diff --git a/Cargo.lock b/Cargo.lock
index dd1fa0a..d93203c 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -564,7 +564,7 @@ dependencies = [
 [[package]]
 name = "comline-codegen"
 version = "0.1.0"
-source = "git+https://github.com/ComlineProject/generation?rev=9b8336e4acd0a1f10b75aa851c36571f4e1d0d47#9b8336e4acd0a1f10b75aa851c36571f4e1d0d47"
+source = "git+https://github.com/ComlineProject/generation?rev=ac4425c32f88f98a2a3bfb971a209c173c6559a8#ac4425c32f88f98a2a3bfb971a209c173c6559a8"
 dependencies = [
  "comline-core",
  "eyre",
@@ -578,7 +578,7 @@ dependencies = [
 [[package]]
 name = "comline-codegen-rust"
 version = "0.1.0"
-source = "git+https://github.com/ComlineProject/comline-rust?rev=89530a72f37180517e1c70f88437b1bedf1e703a#89530a72f37180517e1c70f88437b1bedf1e703a"
+source = "git+https://github.com/ComlineProject/comline-rust?rev=8d0d659d100d41d64d203a7890a6b15471cde802#8d0d659d100d41d64d203a7890a6b15471cde802"
 dependencies = [
  "comline-codegen",
  "comline-core",
@@ -588,7 +588,7 @@ dependencies = [
 [[package]]
 name = "comline-codegen-typescript"
 version = "0.1.0"
-source = "git+https://github.com/ComlineProject/comline-typescript?rev=82447d54a8616a1ed37e4a7886df25deb2af7baf#82447d54a8616a1ed37e4a7886df25deb2af7baf"
+source = "git+https://github.com/ComlineProject/comline-typescript?rev=37cd70f96260325f37a39be6a15cb858d2e069dc#37cd70f96260325f37a39be6a15cb858d2e069dc"
 dependencies = [
  "comline-codegen",
  "comline-core",
@@ -598,7 +598,7 @@ dependencies = [
 [[package]]
 name = "comline-core"
 version = "0.1.0"
-source = "git+https://github.com/ComlineProject/core?rev=2be483f5adc303bd39c76e11f930ec2340eee57a#2be483f5adc303bd39c76e11f930ec2340eee57a"
+source = "git+https://github.com/ComlineProject/core?rev=525939352b79538ce5e9b41ae6713ee6bd26a25e#525939352b79538ce5e9b41ae6713ee6bd26a25e"
 dependencies = [
  "ariadne",
  "blake3",
@@ -627,12 +627,12 @@ dependencies = [
 [[package]]
 name = "comline-core-stdlib"
 version = "0.1.0"
-source = "git+https://github.com/ComlineProject/core?rev=2be483f5adc303bd39c76e11f930ec2340eee57a#2be483f5adc303bd39c76e11f930ec2340eee57a"
+source = "git+https://github.com/ComlineProject/core?rev=525939352b79538ce5e9b41ae6713ee6bd26a25e#525939352b79538ce5e9b41ae6713ee6bd26a25e"
 
 [[package]]
 name = "comline-doc-html"
 version = "0.1.0"
-source = "git+https://github.com/ComlineProject/generation?rev=9b8336e4acd0a1f10b75aa851c36571f4e1d0d47#9b8336e4acd0a1f10b75aa851c36571f4e1d0d47"
+source = "git+https://github.com/ComlineProject/generation?rev=ac4425c32f88f98a2a3bfb971a209c173c6559a8#ac4425c32f88f98a2a3bfb971a209c173c6559a8"
 dependencies = [
  "comline-codegen",
  "eyre",
@@ -643,7 +643,7 @@ dependencies = [
 [[package]]
 name = "comline-doc-markdown"
 version = "0.1.0"
-source = "git+https://github.com/ComlineProject/generation?rev=9b8336e4acd0a1f10b75aa851c36571f4e1d0d47#9b8336e4acd0a1f10b75aa851c36571f4e1d0d47"
+source = "git+https://github.com/ComlineProject/generation?rev=ac4425c32f88f98a2a3bfb971a209c173c6559a8#ac4425c32f88f98a2a3bfb971a209c173c6559a8"
 dependencies = [
  "comline-codegen",
  "eyre",
diff --git a/Cargo.toml b/Cargo.toml
index 65c57c0..1bc7615 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -32,20 +32,20 @@ eyre = "0.6.8"
 # needs real I/O (git fetch, filesystem), so it's off by default for
 # `comline-core`'s wasm32 consumers (the playground editor, the language
 # server); the CLI is the one consumer that actually runs `comline build`.
-comline-core = { git = "https://github.com/ComlineProject/core", rev = "2be483f5adc303bd39c76e11f930ec2340eee57a", features = ["deps"] }
+comline-core = { git = "https://github.com/ComlineProject/core", rev = "525939352b79538ce5e9b41ae6713ee6bd26a25e", features = ["deps"] }
 # All three pinned to revs that agree on one `comline-codegen`, and bumped
 # together: comline-rust and comline-typescript's codegen crates consume
 # `comline-codegen`'s types, so the rev below must be byte-identical to the
 # one *they* pin - Cargo only unifies a git dependency across identical rev
 # strings, and two copies of `GenRequest` are two incompatible types.
-comline-codegen = { git = "https://github.com/ComlineProject/generation", rev = "9b8336e4acd0a1f10b75aa851c36571f4e1d0d47" }
+comline-codegen = { git = "https://github.com/ComlineProject/generation", rev = "ac4425c32f88f98a2a3bfb971a209c173c6559a8" }
 # The official Markdown and HTML documentation renderers (`comline doc`),
 # linked in like the official generators. Same generation rev as
 # `comline-codegen`.
-comline-doc-markdown = { git = "https://github.com/ComlineProject/generation", rev = "9b8336e4acd0a1f10b75aa851c36571f4e1d0d47" }
-comline-doc-html = { git = "https://github.com/ComlineProject/generation", rev = "9b8336e4acd0a1f10b75aa851c36571f4e1d0d47" }
-comline-codegen-rust = { git = "https://github.com/ComlineProject/comline-rust", rev = "89530a72f37180517e1c70f88437b1bedf1e703a", optional = true }
-comline-codegen-typescript = { git = "https://github.com/ComlineProject/comline-typescript", rev = "82447d54a8616a1ed37e4a7886df25deb2af7baf", optional = true }
+comline-doc-markdown = { git = "https://github.com/ComlineProject/generation", rev = "ac4425c32f88f98a2a3bfb971a209c173c6559a8" }
+comline-doc-html = { git = "https://github.com/ComlineProject/generation", rev = "ac4425c32f88f98a2a3bfb971a209c173c6559a8" }
+comline-codegen-rust = { git = "https://github.com/ComlineProject/comline-rust", rev = "8d0d659d100d41d64d203a7890a6b15471cde802", optional = true }
+comline-codegen-typescript = { git = "https://github.com/ComlineProject/comline-typescript", rev = "37cd70f96260325f37a39be6a15cb858d2e069dc", optional = true }
 # `comline conformance`: the conformance runner (corpus loading, judging,
 # profile proofs) and its case format, a public spec. Pinned by git rev.
 comline-runtime-conformance = { git = "https://github.com/ComlineProject/runtime", rev = "4378c91b74ee1ef1debc800a3daf75c874198e70" }
diff --git a/src/changes.rs b/src/changes.rs
index b9286f3..e46a309 100644
--- a/src/changes.rs
+++ b/src/changes.rs
@@ -79,6 +79,11 @@ fn config_line(change: &ConfigChange) -> String {
             "~",
             format!("Changed `wire.framing`: {old} {arrow} {new}"),
         ),
+        ConfigChange::PackageIdChanged { old, new } => mark(
+            "🔄",
+            "~",
+            format!("Changed the package `id` (a different package): {old} {arrow} {new}"),
+        ),
     }
 }
 
diff --git a/src/commands/build.rs b/src/commands/build.rs
index c42cfcf..9fbdc1e 100644
--- a/src/commands/build.rs
+++ b/src/commands/build.rs
@@ -29,6 +29,16 @@ pub fn run(work_dir: &Path, watching: bool) -> Result<()> {
 
 fn build_once(work_dir: &Path) -> Result<()> {
     ui::step(format!("Building project{}", ui::at_path(work_dir)));
+    // Every package has an id (its identity for `comline@2`); one without
+    // gets it here, as one line in config.idp.
+    match comline_core::package::id::ensure_in_config(work_dir) {
+        Ok(Some(id)) => ui::note(format!(
+            "config.idp had no `id`: added `id = \"{id}\"`. Keep it when renaming the \
+             package, and change it in a copy"
+        )),
+        Ok(None) => {}
+        Err(e) => return Err(core_err("couldn't add an id to config.idp", e)),
+    }
     let spinner = ui::spinner("compiling schemas");
     let registry = generator_registry();
     let mut target_warnings = Vec::new();
diff --git a/src/commands/inspect.rs b/src/commands/inspect.rs
index c2ee2eb..a856fd4 100644
--- a/src/commands/inspect.rs
+++ b/src/commands/inspect.rs
@@ -10,6 +10,7 @@ use std::io::Write as _;
 use std::path::Path;
 
 use anstyle::{AnsiColor, Color, Style};
+use comline_core::compat::{self, PackageFacts};
 use comline_core::inspect::{self, Acceptance, Choice, ProtocolSummary, Source};
 use miette::{IntoDiagnostic, Result};
 
@@ -30,9 +31,12 @@ pub fn run(work_dir: &Path, json: bool) -> Result<()> {
     let context = outcome.map_err(|e| core_err("validation failed", e))?;
 
     let protocols = inspect::protocols(&context);
+    // What the latest build records for `comline@2`: each protocol's line,
+    // shape hash and functions' "since". None before the first build.
+    let facts = latest_facts(work_dir);
     let mut out = anstream::stdout().lock();
     if json {
-        let report = serde_json::json!({ "protocols": protocols });
+        let report = serde_json::json!({ "protocols": protocols, "facts": facts });
         writeln!(
             out,
             "{}",
@@ -48,13 +52,61 @@ pub fn run(work_dir: &Path, json: bool) -> Result<()> {
     }
     let text = protocols
         .iter()
-        .map(|p| render(p, ui::plain()))
+        .map(|p| {
+            let mut text = render(p, ui::plain());
+            if !p.dependency {
+                if let Some(facts) = &facts {
+                    text += &render_facts(
+                        facts,
+                        &compat::protocol_path(&p.schema, &p.name),
+                        ui::plain(),
+                    );
+                }
+            }
+            text
+        })
         .collect::<Vec<_>>()
         .join("\n");
     write!(out, "{text}").into_diagnostic()?;
     Ok(())
 }
 
+/// The latest build's facts, if the package was built. Read-only: the
+/// store is never created here.
+fn latest_facts(work_dir: &Path) -> Option<PackageFacts> {
+    use comline_core::package::build::cas::{main_ref, ref_exists};
+    if !ref_exists(work_dir, main_ref()) {
+        return None;
+    }
+    compat::facts(work_dir, None).ok()
+}
+
+/// A protocol's line, shape hash and functions' "since", as the latest
+/// build records them. `path` is its `namespace::Protocol`: facts are kept
+/// per qualified path, so two protocols of one name stay apart.
+pub fn render_facts(facts: &PackageFacts, path: &str, plain: bool) -> String {
+    let Some(p) = facts.protocols.iter().find(|p| p.path == path) else {
+        return String::new();
+    };
+    let dim = |text: &str| {
+        if plain {
+            text.to_string()
+        } else {
+            format!("{DIM}{text}{DIM:#}")
+        }
+    };
+    let mut out = format!(
+        "\n  {}\n",
+        dim(&format!("{} as of build {}", p.path, facts.version))
+    );
+    out += &format!("  {:<10} {}\n", "line", p.line);
+    out += &format!("  {:<10} {}\n", "shape", p.shape_hash);
+    for f in &p.functions {
+        out += &format!("  {:<10} {:<24} {}\n", "since", f.name, f.since);
+    }
+    out
+}
+
 /// One protocol: a header of choices, then a row per guarantee. Fits 80
 /// columns: anything long goes on its own indented line.
 pub fn render(p: &ProtocolSummary, plain: bool) -> String {
diff --git a/src/commands/new.rs b/src/commands/new.rs
index 6279c71..141bec5 100644
--- a/src/commands/new.rs
+++ b/src/commands/new.rs
@@ -129,9 +129,12 @@ fn scaffold_language() -> String {
 
 fn config_idp(name: &str) -> String {
     let language = scaffold_language();
+    // The package's identity: kept by a rename, changed by a copy.
+    let id = comline_core::package::id::config_line(&comline_core::package::id::generate());
     format!(
         "\
 congregation {name}
+{id}
 specification_version = 1
 
 code_generation = {{
diff --git a/tests/cli/build.rs b/tests/cli/build.rs
index 4bb4186..9e419c7 100644
--- a/tests/cli/build.rs
+++ b/tests/cli/build.rs
@@ -23,6 +23,38 @@ fn freezes_an_initial_version() {
     assert!(project.join(".comline").is_dir());
 }
 
+#[test]
+fn adds_a_missing_id_with_a_note_and_keeps_one_there_is() {
+    let temp = tempfile::tempdir().unwrap();
+    let project = fixture_project(temp.path());
+    let before = std::fs::read_to_string(project.join("config.idp")).unwrap();
+    assert!(!before.contains("\nid = "), "{before}");
+
+    build(&project)
+        .success()
+        .stderr(predicate::str::contains("config.idp had no `id`: added"));
+    let after = std::fs::read_to_string(project.join("config.idp")).unwrap();
+    // One line added after `congregation`, nothing else touched.
+    let added: Vec<&str> = after
+        .lines()
+        .filter(|l| !before.lines().any(|b| b == *l))
+        .collect();
+    assert_eq!(added.len(), 1, "{after}");
+    assert!(
+        added[0].starts_with("id = \"") && added[0].len() == "id = \"\"".len() + 32,
+        "{after}"
+    );
+    assert_eq!(after.replace(&format!("{}\n", added[0]), ""), before);
+
+    build(&project)
+        .success()
+        .stderr(predicate::str::contains("had no `id`").not());
+    assert_eq!(
+        std::fs::read_to_string(project.join("config.idp")).unwrap(),
+        after
+    );
+}
+
 /// `fixture_project`, declaring `languages` (and anything after) instead.
 fn declaring(temp: &std::path::Path, languages: &str, rest: &str) -> std::path::PathBuf {
     let project = fixture_project(temp);
diff --git a/tests/cli/new.rs b/tests/cli/new.rs
index 769e0fb..789c00e 100644
--- a/tests/cli/new.rs
+++ b/tests/cli/new.rs
@@ -37,6 +37,12 @@ fn scaffolds_a_buildable_project() {
 
     let config = fs::read_to_string(root.join("config.idp")).unwrap();
     assert!(config.contains("congregation my_api"));
+    // The package's identity, random, on the line after its name.
+    let id = config.lines().nth(1).unwrap();
+    assert!(
+        id.starts_with("id = \"") && id.len() == "id = \"\"".len() + 32,
+        "{config}"
+    );
     assert!(config.contains("code_generation"));
     // The widest promise: the Rust generator's floor.
     assert!(config.contains("rust#1.85.0 = {}"), "{config}");
diff --git a/tests/fixtures/generators/Cargo.lock b/tests/fixtures/generators/Cargo.lock
index bca0cc8..1b6772f 100644
--- a/tests/fixtures/generators/Cargo.lock
+++ b/tests/fixtures/generators/Cargo.lock
@@ -79,7 +79,7 @@ dependencies = [
 [[package]]
 name = "comline-codegen"
 version = "0.1.0"
-source = "git+https://github.com/ComlineProject/generation?rev=9b8336e4acd0a1f10b75aa851c36571f4e1d0d47#9b8336e4acd0a1f10b75aa851c36571f4e1d0d47"
+source = "git+https://github.com/ComlineProject/generation?rev=ac4425c32f88f98a2a3bfb971a209c173c6559a8#ac4425c32f88f98a2a3bfb971a209c173c6559a8"
 dependencies = [
  "comline-core",
  "eyre",
@@ -93,7 +93,7 @@ dependencies = [
 [[package]]
 name = "comline-codegen-rust"
 version = "0.1.0"
-source = "git+https://github.com/ComlineProject/comline-rust?rev=89530a72f37180517e1c70f88437b1bedf1e703a#89530a72f37180517e1c70f88437b1bedf1e703a"
+source = "git+https://github.com/ComlineProject/comline-rust?rev=8d0d659d100d41d64d203a7890a6b15471cde802#8d0d659d100d41d64d203a7890a6b15471cde802"
 dependencies = [
  "comline-codegen",
  "comline-core",
@@ -103,7 +103,7 @@ dependencies = [
 [[package]]
 name = "comline-core"
 version = "0.1.0"
-source = "git+https://github.com/ComlineProject/core?rev=2be483f5adc303bd39c76e11f930ec2340eee57a#2be483f5adc303bd39c76e11f930ec2340eee57a"
+source = "git+https://github.com/ComlineProject/core?rev=525939352b79538ce5e9b41ae6713ee6bd26a25e#525939352b79538ce5e9b41ae6713ee6bd26a25e"
 dependencies = [
  "blake3",
  "ciborium",
@@ -120,12 +120,12 @@ dependencies = [
 [[package]]
 name = "comline-core-stdlib"
 version = "0.1.0"
-source = "git+https://github.com/ComlineProject/core?rev=2be483f5adc303bd39c76e11f930ec2340eee57a#2be483f5adc303bd39c76e11f930ec2340eee57a"
+source = "git+https://github.com/ComlineProject/core?rev=525939352b79538ce5e9b41ae6713ee6bd26a25e#525939352b79538ce5e9b41ae6713ee6bd26a25e"
 
 [[package]]
 name = "comline-doc-html"
 version = "0.1.0"
-source = "git+https://github.com/ComlineProject/generation?rev=9b8336e4acd0a1f10b75aa851c36571f4e1d0d47#9b8336e4acd0a1f10b75aa851c36571f4e1d0d47"
+source = "git+https://github.com/ComlineProject/generation?rev=ac4425c32f88f98a2a3bfb971a209c173c6559a8#ac4425c32f88f98a2a3bfb971a209c173c6559a8"
 dependencies = [
  "comline-codegen",
  "eyre",
@@ -136,7 +136,7 @@ dependencies = [
 [[package]]
 name = "comline-doc-markdown"
 version = "0.1.0"
-source = "git+https://github.com/ComlineProject/generation?rev=9b8336e4acd0a1f10b75aa851c36571f4e1d0d47#9b8336e4acd0a1f10b75aa851c36571f4e1d0d47"
+source = "git+https://github.com/ComlineProject/generation?rev=ac4425c32f88f98a2a3bfb971a209c173c6559a8#ac4425c32f88f98a2a3bfb971a209c173c6559a8"
 dependencies = [
  "comline-codegen",
  "eyre",
diff --git a/tests/fixtures/generators/Cargo.toml b/tests/fixtures/generators/Cargo.toml
index 8d8442a..1385786 100644
--- a/tests/fixtures/generators/Cargo.toml
+++ b/tests/fixtures/generators/Cargo.toml
@@ -12,7 +12,7 @@ publish = false
 [dependencies]
 # The same revs the CLI pins, so the real generator's output is comparable
 # byte for byte with the CLI's built-in one.
-comline-codegen = { git = "https://github.com/ComlineProject/generation", rev = "9b8336e4acd0a1f10b75aa851c36571f4e1d0d47" }
-comline-doc-markdown = { git = "https://github.com/ComlineProject/generation", rev = "9b8336e4acd0a1f10b75aa851c36571f4e1d0d47" }
-comline-doc-html = { git = "https://github.com/ComlineProject/generation", rev = "9b8336e4acd0a1f10b75aa851c36571f4e1d0d47" }
-comline-codegen-rust = { git = "https://github.com/ComlineProject/comline-rust", rev = "89530a72f37180517e1c70f88437b1bedf1e703a" }
+comline-codegen = { git = "https://github.com/ComlineProject/generation", rev = "ac4425c32f88f98a2a3bfb971a209c173c6559a8" }
+comline-doc-markdown = { git = "https://github.com/ComlineProject/generation", rev = "ac4425c32f88f98a2a3bfb971a209c173c6559a8" }
+comline-doc-html = { git = "https://github.com/ComlineProject/generation", rev = "ac4425c32f88f98a2a3bfb971a209c173c6559a8" }
+comline-codegen-rust = { git = "https://github.com/ComlineProject/comline-rust", rev = "8d0d659d100d41d64d203a7890a6b15471cde802" }