fix: preserve failed responses when retrying model calls

Keep failed attempts in the saved transcript and omit only trailing failures from Retry's temporary agent history. Use the matching temporary prefix length when persisting genuinely new output.

Preserve the error notice across plan/compaction markers, refuse Retry after later compaction, and avoid synthesizing results for tool calls inside failed generations while retaining Pi's native filtering.

Verified: 173 focused Retry/session/compaction-projection/practice-record tests, typecheck, changed-file lint, and diff --check. No app launch or real provider calls.

tests/session-core.test.ts

@@ -25,7 +25,7 @@ import { absorbed, pendingCallTool, SessionModel } from "../components/session-c
 import type { ChatInput } from "../src/core/input-events.ts";
 import type { LhMessage } from "../src/core/native-messages.ts";
 import { newUserMessage, newAnswerResult, newThinkingMessage, needsContinuation, endsInDismissal } from "../src/core/native-messages.ts";
-import { newCompactionMarker, newPlanBlockMessage, projectView } from "../src/core/index.ts";
+import { endsInFailedTurn, newCompactionMarker, newPlanBlockMessage, projectView } from "../src/core/index.ts";
 import { dismissedAnswer } from "../src/core/question-core.ts";
 import { buildAnswer, type QuestionData } from "../src/core/question-core.ts";
 
@@ -483,7 +483,7 @@ it("Wave C: markers injected mid-run (custom role, follow-up delivery) append to
 	});
 });
 
-// ─── provider failures: one final-entry rule for live and saved records ──────
+// ─── provider failures: one marker-aware rule for live and saved records ────
 
 describe("provider-error banner (live and saved)", () => {
 	function failed(id = "failed", errorMessage: string | undefined = "Google 500: fixture failure"): LhMessage {
@@ -512,7 +512,7 @@ describe("provider-error banner (live and saved)", () => {
 		assert.equal(model().getState().error, null);
 	});
 
-	it("any later entry supersedes the failure, including plan/compaction markers and aborts", () => {
+	it("substantive later input/output supersedes the failure, including aborts", () => {
 		const failure = failed();
 		const later: LhMessage[] = [
 			newUserMessage("retry"),
@@ -520,8 +520,6 @@ describe("provider-error banner (live and saved)", () => {
 			{ ...assistantMsg("aborted", ""), stopReason: "aborted", errorMessage: "Aborted" } as LhMessage,
 			newThinkingMessage("problem", "my attempt"),
 			resultMsg("call"),
-			newPlanBlockMessage("plan", { kind: "full", nodes: [], edges: [], current: null }),
-			newCompactionMarker("summary", { firstKeptMessageId: failure.id, tokensBefore: 100, model: "fixture", at: "2026-01-01T00:00:00Z" }),
 		];
 		for (const entry of later) {
 			const m = model({ initialMessages: [failure] });
@@ -533,6 +531,31 @@ describe("provider-error banner (live and saved)", () => {
 		}
 	});
 
+	it("plan and compaction markers preserve the banner on sync, adoption and reopen", async () => {
+		const failure = failed();
+		const record = [newUserMessage("topic"), failure];
+		const markers = [
+			newPlanBlockMessage("plan", { kind: "full", nodes: [], edges: [], current: null }),
+			newCompactionMarker("summary", { firstKeptMessageId: failure.id, tokensBefore: 100, model: "fixture", at: "2026-01-01T00:00:00Z" }),
+		];
+		for (const marker of markers) {
+			const saved = [...record, marker];
+			let posts = 0;
+			const m = model({ initialMessages: record, fetch: async () => { posts++; throw new Error("unexpected request"); } });
+			m.setMessages(saved);
+			assert.equal(m.getState().error?.message, failure.role === "assistant" ? failure.errorMessage : undefined);
+			assert.equal(model({ initialMessages: saved }).getState().error?.message, m.getState().error?.message);
+			const adopted = model({ initialMessages: record });
+			adopted.adoptRecord(saved);
+			assert.equal(adopted.getState().error?.message, m.getState().error?.message);
+			assert.equal(endsInFailedTurn(saved), marker.customType === "plan-block", "later compaction removes Retry eligibility, not the error notice");
+			await m.continueIfOwed(saved);
+			assert.equal(posts, 0, "restoring the banner is never an automatic retry");
+			m.setMessages([...saved, newUserMessage("continue from here")]);
+			assert.equal(m.getState().error, null, "new learner input supersedes the notice");
+		}
+	});
+
 	it("a newer live message supersedes the failure before its response finishes", () => {
 		const m = model();
 		m.applyWireEvent({ type: "message_end", message: failed() });
@@ -554,7 +577,7 @@ describe("provider-error banner (live and saved)", () => {
 		assert.equal(m.getState().error?.message, "Google 500: fixture failure");
 	});
 
-	for (const input of [{ type: "text", text: "retry" }, { type: "continue" }] as const) {
+	for (const input of [{ type: "text", text: "retry" }, { type: "continue" }, { type: "retry" }] as const) {
 		it(`hides the old failure during the optimistic ${input.type} wait, then shows a new live failure`, async () => {
 			let acknowledge!: (response: Response) => void;
 			const ack = new Promise<Response>((resolve) => { acknowledge = resolve; });