Migrate effect-utils install/setup path from pnpm back to Bun

We have enough investigation now to define the remaining work for switching the repo back from pnpm to bun.

Scope

• replace the current pnpm-based install/setup path with a Bun-based one
• keep the migration focused on the actual blockers and the repo changes required

Main blockers

1. Nested workspace patchedDependencies is still broken upstream

• https://github.com/oven-sh/bun/issues/27894
• https://github.com/oven-sh/bun/issues/13531

This is the remaining hard blocker for direct Bun installs on the current repo shape.

2. Duplicate-package / type-identity issues required stricter internal alignment

• now mitigated in the repo, but should stay part of migration validation
• https://github.com/oven-sh/bun/issues/27847

3. Bun workspaces are still a canary-only path here

Right now Bun installs work only through a manual harness / staged setup. The repo still needs a real generated Bun workspace/install path.

Changes needed

1. Generate Bun-native workspaces

Genie should emit Bun workspaces for the relevant package roots so Bun installs run against real generated manifests rather than a manual harness.

2. Replace per-package install tasks with an aggregate Bun install root

The current per-package install-task model is a poor fit for Bun because multiple overlapping installs clobber each other and duplicate work.

We likely want a generated aggregate package.json from Genie, similar in spirit to tsconfig.all.json, so Bun can install the full workspace closure in one step.

Example shape:

{
  "private": true,
  "workspaces": [
    "packages/@overeng/genie",
    "packages/@overeng/notion-cli",
    "packages/@overeng/utils"
  ]
}

Goal:

• one Bun install step over the aggregate workspace closure
• no n overlapping per-package Bun installs

The exact topology is still being evaluated, but this should be treated as a core migration change.

3. Choose an interim patch strategy

We still need a Bun-compatible workaround for the patch blocker until upstream is fixed.

Most likely options:

• Bun-only local workspace fork
• another Bun-specific staged install strategy

4. Update Bun / Nix install materialization

The builder/install path needs to use the new Bun workspace topology rather than pnpm-oriented staging assumptions.

5. Update devenv task wiring

Tasks should depend on the new aggregate Bun install step instead of per-package pnpm installs where appropriate.

Conceptually, we want to move from this:

pnpm:install:genie
pnpm:install:notion-cli
pnpm:install:utils
...

to something closer to this:

bun:install

with package-local tasks depending on that shared install root when they need JS dependencies.

6. Re-run Bun canaries on the real generated path

Start with:

• genie
• notion-cli
• megarepo
• utils

Then expand to the broader workspace install path once those are green.

Expected file changes

This will likely touch at least these areas:

Genie generation

• genie/internal.ts
• genie/external.ts
• package-level package.json.genie.ts files
• possibly a new aggregate generated manifest alongside tsconfig.all.json.genie.ts

Package metadata / workspace modeling

• packages/@overeng/genie/src/runtime/package-json/mod.ts
• packages/@overeng/genie/src/runtime/package-json/validators/recompose.ts
• packages/@overeng/genie/src/core/workspace.ts
• generated package.json files for Bun-install roots

Devenv task wiring

• devenv.nix
• nix/devenv-modules/tasks/shared/bun.nix
• nix/devenv-modules/tasks/shared/pnpm.nix
• nix/devenv-modules/tasks/shared/ts.nix
• nix/devenv-modules/tasks/shared/lint-oxc.nix
• nix/devenv-modules/tasks/shared/nix-cli.nix

Nix Bun build/install path

• nix/workspace-tools/lib/mk-bun-cli.nix
• nix/workspace-tools/lib/mk-bun-cli/bun-deps.nix
• package-specific Nix build files that currently assume pnpm-oriented install materialization

Documentation / tracking

• context/workarounds/bun-issues.md
• CHANGELOG.md

Done means

• Bun installs work on real generated manifests, not only via a manual harness
• the remaining patch workaround is encoded in the repo, not manual
• the repo has a single Bun-oriented aggregate install path instead of overlapping per-package Bun installs
• pnpm is no longer the default install/setup path

---

_{Filed by an AI assistant on behalf of @schickling}

Start with genie/internal.ts, genie/external.ts, the package-level package.json.genie.ts files, and the package-json workspace modeling files. Trace how generated manifests and devenv tasks currently materialize installs, then run the Bun canaries for genie, notion-cli, megarepo, and utils on the real generated path. Done means generated Bun workspaces, one aggregate install path, an encoded patch workaround, and no default pnpm setup path.