diff --git a/src/cli/config-manager/add-provider-config.ts b/src/cli/config-manager/add-provider-config.ts
index 833c9882f..b2a400a43 100644
--- a/src/cli/config-manager/add-provider-config.ts
+++ b/src/cli/config-manager/add-provider-config.ts
@@ -1,4 +1,4 @@
-import { writeFileSync } from "node:fs"
+import { readFileSync, writeFileSync } from "node:fs"
 import type { ConfigMergeResult, InstallConfig } from "../types"
 import { getConfigDir } from "./config-context"
 import { ensureConfigDirectoryExists } from "./ensure-config-directory-exists"
@@ -45,7 +45,23 @@ export function addProviderConfig(config: InstallConfig): ConfigMergeResult {
       newConfig.provider = providers
     }
 
-    writeFileSync(path, JSON.stringify(newConfig, null, 2) + "\n")
+    if (format === "jsonc") {
+      const content = readFileSync(path, "utf-8")
+      const providerRegex = /"provider"\s*:\s*\{[\s\S]*?\n  \}/
+      const providerJson = JSON.stringify(newConfig.provider, null, 2)
+        .split("\n")
+        .map((line, i) => (i === 0 ? line : `  ${line}`))
+        .join("\n")
+      if (providerRegex.test(content)) {
+        const newContent = content.replace(providerRegex, `"provider": ${providerJson}`)
+        writeFileSync(path, newContent)
+      } else {
+        const newContent = content.replace(/(\{)/, `$1\n  "provider": ${providerJson},`)
+        writeFileSync(path, newContent)
+      }
+    } else {
+      writeFileSync(path, JSON.stringify(newConfig, null, 2) + "\n")
+    }
     return { success: true, configPath: path }
   } catch (err) {
     return {
diff --git a/src/cli/config-manager/auth-plugins.ts b/src/cli/config-manager/auth-plugins.ts
index 577d80a20..4e4d5718f 100644
--- a/src/cli/config-manager/auth-plugins.ts
+++ b/src/cli/config-manager/auth-plugins.ts
@@ -8,7 +8,7 @@ import { parseOpenCodeConfigFileWithError, type OpenCodeConfig } from "./parse-o
 
 export async function fetchLatestVersion(packageName: string): Promise<string | null> {
   try {
-    const res = await fetch(`https://registry.npmjs.org/${packageName}/latest`)
+    const res = await fetch(`https://registry.npmjs.org/${encodeURIComponent(packageName)}/latest`)
     if (!res.ok) return null
     const data = (await res.json()) as { version: string }
     return data.version
diff --git a/src/cli/config-manager/bun-install.ts b/src/cli/config-manager/bun-install.ts
index 052617e49..f24e77fa2 100644
--- a/src/cli/config-manager/bun-install.ts
+++ b/src/cli/config-manager/bun-install.ts
@@ -39,7 +39,7 @@ export async function runBunInstallWithDetails(): Promise<BunInstallResult> {
       return {
         success: false,
         timedOut: true,
-        error: `bun install timed out after ${BUN_INSTALL_TIMEOUT_SECONDS} seconds. Try running manually: cd ~/.config/opencode && bun i`,
+        error: `bun install timed out after ${BUN_INSTALL_TIMEOUT_SECONDS} seconds. Try running manually: cd ${getConfigDir()} && bun i`,
       }
     }
 
diff --git a/src/cli/config-manager/config-context.ts b/src/cli/config-manager/config-context.ts
index 78eb88d77..67448f29a 100644
--- a/src/cli/config-manager/config-context.ts
+++ b/src/cli/config-manager/config-context.ts
@@ -19,6 +19,9 @@ export function initConfigContext(binary: OpenCodeBinaryType, version: string |
 
 export function getConfigContext(): ConfigContext {
   if (!configContext) {
+    if (process.env.NODE_ENV !== "production") {
+      console.warn("[config-context] getConfigContext() called before initConfigContext(); defaulting to CLI paths.")
+    }
     const paths = getOpenCodeConfigPaths({ binary: "opencode", version: null })
     configContext = { binary: "opencode", version: null, paths }
   }
diff --git a/src/cli/config-manager/deep-merge-record.ts b/src/cli/config-manager/deep-merge-record.ts
index 54c0daa57..b38c26633 100644
--- a/src/cli/config-manager/deep-merge-record.ts
+++ b/src/cli/config-manager/deep-merge-record.ts
@@ -5,6 +5,7 @@ export function deepMergeRecord<TTarget extends Record<string, unknown>>(
   const result: TTarget = { ...target }
 
   for (const key of Object.keys(source) as Array<keyof TTarget>) {
+    if (key === "__proto__" || key === "constructor" || key === "prototype") continue
     const sourceValue = source[key]
     const targetValue = result[key]