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feat(cloudflare): Instrument Agents automatically - #22727
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size-limit report 📦
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andreiborza
commented
Jul 28, 2026
What do you mean we run with v18 locally? Why can't we bump now that we're on v11? |
JPeer264
commented
Jul 28, 2026
Because I need to backport that PR. We can change that anytime now ofc |
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8d6a511Compare| // its base-class chain tells the two apart. Detection walks the module graph (base classes | ||
| // usually live in their own file), so it is limited to the configured DO classes. |
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q: Does that constraint really hold true? I wouldn't be surprised if someone has several classes in one file. Or am I misunderstanding?
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By definition all the classes are in one file, it is just the question if they are defined in the main entrypoint or in other files.
| const code = stripComments(rawCode); | ||
| const shape = emptyShape(); | ||
| // `class X extends Y {` / `class X<T> extends Y<T> {`, optionally exported and/or abstract. |
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What about cases where generics extend, e.g. class X<T extends S> extends Y<T extends Z>?
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True. I'm sure there are more edge cases which we didn't think of just yet.
Added in facc163
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| const CLASS_RE = /\b(?:export\s+(?:default\s+)?)?(?:abstract\s+)?class\s+([A-Za-z_$][\w$]*)([^{]*)\{/g; | ||
| for (const match of code.matchAll(CLASS_RE)) { |
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Bug: The CLASS_RE regex in shapeFromSource() fails to detect anonymous classes like export default class extends Agent {}, causing agent detection to fail for those modules.
Severity: MEDIUM
Suggested Fix
Modify the CLASS_RE regex to make the class name capture group optional. This will allow it to correctly match and parse anonymous default exported classes.
Prompt for AI Agent
Review the code at the location below. A potential bug has been identified by an AI
agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's
not valid.
Location: packages/cloudflare/src/vite/moduleShape.ts#L213-L214
Potential issue: The regex `CLASS_RE` used in `shapeFromSource()` to parse module shapes
requires a class name to be present after the `class` keyword. This means it will not
match an anonymous default export, such as `export default class extends Agent {}`. When
this pattern is used in a module, `defaultExportIsClass` is not set on the module's
shape. Consequently, when `isAgentBinding()` later checks the module, it incorrectly
determines that the default export is not an agent, leading to a failure in agent
detection. The code seems to anticipate this pattern, as `shapeFromAst()` handles it,
but the regex-based fallback does not.
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Oh this seems relevant too, speaking of edge-cases @JPeer264
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You can't export default a DurableObject.
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Since
instrumentAgentWithSentryis here, it also needs to be supported within the Vite plugin and itsautoInstrumentflag. The issue here is that we need to parse through the imports in order to understand where theAgentimport is coming from. (The majority of the changes are tests again)It could also be that external libraries are extending from
Agent, such asMcpAgent, and these need to be wrapped too. It is super hacky but it works.For the tests I wished to add them in the
cloudflare-integration-tests, but unfortunatelyagentsneeds Node v20+ and locally we run with v18, so it wouldn't work without either bumping Nodejs or making the tests their own package so they are independent.