diff --git a/docs/23_TRAVERSABILITY_AND_STATIC_OBSTACLE_STACK_DECISION.md b/docs/23_TRAVERSABILITY_AND_STATIC_OBSTACLE_STACK_DECISION.md
index 2082e95..ee5896e 100644
--- a/docs/23_TRAVERSABILITY_AND_STATIC_OBSTACLE_STACK_DECISION.md
+++ b/docs/23_TRAVERSABILITY_AND_STATIC_OBSTACLE_STACK_DECISION.md
@@ -279,6 +279,13 @@ failure.
 - Run upstream sample/demo data first to prove the unmodified components.
 - Measure component latency and memory before adding Mission Core adapters.
 
+T1 completed on `2026-08-26` with an upstream candidate rejection. The pinned
+sources build, but the Ground Consistency suite passes only `11/12` gtests;
+`testBoundsReflectFootprint` fails because the test fixture has no configured
+footprint. The sealed evidence and complete run ledger are recorded in
+[`experiments/perception/M49_T1_GSEG3D_UPSTREAM_QUALIFICATION_2026-08-26.md`](../experiments/perception/M49_T1_GSEG3D_UPSTREAM_QUALIFICATION_2026-08-26.md).
+Candidate A receives no replay or runtime authority in this revision set.
+
 ### T2 — Candidate A RAVNOVES00 replay
 
 - Feed the bounded causal local cloud with exact pose lineage.
@@ -314,7 +321,7 @@ failure.
 
 ## Immediate next action
 
-Resume T1 for Candidate A only after the Worker resource gate in the T0 report
-passes. No LOW-STEP tuning, new object model, camera resize, fisheye
-rectification, manual dataset or parallel heavy Worker job is authorized by
-this decision.
+Run the isolated upstream qualification for Candidate B, TRAVEL. Candidate A
+T2 replay is blocked by the failed unmodified T1 gate. No LOW-STEP tuning, new
+object model, camera resize, fisheye rectification, manual dataset or parallel
+heavy Worker job is authorized by this decision.
diff --git a/experiments/perception/M49_T1_GSEG3D_UPSTREAM_QUALIFICATION_2026-08-26.md b/experiments/perception/M49_T1_GSEG3D_UPSTREAM_QUALIFICATION_2026-08-26.md
new file mode 100644
index 0000000..8310b20
--- /dev/null
+++ b/experiments/perception/M49_T1_GSEG3D_UPSTREAM_QUALIFICATION_2026-08-26.md
@@ -0,0 +1,93 @@
+# M4.9 T1 GSeg3D upstream qualification — 2026-08-26
+
+Status: **rejected as an unmodified Candidate A stack**; RAVNOVES00 replay and
+all navigation or actuation authority remain disabled
+
+## Decision
+
+The pinned GSeg3D, ROS 2 wrapper and Nav2 Ground Consistency sources build in
+an isolated Worker 006 container. The unmodified Ground Consistency test suite
+does not pass: `11/12` gtests pass and
+`GroundConsistencyLayerTest.testBoundsReflectFootprint` fails.
+
+The failure is inside the pinned upstream candidate rather than the Mission
+Core replay adapter. The layer logs that no footprint is configured, skips
+footprint clearing and leaves `max_x/max_y` at `0`, while its own test requires
+both bounds to be at least `1.0`.
+
+Mission Core therefore does not call this revision set plug-and-play ready,
+does not patch upstream silently and does not start Candidate A RAVNOVES00
+replay. This result does not prove that the GSeg3D algorithm is unusable. It
+proves that the exact unmodified stack frozen for T1 fails its admission gate.
+
+## Frozen identity
+
+| Component | Revision |
+| --- | --- |
+| DFKI `ground_segmentation` | `116f510485ea5b4707e2b476958d34a5a067f647` |
+| DFKI `ground_segmentation_ros2` | `5c5ba6f5ca0d682db2d59b2ad2f6a317ee938b95` |
+| DFKI `nav2_ground_consistency_costmap_plugin` | `41cec620efba6c370dccfc59a6ec1134775ff48a` |
+| Final Mission Core qualification source | `316f0d7f8582f47cdd2a05e7e7404cfe33a40d6d` |
+| Final deterministic Worker artifact | `f681ba58aa3c69b7cd3572fda4abc1c4303bf73d62262fb1c534e220f7136801` |
+| Worker image | `sha256:57a481faa9ad50d69a5aae537ed24c1770867413b38e91399060c5dd448b3471` |
+
+The final artifact was built twice locally with identical SHA-256, copied to a
+new immutable Worker release directory, verified again before extraction and
+run through the interactive Worker executor. The image size is
+`1,172,862,313` bytes.
+
+## Run ledger
+
+| Run | Outcome | Interpretation |
+| --- | --- | --- |
+| `upstream-001` | pre-build failure | Non-interactive Docker credential helper; no candidate result |
+| `upstream-002` | pre-build failure | Isolated Docker config was still evaluated in the non-interactive SSH context; no candidate result |
+| `upstream-003` | harness failure | Image built; strict shell nounset conflicted with the standard ROS 2 setup hook |
+| `upstream-004` | harness failure | Test command omitted the merged-install layout used during the image build |
+| `upstream-005` | **candidate test failure** | Harness reached the pinned upstream gtests; `11/12` passed and footprint-bound test failed |
+
+The two harness failures were corrected in new content-addressed artifacts and
+were never presented as candidate failures. No identical failed artifact was
+retried.
+
+## Sealed final evidence
+
+Worker output root:
+
+`D:\NDC_MISSIONCORE\runtime\results\m49-t1-gseg3d\upstream-005`
+
+| File | Bytes | SHA-256 |
+| --- | ---: | --- |
+| `result.json` | `640` | `6ff189d7c160fe98063672a848ced205199e7bd3ed3de568b1638b7e325848ac` |
+| `qualification.log` | `37,813` | `ffafad5cc09ec3d46302111ed0fe9ec6c02d0dbd982bc7307c28b44db071abba` |
+| `resource.txt` | `772` | `5955b1eb01a7f587efaeb3f9d547b80e44c1d6651f4b2c9906b47d11e8a5f894` |
+
+The GSeg3D core checkout exposes no CTest tests in the selected build, so its
+`ctest` step reports `No tests were found` and returns success. The decisive
+executable evidence is the Ground Consistency suite, which does contain twelve
+tests and returns one failure.
+
+## Resource and isolation result
+
+- Worker 006 remained the only execution host.
+- The candidate build/test used CPU and did not request CUDA, Vulkan or a GPU
+  lease.
+- The concurrent approximately `47–51%` GPU utilization and roughly `9 GiB`
+  VRAM belonged to `sentinel-frigate`, not GAUSS or this qualification.
+- Canonical `ndc-mission-core-triton` remained `running/healthy` after the
+  final run.
+- Temporary candidate containers and the one-shot scheduled task were removed
+  after evidence capture.
+- No Mission Core source evidence, GAUSS process, Frigate process or canonical
+  Triton image was stopped, rebuilt or replaced.
+
+## Authority boundary and next action
+
+Candidate A has no RAVNOVES00 quality, realtime, navigation, collision-safety
+or actuation authority. T2 is blocked for this exact unmodified revision set.
+
+The next sequential action is an isolated upstream qualification of Candidate
+B, TRAVEL, at its frozen revision. Its GPL-3.0 license limits it to evaluation
+until a separate distribution decision is made. Camera/LiDAR vegetation
+arbitration remains an independent product requirement and is not waived by
+any terrain candidate.