diff --git a/CHANGELOG.md b/CHANGELOG.md
index f515755..e16187d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -24,11 +24,14 @@ adheres to [Semantic Versioning](https://semver.org/).
   the wire format: `usage.cacheRead`/`cacheWrite`/`totalTokens`,
   `errorMessage`, and `providerMetadata`. Session files and `save_messages`
   blobs written by older versions still load (`serde` aliases accept the old
-  names); files **written** by 0.13 use the new names, so they are not
-  readable by yoagent < 0.13. The full nested payload shape (message,
-  content blocks, usage) is now frozen by an exact-JSON snapshot test.
-- `serde` minimum version is now `1.0.181` (needed for `rename_all_fields`
-  on the event wire format). Released July 2023; no practical impact.
+  names). Files **written** by 0.13 load in older versions *without error*,
+  but the renamed fields are silently dropped there: cache/total token
+  counts read as 0, and `errorMessage`/`providerMetadata` — including
+  Gemini thought signatures — are lost. Don't round-trip session files
+  through yoagent < 0.13. The full nested payload shape (message, content
+  blocks, usage) is frozen by an exact-JSON snapshot test.
+- `serde` minimum version is now `1.0.177` (the release that added
+  `rename_all_fields`, July 2023); no practical impact.
 
 ## 0.12.0
 
diff --git a/Cargo.toml b/Cargo.toml
index 1ef5d55..b4434fe 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -18,8 +18,8 @@ exclude = ["docs/images/*", "docs/theme/*", ".github/*", "scripts/*"]
 tokio = { version = "1", features = ["rt", "sync", "fs", "macros", "process", "time", "io-util"] }
 tokio-util = "0.7"
 tokio-stream = "0.1"
-# 1.0.181 floor: rename_all_fields on the AgentEvent wire format
-serde = { version = "1.0.181", features = ["derive"] }
+# 1.0.177 floor: the release that added rename_all_fields (AgentEvent wire format)
+serde = { version = "1.0.177", features = ["derive"] }
 serde_json = "1"
 async-trait = "0.1"
 thiserror = "2"
diff --git a/docs/concepts/messages-events.md b/docs/concepts/messages-events.md
index f58057d..5ab1b53 100644
--- a/docs/concepts/messages-events.md
+++ b/docs/concepts/messages-events.md
@@ -148,10 +148,14 @@ This shape is a **public contract** frozen by snapshot tests — variant tags,
 field names, and the tagging scheme won't change in minor releases.
 
 Streaming semantics: clients accumulate text from each `MessageUpdate`'s
-`delta`; the `message` field during streaming is a placeholder (its `content`
-fills in only when the message completes). The full message arrives with
-`MessageEnd` — a client that misses events (e.g. a lagged websocket
-subscriber) resyncs from the next `MessageEnd` without replay.
+`delta`; the `message` field during streaming is an empty-content
+placeholder (the complete message arrives as a new value in `MessageEnd`).
+Reset accumulation on each `MessageStart` — after a transient provider
+error the stream restarts from a fresh `MessageStart` with no closing
+`MessageEnd` for the abandoned attempt, so a client that doesn't reset
+duplicates the replayed text. A client that misses events entirely (e.g. a
+lagged websocket subscriber) resyncs from the next `MessageEnd` without
+replay.
 
 ## StreamDelta
 
diff --git a/docs/concepts/persistence.md b/docs/concepts/persistence.md
index e0240b3..d74679f 100644
--- a/docs/concepts/persistence.md
+++ b/docs/concepts/persistence.md
@@ -50,12 +50,16 @@ Messages serialize as a JSON array. Each message is tagged by role:
     "stopReason": "stop",
     "model": "claude-sonnet-5",
     "provider": "anthropic",
-    "usage": {"input": 100, "output": 50, "cache_read": 0, "cache_write": 0, "total_tokens": 150},
+    "usage": {"input": 100, "output": 50, "cacheRead": 0, "cacheWrite": 0, "totalTokens": 150},
     "timestamp": 1700000001000
   }
 ]
 ```
 
+As of 0.13 all field names are camelCase; the pre-0.13 snake_case names
+(`cache_read`, `cache_write`, `total_tokens`, `error_message`,
+`provider_metadata`) are still accepted when loading older files.
+
 Extension messages use a nested structure:
 
 ```json
diff --git a/tests/serialization_test.rs b/tests/serialization_test.rs
index 1a82c0b..453ce02 100644
--- a/tests/serialization_test.rs
+++ b/tests/serialization_test.rs
@@ -376,7 +376,9 @@ fn test_stream_delta_every_variant_roundtrips() {
 
 /// The frozen `"type"` tag for every `AgentEvent` variant. Exhaustive match
 /// with NO wildcard arm on purpose: adding a variant fails to compile here
-/// until its wire tag is pinned (and a sample added to `all_agent_events`).
+/// until its wire tag is pinned. Keep [`EVENT_VARIANT_COUNT`] and the sample
+/// in `all_agent_events` in step — the count assertion below fails until the
+/// new variant is actually exercised, closing the other half of the freeze.
 /// A tag change is a breaking change for wire clients — do not edit casually.
 fn expected_event_tag(event: &AgentEvent) -> &'static str {
     match event {
@@ -404,9 +406,19 @@ fn expected_delta_tag(delta: &StreamDelta) -> &'static str {
     }
 }
 
+/// Number of arms in `expected_event_tag` — bump together with the match.
+const EVENT_VARIANT_COUNT: usize = 12;
+
 #[test]
 fn test_agent_event_type_tags_are_frozen() {
-    for event in all_agent_events() {
+    let events = all_agent_events();
+    assert_eq!(
+        events.len(),
+        EVENT_VARIANT_COUNT,
+        "a variant was added to expected_event_tag without a sample in all_agent_events — \
+         the new variant's tag and round-trip are untested until one is added"
+    );
+    for event in events {
         let v: serde_json::Value = serde_json::to_value(&event).expect("serialize");
         assert_eq!(
             v["type"],