fix(mcp-client): distinguish failure from loss

The reconnect supervisor used connection lost for every transition into backoff, including an initial startup attempt that never established a connection and later retry attempts that also failed. That wording implied a previously healthy generation and obscured whether any tools had ever been registered.

Capture whether the generation had reached the established state before scheduling recovery. Established disconnects retain connection lost/reconnecting; startup and retry failures now report connection failed/retrying. The reconnect-disabled diagnostic uses the same distinction while preserving its concrete manual-recovery guidance.

Unit assertions cover established loss, initial failure, retry failure, and both reconnect-disabled branches. Focused package coverage remains 100%, and the bilingual Agent Note records the observable state vocabulary.

packages/mcp/mcp-client/src/connection.ts

@@ -190,11 +190,12 @@ export function startConnection(ctx: Context, config: Config, policy: ResolvedRe
   }
 
   function scheduleReconnect(): void {
+    const lostEstablishedConnection = connectedAt !== undefined
     if (!policy.enabled) {
-      const detail = connectedAt !== undefined
-        ? 'registered tools will fail until an HMR reload or Host restart'
-        : 'no tools were registered; reload the plugin or restart the Host to connect'
-      ctx.logger.error(`${label}: connection lost and reconnect is disabled — ${detail}`)
+      const message = lostEstablishedConnection
+        ? 'connection lost and reconnect is disabled — registered tools will fail until an HMR reload or Host restart'
+        : 'connection failed and reconnect is disabled — no tools were registered; reload the plugin or restart the Host to connect'
+      ctx.logger.error(`${label}: ${message}`)
       return
     }
     // A connection that stayed up past the stability window (= maxDelayMs, the
@@ -213,7 +214,8 @@ export function startConnection(ctx: Context, config: Config, policy: ResolvedRe
       return
     }
     const delayMs = Math.min(policy.maxDelayMs, policy.initialDelayMs * 2 ** (failedAttempts - 1))
-    ctx.logger.warn(`${label}: connection lost; reconnecting in ${delayMs}ms (attempt ${failedAttempts}/${policy.maxAttempts})`)
+    const action = lostEstablishedConnection ? 'connection lost; reconnecting' : 'connection failed; retrying'
+    ctx.logger.warn(`${label}: ${action} in ${delayMs}ms (attempt ${failedAttempts}/${policy.maxAttempts})`)
     reconnectTimer = setTimeout(() => {
       reconnectTimer = undefined
       settling = connectGeneration(false)

packages/mcp/mcp-client/tests/reconnect.spec.ts

@@ -191,6 +191,7 @@ describe('reconnect supervisor', () => {
     // Initial connect + exactly maxAttempts reconnect attempts.
     expect(mockConnect).toHaveBeenCalledTimes(3)
     expect(warns.some(line => line.includes('connection attempt failed: Error: server gone'))).toBe(true)
+    expect(warns.some(line => line.includes('connection failed; retrying in 4ms (attempt 2/2)'))).toBe(true)
     await sleep(30)
     expect(mockConnect).toHaveBeenCalledTimes(3)
   })
@@ -222,6 +223,7 @@ describe('reconnect supervisor', () => {
   })
 
   it('does not start a replacement until a failed generation reports that it closed', async () => {
+    const { warns } = captureLogs(ctx)
     mockConnect.mockRejectedValueOnce(new Error('initialize failed'))
     // Model the SDK's fire-and-forget close after initialize fails: the
     // harness's second close call returns, but the child has not exited yet.
@@ -235,6 +237,7 @@ describe('reconnect supervisor', () => {
     instances[0]!.onclose?.()
     await applying
     await vi.waitFor(() => { expect(instances).toHaveLength(2) })
+    expect(warns.some(line => line.includes('connection failed; retrying in 2ms (attempt 1/2)'))).toBe(true)
   })
 
   it('stops reconnecting when a failed generation never reports that it closed', async () => {
@@ -329,7 +332,7 @@ describe('reconnect supervisor', () => {
     expect(mockConnect).toHaveBeenCalledTimes(1)
     // Pre-reconnect contract: the generation stays registered until disposal.
     expect(ctx.tools.get('mcp__srv__remote')).toBeDefined()
-    expect(errors.some(line => line.includes('reconnect is disabled'))).toBe(true)
+    expect(errors.some(line => line.includes('connection lost and reconnect is disabled'))).toBe(true)
   })
   it('reconnect disabled after a failed initial connect reports no registered tools', async () => {
     const { errors } = captureLogs(ctx)
@@ -337,6 +340,7 @@ describe('reconnect supervisor', () => {
     await apply(ctx, stdioConfig({ enabled: false }))
     await sleep(30)
     expect(ctx.tools.get('mcp__srv__remote')).toBeUndefined()
+    expect(errors.some(line => line.includes('connection failed and reconnect is disabled'))).toBe(true)
     expect(errors.some(line => line.includes('no tools were registered'))).toBe(true)
   })