ENG-9646: Reflex Init --agents

[amsraman]

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[linear-code]

ENG-9646

[greptile-apps]

Greptile Summary

This PR adds a --agents flag to reflex init that downloads a starter AGENTS.md from the canonical reflex-dev/agent-skills repo and writes it to the project root, while never overwriting an existing file. It also adds an AI-agent-oriented info block to the installation docs.

• initialize_agents_md() in frontend_skeleton.py performs an HTTP fetch, guards against overwrites, and aborts on failure — but the exception handler only catches httpx.HTTPError, missing all httpx.RequestError subclasses (connection errors, timeouts), so network failures produce an unhandled traceback rather than the intended clean SystemExit(1). The same gap causes the bundled test_initialize_agents_md_aborts_on_fetch_failure test to fail since it raises httpx.ConnectError.
• Constants and CLI wiring follow the existing project patterns cleanly.

Confidence Score: 3/5

The new --agents path has a real defect in its error handling that would produce an unhandled traceback on any network failure and would also break the bundled test verifying that behaviour.

The exception handler in initialize_agents_md catches only httpx.HTTPError, which does not cover httpx.RequestError subclasses (ConnectError, TimeoutException, etc.). Any network-level failure escapes as an unhandled exception, and the accompanying test that exercises exactly this failure mode would itself fail for the same reason. The rest of the change is straightforward and follows existing patterns.

reflex/utils/frontend_skeleton.py and tests/units/utils/test_utils.py need attention for the exception-handling gap.

Important Files Changed

Filename	Overview
reflex/utils/frontend_skeleton.py	Adds initialize_agents_md(); exception handler only catches httpx.HTTPError, missing RequestError subclasses (ConnectError, TimeoutException) so network failures escape unhandled.
tests/units/utils/test_utils.py	Adds three tests for initialize_agents_md; test_initialize_agents_md_aborts_on_fetch_failure patches net.get to raise ConnectError but the production code won't catch it, so the test itself would fail.
packages/reflex-base/src/reflex_base/constants/config.py	Adds AgentsMd SimpleNamespace with FILE and CANONICAL_URL constants; clean and follows existing patterns.
packages/reflex-base/src/reflex_base/constants/init.py	Exports AgentsMd from constants; correctly added to both import and all.
reflex/reflex.py	Adds --agents CLI flag wired to _init; correctly placed after gitignore init and before template messaging.
docs/ai_builder/integrations/agents_md.md	Documentation updated to describe reflex init --agents; clear and accurate.
docs/getting_started/installation.md	Adds an AI-agent-facing info block and starter rules file to the installation page; no functional impact.

_{Reviews (1): Last reviewed commit: "change source" | Re-trigger Greptile}

[greptile-apps]

httpx.HTTPError only covers HTTP-protocol-level errors (like HTTPStatusError for non-2xx responses). Network-level errors — httpx.ConnectError, httpx.TimeoutException, httpx.ReadTimeout, etc. — are subclasses of httpx.RequestError, which is not a subclass of httpx.HTTPError. If the GitHub raw URL is unreachable (DNS failure, timeout, firewall), the exception escapes unhandled and the user sees a raw traceback instead of the clean error message. The companion test test_initialize_agents_md_aborts_on_fetch_failure patches net.get to raise httpx.ConnectError and asserts SystemExit, but with the current catch clause that test will also fail at runtime because ConnectError is not caught.

Suggested change

	except httpx.HTTPError as e:
	console.error(f"Failed to fetch AGENTS.md from {url} due to {e}.")
	raise SystemExit(1) from None
	except (httpx.HTTPError, httpx.RequestError) as e:
	console.error(f"Failed to fetch AGENTS.md from {url} due to {e}.")
	raise SystemExit(1) from None

[codspeed-hq]

Merging this PR will degrade performance by 3.37%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

❌ 2 regressed benchmarks
✅ 24 untouched benchmarks
⏩ 8 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	test_from_event_type[lambda_event_spec]	53.8 µs	55.8 µs	-3.42%
❌	test_from_event_type[event_spec]	51.9 µs	53.7 µs	-3.31%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing aditya/init-agentsmd (9f89e0b) with main (31f785e)}

Footnotes

1. 8 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[adhami3310]

did you test the efficacy of this line

[adhami3310]

we should have a starter marker and finish marker so one can add other things in AGENTS.md

[adhami3310]

i thought we wanted this be turned on by default?