diff --git a/modules/home-manager/coding/opencode.nix b/modules/home-manager/coding/opencode.nix
new file mode 100644
index 0000000..6420abb
--- /dev/null
+++ b/modules/home-manager/coding/opencode.nix
@@ -0,0 +1,156 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+with lib; let
+  cfg = config.coding.opencode;
+in {
+  options.coding.opencode = {
+    enable = mkEnableOption "opencode AI coding assistant";
+
+    agentsInput = mkOption {
+      type = types.nullOr types.anything;
+      default = null;
+      description = ''
+        The `agents` flake input (your personal AGENTS repo).
+        When set, skills, context, commands, prompts and the agents.json
+        are all symlinked from this input.
+      '';
+    };
+
+    externalSkills = mkOption {
+      type = types.listOf (types.submodule {
+        options = {
+          src = mkOption {
+            type = types.anything;
+            description = "Flake input pointing to a skills repository root.";
+          };
+          skillsDir = mkOption {
+            type = types.str;
+            default = "skills";
+            description = ''
+              Subdirectory inside src that contains skill folders.
+            '';
+          };
+          selectSkills = mkOption {
+            type = types.nullOr (types.listOf types.str);
+            default = null;
+            description = ''
+              List of skill names to cherry-pick from this source.
+              null means include every skill found in skillsDir.
+            '';
+          };
+        };
+      });
+      default = [];
+      description = ''
+        External skill sources passed to mkOpencodeSkills.
+        Each entry maps directly to an element of the externalSkills
+        list accepted by the AGENTS flake's lib.mkOpencodeSkills.
+      '';
+      example = literalExpression ''
+        [
+          { src = inputs.skills-anthropic; selectSkills = [ "claude-api" ]; }
+          { src = inputs.skills-vercel; }
+        ]
+      '';
+    };
+
+    ohMyOpencodeSettings = mkOption {
+      type = types.attrs;
+      default = {};
+      description = ''
+        Attributes merged (via recursiveUpdate) on top of the default
+        oh-my-opencode.json. Use this to set provider-specific model
+        assignments per machine.
+      '';
+      example = literalExpression ''
+        {
+          agents.sisyphus.model = "anthropic/claude-opus-4-5";
+          categories.ultrabrain.model = "anthropic/claude-opus-4-5";
+        }
+      '';
+    };
+
+    extraSettings = mkOption {
+      type = types.attrs;
+      default = {};
+      description = ''
+        Extra opencode settings merged (via mkMerge) into
+        programs.opencode.settings. Use this to add provider
+        configuration that is specific to a machine or organisation.
+      '';
+      example = literalExpression ''
+        {
+          provider.anthropic = {
+            name = "Anthropic";
+            models."claude-opus-4-5" = { limit.context = 200000; };
+          };
+        }
+      '';
+    };
+  };
+
+  config = mkIf cfg.enable {
+    # --- Skills (merged from personal AGENTS repo + optional external skills) ---
+    xdg.configFile."opencode/skills" = mkIf (cfg.agentsInput != null) {
+      source = cfg.agentsInput.lib.mkOpencodeSkills {
+        inherit pkgs;
+        customSkills = "${cfg.agentsInput}/skills";
+        externalSkills = map (entry:
+          {inherit (entry) src skillsDir;}
+          // optionalAttrs (entry.selectSkills != null) {inherit (entry) selectSkills;}
+        ) cfg.externalSkills;
+      };
+    };
+
+    # --- Static config dirs from AGENTS repo ---
+    xdg.configFile."opencode/context" = mkIf (cfg.agentsInput != null) {
+      source = "${cfg.agentsInput}/context";
+    };
+    xdg.configFile."opencode/commands" = mkIf (cfg.agentsInput != null) {
+      source = "${cfg.agentsInput}/commands";
+    };
+    xdg.configFile."opencode/prompts" = mkIf (cfg.agentsInput != null) {
+      source = "${cfg.agentsInput}/prompts";
+    };
+
+    # --- Core opencode program settings ---
+    programs.opencode = {
+      enable = true;
+      enableMcpIntegration = true;
+      settings = mkMerge [
+        {
+          theme = "opencode";
+          plugin = ["oh-my-opencode"];
+          formatter = {
+            alejandra = {
+              command = ["alejandra" "-q" "-"];
+              extensions = [".nix"];
+            };
+          };
+        }
+        # Load agents.json from AGENTS repo when available
+        (mkIf (cfg.agentsInput != null) {
+          agent = builtins.fromJSON (builtins.readFile "${cfg.agentsInput}/agents/agents.json");
+        })
+        # Machine/org-specific provider config
+        cfg.extraSettings
+      ];
+    };
+
+    # --- oh-my-opencode plugin config ---
+    # Base defaults (no models — those must be set per machine via ohMyOpencodeSettings)
+    home.file.".config/opencode/oh-my-opencode.json".text = builtins.toJSON (
+      recursiveUpdate
+      {
+        "$schema" = "https://raw.githubusercontent.com/code-yeongyu/oh-my-opencode/master/assets/oh-my-opencode.schema.json";
+        google_auth = false;
+        disabled_mcps = ["context7" "websearch"];
+      }
+      cfg.ohMyOpencodeSettings
+    );
+  };
+}