feat: projects as backend sources with system prompt injection

Move projects from Tauri IPC commands to the ACP sources system, making
them a backend-managed entity available to all clients (desktop, CLI, TUI).

Backend: Add Project to SourceType, properties bag on SourceEntry, project
storage in Paths::data_dir()/projects/, system prompt injection in agent
reply, _goose/session/set_project ACP method, includeProjectSources flag
for listing skills from project working directories.

Frontend: Rewrite projects API from Tauri invoke to ACP ext methods, remove
buildProjectSystemPrompt (backend handles it now), add project picker to
CreateSkillDialog, show project badges on non-global skills.

Delete ui/goose2/src-tauri/src/commands/projects.rs (508 lines).

Signed-off-by: Douwe Osinga <douwe@squareup.com>

Author: sunilkumarvalmiki

crates/goose-acp/acp-meta.json

@@ -110,6 +110,11 @@
       "requestType": "UnarchiveSessionRequest",
       "responseType": "EmptyResponse"
     },
+    {
+      "method": "_goose/session/set_project",
+      "requestType": "SetSessionProjectRequest",
+      "responseType": "EmptyResponse"
+    },
     {
       "method": "_goose/sources/create",
       "requestType": "CreateSourceRequest",

crates/goose-acp/acp-schema.json

@@ -795,6 +795,27 @@
       "x-side": "agent",
       "x-method": "_goose/session/unarchive"
     },
+    "SetSessionProjectRequest": {
+      "type": "object",
+      "properties": {
+        "sessionId": {
+          "type": "string"
+        },
+        "projectId": {
+          "type": [
+            "string",
+            "null"
+          ],
+          "description": "The source name (kebab-case ID) of the project, or null to clear."
+        }
+      },
+      "required": [
+        "sessionId"
+      ],
+      "description": "Set or clear the project associated with a session.",
+      "x-side": "agent",
+      "x-method": "_goose/session/set_project"
+    },
     "CreateSourceRequest": {
       "type": "object",
       "properties": {
@@ -819,6 +840,11 @@
             "null"
           ],
           "description": "Absolute path to the project root. Required when `global` is false."
+        },
+        "properties": {
+          "type": "object",
+          "additionalProperties": {},
+          "description": "Arbitrary key/value metadata."
         }
       },
       "required": [
@@ -835,7 +861,8 @@
     "SourceType": {
       "type": "string",
       "enum": [
-        "skill"
+        "skill",
+        "project"
       ],
       "description": "The type of source entity."
     },
@@ -874,6 +901,11 @@
         "global": {
           "type": "boolean",
           "description": "True when the source lives in the user's global sources directory; false\nwhen it lives inside a specific project."
+        },
+        "properties": {
+          "type": "object",
+          "additionalProperties": {},
+          "description": "Arbitrary key/value pairs for type-specific metadata (e.g. icon, color,\npreferredProvider for projects). Stored in the frontmatter."
         }
       },
       "required": [
@@ -949,6 +981,11 @@
             "string",
             "null"
           ]
+        },
+        "properties": {
+          "type": "object",
+          "additionalProperties": {},
+          "description": "Arbitrary key/value metadata. Replaces all existing properties."
         }
       },
       "required": [
@@ -1621,6 +1658,15 @@
                   "description": "Params for _goose/session/unarchive",
                   "title": "UnarchiveSessionRequest"
                 },
+                {
+                  "allOf": [
+                    {
+                      "$ref": "#/$defs/SetSessionProjectRequest"
+                    }
+                  ],
+                  "description": "Params for _goose/session/set_project",
+                  "title": "SetSessionProjectRequest"
+                },
                 {
                   "allOf": [
                     {

crates/goose-acp/src/server.rs

@@ -1512,9 +1512,17 @@ impl GooseAcpAgent {
             .and_then(|v| v.as_str())
             .map(|s| s.to_string());
 
+        let requested_project = args
+            .meta
+            .as_ref()
+            .and_then(|m| m.get("project_id"))
+            .and_then(|v| v.as_str())
+            .map(|s| s.to_string());
+
         // Create the Thread — this IS the ACP session from the client's perspective.
         let thread_metadata = goose::session::ThreadMetadata {
             provider_id: requested_provider.clone(),
+            project_id: requested_project,
             mode: Some(self.goose_mode.to_string()),
             ..Default::default()
         };
@@ -3115,18 +3123,47 @@ impl GooseAcpAgent {
         Ok(EmptyResponse {})
     }
 
+    #[custom_method(SetSessionProjectRequest)]
+    async fn on_set_session_project(
+        &self,
+        req: SetSessionProjectRequest,
+    ) -> Result<EmptyResponse, sacp::Error> {
+        let thread_id = req.session_id.clone();
+        let project_id = req.project_id.clone();
+        self.update_thread_metadata(&thread_id, move |meta| {
+            meta.project_id = project_id;
+        })
+        .await?;
+        Ok(EmptyResponse {})
+    }
+
     #[custom_method(CreateSourceRequest)]
     async fn on_create_source(
         &self,
         req: CreateSourceRequest,
     ) -> Result<CreateSourceResponse, sacp::Error> {
+        // Resolve project_id to project_dir when creating a project-scoped source.
+        let project_dir = match (&req.project_id, &req.project_dir) {
+            (Some(pid), _) if !req.global => {
+                let dirs = goose::sources::project_working_dirs(pid);
+                Some(dirs.into_iter().next().ok_or_else(|| {
+                    sacp::Error::invalid_params().data(format!(
+                        "Project \"{}\" has no working directories configured",
+                        pid
+                    ))
+                })?)
+            }
+            (_, Some(pd)) => Some(pd.clone()),
+            _ => None,
+        };
         let source = goose::sources::create_source(
             req.source_type,
             &req.name,
             &req.description,
             &req.content,
             req.global,
-            req.project_dir.as_deref(),
+            project_dir.as_deref(),
+            req.properties,
         )?;
         Ok(CreateSourceResponse { source })
     }
@@ -3136,7 +3173,11 @@ impl GooseAcpAgent {
         &self,
         req: ListSourcesRequest,
     ) -> Result<ListSourcesResponse, sacp::Error> {
-        let sources = goose::sources::list_sources(req.source_type, req.project_dir.as_deref())?;
+        let sources = goose::sources::list_sources(
+            req.source_type,
+            req.project_dir.as_deref(),
+            req.include_project_sources,
+        )?;
         Ok(ListSourcesResponse { sources })
     }
 
@@ -3152,6 +3193,7 @@ impl GooseAcpAgent {
             &req.content,
             req.global,
             req.project_dir.as_deref(),
+            req.properties,
         )?;
         Ok(UpdateSourceResponse { source })
     }

crates/goose-sdk/src/custom_requests.rs

@@ -215,6 +215,16 @@ pub struct UnarchiveSessionRequest {
     pub session_id: String,
 }
 
+/// Set or clear the project associated with a session.
+#[derive(Debug, Default, Clone, Serialize, Deserialize, JsonSchema, JsonRpcRequest)]
+#[request(method = "_goose/session/set_project", response = EmptyResponse)]
+#[serde(rename_all = "camelCase")]
+pub struct SetSessionProjectRequest {
+    pub session_id: String,
+    /// The source name (kebab-case ID) of the project, or null to clear.
+    pub project_id: Option<String>,
+}
+
 /// Export a session as a JSON string.
 #[derive(Debug, Default, Clone, Serialize, Deserialize, JsonSchema, JsonRpcRequest)]
 #[request(method = "_goose/session/export", response = ExportSessionResponse)]
@@ -302,6 +312,7 @@ pub struct ProviderConfigKey {
 pub enum SourceType {
     #[default]
     Skill,
+    Project,
 }
 
 /// A source — a user-editable entity backed by an on-disk directory. Sources
@@ -319,6 +330,10 @@ pub struct SourceEntry {
     /// True when the source lives in the user's global sources directory; false
     /// when it lives inside a specific project.
     pub global: bool,
+    /// Arbitrary key/value pairs for type-specific metadata (e.g. icon, color,
+    /// preferredProvider for projects). Stored in the frontmatter.
+    #[serde(default, skip_serializing_if = "std::collections::HashMap::is_empty")]
+    pub properties: std::collections::HashMap<String, serde_json::Value>,
 }
 
 /// Create a new source (global or project-scoped).
@@ -335,6 +350,14 @@ pub struct CreateSourceRequest {
     /// Absolute path to the project root. Required when `global` is false.
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub project_dir: Option<String>,
+    /// Project source ID. When set with `global: false`, the backend resolves
+    /// the project's first working directory automatically. Takes precedence
+    /// over `project_dir`.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub project_id: Option<String>,
+    /// Arbitrary key/value metadata.
+    #[serde(default, skip_serializing_if = "std::collections::HashMap::is_empty")]
+    pub properties: std::collections::HashMap<String, serde_json::Value>,
 }
 
 #[derive(Debug, Default, Clone, Serialize, Deserialize, JsonSchema, JsonRpcResponse)]
@@ -353,6 +376,10 @@ pub struct ListSourcesRequest {
     pub source_type: Option<SourceType>,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub project_dir: Option<String>,
+    /// When true, also scan the working directories of all known projects for
+    /// project-scoped sources (e.g. skills stored under `{workingDir}/.agents/skills/`).
+    #[serde(default)]
+    pub include_project_sources: bool,
 }
 
 #[derive(Debug, Default, Clone, Serialize, Deserialize, JsonSchema, JsonRpcResponse)]
@@ -374,6 +401,9 @@ pub struct UpdateSourceRequest {
     pub global: bool,
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub project_dir: Option<String>,
+    /// Arbitrary key/value metadata. Replaces all existing properties.
+    #[serde(default, skip_serializing_if = "std::collections::HashMap::is_empty")]
+    pub properties: std::collections::HashMap<String, serde_json::Value>,
 }
 
 #[derive(Debug, Default, Clone, Serialize, Deserialize, JsonSchema, JsonRpcResponse)]

crates/goose/src/agents/agent.rs

@@ -334,6 +334,24 @@ impl Agent {
         messages
     }
 
+    async fn load_project_instructions(&self, session: &Session) -> Option<String> {
+        let thread_id = session.thread_id.as_deref()?;
+        let thread_mgr =
+            crate::session::ThreadManager::new(self.config.session_manager.storage().clone());
+        let thread = thread_mgr.get_thread(thread_id).await.ok()?;
+        let project_id = thread.metadata.project_id.as_deref()?;
+        let entry = crate::sources::read_project(project_id).ok()?;
+        let mut parts = Vec::new();
+        parts.push(format!("# Project: {}", entry.name));
+        if !entry.description.is_empty() {
+            parts.push(entry.description.clone());
+        }
+        if !entry.content.is_empty() {
+            parts.push(entry.content.clone());
+        }
+        Some(parts.join("\n\n"))
+    }
+
     async fn prepare_reply_context(
         &self,
         session_id: &str,
@@ -1194,6 +1212,14 @@ impl Agent {
             goose_mode,
             initial_messages,
         } = context;
+
+        // Inject project instructions into the system prompt when the thread
+        // has a project_id set. This replaces the frontend-side prompt assembly
+        // that previously prepended project context to every user message.
+        if let Some(project_addendum) = self.load_project_instructions(&session).await {
+            system_prompt = format!("{system_prompt}\n\n{project_addendum}");
+        }
+
         self.reset_retry_attempts().await;
 
         let provider = self.provider().await?;