feat(server,web): import and export Trace files in the trace viewer (#73)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

packages/server/src/api/types.ts

@@ -939,6 +939,20 @@ export interface AgentTracesResponse {
   dates: AgentTraceDateGroup[];
 }
 
+export interface TraceImportRequest {
+  /** Base64 of the Trace file content (JSON Lines; the first record must be `session_meta`). */
+  dataBase64: string;
+}
+
+export interface TraceImportResponse {
+  /** Session id taken from the imported file's `session_meta`. */
+  sessionId: string;
+  /** Allocated file index: always 1 — an import creates a new Session (a duplicate session id is rejected with 409 `trace_session_exists`). */
+  index: number;
+  /** Date directory the file landed in (local yyyy-mm-dd from the first record's timestamp, matching the Trace Writer's convention). */
+  date: string;
+}
+
 // ---------------------------------------------------------------------------
 // Usage and cost statistics
 // ---------------------------------------------------------------------------

packages/server/src/http/routes/agent-traces.ts

@@ -1,17 +1,32 @@
 /**
  * Agent-level Trace browsing routes:
  *   - GET /api/projects/:p/agents/:a/traces — drills down Agent -> date -> Session -> index (reverse order);
- *   - GET /api/projects/:p/agents/:a/traces/:sessionId/:index (including /analysis) —
+ *   - GET /api/projects/:p/agents/:a/traces/:sessionId/:index (including /analysis, /download) —
  *     read-only Trace detail endpoints (FD-3): locate the Trace file directly by
  *     (projectId, agentId, sessionId), without depending on the sessions table for
  *     tracking — any entry visible in the directory tree (subagent child Sessions,
  *     CLI-created Sessions) can be opened and read; access is enforced by requireProjectAccess.
+ *   - POST /api/projects/:p/agents/:a/traces/import — uploads a Trace JSONL file (owner
+ *     only, mirroring the Agent snapshot import); the file names itself via its
+ *     session_meta and always becomes index 001 of a new Session — a session id the
+ *     Agent already has is rejected with 409 trace_session_exists.
  */
 import { Hono } from "hono";
 import type { AppEnv } from "../../auth/middleware.js";
-import { paginationQuery, positiveIntParam, requireValidId } from "../validate.js";
+import type { TraceImportResponse } from "../../api/types.js";
+import {
+  badRequest,
+  paginationQuery,
+  positiveIntParam,
+  readJson,
+  requireString,
+  requireValidId,
+} from "../validate.js";
 import type { AppDeps } from "../../app.js";
 
+/** Import file size cap: aligned with the snapshot import (stays within the 20MB body limit after base64). */
+const MAX_TRACE_BYTES = 14 * 1024 * 1024;
+
 export function agentTracesRoutes(deps: AppDeps): Hono<AppEnv> {
   const app = new Hono<AppEnv>();
 
@@ -44,5 +59,47 @@ export function agentTracesRoutes(deps: AppDeps): Hono<AppEnv> {
     return c.json(await deps.traceService.analyze(projectId, agentId, sessionId, index));
   });
 
+  // Raw-file download (any member, like the snapshot export): the file is served verbatim
+  // as an attachment, so what's downloaded can be re-imported byte-compatibly.
+  app.get("/:sessionId/:index/download", async (c) => {
+    const projectId = requireValidId(c, "projectId");
+    const agentId = requireValidId(c, "agentId");
+    const sessionId = requireValidId(c, "sessionId");
+    deps.projectService.requireProjectAccess(c.var.user.userId, projectId);
+    const index = positiveIntParam(c, "index");
+    const bytes = await deps.traceService.readFileRaw(projectId, agentId, sessionId, index);
+    const fileName = `${sessionId}_${String(index).padStart(3, "0")}.jsonl`;
+    return new Response(new Uint8Array(bytes), {
+      headers: {
+        "Content-Type": "application/x-ndjson",
+        "Content-Disposition": `attachment; filename*=UTF-8''${encodeURIComponent(fileName)}`,
+        "X-Content-Type-Options": "nosniff",
+      },
+    });
+  });
+
+  // Trace file upload (owner only, mirroring the Agent snapshot import): the route checks the
+  // transport shape (base64, size); the content itself — JSONL, leading session_meta, a
+  // filename-safe session_id — is validated by the service right where the path is built.
+  app.post("/import", async (c) => {
+    const projectId = requireValidId(c, "projectId");
+    const agentId = requireValidId(c, "agentId");
+    deps.projectService.requireProjectOwner(c.var.user.userId, projectId);
+    await deps.agentConfigService.requireExists(projectId, agentId);
+    const body = await readJson(c);
+    const dataBase64 = requireString(body, "dataBase64", { minLen: 1, maxLen: 20 * 1024 * 1024 });
+    const bytes = Buffer.from(dataBase64, "base64");
+    if (bytes.byteLength === 0) throw badRequest("Import file is empty.");
+    if (bytes.byteLength > MAX_TRACE_BYTES) {
+      throw badRequest("Import file exceeds the 14MB limit.");
+    }
+    const res: TraceImportResponse = await deps.traceService.importTraceFile(
+      projectId,
+      agentId,
+      bytes.toString("utf8"),
+    );
+    return c.json(res);
+  });
+
   return app;
 }

packages/server/src/services/trace-service.ts

@@ -13,6 +13,8 @@ import fs from "node:fs/promises";
 import path from "node:path";
 import {
   agentsDir,
+  isSessionMeta,
+  parseTraceLines,
   parseUserSteeringText,
   readTraceTolerant,
   tracesDir,
@@ -25,15 +27,24 @@ import type {
   TraceAnalysisResponse,
   TraceEventsResponse,
   TraceFileInfo,
+  TraceImportResponse,
   TraceModelSegment,
   TraceTaskStats,
   TraceToolSpan,
   UsageTrendPointInTrace,
 } from "../api/types.js";
 import { HttpError } from "../http/errors.js";
+import { formatLocalDate } from "../internal/dates.js";
 
 const TRACE_FILE_RE = /^(.+)_(\d{3})\.jsonl$/;
 
+/**
+ * session_id an imported Trace file may declare: same alphabet as resource ids plus a length
+ * cap. The value becomes part of the target **filename**, so this is a path-traversal defense,
+ * checked right next to the path construction — never trust the caller to have validated it.
+ */
+const IMPORT_SESSION_ID_RE = /^[A-Za-z0-9_-]{1,128}$/;
+
 /** Recursion depth cap for sub-session expansion (run_subagent depth is already constrained by the SDK; this is just a defensive backstop against cycles). */
 const MAX_SUBAGENT_DEPTH = 4;
 
@@ -687,6 +698,16 @@ export class TraceService {
     sessionId: string,
     index: number,
   ): Promise<OmniMessage[]> {
+    const file = await this.locateByIndex(projectId, agentId, sessionId, index);
+    return readTraceTolerant(file.path);
+  }
+
+  private async locateByIndex(
+    projectId: string,
+    agentId: string,
+    sessionId: string,
+    index: number,
+  ): Promise<LocatedFile> {
     const files = await this.locateAll(projectId, agentId, sessionId);
     const file = files.find((f) => f.index === index);
     if (!file) {
@@ -696,6 +717,80 @@ export class TraceService {
         `This Session has no Trace file with index ${index}.`,
       );
     }
-    return readTraceTolerant(file.path);
+    return file;
+  }
+
+  /** Raw bytes of the Trace file at the given index (export/download: the file is served verbatim). */
+  async readFileRaw(
+    projectId: string,
+    agentId: string,
+    sessionId: string,
+    index: number,
+  ): Promise<Buffer> {
+    const file = await this.locateByIndex(projectId, agentId, sessionId, index);
+    return fs.readFile(file.path);
+  }
+
+  /**
+   * Imports an uploaded Trace file (raw JSONL content). Validates the content itself —
+   * parseable JSONL whose first record is a `session_meta` carrying a filename-safe
+   * `session_id` (400 invalid_trace otherwise) — then writes it under the Agent's traces
+   * directory as a **new Session**: a session id the Agent already has is rejected with
+   * 409 `trace_session_exists` (splicing a further index into an existing Session would
+   * corrupt its concatenated transcript, silently become its resume point, and could
+   * collide with a live Writer's rotation), so the imported file is always index 1. The
+   * date dir comes from the first record's timestamp (falling back to now), formatted as
+   * a **local** date — the same convention as core's Trace Writer — so an export →
+   * import round-trip lands in the same date dir on non-UTC servers.
+   */
+  async importTraceFile(
+    projectId: string,
+    agentId: string,
+    content: string,
+  ): Promise<TraceImportResponse> {
+    const invalid = (message: string) => new HttpError(400, "invalid_trace", message);
+    let records: OmniMessage[];
+    try {
+      records = parseTraceLines(content);
+    } catch {
+      throw invalid("The file is not valid Trace JSONL.");
+    }
+    if (records.length === 0) throw invalid("The file contains no Trace records.");
+    const first = records[0]!;
+    if (!isSessionMeta(first))
+      throw invalid("The first record of a Trace file must be session_meta.");
+    // The payload type declares session_id: string, but the value came from user-supplied JSON —
+    // re-check the runtime shape before it becomes part of a filename.
+    const sessionId: unknown = (first.payload as { session_id?: unknown }).session_id;
+    if (typeof sessionId !== "string" || !IMPORT_SESSION_ID_RE.test(sessionId)) {
+      throw invalid("session_meta carries a missing or invalid session_id.");
+    }
+    const duplicate = () =>
+      new HttpError(
+        409,
+        "trace_session_exists",
+        `This Agent already has a Session with id ${sessionId}; a duplicate Trace cannot be imported.`,
+      );
+    if ((await this.locateAll(projectId, agentId, sessionId)).length > 0) throw duplicate();
+    const ts = Date.parse(first.timestamp);
+    const date = formatLocalDate(Number.isNaN(ts) ? new Date() : new Date(ts));
+    const index = 1;
+    const dir = path.join(tracesDir(this.root, projectId, agentId), date);
+    await fs.mkdir(dir, { recursive: true });
+    const file = path.join(dir, `${sessionId}_${String(index).padStart(3, "0")}.jsonl`);
+    try {
+      // Normalize to exactly one trailing newline (the JSONL convention the writer
+      // follows). `wx` closes the check-then-write race: two concurrent imports of the
+      // same new session id both pass the locateAll check, but only one can create the
+      // file — the loser's EEXIST maps to the same 409 as the pre-check.
+      await fs.writeFile(file, content.replace(/\n+$/, "") + "\n", {
+        encoding: "utf8",
+        flag: "wx",
+      });
+    } catch (err) {
+      if ((err as NodeJS.ErrnoException).code === "EEXIST") throw duplicate();
+      throw err;
+    }
+    return { sessionId, index, date };
   }
 }