Method writePartial

src/node/services/historyService.ts:1178–1202

* Write a partial message to disk.

(workspaceId: string, message: MuxMessage)

   * Write a partial message to disk.
   */
  async writePartial(workspaceId: string, message: MuxMessage): Promise<Result<void>> {
    return this.fileLocks.withLock(workspaceId, async () => {
      try {
        const workspaceDir = this.config.getSessionDir(workspaceId);
        await ensurePrivateDir(workspaceDir);
        const partialPath = this.getPartialPath(workspaceId);

        const partialMessage: MuxMessage = {
          ...message,
          metadata: {
            ...message.metadata,
            partial: true,
          },
        };

        // Atomic write: writes to temp file then renames, preventing corruption
        // if app crashes mid-write (prevents "Unexpected end of JSON input" on read)
        await writeFileAtomic(partialPath, JSON.stringify(partialMessage, null, 2));
        return Ok(undefined);
      } catch (error) {
        const errorMessage = getErrorMessage(error);
        return Err(`Failed to write partial: ${errorMessage}`);
      }
    });
  }

  /**
   * Delete the partial message file for a workspace.