diff --git a/core/libs/prx/libSceAgcDriver/Unimplemented.cpp b/core/libs/prx/libSceAgcDriver/Unimplemented.cpp
index 7b2d31ea6..f0b486c58 100644
--- a/core/libs/prx/libSceAgcDriver/Unimplemented.cpp
+++ b/core/libs/prx/libSceAgcDriver/Unimplemented.cpp
@@ -40,4 +40,11 @@ int APS5_VABI sceAgcDriverSetSubmitValidationConfig() {
  return 0;
 }
 
+int APS5_VABI sceAgcDriverGetHsOffchipParam(uint16_t* first, uint16_t* second) {
+    (void)first;
+    (void)second;
+    NotImplemented_nid_no_patch(__func__);
+    return 0;
+}
+
 }
diff --git a/docs/dev/debt/libSceAgcDriver.md b/docs/dev/debt/libSceAgcDriver.md
index 0a8e13c84..0fe00cfd3 100644
--- a/docs/dev/debt/libSceAgcDriver.md
+++ b/docs/dev/debt/libSceAgcDriver.md
@@ -21,6 +21,7 @@
 - [Depth fast clear through HTILE](../../../core/libs/prx/libSceAgcDriver/Graphics/src/DepthSurface.cpp) (libSceAgcDriver) - a surface cleared by an HTILE fill is cleared to DB_DEPTH_CLEAR, also when it is next sampled. For a depth-only HTILE the clear word also carries a value (radv writes `minz = maxz = round(depth * 0x3fff)`, `HTILE_Z_CLEAR_REG` in Mesa's `src/amd/common/ac_descriptors.h`, and allows TC-compatible fast clears only to 0.0 or 1.0); which of the two the texture unit returns for a cleared tile was not measured.
 - [Depth-only and stencil HTILE fill](../../../core/libs/prx/libSceAgcDriver/Graphics/src/DepthSurface.cpp) (libSceAgcDriver) - in a whole-HTILE fill, ZMask (bits 0-3) 0 clears the depth and SMem (bits 8-9) 0 clears the stencil, while SMem 3 leaves the stencil alone (`HtileFillClears`); other SMem values are taken to leave it alone too. The bit meanings follow the gfx10 HTILE layout as the code reads it, not a measurement; `agc_driver_depth_fast_clear_submit` pins them for the paths the Driver takes.
 - [HTILE address of a depth array slice](../../../core/libs/prx/libSceAgcDriver/Graphics/src/State.cpp) (libSceAgcDriver) - `decodeDepth` adds the `DB_DEPTH_VIEW` slice offset to the Z and stencil addresses but not to `htileAddress`, so every slice of a layered depth target shares slice 0's HTILE address and a fill of slice 0's HTILE marks all slices cleared. Astro's Playroom fills the HTILE of each of its three shadow cascades 0x40000 apart (0x24000 bytes of tiles each) back to back before drawing, so the result is still right there; a title that clears one slice between draws to another would lose depth. The per-slice HTILE stride is not derived yet.
+- [sceAgcDriverGetHsOffchipParam](../../../core/libs/prx/libSceAgcDriver/Unimplemented.cpp) (libSceAgcDriver, NID `r28hEh6cNH0`) - declared as a throwing stub. The two `uint16_t` output pointers and integer return type follow [ps5-vulkan](https://github.com/blackbearreloaded/ps5-vulkan/blob/4bb0c8b1423698a7369efc22b829bf16a99e7128/native/tess_driver_import_stub.c#L10), which reads the pair before it binds a tessellation factor ring. The meaning of the two values, their initial state and how they relate to `sceAgcDriverSetHsOffchipParam`, which keeps nothing here, are unknown; the stub does not write caller memory. PPSA99011 imports it
 
 ### Functional