feat(e2b): carry template home on runtime handles

[khaliqgant]

Part of the exact E2B fleet path. Static gates and cross-repo review are recorded by Relayflow e2b-live-fleet-0901. Live dev proof follows merge and deployment; this PR does not claim production activation.

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Summary by cubic

Carries the template's home directory onto E2B runtime handles so callers no longer need to pass a home dir per launch or lookup, and bumps @agent-relay/sandbox to 0.1.12.

• Adds a defaultHomeDir runtime option that launch and lookup handles now inherit.
• Blank per-call homeDir overrides fall back to the default instead of erasing it.
• Creating a runtime with an explicitly blank defaultHomeDir throws an error.
• Records the completed release trajectory for the 0.1.12 publish.

^{Written for commit 5061e48. Summary will update on new commits.}

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-01T08:23:13.818199Z	175a746	PR opened

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Reviewing files that changed from the base of the PR and between 1455ce7 and 5061e48.

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• package-lock.json is excluded by !**/package-lock.json

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• .agentworkforce/trajectories/completed/2026-09/traj_h8qiliylqnav/summary.md
• .agentworkforce/trajectories/completed/2026-09/traj_h8qiliylqnav/trajectory.json
• src/e2b/runtime.test.ts

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📝 Walkthrough

Walkthrough

The E2B runtime adds a validated defaultHomeDir option. Blank home directory overrides now fall back to this default across launch, attach, and lookup paths. Tests cover validation and propagation. The package version changes to 0.1.12.

Changes

Default home directory

Layer / File(s)	Summary
Runtime default contract src/e2b/runtime.ts, src/e2b/runtime.test.ts	E2BSandboxRuntimeOptions supports defaultHomeDir. The runtime trims and validates the value. Tests cover blank configuration and helper support.
Home directory resolution and handle propagation src/e2b/runtime.ts, src/e2b/runtime.test.ts, package.json	Launch, attach, and lookup paths resolve blank values to the runtime default. Tests verify handle propagation. The package version changes to 0.1.12.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: 🔵 Low · up to 1455c

This change centralizes the home directory used by launched, attached, and looked-up sandbox handles, but an attached or discovered sandbox could receive a default that does not match its actual environment and cause home-relative operations to use the wrong path. The PR is mergeable with explicit owner awareness or follow-up to validate the default for attached and looked-up sandboxes.

Poem

A rabbit reads each line,
The patch grows clear beneath the moon,
Small changes hop in place,
Tests guard the garden path,
Reviews bloom before the dawn.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 2 files. (1 skipped: 1 …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the primary change: carrying the template home directory onto E2B runtime handles.
Description check	✅ Passed	The description directly explains the defaultHomeDir option, fallback behavior, validation, and version update in the changeset.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 2 files. (1 skipped: 1 unsupported.)

✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch agent/e2b-home-contract-0901

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[cubic-dev-ai]

All reported issues were addressed across 1 file (changes from recent commits).

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[cubic-dev-ai]

All reported issues were addressed

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>