diff --git a/crates/source-map-gen/src/regen_main.rs b/crates/source-map-gen/src/regen_main.rs
index 586676c5..c93aa8e7 100644
--- a/crates/source-map-gen/src/regen_main.rs
+++ b/crates/source-map-gen/src/regen_main.rs
@@ -1,4 +1,4 @@
-//! CLI binary that regenerates `.huskies/source-map.json` from scratch.
+//! CLI binary for manual regeneration of `.huskies/source-map.json`.
 //!
 //! Usage: `source-map-regen [--project-root <path>]`
 //!
@@ -6,8 +6,10 @@
 //! extracts public item signatures, and writes a fresh sorted JSON map. The output
 //! is byte-identical across runs on the same source tree (deterministic).
 //!
-//! Intended to be called from the pre-commit quality gate (`script/check`) so that
-//! every commit captures an accurate, stale-entry-free snapshot of the source map.
+//! The pre-commit gate (`script/check`) no longer calls this binary directly — map
+//! regeneration is now inlined into the coder spawn path (`local_prompt.rs`) so every
+//! agent session starts with a fresh snapshot. This binary is kept as an escape hatch
+//! for manual out-of-band regeneration (e.g. after bulk refactors outside the pipeline).
 
 use source_map_gen::regenerate_source_map;
 use std::path::Path;
diff --git a/script/check b/script/check
index a0eefb24..b9fd69cd 100755
--- a/script/check
+++ b/script/check
@@ -13,9 +13,5 @@ cargo fmt --manifest-path "$PROJECT_ROOT/Cargo.toml" --all --check
 echo "=== Running cargo clippy ==="
 cargo clippy --manifest-path "$PROJECT_ROOT/Cargo.toml" --workspace --all-targets -- -D warnings
 
-echo "=== Regenerating source map ==="
-cargo run --manifest-path "$PROJECT_ROOT/Cargo.toml" -p source-map-gen --bin source-map-regen --quiet -- --project-root "$PROJECT_ROOT"
-git -C "$PROJECT_ROOT" add .huskies/source-map.json
-
 echo "=== Checking doc coverage on changed files ==="
 cargo run --manifest-path "$PROJECT_ROOT/Cargo.toml" -p source-map-gen --bin source-map-check --quiet -- --worktree "$PROJECT_ROOT" --base master
diff --git a/server/src/agents/local_prompt.rs b/server/src/agents/local_prompt.rs
index e848617e..ee9867d0 100644
--- a/server/src/agents/local_prompt.rs
+++ b/server/src/agents/local_prompt.rs
@@ -60,6 +60,13 @@ pub fn read_project_local_prompt(project_root: &Path) -> Option<String> {
         sections.push((rel_path, trimmed.to_string()));
     }
 
+    // Regenerate the source map so agents always start from a fresh snapshot.
+    // Failure is non-fatal: log it and fall through to whatever is on disk.
+    let map_path = project_root.join(SOURCE_MAP_REL);
+    if let Err(e) = source_map_gen::regenerate_source_map(project_root, &map_path) {
+        crate::slog!("[agents] source-map regen failed (non-fatal): {}", e);
+    }
+
     // Read source-map.json (after AGENT.md) with a byte cap.
     let source_map_content = read_source_map_section(project_root);
 
@@ -387,6 +394,86 @@ mod tests {
         );
     }
 
+    // ── Regen-on-spawn tests ─────────────────────────────────────────────────
+
+    fn init_git_repo(dir: &Path) {
+        let run = |args: &[&str]| {
+            std::process::Command::new("git")
+                .args(args)
+                .current_dir(dir)
+                .output()
+                .unwrap();
+        };
+        run(&["init"]);
+        run(&["config", "user.email", "test@test.com"]);
+        run(&["config", "user.name", "Test"]);
+        run(&["commit", "--allow-empty", "-m", "init"]);
+    }
+
+    /// Happy path: regen runs successfully and the fresh map is included in the bundle.
+    #[test]
+    fn regen_creates_map_on_coder_spawn() {
+        let tmp = tempfile::tempdir().unwrap();
+        init_git_repo(tmp.path());
+
+        // Write a tracked Rust file so git ls-files has something to index.
+        write_file(
+            tmp.path(),
+            "lib.rs",
+            "//! Module doc.\n\n/// A function.\npub fn hello() {}\n",
+        );
+        std::process::Command::new("git")
+            .args(["add", "lib.rs"])
+            .current_dir(tmp.path())
+            .output()
+            .unwrap();
+        std::process::Command::new("git")
+            .args(["commit", "-m", "add lib.rs"])
+            .current_dir(tmp.path())
+            .output()
+            .unwrap();
+
+        // Write an orientation file so we get Some back.
+        write_file(tmp.path(), "CLAUDE.md", "agent hints");
+
+        // Map does not exist yet.
+        let map_path = tmp.path().join(SOURCE_MAP_REL);
+        assert!(!map_path.exists(), "map must not exist before spawn");
+
+        let result = read_project_local_prompt(tmp.path());
+        assert!(
+            result.is_some(),
+            "bundle must be Some when CLAUDE.md present"
+        );
+
+        // Regen should have written the map.
+        assert!(
+            map_path.exists(),
+            "regen must have written source-map.json during spawn"
+        );
+    }
+
+    /// Fallback: regen fails (no git repo) but a stale map on disk is still read.
+    #[test]
+    fn regen_fails_stale_map_still_readable() {
+        let tmp = tempfile::tempdir().unwrap();
+        // No git repo — regen will fail with "git ls-files" error.
+
+        write_file(tmp.path(), "CLAUDE.md", "agent hints");
+        // Write a stale map manually.
+        write_file(
+            tmp.path(),
+            SOURCE_MAP_REL,
+            r#"{"stale/entry.rs": ["fn old"]}"#,
+        );
+
+        let result = read_project_local_prompt(tmp.path()).unwrap();
+        assert!(
+            result.contains("stale/entry.rs"),
+            "stale map must still be readable after regen failure: {result}"
+        );
+    }
+
     #[test]
     #[allow(clippy::string_slice)] // sm_start is derived from str::find — always a char boundary
     fn source_map_truncated_at_byte_cap() {