Add provider events to browser bridge

docs/browser-bridge.md

@@ -71,8 +71,12 @@ its CLI/tools. It does not own or serve the browser bridge.
 
 Unsupported methods return an EIP-1193-style error object with code `4200`.
 
-`personal_sign`, `eth_sendTransaction`, broad signing, hardware wallets, Kohaku, native messaging, and
-store distribution are intentionally not implemented in this PR.
+The injected provider also exposes `isConnected()`, `on`, and `removeListener` with a minimal event
+surface for `accountsChanged`, `chainChanged`, `connect`, and `disconnect`.
+
+`personal_sign`, `eth_sendTransaction`, broad signing, hardware wallets, native messaging, and store
+distribution are intentionally not implemented in this bridge slice. Kohaku remains useful for
+wallet-internal provider/backend integration, not as the browser-facing dapp provider.
 
 ## Dapp sessions
 

extension/injected.js

@@ -1,12 +1,14 @@
 (() => {
   let nextId = 1;
   const pending = new Map();
+  const listeners = new Map();
 
   class DeckardProvider {
     constructor() {
       this.isDeckard = true;
       this.selectedAddress = null;
       this.chainId = null;
+      this._connected = true;
     }
 
     request(args) {
@@ -29,12 +31,29 @@
       });
     }
 
-    on() {
-      // Event emitter support is intentionally out of scope for this milestone.
+    isConnected() {
+      return this._connected;
+    }
+
+    on(eventName, listener) {
+      if (typeof listener !== 'function') {
+        return this;
+      }
+      const eventListeners = listeners.get(eventName) ?? new Set();
+      eventListeners.add(listener);
+      listeners.set(eventName, eventListeners);
       return this;
     }
 
-    removeListener() {
+    removeListener(eventName, listener) {
+      const eventListeners = listeners.get(eventName);
+      if (!eventListeners) {
+        return this;
+      }
+      eventListeners.delete(listener);
+      if (eventListeners.size === 0) {
+        listeners.delete(eventName);
+      }
       return this;
     }
   }
@@ -45,6 +64,22 @@
     return error;
   }
 
+  function emit(eventName, payload) {
+    const eventListeners = listeners.get(eventName);
+    if (!eventListeners) {
+      return;
+    }
+    for (const listener of [...eventListeners]) {
+      try {
+        listener(payload);
+      } catch (error) {
+        setTimeout(() => {
+          throw error;
+        });
+      }
+    }
+  }
+
   const provider = new DeckardProvider();
 
   window.addEventListener('message', (event) => {
@@ -57,15 +92,41 @@
     pending.delete(message.id);
 
     if (message.error) {
+      if (message.error.code === 4900 && provider._connected) {
+        provider._connected = false;
+        emit('disconnect', providerError(4900, message.error.message));
+      }
       entry.reject(providerError(message.error.code, message.error.message));
       return;
     }
 
+    if (!provider._connected) {
+      provider._connected = true;
+      emit('connect', { chainId: provider.chainId });
+    }
+
     if (entry.method === 'eth_chainId') {
+      const previousChainId = provider.chainId;
       provider.chainId = message.result;
+      if (previousChainId && previousChainId !== message.result) {
+        emit('chainChanged', message.result);
+      }
     }
     if (entry.method === 'eth_requestAccounts' && Array.isArray(message.result)) {
-      provider.selectedAddress = message.result[0] || null;
+      const previousAddress = provider.selectedAddress;
+      const nextAddress = message.result[0] || null;
+      provider.selectedAddress = nextAddress;
+      if (previousAddress !== nextAddress) {
+        emit('accountsChanged', message.result);
+      }
+    }
+    if (entry.method === 'eth_accounts' && Array.isArray(message.result)) {
+      const previousAddress = provider.selectedAddress;
+      const nextAddress = message.result[0] || null;
+      provider.selectedAddress = nextAddress;
+      if (previousAddress !== nextAddress) {
+        emit('accountsChanged', message.result);
+      }
     }
     entry.resolve(message.result);
   });

tests/extension/browser-bridge-extension.spec.ts

@@ -28,25 +28,40 @@ test('local dapp can connect through the injected provider', async ({ page }, te
     if (!provider) {
       throw new Error('window.ethereum missing');
     }
+    const events: Array<{ name: string; payload: unknown }> = [];
+    const removedEvents: unknown[] = [];
+    const removedListener = (payload: unknown) => removedEvents.push(payload);
+    provider.on('accountsChanged', (payload) => events.push({ name: 'accountsChanged', payload }));
+    provider.on('accountsChanged', removedListener);
+    provider.removeListener('accountsChanged', removedListener);
     const accountsBefore = await provider.request({ method: 'eth_accounts' });
+    const connectedBefore = provider.isConnected();
     const requestAccounts = await provider.request({ method: 'eth_requestAccounts' });
     const accountsAfter = await provider.request({ method: 'eth_accounts' });
     const chainId = await provider.request({ method: 'eth_chainId' });
     return {
       accountsBefore,
+      connectedBefore,
       requestAccounts,
       accountsAfter,
       chainId,
+      connectedAfter: provider.isConnected(),
+      events,
+      removedEvents,
       isDeckard: Boolean(provider.isDeckard),
       selectedAddress: provider.selectedAddress,
     };
   });
 
   expect(providerState).toEqual({
     accountsBefore: [],
+    connectedBefore: true,
     requestAccounts: [mockAccount],
     accountsAfter: [mockAccount],
     chainId: '0xaa36a7',
+    connectedAfter: true,
+    events: [{ name: 'accountsChanged', payload: [mockAccount] }],
+    removedEvents: [],
     isDeckard: true,
     selectedAddress: mockAccount,
   });
@@ -70,6 +85,9 @@ declare global {
     ethereum?: {
       isDeckard?: boolean;
       selectedAddress?: string | null;
+      isConnected(): boolean;
+      on(eventName: string, listener: (payload: unknown) => void): Window['ethereum'];
+      removeListener(eventName: string, listener: (payload: unknown) => void): Window['ethereum'];
       request(args: { method: string; params?: unknown[] }): Promise<unknown>;
     };
   }

tests/extension/real-daemon.spec.ts

@@ -29,25 +29,40 @@ test('local dapp can connect through the extension to a real unlocked daemon', a
       if (!provider) {
         throw new Error('window.ethereum missing');
       }
+      const events: Array<{ name: string; payload: unknown }> = [];
+      const removedEvents: unknown[] = [];
+      const removedListener = (payload: unknown) => removedEvents.push(payload);
+      provider.on('accountsChanged', (payload) => events.push({ name: 'accountsChanged', payload }));
+      provider.on('accountsChanged', removedListener);
+      provider.removeListener('accountsChanged', removedListener);
       const accountsBefore = await provider.request({ method: 'eth_accounts' });
+      const connectedBefore = provider.isConnected();
       const requestAccounts = await provider.request({ method: 'eth_requestAccounts' });
       const accountsAfter = await provider.request({ method: 'eth_accounts' });
       const chainId = await provider.request({ method: 'eth_chainId' });
       return {
         accountsBefore,
+        connectedBefore,
         requestAccounts,
         accountsAfter,
         chainId,
+        connectedAfter: provider.isConnected(),
+        events,
+        removedEvents,
         isDeckard: Boolean(provider.isDeckard),
         selectedAddress: provider.selectedAddress,
       };
     });
 
     expect(providerState).toEqual({
       accountsBefore: [],
+      connectedBefore: true,
       requestAccounts: [realDaemonAccount],
       accountsAfter: [realDaemonAccount],
       chainId: realDaemonChainId,
+      connectedAfter: true,
+      events: [{ name: 'accountsChanged', payload: [realDaemonAccount] }],
+      removedEvents: [],
       isDeckard: true,
       selectedAddress: realDaemonAccount,
     });
@@ -86,7 +101,7 @@ for (const failure of [
     message: 'different chain',
   },
 ]) {
-  test(`real daemon bridge reports ${failure.name}`, async ({}, testInfo) => {
+  test(`real daemon bridge reports ${failure.name}`, async ({ page }, testInfo) => {
     const runtime = await startRealDaemonBridge(failure.scenario, testInfo.title);
     try {
       const chainId = await requestBridge('eth_chainId', 1);
@@ -101,6 +116,51 @@ for (const failure of [
         code: 4900,
       });
       expect(requestAccounts.error.message).toContain(failure.message);
+
+      await page.goto('/');
+      await expect(page.locator('#output')).toContainText('window.ethereum detected');
+
+      const providerState = await page.evaluate(async () => {
+        const provider = window.ethereum;
+        if (!provider) {
+          throw new Error('window.ethereum missing');
+        }
+        const disconnects: Array<{ code?: number; message?: string }> = [];
+        provider.on('disconnect', (error) => {
+          const providerError = error as Error & { code?: number };
+          disconnects.push({
+            code: error instanceof Error ? providerError.code : undefined,
+            message: error instanceof Error ? providerError.message : undefined,
+          });
+        });
+        let requestError: { code?: number; message?: string } | undefined;
+        try {
+          await provider.request({ method: 'eth_requestAccounts' });
+        } catch (error) {
+          const providerError = error as Error & { code?: number };
+          requestError = {
+            code: error instanceof Error ? providerError.code : undefined,
+            message: error instanceof Error ? providerError.message : undefined,
+          };
+        }
+        return {
+          connected: provider.isConnected(),
+          disconnects,
+          requestError,
+        };
+      });
+
+      expect(providerState.connected).toBe(false);
+      expect(providerState.disconnects).toEqual([
+        expect.objectContaining({
+          code: 4900,
+        }),
+      ]);
+      expect(providerState.disconnects[0]?.message).toContain(failure.message);
+      expect(providerState.requestError).toMatchObject({
+        code: 4900,
+      });
+      expect(providerState.requestError?.message).toContain(failure.message);
     } finally {
       await runtime.stop();
     }
@@ -112,6 +172,9 @@ declare global {
     ethereum?: {
       isDeckard?: boolean;
       selectedAddress?: string | null;
+      isConnected(): boolean;
+      on(eventName: string, listener: (payload: unknown) => void): Window['ethereum'];
+      removeListener(eventName: string, listener: (payload: unknown) => void): Window['ethereum'];
       request(args: { method: string; params?: unknown[] }): Promise<unknown>;
     };
   }

wallet-relevant-eips.md

@@ -100,7 +100,7 @@ browser-extension architecture, not as standards targets.
 | Category | Title | Source | Wallet relevance | Implementation importance | Additional notes |
 | --- | --- | --- | --- | --- | --- |
 | Architecture | Privacy-first Ethereum tooling | [kohaku/README.md](https://github.com/ethereum/kohaku/blob/master/README.md) | Positions Kohaku as reusable wallet infrastructure for privacy-preserving Ethereum UX. | High | Production integration still needs security review for each reused package. |
-| Dapp bridge | EIP-1193 provider abstraction | [kohaku/crates/eip-1193-provider/README.md](https://github.com/ethereum/kohaku/blob/master/crates/eip-1193-provider/README.md), [kohaku/packages/provider/README.md](https://github.com/ethereum/kohaku/blob/master/packages/provider/README.md) | Useful for keeping the browser extension provider thin while routing requests into native, WASM, Ethers, Viem, Helios, or Colibri backends. | Critical | Fits the desktop-wallet model where the extension is only the dapp transport and the desktop app owns policy, accounts, and signing. |
+| Provider/backend abstraction | Kohaku EIP-1193-style provider seam | [kohaku/crates/eip-1193-provider/README.md](https://github.com/ethereum/kohaku/blob/master/crates/eip-1193-provider/README.md), [kohaku/packages/provider/README.md](https://github.com/ethereum/kohaku/blob/master/packages/provider/README.md) | Useful for routing wallet-internal reads into native, WASM, Ethers, Viem, Helios, or Colibri backends. | Critical | This is not a drop-in browser wallet provider; Deckard still owns the injected dapp boundary, origin permissions, events, policy, accounts, and signing. |
 | Privacy infrastructure | Private RPC and light-client posture | [kohaku/docs/pages/practices.mdx](https://github.com/ethereum/kohaku/blob/master/docs/pages/practices.mdx), [kohaku/docs/pages/privacy.mdx](https://github.com/ethereum/kohaku/blob/master/docs/pages/privacy.mdx) | Reduces wallet activity leakage from default RPCs and centralized indexing. | High | Kohaku docs call out user-defined RPCs, Helios-style verification, and optional network privacy routing as wallet best practices. |
 | Account UX | Many accounts, many identities | [kohaku/docs/pages/practices.mdx](https://github.com/ethereum/kohaku/blob/master/docs/pages/practices.mdx), [kohaku/docs/pages/privacy.mdx](https://github.com/ethereum/kohaku/blob/master/docs/pages/privacy.mdx) | Encourages per-context accounts and easy account creation during dapp connection. | High | This should influence the extension connect flow: choosing or creating an account should be part of the permission grant, not only a global wallet setting. |
 | Plugin system | Standardized private-transaction plugin interface | [kohaku/packages/plugins/README.md](https://github.com/ethereum/kohaku/blob/master/packages/plugins/README.md) | Lets the wallet expose shield, transfer, unshield, balance, and broadcast flows across multiple privacy protocols through one host interface. | High | Host responsibilities include storage, network fetch, keystore derivation, and Ethereum provider access; this maps cleanly to a desktop wallet core. |