feat(coding-agent): add after_provider_response hook closes #3128

packages/coding-agent/docs/extensions.md

@@ -246,6 +246,7 @@ user sends prompt ────────────────────
   │   ├─► turn_start                               │       │
   │   ├─► context (can modify messages)            │       │
   │   ├─► before_provider_request (can inspect or replace payload)
+  │   ├─► after_provider_response (status + headers, before stream consume)
   │   │                                            │       │
   │   │   LLM responds, may call tools:            │       │
   │   │     ├─► tool_execution_start               │       │
@@ -534,6 +535,22 @@ pi.on("before_provider_request", (event, ctx) => {
 
 This is mainly useful for debugging provider serialization and cache behavior.
 
+#### after_provider_response
+
+Fired after an HTTP response is received and before its stream body is consumed. Handlers run in extension load order.
+
+```typescript
+pi.on("after_provider_response", (event, ctx) => {
+  // event.status - HTTP status code
+  // event.headers - normalized response headers
+  if (event.status === 429) {
+    console.log("rate limited", event.headers["retry-after"]);
+  }
+});
+```
+
+Header availability depends on provider and transport. Providers that abstract HTTP responses may not expose headers.
+
 ### Model Events
 
 #### model_select
@@ -2231,7 +2248,7 @@ All examples in [examples/extensions/](../examples/extensions/).
 | `dirty-repo-guard.ts` | Warn on dirty git repo | `on("session_before_*")`, `exec` |
 | `input-transform.ts` | Transform user input | `on("input")` |
 | `model-status.ts` | React to model changes | `on("model_select")`, `setStatus` |
-| `provider-payload.ts` | Inspect or patch provider payloads | `on("before_provider_request")` |
+| `provider-payload.ts` | Inspect payloads and provider response headers | `on("before_provider_request")`, `on("after_provider_response")` |
 | `system-prompt-header.ts` | Display system prompt info | `on("agent_start")`, `getSystemPrompt` |
 | `claude-rules.ts` | Load rules from files | `on("session_start")`, `on("before_agent_start")` |
 | `file-trigger.ts` | File watcher triggers messages | `sendMessage` |