fix: empty-prompt error now returns non-null hint via newline-delimited usage string

claw '' and claw '   ' returned empty_prompt + hint:null because the
error message had no newline delimiter. Added usage hint. 61 CLI
contract tests pass.

.github/hooks/pre-push

@@ -13,7 +13,7 @@ cd "$repo_root"
 
 if [[ -x scripts/roadmap-check-ids.sh ]]; then
   echo "pre-push: scripts/roadmap-check-ids.sh" >&2
-  scripts/roadmap-check-ids.sh >&2
+  scripts/roadmap-check-ids.sh
 fi
 
 if [[ "${SKIP_CLAW_PRE_PUSH_BUILD:-}" == "1" ]]; then

ROADMAP.md

@@ -7735,3 +7735,27 @@ Original filing (2026-04-18): the session emitted `SessionStart hook (completed)
 783. **`claw --output-format json init` success envelope was missing `hint` field; idempotent re-init was not structurally detectable** — dogfooded 2026-05-27 on `32c9276f`. The init JSON envelope had no `hint` field (absent, not null), and no field to distinguish a fresh init from a re-init without checking `created.len() == 0`. Orchestrators had to inspect `created` array length to detect idempotent behavior. Fix: (1) added `hint` field to init JSON envelope — fresh path points at `CLAUDE.md + doctor`; idempotent path says "already initialised, run doctor"; (2) added `already_initialized: bool` field — `true` when `created` and `updated` are both empty (all artifacts skipped). Both test cases (fresh + re-init) covered by `init_json_envelope_has_hint_and_already_initialized_783`. 42 CLI contract tests pass. [SCOPE: claw-code] Source: Jobdori init-envelope probe on `32c9276f`, 2026-05-27.
 
 784. **`claw export` had two opaque arg-error paths returning `error_kind:"unknown"` + `hint:null`** — dogfooded 2026-05-27 on `81fe0ccb` (pinpoint by Gaebal-gajae). `claw export --output` (missing flag value) emitted plain `"missing value for --output"` with no typed prefix; `claw export a.md b.md` (extra positional) emitted plain `"unexpected export argument: second.md"`. Both classified as `unknown+null`. Fix: (1) `--output` missing-value error now uses `missing_flag_value:` prefix + `\n` usage hint; (2) extra positional now uses `unexpected_extra_args:` prefix + `\n` usage hint; (3) classifier `unexpected_extra_args` arm extended to match both `starts_with("unexpected extra arguments")` (prose form, #766) and `starts_with("unexpected_extra_args:")` (typed prefix form, #784). Integration test `export_arg_errors_have_typed_kind_and_hint_784` covers both paths. 43 CLI contract tests pass. [SCOPE: claw-code] Source: Gaebal-gajae pinpoint + Jobdori implementation on `81fe0ccb`, 2026-05-27.
+
+785. **`claw dump` (typo/near-miss for dump-manifests) returned `error_kind:"unknown"` — no classifier arm for `"unknown subcommand:"` prose prefix** — dogfooded 2026-05-27 on `e628b4bb`. Any unknown top-level subcommand that triggers the suggestion path emitted `"unknown subcommand: <x>.\nDid you mean <y>"` but `classify_error_kind` had no arm for that prefix; all fell to the `"unknown"` catch-all. The hint was non-null (the suggestion text was extracted by `split_error_hint`) but `error_kind` was undifferentiated. Fix: added `starts_with("unknown subcommand:")` → `"unknown_subcommand"` arm. Unit test assertion + integration test `unknown_subcommand_returns_typed_kind_785` using `claw dump` as the trigger. 44 CLI contract tests pass. [SCOPE: claw-code] Source: Jobdori subcommand-classifier probe on `e628b4bb`, 2026-05-27.
+
+786. **`claw dump-manifests --manifests-dir` (missing value) and `--manifests-dir=` (empty) both returned `error_kind:"unknown"` + `hint:null`** — dogfooded 2026-05-27 on `87f43347` (pinpoint by Gaebal-gajae). Both missing `--manifests-dir` branches in `parse_dump_manifests_args` emitted plain `"--manifests-dir requires a path"` with no typed prefix; `classify_error_kind` had no matching arm so they fell to `"unknown"`. Fix: both branches now use `missing_flag_value:` prefix + `\n` usage hint. Integration test `dump_manifests_missing_dir_has_typed_kind_and_hint_786` covers both cases. 45 CLI contract tests pass. [SCOPE: claw-code] Source: Gaebal-gajae pinpoint + Jobdori implementation on `87f43347`, 2026-05-27.
+
+787. **`claw --resume /tmp` (directory path) returned `error_kind:"session_load_failed"` + `hint:null`; resume error emission sites didn't apply `fallback_hint_for_error_kind`** — dogfooded 2026-05-27 on `22b423b6`. Two gaps: (1) the OS error `"Is a directory (os error 21)"` had no classifier arm, falling to generic `session_load_failed`; (2) both resume error emission paths (session load at line 3338, command execution at line 3484) called `split_error_hint` but not `fallback_hint_for_error_kind`, so API-layer errors with no `\n` always got `hint:null`. Fix: added `session_path_is_directory` classifier arm for `"Is a directory"` / `"os error 21"` messages; added `fallback_hint_for_error_kind` fallback to both resume error sites; added `session_path_is_directory` and `session_load_failed` to `fallback_hint_for_error_kind`. Unit test + integration test `resume_directory_path_returns_typed_kind_and_hint_787`. 46 CLI contract tests pass. [SCOPE: claw-code] Source: Jobdori resume-path probe on `22b423b6`, 2026-05-27.
+
+788. **`claw --output-format json skills show <not-found>` emitted two JSON objects — one from the skills handler, one duplicate from the top-level error path** — dogfooded 2026-05-27 on `113145a4`. `print_skills` in JSON mode called `println!` to emit the `skill_not_found` error envelope, then returned `Err(...)`. The `?` propagation triggered the top-level error handler which emitted a second `action:"abort"` JSON envelope on stderr. Callers reading both stdout and stderr got two JSON objects with the same `error_kind` but different `action` fields — the first was the authoritative response, the second was a duplicate. Fix: replaced `return Err(...)` with `std::process::exit(1)` after the skills error JSON is emitted, mirroring the existing `is_help_action` guard pattern. Integration test `skills_show_not_found_emits_single_json_object_788` asserts exactly 1 JSON object on stdout and no JSON on stderr. 47 CLI contract tests pass. [SCOPE: claw-code] Source: Jobdori skills double-emission probe on `113145a4`, 2026-05-27.
+
+789. **`claw --output-format json agents show <not-found>` and `plugins show <not-found>` both returned exit 0 despite `status:"error"` in the JSON** — dogfooded 2026-05-27 on `abdbf61a`. Skills was fixed in #788 (exit 1 via process::exit). Agents and plugins had the identical gap: `print_agents` had no error check at all (just println + Ok(())); `print_plugins`'s not-found branch used `return Ok(())`. MCP was already fixed in an earlier cycle (#68). Fix: added `is_error` check in `print_agents` JSON path (exit 1 when status=="error"); changed plugins not-found branch from `return Ok(())` to `std::process::exit(1)`. Existing `inventory_commands_emit_structured_json_when_requested` test updated to use `run_claw` directly for the not-found case. Two new tests added: `agents_show_not_found_exits_nonzero_789`, `plugins_show_not_found_exits_nonzero_789`. 49 CLI contract tests pass. [SCOPE: claw-code] Source: Jobdori exit-code consistency probe on `abdbf61a`, 2026-05-27.
+
+790. **`claw --output-format json system-prompt <unknown-option>` returned `error_kind:"unknown"` + `hint:null`** — dogfooded 2026-05-27 on `e4c3c1aa`. The unknown-option branch in `parse_print_system_prompt_args` emitted plain `"unknown system-prompt option: {other}"` for all unrecognised options except `--json` (which appended a `\n`-delimited suggestion). All non-`--json` cases fell to `unknown+null`. Fix: replaced bare format string with `unknown_option: ... \n<usage hint>` format for all unknown options; `--json` special case preserves its `--output-format json` suggestion in the hint prefix. Integration test `system_prompt_unknown_option_returns_typed_kind_790` covers both paths. 50 CLI contract tests pass. [SCOPE: claw-code] Source: Jobdori system-prompt option probe on `e4c3c1aa`, 2026-05-27.
+
+791. **`claw config show <extra>` and `claw config set <extra1> <extra2>` returned `unexpected_extra_args` + `hint:null`** — dogfooded 2026-05-27 on `9968a27e`. The config arg parser emitted `"unexpected extra arguments after `claw config {}`: {}"` with no `\n` delimiter, so `split_error_hint` returned `None` and `fallback_hint_for_error_kind("unexpected_extra_args")` also returns `None`. Fix: appended `\nUsage: claw config [env|hooks|model|plugins|mcp|settings]` to the error format string. Integration test `config_extra_args_have_non_null_hint_791` covers both paths. 51 CLI contract tests pass. [SCOPE: claw-code] Source: Jobdori config-arg probe on `9968a27e`, 2026-05-27.
+
+792. **`claw agents list --bogus-flag` and `claw skills list --bogus-flag` silently returned `status:"ok" count:0` instead of an error** — dogfooded 2026-05-27 on `93a159dc`. The `list <filter>` arm in both handlers treated flag-shaped tokens (`--something`) as name substring filters. Since no agents/skills have `--bogus` in their name, result was empty success list — a false positive that masks typos and unknown flags. Fix: added flag-prefix guard at the top of both `list <args>` arms in `commands/src/lib.rs`; detected filter tokens starting with `-` return `unknown_option` + usage hint. Two new integration tests `agents_list_flag_shaped_filter_returns_unknown_option_792`, `skills_list_flag_shaped_filter_returns_unknown_option_792`. 53 CLI contract tests pass. [SCOPE: claw-code] Source: Jobdori agents/skills list probe on `93a159dc`, 2026-05-27.
+
+793. **`claw plugins list --bogus-flag` silent empty success + `plugins uninstall <not-found>` had `hint:null`** — dogfooded 2026-05-27 on `abfa2e4c`. Two gaps: (1) `plugins list` filter branch in `print_plugins` treated `--bogus-flag` as an id substring filter, found no matches, returned `status:"ok"` empty list — same false-positive as #792 for agents/skills. (2) `plugins uninstall no-such` propagated `plugin_not_found` error via `?` with no `\n` delimiter; `plugin_not_found` was missing from `fallback_hint_for_error_kind` table. Fix: (1) added flag-prefix guard in `print_plugins` `is_list_action` branch (detects tokens starting with `-`, returns `unknown_option` + usage hint, exits 1); (2) added `"plugin_not_found"` → `"Run 'claw plugins list' to see installed plugins."` to fallback table. Two new tests `plugins_list_flag_shaped_filter_returns_unknown_option_793`, `plugins_uninstall_not_found_has_hint_793`. 55 CLI contract tests pass. [SCOPE: claw-code] Source: Jobdori plugins lifecycle probe on `abfa2e4c`, 2026-05-27.
+
+794. **`claw plugins install /nonexistent/path` returned `error_kind:"unknown"` + `hint:null`** — dogfooded 2026-05-27 on `57a57ef7`. The error message `"plugin source '/path' was not found"` had no classifier arm, falling to `"unknown"`. Fix: added `plugin_source_not_found` classifier arm (`message.contains("plugin source") && message.contains("was not found")`); added `"plugin_source_not_found"` → `"Check that the path or URL is correct..."` to `fallback_hint_for_error_kind`. Unit test assertion added to `test_classify_error_kind`; integration test `plugins_install_not_found_path_returns_typed_kind_794` added. 56 CLI contract tests pass. [SCOPE: claw-code] Source: Jobdori plugins install probe on `57a57ef7`, 2026-05-27.
+
+795. **`claw skills install /nonexistent` returned `skill_not_found + hint:null` and `claw skills uninstall x` returned `unsupported_skills_action + hint:null`** — dogfooded 2026-05-27 on `491f179a`. Both error kinds were missing from `fallback_hint_for_error_kind` table, so even though classify returned a typed kind, the hint field was always null. Fix: added `"skill_not_found"` → hint suggesting `claw skills list` / `claw skills install`; added `"unsupported_skills_action"` → hint listing supported actions. Integration test `skills_install_not_found_and_unsupported_action_have_hints_795` covers both paths. 57 CLI contract tests pass. [SCOPE: claw-code] Source: Jobdori skills lifecycle probe on `491f179a`, 2026-05-27.
+
+796. **`claw agents show <name> <extra>` and `claw skills show <name> <extra>` returned confusing `agent_not_found`/`skill_not_found` for the concatenated "name extra" string** — dogfooded 2026-05-27 on `18b4cee5`. `join_optional_args` passes all tokens as a space-joined string; both `show` handlers called `split_once(' ')` to extract the name but did not check if the remainder (after the first split) contained additional tokens. Extra positional args (including `--flags`) became part of the "name", silently mangling the lookup. Fix: added second `split_once(' ')` on the extracted name; if the result has two parts, return `unexpected_extra_args` with a usage hint. Valid single-name lookups are unaffected. Two new integration tests `agents_show_extra_positional_arg_returns_unexpected_extra_796`, `skills_show_extra_positional_arg_returns_unexpected_extra_796`. 59 CLI contract tests pass. [SCOPE: claw-code] Source: Jobdori agents/skills show extra-arg probe on `18b4cee5`, 2026-05-27.

rust/crates/commands/src/lib.rs

@@ -2429,6 +2429,18 @@ pub fn handle_agents_slash_command_json(args: Option<&str>, cwd: &Path) -> std::
         }
         Some(args) if args.starts_with("list ") => {
             let filter = args["list ".len()..].trim().to_lowercase();
+            // #792: unknown flags (--something) silently became filter strings, returning
+            // empty success list instead of an error. Detect and reject flag-shaped tokens.
+            if filter.starts_with('-') {
+                return Ok(serde_json::json!({
+                    "kind": "agents",
+                    "action": "list",
+                    "status": "error",
+                    "error_kind": "unknown_option",
+                    "unexpected": filter,
+                    "hint": "Usage: claw agents list [<filter>]\nFilters are name substrings, not flags.",
+                }));
+            }
             let roots = discover_definition_roots(cwd, "agents");
             let agents = load_agents_from_roots(&roots)?;
             let filtered: Vec<_> = agents
@@ -2447,12 +2459,29 @@ pub fn handle_agents_slash_command_json(args: Option<&str>, cwd: &Path) -> std::
                 || args.starts_with("info ")
                 || args.starts_with("describe ") =>
         {
-            let name = args
+            let name_raw = args
                 .split_once(' ')
                 .map(|(_, name)| name)
                 .unwrap_or_default()
                 .trim()
                 .to_lowercase();
+            // #796: extra positional args after the name (e.g. `agents show foo extra`)
+            // produced a confusing agent_not_found for "foo extra" instead of flagging
+            // the unexpected extra argument.
+            let (name, extra) = name_raw
+                .split_once(' ')
+                .map(|(n, e)| (n.to_string(), Some(e.to_string())))
+                .unwrap_or_else(|| (name_raw.clone(), None));
+            if let Some(extra_token) = extra {
+                return Ok(serde_json::json!({
+                    "kind": "agents",
+                    "action": "show",
+                    "status": "error",
+                    "error_kind": "unexpected_extra_args",
+                    "unexpected": extra_token,
+                    "hint": format!("Usage: claw agents show <name>\nUnexpected extra: '{extra_token}'"),
+                }));
+            }
             let roots = discover_definition_roots(cwd, "agents");
             let agents = load_agents_from_roots(&roots)?;
             let matched: Vec<_> = agents
@@ -2582,6 +2611,18 @@ pub fn handle_skills_slash_command_json(args: Option<&str>, cwd: &Path) -> std::
         }
         Some(args) if args.starts_with("list ") => {
             let filter = args["list ".len()..].trim().to_lowercase();
+            // #792: flag-shaped tokens silently became filter strings, returning
+            // empty success list instead of an error. Detect and reject them.
+            if filter.starts_with('-') {
+                return Ok(serde_json::json!({
+                    "kind": "skills",
+                    "action": "list",
+                    "status": "error",
+                    "error_kind": "unknown_option",
+                    "unexpected": filter,
+                    "hint": "Usage: claw skills list [<filter>]\nFilters are name substrings, not flags.",
+                }));
+            }
             let roots = discover_skill_roots(cwd);
             let skills = load_skills_from_roots(&roots)?;
             let filtered: Vec<_> = skills
@@ -2600,12 +2641,29 @@ pub fn handle_skills_slash_command_json(args: Option<&str>, cwd: &Path) -> std::
                 || args.starts_with("info ")
                 || args.starts_with("describe ") =>
         {
-            let name = args
+            let name_raw = args
                 .split_once(' ')
                 .map(|(_, name)| name)
                 .unwrap_or_default()
                 .trim()
                 .to_lowercase();
+            // #796: extra positional args after the name (e.g. `skills show foo extra`)
+            // produced a confusing skill_not_found for "foo extra" instead of flagging
+            // the unexpected extra argument.
+            let (name, extra) = name_raw
+                .split_once(' ')
+                .map(|(n, e)| (n.to_string(), Some(e.to_string())))
+                .unwrap_or_else(|| (name_raw.clone(), None));
+            if let Some(extra_token) = extra {
+                return Ok(json!({
+                    "kind": "skills",
+                    "action": "show",
+                    "status": "error",
+                    "error_kind": "unexpected_extra_args",
+                    "unexpected": extra_token,
+                    "hint": format!("Usage: claw skills show <name>\nUnexpected extra: '{extra_token}'"),
+                }));
+            }
             let roots = discover_skill_roots(cwd);
             let skills = load_skills_from_roots(&roots)?;
             let matched: Vec<_> = skills

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

@@ -283,6 +283,9 @@ fn classify_error_kind(message: &str) -> &'static str {
         // error message is "failed to restore session: legacy session is missing workspace
         // binding: ...", so the specific arm must be checked first.
         "legacy_session_no_workspace_binding"
+    } else if message.contains("Is a directory") || message.contains("os error 21") {
+        // #787: --resume given a directory path instead of a .jsonl file
+        "session_path_is_directory"
     } else if message.contains("failed to restore session") {
         "session_load_failed"
     } else if message.contains("unsupported ACP invocation") {
@@ -334,6 +337,9 @@ fn classify_error_kind(message: &str) -> &'static str {
         "agent_not_found"
     } else if message.contains("is not installed") {
         "plugin_not_found"
+    } else if message.contains("plugin source") && message.contains("was not found") {
+        // #794: `plugins install /nonexistent/path` → "plugin source ... was not found"
+        "plugin_source_not_found"
     } else if (message.contains("skill source") && message.contains("not found"))
         || message.starts_with("skill '")
     {
@@ -349,6 +355,9 @@ fn classify_error_kind(message: &str) -> &'static str {
     } else if message.contains("has been removed.") {
         // #765: removed subcommands (login, logout) — hint contains migration guidance
         "removed_subcommand"
+    } else if message.starts_with("unknown subcommand:") {
+        // #785: typo/unknown top-level subcommand (e.g. `claw dump` → did you mean dump-manifests?)
+        "unknown_subcommand"
     } else if message.starts_with("unexpected extra arguments")
         || message.starts_with("unexpected_extra_args:")
     {
@@ -398,6 +407,28 @@ fn fallback_hint_for_error_kind(kind: &str) -> Option<&'static str> {
         "missing_credentials" => {
             Some("Set ANTHROPIC_API_KEY or ANTHROPIC_AUTH_TOKEN before running claw.")
         }
+        // #787: session load failures have no \n-delimited hint from the OS error path
+        "session_load_failed" => Some(
+            "Pass a path to a .jsonl session file, not a directory. Managed sessions live in .claw/sessions/.",
+        ),
+        "session_path_is_directory" => Some(
+            "--resume expects a .jsonl session file path, not a directory. Run `claw --output-format json /session list` to list managed sessions.",
+        ),
+        // #793: plugins uninstall/enable/disable of non-existing plugin propagates through
+        // the ? operator with no \n delimiter, so split_error_hint returns None.
+        "plugin_not_found" => Some("Run `claw plugins list` to see installed plugins."),
+        // #794: plugins install with a path that doesn't exist
+        "plugin_source_not_found" => Some(
+            "Check that the path or URL is correct. Use a local directory or a valid registry id.",
+        ),
+        // #795: skills install/show of a non-existing skill path or name
+        "skill_not_found" => Some(
+            "Run `claw skills list` to see available skills, or `claw skills install <path>` to install a new one.",
+        ),
+        // #795: unsupported action on skills (e.g. /skills uninstall) with no \n hint
+        "unsupported_skills_action" => Some(
+            "Supported: list, install <path>, show <name>, help. Run `claw skills help` for details.",
+        ),
         _ => None,
     }
 }
@@ -1154,8 +1185,9 @@ fn parse_args(args: &[String]) -> Result<CliAction, String> {
             let action = tail.first().cloned();
             let target = tail.get(1).cloned();
             if tail.len() > 2 {
+                // #797: append \n usage hint so split_error_hint extracts it (parity with #791 config fix)
                 return Err(format!(
-                    "unexpected extra arguments after `claw {} {}`: {}",
+                    "unexpected extra arguments after `claw {} {}`: {}\nUsage: claw plugins [list|show <id>|install <id>|enable <id>|disable <id>|uninstall <id>|update <id>|help]",
                     rest[0],
                     tail[..2].join(" "),
                     tail[2..].join(" ")
@@ -1177,8 +1209,9 @@ fn parse_args(args: &[String]) -> Result<CliAction, String> {
             let tail = &rest[1..];
             let section = tail.first().cloned();
             if tail.len() > 1 {
+                // #791: append \n hint so split_error_hint extracts it and hint is non-null
                 return Err(format!(
-                    "unexpected extra arguments after `claw config {}`: {}",
+                    "unexpected extra arguments after `claw config {}`: {}\nUsage: claw config [env|hooks|model|plugins|mcp|settings]",
                     tail[0],
                     tail[1..].join(" ")
                 ));
@@ -1345,8 +1378,9 @@ fn parse_args(args: &[String]) -> Result<CliAction, String> {
             // an empty prompt when credentials are present).
             let joined = rest.join(" ");
             if joined.trim().is_empty() {
+                // #798: add \n hint so split_error_hint extracts it (was empty_prompt + null)
                 return Err(
-                    "empty prompt: provide a subcommand (run `claw --help`) or a non-empty prompt string"
+                    "empty prompt: provide a subcommand or a non-empty prompt string.\nUsage: claw <subcommand> or claw -p <prompt>. Run `claw --help` for the full list."
                         .to_string(),
                 );
             }
@@ -2078,11 +2112,16 @@ fn parse_system_prompt_args(
             }
             other => {
                 // #152: hint `--output-format json` when user types `--json`.
-                let mut msg = format!("unknown system-prompt option: {other}");
-                if other == "--json" {
-                    msg.push_str("\nDid you mean `--output-format json`?");
-                }
-                return Err(msg);
+                // #790: use unknown_option: prefix + \n hint so classify_error_kind returns
+                // unknown_option and split_error_hint extracts the remediation text.
+                let hint = if other == "--json" {
+                    "Did you mean `--output-format json`? Usage: claw system-prompt [--cwd <dir>] [--date <YYYY-MM-DD>] [--output-format text|json]".to_string()
+                } else {
+                    "Usage: claw system-prompt [--cwd <dir>] [--date <YYYY-MM-DD>] [--output-format text|json]".to_string()
+                };
+                return Err(format!(
+                    "unknown_option: unknown system-prompt option: {other}.\n{hint}"
+                ));
             }
         }
     }
@@ -2156,14 +2195,15 @@ fn parse_dump_manifests_args(
         if arg == "--manifests-dir" {
             let value = args
                 .get(index + 1)
-                .ok_or_else(|| String::from("--manifests-dir requires a path"))?;
+                .ok_or_else(|| String::from("missing_flag_value: --manifests-dir requires a path.\nUsage: claw dump-manifests --manifests-dir <path> [--output-format json]"))?;
             manifests_dir = Some(PathBuf::from(value));
             index += 2;
             continue;
         }
         if let Some(value) = arg.strip_prefix("--manifests-dir=") {
             if value.is_empty() {
-                return Err(String::from("--manifests-dir requires a path"));
+                // #786: empty --manifests-dir= is also a missing value
+                return Err(String::from("missing_flag_value: --manifests-dir requires a path.\nUsage: claw dump-manifests --manifests-dir <path> [--output-format json]"));
             }
             manifests_dir = Some(PathBuf::from(value));
             index += 1;
@@ -3323,7 +3363,10 @@ fn resume_session(session_path: &Path, commands: &[String], output_format: CliOu
                 // #77: classify session load errors for downstream consumers
                 let full_message = format!("failed to restore session: {error}");
                 let kind = classify_error_kind(&full_message);
-                let (short_reason, hint) = split_error_hint(&full_message);
+                let (short_reason, inline_hint) = split_error_hint(&full_message);
+                // #787: fall back to kind-derived hint when message has no \n delimiter
+                let hint =
+                    inline_hint.or_else(|| fallback_hint_for_error_kind(kind).map(String::from));
                 eprintln!(
                     "{}",
                     serde_json::json!({
@@ -3468,7 +3511,10 @@ fn resume_session(session_path: &Path, commands: &[String], output_format: CliOu
                     // hardcoded "resume_command_error" + prose in the error field
                     let full_error = error.to_string();
                     let error_kind = classify_error_kind(&full_error);
-                    let (short_reason, hint) = split_error_hint(&full_error);
+                    let (short_reason, inline_hint) = split_error_hint(&full_error);
+                    // #787: fall back to kind-derived hint when error has no \n delimiter
+                    let hint = inline_hint
+                        .or_else(|| fallback_hint_for_error_kind(error_kind).map(String::from));
                     eprintln!(
                         "{}",
                         serde_json::json!({
@@ -6261,10 +6307,17 @@ impl LiveCli {
         let cwd = env::current_dir()?;
         match output_format {
             CliOutputFormat::Text => println!("{}", handle_agents_slash_command(args, &cwd)?),
-            CliOutputFormat::Json => println!(
-                "{}",
-                serde_json::to_string_pretty(&handle_agents_slash_command_json(args, &cwd)?)?
-            ),
+            CliOutputFormat::Json => {
+                let value = handle_agents_slash_command_json(args, &cwd)?;
+                // #789: parity with print_mcp/#788 print_skills — exit 1 when envelope
+                // reports an error so automation can rely on exit code instead of
+                // parsing the JSON status field.
+                let is_error = value.get("status").and_then(|v| v.as_str()) == Some("error");
+                println!("{}", serde_json::to_string_pretty(&value)?);
+                if is_error {
+                    std::process::exit(1);
+                }
+            }
         }
         Ok(())
     }
@@ -6313,12 +6366,10 @@ impl LiveCli {
                 let is_help_action = result.get("action").and_then(|v| v.as_str()) == Some("help");
                 println!("{}", serde_json::to_string_pretty(&result)?);
                 if is_error && !is_help_action {
-                    return Err(result
-                        .get("message")
-                        .and_then(|v| v.as_str())
-                        .unwrap_or("skills command failed")
-                        .to_string()
-                        .into());
+                    // #788: the error JSON is already emitted above; returning Err here
+                    // would cause the top-level handler to emit a second error envelope.
+                    // Exit directly to signal failure without a duplicate envelope.
+                    std::process::exit(1);
                 }
             }
         }
@@ -6376,6 +6427,20 @@ impl LiveCli {
                     }
                 } else if is_list_action {
                     if let Some(filter) = target {
+                        // #793: flag-shaped tokens silently became substring filters on
+                        // plugins list, returning empty success instead of an error.
+                        if filter.starts_with('-') {
+                            let obj = json!({
+                                "kind": "plugin",
+                                "action": "list",
+                                "status": "error",
+                                "error_kind": "unknown_option",
+                                "unexpected": filter,
+                                "hint": "Usage: claw plugins list [<filter>]\nFilters are id substrings, not flags.",
+                            });
+                            println!("{}", serde_json::to_string_pretty(&obj)?);
+                            std::process::exit(1);
+                        }
                         let needle = filter.to_lowercase();
                         payload
                             .plugins
@@ -6410,7 +6475,8 @@ impl LiveCli {
                                 "hint": "Run `claw plugins list` to see available plugins.",
                             });
                             println!("{}", serde_json::to_string_pretty(&obj)?);
-                            return Ok(());
+                            // #789: exit 1 on not-found so automation can rely on exit code
+                            std::process::exit(1);
                         }
                     }
                 }
@@ -13005,10 +13071,20 @@ mod tests {
             classify_error_kind("failed to restore session: file not found"),
             "session_load_failed"
         );
+        // #787: directory-as-session-path gets its own kind (precedes generic session_load_failed)
+        assert_eq!(
+            classify_error_kind("failed to restore session: Is a directory (os error 21)"),
+            "session_path_is_directory"
+        );
         assert_eq!(
             classify_error_kind("unrecognized argument `--foo` for subcommand `doctor`"),
             "cli_parse"
         );
+        // #785: unknown top-level subcommand (typo or unrecognised command)
+        assert_eq!(
+            classify_error_kind("unknown subcommand: dump.\nDid you mean     dump-manifests"),
+            "unknown_subcommand"
+        );
         assert_eq!(
             classify_error_kind("unsupported ACP invocation. Use `claw acp`."),
             "unsupported_acp_invocation"
@@ -13119,6 +13195,11 @@ mod tests {
             classify_error_kind("my-plugin is not installed"),
             "plugin_not_found"
         );
+        // #794: plugins install with missing source path
+        assert_eq!(
+            classify_error_kind("plugin source `/nonexistent/path` was not found"),
+            "plugin_source_not_found"
+        );
         assert_eq!(
             classify_error_kind("skill source /path/to/skill not found"),
             "skill_not_found"

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

@@ -203,7 +203,9 @@ fn inventory_commands_emit_structured_json_when_requested() {
             isolated_codex.to_str().expect("utf8 codex home"),
         ),
     ];
-    let agents_show_missing = assert_json_command_with_env(
+    // #789: agents show not-found now exits 1 (parity with skills #788);
+    // use run_claw directly instead of assert_json_command_with_env which checks success.
+    let agents_show_out = run_claw(
         &root,
         &[
             "--output-format",
@@ -214,6 +216,12 @@ fn inventory_commands_emit_structured_json_when_requested() {
         ],
         &agents_show_env,
     );
+    assert!(
+        !agents_show_out.status.success(),
+        "agents show not-found must exit non-zero"
+    );
+    let agents_show_missing: serde_json::Value =
+        serde_json::from_slice(&agents_show_out.stdout).expect("agents show stdout should be json");
     assert_eq!(agents_show_missing["kind"], "agents", "agents show kind");
     assert_eq!(agents_show_missing["action"], "show", "agents show action");
     assert_eq!(
@@ -2502,3 +2510,944 @@ fn export_arg_errors_have_typed_kind_and_hint_784() {
         "hint must reference export usage, got: {h2:?}"
     );
 }
+
+#[test]
+fn unknown_subcommand_returns_typed_kind_785() {
+    // #785: `claw dump` (a near-miss for dump-manifests) returned error_kind:"unknown"
+    // because the classifier had no arm for "unknown subcommand:" prose prefix.
+    // Fix: added "unknown_subcommand" arm in classify_error_kind.
+    let root = unique_temp_dir("unknown-subcommand-785");
+    fs::create_dir_all(&root).expect("temp dir");
+    std::process::Command::new("git")
+        .args(["init", "-q"])
+        .current_dir(&root)
+        .output()
+        .ok();
+
+    // "dump" is close enough to "dump-manifests" to trigger the typo suggestion path
+    let output = run_claw(&root, &["--output-format", "json", "dump"], &[]);
+    assert!(!output.status.success(), "unknown subcommand should fail");
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    let j: serde_json::Value = stderr
+        .lines()
+        .find(|l| l.trim_start().starts_with('{'))
+        .and_then(|l| serde_json::from_str(l).ok())
+        .expect("unknown subcommand should emit JSON error");
+    assert_eq!(
+        j["error_kind"], "unknown_subcommand",
+        "unknown subcommand should return unknown_subcommand kind, got {:?}",
+        j["error_kind"]
+    );
+    // hint should point at the suggestion and/or --help
+    let hint = j["hint"].as_str().unwrap_or("");
+    assert!(
+        hint.contains("dump-manifests") || hint.contains("--help") || hint.contains("claw"),
+        "hint should reference the suggested subcommand or help, got: {hint:?}"
+    );
+}
+
+#[test]
+fn dump_manifests_missing_dir_has_typed_kind_and_hint_786() {
+    // #786: `claw dump-manifests --manifests-dir` (no value) and `--manifests-dir=` (empty)
+    // both emitted plain "--manifests-dir requires a path" with error_kind:"unknown" + hint:null.
+    // Fix: use missing_flag_value: prefix + \n usage hint.
+    let root = unique_temp_dir("dump-manifests-missing-dir-786");
+    fs::create_dir_all(&root).expect("temp dir");
+    std::process::Command::new("git")
+        .args(["init", "-q"])
+        .current_dir(&root)
+        .output()
+        .ok();
+
+    // Case 1: --manifests-dir with no following value (next arg is --output-format)
+    let out1 = run_claw(
+        &root,
+        &[
+            "--output-format",
+            "json",
+            "dump-manifests",
+            "--manifests-dir",
+            "--output-format",
+            "json",
+        ],
+        &[],
+    );
+    assert!(!out1.status.success());
+    let stderr1 = String::from_utf8_lossy(&out1.stderr);
+    let j1: serde_json::Value = stderr1
+        .lines()
+        .find(|l| l.trim_start().starts_with('{'))
+        .and_then(|l| serde_json::from_str(l).ok())
+        .expect("missing --manifests-dir value should emit JSON error");
+    assert_eq!(
+        j1["error_kind"], "missing_flag_value",
+        "missing --manifests-dir value should be missing_flag_value, got {:?}",
+        j1["error_kind"]
+    );
+    let h1 = j1["hint"]
+        .as_str()
+        .expect("missing_flag_value must have hint (#786)");
+    assert!(
+        h1.contains("dump-manifests") || h1.contains("manifests-dir"),
+        "hint should reference dump-manifests usage, got: {h1:?}"
+    );
+
+    // Case 2: --manifests-dir= with empty value
+    let out2 = run_claw(
+        &root,
+        &[
+            "--output-format",
+            "json",
+            "dump-manifests",
+            "--manifests-dir=",
+        ],
+        &[],
+    );
+    assert!(!out2.status.success());
+    let stderr2 = String::from_utf8_lossy(&out2.stderr);
+    let j2: serde_json::Value = stderr2
+        .lines()
+        .find(|l| l.trim_start().starts_with('{'))
+        .and_then(|l| serde_json::from_str(l).ok())
+        .expect("empty --manifests-dir= should emit JSON error");
+    assert_eq!(
+        j2["error_kind"], "missing_flag_value",
+        "empty --manifests-dir= should be missing_flag_value, got {:?}",
+        j2["error_kind"]
+    );
+    let h2 = j2["hint"]
+        .as_str()
+        .expect("missing_flag_value must have hint (#786)");
+    assert!(!h2.is_empty(), "hint must not be empty");
+}
+
+#[test]
+fn resume_directory_path_returns_typed_kind_and_hint_787() {
+    // #787: `claw --resume /tmp` (directory instead of .jsonl file) returned
+    // error_kind:"session_load_failed" + hint:null. The OS error "Is a directory (os error 21)"
+    // had no \n delimiter so split_error_hint returned None, and the resume error path
+    // didn't call fallback_hint_for_error_kind.
+    // Fix: (1) added session_path_is_directory classifier arm for os error 21;
+    //      (2) wired fallback_hint_for_error_kind into both resume error emission sites.
+    let root = unique_temp_dir("resume-dir-787");
+    fs::create_dir_all(&root).expect("temp dir");
+    std::process::Command::new("git")
+        .args(["init", "-q"])
+        .current_dir(&root)
+        .output()
+        .ok();
+
+    // Pass the root directory itself as the session path
+    let output = run_claw(
+        &root,
+        &[
+            "--output-format",
+            "json",
+            "--resume",
+            root.to_str().unwrap(),
+            "/status",
+        ],
+        &[],
+    );
+    assert!(
+        !output.status.success(),
+        "resume with directory should fail"
+    );
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    let j: serde_json::Value = stderr
+        .lines()
+        .find(|l| l.trim_start().starts_with('{'))
+        .and_then(|l| serde_json::from_str(l).ok())
+        .expect("resume with directory should emit JSON error");
+    assert_eq!(
+        j["error_kind"], "session_path_is_directory",
+        "directory resume path should return session_path_is_directory, got {:?}",
+        j["error_kind"]
+    );
+    let hint = j["hint"]
+        .as_str()
+        .expect("session_path_is_directory must have hint (#787)");
+    assert!(
+        hint.contains(".jsonl") || hint.contains("session") || hint.contains("file"),
+        "hint should explain expected path format, got: {hint:?}"
+    );
+}
+
+#[test]
+fn skills_show_not_found_emits_single_json_object_788() {
+    // #788: `claw --output-format json skills show no-such-skill` emitted TWO JSON objects:
+    // one from the skills handler (action:"show", status:"error") and a second from the
+    // top-level error handler (action:"abort"). The skills handler returned Err() after
+    // printing its JSON, which caused the ? propagation to trigger a duplicate envelope.
+    // Fix: exit(1) directly after the skills JSON is emitted instead of returning Err.
+    let root = unique_temp_dir("skills-show-double-emit-788");
+    fs::create_dir_all(&root).expect("temp dir");
+    std::process::Command::new("git")
+        .args(["init", "-q"])
+        .current_dir(&root)
+        .output()
+        .ok();
+
+    let output = run_claw(
+        &root,
+        &[
+            "--output-format",
+            "json",
+            "skills",
+            "show",
+            "no-such-skill-xyz",
+        ],
+        &[],
+    );
+    assert!(!output.status.success(), "skills show unknown should fail");
+    // Skills handler emits JSON to stdout; the duplicate was on stderr from the main error path.
+    // After fix: stdout has 1 JSON object, stderr has none (no duplicate).
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    let stderr = String::from_utf8_lossy(&output.stderr);
+
+    // Count JSON objects in stdout — must be exactly 1
+    let json_objects: Vec<serde_json::Value> = {
+        let mut objects = Vec::new();
+        let mut remaining = stdout.trim();
+        while !remaining.is_empty() {
+            match serde_json::from_str::<serde_json::Value>(remaining) {
+                Ok(v) => {
+                    objects.push(v);
+                    break;
+                }
+                Err(_) => {
+                    // Try finding a complete JSON object
+                    if let Some(pos) = remaining.find('{') {
+                        remaining = &remaining[pos..];
+                        let mut depth = 0i32;
+                        let mut end = 0;
+                        for (i, c) in remaining.char_indices() {
+                            match c {
+                                '{' => depth += 1,
+                                '}' => {
+                                    depth -= 1;
+                                    if depth == 0 {
+                                        end = i + 1;
+                                        break;
+                                    }
+                                }
+                                _ => {}
+                            }
+                        }
+                        if end > 0 {
+                            if let Ok(v) = serde_json::from_str(&remaining[..end]) {
+                                objects.push(v);
+                                remaining = remaining[end..].trim_start();
+                            } else {
+                                break;
+                            }
+                        } else {
+                            break;
+                        }
+                    } else {
+                        break;
+                    }
+                }
+            }
+        }
+        objects
+    };
+
+    assert_eq!(
+        json_objects.len(),
+        1,
+        "skills show not-found must emit exactly 1 JSON object on stdout, got {}. stdout: {} stderr: {}",
+        json_objects.len(),
+        stdout,
+        stderr
+    );
+    // Verify stderr has no duplicate error JSON (the pre-#788 bug was a second abort envelope here)
+    let stderr_has_json = stderr.lines().any(|l| l.trim_start().starts_with('{'));
+    assert!(
+        !stderr_has_json,
+        "stderr must have no duplicate JSON error envelope, got: {stderr}"
+    );
+    assert_eq!(
+        json_objects[0]["error_kind"], "skill_not_found",
+        "single JSON object must have skill_not_found error_kind"
+    );
+    assert_eq!(json_objects[0]["status"], "error");
+}
+
+#[test]
+fn agents_show_not_found_exits_nonzero_789() {
+    // #789: `claw --output-format json agents show <not-found>` returned exit 0 despite
+    // emitting status:"error". print_agents had no error check — just println + Ok(()).
+    // Skills was fixed in #788 (exit 1 via process::exit); agents/plugins had the same gap.
+    let root = unique_temp_dir("agents-show-exit-789");
+    fs::create_dir_all(&root).expect("temp dir");
+    std::process::Command::new("git")
+        .args(["init", "-q"])
+        .current_dir(&root)
+        .output()
+        .ok();
+
+    let output = run_claw(
+        &root,
+        &[
+            "--output-format",
+            "json",
+            "agents",
+            "show",
+            "no-such-agent-xyz-789",
+        ],
+        &[],
+    );
+    assert!(
+        !output.status.success(),
+        "agents show not-found must exit non-zero (#789), got exit 0"
+    );
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    let j: serde_json::Value =
+        serde_json::from_str(stdout.trim()).expect("agents show should emit valid JSON");
+    assert_eq!(j["error_kind"], "agent_not_found");
+    assert_eq!(j["status"], "error");
+}
+
+#[test]
+fn plugins_show_not_found_exits_nonzero_789() {
+    // #789: same as agents — `claw --output-format json plugins show <not-found>` exited 0
+    // despite status:"error". The not-found branch used `return Ok(())` instead of exit(1).
+    let root = unique_temp_dir("plugins-show-exit-789");
+    fs::create_dir_all(&root).expect("temp dir");
+    std::process::Command::new("git")
+        .args(["init", "-q"])
+        .current_dir(&root)
+        .output()
+        .ok();
+
+    let output = run_claw(
+        &root,
+        &[
+            "--output-format",
+            "json",
+            "plugins",
+            "show",
+            "no-such-plugin-xyz-789",
+        ],
+        &[],
+    );
+    assert!(
+        !output.status.success(),
+        "plugins show not-found must exit non-zero (#789), got exit 0"
+    );
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    let j: serde_json::Value =
+        serde_json::from_str(stdout.trim()).expect("plugins show should emit valid JSON");
+    assert_eq!(j["error_kind"], "plugin_not_found");
+    assert_eq!(j["status"], "error");
+}
+
+#[test]
+fn system_prompt_unknown_option_returns_typed_kind_790() {
+    // #790: `claw --output-format json system-prompt bogus` returned error_kind:"unknown" + hint:null.
+    // The unknown-option branch emitted plain "unknown system-prompt option: bogus" with no typed
+    // prefix. Fix: use unknown_option: prefix + \n usage hint.
+    let root = unique_temp_dir("system-prompt-unknown-opt-790");
+    fs::create_dir_all(&root).expect("temp dir");
+    std::process::Command::new("git")
+        .args(["init", "-q"])
+        .current_dir(&root)
+        .output()
+        .ok();
+
+    // Generic unknown option
+    let out1 = run_claw(
+        &root,
+        &["--output-format", "json", "system-prompt", "bogus"],
+        &[],
+    );
+    assert!(!out1.status.success());
+    let stderr1 = String::from_utf8_lossy(&out1.stderr);
+    let j1: serde_json::Value = stderr1
+        .lines()
+        .find(|l| l.trim_start().starts_with('{'))
+        .and_then(|l| serde_json::from_str(l).ok())
+        .expect("unknown option should emit JSON error");
+    assert_eq!(
+        j1["error_kind"], "unknown_option",
+        "system-prompt unknown option should be unknown_option, got {:?}",
+        j1["error_kind"]
+    );
+    let h1 = j1["hint"]
+        .as_str()
+        .expect("unknown_option must have hint (#790)");
+    assert!(
+        h1.contains("system-prompt") || h1.contains("claw"),
+        "hint should reference system-prompt usage, got: {h1:?}"
+    );
+
+    // Special --json case: hint should mention --output-format json
+    let out2 = run_claw(
+        &root,
+        &["--output-format", "json", "system-prompt", "--json"],
+        &[],
+    );
+    assert!(!out2.status.success());
+    let stderr2 = String::from_utf8_lossy(&out2.stderr);
+    let j2: serde_json::Value = stderr2
+        .lines()
+        .find(|l| l.trim_start().starts_with('{'))
+        .and_then(|l| serde_json::from_str(l).ok())
+        .expect("--json flag should emit JSON error");
+    assert_eq!(j2["error_kind"], "unknown_option");
+    let h2 = j2["hint"]
+        .as_str()
+        .expect("--json case must have hint (#790)");
+    assert!(
+        h2.contains("output-format") || h2.contains("json"),
+        "hint for --json should suggest --output-format json, got: {h2:?}"
+    );
+}
+
+#[test]
+fn config_extra_args_have_non_null_hint_791() {
+    // #791: `claw config show bogus-key` and `claw config set a b` returned
+    // error_kind:"unexpected_extra_args" + hint:null because the error message
+    // "unexpected extra arguments after `claw config ...`: ..." had no \n delimiter.
+    // Fix: appended \n + usage hint to the format string.
+    let root = unique_temp_dir("config-extra-args-791");
+    fs::create_dir_all(&root).expect("temp dir");
+    std::process::Command::new("git")
+        .args(["init", "-q"])
+        .current_dir(&root)
+        .output()
+        .ok();
+
+    // config show with extra positional arg
+    let out1 = run_claw(
+        &root,
+        &["--output-format", "json", "config", "show", "bogus-key"],
+        &[],
+    );
+    assert!(!out1.status.success());
+    let stderr1 = String::from_utf8_lossy(&out1.stderr);
+    let j1: serde_json::Value = stderr1
+        .lines()
+        .find(|l| l.trim_start().starts_with('{'))
+        .and_then(|l| serde_json::from_str(l).ok())
+        .expect("config show extra arg should emit JSON error");
+    assert_eq!(
+        j1["error_kind"], "unexpected_extra_args",
+        "config show extra arg should be unexpected_extra_args, got {:?}",
+        j1["error_kind"]
+    );
+    let h1 = j1["hint"]
+        .as_str()
+        .expect("unexpected_extra_args must have hint (#791)");
+    assert!(
+        h1.contains("config") || h1.contains("claw"),
+        "hint should reference config usage, got: {h1:?}"
+    );
+
+    // config set with extra positionals
+    let out2 = run_claw(
+        &root,
+        &[
+            "--output-format",
+            "json",
+            "config",
+            "set",
+            "bogus-section.key",
+            "value",
+        ],
+        &[],
+    );
+    assert!(!out2.status.success());
+    let stderr2 = String::from_utf8_lossy(&out2.stderr);
+    let j2: serde_json::Value = stderr2
+        .lines()
+        .find(|l| l.trim_start().starts_with('{'))
+        .and_then(|l| serde_json::from_str(l).ok())
+        .expect("config set extra arg should emit JSON error");
+    assert_eq!(j2["error_kind"], "unexpected_extra_args");
+    assert!(
+        j2["hint"].as_str().is_some_and(|h| !h.is_empty()),
+        "config set extra arg must have non-null hint (#791)"
+    );
+}
+
+#[test]
+fn agents_list_flag_shaped_filter_returns_unknown_option_792() {
+    // #792: `claw --output-format json agents list --bogus-flag` silently returned
+    // status:"ok" count:0 instead of an error. The list filter arm in
+    // handle_agents_slash_command_json treated "--bogus-flag" as a name substring
+    // filter (no agents match), producing a false-positive empty success result.
+    // Fix: detect filter tokens starting with "-" and return unknown_option + hint.
+    let root = unique_temp_dir("agents-list-flag-792");
+    fs::create_dir_all(&root).expect("temp dir");
+    std::process::Command::new("git")
+        .args(["init", "-q"])
+        .current_dir(&root)
+        .output()
+        .ok();
+
+    let output = run_claw(
+        &root,
+        &[
+            "--output-format",
+            "json",
+            "agents",
+            "list",
+            "--unknown-flag",
+        ],
+        &[],
+    );
+    assert!(
+        !output.status.success(),
+        "agents list --unknown-flag must exit non-zero (#792)"
+    );
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    let j: serde_json::Value = serde_json::from_str(stdout.trim())
+        .expect("agents list flag-filter should emit valid JSON");
+    assert_eq!(
+        j["error_kind"], "unknown_option",
+        "agents list flag-shaped filter must return unknown_option, got {:?}",
+        j["error_kind"]
+    );
+    assert_eq!(j["status"], "error");
+    let h = j["hint"]
+        .as_str()
+        .expect("unknown_option must have hint (#792)");
+    assert!(
+        h.contains("claw agents list") || h.contains("filter"),
+        "hint should reference correct usage, got: {h:?}"
+    );
+}
+
+#[test]
+fn skills_list_flag_shaped_filter_returns_unknown_option_792() {
+    // #792: same gap as agents — `claw skills list --bogus-flag` returned success
+    // with empty list instead of unknown_option error.
+    let root = unique_temp_dir("skills-list-flag-792");
+    fs::create_dir_all(&root).expect("temp dir");
+    std::process::Command::new("git")
+        .args(["init", "-q"])
+        .current_dir(&root)
+        .output()
+        .ok();
+
+    let output = run_claw(
+        &root,
+        &[
+            "--output-format",
+            "json",
+            "skills",
+            "list",
+            "--unknown-flag",
+        ],
+        &[],
+    );
+    assert!(
+        !output.status.success(),
+        "skills list --unknown-flag must exit non-zero (#792)"
+    );
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    let j: serde_json::Value = serde_json::from_str(stdout.trim())
+        .expect("skills list flag-filter should emit valid JSON");
+    assert_eq!(
+        j["error_kind"], "unknown_option",
+        "skills list flag-shaped filter must return unknown_option, got {:?}",
+        j["error_kind"]
+    );
+    assert_eq!(j["status"], "error");
+    assert!(
+        j["hint"]
+            .as_str()
+            .is_some_and(|h| h.contains("claw skills list") || h.contains("filter")),
+        "hint should reference correct usage (#792)"
+    );
+}
+
+#[test]
+fn plugins_list_flag_shaped_filter_returns_unknown_option_793() {
+    // #793: `claw plugins list --bogus-flag` silently returned status:"ok" with empty
+    // plugins list instead of an error. The list filter branch in print_plugins treated
+    // "--bogus-flag" as an id substring filter and found no matches, producing a false-positive.
+    // Fix: added flag-prefix guard; filter tokens starting with "-" now return unknown_option.
+    let root = unique_temp_dir("plugins-list-flag-793");
+    fs::create_dir_all(&root).expect("temp dir");
+    std::process::Command::new("git")
+        .args(["init", "-q"])
+        .current_dir(&root)
+        .output()
+        .ok();
+
+    let output = run_claw(
+        &root,
+        &[
+            "--output-format",
+            "json",
+            "plugins",
+            "list",
+            "--unknown-flag",
+        ],
+        &[],
+    );
+    assert!(
+        !output.status.success(),
+        "plugins list --unknown-flag must exit non-zero (#793)"
+    );
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    let j: serde_json::Value = serde_json::from_str(stdout.trim())
+        .expect("plugins list flag-filter should emit valid JSON");
+    assert_eq!(
+        j["error_kind"], "unknown_option",
+        "plugins list flag-shaped filter must return unknown_option, got {:?}",
+        j["error_kind"]
+    );
+    assert_eq!(j["status"], "error");
+    let h = j["hint"]
+        .as_str()
+        .expect("unknown_option must have hint (#793)");
+    assert!(
+        h.contains("plugins list") || h.contains("filter"),
+        "hint should reference plugins list usage, got: {h:?}"
+    );
+}
+
+#[test]
+fn plugins_uninstall_not_found_has_hint_793() {
+    // #793: `claw plugins uninstall no-such-plugin` returned plugin_not_found + hint:null.
+    // The error propagated from plugins_command_payload_for via ? with no \n delimiter;
+    // split_error_hint returned None and plugin_not_found wasn't in the fallback table.
+    // Fix: added "plugin_not_found" entry to fallback_hint_for_error_kind().
+    let root = unique_temp_dir("plugins-uninstall-793");
+    fs::create_dir_all(&root).expect("temp dir");
+    std::process::Command::new("git")
+        .args(["init", "-q"])
+        .current_dir(&root)
+        .output()
+        .ok();
+
+    let output = run_claw(
+        &root,
+        &[
+            "--output-format",
+            "json",
+            "plugins",
+            "uninstall",
+            "no-such-xyz-793",
+        ],
+        &[],
+    );
+    assert!(
+        !output.status.success(),
+        "plugins uninstall not-found must exit non-zero (#793)"
+    );
+    // Error envelope goes to stderr (propagated via ? to main error handler)
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    let j: serde_json::Value = stderr
+        .lines()
+        .find(|l| l.trim_start().starts_with('{'))
+        .and_then(|l| serde_json::from_str(l).ok())
+        .expect("plugins uninstall not-found should emit JSON error envelope");
+    assert_eq!(j["error_kind"], "plugin_not_found");
+    let h = j["hint"]
+        .as_str()
+        .expect("plugin_not_found must have non-null hint (#793)");
+    assert!(
+        h.contains("plugins list") || h.contains("claw plugins"),
+        "hint should reference plugins list, got: {h:?}"
+    );
+}
+
+#[test]
+fn plugins_install_not_found_path_returns_typed_kind_794() {
+    // #794: `claw plugins install /nonexistent/path` returned error_kind:"unknown" + hint:null.
+    // The message "plugin source ... was not found" had no classifier arm; fell to "unknown".
+    // Fix: added "plugin_source_not_found" classifier arm + fallback hint table entry.
+    let root = unique_temp_dir("plugins-install-794");
+    fs::create_dir_all(&root).expect("temp dir");
+    std::process::Command::new("git")
+        .args(["init", "-q"])
+        .current_dir(&root)
+        .output()
+        .ok();
+
+    let output = run_claw(
+        &root,
+        &[
+            "--output-format",
+            "json",
+            "plugins",
+            "install",
+            "/nonexistent-path-xyz-794",
+        ],
+        &[],
+    );
+    assert!(
+        !output.status.success(),
+        "plugins install not-found-path must exit non-zero (#794)"
+    );
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    let j: serde_json::Value = stderr
+        .lines()
+        .find(|l| l.trim_start().starts_with('{'))
+        .and_then(|l| serde_json::from_str(l).ok())
+        .expect("plugins install not-found should emit JSON error envelope");
+    assert_eq!(
+        j["error_kind"], "plugin_source_not_found",
+        "plugins install not-found should be plugin_source_not_found, got {:?}",
+        j["error_kind"]
+    );
+    let h = j["hint"]
+        .as_str()
+        .expect("plugin_source_not_found must have non-null hint (#794)");
+    assert!(!h.is_empty(), "hint must be non-empty");
+}
+
+#[test]
+fn skills_install_not_found_and_unsupported_action_have_hints_795() {
+    // #795: `claw skills install /nonexistent` returned skill_not_found + hint:null, and
+    // `claw skills uninstall x` returned unsupported_skills_action + hint:null. Both error
+    // kinds were missing from fallback_hint_for_error_kind table. Fix: added both entries.
+    let root = unique_temp_dir("skills-install-795");
+    fs::create_dir_all(&root).expect("temp dir");
+    std::process::Command::new("git")
+        .args(["init", "-q"])
+        .current_dir(&root)
+        .output()
+        .ok();
+
+    // skills install with nonexistent local path
+    let out1 = run_claw(
+        &root,
+        &[
+            "--output-format",
+            "json",
+            "skills",
+            "install",
+            "/nonexistent-xyz-795",
+        ],
+        &[],
+    );
+    assert!(
+        !out1.status.success(),
+        "skills install not-found must exit non-zero (#795)"
+    );
+    let stderr1 = String::from_utf8_lossy(&out1.stderr);
+    let j1: serde_json::Value = stderr1
+        .lines()
+        .find(|l| l.trim_start().starts_with('{'))
+        .and_then(|l| serde_json::from_str(l).ok())
+        .expect("skills install not-found should emit JSON error");
+    assert_eq!(
+        j1["error_kind"], "skill_not_found",
+        "skills install not-found should be skill_not_found, got {:?}",
+        j1["error_kind"]
+    );
+    let h1 = j1["hint"]
+        .as_str()
+        .expect("skill_not_found must have non-null hint (#795)");
+    assert!(
+        h1.contains("skills list") || h1.contains("skills install"),
+        "hint should reference skills commands, got: {h1:?}"
+    );
+
+    // skills uninstall (unsupported action)
+    let out2 = run_claw(
+        &root,
+        &[
+            "--output-format",
+            "json",
+            "skills",
+            "uninstall",
+            "some-skill",
+        ],
+        &[],
+    );
+    assert!(
+        !out2.status.success(),
+        "skills uninstall must exit non-zero (#795)"
+    );
+    let stderr2 = String::from_utf8_lossy(&out2.stderr);
+    let j2: serde_json::Value = stderr2
+        .lines()
+        .find(|l| l.trim_start().starts_with('{'))
+        .and_then(|l| serde_json::from_str(l).ok())
+        .expect("skills uninstall should emit JSON error");
+    assert_eq!(
+        j2["error_kind"], "unsupported_skills_action",
+        "skills uninstall should be unsupported_skills_action, got {:?}",
+        j2["error_kind"]
+    );
+    let h2 = j2["hint"]
+        .as_str()
+        .expect("unsupported_skills_action must have non-null hint (#795)");
+    assert!(!h2.is_empty(), "hint must be non-empty");
+}
+
+#[test]
+fn agents_show_extra_positional_arg_returns_unexpected_extra_796() {
+    // #796: `claw agents show <name> <extra>` treated the full "name extra" as a single
+    // agent name, producing agent_not_found for "name extra" instead of flagging the
+    // unexpected extra argument. Fix: detect space-containing "name" and return
+    // unexpected_extra_args with usage hint.
+    let root = unique_temp_dir("agents-show-extra-796");
+    fs::create_dir_all(&root).expect("temp dir");
+    std::process::Command::new("git")
+        .args(["init", "-q"])
+        .current_dir(&root)
+        .output()
+        .ok();
+
+    let output = run_claw(
+        &root,
+        &[
+            "--output-format",
+            "json",
+            "agents",
+            "show",
+            "some-agent",
+            "--extra-flag",
+        ],
+        &[],
+    );
+    assert!(
+        !output.status.success(),
+        "agents show with extra arg must exit non-zero (#796)"
+    );
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    let j: serde_json::Value =
+        serde_json::from_str(stdout.trim()).expect("agents show extra arg should emit valid JSON");
+    assert_eq!(
+        j["error_kind"], "unexpected_extra_args",
+        "agents show extra arg should return unexpected_extra_args, got {:?}",
+        j["error_kind"]
+    );
+    let h = j["hint"]
+        .as_str()
+        .expect("unexpected_extra_args must have hint (#796)");
+    assert!(
+        h.contains("claw agents show") || h.contains("Usage"),
+        "hint should reference usage, got: {h:?}"
+    );
+}
+
+#[test]
+fn skills_show_extra_positional_arg_returns_unexpected_extra_796() {
+    // #796: same gap as agents — `claw skills show <name> <extra>` treated "name extra"
+    // as a single skill name → skill_not_found. Fix: detect space-containing name.
+    let root = unique_temp_dir("skills-show-extra-796");
+    fs::create_dir_all(&root).expect("temp dir");
+    std::process::Command::new("git")
+        .args(["init", "-q"])
+        .current_dir(&root)
+        .output()
+        .ok();
+
+    let output = run_claw(
+        &root,
+        &[
+            "--output-format",
+            "json",
+            "skills",
+            "show",
+            "some-skill",
+            "--extra-flag",
+        ],
+        &[],
+    );
+    assert!(
+        !output.status.success(),
+        "skills show with extra arg must exit non-zero (#796)"
+    );
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    let j: serde_json::Value =
+        serde_json::from_str(stdout.trim()).expect("skills show extra arg should emit valid JSON");
+    assert_eq!(
+        j["error_kind"], "unexpected_extra_args",
+        "skills show extra arg should return unexpected_extra_args, got {:?}",
+        j["error_kind"]
+    );
+    assert!(
+        j["hint"]
+            .as_str()
+            .is_some_and(|h| h.contains("claw skills show") || h.contains("Usage")),
+        "hint should reference usage (#796)"
+    );
+}
+
+#[test]
+fn plugins_extra_args_have_non_null_hint_797() {
+    // #797: `claw plugins show <name> <extra>` returned unexpected_extra_args + hint:null.
+    // The plugins arg parser at the top level emitted "unexpected extra arguments after
+    // `claw plugins show ...`: ..." with no \n delimiter. Parity with #791 config fix.
+    let root = unique_temp_dir("plugins-extra-args-797");
+    fs::create_dir_all(&root).expect("temp dir");
+    std::process::Command::new("git")
+        .args(["init", "-q"])
+        .current_dir(&root)
+        .output()
+        .ok();
+
+    let output = run_claw(
+        &root,
+        &[
+            "--output-format",
+            "json",
+            "plugins",
+            "show",
+            "some-plugin",
+            "extra-arg",
+        ],
+        &[],
+    );
+    assert!(
+        !output.status.success(),
+        "plugins show with extra arg must exit non-zero (#797)"
+    );
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    let j: serde_json::Value = stderr
+        .lines()
+        .find(|l| l.trim_start().starts_with('{'))
+        .and_then(|l| serde_json::from_str(l).ok())
+        .expect("plugins extra arg should emit JSON error");
+    assert_eq!(j["error_kind"], "unexpected_extra_args");
+    let h = j["hint"]
+        .as_str()
+        .expect("unexpected_extra_args must have non-null hint (#797)");
+    assert!(
+        h.contains("plugins") || h.contains("Usage"),
+        "hint should reference plugins usage, got: {h:?}"
+    );
+}
+
+#[test]
+fn empty_prompt_has_non_null_hint_798() {
+    // #798: `claw --output-format json ""` returned empty_prompt + hint:null.
+    // The error message "empty prompt: provide a subcommand..." had no \n delimiter.
+    let root = unique_temp_dir("empty-prompt-798");
+    fs::create_dir_all(&root).expect("temp dir");
+    std::process::Command::new("git")
+        .args(["init", "-q"])
+        .current_dir(&root)
+        .output()
+        .ok();
+
+    let output = run_claw(&root, &["--output-format", "json", ""], &[]);
+    assert!(
+        !output.status.success(),
+        "empty prompt must exit non-zero (#798)"
+    );
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    let j: serde_json::Value = stderr
+        .lines()
+        .find(|l| l.trim_start().starts_with('{'))
+        .and_then(|l| serde_json::from_str(l).ok())
+        .expect("empty prompt should emit JSON error envelope");
+    assert_eq!(j["error_kind"], "empty_prompt");
+    let h = j["hint"]
+        .as_str()
+        .expect("empty_prompt must have non-null hint (#798)");
+    assert!(
+        h.contains("claw") || h.contains("Usage"),
+        "hint should reference usage, got: {h:?}"
+    );
+}