diff --git a/hermes_cli/config.py b/hermes_cli/config.py
index 4669b49e8e059..c258f73995c09 100644
--- a/hermes_cli/config.py
+++ b/hermes_cli/config.py
@@ -1404,14 +1404,19 @@ def _disable_suspicious_mcp_servers(results: Dict[str, Any], quiet: bool) -> Non
 
 def _warn_invalid_platform_toolsets(results: Dict[str, Any], quiet: bool) -> None:
     """Surface invalid toolset names in platform_toolsets: ``resolve_toolset()`` returns [] for an
-    unknown name, silently disabling the affected tools. Best-effort; never blocks migration."""
+    unknown name, silently disabling the affected tools. Best-effort; never blocks migration.
+
+    ``known_plugin_toolsets`` rides along so plugin toolsets — which register only after plugins
+    load, i.e. after this runs — are not reported as unknown on every migration."""
     try:
         from toolsets import validate_toolset
         from hermes_cli.toolset_validation import validate_platform_toolsets
         from hermes_cli.toolset_scope import toolset_allowed_for_platform
 
+        raw_cfg = read_raw_config()
         for w in validate_platform_toolsets(
-                read_raw_config().get("platform_toolsets"), validate_toolset, toolset_allowed_for_platform):
+                raw_cfg.get("platform_toolsets"), validate_toolset, toolset_allowed_for_platform,
+                raw_cfg.get("known_plugin_toolsets")):
             results["warnings"].append(w)
             if not quiet:
                 print(f"  ⚠ {w}")
diff --git a/hermes_cli/toolset_validation.py b/hermes_cli/toolset_validation.py
index 72cbc3a6b9717..759d773da74b1 100644
--- a/hermes_cli/toolset_validation.py
+++ b/hermes_cli/toolset_validation.py
@@ -28,22 +28,46 @@ def _platform_default_is_valid(
         return False
 
 
+def _known_plugin_toolsets(known: object, platform: object) -> set:
+    """Plugin toolset names *known_plugin_toolsets* declares for *platform* (empty when absent).
+
+    ``hermes tools`` writes this section on every save, so it is the config's own record of which
+    plugin-provided toolsets are legitimate. Scoped per platform on purpose: a name declared for
+    one platform must not mask a typo under another.
+    """
+    if not isinstance(known, dict):
+        return set()
+    names = known.get(platform)
+    if isinstance(names, str):  # legacy single-string entry
+        return {names}
+    if not isinstance(names, list):
+        return set()
+    return {n for n in names if isinstance(n, str) and n}
+
+
 def validate_platform_toolsets(
     platform_toolsets: object, is_valid_toolset: Callable[[str], bool],
     is_allowed_for_platform: Callable[[str, str], bool] = toolset_allowed_for_platform,
+    known_plugin_toolsets: object = None,
 ) -> List[str]:
     """Return human-readable warnings for a ``platform_toolsets`` mapping.
     Reports: a toolset name ``is_valid_toolset`` rejects (suggesting ``hermes-<platform>`` when that
     would have been valid); a non-empty mapping resolving to zero valid toolsets (agent would start with
     no tools); a platform with no valid toolsets, checked per-platform because the global net is
     suppressed once any platform is valid; and non-list platform values, which fall back to the platform
-    default. ``is_valid_toolset`` is injected so this does no registry imports or I/O."""
+    default. ``is_valid_toolset`` is injected so this does no registry imports or I/O.
+
+    ``known_plugin_toolsets`` is the raw config section of the same name (``{platform: [name, ...]}``).
+    Plugin toolsets register only after plugins load, which is after config validation runs, so
+    ``is_valid_toolset`` alone reports every one of them as unknown; names listed there for the
+    platform are accepted rather than warned about."""
     warnings: List[str] = []
     if not isinstance(platform_toolsets, dict) or not platform_toolsets:
         return warnings
 
     valid_count = 0
     for platform, raw in platform_toolsets.items():
+        known = _known_plugin_toolsets(known_plugin_toolsets, platform)
         default = _platform_default_toolset(platform)
         default_valid = _platform_default_is_valid(platform, default, is_valid_toolset, is_allowed_for_platform)
         platform_valid_count = 0
@@ -68,10 +92,13 @@ def validate_platform_toolsets(
         for name in raw:
             if not isinstance(name, str) or not name:
                 continue
-            if not is_valid_toolset(name):
+            # A declared plugin toolset is valid even though the registry cannot confirm it yet,
+            # and is_allowed_for_platform would reject it for the same not-yet-loaded reason.
+            known_plugin = name in known
+            if not is_valid_toolset(name) and not known_plugin:
                 hint = f" — did you mean '{default}'?" if default_valid else ""
                 warnings.append(f"platform '{platform}' references unknown toolset '{name}'{hint}")
-            elif is_allowed_for_platform(name, str(platform)):
+            elif known_plugin or is_allowed_for_platform(name, str(platform)):
                 valid_count += 1
                 platform_valid_count += 1
             else:
diff --git a/tests/hermes_cli/test_toolset_validation.py b/tests/hermes_cli/test_toolset_validation.py
index 6663d1bcfb088..1a0987ce8a5ce 100644
--- a/tests/hermes_cli/test_toolset_validation.py
+++ b/tests/hermes_cli/test_toolset_validation.py
@@ -197,3 +197,46 @@ def test_populated_platforms_produce_no_empty_list_warning():
     cfg = {"cli": ["hermes-cli"], "telegram": ["hermes-telegram"]}
     warnings = validate_platform_toolsets(cfg, _is_valid)
     assert warnings == []
+
+
+# --- known_plugin_toolsets: plugin toolsets register after config validation runs ---
+
+def test_declared_plugin_toolset_is_not_flagged_unknown():
+    """A plugin toolset registers only after plugins load — long after this validation runs.
+
+    `known_plugin_toolsets` is the config's own record (written by the `hermes tools` save flow)
+    that the name is legitimate, so it must not be reported as unknown.
+    """
+    cfg = {"cli": ["a2a", "hermes-cli"]}
+    known = {"cli": ["a2a"]}
+    warnings = validate_platform_toolsets(cfg, _is_valid, known_plugin_toolsets=known)
+    assert not any("a2a" in w for w in warnings)
+
+
+def test_declared_plugin_toolset_counts_as_a_valid_toolset():
+    """It must also satisfy the zero-valid-toolsets net, or silencing one warning fires another."""
+    warnings = validate_platform_toolsets({"cli": ["a2a"]}, _is_valid, known_plugin_toolsets={"cli": ["a2a"]})
+    assert warnings == []
+
+
+def test_plugin_toolset_declared_for_another_platform_still_warns():
+    """Per-platform scoping: one platform's plugin names must not mask another's typo."""
+    cfg = {"cli": ["hermes-cli"], "discord": ["a2a"]}
+    warnings = validate_platform_toolsets(cfg, _is_valid, known_plugin_toolsets={"cli": ["a2a"]})
+    assert any("unknown toolset 'a2a'" in w and "'discord'" in w for w in warnings)
+
+
+def test_omitting_known_plugin_toolsets_preserves_existing_behavior():
+    """Default None must behave exactly as before this parameter existed."""
+    assert (validate_platform_toolsets({"cli": ["a2a"]}, _is_valid)
+            == validate_platform_toolsets({"cli": ["a2a"]}, _is_valid, known_plugin_toolsets=None))
+    assert any("unknown toolset 'a2a'" in w for w in validate_platform_toolsets({"cli": ["a2a"]}, _is_valid))
+
+
+@pytest.mark.parametrize("known", [None, {}, {"cli": None}, {"cli": "a2a"}, {"cli": 42}, "nonsense", []])
+def test_malformed_known_plugin_toolsets_never_raises(known):
+    """Config is user-edited YAML: any shape must degrade to 'not declared', never crash migration."""
+    warnings = validate_platform_toolsets({"cli": ["a2a"]}, _is_valid, known_plugin_toolsets=known)
+    # The legacy single-string shape is the one that legitimately suppresses the warning.
+    expected_suppressed = known == {"cli": "a2a"}
+    assert any("unknown toolset 'a2a'" in w for w in warnings) is not expected_suppressed