fix(claude): pass only transcript entries to the rewind session store

The session store parsed each transcript line and cast it to a session
entry without checking it. Keep only JSON objects with a string type, and
cover transcripts with non-entry lines in the real-SDK rewind test.

packages/server/src/server/agent/providers/claude/agent.ts

@@ -2830,9 +2830,11 @@ class ClaudeAgentSession implements AgentSession {
       this.startFreshConversationSession();
       return;
     }
+    const currentSessionId = this.claudeSessionId;
     await revertClaudeConversation({
       sdk: this.rewindSdk,
-      sessionId: this.claudeSessionId,
+      sessionId: currentSessionId,
+      transcriptPath: currentSessionId ? this.resolveHistoryPath(currentSessionId) : null,
       messageId: target.messageId,
       resolveMessageId: (messageId) => this.resolveClaudeMessageId(messageId),
       setSessionId: (sessionId) => {

packages/server/src/server/agent/providers/claude/rewind.test.ts

@@ -1,10 +1,15 @@
-import { describe, expect, test } from "vitest";
+import { randomUUID } from "node:crypto";
+import { mkdirSync, mkdtempSync, readFileSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import path from "node:path";
+import { afterEach, describe, expect, test } from "vitest";
 import type { Query } from "@anthropic-ai/claude-agent-sdk";
 
 import {
   revertClaudeConversation,
   revertClaudeConversationAndFiles,
   revertClaudeFiles,
+  realClaudeRewindSdk,
 } from "./rewind.js";
 import { FakeClaudeSdk } from "./test-rewind-claude-sdk.js";
 
@@ -16,6 +21,7 @@ describe("Claude rewind", () => {
     await revertClaudeConversation({
       sdk: claude,
       sessionId,
+      transcriptPath: "/claude/projects/repo/original-session.jsonl",
       messageId: "user-message-1",
       setSessionId: (nextSessionId) => {
         sessionId = nextSessionId;
@@ -33,6 +39,7 @@ describe("Claude rewind", () => {
     await revertClaudeConversation({
       sdk: claude,
       sessionId,
+      transcriptPath: "/claude/projects/repo/original-session.jsonl",
       messageId: "timeline-message-1",
       resolveMessageId: () => "claude-jsonl-message-1",
       setSessionId: (nextSessionId) => {
@@ -76,6 +83,7 @@ describe("Claude rewind", () => {
       sdk: claude,
       query: claude.createQuery() as Query,
       sessionId,
+      transcriptPath: "/claude/projects/repo/original-session.jsonl",
       messageId: "user-message-1",
       setSessionId: (nextSessionId) => {
         sessionId = nextSessionId;
@@ -87,3 +95,126 @@ describe("Claude rewind", () => {
     expect(sessionId).toBe("forked-before-rehydrate");
   });
 });
+
+interface TranscriptLine {
+  type: "user" | "assistant";
+  uuid: string;
+  parentUuid: string | null;
+  text: string;
+}
+
+function writeTranscript(
+  transcriptPath: string,
+  sessionId: string,
+  lines: Array<TranscriptLine | string>,
+): void {
+  const entries = lines.map((line) => {
+    if (typeof line === "string") return line;
+    const { type, uuid, parentUuid, text } = line;
+    return JSON.stringify({
+      type,
+      uuid,
+      parentUuid,
+      sessionId,
+      cwd: "/repo",
+      timestamp: new Date().toISOString(),
+      message: { role: type, content: text },
+    });
+  });
+  writeFileSync(transcriptPath, `${entries.join("\n")}\n`, "utf8");
+}
+
+function readMessageTexts(transcriptPath: string): string[] {
+  const entries = readFileSync(transcriptPath, "utf8")
+    .trim()
+    .split("\n")
+    .map((line) => JSON.parse(line) as { message?: { content: string } });
+  return entries.flatMap((entry) => (entry.message ? [entry.message.content] : []));
+}
+
+describe("Claude rewind against the Claude SDK", () => {
+  let tempRoot: string | null = null;
+  const previousConfigDir = process.env.CLAUDE_CONFIG_DIR;
+
+  afterEach(() => {
+    if (tempRoot) rmSync(tempRoot, { recursive: true, force: true });
+    tempRoot = null;
+    if (previousConfigDir === undefined) {
+      delete process.env.CLAUDE_CONFIG_DIR;
+    } else {
+      process.env.CLAUDE_CONFIG_DIR = previousConfigDir;
+    }
+  });
+
+  test("forks a session that lives in a provider's own CLAUDE_CONFIG_DIR", async () => {
+    tempRoot = mkdtempSync(path.join(tmpdir(), "claude-rewind-config-dir-"));
+    // The provider sets CLAUDE_CONFIG_DIR for Claude Code; the daemon's own environment does not.
+    delete process.env.CLAUDE_CONFIG_DIR;
+    const projectDir = path.join(tempRoot, "custom-claude-dir", "projects", "-repo");
+    mkdirSync(projectDir, { recursive: true });
+    const sessionId = randomUUID();
+    const firstUser = randomUUID();
+    const firstReply = randomUUID();
+    const secondUser = randomUUID();
+    const transcriptPath = path.join(projectDir, `${sessionId}.jsonl`);
+    writeTranscript(transcriptPath, sessionId, [
+      { type: "user", uuid: firstUser, parentUuid: null, text: "first" },
+      { type: "assistant", uuid: firstReply, parentUuid: firstUser, text: "first reply" },
+      { type: "user", uuid: secondUser, parentUuid: firstReply, text: "second" },
+      { type: "assistant", uuid: randomUUID(), parentUuid: secondUser, text: "second reply" },
+    ]);
+    let currentSessionId = sessionId;
+
+    await revertClaudeConversation({
+      sdk: realClaudeRewindSdk,
+      sessionId,
+      transcriptPath,
+      messageId: firstReply,
+      setSessionId: (nextSessionId) => {
+        currentSessionId = nextSessionId;
+      },
+    });
+
+    expect(currentSessionId).not.toBe(sessionId);
+    expect(readMessageTexts(path.join(projectDir, `${currentSessionId}.jsonl`))).toEqual([
+      "first",
+      "first reply",
+    ]);
+  });
+
+  test("skips transcript lines that are not entries when forking", async () => {
+    tempRoot = mkdtempSync(path.join(tmpdir(), "claude-rewind-config-dir-"));
+    delete process.env.CLAUDE_CONFIG_DIR;
+    const projectDir = path.join(tempRoot, "custom-claude-dir", "projects", "-repo");
+    mkdirSync(projectDir, { recursive: true });
+    const sessionId = randomUUID();
+    const firstUser = randomUUID();
+    const firstReply = randomUUID();
+    const transcriptPath = path.join(projectDir, `${sessionId}.jsonl`);
+    writeTranscript(transcriptPath, sessionId, [
+      "null",
+      { type: "user", uuid: firstUser, parentUuid: null, text: "first" },
+      "[1, 2]",
+      '"text"',
+      "{}",
+      { type: "assistant", uuid: firstReply, parentUuid: firstUser, text: "first reply" },
+      { type: "user", uuid: randomUUID(), parentUuid: firstReply, text: "second" },
+    ]);
+    let currentSessionId = sessionId;
+
+    await revertClaudeConversation({
+      sdk: realClaudeRewindSdk,
+      sessionId,
+      transcriptPath,
+      messageId: firstReply,
+      setSessionId: (nextSessionId) => {
+        currentSessionId = nextSessionId;
+      },
+    });
+
+    expect(readMessageTexts(path.join(projectDir, `${currentSessionId}.jsonl`))).toEqual([
+      "first",
+      "first reply",
+    ]);
+  });
+});

packages/server/src/server/agent/providers/claude/rewind.ts

@@ -1,29 +1,90 @@
-import { forkSession as claudeForkSession, type Query } from "@anthropic-ai/claude-agent-sdk";
+import { appendFile, readFile } from "node:fs/promises";
+import path from "node:path";
+import {
+  forkSession as claudeForkSession,
+  type Query,
+  type SessionStore,
+  type SessionStoreEntry,
+} from "@anthropic-ai/claude-agent-sdk";
 
 export interface ClaudeRewindSdk {
   forkSession(
     sessionId: string,
-    options: { upToMessageId: string },
+    options: { upToMessageId: string; transcriptPath: string },
   ): Promise<{ sessionId: string }>;
 }
 
+// On its own, the SDK looks for the session under the daemon's CLAUDE_CONFIG_DIR, while a
+// provider can point Claude Code at another one. Forking through a store rooted at the
+// transcript's folder reads the session where Claude Code wrote it and writes the fork beside it.
 export const realClaudeRewindSdk: ClaudeRewindSdk = {
-  forkSession: claudeForkSession,
+  forkSession: (sessionId, options) =>
+    claudeForkSession(sessionId, {
+      upToMessageId: options.upToMessageId,
+      sessionStore: projectFolderSessionStore(path.dirname(options.transcriptPath)),
+    }),
 };
 
+function projectFolderSessionStore(projectFolder: string): SessionStore {
+  const transcriptPath = (sessionId: string) => path.join(projectFolder, `${sessionId}.jsonl`);
+  return {
+    async load({ sessionId }) {
+      let text: string;
+      try {
+        text = await readFile(transcriptPath(sessionId), "utf8");
+      } catch (error) {
+        if ((error as NodeJS.ErrnoException).code === "ENOENT") return null;
+        throw error;
+      }
+      return parseTranscriptEntries(text);
+    },
+    async append({ sessionId }, entries) {
+      const lines = entries.map((entry) => `${JSON.stringify(entry)}\n`).join("");
+      await appendFile(transcriptPath(sessionId), lines, "utf8");
+    },
+  };
+}
+
+function parseTranscriptEntries(text: string): SessionStoreEntry[] {
+  const entries: SessionStoreEntry[] = [];
+  for (const line of text.split("\n")) {
+    if (!line.trim()) continue;
+    let parsed: unknown;
+    try {
+      parsed = JSON.parse(line);
+    } catch {
+      // Skip a line that is not JSON, as the SDK's own transcript reader does.
+      continue;
+    }
+    if (isSessionStoreEntry(parsed)) entries.push(parsed);
+  }
+  return entries;
+}
+
+function isSessionStoreEntry(value: unknown): value is SessionStoreEntry {
+  return (
+    typeof value === "object" &&
+    value !== null &&
+    !Array.isArray(value) &&
+    typeof (value as { type?: unknown }).type === "string"
+  );
+}
+
 export async function revertClaudeConversation(input: {
   sdk: ClaudeRewindSdk;
   sessionId: string | null;
+  transcriptPath: string | null;
   messageId: string;
   resolveMessageId?: (messageId: string) => string | Promise<string>;
   setSessionId: (sessionId: string) => void;
 }): Promise<void> {
-  if (!input.sessionId) {
+  if (!input.sessionId || !input.transcriptPath) {
     throw new Error("Claude session is not ready for rewind");
   }
   const messageId = (await input.resolveMessageId?.(input.messageId)) ?? input.messageId;
   const fork = await input.sdk.forkSession(input.sessionId, {
     upToMessageId: messageId,
+    transcriptPath: input.transcriptPath,
   });
   input.setSessionId(fork.sessionId);
 }
@@ -44,6 +105,7 @@ export async function revertClaudeConversationAndFiles(input: {
   sdk: ClaudeRewindSdk;
   query: Query;
   sessionId: string | null;
+  transcriptPath: string | null;
   messageId: string;
   resolveMessageId?: (messageId: string) => string | Promise<string>;
   setSessionId: (sessionId: string) => void;

packages/server/src/server/agent/providers/claude/test-rewind-claude-sdk.ts

@@ -12,7 +12,7 @@ export class FakeClaudeSdk implements ClaudeRewindSdk {
 
   async forkSession(
     _sessionId: string,
-    options: { upToMessageId: string },
+    options: { upToMessageId: string; transcriptPath: string },
   ): Promise<{ sessionId: string }> {
     this.recordedForks.push({ upToMessageId: options.upToMessageId });
     return { sessionId: this.nextSessionId };