diff --git a/extensions/matrix/src/matrix/accounts.ts b/extensions/matrix/src/matrix/accounts.ts
index 385c99864a8..2da5614abf1 100644
--- a/extensions/matrix/src/matrix/accounts.ts
+++ b/extensions/matrix/src/matrix/accounts.ts
@@ -18,7 +18,10 @@ function listConfiguredAccountIds(cfg: CoreConfig): string[] {
   if (!accounts || typeof accounts !== "object") {
     return [];
   }
-  return Object.keys(accounts).filter(Boolean);
+  // Normalize keys so listing and resolution use the same semantics
+  return Object.keys(accounts)
+    .filter(Boolean)
+    .map((id) => normalizeAccountId(id));
 }
 
 export function listMatrixAccountIds(cfg: CoreConfig): string[] {
@@ -43,7 +46,18 @@ function resolveAccountConfig(cfg: CoreConfig, accountId: string): MatrixConfig
   if (!accounts || typeof accounts !== "object") {
     return undefined;
   }
-  return accounts[accountId] as MatrixConfig | undefined;
+  // Direct lookup first (fast path for already-normalized keys)
+  if (accounts[accountId]) {
+    return accounts[accountId] as MatrixConfig;
+  }
+  // Fall back to case-insensitive match (user may have mixed-case keys in config)
+  const normalized = normalizeAccountId(accountId);
+  for (const key of Object.keys(accounts)) {
+    if (normalizeAccountId(key) === normalized) {
+      return accounts[key] as MatrixConfig;
+    }
+  }
+  return undefined;
 }
 
 export function resolveMatrixAccount(params: {
diff --git a/extensions/matrix/src/matrix/client/config.ts b/extensions/matrix/src/matrix/client/config.ts
index 3e48c28e99d..7fbb281d9bf 100644
--- a/extensions/matrix/src/matrix/client/config.ts
+++ b/extensions/matrix/src/matrix/client/config.ts
@@ -22,8 +22,16 @@ export function resolveMatrixConfigForAccount(
   const normalizedAccountId = normalizeAccountId(accountId);
   const matrixBase = cfg.channels?.matrix ?? {};
 
-  // Try to get account-specific config first
-  const accountConfig = matrixBase.accounts?.[normalizedAccountId];
+  // Try to get account-specific config first (direct lookup, then case-insensitive fallback)
+  let accountConfig = matrixBase.accounts?.[normalizedAccountId];
+  if (!accountConfig && matrixBase.accounts) {
+    for (const key of Object.keys(matrixBase.accounts)) {
+      if (normalizeAccountId(key) === normalizedAccountId) {
+        accountConfig = matrixBase.accounts[key];
+        break;
+      }
+    }
+  }
 
   // Merge: account-specific values override top-level values
   // For DEFAULT_ACCOUNT_ID with no accounts, use top-level directly