codex: preserve generated local machine state

dotfiles/codex/config.toml

@@ -5,7 +5,9 @@ personality = "pragmatic"
 suppress_unstable_features_warning = true
 
 # Portable Codex defaults. Machine-local additions are appended from
-# dotfiles/codex/config.local.toml by Home Manager.
+# dotfiles/codex/config.local.toml by Home Manager. Codex-owned local
+# state, including project trust settings, is harvested there before
+# this file is regenerated.
 
 [mcp_servers.chrome-devtools]
 command = "npx"

nix-shared/home-manager/codex-generated-skills.nix

@@ -73,6 +73,8 @@ in {
       base=${lib.escapeShellArg "${cfg.worktreeCodexDir}/config.toml"}
       local_config=${lib.escapeShellArg "${cfg.worktreeCodexDir}/config.local.toml"}
       target="$codex_home/config.toml"
+      begin_marker="# BEGIN AUTO-GENERATED CODEX MACHINE STATE"
+      end_marker="# END AUTO-GENERATED CODEX MACHINE STATE"
 
       if [ ! -r "$base" ]; then
         echo "Missing shared Codex config at $base" >&2
@@ -80,6 +82,96 @@ in {
       fi
 
       mkdir -p "$codex_home"
+
+      if [ -r "$target" ]; then
+        mkdir -p "$(dirname "$local_config")"
+        local_state="$(mktemp "$codex_home/config.local-state.XXXXXX")"
+        local_tmp="$(mktemp "$codex_home/config.local.toml.XXXXXX")"
+        trap 'rm -f "$tmp" "$local_state" "$local_tmp"' EXIT
+
+        ${lib.getExe pkgs.gawk} \
+          -v begin_marker="$begin_marker" \
+          -v end_marker="$end_marker" '
+          FNR == NR {
+            if ($0 ~ /^\[[^]]+\]$/) {
+              base_sections[$0] = 1
+            }
+            next
+          }
+
+          function flush_block() {
+            if (keep && section != "" && !(section in base_sections)) {
+              if (printed) {
+                print ""
+              }
+              printf "%s", block
+              printed = 1
+            }
+          }
+
+          $0 == begin_marker || $0 == end_marker {
+            next
+          }
+
+          /^\[[^]]+\]$/ {
+            flush_block()
+            section = $0
+            keep = ($0 ~ /^\[projects\./ || $0 ~ /^\[tui\./)
+            block = $0 "\n"
+            next
+          }
+
+          section != "" {
+            block = block $0 "\n"
+          }
+
+          END {
+            flush_block()
+          }
+        ' "$base" "$target" > "$local_state"
+
+        if [ -s "$local_state" ] || { [ -r "$local_config" ] && grep -Fqx "$begin_marker" "$local_config"; }; then
+          if [ -r "$local_config" ]; then
+            ${lib.getExe pkgs.gawk} \
+              -v begin_marker="$begin_marker" \
+              -v end_marker="$end_marker" '
+              $0 == begin_marker {
+                skip = 1
+                next
+              }
+
+              $0 == end_marker {
+                skip = 0
+                next
+              }
+
+              !skip {
+                print
+              }
+            ' "$local_config" > "$local_tmp"
+          else
+            : > "$local_tmp"
+          fi
+
+          if [ -s "$local_tmp" ] && [ -s "$local_state" ]; then
+            printf '\n' >> "$local_tmp"
+          fi
+
+          if [ -s "$local_state" ]; then
+            printf '%s\n' "$begin_marker" >> "$local_tmp"
+            cat "$local_state" >> "$local_tmp"
+            printf '%s\n' "$end_marker" >> "$local_tmp"
+          fi
+
+          chmod 600 "$local_tmp"
+          mv -f "$local_tmp" "$local_config"
+        else
+          rm -f "$local_tmp"
+        fi
+
+        rm -f "$local_state"
+      fi
+
       tmp="$(mktemp "$codex_home/config.toml.XXXXXX")"
       trap 'rm -f "$tmp"' EXIT
       chmod 600 "$tmp"