[martijnwalraven]

The transform inserts its runtime import and generated validators at offset zero of a module. Two kinds of module break on that:

• A module that begins with a directive, such as "use client" in a Next.js app, loses it from the directive prologue once an import sits above it, so the framework no longer treats the module as a client component. The symptom in Next.js 16 is a decorated class in a "use client" file compiling as a server module.
• A module that begins with a hashbang does not parse after the insert ('#!' can only be used at the start of a file).

This moves the insert to after the hashbang and after the last directive of the prologue, in preludeEdit. Nothing else in the transform changes.

Tested with three cases in transform-module.test.ts, each parsing the output: a prologue of two directives after a comment, a hashbang alone, and a hashbang followed by directives; a string literal after an import is left where it is, since it is no directive. Found while running the transform under Turbopack in a Next.js 16.3.6 app, where the "use client" case showed up first.

Changeset: patch for capnweb-validate.

[changeset-bot]

🦋 Changeset detected

Latest commit: 5079f8c

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
capnweb-validate	Patch

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[martijnwalraven]

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[ndisidore]

@clanky-the-clanker review this

[clanky-the-clanker]

✅ Approved — No issues found. preludeEdit correctly moves the inserted import and validators after the hashbang and the directive prologue, and the new tests parse the transformed output.

_{The decision is advisory: this comment never approves, blocks or requests changes on the pull request.}

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✅ All checks passed

📋 Code Quality: ✅ LGTM

I found no problems in preludeEdit or its tests.

• Where the insert goes: preludeEdit places the prelude after the hashbang (ts.getShebang) and after the last string-literal expression statement at the top of the module. The scan stops at the first statement that isn't a plain string literal. That means a string literal after an import is left where it is, and so are template literals and parenthesized strings, which is correct because none of them are directives.
• Hashbang: ts.getShebang returns the hashbang line without its trailing newline. The inserted text starts with \n, so the hashbang stays alone on line 1.
• No prologue: A module with no hashbang and no directives is still edited at offset 0, so that case behaves exactly as before.
• Tests: The new tests cover directives after a comment, a hashbang alone, and a hashbang followed by directives. Each one checks that the output parses and that the directives and the runtime import come in the right order.

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📝 Documentation: ✅ LGTM

The changeset entry and the new code comment both describe the behaviour change accurately.

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_{Reviewed commit: 5079f8c8}