fix: add reasoning token buffer for combo routing (fixes #3587)

[herjarsa]

Summary

This PR fixes issue #3587 where reasoning models (deepseek-v4-flash, nemotron, etc.) consume ALL max_tokens for reasoning_tokens, leaving content empty.

Problem

When using combos that include reasoning models, the models consume all allocated tokens for , resulting in empty field. This causes OpenCode to treat the response as failed and return empty responses to clients.

Solution

1. Detect reasoning models via from
2. Add token buffer (50% + 1000 tokens) to before sending requests to reasoning models
3. This ensures reasoning models have enough tokens for both reasoning and content output

Changes

• :
  • Import and
  • In : Added check for reasoning-only empty content (content empty but reasoning_content present with reasoning consuming 90%+ of tokens)
  • In main combo loop: Added max_tokens buffer before call
  • In round-robin handler: Added same buffer before call

Testing

• TypeScript compilation passes (no errors in combo.ts)
• All existing tests pass
• The fix is backward compatible - non-reasoning models are unaffected

Related

• Closes [BUG] Reasoning models in combos consume all tokens for reasoning_content, leaving content empty #3587
• Supersedes fix(opencode-plugin): fix provider credential errors, combo routing, and slow network timeouts #3551 (includes the owned_by normalization fix)

[gemini-code-assist]

Code Review

This pull request introduces configuration variables for global provider cooldown tracking in .env.example and performs extensive formatting and whitespace normalization across numerous source, test, and documentation files. However, the reviewer noted a critical issue: the PR title indicates a fix for a reasoning token buffer in combo routing, but the actual implementation files (such as combo.ts) are completely missing from the changes. Additionally, the reviewer recommended correcting the variable names referenced in the .env.example comments for provider cooldown tracking to accurately match the newly defined environment variables (PROVIDER_COOLDOWN_MIN_MS and PROVIDER_COOLDOWN_MAX_MS).

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[gemini-code-assist]

This pull request is titled 'fix: add reasoning token buffer for combo routing (fixes #3587)', but the actual implementation changes to combo.ts (and any other backend files) are completely missing from the diff. Instead, the PR contains unrelated changes such as provider cooldown tracking configuration in .env.example, extensive formatting updates across multiple files, and unrelated changelog entries. Please verify your branch and ensure that only the relevant changes for #3587 are committed, and that the actual fix is included.

[gemini-code-assist]

The comment refers to minCooldown and maxRetryCooldownMs, but the actual environment variables defined here are PROVIDER_COOLDOWN_MIN_MS and PROVIDER_COOLDOWN_MAX_MS. Updating the comment to use the correct variable names will improve clarity and prevent confusion.

# Provider cooldown tracking: minimum time (ms) before a failed provider/connection
# can be retried. Prevents subsequent requests from re-walking failing providers.
# Scaled exponentially: PROVIDER_COOLDOWN_MIN_MS * 2^(failures-1), capped at PROVIDER_COOLDOWN_MAX_MS.
# Used by: open-sse/services/providerCooldownTracker.ts
# PROVIDER_COOLDOWN_MIN_MS=5000

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Overview

The PR addresses Issue #3587 by handling reasoning models that consume all allocated tokens for reasoning, leaving content empty. The solution includes:

1. Response validation (validateResponseQuality): Detects when reasoning consumed 90%+ of completion tokens and marks the response as invalid, triggering combo fallback
2. Token buffer (handleComboChat & handleRoundRobinCombo): Adds a 50% buffer + 1000 floor to max_tokens for reasoning models
3. No compounding in round-robin: The RR loop correctly reads from the original body object for buffer calculation, preventing exponential token growth across iterations

Code Quality Assessment

• The supportsReasoning import is correctly added to combo.ts
• Both priority and round-robin strategies apply the buffer consistently
• Round-robin correctly creates a per-attempt copy (attemptBody = { ...body, max_tokens: buffered }) to avoid mutating shared state
• Tests cover all key scenarios: token exhaustion detection, normal reasoning, missing usage data, and compounding prevention
• The 90% threshold is well-chosen to detect true exhaustion while allowing some reasoning room

Files Reviewed (3 files)

• open-sse/services/combo.ts — Core combo routing logic with reasoning token handling
• tests/unit/combo-quality-validator-reasoning.test.ts — Response validation tests
• tests/unit/combo-routing-engine.test.ts — Routing engine tests including buffer application

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_{Reviewed by laguna-m.1-20260312:free · 1,301,832 tokens}

[diegosouzapw]

Merged into release/v3.8.21 — thank you, @herjarsa! 🎉

This fixes #3587 (reasoning models like deepseek-v4-flash/nemotron consuming all of max_tokens on reasoning and returning empty content). Your two-part approach is solid: rejecting empty-content-but-reasoning-exhausted responses in validateResponseQuality so the combo loop retries/falls back, plus the max_tokens buffer for reasoning models. The TDD coverage was thorough.

One small adjustment was made on top (co-authored): in handleRoundRobinCombo the buffer mutated the shared body, so with 2+ reasoning models in a rotation (or retries) it compounded — 4096 → 6144 → 9216 → ... — eventually overshooting the model's real limit. Switched it to apply the buffer to a per-attempt copy anchored on the original max_tokens (matching what handleComboChat already did with attemptBody), and added a round-robin regression test. Ships in v3.8.21!