Show HN: OSS Agent I built topped the TerminalBench on Gemini-3-flash-preview

20 hours ago (github.com)

Scored 65.2% vs google's official 47.8%, and the existing top closed source model Junie CLI's 64.3%.

Since there are a lot of reports of deliberate cheating on TerminalBench 2.0 lately (https://debugml.github.io/cheating-agents/), I would like to also clarify a few things

1. Absolutely no {agents/skills}.md files were inserted at any point. No cheating mechanisms whatsoever

2. The cli agent was run in leaderboard compliant way (no modification of resources or timeouts)

3. The full terminal bench run was done using the fully open source version of the agent, no difference between what is on github and what was run.

I was originally going to wait for it to land on the leaderboard, but it has been 8 days and the maintainers do not respond unfortunately (there is a large backlog of the pull requests on their HF) so I decided to post anyways.

HF PR: https://huggingface.co/datasets/harborframework/terminal-ben...

It is astounding how much the harness matters, based on this and other experiments I have done.

Interesting things Dirac does:

1. Uses an optimized version of Hash-Anchored edits for file editing (https://dirac.run/posts/hash-anchors-myers-diff-single-token)

2. Utilizes language's AST to decide what to fetch into context, entirely avoids large code file reads

3. Batches all operations. Does large number of reads/edits simultaneously (you can see a video demo for deepseek-v4-flash here https://www.reddit.com/r/LocalLLaMA/comments/1suhdki/tested_...)

4. Allows the model to execute code to analyze things on the fly, so the model can simply write bash/python/perl script to accomplish things where appropriate

5. A lot of context curation and opportunistic context updates, i.e. put into context anything that you are certain model would ask next

  • I always wondered why AST's were not more of a part in both editing and scoping of changes/parsing code. I thought I read an article where they said 'grep' was just as effective. It kinda made sense for the case they were talking about.

    • I think we should use ASTS more, not for performance, but for easier code review.

      Changes that are primarily code refactorings, like breaking up a large module into a bunch of smaller ones, or renaming a commonly-used class, are extremely tedious to review, both in LLM generated diffs and human-written PRs. You still have to do it; LLMs have a habit of mangling comments when moving code across files, while for a human, an unassuming "rename FooAPIClient to LegacyFooAPIClient" PR is the best place to leave a backdoor when taking over a developer's account. Nevertheless, many developers just LGTM changes like this because of the tedium involved in reviewing them.

      If one could express such changes as a simple AST-wrangling script in a domain-specific language, which would then be executed in a trusted environment after being reviewed, that would decrease the review burden considerably.

      I believe that with agentic development, the most important constraint we have is human time. Making the LLM better and faster won't help us much if the human still needs to spend a majority of their time reading code. We should do what we can to give us less code to read, without losing confidence in the changes that the LLM makes.

    • Grep is effective for the most part, except for situations like when you have huge codebases and the thing you're looking for is used in too many places both as symbol and non-symbol.

      Another annoying thing about plain grep is, LLMs often end up pulling in bundled packages when using grep where 1 line is large enough to ruin the context window

      1 reply →

    • It's not intuitive to humans, even after learning parsing theory. I can do basic name refactorings. I've even written neovim plugins to do 1 specific thing with the AST (dfs down and delete one subtree which I understand). Those are fine.

      I would not be comfortable doing an on-the-fly "rewrite all subtrees that match this pattern" kind of edit.

      It seems like a tool that's good for LLM's though.

      1 reply →

    • I just realized that the fact that LLMs work so well for me in Clojure might be partly because of the clojure-mcp tools. They provide structural browsing and editing.

    • Has anybody thought about encoding AST tokens as LLM tokens, similar to how different words can have different meanings and that's reflected in their embedding?

      1 reply →

  • Anchor based editing requires injecting new anchors to the context, and dirac does so via a diff. So how is this more efficient (token-wise) than search and replace?? Even at a single token per hash. Also, code is read more than written so these just add up. I experimented once with stable anchors, albeit longer than a single token, and found it a downgrade.

    My conclusion is that the efficiency dirac sees comes mainly from showing file skeleton by default

    • I'm not sure one way or another but I've been using a related tool called Tilth by another poster here. It doesn't do anchor-based editing, but it does do syntax-aware search and will e.g. report the line range for function definitions, provide file outlines with line numbers on a file name match, etc.

      https://github.com/jahala/tilth

      2 replies →

    • > My conclusion is that the efficiency dirac sees comes mainly from showing file skeleton by default

      how hard do you think it would be to bring this optimization to oh-my-pi and opencode? I am testing dirac and it's very cool but the tooling isn't there yet comparing to oh-my-pi in terms of UX.

      2 replies →

  • > Batches all operations. Does large number of reads/edits simultaneously...

    I wasn't sure what this meant, so I looked at the source. It seems to be referring to tool APIs being designed around taking multiple targets as a list parameter, instead of hoping the model makes appropriately parallel tool calls. (This matches my experience btw, models are reluctant to make a large number of parallel calls simultaneously, and this seems more pronounced with weaker models.)

    • I think Anthropic may have mentioned this first, this pattern is also something my custom agent's tools are designed around, pretty sure I picked it up from them.

  • Instead of burning tokens on SOTA models, why not use a dirt-cheap specialised model for file editing?

    Where the SOTA model just makes a cheaper model to make edits, and it does so.

    • Yeah I also believe that there are plenty of efficiency gains available by using different models for different tasks. Reasoning models such as opus should only be used for the main planning and decision flows, but sub operations (exploring, applying edits etc etc) could be delegated to smaller and cheaper models. You also end up with a much smaller context for the main big model

  • Is there a complete list of the tools somewhere? I'm interested in how you chose to expose the AST specifically. In my own harness attempts I wanted to keep the number of tools absolutely minimal and briefly experimented with including an AST lib to use via an execute_python tool (plus some examples in the system prompt). Results were mixed though, with most models preferring ripgrep.

  • It would be really cool to do a causality investigation to determine which one of these boosts it so much / quantify how much each matters. Who knows, they may all interact in a sum-is-greater-than-parts way that only improves the score when shipped altogether.

  • Did you consider incorporating ast-grep or gritql?

    Congratulations, great work.

    • Can't speak for OP but I tried providing ast-grep in the execution context of an execute_bash tool, but even with pretty aggressive steering most models just don't seem to use it a lot. More expensive/SOTA models or higher reasoning increases the chances but lowers speed and raises cost. Maybe due to training bias for exploration tasks?

      3 replies →

It's really interesting how much the AI harness seems to matter. Going from 48% via Google's official results to 65% is a huge jump. I feel like I'm constantly seeing results that compare models and rarely seeing results that compare harnesses.

Is there a leaderboard out there comparing harness results using the same models?

  • Maybe the future isn't a human-like centralized intelligence but an octopus-like decentralized intelligence where more focus is placed on making the harness itself "smart"

  • For my local tests the past few months on the same local model, I’ve found Claude Code to be way better than OpenCode, and OpenCode to be better than Codex.

1. Would be good to benchmark at least one other model from a different family to see if it indeed generalizes. Minimax 2.7 seems a good candidate to keep it affordable. Until then we can't really tell if it's just overfit on Gemini 3 Flash.

2. Until then your landing page needs to mention all the numbers are just from running on Gemini 3 Flash. Currently there's no mention at all of Gemini.

3. Assuming that cheaper also means faster in this case where model is equal? If so, then why not add this to the benchmarks to highlight another advantage - time until completion of the tasks. If it's the opposite and it takes longer (seems unlikely), then it would be transparent to note this.

4. Would be good to note if it does or does not support skills, (nested) AGENTS.md, MCP and so on for people considering migrating.

  • Good points.

    1. I have been trying to benchmark openweights models but keep running into timeouts due to slow inference (terminal bench tasks have strict timeouts that you are not allowed to modify). Posted my frustration here https://www.reddit.com/r/LocalLLaMA/comments/1stgt39/the_fru...

    2. Done (updated github readme)

    3. Yes, on an average the times were shorter, but I did not benchmark it because at random times, the model outputs get slower, so it is not a rigorous benchmark

    4. Added info on this too

    • 1. Good point, didn't know about the timeouts, that's rough for the benchmarks. Though they IMO don't necessarily be "SWE-official" to have value, if the only difference is disabling those.

      3. Maybe you could instead provide a measure of output tokens used (including thinking), as that's a reasonable measure for speed. I guess input tokens would be similar unless the AST usage and hashes etc increases them a lot? Seems unlikely.

  • I tried it with minimax 2.7 and it really didn’t like the editing tool; collapsing rather quickly to using sed to edit files.

    I guess it makes sense that models don’t generalize perfectly to arbitrary tools but are biased to those in its training data, especially for a common operation like editing files.

    The Gemini family might be a good pick here since it generally underperforms in agentic tasks (due to lack of training data or other reasons) and thus might not have this inherent bias towards specific tools.

I haven't tried it, but I'm curious why you decided to implement a whole new harness over just writing extensions in pi. From whatever I've done with pi so far, the extension api is quite extensive. Hash anchored edits, for example, can definitely be implemented in pi. Anyhow, thank you for showing us your project and will be checking it out later. Cheers!

  • A few months ago one afternoon I was very frustrated with how slow Cline was being so decided to look under the hood. Decided to make a couple of changes. Got sucked in. About 70k lines of change, another 40k lines of deletions and two months later, here we are.

  • I've been looking into local LLMs and new harnesses recently, how good is Pi compared to OpenCode, I'm seeing that it's a lot better? What are the best models and customizations for it to fully utilize it?

I had a chance to look at this and noticed you were sending telemetry to an endpoint you control: https://dirac.run/v1/event. It doesn't seem like you're sending anything obviously sensitive or doing anything in bad faith (though, I do see api errors being sent, which could potentially leak sensitive info), but you gotta admit that that's scary seeing you as the sole dev for this. Plus, it's opt out too. Sorry, it's no go for me.

  • Here's all the telemetry:

    1. Telemetry to dirac.run/v1/event — Sends machine ID, token usage, model info, events, errors (first 500 chars), and platform info. Hardcoded API key. Defaults to opt-in (setting is "unset", not "disabled").

    2. Feature flags from dirac.run/v1/event/decide — Polls every 60 minutes with your machine ID. Always enabled, independent of telemetry opt-out. No way to disable without code changes.

    3. Web tools route through api.dirac.run — Web search and web fetch tools proxy through Dirac's own API server, sending your request content plus system headers (platform, version, machine ID).

    4. Model list fetches — Calls OpenRouter, HuggingFace, Groq, etc. for model listings even when using the Anthropic provider.

    • > Web tools route through api.dirac.run

      This is something that needs to be deprecated entirely. The web fetch tool no longer is used or works. There is nothing even listening at api.dirac.run. This was the result of me stretching my capacity too thin and bulk renaming cline.bot to dirac.run

      UPDATE (+1h): both Web search and web fetch tools are now nuked.

  • Thanks! Since it is a Cline fork, the telemetry mechanism is inherited. I left it as it might help debug issues. There is no evil purpose behind it nor does it create or store any PII

"astounding how much the harness matters" is the right read and it should be the lasting one. the model is rentable, the prompts are rentable, the benchmark numbers are mostly a function of the harness around them. swapping Gemini for Sonnet underneath the same harness has a smaller bench delta than swapping the harness around the model. the cheating-agents post you linked is the same observation through a different lens, the harness is what's being measured, the model is just the substrate.

that said context management seem to be solving today model problems, more than being an universal property, and will probably be obsoleted a few model generations down the road, as tool obsoleted RAG context injection from question embeddings.

Great job and congrats! Working on my own harness has been one of my favorite side projects in the past couple of weeks, of course I never finish anything... But I'm very interested in your experience with the following:

1. Context management - specifically pruning old tool call responses, truncation of tool output and automatic compaction. Those have worked pretty great for me, benefits of reducing context greatly seem to outweigh gains from "remembering" everything. I always leave short summaries though.

2. "Subagents" - my latest attempts revolve around not exposing any tools for the main agent at all, except for a run_agent tool where the subagent has access to the classic search/execute/fetch tools. My theory is that if subagents return concise summaries this would automatically keep the parent agent context clean for much longer. Still experimenting though, writing prompts for subagents may also be too far outside of the current training sets.

  • Thanks.

    1. Context management - Don't bother with pruning unless your API doesn't support caching. Every prune breaks the cache and you lose the 90% discounted caching rate

    2. I did some work improving Cline's subagent feature that Dirac inherited. In my experience, not all models are trained effectively to delegate work, so YMMV. A common pitfall to watch is, what happens if one or more subagents get stuck in a loop or for whatever reason don't return? You need a mechanism to control them from the main agent

    • It depends where you prune and how the specific prefix cache you're targeting works. Pruning or condensing recent items that are unnecessary probably pays for itself.

    • 1. For me pruning is a bit less about cost than performance. Recent research suggests lower context size is nearly always better, and many harnesses implement a sliding window for tool output pruning. Also not every provider supports caching, and if they do it might have expired (especially on restored sessions).

      2. That's a good hint, I'm currently only trying with tighter turn and token limits for subagents and an error summary on exceeding them. Not sure how else (besides steering and prompt engineering) to ensure the subagent doesn't go wild...

Very interesting, especially the harness point, how much of performance is in the wrapper tools (when I almost run out of credits, I change my model to a smaller one and try to give it more structured prompts; very often gpt-5.4-mini with structure works better than gpt-5.4 with vibes)

This inspired me to start a "skill distillery" [0] where I take good agent workflow ideas and turning them into small, inspectable/installable skills.

The first one is dirac-workflow, based on Dirac's structural code workflow. It's not a Dirac clone tho, it has no runtime, persistent AST index, hash-anchor editing engine, or benchmark harness. Just a small AST helper and the workflow discipline as a portable skill.

I also dogfooded it on the Dirac repo itself and included a short report.

Would appreciate feedback from the original author, if the prompts and tools [1] are representative.

[0] https://github.com/ouatu-ro/skill-distillery

[1] https://github.com/ouatu-ro/skill-distillery/blob/main/skill...

This is fascinating, and aligned with my experience working on harnesses. I bet there is still significant upside left on the table with that same model.

There was a narrative last year by Anthropic that each new model release had them making the harness closer to a simple while loop with tools, but now it seems to be going in the other direction. There's just so much to explore with harnesses. Rolling context windows (instead of compaction) have been very powerful in my work with agentic harnesses, while keeping a persistent high level summary and a detailed automated feedback pipeline (granted, this is easier said than done if you don't have specific, consistent goals for your agent like we do).

I am using dirac with Kimi 2.6 for refactoring a rust codebase. I have a Clean Architecture design which is being reinforced. The scope of work is laid out in a Beads epic with sub-issues. The planning was done with gpt5.5, and gpt5.5 is checking the work is complete. I have found that dirac is more productive on large codebase refactoring than OpenCode which actually trashed the .rs file and had to revert the code.

Interesting. Would love a comparison to pi.dev (Not Ohmypi)

How does this perform in day to day coding tasks, outside of benchmarks?

  • https://github.com/dirac-run/dirac#-evals

    README has eval of 8 tasks over 7 agents (including both pi and omp). Pi-mono costs second lowest across the 8 tasks (after Dirac) but occasionally misses produces incomplete changes.

    Interestingly, 2 tasks where pi missed some changes both were the tasks that benefitted from AST symbol understanding (e.g. find all instances of things that refer to this symbol and change those things). Since pi relies on bash type tooling, it missed some occurrences

    • Going to assume you didnt capture the data but could you add time taken to completion for each if you have it?

Very interesting! I've often thought static analysis could really help agents (I wrote this last summer: https://martinalderson.com/posts/claude-code-static-analysis...), but despite being hyped for LSPs in Claude Code it turned out to be very underwhelming (for many of the reasons that they can be annoying in a "real" IDE, ie static analysis starts firing mid edit and complaining and cached analysis getting stuck).

Curious to know if this has been an issue with your AST approach on larger projects?

The hash line based numbering is very interesting too (though I see on Opus 4.5+ far far fewer editing errors).

I've often thought that even if model progress stopped today, we'd still have _years_ of improvements thru harness iteration.

  • Wrt LSP, it uses the default LSP mechanism of the ide provider.

    For AST, it uses tree-sitter WASMs (ships them with the package), and maintains queries (https://github.com/dirac-run/dirac/tree/master/src/services/...)

    To keep performance fast, it stores the symbols DB (using sqlite) in the workspace's directory and incrementally updates it based on timestamps. Then it uses this DB to resolve symbol queries

    • Yes I understand, but do you not have issues that it drifts out of date and confuses the agents (especially on longer running tasks)?

      Like even "full" Visual Studio and Resharper have issues with this. Eg, you start editing file x, 'intellisense' runs, says there are loads of errors... because you haven't finished editing yet.

      2 replies →

Sounds great, I saw your first post but haven't had the time to try it out.

It's unfortunate that this is explicitly a fork of Cline but the commit history stops at a gigantic "initial commit". There is not even the cline history + a giant "initial version of Dirac" commit on top, which is a bit sad :)

  • Importing git history is ugly but do-able. I had to do that at a previous job (splitting a git repo in two pieces or importing commit history from SVN).

    I can take a look and try to create a PR around this if there is interest.

Nice work. I adopted this to use with my workplace's LLM proxy with a few small changes to the api/config files. Works flawlessly.

I’ve haven’t had great experiences with Gemini for coding yet. I’m doing reasonably simple full stack Go apps. Tried Gemini-ClI, antigravity, Pi.

The problems I’ve experienced are less adept at picking the right bash commands to build and test the Go app, and not following idiomatic Go or code base patterns for changes.

A skill hasn’t helped much.

Will need to try this and open code next.

Really impressive results. The point about the harness mattering more than the model is spot on — we've seen similar patterns in our own work.

One thing that stood out to me is your use of hash-anchored edits + AST-based context selection. We're building something in a similar direction with the Sovereign AI Stack, but with a stronger focus on governance and verification.

Curious — did you run into issues with context drift when using AST queries on very large codebases? We found that combining it with incremental symbol DB updates helped a lot.

Congrats on the results!

  • I'd be curious to hear more about your work on the 'Sovereign AI Stack'. I'm also working on a project that prioritizes governance and verification and I'd love to compare notes.

Can't OpenCode reach the same just developing this as a feature or plug-in? Like anchored edit?

  • Sure. Dirac is just a fork of the Cline harness and obviously OpenCode could take the same techniques and implement them. I don't know how difficult it would be to implement them in OpenCode, but given that Dirac and OpenCode are both open source, a future version of OpenCode could always be a re-branded Dirac (I'm sure there are ways to implement Dirac's techniques without having to completely replace OpenCode's underlying code base, but this illustrates that at the extreme, they could clearly just take Dirac in its entirety to get the same results).

I would like if some of that functionality is extracted in CLI tools. Then every coding agent can use it.

Is it still advisable to use something like codebase-memory-mcp for large codebases, or is Dirac doing fine without that?

Stared it. will try it later. one question though, to make it simpler for me, in what tasks does this model shine, how do you improve the score? I already use some skills to cut down CC costs, like caveman, rtk cli and a few others. just want to understand

Would you encourage others to make their own agents? I’ve been looking for a new Emacs side quest, and there seems to be a lot of low-level libraries

Very cool and interesting direction. I'm interested to see how easy it is to extend the harness's language support.

The Hash-anchor edit guy! Sincerely great idea, I used it in my own toy harness to good effect. I just checked this out, never tried it before, and its great! Clearly a well-iterated design with good choices made.

It is so refreshing to see real FOSS and not a grift. Simple openrouter api key, and I'm going.

This is what I'm using from now on. You are doing the best work in this space.

harness definitely makes a difference for the benchmarks. I ran my agent Camera Search against a few benchmarks and was able to beat Opus 4.7.

I created a real world benchmark, for mining, oil&gas, construction ect. called FieldOps-bench and it basically proves that vertical agents and specialized harness, tool, systems outperforms SOTA models alone still.

I keep trying to use dirac-cli with codex and it won't work: Error: Codex API error: Codex API request failed: 400.

Any ideas?

  • Assuming you logged in with OAuth, I am guessing you are trying to use gpt-5.5?

    In my tests, it worked using gpt-5.4 for me and I assumed gpt-5.5 is not available to me because I am on the free plan

    Do you have the subscription that allows 5.5? If so, I can look into what changed in API. Sorry I rarely use openAI so it is a bit of an untrodden path

    • Yes I'm on ChatGPT Pro (OAuth) and I'm trying to use gpt-5.5-xhigh.

      That was the issue, 5.4 works just fine.

      Support for service: priority (GPT /fast mode) would also be cool!

      1 reply →

hey there! thanks for the project!

I was intrigued with the claims so I wanted to test it myself.

First I (vibe)made an AUR package I could use to install it from git source, from master: https://aur.archlinux.org/packages/dirac-cli-git

Then I went in to see what's what, but I there isn't support for gemini-cli login, and importing from opencode doesn't work, failing with a message "Something went wrong. Could not read API keys from OpenCode config.". `dirac auth --verbose` doesn't seem to do anything.

Sorry for reporting it here, but it seems that GitHub is throwing a tantrum again and your issues page's been knocked out.

It was able to login with my OpenAI sub though, so let's see how's that.

EDIT: headsup, only gpt-5.4 seems to work, gpt-5.4-pro and gpt-5.5-2026-04-23 all throw api error 400, maybe by no fault of your own. OpenAI has been deliberately hindering third-party agents lately, as oh-my-pi ceased to work last week with all gpt models, either throwing an error or having a ludicrously low api rate limit.

  • Hey thanks for doing this! I will be looking into the gpt versions.

    It doesn't support gemini CLI because google seems to ban users for using it, there was a big controversy about it some time ago so I decided to leave it alone for now. Also, feel free to reach out to me if you want to discuss anything specific

woow, looks very good. I'm wondering if you do any optimizations for cli in general, since you're not using MCP. I'm building my own CLI for AI Agents, and was always concerned with context rot.

How do I connect it to a local llama.cpp instance?

  • It supports LMStudio or you can start a local endpoint, then run

    OPENAI_COMPATIBLE_CUSTOM_KEY="xxx" dirac -y --provider "https://localhost/v1" --model <model_name> "hi..."

Sorry I couldn’t really figure out if this was a harness, a fine tuned model, or both. Can we use Qwen with this for example? Is the performance expected to be better in that case?

  • The model was the default gemini-3-flash-preview.

    Harness was https://www.npmjs.com/package/dirac-cli

    Since Dirac is Cline's heavily modified fork, it supports all models Cline supported, including Qwen and all popular open/closed models

    As a matter of fact, I am trying to run terminal bench 2.0 using some OSS models at the moment but the slow inference speeds are causing tasks to timeout

Ha! I had an idea to do something like that myself over the weekend after trying Junie and Mistral to write some test for my personal project, that took literally hours! because Qwen 3.5 I am using locally can run 10k prompt for 10mins. Which should not be the case if agent would ask really simple questions like:

- what tool you need?

- what would be parameters for the tool

- what method you want to read?

instead of sending few kilobytes of build output and waiting for response. Oh well.. Good thing someone already did that!

Right now, top two harness on Terminal Bench are Codex and Forge Code. I wonder how Dirac compares to them.

Forge Code is awesome and I plan to test Dirac, too.