diff --git a/app/api/keys/route.ts b/app/api/keys/route.ts
index 9446d47..90f5d0f 100644
--- a/app/api/keys/route.ts
+++ b/app/api/keys/route.ts
@@ -10,7 +10,8 @@
  * tests/auth-provider-keys.test.ts) — the settings UI reads it optionally
  * with a graceful fallback.
  *
- * Masked only — last 4 + length; PLAINTEXT NEVER LEAVES THE STORE THROUGH
+ * Masked only — last 4 + length for ordinary keys; custom keys are fully
+ * redacted at every length (no credential suffix). PLAINTEXT NEVER LEAVES THE STORE THROUGH
  * THIS API (owner decision). `source` tells the page whether the live
  * value comes from the environment (dev .env.local / launch env) or the
  * file, and `shadowedByEnv` explains why a saved key is not the live one
diff --git a/src/core/auth-keys.ts b/src/core/auth-keys.ts
index 492ff15..b92faf7 100644
--- a/src/core/auth-keys.ts
+++ b/src/core/auth-keys.ts
@@ -207,7 +207,8 @@ export interface AuthKeyStatus {
 	info: AuthKeyInfo | null;
 	/** A key is present when EITHER the environment or the file has it. */
 	present: boolean;
-	/** The masked tail + character count, e.g. "…ab12 (64 chars)". */
+	/** Ordinary masked tail + count, e.g. "…ab12 (64 chars)"; custom keys
+	 * use full redaction, with no credential characters at any length. */
 	masked: string | null;
 	/** Where the live value comes from, given env-wins precedence. */
 	source: "env" | "file" | "none";
diff --git a/src/server/keys.ts b/src/server/keys.ts
index 5bb2b6a..3e197f1 100644
--- a/src/server/keys.ts
+++ b/src/server/keys.ts
@@ -162,7 +162,9 @@ export function resolveKeyStatuses(
 			id,
 			info: AUTH_KEYS.find((k) => k.id === id) ?? null,
 			present: live !== undefined,
-			masked: live !== undefined ? `${maskKey(live)} (${live.trim().length} chars)` : null,
+			// Custom keys may be one character: even a masked suffix can expose
+			// the entire credential. Preserve inventory, return no key characters.
+			masked: live !== undefined ? id === CUSTOM_PROVIDER.envVar ? "••••" : `${maskKey(live)} (${live.trim().length} chars)` : null,
 			source: isRealEnv ? "env" : live !== undefined ? "file" : "none",
 			shadowedByEnv: isRealEnv && fileValue !== undefined && envValue !== fileValue,
 		});
diff --git a/tests/custom-provider-boundaries.test.ts b/tests/custom-provider-boundaries.test.ts
index 2ea1006..7c86a88 100644
--- a/tests/custom-provider-boundaries.test.ts
+++ b/tests/custom-provider-boundaries.test.ts
@@ -52,6 +52,32 @@ test("new keys have no arbitrary minimum; the exact probed key is stored", async
 	assert.equal(keys.keyValue(CUSTOM_PROVIDER.envVar), "k");
 	const body = await get().text(); assert.ok(!body.includes("Bearer"));
 });
+test("actual GET /api/keys fully redacts every custom key length and preserves other providers", async () => {
+	const inventory = await import("../app/api/keys/route.ts");
+	const rows = async () => (await (await inventory.GET()).json()).keys as import("../src/core/auth-keys.ts").AuthKeyStatus[];
+	assert.equal(keys.saveKey("OPENAI_API_KEY", "ordinary-provider-key-abcd").ok, true);
+	const ordinary = (await rows()).find(row => row.id === "OPENAI_API_KEY")!;
+	assert.equal(ordinary.masked, "…abcd (26 chars)");
+	try {
+		for (const value of ["1", "12", "123", "1234", "synthetic-custom-secret-longer-than-four"]) {
+			assert.equal((await mutate({ baseUrl: "http://new/v1", authMode: "apiKey", key: value })).status, 200);
+			assert.equal(keys.keyValue(CUSTOM_PROVIDER.envVar), value, "short keys still save unchanged");
+			const statuses = await rows();
+			const custom = statuses.find(row => row.id === CUSTOM_PROVIDER.envVar)!;
+			assert.equal(custom.masked, "••••"); assert.equal(custom.present, true); assert.equal(custom.source, "file");
+			assert.ok(!JSON.stringify(custom).includes(value));
+			assert.deepEqual(statuses.find(row => row.id === "OPENAI_API_KEY"), ordinary);
+		}
+		process.env.LH_IGNORE_ENV_KEYS = "0";
+		process.env[CUSTOM_PROVIDER.envVar] = "765"; authEnvRecord().realEnv.add(CUSTOM_PROVIDER.envVar);
+		const custom = (await rows()).find(row => row.id === CUSTOM_PROVIDER.envVar)!;
+		assert.equal(custom.masked, "••••"); assert.equal(custom.source, "env"); assert.equal(custom.present, true); assert.equal(custom.shadowedByEnv, true);
+		assert.ok(!JSON.stringify(custom).includes("765"));
+	} finally {
+		authEnvRecord().realEnv.delete(CUSTOM_PROVIDER.envVar); delete process.env[CUSTOM_PROVIDER.envVar]; process.env.LH_IGNORE_ENV_KEYS = "1";
+		keys.deleteKey("OPENAI_API_KEY");
+	}
+});
 test("changing destination cannot silently reuse an existing credential", async () => {
 	setFileKey("private-old");
 	const payload = { baseUrl: "http://new/v1", authMode: "apiKey" };