diff --git a/README.md b/README.md
index 078a15146..582c36a1b 100644
--- a/README.md
+++ b/README.md
@@ -337,6 +337,10 @@ The library provides some environment variables, which may be useful:
     - `EP_SUPPRESS_NCCL_CHECK`: `0` or `1`, suppress NCCL version mismatch checking, `0` by default
     - `EP_AVOID_RECORD_STREAM`: `0` or `1`, avoid `record_stream` on output tensors, `0` by default
     - `EP_NUM_TOPK_IDX_BITS`: integer, override the number of bits for top-k index encoding, `0` (auto) by default
+    - `EP_NUM_SUB_PARTS`: integer, per-part sub-part count for the unordered hybrid kernel (JIT-forwarded); `0` (unset) uses the header default `2`, `1` disables sub-parts
+    - `EP_MIN_SUB_TOKENS`: integer, minimum tokens per sub-part before splitting (JIT-forwarded); `0` (unset) uses the header default `1`
+    - `EP_SM100_MIN_SUB_TOKENS`: integer, sm_100+ override for the minimum-tokens-per-sub-part gate (JIT-forwarded); `0` (unset) uses the header default `15`
+    - `EP_MIN_TOKENS_PER_PART`: integer, minimum tokens per scale-out part before splitting (JIT-forwarded); `0` (unset) uses the header default `15`, `1` disables the geometry clamp
 - Networking
     - `EP_NIC_NAME`: string, the default NIC name used to query NIC properties, `mlx5_0` by default
     - `EP_OVERRIDE_RDMA_SL`: integer, override the RDMA service level index for traffic isolation
diff --git a/csrc/jit/compiler.hpp b/csrc/jit/compiler.hpp
index ad01b3cac..433a1a6ca 100644
--- a/csrc/jit/compiler.hpp
+++ b/csrc/jit/compiler.hpp
@@ -70,6 +70,16 @@ class Compiler {
         // TODO: make it more general, e.g. `EP_JIT_EXTRA_FLAGS`
         if (int num_topk_idx_bits = get_env("EP_NUM_TOPK_IDX_BITS", 0); num_topk_idx_bits != 0)
             flags += fmt::format(" -DEP_NUM_TOPK_IDX_BITS={}", num_topk_idx_bits);
+
+        // Part / sub-part geometry defaults in `hybrid_dispatch_unordered.cuh`. They are
+        // device-only (no host caller reads them), so forwarding them as JIT defines cannot
+        // desync host and device, and `flags` is part of `kernel_signature` below, so a
+        // change re-JITs rather than reusing a stale cubin. Tuning them per network/arch
+        // previously required editing the header and reinstalling.
+        for (const auto& name: {"EP_NUM_SUB_PARTS", "EP_MIN_SUB_TOKENS", "EP_SM100_MIN_SUB_TOKENS",
+                                "EP_MIN_TOKENS_PER_PART"})
+            if (int v = get_env(name, 0); v != 0)
+                flags += fmt::format(" -D{}={}", name, v);
     }
 
     virtual ~Compiler() = default;
diff --git a/deep_ep/include/deep_ep/impls/hybrid_dispatch_unordered.cuh b/deep_ep/include/deep_ep/impls/hybrid_dispatch_unordered.cuh
index 816f0571d..d98fa7903 100644
--- a/deep_ep/include/deep_ep/impls/hybrid_dispatch_unordered.cuh
+++ b/deep_ep/include/deep_ep/impls/hybrid_dispatch_unordered.cuh
@@ -55,6 +55,20 @@ static constexpr int kMinSubTokensDefault = (EP_MIN_SUB_TOKENS) > 1 ? (EP_MIN_SU
 #define EP_SM100_MIN_SUB_TOKENS 15
 #endif
 
+// Minimum tokens a scale-out part must carry to be worth its own `flush_part` put, i.e. the
+// part-level analogue of `kMinSubTokensDefault` above. `compute_part_allocation()` only ever
+// caps the part count from ABOVE when the indexed-signal budget is tight, and that budget is
+// loosest exactly when a channel holds the fewest tokens, so small-batch shapes settle on
+// `kMaxParts` -- the worst end of the axis. Set to 1 to disable the clamp entirely, i.e. to
+// restore the previous behaviour exactly (a value of 1 must SHORT-CIRCUIT rather than divide by
+// one: `kNumMaxTokensPerChannel / 1` still clamps whenever a channel holds fewer tokens than the
+// budget allows parts, which is a different geometry from the old code and not a control).
+#ifndef EP_MIN_TOKENS_PER_PART
+#define EP_MIN_TOKENS_PER_PART 15
+#endif
+
+static constexpr int kMinTokensPerPart = (EP_MIN_TOKENS_PER_PART) > 1 ? (EP_MIN_TOKENS_PER_PART) : 1;
+
 template <int kNumSubParts, int kMinSubTokens = kMinSubTokensDefault>
 __device__ __host__ __forceinline__ int num_sub_parts_at(const int& part_tokens) {
     if constexpr (kNumSubParts <= 1) {
@@ -140,9 +154,16 @@ template <bool kDoCPUSync,
           int kNumScaleupRanksPerLane = math::constexpr_ceil_div(kNumScaleupRanks, 32),
           int kNumChannelsPerSM = kNumScaleoutWarps,
           int kNumChannels = kNumScaleoutWarps * kNumSMs,
-          int kNumParts = gin_alloc::constexpr_num_parts(
-              kNumGinSignals, kNumSMs, kNumQPs, (kNumNotifyWarps > 0), kNumScaleoutWarps),
           int kNumMaxTokensPerChannel = math::constexpr_ceil_div(kNumMaxTokensPerRank, kNumChannels),
+          int kNumBudgetParts = gin_alloc::constexpr_num_parts(
+              kNumGinSignals, kNumSMs, kNumQPs, (kNumNotifyWarps > 0), kNumScaleoutWarps),
+          // NOTES: the parentheses around the comparison are load-bearing -- an unparenthesized
+          // `>` inside a template parameter list closes the list instead of comparing (same
+          // reason `(kNumNotifyWarps > 0)` above is wrapped)
+          int kNumGeomParts = kMinTokensPerPart <= 1 ? kNumBudgetParts
+                            : ((kNumMaxTokensPerChannel / kMinTokensPerPart > 1)
+                               ? kNumMaxTokensPerChannel / kMinTokensPerPart : 1),
+          int kNumParts = kNumBudgetParts < kNumGeomParts ? kNumBudgetParts : kNumGeomParts,
           int kPartSize = math::constexpr_ceil_div(kNumMaxTokensPerChannel, kNumParts),
           int kBatchSize = kPartSize,
           int kNumSubParts = kNumSubPartsDefault < kBatchSize ? kNumSubPartsDefault : kBatchSize,