diff --git a/README.md b/README.md
index a10d36e1..4ecbbe7b 100644
--- a/README.md
+++ b/README.md
@@ -8,7 +8,7 @@
 
 CodeGraph parses your codebase with tree-sitter, stores every symbol, edge,
 and file in a local SQLite database (FTS5), and exposes the graph to
-AI agents — Claude Code, Cursor, Codex CLI, opencode, Hermes — over the
+AI agents — Claude Code, Cursor, Codex CLI, opencode, Hermes, Antigravity CLI — over the
 Model Context Protocol (MCP).
 
 Agents that consult the graph instead of grepping the filesystem make
@@ -23,7 +23,7 @@ Agents that consult the graph instead of grepping the filesystem make
 - **Local.** Index lives in `.codegraph/db.sqlite` next to your code. Nothing
   leaves the machine.
 - **Multi-agent.** A single `codegraph install` configures Claude Code, Cursor,
-  Codex, opencode and Hermes in one go.
+  Codex, opencode, Hermes and Antigravity CLI in one go.
 - **Live.** Built-in file watcher keeps the index in sync while the MCP server
   serves your agent.
 
@@ -136,7 +136,7 @@ crates/
   codegraph-graph/      callers / callees / impact radius (BFS)
   codegraph-context/    markdown + JSON context formatters
   codegraph-mcp/        hand-rolled JSON-RPC 2.0 server over stdio
-  codegraph-installer/  Claude / Cursor / Codex / opencode / Hermes targets
+  codegraph-installer/  Claude / Cursor / Codex / opencode / Hermes / Antigravity targets
   codegraph/            CLI binary (clap) + file watcher (notify)
 ```
 
diff --git a/crates/codegraph-installer/src/lib.rs b/crates/codegraph-installer/src/lib.rs
index acdcda4f..8cd231d3 100644
--- a/crates/codegraph-installer/src/lib.rs
+++ b/crates/codegraph-installer/src/lib.rs
@@ -43,6 +43,7 @@ pub trait AgentTarget: Send + Sync {
 
 pub fn registry() -> Vec<Arc<dyn AgentTarget>> {
     vec![
+        Arc::new(targets::antigravity::AntigravityTarget),
         Arc::new(targets::claude::ClaudeTarget),
         Arc::new(targets::cursor::CursorTarget),
         Arc::new(targets::codex::CodexTarget),
diff --git a/crates/codegraph-installer/src/targets/antigravity.rs b/crates/codegraph-installer/src/targets/antigravity.rs
new file mode 100644
index 00000000..09de2267
--- /dev/null
+++ b/crates/codegraph-installer/src/targets/antigravity.rs
@@ -0,0 +1,193 @@
+use crate::{
+    targets::jsonutil, AgentTarget, DetectStatus, InstallOpts, InstallReport, INSTRUCTIONS_MD,
+};
+use anyhow::Result;
+use camino::Utf8PathBuf;
+use serde_json::{json, Value};
+
+pub struct AntigravityTarget;
+
+impl AntigravityTarget {
+    fn config_paths(&self, _opts: &InstallOpts) -> Vec<Utf8PathBuf> {
+        let mut paths = Vec::new();
+        if let Some(home) = dirs::home_dir() {
+            if let Ok(p) = Utf8PathBuf::from_path_buf(home.join(".gemini").join("antigravity-cli").join("mcp_config.json")) {
+                paths.push(p);
+            }
+            if let Ok(p) = Utf8PathBuf::from_path_buf(home.join(".gemini").join("config").join("mcp_config.json")) {
+                paths.push(p);
+            }
+        }
+        if let Some(config) = dirs::config_dir() {
+            if let Ok(p) = Utf8PathBuf::from_path_buf(config.join("gemini").join("antigravity-cli").join("mcp_config.json")) {
+                paths.push(p);
+            }
+            if let Ok(p) = Utf8PathBuf::from_path_buf(config.join("gemini").join("config").join("mcp_config.json")) {
+                paths.push(p);
+            }
+        }
+        paths
+    }
+    
+    fn instructions_paths(&self, _opts: &InstallOpts) -> Vec<Utf8PathBuf> {
+        let mut paths = Vec::new();
+        if let Some(home) = dirs::home_dir() {
+            if let Ok(p) = Utf8PathBuf::from_path_buf(home.join(".gemini").join("antigravity-cli").join("ANTIGRAVITY.md")) {
+                paths.push(p);
+            }
+            if let Ok(p) = Utf8PathBuf::from_path_buf(home.join(".gemini").join("config").join("ANTIGRAVITY.md")) {
+                paths.push(p);
+            }
+        }
+        if let Some(config) = dirs::config_dir() {
+            if let Ok(p) = Utf8PathBuf::from_path_buf(config.join("gemini").join("antigravity-cli").join("ANTIGRAVITY.md")) {
+                paths.push(p);
+            }
+            if let Ok(p) = Utf8PathBuf::from_path_buf(config.join("gemini").join("config").join("ANTIGRAVITY.md")) {
+                paths.push(p);
+            }
+        }
+        paths
+    }
+}
+
+impl AgentTarget for AntigravityTarget {
+    fn id(&self) -> &'static str {
+        "antigravity"
+    }
+    fn label(&self) -> &'static str {
+        "Antigravity CLI"
+    }
+
+    fn detect(&self, opts: &InstallOpts) -> DetectStatus {
+        let paths = self.config_paths(opts);
+        if paths.is_empty() {
+            return DetectStatus::NotFound;
+        }
+
+        let mut all_not_found = true;
+        let mut any_configured = false;
+
+        for p in &paths {
+            if !p.exists() {
+                if let Some(parent) = p.parent() {
+                    if parent.exists() {
+                        all_not_found = false;
+                    }
+                }
+            } else {
+                all_not_found = false;
+                if let Ok(v) = jsonutil::read_or_default(p) {
+                    if v.pointer("/mcpServers/codegraph").is_some() {
+                        any_configured = true;
+                    }
+                }
+            }
+        }
+
+        if any_configured {
+            DetectStatus::AlreadyConfigured
+        } else if all_not_found {
+            DetectStatus::NotFound
+        } else {
+            DetectStatus::Found
+        }
+    }
+
+    fn install(&self, opts: &InstallOpts) -> Result<InstallReport> {
+        let paths = self.config_paths(opts);
+        if paths.is_empty() {
+            return Err(anyhow::anyhow!("no settings paths"));
+        }
+
+        let mut written = Vec::new();
+        let mcp_entry = json!({
+            "command": opts.binary_path.as_str(),
+            "args": serve_args(opts),
+        });
+
+        for settings in &paths {
+            if let Some(parent) = settings.parent() {
+                if !parent.exists() {
+                    std::fs::create_dir_all(parent.as_std_path())?;
+                }
+            }
+                
+            let mut v = jsonutil::read_or_default(settings)?;
+            let mut changed = false;
+            {
+                if !v.is_object() {
+                    v = Value::Object(Default::default());
+                }
+                let obj = v.as_object_mut().unwrap();
+                let servers = obj
+                    .entry("mcpServers")
+                    .or_insert_with(|| Value::Object(Default::default()));
+                let servers = servers
+                    .as_object_mut()
+                    .ok_or_else(|| anyhow::anyhow!("mcpServers not an object"))?;
+                if servers.get("codegraph") != Some(&mcp_entry) {
+                    servers.insert("codegraph".into(), mcp_entry.clone());
+                    changed = true;
+                }
+            }
+
+            if changed {
+                jsonutil::write_pretty(settings, &v)?;
+                written.push(settings.clone());
+            }
+        }
+
+        for md in self.instructions_paths(opts) {
+            let want = INSTRUCTIONS_MD;
+            let existing = std::fs::read_to_string(md.as_std_path()).ok();
+            if existing.as_deref() != Some(want) {
+                if let Some(parent) = md.parent() {
+                    std::fs::create_dir_all(parent.as_std_path())?;
+                }
+                std::fs::write(md.as_std_path(), want)?;
+                written.push(md);
+            }
+        }
+
+        if written.is_empty() {
+            Ok(InstallReport::Unchanged)
+        } else {
+            Ok(InstallReport::Installed(written))
+        }
+    }
+
+    fn uninstall(&self, opts: &InstallOpts) -> Result<InstallReport> {
+        let mut removed = Vec::new();
+        for settings in self.config_paths(opts) {
+            if settings.exists() {
+                let mut v = jsonutil::read_or_default(&settings)?;
+                let mut changed = false;
+                if let Some(servers) = v.pointer_mut("/mcpServers").and_then(|s| s.as_object_mut())
+                {
+                    if servers.remove("codegraph").is_some() {
+                        changed = true;
+                    }
+                }
+                if changed {
+                    jsonutil::write_pretty(&settings, &v)?;
+                    removed.push(settings);
+                }
+            }
+        }
+        if removed.is_empty() {
+            Ok(InstallReport::Unchanged)
+        } else {
+            Ok(InstallReport::Updated(removed))
+        }
+    }
+}
+
+fn serve_args(opts: &InstallOpts) -> Value {
+    let mut args = vec![Value::String("serve".into()), Value::String("--mcp".into())];
+    if let Some(root) = &opts.project_root {
+        args.push(Value::String("--path".into()));
+        args.push(Value::String(root.to_string()));
+    }
+    Value::Array(args)
+}
diff --git a/crates/codegraph-installer/src/targets/mod.rs b/crates/codegraph-installer/src/targets/mod.rs
index c6993371..6a4933e5 100644
--- a/crates/codegraph-installer/src/targets/mod.rs
+++ b/crates/codegraph-installer/src/targets/mod.rs
@@ -1,3 +1,4 @@
+pub mod antigravity;
 pub mod claude;
 pub mod codex;
 pub mod cursor;