diff --git a/docs/adr/0015-test-llama-backend-singleton.md b/docs/adr/0015-test-llama-backend-singleton.md
new file mode 100644
index 0000000..5a98a8b
--- /dev/null
+++ b/docs/adr/0015-test-llama-backend-singleton.md
@@ -0,0 +1,26 @@
+# ADR 0015: Share The Llama Backend In Rust Tests
+
+## Status
+
+Accepted
+
+## Context
+
+`llama-cpp-2` 0.1.151 permits backend initialization only once per process.
+AssistSupport had independent embedding and LLM engine tests that each initialized
+the backend. When the full Rust suite ran in one process, later tests failed with
+`BackendAlreadyInitialized` even though production initialization remained valid.
+
+## Decision
+
+Keep production backend ownership unchanged. Under `cfg(test)`, initialize one
+`LlamaBackend` in a `OnceLock<Arc<LlamaBackend>>` and clone the `Arc` into engine
+tests. Add a source-policy regression test so future tests do not reintroduce
+independent backend initialization.
+
+## Consequences
+
+- Rust engine tests can run together against llama-cpp 0.1.151.
+- The singleton helper is absent from production builds.
+- Tests share process-wide backend state, matching the upstream library contract.
+- Model-loading tests remain ignored unless their model fixture is available.
diff --git a/scripts/ci/require-tests-and-docs.mjs b/scripts/ci/require-tests-and-docs.mjs
index 72ba882..0e0e8f7 100644
--- a/scripts/ci/require-tests-and-docs.mjs
+++ b/scripts/ci/require-tests-and-docs.mjs
@@ -2,7 +2,12 @@ import { execSync } from 'node:child_process';
 
 const defaultBaseRef = (() => {
   try {
-    return execSync('git symbolic-ref refs/remotes/origin/HEAD', { encoding: 'utf8' }).trim().replace('refs/remotes/', '');
+    return execSync('git symbolic-ref refs/remotes/origin/HEAD', {
+      encoding: 'utf8',
+      stdio: ['ignore', 'pipe', 'ignore'],
+    })
+      .trim()
+      .replace('refs/remotes/', '');
   } catch {
     return 'origin/master';
   }
@@ -76,4 +81,4 @@ if (failures.length > 0) {
   process.exit(1);
 }
 
-console.log('Policy checks passed.');
\ No newline at end of file
+console.log('Policy checks passed.');
diff --git a/src-tauri/Cargo.lock b/src-tauri/Cargo.lock
index 41fd753..f11a2ce 100644
--- a/src-tauri/Cargo.lock
+++ b/src-tauri/Cargo.lock
@@ -708,7 +708,7 @@ dependencies = [
  "quote",
  "regex",
  "rustc-hash 1.1.0",
- "shlex",
+ "shlex 1.3.0",
  "syn 1.0.109",
  "which",
 ]
@@ -722,14 +722,14 @@ dependencies = [
  "bitflags 2.11.0",
  "cexpr",
  "clang-sys",
- "itertools 0.13.0",
+ "itertools 0.10.5",
  "log",
  "prettyplease",
  "proc-macro2",
  "quote",
  "regex",
  "rustc-hash 2.1.1",
- "shlex",
+ "shlex 1.3.0",
  "syn 2.0.117",
 ]
 
@@ -1032,14 +1032,14 @@ checksum = "37b2a672a2cb129a2e41c10b1224bb368f9f37a2b16b612598138befd7b37eb5"
 
 [[package]]
 name = "cc"
-version = "1.2.56"
+version = "1.2.66"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "aebf35691d1bfb0ac386a69bac2fde4dd276fb618cf8bf4f5318fe285e821bb2"
+checksum = "f5d6cac793997bd970000024b2934968efe83b382de4fdcf4fcb46b6ee4ad996"
 dependencies = [
  "find-msvc-tools",
  "jobserver",
  "libc",
- "shlex",
+ "shlex 2.0.1",
 ]
 
 [[package]]
@@ -2457,7 +2457,7 @@ dependencies = [
  "libc",
  "option-ext",
  "redox_users",
- "windows-sys 0.61.2",
+ "windows-sys 0.59.0",
 ]
 
 [[package]]
@@ -2489,7 +2489,7 @@ version = "0.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "330c60081dcc4c72131f8eb70510f1ac07223e5d4163db481a04a0befcffa412"
 dependencies = [
- "libloading 0.8.9",
+ "libloading 0.7.4",
 ]
 
 [[package]]
@@ -2717,7 +2717,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "39cab71617ae0d63f51a36d69f866391735b51691dbda63cf6f96d042b63efeb"
 dependencies = [
  "libc",
- "windows-sys 0.61.2",
+ "windows-sys 0.52.0",
 ]
 
 [[package]]
@@ -3147,7 +3147,7 @@ dependencies = [
  "libc",
  "log",
  "rustversion",
- "windows-link 0.2.1",
+ "windows-link 0.1.3",
  "windows-result",
 ]
 
@@ -4090,7 +4090,7 @@ dependencies = [
  "portable-atomic",
  "portable-atomic-util",
  "serde_core",
- "windows-sys 0.61.2",
+ "windows-sys 0.52.0",
 ]
 
 [[package]]
@@ -5149,9 +5149,9 @@ checksum = "6373607a59f0be73a39b6fe456b8192fcc3585f602af20751600e974dd455e77"
 
 [[package]]
 name = "llama-cpp-2"
-version = "0.1.135"
+version = "0.1.151"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "85b660b832461ef32da66c7acedf35251cdc9e13c0e816bc5904b717cd1e5b25"
+checksum = "36ead0925a19d754d5d13761ceb0f0fe49d36f8103c3596588ac1fb8911e5223"
 dependencies = [
  "encoding_rs",
  "enumflags2",
@@ -5163,9 +5163,9 @@ dependencies = [
 
 [[package]]
 name = "llama-cpp-sys-2"
-version = "0.1.135"
+version = "0.1.151"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "95cf8be1ff000b531ac0523c66a9ffce3cef6d09a5d95b21cad745bedb115468"
+checksum = "23c676b02f8f2bdd9d7df7bcca0bd176b27964440998e7aa31c6fe32552964d0"
 dependencies = [
  "bindgen 0.72.1",
  "cc",
@@ -5442,7 +5442,7 @@ dependencies = [
  "png 0.18.1",
  "serde",
  "thiserror 2.0.18",
- "windows-sys 0.61.2",
+ "windows-sys 0.60.2",
 ]
 
 [[package]]
@@ -5593,7 +5593,7 @@ version = "0.50.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7957b9740744892f114936ab4a57b3f487491bbeafaf8083688b16841a4240e5"
 dependencies = [
- "windows-sys 0.61.2",
+ "windows-sys 0.59.0",
 ]
 
 [[package]]
@@ -6509,7 +6509,7 @@ version = "0.14.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "343d3bd7056eda839b03204e68deff7d1b13aba7af2b2fd16890697274262ee7"
 dependencies = [
- "heck 0.5.0",
+ "heck 0.4.1",
  "itertools 0.14.0",
  "log",
  "multimap",
@@ -7228,7 +7228,7 @@ dependencies = [
  "errno",
  "libc",
  "linux-raw-sys 0.11.0",
- "windows-sys 0.61.2",
+ "windows-sys 0.52.0",
 ]
 
 [[package]]
@@ -7674,6 +7674,12 @@ version = "1.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0fda2ff0d084019ba4d7c6f371c95d8fd75ce3524c3cb8fb653a3023f6323e64"
 
+[[package]]
+name = "shlex"
+version = "2.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f8fadd59c855ef2080decdef8ff161eb6661b86933c9d82e5ba29dc602a55aba"
+
 [[package]]
 name = "signal-hook-registry"
 version = "1.4.8"
@@ -7757,7 +7763,7 @@ version = "0.8.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c1c97747dbf44bb1ca44a561ece23508e99cb592e862f22222dcf42f51d1e451"
 dependencies = [
- "heck 0.5.0",
+ "heck 0.4.1",
  "proc-macro2",
  "quote",
  "syn 2.0.117",
@@ -7769,7 +7775,7 @@ version = "0.9.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5f103c50866b8743da9429b8a581d81a27c2d3a9c4ac7df8f8571c1dd7896eda"
 dependencies = [
- "heck 0.5.0",
+ "heck 0.4.1",
  "proc-macro2",
  "quote",
  "syn 2.0.117",
@@ -8395,7 +8401,7 @@ dependencies = [
  "getrandom 0.4.1",
  "once_cell",
  "rustix 1.1.3",
- "windows-sys 0.61.2",
+ "windows-sys 0.52.0",
 ]
 
 [[package]]
@@ -8903,7 +8909,7 @@ dependencies = [
  "png 0.18.1",
  "serde",
  "thiserror 2.0.18",
- "windows-sys 0.61.2",
+ "windows-sys 0.60.2",
 ]
 
 [[package]]
@@ -9566,7 +9572,7 @@ version = "0.1.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c2a7b1c03c876122aa43f3020e6c3c3ee5c05081c9a00739faf7503aeba10d22"
 dependencies = [
- "windows-sys 0.61.2",
+ "windows-sys 0.48.0",
 ]
 
 [[package]]
diff --git a/src-tauri/src/kb/embeddings.rs b/src-tauri/src/kb/embeddings.rs
index fbfdd8f..80a89f7 100644
--- a/src-tauri/src/kb/embeddings.rs
+++ b/src-tauri/src/kb/embeddings.rs
@@ -282,7 +282,7 @@ mod tests {
 
     #[test]
     fn test_engine_creation() {
-        let backend = Arc::new(LlamaBackend::init().expect("backend init"));
+        let backend = crate::test_llama_backend();
         let engine = EmbeddingEngine::new(backend);
         assert!(engine.is_ok());
 
diff --git a/src-tauri/src/lib.rs b/src-tauri/src/lib.rs
index 007817c..7e068a1 100644
--- a/src-tauri/src/lib.rs
+++ b/src-tauri/src/lib.rs
@@ -114,6 +114,15 @@ impl Default for AppState {
     }
 }
 
+#[cfg(test)]
+pub(crate) fn test_llama_backend() -> Arc<LlamaBackend> {
+    static BACKEND: std::sync::OnceLock<Arc<LlamaBackend>> = std::sync::OnceLock::new();
+
+    Arc::clone(BACKEND.get_or_init(|| {
+        Arc::new(LlamaBackend::init().expect("test llama backend should initialize"))
+    }))
+}
+
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
 pub fn run() {
     #[cfg(target_os = "macos")]
diff --git a/src-tauri/src/llm.rs b/src-tauri/src/llm.rs
index c9ea0fc..41258c8 100644
--- a/src-tauri/src/llm.rs
+++ b/src-tauri/src/llm.rs
@@ -514,7 +514,7 @@ mod tests {
 
     #[test]
     fn test_engine_creation() {
-        let backend = Arc::new(LlamaBackend::init().expect("backend init"));
+        let backend = crate::test_llama_backend();
         let engine = LlmEngine::new(backend);
         assert!(engine.is_ok(), "Engine should initialize");
 
@@ -545,7 +545,7 @@ mod tests {
         }
 
         // Create engine
-        let backend = Arc::new(LlamaBackend::init().expect("backend init"));
+        let backend = crate::test_llama_backend();
         let engine = LlmEngine::new(backend).expect("Failed to create engine");
         assert!(!engine.is_model_loaded());
 
diff --git a/src-tauri/tests/llama_backend_singleton_policy.rs b/src-tauri/tests/llama_backend_singleton_policy.rs
new file mode 100644
index 0000000..b9e7db8
--- /dev/null
+++ b/src-tauri/tests/llama_backend_singleton_policy.rs
@@ -0,0 +1,16 @@
+#[test]
+fn engine_tests_share_the_process_wide_llama_backend() {
+    let lib = include_str!("../src/lib.rs");
+    let embeddings = include_str!("../src/kb/embeddings.rs");
+    let llm = include_str!("../src/llm.rs");
+
+    assert!(lib.contains("fn test_llama_backend()"));
+    assert!(embeddings.contains("let backend = crate::test_llama_backend();"));
+    assert_eq!(
+        llm.matches("let backend = crate::test_llama_backend();")
+            .count(),
+        2
+    );
+    assert!(!embeddings.contains("LlamaBackend::init().expect(\"backend init\")"));
+    assert!(!llm.contains("LlamaBackend::init().expect(\"backend init\")"));
+}