diff --git a/changelog.d/fixes/10096-kimi-coding-apikey-save.md b/changelog.d/fixes/10096-kimi-coding-apikey-save.md
new file mode 100644
index 0000000000..2b5f1bb8b6
--- /dev/null
+++ b/changelog.d/fixes/10096-kimi-coding-apikey-save.md
@@ -0,0 +1 @@
+- fix(dashboard): remap unified Kimi Code card API-key save to the admitted `kimi-coding-apikey` connection id, fixing 400 "Invalid provider" on Save (#10096)
diff --git a/src/app/(dashboard)/dashboard/providers/[id]/hooks/useApiKeySave.ts b/src/app/(dashboard)/dashboard/providers/[id]/hooks/useApiKeySave.ts
index 7e5354bc6d..07732aefe6 100644
--- a/src/app/(dashboard)/dashboard/providers/[id]/hooks/useApiKeySave.ts
+++ b/src/app/(dashboard)/dashboard/providers/[id]/hooks/useApiKeySave.ts
@@ -32,6 +32,19 @@ type UseApiKeySaveParams = {
   t: ProviderMessageTranslator;
 };
 
+// Issue #10096: the unified Kimi Code dashboard card shares one page/providerId
+// ("kimi-coding") between OAuth and API-key auth. "kimi-coding" is an
+// OAuth-primary managed id and is NOT an admitted API-key/dual-auth connection
+// id (see isManagedProviderConnectionId in src/lib/providers/catalog.ts), so
+// posting it here 400s with "Invalid provider". The dedicated managed
+// API-key id "kimi-coding-apikey" IS admitted — remap only the POST payload
+// so the saved connection lands under the correct managed id. The OAuth flow
+// (handleOAuthSuccess in ProviderDetailPageClient.tsx) does not go through
+// this hook, so it keeps posting "kimi-coding" unchanged.
+export function resolveApiKeySaveProviderId(providerId: string): string {
+  return providerId === "kimi-coding" ? "kimi-coding-apikey" : providerId;
+}
+
 export function useApiKeySave({
   providerId,
   fetchConnections,
@@ -48,7 +61,10 @@ export function useApiKeySave({
         const res = await fetch("/api/providers", {
           method: "POST",
           headers: { "Content-Type": "application/json" },
-          body: JSON.stringify({ provider: providerId, ...formData }),
+          body: JSON.stringify({
+            provider: resolveApiKeySaveProviderId(providerId),
+            ...formData,
+          }),
         });
         if (res.ok) {
           const connectionData = await res.json();
diff --git a/tests/unit/bug-10096-kimi-coding-apikey-save.test.ts b/tests/unit/bug-10096-kimi-coding-apikey-save.test.ts
new file mode 100644
index 0000000000..54bfda78e7
--- /dev/null
+++ b/tests/unit/bug-10096-kimi-coding-apikey-save.test.ts
@@ -0,0 +1,37 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+
+// Issue #10096: Kimi Code API key validates OK but Save returns 400 "Invalid provider".
+//
+// Root cause: the unified Kimi Code dashboard card's API-key branch posted
+// provider: "kimi-coding" (an OAuth-primary managed id, NOT an admitted
+// API-key connection id) to POST /api/providers, which the backend rejects.
+// The dedicated managed API-key id "kimi-coding-apikey" IS admitted.
+//
+// Fix: resolveApiKeySaveProviderId() in useApiKeySave.ts remaps the posted
+// provider id to "kimi-coding-apikey" for the API-key save flow only, while
+// the OAuth flow (which never calls this hook) keeps posting "kimi-coding".
+
+const { isManagedProviderConnectionId } = await import("../../src/lib/providers/catalog.ts");
+const { resolveApiKeySaveProviderId } = await import(
+  "../../src/app/(dashboard)/dashboard/providers/[id]/hooks/useApiKeySave.ts"
+);
+
+test("Kimi Code API-key save flow remaps to the admitted managed API-key id", () => {
+  assert.equal(
+    resolveApiKeySaveProviderId("kimi-coding"),
+    "kimi-coding-apikey",
+    "the unified Kimi Code card's API-key save flow must post kimi-coding-apikey, not kimi-coding"
+  );
+  assert.equal(
+    isManagedProviderConnectionId(resolveApiKeySaveProviderId("kimi-coding")),
+    true,
+    "the remapped id must be an admitted managed provider connection id (POST /api/providers accepts it)"
+  );
+});
+
+test("resolveApiKeySaveProviderId leaves every other provider id untouched", () => {
+  assert.equal(resolveApiKeySaveProviderId("openai"), "openai");
+  assert.equal(resolveApiKeySaveProviderId("kimi-coding-apikey"), "kimi-coding-apikey");
+  assert.equal(resolveApiKeySaveProviderId("qoder"), "qoder");
+});