uce/docs/setup.md

UCE Runtime Setup

This guide describes how to run UCE behind nginx or Apache. UCE is a FastCGI application server for .uce units; the web server should serve static files directly and forward dynamic .uce requests to the UCE runtime.

Deployment shape

A typical deployment has four pieces:

1. A checked-out or packaged UCE runtime tree.
2. /etc/uce/settings.cfg, read by the UCE runtime at startup.
3. uce.service, a systemd service that builds/starts/restarts the runtime.
4. nginx or Apache as the public HTTP server.

Recommended filesystem layout for a source checkout (replace paths as needed):

/path/to/uce-root                  UCE repository/runtime root (for example `/opt/uce` or `/Code/uce.openfu.com/uce`)
/var/www/html/                     public web root served by nginx/Apache
/etc/uce/settings.cfg              runtime configuration
/run/uce/fastcgi.sock              FastCGI socket used by nginx/Apache
/run/uce/cli.sock                  local CLI/admin/test socket
/var/cache/uce/work                generated source, wasm modules, caches
/var/lib/uce/uploads               multipart upload scratch space
/var/lib/uce/sessions              session files

For packaged installs, the runtime may live under /usr/lib/uce instead of your checkout root. Keep the public web root at /var/www/html or another normal web-root path, not under the runtime source tree.

Build requirements

On Debian/Ubuntu-like systems, install the distro packages first:

apt update
apt install -y clang build-essential libpcre2-dev mariadb-client libmariadb-dev curl rsync ca-certificates

UCE also requires two non-vendored dependencies. WASI SDK is load-bearing at runtime because UCE compiles units on demand during requests and during proactive startup scans. The curl binary is also a pinned runtime package dependency: http_request() and http_request_async() execute it directly with an explicit argument vector for TLS-capable outbound HTTP.

• Wasmtime C API / C++ headers at /opt/wasmtime by default. scripts/build_linux.sh expects:

  • /opt/wasmtime/include/wasmtime.hh
  • /opt/wasmtime/include/wasmtime/*.h
  • /opt/wasmtime/lib/libwasmtime.so

• Pinned WASI SDK at /opt/wasi-sdk by default. scripts/build_core_wasm.sh and request-time scripts/compile_wasm_unit expect:

  • /opt/wasi-sdk/bin/clang++
  • /opt/wasi-sdk/bin/wasm-ld
  • /opt/wasi-sdk/bin/llvm-objcopy

You can use different install locations by setting environment variables before building and in the systemd service environment:

export WASMTIME_HOME=/path/to/wasmtime
export WASI_SDK=/path/to/wasi-sdk

Install one web server:

apt install -y nginx
# or
apt install -y apache2

Build UCE from your repository root:

repo_root=/path/to/uce-root
cd "$repo_root"
bash scripts/build_core_wasm.sh
bash scripts/build_linux.sh

Publish the starter site or your application files into the web root:

mkdir -p /var/www/html
rsync -a site/ /var/www/html/

The main binary is written to:

bin/uce_fastcgi.linux.bin

Installing Wasmtime and WASI SDK

The UCE build does not download these dependencies for you. Install Wasmtime through a compatible distro package or a pinned upstream C API archive. Install WASI SDK with UCE's pinned installer, or unpack the same pinned archive under /opt/wasi-sdk.

Do not use curl | sh installers in production setup scripts. Download archives from the upstream release pages, verify checksums/signatures when available, and record the exact versions in your deployment notes. Avoid installing a release published in the last few days unless you have reviewed it separately.

The expected directories are:

/opt/wasmtime/include/wasmtime.hh
/opt/wasmtime/include/wasmtime/store.h
/opt/wasmtime/lib/libwasmtime.so

/opt/wasi-sdk/bin/clang++
/opt/wasi-sdk/bin/wasm-ld
/opt/wasi-sdk/bin/llvm-objcopy

Install the WASI SDK:

repo_root=/path/to/uce-root
cd "$repo_root"
scripts/install_wasi_sdk.sh
scripts/install_wasi_sdk.sh --check-only

The current pin is documented in docs/wasi-sdk-toolchain.md. The script verifies the archive SHA256 before installing and updates /opt/wasi-sdk to point at the pinned versioned directory.

For Wasmtime, use a compatible distro package or an upstream C API archive. Example flow using an archive you have already chosen and verified:

mkdir -p /opt /tmp/uce-deps
cd /tmp/uce-deps

# Download the Wasmtime C API archive for your architecture from the upstream
# release page, then verify its checksum before unpacking. The archive name
# normally contains "c-api".
sha256sum -c wasmtime-c-api.sha256
mkdir -p /opt/wasmtime
tar -xf wasmtime-*-c-api*.tar.* -C /opt/wasmtime --strip-components=1

After unpacking, verify the tools UCE needs. Also record the exact Wasmtime and WASI SDK versions used. The native build embeds an rpath for $WASMTIME_HOME/lib, so the service environment should use the same WASMTIME_HOME value used during build.

test -f /opt/wasmtime/include/wasmtime.hh
test -f /opt/wasmtime/lib/libwasmtime.so
/opt/wasi-sdk/bin/clang++ --version
/opt/wasi-sdk/bin/wasm-ld --version
/opt/wasi-sdk/bin/llvm-objcopy --version

If your paths differ, export the variables for manual builds:

WASMTIME_HOME=/usr/local/wasmtime WASI_SDK=/usr/local/wasi-sdk bash scripts/build_core_wasm.sh
WASMTIME_HOME=/usr/local/wasmtime WASI_SDK=/usr/local/wasi-sdk bash scripts/build_linux.sh

For systemd, add an override:

systemctl edit uce.service

[Service]
Environment=WASMTIME_HOME=/usr/local/wasmtime
Environment=WASI_SDK=/usr/local/wasi-sdk

Then reload and restart:

systemctl daemon-reload
systemctl restart uce.service

Runtime configuration

Create /etc/uce/settings.cfg from etc/uce/settings.cfg and adjust paths to your checkout root. Replace checkout-specific settings such as WASM_CORE_PATH with <UCE_REPO_ROOT>/bin/wasm/core.wasm or leave it relative to COMPILER_SYS_PATH as appropriate.

Minimum useful settings:

BIN_DIRECTORY=/var/cache/uce/work
TMP_UPLOAD_PATH=/var/lib/uce/uploads
SESSION_PATH=/var/lib/uce/sessions
SESSION_COOKIE_SECURE=1

FCGI_SOCKET_PATH=/run/uce/fastcgi.sock
FCGI_SOCKET_MODE=0666
CLI_SOCKET_PATH=/run/uce/cli.sock
CLI_SOCKET_MODE=0600

SITE_DIRECTORY=/var/www/html
HTTP_DOCUMENT_ROOT=/var/www/html
JIT_COMPILE_ON_REQUEST=1
PROACTIVE_COMPILE_ENABLED=1
PROACTIVE_COMPILE_CHECK_INTERVAL=60

WASM_COMPILE_SCRIPT=scripts/compile_wasm_unit
WASM_BACKEND_VERBOSE=0
WASM_CORE_PATH=<UCE_REPO_ROOT>/bin/wasm/core.wasm
WASM_MEMORY_LIMIT_BYTES=536870912
WASM_EPOCH_DEADLINE_TICKS=200
WASM_EPOCH_PERIOD_MS=50

WORKER_COUNT=4
MAX_MEMORY=16777216
SESSION_TIME=2592000

HTTP_PORT=8080
WS_BROKER_OUTBOUND_TIMEOUT_SECONDS=30

Important settings:

• FCGI_SOCKET_PATH is the Unix socket used for normal .uce requests. Set it explicitly and keep this value and the web-server fastcgi_pass path identical. The reference config uses /run/uce/fastcgi.sock; if you choose /run/uce.sock, use it in both places.
• CLI_SOCKET_PATH is a local HTTP-over-Unix socket used by scripts/uce-cli and test/admin units. Keep it private (CLI_SOCKET_MODE=0600) unless you intentionally delegate admin/test execution to a trusted Unix group (0660).
• FCGI_SOCKET_MODE and CLI_SOCKET_MODE are octal permission modes applied after socket bind. Prefer tightening FCGI_SOCKET_MODE to 0660 when nginx/Apache can share a trusted group with the UCE worker.
• SITE_DIRECTORY is the public site tree to scan for .uce files. Use /var/www/html when the web root is outside the runtime tree; relative paths are resolved from the runtime working directory.
• HTTP_DOCUMENT_ROOT is the root used by the built-in HTTP/WebSocket listener when it resolves upgrade requests. Set it to the same web root as nginx/Apache.
• BIN_DIRECTORY stores generated C++, wasm artifacts, compile output, and runtime caches.
• TMP_UPLOAD_PATH and SESSION_PATH must be writable by the runtime.
• SESSION_COOKIE_SECURE=1 adds the Secure attribute to UCE-managed session cookies and should be used for HTTPS-only deployments. Leave it 0 only for local/plain-HTTP development.
• HTTP_PORT is the built-in HTTP/WebSocket listener used for WebSocket upgrade traffic and direct local probes. Bind/firewall it for local access only; nginx/Apache should be the public entry point.
• WS_BROKER_OUTBOUND_TIMEOUT_SECONDS controls how long a forwarded WS message can remain queued in the broker before being dropped (default 30). Set to 0 to disable the timeout.
• WASM_COMPILE_SCRIPT must point to scripts/compile_wasm_unit unless you provide an equivalent compiler. Relative paths are resolved from the runtime root/COMPILER_SYS_PATH. That script calls scripts/check_unit_wasm.py after linking each unit and uses the pinned WASI SDK on every deployment host.
• WASM_CORE_PATH must point at the built core.wasm file.

After editing settings, restart UCE:

systemctl restart uce.service

systemd service

For source-checkout deployments, install the provided service helper:

repo_root=/path/to/uce-root
cd "$repo_root"
scripts/systemd/manage-uce-service.sh setup

That helper installs scripts/systemd/uce.service from your checked-out tree, rewrites the checked-out repository path into the installed unit and first-time config, creates runtime directories, enables the service, and starts it. Use a custom unit only if you need a nonstandard runtime layout.

Useful commands:

scripts/systemd/manage-uce-service.sh status
scripts/systemd/manage-uce-service.sh restart
scripts/systemd/manage-uce-service.sh logs 200

Equivalent manual systemd service for a source checkout (<UCE_REPO> = checkout root):

[Unit]
Description=UCE FastCGI Runtime
After=network-online.target mariadb.service memcached.service
Wants=network-online.target

[Service]
Type=simple
WorkingDirectory=<UCE_REPO>
RuntimeDirectory=uce
StateDirectory=uce
CacheDirectory=uce
ExecStartPre=/usr/bin/mkdir -p /var/cache/uce/work /var/lib/uce/uploads /var/lib/uce/sessions
ExecStartPre=/usr/bin/rm -f /run/uce/fastcgi.sock
ExecStartPre=/usr/bin/bash <UCE_REPO>/scripts/build_linux.sh
ExecStart=<UCE_REPO>/bin/uce_fastcgi.linux.bin
ExecStopPost=/usr/bin/rm -f /run/uce/fastcgi.sock
Restart=always
RestartSec=2
TimeoutStopSec=15
KillMode=mixed
StandardOutput=journal
StandardError=journal

[Install]
WantedBy=multi-user.target

Install it as /etc/systemd/system/uce.service and run:

systemctl daemon-reload
systemctl enable --now uce.service

Debian package build

To build a Debian package from the repository root:

bash scripts/make_deb.sh 0.1.2

The Debian package creator bundles WASI SDK and Wasmtime by default when /opt/wasi-sdk and /opt/wasmtime are present. Verify the pinned SDK before building:

scripts/install_wasi_sdk.sh --check-only
bash scripts/make_deb.sh 0.1.2

This includes the resolved /opt/wasi-sdk-... tree, /opt/wasi-sdk symlink, resolved /opt/wasmtime-... tree, and /opt/wasmtime symlink in the package. It makes the package large, but keeps request-time unit compilation and runtime linking tied to the toolchain versions that passed the test suite. Set UCE_DEB_BUNDLE_WASI_SDK=0 or UCE_DEB_BUNDLE_WASMTIME=0 only if your deployment provides those exact dependencies separately.

RPM package build

To build an RPM package from the repository root, install rpmbuild on the packaging host, verify the pinned SDK, then run:

scripts/install_wasi_sdk.sh --check-only
bash scripts/make_rpm.sh 0.1.2

The RPM creator mirrors the Debian package layout: runtime files under /usr/lib/uce, public files under /var/www/html, config under /etc/uce/settings.cfg, systemd unit under /usr/lib/systemd/system/uce.service, and bundled /opt/wasi-sdk plus /opt/wasmtime trees by default. Set UCE_RPM_BUNDLE_WASI_SDK=0 or UCE_RPM_BUNDLE_WASMTIME=0 only if your deployment provides those exact dependencies separately.

How request routing works

Static files

The web server should serve ordinary static files directly from the public web root, for example /var/www/html.

Examples:

/style.css
/images/logo.png
/examples/uce-starter/js/site.js

These should not touch the UCE runtime.

Normal .uce page requests

For a request such as:

GET /doc/index.uce?p=component

nginx/Apache forwards the request to FCGI_SOCKET_PATH as FastCGI. The web server must provide CGI/FastCGI variables including:

• SCRIPT_FILENAME — full filesystem path to the .uce file.
• DOCUMENT_ROOT — public web root, normally /var/www/html or whatever nginx/Apache uses as root/DocumentRoot.
• SCRIPT_NAME — URL path to the script, such as /doc/index.uce.
• DOCUMENT_URI — normalized URI path without query string.
• REQUEST_URI — original request URI including query string.
• standard request variables such as method, query string, content type, body length, cookies, and headers.

UCE resolves the unit, compiles it to wasm if needed, creates a request workspace, and calls:

RENDER(Request& context)

The unit writes output with template literals or print(). Response headers and status are set through context.header and context.set_status().

Component and sub-render calls

Inside a request, UCE code can call other units:

component("components/card", props, context);
unit_render("other-page.uce", context);

These calls stay inside the UCE runtime. They are not new HTTP requests and do not go back through nginx or Apache.

WebSocket pages

Any .uce unit can provide both an ordinary page render and WebSocket message handling:

RENDER(Request& context) { ... }  // normal page load
WS(Request& context) { ... }      // later WebSocket messages

The nginx and Apache examples below split traffic by checking for a WebSocket upgrade request on .uce paths. A file such as chat.uce or events.uce can expose WS(Request& context).

Routing split:

• Plain GET /demo/chat.uce should use FastCGI, just like any other page render.
• WebSocket upgrade requests for /demo/chat.uce should proxy to the UCE built-in HTTP/WebSocket listener at HTTP_PORT.

The built-in listener owns the socket lifecycle. When a message arrives, the broker forwards a render-style invocation back to the worker pool so WS(Request& context) runs inside the same wasm runtime model as normal pages.

CLI requests

CLI(Request& context) handlers are not public web endpoints. They are invoked over CLI_SOCKET_PATH:

scripts/uce-cli /tests/cli.uce action=echo message=hello
curl --unix-socket /run/uce/cli.sock http://localhost/tests/cli.uce

Use CLI units for local tests, admin commands, and maintenance tools. Do not expose the CLI socket through nginx or Apache.

Custom runtime HTTP servers

UCE code can start local custom HTTP listeners with server_start_http(). Those are runtime-managed listeners for app-specific local services. They are separate from the public nginx/Apache entry point and should be firewalled or bound locally unless you explicitly want them reachable.

nginx configuration

Required modules

A normal nginx build includes the needed FastCGI and proxy modules. Confirm nginx is installed and can load your config:

nginx -t

WebSocket upgrade map

Put this in the nginx http block if using WebSockets:

map $http_upgrade $connection_upgrade {
    default upgrade;
    ''      close;
}

Server block

Example site config:

server {
    listen 80;
    server_name example.com;

    root /var/www/html;
    index index.uce index.html;

    # Serve static files directly. Directory requests use index.uce when present.
    location / {
        try_files $uri $uri/ =404;
    }

    # UCE page requests use FastCGI. If the client asks to upgrade a .uce
    # request to WebSocket, send that connection to the built-in listener.
    location ~ \.uce$ {
        error_page 418 = @uce_websocket;
        if ($http_upgrade = "websocket") {
            return 418;
        }

        include fastcgi_params;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        fastcgi_param DOCUMENT_ROOT $document_root;
        fastcgi_param SCRIPT_NAME $fastcgi_script_name;
        fastcgi_param DOCUMENT_URI $uri;
        fastcgi_param REQUEST_URI $request_uri;
        fastcgi_pass unix:/run/uce/fastcgi.sock;
    }

    location @uce_websocket {
        proxy_http_version 1.1;
        proxy_set_header Host $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection $connection_upgrade;
        proxy_pass http://127.0.0.1:8080;
    }

    # Defense in depth if the root is changed later.
    location ~ ^/(src|scripts|etc|bin|work|dist|pkg|docs|changelog)/ {
        return 404;
    }
}

Notes:

• fastcgi_pass must match FCGI_SOCKET_PATH.
• proxy_pass must match HTTP_PORT.
• The example routes WebSocket upgrades for .uce paths to the HTTP/WebSocket listener.
• The built-in HTTP/WebSocket listener resolves scripts from HTTP_DOCUMENT_ROOT; do not depend on client-supplied or proxied Script-Filename headers for routing.
• Ordinary .uce page loads continue to use FastCGI.
• Keep root pointed at /var/www/html, not the runtime repository root.
• If your app uses a front controller, replace location / with a try_files rule that ends at /index.uce.

Front-controller variant:

location / {
    try_files $uri $uri/ /index.uce?$query_string;
}

Reload nginx:

nginx -t
systemctl reload nginx

Apache configuration

Apache can run UCE through mod_proxy_fcgi for FastCGI and mod_proxy_wstunnel or mod_proxy_http for WebSocket upgrades.

Enable modules

On Debian/Ubuntu:

a2enmod proxy proxy_fcgi proxy_http proxy_wstunnel rewrite headers setenvif
systemctl restart apache2

VirtualHost example

<VirtualHost *:80>
    ServerName example.com
    DocumentRoot /var/www/html

    <Directory /var/www/html>
        Require all granted
        Options FollowSymLinks
        AllowOverride None
        DirectoryIndex index.uce index.html
    </Directory>

    # Do not expose repository internals if DocumentRoot changes later.
    <LocationMatch "^/(src|scripts|etc|bin|work|dist|pkg|docs|changelog)/">
        Require all denied
    </LocationMatch>

    RewriteEngine On

    # WebSocket upgrade traffic for any .uce unit goes to UCE's built-in HTTP listener.
    RewriteCond %{HTTP:Upgrade} =websocket [NC]
    RewriteCond %{REQUEST_URI} \.uce(?:\?|$) [NC]
    RewriteRule ^/(.*)$ ws://127.0.0.1:8080/$1 [P,L]

    # Normal .uce page loads go to FastCGI.
    <FilesMatch "\.uce$">
        SetHandler "proxy:unix:/run/uce/fastcgi.sock|fcgi://localhost/"
    </FilesMatch>

    # Optional: make the key CGI variables explicit for UCE.
    ProxyFCGISetEnvIf "true" DOCUMENT_ROOT "/var/www/html"
    ProxyFCGISetEnvIf "true" DOCUMENT_URI "%{REQUEST_URI}"
</VirtualHost>

Apache notes:

• SetHandler "proxy:unix:/run/uce/fastcgi.sock|fcgi://localhost/" must use the same socket path as FCGI_SOCKET_PATH.
• The WebSocket rewrite rule must run before the FastCGI handler.
• Plain .uce page loads should not be proxied as WebSockets unless the client sends Upgrade: websocket.
• Apache's FastCGI environment differs by version and module configuration. If UCE cannot resolve a page, inspect the request environment and make sure SCRIPT_FILENAME points to the target file under the web root.

If your Apache version does not populate SCRIPT_FILENAME correctly through SetHandler, use ProxyPassMatch for .uce files instead:

ProxyPassMatch ^/(.*\.uce)$ unix:/run/uce/fastcgi.sock|fcgi://localhost/var/www/html/$1

Use only one FastCGI mapping style at a time (SetHandler or ProxyPassMatch) to avoid duplicate routing.

Permissions

The web server needs permission to connect to /run/uce/fastcgi.sock. Common approaches:

• run UCE and the web server under compatible groups;
• add the web server user (www-data on Debian/Ubuntu) to the socket's group;
• adjust the service or runtime socket mode if needed.

The runtime creates the FastCGI socket and CLI socket under /run/uce. The CLI socket should remain local-only and should not be reachable from the public web server.

Writable paths for the runtime:

/var/cache/uce/work
/var/lib/uce/uploads
/var/lib/uce/sessions
/run/uce

Verification

Check service state:

systemctl status uce.service
journalctl -u uce.service -n 100 --no-pager

Check the FastCGI/web-server path:

curl -i http://127.0.0.1/doc/index.uce -H 'Host: example.com'
curl -i http://127.0.0.1/examples/uce-starter/ -H 'Host: example.com'

Check the local CLI path:

repo_root=/path/to/uce-root
cd "$repo_root"
scripts/uce-cli /tests/cli.uce action=echo message=hello
scripts/run_cli_tests.sh

Check WebSocket routing with a WebSocket client against a .uce endpoint that defines WS(Request& context) through nginx/Apache, not directly against HTTP_PORT:

python3 - <<'PY'
import base64, os, socket
host = "example.com"
path = "/chat.uce"
key = base64.b64encode(os.urandom(16)).decode()
request = (
    f"GET {path} HTTP/1.1\r\n"
    f"Host: {host}\r\n"
    "Upgrade: websocket\r\n"
    "Connection: Upgrade\r\n"
    f"Sec-WebSocket-Key: {key}\r\n"
    "Sec-WebSocket-Version: 13\r\n\r\n"
).encode()
sock = socket.create_connection(("127.0.0.1", 80), timeout=5)
sock.sendall(request)
print(sock.recv(4096).decode("latin1", "replace").split("\r\n", 1)[0])
sock.close()
PY

Operational footguns

• Keep the FastCGI socket path consistent: FCGI_SOCKET_PATH and the web-server fastcgi_pass must match exactly. The reference config uses /run/uce/fastcgi.sock; if you choose /run/uce.sock, use it in both places.
• Keep the public web root separate from the runtime source tree. Replace /opt/uce with your actual checkout path in local examples (for example /opt/uce or /Code/uce.openfu.com/uce), and keep public files under /var/www/html.
• Set HTTP_DOCUMENT_ROOT when the web root is outside the runtime working directory. The built-in HTTP/WebSocket listener resolves upgrade paths from this setting.
• Do not expose CLI_SOCKET_PATH or HTTP_PORT as public entry points. The public path should be nginx/Apache.
• Do not trust Script-Filename request headers from direct HTTP clients. The built-in HTTP listener resolves from HTTP_DOCUMENT_ROOT and rejects .. path segments.
• WASI SDK is a deployment/runtime dependency, not just a developer build tool. UCE compiles units to wasm on demand during requests and during proactive startup scans, so each host must use the pinned SDK version documented in docs/wasi-sdk-toolchain.md.
• After toolchain or compile-script fixes, clear stale failed artifacts under BIN_DIRECTORY; otherwise a later request may report an old compile failure.

Troubleshooting

502 Bad Gateway

Check:

• systemctl status uce.service
• journalctl -u uce.service -n 200 --no-pager
• socket path in web server config equals FCGI_SOCKET_PATH
• web server user can connect to the Unix socket
• SCRIPT_FILENAME resolves to an existing .uce file

Raw .uce source is downloaded or displayed

The .uce request did not match the FastCGI rule. Check location/order rules and confirm the public root is /var/www/html or your chosen web-root path.

Static files 404

Confirm the web server root/DocumentRoot is /var/www/html or your chosen web-root path and that location / or Apache directory rules allow static file reads.

WebSocket page renders but upgrade fails

Check:

• the client sends Upgrade: websocket
• .uce upgrade traffic reaches HTTP_PORT
• nginx/Apache preserves Upgrade and Connection headers
• HTTP_DOCUMENT_ROOT matches the web-server root; if it points at the runtime tree while files live in /var/www/html, the built-in listener will return 404 script not found
• firewall/network policy allows localhost access to HTTP_PORT

Page compiles fail

Check the compile artifact paths shown in the UCE error response and service logs. Generated files and compile output live under BIN_DIRECTORY.

Common compile footguns:

• WASM_COMPILE_SCRIPT is unset or points at a removed script such as scripts/compile; set it to scripts/compile_wasm_unit.
• scripts/check_unit_wasm.py is missing or not executable; scripts/compile_wasm_unit calls it after linking each unit.
• WASI_SDK does not point at the pinned tree with clang++, wasm-ld, llvm-objcopy, and llvm-nm; run scripts/install_wasi_sdk.sh --check-only.
• WASMTIME_HOME does not point at a tree with Wasmtime headers and libwasmtime.so.
• A previous failed compile left stale .compile.txt, .wasm-check.txt, or partial .wasm files under BIN_DIRECTORY.

Failed compile output is persisted under the unit's generated path in BIN_DIRECTORY and may be reused until the source or compiler inputs change. First fix the source/toolchain issue and reload the page. If the cache itself is suspect, stop UCE, move only the affected unit artifact files or directory aside, and restart so the runtime recompiles from source. Avoid deleting the whole BIN_DIRECTORY unless you intentionally want a full rebuild.

CLI commands fail

Check:

• CLI_SOCKET_PATH in /etc/uce/settings.cfg
• /run/uce/cli.sock exists
• scripts/uce-cli --socket /run/uce/cli.sock /ping works
• the target unit defines CLI(Request& context)