OpenSlimedit

An OpenCode plugin that reduces token usage by up to 33% with zero configuration. It compresses tool descriptions, compacts read output, and adds line-range edit support.

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Token Savings at a Glance

Total tokens vs baseline (lower is better)

Claude Opus 4.6     [=================>             ] -21.8%  saved
Claude Sonnet 4.5   [========================>      ] -32.6%  saved
GPT 5.2 Codex       [====================>          ] -26.7%  saved
Minimax M2.5 Free   [==================>            ] -24.8%  saved

Model	Baseline	OpenSlimedit	Saved
Claude Opus 4.6	60,841 tokens	47,590 tokens	-21.8%
Claude Sonnet 4.5	120,884 tokens	81,471 tokens	-32.6%
GPT 5.2 Codex	39,185 tokens	28,713 tokens	-26.7%
Minimax M2.5 Free	28,031 tokens	21,073 tokens	-24.8%

Measured across 4 edit tasks (single-edit, multi-line-replace, multi-edit, large-file-edit) on small test files. Separate sessions, no prompt caching.

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How It Works

Three optimizations that compound across every API call:

1. Tool description compression — Replaces verbose built-in tool descriptions with minimal versions. Since tool schemas are sent with every API call, this saves thousands of input tokens per step.

2. Compact read output — Shortens absolute file paths to relative paths, strips type tags and footer boilerplate from file reads.

3. Line-range edit expansion — Allows the model to specify oldString as a line range like "55-64" instead of reproducing exact file content. The plugin transparently expands the range to the actual lines before the edit tool runs.

No custom tools. No system prompt injection. No modifications to built-in tool behavior. Everything works through lightweight hooks.

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Installation

Prerequisites

• OpenCode with plugin hook support
• Bun runtime

Option 1: Install from npm

npm install openslimedit

or with Bun:

bun add openslimedit

The postinstall script automatically adds the plugin to your project's .opencode/opencode.json config.

Option 2: Install from source

git clone https://github.com/ASidorenkoCode/openslimedit.git
cd openslimedit
bun install

Then add to your OpenCode config:

{
  "plugins": {
    "openslimedit": {
      "module": "file:///path/to/openslimedit/src/index.ts"
    }
  }
}

Start OpenCode

opencode

That's it. The plugin activates automatically and reduces token usage on every interaction.

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Benchmark

We tested multiple approaches to find the most token-efficient editing strategy. All benchmarks run on an isolated test folder with no project context, 1 iteration per case, separate sessions to avoid prompt caching effects.

Test cases: - single-edit — 21-line file, change one word - multi-line-replace — 48-line file, rewrite a function body - multi-edit — 35-line file, 3 separate changes across the file - large-file-edit — 115-line file, add try/catch + retry logic

Approaches tested: - baseline — No plugin, default OpenCode behavior - hashline — Tags every line with a content hash, model references lines by hash instead of reproducing content. Custom tool schema, system prompt injection. - smart_edit — Shortens descriptions of unused tools only + line-range expansion in edit. No custom tools. - OpenSlimedit (current) — Aggressively shortens ALL tool descriptions + compact read output + line-range expansion. No custom tools, no system prompt.

Why Not Hashline?

The hashline approach seemed promising in theory: tag lines with hashes so models don't need to reproduce code. In practice, it increases token usage for most models:

Total token change vs baseline (negative = savings, positive = regression)

Hashline:
  Claude Opus 4.6     ██████████████ +14.0%
  Claude Sonnet 4.5   ███████████████ +15.2%
  GPT 5.2 Codex       █████████████████████████████████████████████████ +49.9%
  Minimax M2.5 Free   █████████ +9.1%

OpenSlimedit:
  Claude Opus 4.6     ▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓ -21.8%
  Claude Sonnet 4.5   ▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓ -32.6%
  GPT 5.2 Codex       ▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓ -26.7%
  Minimax M2.5 Free   ▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓ -24.8%

The hash-tagged read output, custom tool schemas, and system prompt injection add per-step overhead that outweighs any savings from shorter oldString values. The biggest win comes from compressing tool descriptions — they're sent with every API call and the savings compound.

Results — Total Tokens (% vs baseline)

Claude Opus 4.6

Case	Baseline	Hashline	Smart Edit	OpenSlimedit
single-edit	13,419	13,915 (+3.7%)	12,739 (-5.1%)	9,902 (-26.2%)
multi-line-replace	13,965	16,940 (+21.3%)	13,289 (-4.8%)	10,547 (-24.5%)
multi-edit	17,583	19,125 (+8.8%)	16,572 (-5.7%)	13,743 (-21.8%)
large-file-edit	15,874	19,377 (+22.1%)	16,691 (+5.1%)	13,398 (-15.6%)
Total	60,841	69,357 (+14.0%)	59,291 (-2.5%)	47,590 (-21.8%)

Claude Sonnet 4.5

Case	Baseline	Hashline	OpenSlimedit
single-edit	38,111	26,881 (-29.5%)	18,460 (-51.6%)
multi-line-replace	26,997	19,039 (-29.5%)	20,042 (-25.8%)
multi-edit	39,785	47,923 (+20.5%)	19,940 (-49.9%)
large-file-edit	15,991	45,429 (+184.1%)	23,029 (+44.0%)
Total	120,884	139,272 (+15.2%)	81,471 (-32.6%)

GPT 5.2 Codex

Case	Baseline	Hashline	OpenSlimedit
single-edit	8,002	11,208 (+40.1%)	14,027 (+75.3%)
multi-line-replace	8,325	19,350 (+132.4%)	7,019 (-15.7%)
multi-edit	9,510	FAIL	4,797 (-49.5%)
large-file-edit	13,348	8,189 (-38.6%)	2,870 (-78.5%)
Total	39,185	58,747*	28,713 (-26.7%)

*Hashline multi-edit failed (760s timeout loop); total includes failed run

Minimax M2.5 Free

Case	Baseline	Hashline	Smart Edit	OpenSlimedit
single-edit	10,691	11,098 (+3.8%)	9,994 (-6.5%)	7,405 (-30.7%)
multi-line-replace	11,105	12,045 (+8.5%)	10,396 (-6.4%)	1,721 (-84.5%)
multi-edit	2,308	2,331 (+1.0%)	2,357 (+2.1%)	8,034 (+248.1%)
large-file-edit	3,927	5,100 (+29.9%)	3,986 (+1.5%)	3,913 (-0.4%)
Total	28,031	30,574 (+9.1%)	26,733 (-4.6%)	21,073 (-24.8%)

Summary

Model	Hashline	Smart Edit	OpenSlimedit
Claude Opus 4.6	+14.0%	-2.5%	-21.8%
Claude Sonnet 4.5	+15.2%	—	-32.6%
GPT 5.2 Codex	+49.9%*	—	-26.7%
Minimax M2.5 Free	+9.1%	-4.6%	-24.8%

*Includes failed multi-edit run

Key Findings

• Tool description compression is the biggest win. Tool schemas are sent with every API call. Shortening them saves thousands of input tokens per step, and this compounds across multi-step tasks.
• Hashline increases token usage for most models. The hash-tagged read output, custom tool schemas, and system prompt injection add per-step overhead that outweighs the savings from shorter oldString values.
• OpenSlimedit consistently saves 21-33% across all tested models with zero regressions on Opus 4.6. Some models show regressions on individual cases (Minimax on multi-edit, Codex on single-edit) but the total is always significantly lower.
• Custom tools confuse some models. Minimax and Codex struggle with non-standard tool schemas, leading to extra steps or failures. OpenSlimedit avoids this entirely by only modifying descriptions of existing tools.

Note: These benchmarks use small files (21-115 lines). On larger files, the relative savings from tool description compression become even more significant as more API steps are needed.

Raw data — Hashline runs

Mode	Model	Case	Time	Input	Output	Total	Success
hashline	claude-sonnet-4.5	single-edit	10,745 ms	26,582	299	26,881	yes
hashline	claude-sonnet-4.5	multi-line-replace	37,231 ms	17,188	1,851	19,039	yes
hashline	claude-sonnet-4.5	multi-edit	52,668 ms	44,604	3,319	47,923	yes
hashline	claude-sonnet-4.5	large-file-edit	25,097 ms	44,466	963	45,429	yes
hashline	claude-opus-4.6	single-edit	12,994 ms	13,617	298	13,915	yes
hashline	claude-opus-4.6	multi-line-replace	21,080 ms	16,208	732	16,940	yes
hashline	claude-opus-4.6	multi-edit	46,637 ms	17,031	2,094	19,125	yes
hashline	claude-opus-4.6	large-file-edit	25,787 ms	18,401	976	19,377	yes
hashline	gpt-5.2-codex	single-edit	12,458 ms	10,929	279	11,208	yes
hashline	gpt-5.2-codex	multi-line-replace	24,931 ms	18,381	969	19,350	yes
hashline	gpt-5.2-codex	multi-edit	760,890 ms	146,516	53,250	199,766	no
hashline	gpt-5.2-codex	large-file-edit	27,601 ms	6,979	1,210	8,189	yes
hashline	minimax-m2.5-free	single-edit	13,806 ms	10,680	418	11,098	yes
hashline	minimax-m2.5-free	multi-line-replace	56,046 ms	11,082	963	12,045	yes
hashline	minimax-m2.5-free	multi-edit	19,062 ms	1,654	677	2,331	yes
hashline	minimax-m2.5-free	large-file-edit	61,973 ms	3,222	1,878	5,100	yes

Raw data — Baseline runs

Mode	Model	Case	Time	Input	Output	Total	Success
baseline	claude-sonnet-4.5	single-edit	11,107 ms	37,775	336	38,111	yes
baseline	claude-sonnet-4.5	multi-line-replace	12,876 ms	26,541	456	26,997	yes
baseline	claude-sonnet-4.5	multi-edit	17,343 ms	38,890	895	39,785	yes
baseline	claude-sonnet-4.5	large-file-edit	21,273 ms	15,035	956	15,991	yes
baseline	claude-opus-4.6	single-edit	12,464 ms	13,146	273	13,419	yes
baseline	claude-opus-4.6	multi-line-replace	14,016 ms	13,554	411	13,965	yes
baseline	claude-opus-4.6	multi-edit	43,656 ms	15,873	1,710	17,583	yes
baseline	claude-opus-4.6	large-file-edit	20,120 ms	14,981	893	15,874	yes
baseline	gpt-5.2-codex	single-edit	11,662 ms	7,656	346	8,002	yes
baseline	gpt-5.2-codex	multi-line-replace	11,922 ms	8,039	286	8,325	yes
baseline	gpt-5.2-codex	multi-edit	22,087 ms	8,519	991	9,510	yes
baseline	gpt-5.2-codex	large-file-edit	29,591 ms	11,701	1,647	13,348	yes
baseline	minimax-m2.5-free	single-edit	10,740 ms	10,389	302	10,691	yes
baseline	minimax-m2.5-free	multi-line-replace	16,274 ms	10,668	437	11,105	yes
baseline	minimax-m2.5-free	multi-edit	43,462 ms	1,233	1,075	2,308	yes
baseline	minimax-m2.5-free	large-file-edit	20,430 ms	3,250	677	3,927	yes

Raw data — Smart Edit runs

Mode	Model	Case	Time	Input	Output	Total	Success
smart_edit	claude-opus-4.6	single-edit	13,016 ms	12,432	307	12,739	yes
smart_edit	claude-opus-4.6	multi-line-replace	15,812 ms	12,847	442	13,289	yes
smart_edit	claude-opus-4.6	multi-edit	40,820 ms	14,919	1,653	16,572	yes
smart_edit	claude-opus-4.6	large-file-edit	32,170 ms	15,377	1,314	16,691	yes
smart_edit	minimax-m2.5-free	single-edit	11,149 ms	9,707	287	9,994	yes
smart_edit	minimax-m2.5-free	multi-line-replace	21,405 ms	9,992	404	10,396	yes
smart_edit	minimax-m2.5-free	multi-edit	20,998 ms	1,377	980	2,357	yes
smart_edit	minimax-m2.5-free	large-file-edit	41,250 ms	3,212	774	3,986	yes

Raw data — OpenSlimedit runs

Mode	Model	Case	Time	Input	Output	Total	Success
openslimedit	claude-opus-4.6	single-edit	12,126 ms	9,629	273	9,902	yes
openslimedit	claude-opus-4.6	multi-line-replace	15,326 ms	10,066	481	10,547	yes
openslimedit	claude-opus-4.6	multi-edit	41,378 ms	12,095	1,648	13,743	yes
openslimedit	claude-opus-4.6	large-file-edit	28,135 ms	12,161	1,237	13,398	yes
openslimedit	claude-sonnet-4.5	single-edit	10,884 ms	18,148	312	18,460	yes
openslimedit	claude-sonnet-4.5	multi-line-replace	13,208 ms	19,528	514	20,042	yes
openslimedit	claude-sonnet-4.5	multi-edit	20,895 ms	18,985	955	19,940	yes
openslimedit	claude-sonnet-4.5	large-file-edit	20,498 ms	22,053	976	23,029	yes
openslimedit	gpt-5.2-codex	single-edit	8,745 ms	13,841	186	14,027	yes
openslimedit	gpt-5.2-codex	multi-line-replace	10,123 ms	6,770	249	7,019	yes
openslimedit	gpt-5.2-codex	multi-edit	13,653 ms	4,239	558	4,797	yes
openslimedit	gpt-5.2-codex	large-file-edit	14,786 ms	2,206	664	2,870	yes
openslimedit	minimax-m2.5-free	single-edit	15,159 ms	7,140	265	7,405	yes
openslimedit	minimax-m2.5-free	multi-line-replace	14,744 ms	1,316	405	1,721	yes
openslimedit	minimax-m2.5-free	multi-edit	13,289 ms	7,385	649	8,034	yes
openslimedit	minimax-m2.5-free	large-file-edit	21,090 ms	3,214	699	3,913	yes

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Project Structure

``` openslimedit/ ├── src/ │ └── index.ts # Plugin imp