feat(compose): AdoptExisting — reattach existing containers on resume

[bilby91]

Adds UpOptions.AdoptExisting: on Up, reuse any existing (project, service) container unconditionally — start it if stopped, attach if running, and never recreate on config-hash drift.

Why: recreation abandons the containers' writable upperdirs and binds fresh anonymous volumes, which is where a workspace's real state lives (postgres/rabbitmq/minio data). The primary's feature-layered image gets a fresh digest every boot, so hash-based reuse can never match on resume; adoption ignores the hash when the caller says the on-disk state is authoritative.

Consumer: crunchloop/dap feat/runtime-state-topology (crunchloop/dap#4865) sets it on session resume. Validated end to end there (2026-08-24, three-leg round trip on kata + NVMe): the same primary container id survived cold boot → cross-node block-level restore → in-place pod restart, with $HOME upperdir state and anonymous-volume postgres rows intact across all three.

dap currently pins this branch's pseudo-version; merging this and tagging v0.4.3 unblocks that PR.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features
  • Added an option to reuse existing service containers even when configuration or image details have changed.
  • Stopped containers are started automatically, while running containers are reused without recreation.
  • Recreate mode continues to force container replacement when explicitly enabled.

[coderabbitai]

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 1e67951 and 0e14b9b.

📒 Files selected for processing (4)

• compose/orchestrator.go
• compose/orchestrator_test.go
• compose/plan.go
• up.go

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📝 Walkthrough

Walkthrough

The compose flow adds AdoptExisting options. When enabled, existing containers are reused and stopped containers are started without hash or image-digest reconciliation. Recreate disables adoption.

Changes

Existing Container Adoption

Layer / File(s)	Summary
Adoption contract and orchestration wiring up.go, compose/plan.go	UpOptions.AdoptExisting and Plan.AdoptExisting define adoption behavior. Native compose orchestration enables it only when Recreate is false.
Container reuse and regression coverage compose/orchestrator.go, compose/orchestrator_test.go	ensureService starts or reattaches existing containers without drift checks when adoption is enabled. Tests cover adoption and default hash-drift recreation.

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

Merge Risk: ⚪ Minimal · up to 0e14b

The change adds opt-in reuse of existing containers during resume, preserving their state instead of recreating them. No actionable merge-blocking risk remains based on the supplied evidence.

Sequence Diagram(s)

sequenceDiagram
  participant UpOptions
  participant ComposePlan
  participant ensureService
  participant Container
  UpOptions->>ComposePlan: Pass AdoptExisting when Recreate is false
  ComposePlan->>ensureService: Provide adoption setting
  ensureService->>Container: Reuse existing container
  alt Container is stopped
    ensureService->>Container: Start container
  else Container is running
    ensureService->>Container: Reattach to container
  end

Loading

Poem

I’m a rabbit with a container plan,
Reusing what already ran.
Stale hashes no longer sway,
Stopped services wake and stay.
Hop, compose, and start the day!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes reattaching existing containers through the new AdoptExisting feature.
Docstring Coverage	✅ Passed	Docstring check was indeterminate for this PR — some files could not be analyzed in time. Not blocking.
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.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/resume-adopt-existing

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