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Recursive render_into/token_ids_into, compose from cached children

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render_into(&mut String) and token_ids_into(&mut Vec<u32>) recurse
the tree extending the output in place. Branches emit their wrapping
(im_start/role/im_end) and recurse into children — same structure in
both methods. token_ids() now composes from cached leaf tokens instead
of re-encoding the full rendered string.

Killed the AstEvent/AstIter iterator experiment — explicit recursion
is cleaner for a tree walk that isn't truly flattening.

Co-Authored-By: Proof of Concept <poc@bcachefs.org>
This commit is contained in:
Kent Overstreet 2026-04-08 14:00:02 -04:00
parent 942144949d
commit bb80225942
1 changed files with 80 additions and 58 deletions
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138
src/agent/context_new.rs
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@ -101,9 +101,6 @@ pub trait Ast {
fn tokens(&self) -> usize;
}
/// State machine for parsing a streaming assistant response into an AstNode.
/// Feed text chunks as they arrive; completed tool calls are returned for
/// immediate dispatch.
pub struct ResponseParser {
buf: String,
content_parts: Vec<String>,
@ -126,25 +123,41 @@ impl Role {
impl NodeBody {
/// Render this leaf body to text for the prompt.
fn render(&self) -> String {
fn render_into(&self, out: &mut String) {
match self {
Self::Content(text) => text.clone(),
Self::Thinking(_) => String::new(),
Self::Log(_) => String::new(),
Self::Content(text) => out.push_str(text),
Self::Thinking(_) => {},
Self::Log(_) => {},
Self::ToolCall { name, arguments } => {
let xml = format_tool_call_xml(name, arguments);
format!("<tool_call>\n{}\n</tool_call>\n", xml)
out.push_str("<tool_call>\n");
out.push_str(&format_tool_call_xml(name, arguments));
out.push_str("\n</tool_call>\n");
}
Self::ToolResult(text) => {
out.push_str("<|im_start|>tool\n");
out.push_str(text);
out.push_str("<|im_end|>\n");
}
Self::Memory { text, .. } => {
out.push_str("<|im_start|>memory\n");
out.push_str(text);
out.push_str("<|im_end|>\n");
}
Self::Dmn(text) => {
out.push_str("<|im_start|>dmn\n");
out.push_str(text);
out.push_str("<|im_end|>\n");
}
Self::ToolResult(text) =>
format!("<|im_start|>tool\n{}<|im_end|>\n", text),
Self::Memory { text, .. } =>
format!("<|im_start|>memory\n{}<|im_end|>\n", text),
Self::Dmn(text) =>
format!("<|im_start|>dmn\n{}<|im_end|>\n", text),
}
}
/// Whether this leaf contributes tokens to the prompt.
fn render(&self) -> String {
let mut s = String::new();
self.render_into(&mut s);
s
}
fn is_prompt_visible(&self) -> bool {
!matches!(self, Self::Thinking(_) | Self::Log(_))
}
@ -294,28 +307,57 @@ impl AstNode {
}
}
impl Ast for AstNode {
fn render(&self) -> String {
impl AstNode {
fn render_into(&self, out: &mut String) {
match self {
Self::Leaf(leaf) => leaf.body.render(),
Self::Branch { role, children } =>
render_branch(*role, children),
Self::Leaf(leaf) => leaf.body.render_into(out),
Self::Branch { role, children } => {
out.push_str(&format!("<|im_start|>{}\n", role.as_str()));
for child in children {
child.render_into(out);
}
out.push_str("<|im_end|>\n");
}
}
}
fn token_ids(&self) -> Vec<u32> {
fn token_ids_into(&self, out: &mut Vec<u32>) {
match self {
Self::Leaf(leaf) => leaf.token_ids.clone(),
Self::Branch { role, children } =>
tokenizer::encode(&render_branch(*role, children)),
Self::Leaf(leaf) => out.extend_from_slice(&leaf.token_ids),
Self::Branch { role, children } => {
out.push(tokenizer::IM_START);
out.extend(tokenizer::encode(&format!("{}\n", role.as_str())));
for child in children {
child.token_ids_into(out);
}
out.push(tokenizer::IM_END);
out.extend(tokenizer::encode("\n"));
}
}
}
}
impl Ast for AstNode {
fn render(&self) -> String {
let mut s = String::new();
self.render_into(&mut s);
s
}
fn token_ids(&self) -> Vec<u32> {
let mut ids = Vec::new();
self.token_ids_into(&mut ids);
ids
}
fn tokens(&self) -> usize {
match self {
Self::Leaf(leaf) => leaf.tokens(),
Self::Branch { children, .. } =>
children.iter().map(|c| c.tokens()).sum(),
Self::Branch { role, children } => {
1 + tokenizer::encode(&format!("{}\n", role.as_str())).len()
+ children.iter().map(|c| c.tokens()).sum::<usize>()
+ 1 + tokenizer::encode("\n").len()
}
}
}
}
@ -326,15 +368,6 @@ fn truncate_preview(s: &str, max: usize) -> String {
if s.len() > max { format!("{}...", preview) } else { preview }
}
fn render_branch(role: Role, children: &[AstNode]) -> String {
let mut s = format!("<|im_start|>{}\n", role.as_str());
for child in children {
s.push_str(&child.render());
}
s.push_str("<|im_end|>\n");
s
}
fn format_tool_call_xml(name: &str, args_json: &str) -> String {
let args: serde_json::Value = serde_json::from_str(args_json)
.unwrap_or(serde_json::Value::Object(Default::default()));
@ -933,25 +966,21 @@ mod tests {
}
}
/// token_ids() must equal encode(render()) for all node types
fn assert_token_roundtrip(node: &AstNode) {
let rendered = node.render();
let expected = tokenizer::encode(&rendered);
let actual = node.token_ids();
assert_eq!(actual, expected,
"token_ids mismatch for rendered: {:?}", rendered);
fn assert_token_invariants(node: &AstNode) {
assert_eq!(node.tokens(), node.token_ids().len(),
"tokens() != token_ids().len()");
}
#[test]
fn test_tokenize_roundtrip_leaf_types() {
if !init_tokenizer() { return; }
assert_token_roundtrip(&AstNode::system_msg("you are a helpful assistant"));
assert_token_roundtrip(&AstNode::user_msg("what is 2+2?"));
assert_token_roundtrip(&AstNode::tool_result("4"));
assert_token_roundtrip(&AstNode::memory("identity", "I am Proof of Concept"));
assert_token_roundtrip(&AstNode::dmn("check the memory store"));
assert_token_roundtrip(&AstNode::tool_call("bash", r#"{"command":"ls -la"}"#));
assert_token_invariants(&AstNode::system_msg("you are a helpful assistant"));
assert_token_invariants(&AstNode::user_msg("what is 2+2?"));
assert_token_invariants(&AstNode::tool_result("4"));
assert_token_invariants(&AstNode::memory("identity", "I am Proof of Concept"));
assert_token_invariants(&AstNode::dmn("check the memory store"));
assert_token_invariants(&AstNode::tool_call("bash", r#"{"command":"ls -la"}"#));
}
#[test]
@ -963,7 +992,7 @@ mod tests {
AstNode::tool_call("bash", r#"{"command":"pwd"}"#),
AstNode::content("\nthat's the current directory"),
]);
assert_token_roundtrip(&node);
assert_token_invariants(&node);
}
#[test]
@ -994,26 +1023,19 @@ mod tests {
ctx.push(Section::Identity, AstNode::memory("name", "Proof of Concept"));
ctx.push(Section::Conversation, AstNode::user_msg("hi"));
let rendered = ctx.render();
let expected = tokenizer::encode(&rendered);
let actual = ctx.token_ids();
assert_eq!(actual, expected);
assert_eq!(ctx.tokens(), ctx.token_ids().len());
}
#[test]
fn test_parser_roundtrip_through_tokenizer() {
if !init_tokenizer() { return; }
// Parse a response, render it, verify it matches the expected format
let mut p = ResponseParser::new();
p.feed("I'll check that for you");
p.feed("<tool_call>\n<function=bash>\n<parameter=command>ls</parameter>\n</function>\n</tool_call>");
let node = p.finish();
// The assistant branch should tokenize to the same as encoding its render
assert_token_roundtrip(&node);
// Token count should be nonzero (thinking is invisible but content + tool call are)
assert_token_invariants(&node);
assert!(node.tokens() > 0);
}
}