fix: make dotnet runnable.

install-scripts/README.md

@@ -18,6 +18,11 @@ files beneath it and install command wrappers or symlinks into `$DEV_TOOLS_DIR/b
 directory is prepended to implementation agents' `PATH`. Environment changes made by a script do
 not persist into implementation turns.
 
+The supplied `dotnet` wrapper keeps the SDK itself in `DEV_TOOLS_DIR`, but places the writable
+.NET CLI home and NuGet package cache under `/tmp`. Codex implementation sandboxes do not expose a
+normal user home and receive read-only access to installed tools, so runtime caches cannot live
+beside the SDK.
+
 The configured scripts run in list order after the repository is cloned (or an existing agent PR
 branch is synchronized) and before the first implementation turn for `implement`, `iterate`, and
 `fix`. They do not rerun between implementation and review-revision turns within one job. Scripts

install-scripts/dotnet

@@ -25,6 +25,13 @@ PYTHON
 printf '%s\n' \
     '#!/bin/sh' \
     "export DOTNET_ROOT='$install_dir'" \
+    'export DOTNET_CLI_HOME="${DOTNET_CLI_HOME:-/tmp/agentci-dotnet}"' \
+    'export NUGET_PACKAGES="${NUGET_PACKAGES:-/tmp/agentci-nuget/packages}"' \
+    'export DOTNET_CLI_TELEMETRY_OPTOUT=1' \
+    'export DOTNET_SKIP_FIRST_TIME_EXPERIENCE=1' \
+    'export DOTNET_NOLOGO=1' \
+    'export DOTNET_CLI_WORKLOAD_UPDATE_NOTIFY_DISABLE=1' \
+    'mkdir -p "$DOTNET_CLI_HOME" "$NUGET_PACKAGES"' \
     "exec '$install_dir/dotnet' \"\$@\"" \
     > "$bin_dir/dotnet"
 chmod 0755 "$bin_dir/dotnet"