How many tokens does a complex bug fix take with AI?
A complex bug fix typically takes about 420,000 tokens to build with an AI coding agent (roughly 158,000–948,000 depending on complexity), about $1.20 at today's GPT-4o prices ($0.4550–$2.73). This is the build-time (developer) cost, not the cost of running the finished feature.
A complex bug is expensive because most of the work is investigation: the agent explores the codebase, forms and tests hypotheses, and iterates. That reading and re-reading is where the tokens go, long before it writes the fix.
Token & cost ranges
Cost uses GPT-4o at current prices. Verified 29 July 2026.
| Scenario | Input tokens | Output tokens | Total tokens | Est. cost |
|---|---|---|---|---|
| Low (simple) | 150,000 | 8,000 | 158,000 | $0.4550 |
| Typical | 400,000 | 20,000 | 420,000 | $1.20 |
| High (complex) | 900,000 | 48,000 | 948,000 | $2.73 |
Typical cost by model
The same typical token estimate priced across a few common coding models.
| Model | Typical cost | Range (low–high) |
|---|---|---|
| GPT-4o | $1.20 | $0.4550 – $2.73 |
| GPT-4o mini | $0.0720 | $0.0273 – $0.1638 |
| Claude Sonnet 4.6 | $1.50 | $0.5700 – $3.42 |
| Gemini 2.0 Flash | $0.0480 | $0.0182 – $0.1092 |
How we estimate this
A complex bug spans multiple files or needs investigation — the agent explores, forms hypotheses, and iterates over several turns. Input tokens dominate because an agent re-sends file context on every turn; output is the generated code, diffs and tests. Treat these as planning ranges, not a quote — your real usage depends on codebase size, model, prompt caching and how many iterations it takes.
Examples of this size
- A race condition or intermittent failure
- A bug crossing service boundaries
- A regression with an unclear root cause
Estimate it with your own model
Plug in your model, complexity and prompt-caching to get a tailored range.
Frequently asked questions
How many tokens does a complex bug fix take to build with AI?+
A complex bug fix typically takes about 420,000 tokens to build with an AI coding agent (roughly 158,000–948,000 depending on complexity), about $1.20 at today's GPT-4o prices ($0.4550–$2.73). This is the build-time (developer) cost, not the cost of running the finished feature.
Is this the cost to build it or to run it?+
This is the build-time (developer) cost — the tokens an AI coding agent burns while implementing the work. Running the finished feature is a separate, usually much smaller per-request cost.
Why is the range so wide?+
A complex bug spans multiple files or needs investigation — the agent explores, forms hypotheses, and iterates over several turns. Input tokens dominate because an agent re-sends file context on every turn; output is the generated code, diffs and tests. Treat these as planning ranges, not a quote — your real usage depends on codebase size, model, prompt caching and how many iterations it takes.
How can I lower the cost?+
Split large work into smaller pieces, enable prompt caching so re-sent context is billed at the cheaper cache-read rate, and use a cheaper model for routine steps. Try your own model in the Cost to build X estimator.