fix(acp): deliver Pi session prompts through the fork

crates/buzz-acp/TESTING.md

@@ -0,0 +1,57 @@
+# Pi adapter integration
+
+Buzz's Pi preset uses [salman1993/pi-acp](https://github.com/salman1993/pi-acp).
+Requires Node.js 22 or newer. Install Pi and configure its model provider,
+then install the adapter directly from the fork:
+
+```sh
+npm install -g @earendil-works/pi-coding-agent
+pi
+npm install -g --install-links=true git+https://github.com/salman1993/pi-acp.git#main
+```
+
+Restart Buzz, then select **Pi** as the agent harness. Buzz starts `pi-acp`
+automatically. Run the same adapter install command again to update it.
+The unscoped `npm install -g pi-acp` command installs the upstream package,
+without these extensions. Use fresh sessions to replace old user-framed
+standing instructions.
+
+Buzz adds `-- --skill <harness-cwd>/.agents/skills` when launching `pi-acp`.
+An existing separator and explicit Pi options are preserved. Managed agents
+run from the Buzz nest (normally `~/.buzz`): Desktop sets the `buzz-acp` child
+CWD through `default_agent_workdir()`, and adapters inherit it. The default
+skill directory is that launch workspace's `.agents/skills`. Standalone CLI
+launches use the caller's working directory.
+The path is fixed at adapter launch and applies to every Pi subprocess.
+
+The full composed session prompt is sent as a replacement string through the
+provisional top-level `session/new.params.systemPrompt` field. Buzz recognizes
+`pi-acp` by the agent name returned during initialization, regardless of protocol
+version. No custom capability negotiation or legacy Pi prompt fallback is used.
+Session titles continue to use `_meta.sessionTitle`.
+
+## Validation
+
+Activate Hermit from the Buzz repository root, then run the package tests:
+
+```sh
+. ./bin/activate-hermit
+cargo test -p buzz-acp
+```
+
+To exercise the real adapter through Buzz's production session composer:
+
+```sh
+BUZZ_TEST_PI_ACP=/absolute/pi-acp/dist/index.js \
+  cargo test -p buzz-acp real_pi_preserves -- --ignored
+```
+
+This test requires Node and Pi on PATH. It isolates HOME and Pi settings,
+disables extensions and context files, and uses a synthetic transcript without
+model calls. It inspects Pi's effective prompt through RPC HTML export after
+switching sessions and restarting the adapter. Base, persona, team, core memory,
+huddle, canvas, and the extra skill must each appear once, without another
+session's instructions or Pi's default coding preamble.
+
+HTML export reports the exporting process's current system prompt. It cannot
+recover a historical prompt from an old transcript alone.

crates/buzz-acp/src/acp.rs

@@ -460,8 +460,17 @@ impl AcpClient {
         use std::process::Stdio;
 
         let mut cmd = tokio::process::Command::new(command);
-        cmd.args(args)
-            .stdin(Stdio::piped())
+        cmd.args(args);
+        if crate::config::normalize_agent_command_identity(command) == "pi-acp" {
+            if !args.iter().any(|arg| arg == "--") {
+                cmd.arg("--");
+            }
+            // Desktop launches buzz-acp in the Buzz nest; adapters inherit that
+            // workspace. Keep managed skills tied to launch CWD across sessions.
+            cmd.arg("--skill")
+                .arg(std::env::current_dir()?.join(".agents/skills"));
+        }
+        cmd.stdin(Stdio::piped())
             .stdout(Stdio::piped())
             // Inherit stderr so agent logs are visible in the harness terminal.
             .stderr(Stdio::inherit())
@@ -637,7 +646,7 @@ impl AcpClient {
     ///
     /// - `None` — no system-prompt field in the request (legacy framing).
     /// - `Some(SystemPromptTransport::Field(text))` — bare `systemPrompt` field
-    ///   (ACP protocol v2, buzz-agent, goose unused).
+    ///   (ACP protocol v2, buzz-agent, pi-acp; goose unused).
     /// - `Some(SystemPromptTransport::ClaudeMeta(text))` — `_meta.systemPrompt`
     ///   as `{"append": text}`, keeping claude-agent-acp's native preset intact.
     ///
@@ -2131,9 +2140,7 @@ pub struct SessionNewResponse {
 
 /// How to deliver a system prompt on `session/new`.
 ///
-/// The two variants match the two mechanisms supported by current adapters:
-///
-/// - **`Field`** — bare `systemPrompt` field (ACP protocol v2, buzz-agent).
+/// - **`Field`** — bare `systemPrompt` field (ACP protocol v2, buzz-agent, pi-acp).
 /// - **`ClaudeMeta`** — `_meta.systemPrompt: {"append": text}`, used by
 ///   `claude-agent-acp` to append to the adapter's own native system prompt
 ///   while keeping its tool-use preset intact.
@@ -3631,123 +3638,7 @@ mod tests {
 
     // ── claude-agent-acp _meta.systemPrompt transport ─────────────────────
 
-    #[tokio::test]
-    async fn session_new_full_sends_claude_meta_system_prompt_when_claude_meta_transport() {
-        // When ClaudeMeta transport is requested, the prompt must appear as
-        // _meta.systemPrompt: {"append": text} — never as a bare systemPrompt field.
-        let script = r#"
-            read -t 2 _init
-            echo '{"jsonrpc":"2.0","id":0,"result":{"protocolVersion":1,"agentCapabilities":{}}}'
-            read -t 2 REQ
-            echo '{"jsonrpc":"2.0","id":1,"result":{"sessionId":"ses_claude","_receivedRequest":'"$REQ"'}}'
-            sleep 1
-        "#;
-        let mut client = spawn_script(script).await;
-        client
-            .initialize()
-            .await
-            .expect("initialize should succeed");
-
-        let resp = client
-            .session_new_full(
-                "/tmp",
-                vec![],
-                Some(SystemPromptTransport::ClaudeMeta("Be concise")),
-                None,
-            )
-            .await
-            .expect("session_new_full should succeed");
-
-        let received = &resp.raw["_receivedRequest"];
-        assert!(
-            received["params"].get("systemPrompt").is_none(),
-            "bare systemPrompt must not be present for ClaudeMeta transport"
-        );
-        assert_eq!(
-            received["params"]["_meta"]["systemPrompt"]["append"].as_str(),
-            Some("Be concise"),
-            "_meta.systemPrompt.append must carry the prompt text"
-        );
-    }
-
-    #[tokio::test]
-    async fn session_new_full_merges_claude_meta_and_session_title_into_single_meta_object() {
-        // Both ClaudeMeta prompt and session_title must coexist under _meta —
-        // the prompt must not clobber sessionTitle or vice versa.
-        let script = r#"
-            read -t 2 _init
-            echo '{"jsonrpc":"2.0","id":0,"result":{"protocolVersion":1,"agentCapabilities":{}}}'
-            read -t 2 REQ
-            echo '{"jsonrpc":"2.0","id":1,"result":{"sessionId":"ses_merged","_receivedRequest":'"$REQ"'}}'
-            sleep 1
-        "#;
-        let mut client = spawn_script(script).await;
-        client
-            .initialize()
-            .await
-            .expect("initialize should succeed");
-
-        let resp = client
-            .session_new_full(
-                "/tmp",
-                vec![],
-                Some(SystemPromptTransport::ClaudeMeta("Be concise")),
-                Some("Fizz · #buzz-dev"),
-            )
-            .await
-            .expect("session_new_full should succeed");
-
-        let received = &resp.raw["_receivedRequest"];
-        assert_eq!(
-            received["params"]["_meta"]["systemPrompt"]["append"].as_str(),
-            Some("Be concise"),
-            "_meta.systemPrompt.append must be present"
-        );
-        assert_eq!(
-            received["params"]["_meta"]["sessionTitle"].as_str(),
-            Some("Fizz · #buzz-dev"),
-            "_meta.sessionTitle must be present alongside systemPrompt"
-        );
-    }
-
-    // ── Goose-native steer scaffold (PR follow-up to #1160) ──────────────
-
-    /// Helper: spawn an inert `cat` subprocess so we have a real AcpClient
-    /// to drive `handle_session_update` against. `cat` never writes back,
-    /// which is fine — these tests don't read from the agent, they just
-    /// feed JSON into the parser.
-    async fn spawn_inert_client() -> AcpClient {
-        AcpClient::spawn("cat", &[], &[], false)
-            .await
-            .expect("spawn cat as inert client")
-    }
-
-    /// Build a `session/update` JSON-RPC notification carrying a
-    /// `session_info_update` with the given `_meta.goose.activeRunId` value.
-    /// Pass `None` to omit the `activeRunId` field entirely.
-    ///
-    /// `_meta` is nested inside the `update` object (per the ACP
-    /// `SessionInfoUpdate` schema), matching what goose and buzz-agent
-    /// emit on the wire.
-    fn session_info_update_msg(active_run_id: Option<serde_json::Value>) -> serde_json::Value {
-        let mut goose = serde_json::Map::new();
-        if let Some(v) = active_run_id {
-            goose.insert("activeRunId".to_string(), v);
-        }
-        let mut meta = serde_json::Map::new();
-        meta.insert("goose".to_string(), serde_json::Value::Object(goose));
-        serde_json::json!({
-            "jsonrpc": "2.0",
-            "method": "session/update",
-            "params": {
-                "sessionId": "test-session",
-                "update": {
-                    "sessionUpdate": "session_info_update",
-                    "_meta": serde_json::Value::Object(meta),
-                },
-            }
-        })
-    }
+    include!("acp/system_prompt_tests.rs");
 
     #[tokio::test]
     async fn active_run_id_sets_on_string() {

crates/buzz-acp/src/acp/system_prompt_tests.rs

@@ -0,0 +1,117 @@
+#[tokio::test]
+async fn session_new_full_sends_claude_meta_system_prompt_when_claude_meta_transport() {
+    // When ClaudeMeta transport is requested, the prompt must appear as
+    // _meta.systemPrompt: {"append": text} — never as a bare systemPrompt field.
+    let script = r#"
+            read -t 2 _init
+            echo '{"jsonrpc":"2.0","id":0,"result":{"protocolVersion":1,"agentCapabilities":{}}}'
+            read -t 2 REQ
+            echo '{"jsonrpc":"2.0","id":1,"result":{"sessionId":"ses_claude","_receivedRequest":'"$REQ"'}}'
+            sleep 1
+        "#;
+    let mut client = spawn_script(script).await;
+    client
+        .initialize()
+        .await
+        .expect("initialize should succeed");
+
+    let resp = client
+        .session_new_full(
+            "/tmp",
+            vec![],
+            Some(SystemPromptTransport::ClaudeMeta("Be concise")),
+            None,
+        )
+        .await
+        .expect("session_new_full should succeed");
+
+    let received = &resp.raw["_receivedRequest"];
+    assert!(
+        received["params"].get("systemPrompt").is_none(),
+        "bare systemPrompt must not be present for ClaudeMeta transport"
+    );
+    assert_eq!(
+        received["params"]["_meta"]["systemPrompt"]["append"].as_str(),
+        Some("Be concise"),
+        "_meta.systemPrompt.append must carry the prompt text"
+    );
+}
+
+#[tokio::test]
+async fn session_new_full_merges_claude_meta_and_session_title_into_single_meta_object() {
+    // Both ClaudeMeta prompt and session_title must coexist under _meta —
+    // the prompt must not clobber sessionTitle or vice versa.
+    let script = r#"
+            read -t 2 _init
+            echo '{"jsonrpc":"2.0","id":0,"result":{"protocolVersion":1,"agentCapabilities":{}}}'
+            read -t 2 REQ
+            echo '{"jsonrpc":"2.0","id":1,"result":{"sessionId":"ses_merged","_receivedRequest":'"$REQ"'}}'
+            sleep 1
+        "#;
+    let mut client = spawn_script(script).await;
+    client
+        .initialize()
+        .await
+        .expect("initialize should succeed");
+
+    let resp = client
+        .session_new_full(
+            "/tmp",
+            vec![],
+            Some(SystemPromptTransport::ClaudeMeta("Be concise")),
+            Some("Fizz · #buzz-dev"),
+        )
+        .await
+        .expect("session_new_full should succeed");
+
+    let received = &resp.raw["_receivedRequest"];
+    assert_eq!(
+        received["params"]["_meta"]["systemPrompt"]["append"].as_str(),
+        Some("Be concise"),
+        "_meta.systemPrompt.append must be present"
+    );
+    assert_eq!(
+        received["params"]["_meta"]["sessionTitle"].as_str(),
+        Some("Fizz · #buzz-dev"),
+        "_meta.sessionTitle must be present alongside systemPrompt"
+    );
+}
+
+// ── Goose-native steer scaffold (PR follow-up to #1160) ──────────────
+
+/// Helper: spawn an inert `cat` subprocess so we have a real AcpClient
+/// to drive `handle_session_update` against. `cat` never writes back,
+/// which is fine — these tests don't read from the agent, they just
+/// feed JSON into the parser.
+async fn spawn_inert_client() -> AcpClient {
+    AcpClient::spawn("cat", &[], &[], false)
+        .await
+        .expect("spawn cat as inert client")
+}
+
+/// Build a `session/update` JSON-RPC notification carrying a
+/// `session_info_update` with the given `_meta.goose.activeRunId` value.
+/// Pass `None` to omit the `activeRunId` field entirely.
+///
+/// `_meta` is nested inside the `update` object (per the ACP
+/// `SessionInfoUpdate` schema), matching what goose and buzz-agent
+/// emit on the wire.
+fn session_info_update_msg(active_run_id: Option<serde_json::Value>) -> serde_json::Value {
+    let mut goose = serde_json::Map::new();
+    if let Some(v) = active_run_id {
+        goose.insert("activeRunId".to_string(), v);
+    }
+    let mut meta = serde_json::Map::new();
+    meta.insert("goose".to_string(), serde_json::Value::Object(goose));
+    serde_json::json!({
+        "jsonrpc": "2.0",
+        "method": "session/update",
+        "params": {
+            "sessionId": "test-session",
+            "update": {
+                "sessionUpdate": "session_info_update",
+                "_meta": serde_json::Value::Object(meta),
+            },
+        }
+    })
+}