diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 7c1cc036..b7a750d9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -161,6 +161,185 @@ jobs:
       - name: Run tests
         run: cargo test --all-features
 
+  # ──────────────────────────────────────────────────────────────
+  # Interface boot smoke: build each changed Rust worker from source,
+  # boot it against a live engine exactly as the registry-publish flow
+  # does, and assert its interface is collectable & non-empty. This is
+  # the PR-time guard for the class of failure that broke publish in
+  # #104 (database/v0.2.6): the worker compiled and passed the 2s
+  # liveness check but then crashed building its SQLite pool because
+  # the default `sqlite:./data/iii.db` parent dir was missing — so
+  # `Collect worker interface` timed out at release time, never on PRs.
+  # Scoped to Rust workers (the binary-deploy bucket where this lives);
+  # building from source means a clean checkout with no `data/` dir,
+  # which is precisely the condition that triggered the crash.
+  # ──────────────────────────────────────────────────────────────
+  interface-smoke:
+    name: "${{ matrix.worker }}: interface boot smoke"
+    needs: discover
+    if: needs.discover.outputs.rust != '[]'
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    strategy:
+      fail-fast: false
+      matrix:
+        worker: ${{ fromJSON(needs.discover.outputs.rust) }}
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+
+      - run: pip install --quiet pyyaml
+
+      - name: Rewrite SSH to HTTPS for public deps
+        run: git config --global url."https://github.com/".insteadOf "ssh://git@github.com/"
+
+      - uses: dtolnay/rust-toolchain@stable
+
+      - uses: Swatinem/rust-cache@v2
+        with:
+          workspaces: ${{ matrix.worker }} -> target
+
+      # Workers that embed a Vite SPA into the binary (e.g. console) have a
+      # build.rs that shells out to pnpm. Pre-build the dist so `cargo build`
+      # short-circuits it — mirrors the `rust` job above.
+      - name: Setup pnpm (workers with bundled web/)
+        if: hashFiles(format('{0}/web/package.json', matrix.worker)) != ''
+        uses: pnpm/action-setup@v4
+        with:
+          version: 10
+
+      - name: Setup Node (workers with bundled web/)
+        if: hashFiles(format('{0}/web/package.json', matrix.worker)) != ''
+        uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: 'pnpm'
+          cache-dependency-path: ${{ matrix.worker }}/web/pnpm-lock.yaml
+
+      - name: Pre-build SPA bundle
+        if: hashFiles(format('{0}/web/package.json', matrix.worker)) != ''
+        working-directory: ${{ matrix.worker }}/web
+        run: |
+          pnpm install --frozen-lockfile
+          pnpm build
+
+      # Build with default features so we boot the same artifact that ships
+      # in the GitHub Release (`_rust-binary.yml` builds default features).
+      - name: Build worker binary
+        working-directory: ${{ matrix.worker }}
+        run: cargo build
+
+      - name: Install iii CLI + engine
+        env:
+          VERSION: '0.17.0'
+        run: |
+          set -euo pipefail
+          curl -fsSL https://install.iii.dev/iii/main/install.sh -o /tmp/install-iii.sh
+          sh /tmp/install-iii.sh
+          {
+            echo "$HOME/.local/bin"
+            echo "$HOME/.iii/bin"
+          } >> "$GITHUB_PATH"
+          export PATH="$HOME/.local/bin:$HOME/.iii/bin:$PATH"
+          iii --version
+
+      - name: Start III engine
+        run: |
+          set -euo pipefail
+          printf 'workers: []\n' > config.yaml
+          iii --config config.yaml --no-update-check > iii-engine.log 2>&1 &
+          echo "$!" > iii-engine.pid
+
+          for _ in {1..60}; do
+            if ! kill -0 "$(cat iii-engine.pid)" 2>/dev/null; then
+              echo "::error::iii engine exited before becoming ready"
+              cat iii-engine.log
+              exit 1
+            fi
+            if iii trigger 'engine::workers::list' --json '{}' >/dev/null 2>&1; then
+              exit 0
+            fi
+            sleep 1
+          done
+
+          echo "::error::iii engine did not become ready"
+          cat iii-engine.log || true
+          exit 1
+
+      - name: Snapshot engine baselines
+        run: |
+          set -euo pipefail
+          iii trigger 'engine::triggers::list' --json '{"include_internal": false}' \
+            > trigger-types-baseline.json
+          iii trigger 'engine::workers::list' --json '{}' > workers-baseline.json
+
+      - name: Start worker from source
+        env:
+          WORKER: ${{ matrix.worker }}
+        run: |
+          set -euo pipefail
+          # Resolve the cargo bin name the same way the publish flow does
+          # (iii.worker.yaml `bin:`, falling back to the worker name).
+          bin=$(WORKER="$WORKER" python3 -c 'import os, sys, pathlib; sys.path.insert(0, ".github/scripts"); import _lib; m = _lib.read_iii_worker_yaml(pathlib.Path(os.environ["WORKER"])); print(m.bin or m.name)')
+
+          worker_log="worker-$WORKER.log"
+          # Run from inside the worker dir — this is what makes a relative
+          # default db path (sqlite:./data/iii.db) resolve against a clean
+          # checkout with no data/ dir, reproducing the publish boot exactly.
+          pushd "$WORKER" >/dev/null
+          echo "Starting local worker: (cd $WORKER && ./target/debug/$bin)"
+          "./target/debug/$bin" > "../$worker_log" 2>&1 &
+          echo "$!" > ../worker.pid
+          popd >/dev/null
+
+          sleep 2
+          if ! kill -0 "$(cat worker.pid)" 2>/dev/null; then
+            echo "::error::$WORKER exited before interface collection"
+            cat "$worker_log" || true
+            exit 1
+          fi
+
+      - name: Collect worker interface
+        env:
+          WORKER: ${{ matrix.worker }}
+        run: |
+          set -euo pipefail
+          python3 .github/scripts/collect_worker_interface.py \
+            --worker "$WORKER" \
+            --out worker-interface.json \
+            --wait-seconds 120 \
+            --trigger-types-baseline trigger-types-baseline.json \
+            --workers-baseline workers-baseline.json
+
+      - name: Assert worker interface was collected
+        run: |
+          set -euo pipefail
+          python3 .github/scripts/collect_worker_interface.py \
+            --assert-non-empty --assert-file worker-interface.json
+
+      - name: Dump logs on failure
+        if: failure()
+        run: |
+          echo "::group::iii engine log"
+          tail -n 200 iii-engine.log || true
+          echo "::endgroup::"
+          echo "::group::worker log"
+          tail -n 200 "worker-${{ matrix.worker }}.log" || true
+          echo "::endgroup::"
+
+      - name: Stop processes
+        if: always()
+        run: |
+          if [[ -f worker.pid ]]; then
+            kill "$(cat worker.pid)" 2>/dev/null || true
+          fi
+          if [[ -f iii-engine.pid ]]; then
+            kill "$(cat iii-engine.pid)" 2>/dev/null || true
+          fi
+
   # ──────────────────────────────────────────────────────────────
   # Node per-worker lint (biome) + test
   # ──────────────────────────────────────────────────────────────
diff --git a/database/Cargo.lock b/database/Cargo.lock
index 80e21e38..69dc9110 100644
--- a/database/Cargo.lock
+++ b/database/Cargo.lock
@@ -596,7 +596,7 @@ checksum = "a4ae5f15dda3c708c0ade84bfee31ccab44a3da4f88015ed22f63732abe300c8"
 
 [[package]]
 name = "database"
-version = "0.2.5"
+version = "0.2.7"
 dependencies = [
  "anyhow",
  "async-trait",
diff --git a/database/Cargo.toml b/database/Cargo.toml
index b87ccc04..2c72efff 100644
--- a/database/Cargo.toml
+++ b/database/Cargo.toml
@@ -2,7 +2,7 @@
 
 [package]
 name = "database"
-version = "0.2.6"
+version = "0.2.7"
 edition = "2021"
 publish = false
 
diff --git a/database/src/pool/sqlite.rs b/database/src/pool/sqlite.rs
index 933627a0..3a3ebe3d 100644
--- a/database/src/pool/sqlite.rs
+++ b/database/src/pool/sqlite.rs
@@ -37,6 +37,23 @@ impl SqlitePool {
         let manager = if path == ":memory:" || path.starts_with(":memory:") {
             SqliteConnectionManager::memory()
         } else {
+            // SQLite opens (and, with the default flags, creates) the database
+            // *file*, but it will NOT create missing parent directories — a
+            // fresh `sqlite:./data/iii.db` boot where `./data` does not yet
+            // exist fails at pool-build time with `unable to open database
+            // file`. r2d2 eagerly opens connections in `build()`, so this
+            // surfaces as a hard startup crash (exactly what broke the registry
+            // publish CI: the worker is launched from a clean checkout with no
+            // `data/` dir). Create the parent dir up front so the default
+            // config — and any relative/nested sqlite path — boots cleanly.
+            if let Some(parent) = parent_dir_to_create(path) {
+                std::fs::create_dir_all(&parent).map_err(|e| DbError::ConfigError {
+                    message: format!(
+                        "sqlite: could not create parent directory {}: {e}",
+                        parent.display()
+                    ),
+                })?;
+            }
             SqliteConnectionManager::file(path)
         };
         let inner = R2Pool::builder()
@@ -78,6 +95,28 @@ impl SqlitePool {
     }
 }
 
+/// Compute the parent directory that must exist before SQLite can open
+/// `path`, or `None` when there is nothing to create. Pure (does no IO) so
+/// the path-parsing rules can be unit-tested without touching the filesystem.
+///
+/// Returns `None` for:
+///   - in-memory databases (`:memory:`, `file::memory:?cache=shared`),
+///   - bare filenames (`iii.db`) whose parent is the current directory.
+///
+/// Handles `file:` URI forms and strips any `?query` suffix (e.g.
+/// `file:./data/iii.db?mode=rwc`) before extracting the parent.
+fn parent_dir_to_create(path: &str) -> Option<std::path::PathBuf> {
+    let without_scheme = path.strip_prefix("file:").unwrap_or(path);
+    let file_part = without_scheme.split('?').next().unwrap_or(without_scheme);
+    if file_part.is_empty() || file_part.contains(":memory:") {
+        return None;
+    }
+    match std::path::Path::new(file_part).parent() {
+        Some(parent) if !parent.as_os_str().is_empty() => Some(parent.to_path_buf()),
+        _ => None,
+    }
+}
+
 /// `r2d2::get_timeout` returns one error type (`r2d2::Error`) for both
 /// "no connection became free in time" and "the underlying connection
 /// manager kept failing to open a connection until we hit the timeout".
@@ -194,4 +233,67 @@ mod tests {
             other => panic!("expected PoolTimeout, got {other:?}"),
         }
     }
+
+    #[test]
+    fn parent_dir_to_create_skips_in_memory_forms() {
+        assert_eq!(parent_dir_to_create(":memory:"), None);
+        assert_eq!(parent_dir_to_create("file::memory:?cache=shared"), None);
+    }
+
+    #[test]
+    fn parent_dir_to_create_skips_bare_filename() {
+        // No directory component → SQLite creates the file in the CWD.
+        assert_eq!(parent_dir_to_create("iii.db"), None);
+        assert_eq!(parent_dir_to_create(""), None);
+    }
+
+    #[test]
+    fn parent_dir_to_create_returns_nested_dir() {
+        assert_eq!(
+            parent_dir_to_create("./data/iii.db"),
+            Some(std::path::PathBuf::from("./data"))
+        );
+        assert_eq!(
+            parent_dir_to_create("/var/lib/iii/db.sqlite"),
+            Some(std::path::PathBuf::from("/var/lib/iii"))
+        );
+    }
+
+    #[test]
+    fn parent_dir_to_create_handles_file_uri_and_query() {
+        assert_eq!(
+            parent_dir_to_create("file:./data/iii.db?mode=rwc"),
+            Some(std::path::PathBuf::from("./data"))
+        );
+    }
+
+    /// Regression for the registry-publish crash: a fresh boot with the
+    /// default `sqlite:./data/iii.db` config (and no pre-existing `data/`
+    /// dir) must succeed. r2d2 opens connections eagerly in `build()`, so
+    /// before the fix `SqlitePool::new` returned
+    /// `unable to open database file` and the worker died on startup, making
+    /// interface collection time out. `SqlitePool::new` now creates the
+    /// missing parent directory, so the pool builds and a query runs.
+    #[tokio::test(flavor = "multi_thread")]
+    async fn file_pool_creates_missing_parent_dir() {
+        let tmp = tempfile::tempdir().unwrap();
+        // Point at a *nested* path that does not exist yet, mirroring the
+        // default `./data/iii.db` shape (two missing levels for good measure).
+        let db_path = tmp.path().join("data").join("nested").join("iii.db");
+        assert!(!db_path.parent().unwrap().exists());
+        let url = format!("sqlite:{}", db_path.display());
+
+        let pool = SqlitePool::new(&url, &PoolConfig::default())
+            .expect("pool should build after creating the missing parent dir");
+        assert!(db_path.parent().unwrap().exists());
+
+        let conn = pool.acquire().await.unwrap();
+        let result: i64 = tokio::task::spawn_blocking(move || {
+            conn.with(|c| c.query_row("SELECT 1", [], |row| row.get(0)))
+                .unwrap()
+        })
+        .await
+        .unwrap();
+        assert_eq!(result, 1);
+    }
 }
diff --git a/database/tests/integration.rs b/database/tests/integration.rs
index c08d84f3..b7d40274 100644
--- a/database/tests/integration.rs
+++ b/database/tests/integration.rs
@@ -186,3 +186,61 @@ async fn apply_config_updates_list_snapshot() {
 fn binary_name_matches_manifest() {
     assert_eq!(database::worker_name(), "database");
 }
+
+/// Regression for the registry-publish crash (`unable to open database file:
+/// ./data/iii.db`). This drives the *startup* dispatch path the worker uses at
+/// boot — `pool::build` (called by `main.rs` via `configuration::build_pools`)
+/// — for a file-backed sqlite database whose parent directory does not exist
+/// yet, mirroring the default `sqlite:./data/iii.db` config running from a
+/// clean checkout. The pool must build (creating the parent dir) and serve a
+/// connection rather than dying on startup.
+#[tokio::test(flavor = "multi_thread")]
+async fn build_pool_creates_missing_sqlite_parent_dir() {
+    let tmp = tempfile::tempdir().unwrap();
+    let db_path = tmp.path().join("data").join("iii.db");
+    assert!(!db_path.parent().unwrap().exists());
+
+    let url = format!("sqlite:{}", db_path.display());
+    let yaml = format!("databases:\n  primary:\n    url: \"{url}\"\n");
+    let cfg = WorkerConfig::from_yaml(&yaml).unwrap();
+
+    let mut pools = HashMap::new();
+    for (name, db) in &cfg.databases {
+        let p = pool::build(name, db)
+            .await
+            .expect("startup pool build must create the missing parent dir");
+        pools.insert(name.clone(), p);
+    }
+    assert!(db_path.parent().unwrap().exists());
+
+    let st = AppState {
+        pools: Arc::new(RwLock::new(pools)),
+        config: Arc::new(RwLock::new(cfg)),
+        handles: Arc::new(HandleRegistry::new()),
+        transactions: TxRegistry::new(),
+        log: Logger::new(),
+    };
+
+    // The freshly-created on-disk db is usable end-to-end.
+    execute::handle(
+        &st,
+        serde_json::from_value::<ExecuteReq>(json!({
+            "db": "primary",
+            "sql": "CREATE TABLE t (id INTEGER PRIMARY KEY)"
+        }))
+        .unwrap(),
+    )
+    .await
+    .unwrap();
+    let r = query::handle(
+        &st,
+        serde_json::from_value::<QueryReq>(json!({
+            "db": "primary",
+            "sql": "SELECT count(*) AS n FROM t"
+        }))
+        .unwrap(),
+    )
+    .await
+    .unwrap();
+    assert_eq!(r.row_count, 1);
+}
diff --git a/harness/README.md b/harness/README.md
index 758e9cbb..1c15bff6 100644
--- a/harness/README.md
+++ b/harness/README.md
@@ -49,7 +49,7 @@ Rust workers (`shell`, `iii-directory`) and engine builtins (`state::*`, `stream
 
 1. Install iii: `curl -fsSL https://install.iii.dev/iii/main/install.sh | sh`
 2. Verify the install: `iii --version`
-3. Add the harness and console workers: `iii worker add harness console`
+3. Add the harness and console workers: `iii worker add harness console coder`
 4. Start the engine: `iii --config config.yaml`
 5. Open the [console](https://workers.iii.dev/workers/console) at `http://127.0.0.1:3113`