Add Rust model allowlist support on pinned SDK base

[jpbufe3]

Integrations pinned to SDK commit c672e716473da0be4da7ad807df8d21259623640 need the Rust model allowlist contract without pulling in later unrelated SDK changes. This compatibility PR ports only that surface onto the exact pinned base.

Summary

• Add optional allowed_models fields and fluent builders to SessionConfig and ResumeSessionConfig, serialized as allowedModels and omitted when unrestricted.
• Add the generated typed session.model.setAllowedModels RPC request/result surface for replacing or clearing a running session's restriction.
• Cover defaults, Debug output, create/resume wire conversion, request serialization, method routing, session ID injection, and typed result deserialization.

The SDK preserves exact caller-provided IDs; the runtime remains responsible for validation, policy intersection, fallback selection, and enforcement across child, sub-agent, Auto, and remote execution paths.

Testing

• COPILOT_SKIP_CLI_DOWNLOAD=1 cargo test --all-features allowed_models
• cargo +nightly-2026-04-14 fmt --check

[Copilot]

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Copilot review overview

Review tier: Lite
Findings: 1

New issues introduced by this change (1)

Severity	Finding
	rust/​src/​wire.rs — The PR contract depends on this field serializing as allowedModels. This currently relies on any…

What changed in this PR

Ports the Rust “model allowlist” contract onto an SDK base pinned to a specific commit, adding config fields and an RPC method to set/clear allowed model IDs without pulling additional SDK changes.

Changes:

• Add allowed_models to SessionConfig and ResumeSessionConfig, including builders and wire conversion.
• Add typed session.model.setAllowedModels RPC method plus request/result types and method constant.
• Add unit/integration tests covering serialization, wire conversion, routing, and result deserialization.

File	Description
rust/​src/​types.rs	Adds allowed_models fields/builders and wires them into create/resume payloads; adds unit tests.
rust/​src/​wire.rs	Adds allowed_models to create/resume wire structs for JSON serialization.
rust/​src/​generated/​api_types.rs	Introduces RPC method constant and request/result types for setAllowedModels.
rust/​src/​generated/​rpc.rs	Adds the session.model.setAllowedModels RPC call surface with sessionId injection.
rust/​tests/​session_test.rs	Adds integration tests for request/response serialization and RPC dispatch.

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[SteveSandersonMS]

Thanks for the contribution! I looked into this and found session.model.setAllowedModels isn't implemented by the shipped Copilot CLI runtime (v1.0.81-11) — calling it against a real session returns -32601 Unhandled method, unlike other session methods (e.g. session.abort) which work fine. The codegen change also hand-injects this method into the schema rather than reading it from the real runtime contract, and it's Rust-only even though model-allowlisting would need to be consistent across all SDK languages.

Could you clarify the plan for landing this in the runtime first? Once the runtime actually implements session.model.setAllowedModels and it shows up in the real api.schema.json, we can regenerate for all six SDKs together (with a real end-to-end test against the runtime, not just mocked dispatch tests) rather than hand-injecting a Rust-only stub here.

I'm moving this to draft for tracking — please mark it ready for review once the runtime side has landed.

[jpbufe3]

Could you clarify the plan for landing this in the runtime first?

Agreed on the sequencing. The runtime implementation is github/copilot-agent-runtime#18943 and is still open; this SDK compatibility branch supports the dependent github/github-app#14584 work and should remain draft until the runtime PR lands.

The shipped runtime returning -32601 is expected until that implementation is merged and released. Once the runtime publishes the canonical api.schema.json, the live RPC should be regenerated from that schema, the temporary Rust-only overlay removed, and broader cross-SDK generation/E2E coverage handled from the real runtime contract before this is marked ready.

[jpbufe3]

https://github.com/github/copilot-agent-runtime/pull/18943has merged and is being staged for prerelease! Reopening for review cc @SteveSandersonMS

[SteveSandersonMS]

Thanks for the update, and glad to see github/copilot-agent-runtime#18943 landed! I re-validated against the newest available runtime build (@github/copilot@1.0.84-1, published 2026-09-04) since that's the most recent CLI/runtime the SDK could actually pull:

• schemas/api.schema.json in that package still has no session.model.setAllowedModels entry and no allowedModels field anywhere.
• I spun up the real copilot --server --stdio binary from that package, created a live session, and called the method directly — same result as before:

  → session.model.setAllowedModels {"sessionId": "<real-id>", "allowedModels": ["gpt-5"]}
  ← {"error": {"code": -32601, "message": "Unhandled method session.model.setAllowedModels"}}
  

That's expected, since the runtime PR merged 2026-09-08, four days after that CLI build was cut — the fix hasn't shipped in any published runtime/CLI package yet ("staged for prerelease" isn't the same as available). The SDK's own codegen still fabricates the schema entry itself (addModelSetAllowedModelsToApiSchema) rather than reading it from a real, shipped api.schema.json, so nothing here would catch drift if the eventual real contract differs from what's hand-coded (field names, error semantics, etc.).

I'd like to hold this in draft until a published @github/copilot release actually contains the runtime change, at which point we should regenerate the Rust types directly from the real schema (dropping addModelSetAllowedModelsToApiSchema) and add a real end-to-end test that exercises session.model.setAllowedModels against that shipped runtime rather than only the mocked mock-server tests. Please re-open once you can point at a published CLI/runtime version where the real schema includes this method — happy to take another look right away at that point.