Clone copilot SessionConfig.Tools before appending per-run tools

[PratikDhanave]

What

copySessionConfig did clone := *source, a shallow copy that leaves clone.Tools aliasing the shared provider-held p.cfg.SessionConfig.Tools, and copyResumeSessionConfig assigned Tools: source.Tools directly. Both sessionConfig and resumeSessionConfig then run cfg.Tools = append(cfg.Tools, copilotTools(options)...) per run.

When the user-supplied Tools slice has spare capacity, that append writes the per-run tools into the caller's backing array, and two concurrent runs of the same agent write into the same index — a data race and a corrupted tool list.

The fix clones the slice before appending: clone.Tools = slices.Clone(source.Tools) and Tools: slices.Clone(source.Tools). slices is already imported.

Why

Each run must own its Tools slice so appending per-run tools never mutates the shared session config or another concurrent run. This mirrors the clone-before-append fixes already merged in #529 and #555, keeping copilot session setup consistent with the rest of the port.

Testing

Added copilot_internal_test.go covering both sessionConfig and resumeSessionConfig: a provider whose SessionConfig.Tools has spare capacity is invoked twice with a per-run tool, asserting the shared config is unchanged and that neither returned slice shares a backing array with the shared config or with each other. The tests fail before the fix and pass after. go build ./..., go vet ./provider/copilotprovider/..., and go test ./provider/copilotprovider/... all pass.

[Copilot]

Pull request overview

This PR fixes a concurrency/data-race risk in the Copilot provider’s session configuration building by ensuring each run owns its own SessionConfig.Tools slice before per-run tools are appended.

Changes:

• Clone SessionConfig.Tools in copySessionConfig to avoid aliasing provider-held config state.
• Clone SessionConfig.Tools in copyResumeSessionConfig for the same reason when resuming sessions.
• Add internal tests validating that per-run tool appends do not share backing arrays with the provider config (or across runs).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
provider/copilotprovider/copilot.go	Clones Tools slices in session config copy helpers to prevent shared backing arrays and data races when appending per-run tools.
provider/copilotprovider/copilot_internal_test.go	Adds regression tests ensuring per-run tool appends do not mutate or alias the provider’s shared SessionConfig.Tools backing array.

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[github-actions]

Parity Review: No Cross-Repo Consistency Issues

This PR fixes a data race in two unexported helper functions — copySessionConfig and copyResumeSessionConfig — inside provider/copilotprovider. The changes (slices.Clone before appending per-run tools) are purely internal correctness fixes with no effect on any exported Go API or observable user-facing behavior.

Scope verdict: Out of scope for parity review. No exported identifiers were added, removed, or changed. No user-visible defaults, option shapes, or runtime behaviors were altered.

Label status: No public-api-change label is warranted. The existing parity-approved label correctly reflects this PR.

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