From 4e7158a5ce92bb29435d21579ec949114b1a77c0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20M=C3=BCller?= <sebastian@primeintellect.ai>
Date: Thu, 1 Oct 2026 10:21:28 -0700
Subject: [PATCH] fix(acp): image prompt blocks reach the daemon session
 (#3248)

---
 crates/pa-cli/tests/acp_mode_e2e.rs           | 54 +++++++++++++++++++
 crates/pa-daemon/src/acp/daemon.rs            | 11 +++-
 crates/pa-daemon/src/worker/input.rs          |  5 +-
 .../src/worker/prompt_image_tests.rs          |  5 ++
 4 files changed, 72 insertions(+), 3 deletions(-)

diff --git a/crates/pa-cli/tests/acp_mode_e2e.rs b/crates/pa-cli/tests/acp_mode_e2e.rs
index 0dba9a772..bb60b2c0f 100644
--- a/crates/pa-cli/tests/acp_mode_e2e.rs
+++ b/crates/pa-cli/tests/acp_mode_e2e.rs
@@ -893,6 +893,60 @@ fn acp_daemon_attached_prompt_after_cancel_runs() {
     );
 }
 
+#[test]
+fn acp_daemon_attached_image_only_prompt_reaches_the_session() {
+    let (mut client, socket) = AcpChild::spawn_daemon_attached(
+        &["--mode", "acp", "--no-session"],
+        &json!({ "engine": "faux", "responses": ["SAW-IMAGE"] }),
+    );
+    let init = client.request("initialize", &initialize_params());
+    let _ = client.wait_response(init, TIMEOUT);
+    let new = client.request("session/new", &json!({ "mcpServers": [] }));
+    let (new_response, _) = client.wait_response(new, TIMEOUT);
+    let session_id = new_response["result"]["sessionId"]
+        .as_str()
+        .unwrap()
+        .to_string();
+    // 1x1 PNG
+    let png = "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mP8z8BQDwAEhQGAhKmMIQAAAABJRU5ErkJggg==";
+    let prompt = client.request(
+        "session/prompt",
+        &json!({
+            "sessionId": session_id,
+            "prompt": [
+                { "type": "image", "data": png, "mimeType": "image/png" },
+            ],
+        }),
+    );
+    let (prompt_response, _) = client.wait_response(prompt, TIMEOUT);
+    assert_eq!(
+        prompt_response["result"]["stopReason"], "end_turn",
+        "an image-only prompt runs a turn: {prompt_response}"
+    );
+    // The stored user row carries the image: an empty text block first,
+    // then the images (TS `_buildPromptContent`).
+    let list = daemon_request(&socket, "img-list", &json!({ "type": "list" }));
+    let active_session_id = &list["data"]["sessions"][0]["activeSessionId"];
+    let messages = daemon_request(
+        &socket,
+        "img-msgs",
+        &json!({ "type": "get_messages", "activeSessionId": active_session_id }),
+    );
+    let user = messages["data"]["messages"]
+        .as_array()
+        .unwrap()
+        .iter()
+        .find(|m| m["role"] == "user")
+        .unwrap();
+    assert_eq!(
+        user["content"],
+        json!([
+            { "type": "text", "text": "" },
+            { "type": "image", "data": png, "mimeType": "image/png" },
+        ])
+    );
+}
+
 /// Stop the sandboxed supervisor a test spawned (the shared-daemon
 /// product behavior leaves it running; a test owns its sandbox).
 fn shutdown_sandboxed_daemon(socket: &std::path::Path) {
diff --git a/crates/pa-daemon/src/acp/daemon.rs b/crates/pa-daemon/src/acp/daemon.rs
index 56de9fafd..17f37ed35 100644
--- a/crates/pa-daemon/src/acp/daemon.rs
+++ b/crates/pa-daemon/src/acp/daemon.rs
@@ -796,7 +796,16 @@ async fn handle_session_prompt(
         message: admitted.text,
         input: pa_types::daemon::PromptInput {
             content: None,
-            images: None,
+            // The image blocks ride the wire form `parse_prompt_images`
+            // reads (`{type, data, mimeType}`); TS forwards `images`
+            // only when the prompt carries any.
+            images: (!admitted.images.is_empty()).then(|| {
+                json!(admitted
+                    .images
+                    .into_iter()
+                    .map(|image| json!({ "type": "image", "data": image.data, "mimeType": image.mime_type }))
+                    .collect::<Vec<_>>())
+            }),
             // TS sends `followUp` + `queueIfBusy: true` on every ACP
             // prompt (acp-mode.ts): a prompt carrying a streaming
             // behavior is the worker's resume site for the post-abort
diff --git a/crates/pa-daemon/src/worker/input.rs b/crates/pa-daemon/src/worker/input.rs
index 6ab574780..c26c61c32 100644
--- a/crates/pa-daemon/src/worker/input.rs
+++ b/crates/pa-daemon/src/worker/input.rs
@@ -20,7 +20,9 @@ impl Worker {
             .get("message")
             .and_then(Value::as_str)
             .unwrap_or_default();
-        if message.is_empty() {
+        // TS has no empty check; this port still rejects a prompt with neither text nor images.
+        let images = parse_prompt_images(payload);
+        if message.is_empty() && images.is_empty() {
             return response_failure(None, "prompt", "Prompt cannot be empty", None);
         }
         let streaming_behavior = payload.get("streamingBehavior").and_then(Value::as_str);
@@ -42,7 +44,6 @@ impl Worker {
                 );
             }
         }
-        let images = parse_prompt_images(payload);
         // TS daemon prompts map `resumeIfIdle` to
         // `command.streamingBehavior !== undefined`: while the queued-input
         // suspension is set (post `abort`/manual `compact`), a plain prompt
diff --git a/crates/pa-daemon/src/worker/prompt_image_tests.rs b/crates/pa-daemon/src/worker/prompt_image_tests.rs
index 6f3ca8aeb..3fcebbaf9 100644
--- a/crates/pa-daemon/src/worker/prompt_image_tests.rs
+++ b/crates/pa-daemon/src/worker/prompt_image_tests.rs
@@ -86,4 +86,9 @@ async fn prompt_with_images_queues_the_images_with_the_message() {
         }],
         "the attachment rides the queue item"
     );
+    // A prompt with neither text nor images stays rejected (this port's
+    // guard; the TS worker has no empty check).
+    let rejected = worker.dispatch("prompt", &json!({ "message": "" })).await;
+    assert!(!rejected.success);
+    assert_eq!(rejected.error.as_deref(), Some("Prompt cannot be empty"));
 }
-- 
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