fix(runtime): preserve workspace reuse and SSH streams

[skevetter]

Existing MicroSandbox workspaces could stall during SSH handshakes, lose guest stderr through JSON log parsing, or omit the external runtime binary when the content folder already existed. Reusing an external VM also needed a read-only ownership check so incompatible developer identity or mount-policy changes preserve the VM and return explicit recreation guidance.

Prepare declared binaries for existing content folders, keep guest stderr separate from helper diagnostics, preserve raw binary stdout through the container tunnel, and negotiate ReusePreflight before workspace reuse. Failed initialization preserves records and SSH configuration belonging to an existing same-UID workspace, including when its content directory is missing. Failed source transfer removes only content created by that attempt, so retries prepare it again while existing records and content stay intact. A failed binary download also preserves preexisting managed content; failed first-time preparation cleans up newly created state. For local-folder sources, failed binary preparation removes newly created records and SSH entries while preserving user-owned files, including local sources at the managed content path. Text redaction can retain the last byte of an SSH packet when it matches a secret prefix, stalling the peer; tunnel commands now bypass that text filter while ordinary command output remains redacted.

For external runtimes, refresh creation-time developer identity only when runtime ownership validation is negotiated, retaining prior identity resolution for unsupported runtimes. For supported runtimes, retain image and feature metadata, including older managed workspaces with a structural signature. Preserve unmarked image metadata because its creation-config provenance is ambiguous.

Use published SDK v1.5.2 and external provider v0.1.5. The SDK supervisor reaps only its leased command group so detached MicroSandbox VMM sessions do not block operation cleanup; the provider reports the protocol's stopped state after Stop. The shared built-in/external E2E scenario covers binary SSH streams, separate non-newline stderr and exit status, agent delivery, identity and mount ownership, stop/start, recreation, VM-local data preservation on rejected reuse, and deletion. CI installs checksum-pinned MicroSandbox 0.7.7, requires KVM, and bounds each scenario and job.

Validation: thirteen targeted packages passed race tests with published dependencies; the three affected packages were rerun after the local-folder cleanup fix. Deterministic regressions fail before the raw-stream, unsupported-identity, and existing-state cleanup fixes and pass afterward; ownership tests also cover same-UID reuse without content, UID replacement, untrusted incoming flags, cloning, and non-persistence; interrupted source transfer is retried after removing newly created partial content, including fallback-config recreation, while preexisting content survives; ordinary text redaction and first-time cleanup remain covered. The local agentworkspace suite excludes only its preexisting environment-dependent Docker-discovery test. An unchanged external-host timing assertion passed with the full package on an isolated retry after concurrent testing exceeded its existing wall-clock bound. Published provider binaries passed checksum verification; release CI passed native packaging and real host installation. Strict lint and all pre-commit hooks (including formatting and actionlint) passed. A fresh complete committed local CodeRabbit review covered all 23 PR files with zero findings. Module tidy/verification passed. Both real VM scenarios and all 72 CI jobs passed on the current head. The Windows cancellation test passed on one targeted retry after an intermittent cleanup failure in unchanged code; its successful retry ran both cancellation scenarios. Fresh Greptile scored the current head 5/5 with no new actionable issues. The fresh full remote CodeRabbit review completed with no actionable findings and no retained architecture-level concerns. It covered all 22 selected files; its configured go.sum exclusion is covered by the complete 23-file local review and module verification. All actionable review threads are resolved, and all 23 PR commits have valid GitHub signatures.

This is the lifecycle and ownership baseline. Complete parity, later D5 scenarios, and replacement of the built-in provider remain outside this PR.

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📥 Commits

Reviewing files that changed from the base of the PR and between 4e77d10 and 6b8c1ad.

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⛔ Files ignored due to path filters (1)

• go.sum is excluded by !**/*.sum

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📒 Files selected for processing (22)

• .github/workflows/pr-ci.yml
• THIRD_PARTY_LICENSES.md
• cmd/internal/agentworkspace/binaries_test.go
• cmd/internal/agentworkspace/up.go
• cmd/internal/container_tunnel.go
• cmd/workspace/ssh.go
• e2e/tests/up/provider_microsandbox.go
• go.mod
• pkg/agent/agent.go
• pkg/agent/ownership_test.go
• pkg/client/clientimplementation/workspace_client.go
• pkg/devcontainer/command_test.go
• pkg/devcontainer/reuse_preflight_test.go
• pkg/devcontainer/run.go
• pkg/devcontainer/single.go
• pkg/driver/external/capabilities.go
• pkg/driver/external/lifecycle.go
• pkg/driver/external/reuse_test.go
• pkg/driver/types.go
• pkg/provider/env.go
• pkg/provider/workspace.go
• sites/docs-devsy-sh/content/docs/developing-providers/runtime-protocol.mdx

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📝 Walkthrough

Walkthrough

The changes add optional workspace reuse preflight, expand Microsandbox end-to-end testing, preserve workspace content during preparation failures, and update command output handling.

Changes

Workspace reuse preflight

Layer / File(s)	Summary
Preflight contract and external runtime call pkg/driver/types.go, pkg/driver/external/*, go.mod, THIRD_PARTY_LICENSES.md	Adds the reuse-preflight driver contract and external runtime call. Updates the runtime SDK to v1.5.2.
Runner identity and preflight handling pkg/devcontainer/single.go	Resolves the effective remote user and runs supported preflight before recreation scheduling. A preflight error stops processing before recreation scheduling.
Preflight tests and protocol documentation pkg/devcontainer/reuse_preflight_test.go, pkg/driver/external/reuse_test.go, sites/docs-devsy-sh/content/docs/developing-providers/runtime-protocol.mdx	Adds tests for preflight, identity selection, and creation paths. Documents the optional protocol capability and its responses.

Microsandbox parity testing

Layer / File(s)	Summary
Pinned Microsandbox CI setup .github/workflows/pr-ci.yml, sites/docs-devsy-sh/content/docs/developing-providers/runtime-protocol.mdx	Pins the Linux Microsandbox release, verifies its checksum and KVM access, and sets test and job deadlines. The documentation describes the parity gate.
Provider lifecycle and SSH contract e2e/tests/up/provider_microsandbox.go	Runs lifecycle and ownership checks against the built-in and external providers. Adds checks for identity-change handling, workspace deletion, SSH streams, and exit status.

Workspace initialization and ownership

Layer / File(s)	Summary
Workspace ownership state pkg/provider/workspace.go, pkg/agent/agent.go, pkg/provider/env.go, pkg/agent/ownership_test.go	Records same-UID workspace reuse during initialization, preserves the field when cloning workspace information, and tests ownership handling.
Preparation failure handling and tests cmd/internal/agentworkspace/up.go, cmd/internal/agentworkspace/binaries_test.go, pkg/client/clientimplementation/workspace_client.go	Preserves existing workspace content after preparation failures and cleans up newly created content. Adds an option to retain workspace content during deletion. Tests cover checksums, preservation, cleanup, and retry behavior.

Command output and SSH streams

Layer / File(s)	Summary
Raw stdout and SSH stderr routing pkg/devcontainer/run.go, pkg/devcontainer/command_test.go, cmd/internal/container_tunnel.go, cmd/workspace/ssh.go	Passes RawStdout to the command driver and enables it for tunnel commands. Tests check raw binary output and default redaction. Guest-command stderr and outer SSH helper stderr use separate destinations.

Priority: ⬇️ Low

Estimated code review effort: 4 (Complex) | ~45 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant SingleRunner
  participant ExternalHost
  participant RuntimeDriver
  SingleRunner->>SingleRunner: Resolve effective remote user
  SingleRunner->>ExternalHost: ReusePreflight(workspaceID, remoteUser)
  ExternalHost->>RuntimeDriver: Send workspace-scoped preflight request
  RuntimeDriver-->>ExternalHost: Return preflight result
  ExternalHost-->>SingleRunner: Return error or success

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Merge Risk

Merge Risk: ⚪ Minimal · up to 6b8c1

No identified issue currently blocks merging. The enabled Microsandbox test deadline warrants normal CI monitoring.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 6b8c1

The design checks workspace compatibility before reuse and preserves existing files when setup fails. No new privilege expansion or diagnostic secret exposure was demonstrated, but provider-side enforcement and interrupted setup remain incompletely established.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The assessed changes affect the selected workspace's reuse decision, managed records and content, SSH configuration, and existing tunnel output. Each preflight request names one workspace and remote user; that request scope does not establish confinement of the external runtime's broader authority.

Trust Boundaries and Controls

• observed — The new runner-level raw-output option bypasses stdout text filtering for tunnel protocol transport. The existing external driver still independently redacts stderr, and ordinary command callers leave raw mode disabled. Checked protocol callers keep raw stdout separate from diagnostic writers.
• inferred — The host controls preflight ordering and error propagation, but cannot itself guarantee that a provider implements the advertised check without mutation. The interface specifies that guarantee, and fake-runtime tests check preservation; production ownership and mount-policy enforcement remain unverified in this pass.

Resilience and Maintainability Implications

• inferred — Directory existence is not an atomic ownership claim, but this limitation predates the PR: the base already removed the shared content path on binary-preparation failure and performed broader cleanup on initialization errors. Normal non-platform up acquires a workspace lock before dispatch. Concurrent platform initialization and abrupt termination recovery remain incompletely established rather than supported new findings.

Hardening Proposals

• proposed — Where initialization can run without the host workspace lock, use an atomic per-attempt content claim or equivalent workspace-scoped serialization so failure cleanup cannot remove another initializer's content.

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🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 13.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 30 functions across 18 files. (4 skipped:…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main changes: preserving workspace reuse behavior and SSH stream handling.

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Full details: Docstring Coverage

Explanation

Docstring coverage is 13.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 30 functions across 18 files. (4 skipped: 4 unsupported.)

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[skevetter]

@greptileai review

[greptile-apps]

Confidence Score: 5/5

[High impact] The PR appears safe to merge; no actionable new issue was found.

Summary

This PR preserves workspace state on failed initialization and keeps SSH streams separate from text logs.

• Workspace setup prepares existing content and preserves data it does not own.
• Supported runtimes check ownership before reusing an existing workspace.
• SSH tunnels carry raw stdout and keep guest stderr separate.
• MicroSandbox lifecycle coverage runs against both provider implementations.

The earlier, unnumbered source-retry finding is addressed: newly created partial content is removed while reused records and SSH settings remain intact.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart TD
  A[Initialize workspace] --> B{Same UID record exists?}
  B -->|Yes| C[Preserve reused records on failure]
  B -->|No| D[Track newly created records]
  C --> E[Prepare binaries and source]
  D --> E
  E -->|Source fails| F[Remove only newly created content]
  E -->|Success| G{Existing VM and reuse supported?}
  G -->|Yes| H[ReusePreflight]
  H -->|Rejected| I[Return recreation guidance; keep VM]
  H -->|Accepted| J[Reuse workspace]
  G -->|No| K[Follow existing creation or reuse path]

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_{Reviews (6) · Last reviewed commit: "fix(workspace): clean failed local-sourc..." · Reviewed by Greptile}

[mergify]

This pull request does not currently match the merge queue conditions, so it cannot be queued from here. The box comes back if it matches again.

[skevetter]

The retained security architecture finding about initialization cleanup was valid and is fixed in f618d39. Binary preparation failures for preexisting content now retain their cause through a typed error that prevents the enclosing Up initialization handler from deleting workspace state. The regression exercises real source preparation and the destructive error handler using managed workspace records, content and SSH configuration: it failed before the fix when workspace.json was deleted, and now verifies preservation. First-time failures still remove newly initialized state. Race tests, strict lint, all pre-commit hooks and module verification pass.

The concurrency hardening proposal is an assurance limitation rather than an observed bypass. Published MicroSandbox ReusePreflight takes the context-aware lifecycle gate, performs only Find, and has state/label preservation and cancellation tests. Preflight is a read-only compatibility check for the Up reuse path; this PR does not claim universal SSH authorization or a cross-RPC transaction.

The docstring coverage warning includes private helpers and tests; exported contracts are documented, and adding comments that restate these implementations would not improve their clarity. CodeRabbit's configured path filter excludes go.sum; the complete local review includes it and module verification validates the dependency checksums. Final-head CI and fresh remote reviews are required after this fix before merge.

The fresh local review's suggestion to route runInteractiveTunnelSession's Exec stderr to its callback argument conflates the SSH transport with the inner guest session. Exec launches internal ssh-server; that outer helper's stderr is structured diagnostics and belongs in params.writer. machine.StartSSHSession separately passes the raw os.Stderr destination to RunSSHSession, whose wireSessionStdio receives guest stderr through the inner SSH channel. The actual built-in and external VM tests verify non-newline guest stderr and exit 23. Changing the outer callback would mix helper diagnostics into user output, so that suggestion requires no code change.

[skevetter]

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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @cmd/internal/agentworkspace/up.go:
- Around line 248-251: Propagate whether the workspace record was reused from
the same-UID reuse decision through initialization; do not add a nonexistent
field to AgentWorkspaceInfo or use ContentFolder existence as a proxy for
ownership. Update the error path around downloadWorkspaceBinaries and
handleInitError so this failure preserves reused workspace records and SSH
configuration, while newly created workspaces retain the existing cleanup
behavior.

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• cmd/internal/agentworkspace/binaries_test.go
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Review comments at @cmd/internal/agentworkspace/up.go:
- Line 622: Track whether the content folder existed before `InitContentFolder`
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• Run ID: e586502b-d930-4798-a64b-78f59cfa7564

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⛔ Files ignored due to path filters (1)

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📒 Files selected for processing (21)

• .github/workflows/pr-ci.yml
• THIRD_PARTY_LICENSES.md
• cmd/internal/agentworkspace/binaries_test.go
• cmd/internal/agentworkspace/up.go
• cmd/internal/container_tunnel.go
• cmd/workspace/ssh.go
• e2e/tests/up/provider_microsandbox.go
• go.mod
• pkg/agent/agent.go
• pkg/agent/ownership_test.go
• pkg/devcontainer/command_test.go
• pkg/devcontainer/reuse_preflight_test.go
• pkg/devcontainer/run.go
• pkg/devcontainer/single.go
• pkg/driver/external/capabilities.go
• pkg/driver/external/lifecycle.go
• pkg/driver/external/reuse_test.go
• pkg/driver/types.go
• pkg/provider/env.go
• pkg/provider/workspace.go
• sites/docs-devsy-sh/content/docs/developing-providers/runtime-protocol.mdx

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Inline comments:
Review comments at @cmd/internal/agentworkspace/up.go:
- Around line 267-285: Update the new-workspace error handling around
downloadWorkspaceBinaries and handleInitError so an existing
Workspace.Source.LocalFolder failure removes the newly created workspace record
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local folder. Preserve the existing cleanup protection for workspaces that
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📒 Files selected for processing (21)

• .github/workflows/pr-ci.yml
• THIRD_PARTY_LICENSES.md
• cmd/internal/agentworkspace/binaries_test.go
• cmd/internal/agentworkspace/up.go
• cmd/internal/container_tunnel.go
• cmd/workspace/ssh.go
• e2e/tests/up/provider_microsandbox.go
• go.mod
• pkg/agent/agent.go
• pkg/agent/ownership_test.go
• pkg/devcontainer/command_test.go
• pkg/devcontainer/reuse_preflight_test.go
• pkg/devcontainer/run.go
• pkg/devcontainer/single.go
• pkg/driver/external/capabilities.go
• pkg/driver/external/lifecycle.go
• pkg/driver/external/reuse_test.go
• pkg/driver/types.go
• pkg/provider/env.go
• pkg/provider/workspace.go
• sites/docs-devsy-sh/content/docs/developing-providers/runtime-protocol.mdx

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