feat(sdk): restore transform callback with placeholder context

[mishushakov]

Summary

• Reintroduces the transform callback variant for SandboxNetworkRule (JS + Python): in addition to a static { headers: ... } object, transform can be a function receiving a typed SandboxNetworkTransformContext whose fields (sandboxId, teamId, executionId, identity.jwt / sandbox_id, team_id, execution_id, identity.jwt) are literal placeholder strings (${e2b.sandboxId}, etc.). The callback is invoked at sandbox-creation time; the resolved object — with placeholders intact — goes on the wire, and the egress proxy substitutes them per request.
• Exports SandboxNetworkTransformContext from both SDKs.
• Stacked on top of feat(sdk): support structured network rules with per-host transforms #1286, which ships only the static transform shape. Implemented as a straight revert of the stripping commit so the diff is small and the two PRs land cleanly in order.
• Placeholder-resolution contract tests (transform callback resolves sandboxId placeholder in JS, test_transform_callback_resolves_sandbox_id in Python sync + async) are restored but left commented out / disabled until the proxy-side placeholder resolution ships.

Example — inject the sandbox's identity JWT (resolved per request)

await Sandbox.create({
  network: {
    allowOut: ({ rules }) => [...rules.keys()],
    rules: {
      'api.internal.example.com': [
        {
          transform: ({ identity, sandboxId }) => ({
            headers: {
              Authorization: `Bearer ${identity.jwt}`,
              'X-Sandbox-Id': sandboxId,
            },
          }),
        },
      ],
    },
  },
})

Sandbox(
    network={
        "allow_out": lambda ctx: list(ctx.rules.keys()),
        "rules": {
            "api.internal.example.com": [
                {
                    "transform": lambda ctx: {
                        "headers": {
                            "Authorization": f"Bearer {ctx.identity.jwt}",
                            "X-Sandbox-Id": ctx.sandbox_id,
                        },
                    },
                },
            ],
        },
    },
)

Notes

• Callbacks run client-side at create-time; the SDK never resolves the placeholders itself. The wire payload contains the literal ${e2b.*} strings.
• Depends on egress-proxy support for ${e2b.sandboxId}, ${e2b.teamId}, ${e2b.executionId}, ${e2b.identity.jwt} substitution before the disabled tests can be re-enabled.

Test plan

• CI green (typecheck/lint/format on both SDKs)
• Once proxy placeholder substitution ships, re-enable transform callback resolves sandboxId placeholder (JS) and test_transform_callback_resolves_sandbox_id (Python sync + async) and verify end-to-end against httpbin.e2b.team

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Latest commit: 156c0a9

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[cursor]

PR Summary

Medium Risk
Adds a new callback path in network rule serialization in both JS and Python; incorrect transforms or unexpected placeholder usage could affect egress request behavior. Proxy-side placeholder substitution is not enforced/tested here, increasing integration risk.

Overview
Reintroduces SandboxNetworkRule.transform as a callable in the JS and Python SDKs, but the callback only receives frozen literal placeholder strings and the result is sent to the API without validation. The end-to-end placeholder-resolution tests are present but commented out, so the new callback behavior is not exercised in CI.

^{Reviewed by Cursor Bugbot for commit 156c0a9. Bugbot is set up for automated code reviews on this repo. Configure here.}

[github-actions]

Package Artifacts

Built from 20f08c4. Download artifacts from this workflow run.

JS SDK (e2b@2.19.2-mishushakov-network-transform-callback.0):

npm install ./e2b-2.19.2-mishushakov-network-transform-callback.0.tgz

CLI (@e2b/cli@2.10.1-mishushakov-network-transform-callback.0):

npm install ./e2b-cli-2.10.1-mishushakov-network-transform-callback.0.tgz

Python SDK (e2b==2.20.1+mishushakov-network-transform-callback):

pip install ./e2b-2.20.1+mishushakov.network.transform.callback-py3-none-any.whl