[teamleaderleo]

Two build scripts read their own crate folder with the compile-time env!("CARGO_MANIFEST_DIR"). When a build cache reuses a build script binary compiled in another checkout, that path points into the old checkout:

• cmux-browser-host/build.rs panics reading a js/manifest.json that no longer exists. This broke a chat-open benchmark build on a fleet worker: the step read …/steps/<old step>/src/cmux-tui/crates/cmux-browser-host/js/manifest.json while the source was in another slot.
• cmux-tailnet/build.rs reads patches/ with unwrap_or_default, so it silently builds with no patches.

Both now read CARGO_MANIFEST_DIR at run time; Cargo sets it for every build script run. No other build.rs uses env!("CARGO_MANIFEST_DIR").

Small change: two lines of logic in two build scripts. Risk: none beyond the build itself; the variable is always set when Cargo runs a build script.

Agent session: agent session

🤖 Generated with Claude Code

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Summary by cubic

Fixes build script caching failures by reading CARGO_MANIFEST_DIR at run time instead of compile time in two build scripts. When a cached build script binary is reused from a different checkout, env! keeps the old checkout's path; cmux-browser-host then panics on a missing js/manifest.json, and cmux-tailnet silently builds without its patches.

^{Written for commit b1b9f45. Summary will update on new commits.}

[github-actions]

cmux status _{(one comment, edited in place; each line is updated by the job that owns it)}

Review b1b9f45: HQ feed card · gallery before/after runs · checks

App of this head (app.zip, kept 1 day)

gh workflow run reload-build.yml -R manaflow-ai/cmux --ref feat-cmux-next -f tag=pr33741 -f ref=lane/build-rs-runtime-manifest-dir -f platform=macos -f backend_mode=local

Shipped in:

• cmux NEXT nightly 1.0.0-nightly.4163622263401 (295594d2f3)
• cmux NEXT nightly 1.0.0-nightly.4163731153001 (b4970032cd)

[teamleaderleo]

Review (claude-sonnet-5-5): SHIP at b1b9f45

Review (subagent claude-sonnet-5-5): SHIP at b1b9f45

Cargo always sets CARGO_MANIFEST_DIR in a build script's run-time environment. Both edits compile by inspection, and the joined paths and rerun-if-changed output are the same as before. No other build.rs uses env!("CARGO_MANIFEST_DIR"); grep confirms it.

Follow-ups: none.

[blacksmith-sh]

Found 1 test failure on Blacksmith runners:

Failure

Test	View Logs
test_every_compile_job_names_its_warm_sources (main.ThisTree.test_every_compile_job _names_its_warm_sources)/ test_every_compile_job_names_its_warm_sources (main.ThisTree.test_every_compile_job _names_its_warm_sources)	View Logs

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