diff --git a/agent/redact.py b/agent/redact.py
index ea70246a90797..fe770e2e27f7b 100644
--- a/agent/redact.py
+++ b/agent/redact.py
@@ -939,6 +939,78 @@ def redact_terminal_output(
     return redact_sensitive_text(output, force=force, code_file=code_file)
 
 
+# Credential-suffixed env var names whose VALUES are treated as exact-match
+# secrets (e.g. MY_SERVICE_TOKEN, OPENAI_API_KEY, DB_PASSWORD). This is the
+# opaque-value pass: shape-based redaction (vendor prefixes, URL creds, auth
+# headers) cannot catch values applied from Bitwarden/1Password/command
+# secret sources under arbitrary names (``DATABASE_URL``, ``FOO``), or
+# credential-suffixed env values like ``MY_SERVICE_TOKEN=abc123randomstring``.
+_CREDENTIAL_VALUE_SUFFIXES = ("_API_KEY", "_TOKEN", "_SECRET", "_KEY", "_PASSWORD")
+
+# Minimum value length before an exact-value mask is applied. Shorter values
+# (e.g. ``PIN=1234``) collide with ordinary prose too easily to mask safely.
+_SECRET_VALUE_MIN_LEN = 6
+
+
+def _known_secret_values() -> set[str]:
+    """Return exact values of credential-suffixed environment variables.
+
+    Snapshot at call time so values set after import are still caught. Only
+    values of length >= ``_SECRET_VALUE_MIN_LEN`` are returned — shorter
+    values collide with ordinary prose too easily to mask safely.
+    """
+    values: set[str] = set()
+    for name, value in os.environ.items():
+        if (
+            value
+            and len(value) >= _SECRET_VALUE_MIN_LEN
+            and name.upper().endswith(_CREDENTIAL_VALUE_SUFFIXES)
+        ):
+            values.add(value)
+    return values
+
+
+def mask_known_secret_values(
+    text: str,
+    extra_values: set[str] | None = None,
+) -> str:
+    """Replace exact matches of known secret values with ``***``.
+
+    "Known" values are: (a) the values of env vars whose name ends with a
+    credential suffix (``_API_KEY`` / ``_TOKEN`` / ``_SECRET`` / ``_KEY`` /
+    ``_PASSWORD``) and whose value is at least 6 chars long, and (b) any
+    ``extra_values`` supplied by the caller — e.g. values applied from
+    Bitwarden/1Password/command secret sources under arbitrary names like
+    ``DATABASE_URL``.
+
+    This is the exact-value complement to the shape-based patterns in
+    :func:`redact_sensitive_text`. It is deliberately unconditional (not
+    gated on ``security.redact_secrets``) because an exact secret value can
+    never be confused with prose: egress of applied values is the
+    highest-severity disclosure channel, so the mask must not be skippable.
+
+    Falsy ``text`` is returned unchanged. Never raises: any failure (e.g. an
+    unhashable ``extra_values`` member) falls back to returning ``text``.
+    """
+    if not text:
+        return text
+    try:
+        known = _known_secret_values()
+        if extra_values:
+            known.update(
+                v
+                for v in extra_values
+                if isinstance(v, str) and len(v) >= _SECRET_VALUE_MIN_LEN
+            )
+        if not known:
+            return text
+        for value in known:
+            text = text.replace(value, "***")
+    except Exception:  # noqa: BLE001 — masking must never raise or corrupt output
+        return text
+    return text
+
+
 # Substrings used to gate ``_PREFIX_RE`` execution. If none of these appear in
 # the input string, the prefix regex cannot match anything, so we skip it.
 # False positives are fine (they just run the regex, which then matches
diff --git a/agent/tool_dispatch_helpers.py b/agent/tool_dispatch_helpers.py
index f7f003f24abb0..84f632f352069 100644
--- a/agent/tool_dispatch_helpers.py
+++ b/agent/tool_dispatch_helpers.py
@@ -554,8 +554,45 @@ def make_tool_result_message(
     neutralized and framed). Non-text parts (e.g. image_url) are preserved.
     The outer list itself is rebuilt rather than returned by identity, so
     callers should compare by value, not by ``is``.
+
+    After wrapping, exact values of applied/known secrets are masked (``***``)
+    before the message is sent to the provider — shape-based redaction (vendor
+    prefixes, URL creds, auth headers) cannot catch opaque values applied from
+    Bitwarden/1Password/command secret sources under arbitrary names
+    (``DATABASE_URL``, ``FOO``), or credential-suffixed env values. Masking is
+    best-effort: any failure skips it without breaking message construction.
     """
     wrapped = _maybe_wrap_untrusted(name, content)
+    # Exact-value egress masking (see agent/redact.mask_known_secret_values).
+    # Lazy imports keep this hot path free of module-load weight and let
+    # per-profile secret snapshots be resolved at call time.
+    try:
+        from agent.redact import mask_known_secret_values
+        from hermes_cli.env_loader import get_secret_source_values
+        from hermes_constants import get_hermes_home
+
+        extra_values: set[str] | None = None
+        try:
+            home = get_hermes_home()
+            applied = get_secret_source_values(home)
+            if applied:
+                extra_values = set(applied.values())
+        except Exception:
+            extra_values = None
+
+        if isinstance(wrapped, str):
+            wrapped = mask_known_secret_values(wrapped, extra_values)
+        elif isinstance(wrapped, list):
+            wrapped = [
+                {**part, "text": mask_known_secret_values(part["text"], extra_values)}
+                if isinstance(part, dict)
+                and part.get("type") == "text"
+                and isinstance(part.get("text"), str)
+                else part
+                for part in wrapped
+            ]
+    except Exception as exc:  # noqa: BLE001 — masking must never break egress
+        logger.debug("Exact-value egress masking skipped for %s: %s", name, exc)
     message = {
         "role": "tool",
         "name": name,
diff --git a/tests/agent/test_redact.py b/tests/agent/test_redact.py
index 68307c7381d2a..b4823065fda7d 100644
--- a/tests/agent/test_redact.py
+++ b/tests/agent/test_redact.py
@@ -1,10 +1,16 @@
 """Tests for agent.redact -- secret masking in logs and output."""
 
+import json
 import logging
 
 import pytest
 
-from agent.redact import redact_cdp_url, redact_sensitive_text, RedactingFormatter
+from agent.redact import (
+    mask_known_secret_values,
+    redact_cdp_url,
+    redact_sensitive_text,
+    RedactingFormatter,
+)
 
 
 @pytest.fixture(autouse=True)
@@ -831,3 +837,116 @@ def test_plural_keys_still_redacted(self):
         assert "hunter2hunter2hunter2hh" not in result
 
 
+class TestExactValueMasking:
+    """mask_known_secret_values: exact-value masking of known secret VALUES.
+
+    Shape-based redaction (vendor prefixes, URL creds, auth headers) cannot
+    catch opaque secret values applied from Bitwarden/1Password/command
+    secret sources under arbitrary names (``DATABASE_URL``, ``FOO``), or
+    credential-suffixed env values like ``MY_SERVICE_TOKEN=abc123randomstring``.
+    This pass masks the exact values wherever they appear.
+    """
+
+    def test_masks_credential_suffixed_env_value(self, monkeypatch):
+        monkeypatch.setenv("MY_SERVICE_TOKEN", "opaque-secret-value-xyz")
+        result = mask_known_secret_values("the token is opaque-secret-value-xyz here")
+        assert "opaque-secret-value-xyz" not in result
+        assert "***" in result
+
+    def test_masks_lowercase_env_name_value(self, monkeypatch):
+        """Suffix match is case-insensitive — a lowercase env var name
+        (e.g. from a .env carrying ``db_password=``) must still be caught."""
+        monkeypatch.setenv("db_password", "opaque-lowercase-pw-value")
+        result = mask_known_secret_values("the db password is opaque-lowercase-pw-value")
+        assert "opaque-lowercase-pw-value" not in result
+        assert "***" in result
+
+    def test_masks_extra_values(self):
+        result = mask_known_secret_values(
+            "connecting to postgres://user:supersecret@db",
+            extra_values={"supersecret"},
+        )
+        assert "supersecret" not in result
+        assert "***" in result
+
+    def test_short_values_not_masked(self, monkeypatch):
+        """Values under 6 chars collide with ordinary prose — never masked."""
+        monkeypatch.setenv("MY_SERVICE_TOKEN", "abc12")
+        text = "the value abc12 is short and must stay"
+        assert mask_known_secret_values(text) == text
+
+    def test_falsy_text_unchanged(self):
+        assert mask_known_secret_values("") == ""
+        assert mask_known_secret_values(None) is None
+
+    def test_never_raises_on_bad_extra_values(self):
+        text = "some plain output text"
+        assert mask_known_secret_values(text, extra_values={42}) == text
+
+
+class TestToolResultEgressExactValueMasking:
+    """make_tool_result_message masks applied secret values before egress."""
+
+    def _patch_secret_sources(self, monkeypatch, tmp_path):
+        monkeypatch.setattr(
+            "hermes_cli.env_loader.get_secret_source_values",
+            lambda home: {"DATABASE_URL": "postgres://user:supersecret@db"},
+        )
+        monkeypatch.setattr("hermes_constants.get_hermes_home", lambda: tmp_path)
+
+    def test_plain_string_content_masks_applied_secret(self, monkeypatch, tmp_path):
+        self._patch_secret_sources(monkeypatch, tmp_path)
+        from agent.tool_dispatch_helpers import make_tool_result_message
+
+        result = make_tool_result_message(
+            "terminal",
+            "connecting to postgres://user:supersecret@db",
+            "call_1",
+        )
+        assert "supersecret" not in json.dumps(result["content"])
+        assert "***" in result["content"]
+
+    def test_multimodal_text_masked_image_preserved(self, monkeypatch, tmp_path):
+        self._patch_secret_sources(monkeypatch, tmp_path)
+        from agent.tool_dispatch_helpers import make_tool_result_message
+
+        image_part = {
+            "type": "image_url",
+            "image_url": {"url": "data:image/png;base64,AAAA"},
+        }
+        content = [
+            {"type": "text", "text": "db is postgres://user:supersecret@db"},
+            image_part,
+        ]
+        result = make_tool_result_message("computer_use", content, "call_2")
+        parts = result["content"]
+        assert isinstance(parts, list)
+        text_parts = [p for p in parts if p.get("type") == "text"]
+        assert text_parts, "text part missing from rebuilt list"
+        assert "supersecret" not in text_parts[0]["text"]
+        assert "***" in text_parts[0]["text"]
+        image_parts = [p for p in parts if p.get("type") == "image_url"]
+        assert image_parts == [image_part]
+
+    def test_message_construction_survives_secret_source_failure(self, monkeypatch):
+        """Best-effort: an exception in secret-source resolution must not break
+        message construction."""
+        monkeypatch.setattr(
+            "hermes_cli.env_loader.get_secret_source_values",
+            lambda home: (_ for _ in ()).throw(RuntimeError("boom")),
+        )
+        monkeypatch.setattr(
+            "hermes_constants.get_hermes_home",
+            lambda: (_ for _ in ()).throw(RuntimeError("boom")),
+        )
+        from agent.tool_dispatch_helpers import make_tool_result_message
+
+        result = make_tool_result_message(
+            "terminal",
+            "connecting to postgres://user:supersecret@db",
+            "call_3",
+        )
+        assert result["tool_call_id"] == "call_3"
+        assert result["name"] == "terminal"
+
+