refactor(redact): canonical mask_secret helper; fix status.py DIM drift (#17207)

Three modules independently implemented the same "preserve head+tail of
a secret, mask the middle" logic with slightly different behaviors that
had started to drift:

  hermes_cli/config.py redact_key  — 12-char floor, 4+4, DIM '(not set)'
  hermes_cli/status.py redact_key  — 12-char floor, 4+4, plain '(not set)'  ← drift
  hermes_cli/dump.py _redact       — 12-char floor, 4+4, empty string

The visible bug: 'hermes status' displayed the '(not set)' placeholder
in plain text while 'hermes config' showed it in dim text. Same concept,
inconsistent UI.

Introduces mask_secret() in agent/redact.py as the canonical helper,
with head/tail/floor/placeholder/empty kwargs. The three call sites
become one-line wrappers that differ only in the 'empty' handling:

  config.redact_key  → mask_secret(k, empty=color('(not set)', Colors.DIM))
  status.redact_key  → mask_secret(k, empty=color('(not set)', Colors.DIM))
  dump._redact       → mask_secret(v)  # empty → ''

agent.redact._mask_token (log redactor, different policy: 18-char floor,
6+4 visible, '***' on empty) also ports to mask_secret but retains its
own empty-case handling to preserve the historical '***' return.

Net: the three display-time redactors now agree on formatting, the
canonical helper lives in one place, and future tweaks (e.g. adding
bullet-point masking, changing the head/tail widths) happen once.

Verified:
- 3/3 tests/hermes_cli/test_web_server.py::TestRedactKey pass
- 89/89 agent/tests/test_redact.py + tests/tools/test_browser_secret_exfil.py
  + tests/hermes_cli/test_redact_config_bridge.py pass
- Live 'hermes status', 'hermes config', 'hermes dump' all render the
  same way they did before (verified against actual env with real
  keys: OpenRouter, Firecrawl, Browserbase, FAL, Tinker all show
  'prefix...suffix'; Kimi shows '***' at <12 chars; unset shows
  '(not set)' uniformly).

Co-authored-by: teknium1 <teknium@users.noreply.github.com>

agent/redact.py

@@ -184,11 +184,59 @@ _PREFIX_RE = re.compile(
 )
 
 
+def mask_secret(
+    value: str,
+    *,
+    head: int = 4,
+    tail: int = 4,
+    floor: int = 12,
+    placeholder: str = "***",
+    empty: str = "",
+) -> str:
+    """Mask a secret for display, preserving ``head`` and ``tail`` characters.
+
+    Canonical helper for display-time redaction across Hermes — used by
+    ``hermes config``, ``hermes status``, ``hermes dump``, and anywhere
+    a secret needs to be shown truncated for debuggability while still
+    keeping the bulk hidden.
+
+    Args:
+        value:       The secret to mask. ``None``/empty returns ``empty``.
+        head:        Leading characters to preserve. Default 4.
+        tail:        Trailing characters to preserve. Default 4.
+        floor:       Values shorter than ``head + tail + floor_margin`` are
+                     fully masked (returns ``placeholder``). Default 12 —
+                     matches the existing config/status/dump convention.
+        placeholder: Value returned for too-short inputs. Default ``"***"``.
+        empty:       Value returned when ``value`` is falsy (None, ""). The
+                     caller can override this to e.g. ``color("(not set)",
+                     Colors.DIM)`` for user-facing display.
+
+    Examples:
+        >>> mask_secret("sk-proj-abcdef1234567890")
+        'sk-p...7890'
+        >>> mask_secret("short")                         # fully masked
+        '***'
+        >>> mask_secret("")                              # empty default
+        ''
+        >>> mask_secret("", empty="(not set)")           # empty override
+        '(not set)'
+        >>> mask_secret("long-token", head=6, tail=4, floor=18)
+        '***'
+    """
+    if not value:
+        return empty
+    if len(value) < floor:
+        return placeholder
+    return f"{value[:head]}...{value[-tail:]}"
+
+
 def _mask_token(token: str) -> str:
-    """Mask a token, preserving prefix for long tokens."""
-    if len(token) < 18:
+    """Mask a log token — conservative 18-char floor, preserves 6 prefix / 4 suffix."""
+    # Empty input: historically this returned "***" rather than "". Preserve.
+    if not token:
         return "***"
-    return f"{token[:6]}...{token[-4:]}"
+    return mask_secret(token, head=6, tail=4, floor=18)
 
 
 def _redact_query_string(query: str) -> str:

hermes_cli/config.py

@@ -4013,12 +4013,13 @@ def get_env_value(key: str) -> Optional[str]:
 # =============================================================================
 
 def redact_key(key: str) -> str:
-    """Redact an API key for display."""
-    if not key:
-        return color("(not set)", Colors.DIM)
-    if len(key) < 12:
-        return "***"
-    return key[:4] + "..." + key[-4:]
+    """Redact an API key for display.
+
+    Thin wrapper over :func:`agent.redact.mask_secret` — preserves the
+    "(not set)" placeholder in dim color for the empty case.
+    """
+    from agent.redact import mask_secret
+    return mask_secret(key, empty=color("(not set)", Colors.DIM))
 
 
 def show_config():

hermes_cli/dump.py

@@ -33,12 +33,14 @@ def _get_git_commit(project_root: Path) -> str:
 
 
 def _redact(value: str) -> str:
-    """Redact all but first 4 and last 4 chars."""
-    if not value:
-        return ""
-    if len(value) < 12:
-        return "***"
-    return value[:4] + "..." + value[-4:]
+    """Redact all but first 4 and last 4 chars.
+
+    Thin wrapper over :func:`agent.redact.mask_secret`. Returns ``""`` for
+    an empty value (matches the historical behavior of this helper —
+    ``hermes dump`` formats empty values as blank, not as ``"(not set)"``).
+    """
+    from agent.redact import mask_secret
+    return mask_secret(value)
 
 
 def _gateway_status() -> str:

hermes_cli/status.py

@@ -26,12 +26,15 @@ def check_mark(ok: bool) -> str:
     return color("✗", Colors.RED)
 
 def redact_key(key: str) -> str:
-    """Redact an API key for display."""
-    if not key:
-        return "(not set)"
-    if len(key) < 12:
-        return "***"
-    return key[:4] + "..." + key[-4:]
+    """Redact an API key for display.
+
+    Thin wrapper over :func:`agent.redact.mask_secret`. Preserves the
+    "(not set)" placeholder in dim color to match ``hermes config``'s
+    output (previously this variant was missing the DIM color —
+    consolidated via PR that also introduced ``mask_secret``).
+    """
+    from agent.redact import mask_secret
+    return mask_secret(key, empty=color("(not set)", Colors.DIM))
 
 
 def _format_iso_timestamp(value) -> str: