Complete Fast Auto-tier support across SDKs - #2669
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Copilot review overview
🟢 Approval recommended
Functional coverage is comprehensive; only a non-blocking documentation-formatting correction remains.
Review tier: Balanced
Findings: 1
Open (1)
What changed in this PR
Adds complete Fast Auto-tier support across all six SDKs, lifecycle tests, replay fixtures, and documentation.
Changes:
- Exposes and forwards the canonical
fasttier. - Adds deterministic lifecycle and failure-path E2E coverage.
- Documents compatibility and runtime-owned fallback behavior.
| File | Description |
|---|---|
test/snapshots/auto_tier/should_restore_and_override_fast_auto_tier_on_cold_resume.yaml |
Adds cold-resume responses. |
test/snapshots/auto_tier/should_preserve_effective_tier_when_fast_activation_fails.yaml |
Adds activation-failure responses. |
test/snapshots/auto_tier/should_commit_fast_auto_tier_after_successful_turn.yaml |
Adds successful-commit response. |
test/harness/replayingCapiProxy.ts |
Replays ordered /auto responses. |
test/harness/replayingCapiProxy.test.ts |
Tests response ordering and status codes. |
rust/tests/e2e/auto_tier.rs |
Covers Rust Fast lifecycle behavior. |
rust/tests/api_types_test.rs |
Tests Rust Fast serialization. |
rust/src/types.rs |
Documents Fast and tests CAPI forwarding. |
rust/README.md |
Documents Rust Fast usage. |
python/test_event_forward_compatibility.py |
Tests Python Fast events. |
python/test_client.py |
Tests Python request forwarding. |
python/README.md |
Documents Python Fast usage. |
python/e2e/test_auto_tier_e2e.py |
Covers Python Fast lifecycle behavior. |
python/copilot/session.py |
Adds Fast to the public type. |
python/copilot/client.py |
Documents the Fast CAPI option. |
nodejs/test/session-event-types.test.ts |
Tests Node.js Fast event types. |
nodejs/test/e2e/auto_tier.e2e.test.ts |
Covers Node.js Fast lifecycle behavior. |
nodejs/test/client.test.ts |
Tests Node.js Fast forwarding. |
nodejs/README.md |
Documents Node.js Fast usage. |
java/sdk/src/test/java/com/github/copilot/SessionAutoTierSwitchTest.java |
Tests Java Fast switching. |
java/sdk/src/test/java/com/github/copilot/SessionAutoTierEventTest.java |
Tests Java Fast events. |
java/sdk/src/test/java/com/github/copilot/CapiSessionOptionsTest.java |
Tests Java CAPI serialization. |
java/sdk/src/test/java/com/github/copilot/AutoTierIT.java |
Covers Java Fast lifecycle behavior. |
java/sdk/src/main/java/com/github/copilot/rpc/AutoTier.java |
Adds the Java Fast enum value. |
java/README.md |
Documents Java Fast usage. |
go/session_test.go |
Tests Go Fast switching. |
go/session_event_serialization_test.go |
Tests Go Fast events. |
go/README.md |
Documents Go Fast usage. |
go/internal/e2e/auto_tier_e2e_test.go |
Covers Go Fast lifecycle behavior. |
go/client_test.go |
Tests Go CAPI forwarding. |
dotnet/test/Unit/SessionEventSerializationTests.cs |
Tests .NET Fast events. |
dotnet/test/Unit/ClientSessionLifetimeTests.cs |
Tests .NET Fast forwarding. |
dotnet/test/E2E/AutoTierE2ETests.cs |
Covers .NET Fast lifecycle behavior. |
dotnet/README.md |
Documents .NET Fast usage. |
docs/features/session-persistence.md |
Documents Fast persistence semantics. |
CHANGELOG.md |
Records cross-SDK Fast support. |
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Looks good overall. The Fast Auto-tier support seems consistent across all six SDKs, and the E2E coverage and docs updates look solid. I didn’t notice any major issues from the changes.
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stephentoub
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Sep 16, 2026
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Sep 16, 2026
stephentoub
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September 16, 2026 04:20
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Add Fast Auto-tier exposure, contract tests, and lifecycle E2E coverage across the SDKs while preserving runtime-owned eligibility and omitted-tier semantics. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Restrict routing-dependent lifecycle tests to CAPI while retaining direct-provider coverage for the other Auto-tier tests. Apply Python formatting and documentation punctuation fixes. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Address maintainer feedback consistently across feature documentation, SDK READMEs, the changelog, and API comments while preserving routing and runtime-error guidance. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Cross-SDK Consistency Review — PR #2669Reviewed all 35 changed files against the authoritative PR diff ( Findings: no consistency issues. The change is applied uniformly across all six SDKs:
No inline comments needed — API naming follows each language's existing convention for
|
This was referenced Sep 16, 2026
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Why
Fast is now a canonical runtime Auto tier. The SDKs should expose and preserve that value consistently across public APIs, request forwarding, lifecycle events, and documentation without making SDK-side eligibility or fallback decisions.
What changed
/autoresponses with optional status codes.1.0.84-0or later.Out of scope
This does not add recommendation presentation, acceptance, dismissal, deduplication, telemetry, or SDK-side Fast eligibility policy. The SDKs continue to forward runtime errors from older or incompatible Copilot CLI versions instead of downgrading or silently ignoring Fast.
Validation
uv run pytest e2e/test_auto_tier_e2e.py -v~/Documents/testing/complete-auto-tier-support-v2/run-scenario.sh run 01-public-contract-fast --yes~/Documents/testing/complete-auto-tier-support-v2/run-scenario.sh run 02-six-sdk-fast-lifecycle --yes~/Documents/testing/complete-auto-tier-support-v2/run-scenario.sh run 03-consumer-doc-semantics --yes~/Documents/testing/complete-auto-tier-support-v2/run-scenario.sh verify 01-public-contract-fast~/Documents/testing/complete-auto-tier-support-v2/run-scenario.sh verify 02-six-sdk-fast-lifecycle~/Documents/testing/complete-auto-tier-support-v2/run-scenario.sh verify 03-consumer-doc-semanticsgit diff --checkAUTO_V2_ENDPOINT,1.0.84-2, and placeholder Fast-version reference check returned no matches.