Pydantic AI as an agentic engine

[dsfaccini]

hey guys! @strawgate brought agentic workflows to our attention a couple months ago and we've been
using them since then (https://github.com/pydantic/pydantic-ai/tree/main/.github/workflows, pydantic/pydantic-ai#7211, pydantic/pydantic-ai#7253 (review)).

in parallel we've been running our own handrolled agent that does triage and review in our repo pydantic/pydantic-ai#7235 (comment).

we like agentic workflows and want to keep using them, while also dogfooding our own stack, which
is why we want to build a Pydantic AI based engine pydantic/pydantic-ai-harness#569 following the third-party model in your https://github.github.io/gh-aw/reference/engines/

claude's helping me build it so I'll leave its description below, + some questions we have for you guys so we can make the right choices

thank you for your time and attention!

---

the shape. An owner-maintained engine definition (engine: {id: pydantic-ai, behaviors: ...})
published in pydantic-ai-harness and imported
pinned to a tag, backed by a headless coding-agent CLI installed via runtimes: {uv: {}} +
pre-agent-steps (the aider.md pattern), with secret-strategy: universal-llm-consumer for
auth. Nothing needs to live in your repo or binary -- users import the definition from ours.

built already (pydantic-ai-harness#569):
the engine definition and a smoke workflow, compile-tested:

• a new pydantic-ai engine id imported from a shared definition compiles clean with --strict on
  v0.85.4. we bisected the releases: v0.84.3 still rejects new ids, the Refactoring opencode integration for shared workflows #50145 fix lands in v0.84.4.
  we'll document v0.85.4 as our minimum supported version.
• cross-repo pinned imports (owner/repo/path.md@tag) resolve, SHA-pin, and vendor correctly --
  tag, branch, and bare-SHA refs all work.
• one docs/UX note from testing: the bare-string form (engine: pydantic-ai) errors even when the
  definition is imported -- only the object form (engine: {id: pydantic-ai}) works, and the error
  message doesn't hint at that. cost us a minute; will cost every new user a minute.

being built now: the CLI itself. pydantic-ai-harness ships all the pieces a coding agent needs
(sandboxed filesystem + shell tools, repo context loading, planning, context compaction) but no
console entry point yet -- that's the gap we're closing, designed against your engine contract from
day one: prompt in, one-shot run, exit code out, MCP config consumed from the gateway so safe
outputs flow through the standard safeoutputs server.

three questions where your answers change what we build:

1. install. behaviors.installation.package-manager values other than npm compile clean but
   silently emit no install step. we're fine on the pre-agent-steps path -- but a compile warning
   for non-npm values would save the next Python/Rust engine author a confusing afternoon. want an
   issue/PR for that?
2. logs and metrics. behavior-defined engines get no log parser: no conversation rendering in
   the step summary, and gh aw logs / gh aw audit report zero tokens and turns (AI-credit
   accounting through the proxy still works). we get why -- GitHub Agentic Workflow Engine Enhancement Proposal #20416 scoped declarative log parsing
   out as a non-goal -- but that was before imported engines became the recommended route for third
   parties. is there appetite for a hook here, e.g. a documented streaming-JSONL schema plus
   parse_custom_log.cjs promoted to a real contract? we'd emit whatever schema you standardize,
   and we're happy to contribute the parser.
3. discoverability. once our definition is live and smoke-tested, would you take a link to it
   from the third-party agent guide?
   not asking for a row in the engines table or any support commitment from you -- just a pointer
   for people searching "how do I run X on gh-aw".

whatever shape this takes, we intend to maintain it long-term -- so if any assumption above looks
wrong, tell us now and we'll adjust before we ship :)

[pelikhan]

@copilot allow allow behavior driver parsers to define log parsers.

[pelikhan]

Added log-parser in the latest build.