feat(kern): kern_get MCP tool, recipients remove, machine payments docs

- Add kern_get MCP tool (direct mode — decrypt and return a credential)
- Implement kern recipients remove (walks all .recipients files)
- Implement kern recipients list (shows recipients per folder)
- Add machine payments section to README (Stripe MPP, x402 roadmap)
- Restore CI badge in README

Author: mirkokiefer

README.md

@@ -1,5 +1,7 @@
 # kern
 
+[![tests](https://github.com/daslabhq/kern/actions/workflows/test.yml/badge.svg)](https://github.com/daslabhq/kern/actions/workflows/test.yml)
+
 The agent wallet. Hold credentials — agents use them without seeing them.
 
 ```bash
@@ -169,6 +171,21 @@ kern secret rewrap
 kern secret rotate tokens/github  # rotate what they had access to
 ```
 
+## Machine payments
+
+The same proxy that protects API keys protects payment credentials. An agent that purchases compute, calls paid APIs, or manages subscriptions needs payment keys — but shouldn't hold them.
+
+```typescript
+// agent charges a customer — never sees sk_live_*
+const resp = await wallet.fetch("tokens/stripe", "https://api.stripe.com/v1/payment_intents", {
+    method: "POST",
+    headers: { "Content-Type": "application/x-www-form-urlencoded" },
+    body: "amount=2000&currency=usd&automatic_payment_methods[enabled]=true",
+});
+```
+
+Works with [Stripe MPP](https://docs.stripe.com/payments/machine/mpp) for machine-to-machine payments and any API that takes Bearer auth. [x402](https://www.x402.org/) support — auto-negotiating `402 Payment Required` responses — is on the roadmap.
+
 ## CLI
 
 ```bash
@@ -186,7 +203,7 @@ kern fetch SECRET URL [OPTIONS]    # proxy request (credential stays in wallet)
   --method POST                    # HTTP method (default GET)
   --body '{"key": "val"}'          # request body
 
-kern recipients list               # show recipients
+kern recipients                    # list all recipients
 kern recipients remove KEY         # remove from all folders
 
 kern mcp                           # start MCP server

bin/kern.ts

@@ -2,7 +2,7 @@
 // kern CLI — the agent wallet
 
 import { generateIdentity, loadIdentityFromHost, openVault, openWallet } from "../src/index.js";
-import { writeFileSync, mkdirSync, existsSync, readFileSync } from "fs";
+import { writeFileSync, mkdirSync, existsSync, readFileSync, readdirSync, statSync } from "fs";
 import { dirname, join } from "path";
 import { homedir } from "os";
 
@@ -16,7 +16,7 @@ async function main() {
         case "identity": return cmdIdentity(sub, args.slice(2));
         case "secret":
         case "secrets":  return cmdSecret(sub, args.slice(2));
-        case "recipients": return cmdRecipients();
+        case "recipients": return cmdRecipients(sub, args.slice(2));
         case "fetch":    return cmdFetch(args.slice(1));
         case "mcp":      return cmdMcp();
         case "serve":    return cmdServe();
@@ -40,7 +40,8 @@ function help() {
 `  kern secret delete NAME\n` +
 `  kern secret rewrap\n\n` +
 `  kern fetch SECRET URL [--method METHOD] [--body BODY]\n\n` +
-`  kern recipients\n\n` +
+`  kern recipients                 list all recipients\n` +
+`  kern recipients remove KEY      remove from all folders\n\n` +
 `env: KERN_AGE_KEY (private key)  KERN_VAULT_DIR (default ./secrets)\n`);
 }
 
@@ -147,14 +148,57 @@ async function cmdFetch(rest: string[]) {
     process.exit(resp.ok ? 0 : 1);
 }
 
-function cmdRecipients() {
+function cmdRecipients(sub?: string, rest?: string[]) {
     const dir = process.env.KERN_VAULT_DIR ?? process.env.KORN_VAULT_DIR ?? "./secrets";
-    const file = join(dir, ".recipients");
-    if (!existsSync(file)) {
-        console.error(`no ${file} — create it with one age pubkey per line`);
+
+    if (sub === "remove") {
+        const key = rest?.[0];
+        if (!key) { console.error("usage: kern recipients remove KEY"); process.exit(1); }
+        let removed = 0;
+        const walk = (d: string) => {
+            const file = join(d, ".recipients");
+            if (existsSync(file)) {
+                const lines = readFileSync(file, "utf8").split("\n");
+                const filtered = lines.filter(l => l.trim() !== key);
+                if (filtered.length < lines.length) {
+                    writeFileSync(file, filtered.join("\n"));
+                    removed++;
+                }
+            }
+            if (!existsSync(d)) return;
+            for (const ent of readdirSync(d)) {
+                if (ent.startsWith(".")) continue;
+                const full = join(d, ent);
+                if (statSync(full).isDirectory()) walk(full);
+            }
+        };
+        walk(dir);
+        if (removed) console.log(`✓ removed from ${removed} .recipients file${removed > 1 ? "s" : ""}`);
+        else console.log(`key not found in any .recipients file`);
+        return;
+    }
+
+    if (!existsSync(dir)) {
+        console.error(`no vault at ${dir}`);
         process.exit(1);
     }
-    process.stdout.write(readFileSync(file, "utf8"));
+    const walk = (d: string, prefix: string) => {
+        const file = join(d, ".recipients");
+        if (existsSync(file)) {
+            const keys = readFileSync(file, "utf8")
+                .split("\n").map(l => l.trim()).filter(l => l && !l.startsWith("#"));
+            if (keys.length) {
+                console.log(`${prefix || "."}:`);
+                for (const k of keys) console.log(`  ${k}`);
+            }
+        }
+        for (const ent of readdirSync(d)) {
+            if (ent.startsWith(".")) continue;
+            const full = join(d, ent);
+            if (statSync(full).isDirectory()) walk(full, prefix ? `${prefix}/${ent}` : ent);
+        }
+    };
+    walk(dir, "");
 }
 
 async function readSecretInput(prompt: string): Promise<string> {

src/mcp.ts

@@ -4,6 +4,7 @@
 //   kern_status    — wallet health (credential count, recipient count)
 //   kern_list      — list credential names (no values)
 //   kern_fetch     — proxy HTTP request (credential stays in wallet)
+//   kern_get       — decrypt and return a credential (direct mode)
 //   kern_add       — add a credential via browser form (never through LLM)
 //   kern_rotate    — rotate a credential via browser form
 //   kern_remove    — remove a credential
@@ -111,6 +112,31 @@ export async function startMcpServer() {
         }
       },
     },
+    {
+      name: "kern_get",
+      description: "Decrypt and return a credential value (direct mode). Use kern_fetch instead when possible — it keeps the credential in the wallet.",
+      inputSchema: {
+        type: "object",
+        required: ["name"],
+        properties: {
+          name: { type: "string", description: "Credential name (e.g. tokens/openai)" },
+        },
+      },
+      handler: async (args, respond) => {
+        const name = args.name as string;
+        try {
+          const value = await wallet.get(name);
+          respond(undefined, {
+            content: [{ type: "text", text: value }],
+          });
+        } catch (e: any) {
+          respond(undefined, {
+            content: [{ type: "text", text: `Error: ${e.message}` }],
+            isError: true,
+          });
+        }
+      },
+    },
     {
       name: "kern_add",
       description: "Add a credential to the wallet. Opens a secure browser form where the user pastes the value. It never passes through the LLM.",