meta: emit nixpkgs follows for agents that declare it (closes #355)

hive-c0re/src/meta.rs

@@ -239,6 +239,68 @@ fn render_flake(
     context_window_tokens: &std::collections::HashMap<String, u64>,
     agents: &[AgentSpec],
 ) -> String {
+    render_flake_with_lookup(
+        hyperhive_flake,
+        dashboard_port,
+        operator_pronouns,
+        context_window_tokens,
+        agents,
+        agent_canonical_inputs,
+    )
+}
+
+/// Canonical inputs meta knows how to dedup. An agent that declares one
+/// of these as a top-level input in its own `flake.nix` will get a
+/// `follows = "<name>"` line emitted in meta — collapsing the
+/// otherwise-separate-but-identical `nixpkgs_N` nodes into a single
+/// meta-level reference (#355).
+const CANONICAL_INPUTS: &[&str] = &["nixpkgs", "nixpkgs-unstable"];
+
+/// Read an agent's applied `flake.lock` and return the subset of
+/// `CANONICAL_INPUTS` it declares as direct (root-level) inputs.
+/// Returns an empty vec when the lock is missing or unparsable —
+/// safe degradation, the worst case is no dedup for that agent.
+fn agent_canonical_inputs(name: &str) -> Vec<&'static str> {
+    let path = std::path::PathBuf::from(format!("{APPLIED_ROOT}/{name}/flake.lock"));
+    let Ok(raw) = std::fs::read_to_string(&path) else {
+        return Vec::new();
+    };
+    let Ok(json) = serde_json::from_str::<serde_json::Value>(&raw) else {
+        return Vec::new();
+    };
+    let Some(nodes) = json.get("nodes").and_then(|v| v.as_object()) else {
+        return Vec::new();
+    };
+    let Some(root_name) = json.get("root").and_then(|v| v.as_str()) else {
+        return Vec::new();
+    };
+    let Some(root_inputs) = nodes
+        .get(root_name)
+        .and_then(|n| n.get("inputs"))
+        .and_then(|v| v.as_object())
+    else {
+        return Vec::new();
+    };
+    CANONICAL_INPUTS
+        .iter()
+        .copied()
+        .filter(|canon| root_inputs.contains_key(*canon))
+        .collect()
+}
+
+/// Inner render helper accepting a lookup fn so tests can stub the
+/// agent flake-lock introspection.
+fn render_flake_with_lookup<F>(
+    hyperhive_flake: &str,
+    dashboard_port: u16,
+    operator_pronouns: &str,
+    context_window_tokens: &std::collections::HashMap<String, u64>,
+    agents: &[AgentSpec],
+    lookup: F,
+) -> String
+where
+    F: Fn(&str) -> Vec<&'static str>,
+{
     use std::fmt::Write as _;
     let mut out = String::new();
     out.push_str("{\n  description = \"hyperhive deployed agents\";\n  inputs = {\n");
@@ -263,6 +325,21 @@ fn render_flake(
             "    agent-{}.url = \"git+file://{APPLIED_ROOT}/{}\";",
             spec.name, spec.name,
         );
+        // For each canonical input the agent declares in its own
+        // `flake.nix` (detected by reading its applied `flake.lock`),
+        // emit `inputs.agent-<name>.inputs.<canon>.follows = "<canon>"`.
+        // Collapses three otherwise-separate-but-identical nixpkgs
+        // nodes (root + agent-bitburner's + agent-dmatrix's) into one
+        // (closes #355). Skipped silently for agents that don't
+        // declare the input — emitting follows on a non-existent
+        // input would error at `nix flake lock` time.
+        for canon in lookup(&spec.name) {
+            let _ = writeln!(
+                out,
+                "    agent-{}.inputs.{canon}.follows = \"{canon}\";",
+                spec.name,
+            );
+        }
     }
     out.push_str("  };\n  outputs =\n    { self, hyperhive, ... }@inputs:\n    let\n");
     // Free-text operator string — escape backslash + double-quote so a
@@ -387,6 +464,68 @@ mod tests {
         assert!(out.contains("hyperhive.inputs.nixpkgs.follows = \"nixpkgs\""));
         assert!(out.contains("hyperhive.inputs.nixpkgs-unstable.follows = \"nixpkgs-unstable\""));
     }
+
+    #[test]
+    fn render_flake_emits_follows_for_agents_declaring_nixpkgs() {
+        // Stub lookup: pretend `bitburner` declares `nixpkgs` at its
+        // root, while `argus` has no canonical inputs at all.
+        let lookup = |name: &str| -> Vec<&'static str> {
+            match name {
+                "bitburner" => vec!["nixpkgs"],
+                "dmatrix" => vec!["nixpkgs", "nixpkgs-unstable"],
+                _ => vec![],
+            }
+        };
+        let out = render_flake_with_lookup(
+            "github:example/hyperhive",
+            8000,
+            "she/her",
+            &std::collections::HashMap::new(),
+            &[
+                sample_spec("argus", false, 9001),
+                sample_spec("bitburner", false, 9002),
+                sample_spec("dmatrix", false, 9003),
+            ],
+            lookup,
+        );
+        // bitburner declares nixpkgs → follows emitted.
+        assert!(
+            out.contains("agent-bitburner.inputs.nixpkgs.follows = \"nixpkgs\""),
+            "missing bitburner nixpkgs follows:\n{out}"
+        );
+        // dmatrix declares both → both follows emitted.
+        assert!(out.contains("agent-dmatrix.inputs.nixpkgs.follows = \"nixpkgs\""));
+        assert!(
+            out.contains("agent-dmatrix.inputs.nixpkgs-unstable.follows = \"nixpkgs-unstable\"")
+        );
+        // argus declares neither → no follows emitted for it. Asserting
+        // ABSENCE is the important bit: emitting a follows on a
+        // non-existent input errors at `nix flake lock` time.
+        assert!(
+            !out.contains("agent-argus.inputs.nixpkgs"),
+            "argus shouldn't have nixpkgs follows:\n{out}"
+        );
+    }
+
+    #[test]
+    fn render_flake_skips_canonical_follows_when_lookup_returns_empty() {
+        let out = render_flake_with_lookup(
+            "github:example/hyperhive",
+            8000,
+            "she/her",
+            &std::collections::HashMap::new(),
+            &[sample_spec("alice", false, 9001)],
+            |_| Vec::new(),
+        );
+        // No agent-side follows when the lookup reports nothing
+        // declared — protects agents whose flake.lock can't be read
+        // (missing / unparsable) from being broken by a follows on a
+        // non-existent input.
+        assert!(
+            !out.contains("agent-alice.inputs."),
+            "alice shouldn't have any inputs follows:\n{out}"
+        );
+    }
 }
 
 async fn git_is_clean(dir: &Path) -> Result<bool> {