feat(compaction): support SubAPI native remote compaction

- support sub-api/openai-responses through the public Responses endpoint
- preserve explicit Authorization and support header-only authentication
- retain Codex JWT requirements and native compaction failure fallback
- restore SubAPI checkpoints and preserve portable model-switching summaries
- add provider, authentication and checkpoint lifecycle regression tests
- document compatibility requirements and the Sub2API protocol reference

pi-compaction/index.ts

@@ -14,21 +14,19 @@ import {
   type SessionEntry,
 } from "@earendil-works/pi-coding-agent";
 import { DEFAULT_CONFIG, loadConfig } from "./src/config.js";
+import { buildNativeCompactionTransport, isNativeCompactionModel } from "./src/native-provider.js";
 import {
-  buildCodexHeaders,
   buildCompactionRequestBody,
   buildReplacementHistory,
   buildToolPayload,
   callRemoteCompaction,
   findNativeCheckpoint,
   isJsonObject,
-  isOpenAICodexModel,
   mergeFeatureHeader,
   messagesToResponseItems,
   modelKey,
   NATIVE_COMPACTION_KIND,
   NATIVE_COMPACTION_VERSION,
-  resolveCodexResponsesUrl,
   stripInputFromPayload,
   type JsonObject,
   type NativeCompactionDetails,
@@ -364,12 +362,12 @@ export default function piCompactionExtension(pi: ExtensionAPI): void {
   });
 
   pi.on("before_provider_headers", (event, ctx) => {
-    if (isOpenAICodexModel(ctx.model)) setFeatureHeader(event.headers);
+    if (isNativeCompactionModel(ctx.model)) setFeatureHeader(event.headers);
   });
 
   pi.on("before_provider_request", (event, ctx) => {
     const model = ctx.model;
-    if (!model || !isOpenAICodexModel(model) || !isJsonObject(event.payload)) return undefined;
+    if (!model || !isNativeCompactionModel(model) || !isJsonObject(event.payload)) return undefined;
     const runtime = runtimeFor(ctx);
     const sessionId = ctx.sessionManager.getSessionId();
     payloads.set(sessionId, { modelKey: modelKey(model), payload: stripInputFromPayload(event.payload) });
@@ -401,7 +399,7 @@ export default function piCompactionExtension(pi: ExtensionAPI): void {
 
     const model = ctx.model;
     if (!model) return undefined;
-    if (!runtime.config.native.enabled || !isOpenAICodexModel(model)) {
+    if (!runtime.config.native.enabled || !isNativeCompactionModel(model)) {
       try {
         const auth = await ctx.modelRegistry.getApiKeyAndHeaders(model);
         if (!auth.ok) return undefined;
@@ -438,7 +436,7 @@ export default function piCompactionExtension(pi: ExtensionAPI): void {
 
     try {
       const auth = await ctx.modelRegistry.getApiKeyAndHeaders(model);
-      if (!auth.ok || !auth.apiKey) throw new Error(auth.ok ? "Codex authentication unavailable" : auth.error);
+      if (!auth.ok) throw new Error(auth.error);
       const currentCheckpoint = checkpoint.status === "valid" ? checkpoint.checkpoint.details : undefined;
       const input = codexInput(model, runtime, snapshot, currentCheckpoint);
       const sessionId = ctx.sessionManager.getSessionId();
@@ -451,10 +449,9 @@ export default function piCompactionExtension(pi: ExtensionAPI): void {
         tools: buildToolPayload(pi.getAllTools(), pi.getActiveTools()),
         sessionId,
       });
-      if (ctx.hasUI) ctx.ui.notify("pi-compaction: creating Codex native checkpoint…", "info");
+      if (ctx.hasUI) ctx.ui.notify(`pi-compaction: creating ${model.provider} native checkpoint...`, "info");
       const remote = await callRemoteCompaction({
-        url: resolveCodexResponsesUrl(model.baseUrl),
-        headers: buildCodexHeaders({ apiKey: auth.apiKey, headers: cleanHeaders(auth.headers), sessionId }),
+        ...buildNativeCompactionTransport({ model, apiKey: auth.apiKey, headers: cleanHeaders(auth.headers), sessionId }),
         body,
         signal: event.signal,
       });