From 42f1e888c4ba73a5a595227d6bc8f76fe5750b80 Mon Sep 17 00:00:00 2001
From: Kent Overstreet <kent.overstreet@linux.dev>
Date: Thu, 2 Apr 2026 02:00:14 -0400
Subject: [PATCH] Journal: flat 5% context window budget, skip plan_context

Render journal entries directly with ## headers instead of going
through the plan_context/render_journal_text pipeline. 5% of
model context window (~6500 tokens for Qwen 128K). Simpler and
predictable.

Co-Authored-By: Proof of Concept <poc@bcachefs.org>
---
 src/agent/runner.rs | 28 +++++++++++++---------------
 1 file changed, 13 insertions(+), 15 deletions(-)

diff --git a/src/agent/runner.rs b/src/agent/runner.rs
index dd22d66..8823b95 100644
--- a/src/agent/runner.rs
+++ b/src/agent/runner.rs
@@ -816,15 +816,17 @@ impl Agent {
             journal_nodes.len()
         };
 
-        // Walk backwards from cutoff, accumulating entries within token budget
+        // Walk backwards from cutoff, accumulating entries within 5% of context
         let count = |s: &str| self.tokenizer.encode_with_special_tokens(s).len();
-        let journal_budget_tokens = 10_000; // ~8% of 128K context
+        let context_window = crate::agent::context::model_context_window(&self.client.model);
+        let journal_budget = context_window * 5 / 100;
+
         let mut entries = Vec::new();
         let mut total_tokens = 0;
 
         for node in journal_nodes[..cutoff_idx].iter().rev() {
             let tokens = count(&node.content);
-            if total_tokens + tokens > journal_budget_tokens && !entries.is_empty() {
+            if total_tokens + tokens > journal_budget && !entries.is_empty() {
                 break;
             }
             entries.push(journal::JournalEntry {
@@ -834,23 +836,19 @@ impl Agent {
             });
             total_tokens += tokens;
         }
-        entries.reverse(); // chronological order
+        entries.reverse();
 
         if entries.is_empty() {
             return;
         }
 
-        let context_message = self.context.render_context_message();
-        let plan = crate::agent::context::plan_context(
-            &self.context.system_prompt,
-            &context_message,
-            &[],
-            &entries,
-            &self.client.model,
-            &count,
-        );
-
-        self.context.journal = crate::agent::context::render_journal_text(&entries, &plan);
+        // Render directly — no plan_context needed
+        let mut text = String::from("[Earlier — from your journal]\n\n");
+        for entry in &entries {
+            use std::fmt::Write;
+            writeln!(text, "## {}\n{}\n", entry.timestamp.format("%Y-%m-%dT%H:%M"), entry.content).ok();
+        }
+        self.context.journal = text;
     }
 
     /// Re-render the context message in self.messages from live ContextState.