d.code? with
+        | some (.string s) => s
+        | some (.int n) => toString n
+        | none => "-"
+      let related := (d.relatedInformation?.getD #[]).size
+      let tags := (d.tags?.getD #[]).size
+      let msg := d.message.replace "\n" " ⏎ "
+      let dataLen := d.data?.map (·.compress.length) |>.getD 0
+      println s!"  L{line}:{col} {severityName d.severity?} [{code}] tags={tags} related={related} data={dataLen}b"
+      println s!"    msg: {msg}"
+      for ri in d.relatedInformation?.getD #[] do
+        let rline := ri.location.range.start.line
+        println s!"      ↳ L{rline}: {ri.message}"
+      if let some json := d.data? then
+        println s!"      data: {json.compress}"
+
+    Ipc.shutdown 2
+    discard <| Ipc.waitForExit
+
+  return 0
diff --git a/script/lakefile.toml b/script/lakefile.toml
index 8b289cfd8086..da0ae0ae1bec 100644
--- a/script/lakefile.toml
+++ b/script/lakefile.toml
@@ -3,3 +3,7 @@ name = "scripts"
 [[lean_exe]]
 name = "modulize"
 root = "Modulize"
+
+[[lean_exe]]
+name = "lsp-probe"
+root = "LspProbe"