From f8c0da0ebf36427c95a4e78bdd3eea27889a67cc Mon Sep 17 00:00:00 2001
From: rob thijssen <grenade@rob.tn>
Date: Thu, 4 Jun 2026 14:53:56 +0300
Subject: [PATCH] =?UTF-8?q?fix(neuron):=20TP-vision=20Stage=200=20?=
 =?UTF-8?q?=E2=80=94=20reject=20image=20requests=20on=20the=20TP=20path?=
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The TP inference path has no vision tower, and the TP dispatch in
chat_completion / inference_stream returns before the VisionUnsupported
guard runs — so an image request to a TP-loaded model (e.g. beast's
tp=2 Qwen3.6-27B) was silently dropped and answered from text alone,
the exact issue-#3 confident-hallucination pattern Stage C killed for
single-GPU.

Add the request_has_images → VisionUnsupported guard to both
chat_completion_tp and inference_tp_stream, before prefill / before the
SSE stream opens, so beast returns a clean 400 vision_unsupported. The
guard is unconditional for now (TP has no tower); Stage 3 makes it
conditional on the TP model's has_vision once real TP-vision lands.

Detection is covered by the existing request_has_images unit test; the
guard itself is cuda-gated (validated by CI's CUDA type-check).

Refs TP-vision plan Stage 0.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 .claude/scheduled_tasks.lock        |  1 +
 crates/neuron/src/harness/candle.rs | 26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+)
 create mode 100644 .claude/scheduled_tasks.lock

diff --git a/.claude/scheduled_tasks.lock b/.claude/scheduled_tasks.lock
new file mode 100644
index 0000000..7850727
--- /dev/null
+++ b/.claude/scheduled_tasks.lock
@@ -0,0 +1 @@
+{"sessionId":"a27586bb-2ca7-4e92-8d82-12f41b39f392","pid":3106893,"procStart":"59753850","acquiredAt":1780571089798}
\ No newline at end of file
diff --git a/crates/neuron/src/harness/candle.rs b/crates/neuron/src/harness/candle.rs
index 701f323..7daad46 100644
--- a/crates/neuron/src/harness/candle.rs
+++ b/crates/neuron/src/harness/candle.rs
@@ -2739,6 +2739,18 @@ impl CandleHarness {
             return Err(poisoned_error(&model_id));
         }
 
+        // Stage 0 (TP-vision): the TP path has no vision tower yet, so
+        // an image-bearing request can't be honoured. Reject it cleanly
+        // with `vision_unsupported` instead of silently dropping the
+        // image and answering from text alone (the issue-#3 confident-
+        // hallucination pattern). Made conditional on the TP model's
+        // `has_vision` once Stage 3 wires real TP-vision.
+        if request_has_images(&request) {
+            let _g = span.enter();
+            tracing::warn!("TP chat_completion: rejecting image request, TP vision unsupported");
+            return Err(InferenceError::VisionUnsupported { model_id });
+        }
+
         let tp_for_marker = Arc::clone(&tp);
         let handle = tokio::spawn(chat_completion_tp_inner(tp, request).instrument(span.clone()));
         match handle.await {
@@ -2816,6 +2828,20 @@ impl CandleHarness {
             return Err(poisoned_error(&request.model));
         }
 
+        // Stage 0 (TP-vision): reject image requests on the TP streaming
+        // path before opening the SSE stream — the TP path has no vision
+        // tower yet, so honouring the image is impossible and silently
+        // dropping it would hallucinate. Returns a clean 400; made
+        // conditional on `has_vision` in Stage 3.
+        if request_has_images(&request) {
+            tracing::warn!(
+                "TP chat_completion (stream): rejecting image request, TP vision unsupported"
+            );
+            return Err(InferenceError::VisionUnsupported {
+                model_id: request.model.clone(),
+            });
+        }
+
         let prompt = build_prompt_for_request(tp.chat_template.as_deref(), &request);
         let encoding = tp
             .tokenizer