Bug: AWS Bedrock fails in Asia Pacific regions with invalid model identifier error

[datanerdie]

Bug: AWS Bedrock fails in Asia Pacific regions with "invalid model identifier" error

Description

When using OpenCode with AWS Bedrock in Asia Pacific regions (e.g., ap-southeast-2), OpenCode attempts to use EU inference profile models (eu.anthropic.claude-haiku-4-5-20251001-v1:0) which don't exist in these regions, causing "The provided model identifier is invalid" errors.

Environment

• OpenCode Version: Latest (main branch)
• Region: ap-southeast-2 (Sydney, Australia)
• AWS Profile: Configured with valid credentials
• Provider: amazon-bedrock
• Configuration:

  {
    "provider": {
      "amazon-bedrock": {
        "options": {
          "region": "ap-southeast-2",
          "profile": "bedrock-user"
        }
      }
    }
  }

Steps to Reproduce

1. Configure AWS Bedrock provider with ap-southeast-2 region
2. Configure oh-my-opencode agents to use Bedrock models:

   {
     "agents": {
       "build": {
         "model": "amazon-bedrock/anthropic.claude-sonnet-4-5-20250929-v1:0"
       }
     }
   }

3. Run any OpenCode command that triggers the title generation agent
4. Observe error logs showing EU model being used

Expected Behavior

OpenCode should:

1. Detect the ap-southeast-2 region
2. Select appropriate models for that region:
   • Direct models: anthropic.claude-haiku-4-5-20251001-v1:0
   • Global profiles: global.anthropic.claude-haiku-4-5-20251001-v1:0
   • AU profiles: au.anthropic.claude-haiku-4-5-20251001-v1:0 (for Australia)

Actual Behavior

OpenCode incorrectly selects EU inference profile models:

ERROR service=llm providerID=amazon-bedrock modelID=eu.anthropic.claude-haiku-4-5-20251001-v1:0
error={"error":{"statusCode":400,"responseBody":"{\"message\":\"The provided model identifier is invalid.\"}"}}

The API correctly calls the ap-southeast-2 endpoint but with an invalid EU model ID:

https://bedrock-runtime.ap-southeast-2.amazonaws.com/model/eu.anthropic.claude-haiku-4-5-20251001-v1%3A0/converse-stream

Root Cause

The bug is in the getSmallModel() function in /packages/opencode/src/provider/provider.ts (lines 1174-1195).

Problem 1: Incomplete Prefix List (Line 1175)

const crossRegionPrefixes = ["global.", "us.", "eu."]  // ❌ Missing "au.", "apac.", "jp."

This doesn't match the complete list used in getModel() at line 243:

const crossRegionPrefixes = ["global.", "us.", "eu.", "jp.", "apac.", "au."]  // ✅

Problem 2: Region Check Only for US/EU (Line 1188)

if (regionPrefix === "us" || regionPrefix === "eu") {  // ❌ Ignores all other regions!
  const regionalMatch = candidates.find((m) => m.startsWith(`${regionPrefix}.`))
  if (regionalMatch) return getModel(providerID, regionalMatch)
}

For ap-southeast-2:

• regionPrefix = "ap" (from region.split("-")[0])
• Condition evaluates to false
• Regional model selection is completely skipped

Proposed Fix

Option 1: Add AP Region Support (Recommended)

if (providerID === "amazon-bedrock") {
  const crossRegionPrefixes = ["global.", "us.", "eu.", "jp.", "apac.", "au."]  // Add missing prefixes
  const candidates = Object.keys(provider.models).filter((m) => m.includes(item))

  // 1. Try global prefix (works everywhere)
  const globalMatch = candidates.find((m) => m.startsWith("global."))
  if (globalMatch) return getModel(providerID, globalMatch)

  // 2. Try regional prefix
  const region = provider.options?.region
  if (region) {
    let regionPrefix = region.split("-")[0]

    // Map region prefixes to inference profile prefixes
    if (regionPrefix === "ap") {
      if (["ap-southeast-2", "ap-southeast-4"].includes(region)) {
        regionPrefix = "au"  // Australia regions
      } else if (region === "ap-northeast-1") {
        regionPrefix = "jp"  // Tokyo region
      } else {
        regionPrefix = "apac"  // Other APAC regions
      }
    }

    if (["us", "eu", "au", "jp", "apac"].includes(regionPrefix)) {
      const regionalMatch = candidates.find((m) => m.startsWith(`${regionPrefix}.`))
      if (regionalMatch) return getModel(providerID, regionalMatch)
    }
  }

  // 3. Try unprefixed model
  const unprefixed = candidates.find((m) => !crossRegionPrefixes.some((p) => m.startsWith(p)))
  if (unprefixed) return getModel(providerID, unprefixed)
}

Option 2: Fallback to Global for Unsupported Regions (Simpler)

if (regionPrefix === "us" || regionPrefix === "eu") {
  const regionalMatch = candidates.find((m) => m.startsWith(`${regionPrefix}.`))
  if (regionalMatch) return getModel(providerID, regionalMatch)
} else {
  // For other regions, prefer global profiles
  const globalMatch = candidates.find((m) => m.startsWith("global."))
  if (globalMatch) return getModel(providerID, globalMatch)
}

Additional Context

• The main getModel() function (lines 240-320) correctly handles AP regions with proper au., jp., and apac. prefix mapping
• The inconsistency is only in getSmallModel() used for background tasks like title generation
• All AWS Bedrock tests in /test/provider/amazon-bedrock.test.ts use only us-east-1 and eu-west-1 regions, which is why this bug wasn't caught

Impact

• Affected regions: All Asia Pacific regions (ap-*), Japan (ap-northeast-1), and potentially other non-US/EU regions
• Affected users: Anyone using AWS Bedrock outside US/EU regions
• Workaround: Remove oh-my-opencode plugin (OpenCode falls back to Anthropic API)

Test Coverage Suggestion

Add test cases for AP regions in amazon-bedrock.test.ts:

test("Bedrock: getSmallModel works in ap-southeast-2 region", async () => {
  await using tmp = await tmpdir({
    init: async (dir) => {
      await Bun.write(
        path.join(dir, "opencode.json"),
        JSON.stringify({
          $schema: "https://opencode.ai/config.json",
          provider: {
            "amazon-bedrock": {
              options: {
                region: "ap-southeast-2",
              },
            },
          },
        }),
      )
    },
  })
  await Instance.provide({
    directory: tmp.path,
    init: async () => {
      Env.set("AWS_PROFILE", "default")
    },
    fn: async () => {
      const smallModel = await Provider.getSmallModel("amazon-bedrock")
      expect(smallModel).toBeDefined()
      // Should use global. or au. prefix, NOT eu.
      expect(smallModel?.id).toMatch(/^(global\.|au\.|anthropic\.)/)
      expect(smallModel?.id).not.toMatch(/^eu\./)
    },
  })
})

Related Code

• Bug location: /packages/opencode/src/provider/provider.ts:1147-1211 (getSmallModel())
• Working reference: /packages/opencode/src/provider/provider.ts:240-320 (getModel() - correctly handles AP regions)
• Tests: /packages/opencode/test/provider/amazon-bedrock.test.ts (missing AP region test coverage)

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• Session title generation fails for non-EU Amazon Bedrock regions #12280: Session title generation fails for non-EU Amazon Bedrock regions - same root cause in getSmallModel()
• AWS Bedrock not working on regions outside us-east-1 #467: AWS Bedrock not working on regions outside us-east-1 - regional model selection issue
• [BUG] Bedrock provider: config options.region ignored for model ID prefixing #5812: [BUG] Bedrock provider: config options.region ignored for model ID prefixing - region handling in getModel()
• Bedrock US Opus identified is invalid #12052: Bedrock US Opus identified is invalid - invalid model identifier error
• Opus 4.5 in AWS Bedrock "undefined: The provided model identifier is invalid." #4784: Opus 4.5 in AWS Bedrock "undefined: The provided model identifier is invalid." - same error
• undefined: The provided model identifier is invalid #11037: undefined: The provided model identifier is invalid - similar issue with AWS Bedrock

Feel free to ignore if none of these address your specific case.

[datanerdie]

This issue identifies a remaining bug in PR #12281 which only partially fixed the regional model selection.

PR #12281 closed #12280 but only addressed US/EU regions. The fix is incomplete because:

1. Line 1175: crossRegionPrefixes = ["global.", "us.", "eu."] - missing "au.", "apac.", "jp."
2. Line 1188: if (regionPrefix === "us" || regionPrefix === "eu") - excludes all AP regions

The fix in PR #12281 should have matched the complete logic from getModel() at line 243 which correctly handles all regions including:

• au. prefix for Australia (ap-southeast-2, ap-southeast-4)
• jp. prefix for Japan (ap-northeast-1)
• apac. prefix for other Asia Pacific regions

Affected regions still broken: ap-southeast-2, ap-southeast-4, ap-northeast-1, and other Asia Pacific regions.

Reference: The getModel() function at lines 291-318 shows the correct implementation for handling AP regions.