Carbon toolchain-runtimes not installing

```
2026-07-21 08:14:24,989 lib.installation_context INFO Staging with bwrap --dev-bind / / --tmpfs /opt/compiler-explorer --bind /cefs/84/84079d3044cb4a704f9d5516_carbon-trunk /opt/compiler-explorer/carbon-trunk bash -c '/opt/compiler-explorer/carbon-trunk/bin/carbon build-runtimes --output-directory=carbon-trunk-runtimes --target=x86_64-unknown-linux-gnu'
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/copy.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/copy.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/default.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/default.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/destroy.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/destroy.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/iterate.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/iterate.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/operators.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/operators.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/operators/arithmetic.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/operators/arithmetic.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/operators/as.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/operators/as.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/operators/bitwise.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/operators/bitwise.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/operators/comparison.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/operators/comparison.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/operators/deref.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/operators/deref.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/operators/index.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/operators/index.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/range.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/range.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/types.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/types/bool.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/bool.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/types/char.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/char.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/types/char_literal.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/char_literal.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/types/cpp/int.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/cpp/int.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/types/cpp/nullptr.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/cpp/nullptr.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/types/cpp/void.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/cpp/void.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/types/float.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/float.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/types/float_literal.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/float_literal.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/types/form.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/form.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/types/int.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/int.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/types/int_literal.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/int_literal.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/types/maybe_unformed.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/maybe_unformed.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/types/optional.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/optional.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/types/string.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/string.o`
mapping: `/opt/compiler-explorer/carbon-trunk/lib/carbon/core/prelude/types/uint.carbon` to: `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/uint.o`
error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/copy.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/default.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/destroy.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/iterate.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/operators.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/operators/arithmetic.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/operators/as.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/operators/bitwise.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/operators/comparison.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/operators/deref.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/operators/index.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/range.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/bool.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/char.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/char_literal.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/cpp/int.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/cpp/nullptr.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/cpp/void.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/float.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/float_literal.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/form.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/int.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/int_literal.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/maybe_unformed.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/optional.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/string.o`: No such file or directory

error: could not open output file `carbon-trunk-runtimes/.core.tmp.z71l9g/lib/core/x86_64-unknown-linux-gnu/core/prelude/types/uint.o`: No such file or directory
Please report issues to https://github.com/carbon-language/carbon-lang/issues and include the crash backtrace.
Stack dump:
0. Program arguments: /opt/compiler-explorer/carbon-trunk/bin/carbon build-runtimes --output-directory=carbon-trunk-runtimes --target=x86_64-unknown-linux-gnu
1. Carbon version: 0.0.0-0.nightly.2026.07.21+973e499
#0 0x00005cae38bbe018 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/carbon-trunk/bin/carbon+0x8756018)
#1 0x00005cae38bbad94 llvm::sys::RunSignalHandlers() (/opt/compiler-explorer/carbon-trunk/bin/carbon+0x8752d94)
#2 0x00005cae38bbeae1 SignalHandler(int, siginfo_t*, void*) Signals.cpp:0:0
#3 0x00007304efe45330 (/lib/x86_64-linux-gnu/libc.so.6+0x45330)
#4 0x00007304efe9eb2c __pthread_kill_implementation ./nptl/pthread_kill.c:44:76
#5 0x00007304efe9eb2c __pthread_kill_internal ./nptl/pthread_kill.c:78:10
#6 0x00007304efe9eb2c pthread_kill ./nptl/pthread_kill.c:89:10
#7 0x00007304efe4527e raise ./signal/../sysdeps/posix/raise.c:27:6
#8 0x00007304efe288ff abort ./stdlib/abort.c:81:7
#9 0x00005cae33f7188b Carbon::Internal::CheckFailImpl(char const*, char const*, int, char const*, char const*, llvm::ArrayRef>) (/opt/compiler-explorer/carbon-trunk/bin/carbon+0x3b0988b)
#10 0x00005cae32f2e9f5 (/opt/compiler-explorer/carbon-trunk/bin/carbon+0x2ac69f5)
#11 0x00005cae32f61342 (/opt/compiler-explorer/carbon-trunk/bin/carbon+0x2af9342)
#12 0x00005cae32f6119b Carbon::CarbonPreludeBuilder::Build() && (/opt/compiler-explorer/carbon-trunk/bin/carbon+0x2af919b)
#13 0x00005cae32f5caf2 Carbon::BuildRuntimesSubcommand::RunInternal(Carbon::DriverEnv&) (/opt/compiler-explorer/carbon-trunk/bin/carbon+0x2af4af2)
#14 0x00005cae32f5c01b Carbon::BuildRuntimesSubcommand::Run(Carbon::DriverEnv&) (/opt/compiler-explorer/carbon-trunk/bin/carbon+0x2af401b)
#15 0x00005cae32f55f7a Carbon::Driver::RunCommand(llvm::ArrayRef) (/opt/compiler-explorer/carbon-trunk/bin/carbon+0x2aedf7a)
#16 0x00005cae32f2d60d Carbon::Main(int, char**) busybox_main.cpp:0:0
#17 0x00005cae32f2ae14 main (/opt/compiler-explorer/carbon-trunk/bin/carbon+0x2ac2e14)
#18 0x00007304efe2a1ca __libc_start_call_main ./csu/../sysdeps/nptl/libc_start_call_main.h:74:3
#19 0x00007304efe2a28b call_init ./csu/../csu/libc-start.c:128:20
#20 0x00007304efe2a28b __libc_start_main ./csu/../csu/libc-start.c:347:5
#21 0x00005cae32f2ad65 _start (/opt/compiler-explorer/carbon-trunk/bin/carbon+0x2ac2d65)
CHECK failure at toolchain/driver/carbon_runtimes.cpp:102: compile_driver_.Compile(*driver_env_).success: Failed to compile Carbon prelude.
2026-07-21 08:15:14,789 lib.ce_install INFO compilers/carbon/toolchain-runtimes trunk failed to install: Command '['bwrap', '--dev-bind', '/', '/', '--tmpfs', '/opt/compiler-explorer', '--bind', '/cefs/84/84079d3044cb4a704f9d5516_carbon-trunk', '/opt/compiler-explorer/carbon-trunk', 'bash', '-c', '/opt/compiler-explorer/carbon-trunk/bin/carbon build-runtimes --output-directory=carbon-trunk-runtimes --target=x86_64-unknown-linux-gnu']' returned non-zero exit status 134.
Traceback (most recent call last):
File "/home/ubuntu/infra/bin/lib/ce_install.py", line 766, in install
installable.install()
File "/home/ubuntu/infra/bin/lib/installable/script.py", line 91, in install
self.stage(staging)
File "/home/ubuntu/infra/bin/lib/installable/script.py", line 74, in stage
self.install_context.stage_command(staging, cmd)
File "/home/ubuntu/infra/bin/lib/installation_context.py", line 259, in stage_command
subprocess.check_call(command, cwd=str(cwd or staging.path), env=env)
File "/home/ubuntu/.local/share/uv/python/cpython-3.12.10-linux-x86_64-gnu/lib/python3.12/subprocess.py", line 413, in check_call
raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['bwrap', '--dev-bind', '/', '/', '--tmpfs', '/opt/compiler-explorer', '--bind', '/cefs/84/84079d3044cb4a704f9d5516_carbon-trunk', '/opt/compiler-explorer/carbon-trunk', 'bash', '-c', '/opt/compiler-explorer/carbon-trunk/bin/carbon build-runtimes --output-directory=carbon-trunk-runtimes --target=x86_64-unknown-linux-gnu']' returned non-zero exit status 134.
```

The failure is in the `carbon build-runtimes --output-directory=carbon-trunk-runtimes --target=x86_64-unknown-linux-gnu` invocation shown in the report; start by reproducing it and tracing creation of the reported output path. Done means Carbon toolchain runtimes install successfully without the missing-directory errors or abort.

Written by the indexing model from the issue text.