Embed the coding-agent tracing daemon

[Stephen Belanger (Qard)]

Dependencies

Depends on braintrustdata/braintrust-coding-agent-plugins#1, pinned at commit 3e019e47290318b1332c81311e64647b964c21b8.

That daemon PR in turn depends on braintrustdata/braintrust-sdk-rust#86, pinned at commit d33e806bf6ab9548d37355f6a5098a971ef150aa.

The plugin source cutover is intentionally deferred to stacked braintrustdata/braintrust-coding-agent-plugins#3, which must land only after this daemon is available in a released bt CLI.

Summary

This embeds the shared coding-agent tracing daemon in bt and exposes it as the bt agents command family. bt agents daemon runs the foreground service, while hook, status, and replay provide the integration and diagnostic entry points. The plugin hook shims can therefore use the installed bt executable for daemon lifecycle and transport without shipping another runtime.

bt agents setup codex and bt agents setup claude use the coding agents' own plugin managers to add the official Braintrust marketplaces and install the currently published tracing plugins. Setup also creates the shared tracing settings when needed, enables tracing, and accepts --project for routing. It performs a non-destructive merge: every other setting, including legacy authentication and backend fields needed by currently published plugins, is preserved unchanged. The published plugins can move authentication to the daemon after a bt release containing it is available.

The bt host resolves its normal profile, OAuth, keychain, or API-key credentials for each hook invocation and passes the resulting token, backend URLs, organization, and project to the credential-passive daemon. Hook errors remain fail-open so tracing cannot break a Codex or Claude Code turn.

The daemon is consumed from the exact Git commit of its migration PR rather than through a local path dependency. The integration is rebased on current bt main and preserves the newer top-level update command and command routing introduced there.

CLI regression tests verify the setup, daemon, hook, status, and replay command surface, the hook options, the Codex and Claude plugin-manager invocations, disabled Claude plugin recovery, default and explicit project selection, and preservation of existing metadata and legacy authentication settings. The superseded bt daemon path remains rejected.

Validation

• cargo fmt --check
• cargo check --locked
• cargo test --locked
  • 725 unit tests and all CLI/eval/functions/setup integration suites passed.
• cargo +1.92.0 clippy --locked --all-targets --all-features -- -D warnings
• cargo test --locked --test cli agents_setup_
• Real Claude Code setup in an isolated home:
  • added the official Braintrust marketplace
  • installed trace-claude-code@braintrust-claude-plugin
• Real Codex marketplace listing succeeded in an isolated home. The subsequent marketplace clone was not completed locally because the current published repository is approximately 98 MB and the HTTPS fetch repeatedly stalled.
• Manual isolated lifecycle smoke with the built bt binary:
  • started the embedded tracing service
  • forwarded Codex SessionStart and Stop events through the embedded hook
  • observed the session through the embedded status command
  • verified a redacted two-event journal
  • received /api/project/register, /version, and /logs3 at a local mock Braintrust backend
  • verified emitted root and turn rows, deterministic span IDs, project routing, and braintrust.plugin.codex span-origin metadata

[github-actions]

Latest downloadable build artifacts for this PR commit 3298cdf52986:

• Workflow run: https://github.com/braintrustdata/bt/actions/runs/30556509028
• Download all artifacts (GitHub CLI): gh run download 30556509028 --repo braintrustdata/bt
• Installers are published from main automatically. To publish one for a PR branch, run release-canary manually via workflow_dispatch.

Available artifact names

• artifacts-build-global
• artifacts-build-local-x86_64-apple-darwin
• artifacts-build-local-aarch64-pc-windows-msvc
• artifacts-build-local-x86_64-pc-windows-msvc
• artifacts-build-local-x86_64-unknown-linux-musl
• artifacts-build-local-aarch64-apple-darwin
• artifacts-build-local-x86_64-unknown-linux-gnu
• artifacts-build-local-aarch64-unknown-linux-gnu
• artifacts-plan-dist-manifest
• cargo-dist-cache