kandev/docs/specs/workspaces/system-design/worktree-base-refresh.md

status, system, requirements

status	system	requirements
current	workspaces	REQ-WORKSPACES-WORKTREE-BASE-REFRESH-001

Worktree Base Refresh System Design

Purpose and boundaries

The workspace system owns the repository checkout and the worktree base ref. This design keeps host worktrees local-first while remote materialization stays strict.

The task system owns session launch state and error presentation. The integration system owns provider credentials. Executors own their Git transport and remote workspace preparation.

This design does not refresh a valid worktree that Kandev reuses. It does not change Git commands that an agent runs after launch.

Requirement mapping

Acceptance criterion	Design section
AC-WORKSPACES-WORKTREE-BASE-REFRESH-001.1	Refresh policy
AC-WORKSPACES-WORKTREE-BASE-REFRESH-001.2	Refresh policy
AC-WORKSPACES-WORKTREE-BASE-REFRESH-001.3	Local fallback
AC-WORKSPACES-WORKTREE-BASE-REFRESH-001.4	Base-ref selection
AC-WORKSPACES-WORKTREE-BASE-REFRESH-001.5	Base-ref selection
AC-WORKSPACES-WORKTREE-BASE-REFRESH-001.6	Required materialization
AC-WORKSPACES-WORKTREE-BASE-REFRESH-001.7	Multi-repository launch
AC-WORKSPACES-WORKTREE-BASE-REFRESH-001.8	Required materialization
AC-WORKSPACES-WORKTREE-BASE-REFRESH-001.9	Empty remote
AC-WORKSPACES-WORKTREE-BASE-REFRESH-001.10	Failure and recovery
AC-WORKSPACES-WORKTREE-BASE-REFRESH-001.11	Pull-request base reconciliation
AC-WORKSPACES-WORKTREE-BASE-REFRESH-001.12	Pull-request base reconciliation
AC-WORKSPACES-WORKTREE-BASE-REFRESH-001.13	Missing-base fallback
AC-WORKSPACES-WORKTREE-BASE-REFRESH-001.14	Safe refresh diagnostics

Components and responsibilities

• internal/orchestrator/executor resolves repository paths, refresh routes, credentials, and executor capabilities. It also resolves live GitHub pull- request bases through an injected provider seam.
• internal/worktree.Manager verifies local refs, attempts host refresh, and selects the worktree base. Pull-request base refresh remains strict except for the verified missing-remote-ref fallback.
• internal/repoclone.Cloner materializes provider-managed repositories when no user-owned local checkout supplies the branch.
• internal/github.Service reconciles changed pull-request bases through narrow injected interfaces. Provider lookup and task-repository propagation are best-effort.
• internal/agent/runtime/lifecycle stops launch only when no usable base remains.
• The task projection shows bounded warnings and required-materialization errors.

Data and contracts

repositories.pull_before_worktree remains a persisted user policy. No schema change is necessary.

The preparation fields have these contracts:

Field	Contract
PullBeforeWorktree	Kandev attempts remote refresh before local worktree creation.
RemoteSyncHandled	The configured remote route completed a refresh for this checkout.
RefreshRepository	An optional provider refresh for worktree materialization.

PullBeforeWorktree is not a universal admission gate. Local-ref availability determines whether a failed refresh is recoverable.

The task repository's stored base remains the branch-only comparison target and offline launch fallback. An explicit repository-qualified target takes precedence under the proposed amendment below. The GitHub task-PR row tracks the provider observation; polling propagates a changed non-empty base to the matching task repository.

Pull-request base reconciliation

The executor reads the pull-request number from task-repository metadata and the owner and repository name from the repository entity. For GitHub repository rows with a positive pull-request number, it asks an injected resolver for the current base before materialization. A successful non-empty result overrides the launch request only. A missing resolver, lookup error, or empty result keeps the stored base and does not stop launch.

Once the pull-request task reaches Git refresh, its base remains strict for unproven failures. A proven missing remote base can use only the fallback described below.

The GitHub polling service compares the previous TaskPR.BaseBranch with the incoming non-empty base. On change, it updates the task repository whose task and repository IDs match. When more than one association matches, the checkout branch must also match the pull-request head. Update failures are logged and do not fail the authoritative task-PR sync.

Repository-qualified PR bases

This section implements criteria .15 through .19. It qualifies the branch-only lookup and fallback rules above. Delivery is tracked in the fork PR base resolution package.

Identity and provider lookup

ResolveRemoteDefaultBranch retains its origin-default meaning. It cannot resolve a PR base because its input contains no task or provider identity. Do not replace repositories.default_branch with a PR target.

Extend the executor's PRBaseResolver result beyond a string. The proposed result contains the validated PR identity, head identity, target repository, target branch, and optional observed base OID. Reuse models.ComparisonTarget for repository and branch validation. Keep the observed OID transient; it is neither a merge-base nor a replacement for durable branch identity.

Resolve the provider namespace from the exact attachment's existing binding:

1. Use ComparisonTarget.TargetRepository and its change number when present.
2. For RemoteContribution, use its validated canonical change identity. PR URL tasks already attach to the target repository and configure a source remote.
3. Otherwise use an exact linked TaskPR identity, matched to this attachment and checkout branch. A bare PR number is not globally unique.
4. Legacy metadata-only requests can query the attached repository. Accept the response only after its head repository and branch match the attached checkout. For a RemoteContribution, compare the PR head to the validated source repository and require the PR target repository to match the attachment. An ambiguous or mismatched response cannot resolve a qualified PR base.

Never choose the first PR in a task-wide list. Validate current binding ownership before applying a live retarget. Preserve manual comparison selections and historical associations under the existing task-service reconciliation rules.

githubPRBaseResolver in internal/backendapp/orchestrator.go returns a validated target and optional observed base OID. REST uses base.sha and GraphQL uses baseRefOid. The supported gh pr view/list --json field set does not include baseRefOid; GHClient.GetPR reads .base.sha through gh api and keeps PR details usable if that best-effort OID read fails. A lookup failure can retain a valid stored qualified target, but cannot downgrade that target to a bare branch name. A known cross-repository lookup failure or invalid legacy association cannot fall back to a stored branch without a qualified target; ordinary provider outages remain eligible for the existing stored-base rule.

A stored qualified target can materialize its exact branch without a fresh provider snapshot. The fetched commit supplies the current OID. Without a validated target identity, a known cross-repository request remains unresolved. Same-repository offline branch fallback retains criterion .11.

Preparation and materialization

Carry the qualified target through repoInfo, lifecycle launch and preparation requests, and worktree.CreateRequest. Audit their copy and conversion methods, including multi-repository preparation, workspace-only creation, and recreation. Keep checkout-head fetching separate from target-base fetching. A fork-origin checkout must not fetch an upstream PR number from the fork's refs/pull namespace. Use the validated PR host for that ref or the validated head repository/branch.

Before branch-only fallback, select the explicit target when present. Fetch only its target branch into ComparisonTarget.ComparisonRef(). Resolve the resulting commit OID and return it for Git operations. Retain repository/branch identity for metadata and diagnostics; do not persist a hash as BaseBranch.

Reuse the deterministic comparison remote and collision rules from ADR-2026-08-19-repository-qualified-comparison-targets. Extract reusable Git materialization into internal/common/gitbase rather than importing agentctl process code into the backend. Keep typed consumer errors in their existing owners. Agentctl keeps its asynchronous comparison scheduling. The shared primitive only validates and materializes a target through an injected, classified Git runner. It neither schedules work nor chooses fallback policy.

The remote keeps push disabled. A conflicting configured URL is an error. Commands remain bounded and noninteractive under the existing credential route. This repair grants no additional private-repository credential scope.

When a provider OID is supplied, verify that exact commit against the fetched branch snapshot. A mismatch stops required preparation with a stale-observation error. A later retry obtains fresh provider evidence; no automatic merge occurs. Do not fetch an arbitrary unvalidated SHA or overwrite a user branch.

Remote executor materialization must receive the same qualified target before its base-dependent Git operations. Carry the optional contract through the runtime client and agentctl/server/api/workspace_materialize.go. Keep branch labels separate from resolved refs in existing request validation. An ordinary checkout with no qualified target uses the existing route.

Required materialization failure stops new preparation. A valid reused worktree still follows the existing reuse policy. Background comparison failure still leaves working-tree status usable under the platform status contract.

Recovery and persistence

recoverTaskLaunchBranch currently resolves origin and calls the manual UpdateRepositoryBaseBranch operation. That operation can clear a comparison target, even when the branch name is unchanged.

Reject retry_default for a validated cross-repository binding before any repository-default or task-base write. Preserve the binding and error stamp. Use the existing bounded recovery-error envelope. Do not relabel the action or silently treat it as permission to abandon the target. retry_launch can retry the same qualified preparation. An explicit user-selected base branch is marked in task-repository metadata and remains authoritative across provider refreshes. Only an explicit comparison-target association clears that marker; provider sync and recovery cannot replace the manual selection.

Ordinary retry_default still resolves and updates the repository default. Recovery must check the exact attachment and current error stamp. A second attachment or historical PR cannot supply the selected target.

No database migration is required. Existing contribution/comparison bindings remain the durable identity. New OID observations and preparation refs remain transient. Provider retarget persistence stays in the existing reconciler.

Evidence and compatibility

Tests must distinguish identical branch names in two repositories with different commits. Include a fork-only origin, a non-default PR target, linked worktrees, provider retargeting, target fetch errors, remote collisions, and cancellation. Include two PRs with the same number in different namespaces and a mixed task with one valid repository and one unresolved cross-repository base.

Preserve the completed comparison-target and stacked-PR packages. Their old verification results remain historical. New compatibility results belong to this repair's work orders. Issue #3856 owns the separate reconciliation hint.

Refresh policy

If PullBeforeWorktree is false, Kandev uses the selected local base without a remote request.

If PullBeforeWorktree is true, Kandev attempts the configured refresh before new or recreated host worktrees. A valid reusable worktree bypasses this attempt.

The refresh route still follows the task Git credential policy. A host checkout keeps its configured origin and transport. A provider-managed checkout keeps its exact credential scope.

Local fallback

Before refresh, the worktree manager verifies the selected local ref. If that ref exists, refresh is best effort.

Authentication, network, timeout, Git, and missing-remote-ref errors return the selected local ref. The manager emits a bounded warning and does not include raw credential output.

The fallback does not change local or remote refs. It does not push the local branch.

Pull-request base refresh does not use this local fallback. It remains strict for unproven failures and uses only the verified missing-base fallback below.

Base-ref selection

After a successful fetch, the worktree manager compares local base L and remote base R:

Relationship	Start ref	Result
R contains L	R	The worktree includes current remote commits.
L contains R	L	The worktree preserves local-only commits.
Refs diverge	L	The worktree preserves the selected local history and shows a warning.
Ancestry is unknown	L	The worktree preserves the selected local history and shows a warning.

The manager never resets, rebases, merges, removes, or hides either ref during selection.

Required materialization

Remote access is required when Kandev cannot verify a usable local base. This case includes an explicit remote-only ref and an executor that must clone the repository.

If materialization fails, lifecycle stops launch. The task error identifies the repository and uses a bounded failure class.

Provider selection still follows the existing Git credential policy. A managed HTTPS route must not replace an executor-owned SSH route.

Missing-base fallback

A fetch error that explicitly reports a missing remote ref is the only failed fetch eligible for fallback. When the request carries a different non-empty fallback base, the manager fetches that branch through the same non-interactive route and applies the normal containing-ref checks. Success completes sync, uses the fallback ref, and records a warning naming the requested and fallback branches.

If the fallback is absent or its refresh fails, preparation remains failed. A missing requested or fallback remote ref uses missing_remote_ref; auth, network, timeout, cancellation, and other Git failures keep their existing fail-closed classifications.

Empty remote

An authenticated remote with zero refs uses the marked local baseline from the Empty Remote Repository System Design.

This path creates no remote ref during launch. Publication remains an explicit user action.

Multi-repository launch

Each repository resolves its base independently before agent startup. A local fallback counts as a prepared repository.

If one repository needs remote materialization and has no usable base, the whole task stops before agent startup. The error names that repository.

Failure and recovery

• A refresh error with a valid local base produces a warning and continues.
• A missing local and remote base produces a launch error.
• Caller cancellation stops preparation without a fallback worktree.
• A retry repeats remote materialization only when the task still needs it.
• A valid reused worktree does not refresh or materialize its base again.
• A pull-request base refresh failure stops preparation unless the missing remote ref has a separately refreshed configured fallback.
• A pull-request fallback reports the requested and selected branches and uses missing_remote_ref when no usable fallback exists.

Security

Git stays non-interactive. Host refresh uses the host credential route. Provider refresh uses exact task and repository scope.

Warnings contain a failure class, branch name, and repository identity. They do not contain tokens, credential-helper output, or secret URLs.

Observability

The existing sync progress callback reports a running event and then either a completed event or a failed event. A failed event contains the bounded failure class and repository identity. A successful missing-base fallback reports a completed event and records the branch substitution warning on the worktree. Local fallback reports completion with a warning, not a launch error.

Structured logs record repository identity, refresh route, failure class, and selected fallback ref. Logs exclude credential material and raw remote URLs.

Safe refresh diagnostics

AC .14 extends the existing observability contract. manager_git.go captures combined command output, but failure paths retain only coarse reasons or an exit status. Inspect that output in memory and emit fixed diagnostic values. Do not append raw output to logs, returned errors, or progress events.

Keep the existing policy reason separate from a diagnostic-only diagnostic_code. Add an allow-listed classifier in internal/worktree/refresh_diagnostics.go. It recognizes authentication, SSH public-key rejection, SSH host verification, DNS, connection failure, TLS verification, missing remote ref, non-fast-forward rejection, repository access failure, and lock contention. Unknown output maps to unknown. Context cancellation and execution timeout take precedence over text matches. Each code maps to a fixed English explanation. No explanation includes substrings from Git output. Repository access failure does not assert that credentials are invalid, and lock contention does not assert a stale lock.

Emit one structured diagnostic per failed fetch or pull with operation, repository_path, branch, reason, diagnostic_code, detail, and an exit code when available. The local repository path identifies the checkout without reading its remote URL. Existing failure or fallback logs can carry these fields instead of adding a duplicate diagnostic. Cover both required and best-effort paths, including a failed configured fallback branch.

Classification is observational. Do not feed new diagnostic categories into missing-base fallback eligibility or alter syncFailureCause identities. Preserve context errors and current progress/error payloads. Correct the syncFailureCause comment that implies raw output reaches internal logs. No new logging configuration, subprocess, retry, or persistence is required.

Delivery: Recovery diagnostic fixes.

Related decisions

• Local Worktree Refresh Is Best Effort
• Required Worktree Refresh Fails Closed
• Separate GitHub Automation From Task Git Credential Policy
• Provider-Neutral Git Credential Broker