fix: add tsup config for SDK and bump version to 1.6.0

[KMKoushik]

Summary

• Fix SDK build by moving tsup CLI options to a config file (--noExternal is not a valid CLI option)
• Add tsup.config.ts for proper build configuration
• Bump SDK version from 1.5.7 to 1.6.0

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Summary by cubic

Fixes the SDK build by moving tsup options into tsup.config.ts and bundling @usesend/lib correctly. Bumps the SDK version to 1.6.0.

• Bug Fixes
  • Use noExternal: ["@usesend/lib"] in tsup.config.ts to prevent externalization issues.
  • Enable clean builds and replace CLI flags with a config; build script is now just "tsup".

^{Written for commit ca22d09. Summary will update on new commits.}

Summary by CodeRabbit

Release Notes

• Chores
  • Released SDK version 1.6.0
  • Optimized build process configuration

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Project	Deployment	Review	Updated (UTC)
unsend-marketing	Ready	Preview, Comment	Jan 18, 2026 10:02am

[coderabbitai]

Walkthrough

The change involves refactoring the SDK package's build setup. The version is bumped from 1.5.7 to 1.6.0. The build script in package.json is simplified from a multi-step command with explicit tsup parameters to a single "tsup" invocation. This is accompanied by the creation of a new tsup.config.ts configuration file that specifies the build parameters previously included in the script, including the entry point, output formats (esm and cjs), declaration file generation, and dependency handling.

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes both main changes: adding a tsup config file for the SDK and bumping the version to 1.6.0, which aligns with the changeset and PR objectives.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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[cloudflare-workers-and-pages]

Deploying usesend with    Cloudflare Pages

Latest commit:	ca22d09
Status:	✅  Deploy successful!
Preview URL:	https://d15c7a3b.usesend.pages.dev
Branch Preview URL:	https://fix-sdk-tsup-config.usesend.pages.dev

View logs

[cubic-dev-ai]

No issues found across 2 files