agentHost: Classify cancelled model call telemetry

[Aaron Munger (amunger)]

What

Declare the SDK-forwarded copilotCli/model_call_cancelled event in the Agent Host telemetry forwarder.

The declaration includes:

• bounded model-call cancellation properties and measurements;
• SDK correlation enrichment;
• restricted repository context supplied by the generic runtime pipeline;
• privacy-safe model and request identifier semantics.

No Agent Host turn behavior or public protocol surface changes.

Why

Part of microsoft/vscode-internalbacklog#8247.

The paired runtime change, github/copilot-agent-runtime#15211, adds per-physical-attempt model_call_cancelled telemetry. The generic SDK callback already forwards runtime telemetry into Microsoft telemetry; this change supplies the required GDPR contract.

Existing agentHost.turnCompleted(result=cancelled) remains the cross-provider turn-cancellation signal. This event instead completes the Copilot runtime model-attempt success/error/cancelled denominator.

Data parity

Analytical signal	Historical source	Agent Host source	Parity	Validation
Cancelled physical model attempts	Copilot Chat response.cancelled	copilotCli/model_call_cancelled	≈	Runtime code + VS Code forwarding test; legacy also counted premature stream closure
Model/API/transport/request/timing/token/request-shape dimensions	Local response payload	SDK-forwarded runtime payload	✅ / ≈	Field classifications match the runtime contract
Turn cancellation	response.cancelled was not a turn event	agentHost.turnCompleted(result=cancelled)	Separate signal	Existing behavior unchanged
TTFT, bytes, Auto selection, suspend/resume	Local measurements	Not emitted	⊗	Omitted rather than populated with placeholders

Query and row implications

• Historical model-attempt queries should filter local rows to agent, subagent, background, and compaction request kinds.
• New Agent Host queries should combine copilotCli/response.success, copilotCli/response.error, and copilotCli/model_call_cancelled.
• agentHost.turnCompleted(result=cancelled) must remain a separate per-turn metric.
• The runtime event is one row per actually dispatched cancelled physical model attempt.

Semantic shifts

Signal	Shift	Impact
Cancellation category	Runtime exposes bounded cancellation sources rather than the legacy mixed cancellation bucket	Queries can slice new rows more precisely; historical comparisons remain approximate
Source attribution	Runtime uses normalized interaction and initiator fields	Historical source values require translation
Request identifiers	Non-UUID caller values are hashed	Correlation remains privacy-safe but representation may differ

Targeted ESLint passes.

[Copilot]

Pull request overview

Adds the GDPR contract and forwarding coverage for cancelled Copilot CLI model-call attempts.

Changes:

• Classifies cancellation properties, measurements, repository context, and correlation fields.
• Adds a focused forwarding unit test.

Show a summary per file

File	Description
copilotGitHubTelemetryForwarder.ts	Declares cancellation telemetry classifications.
copilotGitHubTelemetryForwarder.test.ts	Verifies cancellation event forwarding.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Balanced