release(langchain-quickjs): 0.4.0

[github-actions]

Caution

Merging this PR will automatically publish to PyPI and create a GitHub release.

For the full release process, see .github/RELEASING.md.

---

Everything below this line will be the GitHub release body.

---

0.4.0 (2026-06-29)

⚠ BREAKING CHANGES

• quickjs: upgrade to 0.2.0 quickjs-rs (#4067)
• quickjs: add default subagent bridge (#3850)
• quickjs: remove skills_backend (#3843)

Features

• code,quickjs: dynamic subagents UI (#4221) (10bcba2)
• quickjs: add default subagent bridge (#3850) (85fd7c2)
• quickjs: add REPL persistence modes (#3557) (0cda6f3)
• quickjs: prompt tuning on task global (#4066) (a47696f)
• quickjs: upgrade to 0.2.0 quickjs-rs (#4067) (4ffea88)
• sdk: surface subagents via inherited lc_agent_name projection (e0a1ed2)

Bug Fixes

• quickjs: ensure top-level title on subagent response schemas (#4155) (08f917e)
• quickjs: normalize nested undefined tool args (#3935) (1b461a0)
• quickjs: persist top-level JS declarations across evals (#4147) (7574fea)
• quickjs: ptc tools in tools namespace are rendered without prepended tools. in system prompt and task as ptc duplicated task global (#4075) (014a903)
• quickjs: remove skills_backend (#3843) (1159e50)
• quickjs: swarm subagent doesn't allow configuring middleware (#3757) (3394a9d)

---

Everything above this line will be the GitHub release body.

---

Note

A New Contributors section is appended to the GitHub release notes automatically at publish time (see Release Pipeline, step 2).