Agent prompt: debug and PR alchemy-run/alchemy-effect issue #366

alchemy-issue-366-agent-prompt.md

Agent prompt: fix Alchemy issue #366 and submit the PR

You are a coding agent starting with no assumed prior knowledge of Effect, Alchemy v2, Cloudflare Workers, or Durable Objects. Your job is to learn the relevant codebase conventions, reproduce alchemy-run/alchemy-effect issue #366, fix the root cause in Alchemy, add a regression test at the correct seam, and submit a pull request.

Do not treat this prompt as a substitute for investigation. Use it as a briefing and independently verify every important claim against the current repository source and a reproducible failing signal.

Outcome required

1. Clone the current upstream repository:

   git clone https://github.com/alchemy-run/alchemy-effect.git
   cd alchemy-effect

2. Read and follow the repository's own rules and patterns before editing:

   • README.md
   • AGENTS.md
   • CLAUDE.md
   • https://v2.alchemy.run/llms.txt if network access is available
   • relevant docs/examples under website/src/content/docs/, examples/, and existing Cloudflare Worker/Durable Object tests

3. Read issue #366 and use it as the bug contract:

   • alchemy-run/alchemy-effect#366

4. Build a deterministic repro, diagnose the exact call path, apply the smallest idiomatic fix, run the relevant validation, commit, push a branch/fork as needed, and open a PR that references/closes issue #366.

5. Use Alchemy's PR conventions from AGENTS.md:

   • conventional commit-style PR title,
   • no # / ## headings in the PR body,
   • body written to a file and passed through --body-file,
   • no “Testing” / “Test plan” section in the PR body.

Bug to reproduce

Alchemy's Effect-native Worker fetch surface accepts this shape:

fetch: RpcServer.toHttpEffect(Rpcs).pipe(
  Effect.provide(RpcHandlers),
  Effect.provide(RpcSerialization.layerJsonRpc()),
)

The analogous Durable Object fetch surface appears not to handle it correctly. A Durable Object that returns the same fetch: RpcServer.toHttpEffect(...) constructor Effect does not serve the JSON-RPC request as the Worker equivalent does; in the original reproduction it hung/timed out.

The regression test should pin the desired supported behavior, if that is indeed the intended API after you confirm the issue:

An Effect-native Alchemy Durable Object may expose fetch: RpcServer.toHttpEffect(...) in the same declarative style as an Effect-native Alchemy Worker, and a forwarded JSON-RPC HTTP request receives the expected response.

Do not expand the PR into unrelated native Cloudflare RPC serialization work.

Why this likely matters

Effect RPC (effect/unstable/rpc) deliberately has a constructor/request-handler shape. Confirm this in the installed Effect source/docs when investigating, but the relevant fact is:

RpcServer.toHttpEffect(...)
// Effect that constructs and yields the actual HttpEffect request handler

Alchemy Worker fetch currently accepts both a concrete HttpEffect and an Effect<HttpEffect>. Durable Object fetch appears to treat methods.fetch as a concrete HttpEffect only.

You must verify that hypothesis by reading current source and by a repro. Do not blindly patch based on the prompt.

Code paths to study first

Start by learning Alchemy's Cloudflare runtime architecture from source and examples. These paths are particularly relevant:

Worker fetch path

• packages/alchemy/src/Cloudflare/Workers/Worker.ts
  • find how Worker fetch handlers are registered / served
• packages/alchemy/src/Cloudflare/Workers/HttpServer.ts
  • inspect workersHttpHandler(...)
  • inspect serveWebRequest(...)
• packages/alchemy/src/Http.ts
  • inspect safeHttpEffect(...)
  • understand why it supports HttpEffect | Effect<HttpEffect>

Durable Object fetch path

• packages/alchemy/src/Cloudflare/Workers/DurableObjectNamespace.ts
  • understand Effect-native DO construction and wrapping
• packages/alchemy/src/Cloudflare/Workers/Rpc.ts
  • inspect makeDurableObjectBridge(...)
  • inspect its fetch(request) implementation
  • inspect how returned DO methods and native DO RPC are dispatched

Existing tests and examples

• packages/alchemy/test/Cloudflare/Workers/HttpServer.test.ts
  • existing Effect RPC over Worker HTTP coverage
• packages/alchemy/test/Cloudflare/Workers/Rpc.test.ts
  • existing Worker/DO RPC helper coverage and style
• Cloudflare DO tutorial/docs and examples found by searching for DurableObjectNamespace, fetch:, and RpcServer.toHttpEffect

Read neighboring tests before writing a new one. Follow the repo's testing conventions rather than inventing a new harness.

Current diagnosis to independently verify

The suspected inconsistency is:

Worker fetch normalizes the nested RPC Effect

The Worker serving path runs handlers through something equivalent to:

Http.safeHttpEffect(handler)

safeHttpEffect(...) accepts:

HttpEffect | Effect<HttpEffect>

and flattens it when needed.

Durable Object fetch does not use the same normalization

The Durable Object bridge path appears to do approximately:

const fetch = methods.fetch as HttpEffect<never>
const response = await serveWebRequest(request, fetch).pipe(Effect.runPromise)

If methods.fetch is actually the constructor Effect returned by RpcServer.toHttpEffect(...), the DO bridge hands serveWebRequest(...) the wrong level of Effect. That explains why Worker fetch succeeds but the DO fetch version fails.

A local throwaway prototype confirmed a related fact: explicitly flattening at request time made Effect RPC over DO fetch work:

const makeRpcFetch = RpcServer.toHttpEffect(...)

fetch: Effect.gen(function* () {
  return yield* Effect.flatten(makeRpcFetch)
})

Treat that only as a hypothesis aid. Your PR should fix Alchemy's public behavior at the correct centralized seam, not teach users to write this workaround.

Important non-goals / avoid false leads

Do not mix this issue with native Cloudflare JavaScript RPC payload serialization. A separate fact is that arbitrary rich Effect runtime objects (Schema.Class instances, DateTime.Utc, etc.) are not Cloudflare native RPC structured-clone-safe unless encoded. That is not issue #366 and should not be “fixed” in this PR.

This PR is about DO HTTP fetch handling of RpcServer.toHttpEffect(...) / nested HttpEffect construction, and parity with Worker fetch semantics.

Required diagnosis process

Use a disciplined debug loop:

1. Reproduce first. Create the fastest reliable failing signal that exercises the real failure. Prefer an automated test. If a local Cloudflare/Workerd fixture is required, follow existing Alchemy Cloudflare fixture/test patterns.
2. State ranked hypotheses in your working notes before changing source.
3. Instrument sparingly if needed, with clearly removable debug logs.
4. Fix at the central seam, not in a specific example or workaround.
5. Turn the repro into the regression test if it is at the right seam.
6. Remove all debug logging.

Desired regression assertions

Your regression coverage should prove the fix rather than merely “not time out.” It should assert, as appropriate for the chosen seam:

• Durable Object fetch can be declared directly as:

  fetch: RpcServer.toHttpEffect(Rpcs).pipe(...)

• A JSON-RPC POST forwarded to the DO fetch surface returns HTTP 200.

• The JSON result contains the expected RPC payload.

• If the test schema includes an Effect Schema class input, the Effect RPC handler receives decoded typed data, mirroring existing Worker HTTP Effect RPC tests. Keep this minimal; don't overbuild.

If the best test seam cannot exercise the Cloudflare/DO fetch bridge realistically, explain that in the PR/issue working notes and choose the next closest seam deliberately.

Likely shape of the production fix

This is guidance, not a command. Verify and adapt to repo conventions.

A small fix may be to make the Durable Object fetch bridge normalize methods.fetch with the same HTTP helper Worker fetch uses, so it accepts:

HttpEffect | Effect<HttpEffect>

instead of blindly casting to HttpEffect.

You may also need to update a relevant type such as the DO fetch shape so TypeScript reflects the behavior. Keep typing changes narrow and aligned with existing Worker types.

Do not introduce a duplicate hand-rolled flattening helper if the Worker path already has the right abstraction.

Validation expectations

Run the narrowest tests while iterating, then the repository-required relevant checks per AGENTS.md. At minimum, directly observe exit codes for what you claim passes.

Likely commands to consider, adapting to the exact tests you add:

bun install
bun tsc -b
# focused test command for the affected Cloudflare Workers test file(s)

Use the repo's existing scripts/tests rather than guessing where possible. If full cloud live tests need credentials you do not have, still run all local/type checks available, clearly report what is unverified, and keep the PR narrowly evidenced by a deterministic local regression test if feasible.

PR submission

1. Create a branch with a clear name, e.g.:

   git switch -c fix/do-fetch-http-effect-normalization

2. Commit with a conventional message, e.g.:

   fix(cloudflare): normalize durable object fetch http effects

   Adjust wording to match the final actual fix.

3. Push to your fork/branch as appropriate.

4. Open a PR against alchemy-run/alchemy-effect that references:

   Fixes #366

5. PR body should follow repo rules. Keep it short; prefer a concise code snippet showing the fixed supported shape.

Example body structure (adapt to actual change; do not include a Testing heading):

Durable Object fetch now accepts the same nested HTTP-effect constructor shape that Worker fetch already accepts.

```ts
fetch: RpcServer.toHttpEffect(Rpcs).pipe(
  Effect.provide(RpcHandlers),
  Effect.provide(RpcSerialization.layerJsonRpc()),
)

Fixes #366.

Use `gh pr create --body-file /tmp/pr-body.md` or equivalent, not an inline shell-quoted body.

## Final report back

When done, report:

- the exact root cause with source file/function names,
- the regression test added,
- the fix made,
- every validation command with observed exit code,
- the PR URL.