chore: update flake, agents lib, and clean up tracked dotfiles

- Remove .pi* and .td-root files from git index (now in .gitignore)
- Update flake.lock and flake.nix
- Add shells/coding.nix, remove shells/opencode.nix
- Update lib/agents.nix, lib/coding-rules.nix
- Update modules/home-manager/coding/agents/pi.nix
- Update tests for agents and coding-rules
- Update .gitignore

.gitignore

@@ -43,5 +43,5 @@ flake.lock.bak
 .sidecar-start.sh
 .sidecar-base
 .td-root
-.pi-lens
 .cache
+.pi*

.pi-lens/cache/jscpd.json

@@ -1,7 +0,0 @@
-{
-  "success": true,
-  "clones": [],
-  "duplicatedLines": 0,
-  "totalLines": 0,
-  "percentage": 0
-}

.pi-lens/cache/jscpd.meta.json

@@ -1,3 +0,0 @@
-{
-  "timestamp": "2026-04-11T04:17:20.531Z"
-}

.pi-lens/cache/knip.json

@@ -1,9 +0,0 @@
-{
-  "success": false,
-  "issues": [],
-  "unusedExports": [],
-  "unusedFiles": [],
-  "unusedDeps": [],
-  "unlistedDeps": [],
-  "summary": "Failed to parse output"
-}

.pi-lens/cache/knip.meta.json

@@ -1,3 +0,0 @@
-{
-  "timestamp": "2026-04-11T04:17:21.374Z"
-}

.pi-lens/cache/session-start-guidance.json

@@ -1 +0,0 @@
-null

.pi-lens/cache/session-start-guidance.meta.json

@@ -1,3 +0,0 @@
-{
-  "timestamp": "2026-04-19T15:52:39.989Z"
-}

.pi-lens/cache/todo-baseline.json

@@ -1,3 +0,0 @@
-{
-  "items": []
-}

.pi-lens/cache/todo-baseline.meta.json

@@ -1,3 +0,0 @@
-{
-  "timestamp": "2026-04-19T15:42:10.963Z"
-}

.pi-lens/turn-state.json

@@ -1,6 +0,0 @@
-{
-  "files": {},
-  "turnCycles": 0,
-  "maxCycles": 3,
-  "lastUpdated": "2026-04-11T04:17:22.397Z"
-}

.td-root

@@ -1 +0,0 @@
-/home/sascha.koenig/p/NIX/nixpkgs

flake.lock

@@ -1,5 +1,21 @@
 {
   "nodes": {
+    "agents": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1776092721,
+        "narHash": "sha256-avV4Snqp0K57I9s8D61+GHlg9DYZFSIvjaS4d4RYpG8=",
+        "ref": "refs/heads/master",
+        "rev": "0ad41acb03eee0e22cba611b2171a3d3ee30cb10",
+        "revCount": 72,
+        "type": "git",
+        "url": "https://code.m3ta.dev/m3tam3re/AGENTS"
+      },
+      "original": {
+        "type": "git",
+        "url": "https://code.m3ta.dev/m3tam3re/AGENTS"
+      }
+    },
     "basecamp": {
       "inputs": {
         "nixpkgs": [
@@ -96,6 +112,7 @@
     },
     "root": {
       "inputs": {
+        "agents": "agents",
         "basecamp": "basecamp",
         "nixpkgs": "nixpkgs",
         "nixpkgs-master": "nixpkgs-master",

flake.nix

@@ -21,6 +21,12 @@
       url = "github:Fission-AI/OpenSpec";
       inputs.nixpkgs.follows = "nixpkgs";
     };
+
+    # Agent definitions and coding rules
+    agents = {
+      url = "git+https://code.m3ta.dev/m3tam3re/AGENTS";
+      flake = false;
+    };
   };
 
   outputs = {
@@ -81,11 +87,11 @@
 
     # Development shells for various programming environments
     # Usage: nix develop .#<shell-name>
-    # Available shells: default, python, devops, opencode
+    # Available shells: default, python, devops, coding
     devShells = forAllSystems (system: let
       pkgs = pkgsFor system;
     in
-      import ./shells {inherit pkgs inputs;});
+      import ./shells {inherit pkgs inputs; agents = inputs.agents;});
 
     # Formatter for 'nix fmt'
     formatter = forAllSystems (system: (pkgsFor system).alejandra);

lib/agents.nix

@@ -223,7 +223,10 @@
       canonical,
       modelOverrides ? {},
       primaryAgent ? null,
+      codingRules ? null,
     }: let
+      # Import coding-rules lib for concatRulesMd when codingRules is provided
+      codingRulesLib = (import ./coding-rules.nix {inherit lib;});
       # Find the primary agent (there should be exactly one).
       primaryAgents = lib.filterAttrs (_: a: a.mode == "primary") canonical;
       primaryNames = lib.attrNames primaryAgents;
@@ -306,6 +309,17 @@
           "- **" + dn + "**: " + agent.description;
       in
         lib.mapAttrsToList mkEntry subagents;
+      # ── Coding rules section (optional) ────────────────────────
+      # When codingRules is provided, append selected rules to AGENTS.md.
+      # codingRules attrset: { agents, languages, concerns, frameworks }
+      codingRulesSection =
+        if codingRules != null
+        then let
+          section = codingRulesLib.mkRulesMdSection codingRules;
+        in
+          if section != "" then "\n" + section else ""
+        else "";
+
       agentsMd =
         "# Agent Instructions\n"
         + "\n"
@@ -320,7 +334,8 @@
           if subagents == {}
           then ""
           else "## Available Specialists\n\n" + lib.concatStringsSep "\n" specialistEntries + "\n"
-        );
+        )
+        + codingRulesSection;
 
       agentsMdFile = pkgs.writeText "AGENTS.md" agentsMd;
       systemMdFile = pkgs.writeText "SYSTEM.md" primary.systemPrompt;
@@ -346,6 +361,7 @@
       agentsInput,
       tool,
       modelOverrides ? {},
+      codingRules ? null,
     }: let
       canonical = agentsInput.lib.loadAgents;
     in
@@ -362,7 +378,7 @@
       else if tool == "pi"
       then
         agentsLib.renderForPi {
-          inherit pkgs canonical modelOverrides;
+          inherit pkgs canonical modelOverrides codingRules;
         }
       else throw "lib.agents.renderForTool: unknown tool '${tool}'. Must be opencode, claude-code, or pi.";
 
@@ -386,9 +402,10 @@
       agentsInput,
       tool,
       modelOverrides ? {},
+      codingRules ? null,
     }: let
       rendered = agentsLib.renderForTool {
-        inherit pkgs agentsInput tool modelOverrides;
+        inherit pkgs agentsInput tool modelOverrides codingRules;
       };
     in
       if tool == "opencode"

lib/coding-rules.nix

@@ -27,6 +27,7 @@
 # The shellHook creates:
 #   - A `.opencode-rules/` symlink pointing to the AGENTS repository rules directory
 #   - A `coding-rules.json` file with a $schema reference and instructions list
+#   - (Optional) Appends coding rules to `AGENTS.md` for Pi agent discovery
 #
 # The instructions list contains paths relative to the project root, all prefixed
 # with `.opencode-rules/`, making them portable across different project locations.
@@ -43,6 +44,9 @@
   #               (e.g., [ "react" "fastapi" "django" ])
   #   extraInstructions: Optional list of additional instruction paths
   #                      (for custom rules outside standard locations)
+  #   forPi: Whether to also append rules to AGENTS.md for Pi agent (default: true)
+  #          Pi discovers AGENTS.md files by walking parent dirs + cwd and concatenates them.
+  #          When enabled, a delimited block is appended to (or created in) AGENTS.md.
   #
   # Returns:
   #   An attribute set containing:
@@ -83,6 +87,7 @@
     frameworks ? [],
     extraInstructions ? [],
     rulesDir ? ".opencode-rules",
+    forPi ? false,
   }: let
     # Build instructions list by mapping concerns, languages, frameworks to their file paths
     # All paths are relative to project root via the rulesDir symlink
@@ -97,11 +102,46 @@
       "$schema" = "https://opencode.ai/config.json";
       inherit instructions;
     };
+
+    # Pi rules content (concatenated markdown) — only computed when forPi is true
+    piRulesSection =
+      if forPi
+      then mkRulesMdSection {inherit agents languages concerns frameworks;}
+      else "";
+
+    # Bash snippet to append rules to AGENTS.md for Pi discovery.
+    # Uses HTML comment markers for idempotent updates:
+    #   - Removes any existing CODING-RULES block
+    #   - Appends the new block
+    #   - Creates AGENTS.md if it doesn't exist
+    # Note: Uses plain if-then-else instead of lib.optionalString to avoid
+    # forcing the `lib` argument (which may come from import <nixpkgs/lib>)
+    # when forPi is false.
+    piShellHook =
+      if forPi && piRulesSection != ""
+      then ''
+        # Pi agent: append coding rules to AGENTS.md
+        if [ -f AGENTS.md ]; then
+          # Remove existing coding-rules block (if any)
+          sed -i '/<!-- CODING-RULES:START -->/,/<!-- CODING-RULES:END -->/d' AGENTS.md
+          # Append new coding-rules block
+          cat >> AGENTS.md <<'PIRULES_EOF'
+        ${piRulesSection}
+        PIRULES_EOF
+        else
+          # Create AGENTS.md with just the coding rules
+          cat > AGENTS.md <<'PIRULES_EOF'
+        ${piRulesSection}
+        PIRULES_EOF
+        fi
+      ''
+      else "";
   in {
     inherit instructions;
 
     # Shell hook to set up rules in the project
     # Creates a symlink to the AGENTS rules directory and generates coding-rules.json
+    # Optionally appends rules to AGENTS.md for Pi agent discovery
     shellHook = ''
       # Create/update symlink to AGENTS rules directory
       ln -sfn ${agents}/rules ${rulesDir}
@@ -110,8 +150,73 @@
       cat > coding-rules.json <<'RULES_EOF'
       ${builtins.toJSON rulesConfig}
       RULES_EOF
+
+      ${piShellHook}
     '';
   };
+  # Concatenate selected rule files from the AGENTS repository into a single
+  # markdown string. Used by Pi (append to AGENTS.md) and could be used by
+  # other tools that don't support an instructions list.
+  #
+  # Args:
+  #   agents: Path to the AGENTS repository (non-flake input)
+  #   languages: Optional list of language-specific rules to include
+  #   concerns: Optional list of concern rules to include
+  #             Default: [ "coding-style" "naming" "documentation" "testing" "git-workflow" "project-structure" ]
+  #   frameworks: Optional list of framework-specific rules to include
+  #
+  # Returns: A single concatenated markdown string with all selected rules.
+  #
+  # Example:
+  #   concatRulesMd {
+  #     agents = inputs.agents;
+  #     languages = [ "python" ];
+  #     concerns = [ "coding-style" ];
+  #   }
+  #   # Returns: "\n# Coding Style\n\n...python rules...\n"
+  concatRulesMd = {
+    agents,
+    languages ? [],
+    concerns ? [
+      "coding-style"
+      "naming"
+      "documentation"
+      "testing"
+      "git-workflow"
+      "project-structure"
+    ],
+    frameworks ? [],
+  }: let
+    rulePaths =
+      (map (c: {kind = "concerns"; name = c;}) concerns)
+      ++ (map (l: {kind = "languages"; name = l;}) languages)
+      ++ (map (f: {kind = "frameworks"; name = f;}) frameworks);
+
+    readRule = rule: builtins.readFile "${agents}/rules/${rule.kind}/${rule.name}.md";
+    ruleContents = map readRule rulePaths;
+  in
+    lib.concatStringsSep "\n\n" ruleContents;
+
+  # Build a coding rules section suitable for appending to AGENTS.md.
+  # Wraps concatRulesMd output with a header and HTML comment markers
+  # for idempotent updates in project-level shellHooks.
+  #
+  # Args: Same as concatRulesMd
+  #
+  # Returns: A markdown string with start/end markers and a header.
+  mkRulesMdSection = args: let
+    content = concatRulesMd args;
+  in
+    if builtins.stringLength content == 0
+    then ""
+    else ''
+      <!-- CODING-RULES:START -->
+      # Coding Rules
+
+      ${content}
+      <!-- CODING-RULES:END -->
+    '';
+
 in {
-  inherit mkCodingRules;
+  inherit mkCodingRules concatRulesMd mkRulesMdSection;
 }

modules/home-manager/coding/agents/pi.nix

@@ -44,6 +44,60 @@ in
         '';
       };
 
+      codingRules = mkOption {
+        type = types.nullOr (types.submodule {
+          options = {
+            languages = mkOption {
+              type = types.listOf types.str;
+              default = [];
+              description = ''
+                Language-specific coding rules to include
+                (e.g. [ "python" "typescript" "nix" ]).
+                Rule files are read from the AGENTS repo's rules/languages/ directory.
+              '';
+            };
+
+            concerns = mkOption {
+              type = types.listOf types.str;
+              default = [
+                "coding-style"
+                "naming"
+                "documentation"
+                "testing"
+                "git-workflow"
+                "project-structure"
+              ];
+              description = ''
+                Concern rules to include from the AGENTS repo's rules/concerns/ directory.
+              '';
+            };
+
+            frameworks = mkOption {
+              type = types.listOf types.str;
+              default = [];
+              description = ''
+                Framework-specific coding rules to include
+                (e.g. [ "react" "fastapi" ]).
+                Rule files are read from the AGENTS repo's rules/frameworks/ directory.
+              '';
+            };
+          };
+        });
+        default = null;
+        description = ''
+          Coding rules to inject into ~/.pi/agent/AGENTS.md.
+          Rules are read from the AGENTS repository and appended as markdown sections.
+          Requires agentsInput to be set.
+        '';
+        example = literalExpression ''
+          {
+            languages = [ "python" "typescript" ];
+            concerns = [ "coding-style" "testing" ];
+            frameworks = [ "fastapi" ];
+          }
+        '';
+      };
+
       settings = mkOption {
         type = types.submodule {
           freeformType = types.attrsOf types.anything;
@@ -166,6 +220,12 @@ in
 
       piSettings = filterNulls cfg.settings;
 
+      # Coding rules config for renderForPi (only when both agentsInput and codingRules are set)
+      piCodingRules =
+        if cfg.agentsInput != null && cfg.codingRules != null
+        then cfg.codingRules // { agents = cfg.agentsInput; }
+        else null;
+
       # Rendered agents (only computed when agentsInput is set)
       rendered =
         if cfg.agentsInput != null
@@ -175,6 +235,7 @@ in
             canonical = cfg.agentsInput.lib.loadAgents;
             modelOverrides = cfg.modelOverrides;
             primaryAgent = cfg.primaryAgent;
+            codingRules = piCodingRules;
           }
         else null;
 

shells/coding.nix

@@ -0,0 +1,111 @@
+# AI coding agent development environment with coding rules
+# Sets up coding rules for OpenCode and Pi, plus useful companion tools.
+# Usage: nix develop .#coding
+#
+# To enable coding rules, add the agents input to your flake:
+#   agents = {
+#     url = "git+https://code.m3ta.dev/m3tam3re/AGENTS";
+#     flake = false;
+#   };
+{
+  pkgs,
+  lib ? pkgs.lib,
+  inputs ? null,
+  agents ? null,
+}: let
+  # Import the coding-rules library
+  m3taLib = import ../lib {lib = pkgs.lib;};
+
+  # Import custom packages
+  customPackages = import ../pkgs {inherit pkgs inputs;};
+
+  # Create rules configuration only if agents input is provided
+  rulesConfig = lib.optionalAttrs (agents != null) {
+    rules = m3taLib.coding-rules.mkCodingRules {
+      inherit agents;
+
+      # Languages relevant to this repository
+      languages = ["nix" "python" "shell"];
+
+      # Frameworks used in this repo
+      frameworks = ["n8n"];
+
+      # Standard concerns for development
+      concerns = [
+        "coding-style"
+        "naming"
+        "documentation"
+        "testing"
+        "git-workflow"
+        "project-structure"
+      ];
+
+      # Also append rules to AGENTS.md for Pi agent discovery
+      forPi = true;
+    };
+  };
+in
+  pkgs.mkShell {
+    name = "coding";
+
+    # Development tools
+    buildInputs = with pkgs;
+      [
+        # Task management for AI coding sessions
+        customPackages.td
+
+        # Companion tool for CLI agents (diffs, file trees, task management)
+        customPackages.sidecar
+
+        # Code analysis tools
+        customPackages.code2prompt
+
+        # Nix development tools (for this repo)
+        nil
+        alejandra
+        statix
+        deadnix
+      ];
+
+    shellHook = ''
+      echo "🤖 AI Coding Environment"
+      echo ""
+
+      ${
+        if (agents != null)
+        then ''
+          # Set up coding rules for OpenCode + Pi
+          ${rulesConfig.rules.shellHook}
+
+          echo "✅ Coding rules configured (OpenCode + Pi)"
+          echo "   Languages: nix, python, shell"
+          echo "   Frameworks: n8n"
+          echo "   Concerns: coding-style, naming, documentation, testing, git-workflow, project-structure"
+        ''
+        else ''
+          echo "⚠️  Coding rules not configured"
+          echo ""
+          echo "To enable, add the agents input to your flake.nix:"
+          echo ""
+          echo "  agents = {"
+          echo "    url = \"git+https://code.m3ta.dev/m3tam3re/AGENTS\";"
+          echo "    flake = false;"
+          echo "  };"
+        ''
+      }
+
+      echo ""
+      echo "Available tools:"
+      echo "  opencode              - AI coding agent"
+      echo "  td usage --new-session - View current tasks"
+      echo "  sidecar               - Companion tool (diffs, file trees, tasks)"
+      echo "  code2prompt           - Convert code to prompts"
+      echo ""
+      echo "Nix development tools:"
+      echo "  nix flake check    - Check flake validity"
+      echo "  nix fmt .          - Format Nix files"
+      echo "  statix check .     - Lint Nix files"
+      echo "  deadnix .          - Find dead code"
+      echo ""
+    '';
+  }

shells/default.nix

@@ -4,6 +4,7 @@
 {
   pkgs,
   inputs,
+  agents ? null,
 }: {
   # Default shell for working on this repository
   default = pkgs.mkShell {
@@ -32,5 +33,5 @@
   # Import all individual shell environments
   python = import ./python.nix {inherit pkgs inputs;};
   devops = import ./devops.nix {inherit pkgs inputs;};
-  opencode = import ./opencode.nix {inherit pkgs inputs;};
+  coding = import ./coding.nix {inherit pkgs inputs agents;};
 }

shells/opencode.nix

@@ -1,155 +0,0 @@
-# OpenCode development environment with AI coding rules
-# This shell demonstrates the mkCodingRules library provided by this repository
-# Usage: nix develop .#opencode
-#
-# To enable OpenCode rules, add the agents input to your flake:
-#   agents = {
-#     url = "git+https://code.m3ta.dev/m3tam3re/AGENTS";
-#     flake = false;
-#   };
-{
-  pkgs,
-  lib ? pkgs.lib,
-  inputs ? null,
-  agents ? null,
-}: let
-  # Import the coding-rules library
-  m3taLib = import ../lib {lib = pkgs.lib;};
-
-  # Import custom packages
-  customPackages = import ../pkgs {inherit pkgs inputs;};
-
-  # Create rules configuration only if agents input is provided
-  # This demonstrates how to use mkCodingRules in a real project
-  rulesConfig = lib.optionalAttrs (agents != null) {
-    rules = m3taLib.coding-rules.mkCodingRules {
-      # Pass the AGENTS repository path
-      inherit agents;
-
-      # Languages relevant to this repository
-      languages = ["python" "typescript" "nix"];
-
-      # Frameworks used in this repo
-      frameworks = ["n8n"];
-
-      # Standard concerns for development
-      concerns = [
-        "coding-style"
-        "naming"
-        "documentation"
-        "testing"
-        "git-workflow"
-        "project-structure"
-      ];
-    };
-  };
-in
-  pkgs.mkShell {
-    name = "opencode-dev";
-
-    # Development tools
-    buildInputs = with pkgs;
-      [
-        # OpenCode AI coding agent (if inputs are available)
-      ]
-      ++ lib.optionals (inputs != null)
-      [inputs.opencode.packages.${pkgs.stdenv.hostPlatform.system}.opencode]
-      ++ [
-        # Task management for AI coding sessions
-        customPackages.td
-
-        # Companion tool for CLI agents (diffs, file trees, task management)
-        customPackages.sidecar
-
-        # Code analysis tools
-        customPackages.code2prompt
-
-        # Nix development tools (for this repo)
-        nil
-        alejandra
-        statix
-        deadnix
-      ];
-
-    # Shell hook that sets up OpenCode rules
-    shellHook = ''
-      echo "🤖 OpenCode Development Environment"
-      echo ""
-      echo "This environment demonstrates the mkCodingRules library"
-      echo "provided by the m3ta-nixpkgs repository."
-      echo ""
-
-      ${
-        if (agents != null)
-        then ''
-          # Execute the OpenCode rules shellHook
-          ${rulesConfig.rules.shellHook}
-
-          echo "✅ OpenCode rules configured!"
-        ''
-        else ''
-          echo "⚠️  OpenCode rules not configured"
-          echo ""
-          echo "To enable OpenCode rules, add the agents input to your flake.nix:"
-          echo ""
-          echo "  inputs = {"
-          echo "    m3ta-nixpkgs.url = \"git+https://code.m3ta.dev/m3tam3re/nixpkgs\";"
-          echo "    agents = {"
-          echo "      url = \"git+https://code.m3ta.dev/m3tam3re/AGENTS\";"
-          echo "      flake = false;"
-          echo "    };"
-          echo "  };"
-          echo ""
-          echo "Then pass agents to the shell:"
-          echo "  opencode = import ./opencode.nix { inherit pkgs inputs agents; };"
-        ''
-      }
-
-      echo ""
-      echo "Available tools:"
-      echo "  opencode          - AI coding agent"
-      echo "  td usage --new-session - View current tasks"
-      echo "  sidecar           - Companion tool (diffs, file trees, tasks)"
-      echo "  code2prompt       - Convert code to prompts"
-      echo ""
-      echo "Nix development tools:"
-      echo "  nix flake check    - Check flake validity"
-      echo "  nix fmt .          - Format Nix files"
-      echo "  statix check .     - Lint Nix files"
-      echo "  deadnix .          - Find dead code"
-      echo ""
-      ${
-        if (agents == null)
-        then ''
-          echo "💡 Using mkCodingRules in your project:"
-          echo ""
-          echo "Add to your flake.nix:"
-          echo "  inputs = {"
-          echo "    m3ta-nixpkgs.url = \"git+https://code.m3ta.dev/m3tam3re/nixpkgs\";"
-          echo "    agents = {"
-          echo "      url = \"git+https://code.m3ta.dev/m3tam3re/AGENTS\";"
-          echo "      flake = false;"
-          echo "    };"
-          echo "  };"
-          echo ""
-          echo "  outputs = {self, nixpkgs, m3ta-nixpkgs, agents, ...}:"
-          echo "    let"
-          echo "      system = \"x86_64-linux\";"
-          echo "      pkgs = nixpkgs.legacyPackages.''${system};"
-          echo "      m3taLib = m3ta-nixpkgs.lib.''${system};"
-          echo "      rules = m3taLib.coding-rules.mkCodingRules {
-          echo "        inherit agents;"
-          echo "        languages = [\"python\" \"typescript\"];"
-          echo "        frameworks = [\"n8n\"];"
-          echo "      };"
-          echo "    in {"
-          echo "      devShells.''${system}.default = pkgs.mkShell {"
-          echo "        shellHook = rules.shellHook;"
-          echo "      };"
-          echo "    };"
-        ''
-        else ""
-      }
-      echo ""
-    '';
-  }

tests/lib/agents-test.nix

@@ -20,7 +20,67 @@ let
     result = agentsLib.loadCanonical {agentsInput = fakeInput;};
   in
     assert result == {test = {description = "test";};}; {result = "pass";};
+
+  # Test 3: renderForPi accepts codingRules parameter without error (null case)
+  # Verifies that passing codingRules = null produces the same result as omitting it.
+  # Uses a minimal fake canonical set instead of a real agents repo.
+  testPiNullCodingRules = let
+    pkgs = import <nixpkgs> {};
+    canonical = {
+      chiron = {
+        mode = "primary";
+        description = "Test primary agent";
+        display_name = "Chiron";
+        systemPrompt = "You are a test agent.";
+        permissions = {};
+      };
+    };
+    result = agentsLib.renderForPi {
+      inherit pkgs canonical;
+      codingRules = null;
+    };
+    agentsMd = builtins.readFile "${result}/AGENTS.md";
+    hasMarkers = builtins.match ".*CODING-RULES:START.*" agentsMd != null;
+  in
+    assert hasMarkers == false; {result = "pass";};
+
+  # Test 4: renderForPi with codingRules includes rules in AGENTS.md
+  # Uses the real AGENTS repo to read rule files (requires --impure or local path)
+  testPiWithCodingRules = let
+    agentsPath = /home/sascha.koenig/p/AI/AGENTS;
+    pkgs = import <nixpkgs> {};
+    canonical = {
+      chiron = {
+        mode = "primary";
+        description = "Test primary agent";
+        display_name = "Chiron";
+        systemPrompt = "You are a test agent.";
+        permissions = {};
+      };
+    };
+    result = agentsLib.renderForPi {
+      inherit pkgs canonical;
+      codingRules = {
+        agents = agentsPath;
+        concerns = ["coding-style"];
+        languages = [];
+        frameworks = [];
+      };
+    };
+    agentsMd = builtins.readFile "${result}/AGENTS.md";
+    hasStartMarker = builtins.match ".*CODING-RULES:START.*" agentsMd != null;
+    hasEndMarker = builtins.match ".*CODING-RULES:END.*" agentsMd != null;
+    hasCodingStyle = builtins.match ".*Coding Style.*" agentsMd != null;
+    # Also verify agent descriptions are still present
+    hasAgentInstructions = builtins.match ".*Agent Instructions.*" agentsMd != null;
+  in
+    assert hasStartMarker == true;
+    assert hasEndMarker == true;
+    assert hasCodingStyle == true;
+    assert hasAgentInstructions == true; {result = "pass";};
 in {
   unknown-tool-throws = testUnknownTool;
   load-canonical = testLoadCanonical;
+  pi-null-coding-rules = testPiNullCodingRules;
+  pi-with-coding-rules = testPiWithCodingRules;
 }

tests/lib/coding-rules-test.nix

@@ -37,8 +37,74 @@ let
   in
     assert hasSymlink;
     assert hasConfigGen; {result = "pass";};
+
+  # Test 4: forPi=false does not include AGENTS.md logic in shellHook
+  testForPiDisabled = let
+    rules = codingRulesLib.mkCodingRules {
+      agents = "/tmp/fake-agents";
+      forPi = false;
+    };
+    hook = rules.shellHook;
+    hasPiBlock = builtins.match ".*CODING-RULES:START.*" hook != null;
+  in
+    assert hasPiBlock == false; {result = "pass";};
+
+  # Test 5: forPi=true adds CODING-RULES markers to shellHook (when agents path has rules)
+  # Note: This test uses the real AGENTS repo at /home/sascha.koenig/p/AI/AGENTS
+  # It is only run when the path exists.
+  testForPiEnabled = let
+    agentsPath = /home/sascha.koenig/p/AI/AGENTS;
+    rules = codingRulesLib.mkCodingRules {
+      agents = agentsPath;
+      forPi = true;
+      concerns = ["coding-style"];
+      languages = [];
+      frameworks = [];
+    };
+    hook = rules.shellHook;
+    hasPiBlock = builtins.match ".*CODING-RULES:START.*" hook != null;
+    hasCodingStyle = builtins.match ".*Coding Style.*" hook != null;
+  in
+    assert hasPiBlock == true;
+    assert hasCodingStyle == true; {result = "pass";};
+
+  # Test 6: concatRulesMd produces concatenated markdown (with real agents path)
+  testConcatRulesMd = let
+    agentsPath = /home/sascha.koenig/p/AI/AGENTS;
+    md = codingRulesLib.concatRulesMd {
+      agents = agentsPath;
+      concerns = ["coding-style"];
+      languages = [];
+      frameworks = [];
+    };
+    hasHeader = builtins.match ".*Coding Style.*" md != null;
+    hasCritical = builtins.match ".*Critical Rules.*" md != null;
+  in
+    assert hasHeader == true;
+    assert hasCritical == true; {result = "pass";};
+
+  # Test 7: mkRulesMdSection wraps content with markers
+  testRulesMdSection = let
+    agentsPath = /home/sascha.koenig/p/AI/AGENTS;
+    section = codingRulesLib.mkRulesMdSection {
+      agents = agentsPath;
+      concerns = ["coding-style"];
+      languages = [];
+      frameworks = [];
+    };
+    hasStartMarker = builtins.match ".*CODING-RULES:START.*" section != null;
+    hasEndMarker = builtins.match ".*CODING-RULES:END.*" section != null;
+    hasHeader = builtins.match ".*# Coding Rules.*" section != null;
+  in
+    assert hasStartMarker == true;
+    assert hasEndMarker == true;
+    assert hasHeader == true; {result = "pass";};
 in {
   instructions-correct = testInstructions;
   default-rules-dir = testDefaultRulesDir;
   shell-hook = testShellHook;
+  forpi-disabled = testForPiDisabled;
+  forpi-enabled = testForPiEnabled;
+  concat-rules-md = testConcatRulesMd;
+  rules-md-section = testRulesMdSection;
 }