Abstract
Large language models (LLMs) enable agents to solve long-horizon tasks by generating a plan and then executing it in an environment. However, successful planning requires two distinct capabilities: selecting an appropriate plan for the task and executing it faithfully. Existing planner--executor systems can fail at either stage, while final task success alone cannot distinguish selection from execution failures. We therefore study the Plan Declaration--Execution Gap and introduce Planning-as-Routing, where an LLM declares one of four planning modes: Predefined, Sequential, Hierarchical, or Search, and a deterministic router dispatches the task to the corresponding pattern-specific executor. Across four benchmarks and three LLMs, we find three consistent patterns. First, generic Plan+ReAct often fails to preserve declared planning structure, especially for longer plans: across three benchmarks, only (22)--(45%) of trajectories preserve it, whereas pattern-specific executors enforce the intended structure. Second, planning-mode effectiveness varies across environments and models: Search performs best on ALFWorld, Hierarchical on SWE-bench, and the strongest pattern can vary across models within the same benchmark. Third, the largest gains come from execution: pattern-specific executors improve task success from (0.48) to (0.92) on ALFWorld and from (0.36) to (0.44) on SWE-bench Verified over Plan+ReAct. Current LLMs, however, do not reliably select the strongest mode for each task, although few-shot examples improve selection in some benchmark--model combinations. Overall, reliable agent planning requires both effective mode selection and faithful execution: routing substantially closes the execution gap, while task-specific mode selection remains open.
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Publication details
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Cite this article
APA 7
Oota, S. R., Herrera, F., Sagrera, J. C., de Prado, M. L., & Khan, S. (2026). Do LLM Agents Execute the Plans They Declare? From Planning-Mode Declaration to Pattern-Specific Execution. https://omanscience.com/en/articles/do-llm-agents-execute-the-plans-they-declare-from-planning-mode-declaration-to-pattern-specific-execution
MLA 9
Oota, Subba Reddy, et al. "Do LLM Agents Execute the Plans They Declare? From Planning-Mode Declaration to Pattern-Specific Execution." https://omanscience.com/en/articles/do-llm-agents-execute-the-plans-they-declare-from-planning-mode-declaration-to-pattern-specific-execution.
Chicago (author–date)
Oota, Subba Reddy, Francisco Herrera, Jordi Cabot Sagrera, Marcos López de Prado, and Shadab Khan. 2026. "Do LLM Agents Execute the Plans They Declare? From Planning-Mode Declaration to Pattern-Specific Execution." https://omanscience.com/en/articles/do-llm-agents-execute-the-plans-they-declare-from-planning-mode-declaration-to-pattern-specific-execution.
Harvard
Oota, S. R., Herrera, F., Sagrera, J. C., de Prado, M. L. and Khan, S. (2026) 'Do LLM Agents Execute the Plans They Declare? From Planning-Mode Declaration to Pattern-Specific Execution', Available at: https://omanscience.com/en/articles/do-llm-agents-execute-the-plans-they-declare-from-planning-mode-declaration-to-pattern-specific-execution.
Vancouver
Oota SR, Herrera F, Sagrera JC, de Prado ML, Khan S. Do LLM Agents Execute the Plans They Declare? From Planning-Mode Declaration to Pattern-Specific Execution. https://omanscience.com/en/articles/do-llm-agents-execute-the-plans-they-declare-from-planning-mode-declaration-to-pattern-specific-execution
IEEE
S. R. Oota, F. Herrera, J. C. Sagrera, M. L. de Prado, and S. Khan, "Do LLM Agents Execute the Plans They Declare? From Planning-Mode Declaration to Pattern-Specific Execution," https://omanscience.com/en/articles/do-llm-agents-execute-the-plans-they-declare-from-planning-mode-declaration-to-pattern-specific-execution.