Contexel 0.1.17

Contexel

Deterministic, dependency-free context shaping for code-writing agents — the C# build of contexel (also on PyPI and npm).

Tool calls return verbose, duplicated, sometimes hostile data. Contexel sits at the tool → context boundary and shapes it: select the fields that matter, drop duplicates, gate by provenance, quarantine injection patterns, rescore by relevance, truncate, rank, and trim to a token budget — every stage a pure function over List<Dictionary<string, object?>>, every run reproducible, every drop attributable in an audit record.

This package is a parity port, not a re-imagining. The Python implementation is canon; all three languages run their test suites against the same golden vectors (parity/vectors.json, generated by Python), so the same records, policy, and budget produce the same shaped output. Because .NET preserves the int/float distinction, the C# port has a stricter parity envelope than the TypeScript one. Design and boundaries: ADR-002.

Install

dotnet add package Contexel     # zero runtime dependencies, net8.0

Sixty seconds

using Contexel;
using Rec = System.Collections.Generic.Dictionary<string, object?>;

var raw = await SearchTool(userQuery);   // a batch of verbose results

using var t = Trace.Begin(idField: "url");
var r = Stages.Select(raw, new[] { "title", "url", "snippet" });
r = Stages.Dedupe(r, "url");
r = Stages.Rescore(r, userQuery, new[] { "title", "snippet" });
r = Stages.TruncateField(r, "snippet", maxTokens: 120);
r = Stages.Rank(r, "score", desc: true);
r = Stages.TrimToBudget(r, maxTokens: 1500, minRecords: 1);

Console.WriteLine(t.Report());   // per-stage: records in -> out, tokens before -> after
var audit = t.Audit();           // policy fingerprints + which stage dropped which IDs

Or pin the policy at the tool boundary, so the model never sees raw output:

var pipe = new Pipeline(
    new Stage("select", r => Stages.Select(r, new[] { "path", "line", "snippet" })),
    new Stage("dedupe", r => Stages.Dedupe(r, new[] { "path", "line" })),
    new Stage("trim_to_budget", r => Stages.TrimToBudget(r, 2000)));

var searchCode = Shaped.Wrap(pipe, (string query) => Repo.Search(query));
// async tools are awaited, then shaped — same policy, every call

The eight stages

Plus Merge for combining sources, Pipeline/Stage with stable policy fingerprints, Trace/Audit for the governance record, and Tokens.Scoped (AsyncLocal) for concurrency-safe per-tenant token accounting.

Links

• Docs: https://maheshvaikri-code.github.io/contexel/
• Source: https://github.com/maheshvaikri-code/contexel
• License: MIT