diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index d4ea3b9622..24da69780d 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -155,6 +155,7 @@ if (NOT WIN32 OR NOT BUILD_SHARED_LIBS)
     llama_build_and_test(test-grammar-parser.cpp)
     llama_build_and_test(test-grammar-integration.cpp)
     llama_build_and_test(test-llama-grammar.cpp)
+    llama_build_and_test(test-batch-alloc.cpp)
     llama_build_and_test(test-chat.cpp WORKING_DIRECTORY ${PROJECT_SOURCE_DIR})
     target_include_directories(test-chat PRIVATE ${PROJECT_SOURCE_DIR}/tools/server)
     target_link_libraries(test-chat PRIVATE server-context)
diff --git a/tests/test-batch-alloc.cpp b/tests/test-batch-alloc.cpp
new file mode 100644
index 0000000000..66d29d6f51
--- /dev/null
+++ b/tests/test-batch-alloc.cpp
@@ -0,0 +1,674 @@
+#include "testing.h"
+
+#include "llama.h"
+
+#include "../src/llama-batch.h"
+#include "../src/llama-memory.h"
+#include "../src/llama-vocab.h"
+
+#include <cstdlib>
+#include <initializer_list>
+#include <map>
+#include <string>
+#include <utility>
+#include <vector>
+
+// mock memory that only provides per-sequence position ranges
+struct mock_memory : public llama_memory_i {
+    std::map<llama_seq_id, std::pair<llama_pos, llama_pos>> ranges; // seq_id -> [pos_min, pos_max]
+
+    llama_memory_context_ptr init_batch(llama_batch_allocr &, uint32_t, bool) override {  GGML_ASSERT(false && "not implemented"); }
+    llama_memory_context_ptr init_full() override {  GGML_ASSERT(false && "not implemented"); }
+    llama_memory_context_ptr init_update(llama_context *, bool) override { GGML_ASSERT(false && "not implemented"); }
+
+    bool get_can_shift() const override { GGML_ASSERT(false && "not implemented"); }
+
+    void clear(bool) override { GGML_ASSERT(false && "not implemented"); }
+
+    bool seq_rm  (llama_seq_id, llama_pos, llama_pos) override { GGML_ASSERT(false && "not implemented"); }
+    void seq_cp  (llama_seq_id, llama_seq_id, llama_pos, llama_pos) override { GGML_ASSERT(false && "not implemented"); }
+    void seq_keep(llama_seq_id) override { GGML_ASSERT(false && "not implemented"); }
+    void seq_add (llama_seq_id, llama_pos, llama_pos, llama_pos) override { GGML_ASSERT(false && "not implemented"); }
+    void seq_div (llama_seq_id, llama_pos, llama_pos, int) override { GGML_ASSERT(false && "not implemented");  }
+
+    llama_pos seq_pos_min(llama_seq_id seq_id) const override {
+        auto it = ranges.find(seq_id);
+        return it == ranges.end() ? -1 : it->second.first;
+    }
+
+    llama_pos seq_pos_max(llama_seq_id seq_id) const override {
+        auto it = ranges.find(seq_id);
+        return it == ranges.end() ? -1 : it->second.second;
+    }
+
+    std::map<ggml_backend_buffer_type_t, size_t> memory_breakdown() const override { return {}; }
+
+    void state_write(llama_io_write_i &, llama_seq_id, llama_state_seq_flags) const override { GGML_ASSERT(false && "not implemented"); }
+    void state_read (llama_io_read_i &,  llama_seq_id, llama_state_seq_flags) override { GGML_ASSERT(false && "not implemented"); }
+};
+
+// builds embedding batches - an empty llama_vocab rejects all token ids, so
+// the tests use embeddings everywhere except the token validation tests
+struct batch_builder {
+    uint32_t n_embd;
+
+    std::vector<float>     embd;
+    std::vector<llama_pos> pos;
+    std::vector<int32_t>   n_seq_id;
+    std::vector<int8_t>    logits;
+
+    std::vector<std::vector<llama_seq_id>> seq;
+    std::vector<llama_seq_id *>            seq_ptr;
+
+    batch_builder(uint32_t n_embd = 2) : n_embd(n_embd) {}
+
+    // embd values are 100*i + k so that ubatch contents can be traced back to batch indices
+    void add(llama_pos p, std::initializer_list<llama_seq_id> seq_ids, bool output) {
+        const int32_t i = (int32_t) seq.size();
+        for (uint32_t k = 0; k < n_embd; ++k) {
+            embd.push_back(100.0f*i + k);
+        }
+        pos.push_back(p);
+        n_seq_id.push_back((int32_t) seq_ids.size());
+        seq.emplace_back(seq_ids);
+        logits.push_back(output ? 1 : 0);
+    }
+
+    llama_batch make(bool with_pos = true, bool with_seq = true, bool with_logits = true) {
+        seq_ptr.clear();
+        for (auto & s : seq) {
+            seq_ptr.push_back(s.data());
+        }
+        seq_ptr.push_back(nullptr);
+
+        llama_batch res = {};
+        res.n_tokens = (int32_t) seq.size();
+        res.embd     = embd.data();
+        res.pos      = with_pos    ? pos.data()      : nullptr;
+        res.n_seq_id = with_seq    ? n_seq_id.data() : nullptr;
+        res.seq_id   = with_seq    ? seq_ptr.data()  : nullptr;
+        res.logits   = with_logits ? logits.data()   : nullptr;
+
+        return res;
+    }
+};
+
+static void test_init(testing & t) {
+    llama_vocab vocab;
+
+    t.test("rejects_n_seq_max_too_large", [&](testing & t) {
+        batch_builder bb;
+        bb.add(0, {0}, true);
+
+        llama_batch_allocr ba(1);
+        t.assert_true(!ba.init(bb.make(), vocab, nullptr, bb.n_embd, LLAMA_MAX_SEQ + 1, false));
+    });
+
+    t.test("rejects_invalid_token", [&](testing & t) {
+        llama_token tok = 0; // empty vocab -> every token id is out of range
+        llama_batch batch = llama_batch_get_one(&tok, 1);
+
+        llama_batch_allocr ba(1);
+        t.assert_true("token id >= n_tokens", !ba.init(batch, vocab, nullptr, 0, 1, false));
+
+        tok = -1;
+        t.assert_true("negative token id", !ba.init(batch, vocab, nullptr, 0, 1, false));
+    });
+
+    t.test("rejects_invalid_seq_id", [&](testing & t) {
+        llama_batch_allocr ba(1);
+
+        {
+            batch_builder bb;
+            bb.add(0, {4}, true);
+            t.assert_true("seq_id >= n_seq_max", !ba.init(bb.make(), vocab, nullptr, bb.n_embd, 4, false));
+        }
+        {
+            batch_builder bb;
+            bb.add(0, {-1}, true);
+            t.assert_true("negative seq_id", !ba.init(bb.make(), vocab, nullptr, bb.n_embd, 4, false));
+        }
+    });
+
+    t.test("autofill_defaults", [&](testing & t) {
+        batch_builder bb;
+        for (int i = 0; i < 4; ++i) {
+            bb.add(0, {0}, false);
+        }
+
+        llama_batch_allocr ba(1);
+        t.assert_true(ba.init(bb.make(false, false, false), vocab, nullptr, bb.n_embd, 4, false));
+
+        const llama_batch & batch = ba.get_batch();
+
+        t.assert_equal(4u, ba.get_n_tokens());
+
+        for (int i = 0; i < 4; ++i) {
+            t.assert_equal("pos defaults to 0..n-1", i, batch.pos[i]);
+            t.assert_equal("n_seq_id defaults to 1", 1, batch.n_seq_id[i]);
+            t.assert_equal("seq_id defaults to 0",   0, batch.seq_id[i][0]);
+        }
+
+        t.assert_equal("only the last token is an output", 1u, ba.get_n_outputs());
+        t.assert_equal(0, (int) batch.logits[0]);
+        t.assert_equal(1, (int) batch.logits[3]);
+
+        t.assert_equal(0, ba.seq_pos_min(0));
+        t.assert_equal(3, ba.seq_pos_max(0));
+        t.assert_equal(-1, ba.seq_pos_min(1));
+    });
+
+    t.test("output_all", [&](testing & t) {
+        batch_builder bb;
+        for (int i = 0; i < 4; ++i) {
+            bb.add(i, {0}, false);
+        }
+
+        llama_batch_allocr ba(1);
+        t.assert_true(ba.init(bb.make(true, true, false), vocab, nullptr, bb.n_embd, 4, true));
+        t.assert_equal(4u, ba.get_n_outputs());
+    });
+
+    t.test("explicit_logits", [&](testing & t) {
+        batch_builder bb;
+        bb.add(0, {0}, true);
+        bb.add(1, {0}, false);
+        bb.add(2, {0}, true);
+
+        llama_batch_allocr ba(1);
+        t.assert_true(ba.init(bb.make(), vocab, nullptr, bb.n_embd, 4, false));
+        t.assert_equal(2u, ba.get_n_outputs());
+
+        llama_ubatch ub = ba.split_simple(10);
+        t.assert_equal(3u, ub.n_tokens);
+        t.assert_equal(1, (int) ub.output[0]);
+        t.assert_equal(0, (int) ub.output[1]);
+        t.assert_equal(1, (int) ub.output[2]);
+
+        const auto & out_ids = ba.get_out_ids();
+        t.assert_equal((size_t) 2, out_ids.size());
+        t.assert_equal(0, out_ids[0]);
+        t.assert_equal(2, out_ids[1]);
+    });
+
+    t.test("pos_from_memory", [&](testing & t) {
+        mock_memory mem;
+        mem.ranges[0] = {0, 9};
+
+        batch_builder bb;
+        for (int i = 0; i < 3; ++i) {
+            bb.add(0, {0}, false);
+        }
+
+        llama_batch_allocr ba(1);
+        t.assert_true(ba.init(bb.make(false, true, false), vocab, &mem, bb.n_embd, 4, false));
+
+        t.assert_equal("pos continues after memory", 10, ba.seq_pos_min(0));
+        t.assert_equal(12, ba.seq_pos_max(0));
+    });
+
+    t.test("pos_continuity_with_memory", [&](testing & t) {
+        mock_memory mem;
+        mem.ranges[0] = {0, 9};
+
+        llama_batch_allocr ba(1);
+
+        {
+            batch_builder bb;
+            bb.add(10, {0}, false);
+            bb.add(11, {0}, true);
+            t.assert_true("pos_max + 1 is accepted", ba.init(bb.make(), vocab, &mem, bb.n_embd, 4, false));
+        }
+        {
+            batch_builder bb;
+            bb.add(11, {0}, false);
+            bb.add(12, {0}, true);
+            t.assert_true("gap after memory is rejected", !ba.init(bb.make(), vocab, &mem, bb.n_embd, 4, false));
+        }
+        {
+            batch_builder bb;
+            bb.add(9, {0}, false);
+            bb.add(10, {0}, true);
+            t.assert_true("overlap with memory is rejected", !ba.init(bb.make(), vocab, &mem, bb.n_embd, 4, false));
+        }
+    });
+
+    t.test("rejects_non_continuous_positions", [&](testing & t) {
+        batch_builder bb;
+        bb.add(0, {0}, false);
+        bb.add(1, {0}, false);
+        bb.add(3, {0}, true);
+
+        llama_batch_allocr ba(1);
+        t.assert_true(!ba.init(bb.make(), vocab, nullptr, bb.n_embd, 4, false));
+    });
+
+    t.test("rejects_decreasing_positions", [&](testing & t) {
+        batch_builder bb;
+        const llama_pos    pos[7] = {4, 5, 0, 1, 6, 2, 3};
+        const llama_seq_id seq[7] = {0, 0, 1, 1, 0, 1, 0};
+        for (int i = 0; i < 7; ++i) {
+            bb.add(pos[i], {seq[i]}, false);
+        }
+        // seq 0 sees positions 4,5,6,3 in batch order -> the trailing 3 decreases
+
+        llama_batch_allocr ba(1);
+        t.assert_true(!ba.init(bb.make(true, true, false), vocab, nullptr, bb.n_embd, 4, false));
+    });
+
+    t.test("allows_equal_positions_in_seq", [&](testing & t) {
+        batch_builder bb;
+        bb.add(0, {0}, false);
+        bb.add(0, {0}, false);
+        bb.add(1, {0}, true);
+
+        llama_batch_allocr ba(1);
+        t.assert_true(ba.init(bb.make(true, true, false), vocab, nullptr, bb.n_embd, 4, false));
+    });
+
+
+    t.test("rejects_coupled_diverged_seqs", [&](testing & t) {
+        batch_builder bb;
+        bb.add(6, {0, 1}, true);
+
+        llama_batch_allocr ba(1);
+
+        mock_memory mem;
+        mem.ranges[0] = {0, 5};
+        mem.ranges[1] = {2, 5}; // same pos_max, different pos_min -> diverged
+        t.assert_true(!ba.init(bb.make(), vocab, &mem, bb.n_embd, 4, false));
+
+        mem.ranges[1] = {0, 5};
+        t.assert_true(ba.init(bb.make(), vocab, &mem, bb.n_embd, 4, false));
+    });
+}
+
+static void test_split(testing & t) {
+    llama_vocab vocab;
+
+    t.test("split_simple_chunks", [&](testing & t) {
+        batch_builder bb;
+        for (int i = 0; i < 5; ++i) {
+            bb.add(i, {0}, i == 4);
+        }
+
+        llama_batch_allocr ba(1);
+        t.assert_true(ba.init(bb.make(), vocab, nullptr, bb.n_embd, 4, false));
+
+        llama_ubatch ub = ba.split_simple(2);
+        t.assert_equal(2u, ub.n_tokens);
+        t.assert_true(!ub.equal_seqs());
+        t.assert_equal(1u, ub.n_seqs_unq);
+        t.assert_equal(0, ub.seq_id_unq[0]);
+        t.assert_equal(0, ub.seq_idx[0]);
+        for (int i = 0; i < 2; ++i) {
+            t.assert_equal(i, ub.pos[i]);
+            t.assert_equal(1, ub.n_seq_id[i]);
+            t.assert_equal(0, ub.seq_id[i][0]);
+            t.assert_equal(100.0f*i, ub.embd[i*bb.n_embd]);
+            t.assert_equal(100.0f*i + 1, ub.embd[i*bb.n_embd + 1]);
+        }
+
+        ub = ba.split_simple(2);
+        t.assert_equal(2u, ub.n_tokens);
+        t.assert_equal(2, ub.pos[0]);
+        t.assert_equal(3, ub.pos[1]);
+
+        ub = ba.split_simple(2);
+        t.assert_equal(1u, ub.n_tokens);
+        t.assert_equal(4, ub.pos[0]);
+        t.assert_equal(1, (int) ub.output[0]);
+
+        t.assert_equal(5u, ba.get_n_used());
+
+        ub = ba.split_simple(2);
+        t.assert_equal("batch is consumed", 0u, ub.n_tokens);
+
+        const auto & out_ids = ba.get_out_ids();
+        t.assert_equal((size_t) 1, out_ids.size());
+        t.assert_equal(4, out_ids[0]);
+    });
+
+    t.test("split_reset_allows_resplit", [&](testing & t) {
+        batch_builder bb;
+        for (int i = 0; i < 3; ++i) {
+            bb.add(i, {0}, i == 2);
+        }
+
+        llama_batch_allocr ba(1);
+        t.assert_true(ba.init(bb.make(), vocab, nullptr, bb.n_embd, 4, false));
+
+        while (ba.split_simple(1).n_tokens > 0) {
+        }
+        t.assert_equal(3u, ba.get_n_used());
+
+        ba.split_reset();
+        t.assert_equal(0u, ba.get_n_used());
+
+        llama_ubatch ub = ba.split_simple(10);
+        t.assert_equal(3u, ub.n_tokens);
+    });
+
+    t.test("split_equal_unequal_lengths", [&](testing & t) {
+        batch_builder bb;
+        for (int i = 0; i < 4; ++i) {
+            bb.add(i, {0}, i == 3);
+        }
+        for (int i = 0; i < 2; ++i) {
+            bb.add(i, {1}, i == 1);
+        }
+
+        llama_batch_allocr ba(1);
+        t.assert_true(ba.init(bb.make(), vocab, nullptr, bb.n_embd, 4, false));
+
+        llama_ubatch ub = ba.split_equal(8, false, 0);
+        t.assert_true(ub.equal_seqs());
+        t.assert_equal("both seqs advance by the shorter length", 4u, ub.n_tokens);
+        t.assert_equal(2u, ub.n_seq_tokens);
+        t.assert_equal(2u, ub.n_seqs);
+        t.assert_equal(2u, ub.n_seqs_unq);
+        // tokens are grouped per sequence set: [s0 s0 s1 s1]
+        t.assert_equal(0, ub.seq_id[0][0]);
+        t.assert_equal(0, ub.seq_id[1][0]);
+        t.assert_equal(1, ub.seq_id[2][0]);
+        t.assert_equal(1, ub.seq_id[3][0]);
+        t.assert_equal(0, ub.pos[0]);
+        t.assert_equal(1, ub.pos[1]);
+        t.assert_equal(0, ub.pos[2]);
+        t.assert_equal(1, ub.pos[3]);
+
+        ub = ba.split_equal(8, false, 0);
+        t.assert_equal("only seq 0 remains", 2u, ub.n_tokens);
+        t.assert_equal(1u, ub.n_seqs);
+        t.assert_equal(2, ub.pos[0]);
+        t.assert_equal(3, ub.pos[1]);
+
+        ub = ba.split_equal(8, false, 0);
+        t.assert_equal(0u, ub.n_tokens);
+
+        t.assert_equal(6u, ba.get_n_used());
+    });
+
+    t.test("split_equal_coupled", [&](testing & t) {
+        batch_builder bb;
+        bb.add(0, {0, 1}, false);
+        bb.add(1, {0, 1}, true);
+
+        llama_batch_allocr ba(1);
+        t.assert_true(ba.init(bb.make(), vocab, nullptr, bb.n_embd, 4, false));
+
+        llama_ubatch ub = ba.split_equal(4, true, 0);
+        t.assert_equal("sequential split rejects coupled seqs", 0u, ub.n_tokens);
+
+        ub = ba.split_equal(4, false, 0);
+        t.assert_equal(2u, ub.n_tokens);
+        t.assert_equal("one sequence set", 1u, ub.n_seqs);
+        t.assert_equal("two unique seq ids", 2u, ub.n_seqs_unq);
+        t.assert_equal(2, ub.n_seq_id[0]);
+        t.assert_equal(0, ub.seq_idx[0]);
+        t.assert_equal(1, ub.seq_idx[1]);
+    });
+
+    t.test("split_seq_per_sequence", [&](testing & t) {
+        batch_builder bb;
+        for (llama_seq_id s = 0; s < 3; ++s) {
+            bb.add(0, {s}, false);
+            bb.add(1, {s}, true);
+        }
+
+        llama_batch_allocr ba(1);
+        t.assert_true(ba.init(bb.make(), vocab, nullptr, bb.n_embd, 4, false));
+
+        for (llama_seq_id s = 0; s < 3; ++s) {
+            llama_ubatch ub = ba.split_seq(8);
+            t.assert_equal(2u, ub.n_tokens);
+            t.assert_equal(1u, ub.n_seqs);
+            t.assert_equal(s, ub.seq_id[0][0]);
+            t.assert_equal(s, ub.seq_id_unq[0]);
+        }
+
+        t.assert_equal(0u, ba.split_seq(8).n_tokens);
+        t.assert_equal(6u, ba.get_n_used());
+    });
+
+    t.test("ubatch_reserve", [&](testing & t) {
+        llama_batch_allocr ba(1);
+
+        llama_ubatch ub = ba.ubatch_reserve(3, 2);
+        t.assert_equal(6u, ub.n_tokens);
+        t.assert_equal(3u, ub.n_seq_tokens);
+        t.assert_equal(2u, ub.n_seqs);
+        t.assert_equal(2u, ub.n_seqs_unq);
+        t.assert_true(ub.equal_seqs());
+        t.assert_equal(0, ub.seq_id_unq[0]);
+        t.assert_equal(1, ub.seq_id_unq[1]);
+        t.assert_true(ub.token != nullptr);
+        t.assert_true(ub.embd == nullptr);
+    });
+}
+
+static void test_keep_tail(testing & t) {
+    llama_vocab vocab;
+
+    // batch with n_tokens[s] tokens for each seq s, output on the last token of each seq
+    auto make_batch = [](batch_builder & bb, std::initializer_list<int> n_tokens) {
+        llama_seq_id s = 0;
+        for (int n : n_tokens) {
+            for (int i = 0; i < n; ++i) {
+                bb.add(i, {s}, i == n - 1);
+            }
+            ++s;
+        }
+        return bb.make();
+    };
+
+    t.test("noop_when_seqs_complete", [&](testing & t) {
+        batch_builder bb;
+
+        llama_batch_allocr ba(1);
+        t.assert_true(ba.init(make_batch(bb, {2, 2}), vocab, nullptr, bb.n_embd, 4, false));
+
+        llama_ubatch ub = ba.split_equal(4, false, 2);
+        t.assert_equal("both seqs fit whole", 4u, ub.n_tokens);
+        t.assert_equal(2u, ub.n_seqs);
+        t.assert_equal(2u, ub.n_seq_tokens);
+
+        t.assert_equal(0u, ba.split_equal(4, false, 2).n_tokens);
+    });
+
+    t.test("defers_seq_with_short_remainder", [&](testing & t) {
+        batch_builder bb;
+
+        llama_batch_allocr ba(1);
+        t.assert_true(ba.init(make_batch(bb, {2, 3}), vocab, nullptr, bb.n_embd, 4, false));
+
+        // expansion stops at 2 tokens per seq: seq 0 completes, seq 1 would be left
+        // with 1 < n_keep_tail remaining, so it is deferred entirely
+        llama_ubatch ub = ba.split_equal(4, true, 2);
+        t.assert_equal(2u, ub.n_tokens);
+        t.assert_equal(1u, ub.n_seqs);
+        t.assert_equal(0, ub.seq_id[0][0]);
+        t.assert_equal(2u, ba.get_n_used());
+
+        ub = ba.split_equal(4, true, 2);
+        t.assert_equal("deferred seq comes back whole", 3u, ub.n_tokens);
+        t.assert_equal(1u, ub.n_seqs);
+        t.assert_equal(1, ub.seq_id[0][0]);
+        for (int i = 0; i < 3; ++i) {
+            t.assert_equal(i, ub.pos[i]);
+        }
+
+        t.assert_equal(5u, ba.get_n_used());
+        t.assert_equal(0u, ba.split_equal(4, true, 2).n_tokens);
+    });
+
+    t.test("completes_first_seq_when_all_violate", [&](testing & t) {
+        batch_builder bb;
+
+        llama_batch_allocr ba(1);
+        t.assert_true(ba.init(make_batch(bb, {3, 3}), vocab, nullptr, bb.n_embd, 4, false));
+
+        // expansion stops at 2 tokens per seq, leaving both with 1 < n_keep_tail remaining;
+        // seq 0 still fits in n_ubatch, so it is extended to completion and emitted alone
+        llama_ubatch ub = ba.split_equal(4, false, 2);
+        t.assert_equal(3u, ub.n_tokens);
+        t.assert_equal(1u, ub.n_seqs);
+        t.assert_equal(3u, ub.n_seq_tokens);
+        t.assert_equal(0, ub.seq_id[0][0]);
+        for (int i = 0; i < 3; ++i) {
+            t.assert_equal(i, ub.pos[i]);
+        }
+        t.assert_equal(3u, ba.get_n_used());
+
+        ub = ba.split_equal(4, false, 2);
+        t.assert_equal(3u, ub.n_tokens);
+        t.assert_equal(1, ub.seq_id[0][0]);
+        t.assert_equal(6u, ba.get_n_used());
+    });
+
+    t.test("truncates_to_preserve_tail", [&](testing & t) {
+        batch_builder bb;
+
+        llama_batch_allocr ba(1);
+        t.assert_true(ba.init(make_batch(bb, {5}), vocab, nullptr, bb.n_embd, 4, false));
+
+        // 4 tokens would leave a remainder of 1, and the seq does not fit in n_ubatch,
+        // so the ubatch is truncated until n_keep_tail tokens remain
+        llama_ubatch ub = ba.split_equal(4, false, 2);
+        t.assert_equal(3u, ub.n_tokens);
+        t.assert_equal(1u, ub.n_seqs);
+        t.assert_equal(2, ub.pos[2]);
+        t.assert_equal(3u, ba.get_n_used());
+
+        ub = ba.split_equal(4, false, 2);
+        t.assert_equal("trailing tokens stay in one ubatch", 2u, ub.n_tokens);
+        t.assert_equal(3, ub.pos[0]);
+        t.assert_equal(4, ub.pos[1]);
+        t.assert_equal(1, (int) ub.output[1]);
+
+        t.assert_equal(5u, ba.get_n_used());
+    });
+
+    t.test("keeps_full_ubatch_with_sufficient_remainder", [&](testing & t) {
+        batch_builder bb;
+
+        llama_batch_allocr ba(1);
+        t.assert_true(ba.init(make_batch(bb, {6}), vocab, nullptr, bb.n_embd, 4, false));
+
+        llama_ubatch ub = ba.split_equal(4, false, 2);
+        t.assert_equal("remainder >= n_keep_tail, no truncation", 4u, ub.n_tokens);
+
+        ub = ba.split_equal(4, false, 2);
+        t.assert_equal(2u, ub.n_tokens);
+        t.assert_equal(4, ub.pos[0]);
+        t.assert_equal(5, ub.pos[1]);
+
+        t.assert_equal(6u, ba.get_n_used());
+    });
+
+    t.test("multi_seq_prefix_kept", [&](testing & t) {
+        batch_builder bb;
+
+        llama_batch_allocr ba(1);
+        t.assert_true(ba.init(make_batch(bb, {3, 4}), vocab, nullptr, bb.n_embd, 6, false));
+
+        // expansion stops at 3 tokens per seq: seq 0 completes, seq 1 has 1 < n_keep_tail
+        // remaining and is deferred even though its tokens were already gathered
+        llama_ubatch ub = ba.split_equal(6, true, 2);
+        t.assert_equal(3u, ub.n_tokens);
+        t.assert_equal(1u, ub.n_seqs);
+        t.assert_equal(0, ub.seq_id[0][0]);
+        t.assert_equal(3u, ba.get_n_used());
+
+        ub = ba.split_equal(6, true, 2);
+        t.assert_equal(4u, ub.n_tokens);
+        t.assert_equal(1, ub.seq_id[0][0]);
+        t.assert_equal(7u, ba.get_n_used());
+    });
+}
+
+static void test_mrope(testing & t) {
+    llama_vocab vocab;
+
+    t.test("pos_layout_and_split", [&](testing & t) {
+        const uint32_t n_pos = 4;
+        const uint32_t n_embd = 2;
+
+        batch_builder bb(n_embd);
+        bb.add(10, {0}, false);
+        bb.add(11, {0}, true);
+
+        // M-RoPE positions for embeddings are laid out [n_pos][n_tokens]
+        std::vector<llama_pos> pos = {
+            10, 11, // temporal
+             5,  6, // y
+             7,  8, // x
+             0,  0,
+        };
+
+        llama_batch batch = bb.make(false, true, true);
+        batch.pos = pos.data();
+
+        llama_batch_allocr ba(n_pos);
+        t.assert_true(ba.init(batch, vocab, nullptr, n_embd, 4, false));
+
+        llama_ubatch ub = ba.split_simple(2);
+        t.assert_equal(2u, ub.n_tokens);
+        t.assert_equal(n_pos, ub.n_pos);
+        t.assert_true(ub.is_pos_2d());
+
+        const llama_pos expected[8] = {10, 11, 5, 6, 7, 8, 0, 0};
+        for (int i = 0; i < 8; ++i) {
+            t.assert_equal(expected[i], ub.pos[i]);
+        }
+    });
+
+    t.test("pos_jump_allowed", [&](testing & t) {
+        const uint32_t n_pos = 4;
+        const uint32_t n_embd = 2;
+
+        mock_memory mem;
+        mem.ranges[0] = {0, 9};
+
+        llama_batch_allocr ba(n_pos);
+
+        auto try_pos = [&](llama_pos p0) {
+            batch_builder bb(n_embd);
+            bb.add(p0, {0}, true);
+
+            std::vector<llama_pos> pos = {p0, 1, 1, 0};
+
+            llama_batch batch = bb.make(false, true, true);
+            batch.pos = pos.data();
+
+            return ba.init(batch, vocab, &mem, n_embd, 4, false);
+        };
+
+        t.assert_true("gap after memory is allowed",     try_pos(15));
+        t.assert_true("overlap is allowed for embd",     try_pos(9));
+        t.assert_true("pos behind memory is rejected",  !try_pos(8));
+    });
+}
+
+int main(int argc, char ** argv) {
+    testing t;
+
+    const char * verbose = getenv("LLAMA_TEST_VERBOSE");
+    if (verbose) {
+        t.verbose = std::string(verbose) == "1";
+    }
+    if (!t.verbose) {
+        llama_log_set([](ggml_log_level, const char *, void *) {}, nullptr);
+    }
+
+    if (argc > 1) {
+        t.set_filter(argv[1]);
+    }
+
+    t.test("init",      test_init);
+    t.test("split",     test_split);
+    t.test("keep_tail", test_keep_tail);
+    t.test("mrope",     test_mrope);
+
+    return t.summary();
+}