diff --git a/README.md b/README.md
index f1f3bc4..ae9e935 100644
--- a/README.md
+++ b/README.md
@@ -53,20 +53,38 @@ scripts/g1p_smoke.sh  # vectord state survives kill+restart via storaged
 scripts/g2_smoke.sh   # embed → vectord add → search round-trip
 ```
 
-Run them all in any order:
+Or run the full gate via the task runner (see below):
 ```
-for s in scripts/{d1,d2,d3,d4,d5,d6,g1,g1p,g2}_smoke.sh; do "$s" || break; done
+just verify     # vet + tests + 9 smokes; ~33s wall
 ```
 
+## Task runner
+
+```
+just                 # show available recipes
+just verify          # full Sprint 0 gate (vet + tests + 9 smokes)
+just smoke <day>     # single smoke (d1..d6, g1, g1p, g2)
+just doctor          # check cold-start deps; --json for CI
+just install-hooks   # install pre-push hook that runs just verify
+```
+
+After a fresh clone, run `just install-hooks` once so `git push` is
+gated on the same green chain that ran here. Hook lives in
+`.git/hooks/pre-push` (not tracked; recreated by the recipe).
+
 ## Cold-start dependencies
 
 - Go 1.25+ at `/usr/local/go/bin` (arrow-go pulled the 1.25 floor)
 - `gcc` + `libc-dev` for the DuckDB cgo binding (ADR-001 §1.1)
+- `just` task runner (`apt install just` on Debian 13+)
 - MinIO running on `:9000` with bucket `lakehouse-go-primary`
 - Ollama running on `:11434` with `nomic-embed-text` loaded (G2)
 - `/etc/lakehouse/secrets-go.toml` with `[s3.primary]` credentials
   (storaged + queryd both read this)
 
+`just doctor` probes all of the above and reports the fix command
+for each missing dep. CI / scripts can use `just doctor --json`.
+
 ## Layout
 
 ```
diff --git a/justfile b/justfile
new file mode 100644
index 0000000..560a9a5
--- /dev/null
+++ b/justfile
@@ -0,0 +1,103 @@
+# golangLAKEHOUSE — task runner.
+#
+# Sprint 0 acceptance gate (R-004): smokes are no longer documentation
+# only — `just verify` is the single command that runs vet + tests +
+# the 9 smokes. The pre-push hook calls this; CI calls this; reviewers
+# call this. One source of truth.
+#
+# Usage:
+#   just                  # alias for `just --list`
+#   just verify           # vet + test + all 9 smokes (full gate)
+#   just smoke <day>      # single smoke (d1..d6, g1, g1p, g2)
+#   just smoke-all        # all 9 smokes only
+#   just doctor           # dependency probe
+#   just fmt / vet / test / build
+
+# Go lives at /usr/local/go/bin per ADR-001 §1.x; prepend so every
+# recipe sees it without depending on the parent shell's PATH.
+export PATH := "/usr/local/go/bin:" + env('PATH', '')
+
+# Default recipe shows the menu so `just` alone is a discoverable entry point.
+default:
+    @just --list
+
+# Full Sprint 0 gate: vet + tests + 9 smokes. Pre-push hook calls this.
+verify: vet test smoke-all
+    @echo ""
+    @echo "[verify] PASS — go vet + go test + 9 smokes all green"
+
+# Static analysis. Runs first so we fail fast on syntax / shape issues.
+vet:
+    @echo "[vet] go vet ./..."
+    @go vet ./...
+
+# Go unit tests, short mode. Excludes hardware-in-the-loop tags.
+test:
+    @echo "[test] go test -short -count=1 ./..."
+    @go test -short -count=1 ./...
+
+# Format Go source. Idempotent; CI can run with --check via `just fmt-check`.
+fmt:
+    @gofmt -w cmd internal scripts
+
+# Verify formatting without modifying. Non-zero exit means run `just fmt`.
+fmt-check:
+    @diff -u <(echo -n) <(gofmt -d cmd internal scripts)
+
+# Build every binary into bin/. Mirrors what each smoke does internally.
+build:
+    @echo "[build] go build -o bin/ ./cmd/..."
+    @go build -o bin/ ./cmd/...
+
+# Single smoke. Day is the suffix before _smoke.sh — d1, d2, …, g2.
+smoke day:
+    @bash scripts/{{day}}_smoke.sh
+
+# All 9 smokes in dependency order. Halts on first failure.
+smoke-all:
+    #!/usr/bin/env bash
+    set -euo pipefail
+    for day in d1 d2 d3 d4 d5 d6 g1 g1p g2; do
+        printf "[smoke-all] %s ... " "$day"
+        SECONDS=0
+        if bash "scripts/${day}_smoke.sh" >/tmp/smoke_${day}.log 2>&1; then
+            printf "PASS (%ss)\n" "$SECONDS"
+        else
+            printf "FAIL (%ss)\n" "$SECONDS"
+            echo ""
+            echo "  last 20 lines of /tmp/smoke_${day}.log:"
+            tail -20 "/tmp/smoke_${day}.log" | sed 's/^/    /'
+            exit 1
+        fi
+    done
+
+# Dependency probe. Add --json for machine-readable output.
+doctor *args:
+    @bash scripts/doctor.sh {{args}}
+
+# Install pre-push hook so `git push` runs `just verify` first.
+install-hooks:
+    #!/usr/bin/env bash
+    set -euo pipefail
+    HOOK=".git/hooks/pre-push"
+    cat > "$HOOK" <<'HOOK'
+    #!/usr/bin/env bash
+    # golangLAKEHOUSE pre-push hook (managed by `just install-hooks`).
+    # Runs the Sprint 0 gate before letting commits leave this machine.
+    set -e
+    cd "$(git rev-parse --show-toplevel)"
+    echo "[pre-push] running just verify ..."
+    if ! just verify; then
+        echo ""
+        echo "[pre-push] FAIL — push aborted. Fix the gate or use --no-verify (NOT recommended)."
+        exit 1
+    fi
+    HOOK
+    chmod +x "$HOOK"
+    echo "[install-hooks] $HOOK installed and executable"
+
+# Clean built binaries + smoke logs. Does NOT touch reports/ or data/.
+clean:
+    @rm -rf bin/
+    @rm -f /tmp/smoke_*.log
+    @echo "[clean] bin/ removed, smoke logs cleared"
diff --git a/scripts/doctor.sh b/scripts/doctor.sh
new file mode 100755
index 0000000..2bb1cce
--- /dev/null
+++ b/scripts/doctor.sh
@@ -0,0 +1,147 @@
+#!/usr/bin/env bash
+# Dependency probe for golangLAKEHOUSE.
+# Sprint 0 / S0.1 — surfaces every cold-start dep as a structured
+# checklist. With --json, emits machine-readable shape for CI.
+#
+# Exit 0 = all green. Exit 1 = at least one missing dep.
+
+set -uo pipefail
+
+# Mode: text (default) or json
+JSON=0
+for arg in "$@"; do
+    case "$arg" in
+        --json) JSON=1 ;;
+        -h|--help)
+            echo "Usage: $0 [--json]"
+            echo "  Probes Go, gcc, MinIO, Ollama, secrets-go.toml."
+            echo "  Default output is human-readable; --json emits structured findings."
+            exit 0 ;;
+    esac
+done
+
+# Findings accumulator. Each entry: <name>|<status>|<detail>|<fix>
+# status ∈ {ok, missing, wrong-version, unreachable}
+findings=()
+
+probe() {
+    findings+=("$1|$2|$3|$4")
+}
+
+# 1. Go ≥1.25 (arrow-go pulled the floor up — see ADR-001 §1.x)
+if go_path="$(command -v go 2>/dev/null)"; then
+    go_ver="$(go version 2>/dev/null | awk '{print $3}' | sed 's/^go//')"
+    case "$go_ver" in
+        1.25*|1.26*|1.27*) probe "go" "ok" "$go_ver at $go_path" "" ;;
+        *)                 probe "go" "wrong-version" "$go_ver at $go_path (need ≥1.25)" \
+                                  "curl -L https://go.dev/dl/go1.25.0.linux-amd64.tar.gz | sudo tar -C /usr/local -xz" ;;
+    esac
+else
+    probe "go" "missing" "not in PATH" \
+          "curl -L https://go.dev/dl/go1.25.0.linux-amd64.tar.gz | sudo tar -C /usr/local -xz && export PATH=\$PATH:/usr/local/go/bin"
+fi
+
+# 2. gcc (DuckDB cgo binding per ADR-001 §1.1)
+if gcc_path="$(command -v gcc 2>/dev/null)"; then
+    gcc_ver="$(gcc --version 2>/dev/null | head -1 | awk '{print $NF}')"
+    probe "gcc" "ok" "$gcc_ver at $gcc_path" ""
+else
+    probe "gcc" "missing" "not in PATH" "sudo apt install -y build-essential"
+fi
+
+# 3. MinIO at :9000 with bucket lakehouse-go-primary
+if curl -sf --max-time 2 http://localhost:9000/minio/health/live >/dev/null 2>&1; then
+    # bucket existence — use mc if available, else fall back to noting it
+    if command -v mc >/dev/null 2>&1; then
+        if mc ls local/lakehouse-go-primary >/dev/null 2>&1; then
+            probe "minio" "ok" "live at :9000, bucket lakehouse-go-primary present" ""
+        else
+            probe "minio" "missing" "live at :9000 but bucket lakehouse-go-primary absent" \
+                  "mc mb local/lakehouse-go-primary"
+        fi
+    else
+        probe "minio" "ok" "live at :9000 (bucket presence not verified — install mc to check)" ""
+    fi
+else
+    probe "minio" "unreachable" "no /minio/health/live response on :9000" \
+          "sudo systemctl start minio  # or restart"
+fi
+
+# 4. Ollama at :11434 with nomic-embed-text loaded (G2 default model)
+if ollama_resp="$(curl -sf --max-time 3 http://localhost:11434/api/tags 2>/dev/null)"; then
+    if echo "$ollama_resp" | grep -q '"name":"nomic-embed-text:latest"'; then
+        probe "ollama" "ok" "live at :11434, nomic-embed-text loaded" ""
+    else
+        probe "ollama" "missing" "live at :11434 but nomic-embed-text not loaded" \
+              "ollama pull nomic-embed-text"
+    fi
+else
+    probe "ollama" "unreachable" "no /api/tags response on :11434" \
+          "sudo systemctl start ollama"
+fi
+
+# 5. /etc/lakehouse/secrets-go.toml
+if [ -f /etc/lakehouse/secrets-go.toml ]; then
+    if [ -r /etc/lakehouse/secrets-go.toml ]; then
+        if grep -q '\[s3.primary\]' /etc/lakehouse/secrets-go.toml 2>/dev/null; then
+            probe "secrets" "ok" "/etc/lakehouse/secrets-go.toml present, contains [s3.primary]" ""
+        else
+            probe "secrets" "missing" "/etc/lakehouse/secrets-go.toml missing [s3.primary] section" \
+                  "edit /etc/lakehouse/secrets-go.toml to add [s3.primary] with access_key_id + secret_access_key"
+        fi
+    else
+        probe "secrets" "missing" "/etc/lakehouse/secrets-go.toml exists but unreadable by current user" \
+              "sudo chmod 0644 /etc/lakehouse/secrets-go.toml  # or run as the user that can read it"
+    fi
+else
+    probe "secrets" "missing" "/etc/lakehouse/secrets-go.toml not present" \
+          "sudo install -m 0644 /dev/stdin /etc/lakehouse/secrets-go.toml < secrets-go.toml.example"
+fi
+
+# Summarize
+exit_code=0
+for f in "${findings[@]}"; do
+    case "$(echo "$f" | cut -d'|' -f2)" in
+        ok) ;;
+        *) exit_code=1 ;;
+    esac
+done
+
+if [ "$JSON" -eq 1 ]; then
+    printf '{\n'
+    printf '  "deps": [\n'
+    last=$((${#findings[@]} - 1))
+    for i in "${!findings[@]}"; do
+        IFS='|' read -r name status detail fix <<< "${findings[$i]}"
+        printf '    {"name":"%s","status":"%s","detail":"%s","fix":"%s"}' \
+               "$name" "$status" \
+               "$(echo "$detail" | sed 's/"/\\"/g')" \
+               "$(echo "$fix" | sed 's/"/\\"/g')"
+        [ "$i" -lt "$last" ] && printf ','
+        printf '\n'
+    done
+    printf '  ],\n'
+    printf '  "ok": %s\n' "$([ $exit_code -eq 0 ] && echo true || echo false)"
+    printf '}\n'
+else
+    echo "[doctor] dependency probe:"
+    for f in "${findings[@]}"; do
+        IFS='|' read -r name status detail fix <<< "$f"
+        case "$status" in
+            ok)              printf "  ✓ %-7s  %s\n" "$name" "$detail" ;;
+            missing)         printf "  ✗ %-7s  %s\n" "$name" "$detail"
+                             [ -n "$fix" ] && printf "      fix: %s\n" "$fix" ;;
+            wrong-version)   printf "  ⚠ %-7s  %s\n" "$name" "$detail"
+                             [ -n "$fix" ] && printf "      fix: %s\n" "$fix" ;;
+            unreachable)     printf "  ✗ %-7s  %s\n" "$name" "$detail"
+                             [ -n "$fix" ] && printf "      fix: %s\n" "$fix" ;;
+        esac
+    done
+    if [ "$exit_code" -eq 0 ]; then
+        echo "[doctor] all dependencies green"
+    else
+        echo "[doctor] one or more dependencies need attention"
+    fi
+fi
+
+exit "$exit_code"