From 65642dcf3c9ca0bc009bfd3ef8fce24c59202807 Mon Sep 17 00:00:00 2001
From: Meta Vens <rwvens@hotmail.com>
Date: Wed, 11 Nov 2026 23:11:56 +0100
Subject: [PATCH] usage-per-turn: model ids are field-safe and the cache-write
 TTL split is carried

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
---
 crates/mind-body/src/self_run.rs       | 14 ++++++++++++--
 crates/mind-body/src/self_run/tests.rs | 23 +++++++++++++++++++++++
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/crates/mind-body/src/self_run.rs b/crates/mind-body/src/self_run.rs
index fb6bfed..957373e 100644
--- a/crates/mind-body/src/self_run.rs
+++ b/crates/mind-body/src/self_run.rs
@@ -1051,6 +1051,11 @@ fn describe_result(event: &serde_json::Map<String, Value>) -> String {
     format!("{}: {}", result_head(event), result_text(event))
 }
 
+/// A model id as one journal field: every byte outside `[A-Za-z0-9._:/-]` is `%XX`, so a space, `;`, `=` or newline in an id the CLI reports cannot split the line or forge a segment. Real ids pass unchanged.
+fn field_safe(id: &str) -> String {
+    id.bytes().map(|b| if b.is_ascii_alphanumeric() || b"._:/-".contains(&b) { (b as char).to_string() } else { format!("%{b:02X}") }).collect()
+}
+
 /// What a result spent, as one journal line: its tokens by model for this turn alone, read from
 /// `model_usage_since_last_result`. `modelUsage` is the session's running total on a resumed
 /// session, so it is never the source. Usage the result did not report, or reported
@@ -1065,12 +1070,17 @@ fn usage_line(event: &serde_json::Map<String, Value>) -> String {
             .iter()
             .map(|(model, counts)| {
                 let count = |name: &str| counts.get(name).and_then(Value::as_u64);
+                // The 5m and 1h cache writes are priced apart; each is carried when the envelope has it and left out when it does not.
+                let ttl = |label: &str, name: &str| count(name).map(|n| format!(" cache_creation_{label} {n}")).unwrap_or_default();
                 Some(format!(
-                    "{model} input {} cache_read {} cache_creation {} output {}",
+                    "{} input {} cache_read {} cache_creation {} output {}{}{}",
+                    field_safe(model),
                     count("inputTokens")?,
                     count("cacheReadInputTokens")?,
                     count("cacheCreationInputTokens")?,
-                    count("outputTokens")?
+                    count("outputTokens")?,
+                    ttl("5m", "cacheCreationEphemeral5mInputTokens"),
+                    ttl("1h", "cacheCreationEphemeral1hInputTokens"),
                 ))
             })
             .collect()
diff --git a/crates/mind-body/src/self_run/tests.rs b/crates/mind-body/src/self_run/tests.rs
index 16d0339..3bb064c 100644
--- a/crates/mind-body/src/self_run/tests.rs
+++ b/crates/mind-body/src/self_run/tests.rs
@@ -542,6 +542,29 @@ fn each_model_in_the_turns_usage_is_its_own_segment() {
     );
 }
 
+#[test]
+fn a_model_id_cannot_split_the_line_or_forge_a_segment() {
+    let counts = json!({"inputTokens": 1, "cacheReadInputTokens": 2, "cacheCreationInputTokens": 3, "outputTokens": 4});
+    let line = json!({"type": "result", "result_index": 0, "model_usage_since_last_result": {"evil
+usage turn 9: x input 9; y=1": counts}}).to_string();
+    let journal = journal_of(&line);
+    assert_eq!(journal.lines().count(), 2, "{journal}");
+    assert_eq!(usage_lines(&journal), ["usage turn 0: evil%0Ausage%20turn%209:%20x%20input%209%3B%20y%3D1 input 1 cache_read 2 cache_creation 3 output 4"]);
+}
+
+#[test]
+fn the_cache_write_split_is_carried_when_reported_and_left_out_when_not() {
+    let mut entry = json!({"inputTokens": 1, "cacheReadInputTokens": 2, "cacheCreationInputTokens": 7, "outputTokens": 4});
+    let journal = |entry: &Value| journal_of(&json!({"type": "result", "result_index": 0, "model_usage_since_last_result": {"m": entry}}).to_string());
+    entry["cacheCreationEphemeral5mInputTokens"] = json!(3);
+    entry["cacheCreationEphemeral1hInputTokens"] = json!(4);
+    assert_eq!(usage_lines(&journal(&entry)), ["usage turn 0: m input 1 cache_read 2 cache_creation 7 output 4 cache_creation_5m 3 cache_creation_1h 4"]);
+    entry.as_object_mut().unwrap().remove("cacheCreationEphemeral5mInputTokens");
+    assert_eq!(usage_lines(&journal(&entry)), ["usage turn 0: m input 1 cache_read 2 cache_creation 7 output 4 cache_creation_1h 4"]);
+    entry.as_object_mut().unwrap().remove("cacheCreationEphemeral1hInputTokens");
+    assert_eq!(usage_lines(&journal(&entry)), ["usage turn 0: m input 1 cache_read 2 cache_creation 7 output 4"]);
+}
+
 #[test]
 fn an_unreported_usage_is_said_never_zero() {
     let whole = json!({"inputTokens": 1, "cacheReadInputTokens": 2, "cacheCreationInputTokens": 3, "outputTokens": 4});