docs: capture Copilot runtime research (#1667)

Author: christso

docs/solutions/best-practices/prefer-copilot-cli-and-replay-over-sdk-for-beta-evals.md

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+---
+title: "Prefer Copilot CLI and replay over Copilot SDK for beta eval runs"
+module: copilot provider runtime
+date: 2026-07-05
+problem_type: best_practice
+component: tooling
+severity: medium
+tags:
+  - copilot
+  - copilot-cli
+  - copilot-sdk
+  - replay
+  - provider-runtime
+  - dogfood
+applies_when:
+  - Choosing the canonical Copilot target for live coding-agent evals
+  - Copilot SDK child-runner starts but returns empty output or hangs
+  - Comparing AgentV against Harbor/Entire-style Copilot integrations
+---
+
+# Prefer Copilot CLI and replay over Copilot SDK for beta eval runs
+
+## Context
+
+AgentV supports coding-agent targets through provider adapters plus normalized run
+artifacts. For Copilot, there are three plausible paths:
+
+- Active execution through `copilot-cli`.
+- Import/replay from recorded Copilot session events.
+- Active execution through `copilot-sdk`.
+
+During `av-t2o5.3`, the SDK child-runner dependency and path issues were fixed and
+live dogfood passed for Pi SDK, Codex SDK, and Claude SDK. Copilot SDK still produced
+an empty result envelope and then hung until timeout, with the full eval reporting a
+`SIGTERM` from the child runner. The earlier TCP transport fix avoided one stdio
+`EPIPE` class, but did not make the SDK path reliable enough to be the canonical beta
+Copilot runtime.
+
+Peer-framework evidence points the same way for eval harnesses:
+
+- Harbor runs Copilot through `copilot --prompt ... --yolo --output-format json` and
+  converts the JSONL output into a trajectory.
+- Entire captures Copilot CLI session events and has Copilot-specific token-validation
+  handling for `~/.copilot/session-state/<session-id>/events.jsonl`.
+- Promptfoo and DeepEval do not expose a Copilot SDK provider in their local clones.
+- Vercel `next-evals-oss` result bundles provide normalized and raw transcripts, not
+  a Copilot SDK execution path.
+
+## Guidance
+
+Use `copilot-cli` and replay/import as the supported Copilot paths for beta evals.
+Keep `copilot-sdk` explicit and experimental until live dogfood shows stable process
+lifecycle, non-empty output, and artifact finalization.
+
+Do not model Copilot replay as a separate `copilot-log` target provider. Record or
+import provider-specific events into AgentV's normalized transcript/cassette format,
+then run graders against that replay source. This avoids one log target per provider
+while preserving raw sidecars for debugging.
+
+## Why This Matters
+
+The eval result is only useful after AgentV writes the normalized transcript, raw
+transcript sidecar, grader artifacts, and run indexes. A provider path that starts but
+hangs after returning an empty envelope can waste live-agent budget and still leave
+unclear artifacts.
+
+CLI plus replay also matches the repo-native model: active runs create filesystem
+artifacts, and later grading can reuse those artifacts without re-running an expensive
+coding agent.
+
+## When to Apply
+
+Prefer this shape for live Copilot evals:
+
+```yaml
+targets:
+  - id: copilot-local
+    provider: copilot-cli
+    config:
+      command: ["copilot"]
+```
+
+Prefer a provider-neutral replay target for grader iteration:
+
+```yaml
+targets:
+  - id: copilot-replay
+    provider: replay
+    transcript: .agentv/transcripts/copilot-session.jsonl
+```
+
+Use `copilot-sdk` only when the task explicitly exercises that provider:
+
+```yaml
+targets:
+  - id: copilot-sdk-experimental
+    provider: copilot-sdk
+```
+
+## Related
+
+- `packages/core/src/evaluation/providers/copilot-sdk.ts` - SDK runtime boundary.
+- `apps/cli/src/commands/import/copilot.ts` - Copilot session import boundary.
+- `docs/solutions/best-practices/prefer-copilot-sdk-tcp-for-owned-runtimes.md` -
+  narrower TCP transport lesson.
+- `docs/solutions/best-practices/prefer-isolated-runtime-boundaries-for-agent-sdk-providers.md`
+  - child-process boundary for SDK providers.