move hive-sh4re's harness_dir() into hive-agent-sock, drop the dev-fallback derivation

hive-agent-sock/src/lib.rs

@@ -18,6 +18,8 @@ use serde::{Deserialize, Serialize};
 
 use hive_sh4re::LooseEnd;
 
+pub mod paths;
+
 /// In-container path of the harness-served in-agent socket. The harness
 /// binds it on boot; the in-container producers dial it for todo ops.
 /// (Placeholder default — the harness + producers resolve the real path

hive-agent-sock/src/paths.rs

@@ -0,0 +1,30 @@
+//! In-container harness-directory resolution, shared by the harness
+//! itself and every producer daemon that dials the in-agent socket
+//! (`hive-bash-mcp`, and any future producer that writes artifacts
+//! alongside the harness's own state).
+
+use std::path::PathBuf;
+
+/// Base harness directory for the current agent. Reads
+/// `HYPERHIVE_HARNESS_DIR`, always injected by the meta flake's
+/// `systemd.globalEnvironment` for every in-container service
+/// (`nix/host-modules` — see `hive-c0re/src/meta.rs`'s per-agent
+/// environment block). Every process this crate's wire types serve
+/// (the harness, `hive-bash-daemon`, ...) runs under that same
+/// environment, so there is no legitimate runtime path where it's
+/// unset — a missing var means the container is misconfigured, not
+/// that a fallback derivation should paper over it.
+///
+/// # Panics
+///
+/// Panics if `HYPERHIVE_HARNESS_DIR` is not set. Deliberate: a wrong
+/// silently-derived path here means task files, sqlite stores, and the
+/// in-agent socket itself could resolve to the wrong directory — a
+/// loud crash at startup beats a quiet cross-agent path collision.
+#[must_use]
+pub fn harness_dir() -> PathBuf {
+    PathBuf::from(
+        std::env::var_os("HYPERHIVE_HARNESS_DIR")
+            .expect("HYPERHIVE_HARNESS_DIR must be set — the meta flake injects it for every in-container service; a missing value means the container's environment is misconfigured"),
+    )
+}

hive-agent/src/paths.rs

@@ -31,13 +31,13 @@ pub fn state_dir() -> PathBuf {
 /// (`hyperhive-events.sqlite`, `hyperhive-turn-stats.sqlite`,
 /// `hyperhive-model`) so they do not appear inside the agent-visible
 /// `/agents/{label}/state` tree. Delegates to the shared canonical
-/// resolver in `hive_sh4re::paths` so the harness + every out-of-process
-/// MCP daemon resolve this identically (reads `HYPERHIVE_HARNESS_DIR`,
-/// then a `harness/` sibling of `HYPERHIVE_STATE_DIR`, then
-/// `/agents/{HIVE_LABEL}/harness`).
+/// resolver in `hive_agent_sock::paths` so the harness + every
+/// out-of-process MCP daemon resolve this identically (reads
+/// `HYPERHIVE_HARNESS_DIR`, always injected by the meta flake — panics
+/// if it's unset rather than silently deriving a fallback path).
 #[must_use]
 pub fn harness_dir() -> PathBuf {
-    hive_sh4re::paths::harness_dir()
+    hive_agent_sock::paths::harness_dir()
 }
 
 /// Consolidated harness-local state db — todos + reminders + the questions

hive-bash-mcp/src/paths.rs

@@ -6,12 +6,12 @@
 use std::path::PathBuf;
 
 /// Base harness directory. Shared resolution lives in
-/// `hive_sh4re::paths::harness_dir` so the harness + every MCP daemon
-/// agree on the layout. Re-exported here as the base for the per-agent
-/// artifact paths below.
+/// `hive_agent_sock::paths::harness_dir` so the harness + every MCP
+/// daemon agree on the layout. Re-exported here as the base for the
+/// per-agent artifact paths below.
 #[must_use]
 pub fn harness_dir() -> PathBuf {
-    hive_sh4re::paths::harness_dir()
+    hive_agent_sock::paths::harness_dir()
 }
 
 /// Base directory for task files.

hive-sh4re/src/paths.rs

@@ -1,33 +1,8 @@
-//! Shared in-container filesystem-path resolution.
-//!
-//! Every process that runs inside an agent container - the harness plus
-//! the out-of-process MCP daemons (bash, matrix, ...) - must resolve the
-//! harness directory layout identically. These helpers live here so the
-//! resolution exists in exactly one place rather than being mirrored
-//! across crates.
-
-use std::path::PathBuf;
-
-/// Base harness directory for the current agent. Uses `HYPERHIVE_HARNESS_DIR`
-/// if set (injected by the hive-c0re meta flake after the harness/state
-/// split). For pre-split / dev deployments where it isn't set, falls back to
-/// a `harness/` sibling of `HYPERHIVE_STATE_DIR`, and finally to
-/// `/agents/{HIVE_LABEL}/harness` when neither dir env var is present — the
-/// shape the harness derives from its label alone.
-#[must_use]
-pub fn harness_dir() -> PathBuf {
-    if let Some(p) = std::env::var_os("HYPERHIVE_HARNESS_DIR") {
-        return PathBuf::from(p);
-    }
-    if let Some(state) = std::env::var_os("HYPERHIVE_STATE_DIR") {
-        let state_path = PathBuf::from(&state);
-        if let Some(parent) = state_path.parent() {
-            return parent.join("harness");
-        }
-    }
-    let label = std::env::var("HIVE_LABEL").unwrap_or_default();
-    PathBuf::from(format!("/agents/{label}/harness"))
-}
+//! Shared filename constants for in-container filesystem paths. Harness
+//! *directory* resolution itself lives in `hive_agent_sock::paths`
+//! (every in-container producer already depends on that crate for the
+//! socket wire types) — this module only keeps the bits that also need
+//! to be reachable from the host side (`hive-c0re`).
 
 /// File name of the pause marker inside the harness dir. Re-exported from
 /// `hive-priv-sock`, which owns the definition because hive-priv (root) is

nix/agent-modules/mcp.nix

@@ -261,9 +261,9 @@ in
         # injected via systemd.globalEnvironment by the meta flake
         # (set to /agents/<name>/harness and /agents/<name>/state
         # respectively). The daemon uses these to derive its task +
-        # loose-ends dir paths; without them it falls back to deriving
-        # harness/ as a sibling of state/, which produces the same
-        # value but is less robust if the two vars ever diverge.
+        # loose-ends dir paths; `hive_agent_sock::paths::harness_dir`
+        # panics loudly if HYPERHIVE_HARNESS_DIR is unset rather than
+        # deriving a fallback, since every service here always gets it.
       };
       serviceConfig = {
         ExecStart = "${config.hyperhive.packages.hive-bash-daemon}/bin/hive-bash-daemon --http 127.0.0.1:${toString config.hyperhive.mcp.bashHttpPort}";