diff --git a/src/agent/context.rs b/src/agent/context.rs
index a6b38d5..bee049d 100644
--- a/src/agent/context.rs
+++ b/src/agent/context.rs
@@ -47,55 +47,44 @@ pub struct ContextPlan {
 /// it's what's happening now. Journal fills the rest, newest first.
 ///
 /// Returns (messages, journal_text) — caller stores journal_text in ContextState.
-pub fn build_context_window(
+/// Trim conversation to fit within the context budget.
+/// Returns the trimmed conversation messages (oldest dropped first).
+pub fn trim_conversation(
     context: &ContextState,
     conversation: &[Message],
     model: &str,
     tokenizer: &CoreBPE,
-) -> (Vec<Message>, String) {
-    let journal_path = journal::default_journal_path();
-    let all_entries = journal::parse_journal(&journal_path);
-    dbglog!("[ctx] {} journal entries from {}", all_entries.len(), journal_path.display());
+) -> Vec<Message> {
     let count = |s: &str| tokenizer.encode_with_special_tokens(s).len();
-
-    let system_prompt = context.system_prompt.clone();
-    let context_message = context.render_context_message();
-
-    // Cap memory to 50% of the context budget so conversation always
-    // gets space. Truncate at the last complete section boundary.
     let max_tokens = context_budget_tokens(model);
-    let memory_cap = max_tokens / 2;
-    let memory_tokens = count(&context_message);
-    let context_message = if memory_tokens > memory_cap {
-        dbglog!("[ctx] memory too large: {} tokens > {} cap, truncating", memory_tokens, memory_cap);
-        truncate_at_section(&context_message, memory_cap, &count)
-    } else {
-        context_message
-    };
 
-    let recent_start = find_journal_cutoff(conversation, all_entries.last());
-    dbglog!("[ctx] journal cutoff: {} of {} conversation messages are 'recent'",
-        conversation.len() - recent_start, conversation.len());
-    let recent = &conversation[recent_start..];
+    let identity_cost = count(&context.system_prompt)
+        + context.personality.iter().map(|(_, c)| count(c)).sum::<usize>();
+    let journal_cost: usize = context.journal.iter().map(|e| count(&e.content)).sum();
+    let reserve = max_tokens / 4;
+    let available = max_tokens
+        .saturating_sub(identity_cost)
+        .saturating_sub(journal_cost)
+        .saturating_sub(reserve);
 
-    let plan = plan_context(
-        &system_prompt,
-        &context_message,
-        recent,
-        &all_entries,
-        model,
-        &count,
-    );
+    // Trim oldest messages until we fit
+    let msg_costs: Vec<usize> = conversation.iter()
+        .map(|m| msg_token_count(tokenizer, m)).collect();
+    let total: usize = msg_costs.iter().sum();
 
-    let journal_text = render_journal_text(&all_entries, &plan);
-    dbglog!("[ctx] plan: header_start={} full_start={} entry_count={} conv_trim={} journal_text={} chars",
-        plan.header_start, plan.full_start, plan.entry_count, plan.conv_trim, journal_text.len());
+    let mut skip = 0;
+    let mut trimmed = total;
+    while trimmed > available && skip < conversation.len() {
+        trimmed -= msg_costs[skip];
+        skip += 1;
+    }
 
-    let messages = assemble_context(
-        system_prompt, context_message, &journal_text,
-        recent, &plan,
-    );
-    (messages, journal_text)
+    // Walk forward to user message boundary
+    while skip < conversation.len() && conversation[skip].role != Role::User {
+        skip += 1;
+    }
+
+    conversation[skip..].to_vec()
 }
 
 pub fn plan_context(
diff --git a/src/agent/runner.rs b/src/agent/runner.rs
index eb4824c..c145bd2 100644
--- a/src/agent/runner.rs
+++ b/src/agent/runner.rs
@@ -967,7 +967,7 @@ impl Agent {
     fn do_compact(&mut self) {
         let conversation: Vec<Message> = self.context.entries.iter()
             .map(|e| e.api_message().clone()).collect();
-        let (messages, _) = crate::agent::context::build_context_window(
+        let messages = crate::agent::context::trim_conversation(
             &self.context,
             &conversation,
             &self.client.model,
@@ -1030,7 +1030,7 @@ impl Agent {
             .collect();
         dbglog!("[restore] {} messages after filtering system", conversation.len());
 
-        let (messages, _) = crate::agent::context::build_context_window(
+        let messages = crate::agent::context::trim_conversation(
             &self.context,
             &conversation,
             &self.client.model,