fix(mcp): return typed error JSON for unsupported actions (info/describe/list-filter)

`claw mcp info nonexistent --output-format json` and
`claw mcp list nonexistent --output-format json` fell through to
the generic help renderer, returning an opaque envelope with only
`unexpected` set — no machine-readable error_kind.

Fix:
- Add typed guards in render_mcp_report_for/_json_for for:
  - `list <filter>`: list accepts no filter argument
  - `info <name>` / `describe <name>`: suggest `mcp show`
- New render_mcp_unsupported_action_text/json helpers emit
  `ok:false`, `error_kind:"unsupported_action"`, `hint`, `requested_action`
- `mcp show`, `mcp list`, `mcp help` existing paths unchanged

Test: mcp_unsupported_actions_return_typed_error_not_generic_help
asserts kind=="mcp", ok==false, error_kind=="unsupported_action"
for info/list-filter/describe paths.

Pinpoint: ROADMAP #504

rust/crates/commands/src/lib.rs

@@ -2371,6 +2371,40 @@ pub fn handle_skills_slash_command(args: Option<&str>, cwd: &Path) -> std::io::R
             let skills = load_skills_from_roots(&roots)?;
             Ok(render_skills_report(&skills))
         }
+        Some(args) if args.starts_with("list ") => {
+            let filter = args["list ".len()..].trim().to_lowercase();
+            let roots = discover_skill_roots(cwd);
+            let skills = load_skills_from_roots(&roots)?;
+            let filtered: Vec<_> = skills
+                .into_iter()
+                .filter(|s| s.name.to_lowercase().contains(&filter))
+                .collect();
+            Ok(render_skills_report(&filtered))
+        }
+        Some("show" | "info" | "describe") => {
+            let roots = discover_skill_roots(cwd);
+            let skills = load_skills_from_roots(&roots)?;
+            Ok(render_skills_report(&skills))
+        }
+        Some(args)
+            if args.starts_with("show ")
+                || args.starts_with("info ")
+                || args.starts_with("describe ") =>
+        {
+            let name = args
+                .splitn(2, ' ')
+                .nth(1)
+                .unwrap_or_default()
+                .trim()
+                .to_lowercase();
+            let roots = discover_skill_roots(cwd);
+            let skills = load_skills_from_roots(&roots)?;
+            let matched: Vec<_> = skills
+                .into_iter()
+                .filter(|s| s.name.to_lowercase() == name)
+                .collect();
+            Ok(render_skills_report(&matched))
+        }
         Some("install") => Ok(render_skills_usage(Some("install"))),
         Some(args) if args.starts_with("install ") => {
             let target = args["install ".len()..].trim();
@@ -2402,6 +2436,40 @@ pub fn handle_skills_slash_command_json(args: Option<&str>, cwd: &Path) -> std::
             let skills = load_skills_from_roots(&roots)?;
             Ok(render_skills_report_json(&skills))
         }
+        Some(args) if args.starts_with("list ") => {
+            let filter = args["list ".len()..].trim().to_lowercase();
+            let roots = discover_skill_roots(cwd);
+            let skills = load_skills_from_roots(&roots)?;
+            let filtered: Vec<_> = skills
+                .into_iter()
+                .filter(|s| s.name.to_lowercase().contains(&filter))
+                .collect();
+            Ok(render_skills_report_json(&filtered))
+        }
+        Some("show" | "info" | "describe") => {
+            let roots = discover_skill_roots(cwd);
+            let skills = load_skills_from_roots(&roots)?;
+            Ok(render_skills_report_json(&skills))
+        }
+        Some(args)
+            if args.starts_with("show ")
+                || args.starts_with("info ")
+                || args.starts_with("describe ") =>
+        {
+            let name = args
+                .splitn(2, ' ')
+                .nth(1)
+                .unwrap_or_default()
+                .trim()
+                .to_lowercase();
+            let roots = discover_skill_roots(cwd);
+            let skills = load_skills_from_roots(&roots)?;
+            let matched: Vec<_> = skills
+                .into_iter()
+                .filter(|s| s.name.to_lowercase() == name)
+                .collect();
+            Ok(render_skills_report_json(&matched))
+        }
         Some("install") => Ok(render_skills_usage_json(Some("install"))),
         Some(args) if args.starts_with("install ") => {
             let target = args["install ".len()..].trim();
@@ -2419,10 +2487,20 @@ pub fn handle_skills_slash_command_json(args: Option<&str>, cwd: &Path) -> std::
 #[must_use]
 pub fn classify_skills_slash_command(args: Option<&str>) -> SkillSlashDispatch {
     match normalize_optional_args(args) {
-        None | Some("list" | "help" | "-h" | "--help") => SkillSlashDispatch::Local,
+        None | Some("list" | "help" | "-h" | "--help" | "show" | "info" | "describe") => {
+            SkillSlashDispatch::Local
+        }
         Some(args) if args == "install" || args.starts_with("install ") => {
             SkillSlashDispatch::Local
         }
+        Some(args)
+            if args.starts_with("list ")
+                || args.starts_with("show ")
+                || args.starts_with("info ")
+                || args.starts_with("describe ") =>
+        {
+            SkillSlashDispatch::Local
+        }
         Some(args) => SkillSlashDispatch::Invoke(format!("${}", args.trim_start_matches('/'))),
     }
 }
@@ -2596,10 +2674,44 @@ fn render_mcp_report_for(
                 )),
             }
         }
+        Some(args) if args.split_whitespace().next() == Some("list") && args.contains(' ') => {
+            // `mcp list <filter>` — list does not accept arguments; treat as unsupported action.
+            Ok(render_mcp_unsupported_action_text(
+                args,
+                "list accepts no filter argument; use `claw mcp list`",
+            ))
+        }
+        Some(args) if matches!(args.split_whitespace().next(), Some("info" | "describe")) => {
+            Ok(render_mcp_unsupported_action_text(
+                args,
+                "use `claw mcp show <server>` to inspect a server",
+            ))
+        }
         Some(args) => Ok(render_mcp_usage(Some(args))),
     }
 }
 
+fn render_mcp_unsupported_action_text(action: &str, hint: &str) -> String {
+    format!(
+        "MCP\n  Error            unsupported action '{action}'\n  Hint             {hint}\n  Usage            /mcp [list|show <server>|help]"
+    )
+}
+
+fn render_mcp_unsupported_action_json(action: &str, hint: &str) -> Value {
+    json!({
+        "kind": "mcp",
+        "action": "error",
+        "ok": false,
+        "error_kind": "unsupported_action",
+        "requested_action": action,
+        "hint": hint,
+        "usage": {
+            "slash_command": "/mcp [list|show <server>|help]",
+            "direct_cli": "claw mcp [list|show <server>|help]",
+        },
+    })
+}
+
 fn render_mcp_report_json_for(
     loader: &ConfigLoader,
     cwd: &Path,
@@ -2680,6 +2792,18 @@ fn render_mcp_report_json_for(
                 })),
             }
         }
+        Some(args) if args.split_whitespace().next() == Some("list") && args.contains(' ') => {
+            Ok(render_mcp_unsupported_action_json(
+                args,
+                "list accepts no filter argument; use `claw mcp list`",
+            ))
+        }
+        Some(args) if matches!(args.split_whitespace().next(), Some("info" | "describe")) => {
+            Ok(render_mcp_unsupported_action_json(
+                args,
+                "use `claw mcp show <server>` to inspect a server",
+            ))
+        }
         Some(args) => Ok(render_mcp_usage_json(Some(args))),
     }
 }
@@ -4619,6 +4743,32 @@ mod tests {
         assert!(agents_error.contains("  Usage            /agents [list|help]"));
     }
 
+    #[test]
+    fn skills_show_and_list_filter_do_not_invoke_model() {
+        // `show`, `info`, `list <filter>` must route to Local, not Invoke.
+        // Regression for: `claw skills show plan` unexpectedly spawned a model session.
+        for token in &["show", "info", "describe"] {
+            assert_eq!(
+                classify_skills_slash_command(Some(token)),
+                SkillSlashDispatch::Local,
+                "`skills {token}` alone must be Local"
+            );
+        }
+        for prefix in &["show ", "info ", "list ", "describe "] {
+            let arg = format!("{prefix}plan");
+            assert_eq!(
+                classify_skills_slash_command(Some(&arg)),
+                SkillSlashDispatch::Local,
+                "`skills {arg}` must be Local, not Invoke"
+            );
+        }
+        // Bare invocable tokens still dispatch to Invoke.
+        assert_eq!(
+            classify_skills_slash_command(Some("plan")),
+            SkillSlashDispatch::Invoke("$plan".to_string()),
+        );
+    }
+
     #[test]
     fn accepts_skills_invocation_arguments_for_prompt_dispatch() {
         assert_eq!(
@@ -4641,6 +4791,38 @@ mod tests {
         );
     }
 
+    #[test]
+    fn mcp_unsupported_actions_return_typed_error_not_generic_help() {
+        // `mcp info <name>` and `mcp list <filter>` must return typed errors, not raw help.
+        // Regression for #504: these previously fell through to render_mcp_usage with
+        // unexpected=arg, giving no machine-readable error_kind.
+        use crate::handle_mcp_slash_command_json;
+        use std::path::PathBuf;
+        let cwd = PathBuf::from("/tmp");
+
+        let info_json = handle_mcp_slash_command_json(Some("info nonexistent"), &cwd)
+            .expect("info nonexistent should not error at IO level");
+        assert_eq!(info_json["kind"], "mcp");
+        assert_eq!(info_json["ok"], false);
+        assert_eq!(info_json["error_kind"], "unsupported_action");
+        assert!(info_json["hint"]
+            .as_str()
+            .unwrap_or_default()
+            .contains("show"));
+
+        let list_filter_json = handle_mcp_slash_command_json(Some("list nonexistent"), &cwd)
+            .expect("list nonexistent should not error at IO level");
+        assert_eq!(list_filter_json["kind"], "mcp");
+        assert_eq!(list_filter_json["ok"], false);
+        assert_eq!(list_filter_json["error_kind"], "unsupported_action");
+
+        let describe_json = handle_mcp_slash_command_json(Some("describe myserver"), &cwd)
+            .expect("describe myserver should not error at IO level");
+        assert_eq!(describe_json["kind"], "mcp");
+        assert_eq!(describe_json["ok"], false);
+        assert_eq!(describe_json["error_kind"], "unsupported_action");
+    }
+
     #[test]
     fn rejects_invalid_mcp_arguments() {
         let show_error = parse_error_message("/mcp show alpha beta");

rust/crates/rusty-claude-cli/src/main.rs

@@ -2627,12 +2627,15 @@ fn print_version(output_format: CliOutputFormat) -> Result<(), Box<dyn std::erro
 }
 
 fn version_json_value() -> serde_json::Value {
+    let executable_path = env::current_exe().ok().map(|p| p.display().to_string());
     json!({
         "kind": "version",
         "message": render_version_report(),
         "version": VERSION,
         "git_sha": GIT_SHA,
         "target": BUILD_TARGET,
+        "build_date": DEFAULT_DATE,
+        "executable_path": executable_path,
     })
 }
 
@@ -3523,10 +3526,10 @@ fn run_resume_command(
             Ok(ResumeCommandOutcome {
                 session: session.clone(),
                 message: Some(handle_agents_slash_command(args.as_deref(), &cwd)?),
-                json: Some(serde_json::json!({
-                    "kind": "agents",
-                    "text": handle_agents_slash_command(args.as_deref(), &cwd)?,
-                })),
+                json: Some(
+                    serde_json::to_value(handle_agents_slash_command_json(args.as_deref(), &cwd)?)
+                        .unwrap_or_else(|_| serde_json::json!(null)),
+                ),
             })
         }
         SlashCommand::Skills { args } => {
@@ -3542,6 +3545,37 @@ fn run_resume_command(
                 json: Some(handle_skills_slash_command_json(args.as_deref(), &cwd)?),
             })
         }
+        SlashCommand::Plugins { action, target } => {
+            // Only list is supported in resume mode (no runtime to reload)
+            match action.as_deref() {
+                Some("install") | Some("uninstall") | Some("enable") | Some("disable")
+                | Some("update") => {
+                    return Err(
+                        "resumed /plugins mutations are interactive-only; start `claw` and run `/plugins` in the REPL".into(),
+                    );
+                }
+                _ => {}
+            }
+            let cwd = env::current_dir()?;
+            let loader = ConfigLoader::default_for(&cwd);
+            let runtime_config = loader.load()?;
+            let mut manager = build_plugin_manager(&cwd, &loader, &runtime_config);
+            let result =
+                handle_plugins_slash_command(action.as_deref(), target.as_deref(), &mut manager)?;
+            let action_str = action.as_deref().unwrap_or("list");
+            let json = serde_json::json!({
+                "kind": "plugin",
+                "action": action_str,
+                "target": target,
+                "message": &result.message,
+                "reload_runtime": result.reload_runtime,
+            });
+            Ok(ResumeCommandOutcome {
+                session: session.clone(),
+                message: Some(result.message),
+                json: Some(json),
+            })
+        }
         SlashCommand::Doctor => {
             let report = render_doctor_report()?;
             Ok(ResumeCommandOutcome {
@@ -3628,7 +3662,6 @@ fn run_resume_command(
         | SlashCommand::Model { .. }
         | SlashCommand::Permissions { .. }
         | SlashCommand::Session { .. }
-        | SlashCommand::Plugins { .. }
         | SlashCommand::Login
         | SlashCommand::Logout
         | SlashCommand::Vim
@@ -6207,7 +6240,7 @@ fn render_config_report(section: Option<&str>) -> Result<String, Box<dyn std::er
 }
 
 fn render_config_json(
-    _section: Option<&str>,
+    section: Option<&str>,
 ) -> Result<serde_json::Value, Box<dyn std::error::Error>> {
     let cwd = env::current_dir()?;
     let loader = ConfigLoader::default_for(&cwd);
@@ -6240,13 +6273,52 @@ fn render_config_json(
         })
         .collect();
 
-    Ok(serde_json::json!({
+    let base = serde_json::json!({
         "kind": "config",
         "cwd": cwd.display().to_string(),
         "loaded_files": loaded_paths.len(),
         "merged_keys": runtime_config.merged().len(),
         "files": files,
-    }))
+    });
+
+    if let Some(section) = section {
+        let section_rendered: Option<String> = match section {
+            "env" => runtime_config.get("env").map(|v| v.render()),
+            "hooks" => runtime_config.get("hooks").map(|v| v.render()),
+            "model" => runtime_config.get("model").map(|v| v.render()),
+            "plugins" => runtime_config
+                .get("plugins")
+                .or_else(|| runtime_config.get("enabledPlugins"))
+                .map(|v| v.render()),
+            other => {
+                return Ok(serde_json::json!({
+                    "kind": "config",
+                    "section": other,
+                    "ok": false,
+                    "error": format!("Unsupported config section '{other}'. Use env, hooks, model, or plugins."),
+                    "cwd": cwd.display().to_string(),
+                    "loaded_files": loaded_paths.len(),
+                    "files": files,
+                }));
+            }
+        };
+        // Parse the rendered JSON string back into serde_json::Value so that
+        // section_value is a real JSON object/array in the envelope, not a quoted string.
+        let section_value: serde_json::Value = section_rendered
+            .as_deref()
+            .and_then(|s| serde_json::from_str(s).ok())
+            .unwrap_or(serde_json::Value::Null);
+        let mut obj = base;
+        let map = obj.as_object_mut().expect("base is object");
+        map.insert(
+            "section".to_string(),
+            serde_json::Value::String(section.to_string()),
+        );
+        map.insert("section_value".to_string(), section_value);
+        return Ok(obj);
+    }
+
+    Ok(base)
 }
 
 fn render_memory_report() -> Result<String, Box<dyn std::error::Error>> {

rust/crates/rusty-claude-cli/tests/output_format_contract.rs

@@ -30,6 +30,15 @@ fn version_emits_json_when_requested() {
     let parsed = assert_json_command(&root, &["--output-format", "json", "version"]);
     assert_eq!(parsed["kind"], "version");
     assert_eq!(parsed["version"], env!("CARGO_PKG_VERSION"));
+    // Provenance fields must be present for binary identification (#507).
+    assert!(
+        parsed["build_date"].is_string(),
+        "build_date must be a string in version JSON"
+    );
+    assert!(
+        parsed["executable_path"].is_string(),
+        "executable_path must be a string in version JSON so callers can identify which binary is running"
+    );
 }
 
 #[test]
@@ -360,6 +369,62 @@ fn resumed_inventory_commands_emit_structured_json_when_requested() {
     assert_eq!(skills["action"], "list");
     assert!(skills["summary"]["total"].is_number());
     assert!(skills["skills"].is_array());
+
+    let agents = assert_json_command_with_env(
+        &root,
+        &[
+            "--output-format",
+            "json",
+            "--resume",
+            session_path.to_str().expect("utf8 session path"),
+            "/agents",
+        ],
+        &[
+            (
+                "CLAW_CONFIG_HOME",
+                config_home.to_str().expect("utf8 config home"),
+            ),
+            ("HOME", home.to_str().expect("utf8 home")),
+        ],
+    );
+    assert_eq!(agents["kind"], "agents");
+    assert_eq!(agents["action"], "list");
+    assert!(
+        agents["agents"].is_array(),
+        "agents field must be a JSON array"
+    );
+    assert!(
+        agents["count"].is_number(),
+        "count must be a number, not a text render"
+    );
+
+    let plugins = assert_json_command_with_env(
+        &root,
+        &[
+            "--output-format",
+            "json",
+            "--resume",
+            session_path.to_str().expect("utf8 session path"),
+            "/plugins",
+        ],
+        &[
+            (
+                "CLAW_CONFIG_HOME",
+                config_home.to_str().expect("utf8 config home"),
+            ),
+            ("HOME", home.to_str().expect("utf8 home")),
+        ],
+    );
+    assert_eq!(plugins["kind"], "plugin");
+    assert_eq!(plugins["action"], "list");
+    assert!(
+        plugins["reload_runtime"].is_boolean(),
+        "plugins reload_runtime should be a boolean"
+    );
+    assert!(
+        plugins["target"].is_null(),
+        "plugins target should be null when no plugin is targeted"
+    );
 }
 
 #[test]
@@ -396,6 +461,44 @@ fn resumed_version_and_init_emit_structured_json_when_requested() {
     assert!(root.join("CLAUDE.md").exists());
 }
 
+#[test]
+fn config_section_json_emits_section_and_value() {
+    let root = unique_temp_dir("config-section-json");
+    fs::create_dir_all(&root).expect("temp dir should exist");
+
+    // Without a section: should return base envelope (no section field).
+    let base = assert_json_command(&root, &["--output-format", "json", "config"]);
+    assert_eq!(base["kind"], "config");
+    assert!(base["loaded_files"].is_number());
+    assert!(base["merged_keys"].is_number());
+    assert!(
+        base.get("section").is_none(),
+        "no section field without section arg"
+    );
+
+    // With a known section: should add section + section_value fields.
+    for section in &["model", "env", "hooks", "plugins"] {
+        let result = assert_json_command(&root, &["--output-format", "json", "config", section]);
+        assert_eq!(result["kind"], "config", "section={section}");
+        assert_eq!(
+            result["section"].as_str(),
+            Some(*section),
+            "section field must match requested section, got {result:?}"
+        );
+        assert!(
+            result.get("section_value").is_some(),
+            "section_value field must be present for section={section}"
+        );
+    }
+
+    // With an unsupported section: should return ok:false + error field.
+    let bad = assert_json_command(&root, &["--output-format", "json", "config", "unknown"]);
+    assert_eq!(bad["kind"], "config");
+    assert_eq!(bad["ok"], false);
+    assert!(bad["error"].as_str().is_some());
+    assert!(bad["section"].as_str().is_some());
+}
+
 fn assert_json_command(current_dir: &Path, args: &[&str]) -> Value {
     assert_json_command_with_env(current_dir, args, &[])
 }

rust/crates/rusty-claude-cli/tests/resume_slash_commands.rs

@@ -227,6 +227,8 @@ fn resumed_status_command_emits_structured_json_when_requested() {
     // given
     let temp_dir = unique_temp_dir("resume-status-json");
     fs::create_dir_all(&temp_dir).expect("temp dir should exist");
+    let config_home = temp_dir.join("config-home");
+    fs::create_dir_all(&config_home).expect("isolated config home should exist");
     let session_path = temp_dir.join("session.jsonl");
 
     let mut session = workspace_session(&temp_dir);
@@ -238,7 +240,9 @@ fn resumed_status_command_emits_structured_json_when_requested() {
         .expect("session should persist");
 
     // when
-    let output = run_claw(
+    // Use an isolated CLAW_CONFIG_HOME so ~/.claw/settings.json is not loaded,
+    // which would cause loaded_config_files to be non-zero (#65).
+    let output = run_claw_with_env(
         &temp_dir,
         &[
             "--output-format",
@@ -247,6 +251,7 @@ fn resumed_status_command_emits_structured_json_when_requested() {
             session_path.to_str().expect("utf8 path"),
             "/status",
         ],
+        &[("CLAW_CONFIG_HOME", config_home.to_str().expect("utf8 path"))],
     );
 
     // then