diff --git a/packages/opencode/src/server/routes/instance/httpapi/groups/config.ts b/packages/opencode/src/server/routes/instance/httpapi/groups/config.ts
index 0fd2d19..42a5768 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/groups/config.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/groups/config.ts
@@ -16,6 +16,7 @@ export const ConfigApi = HttpApi.make("config")
         HttpApiEndpoint.get("get", root, {
           query: WorkspaceRoutingQuery,
           success: described(ConfigV1.Info, "Get config info"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "config.get",
@@ -38,6 +39,7 @@ export const ConfigApi = HttpApi.make("config")
         HttpApiEndpoint.get("providers", `${root}/providers`, {
           query: WorkspaceRoutingQuery,
           success: described(Provider.ConfigProvidersResult, "List of providers"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "config.providers",
diff --git a/packages/opencode/src/server/routes/instance/httpapi/groups/experimental.ts b/packages/opencode/src/server/routes/instance/httpapi/groups/experimental.ts
index 5e40fcd..af2cdb2 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/groups/experimental.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/groups/experimental.ts
@@ -108,6 +108,7 @@ export const ExperimentalApi = HttpApi.make("experimental")
         HttpApiEndpoint.get("capabilities", ExperimentalPaths.capabilities, {
           query: WorkspaceRoutingQuery,
           success: described(CapabilitiesResponse, "Experimental capabilities"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "experimental.capabilities.get",
@@ -224,6 +225,7 @@ export const ExperimentalApi = HttpApi.make("experimental")
         HttpApiEndpoint.get("session", ExperimentalPaths.session, {
           query: SessionListQuery,
           success: described(Schema.Array(Session.GlobalInfo), "List of sessions"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "experimental.session.list",
@@ -248,6 +250,7 @@ export const ExperimentalApi = HttpApi.make("experimental")
         HttpApiEndpoint.get("resource", ExperimentalPaths.resource, {
           query: WorkspaceRoutingQuery,
           success: described(Schema.Record(Schema.String, MCP.Resource), "MCP resources"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "experimental.resource.list",
diff --git a/packages/opencode/src/server/routes/instance/httpapi/groups/global.ts b/packages/opencode/src/server/routes/instance/httpapi/groups/global.ts
index 97b72dc..0038147 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/groups/global.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/groups/global.ts
@@ -75,6 +75,7 @@ export const GlobalApi = HttpApi.make("global").add(
     .add(
       HttpApiEndpoint.get("health", GlobalPaths.health, {
         success: described(GlobalHealth, "Health information"),
+        error: HttpApiError.BadRequest,
       }).annotateMerge(
         OpenApi.annotations({
           identifier: "global.health",
@@ -84,6 +85,7 @@ export const GlobalApi = HttpApi.make("global").add(
       ),
       HttpApiEndpoint.get("event", GlobalPaths.event, {
         success: GlobalEventSchema,
+        error: HttpApiError.BadRequest,
       }).annotateMerge(
         OpenApi.annotations({
           identifier: "global.event",
@@ -93,6 +95,7 @@ export const GlobalApi = HttpApi.make("global").add(
       ),
       HttpApiEndpoint.get("configGet", GlobalPaths.config, {
         success: described(ConfigV1.Info, "Get global config info"),
+        error: HttpApiError.BadRequest,
       }).annotateMerge(
         OpenApi.annotations({
           identifier: "global.config.get",
@@ -113,6 +116,7 @@ export const GlobalApi = HttpApi.make("global").add(
       ),
       HttpApiEndpoint.post("dispose", GlobalPaths.dispose, {
         success: described(Schema.Boolean, "Global disposed"),
+        error: HttpApiError.BadRequest,
       }).annotateMerge(
         OpenApi.annotations({
           identifier: "global.dispose",
diff --git a/packages/opencode/src/server/routes/instance/httpapi/groups/mcp.ts b/packages/opencode/src/server/routes/instance/httpapi/groups/mcp.ts
index a6fb064..e45573f 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/groups/mcp.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/groups/mcp.ts
@@ -45,6 +45,7 @@ export const McpApi = HttpApi.make("mcp")
         HttpApiEndpoint.get("status", McpPaths.status, {
           query: WorkspaceRoutingQuery,
           success: described(Schema.Record(Schema.String, MCP.Status), "MCP server status"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "mcp.status",
diff --git a/packages/opencode/src/server/routes/instance/httpapi/groups/permission.ts b/packages/opencode/src/server/routes/instance/httpapi/groups/permission.ts
index 79959db..9101c33 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/groups/permission.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/groups/permission.ts
@@ -21,6 +21,7 @@ export const PermissionApi = HttpApi.make("permission")
         HttpApiEndpoint.get("list", root, {
           query: WorkspaceRoutingQuery,
           success: described(Schema.Array(PermissionV1.Request), "List of pending permissions"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "permission.list",
diff --git a/packages/opencode/src/server/routes/instance/httpapi/groups/project.ts b/packages/opencode/src/server/routes/instance/httpapi/groups/project.ts
index fd0c131..90be12c 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/groups/project.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/groups/project.ts
@@ -22,6 +22,7 @@ export const ProjectApi = HttpApi.make("project")
         HttpApiEndpoint.get("list", root, {
           query: WorkspaceRoutingQuery,
           success: described(Schema.Array(Project.Info), "List of projects"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "project.list",
@@ -32,6 +33,7 @@ export const ProjectApi = HttpApi.make("project")
         HttpApiEndpoint.get("current", `${root}/current`, {
           query: WorkspaceRoutingQuery,
           success: described(Project.Info, "Current project information"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "project.current",
@@ -42,6 +44,7 @@ export const ProjectApi = HttpApi.make("project")
         HttpApiEndpoint.post("initGit", `${root}/git/init`, {
           query: WorkspaceRoutingQuery,
           success: described(Project.Info, "Project information after git initialization"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "project.initGit",
@@ -66,6 +69,7 @@ export const ProjectApi = HttpApi.make("project")
           params: { projectID: ProjectV2.ID },
           query: WorkspaceRoutingQuery,
           success: described(ProjectV2.Directories, "Project directories"),
+          error: [HttpApiError.BadRequest, ProjectNotFoundError],
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "project.directories",
diff --git a/packages/opencode/src/server/routes/instance/httpapi/groups/pty.ts b/packages/opencode/src/server/routes/instance/httpapi/groups/pty.ts
index ead86af..9f4f301 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/groups/pty.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/groups/pty.ts
@@ -44,6 +44,7 @@ export const PtyApi = HttpApi.make("pty")
         HttpApiEndpoint.get("shells", PtyPaths.shells, {
           query: WorkspaceRoutingQuery,
           success: described(Schema.Array(ShellItem), "List of shells"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "pty.shells",
@@ -54,6 +55,7 @@ export const PtyApi = HttpApi.make("pty")
         HttpApiEndpoint.get("list", PtyPaths.list, {
           query: WorkspaceRoutingQuery,
           success: described(Schema.Array(Pty.Info), "List of sessions"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "pty.list",
diff --git a/packages/opencode/src/server/routes/instance/httpapi/groups/question.ts b/packages/opencode/src/server/routes/instance/httpapi/groups/question.ts
index e9e6342..673ff27 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/groups/question.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/groups/question.ts
@@ -22,6 +22,7 @@ export const QuestionApi = HttpApi.make("question")
         HttpApiEndpoint.get("list", root, {
           query: WorkspaceRoutingQuery,
           success: described(Schema.Array(Question.Request), "List of pending questions"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "question.list",
diff --git a/packages/opencode/src/server/routes/instance/httpapi/groups/sync.ts b/packages/opencode/src/server/routes/instance/httpapi/groups/sync.ts
index ca9b1cd..7e9fd1b 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/groups/sync.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/groups/sync.ts
@@ -49,6 +49,7 @@ export const SyncApi = HttpApi.make("sync")
         HttpApiEndpoint.post("start", SyncPaths.start, {
           query: WorkspaceRoutingQuery,
           success: described(Schema.Boolean, "Workspace sync started"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "sync.start",
diff --git a/packages/opencode/src/server/routes/instance/httpapi/groups/tui.ts b/packages/opencode/src/server/routes/instance/httpapi/groups/tui.ts
index 849c416..932dbfc 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/groups/tui.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/groups/tui.ts
@@ -68,6 +68,7 @@ export const TuiApi = HttpApi.make("tui")
         HttpApiEndpoint.post("openHelp", TuiPaths.openHelp, {
           query: WorkspaceRoutingQuery,
           success: described(Schema.Boolean, "Help dialog opened successfully"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "tui.openHelp",
@@ -78,6 +79,7 @@ export const TuiApi = HttpApi.make("tui")
         HttpApiEndpoint.post("openSessions", TuiPaths.openSessions, {
           query: WorkspaceRoutingQuery,
           success: described(Schema.Boolean, "Session dialog opened successfully"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "tui.openSessions",
@@ -88,6 +90,7 @@ export const TuiApi = HttpApi.make("tui")
         HttpApiEndpoint.post("openThemes", TuiPaths.openThemes, {
           query: WorkspaceRoutingQuery,
           success: described(Schema.Boolean, "Theme dialog opened successfully"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "tui.openThemes",
@@ -98,6 +101,7 @@ export const TuiApi = HttpApi.make("tui")
         HttpApiEndpoint.post("openModels", TuiPaths.openModels, {
           query: WorkspaceRoutingQuery,
           success: described(Schema.Boolean, "Model dialog opened successfully"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "tui.openModels",
@@ -108,6 +112,7 @@ export const TuiApi = HttpApi.make("tui")
         HttpApiEndpoint.post("submitPrompt", TuiPaths.submitPrompt, {
           query: WorkspaceRoutingQuery,
           success: described(Schema.Boolean, "Prompt submitted successfully"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "tui.submitPrompt",
@@ -118,6 +123,7 @@ export const TuiApi = HttpApi.make("tui")
         HttpApiEndpoint.post("clearPrompt", TuiPaths.clearPrompt, {
           query: WorkspaceRoutingQuery,
           success: described(Schema.Boolean, "Prompt cleared successfully"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "tui.clearPrompt",
@@ -141,6 +147,7 @@ export const TuiApi = HttpApi.make("tui")
           query: WorkspaceRoutingQuery,
           payload: TuiEvent.ToastShow.data,
           success: described(Schema.Boolean, "Toast notification shown successfully"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "tui.showToast",
@@ -175,6 +182,7 @@ export const TuiApi = HttpApi.make("tui")
         HttpApiEndpoint.get("controlNext", TuiPaths.controlNext, {
           query: WorkspaceRoutingQuery,
           success: described(TuiRequestPayload, "Next TUI request"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "tui.control.next",
@@ -186,6 +194,7 @@ export const TuiApi = HttpApi.make("tui")
           query: WorkspaceRoutingQuery,
           payload: Schema.Unknown,
           success: described(Schema.Boolean, "Response submitted successfully"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "tui.control.response",
diff --git a/packages/opencode/src/server/routes/instance/httpapi/groups/workspace.ts b/packages/opencode/src/server/routes/instance/httpapi/groups/workspace.ts
index 09a6e67..60646d6 100644
--- a/packages/opencode/src/server/routes/instance/httpapi/groups/workspace.ts
+++ b/packages/opencode/src/server/routes/instance/httpapi/groups/workspace.ts
@@ -53,6 +53,7 @@ export const WorkspaceApi = HttpApi.make("workspace")
         HttpApiEndpoint.get("adapters", WorkspacePaths.adapters, {
           query: WorkspaceRoutingQuery,
           success: described(Schema.Array(WorkspaceAdapterEntry), "Workspace adapters"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "experimental.workspace.adapter.list",
@@ -63,6 +64,7 @@ export const WorkspaceApi = HttpApi.make("workspace")
         HttpApiEndpoint.get("list", WorkspacePaths.list, {
           query: WorkspaceRoutingQuery,
           success: described(Schema.Array(Workspace.Info), "Workspaces"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "experimental.workspace.list",
@@ -85,6 +87,7 @@ export const WorkspaceApi = HttpApi.make("workspace")
         HttpApiEndpoint.post("syncList", WorkspacePaths.syncList, {
           query: WorkspaceRoutingQuery,
           success: described(HttpApiSchema.NoContent, "Workspace list synced"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "experimental.workspace.syncList",
@@ -95,6 +98,7 @@ export const WorkspaceApi = HttpApi.make("workspace")
         HttpApiEndpoint.get("status", WorkspacePaths.status, {
           query: WorkspaceRoutingQuery,
           success: described(Schema.Array(Workspace.ConnectionStatus), "Workspace status"),
+          error: HttpApiError.BadRequest,
         }).annotateMerge(
           OpenApi.annotations({
             identifier: "experimental.workspace.status",