Evidence and method

This edition is grounded in the supplied 2026-08-29 source snapshot, complete public example files and a recorded completed verification report.

Repository citations throughout refer to that snapshot. They are not links to an assumed upstream commit. The installed custom host can differ from a published npm package or upstream source with a similar version string.

Recorded completed checks

The supplied report records:

• 312 passing contract tests
• 22 test files
• 1,039 assertions
• 0 failed tests
• Bun 1.3.14
• Host reported as omp/18.0.7
• Strict typecheck of all supplied public example TypeScript files
• 44 passing isolated example scenarios
• Two resolved review findings

The two recorded corrections were:

1. Permission revocation: an in-flight Review Desk dialog now gets aborted and generation-invalidated; a late positive RPC response cannot recreate the grant.
2. Binding lifetime: Field Notes is accurately described as factory-local. newSession() and switchSession() reuse its closures; a new binding starts fresh.

Exact contract-test command recorded

The following is the completed command from the supplied report. It is also a reproduction recipe for a matching installed source checkout—not a command available inside the example ZIP alone.

Terminal shell—recorded repository-root test command:

bun test \
  packages/coding-agent/test/extensions-runner.test.ts \
  packages/coding-agent/test/extensions-discovery.test.ts \
  packages/coding-agent/test/extension-delivery.test.ts \
  packages/coding-agent/test/extension-delivery-lifecycle.test.ts \
  packages/coding-agent/test/extension-provider-registration-rollback.test.ts \
  packages/coding-agent/test/extension-prepared-rebind.test.ts \
  packages/coding-agent/test/extension-flag-dispatch.test.ts \
  packages/coding-agent/test/extension-flag-initial-message.test.ts \
  packages/coding-agent/test/cli-explicit-extension-isolation.test.ts \
  packages/coding-agent/test/plugin-extensions-discovery.test.ts \
  packages/coding-agent/test/rpc-extension-ui.test.ts \
  packages/coding-agent/test/sdk-file-write-fallback-extension.test.ts \
  packages/coding-agent/test/sdk-extensions-per-session-binding.test.ts \
  packages/coding-agent/test/sdk-preloaded-extensions-isolation.test.ts \
  packages/coding-agent/test/sdk-restricted-extension-provider.test.ts \
  packages/coding-agent/test/extension-context-project-trust.test.ts \
  packages/coding-agent/test/extension-workspace-package-resolution.test.ts \
  packages/coding-agent/test/issue-4919-extension-autocomplete-provider.test.ts \
  packages/coding-agent/test/extensibility/ext-model-query.test.ts \
  packages/coding-agent/test/discovery/disabled-extensions.test.ts \
  packages/coding-agent/test/acp-agent.test.ts \
  packages/coding-agent/test/status-text-sanitization.test.ts

The strict public-example typecheck used tsgo through a separate validation workspace’s bun check command. The downloadable Package Lab manifest does not declare a check script. Do not assume running bun check in an arbitrary extracted directory reproduces that validation configuration.

What the observations establish

The example scenarios used actual production components where named:

• discovery and module loading;
• factory binding and prepared rebinding;
• runner dispatch and tool adapters;
• real JSONL session storage;
• real SDK construction;
• real RPC request/response streams;
• real TUI controller, focus dispatch and a terminal emulator;
• real renderer width/sanitization behavior.

Seed Desk’s confirmation responses were simulated at the UI seam. Review Desk’s native check used a surrounding mode fixture. Some existing lifecycle contract tests used mock models to test scheduling and consumption.

These distinctions matter. A test can exercise a real coordinator while deliberately replacing the provider.

What is not claimed

The supplied proof does not establish:

• live provider inference or OAuth against a real account;
• actual package installation, registry publication or marketplace deployment;
• a real elevated file broker;
• physical-terminal visual correctness across terminals;
• full Seed Desk autocomplete/Enter smoke;
• arbitrary remote-client accessibility;
• browser/UI publication verification for this workbook;
• complete-repository test coverage;
• cross-process reservation or delivery coordination.

The newly authored exercises in this manuscript are source-backed teaching code, not additions to the supplied completed-check totals. No new execution is claimed during manuscript authoring.

Material prerequisites and missing context

Some outcomes necessarily require evidence outside this bundle:

• A real provider needs its actual endpoint, auth flow and transport behavior.
• A privileged file fallback needs a real host broker and filesystem policy.
• A remote UI needs a client that implements the negotiated dialogs and cancellation behavior.
• Declarative theme creation needs the matching host’s theme-file schema.
• Standalone shell/script-tool protocols should be checked in their own loader implementation rather than inferred from discovery metadata.
• Exact hot-reload behavior depends on the frontend path that performs reload, not only on the module loader’s import support.

Where public types or older prose disagree with current code, this workbook uses the narrower implementation-backed behavior: RPC can have semantic UI, command handlers do not automatically inherit event timeouts, ctx.reload() is not promised to rebind factories, and metadata discovery is not execution.

Source families used

The principal reference locations are:

• packages/coding-agent/src/extensibility/extensions/types.ts
• packages/coding-agent/src/extensibility/extensions/loader.ts
• packages/coding-agent/src/extensibility/extensions/runner.ts
• packages/coding-agent/src/extensibility/extensions/wrapper.ts
• packages/coding-agent/src/extensibility/extensions/model-api.ts
• packages/coding-agent/src/extensibility/extensions/managed-timers.ts
• packages/coding-agent/src/session/agent-session.ts
• packages/coding-agent/src/session/session-manager.ts
• packages/coding-agent/src/session/extension-delivery.ts
• packages/coding-agent/src/sdk.ts
• packages/coding-agent/src/main.ts
• packages/coding-agent/src/discovery/builtin.ts
• packages/coding-agent/src/discovery/helpers.ts
• packages/coding-agent/src/discovery/gemini.ts
• packages/coding-agent/src/extensibility/plugins/loader.ts
• packages/coding-agent/src/extensibility/plugins/manager.ts
• packages/coding-agent/src/config/model-registry.ts
• packages/coding-agent/src/modes/controllers/extension-ui-controller.ts
• packages/coding-agent/src/modes/rpc/rpc-mode.ts
• packages/coding-agent/src/modes/acp/acp-agent.ts
• packages/coding-agent/src/tools/file-write-fallback.ts
• packages/tui/src/components/composer/types.ts

The public examples are available through the complete ZIP and the individual file links in their chapters. Private runners, private state, credentials and local proof artifacts are not part of those downloads.

The process to carry forward is simple:

Choose the smallest appropriate surface. Give humans and models explicit contracts. Make state lifetimes visible. Test the real boundary that matters. Distribute only what another reader can inspect, operate and verify.