fix(build): thread caller PATH per request into daemon tool resolution (#1219)

[zackees]

Closes #1219

Problem

Tool resolution for bare-name spawns was bound to whichever environment spawned the daemon — for up to 12 h (IDLE_TIMEOUT). Two byte-identical builds could resolve different toolchains (esptool, the Python that runs extra_scripts, objcopy) depending only on which shell started the daemon. This is the mechanism behind the #1217 FastLED CI outage.

Fix

Forward the CLI caller's PATH on every build request and use it at the bare-name spawn sites (issue's "suggested direction 1"):

• Plumbing (mirrors the existing src_dir/pio_env forwarding): CLI sets caller_path from its own env → BuildRequest (serde-optional; old clients omit it and get today's behavior — HTTP API stays backward compatible) → daemon handler → BuildParams.caller_path.
• Spawn sites now resolving against the caller's PATH (child PATH is replaced via run_command's env overlay; None ⇒ legacy daemon env):
  • esp32_linker esptool elf2image fallback, and both boot_artifacts spawns (gen_esp32part python + bootloader elf2image)
  • esp8266_linker bare-esptool conversion
  • script_runtime: find_python_with_path probe and the interpreter invocation that runs extra_scripts (so imports/subprocess resolution inside the script see the same environment the probe did)
  • ch32v_linker objcopy (via a new LinkerBase::objcopy_firmware_with_env; AVR/Teensy callers unchanged)
• Scope: build path only. Deploy-side threading is feat(deploy): thread caller_path into deployers — bare-name deploy-time spawns still resolve against daemon PATH (follow-up to #1219) #1234 (deploy's BuildParams literal carries an explicit None + comment pointing there).

Latent Windows bug fixed along the way

The new contract test exposed that compute_env kept both Path (parent spelling) and PATH (overlay) entries; Command::env's case-insensitive child-env map let whichever applied last silently win — i.e. a PATH overlay could be discarded. compute_env now drops case-variant keys before inserting an overlay var, with a real child-process test asserting the overlay value is exactly what the child sees.

Tests

• env_overlay_path_reaches_child_over_case_variant (fbuild-core, real child process)
• test_find_python_with_path_replaces_inherited_path (empty-dir PATH must make the probe fail even though the daemon env has python — the load-bearing regression; on Windows the strict assertion skips when %WINDIR%\py.exe exists, since the OS's system-dir exe fallback for py is Windows resolution, not a PATH leak) + ..._none_matches_find_python
• build_request_caller_path_defaults_to_none / ..._forwarded (daemon serde compat)
• test_with_caller_path_stores_value (ch32v builder)

Validation

• soldr cargo check --workspace --all-targets — clean
• soldr cargo clippy --workspace --all-targets -- -D warnings — clean
• soldr cargo fmt --all — applied (includes a formatting-only normalization of daemon_crash_recovery.rs from test(cli): pin daemon crash-recovery with a real-process regression test (#1228) #1232)
• Touched-crate suites all green: fbuild-build-engine 388 passed, fbuild-core 262, fbuild-daemon 228 (+12 suites), fbuild-build-esp 98, fbuild-build-mcu 63, fbuild-cli 262, fbuild-build 19 suites ok.

🤖 Generated with Claude Code

[coderabbitai]

Warning

Review limit reached

@zackees, you've reached your PR review limit, so we couldn't start this review.

Next review available in: 35 minutes

Enable usage-based reviews in Billing to review now. Otherwise, wait until the next included review is available.
You're only billed for reviews past your plan's rate limits ($0.25/file).

How can I continue?

After more reviews become available, a review can be triggered using the @coderabbitai review command as a PR comment. Alternatively, push new commits to this PR.

To avoid repeated limits, reduce automatic review volume by pausing incremental auto-reviews earlier, using label-based review opt-in, excluding WIP or generated PR titles, or requesting reviews manually when the PR is ready. If your team needs uninterrupted high-volume reviews, an organization admin can enable usage-based reviews.

How do review limits work?

CodeRabbit enforces per-developer PR review limits for each organization. Most developers receive the normal plan review availability.

For paid Pro and Pro+ PR reviews, CodeRabbit uses adaptive limits for sustained high-volume activity. When a developer's recent PR review activity reaches the 95th percentile or higher among CodeRabbit users, additional reviews become available more gradually as earlier reviews age out of the rolling window.

Please refer docs for additional details.

Review details

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 7329ea96-1232-4abf-b584-005da38d6cb8

📥 Commits

Reviewing files that changed from the base of the PR and between e460949 and 01d3634.

📒 Files selected for processing (33)

• crates/fbuild-build-engine/src/lib.rs
• crates/fbuild-build-engine/src/linker.rs
• crates/fbuild-build-engine/src/pipeline/context.rs
• crates/fbuild-build-engine/src/script_runtime.rs
• crates/fbuild-build-engine/src/script_runtime_tests.rs
• crates/fbuild-build-esp/src/esp32/esp32_linker.rs
• crates/fbuild-build-esp/src/esp32/orchestrator/boot_artifacts.rs
• crates/fbuild-build-esp/src/esp32/orchestrator/build.rs
• crates/fbuild-build-esp/src/esp8266/esp8266_linker.rs
• crates/fbuild-build-esp/src/esp8266/orchestrator.rs
• crates/fbuild-build-mcu/src/ch32v/ch32v_linker.rs
• crates/fbuild-build-mcu/src/ch32v/orchestrator.rs
• crates/fbuild-build/src/compile_many.rs
• crates/fbuild-build/tests/avr_build.rs
• crates/fbuild-build/tests/clangd_check_parity.rs
• crates/fbuild-build/tests/eh_frame_strip_esp32.rs
• crates/fbuild-build/tests/esp32_build.rs
• crates/fbuild-build/tests/nxplpc_build_flags.rs
• crates/fbuild-build/tests/nxplpc_core_compile_commands.rs
• crates/fbuild-build/tests/stm32_acceptance.rs
• crates/fbuild-build/tests/teensy30_acceptance.rs
• crates/fbuild-build/tests/teensy_build.rs
• crates/fbuild-build/tests/teensylc_acceptance.rs
• crates/fbuild-cli/src/cli/build.rs
• crates/fbuild-cli/src/cli/clean.rs
• crates/fbuild-cli/src/daemon_client/types.rs
• crates/fbuild-cli/src/mcp/tools.rs
• crates/fbuild-core/src/subprocess.rs
• crates/fbuild-daemon/src/handlers/emulator/select.rs
• crates/fbuild-daemon/src/handlers/emulator/tests_process.rs
• crates/fbuild-daemon/src/handlers/operations/build.rs
• crates/fbuild-daemon/src/handlers/operations/deploy.rs
• crates/fbuild-daemon/src/models.rs

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}