Implement proposal 0042 (reserved keys)

[chris-colinsky]

Summary

• Extends the observability §3.4 reserved exact-key-name set from 21 to 24 entries with branch_name, detached, and detached_from_invocation_id. Without reservation, a caller key matching one of these would silently shadow the OA-emitted Langfuse top-level metadata field — same hazard 0041 closed for its 20 names.
• Relocates observation.metadata.detached: true from the detached-side dispatch observation onto the parent-side dispatching observation in the main trace, matching the §8.4.2 row 0042 added (link observation for detached subgraphs; parent fan-out node observation for detached fan-outs).
• Bumps spec pin v0.31.0 → v0.34.0 (absorbs 0038 Gemini wire-format and 0020 sessions as not-yet-implemented). Defers the 10 new Gemini conformance fixtures.
• conformance.toml updates: 0040 not-yet → implemented (shipped in Implement 0040 open-span metadata update #96); 0042 added; 0020 / 0038 added as not-yet.

First of three PRs landing on main for the v0.11.0 release. Follow-on PRs cover proposal 0043 (Langfuse trace.input / trace.output) and proposal 0044 (parallel-branches dispatch span, pending spec acceptance).

Test plan

• uv run pytest tests/ -q — 987 passed, 200 skipped, 0 failed
• uv run pyright src/openarmature — 0 errors
• uv run ruff check src/ tests/ — clean
• uv run python scripts/check_conformance_manifest.py — 39 entries, all consistent
• Conformance fixture 033 (detached-trace mode) passes against the relocated detached: true placement
• Nine new unit tests in test_observability_metadata.py covering boundary + set_invocation_metadata + invoke() paths for each of the three new reserved names

[Copilot]

Pull request overview

Implements spec proposal 0042 by extending the reserved invocation-metadata key set with branch_name, detached, and detached_from_invocation_id, and relocating Langfuse's detached: true flag onto the parent-side dispatching observation. Also bumps the pinned spec version from v0.31.0 to v0.34.0 (absorbing not-yet-implemented 0038 Gemini and 0020 sessions) and marks 0040 as implemented in the conformance manifest.

Changes:

• Add three reserved exact key names to _RESERVED_KEY_NAMES with matching boundary, set_invocation_metadata, and invoke() rejection tests.
• Move detached: True from the detached-side dispatch observations to the parent-side link / fan-out node observations in the Langfuse observer.
• Bump spec pin to v0.34.0 across pyproject.toml, __init__.py, AGENTS.md, conformance.toml, smoke test, and CHANGELOG, and update conformance manifest entries (0040 implemented; 0042 added; 0020/0038 not-yet) plus Gemini fixture deferrals.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/openarmature/observability/metadata.py	Add 3 new reserved exact names; update comment to reference 0041+0042.
src/openarmature/observability/langfuse/observer.py	Move detached: True from detached-side dispatch metadata to parent-side link/fan-out node metadata.
tests/unit/test_observability_metadata.py	Nine new tests covering all three rejection paths for each new reserved name.
tests/conformance/test_llm_provider.py	Defer 044–053 Gemini provider fixtures (0038 not-yet).
tests/conformance/test_fixture_parsing.py	Defer 044–053 Gemini fixture parse tests (0038 not-yet).
conformance.toml	Bump spec pin to v0.34.0; mark 0040 implemented; add 0042 implemented and 0038/0020 not-yet.
pyproject.toml, src/openarmature/init.py, src/openarmature/AGENTS.md, tests/test_smoke.py	Sync spec version to v0.34.0.
CHANGELOG.md	Document the reserved-key extension, detached relocation, and spec-pin bump.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.