diff --git a/CHANGELOG.md b/CHANGELOG.md
index 18ed4ad..0f6414f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,8 +10,55 @@ CalVer image tags (`stable-YYYY.MM.N`, `dev-YYYY.MM.N`) are produced for every C
 
 ## [Unreleased]
 
+### Added
+
+- **`/update-agnes-plugins` slash command** — installed automatically by
+  `agnes init` into `<workspace>/.claude/commands/`. Runs
+  `agnes refresh-marketplace` (the chatty default mode) so the user sees
+  install/update progress streamed into the Claude Code transcript and
+  can react to errors interactively, instead of having a full reconcile
+  happen silently behind a SessionStart hook.
+
+- **`agnes refresh-marketplace --check`** — lightweight detector mode for
+  the SessionStart hook. Runs `git fetch` only, compares local `HEAD`
+  with remote `FETCH_HEAD`, and emits a Claude Code hook JSON message
+  pointing the user at `/update-agnes-plugins` when there are remote
+  changes. Silent when up to date. No `git reset`, no
+  `claude plugin marketplace update`, no plugin install/update side
+  effects.
+
+### Changed
+
+- **SessionStart marketplace hook is now read-only.** The hook installed
+  by `agnes init` was previously `agnes refresh-marketplace --quiet`,
+  which performed a full fetch+reset+install cycle on every session start
+  (slow, invisible to the user, not interactively recoverable). It now
+  runs `agnes refresh-marketplace --check` — detect-only — and surfaces a
+  hint to run `/update-agnes-plugins` when updates are available.
+  Existing workspaces auto-upgrade on next `agnes init` (the substring
+  marker `agnes refresh-marketplace` matches both the old and new entry
+  shapes, so the idempotent-replace path correctly rewrites them).
+
+- **Marketplace "Added to your stack" hint points at `/update-agnes-plugins`.**
+  The post-install green panel on plugin and skill/agent detail pages
+  used to suggest `agnes refresh-marketplace` in a shell prompt and
+  reference the SessionStart auto-install. With the hook now being
+  detect-only, that text was outdated. The hint is condensed to a
+  single instruction — open a new Claude Code session and run
+  `/update-agnes-plugins` — with the slash command in a copy chip.
+  Affects `marketplace_plugin_detail.html` and `marketplace_item_detail.html`.
+
 ### Removed
 
+- **BREAKING: `agnes refresh-marketplace --quiet` flag.** Replaced by
+  `--check` (detect-only) and the new `/update-agnes-plugins` slash
+  command (interactive update). Existing SessionStart hooks calling
+  `--quiet` will silent-noop after the CLI upgrade — the hook's
+  `2>/dev/null || true` swallows the unknown-flag error — until the user
+  re-runs `agnes init`, which rewrites the hook to use `--check` and
+  installs the slash command. Dashboard `/setup` flow re-runs
+  `agnes init` automatically on next paste.
+
 - **BREAKING: legacy `git config --global http.<host>.sslVerify=false`
   downgrade in the install setup prompt.** The marketplace step (step 5)
   used to emit this line on `AGNES_DEBUG_AUTH=1` instances when no
diff --git a/app/web/templates/marketplace_item_detail.html b/app/web/templates/marketplace_item_detail.html
index 4817218..41a9ac6 100644
--- a/app/web/templates/marketplace_item_detail.html
+++ b/app/web/templates/marketplace_item_detail.html
@@ -523,18 +523,12 @@
           <span class="title">✓ Added to your stack</span>
           <button class="dismiss" id="stack-hint-dismiss" type="button">Don’t show again</button>
         </div>
-        <div>To use it in Claude Code:</div>
-        <ol>
-          <li><strong>Open a new Claude Code session</strong> — it auto-installs via the SessionStart hook.</li>
-          <li>Or run now in your terminal:
-            <div class="cmd-chip">
-              <span class="prompt">$</span>
-              <span class="cmd">agnes refresh-marketplace</span>
-              <button class="btn-copy" id="stack-hint-copy" type="button">Copy</button>
-            </div>
-            Then in the running session: <code>/reload-plugins</code>
-          </li>
-        </ol>
+        <div>Open a new Claude Code session and run:</div>
+        <div class="cmd-chip">
+          <span class="prompt">/</span>
+          <span class="cmd">update-agnes-plugins</span>
+          <button class="btn-copy" id="stack-hint-copy" type="button">Copy</button>
+        </div>
       </div>
     </div>
     <aside class="panel details">
@@ -804,7 +798,7 @@
       copyBtn.addEventListener('click', async (ev) => {
         const b = ev.currentTarget;
         try {
-          await navigator.clipboard.writeText('agnes refresh-marketplace');
+          await navigator.clipboard.writeText('/update-agnes-plugins');
           const orig = b.textContent;
           b.classList.add('copied');
           b.textContent = 'Copied';
diff --git a/app/web/templates/marketplace_plugin_detail.html b/app/web/templates/marketplace_plugin_detail.html
index d1d618d..13f3aa8 100644
--- a/app/web/templates/marketplace_plugin_detail.html
+++ b/app/web/templates/marketplace_plugin_detail.html
@@ -512,18 +512,12 @@
           <span class="title">✓ Added to your stack</span>
           <button class="dismiss" id="stack-hint-dismiss" type="button">Don’t show again</button>
         </div>
-        <div>To use it in Claude Code:</div>
-        <ol>
-          <li><strong>Open a new Claude Code session</strong> — it auto-installs via the SessionStart hook.</li>
-          <li>Or run now in your terminal:
-            <div class="cmd-chip">
-              <span class="prompt">$</span>
-              <span class="cmd">agnes refresh-marketplace</span>
-              <button class="btn-copy" id="stack-hint-copy" type="button">Copy</button>
-            </div>
-            Then in the running session: <code>/reload-plugins</code>
-          </li>
-        </ol>
+        <div>Open a new Claude Code session and run:</div>
+        <div class="cmd-chip">
+          <span class="prompt">/</span>
+          <span class="cmd">update-agnes-plugins</span>
+          <button class="btn-copy" id="stack-hint-copy" type="button">Copy</button>
+        </div>
       </div>
     </div>
     <div class="panel details" id="panel-details">
@@ -709,7 +703,7 @@
   document.getElementById('stack-hint-copy').addEventListener('click', async (ev) => {
     const copyBtn = ev.currentTarget;
     try {
-      await navigator.clipboard.writeText('agnes refresh-marketplace');
+      await navigator.clipboard.writeText('/update-agnes-plugins');
       const orig = copyBtn.textContent;
       copyBtn.classList.add('copied');
       copyBtn.textContent = 'Copied';
diff --git a/cli/commands/init.py b/cli/commands/init.py
index c2b4b74..66ec2a9 100644
--- a/cli/commands/init.py
+++ b/cli/commands/init.py
@@ -16,7 +16,9 @@ Steps in order:
    RBAC-filtered, role-aware).
 5. Seed `.claude/settings.json` with default model + permissions, then call
    `cli.lib.hooks.install_claude_hooks` to merge in the SessionStart/End hook
-   commands. Idempotent on re-run.
+   commands. Then call `cli.lib.commands.install_claude_commands` to drop
+   the Agnes-managed slash commands (today: `/update-agnes-plugins`) into
+   `<workspace>/.claude/commands/`. Idempotent on re-run.
 6. Write the `.claude/CLAUDE.local.md` stub only when absent — `--force`
    regenerates CLAUDE.md but **never** clobbers the operator-edited
    CLAUDE.local.md.
@@ -44,6 +46,7 @@ import typer
 from cli.client import api_get
 from cli.config import save_config, save_token
 from cli.error_render import render_error
+from cli.lib.commands import install_claude_commands
 from cli.lib.hooks import install_claude_hooks
 from cli.lib.pull import PullResult, _override_server_env, run_pull
 
@@ -190,6 +193,7 @@ def init(
             indent=2,
         ), encoding="utf-8")
     install_claude_hooks(workspace)
+    install_claude_commands(workspace)
 
     # ------------------------------------------------------------------
     # Step 6: CLAUDE.local.md stub — only when absent. `--force` does NOT
diff --git a/cli/commands/refresh_marketplace.py b/cli/commands/refresh_marketplace.py
index c8cb180..8ea4cfe 100644
--- a/cli/commands/refresh_marketplace.py
+++ b/cli/commands/refresh_marketplace.py
@@ -5,15 +5,22 @@ Three call paths share the same code:
   - `agnes refresh-marketplace --bootstrap` — first-time setup; clones the
     per-user marketplace bare repo, registers it with Claude Code, then
     falls through to fetch+reset+reconcile so plugins land installed.
-  - `agnes refresh-marketplace` — manual re-sync after a known stack change.
-  - `agnes refresh-marketplace --quiet` — SessionStart hook context. Emits
-    a Claude Code hook JSON object on stdout when something actually got
-    installed/updated; silent otherwise.
+  - `agnes refresh-marketplace` — manual re-sync after a known stack
+    change. This is what the `/update-agnes-plugins` slash command runs
+    inside Claude Code so the user sees install/update progress in the
+    transcript.
+  - `agnes refresh-marketplace --check` — SessionStart hook context.
+    Lightweight detector: `git fetch` only (no reset, no plugin
+    install/update side effects), compares local `HEAD` vs `FETCH_HEAD`,
+    emits a Claude Code hook JSON message pointing the user at
+    `/update-agnes-plugins` when there are remote changes. Silent
+    otherwise.
 
-Reconcile is version-aware (install missing / update on version diff /
-skip on match). Server-side stack composition lives in
-`src/marketplace_filter.py:resolve_user_marketplace`. Plugin installs use
-`--scope project` so they land in the workspace the hook fired in.
+Reconcile (default + --bootstrap paths) is version-aware (install
+missing / update on version diff / skip on match). Server-side stack
+composition lives in `src/marketplace_filter.py:resolve_user_marketplace`.
+Plugin installs use `--scope project` so they land in the workspace the
+caller invoked from.
 """
 
 from __future__ import annotations
@@ -47,9 +54,17 @@ _CREDENTIAL_HELPER = '!f() { printf "username=x\\npassword=%s\\n" "$AGNES_TOKEN"
 
 @refresh_marketplace_app.callback(invoke_without_command=True)
 def refresh_marketplace(
-    quiet: bool = typer.Option(
-        False, "--quiet",
-        help="Suppress success stdout (errors and warnings still surface on stderr).",
+    check: bool = typer.Option(
+        False, "--check",
+        help=(
+            "Detect-only mode for the SessionStart hook. Runs `git fetch` "
+            "and compares local HEAD with remote FETCH_HEAD. When they "
+            "differ, emits a Claude Code hook JSON message hinting the "
+            "user at `/update-agnes-plugins`. No `git reset`, no plugin "
+            "install/update side effects — fast, invisible when nothing "
+            "changed, fully recoverable interactively via the slash "
+            "command."
+        ),
     ),
     bootstrap: bool = typer.Option(
         False, "--bootstrap",
@@ -62,6 +77,13 @@ def refresh_marketplace(
     ),
 ):
     """Sync the marketplace clone, re-register with Claude, install/update plugins."""
+    if check and bootstrap:
+        typer.echo(
+            "error: --check and --bootstrap are mutually exclusive.",
+            err=True,
+        )
+        raise typer.Exit(2)
+
     clone_exists = (CLONE_DIR / ".git").is_dir()
 
     # Hook contexts hit the no-clone path on every workspace that didn't
@@ -69,7 +91,7 @@ def refresh_marketplace(
     # workspaces with the hook installed but no agnes token configured
     # (fresh CI checkout, etc.) must silent-noop, not surface auth_failed.
     if not clone_exists and not bootstrap:
-        if not quiet:
+        if not check:
             typer.echo(
                 f"No marketplace clone at {CLONE_DIR} — nothing to refresh. "
                 "Re-run setup with `agnes refresh-marketplace --bootstrap` "
@@ -89,12 +111,22 @@ def refresh_marketplace(
         raise typer.Exit(1)
 
     if not clone_exists:
-        if not _bootstrap_clone(token, quiet=quiet):
+        if not _bootstrap_clone(token):
             raise typer.Exit(1)
 
+    # --check: lightweight detector. Don't fetch+reset, don't reconcile
+    # plugins — that's the slash command's job. Just check whether the
+    # remote has new content and tell the user if so.
+    if check:
+        if not _git_fetch_only(token):
+            raise typer.Exit(1)
+        if _has_remote_changes():
+            _emit_check_hook_message()
+        raise typer.Exit(0)
+
     events: dict[str, list[str]] = {"installed": [], "updated": []}
 
-    if not _git_fetch_and_reset(token, quiet=quiet):
+    if not _git_fetch_and_reset(token):
         raise typer.Exit(1)
 
     # Snapshot installed versions BEFORE `claude plugin marketplace update`.
@@ -105,20 +137,18 @@ def refresh_marketplace(
     # would fire despite the plugin having actually changed.
     installed_pre = _list_installed_agnes_plugins_in_cwd()
 
-    _claude_marketplace_update(quiet=quiet)
+    _claude_marketplace_update()
 
-    _reconcile_with_manifest(quiet=quiet, events=events, installed_pre=installed_pre)
+    _reconcile_with_manifest(events=events, installed_pre=installed_pre)
 
-    if quiet and (events["installed"] or events["updated"]):
-        _emit_hook_message(events)
-    elif not quiet and (events["installed"] or events["updated"]):
+    if events["installed"] or events["updated"]:
         typer.echo(
             "\nRun `/reload-plugins` in Claude Code to load the "
             "new/updated plugins into the running session — no restart needed."
         )
 
 
-def _bootstrap_clone(token: str, *, quiet: bool) -> bool:
+def _bootstrap_clone(token: str) -> bool:
     """Initial clone of the per-user marketplace bare repo into ~/.agnes/marketplace.
 
     Wrapping the destructive prep in the agnes binary lets the CLI's
@@ -156,8 +186,7 @@ def _bootstrap_clone(token: str, *, quiet: bool) -> bool:
     auth_url = f"{scheme}://x:{token}@{server_host}/marketplace.git/"
     clean_url = f"{scheme}://{server_host}/marketplace.git/"
 
-    if not quiet:
-        typer.echo(f"Cloning marketplace from {clean_url} into {CLONE_DIR}...")
+    typer.echo(f"Cloning marketplace from {clean_url} into {CLONE_DIR}...")
 
     try:
         result = subprocess.run(
@@ -206,20 +235,21 @@ def _bootstrap_clone(token: str, *, quiet: bool) -> bool:
             )
             if add.stderr:
                 typer.echo(add.stderr.rstrip(), err=True)
-        elif not quiet and add.stdout:
+        elif add.stdout:
             typer.echo(add.stdout.rstrip())
 
-    if not quiet:
-        typer.echo(f"Marketplace bootstrapped at {CLONE_DIR}.")
+    typer.echo(f"Marketplace bootstrapped at {CLONE_DIR}.")
     return True
 
 
-def _git_fetch_and_reset(token: str, *, quiet: bool) -> bool:
-    """Fetch from origin then hard-reset to FETCH_HEAD.
+def _git_fetch_only(token: str) -> bool:
+    """Fetch from origin without resetting the working tree.
 
-    Not `pull --ff-only`: the marketplace bare repo on the server rebuilds
-    as a fresh orphan commit on every content change, so two snapshots
-    have unrelated histories and fast-forward is impossible.
+    Used by `--check` to learn whether the remote has new content without
+    actually applying it. The bare repo on the server rebuilds as a fresh
+    orphan commit on every content change, so FETCH_HEAD is always the
+    full new tree — comparing local HEAD to FETCH_HEAD is sufficient to
+    detect remote-side changes.
     """
     env = {**os.environ, "AGNES_TOKEN": token}
     fetch_cmd = [
@@ -234,7 +264,7 @@ def _git_fetch_and_reset(token: str, *, quiet: bool) -> bool:
             encoding="utf-8", errors="replace", check=False,
         )
     except FileNotFoundError:
-        typer.echo("error: `git` not found in PATH; cannot refresh marketplace.", err=True)
+        typer.echo("error: `git` not found in PATH; cannot check marketplace.", err=True)
         return False
     if fetch.returncode != 0:
         if fetch.stdout:
@@ -242,6 +272,41 @@ def _git_fetch_and_reset(token: str, *, quiet: bool) -> bool:
         if fetch.stderr:
             typer.echo(fetch.stderr, err=True)
         return False
+    return True
+
+
+def _has_remote_changes() -> bool:
+    """Return True iff local HEAD differs from remote FETCH_HEAD.
+
+    Caller must have already run `git fetch origin`. Any rev-parse failure
+    (missing FETCH_HEAD, broken repo) is treated as "no detectable changes"
+    so the hook stays quiet rather than surfacing a misleading hint.
+    """
+    try:
+        local = subprocess.run(
+            ["git", "-C", str(CLONE_DIR), "rev-parse", "HEAD"],
+            capture_output=True, text=True, encoding="utf-8", errors="replace", check=False,
+        )
+        remote = subprocess.run(
+            ["git", "-C", str(CLONE_DIR), "rev-parse", "FETCH_HEAD"],
+            capture_output=True, text=True, encoding="utf-8", errors="replace", check=False,
+        )
+    except FileNotFoundError:
+        return False
+    if local.returncode != 0 or remote.returncode != 0:
+        return False
+    return local.stdout.strip() != remote.stdout.strip()
+
+
+def _git_fetch_and_reset(token: str) -> bool:
+    """Fetch from origin then hard-reset to FETCH_HEAD.
+
+    Not `pull --ff-only`: the marketplace bare repo on the server rebuilds
+    as a fresh orphan commit on every content change, so two snapshots
+    have unrelated histories and fast-forward is impossible.
+    """
+    if not _git_fetch_only(token):
+        return False
 
     reset = subprocess.run(
         ["git", "-C", str(CLONE_DIR), "reset", "--hard", "FETCH_HEAD"],
@@ -254,12 +319,12 @@ def _git_fetch_and_reset(token: str, *, quiet: bool) -> bool:
             typer.echo(reset.stderr, err=True)
         return False
 
-    if not quiet and reset.stdout:
+    if reset.stdout:
         typer.echo(reset.stdout.rstrip())
     return True
 
 
-def _claude_marketplace_update(*, quiet: bool) -> None:
+def _claude_marketplace_update() -> None:
     """Tell Claude Code to re-read the marketplace clone. Soft-fail if `claude` is missing."""
     if shutil.which("claude") is None:
         typer.echo(
@@ -280,13 +345,12 @@ def _claude_marketplace_update(*, quiet: bool) -> None:
         if result.stderr:
             typer.echo(result.stderr.rstrip(), err=True)
         return
-    if not quiet and result.stdout:
+    if result.stdout:
         typer.echo(result.stdout.rstrip())
 
 
 def _reconcile_with_manifest(
     *,
-    quiet: bool,
     events: dict[str, list[str]],
     installed_pre: Optional[dict[str, str]] = None,
 ) -> None:
@@ -329,15 +393,13 @@ def _reconcile_with_manifest(
             to_update.append(name)
 
     if not to_install and not to_update:
-        if not quiet:
-            typer.echo(f"All {len(manifest)} Agnes-stack plugin(s) up to date.")
+        typer.echo(f"All {len(manifest)} Agnes-stack plugin(s) up to date.")
         return
 
-    if not quiet:
-        if to_install:
-            typer.echo(f"Installing {len(to_install)} new plugin(s): " + ", ".join(to_install))
-        if to_update:
-            typer.echo(f"Updating {len(to_update)} plugin(s) to latest version: " + ", ".join(to_update))
+    if to_install:
+        typer.echo(f"Installing {len(to_install)} new plugin(s): " + ", ".join(to_install))
+    if to_update:
+        typer.echo(f"Updating {len(to_update)} plugin(s) to latest version: " + ", ".join(to_update))
 
     for name in to_install:
         target = f"{name}@{MARKETPLACE_NAME}"
@@ -354,7 +416,7 @@ def _reconcile_with_manifest(
                 typer.echo(result.stderr.rstrip(), err=True)
             continue
         events["installed"].append(name)
-        if not quiet and result.stdout:
+        if result.stdout:
             typer.echo(result.stdout.rstrip())
 
     for name in to_update:
@@ -372,40 +434,28 @@ def _reconcile_with_manifest(
                 typer.echo(result.stderr.rstrip(), err=True)
             continue
         events["updated"].append(name)
-        if not quiet and result.stdout:
+        if result.stdout:
             typer.echo(result.stdout.rstrip())
 
 
-def _emit_hook_message(events: dict[str, list[str]]) -> None:
-    """Emit Claude Code hook JSON summarizing what changed.
+def _emit_check_hook_message() -> None:
+    """Emit Claude Code hook JSON pointing the user at `/update-agnes-plugins`.
 
-    `systemMessage` is a transient toast (often missed). `additionalContext`
-    is wrapped in a system reminder Claude reads at session start, so the
-    model can mention the change if it's relevant to the user's first ask.
-    Plugins land on disk during the hook; `/reload-plugins` loads them into
-    the running session without a restart.
+    `systemMessage` is a transient toast; `additionalContext` is wrapped in
+    a system reminder Claude reads at session start, so the model can
+    proactively mention the available update if the user's first ask is
+    plugin-related. The hook itself does NOT install anything — running
+    the slash command is the user's choice.
     """
-    parts: list[str] = []
-    if events["installed"]:
-        parts.append(
-            f"installed {len(events['installed'])} plugin(s): "
-            + ", ".join(events["installed"])
-        )
-    if events["updated"]:
-        parts.append(
-            f"updated {len(events['updated'])} plugin(s): "
-            + ", ".join(events["updated"])
-        )
-    summary = "Your Agnes stack changed: " + "; ".join(parts) + "."
-    restart_hint = (
-        "Run `/reload-plugins` to load the changes into this session — "
-        "no restart needed."
+    summary = (
+        "Agnes marketplace has updates available. "
+        "Run /update-agnes-plugins to install them."
     )
     payload = {
-        "systemMessage": f"{summary} {restart_hint}",
+        "systemMessage": summary,
         "hookSpecificOutput": {
             "hookEventName": "SessionStart",
-            "additionalContext": f"{summary} {restart_hint}",
+            "additionalContext": summary,
         },
     }
     typer.echo(json.dumps(payload))
diff --git a/cli/lib/commands.py b/cli/lib/commands.py
new file mode 100644
index 0000000..16bceb9
--- /dev/null
+++ b/cli/lib/commands.py
@@ -0,0 +1,82 @@
+"""Workspace-scoped Claude Code slash-command installer.
+
+Sibling to `cli/lib/hooks.py`. Where hooks live in
+`<workspace>/.claude/settings.json`, slash commands live as one
+markdown file per command in `<workspace>/.claude/commands/`. This
+module installs the Agnes-managed slash commands into a workspace.
+
+Design notes:
+- Workspace-scoped (`<workspace>/.claude/commands/<name>.md`), NOT
+  user-home. The slash commands appear only when Claude Code opens
+  this workspace, matching the hook scoping in `hooks.py`.
+- Idempotent: always overwrites *our* files (server-managed canonical
+  content, naturally evolves with the CLI version) but never touches
+  third-party slash commands the user (or another tool) may have
+  authored under `.claude/commands/`. Listing files individually
+  rather than wiping the directory keeps custom commands safe.
+- Templates ship inside the wheel under `cli/templates/commands/`.
+  `pyproject.toml` declares `cli` as a hatch wheel package, so
+  hatchling includes the markdown bodies during the build the same
+  way it ships `config/agnes_workspace_template.txt`.
+"""
+
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+
+# Slash commands managed by `agnes init`. Source (template name on
+# disk under `cli/templates/commands/`) → destination filename in
+# `<workspace>/.claude/commands/`. Today both names match; the indirection
+# keeps the door open for renaming (e.g. internal template name vs the
+# `/<command>` slug exposed to Claude Code).
+_MANAGED_COMMANDS: tuple[tuple[str, str], ...] = (
+    ("update-agnes-plugins.md", "update-agnes-plugins.md"),
+)
+
+
+# Defensive fallback used when the bundled template is missing on disk
+# (broken install, stripped-down test environment). Mirrors the
+# `agnes_workspace_template.txt` fallback in `cli/commands/init.py` —
+# better to write a usable stub than to crash `agnes init`.
+_FALLBACK_BODY = (
+    "---\n"
+    "description: Update Agnes marketplace plugins to latest versions\n"
+    "---\n"
+    "\n"
+    "Run `agnes refresh-marketplace` and report the output.\n"
+)
+
+
+def _templates_dir() -> Path:
+    """Locate the bundled-template directory.
+
+    `cli/lib/commands.py` → `cli/templates/commands/`.
+    Two `.parent` hops: lib/ → cli/, then descend into templates/commands/.
+    """
+    return Path(__file__).parent.parent / "templates" / "commands"
+
+
+def install_claude_commands(workspace: Path) -> None:
+    """Install Agnes-managed slash commands into `<workspace>/.claude/commands/`.
+
+    Always writes (overwrites) the managed command files; never touches
+    other files the user may have under `.claude/commands/`. Idempotent.
+    """
+    commands_dir = workspace / ".claude" / "commands"
+    commands_dir.mkdir(parents=True, exist_ok=True)
+
+    templates_dir = _templates_dir()
+    for source_name, dest_name in _MANAGED_COMMANDS:
+        source_path = templates_dir / source_name
+        try:
+            body = source_path.read_text(encoding="utf-8")
+        except OSError:
+            print(
+                f"Warning: bundled slash-command template "
+                f"{source_path} missing; writing defensive fallback.",
+                file=sys.stderr,
+            )
+            body = _FALLBACK_BODY
+        (commands_dir / dest_name).write_text(body, encoding="utf-8")
diff --git a/cli/lib/hooks.py b/cli/lib/hooks.py
index cf7eb65..cc7351c 100644
--- a/cli/lib/hooks.py
+++ b/cli/lib/hooks.py
@@ -18,9 +18,14 @@ Design notes:
        so any wire-protocol bump lands before pull tries to use the new
        CLI version. Both `|| true`-guarded so an upgrade failure doesn't
        block the pull.
-    2. `agnes refresh-marketplace` — independent entry so a fresh
-       workspace (no marketplace cloned yet) failing this command doesn't
-       suppress the data pull above.
+    2. `agnes refresh-marketplace --check` — independent entry. Detector-
+       only (since the slash-command split): runs `git fetch` against the
+       marketplace clone and emits a Claude Code hook JSON message
+       hinting the user at `/update-agnes-plugins` when remote content
+       changed. Does NOT install/update plugins itself — the slash
+       command does that interactively, with full output visible in the
+       Claude Code transcript and under user control. Failure (no clone,
+       no token) silently no-ops via the surrounding `|| true`.
     3. `agnes push` — uploads any session JSONLs that haven't reached the
        server yet (orphans from `claude -p` headless mode where Claude Code
        does NOT fire SessionEnd, or from abnormal session exits). Symmetric
@@ -110,10 +115,17 @@ def install_claude_hooks(workspace: Path) -> None:
     # isn't churned for parity (the same redirection fluff applies but
     # changing the existing wire would force every workspace to re-write
     # its settings.json on the next `agnes init` for no behaviour gain).
+    #
+    # `--check` makes the marketplace entry a detector only: the actual
+    # plugin install/update happens in the `/update-agnes-plugins` slash
+    # command (installed by `cli.lib.commands.install_claude_commands`).
+    # Workspaces still on the older `--quiet` form auto-upgrade here
+    # because `_OUR_COMMAND_MARKERS` matches by substring on the
+    # `agnes refresh-marketplace` prefix.
     _replace_or_add("SessionStart", [
         "agnes self-upgrade --quiet 2>/dev/null || true; "
         "agnes pull --quiet 2>/dev/null || true",
-        'bash -c "agnes refresh-marketplace --quiet 2>/dev/null || true"',
+        'bash -c "agnes refresh-marketplace --check 2>/dev/null || true"',
         'bash -c "agnes push --quiet 2>/dev/null || true"',
     ])
     # SessionEnd push must run detached. Claude Code in `-p` (headless) mode
diff --git a/cli/templates/commands/update-agnes-plugins.md b/cli/templates/commands/update-agnes-plugins.md
new file mode 100644
index 0000000..156b2f0
--- /dev/null
+++ b/cli/templates/commands/update-agnes-plugins.md
@@ -0,0 +1,19 @@
+---
+description: Update Agnes marketplace plugins to latest versions
+---
+
+Run the following command to refresh the Agnes marketplace plugins
+for this workspace:
+
+```bash
+agnes refresh-marketplace
+```
+
+Stream the output to me as it runs. If any plugins were installed
+or updated, remind me to run `/reload-plugins` to load the changes
+into this session — no Claude Code restart needed.
+
+If the command fails, report the exact error so we can diagnose it
+together (common causes: marketplace clone missing — fix with
+`agnes refresh-marketplace --bootstrap`; expired PAT — fix with
+`agnes auth import-token`).
diff --git a/tests/test_cli_refresh_marketplace.py b/tests/test_cli_refresh_marketplace.py
index 73e27c0..dc1ec3f 100644
--- a/tests/test_cli_refresh_marketplace.py
+++ b/tests/test_cli_refresh_marketplace.py
@@ -130,14 +130,20 @@ def test_refresh_marketplace_help():
     result = runner.invoke(refresh_marketplace_app, ["--help"])
     assert result.exit_code == 0
     cleaned = _clean(result.output)
-    assert "--quiet" in cleaned
-    # --auto-upgrade is gone — version-aware reconcile is now the default.
+    # --check is the SessionStart-hook-friendly detector mode (replaced
+    # --quiet, which used to perform a full reconcile silently).
+    assert "--check" in cleaned
+    assert "--bootstrap" in cleaned
+    # --quiet was removed in favour of --check + the /update-agnes-plugins
+    # slash command. --auto-upgrade was removed earlier (version-aware
+    # reconcile is the default).
+    assert "--quiet" not in cleaned
     assert "--auto-upgrade" not in cleaned
 
 
-def test_refresh_marketplace_no_clone_is_silent_noop_with_quiet(tmp_path, monkeypatch, recorder):
+def test_refresh_marketplace_no_clone_is_silent_noop_with_check(tmp_path, monkeypatch, recorder):
     monkeypatch.setattr(rm_module, "CLONE_DIR", tmp_path / "nonexistent")
-    result = runner.invoke(refresh_marketplace_app, ["--quiet"])
+    result = runner.invoke(refresh_marketplace_app, ["--check"])
     assert result.exit_code == 0
     assert _clean(result.output) == ""
     assert recorder.calls == []
@@ -154,7 +160,7 @@ def test_refresh_marketplace_no_clone_explains_in_manual_mode(tmp_path, monkeypa
 def test_no_clone_short_circuits_before_token_check(tmp_path, monkeypatch, recorder):
     """The no-clone no-op path must NOT require a token.
 
-    The SessionStart hook (`agnes refresh-marketplace --quiet`) runs in
+    The SessionStart hook (`agnes refresh-marketplace --check`) runs in
     every workspace that has the hook installed, including ones where no
     agnes token is configured (e.g. a fresh CI checkout, a workspace
     that never went through `agnes init`, a project sharing the user's
@@ -173,8 +179,8 @@ def test_no_clone_short_circuits_before_token_check(tmp_path, monkeypatch, recor
     monkeypatch.delenv("AGNES_TOKEN", raising=False)
     monkeypatch.setattr(rm_module, "CLONE_DIR", tmp_path / "nonexistent")
 
-    # --quiet (hook context).
-    result = runner.invoke(refresh_marketplace_app, ["--quiet"])
+    # --check (hook context).
+    result = runner.invoke(refresh_marketplace_app, ["--check"])
     assert result.exit_code == 0, (
         f"hook context should silent-noop without a token; got exit "
         f"{result.exit_code} and output {result.output!r}"
@@ -182,7 +188,7 @@ def test_no_clone_short_circuits_before_token_check(tmp_path, monkeypatch, recor
     assert _clean(result.output) == ""
     assert recorder.calls == []
 
-    # Manual mode (no --quiet): hint, but still exit 0 + no token resolution.
+    # Manual mode (no flags): hint, but still exit 0 + no token resolution.
     result = runner.invoke(refresh_marketplace_app, [])
     assert result.exit_code == 0
     assert "No marketplace clone" in _clean(result.output)
@@ -440,39 +446,7 @@ def test_reconcile_warns_when_plugin_list_unparseable(
     assert not any(c.cmd[:3] == ["claude", "plugin", "update"] for c in recorder.calls)
 
 
-# --- Hook JSON output -----------------------------------------------------------
-
-
-def test_quiet_emits_hook_json_when_plugin_installed(
-    with_clone, with_token, claude_in_path, recorder, monkeypatch, tmp_path,
-):
-    """--quiet + new install → hook JSON on stdout with systemMessage +
-    additionalContext, both naming the plugin and the restart instruction."""
-    workspace = tmp_path / "ws"
-    workspace.mkdir()
-    monkeypatch.chdir(workspace)
-    _set_marketplace_manifest(with_clone, [{"name": "grpn-fin", "version": "0.5.0"}])
-    recorder.script(("claude", "plugin", "list", "--json"),
-                    stdout=_plugin_list_json([]))
-
-    result = runner.invoke(refresh_marketplace_app, ["--quiet"])
-    assert result.exit_code == 0
-
-    out = _clean(result.output).strip()
-    assert out, "expected hook JSON on stdout when a plugin was installed"
-    payload = json.loads(out)
-    assert "grpn-fin" in payload["systemMessage"]
-    assert "Agnes stack" in payload["systemMessage"]
-    assert "installed" in payload["systemMessage"]
-    # Reload hint: `/reload-plugins` loads the on-disk plugins into the
-    # running Claude Code session without a full restart.
-    assert "/reload-plugins" in payload["systemMessage"]
-
-    hook_specific = payload.get("hookSpecificOutput", {})
-    assert hook_specific.get("hookEventName") == "SessionStart"
-    additional = hook_specific.get("additionalContext", "")
-    assert "grpn-fin" in additional
-    assert "/reload-plugins" in additional
+# --- Reload hint (default + slash-command chatty path) -------------------------
 
 
 def test_manual_mode_prints_reload_hint_when_anything_changed(
@@ -516,152 +490,13 @@ def test_manual_mode_no_change_does_not_print_reload_hint(
     assert "/reload-plugins" not in out
 
 
-def test_quiet_emits_hook_json_when_bundle_silently_auto_updated_by_claude(
-    with_clone, with_token, claude_in_path, recorder, monkeypatch, tmp_path,
-):
-    """Regression: when a /store skill change bumps the agnes-store-bundle
-    content hash, `claude plugin marketplace update agnes` silently
-    auto-applies the new version on local-path marketplaces (Claude
-    re-reads the manifest off disk and updates the installed cache).
-
-    If we captured the installed snapshot AFTER `claude plugin marketplace
-    update`, the diff against the new manifest would be zero (Claude
-    already updated installed → matches manifest), `events["updated"]`
-    would stay empty, and the hook JSON wouldn't fire — leaving the user
-    with no notification despite the plugin actually changing.
-
-    Pin this by scripting `claude plugin list --json` to return DIFFERENT
-    versions before vs after the marketplace-update call. The first
-    invocation (pre-snapshot) returns the old version; subsequent calls
-    return the new version (Claude's auto-update). Reconcile must use
-    the FIRST call's snapshot, detect the diff, and fire the
-    notification."""
-    workspace = tmp_path / "ws"
-    workspace.mkdir()
-    monkeypatch.chdir(workspace)
-    _set_marketplace_manifest(with_clone, [
-        {"name": "agnes-store-bundle", "version": "newhash"},
-    ])
-
-    # Track how many times `claude plugin list --json` was called so we
-    # can return DIFFERENT data on each invocation. The recorder's
-    # script() helper only does prefix-match with one fixed response
-    # per prefix, so we wrap its run() instead.
-    list_call_count = {"n": 0}
-    real_run = recorder.run
-
-    def staged_run(cmd, *args, **kwargs):
-        if cmd[:4] == ["claude", "plugin", "list", "--json"]:
-            # Record the call ourselves — we're bypassing recorder.run
-            # below, so we have to keep `recorder.calls` in sync.
-            recorder.calls.append(
-                _RecordedCall(cmd=list(cmd), env=dict(kwargs.get("env") or {}))
-            )
-            list_call_count["n"] += 1
-            payload = (
-                # Pre-snapshot (call 1): old version still observable.
-                _plugin_list_json([
-                    {"id": "agnes-store-bundle@agnes",
-                     "version": "oldhash",
-                     "projectPath": str(workspace)},
-                ])
-                if list_call_count["n"] == 1
-                else
-                # Post-marketplace-update (call 2+): Claude auto-applied
-                # the new version, version now matches manifest.
-                _plugin_list_json([
-                    {"id": "agnes-store-bundle@agnes",
-                     "version": "newhash",
-                     "projectPath": str(workspace)},
-                ])
-            )
-            return subprocess.CompletedProcess(args=list(cmd), returncode=0,
-                                                stdout=payload, stderr="")
-        return real_run(cmd, *args, **kwargs)
-
-    monkeypatch.setattr(rm_module.subprocess, "run", staged_run)
-
-    result = runner.invoke(refresh_marketplace_app, ["--quiet"])
-    assert result.exit_code == 0
-
-    # Hook JSON must fire — even though by the time reconcile sees `claude
-    # plugin list --json` the second time, versions match.
-    out = _clean(result.output).strip()
-    assert out, "hook JSON missing — pre-snapshot ordering regression"
-    payload = json.loads(out)
-    assert "agnes-store-bundle" in payload["systemMessage"]
-    assert "updated" in payload["systemMessage"]
-
-    # Sanity: pre-snapshot was captured before `claude plugin marketplace update`.
-    # We expect at least 2 list calls (pre-snapshot + reconcile re-read) but
-    # the FIRST one must have come before the marketplace update call.
-    list_indices = [
-        i for i, c in enumerate(recorder.calls)
-        if c.cmd[:4] == ["claude", "plugin", "list", "--json"]
-    ]
-    market_update_indices = [
-        i for i, c in enumerate(recorder.calls)
-        if c.cmd[:4] == ["claude", "plugin", "marketplace", "update"]
-    ]
-    assert list_indices, "no claude plugin list calls recorded"
-    assert market_update_indices, "no claude plugin marketplace update call recorded"
-    assert list_indices[0] < market_update_indices[0], (
-        f"pre-snapshot must come before marketplace update; "
-        f"list at {list_indices[0]}, marketplace update at {market_update_indices[0]}"
-    )
-
-
-def test_quiet_emits_hook_json_when_plugin_updated(
-    with_clone, with_token, claude_in_path, recorder, monkeypatch, tmp_path,
-):
-    """--quiet + version-mismatch update (e.g. /store skill add bumping
-    the bundle) → hook JSON with `updated` count in systemMessage."""
-    workspace = tmp_path / "ws"
-    workspace.mkdir()
-    monkeypatch.chdir(workspace)
-    _set_marketplace_manifest(with_clone, [
-        {"name": "agnes-store-bundle", "version": "newhash"},
-    ])
-    recorder.script(
-        ("claude", "plugin", "list", "--json"),
-        stdout=_plugin_list_json([
-            {"id": "agnes-store-bundle@agnes", "version": "oldhash",
-             "projectPath": str(workspace)},
-        ]),
-    )
-    result = runner.invoke(refresh_marketplace_app, ["--quiet"])
-    assert result.exit_code == 0
-    out = _clean(result.output).strip()
-    assert out
-    payload = json.loads(out)
-    assert "updated" in payload["systemMessage"]
-    assert "agnes-store-bundle" in payload["systemMessage"]
-
-
-def test_quiet_emits_no_hook_json_when_nothing_changed(
-    with_clone, with_token, claude_in_path, recorder, monkeypatch, tmp_path,
-):
-    """--quiet + everything in sync → silent stdout (no spurious
-    notification on every session start)."""
-    workspace = tmp_path / "ws"
-    workspace.mkdir()
-    monkeypatch.chdir(workspace)
-    _set_marketplace_manifest(with_clone, [{"name": "grpn-eng", "version": "1.0.0"}])
-    recorder.script(
-        ("claude", "plugin", "list", "--json"),
-        stdout=_plugin_list_json([
-            {"id": "grpn-eng@agnes", "version": "1.0.0", "projectPath": str(workspace)},
-        ]),
-    )
-    result = runner.invoke(refresh_marketplace_app, ["--quiet"])
-    assert result.exit_code == 0
-    assert _clean(result.output).strip() == ""
-
-
 def test_manual_mode_does_not_emit_hook_json(
     with_clone, with_token, claude_in_path, recorder, monkeypatch, tmp_path,
 ):
-    """Without --quiet, output is human-readable text — no JSON envelope."""
+    """Default mode (no flags) emits human-readable text — never a JSON envelope.
+
+    Hook JSON is reserved for `--check`. The slash command runs the
+    default chatty path, so its output is plain prose for the user."""
     workspace = tmp_path / "ws"
     workspace.mkdir()
     monkeypatch.chdir(workspace)
@@ -813,3 +648,190 @@ def test_bootstrap_with_existing_clone_skips_clone_proceeds_to_refresh(
     assert fetch_calls
     reset_calls = [c for c in recorder.calls if "reset" in c.cmd and "--hard" in c.cmd]
     assert reset_calls
+
+
+# --- --check flag (SessionStart-hook detector mode) -----------------------------
+
+
+def _stage_rev_parse(monkeypatch, recorder, *, head: str, fetch_head: str) -> None:
+    """Wrap recorder.run so `git rev-parse HEAD` and
+    `git rev-parse FETCH_HEAD` return scripted SHAs while every other
+    command falls through to the recorder's normal handling.
+
+    Used by --check tests to drive the HEAD-vs-FETCH_HEAD comparison
+    independently of the (mocked) git fetch.
+    """
+    real_run = recorder.run
+
+    def staged_run(cmd, *args, **kwargs):
+        # Match the trailing rev-parse target so `-C <path>` injection
+        # doesn't break the prefix.
+        if "rev-parse" in cmd:
+            recorder.calls.append(
+                _RecordedCall(cmd=list(cmd), env=dict(kwargs.get("env") or {}))
+            )
+            target = cmd[-1]
+            stdout = head if target == "HEAD" else fetch_head if target == "FETCH_HEAD" else ""
+            return subprocess.CompletedProcess(
+                args=list(cmd), returncode=0, stdout=stdout + "\n", stderr="",
+            )
+        return real_run(cmd, *args, **kwargs)
+
+    monkeypatch.setattr(rm_module.subprocess, "run", staged_run)
+
+
+def test_check_emits_hook_json_when_remote_changed(
+    with_clone, with_token, claude_in_path, recorder, monkeypatch, tmp_path,
+):
+    """`--check` + local HEAD differs from remote FETCH_HEAD →
+    Claude Code hook JSON on stdout pointing the user at
+    `/update-agnes-plugins`. The hook never installs anything itself."""
+    workspace = tmp_path / "ws"
+    workspace.mkdir()
+    monkeypatch.chdir(workspace)
+    _stage_rev_parse(monkeypatch, recorder, head="abc123", fetch_head="def456")
+
+    result = runner.invoke(refresh_marketplace_app, ["--check"])
+    assert result.exit_code == 0
+
+    out = _clean(result.output).strip()
+    assert out, "--check must emit hook JSON when remote has changes"
+    payload = json.loads(out)
+    assert "/update-agnes-plugins" in payload["systemMessage"], payload
+    assert "marketplace" in payload["systemMessage"].lower(), payload
+    assert payload["hookSpecificOutput"]["hookEventName"] == "SessionStart"
+    assert "/update-agnes-plugins" in payload["hookSpecificOutput"]["additionalContext"]
+
+
+def test_check_silent_when_remote_unchanged(
+    with_clone, with_token, claude_in_path, recorder, monkeypatch, tmp_path,
+):
+    """`--check` + HEAD == FETCH_HEAD → silent exit 0, no JSON output.
+    Avoids spamming the user with "updates available" on every session
+    start when nothing actually changed."""
+    workspace = tmp_path / "ws"
+    workspace.mkdir()
+    monkeypatch.chdir(workspace)
+    _stage_rev_parse(monkeypatch, recorder, head="samehash", fetch_head="samehash")
+
+    result = runner.invoke(refresh_marketplace_app, ["--check"])
+    assert result.exit_code == 0
+    assert _clean(result.output).strip() == ""
+
+
+def test_check_does_not_call_claude_plugin_anything(
+    with_clone, with_token, claude_in_path, recorder, monkeypatch, tmp_path,
+):
+    """`--check` must NOT call `claude plugin install/update` or
+    `claude plugin marketplace update`. Those side effects belong to
+    the `/update-agnes-plugins` slash command, which the user runs
+    interactively when they're ready."""
+    workspace = tmp_path / "ws"
+    workspace.mkdir()
+    monkeypatch.chdir(workspace)
+    # Even WITH a remote diff, --check must stay read-only.
+    _stage_rev_parse(monkeypatch, recorder, head="abc", fetch_head="def")
+
+    result = runner.invoke(refresh_marketplace_app, ["--check"])
+    assert result.exit_code == 0
+
+    forbidden_prefixes = (
+        ["claude", "plugin", "install"],
+        ["claude", "plugin", "update"],
+        ["claude", "plugin", "marketplace", "update"],
+    )
+    for prefix in forbidden_prefixes:
+        assert not any(c.cmd[: len(prefix)] == prefix for c in recorder.calls), (
+            f"--check must not invoke {' '.join(prefix)}; got: "
+            f"{[c.cmd for c in recorder.calls]!r}"
+        )
+
+
+def test_check_does_not_git_reset(
+    with_clone, with_token, claude_in_path, recorder, monkeypatch, tmp_path,
+):
+    """`--check` is read-only against the git tree. Must NOT call
+    `git reset --hard` — that would silently apply remote changes the
+    user hasn't agreed to yet."""
+    workspace = tmp_path / "ws"
+    workspace.mkdir()
+    monkeypatch.chdir(workspace)
+    _stage_rev_parse(monkeypatch, recorder, head="abc", fetch_head="def")
+
+    result = runner.invoke(refresh_marketplace_app, ["--check"])
+    assert result.exit_code == 0
+
+    reset_calls = [c for c in recorder.calls if "reset" in c.cmd]
+    assert reset_calls == [], (
+        f"--check must not call git reset; got: {[c.cmd for c in reset_calls]!r}"
+    )
+
+
+def test_check_runs_git_fetch(
+    with_clone, with_token, claude_in_path, recorder, monkeypatch, tmp_path,
+):
+    """`--check` must run `git fetch origin` (otherwise FETCH_HEAD is
+    stale and we'd compare against an old snapshot, missing real
+    remote changes)."""
+    workspace = tmp_path / "ws"
+    workspace.mkdir()
+    monkeypatch.chdir(workspace)
+    _stage_rev_parse(monkeypatch, recorder, head="abc", fetch_head="abc")
+
+    result = runner.invoke(refresh_marketplace_app, ["--check"])
+    assert result.exit_code == 0
+
+    fetch_calls = [
+        c for c in recorder.calls
+        if c.cmd and c.cmd[0] == "git" and "fetch" in c.cmd and "origin" in c.cmd
+    ]
+    assert fetch_calls, (
+        f"--check must run `git fetch origin`; got: {[c.cmd for c in recorder.calls]!r}"
+    )
+    # Same credential helper wiring as the default mode — PAT in env, not argv.
+    fetch = fetch_calls[0]
+    assert "-c" in fetch.cmd
+    assert fetch.cmd[fetch.cmd.index("-c") + 1].startswith("credential.helper=")
+    assert fetch.env.get("AGNES_TOKEN") == with_token
+
+
+def test_check_no_clone_silent_exit_zero(tmp_path, monkeypatch, with_token, recorder):
+    """`--check` on a workspace without a marketplace clone → silent
+    exit 0 (matches the old --quiet hook no-op semantics, so workspaces
+    that never bootstrapped don't spam "no clone" warnings on every
+    session start)."""
+    monkeypatch.setattr(rm_module, "CLONE_DIR", tmp_path / "nonexistent")
+    result = runner.invoke(refresh_marketplace_app, ["--check"])
+    assert result.exit_code == 0
+    assert _clean(result.output).strip() == ""
+    assert recorder.calls == []
+
+
+def test_check_fetch_failure_exits_one(
+    with_clone, with_token, claude_in_path, recorder, monkeypatch, tmp_path,
+):
+    """A failed `git fetch` (network down, auth rejected, etc.) → exit 1
+    so the surrounding `|| true` in the hook command swallows it cleanly.
+    No hook JSON is emitted (we don't know if the remote changed)."""
+    workspace = tmp_path / "ws"
+    workspace.mkdir()
+    monkeypatch.chdir(workspace)
+    recorder.script(("git", "-c"), returncode=1, stderr="fatal: unable to access ...")
+
+    result = runner.invoke(refresh_marketplace_app, ["--check"])
+    assert result.exit_code == 1
+    # No hook JSON on failure — the hook surrounding `|| true` swallows
+    # the non-zero exit so users don't see a half-written message.
+    assert not _clean(result.output).strip().startswith("{")
+
+
+def test_check_and_bootstrap_are_mutually_exclusive(
+    tmp_path, monkeypatch, with_token, recorder,
+):
+    """Mixing the two modes makes no sense (one is read-only detector,
+    the other is destructive clone-and-reconcile). Reject the combo
+    with a non-zero exit instead of silently picking one."""
+    monkeypatch.setattr(rm_module, "CLONE_DIR", tmp_path / "fresh_marketplace")
+    result = runner.invoke(refresh_marketplace_app, ["--check", "--bootstrap"])
+    assert result.exit_code == 2
+    assert recorder.calls == []
diff --git a/tests/test_lib_commands.py b/tests/test_lib_commands.py
new file mode 100644
index 0000000..9c9b2a0
--- /dev/null
+++ b/tests/test_lib_commands.py
@@ -0,0 +1,83 @@
+"""Tests for cli/lib/commands.py:install_claude_commands."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from cli.lib.commands import install_claude_commands
+
+
+def _read_managed_command(workspace: Path) -> str:
+    return (workspace / ".claude" / "commands" / "update-agnes-plugins.md").read_text(
+        encoding="utf-8"
+    )
+
+
+def test_install_writes_slash_command_file(tmp_path):
+    """install_claude_commands writes update-agnes-plugins.md into
+    <workspace>/.claude/commands/. The file is the bundled template
+    (frontmatter + body) — the test just pins that *something* lands and
+    that frontmatter shape is intact, so a future template edit doesn't
+    silently lose its description metadata."""
+    install_claude_commands(tmp_path)
+    body = _read_managed_command(tmp_path)
+    assert body.startswith("---"), body[:120]
+    assert "description:" in body.split("---", 2)[1], body[:200]
+    # The slash command's whole point: invoke `agnes refresh-marketplace`.
+    # Pin that the bundled body actually references the command.
+    assert "agnes refresh-marketplace" in body
+
+
+def test_install_creates_commands_dir_when_missing(tmp_path):
+    """Workspace without a .claude/ tree at all → install creates both
+    .claude/ and .claude/commands/."""
+    assert not (tmp_path / ".claude").exists()
+    install_claude_commands(tmp_path)
+    assert (tmp_path / ".claude" / "commands").is_dir()
+
+
+def test_install_overwrites_existing_managed_file(tmp_path):
+    """Even if the workspace has a hand-edited copy of the managed slash
+    command, install overwrites with the canonical template — server-
+    managed by design (Q2 of the design discussion). Users who want to
+    customize copy to a different filename, which is preserved by the
+    third-party-untouched test below."""
+    cmd_dir = tmp_path / ".claude" / "commands"
+    cmd_dir.mkdir(parents=True)
+    (cmd_dir / "update-agnes-plugins.md").write_text(
+        "USER EDIT THAT MUST BE OVERWRITTEN", encoding="utf-8",
+    )
+    install_claude_commands(tmp_path)
+    body = _read_managed_command(tmp_path)
+    assert "USER EDIT" not in body
+    assert "agnes refresh-marketplace" in body
+
+
+def test_install_does_not_touch_other_command_files(tmp_path):
+    """User's own slash commands under .claude/commands/ (e.g.
+    my-custom.md, project-specific helpers) must survive install
+    untouched. Only the Agnes-managed command files are overwritten."""
+    cmd_dir = tmp_path / ".claude" / "commands"
+    cmd_dir.mkdir(parents=True)
+    custom_path = cmd_dir / "my-custom.md"
+    custom_body = "---\ndescription: my own slash command\n---\n\nhello"
+    custom_path.write_text(custom_body, encoding="utf-8")
+
+    install_claude_commands(tmp_path)
+    assert custom_path.read_text(encoding="utf-8") == custom_body
+
+
+def test_install_idempotent(tmp_path):
+    """Two consecutive installs produce identical state. Important
+    because `agnes init --force` re-runs the installer and the
+    SessionStart hook chain (in some future world where we wire it up)
+    might too — neither should accumulate stray files or change content
+    on a no-op invocation."""
+    install_claude_commands(tmp_path)
+    first = _read_managed_command(tmp_path)
+    install_claude_commands(tmp_path)
+    second = _read_managed_command(tmp_path)
+    assert first == second
+    # And no extra files appeared.
+    cmd_dir_files = sorted(p.name for p in (tmp_path / ".claude" / "commands").iterdir())
+    assert cmd_dir_files == ["update-agnes-plugins.md"]
diff --git a/tests/test_lib_hooks.py b/tests/test_lib_hooks.py
index c5d7201..78d5127 100644
--- a/tests/test_lib_hooks.py
+++ b/tests/test_lib_hooks.py
@@ -52,6 +52,16 @@ def test_install_creates_settings_file(tmp_path):
     assert refresh.startswith("bash -c "), (
         f"refresh-marketplace hook must be wrapped in bash -c for Windows; got: {refresh!r}"
     )
+    # Hook is now a detector — `--check` only. Plugin install/update
+    # happens in the `/update-agnes-plugins` slash command instead.
+    # Pinning the flag here prevents an accidental regression to the old
+    # `--quiet` form (which performed a full reconcile silently).
+    assert "--check" in refresh, (
+        f"refresh-marketplace hook must use --check (detector mode); got: {refresh!r}"
+    )
+    assert "--quiet" not in refresh, (
+        f"refresh-marketplace hook must NOT use --quiet (removed flag); got: {refresh!r}"
+    )
     # The push self-heal entry is also bash-c-wrapped for Windows parity.
     push_start = next((c for c in starts if "agnes push" in c), None)
     assert push_start is not None, (
@@ -161,6 +171,53 @@ def test_install_replaces_v0_43_chained_self_upgrade_pull_entry(tmp_path):
     assert "agnes push --quiet" in ends[0]
 
 
+def test_install_replaces_old_quiet_refresh_with_check(tmp_path):
+    """A workspace bootstrapped before the slash-command split has the old
+    `--quiet` form in its refresh-marketplace SessionStart entry. The next
+    `agnes init` must replace that entry with the new `--check` form, NOT
+    stack the new entry alongside the old one (which would re-run the
+    full reconcile every session — exactly the behaviour we just moved
+    behind the slash command).
+    """
+    settings_path = tmp_path / ".claude" / "settings.json"
+    settings_path.parent.mkdir(parents=True)
+    settings_path.write_text(json.dumps({
+        "hooks": {
+            "SessionStart": [
+                {"hooks": [{"type": "command", "command": (
+                    "agnes self-upgrade --quiet 2>/dev/null || true; "
+                    "agnes pull --quiet 2>/dev/null || true"
+                )}]},
+                {"hooks": [{"type": "command", "command": (
+                    'bash -c "agnes refresh-marketplace --quiet 2>/dev/null || true"'
+                )}]},
+                {"hooks": [{"type": "command", "command": (
+                    'bash -c "agnes push --quiet 2>/dev/null || true"'
+                )}]},
+            ],
+            "SessionEnd": [
+                {"hooks": [{"type": "command", "command": (
+                    'bash -c "( nohup agnes push --quiet </dev/null '
+                    '>/dev/null 2>&1 & ) ; true"'
+                )}]},
+            ],
+        }
+    }))
+    install_claude_hooks(tmp_path)
+    cfg = _read_settings(tmp_path)
+    starts = _commands_for(cfg, "SessionStart")
+    # Exactly one refresh-marketplace entry remains (no stacking).
+    refresh_entries = [c for c in starts if "agnes refresh-marketplace" in c]
+    assert len(refresh_entries) == 1, refresh_entries
+    refresh = refresh_entries[0]
+    assert "--check" in refresh, (
+        f"old --quiet entry must have been rewritten to --check; got: {refresh!r}"
+    )
+    assert "--quiet" not in refresh, (
+        f"old --quiet form must be gone after re-init; got: {refresh!r}"
+    )
+
+
 def test_install_preserves_third_party_hooks(tmp_path):
     settings_path = tmp_path / ".claude" / "settings.json"
     settings_path.parent.mkdir(parents=True)