From 8a9e66aca9cc6dbaecd14f783bddb90edb704777 Mon Sep 17 00:00:00 2001
From: lkdvos <ldevos98@gmail.com>
Date: Wed, 6 May 2026 14:21:00 -0400
Subject: [PATCH] Pass correct views to `SymTridiagonal`

---
 src/factorizations/lanczos.jl | 4 +++-
 test/issues.jl                | 7 +++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/factorizations/lanczos.jl b/src/factorizations/lanczos.jl
index 7d8a7c3a..01ffdff4 100644
--- a/src/factorizations/lanczos.jl
+++ b/src/factorizations/lanczos.jl
@@ -50,7 +50,9 @@ function basis(F::LanczosFactorization)
     return length(F.V) == F.k ? F.V :
         error("Not keeping vectors during Lanczos factorization")
 end
-rayleighquotient(F::LanczosFactorization) = SymTridiagonal(F.αs, F.βs)
+function rayleighquotient(F::LanczosFactorization)
+    return SymTridiagonal(view(F.αs, 1:(F.k)), view(F.βs, 1:(F.k - 1)))
+end
 residual(F::LanczosFactorization) = F.r
 @inbounds normres(F::LanczosFactorization) = F.βs[F.k]
 rayleighextension(F::LanczosFactorization) = SimpleBasisVector(F.k, F.k)
diff --git a/test/issues.jl b/test/issues.jl
index f2edc5d3..cdc9581f 100644
--- a/test/issues.jl
+++ b/test/issues.jl
@@ -27,3 +27,10 @@ end
     @test info.numops == 2
     @test info.normres == 0.0
 end
+
+# https://github.com/Jutho/KrylovKit.jl/issues/156
+@testset "Issue #156" begin
+    vals, vecs, info = eigsolve([1 0; 0 1])
+    @test info.converged ≥ 1
+    @test all(≈(1.0), vals[1:(info.converged)])
+end