diff --git a/README.md b/README.md
index 0d74bba..7b1d4aa 100644
--- a/README.md
+++ b/README.md
@@ -227,6 +227,7 @@ version = "1.0.0"
 description = "Web development MCP stack"
 authors = ["yourname"]
 keywords = ["web", "browser", "git"]
+min_tool_version = "0.4.0"    # optional: minimum weave version required
 
 [[servers]]
 name = "puppeteer"
@@ -247,6 +248,7 @@ Packs can also declare:
 - **Slash commands / skills** — copied into `~/.claude/commands/` or `~/.codex/skills/`
 - **System prompt fragments** — appended to `CLAUDE.md` / `GEMINI.md` / `AGENTS.md` between tagged delimiters
 - **Settings fragments** — deep-merged into Claude Code and Gemini CLI JSON settings; merged as top-level keys in Codex CLI's TOML config
+- **Minimum tool version** — `min_tool_version` rejects install on older weave versions
 - **Environment variable declarations** — written as `${VAR}` references, never values
 
 > [!IMPORTANT]
diff --git a/src/core/install.rs b/src/core/install.rs
index 12d81ad..1174792 100644
--- a/src/core/install.rs
+++ b/src/core/install.rs
@@ -17,6 +17,27 @@ use crate::core::resolver::Resolver;
 use crate::core::store::Store;
 use crate::error::{Result, WeaveError};
 
+/// Check that the current weave version satisfies the pack's `min_tool_version`.
+///
+/// Returns `Ok(())` if the pack has no `min_tool_version` requirement or if the
+/// current version meets or exceeds it.  Returns `Err(IncompatibleToolVersion)`
+/// otherwise.  This check runs in both normal and dry-run paths so users always
+/// see version incompatibilities early.
+pub fn check_min_tool_version(pack: &Pack) -> Result<()> {
+    if let Some(ref min_version) = pack.min_tool_version {
+        let current = semver::Version::parse(env!("CARGO_PKG_VERSION"))
+            .expect("CARGO_PKG_VERSION is always valid semver");
+        if current < *min_version {
+            return Err(WeaveError::IncompatibleToolVersion {
+                pack_name: pack.name.clone(),
+                required: min_version.clone(),
+                current,
+            });
+        }
+    }
+    Ok(())
+}
+
 /// Returns the names of adapters that a pack would target, based on the pack's
 /// `targets` flags and which adapters are installed.
 pub fn target_adapters(pack: &Pack, adapters: &[Box<dyn CliAdapter>]) -> Vec<String> {
@@ -124,6 +145,7 @@ pub fn install_from_registry(
                         reason: "registry release missing pack.toml".to_string(),
                     })?;
             let pack = Pack::from_toml(pack_toml, &std::path::PathBuf::from("pack.toml"))?;
+            check_min_tool_version(&pack)?;
 
             // Validate manifest matches what was resolved, same as the normal path.
             if pack.name != *name {
@@ -177,6 +199,7 @@ pub fn install_from_registry(
 
         // Load the pack manifest
         let pack = Pack::load(&pack_dir)?;
+        check_min_tool_version(&pack)?;
 
         // Validate that the manifest matches what was resolved.
         if pack.name != *name {
@@ -303,6 +326,7 @@ pub fn install_local(
     dry_run: bool,
 ) -> Result<LocalInstallResult> {
     let pack = Pack::load(path)?;
+    check_min_tool_version(&pack)?;
 
     let name = &pack.name;
     let version = &pack.version;
@@ -612,6 +636,86 @@ mod tests {
     use std::collections::HashSet;
     use std::path::PathBuf;
 
+    /// Helper: build a Pack from TOML for testing.
+    fn pack_from_toml(toml: &str) -> Pack {
+        Pack::from_toml(toml, &PathBuf::from("test.toml")).unwrap()
+    }
+
+    // ── min_tool_version tests ──────────────────────────────────────────────
+
+    #[test]
+    fn check_min_tool_version_higher_than_current_errors() {
+        let toml = r#"
+[pack]
+name = "future-pack"
+version = "1.0.0"
+description = "Needs a future weave"
+authors = ["tester"]
+min_tool_version = "99.0.0"
+"#;
+        let pack = pack_from_toml(toml);
+        let result = check_min_tool_version(&pack);
+        assert!(
+            result.is_err(),
+            "should fail when min_tool_version exceeds current"
+        );
+        let err_msg = result.unwrap_err().to_string();
+        assert!(
+            err_msg.contains("99.0.0"),
+            "error should mention required version: {err_msg}"
+        );
+        assert!(
+            err_msg.contains("please upgrade"),
+            "error should tell user to upgrade: {err_msg}"
+        );
+        assert!(
+            err_msg.contains("future-pack"),
+            "error should mention pack name: {err_msg}"
+        );
+    }
+
+    #[test]
+    fn check_min_tool_version_equal_to_current_succeeds() {
+        let current_version = env!("CARGO_PKG_VERSION");
+        let toml = format!(
+            r#"
+[pack]
+name = "current-pack"
+version = "1.0.0"
+description = "Needs exactly the current weave"
+authors = ["tester"]
+min_tool_version = "{current_version}"
+"#
+        );
+        let pack = pack_from_toml(&toml);
+        let result = check_min_tool_version(&pack);
+        assert!(
+            result.is_ok(),
+            "should succeed when min_tool_version equals current: {:?}",
+            result.err()
+        );
+    }
+
+    #[test]
+    fn check_min_tool_version_none_succeeds() {
+        let toml = r#"
+[pack]
+name = "no-min-pack"
+version = "1.0.0"
+description = "No min_tool_version specified"
+authors = ["tester"]
+"#;
+        let pack = pack_from_toml(toml);
+        let result = check_min_tool_version(&pack);
+        assert!(
+            result.is_ok(),
+            "should succeed when min_tool_version is absent: {:?}",
+            result.err()
+        );
+    }
+
+    // ── apply_to_adapters rollback tests ────────────────────────────────────
+
     /// A mock adapter that succeeds on apply.
     struct SucceedAdapter {
         adapter_name: &'static str,
@@ -736,25 +840,18 @@ mod tests {
 
         let (applied, errors) = apply_to_adapters(&resolved, &adapters, &options);
 
-        // applied should be empty because rollback occurred
         assert!(
             applied.is_empty(),
             "expected empty applied list after rollback, got: {applied:?}"
         );
-
-        // Should have errors: one for the failure, one for the rollback
         assert!(
             errors.len() >= 2,
             "expected at least 2 errors (failure + rollback), got: {errors:?}"
         );
-
-        // The first error should be from the failing adapter
         assert!(
             errors[0].contains("Gemini CLI"),
             "first error should mention failing adapter: {errors:?}"
         );
-
-        // The second error should mention the rollback
         assert!(
             errors[1].contains("rolled back"),
             "second error should mention rollback: {errors:?}"
@@ -774,9 +871,7 @@ mod tests {
 
         let (applied, errors) = apply_to_adapters(&resolved, &adapters, &options);
 
-        // applied should be empty — the first adapter failed before any succeeded
         assert!(applied.is_empty());
-        // Only one error — the failure itself, no rollbacks needed
         assert_eq!(errors.len(), 1);
         assert!(errors[0].contains("Gemini CLI"));
     }
diff --git a/src/core/use_profile.rs b/src/core/use_profile.rs
index acda5f2..1b2ba70 100644
--- a/src/core/use_profile.rs
+++ b/src/core/use_profile.rs
@@ -243,8 +243,20 @@ pub fn switch(
                 &installed.version,
                 Some(&installed.source),
             ) {
-                Ok(pack) => crate::core::install::target_adapters(&pack, adapters),
-                Err(_) => adapters.iter().map(|a| a.name().to_string()).collect(),
+                Ok(pack) => {
+                    crate::core::install::check_min_tool_version(&pack)?;
+                    crate::core::install::target_adapters(&pack, adapters)
+                }
+                Err(_) => {
+                    // Pack not in local cache — version compatibility and target
+                    // adapters cannot be verified in dry-run mode.
+                    log::warn!(
+                        "pack {}@{} not cached locally — dry-run preview may be approximate",
+                        installed.name,
+                        installed.version
+                    );
+                    adapters.iter().map(|a| a.name().to_string()).collect()
+                }
             };
             apply_result.applied_adapters = target_names;
         } else {
@@ -265,6 +277,8 @@ pub fn switch(
                 }
             };
 
+            crate::core::install::check_min_tool_version(&pack)?;
+
             let resolved = ResolvedPack {
                 pack,
                 source: installed.source.clone(),
diff --git a/src/error.rs b/src/error.rs
index 004f08c..896bce9 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -25,6 +25,15 @@ pub enum WeaveError {
     #[error("pack '{name}' is not installed — {hint}")]
     NotInstalled { name: String, hint: String },
 
+    #[error(
+        "pack '{pack_name}' requires weave {required} or later, but this is weave {current} — please upgrade"
+    )]
+    IncompatibleToolVersion {
+        pack_name: String,
+        required: semver::Version,
+        current: semver::Version,
+    },
+
     // Install/update validation errors
     #[error(
         "pack manifest {field} '{actual}' does not match resolved {field} '{expected}' — the archive may be corrupt or tampered"
diff --git a/tests/e2e/cli_install.rs b/tests/e2e/cli_install.rs
index 3888b62..31f6906 100644
--- a/tests/e2e/cli_install.rs
+++ b/tests/e2e/cli_install.rs
@@ -580,3 +580,36 @@ async fn remove_http_server_cleans_up() {
         "remote-api should be removed from ~/.claude.json after pack removal"
     );
 }
+
+// ── min_tool_version enforcement ──────────────────────────────────────────────
+
+#[cfg(not(target_os = "windows"))]
+#[tokio::test]
+async fn install_local_pack_with_incompatible_min_tool_version() {
+    let env = TestEnv::new().await;
+
+    // Create a local pack that requires a far-future weave version.
+    let pack_dir = env.project_dir.path().join("future-pack");
+    std::fs::create_dir_all(&pack_dir).unwrap();
+    std::fs::write(
+        pack_dir.join("pack.toml"),
+        r#"[pack]
+name = "future-pack"
+version = "0.1.0"
+description = "requires future weave"
+authors = ["tester"]
+min_tool_version = "99.0.0"
+"#,
+    )
+    .unwrap();
+
+    env.weave_cmd()
+        .args(["install", "./future-pack"])
+        .assert()
+        .failure()
+        .stderr(
+            predicate::str::contains("99.0.0")
+                .and(predicate::str::contains("please upgrade"))
+                .from_utf8(),
+        );
+}