Failed response: `Cannot read properties of undefined (reading 'text')`

Claude via Copilot, 16k token limit

61686 [Stderr] Failed to calculate number of tokens, falling back to approximate count Error: Unknown model
61686 [Stderr]     at getEncodingNameForModel (/snapshot/appmap-js/node_modules/js-tiktoken/dist/lite.cjs:239:13)
61686 [Stderr]     at encodingForModel (/snapshot/appmap-js/node_modules/@langchain/core/dist/utils/tiktoken.cjs:23:59)
61686 [Stderr]     at ChatOpenAI.getNumTokens (/snapshot/appmap-js/node_modules/@langchain/core/dist/language_models/base.cjs:205:75)
61686 [Stderr]     at /snapshot/appmap-js/node_modules/@langchain/openai/dist/chat_models.cjs:1268:42
61686 [Stderr]     at Array.map (<anonymous>)
61686 [Stderr]     at ChatOpenAI.getNumTokensFromMessages (/snapshot/appmap-js/node_modules/@langchain/openai/dist/chat_models.cjs:1267:60)
61686 [Stderr]     at ChatOpenAI.getEstimatedTokenCountFromPrompt (/snapshot/appmap-js/node_modules/@langchain/openai/dist/chat_models.cjs:1215:34)
61686 [Stderr]     at ChatOpenAI._generate (/snapshot/appmap-js/node_modules/@langchain/openai/dist/chat_models.cjs:1141:49)
61686 [Stderr]     at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
61686 [Stderr]     at async Promise.allSettled (index 0)
61686 [Stderr]     at async ChatOpenAI._generateUncached (/snapshot/appmap-js/node_modules/@langchain/core/dist/language_models/chat_models.cjs:176:29)
61686 [Stderr]     at async LLMChain._call (/snapshot/appmap-js/node_modules/langchain/dist/chains/llm_chain.cjs:162:37)
61686 [Stderr]     at async LLMChain.invoke (/snapshot/appmap-js/node_modules/langchain/dist/chains/base.cjs:58:28)
61686 [Stderr]     at async LLMChain.predict (/snapshot/appmap-js/node_modules/langchain/dist/chains/llm_chain.cjs:188:24)
61686 [Stderr]     at async ConversationSummaryMemory.predictNewSummary (/snapshot/appmap-js/node_modules/langchain/dist/memory/summary.cjs:71:16)
61686 [Stderr]     at async LangchainMemoryService.predictSummary (/snapshot/appmap-js/packages/navie/dist/services/memory-service.js:19:25)
61686 [Stderr]     at async ExplainCommand.execute (/snapshot/appmap-js/packages/navie/dist/commands/explain-command.js:101:29)
61686 [Stderr]     at async Navie.execute (/snapshot/appmap-js/packages/navie/dist/navie.js:168:30)
61686 [Stderr]     at async LocalNavie.ask (/snapshot/appmap-js/packages/cli/built/rpc/explain/navie/navie-local.js)
61686 [Stderr]     at async Explain.explain (/snapshot/appmap-js/packages/cli/built/rpc/explain/explain.js)
61686 [Stderr] Failed to calculate number of tokens, falling back to approximate count Error: Unknown model
61686 [Stderr]     at getEncodingNameForModel (/snapshot/appmap-js/node_modules/js-tiktoken/dist/lite.cjs:239:13)
61686 [Stderr]     at encodingForModel (/snapshot/appmap-js/node_modules/@langchain/core/dist/utils/tiktoken.cjs:23:59)
61686 [Stderr]     at ChatOpenAI.getNumTokens (/snapshot/appmap-js/node_modules/@langchain/core/dist/language_models/base.cjs:205:75)
61686 [Stderr]     at /snapshot/appmap-js/node_modules/@langchain/openai/dist/chat_models.cjs:1269:42
61686 [Stderr]     at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
61686 [Stderr]     at async Promise.all (index 0)
61686 [Stderr]     at async ChatOpenAI.getNumTokensFromMessages (/snapshot/appmap-js/node_modules/@langchain/openai/dist/chat_models.cjs:1267:33)
61686 [Stderr]     at async ChatOpenAI.getEstimatedTokenCountFromPrompt (/snapshot/appmap-js/node_modules/@langchain/openai/dist/chat_models.cjs:1215:23)
61686 [Stderr]     at async ChatOpenAI._generate (/snapshot/appmap-js/node_modules/@langchain/openai/dist/chat_models.cjs:1141:38)
61686 [Stderr]     at async Promise.allSettled (index 0)
61686 [Stderr]     at async ChatOpenAI._generateUncached (/snapshot/appmap-js/node_modules/@langchain/core/dist/language_models/chat_models.cjs:176:29)
61686 [Stderr]     at async LLMChain._call (/snapshot/appmap-js/node_modules/langchain/dist/chains/llm_chain.cjs:162:37)
61686 [Stderr]     at async LLMChain.invoke (/snapshot/appmap-js/node_modules/langchain/dist/chains/base.cjs:58:28)
61686 [Stderr]     at async LLMChain.predict (/snapshot/appmap-js/node_modules/langchain/dist/chains/llm_chain.cjs:188:24)
61686 [Stderr]     at async ConversationSummaryMemory.predictNewSummary (/snapshot/appmap-js/node_modules/langchain/dist/memory/summary.cjs:71:16)
61686 [Stderr]     at async LangchainMemoryService.predictSummary (/snapshot/appmap-js/packages/navie/dist/services/memory-service.js:19:25)
61686 [Stderr]     at async ExplainCommand.execute (/snapshot/appmap-js/packages/navie/dist/commands/explain-command.js:101:29)
61686 [Stderr]     at async Navie.execute (/snapshot/appmap-js/packages/navie/dist/navie.js:168:30)
61686 [Stderr]     at async LocalNavie.ask (/snapshot/appmap-js/packages/cli/built/rpc/explain/navie/navie-local.js)
61686 [Stderr]     at async Explain.explain (/snapshot/appmap-js/packages/cli/built/rpc/explain/explain.js)

Start with packages/navie/dist/services/memory-service.js and follow the call chain through ExplainCommand.execute and packages/cli/built/rpc/explain/explain.js. Reproduce the Claude via Copilot request with the 16k token limit, identify why the response reaches the undefined text error after the unknown-model warning, and verify that the request completes without the reported failure.