diff --git a/docs/re/structures/ui-render-tone-curve.md b/docs/re/structures/ui-render-tone-curve.md
index ec41a6fd..ac1dd110 100644
--- a/docs/re/structures/ui-render-tone-curve.md
+++ b/docs/re/structures/ui-render-tone-curve.md
@@ -215,6 +215,50 @@ LOG_LEVEL=3` (both are needed — kernel calls log at Debug) and look for
 emulator only to **boot**, not to reach a menu: video init happens in the first
 seconds. This had been parked behind the title-screen blocker for no reason.
 
+## 🔴 The direct observation: ATTEMPTED, BLOCKED by the build tree (2026-08-30)
+
+This page records the game's ramp write as *"inferred from a closed chain, not
+directly observed"*, the chain being that the swap-path stage is a pure 256-entry
+LUT and that an unwritten table is identity (`i * 0x3FF / 0xFF`). The direct
+observation is a log in Canary's own write path, which `/canary` being read-write
+makes available. Attempted; blocked, and the blocker is worth recording.
+
+**The patch** — `command_processor.cc`, inside `XE_GPU_REG_DC_LUT_SEQ_COLOR`, on
+each completed 256-entry sweep:
+
+```cpp
+if (gamma_ramp_rw_index.rw_index == 255 && gamma_ramp_rw_component_ == 2) {
+  auto id = [](uint32_t i) { return i * 0x3FFu / 0xFFu; };
+  XELOGI("[RE-GAMMA] full 256-entry ramp written (sweep #{})", ++re_gamma_sweeps_);
+  for (uint32_t i : {0u, 64u, 128u, 192u, 255u}) {
+    const auto& e = gamma_ramp_256_entry_table_[i];
+    XELOGI("[RE-GAMMA]   [{:3}] r={:4} g={:4} b={:4}   identity={:4}{}",
+           i, uint32_t(e.color_10_red), uint32_t(e.color_10_green),
+           uint32_t(e.color_10_blue), id(i),
+           uint32_t(e.color_10_red) == id(i) ? "" : "   <- NOT identity");
+  }
+}
+```
+plus `uint32_t re_gamma_sweeps_ = 0;` beside `gamma_ramp_rw_component_` in the
+header. It prints each written ramp against the identity the source documents, so
+a written ramp is distinguishable from an unwritten one **by reading the log**.
+
+🔴 **Blocked: the build tree cannot regenerate.** `/sylph-home/re/canary-build` was
+configured with `-S/work/xenia-canary`, and **that path does not exist** — the tree
+was configured against a source location this container no longer has. `ninja`
+fails at the CMake regeneration step before compiling anything. Reconfiguring
+against `/canary` would almost certainly trigger a near-full Xenia rebuild, which
+is not a thing to start on the way to one log line.
+
+✅ **The patch was REVERTED and `/canary` verified byte-identical to its backup.**
+Leaving instrumented source that the running binary does not contain is the
+source-and-binary-disagree trap this corpus has hit repeatedly — a later reader
+would find the logging in the tree and conclude it is live.
+
+⚠️ So the ramp write **remains inferred, not observed**, exactly as this page
+already says. What is new is the reach: the experiment is *written*, and the
+obstacle is a build-tree path rather than anything about the game.
+
 ## What a port should do with this
 
 Treat it as **authored**, not transcribed. If the goal is to match the emulator —